Sample records for sahel

  1. Tree Density and Species Decline in the African Sahel Attributable to Climate

    NASA Technical Reports Server (NTRS)

    Gonzalez, Patrick; Tucker, Compton J.; Sy, H.

    2012-01-01

    Increased aridity and human population have reduced tree cover in parts of the African Sahel and degraded resources for local people. Yet, tree cover trends and the relative importance of climate and population remain unresolved. From field measurements, aerial photos, and Ikonos satellite images, we detected significant 1954-2002 tree density declines in the western Sahel of 18 +/- 14% (P = 0.014, n = 204) and 17 +/- 13% (P = 0.0009, n = 187). From field observations, we detected a significant 1960-2000 species richness decline of 21 +/- 11% (P = 0.0028, n = 14) across the Sahel and a southward shift of the Sahel, Sudan, and Guinea zones. Multivariate analyses of climate, soil, and population showed that temperature most significantly (P < 0.001) explained tree cover changes. Multivariate and bivariate tests and field observations indicated the dominance of temperature and precipitation, supporting attribution of tree cover changes to climate variability. Climate change forcing of Sahel climate variability, particularly the significant (P < 0.05) 1901-2002 temperature increases and precipitation decreases in the research areas, connects Sahel tree cover changes to global climate change. This suggests roles for global action and local adaptation to address ecological change in the Sahel.

  2. North Atlantic salinity as a predictor of Sahel rainfall.

    PubMed

    Li, Laifang; Schmitt, Raymond W; Ummenhofer, Caroline C; Karnauskas, Kristopher B

    2016-05-01

    Water evaporating from the ocean sustains precipitation on land. This ocean-to-land moisture transport leaves an imprint on sea surface salinity (SSS). Thus, the question arises of whether variations in SSS can provide insight into terrestrial precipitation. This study provides evidence that springtime SSS in the subtropical North Atlantic ocean can be used as a predictor of terrestrial precipitation during the subsequent summer monsoon in Africa. Specifically, increased springtime SSS in the central to eastern subtropical North Atlantic tends to be followed by above-normal monsoon-season precipitation in the African Sahel. In the spring, high SSS is associated with enhanced moisture flux divergence from the subtropical oceans, which converges over the African Sahel and helps to elevate local soil moisture content. From spring to the summer monsoon season, the initial water cycling signal is preserved, amplified, and manifested in excessive precipitation. According to our analysis of currently available soil moisture data sets, this 3-month delay is attributable to a positive coupling between soil moisture, moisture flux convergence, and precipitation in the Sahel. Because of the physical connection between salinity, ocean-to-land moisture transport, and local soil moisture feedback, seasonal forecasts of Sahel precipitation can be improved by incorporating SSS into prediction models. Thus, expanded monitoring of ocean salinity should contribute to more skillful predictions of precipitation in vulnerable subtropical regions, such as the Sahel.

  3. North Atlantic salinity as a predictor of Sahel rainfall

    PubMed Central

    Li, Laifang; Schmitt, Raymond W.; Ummenhofer, Caroline C.; Karnauskas, Kristopher B.

    2016-01-01

    Water evaporating from the ocean sustains precipitation on land. This ocean-to-land moisture transport leaves an imprint on sea surface salinity (SSS). Thus, the question arises of whether variations in SSS can provide insight into terrestrial precipitation. This study provides evidence that springtime SSS in the subtropical North Atlantic ocean can be used as a predictor of terrestrial precipitation during the subsequent summer monsoon in Africa. Specifically, increased springtime SSS in the central to eastern subtropical North Atlantic tends to be followed by above-normal monsoon-season precipitation in the African Sahel. In the spring, high SSS is associated with enhanced moisture flux divergence from the subtropical oceans, which converges over the African Sahel and helps to elevate local soil moisture content. From spring to the summer monsoon season, the initial water cycling signal is preserved, amplified, and manifested in excessive precipitation. According to our analysis of currently available soil moisture data sets, this 3-month delay is attributable to a positive coupling between soil moisture, moisture flux convergence, and precipitation in the Sahel. Because of the physical connection between salinity, ocean-to-land moisture transport, and local soil moisture feedback, seasonal forecasts of Sahel precipitation can be improved by incorporating SSS into prediction models. Thus, expanded monitoring of ocean salinity should contribute to more skillful predictions of precipitation in vulnerable subtropical regions, such as the Sahel. PMID:27386525

  4. Diagnosing Mechanisms of Oceanic Influence on Sahel Precipitation Variability

    NASA Astrophysics Data System (ADS)

    Pomposi, Catherine A.

    The West African Monsoon (WAM) is a significant component of the global monsoon system and plays a key role in the annual cycle of precipitation in the Sahel region of Africa (10°N to 20°N) during the summer months (July to September). Rainfall in the Sahel varies on timescales ranging from seasons to millennia as a result of changes in the WAM. In the last century, the Sahel experienced a relatively wet period (prior to the 1960s) followed by a period of severe drought (1970s-1980s) with higher-frequency variability superimposed on this low-frequency background signal. Understanding precipitation variability like that which occurred over the 20th Century and its impact on Sahel precipitation is critically important for skillful hydroclimate predictions and disaster preparedness in the region. Previous work has shown that the WAM responds to both internal atmospheric variability and external oceanic forcing. A large fraction of 20th Century Sahel rainfall variability has been linked to nearby and remote oceanic forcing from the Atlantic, Pacific, and Indian Oceans, suggesting that the ocean is the primary driver of variability. However, the mechanisms underlying the influence of sea surface temperature (SST) forcing to land based precipitation and the relative importance of the roles of different basins are not as well understood. To this end, the work completed in this thesis examines the physical mechanisms linking oceanic forcing to recent precipitation variability in the Sahel and identifies them alongside large-scale environmental conditions. A series of moisture budget decomposition studies are performed for the Sahel in order to understand the processes that govern regional hydroclimate variability on decadal and interannual time scales. The results show that the oceanic forcing of atmospheric mass convergence and divergence explains the moisture balance patterns in the region to first order on the timescales considered. On decadal timescales, forcing by

  5. Impact of internal variability on projections of Sahel precipitation change

    NASA Astrophysics Data System (ADS)

    Monerie, Paul-Arthur; Sanchez-Gomez, Emilia; Pohl, Benjamin; Robson, Jon; Dong, Buwen

    2017-11-01

    The impact of the increase of greenhouse gases on Sahelian precipitation is very uncertain in both its spatial pattern and magnitude. In particular, the relative importance of internal variability versus external forcings depends on the time horizon considered in the climate projection. In this study we address the respective roles of the internal climate variability versus external forcings on Sahelian precipitation by using the data from the CESM Large Ensemble Project, which consists of a 40 member ensemble performed with the CESM1-CAM5 coupled model for the period 1920-2100. We show that CESM1-CAM5 is able to simulate the mean and interannual variability of Sahel precipitation, and is representative of a CMIP5 ensemble of simulations (i.e. it simulates the same pattern of precipitation change along with equivalent magnitude and seasonal cycle changes as the CMIP5 ensemble mean). However, CESM1-CAM5 underestimates the long-term decadal variability in Sahel precipitation. For short-term (2010-2049) and mid-term (2030-2069) projections the simulated internal variability component is able to obscure the projected impact of the external forcing. For long-term (2060-2099) projections external forcing induced change becomes stronger than simulated internal variability. Precipitation changes are found to be more robust over the central Sahel than over the western Sahel, where climate change effects struggle to emerge. Ten (thirty) members are needed to separate the 10 year averaged forced response from climate internal variability response in the western Sahel for a long-term (short-term) horizon. Over the central Sahel two members (ten members) are needed for a long-term (short-term) horizon.

  6. Skilful prediction of Sahel summer rainfall on inter-annual and multi-year timescales

    PubMed Central

    Sheen, K. L.; Smith, D. M.; Dunstone, N. J.; Eade, R.; Rowell, D. P.; Vellinga, M.

    2017-01-01

    Summer rainfall in the Sahel region of Africa exhibits one of the largest signals of climatic variability and with a population reliant on agricultural productivity, the Sahel is particularly vulnerable to major droughts such as occurred in the 1970s and 1980s. Rainfall levels have subsequently recovered, but future projections remain uncertain. Here we show that Sahel rainfall is skilfully predicted on inter-annual and multi-year (that is, >5 years) timescales and use these predictions to better understand the driving mechanisms. Moisture budget analysis indicates that on multi-year timescales, a warmer north Atlantic and Mediterranean enhance Sahel rainfall through increased meridional convergence of low-level, externally sourced moisture. In contrast, year-to-year rainfall levels are largely determined by the recycling rate of local moisture, regulated by planetary circulation patterns associated with the El Niño-Southern Oscillation. Our findings aid improved understanding and forecasting of Sahel drought, paramount for successful adaptation strategies in a changing climate. PMID:28541288

  7. MODIS EVI-based net primary production in the Sahel 2000-2014

    NASA Astrophysics Data System (ADS)

    Ardö, Jonas; Tagesson, Torbern; Jamali, Sadegh; Khatir, Abdelrahman

    2018-03-01

    Africa is facing resource problems due to increasing demand combined with potential climate-induced changes in supply. Here we aim to quantify resources in terms of net primary production (NPP [g C m-2 yr-1]) of vegetation in the Sahel region for 2000-2014. Using time series of the enhanced vegetation index (EVI) from MODIS, NPP was estimated for the Sahel region with a 500 × 500 m spatial resolution and 8-day temporal resolution. The estimates were based on local eddy covariance flux measurements from six sites in the Sahel region and the carbon use efficiency originating from a dynamic vegetation model. No significant NPP change was found for the Sahel as a region but, for sub-regions, significant changes, both increasing and decreasing, were observed. Substantial uncertainties related to NPP estimates and the small availability of evaluation data makes verification difficult. The simplicity of the methodology used, dependent on earth observation only, is considered an advantage.

  8. Missing pieces of the puzzle: understanding decadal variability of Sahel Rainfall

    NASA Astrophysics Data System (ADS)

    Vellinga, Michael; Roberts, Malcolm; Vidale, Pier-Luigi; Mizielinski, Matthew; Demory, Marie-Estelle; Schiemann, Reinhard; Strachan, Jane; Bain, Caroline

    2015-04-01

    The instrumental record shows that substantial decadal fluctuations affected Sahel rainfall from the West African monsoon throughout the 20th century. Climate models generally underestimate the magnitude of decadal Sahel rainfall changes compared to observations. This shows that the processes that control low-frequency Sahel rainfall change are misrepresented in most CMIP5-era climate models. Reliable climate information of future low-frequency rainfall changes thus remains elusive. Here we identify key processes that control the magnitude of the decadal rainfall recovery in the Sahel since the mid-1980s. We show its sensitivity to model resolution and physics in a suite of experiments with global HadGEM3 model configurations at resolutions between 130-25 km. The decadal rainfall trend increases with resolution and at 60-25 km falls within the observed range. Higher resolution models have stronger increases of moisture supply and of African Easterly wave activity. Easterly waves control the occurrence of strong organised rainfall events which carry most of the decadal trend. Weak rainfall events occur too frequently at all resolutions and at low resolution contribute substantially to the decadal trend. All of this behaviour is seen across CMIP5, including future scenarios. Additional simulations with a global 12km version of HadGEM3 show that treating convection explicitly dramatically improves the properties of Sahel rainfall systems. We conclude that interaction between convective scale and global scale processes is key to decadal rainfall changes in the Sahel. This work is distributed under the Creative Commons Attribution 3.0 Unported License together with an author copyright. This license does not conflict with the regulations of the Crown Copyright.Crown Copyright

  9. Influence of Latent Heating over the Asian and Western Pacific Monsoon Region on Sahel Summer Rainfall.

    PubMed

    He, Shan; Yang, Song; Li, Zhenning

    2017-08-09

    There has been an interdecadal shift towards a less humid state in Sahel summer rainfall since the 1960s. The decreased Sahel summer rainfall was associated with enhanced summer latent heating over the South Asian and western Pacific summer monsoon region and anomalous zonal-vertical cell of the Asian summer monsoon circulation, indicating that the latent heating plays a significant role in the change in Sahel rainfall. The effects of the latent heating over different monsoon domains on the Sahel rainfall are investigated through several model experiments. Results show that the remote monsoon heating mainly affects Sahel rainfall by generating changes in the zonal-vertical atmospheric circulation.

  10. Vegetation Interaction Enhances Interdecadal Climate Variability in the Sahel

    NASA Technical Reports Server (NTRS)

    Zeng, Ning; Neelin, J. David; Lau, William K.-M.

    1999-01-01

    The role of naturally varying vegetation in influencing the climate variability in the Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea surface temperature (SST) variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation significantly, but can reduce year to year variability due to a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall, in particular, the multi-decadal drying trend from the 1950s to the 80s.

  11. Disentangling the effects of climate and people on Sahel vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Seaquist, J. W.; Hickler, T.; Eklundh, L.; Ardö, J.; Heumann, B. W.

    2008-08-01

    The Sahel belt of Africa has been the focus of intensive scientific research since the 1960s, spurred on by the chronic vulnerability of its population to recurring drought and the threat of long-term land degradation. But satellite sensors have recently shown that much of the region has experienced significant increases in photosynthetic activity since the early 1980s, thus re-energizing long-standing debates about the role that people play in shaping land surface status, and thus climate at regional scales. In this paper, we test the hypothesis that people have had a measurable impact on vegetation dynamics in the Sahel for the period 1982 2002. We compare potential natural vegetation dynamics predicted by a process-based ecosystem model with satellite-derived greenness observations, and map the agreement between the two across a geographic grid at a spatial resolution of 0.5°. As aggregated data-model agreement is very good, any local differences between the two could be due to human impact. We then relate this agreement metric to state-of-the-art data sets on demographics, pasture, and cropping. Our findings suggest that demographic and agricultural pressures in the Sahel are unable to account for differences between simulated and observed vegetation dynamics, even for the most densely populated areas. But we do identify a weak, positive correlation between data-model agreement and pasture intensity at the Sahel-wide level. This indicates that herding or grazing does not appreciably affect vegetation dynamics in the region. Either people have not had a significant impact on vegetation dynamics in the Sahel or the identification of a human "footprint" is precluded by inconsistent or subtle vegetation response to complex socio-environmental interactions, and/or limitations in the data used for this study.

  12. Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming

    NASA Astrophysics Data System (ADS)

    Schewe, Jacob; Levermann, Anders

    2017-07-01

    Projections of the response of Sahel rainfall to future global warming diverge significantly. Meanwhile, paleoclimatic records suggest that Sahel rainfall is capable of abrupt transitions in response to gradual forcing. Here we present climate modeling evidence for the possibility of an abrupt intensification of Sahel rainfall under future climate change. Analyzing 30 coupled global climate model simulations, we identify seven models where central Sahel rainfall increases by 40 to 300 % over the 21st century, owing to a northward expansion of the West African monsoon domain. Rainfall in these models is non-linearly related to sea surface temperature (SST) in the tropical Atlantic and Mediterranean moisture source regions, intensifying abruptly beyond a certain SST warming level. We argue that this behavior is consistent with a self-amplifying dynamic-thermodynamical feedback, implying that the gradual increase in oceanic moisture availability under warming could trigger a sudden intensification of monsoon rainfall far inland of today's core monsoon region.

  13. Disentangling the effects of climate and people on Sahel vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Seaquist, J. W.; Hickler, T.; Eklundh, L.; Ardö, J.; Heumann, B. W.

    2009-03-01

    The Sahel belt of Africa has been the focus of intensive scientific research since the 1960s, spurred on by the chronic vulnerability of its population to recurring drought and the threat of long-term land degradation. But satellite sensors have recently shown that much of the region has experienced significant increases in photosynthetic activity since the early 1980s, thus re-energizing long-standing debates about the role that people play in shaping land surface status, and thus climate at regional scales. In this paper, we test the hypothesis that people have had a measurable impact on vegetation dynamics in the Sahel for the period 1982-2002. We compare potential natural vegetation dynamics predicted by a process-based ecosystem model with satellite-derived greenness observations, and map the agreement between the two across a geographic grid at a spatial resolution of 0.5°. As aggregated data-model agreement is very good, any local differences between the two could be due to human impact. We then relate this agreement metric to state-of-the-art data sets on demographics, pasture, and cropping. Our findings suggest that demographic and agricultural pressures in the Sahel are unable to account for differences between simulated and observed vegetation dynamics, even for the most densely populated areas. But we do identify a weak, positive correlation between data-model agreement and pasture intensity at the Sahel-wide level. This indicates that herding or grazing does not appreciably affect vegetation dynamics in the region. Either people have not had a significant impact on vegetation dynamics in the Sahel or the identification of a human "footprint" is precluded by inconsistent or subtle vegetation response to complex socio-environmental interactions, and/or limitations in the data used for this study. We do not exclude the possibility of a greater human influence on vegetation dynamics over the coming decades with changing land use.

  14. Unravelling biodiversity, evolution and threats to conservation in the Sahara-Sahel.

    PubMed

    Brito, José C; Godinho, Raquel; Martínez-Freiría, Fernando; Pleguezuelos, Juan M; Rebelo, Hugo; Santos, Xavier; Vale, Cândida G; Velo-Antón, Guillermo; Boratyński, Zbyszek; Carvalho, Sílvia B; Ferreira, Sónia; Gonçalves, Duarte V; Silva, Teresa L; Tarroso, Pedro; Campos, João C; Leite, João V; Nogueira, Joana; Alvares, Francisco; Sillero, Neftalí; Sow, Andack S; Fahd, Soumia; Crochet, Pierre-André; Carranza, Salvador

    2014-02-01

    Deserts and arid regions are generally perceived as bare and rather homogeneous areas of low diversity. The Sahara is the largest warm desert in the world and together with the arid Sahel displays high topographical and climatic heterogeneity, and has experienced recent and strong climatic oscillations that have greatly shifted biodiversity distribution and community composition. The large size, remoteness and long-term political instability of the Sahara-Sahel, have limited knowledge on its biodiversity. However, over the last decade, there have been an increasing number of published scientific studies based on modern geomatic and molecular tools, and broad sampling of taxa of these regions. This review tracks trends in knowledge about biodiversity patterns, processes and threats across the Sahara-Sahel, and anticipates needs for biodiversity research and conservation. Recent studies are changing completely the perception of regional biodiversity patterns. Instead of relatively low species diversity with distribution covering most of the region, studies now suggest a high rate of endemism and larger number of species, with much narrower and fragmented ranges, frequently limited to micro-hotspots of biodiversity. Molecular-based studies are also unravelling cryptic diversity associated with mountains, which together with recent distribution atlases, allows identifying integrative biogeographic patterns in biodiversity distribution. Mapping of multivariate environmental variation (at 1 km × 1 km resolution) of the region illustrates main biogeographical features of the Sahara-Sahel and supports recently hypothesised dispersal corridors and refugia. Micro-scale water-features present mostly in mountains have been associated with local biodiversity hotspots. However, the distribution of available data on vertebrates highlights current knowledge gaps that still apply to a large proportion of the Sahara-Sahel. Current research is providing insights into key

  15. Analyzing Sanctuary Management in the Sahel

    DTIC Science & Technology

    2015-06-12

    Afghanistan and Iraq, but they often lack the specific skills required for the multicultural , multilingual, and multinational environment of the Sahel...article/2013/11/14/us-africa-usa-military-idUSBRE9AD1AA20131114. Arieff, Alexis. 2013. Crisis in Mali. Washington, DC: U.S. Library of Congress...2011. US Special Operations Forces (SOF): Background and Issues for Congress. Washington, DC: U.S. Library of Congress, Congressional Research Service

  16. Unravelling the Impacts of Climate and People on Vegetation Dynamics in the Sahel 1982- 2002

    NASA Astrophysics Data System (ADS)

    Seaquist, J. W.; Hickler, T.; Eklundh, L.; Ardö, J.; Heumann, B. W.

    2009-05-01

    Satellite sensors have recently shown that much of the Sahel belt of north Africa has experienced significant increases in photosynthetic activity since the early 1980s. This has reignited old debates about the role that people play in shaping land surface status at broad geographical extents. If the human 'footprint' on Sahel vegetation dynamics is measurable, then such impacts may be significant enough alter broad-scale both carbon budgets and climate via land surface atmosphere feedbacks. We test the hypothesis that people have had a measurable impact on vegetation dynamics in the Sahel for the period 1982-2002. We accomplish this by mapping the agreement between potential natural vegetation dynamics predicted by a process-based ecosystem model (Lund Potsdam Jena-Dynamic Global Vegetation Model) and satellite-derived greenness observations (Global Inventory Modelling and Mapping Studies data set) across a geographic grid at a spatial resolution of 0.5 degrees. We then relate this agreement metric to state-of-the-art data sets on demographics, pasture, and cropping. Demographic and agricultural pressures in the Sahel are unable to account for differences between simulated and observed vegetation dynamics, even for the most densely populated areas. But we do identify a weak, positive correlation between data-model agreement and pasture intensity at the Sahel-wide level. This indicates that herding or grazing does not appreciably affect vegetation dynamics in the region. Either people have not had a significant impact on vegetation dynamics in the Sahel or the identification of a human 'footprint' is precluded by inconsistent or subtle vegetation response to complex socio-environmental interactions, and/or limitations in the data used for this study. This research showcases untapped potential for combining ecosystem process models with remote sensing at broad spatial extents for examining the underlying causes of ecosystem change.

  17. Vegetation-rainfall feedbacks across the Sahel: a combined observational and modeling study

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Notaro, M.; Wang, F.; Mao, J.; Shi, X.; Wei, Y.

    2016-12-01

    The Sahel rainfall is characterized by large interannual variability. Past modeling studies have concluded that the Sahel rainfall variability is primarily driven by oceanic forcings and amplified by land-atmosphere interactions. However, the relative importance of oceanic versus terrestrial drivers has never been assessed from observations. The current understanding of vegetation's impacts on climate, i.e. positive vegetation-rainfall feedback through the albedo, moisture, and momentum mechanisms, comes from untested models. Neither the positive vegetation-rainfall feedback, nor the underlying mechanisms, has been fully resolved in observations. The current study fills the knowledge gap about the observed vegetation-rainfall feedbacks, through the application of the multivariate statistical method Generalized Equilibrium Feedback Assessment (GEFA) to observational data. According to GEFA, the observed oceanic impacts dominate over terrestrial impacts on Sahel rainfall, except in the post-monsoon period. Positive leaf area index (LAI) anomalies favor an extended, wetter monsoon across the Sahel, largely due to moisture recycling. The albedo mechanism is not responsible for this positive vegetation feedback on the seasonal-interannual time scale, which is too short for a grass-desert transition. A low-level stabilization and subsidence is observed in response to increased LAI - potentially responsible for a negative vegetation-rainfall feedback. However, the positive moisture feedback overwhelms the negative momentum feedback, resulting in an observed positive vegetation-rainfall feedback. We further applied GEFA to a fully-coupled Community Earth System Model (CESM) control run, as an example of evaluating climate models against the GEFA-based observational benchmark. In contrast to the observed positive vegetation-rainfall feedbacks, CESM simulates a negative vegetation-rainfall feedback across Sahel, peaking in the pre-monsoon season. The simulated negative

  18. Ponds' water balance and runoff of endorheic watersheds in the Sahel

    NASA Astrophysics Data System (ADS)

    Gal, Laetitia; Grippa, Manuela; Kergoat, Laurent; Hiernaux, Pierre; Mougin, Eric; Peugeot, Christophe

    2015-04-01

    The Sahel has been characterized by a severe rainfall deficit since the mid-twentieth century, with extreme droughts in the early seventies and again in the early eighties. These droughts have strongly impacted ecosystems, water availability, fodder resources, and populations living in these areas. However, an increase of surface runoff has been observed during the same period, such as higher "summer discharge" of Sahelian's rivers generating local floods, and a general increase in pond's surface in pastoral areas of central and northern Sahel. This behavior, less rain but more surface runoff is generally referred to as the "Sahelian paradox". Various hypotheses have been put forward to explain this paradoxical situation. The leading role of increase in cropped areas, often cited for cultivated Sahel, does not hold for pastoral areas in central and northern Sahel. Processes such as degradation of vegetation subsequent to the most severe drought events, soils erosion and runoff concentration on shallow soils, which generate most of the water ending up in ponds, seem to play an important role. This still needs to be fully understood and quantified. Our study focuses on a model-based approach to better understand the hydrological changes that affected the Agoufou watershed (Gourma, Mali), typical of the central, non-cultivated Sahel. Like most of the Sahelian basins, the Agoufou watershed is ungauged. Therefore we used indirect data to provide the information required to validate a rainfall-runoff model approach. The pond volume was calculated by combining in-situ water level measurements with pond's surface estimations derived by remote sensing. Using the pond's water balance equation, the variations of pond volume combined to estimates of open water bodies' evaporation and infiltration determined an estimation for the runoff supplying the pond. This estimation highlights a spectacular runoff increase over the last sixty years on the Agoufou watershed. The runoff

  19. Characterization of Heat Waves in the Sahel and associated mechanisms

    NASA Astrophysics Data System (ADS)

    Oueslati, Boutheina; Pohl, Benjamin; Moron, Vincent; Rome, Sandra

    2016-04-01

    Large efforts are made to investigate the heat waves (HW) in developed countries because of their devastating impacts on society, economy and environment. This interest increased after the intense event over Europe during summer 2003. However, HWs are still understudied over developing countries. This is particularly true in West Africa, and especially in the Sahel, where temperatures recurrently reach critical values, such as during the 2010 HW event. Understanding the Sahelian HWs and associated health risks constitute the main objective of ACASIS, a 4-year project funded by the French Agence Nationale de la Recherche. Our work contributes to this project and aims at characterizing the Sahelian HWs and understanding the mechanisms associated with such extreme events. There is no universal definition of a HW event, since it is highly dependent on the sector (human health, agriculture, transport...) and region of interest. In our case, a HW is defined when the heat index of the day and of the night exceeds the 90th percentile for at least 3 consecutive days (Rome et al. 2016, in preparation). This index combines temperature and relative humidity in order to determine the human-perceived equivalent temperature (definition adapted from Steadman, 1979). Intrinsic properties of Sahelian HW are analyzed from the Global Summary of the Day (GSOD) synoptic observations and ERA-interim reanalyses over 1979-2014 during boreal spring seasons (April-May-June), the warmest period of the year in the Central Sahel. ERA-interim captures well the observed interannual variability and seasonal cycle at the regional scale, as well as the 1979-2014 increasing linear trend of springtime HW occurrences in the Sahel. Reanalyses, however, overestimate the duration, spatial extent of HW, and underestimate their intensity. For both GSOD and ERA-interim, we show that, over the last three decades, Sahelian HWs tend to become more frequent, last longer, cover larger areas and reach higher

  20. Desertification, resilience, and re-greening in the African Sahel - a matter of the observation period?

    NASA Astrophysics Data System (ADS)

    Kusserow, Hannelore

    2017-12-01

    Since the turn of the millennium various scientific publications have been discussing a re-greening of the Sahel after the 1980s drought mainly based on coarse-resolution satellite data. However, the author's own field studies suggest that the situation is far more complex and that both paradigms, the encroaching Sahara and the re-greening Sahel, need to be questioned.

    This paper discusses the concepts of desertification, resilience, and re-greening by addressing four main aspects: (i) the relevance of edaphic factors for a vegetation re-greening, (ii-iii) the importance of the selected observation period in the debate on Sahel greening or browning, and (iv) modifications in the vegetation pattern as possible indicators of ecosystem changes (shift from originally diffuse to contracted vegetation patterns).

    The data referred to in this paper cover a time period of more than 150 years and include the author's own research results from the early 1980s until today. A special emphasis, apart from fieldwork data and remote sensing data, is laid on the historical documents.

    The key findings summarised at the end show the following: (i) vegetation recovery predominantly depends on soil types; (ii) when discussing Sahel greening vs. Sahel browning, the majority of research papers only focus on post-drought conditions. Taking pre-drought conditions (before the 1980s) into account, however, is essential to fully understand the situation. Botanical investigations and remote-sensing-based time series clearly show a substantial decline in woody species diversity and cover density compared to pre-drought conditions; (iii) the self-organised patchiness of vegetation is considered to be an important indicator of ecosystem changes.

  1. Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism

    DOE PAGES

    Yu, Yan; Notaro, Michael; Wang, Fuyao; ...

    2017-11-30

    Classic, model-based theory of land-atmosphere interactions across the Sahel promote positive vegetation-rainfall feedbacks dominated by surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback nor its underlying albedo mechanism has been convincingly demonstrated using observational data. Here, we present observational evidence for the region’s proposed positive vegetation-rainfall feedback on the seasonal to interannual time scale, and find that it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism. Positive anomalies of remotely sensed vegetation greenness across the Sahel during the late and post-monsoon periods favor enhanced evapotranspiration, precipitable water, convective activity and rainfall, indicative ofmore » amplified moisture recycling. The identified modest low-level cooling and anomalous atmospheric subsidence in response to positive vegetation greenness anomalies are counter to the responses expected through the classic vegetation-albedo feedback mechanism. The observational analysis further reveals enhanced dust emissions in response to diminished Sahel vegetation growth, potentially contributing to the positive vegetation-rainfall feedback.« less

  2. Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yu, Yan; Notaro, Michael; Wang, Fuyao

    Classic, model-based theory of land-atmosphere interactions across the Sahel promote positive vegetation-rainfall feedbacks dominated by surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback nor its underlying albedo mechanism has been convincingly demonstrated using observational data. Here, we present observational evidence for the region’s proposed positive vegetation-rainfall feedback on the seasonal to interannual time scale, and find that it is associated with a moisture recycling mechanism, rather than the classic albedo-based mechanism. Positive anomalies of remotely sensed vegetation greenness across the Sahel during the late and post-monsoon periods favor enhanced evapotranspiration, precipitable water, convective activity and rainfall, indicative ofmore » amplified moisture recycling. The identified modest low-level cooling and anomalous atmospheric subsidence in response to positive vegetation greenness anomalies are counter to the responses expected through the classic vegetation-albedo feedback mechanism. The observational analysis further reveals enhanced dust emissions in response to diminished Sahel vegetation growth, potentially contributing to the positive vegetation-rainfall feedback.« less

  3. Mesoscale convective systems and nocturnal rainfall over the West African Sahel: role of the Inter-tropical front

    NASA Astrophysics Data System (ADS)

    Vizy, Edward K.; Cook, Kerry H.

    2018-01-01

    A convection-permitting regional model simulation for August 2006 and observations are evaluated to better understand the diurnal cycle of precipitation over the Sahel. In particular, reasons for a nocturnal rainfall maximum over parts of the Sahel during the height of the West African monsoon are investigated. A relationship between mesoscale convective system (MCS) activity and inter-tropical front (ITF)/dryline dynamics is revealed. Over 90% of the Sahel nocturnal rainfall derives from propagating MCSs that have been associated with topography in earlier studies. In contrast, in this case study, 70-90% of the nocturnal rainfall over the southern Sahel (11°N-14°N) west of 15°E is associated with MCSs that originate less than 1000 km upstream (to the north and east) in the afternoon, in a region largely devoid of significant orography. This MCS development occurs in association with the Sahel ITF, combined with atmospheric pre-conditioning. Daytime surface heating generates turbulent mixing that promotes planetary boundary layer (PBL) growth accompanied by a low-level reversal in the meridional flow. This enhances wind convergence in the low-level moist layer within 2°-3° of latitude of the equatorward side of the ITF. MCSs tend to form when this vertical mixing extends to the level of free convection and is accompanied by a mid-tropospheric African easterly wave disturbance to the east. This synoptic disturbance enhances the vertical wind shear and atmospheric instability over the genesis location. These results are found to be robust across the region.

  4. Global warming induced hybrid rainy seasons in the Sahel

    NASA Astrophysics Data System (ADS)

    Salack, Seyni; Klein, Cornelia; Giannini, Alessandra; Sarr, Benoit; Worou, Omonlola N.; Belko, Nouhoun; Bliefernicht, Jan; Kunstman, Harald

    2016-10-01

    The small rainfall recovery observed over the Sahel, concomitant with a regional climate warming, conceals some drought features that exacerbate food security. The new rainfall features include false start and early cessation of rainy seasons, increased frequency of intense daily rainfall, increasing number of hot nights and warm days and a decreasing trend in diurnal temperature range. Here, we explain these mixed dry/wet seasonal rainfall features which are called hybrid rainy seasons by delving into observed data consensus on the reduction in rainfall amount, its spatial coverage, timing and erratic distribution of events, and other atmospheric variables crucial in agro-climatic monitoring and seasonal forecasting. Further composite investigations of seasonal droughts, oceans warming and the regional atmospheric circulation nexus reveal that the low-to-mid-level atmospheric winds pattern, often stationary relative to either strong or neutral El-Niño-Southern-Oscillations drought patterns, associates to basin warmings in the North Atlantic and the Mediterranean Sea to trigger hybrid rainy seasons in the Sahel. More challenging to rain-fed farming systems, our results suggest that these new rainfall conditions will most likely be sustained by global warming, reshaping thereby our understanding of food insecurity in this region.

  5. Using Relative Humidity Forecasts to Manage Meningitis in the Sahel

    NASA Astrophysics Data System (ADS)

    Pandya, R. E.; Adams-Forgor, A.; Akweogno, P.; Awine, T.; Dalaba, M.; Dukic, V.; Dumont, A.; Hayden, M.; Hodgson, A.; Hopson, T. M.; Hugonnet, S.; Yoksas, T. C.

    2012-12-01

    Meningitis epidemics in the Sahel occur quasi-regularly and with devastating impact. In 2008, for example, eighty-eight thousand people contracted meningitis and over five thousand died. Until very recently, the protection provided by the only available vaccine was so limited and short-lived that the only practical strategy for vaccination was reactive: waiting until an epidemic occurred in the region and then vaccinating in that region to prevent the epidemic's further growth. Even with that strategy, there were still times when demand outpaced available vaccine. While a new vaccine has recently been developed that is effective and inexpensive enough to be used more broadly and proactively, it is only effective against the strain of bacteria that causes the most common kind of bacterial meningitis. As a result, there will likely be continued need for reactive vaccination strategies. It is widely known that meningitis epidemics in the Sahel occur only in the dry season. Our project investigated this relationship, and several independent lines of evidence demonstrate a robust relationship between the onset of the rainy season, as marked by weekly average relative humidity above 40%, and the end of meningitis epidemics. These lines of evidence include statistical analysis of two years of weekly meningitis and weather data across the Sahel, cross-correlation of ten years of meningitis and weather data in the Upper East region of northern Ghana, and high-resolution weather simulations of past meningitis seasons to interpolate available weather data. We also adapted two techniques that have been successfully used in public health studies: generalized additive models, which have been used to relate air quality and health, and a linearized version of the compartmental epidemics model that has been used to understand MRSA. Based on these multiple lines of evidence, average weekly relative humidity forecast two weeks in advance appears consistently and strongly related to

  6. Trend in land degradation has been the most contended issue in the Sahel. Trends documented have not been consistent across authors and science disciplines, hence little agreement has been gained on the magnitude and direction of land degradation in the Sahel. Differentiated science outputs are related to methods and data used at various scales.

    NASA Astrophysics Data System (ADS)

    Mbow, C.; Brandt, M.; Fensholt, R.; Ouedraogo, I.; Tagesson, T.

    2015-12-01

    Thematic gaps in land degradation trends in the SahelTrend in land degradation has been the most contended issue for arid and semi-arid regions. In the Sahel, depending to scale of analysis and methods and data used, the trend documented have not been consistent across authors and science disciplines. The assessment of land degradation and the quantification of its effects on land productivity have been assessed for many decades, but little agreement has been gained on the magnitude and direction in the Sahel. This lack of consistency amid science outputs can be related to many methodological underpinnings and data used for various scales of analysis. Assessing biophysical trends on the ground requires long-term ground-based data collection to evaluate and better understand the mechanisms behind land dynamics. The Sahel is seen as greening by many authors? Is that greening geographically consistent? These questions enquire the importance of scale analysis and related drivers. The questions addressed are not only factors explaining loss of tree cover but also regeneration of degraded land. The picture used is the heuristic cycle model to assess loss and damages vs gain and improvements of various land use practices. The presentation will address the following aspects - How much we know from satellite data after 40 years of remote sensing analysis over the Sahel? That section discuss agreement and divergences of evidences and differentiated interpretation of land degradation in the Sahel. - The biophysical factors that are relevant for tracking land degradation in the Sahel. Aspects such detangling human to climate factors and biophysical factors behind land dynamics will be presented - Introduce some specific cases of driver of land architecture transition under the combined influence of climate and human factor. - Based on the above we will conclude with some key recommendations on how to improve land degradation assessment in the Arid region of the Sahel.

  7. Role of Surface Wind and Vegetation Cover in Multi-decadal Variations of Dust Emission in the Sahara and Sahel

    NASA Technical Reports Server (NTRS)

    Kim, Dong; Chin, Mian; Remer, Lorraine A.; Diehl, Thomas L.; Bian, Huisheng; Yu, Hongbin; Brown, Molly E.; Stockwell, William R.

    2016-01-01

    North Africa, the world's largest dust source, is non-uniform, consisting of a permanently arid region (Sahara), a semi-arid region (Sahel), and a relatively moist vegetated region (Savanna), each with very different rainfall patterns and surface conditions. This study aims to better understand the controlling factors that determine the variation of dust emission in North Africa over a 27-year period from 1982 to 2008, using observational data and model simulations. The results show that the model-derived Saharan dust emission is only correlated with the 10-m winds (W10m) obtained from reanalysis data, but the model-derived Sahel dust emission is correlated with both W10m and the Normalized Difference Vegetation Index (NDVI) that is obtained from satellite. While the Saharan dust accounts for 82 of the continental North Africa dust emission (1340-1570 Tg year(exp -1) in the 27-year average, the Sahel accounts for 17 with a larger seasonal and inter-annual variation (230-380 Tg year(exp -1), contributing about a quarter of the transatlantic dust transported to the northern part of South America. The decreasing dust emission trend over the 27-year period is highly correlated with W10m over the Sahara (R equals 0.92). Over the Sahel, the dust emission is correlated with W10m (R 0.69) but is also anti-correlated with the trend of NDVI (R equals 0.65). W10m is decreasing over both the Sahara and the Sahel between 1982 and 2008, and the trends are correlated (R equals 0.53), suggesting that Saharan Sahelian surface winds are a coupled system, driving the inter-annual variation of dust emission.

  8. Atmospheric effects on SMMR and SSM/I 37 GHz polarization difference over the Sahel

    NASA Technical Reports Server (NTRS)

    Choudhury, B. J.; Major, E. R.; Smith, E. A.; Becker, F.

    1992-01-01

    The atmospheric effects on the difference of vertically and horizontally polarized brightness temperatures, Delta(T) observed at 37 GHz frequency of the SMMR on board the Nimbus-7 satellite and SSM/I on board the DMSP-F8 satellite are studied over two 2.5 by 2.5 deg regions within the Sahel and Sudan zones of Africa from January 1985 to December 1986 through radiative transfer analysis using surface temperature, atmospheric water vapor, and cloud optical thickness. It is found that atmospheric effects alone cannot explain the observed temporal variation of Delta(T), although the atmosphere introduces important modulations on the observed seasonal variations of Delta(T) due to rather significant seasonal variation of precipitable water vapor. These Delta(T) data should be corrected for atmospheric effects before any quantitative analysis of land surface change over the Sahel and Sudan zones.

  9. HAPEX-Sahel: A large-scale study of land-atmosphere interactions in the semi-arid tropics

    NASA Technical Reports Server (NTRS)

    Gutorbe, J-P.; Lebel, T.; Tinga, A.; Bessemoulin, P.; Brouwer, J.; Dolman, A.J.; Engman, E. T.; Gash, J. H. C.; Hoepffner, M.; Kabat, P.

    1994-01-01

    The Hydrologic Atmospheric Pilot EXperiment in the Sahel (HAPEX-Sahel) was carried out in Niger, West Africa, during 1991-1992, with an intensive observation period (IOP) in August-October 1992. It aims at improving the parameteriztion of land surface atmospheric interactions at the Global Circulation Model (GCM) gridbox scale. The experiment combines remote sensing and ground based measurements with hydrological and meteorological modeling to develop aggregation techniques for use in large scale estimates of the hydrological and meteorological behavior of large areas in the Sahel. The experimental strategy consisted of a period of intensive measurements during the transition period of the rainy to the dry season, backed up by a series of long term measurements in a 1 by 1 deg square in Niger. Three 'supersites' were instrumented with a variety of hydrological and (micro) meteorological equipment to provide detailed information on the surface energy exchange at the local scale. Boundary layer measurements and aircraft measurements were used to provide information at scales of 100-500 sq km. All relevant remote sensing images were obtained for this period. This program of measurements is now being analyzed and an extensive modelling program is under way to aggregate the information at all scales up to the GCM grid box scale. The experimental strategy and some preliminary results of the IOP are described.

  10. Desertification and a shift of forest species in the West African Sahel

    USGS Publications Warehouse

    Gonzalez, Patrick

    2001-01-01

    Original field data show that forest species richness and tree density in the West African Sahel declined in the last half of the 20th century. Average forest species richness of areas of 4 km2 in Northwest Senegal fell from 64 ?? 2 species ca 1945 to 43 ?? 2 species in 1993, a decrease significant at p < 0.001. Densities of trees of height ???3 m declined from 10 ?? 0.3 trees ha-1 in 1954 to 7.8 ?? 0.3 trees ha-1 in 1989, also significant at p < 0.001. Standing wood biomass fell 2.1 t ha-1 in the period 1956-1993, releasing CO2 at a rate of 60 kgC person-1 yr-1. These changes have shifted vegetation zones toward areas of higher rainfall at an average rate of 500 to 600 m yr-1. Arid Sahel species have expanded in the north, tracking a concomitant retraction of mesic Sudan and Guinean species to the south. Multivariate analyses identify latitude and longitude, proxies for rainfall and temperature, as the most significant factors explaining tree and shrub distribution. The changes also decreased human carrying capacity to below actual population densities. The rural population of 45 people km-2 exceeded the 1993 carrying capacity, for firewood from shrubs, of 13 people km-2 (range 1 to 21 people km-2). As an adaptation strategy, ecological and socioeconomic factors favor the natural regeneration of local species over the massive plantation of exotic species. Natural regeneration is a traditional practice in which farmers select small field trees that they wish to raise to maturity, protect them, and prune them to promote rapid growth of the apical meristem. The results of this research provide evidence for desertification in the West African Sahel. These documented impacts of desertification foreshadow possible future effects of climate change.

  11. Uncertain soil moisture feedbacks in model projections of Sahel precipitation

    NASA Astrophysics Data System (ADS)

    Berg, Alexis; Lintner, Benjamin R.; Findell, Kirsten; Giannini, Alessandra

    2017-06-01

    Given the uncertainties in climate model projections of Sahel precipitation, at the northern edge of the West African Monsoon, understanding the factors governing projected precipitation changes in this semiarid region is crucial. This study investigates how long-term soil moisture changes projected under climate change may feedback on projected changes of Sahel rainfall, using simulations with and without soil moisture change from five climate models participating in the Global Land Atmosphere Coupling Experiment-Coupled Model Intercomparison Project phase 5 experiment. In four out of five models analyzed, soil moisture feedbacks significantly influence the projected West African precipitation response to warming; however, the sign of these feedbacks differs across the models. These results demonstrate that reducing uncertainties across model projections of the West African Monsoon requires, among other factors, improved mechanistic understanding and constraint of simulated land-atmosphere feedbacks, even at the large spatial scales considered here.Plain Language SummaryClimate model projections of <span class="hlt">Sahel</span> rainfall remain notoriously uncertain; understanding the physical processes responsible for this uncertainty is thus crucial. Our study focuses on analyzing the feedbacks of soil moisture changes on model projections of the West African Monsoon under global warming. Soil moisture-atmosphere interactions have been shown in prior studies to play an important role in this region, but the potential feedbacks of long-term soil moisture changes on projected precipitation changes have not been investigated specifically. To isolate these feedbacks, we use targeted simulations from five climate models, with and without soil moisture change. Importantly, we find that climate models exhibit soil moisture-precipitation feedbacks of different sign in this region: in some models soil moisture changes amplify precipitation changes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20111887','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20111887"><span>Assessment of the impact of climate shifts on malaria transmission in the <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bomblies, Arne; Eltahir, Elfatih A B</p> <p>2009-09-01</p> <p>Climate affects malaria transmission through a complex network of causative pathways. We seek to evaluate the impact of hypothetical climate change scenarios on malaria transmission in the <span class="hlt">Sahel</span> by using a novel mechanistic, high spatial- and temporal-resolution coupled hydrology and agent-based entomology model. The hydrology model component resolves individual precipitation events and individual breeding pools. The impact of future potential climate shifts on the representative <span class="hlt">Sahel</span> village of Banizoumbou, Niger, is estimated by forcing the model of Banizoumbou environment with meteorological data from two locations along the north-south climatological gradient observed in the <span class="hlt">Sahel</span>--both for warmer, drier scenarios from the north and cooler, wetter scenarios from the south. These shifts in climate represent hypothetical but historically realistic climate change scenarios. For Banizoumbou climatic conditions (latitude 13.54 N), a shift toward cooler, wetter conditions may dramatically increase mosquito abundance; however, our modeling results indicate that the increased malaria transmissibility is not simply proportional to the precipitation increase. The cooler, wetter conditions increase the length of the sporogonic cycle, dampening a large vectorial capacity increase otherwise brought about by increased mosquito survival and greater overall abundance. Furthermore, simulations varying rainfall event frequency demonstrate the importance of precipitation patterns, rather than simply average or time-integrated precipitation, as a controlling factor of these dynamics. Modeling results suggest that in addition to changes in temperature and total precipitation, changes in rainfall patterns are very important to predict changes in disease susceptibility resulting from climate shifts. The combined effect of these climate-shift-induced perturbations can be represented with the aid of a detailed mechanistic model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018BGeo...15..319Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018BGeo...15..319Z"><span>Impacts of the seasonal distribution of rainfall on vegetation productivity across the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Wenmin; Brandt, Martin; Tong, Xiaoye; Tian, Qingjiu; Fensholt, Rasmus</p> <p>2018-01-01</p> <p>Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy-rainfall events, longer dry spells, and a shifted timing of the wet season. Yet the aboveground net primary productivity (ANPP) in drylands is usually explained by annual-rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tested the importance of rainfall metrics in the wet season (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days, and heavy-rainfall events) for growing season ANPP. We focused on the <span class="hlt">Sahel</span> and northern Sudanian region (100-800 mm yr-1) and applied daily satellite-based rainfall estimates (CHIRPS v2.0) and growing-season-integrated normalized difference vegetation index (NDVI; MODIS) as a proxy for ANPP over the study period: 2001-2015. Growing season ANPP in the arid zone (100-300 mm yr-1) was found to be rather insensitive to variations in the seasonal-rainfall metrics, whereas vegetation in the semi-arid zone (300-700 mm yr-1) was significantly impacted by most metrics, especially by the number of rainy days and timing (onset and cessation) of the wet season. We analysed critical breakpoints for all metrics to test if vegetation response to changes in a given rainfall metric surpasses a threshold beyond which vegetation functioning is significantly altered. It was shown that growing season ANPP was particularly negatively impacted after > 14 consecutive dry days and that a rainfall intensity of ˜ 13 mm day-1 was detected for optimum growing season ANPP. We conclude that the number of rainy days and the timing of the wet season are seasonal-rainfall metrics that are decisive for favourable vegetation growth in the semi-arid <span class="hlt">Sahel</span> and need to be considered when modelling primary productivity from rainfall in the drylands of the <span class="hlt">Sahel</span> and elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A23K..03E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A23K..03E"><span>The impacts of the dust radiative effect on vegetation growth in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evans, S. M.; Shevliakova, E.; Malyshev, S.; Ginoux, P. A.</p> <p>2017-12-01</p> <p>Many studies have been conducted on the effects of dust on rainfall in the <span class="hlt">Sahel</span>, and generally show that African dust weakens the West African Monsoon, drying the region. This drying is often assumed to reduce vegetation cover for the region, providing a positive feedback with dust emission. There are, however, other competing effects of dust that are also important to plant growth, including a reduction in surface temperature, a reduction in downwelling solar radiation, and an increase in the diffuse fraction of that solar radiation. Using the NOAA/GFDL CM3 model coupled to the dynamic vegetation model LM3, we demonstrate that the combined effect of all these processes is to decrease the vegetation coverage and productivity of the <span class="hlt">Sahel</span> and West Africa. We accomplish this by comparing experiments with radiatively active dust to experiments with radiatively invisible dust. We find that in modern conditions, the dust radiative effect reduces the net primary productivity of West Africa and the <span class="hlt">Sahel</span> by up to 30% locally, and when summed over the region accounts for a difference of approximately 0.4 GtC per year. Experiments where the vegetation experiences preindustrial rather than modern CO2 levels show that without carbon fertilization, this loss of productivity would be approximately 10% stronger. In contrast, during preindustrial conditions the vegetation response is less than half as strong, despite the dust induced rainfall and temperature anomalies being similar. We interpret this as the vegetation being less susceptible to drought in a less evaporative climate. These changes in vegetation create the possibility of a dust-vegetation feedback loop whose strength varies with the mean state of the climate, and which may grow stronger in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC13A1052Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC13A1052Y"><span>Mesoscale modeling of smoke radiative feedback over the <span class="hlt">Sahel</span> region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Z.; Wang, J.; Ichoku, C. M.; Ellison, L.; Zhang, F.; Yue, Y.</p> <p>2013-12-01</p> <p>This study employs satellite observations and a fully-coupled meteorology-chemistry-aerosol model, Weather Research and Forecasting model with Chemistry (WRF-Chem) to study the smoke radative feedback on surface energy budget, boundary layer processes, and atmospheric lapse rate in February 2008 over the <span class="hlt">Sahel</span> region. The smoke emission inventories we use come from various sources, including but not limited to the Fire Locating and Modeling of Burning Emissions (FLAMBE) developed by NRL and the Fire Energetic and Emissions Research (FEER) developed by NASA GSFC. Model performance is evaluated using numerous satellite and ground-based datasets: MODIS true color images, ground-based Aerosol Optical Depth (AOD) measurements from AERONET, MODIS AOD retrievals, and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF-Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Statistically, 5% of the CALIPSO valid measurements of aerosols in February 2008 show aerosol layers either above the clouds or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the <span class="hlt">Sahel</span> region. The results further show that the smoke radiative feedbacks are sensitive to assumptions of black carbon and organic carbon ratio in the particle emission inventory. Also investigated is the smoke semi-direct effect as a function of cloud fraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=drought&pg=7&id=EJ106508','ERIC'); return false;" href="https://eric.ed.gov/?q=drought&pg=7&id=EJ106508"><span>Using Case Studies to Teach About Global Issues, The <span class="hlt">Sahel</span>: The "Shore" of Disaster</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hall, Susan J.</p> <p>1974-01-01</p> <p><span class="hlt">Sahel</span> is the Arabic word for "shore" and is applied to the Southern belt of the Sahara Desert now undergoing a severe drought. This article describes the lifestyle of a Tuareg herder as he and his family fight for survival. Discussion questions and possible solution to the problems are provided in the case study. (Author/DE)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2084275','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2084275"><span>Impact of vegetation removal and soil aridation on diurnal temperature range in a semiarid region: Application to the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Liming; Dickinson, Robert E.; Tian, Yuhong; Vose, Russell S.; Dai, Yongjiu</p> <p>2007-01-01</p> <p>Increased clouds and precipitation normally decrease the diurnal temperature range (DTR) and thus have commonly been offered as explanation for the trend of reduced DTR observed for many land areas over the last several decades. Observations show, however, that the DTR was reduced most in dry regions and especially in the West African <span class="hlt">Sahel</span> during a period of unprecedented drought. Furthermore, the negative trend of DTR in the <span class="hlt">Sahel</span> appears to have stopped and may have reversed after the rainfall began to recover. This study develops a hypothesis with climate model sensitivity studies showing that either a reduction in vegetation cover or a reduction in soil emissivity would reduce the DTR by increasing nighttime temperature through increased soil heating and reduced outgoing longwave radiation. Consistent with empirical analyses of observational data, our results suggest that vegetation removal and soil aridation would act to reduce the DTR during periods of drought and human mismanagement over semiarid regions such as the <span class="hlt">Sahel</span> and to increase the DTR with more rainfall and better human management. Other mechanisms with similar effects on surface energy balance, such as increased nighttime downward longwave radiation due to increased greenhouse gases, aerosols, and clouds, would also be expected to have a larger impact on DTR over drier regions. PMID:17986620</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ESD.....8.1191S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ESD.....8.1191S"><span>Future supply and demand of net primary production in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sallaba, Florian; Olin, Stefan; Engström, Kerstin; Abdi, Abdulhakim M.; Boke-Olén, Niklas; Lehsten, Veiko; Ardö, Jonas; Seaquist, Jonathan W.</p> <p>2017-12-01</p> <p>In the 21st century, climate change in combination with increasing demand, mainly from population growth, will exert greater pressure on the ecosystems of the <span class="hlt">Sahel</span> to supply food and feed resources. The balance between supply and demand, defined as the annual biomass required for human consumption, serves as a key metric for quantifying basic resource shortfalls over broad regions.Here we apply an exploratory modelling framework to analyse the variations in the timing and geography of different NPP (net primary production) supply-demand scenarios, with distinct assumptions determining supply and demand, for the 21st century <span class="hlt">Sahel</span>. We achieve this by coupling a simple NPP supply model forced with projections from four representative concentration pathways with a global, reduced-complexity demand model driven by socio-economic data and assumptions derived from five shared socio-economic pathways.For the scenario that deviates least from current socio-economic and climate trends, we find that per capita NPP begins to outstrip supply in the 2040s, while by 2050 half the countries in the <span class="hlt">Sahel</span> experience NPP shortfalls. We also find that despite variations in the timing of the onset of NPP shortfalls, demand cannot consistently be met across the majority of scenarios. Moreover, large between-country variations are shown across the scenarios, in which by the year 2050 some countries consistently experience shortage or surplus, while others shift from surplus to shortage. At the local level (i.e. grid cell), hotspots of total NPP shortfall consistently occur in the same locations across all scenarios but vary in size and magnitude. These hotspots are linked to population density and high demand. For all scenarios, total simulated NPP supply doubles by 2050 but is outpaced by increasing demand due to a combination of population growth and the adoption of diets rich in animal products. Finally, variations in the timing of the onset and end of supply shortfalls stem from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H33B1652N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H33B1652N"><span>Do state-of-the-art CMIP5 ESMs accurately represent observed vegetation-rainfall feedbacks? Focus on the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Notaro, M.; Wang, F.; Yu, Y.; Mao, J.; Shi, X.; Wei, Y.</p> <p>2017-12-01</p> <p>The semi-arid <span class="hlt">Sahel</span> ecoregion is an established hotspot of land-atmosphere coupling. Ocean-land-atmosphere interactions received considerable attention by modeling studies in response to the devastating 1970s-90s <span class="hlt">Sahel</span> drought, which models suggest was driven by sea-surface temperature (SST) anomalies and amplified by local vegetation-atmosphere feedbacks. Vegetation affects the atmosphere through biophysical feedbacks by altering the albedo, roughness, and transpiration and thereby modifying exchanges of energy, momentum, and moisture with the atmosphere. The current understanding of these potentially competing processes is primarily based on modeling studies, with biophysical feedbacks serving as a key uncertainty source in regional climate change projections among Earth System Models (ESMs). In order to reduce this uncertainty, it is critical to rigorously evaluate the representation of vegetation feedbacks in ESMs against an observational benchmark in order to diagnose systematic biases and their sources. However, it is challenging to successfully isolate vegetation's feedbacks on the atmosphere, since the atmospheric control on vegetation growth dominates the atmospheric feedback response to vegetation anomalies and the atmosphere is simultaneously influenced by oceanic and terrestrial anomalies. In response to this challenge, a model-validated multivariate statistical method, Stepwise Generalized Equilibrium Feedback Assessment (SGEFA), is developed, which extracts the forcing of a slowly-evolving environmental variable [e.g. SST or leaf area index (LAI)] on the rapidly-evolving atmosphere. By applying SGEFA to observational and remotely-sensed data, an observational benchmark is established for <span class="hlt">Sahel</span> vegetation feedbacks. In this work, the simulated responses in key atmospheric variables, including evapotranspiration, albedo, wind speed, vertical motion, temperature, stability, and rainfall, to <span class="hlt">Sahel</span> LAI anomalies are statistically assessed in Coupled Model</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12348796','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12348796"><span>[Migration and urbanization in the <span class="hlt">Sahel</span>. Consequences of the Sahelian migrations].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Traore, S</p> <p>1997-10-01</p> <p>The consequences of Sahelian migration are multiple and diverse. In rural areas there may be a loss of income in the short run and a reduced possibility of development in the long run. Apart from its implications for urban growth, Sahelian migration may have four series of consequences in the places of origin. In detaching peasants from their lands, migration may contribute to loss of appreciation and reverence for the lands. Attachment to the lands of the ancestors loses its meaning as soon as questions of survival or economic rationality are raised. Migration contributes to the restructuring of the societies of origin. Increasing monetarization of market relations and introduction of new needs create new norms that favor stronger integration into the world economy. Migration may cause a decline in production because of the loss of the most active population, and it changes the age and sex distribution of households and usually increases their dependency burden. The effects on fertility and mortality are less clear. The effects of migration on the zones of arrival in the <span class="hlt">Sahel</span> depend on the type of area. Conflicts between natives and in-migrants are common in rural-rural migration. Degradation of land may result from the increased demands placed upon it. Migrants to cities in Africa, and especially in the <span class="hlt">Sahel</span>, appear to conserve their cultural values and to transplant and reinterpret their village rules of solidarity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active"><span>2</span></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_2 --> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12321755','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12321755"><span>PVO / NGO initiatives. The Global Dialogues Trust -- "Scenarios from the <span class="hlt">Sahel</span>".</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>1997-01-01</p> <p>Scenarios from the <span class="hlt">Sahel</span> is an HIV/AIDS prevention project for adolescents and young adults in Senegal, Mali, Burkina Faso, and Niger, organized by the Global Dialogues Trust and launched in January 1997. The project invites people aged 24 years and younger to engage in a competition in which they write scenarios for a 1-5 minute video on HIV/AIDS. Those 30 scenarios judged to be the most valuable to the HIV/AIDS prevention effort in the <span class="hlt">Sahel</span> will be developed into video spots by the region's film-makers and screened at cinemas and broadcast on television stations in West Africa. The spots will also be collected upon a compilation video available for use by local nongovernmental organizations in their HIV/AIDS prevention activities in the region. The compilation video will be dubbed from French into local languages and English to facilitate its broad dissemination in the 4 participating countries and their neighbors. The video together with an education pack will also be distributed to local organizations and schools. The project, to be conducted in close partnership with local people and their organizations, will end with its evaluation in June 1998. Global Dialogues Trust is a charitable trust based in the UK dedicated to advance the education of the public throughout the world in all matters concerning the prevention of HIV/AIDS. The organization's main priority is to develop local capacity to fight HIV/AIDS through preventive education.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51C2076Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51C2076Y"><span>Source of humidity in the terrestrial water cycle over the forested monsoon arid of <span class="hlt">Sahel</span>; changes in the water recycle and atmospheric instability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yosef, G.; Avissar, R.; Walko, R. L.; Yakir, D.</p> <p>2017-12-01</p> <p>Land-cover change from low-level shrubs to forest over semi-arid monsoon regions such as the <span class="hlt">Sahel</span>, can significantly influence the surface energy budget and, in turn, the local atmospheric circulation. These regions, influenced at the summer by the monsoon rain following the migration of the tropical convergence zones (ITCZ). And low-level easterly jet that acts as a barrier to the penetration of the precipitation into the semi arid areas. In this study we follow-up first the results of large-scale afforestation numerical experiment in the <span class="hlt">Sahel</span> that changes the local and regional atmospheric circulation and, consequently, increasing of precipitation. We aim for explicitly investigation of the change in the sources and pathways of humidity in the terrestrial water cycle over the <span class="hlt">Sahel</span> as result afforestation. The GCM OLAM was used to performing simulations of afforestation scenarios in the <span class="hlt">Sahel</span>. The area (<span class="hlt">Sahel</span> 2.6 E6 km2) was afforested with a mature pine forest, using the extensive data form the long-term semi-arid Yatir forest in Israel as a reference forest for surface parameterization. The regional effect of the afforestation was analyzed using the following parameters; the index of water recycling (WR), which refers to the contribution of local ET fluxes to precipitation; the Moist Static Energy (MSE), is the sum of the potential, inertial and latent energy; and the vertical motion. The result shows increases of the WR in the south of the afforested area and north of the footprint, mainly as consequences of increasing in the vertical integrated moist flux convergence (MFC). Explaining this mechanism in terms of MSE shows that although the forest area become cooler and stabilizes the atmospheric column, its shift and weaken the African Easterly Jet enable the penetration of additional humidity to increase the MFC. On the other hand positive MSE observed over the northern footprint area mainly as a results of increasing the leant energy (e.g. humidity). Over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CliPD..10.3877M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CliPD..10.3877M"><span>Climatic information of Western <span class="hlt">Sahel</span> (1535-1793 AD) in original documentary sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Millán, V.; Rodrigo, F. S.</p> <p>2014-09-01</p> <p>The <span class="hlt">Sahel</span> is the semi-arid transition zone between arid Sahara and humid tropical Africa, extending approximately 10-20° N from Mauritania in the West to Sudan in the East. The African continent, one of the most vulnerable regions to climate change, is subject to frequent droughts and famine. One climate challenge research is to isolate those aspects of climate variability that are natural from those that are related to human influences. Therefore, the study of climatic conditions before mid-19th century, when anthropogenic influence was of minor importance, is very interesting. In this work the frequency of extreme events, such as droughts and floods, in Western <span class="hlt">Sahel</span> from the 16th to 18th centuries is investigated using documentary data. Original manuscripts with historical chronicles from Walata and Nema (Mauritania), Timbuktu and Arawan (Mali), and Agadez (Niger) have been analyzed. Information on droughts, intense rainfall, storms and floods, as well as socioeconomic aspects (famines, pests, scarcity, prosperity) has been codified in an ordinal scale ranging from -2 (drought and famines) to +2 (floods) to obtain a numerical index of the annual rainfall in the region. Results show wet conditions in the 17th century, as well as dry conditions in the 18th century (interrupted by a short wet period in the 1730s decade).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940038994&hterms=water+africa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dwater%2Bafrica','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940038994&hterms=water+africa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dwater%2Bafrica"><span>Contrasting conditions of surface water balance in wet years and dry years as a possible land surface-atmosphere feedback mechanism in the West African <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lare, A. R.; Nicholson, S. E.</p> <p>1994-01-01</p> <p>The climate of West Africa, in particular the <span class="hlt">Sahel</span>, is characterized by multiyear persistence of anomalously wet or dry conditions. Its Southern Hemisphere counterpart, the Kalahari, lacks the persistence that is evident in the <span class="hlt">Sahel</span> even though both regions are subject to similar large-scale forcing. It has been suggested that land surface-atmosphere feedback contributes to this persistence and to the severity of drought. In this study, surface energy and water balance are quantified for nine stations along a latitudinal transect that extends from the Sahara to the Guinea coast. In the wetter regions of West Africa, the difference between wet and dry years is primarily reflected in the magnitude of runoff. For the <span class="hlt">Sahel</span> and drier locations, evapotranspiration and soil moisture are more sensitive to rainfall anomalies. The increase in evapotranspiration, and hence latent heating, over the <span class="hlt">Sahel</span> in wet years alters the thermal structure and gradients of the overlying atmosphere and thus the strength of the African easterly jet (AEJ) at 700 mb. The difference between dry and wet Augusts corresponds to a decrease in magnitude of the AEJ at 15 deg N on the order of 2.6 m/s, which is consistent with previous studies of observed winds. Spatial patterns were also developed for surface water balance parameters for both West Africa and southern Africa. Over southern Africa, the patterns are not as spatially homogeneous as those over West Africa and are lower in magnitude, thus supporting the suggestion that the persistence of rainfall anomalies in the <span class="hlt">Sahel</span> might be due, at least in part, to land-atmosphere feedback, and that the absence of such persistence in the Kalahari is a consequence of less significant changes in surface water and energy balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1411184M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1411184M"><span>Hydrodynamic behaviour of crusted soils in the <span class="hlt">Sahel</span>: a possible cause for runoff increase?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Malam Abdou, M.; Vandervaere, J.-P.; Bouzou Moussa, I.; Descroix, L.</p> <p>2012-04-01</p> <p>Crusted soils are in extension in the <span class="hlt">Sahel</span>. As rainfall has decreased over the past decades (it is now increasing again in the central <span class="hlt">Sahel</span>) and no significant change was observed in rainfall intensity and in its time and space distribution, it is supposed that land use management is the main cause for crusts cover increase. Fallow shortening, lack of manure, and land overexploitation (wood harvesting, overgrazing) are frequently cited as main factors of soil degradation. Based on field measurements in some small catchments of Western Niger, the hydrodynamics behaviour of the newly crusted soils of this area is described, mostly constituted by erosion crusts. A strong fall in soil saturated conductivity and in the active porosity as well as a rise in bulk density all lead to a quick onset of runoff production. Results are shown from field experiments in sedimentary and basement areas leading to similar conclusions. In both contexts, runoff plot production was measured at the rain event scale from 10-m2 parcels as well as at the catchment outlet. Soil saturated conductivity was reduced by one order of magnitude when crusting occurs, leading to a sharp runoff coefficient increase, from 4% in a weeded millet field and 10% in an old fallow to more than 60% in a erosion-crusted topsoil at the plot scale. At the experimental catchment scale, runoff coefficient has doubled in less than 20 years. In pure Sahelian basins, this resulted in endorheism breaching, and in a widespread river discharge increase. For some right bank tributaries of the Niger River, discharge is three times higher now than before the drought years, in spite of the remaining rainfall deficit. On the other hand, a general increase in flooding hazard frequency is observed in the whole Sahelian stripe. The role of surface crusts in the <span class="hlt">Sahel</span> is discussed leading to the implementation of new experiments in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3611S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3611S"><span>Abrupt aridities in the Levant-<span class="hlt">Sahel</span> linked with solar activities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, M.; Kushnir, Y.</p> <p>2012-04-01</p> <p>Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan <span class="hlt">Sahel</span> and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea and Sahelian lake levels and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the <span class="hlt">Sahel</span> and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an antiphase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However, the records are punctuated by abrupt lake-level drops and extensive expansion of the desert belt at ~8.1, 5.7, 3.3 and 1.4 ka cal BP, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We link these cooling to solar activity variations that were identified in the North Atlantic IRD and cosmogenic isotopes records.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H41L..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H41L..03R"><span>Developing a Shuffled Complex-Self Adaptive Hybrid Evolution (SC-<span class="hlt">SAHEL</span>) Framework for Water Resources Management and Water-Energy System Optimization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rahnamay Naeini, M.; Sadegh, M.; AghaKouchak, A.; Hsu, K. L.; Sorooshian, S.; Yang, T.</p> <p>2017-12-01</p> <p>Meta-Heuristic optimization algorithms have gained a great deal of attention in a wide variety of fields. Simplicity and flexibility of these algorithms, along with their robustness, make them attractive tools for solving optimization problems. Different optimization methods, however, hold algorithm-specific strengths and limitations. Performance of each individual algorithm obeys the "No-Free-Lunch" theorem, which means a single algorithm cannot consistently outperform all possible optimization problems over a variety of problems. From users' perspective, it is a tedious process to compare, validate, and select the best-performing algorithm for a specific problem or a set of test cases. In this study, we introduce a new hybrid optimization framework, entitled Shuffled Complex-Self Adaptive Hybrid EvoLution (SC-<span class="hlt">SAHEL</span>), which combines the strengths of different evolutionary algorithms (EAs) in a parallel computing scheme, and allows users to select the most suitable algorithm tailored to the problem at hand. The concept of SC-<span class="hlt">SAHEL</span> is to execute different EAs as separate parallel search cores, and let all participating EAs to compete during the course of the search. The newly developed SC-<span class="hlt">SAHEL</span> algorithm is designed to automatically select, the best performing algorithm for the given optimization problem. This algorithm is rigorously effective in finding the global optimum for several strenuous benchmark test functions, and computationally efficient as compared to individual EAs. We benchmark the proposed SC-<span class="hlt">SAHEL</span> algorithm over 29 conceptual test functions, and two real-world case studies - one hydropower reservoir model and one hydrological model (SAC-SMA). Results show that the proposed framework outperforms individual EAs in an absolute majority of the test problems, and can provide competitive results to the fittest EA algorithm with more comprehensive information during the search. The proposed framework is also flexible for merging additional EAs, boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12285988','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12285988"><span>The significance of drinking water for population migration in the <span class="hlt">Sahel</span> zone of the Republic of Sudan.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ruppert, H</p> <p>1991-01-01</p> <p>This study examines how the availability of water supplies affects migration in the <span class="hlt">Sahel</span> region of Sudan. More particularly, the author shows that "through the development of watering-places and the opening-up of new water resources, the government influences considerably processes of population migration and regional concentrations of population groups." excerpt</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B31C0032K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B31C0032K"><span>Water, energy and CO2 exchange over a seasonally flooded forest in the <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kergoat, L.; Le Dantec, V.; Timouk, F.; Hiernaux, P.; Mougin, E.; Manuela, G.; Diawara, M.</p> <p>2014-12-01</p> <p>In semi-arid areas like the <span class="hlt">Sahel</span>, perennial water bodies and temporary-flooded lowlands are critical for a number of activities. In some cases, their existence is simply a necessary condition for human societies to establish. They also play an important role in the water and carbon cycle and have strong ecological values. As a result of the strong multi-decadal drought that impacted the <span class="hlt">Sahel</span> in the 70' to 90', a paradoxical increase of ponds and surface runoff has been observed ("Less rain, more water in the ponds", Gardelle 2010). In spite of this, there are excessively few data documenting the consequence of such a paradox on the water and carbon cycle. Here we present 2 years of eddy covariance data collected over the Kelma flooded Acacia forest in the <span class="hlt">Sahel</span> (15.50 °N), in the frame of the AMMA project. The flooded forest is compared to the other major component of this Sahelian landscape: a grassland and a rocky outcrop sites. All sites are involved in the ALMIP2 data/LSM model comparison. The seasonal cycle of the flooded forest strongly departs from the surroundings grassland and bare soil sites. Before the rain season, the forest displays the strongest net radiation and sensible heat flux. Air temperature within the canopy reaches extremely high values. During the flood, it turns to the lowest sensible heat flux. In fact, due to an oasis effect, this flux is negative during the late flood. Water fluxes turn from almost zero in the dry season to strong evaporation during the flood, since it uses additional energy provided by negative sensible heat flux. The eddy covariance fluxes are consistent with sap flow data, showing that the flood greatly increases the length of the growing season. CO2 fluxes over the forest were twice as large as over the grassland, and the growing season was also longer, giving a much larger annual photosynthesis. In view of these data and data over surroundings grasslands and bare soil, as well as data from a long-term ecological</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70037695','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70037695"><span>Geochemical and mineralogical evidence for Sahara and <span class="hlt">Sahel</span> dust additions to Quaternary soils on Lanzarote, eastern Canary Islands, Spain</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Muhs, D.R.; Budahn, J.; Skipp, G.; Prospero, J.M.; Patterson, D.; Bettis, E. Arthur</p> <p>2010-01-01</p> <p>Africa is the most important source of dust in the world today, and dust storms are frequent on the nearby Canary Islands. Previous workers have inferred that the Sahara is the most important source of dust to Canary Islands soils, with little contribution from the <span class="hlt">Sahel</span> region. Soils overlying a late Quaternary basalt flow on Lanzarote, Canary Islands, contain, in addition to volcanic minerals, quartz and mica, exotic to the island's bedrock. Kaolinite in the soils also likely has an exotic origin. Trace-element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and African dust. Major-element geochemistry, clay mineralogy and interpretation of satellite imagery suggest that dust additions to the Canary Islands come not only from the Sahara Desert, but also from the <span class="hlt">Sahel</span> region. ?? Published 2010. This article is a US Government work and is in the public domain in the USA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PIAHS.371..195L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PIAHS.371..195L"><span>Revisiting historical climatic signals to better explore the future: prospects of water cycle changes in Central <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leauthaud, C.; Demarty, J.; Cappelaere, B.; Grippa, M.; Kergoat, L.; Velluet, C.; Guichard, F.; Mougin, E.; Chelbi, S.; Sultan, B.</p> <p>2015-06-01</p> <p>Rainfall and climatic conditions are the main drivers of natural and cultivated vegetation productivity in the semiarid region of Central <span class="hlt">Sahel</span>. In a context of decreasing cultivable area per capita, understanding and predicting changes in the water cycle are crucial. Yet, it remains challenging to project future climatic conditions in West Africa since there is no consensus on the sign of future precipitation changes in simulations coming from climate models. The <span class="hlt">Sahel</span> region has experienced severe climatic changes in the past 60 years that can provide a first basis to understand the response of the water cycle to non-stationary conditions in this part of the world. The objective of this study was to better understand the response of the water cycle to highly variable climatic regimes in Central <span class="hlt">Sahel</span> using historical climate records and the coupling of a land surface energy and water model with a vegetation model that, when combined, simulated the Sahelian water, energy and vegetation cycles. To do so, we relied on a reconstructed long-term climate series in Niamey, Republic of Niger, in which three precipitation regimes can be distinguished with a relative deficit exceeding 25% for the driest period compared to the wettest period. Two temperature scenarios (+2 and +4 °C) consistent with future warming scenarios were superimposed to this climatic signal to generate six virtual future 20-year climate time series. Simulations by the two coupled models forced by these virtual scenarios showed a strong response of the water budget and its components to temperature and precipitation changes, including decreases in transpiration, runoff and drainage for all scenarios but those with highest precipitation. Such climatic changes also strongly impacted soil temperature and moisture. This study illustrates the potential of using the strong climatic variations recorded in the past decades to better understand potential future climate variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12344767','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12344767"><span>[Demography and development in the <span class="hlt">Sahel</span>. The major challenges of the 21st century are already there].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ignegongba, K</p> <p>1992-07-01</p> <p>In the early 1990s, Sahelian governments resolved to carry out direct demographic activities. Many issues essential for development and, in some cases, for the satisfaction of basic needs revolve around education, health, food, environment, employment, and urbanization. The total primary school attendance rate for the nine Sahelian countries is about 40%. The failure of the education system is translated into almost systematic unemployment of graduates and very great ineffectiveness. Education should be adapted to economic conditions and development so as to actually lead to production. For example, it should train persons for agricultural and livestock production. Governments should mobilize necessary resources to improve the quality of education. The current poor health indicators require Sahelian governments in the future to invest and underwrite much to keep up with the rising rate of population growth. Otherwise, young children will always pay the heaviest debt. The impact of AIDS on health resources will risk turning attention away from other fatal diseases. Soil degradation and reduced rainfall make the <span class="hlt">Sahel</span> depend on the importation of food products. The <span class="hlt">Sahel</span> must find ways to reduce this dependence or it will perish while waiting for international generosity. Agricultural and pastoral modes of production are expanding the desert. Sahelians must again find harmony between themselves and their milieu. Youth cannot find jobs. Governments and businesses cut staff to meet conditions of structural adjustment programs. When one worker supports more than 10 persons, the employment problem favors poverty and rising corruption. Soil degradation and low incomes in rural areas, which offer no hope of social promotion, are the chief causes of rural-urban migration in the <span class="hlt">Sahel</span>. The capacity of Sahelian countries to support improvement in rural areas remains a key to many problems, including food self-sufficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1816616V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1816616V"><span>The Crop Risk Zones Monitoring System for resilience to drought in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vignaroli, Patrizio; Rocchi, Leandro; De Filippis, Tiziana; Tarchiani, Vieri; Bacci, Maurizio; Toscano, Piero; Pasqui, Massimiliano; Rapisardi, Elena</p> <p>2016-04-01</p> <p>Food security is still one of the major concerns that Sahelian populations have to face. In the <span class="hlt">Sahel</span>, agriculture is primarily based on rainfed crops and it is often structurally inadequate to manage the climatic variability. The predominantly rainfed cropping system of <span class="hlt">Sahel</span> region is dependent on season quality on a year-to-year basis, and susceptible to weather extremes of droughts and extreme temperatures. Low water-storage capacity and high dependence on rainfed agriculture leave the agriculture sector even more vulnerable to climate risks. Crop yields may suffer significantly with either a late onset or early cessation of the rainy season, as well as with a high frequency of damaging dry spells. Early rains at the beginning of the season are frequently followed by dry spells which may last a week or longer. As the amount of water stored in the soil at this time of the year is negligible, early planted crops can suffer water shortage stresses during a prolonged dry spell. Therefore, the choice of the sowing date is of fundamental importance for farmers. The ability to estimate effectively the onset of the season and potentially dangerous dry spells becomes therefore vital for planning rainfed agriculture practices aiming to minimize risks and maximize yields. In this context, advices to farmers are key drivers for prevention allowing a better adaptation of traditional crop calendar to climatic variability. In the <span class="hlt">Sahel</span>, particularly in CILSS (Permanent Interstates Committee for Drought Control in the <span class="hlt">Sahel</span>) countries, national Early Warning System (EWS) for food security are underpinned by Multidisciplinary Working Groups (MWGs) lead by National Meteorological Services (NMS). The EWSs are mainly based on tools and models utilizing numeric forecasts and satellite data to outlook and monitor the growing season. This approach is focused on the early identification of risks and on the production of information within the prescribed time period for decision</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.H24A..08H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.H24A..08H"><span>Hydrology, Ecology and Pastoralism in the <span class="hlt">Sahel</span>: Abrupt Changes in Surface Water Dynamics in a Coupled Natural-Human System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hanan, N. P.; Prihodko, L.</p> <p>2008-12-01</p> <p>The Sahelian region of Africa is situated to the south of the Sahara desert, stretching from Senegal in the West to Sudan in the East. It is an area with semi-arid climate (300-600 mm mean annual precipitation) and long, severe, dry seasons (8-9 months without rain). Sahelian vegetation consists of extensive annual grasslands, with low tree and shrub density (generally < 5% canopy cover). Though rainfall limits the productivity of Sahelian vegetation, this self-same water limitation means that nutrients are relatively available and the nutrient value and digestibility of Sahelian vegetation is much higher than in the adjacent (wetter) savannas to the south. For this reason, the <span class="hlt">Sahel</span> is a prized grazing resource. However, because domestic animals (cattle, sheep, goats) require regular access to drinking water, most areas of the <span class="hlt">Sahel</span> are only accessible for grazing during the short rainy season while ephemeral surface pools persist. We will describe observations on one such ephemeral pool in northern Mali which underwent an unexpected transition from ephemeral to perennial during the years of average rainfall (1988-1992) following the severe Sahelian drought of 1985-86. As a result of this transformation a small village has established beside the lake and 5-10 thousand cattle now routinely remain in the watershed throughout the dry season. In this paper the dynamics that may have caused the shift from stable ephemeral lake to stable perennial lake, with no long-term increase in rainfall, will be explored. We will examine hypotheses for the change and how it may have arisen through interactions between hydrology, ecology, climate, humans, their livestock, and land use patterns in the lake catchment. It is likely that biological and physical thresholds were exceeded during the drought to trigger a temporary state change in the lake from ephemeral to perennial, which then triggered a socio-economic reorganization. We hypothesize that the resulting change in land use</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NatCC...3..631B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NatCC...3..631B"><span>Building resilience to face recurring environmental crisis in African <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boyd, Emily; Cornforth, Rosalind J.; Lamb, Peter J.; Tarhule, Aondover; Lélé, M. Issa; Brouder, Alan</p> <p>2013-07-01</p> <p>The present food shortages in the Horn of Africa and the West African <span class="hlt">Sahel</span> are affecting 31 million people. Such continuing and future crises require that people in the region adapt to an increasing and potentially irreversible global sustainability challenge. Given this situation and that short-term weather and seasonal climate forecasting have limited skill for West Africa, the Rainwatch project illustrates the value of near real-time monitoring and improved communication for the unfavourable 2011 West African monsoon, the resulting severe drought-induced humanitarian impacts continuing into 2012, and their exacerbation by flooding in 2012. Rainwatch is now coupled with a boundary organization (Africa Climate Exchange, AfClix) with the aim of integrating the expertise and actions of relevant institutions, agencies and stakeholders to broker ground-based dialogue to promote resilience in the face of recurring crisis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790021556','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790021556"><span>An investigation of surface albedo variations during the recent <span class="hlt">sahel</span> drought. [ats 3 observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Norton, C. C.; Mosher, F. R.; Hinton, B.</p> <p>1978-01-01</p> <p>Applications Technology Satellite 3 green sensor data were used to measure surface reflectance variations in the Sahara/<span class="hlt">Sahel</span> during the recent drought period; 1967 to 1974. The magnitude of the seasonal reflectance change is shown to be as much as 80% for years of normal precipitation and less than 50% for drought years. Year to year comparisons during both wet and dry seasons reveal the existence of a surface reflectance cycle coincident with the drought intensity. The relationship between the green reflectance and solar albedo is examined and estimated to be about 0.6 times the reflectance change observed by the green channel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1145D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1145D"><span>Predictability of malaria parameters in <span class="hlt">Sahel</span> under the S4CAST Model.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diouf, Ibrahima; Rodríguez-Fonseca, Belen; Deme, Abdoulaye; Cisse, Moustapha; Ndione, Jaques-Andre; Gaye, Amadou; Suárez-Moreno, Roberto</p> <p>2016-04-01</p> <p>An extensive literature exists documenting the ENSO impacts on infectious diseases, including malaria. Other studies, however, have already focused on cholera, dengue and Rift Valley Fever. This study explores the seasonal predictability of malaria outbreaks over <span class="hlt">Sahel</span> from previous SSTs of Pacific and Atlantic basins. The SST may be considered as a source of predictability due to its direct influence on rainfall and temperature, thus also other related variables like malaria parameters. In this work, the model has been applied to the study of predictability of the Sahelian malaria parameters from the leading MCA covariability mode in the framework of climate and health issue. The results of this work will be useful for decision makers to better access to climate forecasts and application on malaria transmission risk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2806882','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2806882"><span>Solar-powered drip irrigation enhances food security in the Sudano–<span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Burney, Jennifer; Woltering, Lennart; Burke, Marshall; Naylor, Rosamond; Pasternak, Dov</p> <p>2010-01-01</p> <p>Meeting the food needs of Africa’s growing population over the next half-century will require technologies that significantly improve rural livelihoods at minimal environmental cost. These technologies will likely be distinct from those of the Green Revolution, which had relatively little impact in sub-Saharan Africa; consequently, few such interventions have been rigorously evaluated. This paper analyzes solar-powered drip irrigation as a strategy for enhancing food security in the rural Sudano–<span class="hlt">Sahel</span> region of West Africa. Using a matched-pair comparison of villages in northern Benin (two treatment villages, two comparison villages), and household survey and field-level data through the first year of harvest in those villages, we find that solar-powered drip irrigation significantly augments both household income and nutritional intake, particularly during the dry season, and is cost effective compared to alternative technologies. PMID:20080616</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714683D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714683D"><span>Oceanic influence on seasonal malaria outbreaks over Senegal and <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diouf, Ibrahima; Rodríguez de Fonseca, Belen; Deme, Abdoulaye; Cisse Cisse, Moustapha; Ndione Ndione, Jaques-Andre; Gaye, Amadou T.; Suarez, Roberto</p> <p>2015-04-01</p> <p>Beyond assessment and analysis of observed and simulated malaria parameters, this study is furthermore undertaken in the framework of predictability of malaria outbreaks in Senegal and remote regions in <span class="hlt">Sahel</span>, which are found to take place two months after the rainy season. The predictors are the sea surface temperature anomalous patterns at different ocean basins mainly over the Pacific and Atlantic as they are related to changes in air temperature, humidity, rainfall and wind. A relationship between El Niño and anomalous malaria parameters is found. The malaria parameters are calculated with the Liverpool Malaria Model (LMM) using meteorological datasets from different reanalysis products. A hindcast of these parameters is performed using the Sea Surface temperature based Statistical Seasonal ForeCAST (S4CAST) model developed at UCM in order to predict malaria parameters some months in advance. The results of this work will be useful for decision makers to better access to climate forecasts and application on malaria transmission risk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...47.3593M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...47.3593M"><span>Decadal prediction of <span class="hlt">Sahel</span> rainfall: where does the skill (or lack thereof) come from?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mohino, Elsa; Keenlyside, Noel; Pohlmann, Holger</p> <p>2016-12-01</p> <p>Previous works suggest decadal predictions of <span class="hlt">Sahel</span> rainfall could be skillful. However, the sources of such skill are still under debate. In addition, previous results are based on short validation periods (i.e. less than 50 years). In this work we propose a framework based on multi-linear regression analysis to study the potential sources of skill for predicting <span class="hlt">Sahel</span> trends several years ahead. We apply it to an extended decadal hindcast performed with the MPI-ESM-LR model that span from 1901 to 2010 with 1 year sampling interval. Our results show that the skill mainly depends on how well we can predict the timing of the global warming (GW), the Atlantic multidecadal variability (AMV) and, to a lesser extent, the inter-decadal Pacific oscillation signals, and on how well the system simulates the associated SST and West African rainfall response patterns. In the case of the MPI-ESM-LR decadal extended hindcast, the observed timing is well reproduced only for the GW and AMV signals. However, only the West African rainfall response to the AMV is correctly reproduced. Thus, for most of the lead times the main source of skill in the decadal hindcast of West African rainfall is from the AMV. The GW signal degrades skill because the response of West African rainfall to GW is incorrectly captured. Our results also suggest that initialized decadal predictions of West African rainfall can be further improved by better simulating the response of global SST to GW and AMV. Furthermore, our approach may be applied to understand and attribute prediction skill for other variables and regions.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active"><span>3</span></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_3 --> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1110866D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1110866D"><span>The impact of Southern Atlantic moisture source in the precipitation regime of <span class="hlt">Sahel</span> and Brazilian Nordeste using lagrangian models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drumond, A.; Nieto, R.; Gimeno, L.; Ambrizzi, T.; Trigo, R.</p> <p>2009-04-01</p> <p>The socio-economical problems related to the severe droughts observed over Brazilian "Nordeste" and <span class="hlt">Sahel</span> are well known nowadays. Several studies have showed that the precipitation regimes over these regions are influenced by the Inter Tropical Convergence Zone (ITCZ) variability, which can be related with the climatic variations observed in the South and North Tropical Atlantic basins. However, a climatological detailed assessment of the annual cycle of the oceanic moisture contribution to both these regions is still needed in order to get a better understanding of their precipitation regimes and variability. To answer this question, a climatological seasonal analysis of the moisture supply from the South Atlantic to the precipitation in the "Nordeste" and <span class="hlt">Sahel</span> was performed using a new Lagrangian method of diagnosis which identifies the humidity contributions to the moisture budget over a region. The applied methodology computes budgets of evaporation minus precipitation by calculating changes in the specific humidity along forward-trajectories for the following 10 days. In order to take into account distinct regional contributions we have divided the South Atlantic basin in several latitudinal bands (with a 5° width), and all air-masses residing over each region were tracked forward using the available 5-year dataset (2000-2004). For the <span class="hlt">Sahel</span>, the preliminary results suggest that the oceanic band northwards 10 degrees south acts as a moisture source for the precipitation along the year and its contribution reaches the maximum during the austral winter, probably related to the ITCZ annual migration over the region. On the other hand, the precipitation over "Nordeste" can be better related to air masses emanating from the oceanic bands between 10 and 20 degrees south. However the response over the region is very heterogeneous spatially and temporally probably due to the high variability of the local climate characteristics. In order to clarify dynamically the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA624013','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA624013"><span>U.S. Army Civil Affairs Forces in the <span class="hlt">Sahel</span>: Developing an Approach to Building Relevant Partner Capacity in Support of U.S. Africa Command</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-06-12</p> <p>There will likely be similar challenges within military institutions of <span class="hlt">Sahel</span> nations. Cultural relativism posits that all religious, ethical , aesthetic...issues of cultural relativism and legality. Since independence, African nations have struggled to adopt borders and systems imposed by outsiders...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC33C..07N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC33C..07N"><span>The <span class="hlt">Sahel</span> Region of West Africa: Examples of Climate Analyses Motivated By Drought Management Needs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ndiaye, O.; Ward, M. N.; Siebert, A. B.</p> <p>2011-12-01</p> <p>The <span class="hlt">Sahel</span> is one of the most drought-prone regions in the world. This paper focuses on climate sources of drought, and some new analyses mostly driven by users needing climate information to help in drought management strategies. The <span class="hlt">Sahel</span> region of West Africa is a transition zone between equatorial climate and vegetation to the south, and desert to the north. The climatology of the region is dominated by dry conditions for most of the year, with a single peak in rainfall during boreal summer. The seasonal rainfall total contains both interannual variability and substantial decadal to multidecadal variability (MDV). This brings climate analysis and drought management challenges across this range of timescales. The decline in rainfall from the wet decades of the 1950s and 60s to the dry decades of the 1970s and 80s has been well documented. In recent years, a moderate recovery has emerged, with seasonal totals in the period 1994-2010 significantly higher than the average rainfall 1970-1993. These MDV rainfall fluctuations have expression in large-scale sea-surface temperature fluctuations in all ocean basins, placing the changes in drought frequency within broader ocean-atmosphere climate fluctuation. We have evaluated the changing character of low seasonal rainfall total event frequencies in the <span class="hlt">Sahel</span> region 1950-2010, highlighting the role of changes in the mean, variance and distribution shape of seasonal rainfall totals as the climate has shifted through the three observed phases. We also consider the extent to which updating climate normals in real-time can damp the bias in expected event frequency, an important issue for the feasibility of index insurance as a drought management tool in the presence of a changing climate. On the interannual timescale, a key factor long discussed for agriculture is the character of rainfall onset. An extended dry spell often occurs early in the rainy season before the crop is fully established, and this often leads to crop</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC42B..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC42B..07S"><span>Applying Customized Climate Advisory Information to Translate Extreme Rainfall Events into Farming Options in the Sudan-<span class="hlt">Sahel</span> of West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salack, S.; Worou, N. O.; Sanfo, S.; Nikiema, M. P.; Boubacar, I.; Paturel, J. E.; Tondoh, E. J.</p> <p>2017-12-01</p> <p>In West Africa, the risk of food insecurity linked to the low productivity of small holder farming increases as a result of rainfall extremes. In its recent evolution, the rainy season in the Sudan-<span class="hlt">Sahel</span> zone presents mixed patterns of extreme climatic events. In addition to intense rain events, the distribution of events is associated with pockets of intra-seasonal long dry spells. The negative consequences of these mixed patterns are obvious on the farm: soil water logging, erosion of arable land, dwartness and dessication of crops, and loss in production. The capacity of local farming communities to respond accordingly to rainfall extreme events is often constrained by lack of access to climate information and advisory on smart crop management practices that can help translate extreme rainfall events into farming options. The objective of this work is to expose the framework and the pre-liminary results of a scheme that customizes climate-advisory information package delivery to subsistence farmers in Bakel (Senegal), Ouahigouya & Dano (Burkina Faso) and Bolgatanga (Ghana) for sustainable family agriculture. The package is based on the provision of timely climate information (48-hours, dekadal & seasonal) embedded with smart crop management practices to explore and exploite the potential advantage of intense rainfall and extreme dry spells in millet, maize, sorghum and cowpea farming communities. It is sent via mobile phones and used on selected farms (i.e agro-climatic farm schools) on which some small on-farm infrastructure were built to alleviate negative impacts of weather. Results provide prominent insight on how co-production of weather/climate information, customized access and guidiance on its use can induce fast learning (capacity building of actors), motivation for adaptation, sustainability, potential changes in cropping system, yields and family income in the face of a rainfall extremes at local scales of Sudan-<span class="hlt">Sahel</span> of West Africa. Keywords: Climate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.4943M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.4943M"><span>Late Holocene interdecadal climate variability in the <span class="hlt">Sahel</span>: inferences from a marine dust record offshore Senegal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.</p> <p>2009-04-01</p> <p>Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid <span class="hlt">Sahel</span> belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of <span class="hlt">Sahel</span> climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70192858','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70192858"><span>Woody vegetation die off and regeneration in response to rainfall variability in the west African <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Brandt, Martin; Tappan, G. Gray; Aziz Diouf, Abdoul; Beye, Gora; Mbow, Cheikh; Fensholt, Rasmus</p> <p>2017-01-01</p> <p>The greening in the Senegalese <span class="hlt">Sahel</span> has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall) led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014–2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of “greening” or “degradation”. While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in <span class="hlt">Sahel</span> responds to its inherent climatic variability and does not follow a linear trend.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAsGe...5..238A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAsGe...5..238A"><span>The hydrogeological conditions in <span class="hlt">Sahel</span> Hasheesh, Eastern Desert, Eg</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdalla, Mohamed A.; Mekhemer, Hatem M.; Mabrou, Walid Abdallah</p> <p>2016-06-01</p> <p>The groundwater development in Egypt in the present time is of a vital importance than in past few years. A comprehensive plan for new land reclamation projects has been recently established. To achieve these plans new sources of water must be available. This has been done by conducting a number of VES'S where interpreted by a comparison with the existing drilled borehole soil samples. The optimum resistivity model is obtained by matching method using "IPI2Win" Moscow State University 2000 software computer programs for resistivity interpretation. The results of the quantitative interpretation of the resistivity curves has been represented as geoelectric sections, showing the thickness and true electric resistivity values of the different geoelectric layers. The results of quantitative interpretation of the vertical electrical soundings show subsurface five geoelectric units and the aquifer system belongs to lower Miocene and the total salinity of 2451.2 ppm. The depth to water surface is 88.05 m and the total dissolved solids are 2451.2 ppm (Mekhemer well). The salt assemblages in <span class="hlt">Sahel</span> Hasheesh are NaCl, MgCl2, MgSO4, CaSO4, Ca(HCO3)2. This marine water is of brackish sodium chloride water type (NaCl).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=331437','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=331437"><span>Modelling surface runoff and water fluxes over contrasted soils in pastoral <span class="hlt">Sahel</span>: evaluation of the ALMIP2 land surface models over the Gourma region in Mali</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>Land surface processes play an important role in West African monsoon variability and land –atmosphere coupling has been shown to be particularly important in the <span class="hlt">Sahel</span>. In addition, the evolution of hydrological systems in this region, and particularly the increase of surface water and runoff coeff...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IREdu..61..465B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IREdu..61..465B"><span>Koranic Education Centres: A viable educational alternative for the disadvantaged learner in <span class="hlt">Sahel</span> Africa?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bah-Lalya, Ibrahima</p> <p>2015-08-01</p> <p>Within the international momentum for achieving Education for All (EFA) and the Millennium Development Goals (MDGs), many African countries have made considerable progress during the last decade in terms of access to basic education. However, a significant number of children enrolled in the early grades of primary schools either repeat classes or drop out and never graduate. Moreover, there are currently about 30 million school-age children in sub-Saharan Africa who have never attended any form of schooling. In view of this situation, sub-Saharan African countries have been looking for alternative options to educate those who have not been accounted for in the formal school system. This note considers informal Koranic Education Centres (KECs) which are trying to fill the gap of schooling in the <span class="hlt">Sahel</span>-Saharan strip. The author looks at the challenges this form of schooling faces and at how to meet them efficiently. He sounds out the possibility of using KECs to cater for those who have been left aside by formal schooling. Based on existing studies, data compiled by educational systems and a study conducted by the Working Group on Non-Formal Education (WGNFE) of the Association for the Development of Education in Africa (ADEA) in four West African countries (Burkina Faso, Mali, Mauritania and Senegal) in 2013, the author of this research note came to the conclusion that a holistic approach, where the two systems (the Koranic and the formal) collaborate and support one another, could effectively contribute to alleviating the dropout predicament and to reducing the number of unschooled children. It could offer a second-chance opportunity to dropout and unschooled children in the <span class="hlt">Sahel</span> and Saharan zone. However, before this can become a viable alternative, a number of major challenges need to be addressed. Through its WGNFE, ADEA intends to further investigate the holistic approach of combining formal "modern" and informal "Koranic" schooling to come up with tangible</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5794140','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5794140"><span>Mapping regional livelihood benefits from local ecosystem services assessments in rural <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sinare, Hanna; Enfors Kautsky, Elin; Ouedraogo, Issa; Gordon, Line J.</p> <p>2018-01-01</p> <p>Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method) and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption) that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the <span class="hlt">Sahel</span>. PMID:29389965</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29389965','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29389965"><span>Mapping regional livelihood benefits from local ecosystem services assessments in rural <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Malmborg, Katja; Sinare, Hanna; Enfors Kautsky, Elin; Ouedraogo, Issa; Gordon, Line J</p> <p>2018-01-01</p> <p>Most current approaches to landscape scale ecosystem service assessments rely on detailed secondary data. This type of data is seldom available in regions with high levels of poverty and strong local dependence on provisioning ecosystem services for livelihoods. We develop a method to extrapolate results from a previously published village scale ecosystem services assessment to a higher administrative level, relevant for land use decision making. The method combines remote sensing (using a hybrid classification method) and interviews with community members. The resulting landscape scale maps show the spatial distribution of five different livelihood benefits (nutritional diversity, income, insurance/saving, material assets and energy, and crops for consumption) that illustrate the strong multifunctionality of the Sahelian landscapes. The maps highlight the importance of a diverse set of sub-units of the landscape in supporting Sahelian livelihoods. We see a large potential in using the resulting type of livelihood benefit maps for guiding future land use decisions in the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913070N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913070N"><span>Impact of aerosols on solar energy production - Scenarios from the <span class="hlt">Sahel</span> Zone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neher, Ina; Meilinger, Stefanie; Crewell, Susanne</p> <p>2017-04-01</p> <p>Solar energy is one option to serve the rising global energy demand with low environmental impact. Building an energy system with a considerable share of solar power requires long-term investment and a careful investigation of potential sites. Therefore, understanding the impacts from varying regionally and locally determined meteorological conditions on solar energy production will influence energy yield projections. Aerosols reduce global solar radiation due to absorption and scattering and therewith solar energy yields. Depending on aerosol size distribution they reduce the direct component of the solar radiation and modify the direction of the diffuse component compared to standard atmospheric conditions without aerosols. The aerosol size distribution and composition in the atmosphere is highly variable due to meteorological and land surface conditions. A quantitative assessment of aerosol effects on solar power yields and its relation to land use change is of particular interest for developing countries countries when analyzing the potential of local power production. This study aims to identify the effect of atmospheric aerosols in three different land use regimes, namely desert, urban/polluted and maritime on the tilted plane of photovoltaic energy modules. Here we focus on the <span class="hlt">Sahel</span> zone, i.e. Niamey, Niger (13.5 N;2.1 E), located at the edge of the Sahara where also detailed measurements of the atmospheric state are available over the year 2006. Guided by observations a model chain is used to determine power yields. The atmospheric aerosol composition will be defined by using the Optical Properties of Aerosols and Clouds (OPAC) library. Direct and diffuse radiation (up- and downward component) are then calculated by the radiative transfer model libRadtran which allows to calculate the diffuse component of the radiance from different azimuth and zenith angles. Then the diffuse radiance will be analytically transformed to an east, south and west facing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A13M..12T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A13M..12T"><span>Representing soil moisture - precipitation feedbacks in the <span class="hlt">Sahel</span>: spatial scale and parameterisation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taylor, C.; Birch, C.; Parker, D.; Guichard, F.; Nikulin, G.; Dixon, N.</p> <p>2013-12-01</p> <p>Land surface properties influence the life cycle of convective systems across West Africa via space-time variability in sensible and latent heat fluxes. Previous observational and modelling studies have shown that areas with strong mesoscale variability in vegetation cover or soil moisture induce coherent structures in the daytime planetary boundary layer. In particular, horizontal gradients in sensible heat flux can induce convergence zones which favour the initiation of deep convection. A recent study based on satellite data (Taylor et al. 2011), illustrated the climatological importance of soil moisture gradients in the initiation of long-lived Mesoscale Convective Systems (MCS) in the <span class="hlt">Sahel</span>. Here we provide a unique assessment of how models of different spatial resolutions represent soil moisture - precipitation feedbacks in the region, and compare their behaviour to observations. Specifically we examine whether the inability of large-scale models to capture the observed preference for afternoon rain over drier soil in semi-arid regions [Taylor et al., 2012] is due to inadequate spatial resolution and/or systematic bias in convective parameterisations. Firstly, we use a convection-permitting simulation at 4km resolution to explore the underlying mechanisms responsible for soil moisture controls on daytime convective initiation in the <span class="hlt">Sahel</span>. The model reproduces very similar spatial structure as the observations in terms of antecedent soil moisture in the vicinity of a large sample of convective initiations. We then examine how this same model, run at coarser resolution, simulates the feedback of soil moisture on daily rainfall. In particular we examine the impact of switching on the convective parameterisation on rainfall persistence, and compare the findings with 10 regional climate models (RCMs). Finally, we quantify the impact of the feedback on dry-spell return times using a simple statistical model. The results highlight important weaknesses in convective</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911952L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911952L"><span>A 60-year reconstructed high-resolution local meteorological data set in Central <span class="hlt">Sahel</span> (1950-2009): evaluation, analysis and application to land surface modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leauthaud, Crystele; Cappelaere, Bernard; Demarty, Jérôme; Guichard, Françoise; Velluet, Cécile; Kergoat, Laurent; Vischel, Théo; Grippa, Manuela; Mouhaimouni, Mohammed; Bouzou Moussa, Ibrahim; Mainassara, Ibrahim; Sultan, Benjamin</p> <p>2017-04-01</p> <p>The <span class="hlt">Sahel</span> has experienced strong climate variability in the past decades. Understanding its implications for natural and cultivated ecosystems is pivotal in a context of high population growth and mainly agriculture-based livelihoods. However, efforts to model processes at the land-atmosphere interface are hindered, particularly when the multi-decadal timescale is targeted, as climatic data are scarce, largely incomplete and often unreliable. This study presents the generation of a long-term, high-temporal resolution, multivariate local climatic data set for Niamey, Central <span class="hlt">Sahel</span>. The continuous series spans the period 1950-2009 at a 30-min timescale and includes ground station-based meteorological variables (precipitation, air temperature, relative and specific humidity, air pressure, wind speed, downwelling long- and short-wave radiation) as well as process-modelled surface fluxes (upwelling long- and short-wave radiation,latent, sensible and soil heat fluxes and surface temperature). A combination of complementary techniques (linear/spline regressions, a multivariate analogue method, artificial neural networks and recursive gap filling) was used to reconstruct missing meteorological data. The complete surface energy budget was then obtained for two dominant land cover types, fallow bush and millet, by applying the meteorological forcing data set to a finely field-calibrated land surface model. Uncertainty in reconstructed data was expressed by means of a stochastic ensemble of plausible historical time series. Climatological statistics were computed at sub-daily to decadal timescales and compared with local, regional and global data sets such as CRU and ERA-Interim. The reconstructed precipitation statistics, ˜1°C increase in mean annual temperature from 1950 to 2009, and mean diurnal and annual cycles for all variables were in good agreement with previous studies. The new data set, denoted NAD (Niamey Airport-derived set) and publicly available, can be used</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1512790D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1512790D"><span>The 25 years long drought in <span class="hlt">Sahel</span> and its impacts on ecosystems: Long term vegetation monitoring from the sky and on the ground</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dardel, Cecile; Kergoat, Laurent; Hiernaux, Pierre; Mougin, Eric; Grippa, Manuela; Tucker, Compton Jim</p> <p>2013-04-01</p> <p>The <span class="hlt">Sahel</span> region is known to be very sensitive to climatic fluctuations. Precipitation interannual variability has immediate and strong consequences on water resources, vegetation production, all affecting human populations. All along its history, <span class="hlt">Sahel</span> had to face extreme climatic events. In the recent past, a 25 years period of persistent drought jeopardized the ecosystems equilibrium. Indeed, from the 1970's to the mid 1990's, precipitations were strongly and repeatedly below average. A debate has grown for years in the scientific community about the evolving trend of ecosystem in <span class="hlt">Sahel</span>: is there desertification, or rehabilitation indicated by a "re-greening" taking place since the 1980's, as observed on satellite data by many scientists? To answer these questions, NDVI (Normalized Difference Vegetation Index) time series derived from NOAA/AVHRR are analyzed and compared to field measurements of the herbaceous aboveground mass, tree inventory and crop phytomass collected in Mali and Niger, from 1984 to 2011 and 1994 to 2011 respectively. The GIMMS-3g NDVI trends analysis from 1981 to 2011 show positive and significant slope values over almost every part of the <span class="hlt">Sahel</span>, except for western Niger and central Sudan, thus reinforcing the "re-greening" hypothesis. Field observations are in good agreement with satellite data. A positive trend is observed over the Gourma in Mali, particularly for periods beginning in the 1980's, showing the ecosystem resilience to drought. A similar recovery is observed in western Niger, but only up to the mid 1990's, then the trend turns negative without being explained by rainfall. While the Gourma is mainly a pastoral land, western Niger is an agro-pastoral region in which cropped surfaces expanded widely over the last decades. For both regions, the re-greening trends are mainly observed on sandy soils, while erosion processes have been observed on shallow soil surfaces, inducing increased run-off and decrease in vegetation cover to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10477958','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10477958"><span>Dealing with extreme environmental degradation: stress and marginalization of <span class="hlt">Sahel</span> dwellers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Van Haaften, E H; Van de Vijver, F J</p> <p>1999-07-01</p> <p>Psychological aspects of environmental degradation are hardly investigated. In the present study these aspects were examined among <span class="hlt">Sahel</span> dwellers, who live in environments with different states of degradation. The degradation was assessed in terms of vegetation cover, erosion, and loss of organic matter. Subjects came from three cultural groups: Dogon (agriculturalists, n = 225), Mossi (agriculturalists, n = 914), and Fulani (pastoralists, n = 844). Questionnaires addressing marginalization, locus of control, and coping were administered. Environmental degradation was associated with higher levels of stress, marginalization, passive coping (avoidance), a more external locus of control, and lower levels of active coping (problem solving and support seeking). Compared to agriculturalists, pastoralists showed a stronger variation in all psychological variables across all regions, from the least to the most environmentally degraded. Women showed higher scores of stress, (external) locus of control, problem solving, and support seeking than men. The interaction of gender and region was significant for several variables. It was concluded that environmental degradation has various psychological correlates: people are likely to display an active approach to environmental degradation as long as the level of degradation is not beyond their control.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JHyd..188..633F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JHyd..188..633F"><span>Carbon dioxide flux, transpiration and light response of millet in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Friborg, T.; Boegh, E.; Soegaard, H.</p> <p>1997-02-01</p> <p>Within the framework of the HAPEX-<span class="hlt">Sahel</span> experiment carried out in Niger during the rainy season of 1992, measurements of fluxes defining the vegetation-atmosphere interaction were conducted over a millet field, for a period of nearly 2 months. These measurements comprised continuous recording of solar radiation, atmospheric carbon dioxide fluxes using the eddy correlation technique, and sap flow through millet plants. Based on biometric measurements of the millet plants comprising height, spacing and leaf area index, the solar radiation is converted to absorbed photosynthetically active radiation (aPAR). The coupling between the three parameters is examined in pairs. The diurnal and seasonal variations are analysed in relation to plant development. A strong linear relationship between aPAR and carbon dioxide assimilation can be established from the measurements, giving a quantum yield of 0.03 mol CO 2 mol -1 quanta. A comparison between CO 2 flux and transpiration shows that this relationship is affected by the water vapour pressure deficit of the atmosphere, but corresponds to the results found for other drought-tolerant C 4 crops.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1211165L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1211165L"><span>Sahara and <span class="hlt">Sahel</span> vulnerability to climate changes, lessons from the past</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lezine, Anne-Marie; Hély, Christelle; Grenier, Christophe; Braconnot, Pascale</p> <p>2010-05-01</p> <p>Since the Sahelian drought in the 1970s, climate variability in north tropical Africa has been the subject of intensive research focusing on the functioning of the Atlantic monsoon system as well as on past variations in rainfall from historical and natural archives. An "abrupt" climate change has been recorded off the Mauritanian coast at the end of the African Humid Period (AHP) 5500 years ago illustrating the onset of the modern climate regime [deMenocal et al., 2000]. At lake Yoa in NE Chad, [Kroepelin et al., 2008] report a "gradual" environmental change. Was this change abrupt or gradual, and amplified or not through vegetation change and feedbacks to the atmosphere is still the subject of debate. Here, we compile paleohydrological and palynological data between 10 and 28°N in the Sahara and <span class="hlt">Sahel</span> with the purpose of understanding the response of the hydrological system and the vegetation cover to rainfall fluctuations from the onset of the AHP. Our data set is extracted from published studies. It is composed of 1651 dated samples from about 420 localities in the present day Sahara and <span class="hlt">Sahel</span>. The occurrence of high and intermediate lake levels, fluvial terraces and wetlands as well as of dune edification are analysed with a 1000 yr period from 16 000 yrs BP to present. Clear trends are observed in the evolution of paleohydrological indicators versus time and latitude showing the progression of the centre of the distribution of humidity from south to north during the humid period and to the south after the AHP. The humidity maximum is observed with some temporal delay as compared to the June solar radiation maximum at 30°N. The reasons are investigated along the line of pure climate based processes and/or hydrological impacts. Further, the overall coherence among these signals is examined. Using climate simulations for different key periods in the Holocene, we investigate the relative impact of the insolation forcing, of the remnant ice sheet in the early</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H33M..01V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H33M..01V"><span>A Tool for Creating Regionally Calibrated High-Resolution Land Cover Data Sets for the West African <span class="hlt">Sahel</span>: Using Machine Learning to Scale Up Hand-Classified Maps in a Data-Sparse Environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Gordon, M.; Van Gordon, S.; Min, A.; Sullivan, J.; Weiner, Z.; Tappan, G. G.</p> <p>2017-12-01</p> <p>Using support vector machine (SVM) learning and high-accuracy hand-classified maps, we have developed a publicly available land cover classification tool for the West African <span class="hlt">Sahel</span>. Our classifier produces high-resolution and regionally calibrated land cover maps for the <span class="hlt">Sahel</span>, representing a significant contribution to the data available for this region. Global land cover products are unreliable for the <span class="hlt">Sahel</span>, and accurate land cover data for the region are sparse. To address this gap, the U.S. Geological Survey and the Regional Center for Agriculture, Hydrology and Meteorology (AGRHYMET) in Niger produced high-quality land cover maps for the region via hand-classification of Landsat images. This method produces highly accurate maps, but the time and labor required constrain the spatial and temporal resolution of the data products. By using these hand-classified maps alongside SVM techniques, we successfully increase the resolution of the land cover maps by 1-2 orders of magnitude, from 2km-decadal resolution to 30m-annual resolution. These high-resolution regionally calibrated land cover datasets, along with the classifier we developed to produce them, lay the foundation for major advances in studies of land surface processes in the region. These datasets will provide more accurate inputs for food security modeling, hydrologic modeling, analyses of land cover change and climate change adaptation efforts. The land cover classification tool we have developed will be publicly available for use in creating additional West Africa land cover datasets with future remote sensing data and can be adapted for use in other parts of the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ClDy...40.1453K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ClDy...40.1453K"><span>A further assessment of vegetation feedback on decadal <span class="hlt">Sahel</span> rainfall variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kucharski, Fred; Zeng, Ning; Kalnay, Eugenia</p> <p>2013-03-01</p> <p>The effect of vegetation feedback on decadal-scale <span class="hlt">Sahel</span> rainfall variability is analyzed using an ensemble of climate model simulations in which the atmospheric general circulation model ICTPAGCM ("SPEEDY") is coupled to the dynamic vegetation model VEGAS to represent feedbacks from surface albedo change and evapotranspiration, forced externally by observed sea surface temperature (SST) changes. In the control experiment, where the full vegetation feedback is included, the ensemble is consistent with the observed decadal rainfall variability, with a forced component 60 % of the observed variability. In a sensitivity experiment where climatological vegetation cover and albedo are prescribed from the control experiment, the ensemble of simulations is not consistent with the observations because of strongly reduced amplitude of decadal rainfall variability, and the forced component drops to 35 % of the observed variability. The decadal rainfall variability is driven by SST forcing, but significantly enhanced by land-surface feedbacks. Both, local evaporation and moisture flux convergence changes are important for the total rainfall response. Also the internal decadal variability across the ensemble members (not SST-forced) is much stronger in the control experiment compared with the one where vegetation cover and albedo are prescribed. It is further shown that this positive vegetation feedback is physically related to the albedo feedback, supporting the Charney hypothesis.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active"><span>4</span></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_4 --> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20234393','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20234393"><span>Linking the sub-Saharan and West Eurasian gene pools: maternal and paternal heritage of the Tuareg nomads from the African <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pereira, Luísa; Cerný, Viktor; Cerezo, María; Silva, Nuno M; Hájek, Martin; Vasíková, Alzbeta; Kujanová, Martina; Brdicka, Radim; Salas, Antonio</p> <p>2010-08-01</p> <p>The Tuareg presently live in the Sahara and the <span class="hlt">Sahel</span>. Their ancestors are commonly believed to be the Garamantes of the Libyan Fezzan, ever since it was suggested by authors of antiquity. Biological evidence, based on classical genetic markers, however, indicates kinship with the Beja of Eastern Sudan. Our study of mitochondrial DNA (mtDNA) sequences and Y chromosome SNPs of three different southern Tuareg groups from Mali, Burkina Faso and the Republic of Niger reveals a West Eurasian-North African composition of their gene pool. The data show that certain genetic lineages could not have been introduced into this population earlier than approximately 9000 years ago whereas local expansions establish a minimal date at around 3000 years ago. Some of the mtDNA haplogroups observed in the Tuareg population were involved in the post-Last Glacial Maximum human expansion from Iberian refugia towards both Europe and North Africa. Interestingly, no Near Eastern mtDNA lineages connected with the Neolithic expansion have been observed in our population sample. On the other hand, the Y chromosome SNPs data show that the paternal lineages can very probably be traced to the Near Eastern Neolithic demic expansion towards North Africa, a period that is otherwise concordant with the above-mentioned mtDNA expansion. The time frame for the migration of the Tuareg towards the African <span class="hlt">Sahel</span> belt overlaps that of early Holocene climatic changes across the Sahara (from the optimal greening approximately 10 000 YBP to the extant aridity beginning at approximately 6000 YBP) and the migrations of other African nomadic peoples in the area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1510981G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1510981G"><span>Predicting local Soil- and Land-units with Random Forest in the Senegalese <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grau, Tobias; Brandt, Martin; Samimi, Cyrus</p> <p>2013-04-01</p> <p>MODIS (MCD12Q1) or Globcover are often the only available global land-cover products, however ground-truthing in the <span class="hlt">Sahel</span> of Senegal has shown that most classes do have any agreement with actual land-cover making those products unusable in any local application. We suggest a methodology, which models local Wolof land- and soil-types in an area in the Senegalese Ferlo around Linguère at different scales. In a first step, interviews with the local population were conducted to ascertain the local denotation of soil units, as well as their agricultural use and woody vegetation mainly growing on them. "Ndjor" are soft sand soils with mainly Combretum glutinosum trees. They are suitable for groundnuts and beans while millet is grown on hard sand soils ("Bardjen") dominated by Balanites aegyptiaca and Acacia tortilis. "Xur" are clayey depressions with a high diversity of tree species. Lateritic pasture sites with dense woody vegetation (mostly Pterocarpus lucens and Guiera senegalensis) have never been used for cropping and are called "All". In a second step, vegetation and soil parameters of 85 plots (~1 ha) were surveyed in the field. 28 different soil parameters are clustered into 4 classes using the WARD algorithm. Here, 81% agree with the local classification. Then, an ordination (NMDS) with 2 dimensions and a stress-value of 9.13% was calculated using the 28 soil parameters. It shows several significant relationships between the soil classes and the fitted environmental parameters which are derived from field data, a digital elevation model, Landsat and RapidEye imagery as well as TRMM rainfall data. Landsat's band 5 reflectance values (1.55 - 1.75 µm) of mean dry season image (2000-2010) has a R² of 0.42 and is the most important of 9 significant variables (5%-level). A random forest classifier is then used to extrapolate the 4 classes to the whole study area based on the 9 significant environmental parameters. At a resolution of 30 m the OBB (out-of-bag) error</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950051156&hterms=desertification&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddesertification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950051156&hterms=desertification&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddesertification"><span>The influence of land surface properties on <span class="hlt">Sahel</span> climate. Part 1: Desertification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xue, Yongkang; Shukla, Jagadish</p> <p>1993-01-01</p> <p>This is a general circulation model sensitivity study of the physical mechanisms of the effects of desertification on the <span class="hlt">Sahel</span> drought. The model vegetation types were changed in the prescribed desertification area, which led to changes in the surface characteristics. The model was integrated for three months (June, July, August) with climatological surface conditions (control) and desertification conditions (anomaly) to examine the summer season response to the changed surface conditions. The control and anomaly experiments consisted of five pairs of integrations with different initial conditions and/or sea surface temperature boundary conditions. In the desertification experiment, the moisture flux convergence and rainfall were reduced in the test area and increased to the immediate south of this area. The simulated anomaly dipole pattern was similar to the observed African drought patterns in which the axis of the maximum rainfall shifts to the south. The circulation changes in the desertification experiment were consistent with those observed during sub-Saharan dry years. The tropical easterly jet was weaker and the African easterly jet was stronger than normal. Further, in agreement with the observations, the easterly wave disturbances were reduced in intensity but not in number. Descending motion dominated the desertification area. The surface energy budget and hydrological cycle were also changed substantially in the anomaly experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22270527','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22270527"><span>Climate variability and environmental stress in the Sudan-<span class="hlt">Sahel</span> zone of West Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mertz, Ole; D'haen, Sarah; Maiga, Abdou; Moussa, Ibrahim Bouzou; Barbier, Bruno; Diouf, Awa; Diallo, Drissa; Da, Evariste Dapola; Dabi, Daniel</p> <p>2012-06-01</p> <p>Environmental change in the Sudan-<span class="hlt">Sahel</span> region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic changes and their perceptions were compared across north-south and west-east rainfall gradients. More than 80% of all households found that rainfall had decreased, especially in the wettest areas. Increases in wind speeds and temperature were perceived by an overall 60-80% of households. Contrary to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources, vegetation, and fauna, but more so in the 500-900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region, especially in the 500-900 mm zones and the western part of SSWA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2987384','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2987384"><span>Linking the sub-Saharan and West Eurasian gene pools: maternal and paternal heritage of the Tuareg nomads from the African <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pereira, Luísa; Černý, Viktor; Cerezo, María; Silva, Nuno M; Hájek, Martin; Vašíková, Alžběta; Kujanová, Martina; Brdička, Radim; Salas, Antonio</p> <p>2010-01-01</p> <p>The Tuareg presently live in the Sahara and the <span class="hlt">Sahel</span>. Their ancestors are commonly believed to be the Garamantes of the Libyan Fezzan, ever since it was suggested by authors of antiquity. Biological evidence, based on classical genetic markers, however, indicates kinship with the Beja of Eastern Sudan. Our study of mitochondrial DNA (mtDNA) sequences and Y chromosome SNPs of three different southern Tuareg groups from Mali, Burkina Faso and the Republic of Niger reveals a West Eurasian-North African composition of their gene pool. The data show that certain genetic lineages could not have been introduced into this population earlier than ∼9000 years ago whereas local expansions establish a minimal date at around 3000 years ago. Some of the mtDNA haplogroups observed in the Tuareg population were involved in the post-Last Glacial Maximum human expansion from Iberian refugia towards both Europe and North Africa. Interestingly, no Near Eastern mtDNA lineages connected with the Neolithic expansion have been observed in our population sample. On the other hand, the Y chromosome SNPs data show that the paternal lineages can very probably be traced to the Near Eastern Neolithic demic expansion towards North Africa, a period that is otherwise concordant with the above-mentioned mtDNA expansion. The time frame for the migration of the Tuareg towards the African <span class="hlt">Sahel</span> belt overlaps that of early Holocene climatic changes across the Sahara (from the optimal greening ∼10 000 YBP to the extant aridity beginning at ∼6000 YBP) and the migrations of other African nomadic peoples in the area. PMID:20234393</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1410479D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1410479D"><span>Remote sensing of desert dust aerosols over the <span class="hlt">Sahel</span> : potential use for health impact studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deroubaix, A. D.; Martiny, N. M.; Chiapello, I. C.; Marticorena, B. M.</p> <p>2012-04-01</p> <p>Since the end of the 70's, remote sensing monitors the desert dust aerosols due to their absorption and scattering properties and allows to make long time series which are necessary for air quality or health impact studies. In the <span class="hlt">Sahel</span>, a huge health problem is the Meningitis Meningococcal (MM) epidemics that occur during the dry season : the dust has been suspected to be crucial to understand their onsets and dynamics. The Aerosol absorption Index (AI) is a semi-quantitative index derived from TOMS and OMI observations in the UV available at a spatial resolution of 1° (1979-2005) and 0.25° (2005-today) respectively. The comparison of the OMI-AI and AERONET Aerosol Optical thickness (AOT) shows a good agreement at a daily time-step (correlation ~0.7). The comparison of the OMI-AI with the Particle Matter (PM) measurement of the Sahelian Dust Transect is lower (~0.4) at a daily time-step but it increases at a weekly time-step (~0.6). The OMI-AI reproduces the dust seasonal cycle over the <span class="hlt">Sahel</span> and we conclude that the OMI-AI product at a 0.25° spatial resolution is suitable for health impact studies, especially at a weekly epidemiological time-step. Despite the AI is sensitive to the aerosol altitude, it provides a daily spatial information on dust. A preliminary investigation analysis of the link between weekly OMI AI and weekly WHO epidemiological data sets is presented in Mali and Niger, showing a good agreement between the AI and the onset of the MM epidemics with a constant lag (between 1 and 2 week). The next of this study is to analyse a deeper AI time series constituted by TOMS and OMI data sets. Based on the weekly ratios PM/AI at 2 stations of the Sahelian Dust Transect, a spatialized proxy for PM from the AI has been developed. The AI as a proxy for PM and other climate variables such as Temperature (T°), Relative Humidity (RH%) and the wind (intensity and direction) could then be used to analyze the link between those variables and the MM epidemics</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12286509','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12286509"><span>[Population resettlement and women's changing roles in the <span class="hlt">Sahel</span>].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ouedraogo, D O</p> <p>1992-01-01</p> <p>For many decision makers in the <span class="hlt">Sahel</span>, relocating populations from poor, over-populated regions to relatively fertile zones regulated by the state seemed the best approach to improving women's conditions, particularly in household affairs. In the original territories, women have their personal fields where they raise vegetables and other products which they sell to secure their own income. During the dry season, they engage in other activities for money (e.g., production and sale of millet beer and sale of pottery). Women have relative economic autonomy. Within the family household and in villages, they isolate themselves in their own spaces (e.g., kitchen and wells) and discuss their specific problems. In government-controlled zones where families resettle, the families are supposed to plant the same varieties of imposed cultivation (e.g., rice) judged to be more productive. They must sow, plow, and harvest using the same techniques. All activities are controlled. Women have no decision power and must submit to the logic of the chief of agricultural production. They no longer have time to dedicate themselves to individual economic activity (especially in irrigated zones, where there are two annual plantings), or to assure a good education for their children. They have little time to dedicate to hygiene and nutrition. These government-controlled agricultural zones have established an exploitation model that contributes to the socioeconomic destabilization of families. The retreat of women's economic power is often accompanied by degradation of family well-being. Agricultural development schemes that involve agricultural migrations have marginalized women even more than they were before resettlement in spite of improvement in family income. It is narrowly linked to short-term development. In conclusion, agricultural resettlement schemes do not improve the status of women.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ESD.....7..969M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ESD.....7..969M"><span>Weather and resource information as tools for dealing with farmer-pastoralist conflicts in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mertz, Ole; Rasmussen, Kjeld; Vang Rasmussen, Laura</p> <p>2016-12-01</p> <p>Conflicts between pastoralists and farmers in the <span class="hlt">Sahel</span> mainly arise from competition over land and water resources or because of livestock damage to crops. Rather than being linked to larger environmental change processes such as climate change, conflicts are often caused by inappropriate zoning of land, governance and unequal power relations between stakeholders. However, conflicts may be affected by more short-term weather and resource information that guide mobility of pastoralists. In this paper, we therefore explore if improved weather and resource information and improvement in its communication could prevent conflicts or reduce their severity. Based on a survey of key stakeholders involved in dissemination of weather and resource information and studies on pastoral access to and use of information, we conclude that improved information may both reduce and increase the level of conflict, depending on the context. Communication of information will need to go beyond just the weather and resource information and also include the multiple options for herd movements as well as providing information on herd crowding and potential conflict areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010QSRv...29.3843K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010QSRv...29.3843K"><span>North Atlantic influence on 19th-20th century rainfall in the Dead Sea watershed, teleconnections with the <span class="hlt">Sahel</span>, and implication for Holocene climate fluctuations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kushnir, Yochanan; Stein, Mordechai</p> <p>2010-12-01</p> <p>The importance of understanding processes that govern the hydroclimate of the Mediterranean Basin is highlighted by the projected significant drying of the region in response to the increase in greenhouse gas concentrations. Here we study the long-term hydroclimatic variability of the central Levant region, situated in the eastern boundary of the Basin, as reveled by instrumental observations and the Holocene record of Dead Sea level variations. Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan <span class="hlt">Sahel</span> and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with a broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea lake level, by lake levels in the <span class="hlt">Sahel</span>, and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the <span class="hlt">Sahel</span> and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an anti-phase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However the records are punctuated by abrupt lake-level drops, which appear to be in-phase and which occur during previously documented</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18810526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18810526"><span>Farmers' perceptions of climate change and agricultural adaptation strategies in rural <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mertz, Ole; Mbow, Cheikh; Reenberg, Anette; Diouf, Awa</p> <p>2009-05-01</p> <p>Farmers in the <span class="hlt">Sahel</span> have always been facing climatic variability at intra- and inter-annual and decadal time scales. While coping and adaptation strategies have traditionally included crop diversification, mobility, livelihood diversification, and migration, singling out climate as a direct driver of changes is not so simple. Using focus group interviews and a household survey, this study analyzes the perceptions of climate change and the strategies for coping and adaptation by sedentary farmers in the savanna zone of central Senegal. Households are aware of climate variability and identify wind and occasional excess rainfall as the most destructive climate factors. Households attribute poor livestock health, reduced crop yields and a range of other problems to climate factors, especially wind. However, when questions on land use and livelihood change are not asked directly in a climate context, households and groups assign economic, political, and social rather than climate factors as the main reasons for change. It is concluded that the communities studied have a high awareness of climate issues, but climatic narratives are likely to influence responses when questions mention climate. Change in land use and livelihood strategies is driven by adaptation to a range of factors of which climate appears not to be the most important. Implications for policy-making on agricultural and economic development will be to focus on providing flexible options rather than specific solutions to uncertain climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21410888','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21410888"><span>Accelerating improvements in nutritional and health status of young children in the <span class="hlt">Sahel</span> region of Sub-Saharan Africa: review of international guidelines on infant and young child feeding and nutrition.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wuehler, Sara E; Hess, Sonja Y; Brown, Kenneth H</p> <p>2011-04-01</p> <p>The United Nations Convention on the Rights of the Child holds governments responsible to ensure children's right to the highest attainable standard of health by providing breastfeeding support, and access to nutritious foods, appropriate health care, and clean drinking water. International experts have identified key child care practices and programmatic activities that are proven to be effective at reducing infant and young child undernutrition, morbidity, and mortality. Nevertheless, progress towards reducing the prevalence of undernutrition has been sporadic across countries of the <span class="hlt">Sahel</span> sub-region of Sub-Saharan Africa. In view of this uneven progress, a working group of international agencies was convened to 'Reposition children's right to adequate nutrition in the <span class="hlt">Sahel</span>.' The first step towards this goal was to organize a situational analysis of the legislative, research, and programmatic activities related to infant and young child nutrition (IYCN) in six countries of the sub-region: Burkina Faso, Chad, Mali, Mauritania, Niger, and Senegal. The purposes of this introductory paper are to review current information concerning the nutritional and health status of infants and young children in the <span class="hlt">Sahel</span> and to summarize international guidelines on optimal IYCN practices. These guidelines were used in completing the above-mentioned situational analyses and encompass specific recommendations on: (i) breastfeeding (introduction within the first hour after birth, exclusivity to 6 months, continuation to at least 24 months); (ii) complementary feeding (introduction at 6 months, use of nutrient dense foods, adequate frequency and consistency, and responsive feeding); (iii) prevention and/or treatment of micronutrient deficiencies (vitamin A, zinc, iron and anaemia, and iodine); (iv) prevention and/or treatment of acute malnutrition; (v) feeding practices adapted to the maternal situation to reduce mother-to-child transmission of HIV; (vi) activities to ensure food</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRD..11813265Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRD..11813265Y"><span>Statistical relationship between surface PM10 concentration and aerosol optical depth over the <span class="hlt">Sahel</span> as a function of weather type, using neural network methodology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yahi, H.; Marticorena, B.; Thiria, S.; Chatenet, B.; Schmechtig, C.; Rajot, J. L.; Crepon, M.</p> <p>2013-12-01</p> <p>work aims at assessing the capability of passive remote-sensed measurements such as aerosol optical depth (AOD) to monitor the surface dust concentration during the dry season in the <span class="hlt">Sahel</span> region (West Africa). We processed continuous measurements of AODs and surface concentrations for the period (2006-2010) in Banizoumbou (Niger) and Cinzana (Mali). In order to account for the influence of meteorological condition on the relationship between PM10 surface concentration and AOD, we decomposed the mesoscale meteorological fields surrounding the stations into five weather types having similar 3-dimensional atmospheric characteristics. This classification was obtained by a clustering method based on nonlinear artificial neural networks, the so-called self-organizing map. The weather types were identified by processing tridimensional fields of meridional and zonal winds and air temperature obtained from European Centre for Medium-Range Weather Forecasts (ECMWF) model output centered on each measurement station. Five similar weather types have been identified at the two stations. Three of them are associated with the Harmattan flux; the other two correspond to northward inflow of the monsoon flow at the beginning or the end of the dry season. An improved relationship has been found between the surface PM10 concentrations and the AOD by using a dedicated statistical relationship for each weather type. The performances of the statistical inversion computed on the test data sets show satisfactory skills for most of the classes, much better than a linear regression. This should permit the inversion of the mineral dust concentration from AODs derived from satellite observations over the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B8..313B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B8..313B"><span>Long-Term Monitoring of Water Dynamics in the <span class="hlt">Sahel</span> Region Using the Multi-Sar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bertram, A.; Wendleder, A.; Schmitt, A.; Huber, M.</p> <p>2016-06-01</p> <p>Fresh water is a scarce resource in the West-African <span class="hlt">Sahel</span> region, seasonally influenced by droughts and floods. Particularly in terms of climate change, the importance of wetlands increases for flora, fauna, human population, agriculture, livestock and fishery. Hence, access to open water is a key factor. Long-term monitoring of water dynamics is of great importance, especially with regard to the spatio-temporal extend of wetlands and drylands. It can predict future trends and facilitate the development of adequate management strategies. Lake Tabalak, a Ramsar wetland of international importance, is one of the most significant ponds in Niger and a refuge for waterbirds. Nevertheless, human population growth increased the pressure on this ecosystem, which is now degrading for all uses. The main objective of the study is a long-term monitoring of the Lake Tabalak's water dynamics to delineate permanent and seasonal water bodies, using weather- and daytime-independent multi-sensor and multi-temporal Synthetic Aperture Radar (SAR) data available for the study area. Data of the following sensors from 1993 until 2016 are used: Sentinel-1A, TerraSARX, ALOS PALSAR-1/2, Envisat ASAR, RADARSAT-1/2, and ERS-1/2. All SAR data are processed with the Multi-SAR-System, unifying the different characteristics of all above mentioned sensors in terms of geometric, radiometric and polarimetric resolution to a consistent format. The polarimetric representation in Kennaugh elements allows fusing single-polarized data acquired by older sensors with multi-polarized data acquired by current sensors. The TANH-normalization guarantees a consistent and therefore comparable description in a closed data range in terms of radiometry. The geometric aspect is solved by projecting all images to an earth-fixed coordinate system correcting the brightness by the help of the incidence angle. The elevation model used in the geocoding step is the novel global model produced by the TanDEM-X satellite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRD..113.7111C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRD..113.7111C"><span>How certain is desiccation in west African <span class="hlt">Sahel</span> rainfall (1930-1990)?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chappell, Adrian; Agnew, Clive T.</p> <p>2008-04-01</p> <p>Hypotheses for the late 1960s to 1990 period of desiccation (secular decrease in rainfall) in the west African <span class="hlt">Sahel</span> (WAS) are typically tested by comparing empirical evidence or model predictions against "observations" of Sahelian rainfall. The outcomes of those comparisons can have considerable influence on the understanding of regional and global environmental systems. Inverse-distance squared area-weighted (IDW) estimates of WAS rainfall observations are commonly aggregated over space to provide temporal patterns without uncertainty. Spatial uncertainty of WAS rainfall was determined using the median approximation sequential indicator simulation. Every year (1930-1990) 300 equally probable realizations of annual summer rainfall were produced to honor station observations, match percentiles of the observed cumulative distributions and indicator variograms and perform adequately during cross validation. More than 49% of the IDW mean annual rainfall fell outside the 5th and 95th percentiles for annual rainfall realization means. The IDW means represented an extreme realization. Uncertainty in desiccation was determined by repeatedly (100,000) sampling the annual distribution of rainfall realization means and by applying Mann-Kendall nonparametric slope detection and significance testing. All of the negative gradients for the entire period were statistically significant. None of the negative gradients for the expected desiccation period were statistically significant. The results support the presence of a long-term decline in annual rainfall but demonstrate that short-term desiccation (1965-1990) cannot be detected. Estimates of uncertainty for precipitation and other climate variables in this or other regions, or across the globe, are essential for the rigorous detection of spatial patterns and time series trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JHyd..375..190B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JHyd..375..190B"><span>Towards an understanding of coupled physical and biological processes in the cultivated <span class="hlt">Sahel</span> - 2. Vegetation and carbon dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boulain, N.; Cappelaere, B.; Ramier, D.; Issoufou, H. B. A.; Halilou, O.; Seghieri, J.; Guillemin, F.; Oï, M.; Gignoux, J.; Timouk, F.</p> <p>2009-08-01</p> <p>SummaryThis paper analyses the dynamics of vegetation and carbon during the West African monsoon season, for millet crop and fallow vegetation covers in the cultivated area of the <span class="hlt">Sahel</span>. Comparing these two dominant land cover types informs on the impact of cultivation on productivity and carbon fluxes. Biomass, leaf area index (LAI) and carbon fluxes were monitored over a 2-year period for these two vegetation systems in the Wankama catchment of the AMMA (African monsoon multidisciplinary analyses) experimental super-site in West Niger. Carbon fluxes and water use efficiency observed at the field scale are confronted with ecophysiological measurements (photosynthetic response to light, and relation of water use efficiency to air humidity) made at the leaf scale for the dominant plant species in the two vegetation systems. The two rainy seasons monitored were dissimilar with respect to rain patterns, reflecting some of the interannual variability. Distinct responses in vegetation development and in carbon dynamics were observed between the two vegetation systems. Vegetation development in the fallow was found to depend more on rainfall distribution along the season than on its starting date. A quite opposite behaviour was observed for the crop vegetation: the date of first rain appears as a principal factor of millet growth. Carbon flux exchanges were well correlated to vegetation development. High responses of photosynthesis to light were observed for the dominant herbaceous and shrub species of the fallow at the leaf and field scales. Millet showed high response at the leaf scale, but a much lesser response at the field scale. This pattern, also observed for water use efficiency, is to be related to the low density of the millet cover. A simple LAI-based model for scaling up the photosynthetic response from leaf to field scale was found quite successful for the fallow, but was less conclusive for the crop, due to spatial variability of LAI. Time/space variations</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29248187','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29248187"><span>Early transfusion on battlefield before admission to role 2: A preliminary observational study during "Barkhane" operation in <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vitalis, V; Carfantan, C; Montcriol, A; Peyrefitte, S; Luft, A; Pouget, T; Sailliol, A; Ausset, S; Meaudre, E; Bordes, J</p> <p>2018-05-01</p> <p>Haemorrage is the leading cause of death after combat related injuries and bleeding management is the cornerstone of management of these casualties. French armed forces are deployed in Barkhane operation in the <span class="hlt">Sahel</span>-Saharan Strip who represents an immense area. Since this constraint implies evacuation times beyond doctrinal timelines, an institutional decision has been made to deploy blood products on the battlefield and transfuse casualties before role 2 admission if indicated. The purpose of this study was to evaluate the transfusion practices on battlefield during the first year following the implementation of this policy. Prospective collection of data about combat related casualties categorized alpha evacuated to a role 2. Battlefield transfusion was defined as any transfusion of blood product (red blood cells, plasma, whole blood) performed by role 1 or Medevac team before admission at a role 2. Patients' characteristics, battlefield transfusions' characteristics and complications were analysed. During the one year study, a total of 29 alpha casualties were included during the period study. Twenty-eight could be analysed, 7/28 (25%) being transfused on battlefield, representing a total of 22 transfusion episodes. The most frequently blood product transfused was French lyophilized plasma (FLYP). Most of transfusion episodes occurred during medevac. Compared to non-battlefield transfused casualties, battlefield transfused casualties suffered more wounded anatomical regions (median number of 3 versus 2, p = 0.04), had a higher injury severity score (median ISS of 45 versus 25, p = 0,01) and were more often transfused at role 2, received more plasma units and whole blood units. There was no difference in evacuation time to role 2 between patients transfused on battlefield and non-transfused patients. There was no complication related to battlefield transfusions. Blood products transfusion onset on battlefield ranged from 75 min to 192 min after</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BGD....1111785D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BGD....1111785D"><span>Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in <span class="hlt">Sahel</span> rangeland (Mali)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delon, C.; Mougin, E.; Serça, D.; Grippa, M.; Hiernaux, P.; Diawara, M.; Galy-Lacaux, C.; Kergoat, L.</p> <p>2014-08-01</p> <p>This work is an attempt to provide seasonal variation of biogenic NO emission fluxes in a sahelian rangeland in Mali (Agoufou, 15.34° N, 1.48° W) for years 2004, 2005, 2006, 2007 and 2008. Indeed, NO is one of the most important precursor for tropospheric ozone, and the contribution of the <span class="hlt">Sahel</span> region in emitting NO is no more considered as negligible. The link between NO production in the soil and NO release to the atmosphere is investigated in this study, by taking into account vegetation litter production and degradation, microbial processes in the soil, emission fluxes, and environmental variables influencing these processes, using a coupled vegetation-litter decomposition-emission model. This model includes the Sahelian-Transpiration-Evaporation-Productivity (STEP) model for the simulation of herbaceous, tree leaf and fecal masses, the GENDEC model (GENeral DEComposition) for the simulation of the buried litter decomposition, and the NO emission model for the simulation of the NO flux to the atmosphere. Physical parameters (soil moisture and temperature, wind speed, sand percentage) which affect substrate diffusion and oxygen supply in the soil and influence the microbial activity, and biogeochemical parameters (pH and fertilization rate related to N content) are necessary to simulate the NO flux. The reliability of the simulated parameters is checked, in order to assess the robustness of the simulated NO flux. Simulated yearly average of NO flux ranges from 0.69 to 1.09 kg(N) ha-1 yr-1, and wet season average ranges from 1.16 to 2.08 kg(N) ha-1 yr-1. These results are in the same order as previous measurements made in several sites where the vegetation and the soil are comparable to the ones in Agoufou. This coupled vegetation-litter decomposition-emission model could be generalized at the scale of the <span class="hlt">Sahel</span> region, and provide information where little data is available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGD....12.1155D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGD....12.1155D"><span>Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in <span class="hlt">Sahel</span> rangeland (Mali)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delon, C.; Mougin, E.; Serça, D.; Grippa, M.; Hiernaux, P.; Diawara, M.; Galy-Lacaux, C.; Kergoat, L.</p> <p>2015-01-01</p> <p>This work is an attempt to provide seasonal variation of biogenic NO emission fluxes in a sahelian rangeland in Mali (Agoufou, 15.34° N, 1.48° W) for years 2004-2008. Indeed, NO is one of the most important precursor for tropospheric ozone, and the contribution of the <span class="hlt">Sahel</span> region in emitting NO is no more considered as negligible. The link between NO production in the soil and NO release to the atmosphere is investigated in this study, by taking into account vegetation litter production and degradation, microbial processes in the soil, emission fluxes, and environmental variables influencing these processes, using a coupled vegetation-litter decomposition-emission model. This model includes the Sahelian-Transpiration-Evaporation-Productivity (STEP) model for the simulation of herbaceous, tree leaf and fecal masses, the GENDEC model (GENeral DEComposition) for the simulation of the buried litter decomposition and microbial dynamics, and the NO emission model (NOFlux) for the simulation of the NO release to the atmosphere. Physical parameters (soil moisture and temperature, wind speed, sand percentage) which affect substrate diffusion and oxygen supply in the soil and influence the microbial activity, and biogeochemical parameters (pH and fertilization rate related to N content) are necessary to simulate the NO flux. The reliability of the simulated parameters is checked, in order to assess the robustness of the simulated NO flux. Simulated yearly average of NO flux ranges from 0.66 to 0.96 kg(N) ha-1 yr-1, and wet season average ranges from 1.06 to 1.73 kg(N) ha-1 yr-1. These results are in the same order as previous measurements made in several sites where the vegetation and the soil are comparable to the ones in Agoufou. This coupled vegetation-litter decomposition-emission model could be generalized at the scale of the <span class="hlt">Sahel</span> region, and provide information where little data is available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16600327','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16600327"><span>Geochemical variations in aeolian mineral particles from the Sahara-<span class="hlt">Sahel</span> Dust Corridor.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moreno, Teresa; Querol, Xavier; Castillo, Sonia; Alastuey, Andrés; Cuevas, Emilio; Herrmann, Ludger; Mounkaila, Mohammed; Elvira, Josep; Gibbons, Wes</p> <p>2006-10-01</p> <p>The Sahara-<span class="hlt">Sahel</span> Dust Corridor runs from Chad to Mauritania and expels huge amounts of mineral aerosols into the Atlantic Ocean. Data on samples collected from Algeria, Chad, Niger, and Western Sahara illustrate how corridor dust mineralogy and chemistry relate to geological source and weathering/transport history. Dusts sourced directly from igneous and metamorphic massifs are geochemically immature, retaining soluble cations (e.g., K, Na, Rb, Sr) and accessory minerals containing HFSE (e.g., Zr, Hf, U, Th) and REE. In contrast, silicate dust chemistry in desert basins (e.g., Bodélé Depression) is influenced by a longer history of transport, physical winnowing (e.g., loss of Zr, Hf, Th), chemical leaching (e.g., loss of Na, K, Rb), and mixing with intrabasinal materials such as diatoms and evaporitic salts. Mineral aerosols blown along the corridor by the winter Harmattan winds mix these basinal and basement materials. Dusts blown into the corridor from sub-Saharan Africa during the summer monsoon source from deeply chemically weathered terrains and are therefore likely to be more kaolinitic and stripped of mobile elements (e.g., Na, K, Mg, Ca, LILE), but retain immobile and resistant elements (e.g., Zr, Hf, REE). Finally, dusts blown southwestwards into the corridor from along the Atlantic Coastal Basin will be enriched in carbonate from Mesozoic-Cenozoic marine limestones, depleted in Th, Nb, and Ta, and locally contaminated by uranium-bearing phosphate deposits.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1022744','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1022744"><span>Mali and Nigeria Should be Established as Key Regional Partners of the United States to Further Mutual Interests for Ensuring Long-Term Security and Stability in the <span class="hlt">Sahel</span> Region</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2016-06-10</p> <p>7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) U.S. Army Command and General Staff College ATTN: ATZL-SWD-GD Fort Leavenworth, KS 66027-2301...AND STABILITY IN THE <span class="hlt">SAHEL</span> REGION A thesis presented to the Faculty of the U.S. Army Command and General Staff College in partial...5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ) Bekaye Samake, MAJ 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1152B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1152B"><span>More Yield with Less Water: Increasing Water Use Efficiency by Capitalizing on the Adaptation of Native Shrubs in the Sudano-<span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bogie, Nathaniel; Bayala, Roger; Diedhiou, Ibrahima; Dick, Richard; Ghezzehei, Teamrat</p> <p>2016-04-01</p> <p>A changing climate along with human and animal population pressure can have a devastating effect on crop yields and food security in the Sudano-<span class="hlt">Sahel</span>. Agricultural solutions to address soil degradation and crop water stress are needed to combat this increasingly difficult situation. Significant differences in crop success have been observed in peanut and millet grown in association with two native evergreen shrubs Piliostigma reticulatum, and Guiera senegalensis at the sites of Nioro du Rip and Keur Matar, respectively. We investigate how farmers can increase crop productivity by capitalizing on the evolutionary adaptation of native shrubs to the harsh Sudano-Sahelian environment as well as the physical mechanisms at work in the system that can lead to more robust yields. Research plots at Keur Matar Arame with no fertilizer added were monitored in 2013 using two soil moisture sensor networks at depths of 10, 20, 40, 60, 100, 200, and 300cm. Cropping season water use total calculated based on beginning and end of season soil moisture and seasonal precipitation data revealed that crop-only plot used 411±32 mm of water, and the crop and shrub plot used 439±42 mm of water. Taking into account the quantity of crop biomass produced and neglecting the shrub biomass produced, the crop and shrub plot had a water use efficiency of 1.60 kg ha-1 mm-1 and the crop only plot had 0.269 kg ha-1 mm-1. Water status was measured three times throughout the season on millet leaves and revealed no significant trends. Handheld NDVI readings revealed significantly higher NDVI values in crop and shrub plots at all measurement dates. These findings build on work that was completed in 2004 at the site, but further increases in crop yields have been shown. Increasing water use efficiency by over 500% can be a great advantage in years of limited water availability such as 2013. Using even the limited resources that farmers possess, this agroforestry technique can be expanded over wide</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3750695','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3750695"><span>Incorporating the effects of humidity in a mechanistic model of Anopheles gambiae mosquito population dynamics in the <span class="hlt">Sahel</span> region of Africa</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2013-01-01</p> <p>Background Low levels of relative humidity are known to decrease the lifespan of mosquitoes. However, most current models of malaria transmission do not account for the effects of relative humidity on mosquito survival. In the <span class="hlt">Sahel</span>, where relative humidity drops to levels <20% for several months of the year, we expect relative humidity to play a significant role in shaping the seasonal profile of mosquito populations. Here, we present a new formulation for Anopheles gambiae sensu lato (s.l.) mosquito survival as a function of temperature and relative humidity and investigate the effect of humidity on simulated mosquito populations. Methods Using existing observations on relationships between temperature, relative humidity and mosquito longevity, we developed a new equation for mosquito survival as a function of temperature and relative humidity. We collected simultaneous field observations on temperature, wind, relative humidity, and anopheline mosquito populations for two villages from the <span class="hlt">Sahel</span> region of Africa, which are presented in this paper. We apply this equation to the environmental data and conduct numerical simulations of mosquito populations using the Hydrology, Entomology and Malaria Transmission Simulator (HYDREMATS). Results Relative humidity drops to levels that are uncomfortable for mosquitoes at the end of the rainy season. In one village, Banizoumbou, water pools dried up and interrupted mosquito breeding shortly after the end of the rainy season. In this case, relative humidity had little effect on the mosquito population. However, in the other village, Zindarou, the relatively shallow water table led to water pools that persisted several months beyond the end of the rainy season. In this case, the decrease in mosquito survival due to relative humidity improved the model’s ability to reproduce the seasonal pattern of observed mosquito abundance. Conclusions We proposed a new equation to describe Anopheles gambiae s.l. mosquito survival as a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ThApC.117..485L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ThApC.117..485L"><span>Seasonal forecasts in the <span class="hlt">Sahel</span> region: the use of rainfall-based predictive variables</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lodoun, Tiganadaba; Sanon, Moussa; Giannini, Alessandra; Traoré, Pierre Sibiry; Somé, Léopold; Rasolodimby, Jeanne Millogo</p> <p>2014-08-01</p> <p>In the <span class="hlt">Sahel</span> region, seasonal predictions are crucial to alleviate the impacts of climate variability on populations' livelihoods. Agricultural planning (e.g., decisions about sowing date, fertilizer application date, and choice of crop or cultivar) is based on empirical predictive indices whose accuracy to date has not been scientifically proven. This paper attempts to statistically test whether the pattern of rainfall distribution over the May-July period contributes to predicting the real onset date and the nature (wet or dry) of the rainy season, as farmers believe. To that end, we considered historical records of daily rainfall from 51 stations spanning the period 1920-2008 and the different agro-climatic zones in Burkina Faso. We performed (1) principal component analysis to identify climatic zones, based on the patterns of intra-seasonal rainfall, (2) and linear discriminant analysis to find the best rainfall-based variables to distinguish between real and false onset dates of the rainy season, and between wet and dry seasons in each climatic zone. A total of nine climatic zones were identified in each of which, based on rainfall records from May to July, we derived linear discriminant functions to correctly predict the nature of a potential onset date of the rainy season (real or false) and that of the rainy season (dry or wet) in at least three cases out of five. These functions should contribute to alleviating the negative impacts of climate variability in the different climatic zones of Burkina Faso.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017HESS...21.4591G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017HESS...21.4591G"><span>The paradoxical evolution of runoff in the pastoral <span class="hlt">Sahel</span>: analysis of the hydrological changes over the Agoufou watershed (Mali) using the KINEROS-2 model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gal, Laetitia; Grippa, Manuela; Hiernaux, Pierre; Pons, Léa; Kergoat, Laurent</p> <p>2017-09-01</p> <p>In recent decades, the <span class="hlt">Sahel</span> has witnessed a paradoxical increase in surface water despite a general precipitation decline. This phenomenon, commonly referred to as <q>the Sahelian paradox</q>, is not completely understood yet. The role of cropland expansion due to the increasing food demand by a growing population has been often put forward to explain this situation for the cultivated <span class="hlt">Sahel</span>. However, this hypothesis does not hold in pastoral areas where the same phenomenon is observed. Several other processes, such as the degradation of natural vegetation following the major droughts of the 1970s and the 1980s, the development of crusted topsoils, the intensification of the rainfall regime and the development of the drainage network, have been suggested to account for this situation. In this paper, a modeling approach is proposed to explore, quantify and rank different processes that could be at play in pastoral <span class="hlt">Sahel</span>. The kinematic runoff and erosion model (KINEROS-2) is applied to the Agoufou watershed (245 km2), in the Gourma region in Mali, which underwent a significant increase of surface runoff during the last 60 years. Two periods are simulated, the <q>past</q> case (1960-1975) preceding the Sahelian drought and the <q>present</q> case (2000-2015). Surface hydrology and land cover characteristics for these two periods are derived by the analysis of aerial photographs, available in 1956, and high-resolution remote sensing images in 2011. The major changes identified are (1) a partial crusting of isolated dunes, (2) an increase of drainage network density, (3) a marked decrease in vegetation with the nonrecovery of tiger bush and vegetation growing on shallow sandy soils, and (4) important changes in soil properties with the apparition of impervious soils instead of shallow sandy soil. The KINEROS-2 model was parameterized to simulate these changes in combination or independently. The results obtained by this model display a significant increase in annual</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC13I0854A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC13I0854A"><span>Diagnosis of vegetation recovery within herbaceous sub-systems in the West African <span class="hlt">Sahel</span> Region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anchang, J.; Hanan, N. P.; Prihodko, L.; Sathyachandran, S. K.; Ji, W.; Ross, C. W.</p> <p>2017-12-01</p> <p>The West African <span class="hlt">Sahel</span> (WAS) region is an extensive water limited environment that features a delicate balance of herbaceous and woody vegetation sub systems. These play an important role in the cycling of carbon while also supporting the dominant agro-pastoral human activities in the region. Quantifying the temporal trends in vegetation with regard to these two systems is therefore very important in assessing resource sustainability and food security. In water limited areas, rainfall is a primary driver of vegetation productivity and past watershed scale studies in the WAS region have shown that increase in the slope of the productivity-to-rainfall relationship is indicative of increasing cover and density of herbaceous plants. Given the importance of grazing resources to the region, we perform a wall-to-wall pixel based analysis of changing short-term vegetation sensitivity to changing annual rainfall (hereafter referred to as dS) to examine temporal trends in herbaceous vegetation health. Results indicate that 43% of the Sahelian region has experienced changes (P < 0.05) in herbaceous vegetation (dS). Areas with significant increases in dS are well distributed across the region, but with major concentrations in North-Central Senegal, South Western and Central Mali and South Western Niger. Positive dS is indicative of herbaceous vegetation recovery, in response to changing management and rainfall conditions that promote long-term herbaceous community recovery following degradation during the 1970-1980s droughts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3087796','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3087796"><span>Selection for Earlier Flowering Crop Associated with Climatic Variations in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vigouroux, Yves; Mariac, Cédric; De Mita, Stéphane; Pham, Jean-Louis; Gérard, Bruno; Kapran, Issoufou; Sagnard, Fabrice; Deu, Monique; Chantereau, Jacques; Ali, Abdou; Ndjeunga, Jupiter; Luong, Viviane; Thuillet, Anne-Céline; Saïdou, Abdoul-Aziz; Bezançon, Gilles</p> <p>2011-01-01</p> <p>Climate changes will have an impact on food production and will require costly adaptive responses. Adapting to a changing environment will be particularly challenging in sub-Saharan Africa where climate change is expected to have a major impact. However, one important phenomenon that is often overlooked and is poorly documented is the ability of agro-systems to rapidly adapt to environmental variations. Such an adaptation could proceed by the adoption of new varieties or by the adaptation of varieties to a changing environment. In this study, we analyzed these two processes in one of the driest agro-ecosystems in Africa, the <span class="hlt">Sahel</span>. We performed a detailed study in Niger where pearl millet is the main crop and covers 65% of the cultivated area. To assess how the agro-system is responding to recent recurrent drought, we analyzed samples of pearl millet landraces collected in the same villages in 1976 and 2003 throughout the entire cultivated area of Niger. We studied phenological and morphological differences in the 1976 and 2003 collections by comparing them over three cropping seasons in a common garden experiment. We found no major changes in the main cultivated varieties or in their genetic diversity. However, we observed a significant shift in adaptive traits. Compared to the 1976 samples, samples collected in 2003 displayed a shorter lifecycle, and a reduction in plant and spike size. We also found that an early flowering allele at the PHYC locus increased in frequency between 1976 and 2003. The increase exceeded the effect of drift and sampling, suggesting a direct effect of selection for earliness on this gene. We conclude that recurrent drought can lead to selection for earlier flowering in a major Sahelian crop. Surprisingly, these results suggest that diffusion of crop varieties is not the main driver of short term adaptation to climatic variation. PMID:21573243</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015BGeo...12.3253D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015BGeo...12.3253D"><span>Modelling the effect of soil moisture and organic matter degradation on biogenic NO emissions from soils in <span class="hlt">Sahel</span> rangeland (Mali)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delon, C.; Mougin, E.; Serça, D.; Grippa, M.; Hiernaux, P.; Diawara, M.; Galy-Lacaux, C.; Kergoat, L.</p> <p>2015-06-01</p> <p>This work is an attempt to provide seasonal variation of biogenic NO emission fluxes in a Sahelian rangeland in Mali (Agoufou, 15.34° N, 1.48° W) for years 2004, 2005, 2006, 2007 and 2008. Indeed, NO is one of the most important precursors for tropospheric ozone, and previous studies have shown that arid areas potentially display significant NO emissions (due to both biotic and abiotic processes). Previous campaigns in the <span class="hlt">Sahel</span> suggest that the contribution of this region in emitting NO is no longer considered as negligible. However, very few data are available in this region, therefore this study focuses on model development. The link between NO production in the soil and NO release to the atmosphere is investigated in this modelling study, by taking into account vegetation litter production and degradation, microbial processes in the soil, emission fluxes, and environmental variables influencing these processes, using a coupled vegetation-litter decomposition-emission model. This model includes the Sahelian Transpiration Evaporation and Productivity (STEP) model for the simulation of herbaceous, tree leaf and faecal masses, the GENDEC model (GENeral DEComposition) for the simulation of the buried litter decomposition and microbial dynamics, and the NO emission model (NOFlux) for the simulation of the NO release to the atmosphere. Physical parameters (soil moisture and temperature, wind speed, sand percentage) which affect substrate diffusion and oxygen supply in the soil and influence the microbial activity, and biogeochemical parameters (pH and fertilization rate related to N content) are necessary to simulate the NO flux. The reliability of the simulated parameters is checked, in order to assess the robustness of the simulated NO flux. Simulated yearly average of NO flux ranges from 2.09 to 3.04 ng(N) m-2 s-1 (0.66 to 0.96 kg(N) ha-1 yr-1), and wet season average ranges from 3.36 to 5.48 ng(N) m-2 s-1 (1.06 to 1.73 kg(N) ha-1 yr-1). These results are of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26630693','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26630693"><span>Phenotypic variations in osmotic lysis of <span class="hlt">Sahel</span> goat erythrocytes in non-ionic glucose media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Igbokwe, Nanacha Afifi; Igbokwe, Ikechukwu Onyebuchi</p> <p>2016-03-01</p> <p>Erythrocyte osmotic lysis in deionised glucose media is regulated by glucose influx, cation efflux, and changes in cell volume after water diffusion. Transmembrane fluxes may be affected by varied expression of glucose transporter protein and susceptibility of membrane proteins to glucose-induced glycosylation and oxidation in various physiologic states. Variations in haemolysis of <span class="hlt">Sahel</span> goat erythrocytes after incubation in hyposmotic non-ionic glucose media, associated with sex, age, late pregnancy, and lactation, were investigated. The osmotic fragility curve in glucose media was sigmoidal with erythrocytes from goats in late pregnancy (PRE) or lactation (LAC) or from kid (KGT) or middle-aged (MGT) goats. Non-sigmoidal phenotype occurred in yearlings (YGT) and old (OGT) goats. The composite fragility phenotype for males and non-pregnant dry (NPD) females was non-sigmoidal. Erythrocytes with non-sigmoidal curves were more stable than those with sigmoidal curves because of inflectional shift of the curve to the left. Erythrocytes tended to be more fragile with male than female sex, KGT and MGT than YGT and OGT, and LAC and PRE than NPD. Thus, sex, age, pregnancy, and lactation affected the haemolytic pattern of goat erythrocytes in glucose media. The physiologic state of the goat affected the in vitro interaction of glucose with erythrocytes, causing variations in osmotic stability with variants of fragility phenotype. Variations in the effect of high extracellular glucose concentrations on the functions of membrane-associated glucose transporter, aquaporins, and the cation cotransporter were presumed to be relevant in regulating the physical properties of goat erythrocytes under osmotic stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H43G1608B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H43G1608B"><span>Role of native shrubs of the <span class="hlt">Sahel</span> in mitigating water and nutrient stresses of agricultural crops</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayala, R.; Ghezzehei, T. A.; Bogie, N. A.; Diedhiou, I.; Dick, R.</p> <p>2015-12-01</p> <p>In the semi arid zone of the <span class="hlt">Sahel</span> native woody shrubs are present in many farmers' fields. The native density of these shrubs is fairly low at around 200 to 300 individuals per hectare. An ongoing study in the Peanut Basin, Senegal has shown a vast improvement in crop yields when annual food crops are planted with the shrub Guiera senegalensis, especially in years of low or irregular precipitation. Shrubs in field plots established in 2003 where a rotation of peanuts and millet are grown are planted at a much higher density of 1500-1830 individuals per hectare. In order to increase the density of shrubs on the landscape, the shrubs must be cultivated. We monitored soil moisture, soil temperature, and growth of recently transplanted individuals at a field station in Thies, Senegal.This study seeks to determine the growth characteristics and water use of young shrubs in order to inform possible future plantations of the shrubs in a more intensely managed agroecosystem. If this technique of intercropping is to be expanded we must not exceed the carrying capacity of the landscape. In vulnerable ecosystems where natural resources are scarce and farming inputs are low, we must work to determine ways of exploiting the adaptation of local agroecosystems to increase the sustainability of agriculture in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930063608&hterms=shrubs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dshrubs','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930063608&hterms=shrubs&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dshrubs"><span>Testing the Li-Strahler four-component canopy reflectance model in the HAPEX-<span class="hlt">Sahel</span> shrub savanna sites using ground reflectance data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Franklin, J.; Duncan, J.</p> <p>1992-01-01</p> <p>The rate at which a light field decays in water is characterized by the diffuse attenuation coefficient k. The Li-Strahler discrete-object canopy reflectance model was tested in two sites, a shrub grass savanna and a degraded shrub savanna on bare soil, in the proposed HAPEX (Hydrologic Atmospheric Pilot Experiment) II/<span class="hlt">Sahel</span> study area in Niger, West Africa. Average site reflectance was predicted for each site from the reflectances and cover proportions of four components: shrub canopy, background (soil or grass and soil), shaded canopy, and shaded background. Component reflectances were sampled in the SPOT wavebands using a hand-held radiometer. Predicted reflectance was compared to average site reflectance measured using the same radiometer mounted on a backpack with measurements recorded every 5 m along two 1-km transects, also in the SPOT (Systeme Probatoire d'Observation de la Terre) bands. Measurements and predictions were made for each of the three days during the summer growing season, approximately two weeks apart. Red, near infrared reflectance, and the NDVI (normalized difference vegetation index) were all predicted with a high degree of accuracy for the shrub/grass site and with reasonable accuracy for the degraded shrub site.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A12D..08B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A12D..08B"><span>Characterization of the impact of land degradation in the <span class="hlt">Sahel</span> on the West African monsoon using an ensemble of climate models from the WAMME project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boone, A. A.; Xue, Y.; Ruth, C.; De Sales, F.; Hagos, S.; Mahanama, S. P. P.; Schiro, K.; Song, G.; Wang, G.; Koster, R. D.; Mechoso, C. R.</p> <p>2014-12-01</p> <p>There is increasing evidence from numerical studies that anthropogenic land-use and land-cover changes (LULCC) can potentially induce significant variations on the regional scale climate. However, the magnitude of these variations likely depends on the local strength of the coupling between the surface and the atmosphere, the magnitude of the surface biophysical changes and how the key processes linking the surface with the atmosphere are parameterized within a particular model framework. One key hot-spot which has received considerable attention is the Sahelian region of West Africa, for which numerous studies have reported a significant increase in anthropogenic pressure on the already limited natural resources in this region, notably in terms of land use conversion and degradation. Thus, there is a pressing need to better understand the impacts of potential land degradation on the West African Monsoon (WAM) system. One of the main goals of the West African Monsoon Modeling andEvaluation project phase 2 (WAMMEII) is to provide basic understandingof LULCC on the regional climate over West Africa, and to evaluate thesensitivity of the seasonal variability of the WAM to LULCC. Theprescribed LULCC is based on recent 50 year period which represents amaximum feasible degradation scenario. In the current study, the LULCCis applied to five state of the art global climate models over afive-year period. The imposed LULCC results in a model-average 5-7%increase in surface albedo: the corresponding lower surface netradiation mainly results in a significant reduction in surfaceevaporation (upwards of 1 mm per day over a large part of the <span class="hlt">Sahel</span>)which leads to less convective heating of the atmosphere, lowermoisture convergence, increased subsidence and reduced cloud coverover the LULCC zone. The overall impact can be characterized as asubstantial drought effect resulting in a reduction in annual rainfallof 20-40% in the <span class="hlt">Sahel</span> and a southward shift of the monsoon. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12344768','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12344768"><span>[Integration of demographic variables into development plans in the <span class="hlt">Sahel</span>].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wane, H R</p> <p>1992-07-01</p> <p>A founding principle of the Program of Action of N'Djamena is the interdependence of population and development and the need for development strategies to take demographic factors into account. The concept of integration of population variables into development has evolved since its introduction in the 1974 World Population Plan of Action from a simple description of population size, growth rates, and distribution to a stress on harmonizing population policies and development policies with macroeconomic variables. The essence of the concept is the consideration given by development policies and programs to the interrelations between population, resources, the environment, and development factors. Population variables and goals should ideally be treated as endogenous variables in development planning, but in practice the extreme complexity of such a systematic approach limits its ability to be made operational. Usually the most crucial problems only are included. Integrated planning is composed of explicit or implicit population policies intended to influence demographic variables and of socioeconomic policies intended to adapt to demographic change. In the <span class="hlt">Sahel</span>, only Senegal, Burkina Faso, and Mali have formal population policies, but around 1980 several countries of the region began to show interest in influencing demographic variables as they did economic variables. Fundamental principles for developing an integration strategy can be applied regardless or whether the plan is based on projections, analysis of interaction of a demographic variable with factors specific to a sector, or a monosectorial or multisectorial demoeconomic planning model. Demographic data is used more frequently in diagnosing problems than in developing projections or formulating objectives. The level of disaggregation of demographic projections and estimates tends to be low, despite the great potential utility of demographic projections in planning. Demographic projections can be useful</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhDT........32D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhDT........32D"><span>Land Cover Land Use change and soil organic carbon under climate variability in the semi-arid West African <span class="hlt">Sahel</span> (1960-2050)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dieye, Amadou M.</p> <p></p> <p>Land Cover Land Use (LCLU) change affects land surface processes recognized to influence climate change at local, national and global levels. Soil organic carbon is a key component for the functioning of agro-ecosystems and has a direct effect on the physical, chemical and biological characteristics of the soil. The capacity to model and project LCLU change is of considerable interest for mitigation and adaptation measures in response to climate change. A combination of remote sensing analyses, qualitative social survey techniques, and biogeochemical modeling was used to study the relationships between climate change, LCLU change and soil organic carbon in the semi-arid rural zone of Senegal between 1960 and 2050. For this purpose, four research hypotheses were addressed. This research aims to contribute to an understanding of future land cover land use change in the semi-arid West African <span class="hlt">Sahel</span> with respect to climate variability and human activities. Its findings may provide insights to enable policy makers at local to national levels to formulate environmentally and economically adapted policy decisions. This dissertation research has to date resulted in two published and one submitted paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1410285J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1410285J"><span>Local knowledge and perception of biological soil crusts by land users in the <span class="hlt">Sahel</span> (Niger)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>J-M Ambouta, K.; Hassan Souley, B.; Malam Issa, O.; Rajot, J. L.; Mohamadou, A.</p> <p>2012-04-01</p> <p>Local knowledge, i.e. knowledge based on accumulation of observations is of great interest for many scientific fields as it can help for identification, evaluation and selection of relevant indicators and furthermore for progress through conservation goals. This study aimed at gathering and understanding the local knowledge and perception of biological soil crusts (BSC) by users of land, pastoralists that cross the <span class="hlt">Sahel</span> and sedentary farmers. The methodological approach is based on a semi-direct surveys conducted on a north-south rainfall gradient (350 to 650 mm/year) including agricultural- and pastoral-dominated areas in western Niger. Denomination, formation processes, occurrence, distribution and role of biological soil crusts are among the major issues of the inquiry. The results of the surveys showed that BSC are mainly identified by the names of "Bankwado" and "Korobanda", respectively in hausa and zarma langages, what means "toad back". Other denominations varying according to region, ethnic groups and users are used. They are all related to the aspects, colors and behaviour of BSC with regard wetting and drying cycle. From the point of view of users depressed areas and land lied fallow are favourable places for the occurrence of BSC, while cultivation and observed changes in rainfall regimes represent negative factors. The formation processes of BSC are mainly related to the occurrence and the impact of rain and wind on soil surface. Their roles in protecting soil against degradation or as an indicator of soil fertility were recognised by at least 83% of farmers and breeders. This study reveals significant aspects of BSC already validated by scientific knowledge. Integrating the two forms of knowledge will help to define relevant indicators of soil surface dynamics and to perform practices to minimize farming and grazing impacts on BSCs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.H33F1700B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.H33F1700B"><span>Simulation of the Impact of Climate Variability on Malaria Transmission in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bomblies, A.; Eltahir, E.; Duchemin, J.</p> <p>2007-12-01</p> <p>A coupled hydrology and entomology model for simulation of malaria transmission and malaria transmitting mosquito population dynamics is presented. Model development and validation is done using field data and observations collected at Banizoumbou and Zindarou, Niger spanning three wet seasons, from 2005 through 2007. The primary model objective is the accurate determination of climate variability effects on village scale malaria transmission. Malaria transmission dependence on climate variables is highly nonlinear and complex. Temperature and humidity affect mosquito longevity, temperature controls parasite development rates in the mosquito as well as subadult mosquito development rates, and precipitation determines the formation and persistence of adequate breeding pools. Moreover, unsaturated zone hydrology influences overland flow, and climate controlled evapotranspiration rates and root zone uptake therefore also influence breeding pool formation. High resolution distributed hydrologic simulation allows representation of the small-scale ephemeral pools that constitute the primary habitat of Anopheles gambiae mosquitoes, the dominant malaria vectors in the Niger <span class="hlt">Sahel</span>. Remotely sensed soil type, vegetation type, and microtopography rasters are used to assign the distributed parameter fields for simulation of the land surface hydrologic response to precipitation and runoff generation. Predicted runoff from each cell flows overland and into topographic depressions, with explicit representation of infiltration and evapotranspiration. The model's entomology component interacts with simulated pools. Subadult (aquatic stage) mosquito breeding is simulated in the pools, and water temperature dependent stage advancement rates regulate adult mosquito emergence into the model domain. Once emerged, adult mosquitoes are tracked as independent individual agents that interact with their immediate environment. Attributes relevant to malaria transmission such as gonotrophic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70157359','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70157359"><span>Re-greening the <span class="hlt">Sahel</span>: farmer-led innovation in Burkina Faso and Niger</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Reij, Chris; Smale, Melinda; Tappan, G. Gray; Spielman, David J.; Pandya-Lorch, Rajul</p> <p>2009-01-01</p> <p> did 30 years ago. These findings suggest a human and environmental success story at a scale not seen anywhere else in Africa. The re-greening of the <span class="hlt">Sahel</span> began when local farmers’ practices were rediscovered and enhanced in simple, low-cost ways by innovative farmers and nongovernmental organizations. An evolving coalition of local, national, and international actors then enabled large-scale diffusion and continued use of these improved practices where they benefited farmers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7834Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7834Z"><span>Satellite-based observations of rain-induced NOx emissions from soils around Lake Chad in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zörner, Jan; Penning de Vries, Marloes; Dörner, Steffen; Sihler, Holger; Beirle, Steffen; Wagner, Thomas</p> <p>2017-04-01</p> <p>Rain-induced emission pulses of NOx (≡ NO + NO2) from soils have been observed in many semi-arid regions over the world. They are induced by the first precipitation of the wet season and are mainly caused by the sudden re-activation of microbes in the soil releasing reactive nitrogen. In this study, a single intense event of pulsed NOx emissions from soils around Lake Chad is investigated. This is achieved by analysing daily tropospheric NO2 vertical column densities (VCDs) as observed by the satellite-based OMI instrument together with other satellite and model data on precipitation, lightning, fire and wind. The study region of Lake Chad and its ecosystems are indispensable to life in the <span class="hlt">Sahel</span> region. Climate variability and unsustainable water utilization, however, caused a drastic decrease in the lakes' surface area which, in turn, lead to extensive land cover changes converting former lake area to shrub land and fertile farm land. The results indicate that the region of Lake Chad does not only show consistent enhancements in average NO2 VCDs in the early months of the wet season compared to its surrounding desert but also exhibits particularly strong NOx emissions shortly after a single large-scale precipitation event in June 2007. NO2 VCDs measured 14 hours after this precipitation event show strong enhancements (2.5*1015 molecules cm-2) compared to the seasonal background VCDs and, moreover, represent the highest detected NO2 VCDs of the entire year. Detailed analysis of potential contributors to the observed NO2 VCDs strongly indicate that fire, lightning and retrieval artefacts cannot explain the NO2 pulse. The estimated emission flux from the soil, calculated based on mass balance, amounts to about 32.3 ng N m-2 s-1, which corresponds to about 65 tonnes of nitrogen released to the atmosphere within one day.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613244L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613244L"><span>Towards a parameterization of convective wind gusts in <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Largeron, Yann; Guichard, Françoise; Bouniol, Dominique; Couvreux, Fleur; Birch, Cathryn; Beucher, Florent</p> <p>2014-05-01</p> <p>] who focused on the wet tropical Pacific region, and linked wind gusts to convective precipitation rates alone, here, we also analyse the subgrid wind distribution during convective events, and quantify the statistical moments (variance, skewness and kurtosis) in terms of mean wind speed and convective indexes such as DCAPE. Next step of the work will be to formulate a parameterization of the cold pool convective gust from those probability density functions and analytical formulaes obtained from basic energy budget models. References : [Carslaw et al., 2010] A review of natural aerosol interactions and feedbacks within the earth system. Atmospheric Chemistry and Physics, 10(4):1701{1737. [Engelstaedter et al., 2006] North african dust emissions and transport. Earth-Science Reviews, 79(1):73{100. [Knippertz and Todd, 2012] Mineral dust aerosols over the sahara: Meteorological controls on emission and transport and implications for modeling. Reviews of Geophysics, 50(1). [Marsham et al., 2011] The importance of the representation of deep convection for modeled dust-generating winds over west africa during summer.Geophysical Research Letters, 38(16). [Marticorena and Bergametti, 1995] Modeling the atmospheric dust cycle: 1. design of a soil-derived dust emission scheme. Journal of Geophysical Research, 100(D8):16415{16. [Menut, 2008] Sensitivity of hourly saharan dust emissions to ncep and ecmwf modeled wind speed. Journal of Geophysical Research: Atmospheres (1984{2012), 113(D16). [Pierre et al., 2012] Impact of vegetation and soil moisture seasonal dynamics on dust emissions over the <span class="hlt">sahel</span>. Journal of Geophysical Research: Atmospheres (1984{2012), 117(D6). [Redelsperger et al., 2000] A parameterization of mesoscale enhancement of surface fluxes for large-scale models. Journal of climate, 13(2):402{421.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC41B0965S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC41B0965S"><span>Evaluation of CMIP5 models in the context of food security assessments in <span class="hlt">Sahel</span> and Eastern Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shukla, S.; Funk, C. C.; Dettinger, M. D.; Robertson, F. R.</p> <p>2012-12-01</p> <p>Global climate change will adversely impact agricultural production in many African countries, mainly in the <span class="hlt">Sahel</span> region and Eastern Africa that are already considered food insecure regions. The impacts of climate change will be particularly severe in these food insecure countries due to their high dependence on domestic agriculture production, rapid population growth, and lack of technological advances. Early planning and the targeted use of resources will therefore be critical to informing and motivating climate change adaptation actions that can save lives and mitigate economic losses. We seek to use Climate Model Intercomparison Project Phase-5 (CMIP5) global climate model projections to assess and attribute food and water security conditions in the above mentioned regions over next two decades or so. As a first order of business, however, we need to understand how the different models represent the tropical ocean response to anthropogenic warming. We pursue this question through an evaluation of the performance of eight different coupled ocean-atmosphere models under the conditions of the 'historical' experiment. The historical experiment forces the simulations with observed 1850-2005 greenhouse gas, aerosol and land cover. While all the models show substantial warming of the tropical oceans, the pattern and atmospheric response to that warming varies substantially. This analysis suggests that the Community Climate System Model (CCSM4) provides the most realistic 1850-2005 changes over the Indo-Pacific. We then present initial downscaling results, based on large scale forcing from the CCSM4, combined with statistical downscaling based on a combination of monthly simulations from Community Atmopsheric Model 4 (CAM4) and observed gridded time series of African rainfall and air temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983IJBm...27..143A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983IJBm...27..143A"><span>Dry season weight losses in Red Sokoto (Maradi) goats reared in the <span class="hlt">Sahel</span> region of Northeastern Nigeria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alaku, O.; Moruppa, S. M.</p> <p>1983-06-01</p> <p>Weight losses in body, carcass, skin and liver were determined during the advanced periods of the West African <span class="hlt">Sahel</span> dry seasons-December to May, when the greatest offtake of livestock for slaughter occurs. Data used were from 131 Red Sokoto goats slaughtered in the Maiduguri abbatoir from 1981 to 1982. Month of slaughter greatly influenced all traits. Weights declined as the dry season advanced with its characteristic rise in ambient temperatures. Weight losses were about 18%, 22%, 45% and 57% from December to May for body, carcass, skin and liver respectively. Percentage slaughter weights were closer to the lower uneconomical limit (45%) than to the upper (65%). As percentages of body weight, declines were from 7.07% to 4.89% and 5.55% to 2.79% for skin and liver weights respectively. Results obtained especially from the allometric regressions of liver and body weights do not quite uphold a prevailing opinion that animals slaughtered during these periods are largely immature. Correlations declined till April, being lowest (P>0.05) in March. Regression coefficients were lower and intercepts higher from January to March. Weight declines must have been largely due to starvation and dehydration. Direct and indirect effects of high ambient temperatures on growth of animals are discussed. Conditions for animal-production could be improved by settling the pastoralists and by avoiding the present necessary seasonal movement of livestock through the provision of forages and water all year round. It would also help if means of meat preservation could be devised and so enable offtake for slaughter to shift to the rainy seasons of the year.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28373743','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28373743"><span>How Does Gender Affect Sustainable Intensification of Cereal Production in the West African <span class="hlt">Sahel</span>? Evidence from Burkina Faso.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Theriault, Veronique; Smale, Melinda; Haider, Hamza</p> <p>2017-04-01</p> <p>Better understanding of gender differences in the adoption of agricultural intensification strategies is crucial for designing effective policies to close the gender gap while sustainably enhancing farm productivity. We examine gender differences in adoption rates, likelihood and determinants of adopting strategy sets that enhance yields, protect crops, and restore soils in the West African <span class="hlt">Sahel</span>, based on analysis of cereal production in Burkina Faso. Applying a multivariate probit model to a nationally representative household panel, we exploit the individual plot as unit of analysis and control for plot manager characteristics along with other covariates. Reflecting the socio-cultural context of farming combined with the economic attributes of inputs, we find that female managers of individual cereal fields are less likely than their male counterparts to adopt yield-enhancing and soil-restoring strategies, although no differential is apparent for yield-protecting strategies. More broadly, gender-disaggregated regressions demonstrate that adoption determinants differ by gender. Plot manager characteristics, including age, marital status, and access to credit or extension services do influence adoption decisions. Furthermore, household resources influence the probability of adopting intensification strategy sets differently by gender of the plot manager. Variables expressing the availability of household labor strongly influence the adoption of soil-restoring strategies by female plot managers. By contrast, household resources such as extent of livestock owned, value of non-farm income, and area planted to cotton affect the adoption choices of male plot managers. Rectifying the male bias in extension services along with improving access to credit, income, and equipment to female plot managers could contribute to sustainable agricultural intensification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1817181F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1817181F"><span>The project RUSSADE: geoethic education to face environmental problems in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ferrero, Elena; Semita, Carlo</p> <p>2016-04-01</p> <p>The hard environmental and climatic conditions in <span class="hlt">Sahel</span> countries affect life choices of younger generations, whose number continues to increase especially in large Sahelian cities, with increasing levels of discomfort and lack of adequate education and governance. To improve job opportunities and consequently the quality of life at all levels of the population, it is important to guarantee a better access to basic natural resources, such as soil, water, food. At the same time it is essential to spread awareness and knowledge of the vulnerability and of the risks that threaten natural resources, both for natural processes and for the interaction with human not sustainable activities. For this purpose, a Master course has been achieved in the project RUSSADE (Réseau des Universités Sahéliennes pour la Sécurité Alimentaire et la Durabilité Environnementale - www.russade.eu), funded in the ACP-EU Cooperation Programme in higher education (EDULINK II). The Master course includes teaching modules dedicated to these issues and takes care of their integration with other modules in the technical and application fields of the rural development. For instance, the objectives of the teaching module "Land and natural resources management" provide for the transmission of skills to diagnose types of soil degradation risks, to guide options for protection, conservation and soil restoration and to identify the components of integrated soil fertility management in particular African contexts (Subunit "Land management"); to choose appropriate methods of management and exploitation of water resources (defining the limits in the use of water resources) (Subunit "Water supply"); to propose alternative solutions concerning conventional energy resources, to know and promote the various possibilities of solar and other renewable energies production (Subunit "Using solar and other renewable energies"). Some teaching modules introduce and discuss risks related to inadequate waste</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1249437-one-year-study-diurnal-cycle-meteorology-clouds-radiation-west-african-sahel-region','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1249437-one-year-study-diurnal-cycle-meteorology-clouds-radiation-west-african-sahel-region"><span>A One-Year Study of the Diurnal Cycle of Meteorology, Clouds, and Radiation in the West African <span class="hlt">Sahel</span> Region</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Marquardt-Collow, Allison; Ghate, Virendra P.; Miller, Mark A.</p> <p></p> <p>The diurnal cycles of meteorological and radiation variables are analyzed during the wet and dry seasons over the <span class="hlt">Sahel</span> region of West Africa during 2006 using surface data collected by the Atmospheric Radiation Measurement (ARM) program’s Mobile Facility, satellite radiation measurements from the Geostationary Earth Radiation Budget (GERB) instrument aboard Meteosat 8, and reanalysis products from the National Center for Environmental Prediction (NCEP). The meteorological analysis builds upon past studies of the diurnal cycle in the region by incorporating diurnal cycles of lower tropospheric wind profiles, thermodynamic profiles, integrated water vapor and liquid water measurements, and cloud radar measurements ofmore » frequency and location. These meteorological measurements are complemented by 3-hour measurements of the diurnal cycles of the TOA and surface shortwave (SW) and longwave (LW) radiative fluxes and cloud radiative effects (CREs), and the atmospheric radiative flux divergence (RFD) and atmospheric CREs. Cirrus cloudiness during the dry season is shown to peak in coverage in the afternoon, while convective clouds during the wet season are shown to peak near dawn and have an afternoon minimum related to the rise of the Lifting Condensation Level into the Saharan Air Layer. The LW and SW RFDs and CREs exhibit diurnal cycles during both seasons, but there is a relatively small difference in the LW cycles during the two seasons (10-30 Wm^(-2) depending on the variable and time of day). Small differences in the TOA CREs during the two seasons are overwhelmed by large differences in the surface SW CREs, which exceed 100 Wm^(-2). A significant surface SW CRE during the wet season combined with a negligible TOA SW CRE produces a diurnal cycle in the atmospheric CRE that is modulated primarily by the SW surface CRE, peaks at midday at ~150 Wm^(-2), and varies widely from day to day.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27428847','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27428847"><span>Phenotypic homogeneity with minor deviance in osmotic fragility of <span class="hlt">Sahel</span> goat erythrocytes in non-ionic sucrose media during various physiologic states.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Igbokwe, Nanacha Afifi; Igbokwe, Ikechukwu Onyebuchi</p> <p>2016-11-01</p> <p>Erythrocyte swelling in non-ionic sucrose media and the subsequent osmotic lysis are influenced by mechanisms of regulatory volume adjustment and osmotic water permeability. Kinetics of transmembrane water and ion fluxes in varied physiologic states may determine the phenotype of erythrocyte osmotic fragility (EOF) and affect estimates of EOF. Effects of sex, age, late pregnancy (third trimester) and lactation on the haemolysis of <span class="hlt">Sahel</span> goat erythrocytes incubated in a series of hyposmotic non-ionic sucrose media were investigated. The fragiligram was sigmoidal in 72 (97%) out of 74 goats. Two male (3%) goats with low and high extreme median erythrocyte fragilities (MEF), had non-sigmoidal curves. The mean fragilities at osmolarities of 30-300 mosmol/L of sucrose and the mean osmolarities responsible for 10%-90% haemolysis (CH10-CH90) were not significantly different between males and non-pregnant dry (NPD) females, amongst the age groups and between pregnant or lactating and NPD female goats. The MEF (CH50) of the goats were at osmolarities of 126-252 mosmol/L (median of data: 171 mosmol/L) with a mean of 175.24±16.20 mosmol/L. Therefore, phenotypic homogeneity of EOF occurred with minor deviance, since EOF variables were not differentiated by sex, age, late pregnancy or lactation. Physiologic states of the goat did not affect EOF phenotype in non-ionic sucrose media. Sigmoidal fragility phenotype seemed to be homogeneously conserved by osmoregulatory mechanisms not partitioned by sex, age, late pregnancy or lactation, but a minor non-sigmoidal curve might have occurred due to altered erythrocyte osmotic behaviour that would require further investigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910016624&hterms=Bank+food&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DBank%2Bfood','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910016624&hterms=Bank+food&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DBank%2Bfood"><span>Specification of parameters for development of a spatial database for drought monitoring and famine early warning in the African <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rochon, Gilbert L.</p> <p>1989-01-01</p> <p>Parameters were described for spatial database to facilitate drought monitoring and famine early warning in the African <span class="hlt">Sahel</span>. The proposed system, referred to as the African Drought and Famine Information System (ADFIS) is ultimately recommended for implementation with the NASA/FEMA Spatial Analysis and Modeling System (SAMS), a GIS/Dymanic Modeling software package, currently under development. SAMS is derived from FEMA'S Integration Emergency Management Information System (IEMIS) and the Pacific Northwest Laborotory's/Engineering Topographic Laboratory's Airland Battlefield Environment (ALBE) GIS. SAMS is primarily intended for disaster planning and resource management applications with the developing countries. Sources of data for the system would include the Developing Economics Branch of the U.S. Dept. of Agriculture, the World Bank, Tulane University School of Public Health and Tropical Medicine's Famine Early Warning Systems (FEWS) Project, the USAID's Foreign Disaster Assistance Section, the World Resources Institute, the World Meterological Institute, the USGS, the UNFAO, UNICEF, and the United Nations Disaster Relief Organization (UNDRO). Satellite imagery would include decadal AVHRR imagery and Normalized Difference Vegetation Index (NDVI) values from 1981 to the present for the African continent and selected Landsat scenes for the Sudan pilot study. The system is initially conceived for the MicroVAX 2/GPX, running VMS. To facilitate comparative analysis, a global time-series database (1950 to 1987) is included for a basic set of 125 socio-economic variables per country per year. A more detailed database for the Sahelian countries includes soil type, water resources, agricultural production, agricultural import and export, food aid, and consumption. A pilot dataset for the Sudan with over 2,500 variables from the World Bank's ANDREX system, also includes epidemiological data on incidence of kwashiorkor, marasmus, other nutritional deficiencies, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985IJBm...29..169A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985IJBm...29..169A"><span>Influence of season on birth weight and weaning age of indigenous Balami and imported Sudan Desert sheep in the <span class="hlt">Sahel</span> region of Northeastern Nigeria</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alaku, O.</p> <p>1985-06-01</p> <p>Data on birth weight and age at weaning for 1,092 (609 indigenous Balami and 483 imported Sudan Desert) sheep born from 1975 to 1979 in a Government farm near Maiduguri were analysed to study the influence of season on birth weight and age at weaning in sheep reared in the <span class="hlt">sahel</span> region of Northeastern Nigeria. The suitability of the Sudan Desert for replacing or upgrading the indigenous Balami was considered. Season, breed, sex and type of birth significantly (P<0.001) influenced birth weight, age at weaning and the average daily gain from birth to weaning of lambs. Heaviest lambs were born during the rainy season-June August. Birth weight was lowest during the dry hot season. Balami lambs were heavier at birth and were weaned earlier with greater average daily gain than the Sudan Desert (P<0.001). Ram lambs were heavier at birth and had greater daily gain than the ewes (P<0.001). Also single-born lambs were heavier at birth and were weaned earlier (P<0.001) than twins. Twining rate in Balami was almost double that in the Sudanese. Survival tended to be greater in Sudanese than in Balami. Birth, twining and survival rates were highest for the dry cold season-born lambs. The dry cold season seems the best lambing season here. In all, the local Balami proved far superior in almost all traits considered. The use of the Sudan Desert here is definitely not econmically justifiable or rational.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1329814-one-year-study-diurnal-cycle-meteorology-clouds-radiation-west-african-sahel-region','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1329814-one-year-study-diurnal-cycle-meteorology-clouds-radiation-west-african-sahel-region"><span>A one-year study of the diurnal cycle of meteorology, clouds and radiation in the West African <span class="hlt">Sahel</span> region</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Collow, Allison B.; Ghate, Virendra P.; Miller, Mark A.; ...</p> <p>2015-09-09</p> <p>Here, the diurnal cycles of meteorological and radiation variables are analysed during the wet and dry seasons over the <span class="hlt">Sahel</span> region of West Africa during 2006 using surface data collected by the Atmospheric Radiation Measurement (ARM) programme's Mobile Facility, satellite radiation measurements from the Geostationary Earth Radiation Budget (GERB) instrument aboard Meteosat 8, and reanalysis products from the National Centers for Environmental Prediction (NCEP). The meteorological analysis builds upon past studies of the diurnal cycle in the region by incorporating diurnal cycles of lower tropospheric wind profiles, thermodynamic profiles, integrated water vapour and liquid water measurements, and cloud radar measurementsmore » of frequency and location. These meteorological measurements are complemented by 3 h measurements of the diurnal cycles of the top-of-atmosphere (TOA) and surface short-wave (SW) and long-wave (LW) radiative fluxes and cloud radiative effects (CREs), and the atmospheric radiative flux divergence (RFD) and atmospheric CREs. Cirrus cloudiness during the dry season is shown to peak in coverage in the afternoon, while convective clouds during the wet season are shown to peak near dawn and have an afternoon minimum related to the rise of the lifting condensation level into the Saharan Air Layer. The LW and SW RFDs and CREs exhibit diurnal cycles during both seasons, but there is a relatively small difference in the LW cycles during the two seasons (10 – 30 W m –2 depending on the variable and time of day). Small differences in the TOA CREs during the two seasons are overwhelmed by large differences in the surface SW CREs, which exceed 100 W m –2. A significant surface SW CRE during the wet season combined with a negligible TOA SW CRE produces a diurnal cycle in the atmospheric CRE that is modulated primarily by the SW surface CRE, peaks at midday at ~150 W m –2, and varies widely from day to day.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1329814','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1329814"><span>A one-year study of the diurnal cycle of meteorology, clouds and radiation in the West African <span class="hlt">Sahel</span> region</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Collow, Allison B.; Ghate, Virendra P.; Miller, Mark A.</p> <p></p> <p>Here, the diurnal cycles of meteorological and radiation variables are analysed during the wet and dry seasons over the <span class="hlt">Sahel</span> region of West Africa during 2006 using surface data collected by the Atmospheric Radiation Measurement (ARM) programme's Mobile Facility, satellite radiation measurements from the Geostationary Earth Radiation Budget (GERB) instrument aboard Meteosat 8, and reanalysis products from the National Centers for Environmental Prediction (NCEP). The meteorological analysis builds upon past studies of the diurnal cycle in the region by incorporating diurnal cycles of lower tropospheric wind profiles, thermodynamic profiles, integrated water vapour and liquid water measurements, and cloud radar measurementsmore » of frequency and location. These meteorological measurements are complemented by 3 h measurements of the diurnal cycles of the top-of-atmosphere (TOA) and surface short-wave (SW) and long-wave (LW) radiative fluxes and cloud radiative effects (CREs), and the atmospheric radiative flux divergence (RFD) and atmospheric CREs. Cirrus cloudiness during the dry season is shown to peak in coverage in the afternoon, while convective clouds during the wet season are shown to peak near dawn and have an afternoon minimum related to the rise of the lifting condensation level into the Saharan Air Layer. The LW and SW RFDs and CREs exhibit diurnal cycles during both seasons, but there is a relatively small difference in the LW cycles during the two seasons (10 – 30 W m –2 depending on the variable and time of day). Small differences in the TOA CREs during the two seasons are overwhelmed by large differences in the surface SW CREs, which exceed 100 W m –2. A significant surface SW CRE during the wet season combined with a negligible TOA SW CRE produces a diurnal cycle in the atmospheric CRE that is modulated primarily by the SW surface CRE, peaks at midday at ~150 W m –2, and varies widely from day to day.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JHyd..375..204R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JHyd..375..204R"><span>Towards an understanding of coupled physical and biological processes in the cultivated <span class="hlt">Sahel</span> - 1. Energy and water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramier, David; Boulain, Nicolas; Cappelaere, Bernard; Timouk, Franck; Rabanit, Manon; Lloyd, Colin R.; Boubkraoui, Stéphane; Métayer, Frédéric; Descroix, Luc; Wawrzyniak, Vincent</p> <p>2009-08-01</p> <p>SummaryThis paper presents an analysis of the coupled cycling of energy and water by semi-arid Sahelian surfaces, based on two years of continuous vertical flux measurements from two homogeneous recording stations in the Wankama catchment, in the West Niger meso-site of the AMMA project. The two stations, sited in a millet field and in a semi-natural fallow savanna plot, sample the two dominant land cover types in this area typical of the cultivated <span class="hlt">Sahel</span>. The 2-year study period enables an analysis of seasonal variations over two full wet-dry seasons cycles, characterized by two contrasted rain seasons that allow capturing a part of the interannual variability. All components of the surface energy budget (four-component radiation budget, soil heat flux and temperature, eddy fluxes) are measured independently, allowing for a quality check through analysis of the energy balance closure. Water cycle monitoring includes rainfall, evapotranspiration (from vapour eddy flux), and soil moisture at six depths. The main modes of observed variability are described, for the various energy and hydrological variables investigated. Results point to the dominant role of water in the energy cycle variability, be it seasonal, interannual, or between land cover types. Rainfall is responsible for nearly as much seasonal variations of most energy-related variables as solar forcing. Depending on water availability and plant requirements, evapotranspiration pre-empts the energy available from surface forcing radiation, over the other dependent processes (sensible and ground heat, outgoing long wave radiation). In the water budget, pre-emption by evapotranspiration leads to very large variability in soil moisture and in deep percolation, seasonally, interannually, and between vegetation types. The wetter 2006 season produced more evapotranspiration than 2005 from the fallow but not from the millet site, reflecting differences in plant development. Rain-season evapotranspiration is nearly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12348797','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12348797"><span>[Contribution of migrations to the process of urbanization].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bocquier, P</p> <p>1997-10-01</p> <p>An average of 22% of the populations of the <span class="hlt">Sahel</span> countries resided in urban areas in the mid-1970s, a lower level than in the rest of sub-Saharan Africa. The proportion urban has increased by about 5.5% annually over the past 2 decades. By 1993, four <span class="hlt">Sahel</span> countries had over 30% of their populations in urban areas, and only Burkina Faso had less than 20% urban. The landlocked <span class="hlt">Sahel</span> countries of Burkina Faso, Mali, Niger, and Chad have maintained rates of urbanization comparable to those of the coastal countries (Cape Verde, Gambia, Mauritania, and Senegal), which had more significant levels of urbanization in the past. The rate of growth of the urban population of all of sub-Saharan Africa was around 5.0% during the past 20 years. Only Dakar among the <span class="hlt">Sahel</span> capitals has a population of over 1 million. Cities are small, and the urban environment is usually limited to the capital. In Guinea-Bissau, for example, the capital concentrates nearly 85% of the urban population. The increased rates of urbanization are due mainly to migration. In the landlocked countries covered by surveys of the Migration and Urbanization Networks in Western Africa (Burkina Faso, Mali, and Niger), the rural exodus was directed primarily to other countries. In Senegal and Mauritania, on the other hand, around two-thirds of migrations were internal. Women contribute more than men to urban growth in the <span class="hlt">Sahel</span>. Returning migrants also show a strong preference for capital cities. Labor markets are international for men but national for women. Urban unemployment rates in the <span class="hlt">Sahel</span> countries studied were lower for migrants than nonmigrants.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120010480&hterms=Physical+Research+Study&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DPhysical%2BResearch%2BStudy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120010480&hterms=Physical+Research+Study&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DPhysical%2BResearch%2BStudy"><span>Studies of 21st-Century Precipitation Trends Over West Africa</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Druyan, Leonard M.</p> <p>2010-01-01</p> <p>West Africa includes a semi-arid zone between the Sahara Desert and the humid Gulf of Guinea coast, approximately between 10 N and 20 N, which is irrigated by summer monsoon rains. This article refers to the region as the <span class="hlt">Sahel</span>. Rain-fed agriculture is the primary sustenance for <span class="hlt">Sahel</span> populations, and severe droughts (in the 1970s and 1980s), therefore, have devastating negative societal impacts. The future frequency of <span class="hlt">Sahel</span> droughts and the evolution of its hydrological balance are therefore of great interest. The article reviews 10 recent research studies that attempt to discover how climate changes will affect the hydrology of the <span class="hlt">Sahel</span> throughout the 21st century. All 10 studies rely on atmosphere ocean global climate model (AOGCM) simulations based on a range of greenhouse gas emissions scenarios. Many of the simulations are contained in the Intergovernmental Panel on Climate Change archives for Assessment Reports #3 and #4. Two of the studies use AOGCM data to drive regional climate models. Seven studies make projections for the first half of the 21st century and eight studies make projections for the second half. Some studies make projections of wetter conditions and some predict more frequent droughts, and each describes the atmospheric processes associated with its prediction. Only one study projects more frequent droughts before 2050, and that is only for continent-wide degradation in vegetation cover. The challenge to correctly simulate <span class="hlt">Sahel</span> rainfall decadal trends is particularly daunting because multiple physical mechanisms compete to drive the trend upwards or downwards. A variety of model deficiencies, regarding the simulation of one or more of these physical processes, taints models climate change projections. Consequently, no consensus emerges regarding the impact of anticipated greenhouse gas forcing on the hydrology of the <span class="hlt">Sahel</span> in the second half of the 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=APG&id=ED281813','ERIC'); return false;" href="https://eric.ed.gov/?q=APG&id=ED281813"><span>Food and Famine: A Game Simulation.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Kvale, Katherine; Delehanty, James</p> <p></p> <p>This game simulates trade and food production in the West African region of the <span class="hlt">Sahel</span> which is susceptible to drought. Players are divided into teams of two and four persons, each team assuming the role of a farming household in the <span class="hlt">Sahel</span>. Teammates collaborate on production and trade decisions under conditions of dearth and plenty. The game…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2335J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2335J"><span>Potential climate effect of mineral aerosols over West Africa: Part II—contribution of dust and land cover to future climate change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ji, Zhenming; Wang, Guiling; Yu, Miao; Pal, Jeremy S.</p> <p>2018-04-01</p> <p>Mineral dust aerosols are an essential component of climate over West Africa, however, little work has been performed to investigate their contributions to potential climate change. A set of regional climate model experiments with and without mineral dust processes and land cover changes is performed to evaluate their climatic effects under the Representative Concentration Pathway 8.5 for two global climate models. Results suggest surface warming to be in the range of 4-8 °C by the end of the century (2081-2100) over West Africa with respect to the present day (1981-2000). The presence of mineral dusts dampens the warming by 0.1-1 °C in all seasons. Accounting for changes in land cover enhances the warming over the north of <span class="hlt">Sahel</span> and dampens it to the south in spring and summer; however, the magnitudes are smaller than those resulting from dusts. Overall dust loadings are projected to increase, with the greatest increase occurring over the Sahara and <span class="hlt">Sahel</span> in summer. Accounting for land cover changes tends to reduce dust loadings over the southern <span class="hlt">Sahel</span>. Future precipitation is projected to decrease by 5-40 % in the western Sahara and <span class="hlt">Sahel</span> and increase by 10-150 % over the eastern <span class="hlt">Sahel</span> and Guinea Coast in JJA. A dipole pattern of future precipitation changes is attributed to dust effects, with decrease in the north by 5-20 % and increase by 5-20 % in the south. Future changes in land cover result in a noisy non-significant response with a tendency for slight wetting in MAM, JJA, and SON and drying in DJF.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ERL....13f4013P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ERL....13f4013P"><span>Rainfall intensification in tropical semi-arid regions: the Sahelian case</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Panthou, G.; Lebel, T.; Vischel, T.; Quantin, G.; Sane, Y.; Ba, A.; Ndiaye, O.; Diongue-Niang, A.; Diopkane, M.</p> <p>2018-06-01</p> <p>An anticipated consequence of ongoing global warming is the intensification of the rainfall regimes meaning longer dry spells and heavier precipitation when it rains, with potentially high hydrological and socio-economic impacts. The semi-arid regions of the intertropical band, such as the <span class="hlt">Sahel</span>, are facing particularly serious challenges in this respect since their population is strongly vulnerable to extreme climatic events. Detecting long term trends in the Sahelian rainfall regime is thus of great societal importance, while being scientifically challenging because datasets allowing for such detection studies are rare in this region. This study addresses this challenge by making use of a large set of daily rain gauge data covering the <span class="hlt">Sahel</span> (defined in this study as extending from 20°W–10°E and from 11°N–18°N) since 1950, combined with an unparalleled 5 minute rainfall observations available since 1990 over the AMMA-CATCH Niger observatory. The analysis of the daily data leads to the assertion that a hydro-climatic intensification is actually taking place in the <span class="hlt">Sahel</span>, with an increasing mean intensity of rainy days associated with a higher frequency of heavy rainfall. This leads in turn to highlight that the return to wetter annual rainfall conditions since the beginning of the 2000s—succeeding the 1970–2000 drought—is by no mean a recovery towards the much smoother regime that prevailed during the 1950s and 1960s. It also provides a vision of the contrasts existing between the West <span class="hlt">Sahel</span> and the East <span class="hlt">Sahel</span>, the East <span class="hlt">Sahel</span> experiencing a stronger increase of extreme rainfall. This regional vision is complemented by a local study at sub-daily timescales carried out thanks to the 5 minute rainfall series of the AMMA-CATCH Niger observatory (12000 km2). The increasing intensity of extreme rainfall is also visible at sub-daily timescales, the annual maximum intensities have increased at an average rate of 2%–6% per decade since 1990 for timescales</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170003425','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170003425"><span>West African Monsoon Decadal Variability and Surface-Related Forcings: Second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Xue, Yongkang; De Sales, Fernando; Lau, William K-M; Boone, Aaron; Kim, Kyu-Myong; Mechoso, Carlos R.; Wang, Guiling; Kucharski, Fred; Schiro, Kathleen; Hosaka, Masahiro; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20170003425'); toggleEditAbsImage('author_20170003425_show'); toggleEditAbsImage('author_20170003425_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20170003425_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20170003425_hide"></p> <p>2016-01-01</p> <p>The second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedbacks of sea surface temperature (SST), land use land cover change (LULCC), and aerosols forcings in the <span class="hlt">Sahel</span> climate system at seasonal to decadal scales. The WAMME II strategy is to apply prescribed observationally based anomaly forcing, i.e., idealized but realistic forcing, in simulations by climate models to test the relative impacts of such forcings in producingamplifying the Sahelian seasonal and decadal climate variability, including the great 20th century drought. This is the first multi-model experiment specifically designed to simultaneously evaluate relative contributions of multiple external forcings to the <span class="hlt">Sahel</span> decadal precipitation anomalies between the 1980s and the 1950s that is used to characterize the <span class="hlt">Sahel</span> 1980s drought in this study. The WAMME II models have consistently demonstrated that SST is the major contributor to the 20th century <span class="hlt">Sahel</span> drought. Under the influence of the maximum possible SST forcing, WAMME II model ensemble mean can produce up to 60 of the precipitation difference between the 1980s and the 1950s. The present paper also delineated the role of SSTs in triggering and maintaining the <span class="hlt">Sahel</span> drought. The impact of SSTs in individual oceans is also examined and consensus and discrepancies are reported. Among the different ocean basins, the WAMME II models show the consensus that the Indian Ocean SST has the largest impact on the precipitation temporal evolution associated with the ITCZ movement before the WAM onset while the Pacific Ocean SST greatly contributes to the summer WAM drought. This paper also compares the SST effect with the LULCC effect. Results show that with prescribed land forcing the WAMME II model ensemble mean produces about 40 of the precipitation difference between the 1980s and the 1950s, which is less than the SST contribution but still of first order</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A41N..05J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A41N..05J"><span>Sensitivity of Sahelian Precipitation to Desert Dust under ENSO variability: a regional modeling study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.</p> <p>2016-12-01</p> <p>Mineral dust is estimated to comprise over half the total global aerosol burden, with a majority coming from the Sahara and <span class="hlt">Sahel</span> region. Bounded by the Sahara Desert to the north and the Sahelian Savannah to the south, the <span class="hlt">Sahel</span> experiences high interannual rainfall variability and a short rainy season during the boreal summer months. Observation-based data for the past three decades indicates a reduced dust emission trend, together with an increase in greening and surface roughness within the <span class="hlt">Sahel</span>. Climate models used to study regional precipitation changes due to Saharan dust yield varied results, both in sign convention and magnitude. Inconsistency of model estimates drives future climate projections for the region that are highly varied and uncertain. We use the NASA-Unified Weather Research and Forecasting (NU-WRF) model to quantify the interaction and feedback between desert dust aerosol and Sahelian precipitation. Using nested domains at fine spatial resolution we resolve changes to mesoscale atmospheric circulation patterns due to dust, for representative phases of El Niño-Southern Oscillation (ENSO). The NU-WRF regional earth system model offers both advanced land surface data and resolvable detail of the mechanisms of the impact of Saharan dust. Results are compared to our previous work assessed over the Western <span class="hlt">Sahel</span> using the Geophysical Fluid Dynamics Laboratory (GFDL) CM2Mc global climate model, and to other previous regional climate model studies. This prompts further research to help explain the dust-precipitation relationship and recent North African dust emission trends. This presentation will offer a quantitative analysis of differences in radiation budget, energy and moisture fluxes, and atmospheric dynamics due to desert dust aerosol over the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170002646','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170002646"><span>Regionalizing Africa: Patterns of Precipitation Variability in Observations and Global Climate Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Badr, Hamada S.; Dezfuli, Amin K.; Zaitchik, Benjamin F.; Peters-Lidard, Christa D.</p> <p>2016-01-01</p> <p>Many studies have documented dramatic climatic and environmental changes that have affected Africa over different time scales. These studies often raise questions regarding the spatial extent and regional connectivity of changes inferred from observations and proxies and/or derived from climate models. Objective regionalization offers a tool for addressing these questions. To demonstrate this potential, applications of hierarchical climate regionalizations of Africa using observations and GCM historical simulations and future projections are presented. First, Africa is regionalized based on interannual precipitation variability using Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) data for the period 19812014. A number of data processing techniques and clustering algorithms are tested to ensure a robust definition of climate regions. These regionalization results highlight the seasonal and even month-to-month specificity of regional climate associations across the continent, emphasizing the need to consider time of year as well as research question when defining a coherent region for climate analysis. CHIRPS regions are then compared to those of five GCMs for the historic period, with a focus on boreal summer. Results show that some GCMs capture the climatic coherence of the <span class="hlt">Sahel</span> and associated teleconnections in a manner that is similar to observations, while other models break the <span class="hlt">Sahel</span> into uncorrelated subregions or produce a <span class="hlt">Sahel</span>-like region of variability that is spatially displaced from observations. Finally, shifts in climate regions under projected twenty-first-century climate change for different GCMs and emissions pathways are examined. A projected change is found in the coherence of the <span class="hlt">Sahel</span>, in which the western and eastern <span class="hlt">Sahel</span> become distinct regions with different teleconnections. This pattern is most pronounced in high-emissions scenarios.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910056462&hterms=water+effects&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dwater%2Beffects','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910056462&hterms=water+effects&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dwater%2Beffects"><span>The effect of water vapour on the normalized difference vegetation index derived for the Sahelian region from NOAA AVHRR data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Justice, Christopher O.; Eck, T. F.; Tanre, Didier; Holben, B. N.</p> <p>1991-01-01</p> <p>The near-infrared channel of the NOAA advanced very high resolution radiometer (AVHRR) contains a water vapor absorption band that affects the determination of the normalized difference vegetation index (NDVI). Daily and seasonal variations in atmospheric water vapor within the <span class="hlt">Sahel</span> are shown to affect the use of the NDVI for the estimation of primary production. This water vapor effect is quantified for the <span class="hlt">Sahel</span> by radiative transfer modeling and empirically using observations made in Mali in 1986.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910028015&hterms=desertification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddesertification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910028015&hterms=desertification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddesertification"><span>Monitoring arid lands using AVHRR-observed visible reflectance and SMMR37-GHz polarization difference</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Choudhury, B. J.</p> <p>1990-01-01</p> <p>Visible reflectance along a transect through the <span class="hlt">Sahel</span> and Sudan zones of Africa has been derived from observations by the AVHRR on the NOAA-7 and NOAA-9 satellites and compared with concurrent observations of the 37-GHz polarization difference by the SMMR on the Nimbus-7 satellite. The study period was January 1982 to December 1986, which included an unprecedented drought during 1984 over the <span class="hlt">Sahel</span> zone. While spatial and temporal patterns of these two data sets are found to be highly correlated, there are also quantitative differences which need to be understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1353352-west-african-monsoon-decadal-variability-surface-related-forcings-second-west-african-monsoon-modeling-evaluation-project-experiment-wamme-ii','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1353352-west-african-monsoon-decadal-variability-surface-related-forcings-second-west-african-monsoon-modeling-evaluation-project-experiment-wamme-ii"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Xue, Yongkang; De Sales, Fernando; Lau, William K. -M.</p> <p></p> <p>The <span class="hlt">Sahel</span> climate system had experienced one of the strongest interdecadal climate variabilities and the longest drought on the planet in the twentieth century. Most modeling studies on the decadal variability of the <span class="hlt">Sahel</span> climate so far have focused on the role of anomalies in either sea surface temperature (SST), land surface processes, or aerosols concentration. The Second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedback of SST, land use land cover change (LULCC), and aerosols forcings in the <span class="hlt">Sahel</span> climate system at seasonal to decadal scales.more » The WAMME II strategy is to apply observationally based anomaly forcing, i.e., “idealized but realistic” forcing, in simulations by general circulation models’ (GCMs) and regional climate models’ (RCMs) to test the relative impacts of such forcings in producing/amplifying the Sahelian seasonal and decadal climate variability, including the 20th century drought. To test individual ocean’s SST effect, a special approach in the experimental design is taken to avoid undermine its effect. This is the first multi-model experiment specifically designed to simultaneously evaluate relative contributions of multiple-external forcings to the <span class="hlt">Sahel</span> drought. This paper presents the major results and preliminary findings of the WAMME II SST experiment, including each ocean’s contribution to the global SST effect, as well as comparison of the SST effect with the LULCC effect. The common empirical orthogonal functions and other analyses are applied to assess and comprehend the discrepancies among the models. In general, the WAMME II models have reached a consensus on SST’s major contribution to the great <span class="hlt">Sahel</span> drought and show that with the maximum possible SST forcing, it can produce up to 60% of the absolute amount of precipitation difference between the 1980s and the 1950s. This paper has 3 also delineated the role of</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160003597&hterms=sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsea','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160003597&hterms=sea&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsea"><span>Variability and Predictability of West African Droughts. A Review in the Role of Sea Surface Temperature Anomalies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rodriguez-Fonseca, Belen; Mohino, Elsa; Mechoso, Carlos R.; Caminade, Cyril; Biasutti, Michela; Gaetani, Marco; Garcia-Serrano, J.; Vizy, Edward K.; Cook, Kerry; Xue, Yongkang; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20160003597'); toggleEditAbsImage('author_20160003597_show'); toggleEditAbsImage('author_20160003597_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20160003597_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20160003597_hide"></p> <p>2015-01-01</p> <p>The <span class="hlt">Sahel</span> experienced a severe drought during the 1970s and 1980s after wet periods in the 1950s and 1960s. Although rainfall partially recovered since the 1990s, the drought had devastating impacts on society. Most studies agree that this dry period resulted primarily from remote effects of sea surface temperature (SST) anomalies amplified by local land surface-atmosphere interactions. This paper reviews advances made during the last decade to better understand the impact of global SST variability on West African rainfall at interannual to decadal time scales. At interannual time scales, a warming of the equatorial Atlantic and Pacific/Indian Oceans results in rainfall reduction over the <span class="hlt">Sahel</span>, and positive SST anomalies over the Mediterranean Sea tend to be associated with increased rainfall. At decadal time scales, warming over the tropics leads to drought over the <span class="hlt">Sahel</span>, whereas warming over the North Atlantic promotes increased rainfall. Prediction systems have evolved from seasonal to decadal forecasting. The agreement among future projections has improved from CMIP3 to CMIP5, with a general tendency for slightly wetter conditions over the central part of the <span class="hlt">Sahel</span>, drier conditions over the western part, and a delay in the monsoon onset. The role of the Indian Ocean, the stationarity of teleconnections, the determination of the leader ocean basin in driving decadal variability, the anthropogenic role, the reduction of the model rainfall spread, and the improvement of some model components are among the most important remaining questions that continue to be the focus of current international projects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ERL.....9j4006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ERL.....9j4006S"><span>Robust features of future climate change impacts on sorghum yields in West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sultan, B.; Guan, K.; Kouressy, M.; Biasutti, M.; Piani, C.; Hammer, G. L.; McLean, G.; Lobell, D. B.</p> <p>2014-10-01</p> <p>West Africa is highly vulnerable to climate hazards and better quantification and understanding of the impact of climate change on crop yields are urgently needed. Here we provide an assessment of near-term climate change impacts on sorghum yields in West Africa and account for uncertainties both in future climate scenarios and in crop models. Towards this goal, we use simulations of nine bias-corrected CMIP5 climate models and two crop models (SARRA-H and APSIM) to evaluate the robustness of projected crop yield impacts in this area. In broad agreement with the full CMIP5 ensemble, our subset of bias-corrected climate models projects a mean warming of +2.8 °C in the decades of 2031-2060 compared to a baseline of 1961-1990 and a robust change in rainfall in West Africa with less rain in the Western part of the <span class="hlt">Sahel</span> (Senegal, South-West Mali) and more rain in Central <span class="hlt">Sahel</span> (Burkina Faso, South-West Niger). Projected rainfall deficits are concentrated in early monsoon season in the Western part of the <span class="hlt">Sahel</span> while positive rainfall changes are found in late monsoon season all over the <span class="hlt">Sahel</span>, suggesting a shift in the seasonality of the monsoon. In response to such climate change, but without accounting for direct crop responses to CO2, mean crop yield decreases by about 16-20% and year-to-year variability increases in the Western part of the <span class="hlt">Sahel</span>, while the eastern domain sees much milder impacts. Such differences in climate and impacts projections between the Western and Eastern parts of the <span class="hlt">Sahel</span> are highly consistent across the climate and crop models used in this study. We investigate the robustness of impacts for different choices of cultivars, nutrient treatments, and crop responses to CO2. Adverse impacts on mean yield and yield variability are lowest for modern cultivars, as their short and nearly fixed growth cycle appears to be more resilient to the seasonality shift of the monsoon, thus suggesting shorter season varieties could be considered a potential</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.9370G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.9370G"><span>West African Monsoon dynamics in idealized simulations: the competitive roles of SST warming and CO2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gaetani, Marco; Flamant, Cyrille; Hourdin, Frederic; Bastin, Sophie; Braconnot, Pascale; Bony, Sandrine</p> <p>2015-04-01</p> <p>The West African Monsoon (WAM) is affected by large climate variability at different timescales, from interannual to multidecadal, with strong environmental and socio-economic impacts associated to climate-related rainfall variability, especially in the Sahelian belt. State-of-the-art coupled climate models still show poor ability in correctly simulating the WAM past variability and also a large spread is observed in future climate projections. In this work, the July-to-September (JAS) WAM variability in the period 1979-2008 is studied in AMIP-like simulations (SST-forced) from CMIP5. The individual roles of global SST warming and CO2 concentration increasing are investigated through idealized experiments simulating a 4K warmer SST and a 4x CO2 concentration, respectively. Results show a dry response in <span class="hlt">Sahel</span> to SST warming, with dryer conditions over western <span class="hlt">Sahel</span>. On the contrary, wet conditions are observed when CO2 is increased, with the strongest response over central-eastern <span class="hlt">Sahel</span>. The precipitation changes are associated to modifications in the regional atmospheric circulation: dry (wet) conditions are associated with reduced (increased) convergence in the lower troposphere, a southward (northward) shift of the African Easterly Jet, and a weaker (stronger) Tropical Easterly Jet. The co-variability between global SST and WAM precipitation is also investigated, highlighting a reorganization of the main co-variability modes. Namely, in the 4xCO2 simulation the influence of Tropical Pacific is dominant, while it is reduced in the 4K simulation, which also shows an increased coupling with the eastern Pacific and the Indian Ocean. The above results suggest a competitive action of SST warming and CO2 increasing on the WAM climate variability, with opposite effects on precipitation. The combination of the observed positive and negative response in precipitation, with wet conditions in central-eastern <span class="hlt">Sahel</span> and dry conditions in western <span class="hlt">Sahel</span>, is consistent with the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MAP...tmp...16O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MAP...tmp...16O"><span>Recent variations in geopotential height associated with West African monsoon variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okoro, Ugochukwu K.; Chen, Wen; Nath, Debashis</p> <p>2018-02-01</p> <p>In the present study, the atmospheric circulation patterns associated with the seasonal West Africa (WA) monsoon (WAM) rainfall variability has been investigated. The observational rainfall data from the Climatic Research Unit (CRU) and atmospheric fields from the National Center for Environmental Prediction (NCEP) reanalysis 2, from 1979 to 2014, have been used. The rainfall variability extremes, classified as wet or dry years, are the outcomes of simultaneous 6-month SPI at the three rainfall zones, which shows increasing trends [Guinea Coast (GC = 0.012 year-1), Eastern Sudano <span class="hlt">Sahel</span> (ESS = 0.045 year-1) and Western Sudano <span class="hlt">Sahel</span> (WSS = 0.056 year-1) from Sen's slope]; however, it is significant only in the <span class="hlt">Sahel</span> region (α = 0.05 and α = 0.001 at ESS and WSS, respectively, from Mann-Kendall test). The vertical profile of the geopotential height (GpH) during the wet and dry years reveals that the 700 hPa anomalies show remarkable pattern at about 8°N to 13°N. This shows varying correlation with the zonal averaged vertically integrated moisture flux convergence and rainfall anomalies, respectively, as well as the oceanic pulsations indexes [Ocean Nino Index (ONI) and South Atlantic Ocean dipole index (SAODI), significant from t test], identified as precursors to the <span class="hlt">Sahel</span> and GC rainfall variability respectively. The role of GpH anomalies at 700 hPa has been identified as the facilitator to the West African Westerly Jet's input to the moisture flux transported over the WA. This is a new perspective of the circulation processes associated with WAM and serves as a basis for modeling investigations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..1111566G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..1111566G"><span>Couplings between the seasonal cycles of surface thermodynamics and radiative fluxes in the semi-arid <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guichard, F.; Kergoat, L.; Mougin, E.; Timouk, F.; Bock, O.; Hiernaux, P.</p> <p>2009-04-01</p> <p>A good knowledge of surface fluxes and atmospheric low levels is central to improving our understanding of the West African monsoon. This study provides a quantitative analysis of the peculiar seasonal and diurnal cycles of surface thermodynamics and radiative fluxes encountered in Central <span class="hlt">Sahel</span>. It is based on a multi-year dataset collected in the Malian Gourma over a sandy soil at 1.5°W-15.3°N (a site referred to as Agoufou) with an automated weather station and a sunphotometer (AERONET), complemented by observations from the AMMA field campaign. The seasonal cycle of this Tropical region is characterized by a broad maximum of temperature in May, following the first minimum of the solar zenith angle by a few weeks, when Agoufou lies within the West African Heat-Low, and a late summer maximum of equivalent potential temperature within the core of the monsoon season, around the second yearly maximum of solar zenith angle, as the temperature reaches its Summer minimum. More broadly, subtle balances between surface air temperature and moisture fields are found on a range of scales. For instance, during the monsoon, apart from August, their opposite daytime fluctuations (warming, drying) lead to an almost flat diurnal cycle of the equivalent potential temperature at the surface. This feature stands out in contrast to other more humid continental regions. Here, the strong dynamics associated with the transition from a drier hot Spring to a brief cooler wet tropical Summer climate involves very large transformations of the diurnal cycles. The Summer increase of surface net radiation, Rnet, is also strong; typically 10-day mean Rnet reaches about 5 times its Winter minimum (~30 W.m-2) in August (~150 W.m-2). A major feature revealed by observations is that this increase is mostly driven by modifications of the surface upwelling fluxes shaped by rainfall events and vegetation phenology (surface cooling and darkening), while the direct impact of atmospheric changes on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........10Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........10Y"><span>Statistical and dynamical assessment of land-ocean-atmosphere interactions across North Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Yan</p> <p></p> <p>North Africa is highly vulnerable to hydrologic variability and extremes, including impacts of climate change. The current understanding of oceanic versus terrestrial drivers of North African droughts and pluvials is largely model-based, with vast disagreement among models in terms of the simulated oceanic impacts and vegetation feedbacks. Regarding oceanic impacts, the relative importance of the tropical Pacific, tropical Indian, and tropical Atlantic Oceans in regulating the North African rainfall variability, as well as the underlying mechanism, remains debated among different modeling studies. Classic theory of land-atmosphere interactions across the <span class="hlt">Sahel</span> ecotone, largely based on climate modeling experiments, has promoted positive vegetation-rainfall feedbacks associated with a dominant surface albedo mechanism. However, neither the proposed positive vegetation-rainfall feedback with its underlying albedo mechanism, nor its relative importance compared with oceanic drivers, has been convincingly demonstrated up to now using observational data. Here, the multivariate Generalized Equilibrium Feedback Assessment (GEFA) is applied in order to identify the observed oceanic and terrestrial drivers of North African climate and quantify their impacts. The reliability of the statistical GEFA method is first evaluated against dynamical experiments within the Community Earth System Model (CESM). In order to reduce the sampling error caused by short data records, the traditional GEFA approach is refined through stepwise GEFA, in which unimportant forcings are dropped through stepwise selection. In order to evaluate GEFA's reliability in capturing oceanic impacts, the atmospheric response to a sea-surface temperature (SST) forcing across the tropical Pacific, tropical Indian, and tropical Atlantic Ocean is estimated independently through ensembles of dynamical experiments and compared with GEFA-based assessments. Furthermore, GEFA's performance in capturing terrestrial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ClDy...37.1313P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ClDy...37.1313P"><span>Diagnosing GCM errors over West Africa using relaxation experiments. Part II: intraseasonal variability and African easterly waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pohl, Benjamin; Douville, Hervé</p> <p>2011-10-01</p> <p>A near-global grid-point nudging of the Arpege-Climat atmospheric General Circulation Model towards ECMWF reanalyses is used to diagnose the regional versus remote origin of the summer model biases and variability over West Africa. First part of this study revealed a limited impact on the monsoon climatology compared to a control experiment without nudging, but a significant improvement of interannual variability, although the amplitude of the seasonal anomalies remained underestimated. Focus is given here on intraseasonal variability of monsoon rainfall and dynamics. The reproducible part of these signals is investigated through 30-member ensemble experiments computed for the 1994 rainy season, a year abnormally wet over the <span class="hlt">Sahel</span> but representative of the model systematic biases. In the control experiment, Arpege-Climat simulates too few rainy days that are associated with too low rainfall amounts over the central and western <span class="hlt">Sahel</span>, in line with the seasonal dry biases. Nudging the model outside Africa tends to slightly increase the number of rainy days over the <span class="hlt">Sahel</span>, but has little effect on associated rainfall amounts. However, results do indicate that a significant part of the monsoon intraseasonal variability simulated by Arpege-Climat is controlled by lateral boundary conditions. Parts of the wet/dry spells over the <span class="hlt">Sahel</span> occur in phase in the 30 members of the nudging experiment, and are therefore embedded in larger-scale variability patterns. Inter-member spread is however not constant across the selected summer season. It is partly controlled by African Easterly Waves, which show dissimilar amplitude from one member to another, but a coherent phasing in all members. A lowpass filtering of the nudging fields suggests that low frequency variations in the lateral boundary conditions can lead to eastward extensions of the African Easterly Jet, creating a favorable environment for easterly waves, while high frequency perturbations seem to control their</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC41B1095W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC41B1095W"><span>Advancing a Model-Validated Statistical Method for Decomposing the Key Oceanic Drivers of Observed Regional Climate Variability and Evaluating Model Performance: Focus on North African Rainfall in CESM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, F.; Notaro, M.; Yu, Y.; Mao, J.; Shi, X.; Wei, Y.</p> <p>2016-12-01</p> <p>North (N.) African rainfall is characterized by dramatic interannual to decadal variability with serious socio-economic ramifications. The <span class="hlt">Sahel</span> and West African Monsoon (WAM) region experienced a dramatic shift to persistent drought by the late 1960s, while the Horn of Africa (HOA) underwent drying since the 1990s. Large disagreementregarding the dominant oceanic drivers of N. African hydrologic variability exists among modeling studies, leading to notable spread in <span class="hlt">Sahel</span> summer rainfall projections for this century among Coupled Model Intercomparison Project models. In order to gain a deeper understanding of the oceanic drivers of N. African rainfall and establish a benchmark for model evaluation, a statistical method, the multivariate Generalized Equilibrium Feedback Assessment, is validated and applied to observations and a control run from the Community Earth System Model (CESM). This study represents the first time that the dominant oceanic drivers of N. African rainfall were evaluated and systematically compared between observations and model simulations. CESM and the observations consistently agree that tropical oceanic modes are the dominant controls of N. African rainfall. During the monsoon season, CESM and observations agree that an anomalously warm eastern tropical Pacific shifts the Walker Circulation eastward, with its descending branch supporting <span class="hlt">Sahel</span> drying. CESM and the observations concur that a warmer tropical eastern Atlantic favors a southward-shifted Intertropical Convergence Zone, which intensifies WAM monsoonal rainfall. An observed reduction in <span class="hlt">Sahel</span> rainfall accompanies this enhanced WAM rainfall, yet is confined to the Atlantic in CESM. During the short rains, both observations and CESM indicate that a positive phase of tropical Indian Ocean dipole (IOD) mode [anomalously warm (cold) in western (eastern) Indian] enhances HOA rainfall. The observed IOD impacts are limited to the short rains, while the simulated impacts are year-round.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdAtS..34..833L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdAtS..34..833L"><span>Interdecadal variability of the Afro-Asian summer monsoon system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Yi; Ding, Yihui; Li, Weijing</p> <p>2017-07-01</p> <p>The Afro-Asian summer monsoon is a zonally planetary-scale system, with a large-scale rainbelt covering Africa, South Asia and East Asia on interdecadal timescales both in the past century (1901-2014) and during the last three decades (1979-2014). A recent abrupt change of precipitation occurred in the late 1990s. Since then, the entire rainbelt of the Afro-Asia monsoon system has advanced northwards in a coordinated way. Consistent increases in precipitation over the Huanghe-Huaihe River valley and the <span class="hlt">Sahel</span> are associated with the teleconnection pattern excited by the warm phase of the Atlantic Multidecadal Oscillation (AMO). A teleconnection wave train, with alternating cyclones/anticyclones, is detected in the upper troposphere. Along the teleconnection path, the configuration of circulation anomalies in North Africa is characterized by coupling of the upper-level anticyclone (divergence) with low-level thermal low pressure (convergence), facilitating the initiation and development of ascending motions in the <span class="hlt">Sahel</span>. Similarly, in East Asia, a coupled circulation pattern also excites ascending motion in the Huanghe-Huaihe River valley. The synchronous increase in precipitation over the <span class="hlt">Sahel</span> and Huanghe-Huaihe River valley can be attributed to the co-occurrences and in-phase changes of ascending motion. On the other hand, the warm phase of the AMO results in significant warming in the upper troposphere in North Africa and the northern part of East Asia. Such warming contributes to intensification of the tropical easterly jet through increasing the meridional pressure gradient both at the entrance region (East Asia) and the exit region (Africa). Accordingly, precipitation over the <span class="hlt">Sahel</span> and Huanghe-Huaihe River valley intensifies, owing to ageostrophic secondary cells. The results of this study provide evidence for a consistent and holistic interdecadal change in the Afro-Asian summer monsoon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28447639','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28447639"><span>Frequency of extreme Sahelian storms tripled since 1982 in satellite observations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Taylor, Christopher M; Belušić, Danijel; Guichard, Françoise; Parker, Douglas J; Vischel, Théo; Bock, Olivier; Harris, Phil P; Janicot, Serge; Klein, Cornelia; Panthou, Gérémy</p> <p>2017-04-26</p> <p>The hydrological cycle is expected to intensify under global warming, with studies reporting more frequent extreme rain events in many regions of the world, and predicting increases in future flood frequency. Such early, predominantly mid-latitude observations are essential because of shortcomings within climate models in their depiction of convective rainfall. A globally important group of intense storms-mesoscale convective systems (MCSs)-poses a particular challenge, because they organize dynamically on spatial scales that cannot be resolved by conventional climate models. Here, we use 35 years of satellite observations from the West African <span class="hlt">Sahel</span> to reveal a persistent increase in the frequency of the most intense MCSs. Sahelian storms are some of the most powerful on the planet, and rain gauges in this region have recorded a rise in 'extreme' daily rainfall totals. We find that intense MCS frequency is only weakly related to the multidecadal recovery of <span class="hlt">Sahel</span> annual rainfall, but is highly correlated with global land temperatures. Analysis of trends across Africa reveals that MCS intensification is limited to a narrow band south of the Sahara desert. During this period, wet-season Sahelian temperatures have not risen, ruling out the possibility that rainfall has intensified in response to locally warmer conditions. On the other hand, the meridional temperature gradient spanning the <span class="hlt">Sahel</span> has increased in recent decades, consistent with anthropogenic forcing driving enhanced Saharan warming. We argue that Saharan warming intensifies convection within Sahelian MCSs through increased wind shear and changes to the Saharan air layer. The meridional gradient is projected to strengthen throughout the twenty-first century, suggesting that the <span class="hlt">Sahel</span> will experience particularly marked increases in extreme rain. The remarkably rapid intensification of Sahelian MCSs since the 1980s sheds new light on the response of organized tropical convection to global warming, and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1166680','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1166680"><span>Assessment of uncertainties in the response of the African monsoon precipitation to land use change simulated by a regional model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hagos, Samson M.; Leung, Lai-Yung Ruby; Xue, Yongkang</p> <p>2014-02-22</p> <p>Land use and land cover over Africa have changed substantially over the last sixty years and this change has been proposed to affect monsoon circulation and precipitation. This study examines the uncertainties on the effect of these changes on the African Monsoon system and <span class="hlt">Sahel</span> precipitation using an ensemble of regional model simulations with different combinations of land surface and cumulus parameterization schemes. Furthermore, the magnitude of the response covers a broad range of values, most of the simulations show a decline in <span class="hlt">Sahel</span> precipitation due to the expansion of pasture and croplands at the expense of trees and shrubsmore » and an increase in surface air temperature.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..895W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..895W"><span>Large-scale control of the Arabian Sea monsoon inversion in August</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Chi-Hua; Wang, S.-Y. Simon; Hsu, Huang-Hsiung</p> <p>2017-12-01</p> <p>The summer monsoon inversion in the Arabian Sea is characterized by a large amount of low clouds and August as the peak season. Atmospheric stratification associated with the monsoon inversion has been considered a local system influenced by the advancement of the India-Pakistan monsoon. Empirical and numerical evidence from this study suggests that the Arabian Sea monsoon inversion is linked to a broader-scale monsoon evolution across the African <span class="hlt">Sahel</span>, South Asia, and East Asia-Western North Pacific (WNP), rather than being a mere byproduct of the India-Pakistan monsoon progression. In August, the upper-tropospheric anticyclone in South Asia extends sideways corresponding with the enhanced precipitation in the subtropical WNP, equatorial Indian Ocean, and African <span class="hlt">Sahel</span> while the middle part of this anticyclone weakens over the Arabian Sea. The increased heating in the adjacent monsoon systems creates a suppression effect on the Arabian Sea, suggesting an apparent competition among the Africa-Asia-WNP monsoon subsystems. The peak <span class="hlt">Sahel</span> rainfall in August, together with enhanced heating in the equatorial Indian Ocean, produces a critical effect on strengthening the Arabian Sea thermal inversion. By contrast, the WNP monsoon onset which signifies the eastward expansion of the subtropical Asian monsoon heating might play a secondary or opposite role in the Arabian Sea monsoon inversion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910029208&hterms=Leading+Change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DLeading%2BChange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910029208&hterms=Leading+Change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DLeading%2BChange"><span>Monitoring land surface change over semi-arid regions using multispectral satellite data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Choudhury, B. J.</p> <p>1990-01-01</p> <p>Visible reflectance and surface temperature are derived from observations by the AVHRR on the NOAA-7 and NOAA-9 satellites and microwave emission at 37-GHz by the SMMR on Nimbus-7 satellite over the <span class="hlt">Sahel</span> and Sudan zones. The AVHRR data is for the period January 1982 to December 1986, while the SMMR data is for the period January 1979 to December 1986. Rainfall data show that both the <span class="hlt">Sahel</span> and Sudan zones experienced a particularly severe drought during 1984, and thus the present analysis shows the patterns leading to and recovering from the 1984 drought. Interrelationships among these multispectral data and the ways these relationships change in response to drought are evaluated in relation to field observations and heat balance models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PApGe.tmp...18D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PApGe.tmp...18D"><span>The Influence of the Regional Hadley and Walker Circulations on Precipitation Patterns over Africa in El Niño, La Niña, and Neutral Years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Oliveira, Cristiano Prestrelo; Aímola, Luis; Ambrizzi, Tércio; Freitas, Ana Carolina Vasques</p> <p>2018-02-01</p> <p>This study focuses on the differential impacts of the positive (El Niño), negative (La Niña), and neutral phases of the El Niño Southern Oscillation (ENSO) on precipitation over Africa during DJF and JJA, evaluated through changes in the regional Hadley and Walker Circulations. Identification of the Hadley and Walker Cells was done using stream function mass transport calculations of ERA-Interim reanalysis data from 1979 to 2014. Analysis of the spatial pattern of precipitation anomalies shows that during DJF, El Niño (La Niña) negatively (positively) impacts precipitation over the African continent. During JJA, El Niño (La Niña) influences precipitation variability over the <span class="hlt">Sahel</span> region, producing positive (negative) anomalies. Negative precipitation anomalies associated with El Niño (DJF) over southern Africa are linked to a strengthening in subsidence of the descending branch of the regional Hadley Cell, and during JJA the negative precipitation anomalies over the <span class="hlt">Sahel</span> are associated with a weakening of the ascending branch of the regional Hadley Cell. During La Niña events in DJF, there is a tendency toward increased convection in southern Africa, associated with a stronger ascending branch and weaker descending branch of the regional Hadley Cell. During La Niña events in JJA, positive precipitation anomalies over the <span class="hlt">Sahel</span> are associated with an intensification of the ascending branch of the regional Hadley Cell north of the equator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29215793','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29215793"><span>Genetic history of the African Sahelian populations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Černý, V; Kulichová, I; Poloni, E S; Nunes, J M; Pereira, L; Mayor, A; Sanchez-Mazas, A</p> <p>2018-03-01</p> <p>From a biogeographic perspective, Africa is subdivided into distinct horizontal belts. Human populations living along the <span class="hlt">Sahel</span>/Savannah belt south of the Sahara desert have often been overshadowed by extensive studies focusing on other African populations such as hunter-gatherers or Bantu in particular. However, the <span class="hlt">Sahel</span> together with the Savannah bordering it in the south is a challenging region where people had and still have to cope with harsh climatic conditions and show resilient behaviours. Besides exponentially growing urban populations, several local groups leading various lifestyles and speaking languages belonging to three main linguistic families still live in rural localities across that region today. Thanks to several years of consistent population sampling throughout this area, the genetic history of the African Sahelian populations has been largely reconstructed and a deeper knowledge has been acquired regarding their adaptation to peculiar environments and/or subsistence modes. Distinct exposures to pathogens-in particular, malaria-likely contributed to their genetic differentiation for HLA genes. In addition, although food-producing strategies spread within the <span class="hlt">Sahel</span>/Savannah belt relatively recently, during the last five millennia according to recent archaeological and archaeobotanical studies, remarkable amounts of genetic differences are also observed between sedentary farmers and more mobile pastoralists at multiple neutral and selected loci, reflecting both demographic effects and genetic adaptations to distinct cultural traits, such as dietary habits. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017IJEaS.106...19A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017IJEaS.106...19A"><span>Coastal uplift west of Algiers (Algeria): pre- and post-Messinian sequences of marine terraces and rasas and their associated drainage pattern</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Authemayou, Christine; Pedoja, Kevin; Heddar, Aicha; Molliex, Stéphane; Boudiaf, Azzedine; Ghaleb, Bassam; Van Vliet Lanoe, Brigitte; Delcaillau, Bernard; Djellit, Hamou; Yelles, Karim; Nexer, Maelle</p> <p>2017-01-01</p> <p>The North Africa passive margin is affected by the ongoing convergence between the African and Eurasian plates. This convergence is responsible for coastal uplift, folding, and reverse faulting on new and reactivated faults on the margin. The active deformation is diffuse and thus rather difficult to locate precisely. We aim to determine how a coastal landscape evolve in this geodynamic setting and gain insights into active tectonics. More particularly, we evidence and quantify coastal uplift pattern of the Chenoua, <span class="hlt">Sahel</span>, and Algiers reliefs (Algeria), using sequences of marine terraces and rasas and computing several morphometric indices from the drainage pattern. Upper and Middle Pleistocene uplift rates are obtained by fossil shoreline mapping and preliminary U/Th dating of associated coastal deposits. Extrapolation of these rates combined to analyses of sea-level referential data and spatial relationships between marine terraces/rasas and other geological markers lead us to tentatively propose an age for the highest coastal indicators (purported the oldest). Values of morphometric indices showing correlations with uplift rate allow us to analyze uplift variation on area devoid of coastal sequence. Geological and geomorphological data suggest that coastal uplift probably occurred since the Middle Miocene. It resulted in the emergence of the Algiers massif, followed by the <span class="hlt">Sahel</span> ridge massif. The <span class="hlt">Sahel</span> ridge has asymmetrically grown by folding from west to east and was affected by temporal variation of uplift. Compared to previous study, the location of the <span class="hlt">Sahel</span> fold axis has been shifted offshore, near the coast. The Chenoua fault vertical motion does not offset significantly the coastal sequence. Mean apparent uplift rates and corrected uplift rates since 120 ka are globally steady all along the coast with a mean value of 0.055 ± 0.015 mm/year (apparent) and of 0.005 ± 0.045 mm/year (corrected for eustasy). Mean apparent coastal uplift rates between 120 and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=biomass&pg=4&id=EJ222349','ERIC'); return false;" href="https://eric.ed.gov/?q=biomass&pg=4&id=EJ222349"><span>The Status of Solar Energy as Fuel.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Hall, D. O.</p> <p>1979-01-01</p> <p>Discused is the biological conversion of solar energy via photosynthesis into stored energy in the form of biomass. Detailed are the research and development programs on biomass of the United States, Canada, Australia, New Zealand, Europe, Brazil, Philippines, <span class="hlt">Sahel</span>, India, and China. (BT)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032181','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032181"><span>Paleoecology reconstruction from trapped gases in a fulgurite from the late Pleistocene of the Libyan Desert</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Navarro, Gonzalez R.; Mahan, S.A.; Singhvi, A.K.; Navarro-Aceves, R.; Rajot, J.-L.; McKay, C.P.; Coll, P.; Raulin, F.</p> <p>2007-01-01</p> <p>When lightning strikes the ground, it heats, melts, and fuses the sand in soils to form glass tubes known as fulgurites. We report here the composition of CO2, CO, and NO contained within the glassy bubbles of a fulgurite from the Libyan Desert. The results show that the fulgurite formed when the ground contained 0.1 wt% organic carbon with a C/N ratio of 10-15 and a ??13C of -13.96???, compositions similar to those found in the present-day semiarid region of the <span class="hlt">Sahel</span>, where the vegetation is dominated by C4, plants. Thermoluminescence dating indicates that this fulgurite formed ???15 k.y. ago. These results imply that the semiarid <span class="hlt">Sahel</span> (at 17??N) reached at least to 24??N at this time, and demonstrate that fulgurite gases and luminescence geochronology can be used in quantitative paleoecology. ?? 2007 Geological Society of America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890048572&hterms=evapotranspiration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Devapotranspiration','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890048572&hterms=evapotranspiration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Devapotranspiration"><span>Improved ground hydrology calculations for global climate models (GCMs) - Soil water movement and evapotranspiration</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abramopoulos, F.; Rosenzweig, C.; Choudhury, B.</p> <p>1988-01-01</p> <p>A physically based ground hydrology model is presented that includes the processes of transpiration, evaporation from intercepted precipitation and dew, evaporation from bare soil, infiltration, soil water flow, and runoff. Data from the Goddard Institute for Space Studies GCM were used as inputs for off-line tests of the model in four 8 x 10 deg regions, including Brazil, <span class="hlt">Sahel</span>, Sahara, and India. Soil and vegetation input parameters were caculated as area-weighted means over the 8 x 10 deg gridbox; the resulting hydrological quantities were compared to ground hydrology model calculations performed on the 1 x 1 deg cells which comprise the 8 x 10 deg gridbox. Results show that the compositing procedure worked well except in the <span class="hlt">Sahel</span>, where low soil water levels and a heterogeneous land surface produce high variability in hydrological quantities; for that region, a resolution better than 8 x 10 deg is needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5488922','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5488922"><span>Consequences of rapid ice sheet melting on the Sahelian population vulnerability</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ramstein, Gilles; Charbit, Sylvie; Vrac, Mathieu; Famien, Adjoua Moïse; Sultan, Benjamin; Swingedouw, Didier; Dumas, Christophe; Gemenne, François; Alvarez-Solas, Jorge; Vanderlinden, Jean-Paul</p> <p>2017-01-01</p> <p>The acceleration of ice sheet melting has been observed over the last few decades. Recent observations and modeling studies have suggested that the ice sheet contribution to future sea level rise could have been underestimated in the latest Intergovernmental Panel on Climate Change report. The ensuing freshwater discharge coming from ice sheets could have significant impacts on global climate, and especially on the vulnerable tropical areas. During the last glacial/deglacial period, megadrought episodes were observed in the <span class="hlt">Sahel</span> region at the time of massive iceberg surges, leading to large freshwater discharges. In the future, such episodes have the potential to induce a drastic destabilization of the Sahelian agroecosystem. Using a climate modeling approach, we investigate this issue by superimposing on the Representative Concentration Pathways 8.5 (RCP8.5) baseline experiment a Greenland flash melting scenario corresponding to an additional sea level rise ranging from 0.5 m to 3 m. Our model response to freshwater discharge coming from Greenland melting reveals a significant decrease of the West African monsoon rainfall, leading to changes in agricultural practices. Combined with a strong population increase, described by different demography projections, important human migration flows could be potentially induced. We estimate that, without any adaptation measures, tens to hundreds million people could be forced to leave the <span class="hlt">Sahel</span> by the end of this century. On top of this quantification, the sea level rise impact over coastal areas has to be superimposed, implying that the <span class="hlt">Sahel</span> population could be strongly at threat in case of rapid Greenland melting. PMID:28584113</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..598K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..598K"><span>Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kemena, Tronje Peer; Matthes, Katja; Martin, Thomas; Wahl, Sebastian; Oschlies, Andreas</p> <p>2017-09-01</p> <p>Afforestation of the Sahara has been proposed as a climate engineering method to sequester a substantial amount of carbon dioxide, potentially effective to mitigate climate change. Earlier studies predicted changes in the atmospheric circulation system. These atmospheric feedbacks raise questions about the self-sustainability of such an intervention, but have not been investigated in detail. Here, we investigate changes in precipitation and circulation in response to Saharan large-scale afforestation and irrigation with NCAR's CESM-WACCM Earth system model. Our model results show a Saharan temperature reduction by 6 K and weak precipitation enhancement by 267 mm/year over the Sahara. Only 26% of the evapotranspirated water re-precipitates over the Saharan Desert, considerably large amounts are advected southward to the <span class="hlt">Sahel</span> zone and enhance the West African monsoon (WAM). Different processes cause circulation and precipitation changes over North Africa. The increase in atmospheric moisture leads to radiative cooling above the Sahara and increased high-level cloud coverage as well as atmospheric warming above the <span class="hlt">Sahel</span> zone. Both lead to a circulation anomaly with descending air over the Sahara and ascending air over the <span class="hlt">Sahel</span> zone. Together with changes in the meridional temperature gradient, this results in a southward shift of the inner-tropical front. The strengthening of the Tropical easterly jet and the northward displacement of the African easterly jet is associated with a northward displacement and strengthening of the WAM precipitation. Our results suggest complex atmospheric circulation feedbacks, which reduce the precipitation potential over an afforested Sahara and enhance WAM precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28736914','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28736914"><span>Internal diversification of non-Sub-Saharan haplogroups in Sahelian populations and the spread of pastoralism beyond the Sahara.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kulichová, Iva; Fernandes, Verónica; Deme, Alioune; Nováčková, Jana; Stenzl, Vlastimil; Novelletto, Andrea; Pereira, Luísa; Černý, Viktor</p> <p>2017-10-01</p> <p>Today, African pastoralists are found mainly in the <span class="hlt">Sahel</span>/Savannah belt spanning 6,000 km from west to east, flanked by the Sahara to the north and tropical rainforests to the south. The most significant group among them are the Fulani who not only keep cattle breeds of possible West Eurasian ancestry, but form themselves a gene pool containing some paternally and maternally-transmitted West Eurasian haplogroups. We generated complete sequences for 33 mitogenomes belonging to haplogroups H1 and U5 (23 and 10, respectively), and genotyped 16 STRs in 65 Y chromosomes belonging to haplogroup R1b-V88. We show that age estimates of the maternal lineage H1cb1, occurring almost exclusively in the Fulani, point to the time when the first cattle herders settled the <span class="hlt">Sahel</span>/Savannah belt. Similar age estimates were obtained for paternal lineage R1b-V88, which occurs today in the Fulani but also in other, mostly pastoral populations. Maternal clade U5b1b1b, reported earlier in the Berbers, shows a shallower age, suggesting another possibly independent input into the Sahelian pastoralist gene pool. Despite the fact that animal domestication originated in the Near East ∼ 10 ka, and that it was from there that animals such as sheep, goats as well as cattle were introduced into Northeast Africa soon thereafter, contemporary cattle keepers in the <span class="hlt">Sahel</span>/Savannah belt show uniparental genetic affinities that suggest the possibility of an ancient contact with an additional ancestral population of western Mediterranean ancestry. © 2017 Wiley Periodicals, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28584113','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28584113"><span>Consequences of rapid ice sheet melting on the Sahelian population vulnerability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Defrance, Dimitri; Ramstein, Gilles; Charbit, Sylvie; Vrac, Mathieu; Famien, Adjoua Moïse; Sultan, Benjamin; Swingedouw, Didier; Dumas, Christophe; Gemenne, François; Alvarez-Solas, Jorge; Vanderlinden, Jean-Paul</p> <p>2017-06-20</p> <p>The acceleration of ice sheet melting has been observed over the last few decades. Recent observations and modeling studies have suggested that the ice sheet contribution to future sea level rise could have been underestimated in the latest Intergovernmental Panel on Climate Change report. The ensuing freshwater discharge coming from ice sheets could have significant impacts on global climate, and especially on the vulnerable tropical areas. During the last glacial/deglacial period, megadrought episodes were observed in the <span class="hlt">Sahel</span> region at the time of massive iceberg surges, leading to large freshwater discharges. In the future, such episodes have the potential to induce a drastic destabilization of the Sahelian agroecosystem. Using a climate modeling approach, we investigate this issue by superimposing on the Representative Concentration Pathways 8.5 (RCP8.5) baseline experiment a Greenland flash melting scenario corresponding to an additional sea level rise ranging from 0.5 m to 3 m. Our model response to freshwater discharge coming from Greenland melting reveals a significant decrease of the West African monsoon rainfall, leading to changes in agricultural practices. Combined with a strong population increase, described by different demography projections, important human migration flows could be potentially induced. We estimate that, without any adaptation measures, tens to hundreds million people could be forced to leave the <span class="hlt">Sahel</span> by the end of this century. On top of this quantification, the sea level rise impact over coastal areas has to be superimposed, implying that the <span class="hlt">Sahel</span> population could be strongly at threat in case of rapid Greenland melting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27..556B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27..556B"><span>Simulation of Rainfall Variability Over West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bader, J.; Latif, M.</p> <p></p> <p>The impact of sea surface temperature (SST) and vegetation on precipitation over West Africa is investigated with the atmospheric general circulation model ECHAM4.x/T42. Ensemble experiments -driven with observed SST- show that At- lantic SST has a significant influence on JJA precipitation over West Africa. Four- teen experiments were performed in which the climatological SST was enhanced or decreased by one Kelvin in certain ocean areas. Changing SST in the eastern tropi- cal Atlantic only caused significant changes along the Guinea Coast, with a positive SSTA increasing rainfall and a negative reducing it. The response was nearly linear. Changing SST in other ocean areas caused significant changes over West Africa, es- pecially in the <span class="hlt">Sahel</span> area. The response is found to be non linear, with only negative SSTA leading to significant reduction in <span class="hlt">Sahel</span> rainfall. Also, the impact of the SSTAs from the different ocean regions was not additive with respect to the rainfall. Four simulations with a coupled model (the simple dynamic vegetation model (SVege) and the ECHAM4-AGCM were coupled) were also performed, driven with observed SST from 1945 to 1998. The standard ECHAM-AGCM -forced by the same observed SST- was able to reproduce the drying trend from the fifties to the mid-eighties in the <span class="hlt">Sahel</span>, but failed to mirror the magnitude of the rainfall anomalies. The coupled model was not only able to reproduce this drying trend, but was also able to better reproduce the amplitudes of the rainfall anomalies. The dynamic vegetation acted like an amplifier, increasing the SST induced rainfall anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4561K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4561K"><span>Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kemena, Tronje Peer; Matthes, Katja; Martin, Thomas; Wahl, Sebastian; Oschlies, Andreas</p> <p>2018-06-01</p> <p>Afforestation of the Sahara has been proposed as a climate engineering method to sequester a substantial amount of carbon dioxide, potentially effective to mitigate climate change. Earlier studies predicted changes in the atmospheric circulation system. These atmospheric feedbacks raise questions about the self-sustainability of such an intervention, but have not been investigated in detail. Here, we investigate changes in precipitation and circulation in response to Saharan large-scale afforestation and irrigation with NCAR's CESM-WACCM Earth system model. Our model results show a Saharan temperature reduction by 6 K and weak precipitation enhancement by 267 mm/year over the Sahara. Only 26% of the evapotranspirated water re-precipitates over the Saharan Desert, considerably large amounts are advected southward to the <span class="hlt">Sahel</span> zone and enhance the West African monsoon (WAM). Different processes cause circulation and precipitation changes over North Africa. The increase in atmospheric moisture leads to radiative cooling above the Sahara and increased high-level cloud coverage as well as atmospheric warming above the <span class="hlt">Sahel</span> zone. Both lead to a circulation anomaly with descending air over the Sahara and ascending air over the <span class="hlt">Sahel</span> zone. Together with changes in the meridional temperature gradient, this results in a southward shift of the inner-tropical front. The strengthening of the Tropical easterly jet and the northward displacement of the African easterly jet is associated with a northward displacement and strengthening of the WAM precipitation. Our results suggest complex atmospheric circulation feedbacks, which reduce the precipitation potential over an afforested Sahara and enhance WAM precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=drought&pg=7&id=EJ131442','ERIC'); return false;" href="https://eric.ed.gov/?q=drought&pg=7&id=EJ131442"><span>Food From the Basin</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Thai, Vu Van</p> <p>1975-01-01</p> <p>This article is concerned with the agricultural and economic development of the <span class="hlt">Sahel</span>, an area characterized by uneven climate. Conditions caused by floods and droughts have necessitated the establishment of water management programs to maintain water quality and quantity. Development of this region is designed to follow environmental conservation…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18..445D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18..445D"><span>Interactions of atmospheric gases and aerosols with the monsoon dynamics over the Sudano-Guinean region during AMMA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deroubaix, Adrien; Flamant, Cyrille; Menut, Laurent; Siour, Guillaume; Mailler, Sylvain; Turquety, Solène; Briant, Régis; Khvorostyanov, Dmitry; Crumeyrolle, Suzanne</p> <p>2018-01-01</p> <p>Carbon monoxide, CO, and fine atmospheric particulate matter, PM2.5, are analyzed over the Guinean Gulf coastal region using the WRF-CHIMERE modeling system and observations during the beginning of the monsoon 2006 (from May to July), corresponding to the Africa Multidisciplinary Monsoon Analysis (AMMA) campaign period. Along the Guinean Gulf coast, the contribution of long-range pollution transport to CO or PM2.5 concentrations is important. The contribution of desert dust PM2.5 concentration decreases from ˜ 38 % in May to ˜ 5 % in July. The contribution of biomass burning PM2.5 concentration from Central Africa increases from ˜ 10 % in May to ˜ 52 % in July. The anthropogenic contribution is ˜ 30 % for CO and ˜ 10 % for PM2.5 during the whole period. When focusing only on anthropogenic pollution, frequent northward transport events from the coast to the <span class="hlt">Sahel</span> are associated with periods of low wind and no precipitation. In June, anthropogenic PM2.5 and CO concentrations are higher than in May or July over the Guinean coastal region. Air mass dynamics concentrate pollutants emitted in the <span class="hlt">Sahel</span> due to a meridional atmospheric cell. Moreover, a part of the pollution emitted remotely at the coast is transported and accumulated over the <span class="hlt">Sahel</span>. Focusing the analysis on the period 8-15 June, anthropogenic pollutants emitted along the coastline are exported toward the north especially at the beginning of the night (18:00 to 00:00 UTC) with the establishment of the nocturnal low level jet. Plumes originating from different cities are mixed for some hours at the coast, leading to high pollution concentration, because of specific disturbed meteorological conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26371296','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26371296"><span>On regreening and degradation in Sahelian watersheds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kaptué, Armel T; Prihodko, Lara; Hanan, Niall P</p> <p>2015-09-29</p> <p>Over many decades our understanding of the impacts of intermittent drought in water-limited environments like the West African <span class="hlt">Sahel</span> has been influenced by a narrative of overgrazing and human-induced desertification. The desertification narrative has persisted in both scientific and popular conception, such that recent regional-scale recovery ("regreening") and local success stories (community-led conservation efforts) in the <span class="hlt">Sahel</span>, following the severe droughts of the 1970s-1980s, are sometimes ignored. Here we report a study of watershed-scale vegetation dynamics in 260 watersheds, sampled in four regions of Senegal, Mali, and Niger from 1983-2012, using satellite-derived vegetation indices as a proxy for net primary production. In response to earlier controversy, we first examine the shape of the rainfall-net primary production relationship and how it impacts conclusions regarding greening or degradation. We conclude that the choice of functional relationship has little quantitative impact on our ability to infer greening or degradation trends. We then present an approach to analyze changes in long-term (decade-scale) average rain-use efficiency (an indicator of slowly responding vegetation structural changes) relative to changes in interannual-scale rainfall sensitivity (an indicator of landscape ability to respond rapidly to rainfall variability) to infer trends in greening/degradation of the watersheds in our sample regions. The predominance of increasing rain-use efficiency in our data supports earlier reports of a "greening" trend across the <span class="hlt">Sahel</span>. However, there are strong regional differences in the extent and direction of change, and in the apparent role of changing woody and herbaceous components in driving those temporal trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4593076','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4593076"><span>On regreening and degradation in Sahelian watersheds</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kaptué, Armel T.; Prihodko, Lara; Hanan, Niall P.</p> <p>2015-01-01</p> <p>Over many decades our understanding of the impacts of intermittent drought in water-limited environments like the West African <span class="hlt">Sahel</span> has been influenced by a narrative of overgrazing and human-induced desertification. The desertification narrative has persisted in both scientific and popular conception, such that recent regional-scale recovery (“regreening”) and local success stories (community-led conservation efforts) in the <span class="hlt">Sahel</span>, following the severe droughts of the 1970s–1980s, are sometimes ignored. Here we report a study of watershed-scale vegetation dynamics in 260 watersheds, sampled in four regions of Senegal, Mali, and Niger from 1983–2012, using satellite-derived vegetation indices as a proxy for net primary production. In response to earlier controversy, we first examine the shape of the rainfall–net primary production relationship and how it impacts conclusions regarding greening or degradation. We conclude that the choice of functional relationship has little quantitative impact on our ability to infer greening or degradation trends. We then present an approach to analyze changes in long-term (decade-scale) average rain-use efficiency (an indicator of slowly responding vegetation structural changes) relative to changes in interannual-scale rainfall sensitivity (an indicator of landscape ability to respond rapidly to rainfall variability) to infer trends in greening/degradation of the watersheds in our sample regions. The predominance of increasing rain-use efficiency in our data supports earlier reports of a “greening” trend across the <span class="hlt">Sahel</span>. However, there are strong regional differences in the extent and direction of change, and in the apparent role of changing woody and herbaceous components in driving those temporal trends. PMID:26371296</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGC22A..05C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGC22A..05C"><span>Future Projections of ENSO and Drought (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cane, M. A.</p> <p>2009-12-01</p> <p>Jule Charney, who was my advisor, worked very broadly - and profoundly - on climate dynamics. In this discussion of the present state of knowledge I will focus on two aspects of climate that I view as legacies of his work: our ability to project climate variability in the tropics and to project drought. (I have in mind his work with Shukla on predictability of monsoons, and Charney 1975, Dynamics of deserts and drought in the <span class="hlt">Sahel</span>., Q. J. Roy. Meteor. Soc., 101, 193-202). First, I will consider the projections of ENSO (El Niño and Southern Oscillation) in a warming world. (My own interest in ENSO was piqued in discussions with Charney and others during the ENSO-influenced blocking events in the late 1970s; in good measure, the approach I took to understanding and modeling ENSO was based in my thesis work.) Current IPCC models differ markedly in their projections of the mean state of the equatorial Pacific, some favoring a more “El Niño- like”, some the opposite. Possible reasons for these disagreements will be considered in the light of our understanding of ENSO and tropical climate more generally. Observational data for the past century and a half will figure prominently. Droughts in the US Southwest have a strong ENSO signal, but IPCC models are fairly consistent in projecting enhanced drought there. The reasons for this will be discussed. Models are less consistent in their predictions of the future <span class="hlt">Sahel</span>. I will discuss what is understood about causes of drought in the <span class="hlt">Sahel</span>, which appear to point toward sea surface temperature as the controlling influence, in contrast to Charney’s albedo hypothesis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JHyd..375..114H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JHyd..375..114H"><span>Sahelian rangeland response to changes in rainfall over two decades in the Gourma region, Mali</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hiernaux, Pierre; Mougin, Eric; Diarra, Lassine; Soumaguel, Nogmana; Lavenu, François; Tracol, Yann; Diawara, Mamadou</p> <p>2009-08-01</p> <p>SummaryTwenty-five rangeland sites were monitored over two decades (1984-2006) first to assess the impact of the 1983-1984 droughts on fodder resources, then to better understand ecosystem functioning and dynamics. Sites are sampled along the south-north bioclimatic gradient in Gourma (Mali), within three main edaphic situations: sandy, loamy-clay and shallow soils. In addition, three levels of grazing pressure where systematically sampled within sandy soils. Located at the northern edge of the area reached by the West African monsoon, the Gourma gradient has recorded extremes in inter-annual variations of rainfall and resulting variations in vegetation growth. Following rainfall variability, inter-annual variability of herbaceous yield increases as climate gets dryer with latitudes at least on the sandy soils sites. Local redistribution of rainfall explains the high patchiness of herbaceous vegetation, especially on shallow soils. Yet spatial heterogeneity of the vegetation does not buffer between year yield variability that increases with spatial heterogeneity. At short term, livestock grazing during the wet season affects plant growth and thus yield in direction and proportions that vary with the timing and intensity of grazing. In the longer term, grazing also impinges upon species composition in many ways. Hence, long histories of heavy grazing promote either long cycle annuals refused by livestock or else short cycle good quality feed species. Primary production is maintained or even increased in the case of refusal such as Sida cordifolia, and is lessened in the case of short cycle species such as Zornia glochidiata. These behaviours explain that the yield anomalies calculated for the rangelands on sandy soils relative to the yield of site less grazed under similar climate tend to be negative in northern <span class="hlt">Sahel</span> where the scenario of short cycle species dominates, while yield anomalies are close to nil in centre <span class="hlt">Sahel</span> and slightly positive in South <span class="hlt">Sahel</span> where</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=tins&pg=6&id=ED222311','ERIC'); return false;" href="https://eric.ed.gov/?q=tins&pg=6&id=ED222311"><span>Tin Aicha Nomad Village.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>American Friends Service Committee, Philadelphia, PA.</p> <p></p> <p>The report details some aspects of the American Friends Service Committee's (AFSC) and the Mali government's cooperative rehabilitation project for nomad families along the shores of Lake Faguibine. Covering the years 1975-81, the report contains five sections. The introduction provides background information on nomads and the <span class="hlt">Sahel</span>; drought,…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26PSL.486...23Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26PSL.486...23Z"><span>Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Wancang; Balsam, William; Williams, Earle; Long, Xiaoyong; Ji, Junfeng</p> <p>2018-03-01</p> <p>Long-range transport of African dust plays an important role in understanding dust-climate relationships including dust source areas, dust pathways and associated atmospheric and/or oceanic processes. Clay-sized Sr-Nd-Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust. We investigated the clay-sized Sr-Nd-Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. The transects are from Mali, Niger/Benin/Togo, Egypt and Morocco. Our results show that the Mali transect on the West African Craton (WAC) produces lower εNd (εNd-mean = -16.38) and εHf (εHf-mean = -9.59) values than the other three transects. The Egyptian transect exhibits the lowest 87Sr/86Sr ratios (87Sr/86Srmean = 0.709842), the highest εHf (εHf-mean = -0.34) and εNd values of the four transects. Comparison of the clay-sized Sr-Nd-Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust's provenance is primarily the western <span class="hlt">Sahel</span> and Sahara as well as the central <span class="hlt">Sahel</span>. Summer emission dust is derived mainly from the western <span class="hlt">Sahel</span> and Sahara regions. The source of transatlantic dust in spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd-Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through the spring and into the summer. The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED242564.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED242564.pdf"><span>Volunteer Notes on Reforestation. A Handbook for Volunteers. Appropriate Technologies for Development. Reprint R-45.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Seefeldt, Steve, Comp.</p> <p></p> <p>Provided in this document are descriptions of reforestation projects and techniques presented by Peace Corps volunteers from Chad, Ivory Coast, Upper Volta, and Niger. The purpose of the document is to aid individuals in trying to find solutions to the problems facing forestry in the <span class="hlt">Sahel</span>. These projects include: (1) reforestation of Ronier palm…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC12A..01N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC12A..01N"><span>A review of our understanding of the role played in the climate system by land surface processes (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicholson, S. E.</p> <p>2013-12-01</p> <p>The paper provides an historical review of research on the impact of the land surface on climate. It commences will the seminal work of Jule Charney on albedo as a potential cause of drought and follows the trail of follow-up studies on the question of desertification and its role in climate. With the exception of a very early paper by Namias, early work was limited mainly to modeling efforts. At the same time, several observational studies provided evidence that land surface feedbacks could enhance and prolong drought, especially in the African <span class="hlt">Sahel</span>. Later work emphasized the role of soil moisture rather than albedo. Several important field studies also examined the role of the land surface. Examples include FIFE, HAPEX-<span class="hlt">Sahel</span> and BOREAS. In recent years some major changes in the concept have occurred. There is now substantial observational evidence of an impact at the mesoscale. The role of land surface feedback on climate has become mainstream. Finally, a new subdiscipline has emerged that emphasizes feedbacks between the water cycle, vegetation and climate, namely ecohydrology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NPGD....1..479G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NPGD....1..479G"><span>On the data-driven inference of modulatory networks in climate science: an application to West African rainfall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>González, D. L., II; Angus, M. P.; Tetteh, I. K.; Bello, G. A.; Padmanabhan, K.; Pendse, S. V.; Srinivas, S.; Yu, J.; Semazzi, F.; Kumar, V.; Samatova, N. F.</p> <p>2014-04-01</p> <p>Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African <span class="hlt">Sahel</span> summer rainfall variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression, and Dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate <span class="hlt">Sahel</span> rainfall, including well-known associations from prior climate knowledge, as well as promising discoveries that invite further research by the climate science community.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC23A0614B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC23A0614B"><span>Quantifying Livestock Heat Stress Impacts in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Broman, D.; Rajagopalan, B.; Hopson, T. M.</p> <p>2014-12-01</p> <p>Livestock heat stress, especially in regions of the developing world with limited adaptive capacity, has a largely unquantified impact on food supply. Though dominated by ambient air temperature, relative humidity, wind speed, and solar radiation all affect heat stress, which can decrease livestock growth, milk production, reproduction rates, and mortality. Indices like the thermal-humidity index (THI) are used to quantify the heat stress experienced from climate variables. Livestock experience differing impacts at different index critical thresholds that are empirically determined and specific to species and breed. This lack of understanding has been highlighted in several studies with a limited knowledge of the critical thresholds of heat stress in native livestock breeds, as well as the current and future impact of heat stress,. As adaptation and mitigation strategies to climate change depend on a solid quantitative foundation, this knowledge gap has limited such efforts. To address the lack of study, we have investigated heat stress impacts in the pastoral system of Sub-Saharan West Africa. We used a stochastic weather generator to quantify both the historic and future variability of heat stress. This approach models temperature, relative humidity, and precipitation, the climate variables controlling heat stress. Incorporating large-scale climate as covariates into this framework provides a better historical fit and allows us to include future CMIP5 GCM projections to examine the climate change impacts on heat stress. Health and production data allow us to examine the influence of this variability on livestock directly, and are considered in conjunction with the confounding impacts of fodder and water access. This understanding provides useful information to decision makers looking to mitigate the impacts of climate change and can provide useful seasonal forecasts of heat stress risk. A comparison of the current and future heat stress conditions based on climate variables for West Africa will be presented, An assessment of current and future risk was obtained by linking climatic heat stress to cattle health and production. Seasonal forecasts of heat stress are also provided by modeling the heat stress climate variables using persistent large-scale climate features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010ACP....1012005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010ACP....1012005C"><span>Variability of aerosol vertical distribution in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cavalieri, O.; Cairo, F.; Fierli, F.; di Donfrancesco, G.; Snels, M.; Viterbini, M.; Cardillo, F.; Chatenet, B.; Formenti, P.; Marticorena, B.; Rajot, J. L.</p> <p>2010-12-01</p> <p>In this work, we have studied the seasonal and inter-annual variability of the aerosol vertical distribution over Sahelian Africa for the years 2006, 2007 and 2008, characterizing the different kind of aerosols present in the atmosphere in terms of their optical properties observed by ground-based and satellite instruments, and their sources searched for by using trajectory analysis. This study combines data acquired by three ground-based micro lidar systems located in Banizoumbou (Niger), Cinzana (Mali) and M'Bour (Senegal) in the framework of the African Monsoon Multidisciplinary Analysis (AMMA), by the AEROsol RObotic NETwork (AERONET) sun-photometers and by the space-based Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the CALIPSO satellite (Cloud-Aerosol Lidar and Infrared Pathfinder Observations). During winter, the lower levels air masses arriving in the Sahelian region come mainly from North, North-West and from the Atlantic area, while in the upper troposphere air flow generally originates from West Africa, crossing a region characterized by the presence of large biomass burning sources. The sites of Cinzana, Banizoumbou and M'Bour, along a transect of aerosol transport from East to West, are in fact under the influence of tropical biomass burning aerosol emission during the dry season, as revealed by the seasonal pattern of the aerosol optical properties, and by back-trajectory studies. Aerosol produced by biomass burning are observed mainly during the dry season and are confined in the upper layers of the atmosphere. This is particularly evident for 2006, which was characterized by a large presence of biomass burning aerosols in all the three sites. Biomass burning aerosol is also observed during spring when air masses originating from North and East Africa pass over sparse biomass burning sources, and during summer when biomass burning aerosol is transported from the southern part of the continent by the monsoon flow. During summer months, the entire Sahelian region is under the influence of Saharan dust aerosols: the air masses in low levels arrive from West Africa crossing the Sahara desert or from the Southern Hemisphere crossing the Guinea Gulf while in the upper layers air masses still originate from North, North-East. The maximum of the desert dust activity is observed in this period which is characterized by large AOD (above 0.2) and backscattering values. It also corresponds to a maximum in the extension of the aerosol vertical distribution (up to 6 km of altitude). In correspondence, a progressive cleaning up of the lowermost layers of the atmosphere is occurring, especially evident in the Banizoumbou and Cinzana sites. Summer is in fact characterized by extensive and fast convective phenomena. Lidar profiles show at times large dust events loading the atmosphere with aerosol from the ground up to 6 km of altitude. These events are characterized by large total attenuated backscattering values, and alternate with very clear profiles, sometimes separated by only a few hours, indicative of fast removal processes occurring, likely due to intense convective and rain activity. The inter-annual variability in the three year monitoring period is not very significant. An analysis of the aerosol transport pathways, aiming at detecting the main source regions, revealed that air originated from the Saharan desert is present all year long and it is observed in the lower levels of the atmosphere at the beginning and at the end of the year. In the central part of the year it extends upward and the lower levels are less affected by air masses from Saharan desert when the monsoon flow carries air from the Guinea Gulf and the Southern Hemisphere inland.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910056466&hterms=livestock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dlivestock','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910056466&hterms=livestock&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dlivestock"><span>Spectral modelling of multicomponent landscapes in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hanan, N. P.; Prince, S. D.; Hiernaux, P. H. Y.</p> <p>1991-01-01</p> <p>Simple additive models are used to examine the infuence of differing soil types on the spatial average spectral reflectance and normalized difference vegetation index (NDVI). The spatial average NDVI is shown to be a function of the brightness (red plus near-infrared reflectances), the NDVI, and the fractional cover of the components. In landscapes where soil and vegetation can be considered the only components, the NDVI-brightness model can be inverted to obtain the NDVI of vegetation. The red and near-infrared component reflectances of soil and vegetation are determined on the basis of aerial photoradiometer data from Mali. The relationship between the vegetation component NDVI and plant cover is found to be better than between the NDVI of the entire landscape and plant cover. It is concluded that the usefulness of this modeling approach depends on the existence of clearly distinguishable landscape components.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA588904','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA588904"><span>Evaluating U.S. and EU Trans <span class="hlt">Sahel</span> Policies</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-03-01</p> <p>elected leaders as well as young Africans who are leaders in civil society and entrepreneurship . Protecting Human Rights, Civil Society, and...GSPC: Newest Franchise in al-Qa‘ida‘s Global Jihad,‖ The Combating Terrorism Center, United States Military Academy, West Point, April 2007, 2. 40</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/26481','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/26481"><span>Social Memory of Short-term and Long-term Variability in the Sahelian Climate</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Roderick J. McIntosh</p> <p>2006-01-01</p> <p>The 170,000 km2 interior floodplain of the Middle Niger (Mali) is a tight mosaic of alluvial and desert microenvironments. The interannual to intermillennial climate change profiles of this fluvial anomaly thrust deep into the <span class="hlt">Sahel</span> and southern Sahara are masterpieces of abrupt phase shifts and unpredictability. Response has been of two kinds. The Office du Niger was...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=contact+AND+area&pg=2&id=EJ1071522','ERIC'); return false;" href="https://eric.ed.gov/?q=contact+AND+area&pg=2&id=EJ1071522"><span>The Sign Language Situation in Mali</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Nyst, Victoria</p> <p>2015-01-01</p> <p>This article gives a first overview of the sign language situation in Mali and its capital, Bamako, located in the West African <span class="hlt">Sahel</span>. Mali is a highly multilingual country with a significant incidence of deafness, for which meningitis appears to be the main cause, coupled with limited access to adequate health care. In comparison to neighboring…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMGC33A1006P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMGC33A1006P"><span>Interactions and Feedbacks Between Land Surface Processes and Water Cycle Dynamics in Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prince, S. D.; Xue, Y.; Song, G.; Cox, P. M.</p> <p>2012-12-01</p> <p>In the past three decades, numerous modeling sensitivity studies have established the importance of detailed vegetation and atmosphere interactions in West African water cycle dynamics. Recently, new evidence has emerged from satellite data analyses that indicate a fully coupled process is needed to explain the relationships discovered in these analyses. In order to elucidate the processes, we have applied the off-line Simplified Simple Biosphere Model version 4/Top-down Representation of Interactive Foliage and Flora Including Dynamics Model (SSiB4/TRIFFID). SSiB4 is a biophysical model based on surface water and energy balance which interacts with TRIFFID by providing the carbon assimilation. TRIFFID is a dynamic vegetation model based on carbon balance. The offline SSiB4/TRIFFID was integrated using the observed precipitation and reanalysis-based meteorological forcing from 1948 to 2006 over West Africa. West Africa has diverse climate and ecosystem regions. It suffered the most severe and longest drought in the world during the 20th century, and has the most pronounced decadal water cycle variability in the planet. The simulation results indicate that the water cycle variability has significant effects on the spatial distributions and temporal variations of plant functional types and leaf area index (LAI), which are generally consistent with those observed from satellites since the 1980s. The simulated vegetation conditions over <span class="hlt">Sahel</span> region exhibited seasonal, inter-annual variations, consistent with West Africa monsoon variability, and the simulated inter-decadal variability in vegetation was consistent with the <span class="hlt">Sahel</span> drought in the 1970s and 1980s and partial recovery in the 1990s and 2000s. To further understand the cause of decadal variability of climate, water cycle and vegetation dynamics, experiments were conducted to investigate the relationship between the LAI, atmospheric carbon dioxide increase and global warming. In one experiment, the 1948</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.3350G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.3350G"><span>Lateral extrusion of Tunisia : Contribution of Jeffara Fault (southern branch) and Petroleum Implications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghedhoui, R.; Deffontaines, B.; Rabia, M. C.</p> <p>2012-04-01</p> <p>Contrasting to the northward African plate motion toward Eurasia and due to its geographic position in the North African margin, since early cretaceous, Tunisia seems to be submitted to an eastward migration. The aim of this work is to study the southern branch of this inferred tectonic splay that may guide the Tunisian extrusion characterised to the east by the Mediterranean sea as a free eastern boundary. The Jeffara Fault zone (southern Tunisia), represent a case example of such deformation faced by Tunisia. Helped by the results of previous researchers (Bouaziz, 1995 ; Rabiaa, 1998 ; Touati et Rodgers, 1998 ; Sokoutis D. et al., 2000 ; Bouaziz et al., 2002 ; Jallouli et al., 2005 ; Deffontaines et al., 2008…), and new evidences developed in this study, we propose a geodynamic Tunisian east extrusion model, due to such the northern African plate migration to the Eurasian one. In this subject, structural geomorphology is undertaken herein based on both geomorphometric drainage network analysis (Deffontaines et al., 1990), the Digital Terrain Model photo-interpretation (SRTM) combined with photo-interpretation of detailed optical images (Landsat ETM+), and confirmed by field work and numerous seismic profiles at depth. All these informations were then integrated within a GIS (Geodatabase) (Deffontaines 1990 ; Deffontaines et al. 1994 ; Deffontaines, 2000 ; Slama, 2008 ; Deffontaines, 2008) and are coherent with the eastern extrusion of the <span class="hlt">Sahel</span> block. We infer that the NW-SE Gafsa-Tozeur, which continue to the Jeffara major fault zone acting as a transtensive right lateral motion since early cretaceous is the southern branch of the <span class="hlt">Sahel</span> block extrusion. Our structural analyses prove the presence of NW-SE right lateral en-echelon tension gashes, NW-SE aligned salt diapirs, numerous folds offsets, en-echelon folds, and so on that parallel this major NW-SE transtensive extrusion fault zone.These evidences confirm the fact that the NW-SE Jeffara faults correspond</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018NatGe..11..328B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018NatGe..11..328B"><span>Reduction of tree cover in West African woodlands and promotion in semi-arid farmlands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brandt, Martin; Rasmussen, Kjeld; Hiernaux, Pierre; Herrmann, Stefanie; Tucker, Compton J.; Tong, Xiaoye; Tian, Feng; Mertz, Ole; Kergoat, Laurent; Mbow, Cheikh; David, John L.; Melocik, Katherine A.; Dendoncker, Morgane; Vincke, Caroline; Fensholt, Rasmus</p> <p>2018-05-01</p> <p>Woody vegetation in farmland acts as a carbon sink and provides ecosystem services for local people, but no macroscale assessments of the impact of management and climate on woody cover exist for drylands. Here we make use of very high spatial resolution satellite imagery to derive wall-to-wall woody cover patterns in tropical West African drylands. Our study reveals that mean woody cover in farmlands along all semi-arid and sub-humid rainfall zones is 16%, on average only 6% lower than in savannahs. In semi-arid <span class="hlt">Sahel</span>, farmland management promotes woody cover around villages (11%), while neighbouring savannahs had on average less woody cover. However, farmlands in sub-humid zones have a greatly reduced woody cover (21%) as compared with savannahs (33%). In the region as a whole, rainfall, terrain and soil are the most important (80%) determinants of woody cover, while management factors play a smaller (20%) role. We conclude that agricultural expansion causes a considerable reduction of trees in woodlands, but observations in <span class="hlt">Sahel</span> indicate that villagers safeguard trees on nearby farmlands which contradicts simplistic ideas of a high negative correlation between population density and woody cover.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NPGeo..22...33G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NPGeo..22...33G"><span>On the data-driven inference of modulatory networks in climate science: an application to West African rainfall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>González, D. L., II; Angus, M. P.; Tetteh, I. K.; Bello, G. A.; Padmanabhan, K.; Pendse, S. V.; Srinivas, S.; Yu, J.; Semazzi, F.; Kumar, V.; Samatova, N. F.</p> <p>2015-01-01</p> <p>Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African <span class="hlt">Sahel</span> summer rainfall~variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression, and dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate <span class="hlt">Sahel</span> rainfall. These relationships fall into two categories: well-known associations from prior climate knowledge, such as the relationship with the El Niño-Southern Oscillation (ENSO) and putative links, such as North Atlantic Oscillation, that invite further research.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1333075-data-driven-inference-modulatory-networks-climate-science-application-west-african-rainfall','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1333075-data-driven-inference-modulatory-networks-climate-science-application-west-african-rainfall"><span>On the data-driven inference of modulatory networks in climate science: An application to West African rainfall</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Gonzalez, II, D. L.; Angus, M. P.; Tetteh, I. K.; ...</p> <p>2015-01-13</p> <p>Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African <span class="hlt">Sahel</span> summer rainfall~variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression,more » and dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate <span class="hlt">Sahel</span> rainfall. As a result, these relationships fall into two categories: well-known associations from prior climate knowledge, such as the relationship with the El Niño–Southern Oscillation (ENSO) and putative links, such as North Atlantic Oscillation, that invite further research.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1393738-state-climate','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1393738-state-climate"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Blunden, Jessica; Arndt, Derek S.</p> <p></p> <p>West Africa refers to the region between 17.5°W (eastern Atlantic coast) and ~15°E (along the western border of Chad) and north of the equator (near Guinean coast) to about 20°N. It is divided into two climatically distinct subregions; the semiarid <span class="hlt">Sahel</span> region (north of about 12°N) and the relatively wet Coast of Guinea region to the south.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA563498','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA563498"><span>Why Failing Terrorist Groups Persist: The Case of Al-Qaeda in the Islamic Maghreb</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-06-01</p> <p>and Nigeria in the South). As an AQ franchise organization their goals now include attacking western interests within the <span class="hlt">Sahel</span>.10 Lastly, AQIM...concerning NEA. 317 Official, interview concerning NEA. 318 Official, interview concerning NEA 76 open society and encouraged entrepreneurship as...focused on criminal entrepreneurship than the AQIM Islamist ideology.359 The Joint Staff does not see an end to AQIM without a significant change in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170003214&hterms=Anthropology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnthropology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170003214&hterms=Anthropology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DAnthropology"><span>Assessing Woody Vegetation Trends in Sahelian Drylands Using MODIS Based Seasonal Metrics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brandt, Martin; Hiernaux, Pierre; Rasmussen, Kjeld; Mbow, Cheikh; Kergoat, Laurent; Tagesson, Torbern; Ibrahim, Yahaya Z.; Wele, Abdoulaye; Tucker, Compton J.; Fensholt, Rasmus</p> <p>2016-01-01</p> <p>Woody plants play a major role for the resilience of drylands and in peoples' livelihoods. However, due to their scattered distribution, quantifying and monitoring woody cover over space and time is challenging. We develop a phenology driven model and train/validate MODIS (MCD43A4, 500m) derived metrics with 178 ground observations from Niger, Senegal and Mali to estimate woody cover trends from 2000 to 2014 over the entire <span class="hlt">Sahel</span>. The annual woody cover estimation at 500 m scale is fairly accurate with an RMSE of 4.3 (woody cover %) and r(exp 2) = 0.74. Over the 15 year period we observed an average increase of 1.7 (+/- 5.0) woody cover (%) with large spatial differences: No clear change can be observed in densely populated areas (0.2 +/- 4.2), whereas a positive change is seen in sparsely populated areas (2.1 +/- 5.2). Woody cover is generally stable in cropland areas (0.9 +/- 4.6), reflecting the protective management of parkland trees by the farmers. Positive changes are observed in savannas (2.5 +/- 5.4) and woodland areas (3.9 +/- 7.3). The major pattern of woody cover change reveals strong increases in the sparsely populated <span class="hlt">Sahel</span> zones of eastern Senegal, western Mali and central Chad, but a decreasing trend is observed in the densely populated western parts of Senegal, northern Nigeria, Sudan and southwestern Niger. This decrease is often local and limited to woodlands, being an indication of ongoing expansion of cultivated areas and selective logging.We show that an overall positive trend is found in areas of low anthropogenic pressure demonstrating the potential of these ecosystems to provide services such as carbon storage, if not over-utilized. Taken together, our results provide an unprecedented synthesis of woody cover dynamics in the<span class="hlt">Sahel</span>, and point to land use and human population density as important drivers, however only partially and locally offsetting a general post-drought increase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A32E..04Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A32E..04Y"><span>Observed Oceanic and Terrestrial Drivers of North African Climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Notaro, M.; Wang, F.; Mao, J.; Shi, X.; Wei, Y.</p> <p>2015-12-01</p> <p>Hydrologic variability can pose a serious threat to the poverty-stricken regions of North Africa. Yet, the current understanding of oceanic versus terrestrial drivers of North African droughts/pluvials is largely model-based, with vast disagreement among models. In order to identify the observed drivers of North African climate and develop a benchmark for model evaluations, the multivariate Generalized Equilibrium Feedback Assessment (GEFA) is applied to observations, remotely sensed data, and reanalysis products. The identified primary oceanic drivers of North African rainfall variability are the Atlantic, tropical Indian, and tropical Pacific Oceans and Mediterranean Sea. During the summer monsoon, positive tropical eastern Atlantic sea-surface temperature (SST) anomalies are associated with a southward shift of the Inter-Tropical Convergence Zone, enhanced ocean evaporation, and greater precipitable water across coastal West Africa, leading to increased West African monsoon (WAM) rainfall and decreased <span class="hlt">Sahel</span> rainfall. During the short rains, positive SST anomalies in the western tropical Indian Ocean and negative anomalies in the eastern tropical Indian Ocean support greater easterly oceanic flow, evaporation over the western ocean, and moisture advection to East Africa, thereby enhancing rainfall. The sign, magnitude, and timing of observed vegetation forcing on rainfall vary across North Africa. The positive feedback of leaf area index (LAI) on rainfall is greatest during DJF for the Horn of Africa, while it peaks in autumn and is weakest during the summer monsoon for the <span class="hlt">Sahel</span>. Across the WAM region, a positive LAI anomaly supports an earlier monsoon onset, increased rainfall during the pre-monsoon, and decreased rainfall during the wet season. Through unique mechanisms, positive LAI anomalies favor enhanced transpiration, precipitable water, and rainfall across the <span class="hlt">Sahel</span> and Horn of Africa, and increased roughness, ascent, and rainfall across the WAM region</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GPC...165..114N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GPC...165..114N"><span>Rainfall over the African continent from the 19th through the 21st century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nicholson, Sharon E.; Funk, Chris; Fink, Andreas H.</p> <p>2018-06-01</p> <p>Most of the African continent is semi-arid and hence prone to extreme variations in rainfall from year to year. The extreme droughts that have plagued the <span class="hlt">Sahel</span> and eastern Africa are particularly well known. This article uses a markedly expanded and updated rainfall data set to examine rainfall variability in 13 sectors that cover most of the continent. Annual rainfall is presented for each sector; the March-to-May and October-November seasons are also examined for equatorial sectors. In each case, the article includes the longest and most comprehensive precipitation gauge series ever published. All time series cover at least a century and most cover roughly one and one-half centuries or more. Although towards the end of the 20th century there was a widespread trend towards more arid conditions, few significant trends are evident over the entire period of record. The largest were downward trends in the <span class="hlt">Sahel</span> and western sectors of North Africa. In those regions, an abrupt reduction in rainfall occurred around 1968, but a synchronous change occurred many other parts of Africa. A recovery did occur in the <span class="hlt">Sahel</span>, but to varying degrees across the east-west expanse of the region. Noteworthy is that the west-to-east rainfall gradient across the region appears to have weakened in recent decades. For the continent as a whole, another change began in the 1980s decade, with more arid conditions persisting at the continental scale until early in the twenty-first century. No other such period of dry conditions occurred within the roughly one and one-half centuries evaluated here. A notable change also occurred at the seasonal level. During the period 1980 to 1998 rainfall during March-to-May was well below the long-term mean throughout most of the area from 20° N to 35° S. At the same time rainfall was above the long-term mean in most of eastern sectors within this latitude span, indicating a change in the seasonality of rainfall of a large part of Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC23C1152S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC23C1152S"><span>Attributing Climate Conditions for Stable Malaria Transmission to Human Activity in sub-Saharan Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sheldrake, L.; Mitchell, D.; Allen, M. R.</p> <p>2015-12-01</p> <p>Temperature and precipitation limit areas of stable malaria transmission, but the effects of climate change on the disease remain controversial. Previously, studies have not separated the influence of anthropogenic climate change and natural variability, despite being an essential step in the attribution of climate change impacts. Ensembles of 2900 simulations of regional climate in sub-Saharan Africa for the year 2013, one representing realistic conditions and the other how climate might have been in the absence of human influence, were used to force a P.falciparium climate suitability model developed by the Mapping Malaria Risk in Africa project. Strongest signals were detected in areas of unstable transmission, indicating their heightened sensitivity to climatic factors. Evidently, impacts of human-induced climate change were unevenly distributed: the probability of conditions being suitable for stable malaria transmission were substantially reduced (increased) in the <span class="hlt">Sahel</span> (Greater Horn of Africa (GHOA), particularly in the Ethiopian and Kenyan highlands). The length of the transmission season was correspondingly shortened in the <span class="hlt">Sahel</span> and extended in the GHOA, by 1 to 2 months, including in Kericho (Kenya), where the role of climate change in driving recent malaria occurrence is hotly contested. Human-induced warming was primarily responsible for positive anomalies in the GHOA, while reduced rainfall caused negative anomalies in the <span class="hlt">Sahel</span>. The latter was associated with anthropogenic impacts on the West African Monsoon, but uncertainty in the RCM's ability to reproduce precipitation trends in the region weakens confidence in the result. That said, outputs correspond well with broad-scale changes in observed endemicity, implying a potentially important contribution of anthropogenic climate change to the malaria burden during the past century. Results support the health-framing of climate risk and help indicate hotspots of climate vulnerability, providing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...67I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...67I"><span>Assessment of moisture budget over West Africa using MERRA-2's aerological model and satellite data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Igbawua, Tertsea; Zhang, Jiahua; Yao, Fengmei; Zhang, Da</p> <p>2018-02-01</p> <p>The study assessed the performance of NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) and MERRA-2 aerological (P-E*) model in reproducing the salient features of West Africa water balance including its components from 1980 to 2013. In this study we have shown that recent reanalysis efforts have generated imbalances between regional integrated precipitation (P) and surface evaporation (E), and the effect is more in the newly released MERRA-2. The atmospheric water balance of MERRA and MERRA-2 were inter-compared and thereafter compared with model forecast output of European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-I) and Japanese 55-year Reanalysis (JRA-55). Results indicated that a bias of 12-20 (5-13) mm/month in MERRA-2 (ERA-I) leads to the classification of the <span class="hlt">Sahel</span> (14°N-20°N) as a moisture source during the West African Summer Monsoon. Comparisons between MERRA/MERRA-2 and prognostic fields from two ERA-I and JRA-55 indicated that the average P-E* in MERRA is 18.94 (52.24) mm/month which is less than ERA-I (JRA-55) over Guinea domain and 25.03 (4.53) mm/month greater than ERA-I (JRA-55) over the <span class="hlt">Sahel</span>. In MERRA-2, average P-E* indicated 25.76 (59.06) mm/month which is less than ERA-I (JRA-55) over Guinea and 73.72 (94.22) mm/month less than ERA-I (JRA-55) over the <span class="hlt">Sahel</span> respectively. These imbalances are due to adjustments in data assimilation methods, satellite calibration and observational data base. The change in convective P parameterization and increased re-evaporation of P in MERRA-2 is suggestive of the cause of positive biases in P and E. The little disagreements between MERRA/MERRA-2 and CRU precipitation highlights one of the major challenges associated with climate research in West Africa and major improvements in observation data and surface fluxes from reanalysis remain vital.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.1521B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.1521B"><span>Africa's Great Green Wall Initiative: a model for restoration success</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berrahmouni, Nora; Sacande, Moctar</p> <p>2014-05-01</p> <p>The Great Green Wall for the Sahara and the <span class="hlt">Sahel</span> Initiative was launched to address the increasing challenges of land degradation, desertification and drought, climate change, food insecurity and poverty in more than 20 countries. Restoration of agro-sylvo-pastoral landscapes and degraded lands is one of the priority interventions initiated, enabling the springing up of green nests of life. When complete, the Great Green Wall of Africa will reverse the seemingly unstoppable desertification and address the development of its drylands' inhabitant rural communities. Today's planting of modest seedlings will grow into vast mosaics of forest and agroforestry landscapes and grasslands, which will provide essential ecosystem goods and services, restore lost livelihoods and create new wealth. The ambition of reforestation efforts within this initiative - the like of which the world has never seen before - sounds like an impossible dream. However, learning from past mistakes and capitalising on current advancement in science and technology, it is a reality that is taking root. Following a successful restoration model that RBG Kew experts have devised, we are helping to mobilise, train and support communities in four border regions in Burkina Faso, Mali and Niger. In collaboration with FAO, the Millennium Seed Bank Partnership is using its unique expertise to ensure that seeds of environmentally well-adapted and economically useful local species are collected and planted in communal gardens and village agroforestry systems managed by the communities themselves. In our first year, an estimated total of 162,000 seedlings and 61 kg of seeds from 40 useful native species, including grasses for livestock, have been planted to cover 237 ha of farmer-managed land in 19 villages. The keen interest it has created has indicated that these figures will rise five-fold in the second year. These green bricks are the foundations of the living wall that will eventually reach across the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.1647C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.1647C"><span>A Climatology of dust emission in northern Africa using surface observations from 1984-2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cowie, Sophie; Knippertz, Peter; Marsham, John</p> <p>2014-05-01</p> <p>The huge quantity of mineral dust emitted annually from northern Africa makes this area crucial to the global dust cycle. Once in the atmosphere, dust aerosols have a significant impact on the global radiation budget, clouds, the carbon cycle and can even act as a fertilizer to rain forests in South America. Current model estimates of dust production from northern Africa are uncertain. At the heart of this problem is insufficient understanding of key dust emitting processes such as haboobs (cold pools generated through evaporation of convective precipitation), low-level jets (LLJs) and dry convection (dust devils and dust plumes). Scarce observations in this region, in particular in the Sahara, make model evaluation difficult. This work uses long-term surface observations from 70 stations situated in the Sahara and <span class="hlt">Sahel</span> to explore the diurnal, seasonal and geographical variations in dust emission events and thresholds. Quality flags are applied to each station to indicate a day-time bias or gaps in the time period 1984-2012. The frequency of dust emission (FDE) is calculated using the present weather codes (WW) of SYNOP reports, where WW = 07,08,09,30-35 and 98. Thresholds are investigated by estimating the wind speeds for which there is a 25%, 50% and 75% probability of dust emission. The 50% threshold is used to calculate strong wind frequency (SWF) and the diagnostic parameter dust uplift potential (DUP); a thresholded cubic function of wind-speed which quantifies the dust generating power of winds. Stations are grouped into 6 areas (North Algeria, Central Sahara, Egypt, West <span class="hlt">Sahel</span>, Central <span class="hlt">Sahel</span> and Sudan) for more in-depth analysis of these parameters. Spatially, thresholds are highest in northern Algeria and lowest in the <span class="hlt">Sahel</span> around the latitude band 16N-21N. Annual mean FDE is anti-correlated with the threshold, showing the importance of spatial variations in thresholds for mean dust emission. The annual cycles of FDE and SWF for the 6 grouped areas are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA583534','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA583534"><span>Employing Inform and Influence Activities to Neutralize Cross-Border Sanctuaries in Counterinsurgency Operations</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-05-20</p> <p>II-9 – II-10. 17 Boehnert, John and Nasi , Jamie, “Military Information Support Operations in the Trans-Sahel” (Special Warfare, January-March 2013...Boehnert, and Nasi , “Military Information Support Operations in the Trans-<span class="hlt">Sahel</span>.” 19 Boehnert and Nasi , “Military Information Support Operations in...messaging nested with strategic objectives. According to Boehnert and Nasi , “All MIST activities are nested in the various theater, operational and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA550277','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA550277"><span>CTC Sentinel. Volume 4, Issue 2, February 2011</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-02-01</p> <p>Brotherhood differs from jihadist groups in that the Broth- erhood rejects violence as a means to alter society, instead advocating political...appear to be working at cross purposes in combating AQIM in the Sahara and <span class="hlt">Sahel</span> and this has created an opening for the group’s different factions to...significant sums. The revenue generated by kidnap operations—which could amount to tens of millions—has reportedly augmented the capabilities of different</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA264618','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA264618"><span>Nigeria: Developing a Strategy for Sub-Saharan Africa</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-04-20</p> <p>single Islamic government. This extension of Islam and consolidation of tne caliphate accounts for the dichotomy between northern and southern Nigeria...in Nigeria and its eventual colonization of Nigeria in the early twentieth century. Northern and Southern Nigeria were officially united as the Colony...south; a still larger dry central plateau, with much open woodland and savanna ; and a strip of semidesert on the fringes of the <span class="hlt">Sahel</span> in the north</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NatCC...3..660H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NatCC...3..660H"><span>Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haywood, Jim M.; Jones, Andy; Bellouin, Nicolas; Stephenson, David</p> <p>2013-07-01</p> <p>The Sahelian drought of the 1970s-1990s was one of the largest humanitarian disasters of the past 50 years, causing up to 250,000 deaths and creating 10 million refugees. It has been attributed to natural variability, over-grazing and the impact of industrial emissions of sulphur dioxide. Each mechanism can influence the Atlantic sea surface temperature gradient, which is strongly coupled to Sahelian precipitation. We suggest that sporadic volcanic eruptions in the Northern Hemisphere also strongly influence this gradient and cause Sahelian drought. Using de-trended observations from 1900 to 2010, we show that three of the four driest Sahelian summers were preceded by substantial Northern Hemisphere volcanic eruptions. We use a state-of-the-art coupled global atmosphere-ocean model to simulate both episodic volcanic eruptions and geoengineering by continuous deliberate injection into the stratosphere. In either case, large asymmetric stratospheric aerosol loadings concentrated in the Northern Hemisphere are a harbinger of Sahelian drought whereas those concentrated in the Southern Hemisphere induce a greening of the <span class="hlt">Sahel</span>. Further studies of the detailed regional impacts on the <span class="hlt">Sahel</span> and other vulnerable areas are required to inform policymakers in developing careful consensual global governance before any practical solar radiation management geoengineering scheme is implemented.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG51B..06V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG51B..06V"><span>Factors Influencing the Sahelian Paradox at the Local Watershed Scale: Causal Inference Insights</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Van Gordon, M.; Groenke, A.; Larsen, L.</p> <p>2017-12-01</p> <p>While the existence of paradoxical rainfall-runoff and rainfall-groundwater correlations are well established in the West African <span class="hlt">Sahel</span>, the hydrologic mechanisms involved are poorly understood. In pursuit of mechanistic explanations, we perform a causal inference analysis on hydrologic variables in three watersheds in Benin and Niger. Using an ensemble of techniques, we compute the strength of relationships between observational soil moisture, runoff, precipitation, and temperature data at seasonal and event timescales. Performing analysis over a range of time lags allows dominant time scales to emerge from the relationships between variables. By determining the time scales of hydrologic connectivity over vertical and lateral space, we show differences in the importance of overland and subsurface flow over the course of the rainy season and between watersheds. While previous work on the paradoxical hydrologic behavior in the <span class="hlt">Sahel</span> focuses on surface processes and infiltration, our results point toward the importance of subsurface flow to rainfall-runoff relationships in these watersheds. The hypotheses generated from our ensemble approach suggest that subsequent explorations of mechanistic hydrologic processes in the region include subsurface flow. Further, this work highlights how an ensemble approach to causal analysis can reveal nuanced relationships between variables even in poorly understood hydrologic systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27703055','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27703055"><span>Long-distance autumn migration across the Sahara by painted lady butterflies: exploiting resource pulses in the tropical savannah.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stefanescu, Constantí; Soto, David X; Talavera, Gerard; Vila, Roger; Hobson, Keith A</p> <p>2016-10-01</p> <p>The painted lady, Vanessa cardui, is a migratory butterfly that performs an annual multi-generational migration between Europe and North Africa. Its seasonal appearance south of the Sahara in autumn is well known and has led to the suggestion that it results from extremely long migratory flights by European butterflies to seasonally exploit the <span class="hlt">Sahel</span> and the tropical savannah. However, this possibility has remained unproven. Here, we analyse the isotopic composition of butterflies from seven European and seven African countries to provide new support for this hypothesis. Each individual was assigned a geographical natal origin, based on its wing stable hydrogen isotope (δ 2 H w ) value and a predicted δ 2 H w basemap for Europe and northern Africa. Natal assignments of autumn migrants collected south of the Sahara confirmed long-distance movements (of 4000 km or more) starting in Europe. Samples from Maghreb revealed a mixed origin of migrants, with most individuals with a European origin, but others having originated in the <span class="hlt">Sahel</span>. Therefore, autumn movements are not only directed to northwestern Africa, but also include southward and northward flights across the Sahara. Through this remarkable behaviour, the productive but highly seasonal region south of the Sahara is incorporated into the migratory circuit of V. cardui. © 2016 The Author(s).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A13M..02T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A13M..02T"><span>Precipitation interannual variability and predictions for West Africa from the National Multi-Model Ensemble dataset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thiaw, W. M.</p> <p>2013-12-01</p> <p>The ability of coupled climate models from the national multi-model ensemble (NMME) dataset to reproduce the basic state and interannual variability of precipitation in West Africa and associated teleconnections is examined. The analysis is for the period 1982-2010 for most of the models, which corresponds to the NMME hindcast period, except for the CFS version 1 (CFSv1) which covers the period 1981-2009. The satellite based CPC African Rainfall Climatology (ARC2) data is used as proxy for observed rainfall and to validate the models. We examine rainfall patterns throughout the year. Models are able to reproduce the north-south migration of precipitation from winter and spring when the area of maximum precipitation is located in Central Africa and the Gulf of Guinea region to the summer when it is in northern Sub-Saharan Africa, and the later return to the south. Models also appropriately place precipitation over the Gulf of Guinea region during the equinoxes in MAM and OND. However, there are considerable differences in the representation of the intensities and locations of the rainfall. Three of the models including the two versions of the NCEP CFS and the NASA models also have a systematic dry (wet) bias over the <span class="hlt">Sahel</span> (Gulf of Guinea region) during the summer rainfall season, while the others show alternating wet and dry biases across West Africa. All models have spatially averaged values of standard deviation lower than that observed. Models are also able to reproduce to some extent the main features of the precipitation variability maximum, but again with deficiencies in the amplitudes and locations. The areas of highest variability are generally depicted, but there are significant differences among the models, and even between the two versions of the CFS. Teleconnections in the models are investigated by first conducting an EOF in the precipitation anomaly fields and then perform a regression of the first or second EOF time series onto the global SST</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003BAMS...84.1741T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003BAMS...84.1741T"><span>Climate Research and Seasonal Forecasting for West Africans: Perceptions, Dissemination, and Use?.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tarhule, Aondover; Lamb, Peter J.</p> <p>2003-12-01</p> <p>Beginning in response to the disastrous drought of 1968 73, considerable research and monitoring have focused on the characteristics, causes, predictability, and impacts of West African Soudano <span class="hlt">Sahel</span> (10° 18°N) rainfall variability and drought. While these efforts have generated substantial information on a range of these topics, very little is known of the extent to which communities, activities at risk, and policy makers are aware of, have access to, or use such information. This situation has prevailed despite Glantz&;s provocative BAMS paper on the use and value of seasonal forecasts for the <span class="hlt">Sahel</span> more than a quarter century ago. We now provide a systematic reevaluation of these issues based on questionnaire responses of 566 participants (in 13 communities) and 26 organizations in Burkina Faso, Mali, Niger, and Nigeria. The results reveal that rural inhabitants have limited access to climate information, with nongovernmental organizations (NGOs) being the most important source. Moreover, the pathways for information flow are generally weakly connected and informal. As a result, utilization of the results of climate research is very low to nonexistent, even by organizations responsible for managing the effects of climate variability. Similarly, few people have access to seasonal climate forecasts, although the vast majority expressed a willingness to use such information when it becomes available. Those respondents with access expressed great enthusiasm and satisfaction with seasonal forecasts. The results suggest that inhabitants of the Soudano <span class="hlt">Sahel</span> savanna are keen for changes that improve their ability to cope with climate variability, but the lack of information on alternative courses of action is a major constraint. Our study, thus, essentially leaves unchanged both Glantz&;s negative “tentative conclusion” and more positive “preliminary assessment” of 25 years ago. Specifically, while many of the infrastructural deficiencies and socioeconomic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HESS...18.3635M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HESS...18.3635M"><span>A review of droughts on the African continent: a geospatial and long-term perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masih, I.; Maskey, S.; Mussá, F. E. F.; Trambauer, P.</p> <p>2014-09-01</p> <p>This paper presents a comprehensive review and analysis of the available literature and information on droughts to build a continental, regional and country level perspective on geospatial and temporal variation of droughts in Africa. The study is based on the review and analysis of droughts occurred during 1900-2013, as well as evidence available from past centuries based on studies on the lake sediment analysis, tree-ring chronologies and written and oral histories and future predictions from the global climate change models. Most of the studies based on instrumental records indicate that droughts have become more frequent, intense and widespread during the last 50 years. The extreme droughts of 1972-1973, 1983-1984 and 1991-1992 were continental in nature and stand unique in the available records. Additionally, many severe and prolonged droughts were recorded in the recent past such as the 1999-2002 drought in northwest Africa, 1970s and 1980s droughts in western Africa (<span class="hlt">Sahel</span>), 2010-2011 drought in eastern Africa (Horn of Africa) and 2001-2003 drought in southern and southeastern Africa, to name a few. The available (though limited) evidence before the 20th century confirms the occurrence of several extreme and multi-year droughts during each century, with the most prolonged and intense droughts that occurred in <span class="hlt">Sahel</span> and equatorial eastern Africa. The complex and highly variant nature of many physical mechanisms such as El Niño-Southern Oscillation (ENSO), sea surface temperature (SST) and land-atmosphere feedback adds to the daunting challenge of drought monitoring and forecasting. The future predictions of droughts based on global climate models indicate increased droughts and aridity at the continental scale but large differences exist due to model limitations and complexity of the processes especially for <span class="hlt">Sahel</span> and northern Africa. However, the available evidence from the past clearly shows that the African continent is likely to face extreme and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014HESSD..11.2679M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014HESSD..11.2679M"><span>A review of droughts in the African continent: a geospatial and long-term perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masih, I.; Maskey, S.; Mussá, F. E. F.; Trambauer, P.</p> <p>2014-03-01</p> <p>This paper presents a comprehensive review and analysis of the available literature and information on droughts to build a continental, regional and country level perspective on geospatial and temporal variation of droughts in Africa. The study is based on the review and analysis of droughts occurred during 1900-2013 as well as evidence available from past centuries based on studies on the lake sediment analysis, tree-ring chronologies and written and oral histories and future predictions from the global climate change models. Most of the studies based on instrumental records indicate that droughts have become more frequent, intense and widespread during the last 50 yr. The extreme droughts of 1972-1973, 1983-1984 and 1991-1992 were continental in nature and stand unique in the available records. Additionally, many severe and prolonged droughts were recorded in the recent past such as the 1999-2002 drought in Northwest Africa, 1970s and 1980s droughts in West Africa (<span class="hlt">Sahel</span>), 2010-2011 drought in East Africa (Horn of Africa) and 2001-2003 drought in Southern and Southeast Africa, to name a few. The available (though limited) evidence before the 20th century confirms the occurrence of several extreme and multi-year droughts during each century, with the most prolonged and intense droughts that occurred in <span class="hlt">Sahel</span> and Equatorial East Africa regions. Complex and highly variant nature of many physical mechanisms such as El Niño-Southern Oscillation (ENSO), Sea Surface Temperature (SST) and land-atmosphere feedback adds to the daunting challenge of drought monitoring and forecasting. The future predictions of droughts based on global climate models indicate increased droughts and aridity at the continental scale but large differences exist due to model limitations and complexity of the processes especially for <span class="hlt">Sahel</span> and North Africa regions. However, the available evidence from the past clearly shows that the African continent is likely to face extreme and widespread</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....16.9457Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....16.9457Z"><span>Multi-satellite sensor study on precipitation-induced emission pulses of NOx from soils in semi-arid ecosystems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zörner, Jan; Penning de Vries, Marloes; Beirle, Steffen; Sihler, Holger; Veres, Patrick R.; Williams, Jonathan; Wagner, Thomas</p> <p>2016-07-01</p> <p>We present a top-down approach to infer and quantify rain-induced emission pulses of NOx ( ≡ NO + NO2), stemming from biotic emissions of NO from soils, from satellite-borne measurements of NO2. This is achieved by synchronizing time series at single grid pixels according to the first day of rain after a dry spell of prescribed duration. The full track of the temporal evolution several weeks before and after a rain pulse is retained with daily resolution. These are needed for a sophisticated background correction, which accounts for seasonal variations in the time series and allows for improved quantification of rain-induced soil emissions. The method is applied globally and provides constraints on pulsed soil emissions of NOx in regions where the NOx budget is seasonally dominated by soil emissions. We find strong peaks of enhanced NO2 vertical column densities (VCDs) induced by the first intense precipitation after prolonged droughts in many semi-arid regions of the world, in particular in the <span class="hlt">Sahel</span>. Detailed investigations show that the rain-induced NO2 pulse detected by the OMI (Ozone Monitoring Instrument), GOME-2 and SCIAMACHY satellite instruments could not be explained by other sources, such as biomass burning or lightning, or by retrieval artefacts (e.g. due to clouds). For the <span class="hlt">Sahel</span> region, absolute enhancements of the NO2 VCDs on the first day of rain based on OMI measurements 2007-2010 are on average 4 × 1014  molec cm-2 and exceed 1 × 1015  molec cm-2 for individual grid cells. Assuming a NOx lifetime of 4 h, this corresponds to soil NOx emissions in the range of 6 up to 65 ng N m-2 s-1, which is in good agreement with literature values. Apart from the clear first-day peak, NO2 VCDs are moderately enhanced (2 × 1014  molec cm-2) compared to the background over the following 2 weeks, suggesting potential further emissions during that period of about 3.3 ng N m-2 s-1</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010GPC....72..318M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010GPC....72..318M"><span>The Acridian plagues, a new Holocene and Pleistocene palaeoclimatic indicator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meco, Joaquín; Petit-Maire, Nicole; Ballester, Javier; Betancort, Juan F.; Ramos, Antonio J. G.</p> <p>2010-07-01</p> <p>Five palaeosols, intercalated within the Quaternary dune beds of Fuerteventura and Lanzarote (Canary Islands), off the Moroccan coast, mark wetter climatic episodes. In all of them, billions of calcified insect ootheca testify to past occurrences of Acridian plagues, such as those reaching the western Sahara following heavy rainfall events over the <span class="hlt">Sahel</span>. The most massive infestation is in the Holocene, and should coincide with the climax of Saharo-Sahelian humidity at the peak of the present interglacial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA284915','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA284915"><span>U.S. Africa Policy: Some Possible Course Adjustment</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1994-08-29</p> <p>installations on behalf of an African Marxist government. A lot of Angola’s oil was exported to the United States; the U.S. companies involved made money. The...country, with major legitimate social service and infrastructure needs and, probably, very greedy leadership, would be able to forego exportation of its...droughts like the <span class="hlt">Sahel</span>-and fully capable of feeding its population and producing for agricultural export . It has diamonds for ready cash. The size of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870018764','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870018764"><span>Investigating the role of the land surface in explaining the interannual variation of the net radiation balance over the Western Sahara and sub-Sahara</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, Eric A.; Nicholson, Sharon</p> <p>1987-01-01</p> <p>The status of the data sets is discussed. Progress was made in both data analysis and modeling areas. The atmospheric and land surface contributions to the net radiation budget over the Sahara-<span class="hlt">Sahel</span> region is being decoupled. The interannual variability of these two processes was investigated and this variability related to seasonal rainfall fluctuations. A modified Barnes objective analysis scheme was developed which uses an eliptic scan pattern and a 3-pass iteration of the difference fields.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA600818','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA600818"><span>Improving Shaping Efforts in Africa’s Maghreb and <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-03-21</p> <p>threat in North Africa to U.S. interests? Al Qaeda in the Islamic Maghreb (AQIM) is a relatively new franchise of Al Qaeda. Upon declaring allegiance...trafficking to finance their operations. Should a West African franchise of Al Qaeda, or any other terrorist organization with local grievances and/or global...solve issues like desertification, poverty, unemployment , social inequalities, and so on. By adapting to this new environment and by reallocating</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.131..937A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.131..937A"><span>Assessing the link between Atlantic Niño 1 and drought over West Africa using CORDEX regional climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Adeniyi, Mojisola Oluwayemisi; Dilau, Kabiru Alabi</p> <p>2018-02-01</p> <p>The skill of Coordinated Regional Climate Downscaling Experiment (CORDEX) models (ARPEGE, CCLM, HIRHAM, RACMO, REMO, PRECIS, RegCM3, RCA, WRF and CRCM) in simulating the climate (precipitation, temperature and drought) of West Africa is determined using a process-based metric. This is done by comparing the CORDEX models' simulated and observed correlation coefficients between Atlantic Niño Index 1 (ATLN1) and the climate over West Africa. Strong positive correlation is observed between ATLN1 and the climate parameters at the Guinea Coast (GC). The Atlantic Ocean has Niño behaviours through the ATLN indices which influence the climate of the tropics. Drought has distinct dipole structure of correlation with ATLN1 (negative at the <span class="hlt">Sahel</span>); precipitation does not have distinct dipole structure of correlation, while temperature has almost a monopole correlation structure with ATLN1 over West Africa. The magnitude of the correlation increases with closeness to the equatorial eastern Atlantic. Correlations between ATLN1 and temperature are mostly stronger than those between ATLN1 and precipitation over the region. Most models have good performance over the GC, but ARPEGE has the highest skill at GC. The PRECIS is the most skilful over Savannah and RCA over <span class="hlt">Sahel</span>. These models can be used to downscale the projected climate at the region of their highest skill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170012198','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170012198"><span>GC13I-0860: An Assessment of Surface Water Detection Methods for the Tahoua Region, Niger</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Herndon, Kelsey E.; Muench, Rebekke; Cherrington, Emil; Griffin, Robert</p> <p>2017-01-01</p> <p>The recent release of several global surface water datasets derived from remotely sensed data has allowed for unprecedented analysis of the earth's hydrologic processes at a global scale. However, some of these datasets fail to identify important sources of surface water, especially small ponds, in the <span class="hlt">Sahel</span>, an arid region of Africa that forms a border zone between the Sahara Desert to the north, and the savannah to the south. These ponds may seem insignificant in the context of wider, global-scale hydrologic processes, but smaller sources of water are important for local and regional hydrologic assessments. Particularly, these smaller water bodies are significant sources of hydration and irrigation for nomadic pastoralists and smallholder farmers throughout the <span class="hlt">Sahel</span>. For this study, several methods of identifying surface water from Landsat 8 OLI, Sentinel 1 SAR, Sentinel 2 MSI, and Planet Dove data were compared to determine the most effective means of delineating these features in the Tahoua Region of Niger. The Automated Water Extraction Index (AWEInsh) had the best performance when validated against very high resolution Digital Globe imagery, with an overall accuracy of 98.6%. This study reiterates the importance of region-specific algorithms and suggests that the AWEInsh method may be the best for delineating surface water in the Sahelian ecozone, likely due to the nature of the exposed geology and lack of dense green vegetation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B41K0200M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B41K0200M"><span>Space-Derived Phenology, Retrieval and Use for Drought and Food Security Monitoring</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meroni, M.; Kayitakire, F.; Rembold, F.; Urbano, F.; Schucknecht, A.; LEO, O.</p> <p>2014-12-01</p> <p>Monitoring vegetation conditions is a critical activity for assessing food security in Africa. Rural populations relying on rain-fed agriculture and livestock grazing are highly exposed to large seasonal and inter-annual fluctuations in water availability. Monitoring the state, evolution, and productivity of vegetation, crops and pastures in particular, is important to conduct food emergency responses and plan for a long-term, resilient, development strategy in this area. The timing of onset, the duration, and the intensity of vegetation growth can be retrieved from space observations and used for food security monitoring to assess seasonal vegetation development and forecast the likely seasonal outcome when the season is ongoing. In this contribution we present a set of phenology-based remote sensing studies in support to food security analysis. Key phenological indicators are retrieved using a model-fit approach applied to SOPT-VEGETATION FAPAR time series. Remote-sensing phenology is first used to estimate i) the impact of the drought in the Horn of Africa, ii) crop yield in Tunisia and, iii) rangeland biomass production in Niger. Then the impact of the start and length of vegetation growing period on the total biomass production is assessed over the <span class="hlt">Sahel</span>. Finally, a probabilistic approach using phenological information to forecast the occurrence of an end-of-season biomass production deficit is applied over the <span class="hlt">Sahel</span> to map hot-spots of drought-related risk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC13I0860H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC13I0860H"><span>An Assessment of Surface Water Detection Algorithms for the Tahoua Region, Niger</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herndon, K. E.; Muench, R.; Cherrington, E. A.; Griffin, R.</p> <p>2017-12-01</p> <p>The recent release of several global surface water datasets derived from remotely sensed data has allowed for unprecedented analysis of the earth's hydrologic processes at a global scale. However, some of these datasets fail to identify important sources of surface water, especially small ponds, in the <span class="hlt">Sahel</span>, an arid region of Africa that forms a border zone between the Sahara Desert to the north, and the savannah to the south. These ponds may seem insignificant in the context of wider, global-scale hydrologic processes, but smaller sources of water are important for local and regional assessments. Particularly, these smaller water bodies are significant sources of hydration and irrigation for nomadic pastoralists and smallholder farmers throughout the <span class="hlt">Sahel</span>. For this study, several methods of identifying surface water from Landsat 8 OLI and Sentinel 1 SAR data were compared to determine the most effective means of delineating these features in the Tahoua Region of Niger. The Modified Normalized Difference Water Index (MNDWI) had the best performance when validated against very high resolution World View 3 imagery, with an overall accuracy of 99.48%. This study reiterates the importance of region-specific algorithms and suggests that the MNDWI method may be the best for delineating surface water in the Sahelian ecozone, likely due to the nature of the exposed geology and lack of dense green vegetation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27917963','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27917963"><span>Mobile pastoralists in Central and West Africa: between conflict, mobile telephony and (im)mobility.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>De Bruijn, M; Amadou, A; Lewa Doksala, E; Sangaré, B</p> <p>2016-11-01</p> <p>The livelihoods of the Fulani mobile pastoralists in the <span class="hlt">Sahel</span>, West and Central Africa are characterised by mobility (related to the needs of their animals), extensive social networks, and a focus on social ties as the basis of status and influence ('wealth in people'). The <span class="hlt">Sahel</span> environment in which many Fulani nomads live has become embroiled in jihadism, conflict, and violence; at the same time, this region has experienced an increase in opportunities to connect through the wireless mobile communication system. This paper analyses the triangle of mobility, communication, and insecurity in order to understand the present-day situation of the nomadic and semi-nomadic Fulani pastoralists and their identity dynamics. The Fulani find themselves caught in between these conflicts, which end their mobility and often lead to the loss of their herds. Will they be able to keep their mobile lifestyle and identity? This article is based on qualitative case studies and the biographical narratives of nomadic and semi-nomadic pastoralists who have lived through conflict and violence in Cameroon, Chad and Mali. These case studies show that, despite the fact that mobile pastoralism has become difficult as a consequence of the conflicts and loss of cattle, the 'mobile' identity is very present and reinforced with the help of mobile telephony, through which social networks and 'wealth in people' are sustained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890040757&hterms=NDVI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DNDVI','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890040757&hterms=NDVI&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DNDVI"><span>Integrated NDVI images for Niger 1986-1987. [Normalized Difference Vegetation Index</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Harrington, John A., Jr.; Wylie, Bruce K.; Tucker, Compton J.</p> <p>1988-01-01</p> <p>Two NOAA AVHRR images are presented which provide a comparison of the geographic distribution of an integration of the normalized difference vegetation index (NDVI) for the <span class="hlt">Sahel</span> zone in Niger for the growing seasons of 1986 and 1987. The production of the images and the application of the images for resource management are discussed. Daily large area coverage with a spatial resolution of 1.1 km at nadir were transformed to the NDVI and geographically registered to produce the images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70168777','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70168777"><span>The need for the International Decade of Natural Hazard Reduction</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Press, F.</p> <p>1990-01-01</p> <p>Over the last 20 years, natural disasters have killed nearly 3 million people and disrupted the lives of over 800 million others. In 2 years there were more than 50 serious natural disasters, including landslides in Italy, France, and Colombia; a typhoon in Korea; wildfires in China and the United State; a windstorm in England; grasshopper plagues in Africa's horns and the <span class="hlt">Sahel</span>; tornadoes in Canada; devastating earthquakes in Soviet Armenia and Tadzhikistan; infestations in Africa; landslides in Brazil; and tornadoes in the United States. </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70162346','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70162346"><span>Can an earthquake prediction and warning system be developed?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>N.N, Ambraseys</p> <p>1990-01-01</p> <p>Over the last 20 years, natural disasters have killed nearly 3 million people and disrupted the lives of over 800 million others. In 2 years there were more than 50 serious natural disasters, including landslides in Italy, France, and Colombia; a typhoon in Korea; wildfires in China and the United States; a windstorm in England; grasshopper plagues in Africa's horn and the <span class="hlt">Sahel</span>; tornadoes in Canada; devastating earthquakes in Soviet Armenia and Tadzhikstand; infestations in Africa; landslides in Brazil; and tornadoes in the United States </p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780004610','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780004610"><span>Localization of an experimental ecological unit in the Maradi region of Nigeria</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mainguet, M.; Canon, L.; Chapelle, A. M.</p> <p>1977-01-01</p> <p>A detailed topographical and geomorphological description of a specific ecological unit in the Maradi region of the <span class="hlt">Sahel</span> in the Niger Republic is presented. Sandy structures are classified into active dunes and covered dunes and an extensives vocabulary is developed to describe sub-categories. The descriptions are based on meteorological data (anemometric and rainfall) from local weather stations, ground observations, aerial photographs and LANDSAT pictures. The problem of dune reactivation and desertification is discussed both from the standpoint of causes and possible counter measures.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996JCli....9.2727S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996JCli....9.2727S"><span>Interannual Tropical Rainfall Variability in General Circulation Model Simulations Associated with the Atmospheric Model Intercomparison Project.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sperber, K. R.; Palmer, T. N.</p> <p>1996-11-01</p> <p>The interannual variability of rainfall over the Indian subcontinent, the African <span class="hlt">Sahel</span>, and the Nordeste region of Brazil have been evaluated in 32 models for the period 1979-88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the <span class="hlt">Sahel</span> are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each model. Evaluation of the interannual variability of a wind shear index over the summer monsoon region indicates that the models exhibit greater fidelity in capturing the large-scale dynamic fluctuations than the regional-scale rainfall variations. A rainfall/SST teleconnection quality control was used to objectively stratify model performance. Skill scores improved for those models that qualitatively simulated the observed rainfall/El Niño- Southern Oscillation SST correlation pattern. This subset of models also had a rainfall climatology that was in better agreement with observations, indicating a link between systematic model error and the ability to simulate interannual variations.A suite of six European Centre for Medium-Range Weather Forecasts (ECMWF) AMIP runs (differing only in their initial conditions) have also been examined. As observed, all-India rainfall was enhanced in 1988 relative to 1987 in each of these realizations. All-India rainfall variability during other years showed little or no predictability, possibly due to internal chaotic dynamics associated with intraseasonal monsoon fluctuations and/or unpredictable land surface process interactions. The interannual variations of Nordeste rainfall were best represented. The State University of New York at Albany/National Center for Atmospheric Research Genesis model was run in five initial condition realizations. In this model, the Nordeste rainfall</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.132..437A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.132..437A"><span>Evaluation of rainfall simulations over West Africa in dynamically downscaled CMIP5 global circulation models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akinsanola, A. A.; Ajayi, V. O.; Adejare, A. T.; Adeyeri, O. E.; Gbode, I. E.; Ogunjobi, K. O.; Nikulin, G.; Abolude, A. T.</p> <p>2018-04-01</p> <p>This study presents evaluation of the ability of Rossby Centre Regional Climate Model (RCA4) driven by nine global circulation models (GCMs), to skilfully reproduce the key features of rainfall climatology over West Africa for the period of 1980-2005. The seasonal climatology and annual cycle of the RCA4 simulations were assessed over three homogenous subregions of West Africa (Guinea coast, Savannah, and <span class="hlt">Sahel</span>) and evaluated using observed precipitation data from the Global Precipitation Climatology Project (GPCP). Furthermore, the model output was evaluated using a wide range of statistical measures. The interseasonal and interannual variability of the RCA4 were further assessed over the subregions and the whole of the West Africa domain. Results indicate that the RCA4 captures the spatial and interseasonal rainfall pattern adequately but exhibits a weak performance over the Guinea coast. Findings from the interannual rainfall variability indicate that the model performance is better over the larger West Africa domain than the subregions. The largest difference across the RCA4 simulated annual rainfall was found in the <span class="hlt">Sahel</span>. Result from the Mann-Kendall test showed no significant trend for the 1980-2005 period in annual rainfall either in GPCP observation data or in the model simulations over West Africa. In many aspects, the RCA4 simulation driven by the HadGEM2-ES perform best over the region. The use of the multimodel ensemble mean has resulted to the improved representation of rainfall characteristics over the study domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H33B1654J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H33B1654J"><span>Projected effects of vegetation feedbacks on drought characteristics with SPEI over West Africa using the RegCM-CLM-CN-DV</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jaehyeong, L.; Kim, Y.; Erfanian, A.; Wang, G.; Um, M. J.</p> <p>2017-12-01</p> <p>This study utilizes the Standardized Precipitation-Evapotranspiration Index (SPEI) to investigate the projected effect of vegetation feedbacks on drought in West Africa using the Regional Climate Model coupled to the NCAR Community Land Model with both the Carbon and Nitrogen module (CN) and Dynamic Vegetation module (DV) activated (RegCM-CLM-CN-DV). The role of vegetation feedbacks is examined based on simulations with and without dynamic vegetation. The four different future climate scenarios from CCSM, GFDL, MIROC and MPI are used as the boundary conditions of RegCM for two historical and future periods, i.e., for 1981 to 2000 and for 2081 to 2100, respectively. Using SPEI, the duration, frequency, severity and spatial extents are quantified over West Africa and analyzed for two regions of the <span class="hlt">Sahel</span> and the Gulf of Guinea. In this study, we find that the estimated annual SPEIs clearly indicate that the projected future droughts over the <span class="hlt">Sahel</span> are enhanced and prolonged when DV is activated. The opposite is shown over the Gulf of Guinea in general. AcknowledgementsThis work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2015R1C1A2A01054800), by the Korea Meteorological Administration R&D Program under Grant KMIPA 2015-6180 and by the Yonsei University Future-leading Research Initiative of 2015(2016-22-0061).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.4564B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.4564B"><span>Role of dust direct radiative effect on the tropical rain belt over Middle East and North Africa: A high-resolution AGCM study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bangalath, Hamza Kunhu; Stenchikov, Georgiy</p> <p>2015-05-01</p> <p>To investigate the influence of direct radiative effect of dust on the tropical summer rain belt across the Middle East and North Africa (MENA), the present study utilizes the high-resolution capability of an Atmospheric General Circulation Model, the High-Resolution Atmospheric Model. Ensembles of Atmospheric Model Intercomparison Project style simulations have been conducted with and without dust radiative impacts, to differentiate the influence of dust on the tropical rain belt. The analysis focuses on summer season. The results highlight the role of dust-induced responses in global- and regional-scale circulations in determining the strength and the latitudinal extent of the tropical rain belt. A significant response in the strength and position of the local Hadley circulation is predicted in response to meridionally asymmetric distribution of dust and the corresponding radiative effects. Significant responses are also found in regional circulation features such as African Easterly Jet and West African Monsoon circulation. Consistent with these dynamic responses at various scales, the tropical rain belt across MENA strengthens and shifts northward. Importantly, the summer precipitation over the semiarid strip south of Sahara, including <span class="hlt">Sahel</span>, increases up to 20%. As this region is characterized by the "<span class="hlt">Sahel</span> drought," the predicted precipitation sensitivity to the dust loading over this region has a wide range of socioeconomic implications. Overall, the study demonstrates the extreme importance of incorporating dust radiative effects and the corresponding circulation responses at various scales, in the simulations and future projections of this region's climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000228','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000228"><span>The Impact of the Atlantic Cold Tongue on West African Monsoon Onset in Regional Model Simulations for 1998-2002</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Druyan, Leonard M.; Fulakeza, Matthew B.</p> <p>2014-01-01</p> <p>The Atlantic cold tongue (ACT) develops during spring and early summer near the Equator in the Eastern Atlantic Ocean and Gulf of Guinea. The hypothesis that the ACT accelerates the timing of West African monsoon (WAM) onset is tested by comparing two regional climate model (RM3) simulation ensembles. Observed sea surface temperatures (SST) that include the ACT are used to force a control ensemble. An idealized, warm SST perturbation is designed to represent lower boundary forcing without the ACT for the experiment ensemble. Summer simulations forced by observed SST and reanalysis boundary conditions for each of five consecutive years are compared to five parallel runs forced by SST with the warm perturbation. The article summarizes the sequence of events leading to the onset of the WAM in the <span class="hlt">Sahel</span> region. The representation of WAM onset in RM3 simulations is examined and compared to Tropical Rainfall Measuring Mission (TRMM), Global Precipitation Climatology Project (GPCP) and reanalysis data. The study evaluates the sensitivity of WAM onset indicators to the presence of the ACT by analysing the differences between the two simulation ensembles. Results show that the timing of major rainfall events and therefore theWAM onset in the <span class="hlt">Sahel</span> are not sensitive to the presence of the ACT. However, the warm SST perturbation does increase downstream rainfall rates over West Africa as a consequence of enhanced specific humidity and enhanced northward moisture flux in the lower troposphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..12212106D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..12212106D"><span>Regional Climate Variability Under Model Simulations of Solar Geoengineering</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dagon, Katherine; Schrag, Daniel P.</p> <p>2017-11-01</p> <p>Solar geoengineering has been shown in modeling studies to successfully mitigate global mean surface temperature changes from greenhouse warming. Changes in land surface hydrology are complicated by the direct effect of carbon dioxide (CO2) on vegetation, which alters the flux of water from the land surface to the atmosphere. Here we investigate changes in boreal summer climate variability under solar geoengineering using multiple ensembles of model simulations. We find that spatially uniform solar geoengineering creates a strong meridional gradient in the Northern Hemisphere temperature response, with less consistent patterns in precipitation, evapotranspiration, and soil moisture. Using regional summertime temperature and precipitation results across 31-member ensembles, we show a decrease in the frequency of heat waves and consecutive dry days under solar geoengineering relative to a high-CO2 world. However in some regions solar geoengineering of this amount does not completely reduce summer heat extremes relative to present day climate. In western Russia and Siberia, an increase in heat waves is connected to a decrease in surface soil moisture that favors persistent high temperatures. Heat waves decrease in the central United States and the <span class="hlt">Sahel</span>, while the hydrologic response increases terrestrial water storage. Regional changes in soil moisture exhibit trends over time as the model adjusts to solar geoengineering, particularly in Siberia and the <span class="hlt">Sahel</span>, leading to robust shifts in climate variance. These results suggest potential benefits and complications of large-scale uniform climate intervention schemes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999GeoRL..26.1267S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999GeoRL..26.1267S"><span>Are revised models better models? A skill score assessment of regional interannual variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sperber, Kenneth R.; Participating AMIP Modelling Groups</p> <p>1999-05-01</p> <p>Various skill scores are used to assess the performance of revised models relative to their original configurations. The interannual variability of all-India, <span class="hlt">Sahel</span> and Nordeste rainfall and summer monsoon windshear is examined in integrations performed under the experimental design of the Atmospheric Model Intercomparison Project. For the indices considered, the revised models exhibit greater fidelity at simulating the observed interannual variability. Interannual variability of all-India rainfall is better simulated by models that have a more realistic rainfall climatology in the vicinity of India, indicating the beneficial effect of reducing systematic model error.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999GeoRL..26.1267P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999GeoRL..26.1267P"><span>Are revised models better models? A skill score assessment of regional interannual variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Participating AMIP Modelling Groups,; Sperber, Kenneth R.</p> <p></p> <p>Various skill scores are used to assess the performance of revised models relative to their original configurations. The interannual variability of all-India, <span class="hlt">Sahel</span> and Nordeste rainfall and summer monsoon windshear is examined in integrations performed under the experimental design of the Atmospheric Model Intercomparison Project. For the indices considered, the revised models exhibit greater fidelity at simulating the observed interannual variability. Interannual variability of all-India rainfall is better simulated by models that have a more realistic rainfall climatology in the vicinity of India, indicating the beneficial effect of reducing systematic model error.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990117066&hterms=Venkataraman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DVenkataraman','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990117066&hterms=Venkataraman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DVenkataraman"><span>Validation of Satellite Retrieved Land Surface Variables</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lakshmi, Venkataraman; Susskind, Joel</p> <p>1999-01-01</p> <p>The effective use of satellite observations of the land surface is limited by the lack of high spatial resolution ground data sets for validation of satellite products. Recent large scale field experiments include FIFE, HAPEX-<span class="hlt">Sahel</span> and BOREAS which provide us with data sets that have large spatial coverage and long time coverage. It is the objective of this paper to characterize the difference between the satellite estimates and the ground observations. This study and others along similar lines will help us in utilization of satellite retrieved data in large scale modeling studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1037974','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1037974"><span>USSOF OPERATIONS IN AFRICA: PROSPECTS FOR FUTURE ENGAGEMENTS IN THE <span class="hlt">SAHEL</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2017-04-03</p> <p>Mechanical Engineering. He also obtained a Master of Arts degree in Terrorism , Organized Crime and Global Security from the Coventry University, United...was a staff officer in the Headquarters Nigerian Air Force, Abuja. iv Abstract As part of the Global War on Terror , AFRICOM was established...to secure the US security interests in Africa. AFRICOM, through the Trans-Saharan Counter Terrorism Partnership uses USSOF to engage Sahelian</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1022813','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1022813"><span>Political Reform, Socio-Religious Change, and Stability in the African <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2016-12-08</p> <p>influencing the capacity of Sahelian states to manage these pressures, and to maintain stability and ensure the social order and effective governance that...in preparation for fieldwork, involved substantial documentary research and the preparation of background papers on each country; regularly weekly...dimensions of elections and electoral management in each of the six countries. This material was initially generated building on our State</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA561296','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA561296"><span>Insecurity and Instability in the <span class="hlt">Sahel</span> Region: The Case of Mali</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-03-19</p> <p>desertification . Great distances separate the three main regional capitals in the area. For example a nomad who knows the region can travel from Kidal to...which makes securing the border and providing government services very difficult. Also, desertification means that locals cannot necessarily rely on...historical Trans- Saharan commerce and its routes are the key factors for the trade.15 Difficult Socio-Political Environment. Desertification has put</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA622451','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA622451"><span>Mokhtar Belmokhtar: One-Eyed Firebrand of North Africa and the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-02-01</p> <p>2010). 8 Philippe Migaux, “The Roots of Islamic Radicalism,” in The History of Terrorism: From Antiquity to Al Qaeda, ed. Gérard Chaliand and...and obeyed.59 AQIM then indicts Belmokhtar for botching several kidnapping operations (including the Fowler case), shopping for weapons in Libya</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991JMS.....1..229B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991JMS.....1..229B"><span>A note on Bjerkne's hypothesis for North Atlantic variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bryan, Kirk; Stouffer, Ron</p> <p>1991-01-01</p> <p>On decadal time-scales the historical surface temperature record over land in the Northern Hemisphere is dominated by polar amplified variations. These variations are coherent with SST anomalies concentrated in the Northwest Atlantic, but extending with lesser amplitude into the North Pacific as well. Bierknes suggested that multi-year SST anomalies in the subpolar North Atlantic were due to irregular changes in the intensity of the thermohaline circulation. In support of the Bjerknes hypothesis there is evidence that winter overturning in the Labrador Sea was suppressed for a brief period from 1967-1969 by a cap of relative fresh water at the surface. Cause and effect are unclear, but this event was associated with a marked cooling of the entire Northern Hemisphere. The difference in SST averaged over the Northern Hemisphere oceans and SST averaged over the Southern Hemisphere oceans from the equator to 40°S is coherent with <span class="hlt">Sahel</span> summer rainfall on decadal time scales. Empirical evidence is supported by numerical experiments with the British Meteorological Office atmospheric climate model which simulate augmented monsoonal rainfall in the <span class="hlt">Sahel</span> region of Africa in response to realistic warm SST anomalies in the Northwest Atlantic. A coupled ocean-atmosphere global model exhibits two equilibrium climate states. One has an active thermohaline circulation in the North Atlantic and the other does not. The two climate states provide an extreme example which illustrates the type of large scale air sea interaction Bjerknes visualized as a mechanism for North Atlantic climate variability on decadal time-scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1422596-validation-statistical-methodology-extracting-vegetation-feedbacks-focus-north-african-ecosystems-community-earth-system-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1422596-validation-statistical-methodology-extracting-vegetation-feedbacks-focus-north-african-ecosystems-community-earth-system-model"><span>Validation of a Statistical Methodology for Extracting Vegetation Feedbacks: Focus on North African Ecosystems in the Community Earth System Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Yu, Yan; Notaro, Michael; Wang, Fuyao</p> <p></p> <p>Generalized equilibrium feedback assessment (GEFA) is a potentially valuable multivariate statistical tool for extracting vegetation feedbacks to the atmosphere in either observations or coupled Earth system models. The reliability of GEFA at capturing the terrestrial impacts on regional climate is demonstrated in this paper using the National Center for Atmospheric Research Community Earth System Model (CESM), with focus on North Africa. The feedback is assessed statistically by applying GEFA to output from a fully coupled control run. To reduce the sampling error caused by short data records, the traditional or full GEFA is refined through stepwise GEFA by dropping unimportantmore » forcings. Two ensembles of dynamical experiments are developed for the <span class="hlt">Sahel</span> or West African monsoon region against which GEFA-based vegetation feedbacks are evaluated. In these dynamical experiments, regional leaf area index (LAI) is modified either alone or in conjunction with soil moisture, with the latter runs motivated by strong regional soil moisture–LAI coupling. Stepwise GEFA boasts higher consistency between statistically and dynamically assessed atmospheric responses to land surface anomalies than full GEFA, especially with short data records. GEFA-based atmospheric responses are more consistent with the coupled soil moisture–LAI experiments, indicating that GEFA is assessing the combined impacts of coupled vegetation and soil moisture. Finally, both the statistical and dynamical assessments reveal a negative vegetation–rainfall feedback in the <span class="hlt">Sahel</span> associated with an atmospheric stability mechanism in CESM versus a weaker positive feedback in the West African monsoon region associated with a moisture recycling mechanism in CESM.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRD..117.3304G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRD..117.3304G"><span>Long-term aerosol measurements in Gran Canaria, Canary Islands: Particle concentration, sources and elemental composition</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gelado-Caballero, MaríA. D.; López-GarcíA, Patricia; Prieto, Sandra; Patey, Matthew D.; Collado, Cayetano; HéRnáNdez-Brito, José J.</p> <p>2012-02-01</p> <p>There are very few sets of long-term measurements of aerosol concentrations over the North Atlantic Ocean, yet such data is invaluable in quantifying atmospheric dust inputs to this ocean region. We present an 8-year record of total suspended particles (TSP) collected at three stations on Gran Canaria Island, Spain (Taliarte at sea level, Tafira 269 m above sea level (a.s.l.) and Pico de la Gorra 1930 m a.s.l.). Using wet and dry deposition measurements, the mean dust flux was calculated at 42.3 mg m-2 d-1. Air mass back trajectories (HYSPLIT, NOAA) suggested that the Sahara desert is the major source of African dust (dominant during 32-50% of days), while the <span class="hlt">Sahel</span> desert was the major source only 2-10% of the time (maximum in summer). Elemental composition ratios of African samples indicate that, despite the homogeneity of the dust in collected samples, some signatures of the bedrocks can still be detected. Differences were found for the <span class="hlt">Sahel</span>, Central Sahara and North of Sahara regions in Ti/Al, Mg/Al and Ca/Al ratios, respectively. Elements often associated with pollution (Pb, Cd, Ni, Zn) appeared to share a common origin, while Cu may have a predominantly local source, as suggested by a decrease in the enrichment factor (EF) of Cu during dust events. The inter-annual variability of dust concentrations is investigated in this work. During winter, African dust concentration measurements at the Pico de la Gorra station were found to correlate with the North Atlantic Oscillation (NAO) index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013029','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013029"><span>Multi-Decadal Aerosol Variations from 1980 to 2009: A Perspective from Observations and a Global Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chin, Mian; Diehl, T.; Tan, Q.; Prospero, J. M.; Kahn, R. A.; Remer, L. A.; Yu, H.; Sayer, A. M.; Bian, H.; Geogdzhayev, I. V.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140013029'); toggleEditAbsImage('author_20140013029_show'); toggleEditAbsImage('author_20140013029_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140013029_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140013029_hide"></p> <p>2014-01-01</p> <p>Aerosol variations and trends over different land and ocean regions during 1980-2009 are analyzed with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model and observations from multiple satellite sensors and ground-based networks. Excluding time periods with large volcanic influences, the tendency of aerosol optical depth (AOD) and surface concentration over polluted land regions is consistent with the anthropogenic emission changes.The largest reduction occurs over Europe, and regions in North America and Russia also exhibit reductions. On the other hand, East Asia and South Asia show AOD increases, although relatively large amount of natural aerosols in Asia makes the total changes less directly connected to the pollutant emission trends. Over major dust source regions, model analysis indicates that the dust emissions over the Sahara and <span class="hlt">Sahel</span> respond mainly to the near-surface wind speed, but over Central Asia they are largely influenced by ground wetness. The decreasing dust trend in the tropical North Atlantic is most closely associated with the decrease of <span class="hlt">Sahel</span> dust emission and increase of precipitation over the tropical North Atlantic, likely driven by the sea surface temperature increase. Despite significant regional trends, the model-calculated global annual average AOD shows little changes over land and ocean in the past three decades, because opposite trends in different regions cancel each other in the global average. This highlights the need for regional-scale aerosol assessment, as the global average value conceals regional changes, and thus is not sufficient for assessing changes in aerosol loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SolE....6..525B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SolE....6..525B"><span>Does Jatropha curcas L. show resistance to drought in the Sahelian zone of West Africa? A case study from Burkina Faso</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayen, P.; Sop, T. K.; Lykke, A. M.; Thiombiano, A.</p> <p>2015-05-01</p> <p>Land degradation is an environmental problem which weakens agro-sylvo-pastoral productivity in sub-Saharan Africa. The most common manifestation of land degradation is the appearance of denuded land. We carried out an experiment to test the effect of three soil and water conservation techniques on survival and growth of Jatropha curcas seedlings transplanted onto two completely denuded lands in the Sahelian and Sudanian zones of Burkina Faso. We implemented an experimental design with three replicates per restoration technique. A total of 174 seedlings were planted in each study site. The results showed that the soil water content varied according to the restoration technique used (df = 2; F = 53.21; p < 0.00) as well as according to study site (df = 1; F = 74.48; p < 0.00). Soil water content was significantly lower in the <span class="hlt">Sahel</span> than in the Sudanian zone. Seedling survival rate varied significantly according to technique used (df = 2; F = 8.91; p = 0.000) and study site (df = 1; F = 9.74; p = 0.003). Survival rate, diameter and seedling height were highest at the Sudanian site. At the Sahelian site, all seedlings died 2 years after establishment. These results suggest that J. curcas is unsuited to denuded land in the Sahelian zone. Most of the plants died in the <span class="hlt">Sahel</span> between April and May, which is the peak of the dry season; this may be an indication that J. curcas may not be as drought-resistant as suggested by the prolific literature which has reported on diverse claims surrounding this plant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SolED...7..639B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SolED...7..639B"><span>Does Jatropha curcas L. show resistance to drought in the Sahelian zone of West Africa? A case study from Burkina Faso</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bayen, P.; Sop, T. K.; Lykke, A. M.; Thiombiano, A.</p> <p>2015-02-01</p> <p>Land degradation is an environmental problem which weakens agro-silvo-pastoral productivity in Sub-Saharan Africa. The most common manifestation of land degradation is the appearance of denuded land. We carried out an experiment to test the effect of three soil and water conservation techniques on survival and growth of Jatropha curcas seedlings transplanted onto two completely denuded lands in the Sahelian and Sudanian zones of Burkina Faso. We implemented an experimental design with three replicates per restoration technique. A total of 174 seedlings were planted in each study site. The results showed that soil water content varied according to the restoration technique used (df = 2; F = 53.21; p < 0.00) as well as according to study site (df = 1; F = 74.48; p < 0.00). Soil water content was significantly lower in the <span class="hlt">Sahel</span> than in the Sudanian zone. Seedling survival rate varied significantly according to technique used (df = 2; F = 8.91; p = 0.000) and study site (df = 1; F = 9.74; p = 0.003). Survival rate, diameter and seedling height were highest at the Sudanian site. At the Sahelian site, all seedlings died two years after establishment. These results suggest that Jatropha curcas is unsuited to denuded land in the Sahelian zone. Most of the plants died in the <span class="hlt">Sahel</span> between April and May, which is the peak of the dry season; this may be an indication that Jatropha may not be as drought-resistant as suggested by the prolific literature which has reported on diverse claims surrounding this plant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28464937','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28464937"><span>Seasonal vaccination against malaria: a potential use for an imperfect malaria vaccine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Greenwood, Brian; Dicko, Alassane; Sagara, Issaka; Zongo, Issaka; Tinto, Halidou; Cairns, Matthew; Kuepfer, Irene; Milligan, Paul; Ouedraogo, Jean-Bosco; Doumbo, Ogobara; Chandramohan, Daniel</p> <p>2017-05-02</p> <p>In many parts of the African <span class="hlt">Sahel</span> and sub-<span class="hlt">Sahel</span>, where malaria remains a major cause of mortality and morbidity, transmission of the infection is highly seasonal. Seasonal malaria chemoprevention (SMC), which involves administration of a full course of malaria treatment to young children at monthly intervals during the high transmission season, is proving to be an effective malaria control measure in these areas. However, SMC does not provide complete protection and it is demanding to deliver for both families and healthcare givers. Furthermore, there is a risk of the emergence in the future of resistance to the drugs, sulfadoxine-pyrimethamine and amodiaquine, that are currently being used for SMC. Substantial progress has been made in the development of malaria vaccines during the past decade and one malaria vaccine, RTS,S/AS01, has received a positive opinion from the European Medicines Authority and will soon be deployed in large-scale, pilot implementation projects in sub-Saharan Africa. A characteristic feature of this vaccine, and potentially of some of the other malaria vaccines under development, is that they provide a high level of efficacy during the period immediately after vaccination, but that this wanes rapidly, perhaps because it is difficult to develop effective immunological memory to malaria antigens in subjects exposed previously to malaria infection. A potentially effective way of using malaria vaccines with high initial efficacy but which provide only a short period of protection could be annual, mass vaccination campaigns shortly before each malaria transmission season in areas where malaria transmission is confined largely to a few months of the year.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29904821','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29904821"><span>Exploring evapotranspiration dynamics over Sub-Sahara Africa (2000-2014).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ndehedehe, Christopher E; Okwuashi, Onuwa; Ferreira, Vagner G; Agutu, Nathan O</p> <p>2018-06-14</p> <p>Monitoring changes in evapotranspiration (ET) is useful in the management of water resources in irrigated agricultural landscapes and in the assessment of crop stress and vegetation conditions of drought-vulnerable regions. Information on the impacts of climate variability on ET dynamics is profitable in developing water management adaptation strategies. Such impacts, however, are generally unreported and not conclusively determined in some regions. In this study, changes in MODIS (Moderate Resolution Imaging Spectroradiometer)-derived ET (2000-2014) over large proportions of Sub-Sahara Africa (SSA) are explored. The multivariate analyses of ET over SSA showed that four leading modes of observed dynamics in ET, accounting for about 90% of the total variability, emanated mostly from some sections of the Sudano-<span class="hlt">Sahel</span> and Congo basin. Based on Man-Kendall's statistics, significant positive trends (α = 0.05) in ET over the Central African Republic and most parts of the <span class="hlt">Sahel</span> region were observed. Over much of the Congo basin nonetheless, ET showed significant (α = 0.05) distributions of widespread negative trends. These trends in ET were rather found to be consistent with observed changes in model soil moisture but not in all locations, perhaps due to inconsistent trends in maximum rainfall and land surface temperature. However, the results of spatio-temporal drought analysis confirm that the extensive ET losses in the Congo basin were somewhat induced by soil moisture deficits. Amidst other prominent drivers of ET, the dynamics of ET over the terrestrial ecosystems of SSA appear to be a more complex phenomenon that may transcend natural climate variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNH53A0135E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNH53A0135E"><span>Impacts of Climate Change on Malaria Transmission in Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eltahir, E. A. B.; Endo, N.; Yamana, T. K.</p> <p>2017-12-01</p> <p>Malaria is a major vector-borne parasitic disease transmitted to humans by Anopheles spp mosquitoes. Africa is the hotspot for malaria transmission where more than 90% of malaria deaths occur every year. Malaria transmission is an intricate function of climatic factors, which non-linearly affect the development of vectors and parasites. We project that the risk of malaria will increase towards the end of the 21st century in east Africa, but decrease in west Africa. We combine a novel malaria transmission simulator, HYDREMATS, that has been developed based on comprehensive multi-year field surveys both in East Africa and West Africa, and the most reliable climate projections through regional dynamical downscaling and rigorous selection of GCMs from among CMIP5 models. We define a bell-shaped relation between malaria intensity and temperature, centered around a temperature of 30°C. Future risks of malaria are projected for two highly populated regions in Africa: the highlands in East Africa and the fringes of the desert in West Africa. In the highlands of East Africa, temperature is substantially colder than this optimal temperature; warmer future climate exacerbate malaria conditions. In the <span class="hlt">Sahel</span> fringes in West Africa, temperature is around this optimal temperature; warming is not likely to exacerbate and might even reduce malaria burden. Unlike the highlands of East Africa, which receive significant amounts of annual rainfall, dry conditions also limit malaria transmission in the <span class="hlt">Sahel</span> fringes in West Africa. This disproportionate risk of malaria due to climate change should guide strategies for climate adaptation over Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1422596-validation-statistical-methodology-extracting-vegetation-feedbacks-focus-north-african-ecosystems-community-earth-system-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1422596-validation-statistical-methodology-extracting-vegetation-feedbacks-focus-north-african-ecosystems-community-earth-system-model"><span>Validation of a Statistical Methodology for Extracting Vegetation Feedbacks: Focus on North African Ecosystems in the Community Earth System Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Yu, Yan; Notaro, Michael; Wang, Fuyao; ...</p> <p>2018-02-05</p> <p>Generalized equilibrium feedback assessment (GEFA) is a potentially valuable multivariate statistical tool for extracting vegetation feedbacks to the atmosphere in either observations or coupled Earth system models. The reliability of GEFA at capturing the terrestrial impacts on regional climate is demonstrated in this paper using the National Center for Atmospheric Research Community Earth System Model (CESM), with focus on North Africa. The feedback is assessed statistically by applying GEFA to output from a fully coupled control run. To reduce the sampling error caused by short data records, the traditional or full GEFA is refined through stepwise GEFA by dropping unimportantmore » forcings. Two ensembles of dynamical experiments are developed for the <span class="hlt">Sahel</span> or West African monsoon region against which GEFA-based vegetation feedbacks are evaluated. In these dynamical experiments, regional leaf area index (LAI) is modified either alone or in conjunction with soil moisture, with the latter runs motivated by strong regional soil moisture–LAI coupling. Stepwise GEFA boasts higher consistency between statistically and dynamically assessed atmospheric responses to land surface anomalies than full GEFA, especially with short data records. GEFA-based atmospheric responses are more consistent with the coupled soil moisture–LAI experiments, indicating that GEFA is assessing the combined impacts of coupled vegetation and soil moisture. Finally, both the statistical and dynamical assessments reveal a negative vegetation–rainfall feedback in the <span class="hlt">Sahel</span> associated with an atmospheric stability mechanism in CESM versus a weaker positive feedback in the West African monsoon region associated with a moisture recycling mechanism in CESM.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140012646','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140012646"><span>Application of Spectral Analysis Techniques in the Intercomparison of Aerosol Data: Part III. Using Combined PCA to Compare Spatiotemporal Variability of MODIS, MISR and OMI Aerosol Optical Depth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.</p> <p>2014-01-01</p> <p>Satellite measurements of global aerosol properties are very useful in constraining aerosol parameterization in climate models. The reliability of different data sets in representing global and regional aerosol variability becomes an essential question. In this study, we present the results of a comparison using combined principal component analysis (CPCA), applied to monthly mean, mapped (Level 3) aerosol optical depth (AOD) product from Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Ozone Monitoring Instrument (OMI). This technique effectively finds the common space-time variability in the multiple data sets by decomposing the combined AOD field. The results suggest that all of the sensors capture the globally important aerosol regimes, including dust, biomass burning, pollution, and mixed aerosol types. Nonetheless, differences are also noted. Specifically, compared with MISR and OMI, MODIS variability is significantly higher over South America, India, and the <span class="hlt">Sahel</span>. MODIS deep blue AOD has a lower seasonal variability in North Africa, accompanied by a decreasing trend that is not found in either MISR or OMI AOD data. The narrow swath of MISR results in an underestimation of dust variability over the Taklamakan Desert. The MISR AOD data also exhibit overall lower variability in South America and the <span class="hlt">Sahel</span>. OMI does not capture the Russian wild fire in 2010 nor the phase shift in biomass burning over East South America compared to Central South America, likely due to cloud contamination and the OMI row anomaly. OMI also indicates a much stronger (boreal) winter peak in South Africa compared with MODIS and MISR.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6268470-forestry-possible-solution-environmental-energy-difficulties-facing-semi-arid-africa-case-upper-volta','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6268470-forestry-possible-solution-environmental-energy-difficulties-facing-semi-arid-africa-case-upper-volta"><span>Forestry as a possible solution to the environmental and energy difficulties facing semi-arid Africa. The case of Upper Volta</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Weinstabel, P.E.; Zech, W.</p> <p>1982-01-01</p> <p>The total annual demand for wood in Upper Volta is about 4.2 million cubic m solid wood, 94% of the population depends on wood for energy (compared with 84% in the <span class="hlt">Sahel</span> states as a whole), and more than 30% of income in urban areas is spent on acquiring wood. Any policy aimed at securing adequate food supplies for the population must therefore be accompanied by a programme for safeguarding energy supplies. Measures which should be included in an integrated energy programme are presented and details are given of Upper Volta's forestry programme. 21 references.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70159369','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70159369"><span>Sequestration of carbon in soil organic matter in Senegal: an overview</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tieszen, Larry L.; Tappan, G. Gray; Toure, A.</p> <p>2004-01-01</p> <p>The project focuses on four objectives in specific locations across the agroecological zones of Senegal. These objectives are: use of soil sampling and biogeochemical modeling to quantify the biophysical potential for carbon sequestration and to determine the sensitivity of the carbon stocks to various management and climate scenarios, to evaluate the socio-economic and cultural requirements necessary for successful project implementation directed toward an aggregation of smallholders to sequester around 100,000 t carbon (C), to support capacity building to develop a Carbon Specialist Team, and to initiate extrapolation from site-specific project areas to the <span class="hlt">Sahel</span> region and the national level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1734g0021N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1734g0021N"><span>Preliminary study of a small beam-down solar tower on sub-Saharan countries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ndiaye, Ahmadou; Thiam, Ababacar; Mbow, Cheikh; Stouffs, Pascal; Azilinon, Dorothé</p> <p>2016-05-01</p> <p>In this present work, a small Beam Down power plant is studied in the <span class="hlt">Sahel</span> region. The preconfigured system is a field of 78 heliostats and a hyperboloid sectioned with a length rhyp = 11.72 m. The simulation made with the software SolTrace shows an efficiency of the field up to 89%. Temperatures from 675.37 K to 809.55 K are achieved and the power intercepted at the receiver input are equal to 96.57 kW, 124.53 9 kW and 98.90 kW respectively at 9 am, 1: 06 pm and 4 pm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9245E..1RD','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9245E..1RD"><span>The application of remote sensing for climate change adaptation in <span class="hlt">Sahel</span> region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Deafalla, Taisser H. H.; Csaplovics, Elmar; El-Abbas, Mustafa M.</p> <p>2014-10-01</p> <p>In recent years, there is no doubt that global climate change (CC) has observable development impacts, which seriously threatens the ability of individuals and communities at all levels. During this process, the clear degradation in the situation of ecosystems has produced a global concern of the urgency to mitigate climate threats and related effects. Assessing the impacts and vulnerability of CC requires accurate, up-to-date and improved information. Coupled with the ready availability of historical remote sensing (RS) data, the reduction in data cost and increased resolution from satellite platforms, RS technology appears poised to make a great impact on planning agencies and providing better understanding the dynamics of the climate system, predict and mitigate the expected global changes and the effects on human civilization involved in mapping Land Use Land Cover (LU/LC) at a variety of spatial scales. This research was designed to study the impact of CC in conflict zones and potential flashpoints in Sudan namely Nuba Mountains, where the community in this area living in fragile and unstable conditions, which making them more vulnerable to the risk of violent conflict and CC effects. And to determine the factors that exacerbate vulnerability in the study area as well as to map and assess the LU/LC change during the period 1984 to 2011 covered the years (1999, 2002 and 2009). Multispectral satellite data (i.e. LANDSAT TM and TERRA ASTER) were used. Change detection techniques were applied to analyze the rate of changes, causal factors as well as the drivers of changes. Recent study showed the importance of spatial variables in tackling CC which promoted the use of maps made within a RS. In addition to provide an input for climate models; and thus plan adaptation strategies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA349121','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA349121"><span>Conflict and Conflict Resolution in the <span class="hlt">Sahel</span>: The Tuareg Insurgency in Mali</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1998-05-01</p> <p>another exodus of Tuaregs—this time from Qadhafi’s military forces. The dissolution of the Libyan- financed Islamic Legion in the late 1980s and the...Liberation of Azawad) FIAA = Le Front Islamique Arabe de l’Azawad (The Islamic Arab Front of Azawad) FPLA MPA ARLA FIAA Indep. units TOTAL 150 120...Afrique, 1580, April 10-16, 1991, pp. 18-23. 10. Quoting new finance minister Zoumana Sako, Sennen Andriamirado, "Les premiers pas du nouveau regime</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170001399','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170001399"><span>Correlation Between Soil Moisture and Dust Emissions: An Investigation for Global Climate Modeling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fredrickson, Carley; Tan, Qian</p> <p>2017-01-01</p> <p>This work is using the newly available NASA SMAP soil moisture measurement data to evaluate its impact on the atmospheric dust emissions. Dust is an important component of atmospheric aerosols, which affects both climate and air quality. In this work, we focused on semi-desert regions, where dust emissions show seasonal variations due to soil moisture changes, i.e. in <span class="hlt">Sahel</span> of Africa. We first identified three Aerosol Robotic Network (AERONET) sites in the <span class="hlt">Sahel</span> (IER_Cinzana, Banizoumbou, and Zinder_Airport). We then utilized measurements of aerosol optical depth (AOD), fine mode fraction, size distribution, and single-scattering albedo and its wave-length dependence to select dust plumes from the available measurements We matched the latitude and longitude of the AERONET station to the corresponding SMAP data cell in the years 2015 and 2016, and calculated their correlation coefficient. Additionally, we looked at the correlation coefficient with a three-day and a five-day shift to check the impact of soil moisture on dust plumes with some time delay. Due to the arid nature of Banizoumbou and Zinder_Airport, no correlation was found to exist between local soil moisture and dust aerosol load. While IER_Cinzana had soil moisture levels above the satellite threshold of 0.02cm3/cm3, R-value approaching zero indicated no presence of a correlation. On the other hand, Ilorin demonstrated a significant negative correlation between aerosol optical depth and soil moisture. When isolating the analysis to Ilorin's dry season, a negative correlation of -0.593 was the largest dust-isolated R-value recorded, suggesting that soil moisture is driven the dust emission in this semi-desert region during transitional season.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010048418&hterms=major+depression&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmajor%2Bdepression','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010048418&hterms=major+depression&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmajor%2Bdepression"><span>Relative Contributions of the Saharan and Sahelian Sources to the Atmospheric Dust Load Over the North Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ginoux, Paul; Chin, M.; Torres, O.; Prospero, J.; Dubovik, O.; Holben, B.; Einaudi, Franco (Technical Monitor)</p> <p>2000-01-01</p> <p>It has long been recognized that Saharan desert is the major source for long range transport of mineral dust over the Atlantic. The contribution from other natural sources to the dust load over the Atlantic has generally been ignored in previous model studies or been replaced by anthropogenically disturbed soil emissions. Recently, Prospero et.at. have identified the major dust sources over the Earth using TOMS aerosol index. They showed that these sources correspond to dry lakes with layers of sediment deposed in the late Holocene or Pleistocene. One of the most active of these sources seem to be the Bodele depression. Chiapello et al. have analyzed the mineralogical composition of dust on the West coast of Africa. They found that Sahelian dust events are the most intense but are less frequent than Saharan plumes. This suggests that the Bodele depression could contribute significantly to the dust load over the Atlantic. The relative contribution of the <span class="hlt">Sahel</span> and Sahara dust sources is of importance for marine biogeochemistry or atmospheric radiation, because each source has a distinct mineralogical composition. We present here a model study of the relative contributions of Sahara and <span class="hlt">Sahel</span> sources to the atmospheric dust aerosols over the North Atlantic. The Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model is used to simulate dust distribution in 1996-1997. Dust particles are labeled depending on their sources. In this presentation, we will present the comparison between the model results and observations from ground based measurements (dust concentration, optical thickness and size distribution) and satellite data (TOMS aerosol index). The relative contribution of each source will then be analyzed spatially and temporally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160003522&hterms=churchill&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dchurchill','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160003522&hterms=churchill&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dchurchill"><span>Combined Effect of El Nino Southern Oscillation and Atlantic Multidecadal Oscillation on Lake Chad Level Variability Region</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Okonkwo, Churchill; Demoz, Belay; Sakai, Ricardo; Ichoku, Charles; Anarado, Chigozie; Adegoke, Jimmy; Amadou, Angelina; Abdullahi, Sanusu Imran</p> <p>2015-01-01</p> <p>In this study, the combined effect of the Atlantic Multidecadal Oscillation (AMO) and El Niño Southern Oscillation (ENSO) on the Lake Chad (LC) level variability is explored. Our results show that the lake level at the Bol monitoring station has a statistically significant correlation with precipitation (R2 = 0.6, at the 99.5% confidence level). The period between the late 1960s and early 1970s marked a turning point in the response of the regional rainfall to climatic drivers, thereby severely affecting the LC level. Our results also suggest that the negative impact of the cold phase of AMO on <span class="hlt">Sahel</span> precipitation masks and supersedes the positive effect of La Niña in the early the 1970s. The drop in the size of LC level from 282.5 m in the early 1960s to about 278.1 m in 1983/1984 was the largest to occur within the period of study (1900-2010) and coincides with the combined cold phase of AMO and strong El Niño phase of ENSO. Further analyses show that the current warm phase of AMO and increasing La Niña episodes appear to be playing a major role in the increased precipitation in the <span class="hlt">Sahel</span> region. The LC level is responding to this increase in precipitation by a gradual recovery, though it is still below the levels of the 1960s. This understanding of the AMO-ENSO-rainfall-LC level association will help in forecasting the impacts of similar combined episodes in the future. These findings also have implications for long-term water resources management in the LC region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22498628','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22498628"><span>Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Booth, Ben B B; Dunstone, Nick J; Halloran, Paul R; Andrews, Timothy; Bellouin, Nicolas</p> <p>2012-04-04</p> <p>Systematic climate shifts have been linked to multidecadal variability in observed sea surface temperatures in the North Atlantic Ocean. These links are extensive, influencing a range of climate processes such as hurricane activity and African <span class="hlt">Sahel</span> and Amazonian droughts. The variability is distinct from historical global-mean temperature changes and is commonly attributed to natural ocean oscillations. A number of studies have provided evidence that aerosols can influence long-term changes in sea surface temperatures, but climate models have so far failed to reproduce these interactions and the role of aerosols in decadal variability remains unclear. Here we use a state-of-the-art Earth system climate model to show that aerosol emissions and periods of volcanic activity explain 76 per cent of the simulated multidecadal variance in detrended 1860-2005 North Atlantic sea surface temperatures. After 1950, simulated variability is within observational estimates; our estimates for 1910-1940 capture twice the warming of previous generation models but do not explain the entire observed trend. Other processes, such as ocean circulation, may also have contributed to variability in the early twentieth century. Mechanistically, we find that inclusion of aerosol-cloud microphysical effects, which were included in few previous multimodel ensembles, dominates the magnitude (80 per cent) and the spatial pattern of the total surface aerosol forcing in the North Atlantic. Our findings suggest that anthropogenic aerosol emissions influenced a range of societally important historical climate events such as peaks in hurricane activity and <span class="hlt">Sahel</span> drought. Decadal-scale model predictions of regional Atlantic climate will probably be improved by incorporating aerosol-cloud microphysical interactions and estimates of future concentrations of aerosols, emissions of which are directly addressable by policy actions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988JCli....1..921A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988JCli....1..921A"><span>Improved Ground Hydrology Calculations for Global Climate Models (GCMs): Soil Water Movement and Evapotranspiration.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abramopoulos, F.; Rosenzweig, C.; Choudhury, B.</p> <p>1988-09-01</p> <p>A physically based ground hydrology model is developed to improve the land-surface sensible and latent heat calculations in global climate models (GCMs). The processes of transpiration, evaporation from intercepted precipitation and dew, evaporation from bare soil, infiltration, soil water flow, and runoff are explicitly included in the model. The amount of detail in the hydrologic calculations is restricted to a level appropriate for use in a GCM, but each of the aforementioned processes is modeled on the basis of the underlying physical principles. Data from the Goddard Institute for Space Studies (GISS) GCM are used as inputs for off-line tests of the ground hydrology model in four 8° × 10° regions (Brazil, <span class="hlt">Sahel</span>, Sahara, and India). Soil and vegetation input parameters are calculated as area-weighted means over the 8° × 10° gridhox. This compositing procedure is tested by comparing resulting hydrological quantities to ground hydrology model calculations performed on the 1° × 1° cells which comprise the 8° × 10° gridbox. Results show that the compositing procedure works well except in the <span class="hlt">Sahel</span> where lower soil water levels and a heterogeneous land surface produce more variability in hydrological quantities, indicating that a resolution better than 8° × 10° is needed for that region. Modeled annual and diurnal hydrological cycles compare well with observations for Brazil, where real world data are available. The sensitivity of the ground hydrology model to several of its input parameters was tested; it was found to be most sensitive to the fraction of land covered by vegetation and least sensitive to the soil hydraulic conductivity and matric potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70032287','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70032287"><span>Climate change and human health: Spatial modeling of water availability, malnutrition, and livelihoods in Mali, Africa</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jankowska, Marta M.; Lopez-Carr, David; Funk, Chris; Husak, Gregory J.; Chafe, Z.A.</p> <p>2012-01-01</p> <p>This study develops a novel approach for projecting climate trends in the <span class="hlt">Sahel</span> in relation to shifting livelihood zones and health outcomes. Focusing on Mali, we explore baseline relationships between temperature, precipitation, livelihood, and malnutrition in 407 Demographic and Health Survey (DHS) clusters with a total of 14,238 children, resulting in a thorough spatial analysis of coupled climate-health dynamics. Results suggest links between livelihoods and each measure of malnutrition, as well as a link between climate and stunting. A ‘front-line’ of vulnerability, related to the transition between agricultural and pastoral livelihoods, is identified as an area where mitigation efforts might be usefully targeted. Additionally, climate is projected to 2025 for the <span class="hlt">Sahel</span>, and demographic trends are introduced to explore how the intersection of climate and demographics may shift the vulnerability ‘front-line’, potentially exposing an additional 6 million people in Mali, up to a million of them children, to heightened risk of malnutrition from climate and livelihood changes. Results indicate that, holding constant morbidity levels, approximately one quarter of a million children will suffer stunting, nearly two hundred thousand will be malnourished, and over one hundred thousand will become anemic in this expanding arid zone by 2025. Climate and health research conducted at finer spatial scales and within shorter projected time lines can identify vulnerability hot spots that are of the highest priority for adaptation interventions; such an analysis can also identify areas with similar characteristics that may be at heightened risk. Such meso-scale coupled human-environment research may facilitate appropriate policy interventions strategically located beyond today’s vulnerability front-line.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70034198','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70034198"><span>Stress transfer among en echelon and opposing thrusts and tear faults: Triggering caused by the 2003 Mw = 6.9 Zemmouri, Algeria, earthquake</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Lin, J.; Stein, R.S.; Meghraoui, M.; Toda, S.; Ayadi, A.; Dorbath, C.; Belabbes, S.</p> <p>2011-01-01</p> <p>The essential features of stress interaction among earthquakes on en echelon thrusts and tear faults were investigated, first through idealized examples and then by study of thrust faulting in Algeria. We calculated coseismic stress changes caused by the 2003 Mw = 6.9 Zemmouri earthquake, finding that a large majority of the Zemmouri afterslip sites were brought several bars closer to Coulomb failure by the coseismic stresses, while the majority of aftershock nodal planes were brought closer to failure by an average of ~2 bars. Further, we calculated that the shallow portions of the adjacent Thenia tear fault, which sustained ~0.25 m slip, were brought >2 bars closer to failure. We calculated that the Coulomb stress increased by 1.5 bars on the deeper portions of the adjacent Boumerdes thrust, which lies just 10–20 km from the city of Algiers; both the Boumerdes and Thenia faults were illuminated by aftershocks. Over the next 6 years, the entire south dipping thrust system extending 80 km to the southwest experienced an increased rate of seismicity. The stress also increased by 0.4 bar on the east <span class="hlt">Sahel</span> thrust fault west of the Zemmouri rupture. Algiers suffered large damaging earthquakes in A.D. 1365 and 1716 and is today home to 3 million people. If these shocks occurred on the east <span class="hlt">Sahel</span> fault and if it has a ~2 mm/yr tectonic loading rate, then enough loading has accumulated to produce a Mw = 6.6–6.9 shock today. Thus, these potentially lethal faults need better understanding of their slip rate and earthquake history.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3741247','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3741247"><span>Knowledge, Attitudes, and Practices Related to Meningitis in Northern Ghana</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hayden, Mary H.; Dalaba, Maxwell; Awine, Timothy; Akweongo, Patricia; Nyaaba, Gertrude; Anaseba, Dominic; Pelzman, Jamie; Hodgson, Abraham; Pandya, Rajul</p> <p>2013-01-01</p> <p>Meningitis has a significant impact in the <span class="hlt">Sahel</span>, but the mechanisms for transmission and factors determining a person's vulnerability are not well understood. Our survey examined the knowledge, attitudes, and practices of people in a meningitis-endemic area in the Upper East region of northern Ghana to identify social, economic, and behavioral factors that may contribute to disease transmission and possible interventions that might improve health outcomes. Key results suggest potential interventions in response to the risk posed by migration, especially seasonal migration, a lack of knowledge about early symptoms causing delayed treatment, and a need for further education about the protective benefits of vaccination. PMID:23775016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920002271&hterms=land+use+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dland%2Buse%2Bchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920002271&hterms=land+use+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dland%2Buse%2Bchange"><span>Synergistic use of multispectral satellite data for monitoring land surface change</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Choudhury, Bhaskar J.</p> <p>1991-01-01</p> <p>Observations by the Advanced Very High Resolution Radiometer (AVHRR) onboard the NOAA satellites were used to compute visible and near infrared reflectances and surface temperature, while passive microwave observations at 37 GHz frequency by the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave Imager (SSM/I) on board, respectively, the Nimbus-7 and DMSP-F8 satellites were used to compute polarization difference. These observations were analyzed along transects from rainforest to desert over northern Africa for the period 1979-1987, which included an unprecedented drought during 1984 over the <span class="hlt">Sahel</span> zone. Model simulations were made to understand the interrelationship among multispectral data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730019631','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730019631"><span>Applications of remote sensing (ERTS) to resource management and development in Sahelien Africa (Republic of Mali)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Macleod, N. H.</p> <p>1973-01-01</p> <p>The primary resource management problem in Sub-Saharan Africa (the <span class="hlt">Sahel</span>) is increasing aridity or desertification. Space observations of sand streams, dune orientations, moisture and vegetation changes and other factors associated with desertification have been made. A second major interest is grazing of cattle, sheep and goats which is associated with major movements of people and animals twice yearly to obtain forage. The changes in available forage are being observed. The location of the cultivators is also being mapped from ERTS imagery. Hydrological analysis is being carried on in the Niger and Bani river watersheds. So far, good imagery of the maximum flood stage has been obtained and assessed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....1710223S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....1710223S"><span>Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schepanski, Kerstin; Heinold, Bernd; Tegen, Ina</p> <p>2017-09-01</p> <p>The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the <span class="hlt">Sahel</span>, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the <span class="hlt">Sahel</span> regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the <span class="hlt">Sahel</span> are predominantly</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA556855','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA556855"><span>Regional Security Cooperation in the Maghreb and <span class="hlt">Sahel</span>: Algeria’s Pivotal Ambivalence</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-02-01</p> <p>between Colombian drug traffickers and AQIM, represented by Abdelkarim Targui, known as “the Tuareg,” held in Guinea Bissau in late October 2010.1...AND ADDRESS(ES) National Defense University,Africa Center for Strategic Studies,300 Fifth Avenue, Building 21, Fort Lesley J . McNair,Washington,DC...Ambassador William M. Bellamy (Ret.) National Defense University 300 Fifth Avenue, Building 21 Fort Lesley J . McNair Washington, DC 20319-5066 Phone</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B8..237V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B8..237V"><span>Re-Emerging Malaria Vectors in Rural <span class="hlt">Sahel</span> (nouna, Burkina Faso): the Paluclim Project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vignolles, Cécile; Sauerborn, Rainer; Dambach, Peter; Viel, Christian; Soubeyroux, Jean-Michel; Sié, Ali; Rogier, Christophe; Tourre, Yves M.</p> <p>2016-06-01</p> <p>The Paluclim project applied the tele-epidemiology approach, linking climate, environment and public health (CNES, 2008), to rural malaria in Nouna (Burkina Faso). It was to analyze the climate impact on vectorial risks, and its consequences on entomological risks forecast. The objectives were to: 1) produce entomological risks maps in the Nouna region, 2) produce dynamic maps on larvae sites and their productivity, 3) study the climate impact on malaria risks, and 4) evaluate the feasibility of strategic larviciding approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC23A0605B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC23A0605B"><span>Soil Modification by Native Shrubs Boosts Crop Productivity in Sudano-Sahelian Agroforestry System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bogie, N. A.; Bayala, R.; Diedhiou, I.; Ghezzehei, T. A.; Dick, R.</p> <p>2014-12-01</p> <p>A changing climate along with human and animal population pressure can have a devastating effect on crop yields and food security in the Sudano-<span class="hlt">Sahel</span>. Agricultural solutions to address soil degradation and crop water stress are needed to combat this increasingly difficult situation. Significant differences in crop success have been observed in peanut and millet grown in association with two native evergreen shrubs Piliostigma reticulatum, and Guiera senegalensis at the sites of Nioro du Rip and Keur Matar, respectively.We investigate how farmers can increase crop productivity by capitalizing on the evolutionary adaptation of native shrubs to the harsh Sudano-Sahelian environment as well as the physical mechanisms at work in the system that can lead to more robust yields. Soil moisture and water potential data were collected during a dry season millet irrigation experiment where stress was imposed in the intercropped system. Despite lower soil moisture content, crops grown in association with shrubs have increased biomass production and a faster development cycle. Hydraulic redistribution is thought to exist in this system and we found diurnal fluctuations in water potential within the intercropped system that increased in magnitude of to 0.4 Mpa per day as the soil dried below 1.0 Mpa during the stress treatment. An isotopic tracer study investigating hydraulic redistribution was carried out by injecting labeled water into shrub roots and sampling shrubs and nearby crops for isotopic analysis of plant water. These findings build on work that was completed in 2004 at the site, but point to lower overall magnitude of diurnal soil water potential fluctuations in dry soils. Using even the limited resources that farmers possess, this agroforestry technique can be expanded over wide swaths of the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4709800','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4709800"><span>Schistosomiasis in school-age children in Burkina Faso after a decade of preventive chemotherapy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ouedraogo, Hamado; Drabo, François; Zongo, Dramane; Bagayan, Mohamed; Bamba, Issouf; Pima, Tiba; Yago-Wienne, Fanny; Toubali, Emily</p> <p>2016-01-01</p> <p>Abstract Objective To assess the impact of a decade of biennial mass administration of praziquantel on schistosomiasis in school-age children in Burkina Faso. Methods In 2013, in a national assessment based on 22 sentinel sites, 3514 school children aged 7–11 years were checked for Schistosoma haematobium and Schistosoma mansoni infection by the examination of urine and stool samples, respectively. We analysed the observed prevalence and intensity of infections and compared these with the relevant results of earlier surveys in Burkina Faso. Findings S. haematobium was detected in 287/3514 school children (adjusted prevalence: 8.76%, range across sentinel sites: 0.0–56.3%; median: 2.5%). The prevalence of S. haematobium infection was higher in the children from the Centre-Est, Est and <span class="hlt">Sahel</span> regions than in those from Burkina Faso’s other eight regions with sentinel sites (P < 0.001). The adjusted arithmetic mean intensity of S. haematobium infection, among all children, was 6.0 eggs per 10 ml urine. Less than 1% of the children in six regions had heavy S. haematobium infections – i.e. at least 50 eggs per 10 ml urine – but such infections were detected in 8.75% (28/320) and 11.56% (37/320) of the children from the Centre-Est and <span class="hlt">Sahel</span> regions, respectively. Schistosoma mansoni was only detected in two regions and 43 children – i.e. 1 (0.31%) of the 320 from Centre-Sud and 42 (8.75%) of the 480 from Hauts Bassins. Conclusion By mass use of preventive chemotherapy, Burkina Faso may have eliminated schistosomiasis as a public health problem in eight regions and controlled schistosome-related morbidity in another three regions. PMID:26769995</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.H43G1607B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.H43G1607B"><span>Drinking From the Same Straw: Crop Growth and Evidence of Water Transfer from Native Shrubs to Millet in a Sahelian Agro-Ecosystem</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bogie, N. A.; Bayala, R.; Fogel, M. L.; Diedhiou, I.; Dick, R.; Ghezzehei, T. A.</p> <p>2015-12-01</p> <p>A changing climate along with human and animal population pressure can have a devastating effect on crop yields and food security in the Sudano-<span class="hlt">Sahel</span>. Agricultural solutions to address soil degradation and crop water stress are needed to combat this increasingly difficult situation. Significant differences in crop success have been observed in peanut and millet grown in association with two native evergreen shrubs Piliostigma reticulatum, and Guiera senegalensis at the sites of Nioro du Rip and Keur Matar, respectively. We investigate how farmers can increase crop productivity by capitalizing on the evolutionary adaptation of native shrubs to the harsh Sudano-Sahelian environment as well as the physical mechanisms at work in the system that can lead to more robust yields. Soil moisture, transpiration rate, crop growth and soil and leaf water potential data were collected during a dry season millet irrigation experiment where stress was imposed in the intercropped system. Despite lower soil moisture content, crops grown in association with shrubs have increased biomass production and a faster development cycle. An isotopic tracer study investigating hydraulic redistribution was carried out by injecting deuterated water into the roots of three shrubs at one meter depth and sampling shrubs and nearby crops for isotopic analysis of plant water. Deuterium Enriched water was found in the shrubs of two out of three plots. Deuterium enriched water was found in the crops and shrubs in all three plots. These findings build on work that was completed in 2004 at the site, but point to larger differences in crop growth and strong evidence for the sharing of hydraulically redistributed water. Using even the limited resources that farmers possess, this agroforestry technique can be expanded over wide swaths of the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25714751','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25714751"><span>Overlooked mountain rock pools in deserts are critical local hotspots of biodiversity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vale, Cândida Gomes; Pimm, Stuart L; Brito, José Carlos</p> <p>2015-01-01</p> <p>The world is undergoing exceptional biodiversity loss. Most conservation efforts target biodiversity hotspots at large scales. Such approach overlooks small-sized local hotspots, which may be rich in endemic and highly threatened species. We explore the importance of mountain rock pools (gueltas) as local biodiversity hotspots in the Sahara-<span class="hlt">Sahel</span>. Specifically, we considered how many vertebrates (total and endemics) use gueltas, what factors predict species richness, and which gueltas are of most priority for conservation. We expected to provide management recommendations, improve local biodiversity conservation, and simultaneously contribute with a framework for future enhancement of local communities' economy. The identification of local hotspots of biodiversity is important for revaluating global conservation priorities. We quantified the number of vertebrate species from each taxonomic group and endemics present in 69 gueltas in Mauritania, then compared these with species present in a surrounding area and recorded in the country. We evaluated the predictors of species number's present in each guelta through a multiple regression model. We ranked gueltas by their priority for conservation taking into account the percentage of endemics and threats to each guelta. Within a mere aggregate extent of 43 ha, gueltas hold about 32% and 78% of the total taxa analysed and endemics of Mauritania, respectively. The number of species present in each guelta increased with the primary productivity and area of gueltas and occurrence of permanent water. Droughts and human activities threaten gueltas, while 64% of them are currently unprotected. Gueltas are crucial for local biodiversity conservation and human activities. They require urgent management plans in Mauritania's mountains. They could provide refugia under climate change being important for long-term conservation of Sahara-<span class="hlt">Sahel</span> biodiversity. Given their disproportional importance in relation to their size, they are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21900078','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21900078"><span>The impact of regional climate change on malaria risk due to greenhouse forcing and land-use changes in tropical Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ermert, Volker; Fink, Andreas H; Morse, Andrew P; Paeth, Heiko</p> <p>2012-01-01</p> <p>Climate change will probably alter the spread and transmission intensity of malaria in Africa. In this study, we assessed potential changes in the malaria transmission via an integrated weather-disease model. We simulated mosquito biting rates using the Liverpool Malaria Model (LMM). The input data for the LMM were bias-corrected temperature and precipitation data from the regional model (REMO) on a 0.5° latitude-longitude grid. A Plasmodium falciparum infection model expands the LMM simulations to incorporate information on the infection rate among children. Malaria projections were carried out with this integrated weather-disease model for 2001 to 2050 according to two climate scenarios that include the effect of anthropogenic land-use and land-cover changes on climate. Model-based estimates for the present climate (1960 to 2000) are consistent with observed data for the spread of malaria in Africa. In the model domain, the regions where malaria is epidemic are located in the <span class="hlt">Sahel</span> as well as in various highland territories. A decreased spread of malaria over most parts of tropical Africa is projected because of simulated increased surface temperatures and a significant reduction in annual rainfall. However, the likelihood of malaria epidemics is projected to increase in the southern part of the <span class="hlt">Sahel</span>. In most of East Africa, the intensity of malaria transmission is expected to increase. Projections indicate that highland areas that were formerly unsuitable for malaria will become epidemic, whereas in the lower-altitude regions of the East African highlands, epidemic risk will decrease. We project that climate changes driven by greenhouse-gas and land-use changes will significantly affect the spread of malaria in tropical Africa well before 2050. The geographic distribution of areas where malaria is epidemic might have to be significantly altered in the coming decades.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC33G..07B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC33G..07B"><span>Do Heat Waves have an Impact on Terrestrial Water Storage?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brena-Naranjo, A.; Teuling, R.; Pedrozo-Acuña, A.</p> <p>2014-12-01</p> <p>Recent works have investigated the impact of heat waves on the surface energy and carbon balance. However, less attention has been given to the impacts on terrestrial hydrology. During the summer of 2010, the occurrence of an exceptional heat wave affected severely the Northern Hemisphere. The extension (more than 2 million km2) and severity of this extreme event caused substantial ecosystem damage (more than 1 million ha of forest fires), economic and human losses (~500 billion USD and more than 17 million of indirect deaths, respectively). This work investigates for the first time the impacts of the 2010 summer heat wave on terrestrial water storage. Our study area comprises three different regions where air temperature records were established or almost established during the summer: Western Russia, the Middle East and Eastern <span class="hlt">Sahel</span>. Anomalies of terrestrial water storage derived from the Gravity Recovery and Climate Experiment (GRACE) were used to infer water storage deficits during the 2003-2013 period. Our analysis shows that Russia experienced the most severe water storage decline, followed by the Middle East, whereas Eastern <span class="hlt">Sahel</span> was not significantly affected. The impact of the heat wave was spatially uniform in Russia but highly variable in the Middle East, with the Northern part substantially more affected than the Southern region. Lag times between maxima air temperatures and lower water storage deficits for Russia and the Middle East were approximately two and seven months, respectively. The results suggest that the response of terrestrial water storage to heat waves is stronger in energy-limited environments than in water-limited regions. Such differences in the magnitude and timing between meteorological and hydrological extremes can be explained by the propagation time between atmospheric water demand and natural or anthropogenic sources of water storage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23661018','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23661018"><span>Identification of single nucleotide polymorphisms in the agouti signaling protein (ASIP) gene in some goat breeds in tropical and temperate climates.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Adefenwa, Mufliat A; Peters, Sunday O; Agaviezor, Brilliant O; Wheto, Matthew; Adekoya, Khalid O; Okpeku, Moses; Oboh, Bola; Williams, Gabriel O; Adebambo, Olufunmilayo A; Singh, Mahipal; Thomas, Bolaji; De Donato, Marcos; Imumorin, Ikhide G</p> <p>2013-07-01</p> <p>The agouti-signaling protein (ASIP) plays a major role in mammalian pigmentation as an antagonist to melanocortin-1 receptor gene to stimulate pheomelanin synthesis, a major pigment conferring mammalian coat color. We sequenced a 352 bp fragment of ASIP gene spanning part of exon 2 and part of intron 2 in 215 animals representing six goat breeds from Nigeria and the United States: West African Dwarf, predominantly black; Red Sokoto, mostly red; and <span class="hlt">Sahel</span>, mostly white from Nigeria; black and white Alpine, brown and white Spanish and white Saanen from the US. Twenty haplotypes from nine mutations representing three intronic, one silent and five missense (p.S19R, p.N35K, p.L36V, p.M42L and p.L45W) mutations were identified in Nigerian goats. Approximately 89 % of Nigerian goats carry haplotype 1 (TGCCATCCG) which seems to be the wild type configuration of mutations in this region of the gene. Although we found no association between these polymorphisms in the ASIP gene and coat color in Nigerian goats, in-silico functional analysis predicts putative deleterious functional impact of the p.L45W mutation on the basic amino-terminal domain of ASIP. In the American goats, two intronic mutations, g.293G>A and g.327C>A, were identified in the Alpine breed, although the g.293G>A mutation is common to American and Nigerian goat populations. All Sannen and <span class="hlt">Sahel</span> goats in this study belong to haplotypes 1 of both populations which seem to be the wild-type composite ASIP haplotype. Overall, there was no clear association of this portion of the ASIP gene interrogated in this study with coat color variation. Therefore, additional genomic analyses of promoter sequence, the entire coding and non-coding regions of the ASIP gene will be required to obtain a definite conclusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4340953','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4340953"><span>Overlooked Mountain Rock Pools in Deserts Are Critical Local Hotspots of Biodiversity</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vale, Cândida Gomes; Pimm, Stuart L.; Brito, José Carlos</p> <p>2015-01-01</p> <p>Background The world is undergoing exceptional biodiversity loss. Most conservation efforts target biodiversity hotspots at large scales. Such approach overlooks small-sized local hotspots, which may be rich in endemic and highly threatened species. We explore the importance of mountain rock pools (gueltas) as local biodiversity hotspots in the Sahara-<span class="hlt">Sahel</span>. Specifically, we considered how many vertebrates (total and endemics) use gueltas, what factors predict species richness, and which gueltas are of most priority for conservation. We expected to provide management recommendations, improve local biodiversity conservation, and simultaneously contribute with a framework for future enhancement of local communities’ economy. The identification of local hotspots of biodiversity is important for revaluating global conservation priorities. Methodology/Principal Findings We quantified the number of vertebrate species from each taxonomic group and endemics present in 69 gueltas in Mauritania, then compared these with species present in a surrounding area and recorded in the country. We evaluated the predictors of species number’s present in each guelta through a multiple regression model. We ranked gueltas by their priority for conservation taking into account the percentage of endemics and threats to each guelta. Within a mere aggregate extent of 43 ha, gueltas hold about 32% and 78% of the total taxa analysed and endemics of Mauritania, respectively. The number of species present in each guelta increased with the primary productivity and area of gueltas and occurrence of permanent water. Droughts and human activities threaten gueltas, while 64% of them are currently unprotected. Conclusion/Significance Gueltas are crucial for local biodiversity conservation and human activities. They require urgent management plans in Mauritania’s mountains. They could provide refugia under climate change being important for long-term conservation of Sahara-<span class="hlt">Sahel</span> biodiversity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12346454','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12346454"><span>[The paradox of motherhood].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ouaidou, N G</p> <p>1990-08-01</p> <p>All Sahelian countries are working to define their population policies. A population policy document avoids dispersion and duplication. It opens the path to efficiency. It makes it easier to achieve governmental socioeconomic objectives. Various recent population-related meetings have at least two points in common: they aim to overstep and improve a given situation and are at the same time some examples of implementing the Ndjamena action program, adopted in January 1989. All these population-centered actions return to the problem of adolescent fertility--a poignant problem. Adolescent pregnancy is a major source of family and social break-ups. This paradox of motherhood makes a violent storm burst in the skies ordinarily serene with joy and hope. It is an enemy perverse to economic development and social progress. Adolescent motherhood is a phenomenon which complicates and aggravates population problems and is taboo to the point it is still imperceptible, unknown. It is a problem of premier importance in the <span class="hlt">Sahel</span>. Pregnancy strikes a woman so very unprepared for motherhood and its demands. It risks the life of a being which is preparing itself to enter the world. Adolescent pregnancy has equally tragic health effects: poorly performed underground abortions and maternal and infant deaths. Adolescent fertility is a burning problem regardless of the perspective (demographic, economic, social, or health). In Sahelian countries, one is beginning to be interested in and to speak about it. It will be necessary to search for solutions. Schools must be a top target for all activities aiming to check adolescent fertility. The emphasis must be on information, education, and responsibility of girls, boys, teachers, and parents. Education and training are of capital importance for socioeconomic development of the <span class="hlt">Sahel</span>. All activities implemented in the education sector should include a large place for family life education in pregnancy prevention.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUSMNB33Q..18H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUSMNB33Q..18H"><span>HABSEED: a Simple Spatially Explicit Meta-Populations Model Using Remote Sensing Derived Habitat Quality Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heumann, B. W.; Guichard, F.; Seaquist, J. W.</p> <p>2005-05-01</p> <p>The HABSEED model uses remote sensing derived NPP as a surrogate for habitat quality as the driving mechanism for population growth and local seed dispersal. The model has been applied to the <span class="hlt">Sahel</span> region of Africa. Results show that the functional response of plants to habitat quality alters population distribution. Plants more tolerant of medium quality habitat have greater distributions to the North while plants requiring only the best habitat are limited to the South. For all functional response types, increased seed production results in diminishing returns. Functional response types have been related to life history tradeoffs and r-K strategies based on the results. Results are compared to remote sensing derived vegetation land cover.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A43C2467C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A43C2467C"><span>Using remote-sensing and the Simple Biosphere model (SiB4) to analyze the seasonality and productivity of the terrestrial biosphere.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheeseman, M.; Denning, S.; Baker, I. T.</p> <p>2017-12-01</p> <p>Understanding the variability and seasonality of carbon fluxes from the terrestrial biosphere is integral to understanding the mechanisms and drivers of the global carbon cycle. However, there are many regions across the globe where in situ observations are sparse, such as the Amazon rainforest and the African <span class="hlt">Sahel</span>. The latest version of the Simple-Biosphere model (SiB4) predicts a suite of biophysical variables such as terrestrial carbon flux (GPP), solar induced fluorescence (SIF), fraction of photosynthetically active radiation (FPAR), and leaf area index (LAI). By comparing modeled values to a suite of satellite and in situ observations we produce a robust analysis of the seasonality and productivity of the terrestrial biosphere in a variety of biome types across the globe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890033121&hterms=evapotranspiration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Devapotranspiration','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890033121&hterms=evapotranspiration&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Devapotranspiration"><span>A GCM simulation study of the influence of Saharan evapotranspiration and surface-albedo anomalies on July circulation and rainfall</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sud, Y. C.; Molod, A.</p> <p>1988-01-01</p> <p>The influence of surface albedo and evapotranspiration anomalies that could result from the hypothetical semiarid vegetation over North Africa on its July circulation and rainfall is examined using the Goddard Laboratory for Atmospheres GCM. It is shown that increased soil moisture and its dependent evapotranspiration produces a cooler and moister PBL over North Africa that is able to support enhanced moist convection and rainfall in <span class="hlt">Sahel</span> and southern Sahara. It is found that lower surface albedo yields even higher moist static energy in the PBL and enhances the local moist convection and rainfall. Modifying the rain-evaporation parameterization in the model produces changes in the hydrological cycle and rainfall anomalies in distant regions. The effects of different falling rain parameterizations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9642744','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9642744"><span>[Strategies to control vitamin A deficiency].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Traoré, L; Banou, A A; Sacko, D; Malvy, D; Schémann, J F</p> <p>1998-01-01</p> <p>Vitamin A deficiency is a major public health problem in the countries of the <span class="hlt">Sahel</span>. It causes xerophthalmia and high rates of child mortality and it occurs mostly in underdeveloped regions. People of all ages may suffer from vitamin A deficiency but it is a particular problem in pre-school-age children. Each year, about 250,000 children throughout the world become blind due to vitamin A deficiency. Measles, pneumonia and diarrhea reduce the child's reserves of retinol and increase the dietary requirement for vitamin A. Improvement of social conditions is a radical approach to preventing vitamin A deficiency. Three strategies are currently in use: horticultural activities and health education; fortification of food products; distribution of high-dose vitamin A capsules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880023473&hterms=desertification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddesertification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880023473&hterms=desertification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Ddesertification"><span>Monitoring global vegetation using Nimbus-7 37 GHz data - Some empirical relations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Choudhury, B. J.; Tucker, C. J.</p> <p>1987-01-01</p> <p>The difference of the vertically and horizontally polarized brightness temperatures observed by the 37 GHz channel of the SMMR on board the Nimbus-7 satellite are correlated temporally with three indicators of vegetation density, namely the temporal variation of the atmospheric CO2 concentration at Mauna Loa (Hawaii), rainfall over the <span class="hlt">Sahel</span> and the normalized difference vegetation index derived from the AVHRR on board the NOAA-7 satellite. SMMR 37 GHz and AVHRR provide complementary data sets for monitoring global vegetation, the 37 GHz data being more suitable for arid and semiarid regions as these data are more sensitive to changes in sparse vegetation. The 37-GHz data might be useful for understanding desertification and indexing Co2 exchange between the biosphere and the atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=Second+AND+chance&pg=6&id=EJ1076244','ERIC'); return false;" href="https://eric.ed.gov/?q=Second+AND+chance&pg=6&id=EJ1076244"><span>Koranic Education Centres: A Viable Educational Alternative for the Disadvantaged Learner in <span class="hlt">Sahel</span> Africa?</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Bah-Lalya, Ibrahima</p> <p>2015-01-01</p> <p>Within the international momentum for achieving Education for All (EFA) and the Millennium Development Goals (MDGs), many African countries have made considerable progress during the last decade in terms of access to basic education. However, a significant number of children enrolled in the early grades of primary schools either repeat classes or…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA271453','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA271453"><span>Agricultural Production Monitoring in the <span class="hlt">Sahel</span> Using Remote Sensing: Present Possibilities and Research Needs</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-01-01</p> <p>during the agricultural season. Satellite remote sensing can contribute significantly to such a system by collecting information on crops and on...well as techniques to derive biophysical variables from remotely-sensed data. Finally, the integration of these remote - sensing techniques with crop</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNH13D1973P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNH13D1973P"><span>Climate Risk Management Strategy in the Tropical Low to Medium Income Countries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parhi, P.; Giannini, A.; Lall, U.</p> <p>2015-12-01</p> <p>The market penetration of index insurance sector, posed as an innovative weather risk management and climate change adaptation tool, is growing in the tropical low to medium income countries. Usually the underwriters such as regional, national or international organizations, banks or (re)insurance companies hold these risk portfolios. The micro-level insurance contracts when aggregated at state, country or regional level, could potentially pose significant systemic risk due to tail dependency, micro-correlation and fat-tail nature of the damage, threatening the survival of this micro-financial risk management sector, ultimately impeding the sustainable development goals. Analyzing the observed inter-annual variability of the tropical climate system, this paper identifies the physical mechanisms for heterogeneous climatic response and suggests that diversification opportunity exists across different regions and seasons. Taking two case studies from tropical Africa, an empirical analysis is done to highlight that El Niño modulates the number of wet days in an opposite way across the two regions and seasons, suggesting the possibility of diversification of the index insurance portfolios across regions and seasons. Specifically, El Niño is associated with drier condition over <span class="hlt">Sahel</span>, while it is associated with wetter condition over Tropical Eastern Africa (TEA), during their respective Jul-Aug-Sep and Oct-Nov-Dec rainy seasons. Such contrasting modulation in the number of wet days can be understood by the phase relationship between the local rainy season and El Niño evolution stage. The transient phase of El Niño, which is in phase with the rainy season (Jul-Sep) over <span class="hlt">Sahel</span>, is characterized by tropospheric stability induced by tropospheric warming without regional North Atlantic sea surface temperature (SST) adjustment. In contrast, the mature phase of El Niño is in phase with the short rainy season (Oct-Dec) over TEA, and is characterized by adjusted warmer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B43A0518L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B43A0518L"><span>Biomass Productivity Dynamics Monitoring and its Drivers in Sahelian Croplands and Rangelands to Support Food Security Policies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leroux, L.</p> <p>2015-12-01</p> <p>Since the Sahelian population livelihood relies mainly on agropastoral activities, accurate information on biomass productivity dynamics and the underlying drivers are needed to manage a wide range of issues such as food security. This study aims to contribute to a better understanding of these drivers in rangeland and cropland, both at the <span class="hlt">Sahel</span> and local scales (an agropastoral site in South-West Niger). At the <span class="hlt">Sahel</span> scale, the MODIS Land Cover product was used to extract cropland and rangeland pixels. By analyzing MODIS NDVI trends together with TRMM3B43 annual rainfall (2000-2010), we developed a new classification scheme allowing to identify areas of persistent decline/improvement in biomass productivity and to separate rainfall-driven dynamics from other factors. The results showed an overall increase of productivity in the rangeland, and both an improvement and a degradation in the cropland. We found strong evidence that the increase in biomass productivity was generally linked to increasing rainfall, while the decrease could be attributed chiefly to other factors exclusively or to a combination of both climate- and human-induced factors (see the attached Figure). At the Niger site scale, biomass trends have been put in relation with a set of potential drivers via a RandomForest model, to define which were the explanatory factors of the observed trends. The factor set covered 5 categories: climate, natural constraints, demography, physical accessibility and land cover changes. We highlighted that tiger bushes areas were particularly prone to pressure due to overgrazing and overexploitation of wood, while positive trends were mainly observed near rivers and in fossil valleys where new agricultural practices might have been promoted. The approach developped here could help to delineate areas with decrease in crop and grassland production and thus to assess the vulnerability of the population, but also to target zones with good potential for planning long</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H42D..08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H42D..08W"><span>Rising Water Storage in the Niger River basin: Clues and Cause</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Werth, S.</p> <p>2016-12-01</p> <p>Heavily populated west African regions along the Niger River are affected by climate and land cover changes, altering the distribution of water resources. To maintain a reliable water supply in the region, water management authorities require knowledge of hydrological changes at various spatial and temporal scales. Local and regional studies reported rising water tables over the last decades as a consequence of complex responses on land use change in the <span class="hlt">Sahel</span> zone. The spatial extend of this responses is not well understood, as of yet. Thus, this study provides an in-depth investigation of long-term changes in the water storages of Niger River basin and its sub-regions by analyzing more than a decade of satellite based gravity data from the Gravity Recovery And Climate Change (GRACE) satellites. Soil moisture data from four global hydrological models serve to separate freshwater resources (WR) from GRACE-based terrestrial water storage variations. Surface water variations from a global water storage model and trends from altimetry data were applied to separate the groundwater component from WR trends. Errors of all datasets are taken into account. Trends in WR are positive, except for the tropical Upper Niger with negative trends. For the Niger basin, a rise in GW stocks was detected. On the subbasin scale, GW changes are positive for the Sahelian Middle Niger and the Benue. The findings confirm previous observations of water tables in the <span class="hlt">Sahel</span> and tropical zones, indicating that reported effects of land use change are relevant on large, i.e. basin and subbasin, scales. Our results have implications for Niger water management strategies. While areas with rising water storage are stocking a comfortable backup to mitigate possible future droughts and to deliver water to remote areas with no access to rivers or reservoirs. Increasing groundwater recharges may be accompanied by a reduction in water quality. This study helps to inform authority's decision to address</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMOS62C0276B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMOS62C0276B"><span>Simulation of Tropical Rainfall Variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bader, J.; Latif, M.</p> <p>2002-12-01</p> <p>The impact of sea surface temperature (SST) - especially the role of the tropical Atlantic meridional SST gradient and the El Nino-Southern Oscillation - on precipitation is investigated with the atmospheric general circulation model ECHAM4/T42. Ensemble experiments - driven with observed SST - show that Atlantic SST has a significant influence on precipitation over West Africa and northeast Brazil. SST sensitivity experiments were performed in which the climatological SST was enhanced or decreased by one Kelvin in certain ocean areas. Changing SST in the eastern tropical Atlantic caused only significant changes along the Guinea Coast, with a positive anomaly (SSTA) increasing rainfall and a negative SSTA reducing it. The response was nearly linear. Changing SST in other ocean areas caused significant changes over West Africa, especially in the <span class="hlt">Sahel</span> area. The response is found to be non linear, with only negative SSTA leading to significant reduction in <span class="hlt">Sahel</span> rainfall. Also, the impact of the SSTAs from the different ocean regions was not additive with respect to the rainfall. The influence of SST on precipitation over northeast Brazil (Nordeste) was also investigated. Three experiments were performed in which the climatological SST was enhanced/decreased or decreased/enhanced by one Kelvin in the North/South Atlantic and increased by two Kelvin in the Nino3 ocean area. All experiments caused significant changes over Nordeste, with an enhanced/reduced SST gradient in the Atlantic increasing/reducing rainfall. The response was nearly linear. The main effect of the Atlantic SST gradient was a shift of the ITCZ, caused by trade wind changes. The ''El Nino'' event generates a significant reduction in Nordeste rainfall. A significant positive SLP anomaly occurs in northeast Brazil which may be associated with the descending branch of the Walker circulation. Also a significant positive SLP over the Atlantic from 30S to 10N north occurs. This results in a reduced SLP</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1614617V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1614617V"><span>Worldwide biogenic soil NOx emission estimates from OMI NO2 observations and the GEOS-Chem model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vinken, Geert; Boersma, Folkert; Maasakkers, Bram; Martin, Randall</p> <p>2014-05-01</p> <p>Bacteria in soils are an important source of biogenic nitrogen oxides (NOx = NO + NO2), which are important precursors for ozone (O3) formation. Furthermore NOx emissions contribute to increased nitrogen deposition and particulate matter formation. Bottom-up estimates of global soil NOx emissions range from 4 to 27 Tg N / yr, reflecting our incomplete knowledge of emission factors and processes driving these emissions. In this study we used, for the first time, OMI NO2 columns on all continents to reduce the uncertainty in soil NOx emissions. Regions and months dominated by soil NOx emissions were identified using a filtering scheme in the GEOS-Chem chemistry transport model. Consequently, we compared OMI observed NO2 observed columns to GEOS-Chem simulated columns and provide constraints for these months in 11 regions. This allows us to provide a top-down emission inventory for 2005 for soil NOx emissions from all continents. Our total global soil NOx emission inventory amounts to 10 Tg N / yr. Our estimate is 4% higher than the GEOS-Chem a priori (Hudman et al., 2012), but substantial regional differences exist (e.g. +20% for <span class="hlt">Sahel</span> and India; and -40% for mid-USA). We furthermore observed a stronger seasonal cycle in the <span class="hlt">Sahel</span> region, indicating directions for possible future improvements to the parameterization currently used in GEOS-Chem. We validated NO2 concentrations simulated with this new top-down inventory against surface NO2 measurements from monitoring stations in Africa, the USA and Europe. On the whole, we conclude that simulations with our new top-down inventory better agree with measurements. Our work shows that satellite retrieved NO2 columns can improve estimates of soil NOx emissions over sparsely monitored remote rural areas. We show that the range in previous estimates of soil NOx emissions is too large, and global emissions are most likely around 10 Tg N/yr, in agreement with the most recent parameterizations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19545045','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19545045"><span>[Will climate and demography have a major impact on malaria in sub-Saharan Africa in the next 20 years?].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saugeon, C; Baldet, T; Akogbeto, M; Henry, M C</p> <p>2009-04-01</p> <p>The purpose of this review of the literature is to present factors possibly affecting the spread of malaria in sub-Saharan Africa over the next 20 years. Malaria is a vector-borne disease that depends on environmental and human constraints. The main environmental limitations involve susceptibility of the vector (mosquitoes of the Anopheles genus) and parasite (Plasmodium falciparum) to climate. Malaria is a stable, endemic disease over most of the African continent. Climatic change can only affect a few regions on the fringes of stable zones (e.g. altitude areas or <span class="hlt">Sahel</span>) where malaria is an unstable, epidemic disease. Higher temperatures could induce a decrease of malaria transmission in regions of the <span class="hlt">Sahel</span> or an increase in the highlands. The extent of these overall trends will depend on the unpredictable occurrence of major meteorological phenomenon as well as on human activities affecting the environment that could lead to dramatic but limited outbreaks in some locations. The most influential human factors could be runaway demographic growth and urban development. Estimations based on modeling studies indicate that urbanization will lead to a 53.5% drop in exposure to malaria by 2030. However this reduction could be less than expected because of adaptation of Anopheles gambiae and An. arabiensis, the main vectors of malaria in sub-Saharan Africa, to the urban environment as well as increasing vector resistance to insecticides. Another unforeseeable factor that could induce unexpected malaria epidemics is mass migration due to war or famine. Finally immunosuppressive illnesses (e.g. HIV and malnutrition) could alter individual susceptibility to malaria. Social constraints also include human activities that modify land use. In this regard land use (e.g. forest clearance and irrigation) is known to influence the burden of malaria that is itself dependent on local determinants of transmission. Overall the most important social constraint for the population will be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.1629E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.1629E"><span>The potential effects of climate change on malaria in tropical Africa using regionalised climate projections</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ermert, V.; Fink, A. H.; Paeth, H.; Morse, A. P.</p> <p>2012-04-01</p> <p>The projected climate change will probably alter the range and transmission potential of malaria in Africa. The potential impacts of climate change on the malaria distribution is assessed for tropical Africa. Bias-corrected regional climate projections with a horizontal resolution of 0.5° are used from the Regional Model (REMO), which include land use and land cover changes. The malaria models employed are the 2010 version of the Liverpool Malaria Model (LMM2010), the Garki model, the Plasmodium falciparum infection model from Smith et al. (2005) (S2005), and the Malaria Seasonality Model (MSM) from the Mapping Malaria Risk in Africa project. The results of the models are compared with data from the Malaria Atlas Project (MAP) and novel validation procedures for the LMM2010 and MSM lend more credence to their results. For climate scenarios A1B and B1 and for 2001-2050, REMO projects an overall drying and warming trend in the African malaria belt, that is largely imposed by the man-made degradation of vegetation. As a result, the malaria projections show a decreased malaria spread in West Africa. The northern <span class="hlt">Sahel</span> is no more suitable for malaria in the projections. More unstable malaria transmission and shorter malaria seasons are expected for various areas farther south. An increase in the malaria epidemic risk is found for more densely populated areas in the southern part of the <span class="hlt">Sahel</span>. In East Africa, higher temperatures and nearly unchanged precipitation patterns lead to longer transmission seasons and an increase in the area of highland malaria. For altitudes up to 2000 m the malaria transmission stabilises and the epidemic risk is reduced but for higher altitudes the risk of malaria epidemics is increased. The results of the more complex and simple malaria models are similar to each other. However, a different response to the warming of highlands is found for the LMM2010 and MSM. This shows the requirement of a multi model uncertainty analysis for the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5886061','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5886061"><span>Large-scale delivery of seasonal malaria chemoprevention to children under 10 in Senegal: an economic analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pitt, Catherine; Ndiaye, Mouhamed; Conteh, Lesong; Sy, Ousmane; Hadj Ba, El; Cissé, Badara; Gomis, Jules F; Gaye, Oumar; Ndiaye, Jean-Louis</p> <p>2017-01-01</p> <p>Abstract Seasonal Malaria Chemoprevention (SMC) is recommended for children under 5 in the <span class="hlt">Sahel</span> and sub-<span class="hlt">Sahel</span>. The burden in older children may justify extending the age range, as has been done effectively in Senegal. We examine costs of door-to-door SMC delivery to children up to 10 years by community health workers (CHWs). We analysed incremental financial and economic costs at district level and below from a health service perspective. We examined project accounts and prospectively collected data from 405 CHWs, 46 health posts, and 4 district headquarters by introducing questionnaires in advance and completing them after each monthly implementation round. Affordability was explored by comparing financial costs of SMC to relevant existing health expenditure levels. Costs were disaggregated by administration month and by health service level. We used linear regression models to identify factors associated with cost variation between health posts. The financial cost to administer SMC to 180 000 children over one malaria season, reaching ∼93% of children with all three intended courses of SMC was $234 549 (constant 2010 USD) or $0.50 per monthly course administered. Excluding research–participation incentives, the financial cost was $0.32 per resident (all ages) in the catchment area, which is 1.2% of Senegal’s general government expenditure on health per capita. Economic costs were 18.7% higher than financial costs at $278 922 or $0.59 per course administered and varied widely between health posts, from $0.38 to $2.74 per course administered. Substantial economies of scale across health posts were found, with the smallest health posts incurring highest average costs per monthly course administered. SMC for children up to 10 is likely to be affordable, particularly where it averts substantial curative care costs. Estimates of likely costs and cost-effectiveness of SMC in other contexts must account for variation in average costs across delivery months</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A44C..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A44C..03W"><span>Identifying robust regional precipitation responses to regional aerosol emissions perturbations in three coupled chemistry-climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Westervelt, D. M.; Fiore, A. M.; Lamarque, J. F.; Previdi, M. J.; Conley, A. J.; Shindell, D. T.; Mascioli, N. R.; Correa, G. J. P.; Faluvegi, G.; Horowitz, L. W.</p> <p>2017-12-01</p> <p>Regional emissions of anthropogenic aerosols and their precursors will likely decrease for the remainder of the 21st century, due to emission reduction policies enacted to protect human health. Although there is some evidence that regional climate effects of aerosols can be significant, we currently lack a robust understanding of the magnitude, spatio-temporal pattern, statistical significance, and physical processes responsible for these influences, especially for precipitation. Here, we aim to quantify systematically the precipitation response to regional changes in aerosols and investigate underlying mechanisms using three fully coupled chemistry-climate models: NOAA Geophysical Fluid Dynamics Laboratory Coupled Model 3 (GFDL-CM3), NCAR Community Earth System Model (CESM), and NASA Goddard Institute for Space Studies ModelE2 (GISS-E2). The central approach we use is to contrast a long control experiment (400 years, run with perpetual year 2000 emissions) with 14 individual aerosol emissions perturbation experiments ( 200 years each). We perturb emissions of sulfur dioxide (SO2) and carbonaceous aerosol (BC and OM) within several world regions and assess which responses are significant relative to internal variability determined by the control run and robust across the three models. Initial results show significant changes in precipitation in several vulnerable regions including the Western <span class="hlt">Sahel</span> and the Indian subcontinent. SO2 emissions reductions from Europe and the United States have the largest impact on precipitation among most of the selected response regions. The precipitation response to emissions changes from these regions projects onto known modes of variability, such as the North Atlantic Oscillation (NAO) and the El Niño Southern Oscillation (ENSO). Across all perturbation experiments, we find a strong linear relationship between the responses of <span class="hlt">Sahel</span> precipitation and the interhemispheric temperature difference, suggesting a common mechanism of an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A44C..03W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A44C..03W"><span>Skill and reliability of experimental GEFS ensemble forecast guidance designed to inform decision-making in reservoir management in California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Westervelt, D. M.; Fiore, A. M.; Lamarque, J. F.; Previdi, M. J.; Conley, A. J.; Shindell, D. T.; Mascioli, N. R.; Correa, G. J. P.; Faluvegi, G.; Horowitz, L. W.</p> <p>2016-12-01</p> <p>Regional emissions of anthropogenic aerosols and their precursors will likely decrease for the remainder of the 21st century, due to emission reduction policies enacted to protect human health. Although there is some evidence that regional climate effects of aerosols can be significant, we currently lack a robust understanding of the magnitude, spatio-temporal pattern, statistical significance, and physical processes responsible for these influences, especially for precipitation. Here, we aim to quantify systematically the precipitation response to regional changes in aerosols and investigate underlying mechanisms using three fully coupled chemistry-climate models: NOAA Geophysical Fluid Dynamics Laboratory Coupled Model 3 (GFDL-CM3), NCAR Community Earth System Model (CESM), and NASA Goddard Institute for Space Studies ModelE2 (GISS-E2). The central approach we use is to contrast a long control experiment (400 years, run with perpetual year 2000 emissions) with 14 individual aerosol emissions perturbation experiments ( 200 years each). We perturb emissions of sulfur dioxide (SO2) and carbonaceous aerosol (BC and OM) within several world regions and assess which responses are significant relative to internal variability determined by the control run and robust across the three models. Initial results show significant changes in precipitation in several vulnerable regions including the Western <span class="hlt">Sahel</span> and the Indian subcontinent. SO2 emissions reductions from Europe and the United States have the largest impact on precipitation among most of the selected response regions. The precipitation response to emissions changes from these regions projects onto known modes of variability, such as the North Atlantic Oscillation (NAO) and the El Niño Southern Oscillation (ENSO). Across all perturbation experiments, we find a strong linear relationship between the responses of <span class="hlt">Sahel</span> precipitation and the interhemispheric temperature difference, suggesting a common mechanism of an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMGC32B..01O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMGC32B..01O"><span>Increasing Megadrought Risk at the Intersection of Decadal to Centennial Variability and Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Overpeck, J. T.; Parsons, L. A.; Loope, G. R.; Ault, T.; Cole, J. E.; Otto-Bliesner, B. L.; Buckle, N.; Stevenson, S.; Fasullo, J.</p> <p>2016-12-01</p> <p>Even more than the 1930's U.S. Dust Bowl Drought, the 20th century <span class="hlt">Sahel</span> drought stands out as the most unprecedented drought of the instrumental era, in part because it extended over multiple decades. Paleoclimatic evidence makes it clear that this <span class="hlt">Sahel</span> drought was nonetheless not really unprecedented - droughts many decades long have occurred in sub-Saharan Africa regularly over the last several thousand years, and these constitute what is now increasingly referred to as "megadrought." Paleoclimatic evidence also makes it clear that all drought-prone semi-arid and arid regions of the globe, including southwestern North America, southeastern Australia, and the Mediterranean/Middle Eastern region likely experienced multiple such multidecadal megadroughts in recent pre-Anthropocene Earth history. In other regions of the globe, including parts of South Asia and Amazonia, short but devastating droughts of the last 50-150 years, were also eclipsed in recent Earth history by much more serious megadrought, although these megadroughts were shorter than the multidecadal droughts of Africa or SW North America. In the past, megadroughts have occurred for reasons that are increasingly well understood in terms of ocean-atmosphere dynamics that led to unusually persistent precipitation deficits. Many of these same dynamics are well simulated in state-of-the-art Earth System Models, and yet comparisons between simulated and observed paleohydroclimatic variability suggests the models generally underestimate the risk of megadrought. Paleohydroclimatic records in some cases overestimate drought persistence, but there appear to be other issues at play that need to be better understood and simulated: positive land-atmosphere feedbacks, overly energetic interannual (i.e., ENSO) modes of variability, and insufficient internal multidecadal to centennial coupled climate system variability. Taking these issues and the impact of anthropogenic climate change into account means that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160000383','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160000383"><span>Advances in Remote Sensing for Vegetation Dynamics and Agricultural Management</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tucker, Compton; Puma, Michael</p> <p>2015-01-01</p> <p>Spaceborne remote sensing has led to great advances in the global monitoring of vegetation. For example, the NASA Global Inventory Modeling and Mapping Studies (GIMMS) group has developed widely used datasets from the Advanced Very High Resolution Radiometer (AVHRR) sensors as well as the Moderate Resolution Imaging Spectroradiometer (MODIS) map imagery and normalized difference vegetation index datasets. These data are valuable for analyzing vegetation trends and variability at the regional and global levels. Numerous studies have investigated such trends and variability for both natural vegetation (e.g., re-greening of the <span class="hlt">Sahel</span>, shifts in the Eurasian boreal forest, Amazonian drought sensitivity) and crops (e.g., impacts of extremes on agricultural production). Here, a critical overview is presented on recent developments and opportunities in the use of remote sensing for monitoring vegetation and crop dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26624632','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26624632"><span>A new brachypterous scarab species, Orphnus longicornis (Coleoptera: Scarabaeidae: Orphninae), from the East African Rift.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Frolov, Andrey; Akhmetova, Lilia</p> <p>2015-11-05</p> <p>The Afrotropical Region is the center of the diversity of the scarab beetle genus Orphnus MacLeay, 1819 (Coleoptera: Scarabaeidae: Orphninae), with 94 species occurring from <span class="hlt">Sahel</span> in the north to Little Karoo in the south (Paulian, 1948; Petrovitz, 1971; Frolov, 2008). The East African Rift is one of the richest regions of the Afrotropics housing more than 20 species of Orphnus (Paulian, 1948; Frolov, 2013), most of which are endemic to this region. Yet the scarab beetle fauna of the East African Rift, and especially the Eastern Arc Mountains, is still inadequately studied. Examination of the material housed in the Museum of Natural History of Humboldt-Universität, Berlin, Germany (ZMHUB), revealed a series of brachypterous Orphnus beetles belonging to an undescribed species. The new species is described and illustrated below.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3183747','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3183747"><span>Migration in the context of vulnerability and adaptation to climate change: insights from analogues</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>McLeman, Robert A.; Hunter, Lori M.</p> <p>2011-01-01</p> <p>Migration is one of the variety of ways by which human populations adapt to environmental changes. The study of migration in the context of anthropogenic climate change is often approached using the concept of vulnerability and its key functional elements: exposure, system sensitivity, and adaptive capacity. This article explores the interaction of climate change and vulnerability through review of case studies of dry-season migration in the West African <span class="hlt">Sahel</span>, hurricane-related population displacements in the Caribbean basin, winter migration of ‘snowbirds’ to the US Sun-belt, and 1930s drought migration on the North American Great Plains. These examples are then used as analogues for identifying general causal, temporal, and spatial dimensions of climate migration, along with potential considerations for policy-making and future research needs. PMID:22022342</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A22D..07M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A22D..07M"><span>Observational Constraints on Ephemeral Wind Gusts that MobilizeSoil Dust Aerosols</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miller, R. L.; Leung, M. F.</p> <p>2017-12-01</p> <p>Dust aerosol models resolve the planetary scale winds that disperse particles throughout the globe, but the winds raising dust are often organized on smaller scales that are below the resolution of the model. These winds, including ephemeral wind gusts associated with boundary layer mixing, are typically parameterized. For example, gusts by dry convective eddies are related to the sensible heat flux. What remains is to constrain the magnitude of the wind gusts using boundary layer measurements, so that dust emission has the correct sensitivity to these gusts, relative to the resolved wind. Here, we use a year of ARM measurements with high temporal resolution from Niamey, Niger in the <span class="hlt">Sahel</span> to evaluate our parameterization. This evaluation is important for dust aerosol models that use 'nudging' to reproduce observed transport patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70120435','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70120435"><span>Atmospheric movement of microorganisms in clouds of desert dust and implications for human health</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Griffin, Dale W.</p> <p>2007-01-01</p> <p>Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and <span class="hlt">Sahel</span> regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17630335','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17630335"><span>Atmospheric movement of microorganisms in clouds of desert dust and implications for human health.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Griffin, Dale W</p> <p>2007-07-01</p> <p>Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and <span class="hlt">Sahel</span> regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3389509','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3389509"><span>Biological alterations and self-reported symptoms among insecticides-exposed workers in Burkina Faso</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Toe, Adama M.; Ilboudo, Sylvain; Ouedraogo, Moustapha; Guissou, Pierre I.</p> <p>2012-01-01</p> <p>Occupationally exposed workers, farm workers and plant protection agents in the <span class="hlt">Sahel</span> region of Burkina Faso were interviewed to assess adverse health effects of insecticides. The subjects were also examined for changes in both hematological and biochemical parameters. The prevalence of liver and kidney dysfunction was found to be quite high among insecticide applicators, especially among plant protection agents. The prevalence of biochemical alterations seems to be correlated to the frequency of insecticide use. However, no significant differences were found between the hematological parameters among farm workers and plant protection agents. The hematological parameters of all the insecticide applicators were normal. The great majority of insecticide applicators (85%) reported symptoms related to insecticide exposure. The use of insecticides in the agriculture of Burkina Faso is threatening to human health. PMID:22783149</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22783149','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22783149"><span>Biological alterations and self-reported symptoms among insecticides-exposed workers in Burkina Faso.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Toe, Adama M; Ilboudo, Sylvain; Ouedraogo, Moustapha; Guissou, Pierre I</p> <p>2012-03-01</p> <p>Occupationally exposed workers, farm workers and plant protection agents in the <span class="hlt">Sahel</span> region of Burkina Faso were interviewed to assess adverse health effects of insecticides. The subjects were also examined for changes in both hematological and biochemical parameters. The prevalence of liver and kidney dysfunction was found to be quite high among insecticide applicators, especially among plant protection agents. The prevalence of biochemical alterations seems to be correlated to the frequency of insecticide use. However, no significant differences were found between the hematological parameters among farm workers and plant protection agents. The hematological parameters of all the insecticide applicators were normal. The great majority of insecticide applicators (85%) reported symptoms related to insecticide exposure. The use of insecticides in the agriculture of Burkina Faso is threatening to human health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1610889L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1610889L"><span>On the added value and sensitivity of WRF to driving conditions over CORDEX-Africa domain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lorente-Plazas, Raquel; García-Díez, Markel; Jimenez-Guerrero, Pedro; Fernández, Jesús; Montavez, Juan Pedro</p> <p>2014-05-01</p> <p> Research Unit of the University of East Anglia are used. The precipitation is compared against the Tropical Rainfall Measuring Mission Project (TRMM) monthly data (0.25deg). The results depict that none of the reanalyses used outperforms the other in representing the African climate, since their performance depends on the variable, season and region assessed. The simulations show a noticeable disagreement for 2-m temperature in north-western Africa, where WRF-JRA tends to underestimate this variable mostly in winter and spring. For the monthly mean daily maximum temperature, WRF-JRA tends to overestimate the temperature in the <span class="hlt">Sahel</span> in summer and in the border between Angola and Namibia in Winter. When comparing with CRU observations, there is a remarkably better spatial representation for the WRF-EI simulation in the North of Africa. However, the behaviour of WRF-EI and WRF-JRA is similar in the South of Africa. Intra-annual variability is well represented except in Atlas mountains where WRF-JRA underestimates temperature. Regarding precipitation, the main differences appear over the <span class="hlt">Sahel</span> region in JAS and in the Congo area during JFM. The comparison with the TRMM data shows a better agreement with the WRF-JRA simulation except during summer in the <span class="hlt">Sahel</span> region. The monthly annual cycle is well captured, except in Ethiopian highlands and Northern West Africa where WRF-JRA (WRF-EI) underestimate (overestimate) the annual cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EnMan..43..790B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EnMan..43..790B"><span>Human Vulnerability to Climate Variability in the <span class="hlt">Sahel</span>: Farmers' Adaptation Strategies in Northern Burkina Faso</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barbier, Bruno; Yacouba, Hamma; Karambiri, Harouna; Zoromé, Malick; Somé, Blaise</p> <p>2009-05-01</p> <p>In this study, the authors investigate farmers’ vulnerability to climate variability and evaluate local adoption of technology and farmers’ perceptions of adaptation strategies to rainfall variability and policies. A survey was conducted in a community in northern Burkina Faso following the crop failure of 2004. In 2006, following a better harvest, another survey was conducted to compare farmers’ actions and reactions during two contrasted rainy seasons. The results confirm that farmers from this community have substantially changed their practices during the last few decades. They have adopted a wide range of techniques that are intended to simultaneously increase crop yield and reduce yield variability. Micro water harvesting (Zaï) techniques have been widely adopted (41%), and a majority of fields have been improved with stone lines (60%). Hay (48%) and sorghum residues are increasingly stored to feed animals during the dry season, making bull and sheep fattening now a common practice. Dry season vegetable production also involves a majority of the population (60%). According to farmers, most of the new techniques have been adopted because of growing land scarcity and new market opportunities, rather than because of climate variability. Population pressure has reached a critical threshold, while land scarcity, declining soil fertility and reduced animal mobility have pushed farmers to intensify agricultural production. These techniques reduce farmers’ dependency on rainfall but are still insufficient to reduce poverty and vulnerability. Thirty-nine percent of the population remains vulnerable after a good rainy season. Despite farmers’ desire to remain in their own communities, migrations are likely to remain a major source of regular income and form of recourse in the event of droughts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA517002','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA517002"><span>Communications Channels in the <span class="hlt">Sahel</span> Using Mauritania, Mali, Niger, and Chad as a Case Study</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2007-05-01</p> <p>issues, family, AIDS, etc. Malians listen to rap, but the lyrics are more positive than Western rap music. Dr. Arnoldi said the beat is similar to...Hassan, eds. The Muse of Modernity: Essays on Culture as Development in Africa. (Trenton: Africa World Press, Inc., 1996). Page 10 of 107 cultural...http://www.nollywood.net/ Essays /p2_articleid/126/p2_page/3>. Theatre for Development encourages community participation, increasing the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70155259','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70155259"><span>Calculating crop water requirement satisfaction in the West Africa <span class="hlt">Sahel</span> with remotely sensed soil moisture</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McNally, Amy; Gregory J. Husak,; Molly Brown,; Carroll, Mark L.; Funk, Christopher C.; Soni Yatheendradas,; Kristi Arsenault,; Christa Peters-Lidard,; Verdin, James</p> <p>2015-01-01</p> <p>The Soil Moisture Active Passive (SMAP) mission will provide soil moisture data with unprecedented accuracy, resolution, and coverage, enabling models to better track agricultural drought and estimate yields. In turn, this information can be used to shape policy related to food and water from commodity markets to humanitarian relief efforts. New data alone, however, do not translate to improvements in drought and yield forecasts. New tools will be needed to transform SMAP data into agriculturally meaningful products. The objective of this study is to evaluate the possibility and efficiency of replacing the rainfall-derived soil moisture component of a crop water stress index with SMAP data. The approach is demonstrated with 0.1°-resolution, ~10-day microwave soil moisture from the European Space Agency and simulated soil moisture from the Famine Early Warning Systems Network Land Data Assimilation System. Over a West Africa domain, the approach is evaluated by comparing the different soil moisture estimates and their resulting Water Requirement Satisfaction Index values from 2000 to 2010. This study highlights how the ensemble of indices performs during wet versus dry years, over different land-cover types, and the correlation with national-level millet yields. The new approach is a feasible and useful way to quantitatively assess how satellite-derived rainfall and soil moisture track agricultural water deficits. Given the importance of soil moisture in many applications, ranging from agriculture to public health to fire, this study should inspire other modeling communities to reformulate existing tools to take advantage of SMAP data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA564149','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA564149"><span>Analytical Tools for the Application of Operational Culture: A Case Study in the Trans-<span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2011-03-28</p> <p>Study Team Working Paper 3: Research Methods Discussion for the Study Team Methods229 Generating Empirical Materials In grounded theory ... research I have conducted using these methods . UNCLASSIFIED Analytical Tools for the Application of Operational Culture: A Case Study in the...Survey and a Case Study ,‖ Kjeller, Norway: FFI Glaser, B. G. & Strauss, A. L. (1967). ―The discovery of grounded theory</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1932751','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1932751"><span>Atmospheric Movement of Microorganisms in Clouds of Desert Dust and Implications for Human Health</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Griffin, Dale W.</p> <p>2007-01-01</p> <p>Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and <span class="hlt">Sahel</span> regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources. PMID:17630335</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740022610','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740022610"><span>Remote sensing experiment in West Africa. [drought effects on desert agriculture and vegetation in Niger</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Macleod, N. H.</p> <p>1974-01-01</p> <p>There are substantial needs of the Sahelien Zone to detail the state of regional agricultural resources in the face of a sixth year of serious drought conditions. While most of the work has been done in the Republic of Niger, the principles which have emerged from the analysis seem to be applicable to much of the <span class="hlt">Sahel</span>. The discussion relates to quite specific rehabilitation and development initiations under consideration in Niger which are based in part upon direct analysis of ERTS imagery of the country, in part on field surveys and on discussions with Nigerian officials and technicians. Again, because the entire Sahelien Zone (including Niger) has large zones of similar ecologic characteristics, modificiations of the approaches suggested for Niger are applicable to the solution of rehabilitation of the desert, the savannah and the woodlands of West Africa in general.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900054617&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmicrowaves%2Bwater%2Bstructure','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900054617&hterms=microwaves+water+structure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dmicrowaves%2Bwater%2Bstructure"><span>A semiempirical model for interpreting microwave emission from semiarid land surfaces as seen from space</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kerr, Yann H.; Njoku, Eni G.</p> <p>1990-01-01</p> <p>A radiative-transfer model for simulating microwave brightness temperatures over land surfaces is described. The model takes into account sensor viewing conditions (spacecraft altitude, viewing angle, frequency, and polarization) and atmospheric parameters over a soil surface characterized by its moisture, roughness, and temperature and covered with a layer of vegetation characterized by its temperature, water content, single scattering albedo, structure, and percent coverage. In order to reduce the influence of atmospheric and surface temperature effects, the brightness temperatures are expressed as polarization ratios that depend primarily on the soil moisture and roughness, canopy water content, and percentage of cover. The sensitivity of the polarization ratio to these parameters is investigated. Simulation of the temporal evolution of the microwave signal over semiarid areas in the African <span class="hlt">Sahel</span> is presented and compared to actual satellite data from the SMMR instrument on Nimbus-7.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=STS065-84-014&hterms=water+africa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dwater%2Bafrica','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=STS065-84-014&hterms=water+africa&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dwater%2Bafrica"><span>STS-65 Earth observation of Lake Chad, Africa, taken aboard Columbia, OV-102</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1994-01-01</p> <p>STS-65 Earth observation taken aboard Columbia, Orbiter Vehicle (OV) 102, shows Lake Chad, Africa. This is another long term ecological monitoring site for NASA scientists. Lake Chad was first photographed from space in 1965. A 25-year length-of-record data set exists for this environmentally important area. A number of these scenes have been digitized, rectified, classified and results show that the lake area has been shrinking and only 15% to 20% of the surface water is visible on space images. NASA's objective in monitoring this lake is to document the intra- and interannual areal changes of the largest standing water body in the Sahelian biome of North Africa. These areal changes are an indicator of the presence or absence of drought across the arguably overpopulated, overgrazed, and over biological carrying capacity limits nations of the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.H31E1437B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.H31E1437B"><span>Temporal and Spatial Separation of Water Use Averts Competition for Soil Water Resources in a Sahelian Agroforestry System</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bogie, N. A.; Bayala, R.; Diedhiou, I.; Dick, R.; Ghezzehei, T. A.</p> <p>2016-12-01</p> <p>A changing climate along with human and animal population pressure can have a devastating effect on crop yields and food security in the Sudano-<span class="hlt">Sahel</span>. Agricultural solutions to address soil degradation and crop water stress are needed to combat this increasingly difficult situation. Large differences in crop success have been observed even during drough stress in peanut and millet grown in association with two native evergreen shrubs, Piliostigma reticulatum, and Guiera senegalensis at the sites of Nioro du Rip and Keur Matar, respectively. We investigate how farmers can increase crop productivity by capitalizing on the evolutionary adaptation of native shrubs to the harsh Sudano-Sahelian environment as well as the physical mechanisms at work in the system that can lead to more robust yields. Research plots at Keur Matar Arame and Nioro du Rip with no fertilizer added were monitored from 2012-2015 using two soil moisture sensor networks at depths of 10, 20, 40, 60, 100, 200, and 300cm. Our data show that there is more water available to crops in the shallow soil layers as a result of a temporal and spatial shift of shrub soil moisture use to deeper layers and the presence of hydraulic redistribution. At the beginning of the dry season just after the crop harvest, maximum weekly transpirational water use descends from 100 to 300cm over the course of one to two months. We hypothesize that after early February, 2-3 months into the dry season, the majority of water use by shrubs comes from below 3m depth. As the first rains come in June-July, the shrubs continue to use deep soil moisture until a significant portion of the soil profile undergoes infiltration. It is during this time that a large difference in hydraulic head can drive hydraulic redistribution, which, in addition to surface shading by the shrub canopy, can help to maintain higher soil moisture in the shallow soil layers near the shrubs. This builds on previous work at the site investigating growing season</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.3536B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.3536B"><span>Implications of land use change in tropical West Africa under global warming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brücher, Tim; Claussen, Martin</p> <p>2015-04-01</p> <p>Northern Africa, and the <span class="hlt">Sahel</span> in particular, are highly vulnerable to climate change, due to strong exposure to increasing temperature, precipitation variability, and population growth. A major link between climate and humans in this region is land use and associated land cover change, mainly where subsistence farming prevails. But how strongly does climate change affect land use and how strongly does land use feeds back into climate change? To which extent may climate-induced water, food and wood shortages exacerbate conflict potential and lead changes in land use and to migration? Estimates of possible changes in African climate vary among the Earth System Models participating in the recent Coupled Model Intercomparison (CMIP5) exercise, except for the region adjacent to the Mediterranean Sea, where a significant decrease of precipitation emerges. While all models agree in a strong temperature increase, rainfall uncertainties for most parts of the Sahara, <span class="hlt">Sahel</span>, and Sudan are higher. Here we present results of complementary experiments based on extreme and idealized land use change scenarios within a future climate.. We use the MPI-ESM forced with a strong green house gas scenario (RCP8.5) and apply an additional land use forcing by varying largely the intensity and kind of agricultural practice. By these transient experiments (until 2100) we elaborate the additional impact on climate due to strong land use forcing. However, the differences are mostly insignificant. The greenhouse gas caused temperature increase and the high variability in the West African Monsoon rainfall superposes the minor changes in climate due to land use. While simulated climate key variables like precipitation and temperature are not distinguishable from the CMIP5 RCP8.5 results, an additional greening is simulated, when crops are demanded. Crops have lower water usage than pastureland has. This benefits available soil water, which is taken up by the natural vegetation and makes it more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A11L0160W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A11L0160W"><span>The Impact of US SO2 Emissions on Clouds and the Hydrological Cycle at Global and Regional Scales in Three Coupled Chemistry-Climate Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Westervelt, D. M.</p> <p>2016-12-01</p> <p>It is widely expected that global and regional emissions of atmospheric aerosols and their precursors will decrease strongly throughout the remainder of the 21st century, due to emission reduction policies enacted to protect human health. Although there is some evidence that these aerosol reductions may lead to significant regional and global climate impacts, we currently lack a full understanding of the magnitude, spatial and temporal pattern, and statistical significance of these influences, especially for clouds and precipitation. Further, we often lack robust understanding of the processes by which regional aerosols influence local and remote climate. Here, we aim to quantify systematically the cloud and hydrological cycle response to regional changes in aerosols through model simulations using three fully coupled chemistry-climate models: NOAA Geophysical Fluid Dynamics Laboratory Coupled Model 3 (GFDL-CM3), NCAR Community Earth System Model (NCAR-CESM1), and NASA Goddard Institute for Space Studies ModelE2 (GISS-E2). The central approach we use is to contrast a long control experiment (400 years) with a collection of long individual perturbation experiments ( 200 years). We perturb emissions of sulfur dioxide (SO2; precursor to sulfate aerosol) in the United States and determine which responses are significant relative to internal variability and robust across the three models. Initial results show robust, statistically significant decreases in cloud droplet number and liquid water path in the source region across the three models due to decreases in sulfate aerosols. Setting SO2 emissions to zero over the U.S. causes both local and remote impacts in precipitation, with notable significant increases in <span class="hlt">Sahel</span> and Arctic precipitation. In 13 of the 15 regions we analyze, the precipitation response to zero U.S. SO2 emissions agrees in sign, with agreement in magnitude to within one standard deviation in many of those regions. U.S. sulfate also impacts the timing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.5600K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.5600K"><span>Impacts of boundary condition changes on regional climate projections over West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Jee Hee; Kim, Yeonjoo; Wang, Guiling</p> <p>2017-06-01</p> <p>Future projections using regional climate models (RCMs) are driven with boundary conditions (BCs) typically derived from global climate models. Understanding the impact of the various BCs on regional climate projections is critical for characterizing their robustness and uncertainties. In this study, the International Center for Theoretical Physics Regional Climate Model Version 4 (RegCM4) is used to investigate the impact of different aspects of boundary conditions, including lateral BCs and sea surface temperature (SST), on projected future changes of regional climate in West Africa, and BCs from the coupled European Community-Hamburg Atmospheric Model 5/Max Planck Institute Ocean Model are used as an example. Historical, future, and several sensitivity experiments are conducted with various combinations of BCs and CO2 concentration, and differences among the experiments are compared to identify the most important drivers for RCMs. When driven by changes in all factors, the RegCM4-produced future climate changes include significantly drier conditions in <span class="hlt">Sahel</span> and wetter conditions along the Guinean coast. Changes in CO2 concentration within the RCM domain alone or changes in wind vectors at the domain boundaries alone have minor impact on projected future climate changes. Changes in the atmospheric humidity alone at the domain boundaries lead to a wetter <span class="hlt">Sahel</span> due to the northward migration of rain belts during summer. This impact, although significant, is offset and dominated by changes of other BC factors (primarily temperature) that cause a drying signal. Future changes of atmospheric temperature at the domain boundaries combined with SST changes over oceans are sufficient to cause a future climate that closely resembles the projection that accounts for all factors combined. Therefore, climate variability and changes simulated by RCMs depend primarily on the variability and change of temperature aspects of the RCM BCs. Moreover, it is found that the response</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.B32B..09N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.B32B..09N"><span>Smallholder Irrigation and Crop Diversification under Climate Change in sub-Saharan Africa: Evidence and Potential for Simultaneous Food Security, Adaptation, and Mitigation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naylor, R.; Burney, J. A.; Postel, S.</p> <p>2011-12-01</p> <p>The poorest populations in sub-Saharan Africa live in rural areas and depend on smallholder agricultural production for their livelihoods. Over 90% of all farmed area in Sub-Saharan Africa is rainfed, with crop production centering on 3-5 months of rainfall. Rapid population growth is reducing land per capita ratios, and low yields for staple crops make food security an increasingly challenging goal. Malnutrition, most noticeable among children, peaks during the dry season. Recent data on aggregate economic growth and investment in Africa hide these patterns of seasonal hunger and income disparity. Perhaps most perversely, smallholder farmers in the dry tropical regions of sub-Saharan Africa are (and will continue to be) some of the earliest and hardest hit by climate change. Our research focuses on the role distributed, small-scale irrigation can play in food security and climate change adaptation in sub-Saharan Africa. As Asia's agricultural success has demonstrated, irrigation, when combined with the availability of inputs (fertilizer) and improved crop varieties, can enable year-round production, growth in rural incomes, and a dramatic reduction in hunger. The situation in Africa is markedly different: agroecological conditions are far more heterogeneous than in Asia and evaporation rates are relatively high; most smallholders lack access to fertilizers; and market integration is constrained by infrastructure, information, and private sector incentives. Yet from a resource perspective, national- and regional-level estimates suggest that Internal Renewable Water Resources (IRWR) are nowhere near fully exploited in Sub-Saharan Africa -- even in the Sudano-<span class="hlt">Sahel</span>, which is considered to be one of the driest regions of the continent. Irrigation can thus be implemented on a much larger scale sustainably. We will present (a) results from controlled, experimental field studies of solar-powered drip irrigation systems in the rural Sudano-<span class="hlt">Sahel</span> region of West Africa. We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B41D0435B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B41D0435B"><span>Evaluating Climate Causation of Conflict in Darfur Using Multi-temporal, Multi-resolution Satellite Image Datasets With Novel Analyses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, I.; Wennbom, M.</p> <p>2013-12-01</p> <p>Climate change, population growth and changes in traditional lifestyles have led to instabilities in traditional demarcations between neighboring ethic and religious groups in the <span class="hlt">Sahel</span> region. This has resulted in a number of conflicts as groups resort to arms to settle disputes. Such disputes often centre on or are justified by competition for resources. The conflict in Darfur has been controversially explained by resource scarcity resulting from climate change. Here we analyse established methods of using satellite imagery to assess vegetation health in Darfur. Multi-decadal time series of observations are available using low spatial resolution visible-near infrared imagery. Typically normalized difference vegetation index (NDVI) analyses are produced to describe changes in vegetation ';greenness' or ';health'. Such approaches have been widely used to evaluate the long term development of vegetation in relation to climate variations across a wide range of environments from the Arctic to the <span class="hlt">Sahel</span>. These datasets typically measure peak NDVI observed over a given interval and may introduce bias. It is furthermore unclear how the spatial organization of sparse vegetation may affect low resolution NDVI products. We develop and assess alternative measures of vegetation including descriptors of the growing season, wetness and resource availability. Expanding the range of parameters used in the analysis reduces our dependence on peak NDVI. Furthermore, these descriptors provide a better characterization of the growing season than the single NDVI measure. Using multi-sensor data we combine high temporal/moderate spatial resolution data with low temporal/high spatial resolution data to improve the spatial representativity of the observations and to provide improved spatial analysis of vegetation patterns. The approach places the high resolution observations in the NDVI context space using a longer time series of lower resolution imagery. The vegetation descriptors</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......496M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......496M"><span>Estimating root-zone soil moisture in the West Africa <span class="hlt">Sahel</span> using remotely sensed rainfall and vegetation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McNally, Amy L.</p> <p></p> <p>Agricultural drought is characterized by shortages in precipitation, large differences between actual and potential evapotranspiration, and soil water deficits that impact crop growth and pasture productivity. Rainfall and other agrometeorological gauge networks in Sub-Saharan Africa are inadequate for drought early warning systems and hence, satellite-based estimates of rainfall and vegetation greenness provide the main sources of information. While a number of studies have described the empirical relationship between rainfall and vegetation greenness, these studies lack a process based approach that includes soil moisture storage. In Chapters I and II, I modeled soil moisture using satellite rainfall inputs and developed a new method for estimating soil moisture with NDVI calibrated to in situ and microwave soil moisture observations. By transforming both NDVI and rainfall into estimates of soil moisture I was able to easily compare these two datasets in a physically meaningful way. In Chapter II, I also show how the new NDVI derived soil moisture can be assimilated into a water balance model that calculates an index of crop water stress. Compared to the analogous rainfall derived estimates of soil moisture and crop stress the NDVI derived estimates were better correlated with millet yields. In Chapter III, I developed a metric for defining growing season drought events that negatively impact millet yields. This metric is based on the data and models used in the Chapters I and II. I then use this metric to evaluate the ability of a sophisticated land surface model to detect drought events. The analysis showed that this particular land surface model's soil moisture estimates do have the potential to benefit the food security and drought early warning communities. With a focus on soil moisture, this dissertation introduced new methods that utilized a variety of data and models for agricultural drought monitoring applications. These new methods facilitate a more quantitative, transparent `convergence of evidence' approach to identifying agricultural drought events that lead to food insecurity. Ideally, these new methods will contribute to better famine early warning and the timely delivery of food aid to reduce the human suffering caused by drought.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1616776D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1616776D"><span>Oceanic influence on seasonal malaria outbreaks over Senegal and <span class="hlt">Sahel</span>. Predictability using S4CAST model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diouf, Ibrahima; Deme, Abdoulaye; Rodriguez-Fonseca, Belen; Suárez-Moreno, Roberto; Cisse, Moustapha; Ndione, Jacques-André; Thierno Gaye, Amadou</p> <p>2014-05-01</p> <p>Senegal and, in general, West African regions are affected by important outbreaks of diseases with destructive consequences for human population, livestock and country's economy. The vector-borne diseases such as mainly malaria, Rift Valley Fever and dengue are affected by the interanual to decadal variability of climate. Analysis of the spatial and temporal variability of climate parameters and associated oceanic patterns is important in order to assess the climate impact on malaria transmission. In this study, the approach developed to study the malaria-climate link is predefined by the QWeCI project (Quantifying Weather and Climate Impacts on Health in Developing Countries). Preliminary observations and simulations results over Senegal Ferlo region, confirm that the risk of malaria transmission is mainly linked to climate parameters such as rainfall, temperature and relative humidity; and a lag of one to two months between the maximum of malaria and the maximum of climate parameters as rainfall is observed. As climate variables are able to be predicted from oceanic SST variability in remote regions, this study explores seasonal predictability of malaria incidence outbreaks from previous sea surface temperatures conditions in different ocean basins. We have found causal or coincident relationship between El Niño and malaria parameters by coupling LMM UNILIV malaria model and S4CAST statistiscal model with the aim of predicting the malaria parameters with more than 6 months in advance. In particular, El Niño is linked to an important decrease of the number of mosquitoes and the malaria incidence. Results from this research, after assessing the seasonal malaria parameters, are expected to be useful for decision makers to better access to climate forecasts and application on health in the framework of rolling back malaria transmission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPA31B2207N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPA31B2207N"><span>Gravity and InSAR remote sensing of groundwater usage in the <span class="hlt">Sahel</span> and Horn of Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neely, W.; Borsa, A. A.; Burney, J. A.; Devlin, K.</p> <p>2016-12-01</p> <p>Changes in the Earth's climatic systems influence agro-ecological conditions on local, regional, and global scales. With the world's highest population growth rate, sub-Saharan Africa faces particularly acute concerns regarding food security and resource management. Historical sources of surface water for agricultural production may become less reliable and/or limited with increased climate variability, and African countries have already begun to depend on more stable sources of groundwater. Expected increases in groundwater usage pose questions about the sustainability of current agricultural practices, which require new sources of information to answer. Due to the logistics and costs to implement in situ networks to monitor regional water security, current remote sensing missions offer an affordable alternative. The Gravity Recovery and Climate Experiment (GRACE) has proven to be effective in quantifying changes in terrestrial water storage (TWS) at the regional scale using near-monthly gravity measurements from orbit. Using over a decade of measurements, we estimate TWS anomalies in Niger and Ethiopia. These anomalies offer a proxy for hydrological stressing, indicating potential targets for additional analysis. We use independent, but complementary, estimates of surface displacements from Interferometric Synthetic Aperture Radar (InSAR) to provide information on local groundwater withdrawal. Using data from ESA's Sentinel 1 mission and JAXA's Advanced Land Observing Satellite (ALOS) missions, we characterize the surface deformation over the past decade in regions of active groundwater pumping using the Small Baseline Subset (SBAS) technique. In particular, we investigate ties of ground motion to known agricultural/industrial land usage near Niamey, Niger and Eastern Oromia, Ethiopia to better understand how human activity affects available groundwater resources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC43B0712L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC43B0712L"><span>West African warming: Investigating Temperature Trends and their relation between Precipitation Trends over West African <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>LY, M., Jr.</p> <p>2014-12-01</p> <p>It is now admitted that the West African region faces a lot of constraints due to the comprehensiveness of the high climate variability and potential climate change. This is mainly due to the lack of a large number of datasets and long-term records as summarized in the in the IPCC reports. This paper aims to provide improved knowledge and evidence on current and future climate conditions, for better manage climate variability over seasons and from year to year and strengthen the capacity to adapt to future climate change. In this regards, we analyse the evolution of some extreme temperature and precipitation indices over a large area of West Africa. Prior results show a general warming trend at individual stations throughout the region during the period from 1960 to 2010, namely negative trends in the number of cool nights, and positive trends in the number of warm days and length of warm spells. Trends in rainfall-related indices are not as uniform as the ones in temperatures, rather they display marked multi-decadal variability, as expected. To refine analyses of temperature variations and their relation to precipitation we investigated on cluster analysis aimed at distinguishing different sub-regions, such as continental and coastal, and relevant seasons, such as wet, dry/cold and dry warm. This will contribute to significantly lower uncertainties by developing better and more tailored temperature and precipitation trends to inform the user communities on climate related risks, as well as enhance their resilience to food insecurity and other climate related disasters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA586478','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA586478"><span>Mercy or Wrath: The Competing Ideologies of Sufism and Wahhabism in North Africa and the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2013-06-10</p> <p>Tunisia are that the governmental encouragement of Sufism as a moderate alternative to Salafism and Wahhabism has met with substantial success in...historical research led us to conclude that while Sufism could be used by governments to encourage moderate alternatives to Salafism or Wahhabism, such...present Algerian president) has actively promoted Sufism as an alternative to Salafism and Wahhabism, his efforts have met with a lukewarm reception</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1031550','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1031550"><span>In Harmony with the Population: Ethnomusicology as a Framework for Countering Violent Extremism in the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2016-12-01</p> <p>digital media , art, multiculturalism, communication flow theory 15. NUMBER OF PAGES 143 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT...and Chad as a Case Study,” 59. 41 methods), and mass communication ( communication to a large audience via mass media ).91 According to a 2007...proliferation of digital technology for at least the foreseeable future. Early communication theorists considered mass- media communication flow to be a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..1412181M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..1412181M"><span>Effects of Medieval Warm Period and Little Ice Age on the hydrology of Mediterranean region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Markonis, Y.; Kossieris, P.; Lykou, A.; Koutsoyiannis, D.</p> <p>2012-04-01</p> <p>Medieval Warm Period (950 - 1250) and Little Ice Age (1450 - 1850) are the most recent periods that reflect the magnitude of natural climate variability. As their names suggest, the first one was characterized by higher temperatures and a generally moister climate, while the opposite happened during the second period. Although their existence is well documented for Northern Europe and North America, recent findings suggest strong evidence in lower latitudes as well. Here we analyze qualitatively the influence of these climatic fluctuations on the hydrological cycle all over the Mediterranean basin, highlighting the spatial characteristics of precipitation and runoff. We use both qualitative estimates from literature review in the field of paleoclimatology and statistical analysis of proxy data series. We investigate possible regional patterns and possible tele-connections with large scale atmospheric circulation phenomena such as North Atlantic Oscillation, Siberian High, African <span class="hlt">Sahel</span> Rainfall and Indian Monsoon.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMGC23A0750H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMGC23A0750H"><span>Linking Regional Satellite Observations with Coupled Human-Ecological Systems in Global Drylands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hutchinson, C.; Reynolds, J. F.</p> <p>2009-12-01</p> <p>The African <span class="hlt">Sahel</span> has attracted consistent attention since a series of droughts in the 1970s and 1980s caused widespread famine and land degradation (desertification). These events spawned international conventions and sustained development efforts to increase food security and reverse poverty for the local populations, and to arrest environmental degradation. Since 1985, several studies using satellite data have described a general “greening” in response to increased rainfall trends. However, some areas show more greening while others less greening than can be explained by precipitation alone (Glob. Env. Change 15- 2005). The debated question is how to explain the residual changes: management, policy, human adaptation, or something else? Placing results in an human-ecological framework could help answer this question. Providing a meaningful assessment will allow national and international agencies to evaluate the effectiveness of alternative approaches to poverty alleviation and environmental restoration in drylands at regional and global scales.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70031359','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70031359"><span>Climate-induced forest dieback as an emergent global phenomenon: Organized oral session at the Ecological Society of America/Society of Ecological Restoration Joint Meeting; San Jose, California, 5-10 August 2007</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Allen, Craig D.; Breshears, David D.</p> <p>2007-01-01</p> <p>An organized oral session at the annual meeting of the Ecological Society of America in San Jose, Calif., posed this question: Is climate-induced drought stress triggering increasing rates and unusual patterns of forest die-off at a global scale? Twenty-nine researchers representing five continents reported on patterns, mechanisms, and projections of forest mortality.Observations include widespread forest dieback or reductions in tree cover and biodiversity in response to drought and warmer temperatures in the African <span class="hlt">Sahel</span> (Patrick Gonzalez, The Nature Conservancy), Mediterranean and alpine Europe (Jorge Castro, Universidad de Granada), and Argentinean Patagonia (Thomas Kitzberger, Universidad Nacional del Comahue). In contrast, although much Eucalyptus mortality has resulted from recent droughts in Australia, warming trends have been less pronounced in the Southern Hemisphere and it is unclear if contemporary climate-induced tree mortality differs from previous historical drought impacts (Rod Fensham, Queensland Herbarium).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29732409','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29732409"><span>Climate models predict increasing temperature variability in poor countries.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bathiany, Sebastian; Dakos, Vasilis; Scheffer, Marten; Lenton, Timothy M</p> <p>2018-05-01</p> <p>Extreme events such as heat waves are among the most challenging aspects of climate change for societies. We show that climate models consistently project increases in temperature variability in tropical countries over the coming decades, with the Amazon as a particular hotspot of concern. During the season with maximum insolation, temperature variability increases by ~15% per degree of global warming in Amazonia and Southern Africa and by up to 10%°C -1 in the <span class="hlt">Sahel</span>, India, and Southeast Asia. Mechanisms include drying soils and shifts in atmospheric structure. Outside the tropics, temperature variability is projected to decrease on average because of a reduced meridional temperature gradient and sea-ice loss. The countries that have contributed least to climate change, and are most vulnerable to extreme events, are projected to experience the strongest increase in variability. These changes would therefore amplify the inequality associated with the impacts of a changing climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/fs/2017/3005/fs20173005_French.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/fs/2017/3005/fs20173005_French.pdf"><span>The landscapes of West Africa—40 years of change</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Cotillon, Suzanne E.</p> <p>2017-02-16</p> <p>What has driven changes in land use and land cover in West Africa over the past 40 years? What trends or patterns can be discerned in those changes? To answer these questions, the U.S. Geological Survey West Africa Land Use Dynamics project partnered with the Permanent Interstate Committee for Drought Control in the <span class="hlt">Sahel</span> and the U.S. Agency for International Development/West Africa to map land use and land cover across the region for  three time periods (years): 1975, 2000, and 2013. This cooperative effort has resulted in the publication of a 219-page atlas, “Landscapes of West Africa: A Window on a Changing World.” The atlas uses satellite imagery, maps, and pictures to tell a complex story of landscape change at regional and national scales. It includes a collection of focused studies, some of which raise cause for concern, and others that provide considerable hope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750038455&hterms=desertification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddesertification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750038455&hterms=desertification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Ddesertification"><span>The first Earth Resources Technology Satellite - Nearly two years of operation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nordberg, W.</p> <p>1974-01-01</p> <p>A brief status report is given of the ERTS-1 satellite system as of June, 1974, and some applications of the ERTS-1 images are discussed. The multispectral images make it possible to identify or measure the quality and composition of water, the potential water content of snow, the moisture and possible composition of soils, the types and state of vegetation cover, and factors relating to stresses on the environment. The orthographic view of the earth provided by the satellite makes it possible to rapidly produce thematic maps, on a scale of 1:250,000, of most areas of the world. The regular, repetitive coverage provided by ERTS-1 every 18 days is important in areas such as water-supply and flood-damage studies. The use of ERTS-1 imagery for land-use planning, wetlands surveying, assessing marine resources, and observing processes such as desertification in the African <span class="hlt">Sahel</span> is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.9783C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.9783C"><span>The Impact of Satellite-Derived Land Surface Temperatures on Numerical Weather Prediction Analyses and Forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Candy, B.; Saunders, R. W.; Ghent, D.; Bulgin, C. E.</p> <p>2017-09-01</p> <p>Land surface temperature (LST) observations from a variety of satellite instruments operating in the infrared have been compared to estimates of surface temperature from the Met Office operational numerical weather prediction (NWP) model. The comparisons show that during the day the NWP model can underpredict the surface temperature by up to 10 K in certain regions such as the <span class="hlt">Sahel</span> and southern Africa. By contrast at night the differences are generally smaller. Matchups have also been performed between satellite LSTs and observations from an in situ radiometer located in Southern England within a region of mixed land use. These matchups demonstrate good agreement at night and suggest that the satellite uncertainties in LST are less than 2 K. The Met Office surface analysis scheme has been adapted to utilize nighttime LST observations. Experiments using these analyses in an NWP model have shown a benefit to the resulting forecasts of near-surface air temperature, particularly over Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Natur.555...48G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Natur.555...48G"><span>Mapping local variation in educational attainment across Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Graetz, Nicholas; Friedman, Joseph; Osgood-Zimmerman, Aaron; Burstein, Roy; Biehl, Molly H.; Shields, Chloe; Mosser, Jonathan F.; Casey, Daniel C.; Deshpande, Aniruddha; Earl, Lucas; Reiner, Robert C.; Ray, Sarah E.; Fullman, Nancy; Levine, Aubrey J.; Stubbs, Rebecca W.; Mayala, Benjamin K.; Longbottom, Joshua; Browne, Annie J.; Bhatt, Samir; Weiss, Daniel J.; Gething, Peter W.; Mokdad, Ali H.; Lim, Stephen S.; Murray, Christopher J. L.; Gakidou, Emmanuela; Hay, Simon I.</p> <p>2018-03-01</p> <p>Educational attainment for women of reproductive age is linked to reduced child and maternal mortality, lower fertility and improved reproductive health. Comparable analyses of attainment exist only at the national level, potentially obscuring patterns in subnational inequality. Evidence suggests that wide disparities between urban and rural populations exist, raising questions about where the majority of progress towards the education targets of the Sustainable Development Goals is occurring in African countries. Here we explore within-country inequalities by predicting years of schooling across five by five kilometre grids, generating estimates of average educational attainment by age and sex at subnational levels. Despite marked progress in attainment from 2000 to 2015 across Africa, substantial differences persist between locations and sexes. These differences have widened in many countries, particularly across the <span class="hlt">Sahel</span>. These high-resolution, comparable estimates improve the ability of decision-makers to plan the precisely targeted interventions that will be necessary to deliver progress during the era of the Sustainable Development Goals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5931768','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5931768"><span>Climate models predict increasing temperature variability in poor countries</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dakos, Vasilis; Scheffer, Marten</p> <p>2018-01-01</p> <p>Extreme events such as heat waves are among the most challenging aspects of climate change for societies. We show that climate models consistently project increases in temperature variability in tropical countries over the coming decades, with the Amazon as a particular hotspot of concern. During the season with maximum insolation, temperature variability increases by ~15% per degree of global warming in Amazonia and Southern Africa and by up to 10%°C−1 in the <span class="hlt">Sahel</span>, India, and Southeast Asia. Mechanisms include drying soils and shifts in atmospheric structure. Outside the tropics, temperature variability is projected to decrease on average because of a reduced meridional temperature gradient and sea-ice loss. The countries that have contributed least to climate change, and are most vulnerable to extreme events, are projected to experience the strongest increase in variability. These changes would therefore amplify the inequality associated with the impacts of a changing climate. PMID:29732409</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29239569','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29239569"><span>Climate impact on malaria in northern Burkina Faso.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tourre, Yves M; Vignolles, Cécile; Viel, Christian; Mounier, Flore</p> <p>2017-11-27</p> <p>The Paluclim project managed by the French Centre National d'Etudes Spatiales (CNES) found that total rainfall for a 3-month period is a confounding factor for the density of malaria vectors in the region of Nouna in the <span class="hlt">Sahel</span> administrative territory of northern Burkina Faso. Following the models introduced in 1999 by Craig et al. and in 2003 by Tanser et al., a climate impact model for malaria risk (using different climate indices) was created. Several predictions of this risk at different temporal scales (i.e. seasonal, inter-annual and low-frequency) were assessed using this climate model. The main result of this investigation was the discovery of a significant link between malaria risk and low-frequency rainfall variability related to the Atlantic Multi-decadal Oscillation (AMO). This result is critical for the health information systems in this region. Knowledge of the AMO phases would help local authorities to organise preparedness and prevention of malaria, which is of particular importance in the climate change context.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC43F1128B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC43F1128B"><span>Future hotspots of increasing temperature variability in tropical countries</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bathiany, S.; Dakos, V.; Scheffer, M.; Lenton, T. M.</p> <p>2017-12-01</p> <p>Resolving how climate variability will change in future is crucial to determining how challenging it will be for societies and ecosystems to adapt to climate change. We show that the largest increases in temperature variability - that are robust between state-of-the art climate models - are concentrated in tropical countries. On average, temperature variability increases by 15% per degree of global warming in Amazonia and Southern Africa during austral summer, and by up to 10% °C-1 in the <span class="hlt">Sahel</span>, India and South East Asia. Southern hemisphere changes can be explained by drying soils, whereas shifts in atmospheric structure play a more important role in the Northern hemisphere. These robust regional changes in variability are associated with monthly timescale events, whereas uncertain changes in inter-annual modes of variability make the response of global temperature variability uncertain. Our results suggest that regional changes in temperature variability will create new inequalities in climate change impacts between rich and poor nations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5347875','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5347875"><span>Cross‐Saharan transport of water vapor via recycled cold pool outflows from moist convection</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Trzeciak, Tomasz M.; Garcia‐Carreras, Luis</p> <p>2017-01-01</p> <p>Abstract Very sparse data have previously limited observational studies of meteorological processes in the Sahara. We present an observed case of convectively driven water vapor transport crossing the Sahara over 2.5 days in June 2012, from the <span class="hlt">Sahel</span> in the south to the Atlas in the north. A daily cycle is observed, with deep convection in the evening generating moist cold pools that fed the next day's convection; the convection then generated new cold pools, providing a vertical recycling of moisture. Trajectories driven by analyses were able to capture the direction of the transport but not its full extent, particularly at night when cold pools are most active, and analyses missed much of the water content of cold pools. The results highlight the importance of cold pools for moisture transport, dust and clouds, and demonstrate the need to include these processes in models in order to improve the representation of Saharan atmosphere. PMID:28344367</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27282595','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27282595"><span>Using self-organizing maps to infill missing data in hydro-meteorological time series from the Logone catchment, Lake Chad basin.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nkiaka, E; Nawaz, N R; Lovett, J C</p> <p>2016-07-01</p> <p>Hydro-meteorological data is an important asset that can enhance management of water resources. But existing data often contains gaps, leading to uncertainties and so compromising their use. Although many methods exist for infilling data gaps in hydro-meteorological time series, many of these methods require inputs from neighbouring stations, which are often not available, while other methods are computationally demanding. Computing techniques such as artificial intelligence can be used to address this challenge. Self-organizing maps (SOMs), which are a type of artificial neural network, were used for infilling gaps in a hydro-meteorological time series in a Sudano-<span class="hlt">Sahel</span> catchment. The coefficients of determination obtained were all above 0.75 and 0.65 while the average topographic error was 0.008 and 0.02 for rainfall and river discharge time series, respectively. These results further indicate that SOMs are a robust and efficient method for infilling missing gaps in hydro-meteorological time series.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004ThApC..77..173C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004ThApC..77..173C"><span>Characterization of potential zones of dust generation at eleven stations in the southern Sahara</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clark, I.; Assamoi, P.; Bertrand, J.; Giorgi, F.</p> <p></p> <p>Synoptic wind data for multi-decadal periods at eleven stations located in the southern Sahara region (Agadez, Atar, Bilma, Dori, Gao, Kayes, Nema, Niamey, Nouadhibou, Ouagadougou and Tessalit) are used to study the monthly dust deflation power over the region. We found that, regardless of the conditions of the soil, the deflation power (or wind efficiency) is not sufficient to generate significant amounts of aerosols south of 15°N. North of this latitude, the deflation power is much larger, with potential zones of either very strong deflation (Nouadhibou and Bilma) or severe deflation (Gao, Tessalit, Nema, Atar, Agadez). Stations in the <span class="hlt">Sahel</span> region such as Gao, Agadez and Tessalit are characterized by a gradual reinforcement of the deflation power between 1970 and 1984 in correspondence of increasing desertification over the region. During this same period, Bilma, a well know region of dust source, experienced a major reduction in deflation power due to shifts in large scale wind patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70018697','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70018697"><span>Remote sensing of ephemeral water bodies in western Niger</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Verdin, J.P.</p> <p>1996-01-01</p> <p>Research was undertaken to evaluate the feasibility of monitoring the small ephemeral water bodies of the <span class="hlt">Sahel</span> with the 1.1 km resolution data of the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR). Twenty-one lakes of western Niger with good ground observation records were selected for examination. Thematic Mapper images from 1988 were first analysed to determine surface areas and temperature differences between water and adjacent land. Six AVHRR scenes from the 1988-89 dry season were then studied. It was found that a lake can be monitored until its surface area drops below 10 ha, in most cases. Furthermore, with prior knowledge of the location and shape of a water body, its surface area can be estimated from AVHRR band 5 data to within about 10 ha. These results are explained by the sharp temperature contrast between water and land, on the order of 13?? C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A41G2378K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A41G2378K"><span>Radiative effect of anthropogenic dust ageing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klingmueller, K.; Lelieveld, J.; Karydis, V.; Stenchikov, G. L.</p> <p>2017-12-01</p> <p>The chemical ageing of mineral dust mixing due to the uptake of air pollution affects the optical and hygroscopical properties of the dust particles and their atmospheric residence time. This results in an anthropogenic radiative forcing associated with mineral dust despite the natural origin of most dust particles. Using the atmospheric chemistry-climate model EMAC with a detailed parametrisation of chemical ageing and an emission scheme accounting for the chemical composition of desert soils, we study the direct radiative forcing globally and regionally. Preliminary results indicate large positive and negative forcings, depending on the region. The predominantly negative top of atmosphere forcing over large parts of the dust belt, from West Africa to East Asia, reaches about -2 W / m2 south of the <span class="hlt">Sahel</span>, in contrast to positive forcings over India and the western Atlantic. Globally averaged, these forcings partially counterbalance, resulting in a negative forcing of -0.04 to -0.05 W / m2, nevertheless representing a considerable fraction of the total dust forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70179623','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70179623"><span>Monitoring grasshopper and locust habitats in Sahelian Africa using GIS and remote sensing technology</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tappan, G. Gray; Moore, Donald G.; Knauseberger, Walter I.</p> <p>1991-01-01</p> <p>Development programmes in Sahelian Africa are beginning to use geographic information system (GIS) technology. One of the GIS and remote sensing programmes introduced to the region in the late 1980s was the use of seasonal vegetation maps made from satellite data to support grasshopper and locust control. Following serious outbreaks of these pests in 1987, the programme addressed a critical need, by national and international crop protection organizations, to monitor site-specific dynamic vegetation conditions associated with grasshopper and locust breeding. The primary products used in assessing vegetation conditions were vegetation index (greenness) image maps derived from National Oceanic and Atmospheric Administration satellite imagery. Vegetation index data were integrated in a GIS with digital cartographic data of individual Sahelian countries. These near-real-time image maps were used regularly in 10 countries for locating potential grasshopper and locust habitats. The programme to monitor vegetation conditions is currently being institutionalized in the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70022555','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70022555"><span>Global characteristics of stream flow seasonality and variability</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Dettinger, M.D.; Diaz, Henry F.</p> <p>2000-01-01</p> <p>Monthly stream flow series from 1345 sites around the world are used to characterize geographic differences in the seasonality and year-to-year variability of stream flow. Stream flow seasonality varies regionally, depending on the timing of maximum precipitation, evapotranspiration, and contributions from snow and ice. Lags between peaks of precipitation and stream flow vary smoothly from long delays in high-latitude and mountainous regions to short delays in the warmest sectors. Stream flow is most variable from year to year in dry regions of the southwest United States and Mexico, the <span class="hlt">Sahel</span>, and southern continents, and it varies more (relatively) than precipitation in the same regions. Tropical rivers have the steadiest flows. El Nin??o variations are correlated with stream flow in many parts of the Americas, Europe, and Australia. Many stream flow series from North America, Europe, and the Tropics reflect North Pacific climate, whereas series from the eastern United States, Europe, and tropical South America and Africa reflect North Atlantic climate variations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1008880','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1008880"><span>United States Counterterrorism Strategy In the Trans-Sahara and the Rise of Salafi-Jihadism In the <span class="hlt">Sahel</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2015-09-01</p> <p>157 “ Anti - Money Laundering /Counter Terrorist Financing ,” United States Department of State, May 10, 2015, http://www.state.gov/j/inl/c/crime...20the%20US%20Homeland.pdf. United States Department of State. “ Anti - Money Laundering /Counter Terrorist Financing ,” May 10, 2015. http://www.state.gov...state security, transnational criminal activity, and extremist financing demands regional collaboration, requiring these states to look past their</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120011801','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120011801"><span>Researching the Link Between Biomass Burning and Drought Across the Northern Sub-Saharan African Savanna/<span class="hlt">Sahel</span> Belt</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ichoku, Charles; Ellison, Luke</p> <p>2012-01-01</p> <p>The northern sub-Saharan African (NSSA) region, bounded by the Sahara, Equator, and the West and East African coastlines, is subjected to intense biomass burning every year during the dry season. This is believed to be one of the drivers of the regional carbon and energy cycles, with serious implications for the water cycle anomalies that probably contribute to drought and desertification. In this presentation, we will discuss a new multi-disciplinary research in the NSSA region, review progress, evaluate preliminary results, and interact with the research and user communities to examine how best to coordinate with other research activities in order to address related environmental issues most effectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.6666Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.6666Z"><span>Rain-induced emission pulses of NOx and HCHO from soils in African regions after dry spells as viewed by satellite sensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zörner, Jan; Penning de Vries, Marloes; Beirle, Steffen; Veres, Patrick; Williams, Jonathan; Wagner, Thomas</p> <p>2014-05-01</p> <p>Outside industrial areas, soil emissions of NOx (stemming from bacterial emissions of NO) represent a considerable fraction of total NOx emissions, and may even dominate in remote tropical and agricultural areas. NOx fluxes from soils are controlled by abiotic and microbiological processes which depend on ambient environmental conditions. Rain-induced spikes in NOx have been observed by in-situ measurements and also satellite observations. However, the estimation of soil emissions over broad geographic regions remains uncertain using bottom-up approaches. Independent, global satellite measurements can help constrain emissions used in chemical models. Laboratory experiments on soil fluxes suggest that significant HCHO emissions from soil can occur. However, it has not been previously attempted to detect HCHO emissions from wetted soils by using satellite observations. This study investigates the evolution of tropospheric NO2 (as a proxy for NOx) and HCHO column densities before and after the first rain fall event following a prolonged dry period in semi-arid regions, deserts as well as tropical regions in Africa. Tropospheric NO2 and HCHO columns retrieved from OMI aboard the AURA satellite, GOME-2 aboard METOP and SCIAMACHY aboard ENVISAT are used to study and inter-compare the observed responses of the trace gases with multiple space-based instruments. The observed responses are prone to be affected by other sources like lightning, fire, influx from polluted air masses, as well measurement errors in the satellite retrieval caused by manifold reasons such as an increased cloud contamination. Thus, much care is taken verify that the observed spikes reflect enhancements in soil emissions. Total column measurements of H2O from GOME-2 give further insight into the atmospheric state and help to explain the increase in humidity before the first precipitation event. The analysis is not only conducted for averages of distinct geographic regions, i.e. the <span class="hlt">Sahel</span>, but also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...43..575D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...43..575D"><span>Simulation of the West African monsoon onset using the HadGEM3-RA regional climate model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Diallo, Ismaïla; Bain, Caroline L.; Gaye, Amadou T.; Moufouma-Okia, Wilfran; Niang, Coumba; Dieng, Mame D. B.; Graham, Richard</p> <p>2014-08-01</p> <p>The performance of the Hadley Centre Global Environmental Model version 3 regional climate model (HadGEM3-RA) in simulating the West African monsoon (WAM) is investigated. We focus on performance for monsoon onset timing and for rainfall totals over the June-July-August (JJA) season and on the model's representation of the underlying dynamical processes. Experiments are driven by the ERA-Interim reanalysis and follow the CORDEX experimental protocol. Simulations with the HadGEM3 global model, which shares a common physical formulation with HadGEM3-RA, are used to gain insight into the causes of HadGEM3-RA simulation errors. It is found that HadGEM3-RA simulations of monsoon onset timing are realistic, with an error in mean onset date of two pentads. However, the model has a dry bias over the <span class="hlt">Sahel</span> during JJA of 15-20 %. Analysis suggests that this is related to errors in the positioning of the Saharan heat low, which is too far south in HadGEM3-RA and associated with an insufficient northward reach of the south-westerly low-level monsoon flow and weaker moisture convergence over the <span class="hlt">Sahel</span>. Despite these biases HadGEM3-RA's representation of the general rainfall distribution during the WAM appears superior to that of ERA-Interim when using Global Precipitation Climatology Project or Tropical Rain Measurement Mission data as reference. This suggests that the associated dynamical features seen in HadGEM3-RA can complement the physical picture available from ERA-Interim. This approach is supported by the fact that the global HadGEM3 model generates realistic simulations of the WAM without the benefit of pseudo-observational forcing at the lateral boundaries; suggesting that the physical formulation shared with HadGEM3-RA, is able to represent the driving processes. HadGEM3-RA simulations confirm previous findings that the main rainfall peak near 10°N during June-August is maintained by a region of mid-tropospheric ascent located, latitudinally, between the cores of</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.9504G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.9504G"><span>Instrumental evidence of an unusually strong West African Monsoon in the 19th century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, David; Ordoñez, Paulina; Ribera, Pedro; Peña-Ortiz, Cristina; Garcia-Herrera, Ricardo; Vega, Inmaculada; Gomez, Francisco de Paula</p> <p>2016-04-01</p> <p>The precipitation in the <span class="hlt">Sahel</span> -which is mainly controlled by the dynamics of the West African Monsoon-, has been in the spot of the climate community for the last three decades due to the persistence of the drought period that started in the 1970s. Unfortunately, reliable meteorological series in this area are only available since the beginning of the 20th Century, thus limiting our understanding of the significance of this period from a long term perspective. Currently, our knowledge of what happened in times previous to the 20th Century essentially relies in documentary or proxy sources. In this work, we present the first instrumental evidence of a 50 year-long period characterised by an unusually strong West African monsoon in the19th Century. Following the recent advances in the generation of climatic indices based on data from ship's logbooks, we used historical wind observations to compute a new index (the so-called ASWI) for characterising the strength of the West African Monsoon. The ASWI is based in the persistence of the southwesterly winds in the [29°W-17°W;7°N-13°N] area and it has been possible to compute it since 1790 for July and since 1839 for August and September. We show that the ASWI is a reliable measure of the monsoon's strength and the Sahelian rainfall. Our new series clearly shows the well-known drought period starting in the 1970s. During this dry period, the West African Monsoon was particularly weak and interestingly, we found that since then, the correlations with different climatic patterns such as the Pacific and Atlantic "El Niño" changed significantly in relation to those of the previous century. Remarkably, our results also show that the period 1839-1890 was characterised by an unusually strong and persistent monsoon. Notwithstanding, two of the few dry years within this period were concurrent with large volcanic eruptions in the Northern Hemisphere. This latter result supports the recently suggested relationship between major</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP23A2291G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP23A2291G"><span>On the Feasibility of Tracking the Monsoon History by Using Ancient Wind Direction Records</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallego, D.; Ribera, P.; Peña-Ortiz, C.; Vega, I.; Gómez, F. D. P.; Ordoñez-Perez, P.; Garcia-Hererra, R.</p> <p>2015-12-01</p> <p>In this work, we use old wind direction records to reconstruct indices for the West African Monsoon (WAM) and the Indian Summer Monsoon (ISM). Since centuries ago, ships departing from the naval European powers circumnavigated Africa in their route to the Far East. Most of these ships took high-quality observations preserved in logbooks. We show that wind direction observations taken aboard ships can be used to track the seasonal wind reversal typical of monsoonal circulations. The persistence of the SW winds in the 20W-17W and 7N-13N region is highly correlated with the WAM strength and <span class="hlt">Sahel</span>'s precipitation. It has been possible to build a WAM index back to the 19th Century. Our results show that in the <span class="hlt">Sahel</span>, the second half of the 19thCentury was significantly wetter than present day. The relation of the WAM with the ENSO cycle, and the Atlantic Multidecadal Oscillation was low and instable from the 1840s to the 1970s, when they abruptly suffered an unprecedented reinforcement which last up to the present day. The persistence of the SSW wind in the 60E-80E and 8N-12N area has been used to track the ISM onset since the 1880s. We found evidences of later than average onset dates during the 1900-1925 and 1970-1990 periods and earlier than average onset between 1940 and 1965. A significant relation between the ISM onset and the PDO restricted to shifts from negative to positive PDO phases has been found. The most significant contribution of our study is the fact that we have shown that it is possible to build consistent monsoon indices of instrumental character using solely direct observations of wind direction. Our indices have been generated by using data currently available in the ICOADS 2.5 database, but a large amount of wind observations for periods previous to the 20thcentury still remain not explored in thousands of logbooks preserved in British archives. The interest of unveil these data to track the monsoons for more than 200 -or even 300 years- it is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15..705G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15..705G"><span>Inter-annual variability of aerosol optical depth over the tropical Atlantic Ocean based on MODIS-Aqua observations over the period 2002-2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gkikas, Antonis; Hatzianastassiou, Nikolaos</p> <p>2013-04-01</p> <p>The tropical Atlantic Ocean is affected by dust and biomass burning aerosol loads transported from the western parts of the Saharan desert and the sub-<span class="hlt">Sahel</span> regions, respectively. The spatial and temporal patterns of this transport are determined by the aerosol emission rates, their deposition (wet and dry), by the latitudinal shift of the Intertropical Convergence Zone (ITCZ) and the prevailing wind fields. More specifically, in summer, Saharan dust aerosols are transported towards the Atlantic Ocean, even reaching the Gulf of Mexico, while in winter the Atlantic Ocean transport takes place in more southern latitudes, near the equator, sometimes reaching the northern parts of South America. In the later case, dust is mixed with biomass burning aerosols originating from agricultural activities in the sub-<span class="hlt">Sahel</span>, associated with prevailing north-easterly airflow (Harmattan winds). Satellite observations are the appropriate tool for describing this African aerosol export, which is important to atmospheric, oceanic and climate processes, offering the advantage of complete spatial coverage. In the present study, we use satellite measurements of aerosol optical depth at 550nm (AOD550nm), on a daily and monthly basis, derived from MODIS-Aqua platform, at 1ox1o spatial resolution (Level 3), for the period 2002-2012. The primary objective is to determine the pixel-level and regional mean anomalies of AOD550nm over the entire study period. The regime of the anomalies of African export is interpreted in relation to the aerosol source areas, precipitation, wind patterns and temporal variability of the North Atlantic Oscillation Index (NAOI). In order to ensure availability of AOD over the Sahara desert, MODIS-Aqua Deep Blue products are also used. As for precipitation, Global Precipitation Climatology Project (GPCP) data at 2.5ox2.5o are used. The wind fields are taken from the National Center for Environmental Prediction (NCEP). Apart from the regime of African aerosol export</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613169E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613169E"><span>Evaluation of reanalysis near-surface winds over northern Africa in Boreal summer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Engelstaedter, Sebastian; Washington, Richard</p> <p>2014-05-01</p> <p>The emission of dust from desert surfaces depends on the combined effects of surface properties such as surface roughness, soil moisture, soil texture and particle size (erodibility) and wind speed (erosivity). In order for dust cycle models to realistically simulate dust emissions for the right reasons, it is essential that erosivity and erodibility controlling factors are represented correctly. There has been a focus on improving dust emission schemes or input fields of soil distribution and texture even though it has been shown that the use of wind fields from different reanalysis datasets to drive the same model can result in significant differences in the dust emissions. Here we evaluate the representation of near-surface wind speed from three different reanalysis datasets (ERA-Interim, CFSR and MERRA) over the North African domain. Reanalysis 10m wind speeds are compared with observations from SYNOP and METAR reports available from the UK Meteorological Office Integrated Data Archive System (MIDAS) Land and Marine Surface Stations Dataset. We compare 6-hourly observations of 10m wind speed between 1 January 1989 and 31 December 2009 from more the 500 surface stations with the corresponding reanalysis values. A station data based mean wind speed climatology for North Africa is presented. Overall, the representation of 10m winds is relatively poor in all three reanalysis datasets with stations in the northern parts of the Sahara still being better simulated (correlation coefficients ~ 0.5) than stations in the <span class="hlt">Sahel</span> (correlation coefficients < 0.3) which points at the reanalyses not being able to realistically capture the <span class="hlt">Sahel</span> dynamics systems. All three reanalyses have a systematic bias towards overestimating wind speed below 3-4 m/s and underestimating wind speed above 4 m/s. This bias becomes larger with increasing wind speed but is independent of the time of day. For instance, 14 m/s observed wind speeds are underestimated on average by 6 m/s in the ERA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999ClDy...15..451F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999ClDy...15..451F"><span>Coupled ocean-atmosphere surface variability and its climate impacts in the tropical Atlantic region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fontaine, B.; Janicot, Serge; Roucou, P.</p> <p></p> <p> processes at the ocean/atmosphere interface that create anomaly gradients in the meridional plane in a way which tends to alter the north-south movement of the seasonal cycle. This appears to be consistent with the intrinsic non-dipole character of the tropical Atlantic surface variability at the interannual time step and over the recent period, but produces abnormal amplitude and/or delayed excursions of the intertropical convergence zone (ITCZ). Connections with continental rainfall are approached through three (NCEP/NCAR and observed) rainfall indexes over the Nordeste region in Brazil, and the Guinea and <span class="hlt">Sahel</span> zones in West Africa. These indices appear to be significantly linked to the SST component of the coupled modes only when the two Atlantic modes+the ENSO-like Nino3 index are taken into account in the regressions. This suggests that thermal forcing of continental rainfall is particularly sensitive to the linear combinations of some basic SST patterns, in particular to those that create meridional thermal gradients. The first mode in the Atlantic is associated with transequatorial pressure, moist static energy and precipitable water anomaly patterns which can explain abnormal location of the ITCZ particularly in northern winter, and hence rainfall variations in Nordeste. The second mode is more associated with in-phase variations of the same variables near the southern edge of the ITCZ, particularly in the Gulf of Guinea during the northern spring and winter. It is primarily linked to the amplitude and annual phase of the ITCZ excursions and thus to rainfall variations in Guinea. Connections with <span class="hlt">Sahel</span> rainfall are less clear due to the difficulty for the model to correctly capture interannual variability over that region but the second Atlantic mode and the ENSO-like Pacific variability are clearly involved in the <span class="hlt">Sahel</span> climate interannual fluctuations: anomalous dry (wet) situations tend to occur when warmer (cooler) waters are present in the eastern Pacific and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17135022','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17135022"><span>Coping strategies and nutritional health in rural Niger: recommendations for consumption of wild plant foods in the <span class="hlt">Sahel</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Glew, Robert S; Vanderjagt, Dorothy</p> <p>2006-01-01</p> <p>People who live in food and water deficit regions of Sahelien West Africa employ various coping strategies as they attempt to meet their food and water needs. In this paper we discuss various coping strategies employed by rural Nigeriens living in the Tanout and Mirriya administrative regions of central Niger. In rural Niger people often harvest or buy wild plant foods to eat. Laboratory studies of the nutritional content of these plants indicate that there are benefits to eating wild plant foods. In this study we summarize the results of field research conducted during the summer of 2002 on the use of wild plant foods in three regions of rural central Niger. Comparing local use of various wild plant foods with major nutrition-related health problems including protein deficiency, essential fatty acid deficiency, iron deficiency and iron deficiency anemia, calcium deficiency rickets, and zinc deficiency, suggests potential recommendations for consumption of these plants. However, further research on the bioavailability of these nutrients is needed to confirm the potential benefits of these plants.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19960395','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19960395"><span>Seasonality of childhood infectious diseases in Niono, Mali.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Findley, S E; Medina, D C; Sogoba, N; Guindo, B; Doumbia, S</p> <p>2010-01-01</p> <p>Common childhood diseases vary seasonally in Mali, much of the <span class="hlt">Sahel</span>, and other parts of the world, yet patterns for multiple diseases have rarely been simultaneously described for extended periods at single locations. In this retrospective longitudinal (1996-2004) investigation, we studied the seasonality of malaria, acute respiratory infection and diarrhoea time-series in the district of Niono, Sahelian Mali. We extracted and analysed seasonal patterns from each time-series with the Multiplicative Holt-Winters and Wavelet Transform methods. Subsequently, we considered hypothetical scenarios where successful prevention and intervention measures reduced disease seasonality by 25 or 50% to assess the impact of health programmes on annual childhood morbidity. The results showed that all three disease time-series displayed remarkable seasonal stability. Malaria, acute respiratory infection and diarrhoea peaked in December, March (and September) and August, respectively. Finally, the annual childhood morbidity stemming from each disease diminished 7-26% in the considered hypothetical scenarios. We concluded that seasonality may assist with guiding the development of integrated seasonal disease calendars for programmatic child health promotion activities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811985P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811985P"><span>Validation of the regional climate model MAR over the CORDEX Africa domain and comparison with other regional models using unpublished data set</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prignon, Maxime; Agosta, Cécile; Kittel, Christoph; Fettweis, Xavier; Michel, Erpicum</p> <p>2016-04-01</p> <p>In the framework of the CORDEX project, we have applied the regional model MAR over the Africa domain at a resolution of 50 km. ERA-Interim and NCEP-NCAR reanalysis have been used as 6 hourly forcing at the MAR boundaries over 1950-2015. While MAR was already been validated over the West Africa, it is the first time that MAR simulations are carried out at the scale of the whole continent. Unpublished daily measurements, covering the <span class="hlt">Sahel</span> and more areas up South, with a large set of variables, are used as validation of MAR, other CORDEX-Africa RCMs and both reanalyses. Comparisons with the CRU and the ECA&D databases are also performed. The unpublished daily data set covers the period 1884-2006 and comes from 1460 stations. The measured variables are wind, evapotranspiration, relative humidity, insolation, rain, surface pressure, temperature, vapour pressure and visibility. It covers 23 countries: Algeria, Benin, Burkina, Canary Islands, Cap Verde, Central Africa, Chad, Congo, Ivory Coast, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Mali, Mauritania, Morocco, Niger, Nigeria, Senegal, Sudan and Togo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22883918','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22883918"><span>Global warming and reproductive health.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Potts, Malcolm; Henderson, Courtney E</p> <p>2012-10-01</p> <p>The largest absolute numbers of maternal deaths occur among the 40-50 million women who deliver annually without a skilled birth attendant. Most of these deaths occur in countries with a total fertility rate of greater than 4. The combination of global warming and rapid population growth in the <span class="hlt">Sahel</span> and parts of the Middle East poses a serious threat to reproductive health and to food security. Poverty, lack of resources, and rapid population growth make it unlikely that most women in these countries will have access to skilled birth attendants or emergency obstetric care in the foreseeable future. Three strategies can be implemented to improve women's health and reproductive rights in high-fertility, low-resource settings: (1) make family planning accessible and remove non-evidenced-based barriers to contraception; (2) scale up community distribution of misoprostol for prevention of postpartum hemorrhage and, where it is legal, for medical abortion; and (3) eliminate child marriage and invest in girls and young women, thereby reducing early childbearing. Copyright © 2012 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70043239','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70043239"><span>Climatic trends over Ethiopia: regional signals and drivers</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jury, Mark R.; Funk, Christopher C.</p> <p>2013-01-01</p> <p>This study analyses observed and projected climatic trends over Ethiopia, through analysis of temperature and rainfall records and related meteorological fields. The observed datasets include gridded station records and reanalysis products; while projected trends are analysed from coupled model simulations drawn from the IPCC 4th Assessment. Upward trends in air temperature of + 0.03 °C year−1 and downward trends in rainfall of − 0.4 mm month−1 year−1 have been observed over Ethiopia's southwestern region in the period 1948-2006. These trends are projected to continue to 2050 according to the Geophysical Fluid Dynamics Lab model using the A1B scenario. Large scale forcing derives from the West Indian Ocean where significant warming and increased rainfall are found. Anticyclonic circulations have strengthened over northern and southern Africa, limiting moisture transport from the Gulf of Guinea and Congo. Changes in the regional Walker and Hadley circulations modulate the observed and projected climatic trends. Comparing past and future patterns, the key features spread westward from Ethiopia across the <span class="hlt">Sahel</span> and serve as an early warning of potential impacts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070010448&hterms=pollution+climate+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpollution%2Bclimate%2Bchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070010448&hterms=pollution+climate+change&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpollution%2Bclimate%2Bchange"><span>Regional and Global Aspects of Aerosols in Western Africa: From Air Quality to Climate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chin, Mian; Diehl, Thomas; Kucsera, Tom; Spinhime, Jim; Palm, Stephen; Holben, Brent; Ginoux, Paul</p> <p>2006-01-01</p> <p>Western Africa is one of the most important aerosol source regions in the world. Major aerosol sources include dust from the world's largest desert Sahara, biomass burning from the <span class="hlt">Sahel</span>, pollution aerosols from local sources and long-range transport from Europe, and biogenic sources from vegetation. Because these sources have large seasonal variations, the aerosol composition over the western Africa changes significantly with time. These aerosols exert large influences on local air quality and regional climate. In this study, we use the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model to analyze satellite lidar data from the GLAS instrument on the ICESat and the sunphotometer data from the ground-based network AERONET taken in both the wet (September - October 2003) and dry (February - March 2004) seasons over western Africa. We will quantify the seasonal variations of aerosol sources and compositions and aerosol spatial (horizontal and vertical) distributions over western Africa. We will also assess the climate impact of western African aerosols. Such studies will be applied to support the international project, Africa Monsoon Multidisciplinary Analysis (AMMA) and to analyze the AMMA data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=118073','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=118073"><span>Dracunculiasis (Guinea Worm Disease) and the Eradication Initiative</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cairncross, Sandy; Muller, Ralph; Zagaria, Nevio</p> <p>2002-01-01</p> <p>Dracunculiasis, also known as guinea worm disease, is caused by the large female of the nematode Dracunculus medinensis, which emerges painfully and slowly from the skin, usually on the lower limbs. The disease can infect animals, and sustainable animal cycles occur in North America and Central Asia but do not act as reservoirs of human infection. The disease is endemic across the <span class="hlt">Sahel</span> belt of Africa from Mauritania to Ethiopia, having been eliminated from Asia and some African countries. It has a significant socioeconomic impact because of the temporary disability that it causes. Dracunculiasis is exclusively caught from drinking water, usually from ponds. A campaign to eradicate the disease was launched in the 1980s and has made significant progress. The strategy of the campaign is discussed, including water supply, health education, case management, and vector control. Current issues including the integration of the campaign into primary health care and the mapping of cases by using geographic information systems are also considered. Finally, some lessons for other disease control and eradication programs are outlined. PMID:11932231</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9775039','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9775039"><span>[Scapulo-thoracic mycetoma. A rare localization, a particular form].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sy, M H; Diouf, S; Ndiaye, A; Dansokho, A V; Ndiaye, P D; Diop, C A; Sèye, S I</p> <p>1998-07-01</p> <p>An uncommon form and a rare localization of mycetoma is reported. The aim of this report was to distinguish this inhabitual form of mycetoma from some tropical diseases like onchocerca and other fungal diseases. A 55 year old man was admitted 10 years after a septic worm-hole for a scapulo-thoracic tumor. This encapsulated mass was a bending and rounded polyfistular one attached to the dorsal aspect of left shoulder. The fistula discharge a serosanguineous or purulent exudate. The characteristic red granule was not visible. The tumor was removed and histological examination was performed. A typical granuloma of red granule of streptomyces pelletieri was found. A good result was obtained with associated cotrimoxazole treatment. Scapulo-thoracic form included: scapular, axillary and chest form of mycetoma. All these localizations are rare. One of them can be complicated by osteitis or pleuro-pulmonary localization. Streptomyces pellitieri is the actinomycetic causal agent. This encapsulated form is uncommon. Scapulo-thoracic mycetoma is rare. Encapsulated and pedicular form is uncommon. Around <span class="hlt">Sahel</span> areas, differential diagnosis must be evoked such as parasitic and mycobacterial infections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70043133','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70043133"><span>Vegetation impoverishment despite greening: a case study from central Senegal</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Herrmann, Stefanie M.; Tappan, G. Gray</p> <p>2013-01-01</p> <p>Recent remote sensing studies have documented a greening trend in the semi-arid <span class="hlt">Sahel</span> and Sudan zones of West Africa since the early 1980s, which challenges the mainstream paradigm of irreversible land degradation in this region. What the greening trend means on the ground, however, has not yet been explored. This research focuses on a region in central Senegal to examine changes in woody vegetation abundance and composition in selected sites by means of a botanical inventory of woody vegetation species, repeat photography, and perceptions of local land users. Despite the greening, an impoverishment of the woody vegetation cover was observed in the studied sites, indicated by an overall reduction in woody species richness, a loss of large trees, an increasing dominance of shrubs, and a shift towards more arid-tolerant, Sahelian species since 1983. Thus, interpretation of the satellite-derived greening trend as an improvement or recovery is not always justified. The case of central Senegal represents only one of several possible pathways of greening throughout the region, all of which result in similar satellite-derived greening signals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880011388','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880011388"><span>Summary of along-track data from the Earth radiation budget satellite for several major desert regions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brooks, David R.; Fenn, Marta A.</p> <p>1988-01-01</p> <p>For several days in January and August 1985, the Earth Radiation Budget Satellite, a component of the Earth Radiation Budget Experiment (ERBE), was operated in an along-track scanning mode. A survey of radiance measurements is given for four desert areas in Africa, the Arabian Peninsula, Australia, and the <span class="hlt">Sahel</span> region of Africa. Each overflight provides radiance information for four scene categories: clear, partly cloudy, mostly cloudy, and overcast. The data presented include the variation of radiance in each scene classification as a function of viewing zenith angle during each overflight of the five target areas. Several features of interest in the development of anisotropic models are evident, including day-night differences in longwave limb darkening and the azimuthal dependence of short wave radiance. There is some evidence that surface features may introduce thermal or visible shadowing that is not incorporated in the usual descriptions of the anisotropic behavior of radiance as viewed from space. The data also demonstrate that the ERBE scene classification algorithms give results that, at least for desert surfaces, are a function of viewing geometry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/unnumbered/70159090/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/unnumbered/70159090/report.pdf"><span>Cattle and cultivators: A study of competition over natural resources in north Senegal</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Freudenberger, Karen Schoonmaker; Wood, Eric</p> <p>1998-01-01</p> <p>This study presents an analysis of the interaction of humans and their environment in the arid <span class="hlt">Sahel</span> ian zone of northern Senegal. It compares a pastoral community which lives primarily from the production of livestock and a farming community whose activities have traditionally centered on crop production. Living side by side but following different strategies for securing their livelihoods, these groups find themselves in increasing conflict over how the diminishing resources of the area should be used. The pastoral livelihood system, as practiced in the case study community of Maka Ndandary, is essentially conservationist in its approach to natural resources. It regulates the activities of community members toward the environment and employs diverse strategies to protect local resources against incursion by outsiders. The agricultural village, represented by the case study of Teud Bitty, takes a much more extractive approach to its resources. As resources have diminished over time, the villagers have become even more aggressive in their attempts to exploit what remains, whether soils or trees ... both within and outside their territory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3384989','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3384989"><span>Famines in Africa: is early warning early enough?</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Jeeyon Janet; Guha-Sapir, Debarati</p> <p>2012-01-01</p> <p>Following the second Sahelian famine in 1984–1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the <span class="hlt">Sahel</span>, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response. PMID:22745628</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22745628','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22745628"><span>Famines in Africa: is early warning early enough?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Jeeyon Janet; Guha-Sapir, Debarati</p> <p>2012-01-01</p> <p>Following the second Sahelian famine in 1984-1985, major investments were made to establish Early Warning Systems. These systems help to ensure that timely warnings and vulnerability information are available to decision makers to anticipate and avert food crises. In the recent crisis in the Horn of Africa, alarming levels of acute malnutrition were documented from March 2010, and by August 2010, an impending food crisis was forecast. Despite these measures, the situation remained unrecognised, and further deteriorated causing malnutrition levels to grow in severity and scope. By the time the United Nations officially declared famine on 20 July 2011, and the humanitarian community sluggishly went into response mode, levels of malnutrition and mortality exceeded catastrophic levels. At this time, an estimated 11 million people were in desperate and immediate need for food. With warnings of food crises in the <span class="hlt">Sahel</span>, South Sudan, and forecast of the drought returning to the Horn, there is an immediate need to institutionalize change in the health response during humanitarian emergencies. Early warning systems are only effective if they trigger an early response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.A71E..05B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.A71E..05B"><span>Forecasting Dust Storms Using the CARMA-Dust Model and MM5 Weather Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnum, B. H.; Winstead, N. S.; Wesely, J.; Hakola, A.; Colarco, P.; Toon, O. B.; Ginoux, P.; Brooks, G.; Hasselbarth, L. M.; Toth, B.; Sterner, R.</p> <p>2002-12-01</p> <p>An operational model for the forecast of dust storms in Northern Africa, the Middle East and Southwest Asia has been developed for the United States Air Force Weather Agency (AFWA). The dust forecast model uses the 5th generation Penn State Mesoscale Meteorology Model (MM5), and a modified version of the Colorado Aerosol and Radiation Model for Atmospheres (CARMA). AFWA conducted a 60 day evaluation of the dust model to look at the model's ability to forecast dust storms for short, medium and long range (72 hour) forecast periods. The study used satellite and ground observations of dust storms to verify the model's effectiveness. Each of the main mesoscale forecast theaters was broken down into smaller sub-regions for detailed analysis. The study found the forecast model was able to forecast dust storms in Saharan Africa and the <span class="hlt">Sahel</span> region with an average Probability of Detection (POD)exceeding 68%, with a 16% False Alarm Rate (FAR). The Southwest Asian theater had average POD's of 61% with FAR's averaging 10%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ESSD...10..815H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ESSD...10..815H"><span>The WASCAL high-resolution regional climate simulation ensemble for West Africa: concept, dissemination and assessment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heinzeller, Dominikus; Dieng, Diarra; Smiatek, Gerhard; Olusegun, Christiana; Klein, Cornelia; Hamann, Ilse; Salack, Seyni; Bliefernicht, Jan; Kunstmann, Harald</p> <p>2018-04-01</p> <p>Climate change and constant population growth pose severe challenges to 21st century rural Africa. Within the framework of the West African Science Service Center on Climate Change and Adapted Land Use (WASCAL), an ensemble of high-resolution regional climate change scenarios for the greater West African region is provided to support the development of effective adaptation and mitigation measures. This contribution presents the overall concept of the WASCAL regional climate simulations, as well as detailed information on the experimental design, and provides information on the format and dissemination of the available data. All data are made available to the public at the CERA long-term archive of the German Climate Computing Center (DKRZ) with a subset available at the PANGAEA Data Publisher for Earth & Environmental Science portal (<a href="https://doi.pangaea.de/10.1594/PANGAEA.880512" target="_blank">https://doi.pangaea.de/10.1594/PANGAEA.880512</a>). A brief assessment of the data are presented to provide guidance for future users. Regional climate projections are generated at high (12 km) and intermediate (60 km) resolution using the Weather Research and Forecasting Model (WRF). The simulations cover the validation period 1980-2010 and the two future periods 2020-2050 and 2070-2100. A brief comparison to observations and two climate change scenarios from the Coordinated Regional Downscaling Experiment (CORDEX) initiative is presented to provide guidance on the data set to future users and to assess their climate change signal. Under the RCP4.5 (Representative Concentration Pathway 4.5) scenario, the results suggest an increase in temperature by 1.5 °C at the coast of Guinea and by up to 3 °C in the northern <span class="hlt">Sahel</span> by the end of the 21st century, in line with existing climate projections for the region. They also project an increase in precipitation by up to 300 mm per year along the coast of Guinea, by up to 150 mm per year in the Soudano region adjacent</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..884F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..884F"><span>Coupled hydrologic and hydraulic modeling of Upper Niger River Basin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fleischmann, Ayan; Siqueira, Vinícius; Paris, Adrien; Collischonn, Walter; Paiva, Rodrigo; Gossett, Marielle; Pontes, Paulo; Calmant, Stephane; Biancamaria, Sylvain; Crétaux, Jean-François; Tanimoune, Bachir</p> <p>2017-04-01</p> <p>The Upper Niger Basin is located in Western Africa, flowing from Guinea Highlands towards the <span class="hlt">Sahel</span> region. In this area lies the seasonally inundated Niger Inland Delta, which supports important environmental services such as habitats for wildlife, climate and flood regulation, as well as large fishery and agricultural areas. In this study, we present the application of MGB-IPH large scale hydrologic and hydrodynamic model for the Upper Niger Basin, totaling c.a. 650,000 km2 and set up until the city of Niamey in Niger. The model couples hydrological vertical balance and runoff generation with hydrodynamic flood wave propagation, by allowing infiltration from floodplains into soil column as well as representing backwater effects and floodplain storage throughout flat areas such as the Inland Delta. The model is forced with TRMM 3B42 daily precipitation and Climate Research Unit (CRU) climatology for the period 2000-2010, and was calibrated against in-situ discharge gauges and validated with in-situ water level, remotely sensed estimations of flooded areas (classification of MODIS imagery) and satellite altimetry (JASON-2 mission). Model results show good predictions for calibrated daily discharge and validated water level and altimetry at stations both upstream and downstream of the delta (Nash-Sutcliffe Efficiency>0.7 for all stations), as well as for flooded areas within the delta region (ENS=0.5; r2=0.8), allowing a good representation of flooding dynamics basinwide and simulation of flooding behavior of both perennial (e.g., Niger main stem) and ephemeral rivers (e.g., Niger Red Flood tributaries in <span class="hlt">Sahel</span>). Coupling between hydrology and hydrodynamic processes indicates an important feedback between floodplain and soil water storage that allows high evapotranspiration rates even after the flood passage around the inner delta area. Also, representation of water retention in floodplain channels and distributaries in the inner delta (e.g., Diaka river</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9496B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9496B"><span>Sahelian springtime heat waves and their evolution over the past 60 years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barbier, Jessica; Guichard, Françoise; Bouniol, Dominique; Couvreux, Fleur; Roehrig, Romain</p> <p>2017-04-01</p> <p>The <span class="hlt">Sahel</span> is a semi-arid region which experiences very high temperature both during day- and night-times: monthly-mean temperatures in Spring typically oscillate between 30 and 40°C. At the same time a strong climatic warming has been observed over the past 60 years in this region: it reaches +1,5°C over April-May. Thus heat waves in this region have severe impacts on health, ecosystem, agriculture and more broadly economical activities, which will probably worsen in the context of climate change. However, heat waves in the <span class="hlt">Sahel</span> remain poorly studied. The present work documents Sahelian heat waves and assesses their evolution across the last 60 years. Properties of heat waves are sensitive to the way they are detected. Here, we use a methodology based on anomalies that allows to filter the seasonal, inter-annual and climatic evolutions, using a percentile-type threshold. It is applied separately to daily maximum and minimum temperatures and leads to two types of heat waves: day- and night-time ones. This separation matters because physical processes linked to minimum and maximum temperatures can be quite distinct. The changes in both types of heat wave were studied over the period 1950-2012 using the Berkeley Earth Surface Temperature gridded product: several heat wave characteristics were investigated, including morphological ones such as the length and the spatial extent of the event, the heat wave intensity and the associated warming trends. We found no significant trends in the frequency, duration and spatial extent of both types of heat waves, while on the other hand their maximum and minimum temperatures displayed significant positive trends. They were mainly explained by the regional warming. By contrast, with a standard climatic heat index using percentile-threshold on raw temperatures, both day- and night-time heat wave frequencies were increasing, and while the day-time heat waves were getting longer and larger, the night-time heat waves were getting</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7089P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7089P"><span>The impact of convection in the West African monsoon region on global weather forecasts - explicit vs. parameterised convection simulations using the ICON model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pante, Gregor; Knippertz, Peter</p> <p>2017-04-01</p> <p>The West African monsoon is the driving element of weather and climate during summer in the <span class="hlt">Sahel</span> region. It interacts with mesoscale convective systems (MCSs) and the African easterly jet and African easterly waves. Poor representation of convection in numerical models, particularly its organisation on the mesoscale, can result in unrealistic forecasts of the monsoon dynamics. Arguably, the parameterisation of convection is one of the main deficiencies in models over this region. Overall, this has negative impacts on forecasts over West Africa itself but may also affect remote regions, as waves originating from convective heating are badly represented. Here we investigate those remote forecast impacts based on daily initialised 10-day forecasts for July 2016 using the ICON model. One set of simulations employs the default setup of the global model with a horizontal grid spacing of 13 km. It is compared with simulations using the 2-way nesting capability of ICON. A second model domain over West Africa (the nest) with 6.5 km grid spacing is sufficient to explicitly resolve MCSs in this region. In the 2-way nested simulations, the prognostic variables of the global model are influenced by the results of the nest through relaxation. The nest with explicit convection is able to reproduce single MCSs much more realistically compared to the stand-alone global simulation with parameterised convection. Explicit convection leads to cooler temperatures in the lower troposphere (below 500 hPa) over the northern <span class="hlt">Sahel</span> due to stronger evaporational cooling. Overall, the feedback of dynamic variables from the nest to the global model shows clear positive effects when evaluating the output of the global domain of the 2-way nesting simulation and the output of the stand-alone global model with ERA-Interim re-analyses. Averaged over the 2-way nested region, bias and root mean squared error (RMSE) of temperature, geopotential, wind and relative humidity are significantly reduced in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JHyd..375...78S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JHyd..375...78S"><span>Relationships between climate, soil moisture and phenology of the woody cover in two sites located along the West African latitudinal gradient</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seghieri, Josiane; Vescovo, Aude; Padel, Karine; Soubie, Remy; Arjounin, Marc; Boulain, Nicolas; de Rosnay, Patricia; Galle, Sylvie; Gosset, Marielle; Mouctar, Abakar H.; Peugeot, Christophe; Timouk, Franck</p> <p>2009-08-01</p> <p>SummaryThe study quantifies the relationships at local scale between phenology and determinants of climate and soil water resources at two sites located along the latitudinal gradient of West Africa, one in the central <span class="hlt">Sahel</span> (Mali), the other in the Sudanian bioclimatic zone (Benin). The aim is to improve our knowledge on possible vegetation response to possible climate change. Within the Sudanian site, average annual rainfall is 1200 mm, extending from April to October, while, in the Sahelian site, it is 370 mm, occurring from June to September. Physical data were collected from the African Monsoon Multidisciplinary Analysis research programme. The phenology of the dominant species was monitored in four types of vegetation cover at the wetter site, and in three types of vegetation cover at the drier site. For each sampled plant, leafing, flowering and fruiting were recorded as binary variables in terms of the presence/absence of phenophases. A small proportion of the variability of each phenophase occurrence is explained by the logit models. However, rainfall rise is significantly linked to leafing probability increase in the Sahelian site but not in the Sudanian site. Day length extension and temperature decrease are significantly correlated with an increase in leafing in the Sudanian site, but not in the Sahelian. On both sites, the increase in cumulative rainfall is not found to be linked to an increased probability of reproductive phenophases (negative or non-significant relationships). Air temperature is positively correlated with flowering rate in the Sudanian site, but, all other factors being constant, no climate factors are found to be highly significant of flowering occurrence in the <span class="hlt">Sahel</span>. Fruiting probability is positively correlated mainly with temperature within the Sahelian site. Leafing occurrence is positively correlated with soil moisture in the 0-1 m layer for the Sudanian site, but not for the Sahelian site. Significant relationships between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.6315G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.6315G"><span>Crop yield monitoring in the <span class="hlt">Sahel</span> using root zone soil moisture anomalies derived from SMOS soil moisture data assimilation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gibon, François; Pellarin, Thierry; Alhassane, Agali; Traoré, Seydou; Baron, Christian</p> <p>2017-04-01</p> <p>West Africa is greatly vulnerable, especially in terms of food sustainability. Mainly based on rainfed agriculture, the high variability of the rainy season strongly impacts the crop production driven by the soil water availability in the soil. To monitor this water availability, classical methods are based on daily precipitation measurements. However, the raingauge network suffers from the poor network density in Africa (1/10000km2). Alternatively, real-time satellite-derived precipitations can be used, but they are known to suffer from large uncertainties which produce significant error on crop yield estimations. The present study proposes to use root soil moisture rather than precipitation to evaluate crop yield variations. First, a local analysis of the spatiotemporal impact of water deficit on millet crop production in Niger was done, from in-situ soil moisture measurements (AMMA-CATCH/OZCAR (French Critical Zone exploration network)) and in-situ millet yield survey. Crop yield measurements were obtained for 10 villages located in the Niamey region from 2005 to 2012. The mean production (over 8 years) is 690 kg/ha, and ranges from 381 to 872 kg/ha during this period. Various statistical relationships based on soil moisture estimates were tested, and the most promising one (R>0.9) linked the 30-cm soil moisture anomalies from mid-August to mid-September (grain filling period) to the crop yield anomalies. Based on this local study, it was proposed to derive regional statistical relationships using 30-cm soil moisture maps over West Africa. The selected approach was to use a simple hydrological model, the Antecedent Precipitation Index (API), forced by real-time satellite-based precipitation (CMORPH, PERSIANN, TRMM3B42). To reduce uncertainties related to the quality of real-time rainfall satellite products, SMOS soil moisture measurements were assimilated into the API model through a Particular Filter algorithm. Then, obtained soil moisture anomalies were compared to 17 years of crop yield estimates from the FAOSTAT database (1998-2014). Results showed that the 30-cm soil moisture anomalies explained 89% of the crop yield variation in Niger, 72% in Burkina Faso, 82% in Mali and 84% in Senegal.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27917976','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27917976"><span>Institutional development and policy frameworks for pastoralism: from local to regional perspectives.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bonfoh, B; Fokou, G; Crump, L; Zinsstag, J; Schelling, E</p> <p>2016-11-01</p> <p>Pastoralists are among the most politically and economically marginalised communities in the world. They have less and less access to the natural resources on which their livelihoods depend and very limited access to basic socio-economic services and infrastructure. This paper builds on a number of studies carried out in the <span class="hlt">Sahel</span>, the Horn of Africa, Central Asia and the Swiss Alps to address the institutional dynamics required for sustainable pastoralism. Specifically, the authors question the way in which institutions and policies are currently shaped and suggest that reforming these could contribute to new avenues for pastoralism. Among the main drivers of pastoralist marginalisation are poor public and private institutional arrangements. The consequences are violent conflict and increased mobility and relocation. Responses to the current weaknesses of pastoralism must encompass inclusive, comprehensive institutions which allow access to resources, economic viability and integration in the new socio-ecological space. The authors argue that those involved in pastoral development in national as well as international arenas, including pastoralist groups, states and agencies, are creatively engaged in a process of innovation for pastoralism, and this will contribute towards new forms of governance and improved institutional and policy frameworks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986JApMe..25..903D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986JApMe..25..903D"><span>A Model for Saharan Dust Transport.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>D'Almeida, Guillaume A.</p> <p>1986-07-01</p> <p>In this paper the source strength and the deposition rate of the dust emerging from the Sahara are assessed. For this purpose a multichannel sunphotometer has been developed and a turbidity network covering 11 stations has been set up in the Sahara, in the <span class="hlt">Sahel</span> region and the surrounding southern area for a duration of about two years. A correlation analysis connecting observed aerosol turbidity parameters and mineral dust mass concentration has been performed during a four-week field campaign in Agadez (Niger). An appropriate box model including the aerosol turbidity parameters, actual wind field data of the source regions, the general circulation pattern over Africa and dry and wet deposition reveals a total mass production of about 630 × 106 and 710 × 106 t yr1 for all suspended particulate matter, 80 × 106 and 90 × 106 t yr1 for aerosol particles smaller than 5 m radius for the years 1981 and 1982 respectively. About 60% of the mass moves southward to the Gulf of Guinea, 28% westward to the equatorial North Atlantic Ocean and 12% northward to Europe. A considerable part is deposited in the Atlantic Ocean and the Mediterranean forming deep-sea sediments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22190490','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22190490"><span>Mid-latitude afforestation shifts general circulation and tropical precipitation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Swann, Abigail L S; Fung, Inez Y; Chiang, John C H</p> <p>2012-01-17</p> <p>We show in climate model experiments that large-scale afforestation in northern mid-latitudes warms the Northern Hemisphere and alters global circulation patterns. An expansion of dark forests increases the absorption of solar energy and increases surface temperature, particularly in regions where the land surface is unable to compensate with latent heat flux due to water limitation. Atmospheric circulation redistributes the anomalous energy absorbed in the northern hemisphere, in particular toward the south, through altering the Hadley circulation, resulting in the northward displacement of the tropical rain bands. Precipitation decreases over parts of the Amazon basin affecting productivity and increases over the <span class="hlt">Sahel</span> and Sahara regions in Africa. We find that the response of climate to afforestation in mid-latitudes is determined by the amount of soil moisture available to plants with the greatest warming found in water-limited regions. Mid-latitude afforestation is found to have a small impact on modeled global temperatures and on global CO(2), but regional heating from the increase in forest cover is capable of driving unintended changes in circulation and precipitation. The ability of vegetation to affect remote circulation has implications for strategies for climate mitigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=STS052-80-064&hterms=ecologic+center&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Decologic%2Bcenter','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=STS052-80-064&hterms=ecologic+center&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Decologic%2Bcenter"><span>Lake Chad, Chad, Africa</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1992-01-01</p> <p>Hydrologic and ecologic changes in the Lake Chad Basin are shown in this Oct 1992 photograph. In space photo documentation, Lake Chad was at its greatest area extent (25,000 sq. km.) during Gemini 9 in June 1966 (see S66-38444). Its reduction during the severe droughts from 1968 to 1974 was first noted during Skylab (1973-1974). After the drought began again in 1982, the lake reached its minimum extent (1,450 sq. km.) in Space Shuttle photographs taken in 1984 and 1985. In this STS-52 photograph, Lake Chad has begun to recover. The area of the open water and interdunal impoundments in the southern basin (the Chari River Basin) is estimated to be 1,900 to 2100 sq. km. Note the green vegetation in the valley of the K'Yobe flow has wetted the northern lake basin for the first time in several years. There is evidence of biomass burning south of the K'Yobe Delta and in the vegetated interdunal areas near the dike in the center of the lake. Also note the dark 'Green Line' of the <span class="hlt">Sahel</span> (the g</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28264261','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28264261"><span>Two new terrestrial species of <i>Hydraena</i> Kugelann from the island of Bioko, Gulf of Guinea (Coleoptera: Hydraenidae).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hernando, Carles; Ribera, Ignacio</p> <p>2017-03-02</p> <p>The knowledge of the Hydraenidae of sub-Saharan Africa, and in particular of the genus Hydraena Kugelann, 1794, is most incomplete. As an example, in southern Africa only three species were described before the revision of Perkins (2014), which raised the number to 31. Only 15 species are currently known from Central Africa, between the <span class="hlt">Sahel</span> and South Africa, all belonging to subgenus Hydraenopsis Janssens, 1972 (Trizzino et al. 2013), but many more remain to be described and discovered. The islands of the Gulf of Guinea are no exception to this lack of knowledge (Jones 1994), and only one species of the family was previously known, H. (Hydraenopsis) pagaluensis Hernando & Ribera, 2001 from Annobón (Hernando & Ribera 2001; Trizzino et al. 2013). In this paper we describe the first known species of Hydraenidae from Bioko, the largest and closest to the continent of these islands. The species were collected by our friend and colleague Vasily Grebennikov during a survey of the forest litter fauna of Annobón and Bioko. Despite considerable efforts no Hydraenidae were found in Annobón, and only these two species, in a single locality, in Bioko.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17058510','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17058510"><span>An example of demographic anthropology, the study of matrimonial exchanges--endogamy, choice of spouse and preferential marriage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cazes, Marie-Hélène</p> <p>2006-09-01</p> <p>The development of demographic studies in anthropology is directly linked to the success of population genetics. The anthropodemographic or anthropogenetic approach is thus underpinned by questions of genetics. While demographers focus on population dynamics and renewal in quantitative terms, population geneticists refer not to individuals but to the sets of genes carried by individuals in a population. Their aim is to detect the factors and processes which influence the genetic evolution of a group, i.e. which modify gene frequencies from one generation to the next. Among them are the factors which affect modes of reproduction. To illustrate the association of these three approaches, i.e. demographic, anthropological and genetic, I use here the example of matrimonial exchanges--which lie at the heart of the population renewal process--among the Dogon of Boni, a Malian ethnic group living in the southern <span class="hlt">Sahel</span>. We can see how successive analyses--starting with endogamy at macroscopic level and moving down to the individual with choice of spouse and preferential marriage-- combining both quantitative and qualitative approaches, can be used to obtain a detailed description of matrimonial exchanges which shed light upon and complement the three different viewpoints.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5234546','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5234546"><span>RAINBIO: a mega-database of tropical African vascular plants distributions</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Dauby, Gilles; Zaiss, Rainer; Blach-Overgaard, Anne; Catarino, Luís; Damen, Theo; Deblauwe, Vincent; Dessein, Steven; Dransfield, John; Droissart, Vincent; Duarte, Maria Cristina; Engledow, Henry; Fadeur, Geoffrey; Figueira, Rui; Gereau, Roy E.; Hardy, Olivier J.; Harris, David J.; de Heij, Janneke; Janssens, Steven; Klomberg, Yannick; Ley, Alexandra C.; Mackinder, Barbara A.; Meerts, Pierre; van de Poel, Jeike L.; Sonké, Bonaventure; Sosef, Marc S. M.; Stévart, Tariq; Stoffelen, Piet; Svenning, Jens-Christian; Sepulchre, Pierre; van der Burgt, Xander; Wieringa, Jan J.; Couvreur, Thomas L. P.</p> <p>2016-01-01</p> <p>Abstract The tropical vegetation of Africa is characterized by high levels of species diversity but is undergoing important shifts in response to ongoing climate change and increasing anthropogenic pressures. Although our knowledge of plant species distribution patterns in the African tropics has been improving over the years, it remains limited. Here we present RAINBIO, a unique comprehensive mega-database of georeferenced records for vascular plants in continental tropical Africa. The geographic focus of the database is the region south of the <span class="hlt">Sahel</span> and north of Southern Africa, and the majority of data originate from tropical forest regions. RAINBIO is a compilation of 13 datasets either publicly available or personal ones. Numerous in depth data quality checks, automatic and manual via several African flora experts, were undertaken for georeferencing, standardization of taxonomic names and identification and merging of duplicated records. The resulting RAINBIO data allows exploration and extraction of distribution data for 25,356 native tropical African vascular plant species, which represents ca. 89% of all known plant species in the area of interest. Habit information is also provided for 91% of these species. PMID:28127234</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28845357','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28845357"><span>Identifying Future Disease Hot Spots: Infectious Disease Vulnerability Index.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moore, Melinda; Gelfeld, Bill; Okunogbe, Adeyemi; Paul, Christopher</p> <p>2017-06-01</p> <p>Recent high-profile outbreaks, such as Ebola and Zika, have illustrated the transnational nature of infectious diseases. Countries that are most vulnerable to such outbreaks might be higher priorities for technical support. RAND created the Infectious Disease Vulnerability Index to help U.S. government and international agencies identify these countries and thereby inform programming to preemptively help mitigate the spread and effects of potential transnational outbreaks. The authors employed a rigorous methodology to identify the countries most vulnerable to disease outbreaks. They conducted a comprehensive review of relevant literature to identify factors influencing infectious disease vulnerability. Using widely available data, the authors created an index for identifying potentially vulnerable countries and then ranked countries by overall vulnerability score. Policymakers should focus on the 25 most-vulnerable countries with an eye toward a potential "disease belt" in the <span class="hlt">Sahel</span> region of Africa. The infectious disease vulnerability scores for several countries were better than what would have been predicted on the basis of economic status alone. This suggests that low-income countries can overcome economic challenges and become more resilient to public health challenges, such as infectious disease outbreaks.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatCC...6..177C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatCC...6..177C"><span>Large rainfall changes consistently projected over substantial areas of tropical land</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chadwick, Robin; Good, Peter; Martin, Gill; Rowell, David P.</p> <p>2016-02-01</p> <p>Many tropical countries are exceptionally vulnerable to changes in rainfall patterns, with floods or droughts often severely affecting human life and health, food and water supplies, ecosystems and infrastructure. There is widespread disagreement among climate model projections of how and where rainfall will change over tropical land at the regional scales relevant to impacts, with different models predicting the position of current tropical wet and dry regions to shift in different ways. Here we show that despite uncertainty in the location of future rainfall shifts, climate models consistently project that large rainfall changes will occur for a considerable proportion of tropical land over the twenty-first century. The area of semi-arid land affected by large changes under a higher emissions scenario is likely to be greater than during even the most extreme regional wet or dry periods of the twentieth century, such as the <span class="hlt">Sahel</span> drought of the late 1960s to 1990s. Substantial changes are projected to occur by mid-century--earlier than previously expected--and to intensify in line with global temperature rise. Therefore, current climate projections contain quantitative, decision-relevant information on future regional rainfall changes, particularly with regard to climate change mitigation policy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC13G1244Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC13G1244Z"><span>Threshold effects in the vegetation response to Holocene climate changes in central Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Y.</p> <p>2015-12-01</p> <p>Understanding the response of ecosystems to past climate is critical for evaluating the impacts of future climate changes. A relatively abrupt vegetation shift in response to the late Holocene gradual climate changes has been well documented for the Sahara-<span class="hlt">Sahel</span> ecosystem. However, whether such threshold shift is of universal significance remains to be further addressed. Here, we examine the vegetation-climate relationships in central Asia based on four newly recovered Holocene pollen records and a synthesis on previously published pollen data. The results show that the orbital-induced gradual climate trend during the Holocene led to two major abrupt vegetation shifts, and that the timings of these shifts are highly dependent of the local rainfall conditions. Instead, the mid-Holocene vegetation remained rather stable despite of the changing climate. These new findings demonstrate generally significant threshold and truncation effects of climate changes on vegetation, as are strongly supported by surface pollen data and LPJ-GUESS modeling. The results also imply that using pollen data to reconstruct past climate changes is not always straightforward. Our findings have important implication for understanding the potential effects of global warming on dryland ecosystem change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4375326','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4375326"><span>Association of Shifting Populations in the Root Zone Microbiome of Millet with Enhanced Crop Productivity in the <span class="hlt">Sahel</span> Region (Africa)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Assigbetse, Komi; Bayala, Roger; Chapuis-Lardy, Lydie; Dick, Richard P.; McSpadden Gardener, Brian B.</p> <p>2015-01-01</p> <p>This study characterized specific changes in the millet root zone microbiome stimulated by long-term woody-shrub intercropping at different sites in Senegal. At the two study sites, intercropping with woody shrubs and shrub residue resulted in a significant increase in millet [Pennisetum glaucum (L.) R. Br.] yield (P < 0.05) and associated patterns of increased diversity in both bacterial and fungal communities in the root zone of the crop. Across four experiments, operational taxonomic units (OTUs) belonging to Chitinophaga were consistently significantly (P < 0.001) enriched in the intercropped samples, and “Candidatus Koribacter” was consistently significantly enriched in samples where millet was grown alone. Those OTUs belonging to Chitinophaga were enriched more than 30-fold in residue-amended samples and formed a distinct subgroup from all OTUs detected in the genus. Additionally, OTUs belonging to 8 fungal genera (Aspergillus, Coniella, Epicoccum, Fusarium, Gibberella, Lasiodiplodia, Penicillium, and Phoma) were significantly (P < 0.005) enriched in all experiments at all sites in intercropped samples. The OTUs of four genera (Epicoccum, Fusarium, Gibberella, and Haematonectria) were consistently enriched at sites where millet was grown alone. Those enriched OTUs in intercropped samples showed consistently large-magnitude differences, ranging from 30- to 1,000-fold increases in abundance. Consistently enriched OTUs in intercropped samples in the genera Aspergillus, Fusarium, and Penicillium also formed phylogenetically distinct subgroups. These results suggest that the intercropping system used here can influence the recruitment of potentially beneficial microorganisms to the root zone of millet and aid subsistence farmers in producing higher-yielding crops. PMID:25681183</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011QSRv...30..737L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011QSRv...30..737L"><span>High-resolution fluvial records of Holocene environmental changes in the <span class="hlt">Sahel</span>: the Yamé River at Ounjougou (Mali, West Africa)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lespez, L.; Le Drezen, Y.; Garnier, A.; Rasse, M.; Eichhorn, B.; Ozainne, S.; Ballouche, A.; Neumann, K.; Huysecom, E.</p> <p>2011-03-01</p> <p>The Yamé river, in the Bandiagara Plateau, Dogon Country, Mali, is characterised by extensive alluvial sedimentary records, particularly in the 1 km long Ounjougou reach where Holocene floodplain pockets are inset in the Pleistocene formations. These alluvial records have been investigated via geomorphologic fieldwork and sedimentologic and micromorphologic analyses and are supported by 79 radiocarbon dates. The alluvial deposits of the valley floor correspond to a vertical accretion of 3-10 m. The reconstruction of fluvial style changes provides evidence of four main aggradation periods. From 11,500 to 8760 cal. BP, the alluvial architecture and grain-size parameters indicate a wandering river. This period included phases of pulsed high-energy floods and avulsion related to a northward shift of the summer monsoon to around 14°N after 11,500 cal. BP. From 7800 to 5300 cal. BP, a swampy floodplain environment with standing water pools within a Sudanian savanna/woodland mosaic corresponds to the culmination of the Holocene humid period. From 3800 cal. BP onwards, rhythmic sedimentation attests to an increase in the duration and/or intensity of the dry season, giving a precise date for the local termination of the Holocene Optimum period. During the last two millennia and for the first time during the Holocene, the alluvial formations are progressively restricted whereas the colluvial deposits increase, indicating strong soil erosion and redeposition within the watershed related to an increase in human impact. Four major periods are characterised by incision (I1: ante 11,500, I2: 8760-7800; I3: 6790-6500 cal. BP; I4; 2400-1700 cal. BP) pointing to dramatic changes in fluvial style. They result from high-energy flood flows during dry spells and confirm the capacity of the floodplain pocket in the upstream reach of the Sahelian belt to record rapid Holocene climatic change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H12E..06E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H12E..06E"><span>The vadose zone as a geoindicator of environmental change and groundwater quality in water-scarce areas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Edmunds, W. M.; Baba Goni, I.; Gaye, C. B.; Jin, L.</p> <p>2013-12-01</p> <p>Inert and reactive tracers in moisture profiles provide considerable potential for the vadose zone to be used as an indicator of rapid environmental change. This indicator is particularly applicable in areas of water stress where long term (decade to century) scale records may be found in deep unsaturated zones in low rainfall areas and provide insights into recent recharge, climate variation and water-rock interactions which generate groundwater quality. Unsaturated zone Cl records obtained by elutriation of moisture are used widely for estimating recharge and water balance studies; isotope profiles (3H, δ2H, δ18O) from total water extraction procedures are used for investigation of residence times and hydrological processes. Apart from water taken using lysimeters, little work has been conducted directly on the geochemistry of pore fluids. This is mainly due to the difficulties of extraction of moisture from unsaturated material with low water contents (typically 2-6 wt%) and since dilution methods can create artifacts. Using immiscible liquid displacement techniques it is now possible to directly investigate the geochemistry of moisture from unsaturated zone materials. Profiles up to 35m from Quaternary sediments from dryland areas of the African <span class="hlt">Sahel</span> (Nigeria, Senegal) as well as Inner Mongolia, China are used to illustrate the breadth of information obtainable from vadose zone profiles. Using pH, major and trace elements and comparing with isotopic data, a better understanding is gained of timescales of water movement, aquifer recharge, environmental records and climate history as well as water-rock interaction and contaminant behaviour. The usefulness of tritium as residence time indicator has now expired following cessation of atmospheric thermonuclear testing and through radioactive decay. Providing the rainfall Cl, moisture contents and bulk densities of the sediments are known, then Cl accumulation can be substituted to estimate timescales. Profiles</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H33E1417P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H33E1417P"><span>The Climate Hazards group InfraRed Precipitation (CHIRP) with Stations (CHIRPS): Development and Validation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peterson, P.; Funk, C. C.; Husak, G. J.; Pedreros, D. H.; Landsfeld, M.; Verdin, J. P.; Shukla, S.</p> <p>2013-12-01</p> <p> climate observations: the monthly Global Historical Climate Network version 2 archive, the daily Global Historical Climate Network archive, the Global Summary of the Day dataset (GSOD), and the daily Global Telecommunication System (GTS) archive provided by NOAA's Climate Prediction Center (CPC). A screening procedure was developed to flag and remove potential false zeros from the daily data, since these potentially spurious data can artificially suppress rainfall totals. Validation: Our validation focused on precipitation products with global coverage, long periods of record and near real-time availability: CHIRP, CHIRPS, CPC-Unified, CFS Reanalysis and ECMWF datasets were compared to GPCC and high quality datasets from Uganda, Colombia and the <span class="hlt">Sahel</span>. The CHIRP and CHIRPS are shown to have low systematic errors (bias) and low mean absolute errors. Analyses in Uganda, Colombia and the <span class="hlt">Sahel</span> indicate that the ECMWF, CPC-Unified and CFS-Reanalysis have large inhomogeneities, making them unsuitable for drought monitoring. The CHIRPS performance appears quite similar to research quality products like the GPCC and GPCP, but with higher resolution and lower latency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19046418','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19046418"><span>Seasonal variation of carbon fluxes in a sparse savanna in semi arid Sudan.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ardö, Jonas; Mölder, Meelis; El-Tahir, Bashir Awad; Elkhidir, Hatim Abdalla Mohammed</p> <p>2008-12-01</p> <p>Large spatial, seasonal and annual variability of major drivers of the carbon cycle (precipitation, temperature, fire regime and nutrient availability) are common in the <span class="hlt">Sahel</span> region. This causes large variability in net ecosystem exchange and in vegetation productivity, the subsistence basis for a major part of the rural population in <span class="hlt">Sahel</span>. This study compares the 2005 dry and wet season fluxes of CO2 for a grass land/sparse savanna site in semi arid Sudan and relates these fluxes to water availability and incoming photosynthetic photon flux density (PPFD). Data from this site could complement the current sparse observation network in Africa, a continent where climatic change could significantly impact the future and which constitute a weak link in our understanding of the global carbon cycle. The dry season (represented by Julian day 35-46, February 2005) was characterized by low soil moisture availability, low evapotranspiration and a high vapor pressure deficit. The mean daily NEE (net ecosystem exchange, Eq. 1) was -14.7 mmol d-1 for the 12 day period (negative numbers denote sinks, i.e. flux from the atmosphere to the biosphere). The water use efficiency (WUE) was 1.6 mmol CO2 mol H2O-1 and the light use efficiency (LUE) was 0.95 mmol CO2 mol PPFD-1. Photosynthesis is a weak, but linear function of PPFD. The wet season (represented by Julian day 266-273, September 2005) was, compared to the dry season, characterized by slightly higher soil moisture availability, higher evapotranspiration and a slightly lower vapor pressure deficit. The mean daily NEE was -152 mmol d-1 for the 8 day period. The WUE was lower, 0.97 mmol CO2 mol H2O-1 and the LUE was higher, 7.2 mumol CO2 mmol PPFD-1 during the wet season compared to the dry season. During the wet season photosynthesis increases with PPFD to about 1600 mumol m-2s-1 and then levels off. Based on data collected during two short periods, the studied ecosystem was a sink of carbon both during the dry and wet season</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=soil+AND+Biologicals&id=ED571736','ERIC'); return false;" href="https://eric.ed.gov/?q=soil+AND+Biologicals&id=ED571736"><span>Land Cover Land Use Change and Soil Organic Carbon under Climate Variability in the Semi-Arid West African <span class="hlt">Sahel</span> (1960-2050)</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Dieye, Amadou M.</p> <p>2016-01-01</p> <p>Land Cover Land Use (LCLU) change affects land surface processes recognized to influence climate change at local, national and global levels. Soil organic carbon is a key component for the functioning of agro-ecosystems and has a direct effect on the physical, chemical and biological characteristics of the soil. The capacity to model and project…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.usgs.gov/of/2003/0028/report.pdf','USGSPUBS'); return false;" href="https://pubs.usgs.gov/of/2003/0028/report.pdf"><span>African dust carries microbes across the ocean: are they affecting human and ecosystem health?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Kellogg, Christina A.; Griffin, Dale W.</p> <p>2003-01-01</p> <p>Atmospheric transport of dust from northwest Africa to the western Atlantic Ocean region may be responsible for a number of environmental hazards, including the demise of Caribbean corals; red tides; amphibian diseases; increased occurrence of asthma in humans; and oxygen depletion (eutrophication) in estuaries. Studies of satellite images suggest that hundreds of millions of tons of dust are trans-ported annually at relatively low altitudes across the Atlantic Ocean to the Caribbean Sea and southeastern United States. The dust emanates from the expanding Sahara/<span class="hlt">Sahel</span> desert region in Africa and carries a wide variety of bacteria and fungi. The U.S. Geological Survey, in collaboration with the NASA/Goddard Spaceflight Center, is conducting a study to identify microbes--bacteria, fungi, viruses--transported across the Atlantic in African soil dust. Each year, millions of tons of desert dust blow off the west African coast and ride the trade winds across the ocean, affecting the entire Caribbean basin, as well as the southeastern United States. Of the dust reaching the U.S., Florida receives about 50 percent, while the rest may range as far north as Maine or as far west as Colorado. The dust storms can be tracked by satellite and take about one week to cross the Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030022775','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030022775"><span>Long-Term Simulation of Dust Distribution with the GOCART Model: Correlation with the North Atlantic Oscillation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ginoux, P.; Prospero, J.; Torres, O.; Chin, M.</p> <p>2002-01-01</p> <p>Global distribution of aeolian dust is simulated from 1981 to 1996 with the Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. The results are assessed with in-situ measurements and the Total Ozone Mapping Spectrometer (TOMS) aerosol products. The annual budget over the different continents and oceans are analyzed. It is found that there is a maximum of 25% difference of global annual emission from the minimum in 1996 to the maximum in 1988. There is a downward trend of dust emission over Africa and East Asia, of 6 and 2 Tg/yr, respectively. The inter-annual variability of dust distribution is analyzed over the North Atlantic and Africa. It is found that in winter most of the North Atlantic and Africa dust loading is correlated with the North Atlantic Oscillation. The GOCART model indicates that a controlling factor of such correlation can be attributed to dust emission from the <span class="hlt">Sahel</span>. The Bodele depression is the major dust source in winter and its inter-annual variability is highly correlated with the NAO. However, it is not possible to conclude without further analysis that the North Atlantic Oscillation is forcing the inter-annual variability of dust emission and in-turn dust concentration over the North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23511910','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23511910"><span>Understanding the role of local management in vegetation recovery around pastoral settlements in northern Kenya.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Roba, Hassan G; Oba, Gufu</p> <p>2013-04-01</p> <p>The recent greening of the <span class="hlt">Sahel</span> region and increase in vegetation cover around pastoral settlements previously described as "man-made deserts", have raised important questions on the permanency of land degradation associated with the over-exploitation of woody plants. Evidence presented is mostly on increased wetness, while management by local communities has received limited attention. This study evaluated changes in woody vegetation cover around the settlements of Kargi and Korr in northern Kenya, using satellite imagery (1986/2000), ecological ground surveys and interviews with local elders, in order to understand long-term changes in vegetation cover and the role of local community in vegetation dynamics. At both settlements, there were increments in vegetation cover and reduction in the extent of bare ground between 1986 and 2000. At Kargi settlement, there were more tree seedlings in the centre of settlement than further away. Mature tree class was more abundant in the centre of Korr than outside the settlement. The success of the regeneration and recovery of tree cover was attributed to the actions of vegetation management initiative including stringent measures by the local Environmental Management Committees. This study provides good evidence that local partnership is important for sustainable management of resources especially in rural areas where the effectiveness of government initiative is lacking.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70159027','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70159027"><span>Trace-metal concentrations in African dust: effects of long-distance transport and implications for human health</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Garrison, Virginia; Lamothe, Paul; Morman, Suzette; Plumlee, Geoffrey S.; Gilkes, Robert; Prakongkep, Nattaporn</p> <p>2010-01-01</p> <p>The Sahara and <span class="hlt">Sahel</span> lose billions of tons of eroded mineral soils annually to the Americas and Caribbean, Europe and Asia via atmospheric transport. African dust was collected from a dust source region (Mali, West Africa) and from downwind sites in the Caribbean [Trinidad-Tobago (TT) and U.S. Virgin Islands (VI)] and analysed for 32 trace-elements. Elemental composition of African dust samples was similar to that of average upper continental crust (UCC), with some enrichment or depletion of specific trace-elements. Pb enrichment was observed only in dust and dry deposition samples from the source region and was most likely from local use of leaded gasoline. Dust particles transported long-distances (VI and TT) exhibited increased enrichment of Mo and minor depletion of other elements relative to source region samples. This suggests that processes occurring during long-distance transport of dust produce enrichment/depletion of specific elements. Bioaccessibility of trace-metals in samples was tested in simulated human fluids (gastric and lung) and was found to be greater in downwind than source region samples, for some metals (e.g., As). The large surface to volume ratio of the dust particles (<2.5 µm) at downwind sites may be a factor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3970615','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3970615"><span>Toxoplasmosis seroprevalence in urban rodents: a survey in Niamey, Niger</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mercier, Aurélien; Garba, Madougou; Bonnabau, Henri; Kane, Mamadou; Rossi, Jean-Pierre; Dardé, Marie-Laure; Dobigny, Gauthier</p> <p>2013-01-01</p> <p>A serological survey of Toxoplasma gondii was conducted on 766 domestic and peridomestic rodents from 46 trapping sites throughout the city of Niamey, Niger. A low seroprevalence was found over the whole town with only 1.96% of the rodents found seropositive. However, differences between species were important, ranging from less than 2% in truly commensal Mastomys natalensis, Rattus rattus and Mus musculus, while garden-associated Arvicanthis niloticus displayed 9.1% of seropositive individuals. This is in line with previous studies on tropical rodents - that we reviewed here - which altogether show that Toxoplasma seroprevalence in rodent is highly variable, depending on many factors such as locality and/or species. Moreover, although we were not able to decipher statistically between habitat or species effect, such a contrast between Nile grass rats and the other rodent species points towards a potentially important role of environmental toxoplasmic infection. This would deserve to be further scrutinised since intra-city irrigated cultures are extending in Niamey, thus potentially increasing Toxoplasma circulation in this yet semi-arid region. As far as we are aware of, our study is one of the rare surveys of its kind performed in Sub-Saharan Africa and the first one ever conducted in the <span class="hlt">Sahel</span>. PMID:23828008</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMNG32A..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMNG32A..03S"><span>Simulation of an Extreme Off Season Rainy Event over Senegal Using WRF ARW Model: A focus on dynamic, thermodynamic processes and predictability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sarr, A.</p> <p>2016-12-01</p> <p>This study investigates less known weather events, Off Season Rain affecting during boreal winter Western parts of <span class="hlt">Sahel</span> region mainly, Senegal, Cape Verde and Mauritania. They are characterized by cloudy conditions at mid level, which can trigger light long lasting rains. In January 2002, an extreme case occurred from 09 to 11th producing unusual heavy rains, which had dramatic consequences on livestock and irrigated crops. The Weather and Research Forecast model (WRF ARW version 3.4) is used to simulate the event, which affected the western coast around the land/ocean interface and caused huge damages in Senegal and Mauritania. The model was able to reasonably simulate the event and its intensity 2 to 3 days in advance, demonstrating the usefulness of such a tools for early warning system (EWS), which could help mitigate the impacts. The location of the rain band was closer to the observed situation in higher resolution domains. The study showed keys dynamic and thermodynamic conditions associated with the event. Precipitable water (PW) evolution played a central role on the intensity of the event. The deep trough, associated with the disturbance, forced a northeast transport of moisture from the Inter Tropical Convergence Zone (ITCZ) over the Ocean towards Senegal and Mauritania.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1376650-climate-mitigation-from-vegetation-biophysical-feedbacks-during-past-three-decades','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1376650-climate-mitigation-from-vegetation-biophysical-feedbacks-during-past-three-decades"><span>Climate mitigation from vegetation biophysical feedbacks during the past three decades</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Zeng, Zhenzhong; Piao, Shilong; Li, Laurent Z. X.</p> <p></p> <p>The surface air temperature response to vegetation changes has been studied for the extreme case of land-cover change; yet, it has never been quantified for the slow but persistent increase in leaf area index (LAI) observed over the past 30 years (Earth greening). We isolate the fingerprint of increasing LAI on surface air temperature using a coupled land–atmosphere global climate model prescribed with satellite LAI observations. Furthermore, we found that the global greening has slowed down the rise in global land-surface air temperature by 0.09 ± 0.02 °C since 1982. This net cooling effect is the sum of cooling frommore » increased evapotranspiration (70%), changed atmospheric circulation (44%), decreased shortwave transmissivity (21%), and warming from increased longwave air emissivity (-29%) and decreased albedo (-6%). The global cooling originated from the regions where LAI has increased, including boreal Eurasia, Europe, India, northwest Amazonia, and the <span class="hlt">Sahel</span>. Increasing LAI did not, but, significantly change surface air temperature in eastern North America and East Asia, where the effects of large-scale atmospheric circulation changes mask local vegetation feedbacks. Overall, the sum of biophysical feedbacks related to the greening of the Earth mitigated 12% of global land-surface warming for the past 30 years.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1251308-impact-equilibrating-hemispheric-albedos-tropical-performance-hadgem2-es-coupled-climate-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1251308-impact-equilibrating-hemispheric-albedos-tropical-performance-hadgem2-es-coupled-climate-model"><span>The impact of equilibrating hemispheric albedos on tropical performance in the HadGEM2-ES coupled climate model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Haywood, Jim M.; Jones, Andy; Dunstone, Nick; ...</p> <p>2016-01-14</p> <p>Despite the fact that the southern hemisphere contains a far greater proportion of dark ocean than the northern hemisphere, the total amount of sunlight reflected from the hemispheres is equal. However, the majority of climate models do not adequately represent this equivalence. Here we examine the impact of equilibrating hemispheric albedos by various idealised methods in a comprehensive coupled climate model and find significant improvements in what have been considered longstanding and apparently intractable model biases. Monsoon precipitation biases almost vanish over all continental land areas, the penetration of monsoon rainfall across the <span class="hlt">Sahel</span> and the west African monsoon “jump”more » become well represented, and indicators of hurricane frequency are significantly improved. The results appear not to be model specific, implying that hemispheric albedo equivalence may provide a fundamental constraint for climate models that must be satisfied if the dynamics driving these processes, in particular the strength of the Hadley cell, are to be adequately represented. Cross-equatorial energy transport is implicated as a crucial component that must be accurately modelled in coupled general circulation models. The results also suggest that the commonly used practice of prescribing sea-surface temperatures in models provides a less accurate represention of precipitation than constraining the hemispheric albedos.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1251308','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1251308"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Haywood, Jim M.; Jones, Andy; Dunstone, Nick</p> <p></p> <p>Despite the fact that the southern hemisphere contains a far greater proportion of dark ocean than the northern hemisphere, the total amount of sunlight reflected from the hemispheres is equal. However, the majority of climate models do not adequately represent this equivalence. Here we examine the impact of equilibrating hemispheric albedos by various idealised methods in a comprehensive coupled climate model and find significant improvements in what have been considered longstanding and apparently intractable model biases. Monsoon precipitation biases almost vanish over all continental land areas, the penetration of monsoon rainfall across the <span class="hlt">Sahel</span> and the west African monsoon “jump”more » become well represented, and indicators of hurricane frequency are significantly improved. The results appear not to be model specific, implying that hemispheric albedo equivalence may provide a fundamental constraint for climate models that must be satisfied if the dynamics driving these processes, in particular the strength of the Hadley cell, are to be adequately represented. Cross-equatorial energy transport is implicated as a crucial component that must be accurately modelled in coupled general circulation models. The results also suggest that the commonly used practice of prescribing sea-surface temperatures in models provides a less accurate represention of precipitation than constraining the hemispheric albedos.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ESASP.674E...5W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ESASP.674E...5W"><span>Evaluation of SEVIRI-Derived Rain Rates and Accumulated Rainfall with TRMM-TMI and Rain Gauge Data over West-Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolters, E. L. A.; Roebeling, R. A.; Stammes, P.; Wang, P.; Ali, A.; Brissebrat, G.</p> <p>2009-11-01</p> <p>Clouds are of paramount importance to the hydrological cycle, as they influence the surface energy balance, thereby constraining the amount of energy available for evaporation, and their contribution through precipitation. Especially in regions where water availability is critical, such as in West-Africa, accurate determination of various terms of the hydrological cycle is warranted. At the Royal Netherlands Meteorological Institute (KNMI), an algorithm to retrieve Cloud Physical Properties (CPP) from mainly visible and near-infrared spectral channel radiances from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard Meteosat-8 and -9 has been developed. Recently, this algorithm as been extended with a rain rate retrieval method. Evaluation of this geophysical quantity has been done with rain radar data over the Netherlands. This paper presents the first results of this rain rate retrieval over West-Africa for June 2006. In addition, the added value of the high temporal and spatial resolution of the SEVIRI instrument is shown. Over land, retrievals are compared with rain gauge observations performed during the African Monsoon Multidisciplinary Analyses (AMMA) project and with a kriged dataset of the Comite Inter-Estate pour la Lutte contre la Secheresse au <span class="hlt">Sahel</span> (CILSS) rain gauge network, whereas rain rate retrievals over ocean are evaluated using Tropical Rainfall Measurement Mission (TRMM) Microwave Imager (TMI) data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12296194','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12296194"><span>[Ministerial Conference on Migration and Urbanization in West Africa: declaration].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p></p> <p>1999-12-01</p> <p>This declaration made by the participants of the Ministerial Conference on Migration and Urbanization in Western Africa, held in Bamako during November 5, 1999, commits the countries of the region to do the following: follow the urbanization process in an effort to make African cities hubs of development and social progress; improve the geographic distribution of populations; bring economic development to mid-sized cities; implement rural development projects and programs, especially in the least advantaged zones; manage urban constraints; define new pathways and coordinated approaches; implement measures which account for those who are newly migrating, such as women and young people; minimize administrative hurdles associated with the return and reintegration of migrants; provide those bodies responsible for urbanization and migration concerns with the communication tools they require; take the necessary measures to facilitate migrants¿ stays and inform potential migrants about the conditions of such stay in host countries; adapt laws to conform with the charters of subregional organizations; consider migration concerns at the commission level; and implement clear, explicit migration policies. Recommendations are offered to the Permanent Interstate Committee Against Drought in the <span class="hlt">Sahel</span> (CILSS) as well as to all subregional organizations. It is hoped that international organizations and partner agencies in development will support countries¿ efforts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008GPC....64..210M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008GPC....64..210M"><span>The history of environmental change and adaptation in eastern Saloum-Senegal—Driving forces and perceptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mbow, Cheikh; Mertz, Ole; Diouf, Awa; Rasmussen, Kjeld; Reenberg, Anette</p> <p>2008-12-01</p> <p>Environmental change in the <span class="hlt">Sahel</span>-Sudan zone of West Africa has been a major issue in development debates over the last decades. Using remote sensing based land cover change analysis, archival data, national and international statistical data, and household interviews, we analyze the drivers of environmental change in Eastern Saloum in Central East Senegal as well as the local perceptions of these changes and adaptation. Being part of the ground nut basin, Eastern Saloum has witnessed rapid environmental degradation caused by the conversion of forest and savanna areas to agricultural land during the last 20-30 years and by a combination of decline in precipitation, soil degradation, a diversity of policies with little concern for the environment, fluctuating markets and population pressure. Farmers perceive the environmental change mainly as land degradation and poor soil fertility, though recent extensification of agriculture counters this effect and has led to increased vegetation cover in marginal areas. They identified erratic climate, agricultural policies, insufficient food production and desire to increase income as the main drivers of change in the area. We conclude that while climate variability has influenced environmental change in the area, various types of State interventions in agriculture and global market fluctuations appear to have been the main underlying causes of environmental degradation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC43B0723F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC43B0723F"><span>Identifying and Investigating the Late-1960s Interhemispheric SST Shift</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Friedman, A. R.; Lee, S. Y.; Liu, Y.; Chiang, J. C. H.</p> <p>2014-12-01</p> <p>The global north-south interhemispheric sea surface temperature (SST) difference experienced a pronounced and rapid decrease in the late 1960s, which has been linked to drying in the <span class="hlt">Sahel</span>, South Asia, and East Asia. However, some basic questions about the interhemispheric SST shift remain unresolved, including its scale and whether the constituent changes in different basins were coordinated. In this study, we systematically investigate the spatial and temporal behavior of the late-1960s interhemispheric SST shift using ocean surface and subsurface observations. We also evaluate potential mechanisms using control and specific-forcing CMIP5 simulations. Using a regime shift detection technique, we identify the late-1960s shift as the most prominent in the historical observational SST record. We additionally examine the corresponding changes in upper-ocean heat content and salinity associated with the shift. We find that there were coordinated upper-ocean cooling and freshening in the subpolar North Atlantic, the region of the largest-magnitude SST decrease during the interhemispheric shift. These upper-ocean changes correspond to a weakened North Atlantic thermohaline circulation (THC). However, the THC decrease does not fully account for the rapid global interhemispheric SST shift, particularly the warming in the extratropical Southern Hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70035622','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70035622"><span>Joint spatiotemporal variability of global sea surface temperatures and global Palmer drought severity index values</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Apipattanavis, S.; McCabe, G.J.; Rajagopalan, B.; Gangopadhyay, S.</p> <p>2009-01-01</p> <p>Dominant modes of individual and joint variability in global sea surface temperatures (SST) and global Palmer drought severity index (PDSI) values for the twentieth century are identified through a multivariate frequency domain singular value decomposition. This analysis indicates that a secular trend and variability related to the El Niño–Southern Oscillation (ENSO) are the dominant modes of variance shared among the global datasets. For the SST data the secular trend corresponds to a positive trend in Indian Ocean and South Atlantic SSTs, and a negative trend in North Pacific and North Atlantic SSTs. The ENSO reconstruction shows a strong signal in the tropical Pacific, North Pacific, and Indian Ocean regions. For the PDSI data, the secular trend reconstruction shows high amplitudes over central Africa including the <span class="hlt">Sahel</span>, whereas the regions with strong ENSO amplitudes in PDSI are the southwestern and northwestern United States, South Africa, northeastern Brazil, central Africa, the Indian subcontinent, and Australia. An additional significant frequency, multidecadal variability, is identified for the Northern Hemisphere. This multidecadal frequency appears to be related to the Atlantic multidecadal oscillation (AMO). The multidecadal frequency is statistically significant in the Northern Hemisphere SST data, but is statistically nonsignificant in the PDSI data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70043241','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70043241"><span>Combining surface reanalysis and remote sensing data for monitoring evapotranspiration</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Marshall, M.; Tu, K.; Funk, C.; Michaelsen, J.; Williams, Pat; Williams, C.; Ardö, J.; Marie, B.; Cappelaere, B.; Grandcourt, A.; Nickless, A.; Noubellon, Y.; Scholes, R.; Kutsch, W.</p> <p>2012-01-01</p> <p>Climate change is expected to have the greatest impact on the world's poor. In the <span class="hlt">Sahel</span>, a climatically sensitive region where rain-fed agriculture is the primary livelihood, expected decreases in water supply will increase food insecurity. Studies on climate change and the intensification of the water cycle in sub-Saharan Africa are few. This is due in part to poor calibration of modeled actual evapotranspiration (AET), a key input in continental-scale hydrologic models. In this study, a model driven by dynamic canopy AET was combined with the Global Land Data Assimilation System realization of the NOAH Land Surface Model (GNOAH) wet canopy and soil AET for monitoring purposes in sub-Saharan Africa. The performance of the hybrid model was compared against AET from the GNOAH model and dynamic model using eight eddy flux towers representing major biomes of sub-Saharan Africa. The greatest improvements in model performance are at humid sites with dense vegetation, while performance at semi-arid sites is poor, but better than individual models. The reduction in errors using the hybrid model can be attributed to the integration of a dynamic vegetation component with land surface model estimates, improved model parameterization, and reduction of multiplicative effects of uncertain data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70187578','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70187578"><span>Monitoring rangeland dynamics in Senegal with advanced very high resolution radiometer data</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Tappan, G. Gray; Tyler, Dean J.; Wehde, M. E.; Moore, Donald G.</p> <p>1992-01-01</p> <p>Time‐series Normalized Difference Vegetation Index (NDVI) data, computed from Advanced Very High Resolution Radiometer data, are being used by regional and national programs in the African <span class="hlt">Sahel</span> to monitor seasonal rangeland conditions. The data are often used as indicators of grazing conditions and drought. However, distinguishing rangelands from other vegetation cover types on NDVI images is difficult. A second complication is that rangeland types and their associated productivity vary geographically by soil type. To effectively assess rangeland conditions, seasonal fluctuations (due to climatic cycles) must be isolated from long‐term production characteristics associated with vegetation type and soil differences. Rangeland NDVI dynamics, including qualitative assessments of rangeland production, and the timing and length of the growing season in Senegal were examined by using 7.4‐km global area coverage satellite data. Analyses were based on 10‐day NDVI composite image data from 1982 through 1989. The NDVI image data were stratified by rangeland and soil polygons derived from locally available resource maps. Time‐series NDVI statistics were calculated from the resource polygons that had been interpreted into high, medium, and low production rangelands. Analysts monitoring rangeland conditions can better identify seasonal anomalies such as drought by comparing production potential within homogeneous; resource polygons with the current NDVI data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.B53B0493B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.B53B0493B"><span>The Hydrology of Malaria: Model Development and Application to a Sahelian Village</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bomblies, A.; Duchemin, J.; Eltahir, E. A.</p> <p>2008-12-01</p> <p>We present a coupled hydrology and entomology model for the mechanistic simulation of local-scale response of malaria transmission to hydrological and climatological determinants in semi-arid, desert fringe environments. The model is applied to the <span class="hlt">Sahel</span> village of Banizoumbou, Niger, to predict interannual variability in malaria vector mosquito populations which lead to variations in malaria transmission. Using a high-resolution, small-scale distributed hydrology model that incorporates remotely-sensed data for land cover and topography, we simulate the formation and persistence of the pools constituting the primary breeding habitat of Anopheles gambiae s.l. mosquitoes, the principal regional malaria vector mosquitoes. An agent-based mosquito population model is coupled to the distributed hydrology model, with aquatic stage and adult stage components. For each individual adult mosquito, the model tracks attributes relevant to population dynamics and malaria transmission, which are updated as mosquitoes interact with their environment, humans, and animals. Weekly field observations were made in 2005 and 2006. The model reproduces mosquito population variability at seasonal and interannual time scales, and highlights individual pool persistence as a dominant control. Future developments to the presented model can be used in the evaluation of impacts of climate change on malaria, as well as the a priori evaluation of environmental management-based interventions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18554774','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18554774"><span>Flood monitoring in a semi-arid environment using spatially high resolution radar and optical data.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Seiler, Ralf; Schmidt, Jana; Diallo, Ousmane; Csaplovics, Elmar</p> <p>2009-05-01</p> <p>The geographic term "Niger Inland Delta" stands for a vast plain of approximately 40,000 km(2), which is situated in the western <span class="hlt">Sahel</span> (Republic of Mali). The Inland Delta is affected by yearly inundation through the variable water levels of the Niger-Bani river system. Due to a good availability of (surface) water, the ecosystem at the Niger Inland Delta serves as resting place stop-over for many migrating birds and other wildlife species as well as economic base for farmers and pastoral people. To foster the sustainable usage of its natural resources and to protect this natural heritage, the entire Niger Inland Delta became RAMSAR site in 2004. This paper aims to test to which extent texture analysis can improve the quality of flood monitoring in a semi-arid environment using spatially high resolution ASAR imaging mode data. We found the Gray Level Dependence Method (GLDM) was most suitable proceeding for our data. Several statistical parameters were calculated via co-occurrence matrices and were used to classify the images in different gradation of soil moisture classes. In a second step we used additional information from spatially high resolution optical data (ASTER) to improve the separability of open water areas from moisture/vegetated areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PApGe.174.1503B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PApGe.174.1503B"><span>The August 1st, 2014 ( M w 5.3) Moderate Earthquake: Evidence for an Active Thrust Fault in the Bay of Algiers (Algeria)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Benfedda, A.; Abbes, K.; Bouziane, D.; Bouhadad, Y.; Slimani, A.; Larbes, S.; Haddouche, D.; Bezzeghoud, M.</p> <p>2017-03-01</p> <p>On August 1st, 2014, a moderate-sized earthquake struck the capital city of Algiers at 05:11:17.6 (GMT+1). The earthquake caused the death of six peoples and injured 420, mainly following a panic movement among the population. Following the main shock, we surveyed the aftershock activity using a portable seismological network (short period), installed from August 2nd, 2014 to August 21st, 2015. In this work, first, we determined the main shock epicenter using the accelerograms recorded by the Algerian accelerograph network (under the coordination of the National Center of Applied Research in Earthquake Engineering-CGS). We calculated the focal mechanism of the main shock, using the inversion of the accelerograph waveforms in displacement that provides a reverse fault with a slight right-lateral component of slip and a compression axis striking NNW-SSE. The obtained scalar seismic moment ( M o = 1.25 × 1017 Nm) corresponds to a moment magnitude of M w = 5.3. Second, the analysis of the obtained aftershock swarm, of the survey, suggests an offshore ENE-WSW, trending and NNW dipping, causative active fault in the bay of Algiers, which may likely correspond to an offshore unknown segment of the <span class="hlt">Sahel</span> active fault.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4501401','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4501401"><span>The global distribution of Crimean-Congo hemorrhagic fever</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Messina, Jane P.; Pigott, David M.; Golding, Nick; Duda, Kirsten A.; Brownstein, John S.; Weiss, Daniel J.; Gibson, Harry; Robinson, Timothy P.; Gilbert, Marius; William Wint, G. R.; Nuttall, Patricia A.; Gething, Peter W.; Myers, Monica F.; George, Dylan B.; Hay, Simon I.</p> <p>2015-01-01</p> <p>Background Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne infection caused by a virus (CCHFV) from the Bunyaviridae family. Domestic and wild vertebrates are asymptomatic reservoirs for the virus, putting animal handlers, slaughter-house workers and agricultural labourers at highest risk in endemic areas, with secondary transmission possible through contact with infected blood and other bodily fluids. Human infection is characterized by severe symptoms that often result in death. While it is known that CCHFV transmission is limited to Africa, Asia and Europe, definitive global extents and risk patterns within these limits have not been well described. Methods We used an exhaustive database of human CCHF occurrence records and a niche modeling framework to map the global distribution of risk for human CCHF occurrence. Results A greater proportion of shrub or grass land cover was the most important contributor to our model, which predicts highest levels of risk around the Black Sea, Turkey, and some parts of central Asia. Sub-Saharan Africa shows more focalized areas of risk throughout the <span class="hlt">Sahel</span> and the Cape region. Conclusions These new risk maps provide a valuable starting point for understanding the zoonotic niche of CCHF, its extent and the risk it poses to humans. PMID:26142451</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18.2687M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18.2687M"><span>Impact of biomass burning on pollutant surface concentrations in megacities of the Gulf of Guinea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menut, Laurent; Flamant, Cyrille; Turquety, Solène; Deroubaix, Adrien; Chazette, Patrick; Meynadier, Rémi</p> <p>2018-02-01</p> <p>In the framework of the Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa (DACCIWA) project, the tropospheric chemical composition in large cities along the Gulf of Guinea is studied using the Weather and Research Forecast and CHIMERE regional models. Simulations are performed for the May-July 2014 period, without and with biomass burning emissions. Model results are compared to satellite data and surface measurements. Using numerical tracer release experiments, it is shown that the biomass burning emissions in Central Africa are impacting the surface aerosol and gaseous species concentrations in Gulf of Guinea cities such as Lagos (Nigeria) and Abidjan (Ivory Coast). Depending on the altitude of the injection of these emissions, the pollutants follow different pathways: directly along the coast or over land towards the <span class="hlt">Sahel</span> before being vertically mixed in the convective boundary layer and transported to the south-west and over the cities. In July 2014, the maximum increase in surface concentrations due to fires in Central Africa is ≈ 150 µg m-3 for CO, ≈ 10 to 20 µg m-3 for O3 and ≈ 5 µg m-3 for PM10. The analysis of the PM10 chemical composition shows that this increase is mainly related to an increase in particulate primary and organic matter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70023757','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70023757"><span>How are climate and marine biological outbreaks functionally linked?</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hayes, M.L.; Bonaventura, J.; Mitchell, T.P.; Prospero, J.M.; Shinn, E.A.; Van Dolah, F.; Barber, R.T.</p> <p>2001-01-01</p> <p>Since the mid-1970s, large-scale episodic events such as disease epidemics, mass mortalities, harmful algal blooms and other population explosions have been occurring in marine environments at an historically unprecedented rate. The variety of organisms involved (host, pathogens and other opportunists) and the absolute number of episodes have also increased during this period. Are these changes coincidental? Between 1972 and 1976, a global climate regime shift took place, and it is manifest most clearly by a change in strength of the North Pacific and North Atlantic pressure systems. Consequences of this regime shift are: (1) prolonged drought conditions in the <span class="hlt">Sahel</span> region of Africa; (2) increased dust supply to the global atmosphere, by a factor of approximately four; (3) increased easterly trade winds across the Atlantic; (4) increased eolian transport of dust to the Atlantic and Caribbean basins; and (5) increased deposition of iron-rich eolian dust to typically iron-poor marine regions. On the basis of well-documented climate and dust observations and the widely accepted increase in marine outbreak rates, this paper proposes that the increased iron supply has altered the micronutrient factors limiting growth of opportunistic organisms and virulence of pathogenic microbes, particularly in macronutrient-rich coastal systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H11L..06T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H11L..06T"><span>Soil moisture - precipitation feedbacks in observations and models (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taylor, C.</p> <p>2013-12-01</p> <p> datasets outside of sparsely-vegetated regions. No evidence is found for afternoon convection developing preferentially above locally moister soils. Higher resolution datasets are used to provide a clearer relationship between soil moisture patterns and convective initiation in both the <span class="hlt">Sahel</span> (Taylor et al 2011) and Europe. The observations indicate a preference for convection to initiate on soil moisture gradients, consistent with many high resolution numerical studies. The ability of models to capture the observed relationships between soil moisture and rainfall in the <span class="hlt">Sahel</span> has been evaluated. This focuses on models run at different resolutions, and with convective parameterisations switched on or off, and highlights issues associated with the parameterisation of convection. Taylor, C.M., Gounou, A., Guichard, F., Harris, P.P., Ellis, R.J.,Couvreux, F., and M. De Kauwe. 2011, Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns, Nature Geoscience, 4, 430-433, doi:10.1038/ngeo1173 Taylor, C.M., de Jeu, R.A.M., Guichard, F., Harris, P.P, and W.A. Dorigo. 2012, Afternoon rain more likely over drier soils, Nature, 489, 423-426, doi:10.1038/nature11377</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950026255','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950026255"><span>Canopy reflectance modelling of semiarid vegetation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Franklin, Janet</p> <p>1994-01-01</p> <p>Three different types of remote sensing algorithms for estimating vegetation amount and other land surface biophysical parameters were tested for semiarid environments. These included statistical linear models, the Li-Strahler geometric-optical canopy model, and linear spectral mixture analysis. The two study areas were the National Science Foundation's Jornada Long Term Ecological Research site near Las Cruces, NM, in the northern Chihuahuan desert, and the HAPEX-<span class="hlt">Sahel</span> site near Niamey, Niger, in West Africa, comprising semiarid rangeland and subtropical crop land. The statistical approach (simple and multiple regression) resulted in high correlations between SPOT satellite spectral reflectance and shrub and grass cover, although these correlations varied with the spatial scale of aggregation of the measurements. The Li-Strahler model produced estimated of shrub size and density for both study sites with large standard errors. In the Jornada, the estimates were accurate enough to be useful for characterizing structural differences among three shrub strata. In Niger, the range of shrub cover and size in short-fallow shrublands is so low that the necessity of spatially distributed estimation of shrub size and density is questionable. Spectral mixture analysis of multiscale, multitemporal, multispectral radiometer data and imagery for Niger showed a positive relationship between fractions of spectral endmembers and surface parameters of interest including soil cover, vegetation cover, and leaf area index.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27144300','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27144300"><span>Effect of Fixed Versus Adjusted Transcutaneous Electrical Nerve Stimulation Amplitude on Chronic Mechanical Low Back Pain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Elserty, Noha; Kattabei, Omaima; Elhafez, Hytham</p> <p>2016-07-01</p> <p>This study aimed to investigate the effect of adjusting pulse amplitude of transcutaneous electrical nerve stimulation versus fixed pulse amplitude in treatment of chronic mechanical low back pain. Randomized clinical trial. El-<span class="hlt">sahel</span> Teaching Hospital, Egypt. Forty-five patients with chronic low back pain assigned to three equal groups. Their ages ranged from 20 to 50 years. The three groups received the same exercise program. Group A received transcutaneous electrical nerve stimulation with fixed pulse amplitude for 40 minutes. Group B received transcutaneous electrical nerve stimulation with adjusted pulse amplitude for 40 minutes, with the pulse amplitude adjusted every 5 minutes. Group C received exercises only. Treatment sessions were applied three times per week for 4 weeks for the three groups. A visual analogue scale was used to assess pain severity, the Oswestry Disability Index was used to assess functional level, and a dual inclinometer was used to measure lumbar range of motion. Evaluations were performed before and after treatment. Visual analogue scale, Oswestry Disability Index, and back range of motion significantly differed between the two groups that received transcutaneous electrical nerve stimulation and the control group and did not significantly differ between fixed and adjusted pulse amplitude of transcutaneous electrical nerve stimulation. Adjusting pulse amplitude of transcutaneous electrical nerve stimulation does not produce a difference in the effect of transcutaneous electrical nerve stimulation used to treat chronic low back pain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70138860','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70138860"><span>Inhalable desert dust, urban emissions, and potentially biotoxic metals in urban Saharan-Sahelian air</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Garrison, Virginia H.; Majewski, Michael S.; Konde, Lassana; Wolf, Ruth E.; Otto, Richard D.; Tsuneoka, Yutaka</p> <p>2014-01-01</p> <p>Saharan dust incursions and particulates emitted from human activities degrade air quality throughout West Africa, especially in the rapidly expanding urban centers in the region. Particulate matter (PM) that can be inhaled is strongly associated with increased incidence of and mortality from cardiovascular and respiratory diseases and cancer. Air samples collected in the capital of a Saharan–Sahelian country (Bamako, Mali) between September 2012 and July 2013 were found to contain inhalable PM concentrations that exceeded World Health Organization (WHO) and US Environmental Protection Agency (USEPA) PM2.5 and PM10 24-h limits 58 – 98% of days and European Union (EU) PM10 24-h limit 98% of days. Mean concentrations were 1.2-to-4.5 fold greater than existing limits. Inhalable PM was enriched in transition metals, known to produce reactive oxygen species and initiate the inflammatory response, and other potentially bioactive and biotoxic metals/metalloids. Eroded mineral dust composed the bulk of inhalable PM, whereas most enriched metals/metalloids were likely emitted from oil combustion, biomass burning, refuse incineration, vehicle traffic, and mining activities. Human exposure to inhalable PM and associated metals/metalloids over 24-h was estimated. The findings indicate that inhalable PM in the Sahara–<span class="hlt">Sahel</span> region may present a threat to human health, especially in urban areas with greater inhalable PM and transition metal exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9018307','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9018307"><span>Ethnic diversity and disease surveillance: Guinea worm among the Fulani in a predominantly Yoruba district of Nigeria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brieger, W R; Oke, G A; Otusanya, S; Adesope, A; Tijanu, J; Banjoko, M</p> <p>1997-01-01</p> <p>Guinea-worm eradication has been progressing internationally and efforts at case containment have begun in most endemic countries. Case containment rests on the assumption that in previous phases of eradication most if not all endemic settlements have been identified. Experiences in the predominantly Yoruba communities of Ifeloju Local Government Area (LGA) in Oyo State, Nigeria, however, have shown that the settlements of ethnic minority groups may be overlooked during initial case searches and subsequent programmes of village-based reporting. The migrant cattle-herding Fulani are found throughout the savannah and <span class="hlt">sahel</span> regions of West Africa. Nearly 3000 live in 60 settlements in Ifeloju. An intensive case search identified 57 cases in 15 settlements. The assumption that village-based health workers (VBHWs) in neighbouring Yoruba farm hamlets would identify cases in the Fulani settlements, known as gaa, proved false. Only 5 endemic gaa were located next to a Yoruba hamlet that had a VBHW, and even then the VBHW did not identify and report the cases in the gaa. Efforts to recruit VBHWs for each endemic gaa are recommended, but only after LGA staff improve the poor relationship between themselves and the Fulani, whom they view as outsiders. The results also imply the need for Guinea worm eradication staff in neighbouring LGAs, states and countries to search actively for the disease among their minority populations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16770692','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16770692"><span>Amino acid, mineral and fatty acid content of pumpkin seeds (Cucurbita spp) and Cyperus esculentus nuts in the Republic of Niger.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Glew, R H; Glew, R S; Chuang, L-T; Huang, Y-S; Millson, M; Constans, D; Vanderjagt, D J</p> <p>2006-06-01</p> <p>Dried seeds and nuts are widely consumed by indigenous populations of the western <span class="hlt">Sahel</span>, especially those who inhabit rural areas. In light of the need for quantitative information regarding the content of particular nutrients in these plant foods, we collected dried pumpkin (Cucurbita spp) seeds and nuts of Cyperus esculentus in the Republic of Niger and analyzed them for their content of essential amino acids, minerals and trace elements, and fatty acids. On a dry weight basis, pumpkin seed contained 58.8% protein and 29.8% fat. However, the lysine score of the protein was only 65% relative to the FAO/WHO protein standard. The pumpkin seed contained useful amounts of linoleic (92 microg/g dry weight) and the following elements (on a microg per g dry weight basis): potassium (5,790), magnesium (5,690), manganese (49.3), zinc (113), selenium (1.29), copper (15.4), chromium (2.84), and molybdenum (0.81), but low amounts of calcium and iron. Except for potassium (5,573 microg/g dry weight) and chromium (2.88 microg/g dry weight), the C. esculentis nuts contained much less of these same nutrients compared to pumpkin seeds. In conclusion, pumpkin seeds represent a useful source of many nutrients essential to humans. The data in this report should of practical value to public health officials in rural areas of sub-Saharan Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983QuRes..19..279B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983QuRes..19..279B"><span>Human response to environmental change in the perspective of future, global climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Butzer, Karl W.</p> <p>1983-05-01</p> <p>Human response to severe environmental stress is conceived and implemented by individuals, but must be approved by the group. These decisions are made with respect to perceived circumstances. Societies are enmeshed within adaptive systems that provide a matrix of opportunities and constraints for a wide range of potential behavioral variability. Such systems repeatedly readjust to short-term crises, e.g., droughts, but persistent and severe environmental stress may require substantial revision of adaptive strategies. The <span class="hlt">Sahel</span> drought of 1968-1973 is an example of a brief but severe crisis, recurring along the Saharan margins perhaps once every 30 years. Closer inspection shows links between intensified intertribal warfare and ecological stress in the lower Omo Valley. The decline of the Egyptian New Kingdom during the 12th century B.C., in response to economic stagnation, sociopolitical instability, dynastic weakness, foreign pressures, and poor Nile floods over 50-70 years, represents a more complex and fundamental modification, with systemic simplification lasting 450 years. Such insights can be applied to future, global climatic change due to increasing atmospheric CO 2. Simulation and paleoclimatic experience suggest a drier climate for the North American and Soviet breadbaskets, to threaten world food supplies at a time of maximum demographic pressures and declining resources. Public perception and remedial planning should receive the attention of Quaternary scientists, in order to preempt an involuntary, global, systemic simplification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25243921','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25243921"><span>Inhalable desert dust, urban emissions, and potentially biotoxic metals in urban Saharan-Sahelian air.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Garrison, V H; Majewski, M S; Konde, L; Wolf, R E; Otto, R D; Tsuneoka, Y</p> <p>2014-12-01</p> <p>Saharan dust incursions and particulates emitted from human activities degrade air quality throughout West Africa, especially in the rapidly expanding urban centers in the region. Particulate matter (PM) that can be inhaled is strongly associated with increased incidence of and mortality from cardiovascular and respiratory diseases and cancer. Air samples collected in the capital of a Saharan-Sahelian country (Bamako, Mali) between September 2012 and July 2013 were found to contain inhalable PM concentrations that exceeded World Health Organization (WHO) and US Environmental Protection Agency (USEPA) PM2.5 and PM10 24-h limits 58 - 98% of days and European Union (EU) PM10 24-h limit 98% of days. Mean concentrations were 1.2-to-4.5 fold greater than existing limits. Inhalable PM was enriched in transition metals, known to produce reactive oxygen species and initiate the inflammatory response, and other potentially bioactive and biotoxic metals/metalloids. Eroded mineral dust composed the bulk of inhalable PM, whereas most enriched metals/metalloids were likely emitted from oil combustion, biomass burning, refuse incineration, vehicle traffic, and mining activities. Human exposure to inhalable PM and associated metals/metalloids over 24-h was estimated. The findings indicate that inhalable PM in the Sahara-<span class="hlt">Sahel</span> region may present a threat to human health, especially in urban areas with greater inhalable PM and transition metal exposure. Published by Elsevier B.V.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GMDD....8.4781L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GMDD....8.4781L"><span>Modelling spatial and temporal vegetation variability with the Climate Constrained Vegetation Index: evidence of CO2 fertilisation and of water stress in continental interiors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Los, S. O.</p> <p>2015-06-01</p> <p>A model was developed to simulate spatial, seasonal and interannual variations in vegetation in response to temperature, precipitation and atmospheric CO2 concentrations; the model addresses shortcomings in current implementations. The model uses the minimum of 12 temperature and precipitation constraint functions to simulate NDVI. Functions vary based on the Köppen-Trewartha climate classification to take adaptations of vegetation to climate into account. The simulated NDVI, referred to as the climate constrained vegetation index (CCVI), captured the spatial variability (0.82 < r <0.87), seasonal variability (median r = 0.83) and interannual variability (median global r = 0.24) in NDVI. The CCVI simulated the effects of adverse climate on vegetation during the 1984 drought in the <span class="hlt">Sahel</span> and during dust bowls of the 1930s and 1950s in the Great Plains in North America. A global CO2 fertilisation effect was found in NDVI data, similar in magnitude to that of earlier estimates (8 % for the 20th century). This effect increased linearly with simple ratio, a transformation of the NDVI. Three CCVI scenarios, based on climate simulations using the representative concentration pathway RCP4.5, showed a greater sensitivity of vegetation towards precipitation in Northern Hemisphere mid latitudes than is currently implemented in climate models. This higher sensitivity is of importance to assess the impact of climate variability on vegetation, in particular on agricultural productivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713431C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713431C"><span>Evaluation and attribution of vegetation contribution to seasonal climate predictability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Catalano, Franco; Alessandri, Andrea; De Felice, Matteo</p> <p>2015-04-01</p> <p>The land surface model of EC-Earth has been modified to include dependence of vegetation densities on the Leaf Area Index (LAI), based on the Lambert-Beer formulation. Effective vegetation fractional coverage can now vary at seasonal and interannual time-scales and therefore affect biophysical parameters such as the surface roughness, albedo and soil field capacity. The modified model is used to perform a real predictability seasonal hindcast experiment. LAI is prescribed using a recent observational dataset based on the third generation GIMMS and MODIS satellite data. Hindcast setup is: 7 months forecast length, 2 start dates (1st May and 1st November), 10 members, 28 years (1982-2009). The effect of the realistic LAI prescribed from observation is evaluated with respect to a control experiment where LAI does not vary. Hindcast results demonstrate that a realistic representation of vegetation significantly improves the forecasts of temperature and precipitation. The sensitivity is particularly large for temperature during boreal winter over central North America and Central Asia. This may be attributed in particular to the effect of the high vegetation component on the snow cover. Summer forecasts are improved in particular for precipitation over Europe, <span class="hlt">Sahel</span>, North America, West Russia and Nordeste. Correlation improvements depends on the links between targets (temperature and precipitation) and drivers (surface heat fluxes, albedo, soil moisture, evapotranspiration, moisture divergence) which varies from region to region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GPC...127...58V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GPC...127...58V"><span>Tree-ring δ18O in African mahogany (Entandrophragma utile) records regional precipitation and can be used for climate reconstructions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>van der Sleen, Peter; Groenendijk, Peter; Zuidema, Pieter A.</p> <p>2015-04-01</p> <p>The availability of instrumental climate data in West and Central Africa is very restricted, both in space and time. This limits the understanding of the regional climate system and the monitoring of climate change and causes a need for proxies that allow the reconstruction of paleoclimatic variability. Here we show that oxygen isotope values (δ18O) in tree rings of Entandrophragma utile from North-western Cameroon correlate to precipitation on a regional to sub-continental scale (1930-2009). All found correlations were negative, following the proposed recording of the 'amount effect' by trees in the tropics. The capacity of E. utile to record the variability of regional precipitation is also confirmed by the significant correlation of tree-ring δ18O with river discharge data (1944-1983), outgoing longwave radiation (a proxy for cloud cover; 1974-2011) and sea surface salinity in the Gulf of Guinea (1950-2011). Furthermore, the high values in the δ18O chronology from 1970 onwards coincide with the <span class="hlt">Sahel</span> drought period. Given that E. utile presents clear annual growth rings, has a wide-spread distribution in tropical Africa and is long lived (> 250 years), we argue that the analysis of oxygen isotopes in growth rings of this species is a promising tool for the study of paleoclimatic variability during the last centuries in West and Central Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.journals.royalsoc.ac.uk/link.asp?id=l06pqmnd8xpuupcy','USGSPUBS'); return false;" href="http://www.journals.royalsoc.ac.uk/link.asp?id=l06pqmnd8xpuupcy"><span>Timing of autumn bird migration under climate change: advances in long-distance migrants, delays in short-distance migrants</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Jenni, L.; Kery, M.</p> <p>2003-01-01</p> <p>As a response to increasing spring temperature in temperate regions in recent years, populations of many plant and animal species, including migratory birds, have advanced the seasonal start of their reproduction or growth. However, the effects of climate changes on subsequent events of the annual cycle remain poorly understood. We investigated long-term changes in the timing of autumn migration in birds, a key event in the annual cycle limiting the reproductive period. Using data spanning a 42-year period, we analysed long-term changes in the passage of 65 species of migratory birds through Western Europe. The autumn passage of migrants wintering south of the Sahara has advanced in recent years, presumably as a result of selection pressure to cross the <span class="hlt">Sahel</span> before its seasonal dry period. In contrast, migrants wintering north of the Sahara have delayed autumn passage. In addition, species with a variable rather than a fixed number of broods per year have delayed passage, possibly because they are free to attempt more broods. Recent climate changes seem to have a simple unidirectional effect on the seasonal onset of reproduction, but complex and opposing effects on the timing of subsequent events in the annual cycle, depending on the ecology and life history of a species. This complicates predictions of overall effects of global warming on avian communities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090023883&hterms=soil+maps&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsoil%2Bmaps','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090023883&hterms=soil+maps&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsoil%2Bmaps"><span>Satellite Mapping of Rain-Induced Nitric Oxide Emissions from Soils</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jaegle, L.; Martin, R. V.; Chance, K.; Steinberger, L.; Kurosu, T. P.; Jacob, D. J.; Modi, A. I.; Yoboue, V.; Sigha-Nkamdjou, L.; Galy-Lacaux, C.</p> <p>2004-01-01</p> <p>We use space-based observations of NO2 columns from the Global Ozone Monitoring Experiment (GOME) to map the spatial and seasonal variations of NOx emissions over Africa during 2000. The GOME observations show not only enhanced tropospheric NO2 columns from biomass burning during the dry season but also comparable enhancements from soil emissions during the rainy season over the <span class="hlt">Sahel</span>. These soil emissions occur in strong pulses lasting 1-3 weeks following the onset of rain, and affect 3 million sq km of semiarid sub-Saharan savanna. Surface observations of NO2 from the International Global Atmospheric Chemistry (IGAC)/Deposition of Biochemically Important Trace Species (DEBITS)/Africa (IDAF) network over West Africa provide further evidence for a strong role for microbial soil sources. By combining inverse modeling of GOME NO2 columns with space-based observations of fires, we estimate that soils contribute 3.3+/-1.8 TgN/year, similar to the biomass burning source (3.8+/-2.1 TgN/year), and thus account for 40% of surface NO(x) emissions over Africa. Extrapolating to all the tropics, we estimate a 7.3 TgN/year biogenic soil source, which is a factor of 2 larger compared to model-based inventories but agrees with observation-based inventories. These large soil NO(x) emissions are likely to significantly contribute to the ozone enhancement originating from tropical Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3089383','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3089383"><span>Random demographic household surveys in highly mobile pastoral communities in Chad</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Béchir, Mahamat; Hattendorf, Jan; Bonfoh, Bassirou; Zinsstag, Jakob; Schelling, Esther</p> <p>2011-01-01</p> <p>Abstract Problem Reliable demographic data is a central requirement for health planning and management, and for the implementation of adequate interventions. This study addresses the lack of demographic data on mobile pastoral communities in the <span class="hlt">Sahel</span>. Approach A total of 1081 Arab, Fulani and Gorane women and 2541 children (1336 boys and 1205 girls) were interviewed and registered by a biometric fingerprint scanner in five repeated random transect demographic and health surveys conducted from March 2007 to January 2008 in the Lake Chad region in Chad. Local setting Important determinants for the planning and implementation of household surveys among mobile pastoral communities include: environmental factors; availability of women for interviews; difficulties in defining “own” children; the need for information-education-communication campaigns; and informed consent of husbands in typically patriarchal societies. Relevant changes Due to their high mobility, only 5% (56/1081) of registered women were encountered twice. Therefore, it was not possible to establish a demographic and health cohort. Lessons learnt Prospective demographic and health cohorts are the most accurate method to assess child mortality and other demographic indices. However, their feasibility in a highly mobile pastoral setting remains to be shown. Future interdisciplinary scientific efforts need to target innovative methods, tools and approaches to include marginalized communities in operational health and demographic surveillance systems. PMID:21556307</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12965011','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12965011"><span>Timing of autumn bird migration under climate change: advances in long-distance migrants, delays in short-distance migrants.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jenni, Lukas; Kéry, Marc</p> <p>2003-07-22</p> <p>As a response to increasing spring temperature in temperate regions in recent years, populations of many plant and animal species, including migratory birds, have advanced the seasonal start of their reproduction or growth. However, the effects of climate changes on subsequent events of the annual cycle remain poorly understood. We investigated long-term changes in the timing of autumn migration in birds, a key event in the annual cycle limiting the reproductive period. Using data spanning a 42-year period, we analysed long-term changes in the passage of 65 species of migratory birds through Western Europe. The autumn passage of migrants wintering south of the Sahara has advanced in recent years, presumably as a result of selection pressure to cross the <span class="hlt">Sahel</span> before its seasonal dry period. In contrast, migrants wintering north of the Sahara have delayed autumn passage. In addition, species with a variable rather than a fixed number of broods per year have delayed passage, possibly because they are free to attempt more broods. Recent climate changes seem to have a simple unidirectional effect on the seasonal onset of reproduction, but complex and opposing effects on the timing of subsequent events in the annual cycle, depending on the ecology and life history of a species. This complicates predictions of overall effects of global warming on avian communities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19..804G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19..804G"><span>Heat waves in Senegal : detection, characterization and associated processes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gnacoussa Sambou, Marie Jeanne; Janicot, Serge; Badiane, Daouda; Pohl, Benjamin; Dieng, Abdou L.; Gaye, Amadou T.</p> <p>2017-04-01</p> <p>Atmospheric configuration and synoptic evolution of patterns associated with Senegalese heat wave (HW) are examined on the period 1979-2014 using the Global Surface Summary of the Day (GSOD) observational database and ERA-Interim reanalysis. Since there is no objective and uniform definition of HW events, threshold methods based on atmospheric variables as daily maximum (Tmax) / minimum (Tmin) temperatures and daily mean apparent temperature (AT) are used to define HW threshold detection. Each criterion is related to a specific category of HW events: Tmax (warm day events), Tmin (warm night events) and AT (combining temperature and moisture). These definitions are used in order to characterize as well as possible the warm events over the Senegalese regions (oceanic versus continental region). Statistics on time evolution and spatial distribution of warm events are carried out over the 2 seasons of maximum temperature (March-May and October-November). For each season, a composite of HW events, as well as the most extended event over Senegal (as a case study) are analyzed using usual atmospheric fields (sea level pressure, geopotential height, total column water content, wind components, 2m temperature). This study is part of the project ACASIS (https://acasis.locean-ipsl.upmc.fr/doku.php) on heat waves occurrences over the <span class="hlt">Sahel</span> and their impact on health. Keywords: heat wave, Senegal, ACASIS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140001070','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140001070"><span>Precipitation Response to Regional Radiative Forcing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shindell, D. T.; Voulgarakis, A.; Faluvegi, G.; Milly, G.</p> <p>2012-01-01</p> <p>Precipitation shifts can have large impacts on human society and ecosystems. Many aspects of how inhomogeneous radiative forcings influence precipitation remain unclear, however. Here we investigate regional precipitation responses to various forcings imposed in different latitude bands in a climate model. We find that several regions show strong, significant responses to most forcings, but that the magnitude and even the sign depends upon the forcing location and type. Aerosol and ozone forcings typically induce larger responses than equivalent carbon dioxide (CO2) forcing, and the influence of remote forcings often outweighs that of local forcings. Consistent with this, ozone and especially aerosols contribute greatly to precipitation changes over the <span class="hlt">Sahel</span> and South and East Asia in historical simulations, and inclusion of aerosols greatly increases the agreement with observed trends in these areas, which cannot be attributed to either greenhouse gases or natural forcings. Estimates of precipitation responses derived from multiplying our Regional Precipitation Potentials (RPP; the response per unit forcing relationships) by historical forcings typically capture the actual response in full transient climate simulations fairly well, suggesting that these relationships may provide useful metrics. The strong sensitivity to aerosol and ozone forcing suggests that although some air quality improvements may unmask greenhouse gas-induced warming, they have large benefits for reducing regional disruption of the hydrologic cycle.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAMES...9.2027G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAMES...9.2027G"><span>Simulating climate and stable water isotopes during the Last Interglacial using a coupled climate-isotope model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gierz, Paul; Werner, Martin; Lohmann, Gerrit</p> <p>2017-09-01</p> <p>Understanding the dynamics of warm climate states has gained increasing importance in the face of anthropogenic climate change, and while it is possible to simulate warm interglacial climates, these simulated results cannot be evaluated without the aid of geochemical proxies. One such proxy is δ18O, which allows for inference about both a climate state's hydrology and temperature. We utilize a stable water isotope equipped climate model to simulate three stages during the Last Interglacial (LIG), corresponding to 130, 125, and 120 kyr before present, using forcings for orbital configuration as well as greenhouse gases. We discover heterogeneous responses in the mean δ18O signal to the climate forcing, with large areas of depletion in the LIG δ18O signal over the tropical Atlantic, the <span class="hlt">Sahel</span>, and the Indian subcontinent, and with enrichment over the Pacific and Arctic Oceans. While we find that the climatology mean relationship between δ18O and temperature remains stable during the LIG, we also discover that this relationship is not spatially consistent. Our results suggest that great care must be taken when comparing δ18O records of different paleoclimate archives with the results of climate models as both the qualitative and quantitative interpretation of δ18O variations as a proxy for past temperature changes may be problematic due to the complexity of the signals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/7283037-volcanic-signal-goddard-institute-space-studies-three-dimensional-model-simulations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/7283037-volcanic-signal-goddard-institute-space-studies-three-dimensional-model-simulations"><span>The volcanic signal in Goddard Institute for Space Studies three-dimensional model simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Robock, A.; Liu, Y.</p> <p>1994-01-01</p> <p>Transient calculations of the Goddard Institute for Space Studies general circulation model for the climatic signal of volcanic eruptions are analyzed. By compositing the output for two different volcanoes for scenario A and five different volcanos for scenario B, the natural variability is suppressed and the volcanic signals are extracted. Significant global means surface air temperature cooling and precipitation reduction are found for several years following the eruptions, with larger changes in the Northern Hemisphere (NH) than in the Southern Hemisphere. The global-average temperature response lasts for more than four years, but the precipitation response disappears after three years. Themore » largest cooling in the model occurs in the NH summer of the year after spring eruptions. Significant zonal-average temperature reductions begin in the tropics immediately after the eruptions and extend to 45[degrees]S-45[degrees]N in the year after the eruptions. In the second year, cooling is still seen from 30[degrees]S to 30[degrees]N. Because of the low variability in this model as compared to the real world, these signals may appear more significant here than they would be attempting to isolate them using real data. The results suggest that volcanoes can enhance the drought in the <span class="hlt">Sahel</span>. No evidence was found that stratospheric aerosols from the low-latitude volcanic eruptions can trigger ENSO events in this model.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960016588','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960016588"><span>Radiative transfer in shrub savanna sites in Niger: Preliminary results from HAPEX-<span class="hlt">Sahel</span>. Part 1: Modelling surface reflectance using a geometric-optical approach</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Franklin, Janet; Duncan, Jeff; Huete, Alfredo R.; vanLeeuwen, W. J. D.; Li, Xiaowen; Begue, Agnes</p> <p>1994-01-01</p> <p>To use optical remote sensing to monitor land surface-climate interactions over large areas, algorithms must be developed to relate multispectral measurements to key variables controlling the exchange of matter (water, carbon dioxide) and energy between the land surface and the atmosphere. The proportion of the ground covered by vegetation and the interception of photosynthetically active radiation (PAR) by vegetation are examples of two variables related to evapotranspiration and primary production, respectively. An areal-proportion model of the multispectral reflectance of shrub savanna, composed of scattered shrubs with a grass, forb or soil understory, predicted the reflectance of two 0.5 km(exp 2) sites as the area-weighted average of the shrub and understory or 'background' reflectances. Although the shaded crown and shaded background have darker reflectances, ignoring them in the area-weighted model is not serious when shrub cover is low and solar zenith angle is small. A submodel predicted the reflectance of the shrub crown as a function of the foliage reflectance and amount of plant material within the crown, and the background reflectance scattered or transmitted through canopy gaps (referred to as a soil-plant 'spectral interaction' term). One may be able to combine these two models to estimate both the fraction of vegetation cover and interception of PAR by green vegetation in a shrub savanna.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18.3817L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18.3817L"><span>Aircraft and ground measurements of dust aerosols over the west African coast in summer 2015 during ICE-D and AER-D</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Dantong; Taylor, Jonathan W.; Crosier, Jonathan; Marsden, Nicholas; Bower, Keith N.; Lloyd, Gary; Ryder, Claire L.; Brooke, Jennifer K.; Cotton, Richard; Marenco, Franco; Blyth, Alan; Cui, Zhiqiang; Estelles, Victor; Gallagher, Martin; Coe, Hugh; Choularton, Tom W.</p> <p>2018-03-01</p> <p>During the summertime, dust from the Sahara can be efficiently transported westwards within the Saharan air layer (SAL). This can lead to high aerosol loadings being observed above a relatively clean marine boundary layer (MBL) in the tropical Atlantic Ocean. These dust layers can impart significant radiative effects through strong visible and IR light absorption and scattering, and can also have indirect impacts by altering cloud properties. The processing of the dust aerosol can result in changes in both direct and indirect radiative effects, leading to significant uncertainty in climate prediction in this region. During August 2015, measurements of aerosol and cloud properties were conducted off the coast of west Africa as part of the Ice in Cloud Experiment - Dust (ICE-D) and AERosol properties - Dust (AER-D) campaigns. Observations were obtained over a 4-week period using the UK Facility for Atmospheric Airborne Measurements (FAAM) BAe 146 aircraft based on Santiago Island, Cabo Verde. Ground-based observations were collected from Praia (14°57' N, 23°29' W; 100 m a.s.l.), also located on Santiago Island. The dust in the SAL was mostly sampled in situ at altitudes of 2-4 km, and the potential dust age was estimated by backward trajectory analysis. The particle mass concentration (at diameter d = 0.1-20 µm) decreased with transport time. Mean effective diameter (Deff) for supermicron SAL dust (d = 1-20 µm) was found to be 5-6 µm regardless of dust age, whereas submicron Deff (d = 0.1-1 µm) showed a decreasing trend with longer transport. For the first time, an airborne laser-induced incandescence instrument (the single particle soot photometer - SP2) was deployed to measure the hematite content of dust. For the <span class="hlt">Sahel</span>-influenced dust in the SAL, the observed hematite mass fraction of dust (FHm) was found to be anti-correlated with the single scattering albedo (SSA, λ = 550 nm, for particles d < 2.5 µm); as potential dust age increased from 2 to 7 days</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23916202','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23916202"><span>[The international man-media Tessékéré (OHMi) Observatory: a research tool to study the complexity of arid ecosystems in <span class="hlt">Sahel</span>].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guissé, Aliou; Boëtsch, Gilles; Ducourneau, Axel; Goffner, Deborah; Gueye, Lamine</p> <p>2013-01-01</p> <p>In the Sahelian zone, the drought phenomenon, combined with anthropic factors (monoculture, bush fires, defect or deficit of manure, overgrazing, etc.), has seriously affected ecological great balances, involving a degradation of the natural resources as well as a fall in agricultural productions, pointing to a process of desertification. To face these challenges, in the course of the 8th ordinary session of the conference of the Heads of States of the African Union held in January 2007 in Addis Ababa (Ethiopia), 11 countries adopted the Panafrican project called the Green Great Wall (GGW). The total objective of the GGW is to contribute i) to the fight against the desert's advance, ii) to the development of the Saharan-Sahelian zones toward a durable management of the natural resources, and iii) to the fight against poverty. It deals with the construction of a set of zones of afforestation crossing the whole African continent in the long term (7000km of which are in the west). Even if some decisions in the launching phase the GGW must be taken quickly, one cannot do without investment in interdisciplinary research. In particular, associating fundamental research and applied research will allow us to ensure the success in the medium and long term of such a large-scale reforestation project. Research segmented in compartmentalized knowledge fields needed to get adequate tools, among which OHMi Tessékéré, initiated by INNEE (Centre national de la recherche scientifique [CNRS]), in partnership with UCAD, constitutes an example. This suitable scientific tool, capable of action flexibility, of self-financing capacity, anchored in civil society, ready to implement a pragmatic and local interdisciplinarity founded currently on the concept of socio-ecological system (SES), is the one we chose to conduct our studies on the Ferlo arid ecosystems. Copyright © 2013 Académie des sciences. Published by Elsevier SAS. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020047055','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020047055"><span>Modeling Feedbacks Between Water and Vegetation in the Climate System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, James R.; Russell, Gary L.; Hansen, James E. (Technical Monitor)</p> <p>2001-01-01</p> <p>Not only is water essential for life on earth, but life itself affects the global hydrologic cycle and consequently the climate of the planet. Whether the global feedbacks between life and the hydrologic cycle tend to stabilize the climate system about some equilibrium level is difficult to assess. We use a global climate model to examine how the presence of vegetation can affect the hydrologic cycle in a particular region. A control for the present climate is compared with a model experiment in which the Sahara Desert is replaced by vegetation in the form of trees and shrubs common to the <span class="hlt">Sahel</span> region. A second model experiment is designed to identify the separate roles of two different effects of vegetation, namely the modified albedo and the presence of roots that can extract moisture from deeper soil layers. The results show that the presence of vegetation leads to increases in precipitation and soil moisture in western Sahara. In eastern Sahara, the changes are less clear. The increase in soil moisture is greater when the desert albedo is replaced by the vegetation albedo than when both the vegetation albedo and roots are added. The effect of roots is to withdraw water from deeper layers during the dry season. One implication of this study is that the insertion of vegetation into the Sahara modifies the hydrologic cycle so that the vegetation is more likely to persist than initially.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EaFut...5..144G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EaFut...5..144G"><span>Climate risk and food security in Mali: A historical perspective on adaptation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Giannini, Alessandra; Krishnamurthy, P. Krishna; Cousin, Rémi; Labidi, Naouar; Choularton, Richard J.</p> <p>2017-02-01</p> <p>We combine socioeconomic data from a large-scale household survey with historical climate data to map the climate sensitivity of availability and access dimensions of food security in Mali, and infer the ways in which at-risk communities may have been impacted by persistent climatic shift. Thirty years after 1982-1984, the period of most intense drought during the protracted late 20th century drying of the <span class="hlt">Sahel</span>, the impact of drought on livelihoods and food security is still recognizable in the Sahelian center of Mali. This impact is expressed in the larger fraction of households in this Sahelian center of the country—the agro-ecological transition between pastoralism in the north, and sedentary agriculture in the south—who practice agriculture but not livestock raising, despite environmental conditions that are suitable to their combination. These households have lower food security and rely more frequently on detrimental nutrition-based coping strategies, such as reducing the quantity or quality of meals. In contrast, the more food secure households show a clear tendency toward livelihood diversification away from subsistence agriculture. These households produce less of what they consume, yet spend less on food in proportion. The analysis points to the value of interdisciplinary research—in this case bridging climate science and vulnerability analysis—to gain a dynamical understanding of complex systems, understanding which may be exploited to address real-world challenges, offering lessons about food security and local adaptation strategies in places among the most vulnerable to climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28451036','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28451036"><span>Influence of shift work on the physical work capacity of Tunisian nurses: a cross-sectional study in two university hospitals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Merchaoui, Irtyah; Bouzgarrou, Lamia; Mnasri, Ahlem; Mghanem, Mounir; Akrout, Mohamed; Malchaire, Jacques; Chaari, Neila</p> <p>2017-01-01</p> <p>This study has been performed to determine the influence of rotating shift work on physical working capacity of Tunisian nurses and to design recommendations to managers so that they implement effective preventive measures. It is a cross-sectional design using a standardized questionnaire and many physical capacity tests on a representative sample of 1181 nurses and nursing assistants from two university hospital centers of the school of Medicine of Monastir located in the Tunisian <span class="hlt">Sahel</span>. 293 participants have been recruited by stratified random sampling according to gender and departments. Maximum Grip strength, 30s sit-to-stand test, one leg test, Fingertip-to-Floor test, Saltsa test and peak expiratory flow were used to assess physical capacity. Work ability was assessed through the workability index. Mental and physical loads were heavily perceived in shift healthcare workers (p=0.01; p=0.02). The maximum grip force was stronger in rotating shift work nurses (p=0.0001). Regarding to the seniority subgroups in each kind of work schedule, the Body Mass Index was increasing with seniority in both schedules. All the physical tests, were better in less-than-ten-year groups. Peak Flow and grip strength were significantly better in less-than-ten-year seniority in shift work group. There is a need to improve the design of the existing shift systems and to reduce as much as possible shift schedule as well as to avoid shift schedule for over-10-year-seniority nurses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3885432','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3885432"><span>Narrow-Front Loop Migration in a Population of the Common Cuckoo Cuculus canorus, as Revealed by Satellite Telemetry</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Willemoes, Mikkel; Strandberg, Roine; Klaassen, Raymond H. G.; Tøttrup, Anders P.; Vardanis, Yannis; Howey, Paul W.; Thorup, Kasper; Wikelski, Martin; Alerstam, Thomas</p> <p>2014-01-01</p> <p>Narrow migration corridors known in diurnal, social migrants such as raptors, storks and geese are thought to be caused by topographical leading line effects in combination with learning detailed routes across generations. Here, we document narrow-front migration in a nocturnal, solitary migrant, the common cuckoo Cuculus canorus, using satellite telemetry. We tracked the migration of adult cuckoos from the breeding grounds in southern Scandinavia (n = 8), to wintering sites in south-western Central Africa (n = 6) and back to the breeding grounds (n = 3). Migration patterns were very complex; in addition to the breeding and wintering sites, six different stopover sites were identified during the 16,000 km annual route that formed a large-scale clockwise loop. Despite this complexity, individuals showed surprisingly similar migration patterns, with very little variation between routes. We compared observed tracks with simulated routes based on vector orientation (with and without effects of barriers on orientation and survival). Observed distances between routes were often significantly smaller than expected if the routes were established on the basis of an innate vector orientation programme. Average distance between individuals in eastern <span class="hlt">Sahel</span> after having migrated more than 5,000 km for example, was merely 164 km. This implies that more sophisticated inherent guiding mechanisms, possibly involving elements of intermediate goal area navigation or more elaborate external cues, are necessary to explain the complex narrow-front migration pattern observed for the cuckoos in this study. PMID:24421890</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170002771&hterms=target&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtarget','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170002771&hterms=target&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtarget"><span>Assimilation of MODIS Dark Target and Deep Blue Observations in the Dust Aerosol Component of NMMB-MONARCH version 1.0</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Di Tomaso, Enza; Schutgens, Nick A. J.; Jorba, Oriol; Perez Garcia-Pando, Carlos</p> <p>2017-01-01</p> <p>A data assimilation capability has been built for the NMMB-MONARCH chemical weather prediction system, with a focus on mineral dust, a prominent type of aerosol. An ensemble-based Kalman filter technique (namely the local ensemble transform Kalman filter - LETKF) has been utilized to optimally combine model background and satellite retrievals. Our implementation of the ensemble is based on known uncertainties in the physical parametrizations of the dust emission scheme. Experiments showed that MODIS AOD retrievals using the Dark Target algorithm can help NMMB-MONARCH to better characterize atmospheric dust. This is particularly true for the analysis of the dust outflow in the <span class="hlt">Sahel</span> region and over the African Atlantic coast. The assimilation of MODIS AOD retrievals based on the Deep Blue algorithm has a further positive impact in the analysis downwind from the strongest dust sources of the Sahara and in the Arabian Peninsula. An analysis-initialized forecast performs better (lower forecast error and higher correlation with observations) than a standard forecast, with the exception of underestimating dust in the long-range Atlantic transport and degradation of the temporal evolution of dust in some regions after day 1. Particularly relevant is the improved forecast over the Sahara throughout the forecast range thanks to the assimilation of Deep Blue retrievals over areas not easily covered by other observational datasets.The present study on mineral dust is a first step towards data assimilation with a complete aerosol prediction system that includes multiple aerosol species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MAP...130..279J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MAP...130..279J"><span>Observed formation of easterly waves over northeast Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jury, Mark R.</p> <p>2018-06-01</p> <p>This study explores the thermodynamic and kinematic features of easterly waves over northeast Africa in July-September season 2005-2015. A daily African easterly wave (AEW) index is formulated from transient satellite rainfall and reanalysis vorticity, and the ten most intense cases are studied by composite analysis. Surface moisture is advected from central Africa towards the Red Sea during AEW formation. The anomalous 600 hPa wind circulation is comprized of a cyclonic-south anticyclonic-north rotor pair and accentuated easterly jet along 17N. Composite convection is initiated over Ethiopia and subsequently intensifies following interaction with a zonal circulation located downstream. Composite AEW temperature anomalies reveal a cool lower-warm upper layer heating profile. 2-8 day variance of satellite OLR reaches a maximum over the southern Arabian Peninsula, suggesting an upstream role for surface heating and the Somali Jet. The large scale environment is analyzed by regression of the AEW index onto daily fields of rainfall, surface air pressure and temperature in July-September season ( N = 1004). The rainfall regression reflects a westward propagating AEW wave-train of higher values on 13N and lower values on 7N with a longitude spacing of 25°. The air pressure and temperature regression features a N-S dipole indicating an anomalous northward ITCZ. A low pressure signal west of the Maritime Continent coupled with a warm zone across the South Indian Ocean coincides with AEW formation over the eastern <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1003593-community-land-model-its-climate-statistics-component-community-climate-system-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1003593-community-land-model-its-climate-statistics-component-community-climate-system-model"><span>The Community Land Model and Its Climate Statistics as a Component of the Community Climate System Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Dickinson, Robert E.; Oleson, Keith; Bonan, Gordon</p> <p>2006-01-01</p> <p>Several multidecadal simulations have been carried out with the new version of the Community Climate System Model (CCSM). This paper reports an analysis of the land component of these simulations. Global annual averages over land appear to be within the uncertainty of observational datasets, but the seasonal cycle over land of temperature and precipitation appears to be too weak. These departures from observations appear to be primarily a consequence of deficiencies in the simulation of the atmospheric model rather than of the land processes. High latitudes of northern winter are biased sufficiently warm to have a significant impact on themore » simulated value of global land temperature. The precipitation is approximately doubled from what it should be at some locations, and the snowpack and spring runoff are also excessive. The winter precipitation over Tibet is larger than observed. About two-thirds of this precipitation is sublimated during the winter, but what remains still produces a snowpack that is very large compared to that observed with correspondingly excessive spring runoff. A large cold anomaly over the Sahara Desert and <span class="hlt">Sahel</span> also appears to be a consequence of a large anomaly in downward longwave radiation; low column water vapor appears to be most responsible. The modeled precipitation over the Amazon basin is low compared to that observed, the soil becomes too dry, and the temperature is too warm during the dry season.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAfES.123...57F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAfES.123...57F"><span>Evidences of "Lago-Mare" episode around the Messinian-Pliocene boundary in eastern Tunisia (central Mediterranean)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frigui, Mouna; Ben Youssef, Mohamed; Ouaja, Mohamed</p> <p>2016-11-01</p> <p>Eight stratigraphic sections, located in northeastern part of the <span class="hlt">Sahel</span> area of Tunisia recorded evidences of "Lago-Mare" episode and events related to the Messinian-Late Pliocene interval. A comparison with previous studies carried on sections from neighboring areas and boreholes data drilled within the Gulf of Hammamet and the Gulf of Gabès, is conducted and gives useful information to characterize the Late Messinian to Late Pliocene events. The most notable feature distinguished in the studied area consists on the lack of gypsum, commonly recorded in relation with the crucial event of the Messinian Salinity Crisis. However, only lagoonal deposits, bearing messinian brackish fauna, are encountered. These sediments are usually attributed to the "Segui" formation or the so called "Mio-Pliocene continental". Thin sections samples and field observations have recognized sands, marls, clays, lacustrine limestone, some gypsum lenses, mud-cracks, lignite and Messinian brackish fauna. Similar deposits were previously described in the Kechabta basin from the Northern Tunisia and in some wells from the Gulf of Gabès and the Gulf of Hammamet. We suggest that all these facies belong to the coeval of the "Lago-Mare" facies within Eastern and Western Mediterranean basins (e.g. Sicily, Mallorca, Libya and Cyprus). Finally, four major erosional surfaces have been recorded within the Late Messinian-Late Pliocene deposits, aged post-Tortonian, intra-Messinian, Late Messinian and intra-Pliocene times. They seem to be the result of local tectonic uplifts and eustatic fluctuations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.8028M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.8028M"><span>Integrating water and carbon fluxes at the ecosystem scale across African ecosystems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Merbold, Lutz; Brümmer, Christian; Archibald, Sally; Ardö, Jonas; Arneth, Almut; Brüggemann, Nicolas; de Grandcourt, Agnes; Kergoat, Laurent; Moffat, Antje M.; Mougin, Eric; Nouvellon, Yann; Saint-Andre, Laurent; Saunders, Matthew; Scholes, Robert J.; Veenendaal, Elmar; Kutsch, Werner L.</p> <p>2013-04-01</p> <p>In this study we report on water and carbon dioxide fluxes, measured using the eddy covariance (EC) technology, from different ecosystems in Sub-Saharan Africa. These sites differed in ecosystem type (C3 plant dominated woodlands to C4 plant dominated grass savannas) and covered the very dry regions of the <span class="hlt">Sahel</span> (250 mm rainfall, Sudan), the tropical areas in Central Africa (1650 mm in Uganda) further south to the subtropical areas in Botswana, Zambia and South Africa (400-900 mm in precipitation). The link between water and carbon dioxide fluxes were evaluated for time periods (see also the corresponding abstract by Bruemmer et al.) without water limitation during the peak growing season. Our results show that plant stomata control ecosystem scale water and carbon dioxide fluxes and mediate between plant growth and plant survival. On continental scale, this switch between maximizing carbon uptake and minimizing water losses, from here on called the "Carbon-Water-Tipping Point" was positively correlated to the mean annual growing season temperature at each site. Even though similar responses of plants were shown at the individual leaf-level scale this has to our knowledge not yet been shown at the ecosystem scale further suggesting a long-term adaptation of the complete ecosystems to certain climatic regions. It remains unclear how this adaption will influence the ecosystem response to ongoing climate change and according temperature increases and changes in precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....1715095M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....1715095M"><span>Characterizing energy budget variability at a Sahelian site: a test of NWP model behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mackie, Anna; Palmer, Paul I.; Brindley, Helen</p> <p>2017-12-01</p> <p>We use observations of surface and top-of-the-atmosphere (TOA) broadband radiation fluxes determined from the Atmospheric Radiation Measurement programme mobile facility, the Geostationary Earth Radiation Budget (GERB) and Spinning Enhanced Visible and Infrared Imager (SEVIRI) instruments and a range of meteorological variables at a site in the <span class="hlt">Sahel</span> to test the ability of the ECMWF Integrated Forecasting System cycle 43r1 to describe energy budget variability. The model has daily average biases of -12 and 18 W m-2 for outgoing longwave and reflected shortwave TOA radiation fluxes, respectively. At the surface, the daily average bias is 12(13) W m-2 for the longwave downwelling (upwelling) radiation flux and -21(-13) W m-2 for the shortwave downwelling (upwelling) radiation flux. Using multivariate linear models of observation-model differences, we attribute radiation flux discrepancies to physical processes, and link surface and TOA fluxes. We find that model biases in surface radiation fluxes are mainly due to a low bias in ice water path (IWP), poor description of surface albedo and model-observation differences in surface temperature. We also attribute observed discrepancies in the radiation fluxes, particularly during the dry season, to the misrepresentation of aerosol fields in the model from use of a climatology instead of a dynamic approach. At the TOA, the low IWP impacts the amount of reflected shortwave radiation while biases in outgoing longwave radiation are additionally coupled to discrepancies in the surface upwelling longwave flux and atmospheric humidity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HESS...17.1079M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HESS...17.1079M"><span>Improving operational land surface model canopy evapotranspiration in Africa using a direct remote sensing approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marshall, M.; Tu, K.; Funk, C.; Michaelsen, J.; Williams, P.; Williams, C.; Ardö, J.; Boucher, M.; Cappelaere, B.; de Grandcourt, A.; Nickless, A.; Nouvellon, Y.; Scholes, R.; Kutsch, W.</p> <p>2013-03-01</p> <p>Climate change is expected to have the greatest impact on the world's economically poor. In the <span class="hlt">Sahel</span>, a climatically sensitive region where rain-fed agriculture is the primary livelihood, expected decreases in water supply will increase food insecurity. Studies on climate change and the intensification of the water cycle in sub-Saharan Africa are few. This is due in part to poor calibration of modeled evapotranspiration (ET), a key input in continental-scale hydrologic models. In this study, a remote sensing model of transpiration (the primary component of ET), driven by a time series of vegetation indices, was used to substitute transpiration from the Global Land Data Assimilation System realization of the National Centers for Environmental Prediction, Oregon State University, Air Force, and Hydrology Research Laboratory at National Weather Service Land Surface Model (GNOAH) to improve total ET model estimates for monitoring purposes in sub-Saharan Africa. The performance of the hybrid model was compared against GNOAH ET and the remote sensing method using eight eddy flux towers representing major biomes of sub-Saharan Africa. The greatest improvements in model performance were at humid sites with dense vegetation, while performance at semi-arid sites was poor, but better than the models before hybridization. The reduction in errors using the hybrid model can be attributed to the integration of a simple canopy scheme that depends primarily on low bias surface climate reanalysis data and is driven primarily by a time series of vegetation indices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27063732','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27063732"><span>Assessment of malaria transmission changes in Africa, due to the climate impact of land use change using Coupled Model Intercomparison Project Phase 5 earth system models.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tompkins, Adrian M; Caporaso, Luca</p> <p>2016-03-31</p> <p>Using mathematical modelling tools, we assessed the potential for land use change (LUC) associated with the Intergovernmental Panel on Climate Change low- and high-end emission scenarios (RCP2.6 and RCP8.5) to impact malaria transmission in Africa. To drive a spatially explicit, dynamical malaria model, data from the four available earth system models (ESMs) that contributed to the LUC experiment of the Fifth Climate Model Intercomparison Project are used. Despite the limited size of the ESM ensemble, stark differences in the assessment of how LUC can impact climate are revealed. In three out of four ESMs, the impact of LUC on precipitation and temperature over the next century is limited, resulting in no significant change in malaria transmission. However, in one ESM, LUC leads to increases in precipitation under scenario RCP2.6, and increases in temperature in areas of land use conversion to farmland under both scenarios. The result is a more intense transmission and longer transmission seasons in the southeast of the continent, most notably in Mozambique and southern Tanzania. In contrast, warming associated with LUC in the <span class="hlt">Sahel</span> region reduces risk in this model, as temperatures are already above the 25-30°C threshold at which transmission peaks. The differences between the ESMs emphasise the uncertainty in such assessments. It is also recalled that the modelling framework is unable to adequately represent local-scale changes in climate due to LUC, which some field studies indicate could be significant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27455838','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27455838"><span>A genome-wide perspective about the diversity and demographic history of seven Spanish goat breeds.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Manunza, Arianna; Noce, Antonia; Serradilla, Juan Manuel; Goyache, Félix; Martínez, Amparo; Capote, Juan; Delgado, Juan Vicente; Jordana, Jordi; Muñoz, Eva; Molina, Antonio; Landi, Vincenzo; Pons, Agueda; Balteanu, Valentin; Traoré, Amadou; Vidilla, Montse; Sánchez-Rodríguez, Manuel; Sànchez, Armand; Cardoso, Tainã Figueiredo; Amills, Marcel</p> <p>2016-07-25</p> <p>The main goal of the current work was to infer the demographic history of seven Spanish goat breeds (Malagueña, Murciano-Granadina, Florida, Palmera, Mallorquina, Bermeya and Blanca de Rasquera) based on genome-wide diversity data generated with the Illumina Goat SNP50 BeadChip (population size, N = 176). Five additional populations from Europe (Saanen and Carpathian) and Africa (Tunisian, Djallonké and <span class="hlt">Sahel</span>) were also included in this analysis (N = 80) for comparative purposes. Our results show that the genetic background of Spanish goats traces back mainly to European breeds although signs of North African admixture were detected in two Andalusian breeds (Malagueña and Murciano-Granadina). In general, observed and expected heterozygosities were quite similar across the seven Spanish goat breeds under analysis irrespective of their population size and conservation status. For the Mallorquina and Blanca de Rasquera breeds, which have suffered strong population declines during the past decades, we observed increased frequencies of large-sized (ROH), a finding that is consistent with recent inbreeding. In contrast, a substantial part of the genome of the Palmera goat breed comprised short ROH, which suggests a strong and ancient founder effect. Admixture with African goats, genetic drift and inbreeding have had different effects across the seven Spanish goat breeds analysed in the current work. This has generated distinct patterns of genome-wide diversity that provide new clues about the demographic history of these populations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870006085','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870006085"><span>Canopy reflectance modeling in a tropical wooded grassland</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simonett, David; Franklin, Janet</p> <p>1986-01-01</p> <p>Geometric/optical canopy reflectance modeling and spatial/spectral pattern recognition is used to study the form and structure of savanna in West Africa. An invertible plant canopy reflectance model is tested for its ability to estimate the amount of woody vegetation from remotely sensed data in areas of sparsely wooded grassland. Dry woodlands and wooded grasslands, commonly referred to as savannas, are important ecologically and economically in Africa, and cover approximately forty percent of the continent by some estimates. The <span class="hlt">Sahel</span> and Sudan savannas make up the important and sensitive transition zone between the tropical forests and the arid Sahara region. The depletion of woody cover, used for fodder and fuel in these regions, has become a very severe problem for the people living there. LANDSAT Thematic Mapper (TM) data is used to stratify woodland and wooded grassland into areas of relatively homogeneous canopy cover, and then an invertible forest canopy reflectance model is applied to estimate directly the height and spacing of the trees in the stands. Because height and spacing are proportional to biomass in some cases, a successful application of the segmentation/modeling techniques will allow direct estimation of tree biomass, as well as cover density, over significant areas of these valuable and sensitive ecosystems. The model being tested in sites in two different bioclimatic zones in Mali, West Africa, will be used for testing the canopy model. Sudanian zone crop/woodland test sites were located in the Region of Segou, Mali.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20062963','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20062963"><span>Spatio-temporal dynamics of genetic diversity in Sorghum bicolor in Niger.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deu, Monique; Sagnard, F; Chantereau, J; Calatayud, C; Vigouroux, Y; Pham, J L; Mariac, C; Kapran, I; Mamadou, A; Gérard, B; Ndjeunga, J; Bezançon, G</p> <p>2010-05-01</p> <p>The dynamics of crop genetic diversity need to be assessed to draw up monitoring and conservation priorities. However, few surveys have been conducted in centres of diversity. Sub-Saharan Africa is the centre of origin of sorghum. Most <span class="hlt">Sahel</span> countries have been faced with major human, environmental and social changes in recent decades, which are suspected to cause genetic erosion. Sorghum is the second staple cereal in Niger, a centre of diversity for this crop. Niger was submitted to recurrent drought period and to major social changes during these last decades. We report here on a spatio-temporal analysis of sorghum genetic diversity, conducted in 71 villages covering the rainfall gradient and range of agro-ecological conditions in Niger's agricultural areas. We used 28 microsatellite markers and applied spatial and genetic clustering methods to investigate change in genetic diversity over a 26-year period (1976-2003). Global genetic differentiation between the two collections was very low (F (st) = 0.0025). Most of the spatial clusters presented no major differentiation, as measured by F (st), and showed stability or an increase in allelic richness, except for two of them located in eastern Niger. The genetic clusters identified by Bayesian analysis did not show a major change between the two collections in the distribution of accessions between them or in their spatial location. These results suggest that farmers' management has globally preserved sorghum genetic diversity in Niger.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.1984Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.1984Y"><span>The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Remer, Lorraine A.; Prospero, Joseph M.; Omar, Ali; Winker, David; Yang, Yuekui; Zhang, Yan; Zhang, Zhibo; Zhao, Chun</p> <p>2015-03-01</p> <p>The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three-dimensional (3-D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7 year average of dust deposition into the Amazon Basin is estimated to be 28 (8-48) Tg a-1 or 29 (8-50) kg ha-1 a-1. The dust deposition shows significant interannual variation that is negatively correlated with the prior-year rainfall in the <span class="hlt">Sahel</span>. The CALIOP-based multiyear mean estimate of dust deposition matches better with estimates from in situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3-D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.006-0.037) Tg P of phosphorus per year, equivalent to 23 (7-39) g P ha-1 a-1 to fertilize the Amazon rainforest. This out-of-basin phosphorus input is comparable to the hydrological loss of phosphorus from the basin, suggesting an important role of African dust in preventing phosphorus depletion on timescales of decades to centuries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GMD....10.1107D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GMD....10.1107D"><span>Assimilation of MODIS Dark Target and Deep Blue observations in the dust aerosol component of NMMB-MONARCH version 1.0</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Di Tomaso, Enza; Schutgens, Nick A. J.; Jorba, Oriol; Pérez García-Pando, Carlos</p> <p>2017-03-01</p> <p>A data assimilation capability has been built for the NMMB-MONARCH chemical weather prediction system, with a focus on mineral dust, a prominent type of aerosol. An ensemble-based Kalman filter technique (namely the local ensemble transform Kalman filter - LETKF) has been utilized to optimally combine model background and satellite retrievals. Our implementation of the ensemble is based on known uncertainties in the physical parametrizations of the dust emission scheme. Experiments showed that MODIS AOD retrievals using the Dark Target algorithm can help NMMB-MONARCH to better characterize atmospheric dust. This is particularly true for the analysis of the dust outflow in the <span class="hlt">Sahel</span> region and over the African Atlantic coast. The assimilation of MODIS AOD retrievals based on the Deep Blue algorithm has a further positive impact in the analysis downwind from the strongest dust sources of the Sahara and in the Arabian Peninsula. An analysis-initialized forecast performs better (lower forecast error and higher correlation with observations) than a standard forecast, with the exception of underestimating dust in the long-range Atlantic transport and degradation of the temporal evolution of dust in some regions after day 1. Particularly relevant is the improved forecast over the Sahara throughout the forecast range thanks to the assimilation of Deep Blue retrievals over areas not easily covered by other observational datasets. The present study on mineral dust is a first step towards data assimilation with a complete aerosol prediction system that includes multiple aerosol species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5689041-paleoclimatic-interpretations-clay-rich-paleosols-potential-limitations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5689041-paleoclimatic-interpretations-clay-rich-paleosols-potential-limitations"><span>Paleoclimatic interpretations for clay-rich paleosols--Potential and limitations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Blodgett, R.H.</p> <p>1992-01-01</p> <p>A worldwide survey of Quaternary Vertisols and pre-Quaternary vertic paleosols indicates that these soils have morphologic features which may allow for a refined assessment of seasonal wet-dry paleoclimates. Optimal development of vertisols occurs under wet/dry tropical and subtropical climates with annual rainfall of 500-1,000 mm/yr. These typic Vertisols'' have well-developed gilgai, subsurface bowl and dome macrostructure, cross-cutting slickensided surfaces, and disseminated pedogenic carbonate nodules. Typic Vertisols occur in central Texas, East Africa, India and Australia. Corresponding typic vertic paleosols have been found in 14 Paleozoic formations of Pangea. Humid Vertisols can be difficult to distinguish from typic forms. In themore » humid group, carbonate nodules are absent or few in number and smaller in size. Nodules commonly show surficial pitting from dissolution. Humid Vertisols occur in East Texas, the central Gulf Coast, Central America, Caribbean, and Papau-New Guinea. Paleosol equivalents have been described in Mesozoic and Carboniferous rocks of North America. Dry Vertisols have subdued gilgai, well-developed surficial mulch, large sediment-filled desiccation cracks, common carbonate nodules, and in some areas, disseminated crystals or veins of gypsum. These soils occur in the southwestern U.S., <span class="hlt">Sahel</span>, and in Australia. Dry vertic paleosols have been identified in Cenozoic deposits of Texas and North Africa. The above assessments may not be possible in composite paleosols or in soils influenced by a shallow water table.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NHESD...2.5171A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NHESD...2.5171A"><span>Floods in the Niger basin - analysis and attribution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aich, V.; Koné, B.; Hattermann, F. F.; Müller, E. N.</p> <p>2014-08-01</p> <p>This study addresses the increasing flood risk in the Niger basin and assesses the damages that arise from flooding. Statistics from three different sources (EM-DAT, Darthmouth Flood Observatory, NatCat Munich RE) on people affected by floods show positive trends for the entire basin beginning in the 1980s. An assessment of four subregions across the Niger basin indicates even exponential trends for the Sahelian and Sudanian regions. These positive trends for flooding damage match up to a time series of annual maximum discharge (AMAX): the strongest trends in AMAX are detected in the Sahelian and Sudanian regions, where the population is also increasing the fastest and vulnerability generally appears to be very high. The joint effect of these three factors can possibly explain the exponential increase in people affected by floods in these subregions. In a second step, the changes in AMAX are attributed to changes in precipitation and land use via a data-based approach within a hypothesis-testing framework. Analysis of rainfall, heavy precipitation and the runoff coefficient shows a coherent picture of a return to wet conditions in the basin, which we identify as the main driver of the increase in AMAX in the Niger basin. The analysis of flashiness (using the Richards-Baker Index) and the focus on the "<span class="hlt">Sahel</span> Paradox" of the Sahelian region reveal an additional influence of land-use change, but it seems minor compared to the increase in precipitation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020069127','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020069127"><span>A Variable-Resolution Stretched-Grid General Circulation Model and Data Assimilation System with Multiple Areas of Interest: Studying the Anomalous Regional Climate Events of 1998</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fox-Rabinovitz, Michael S.; Takacs, Lawrence; Govindaraju, Ravi C.; Atlas, Robert (Technical Monitor)</p> <p>2002-01-01</p> <p>The new stretched-grid design with multiple (four) areas of interest, one at each global quadrant, is implemented into both a stretched-grid GCM (general circulation model) and a stretched-grid data assimilation system (DAS). The four areas of interest include: the U.S./Northern Mexico, the El Nino area/Central South America, India/China, and the Eastern Indian Ocean/Australia. Both the stretched-grid GCM and DAS annual (November 1997 through December 1998) integrations are performed with 50 km regional resolution. The efficient regional down-scaling to mesoscales is obtained for each of the four areas of interest while the consistent interactions between regional and global scales and the high quality of global circulation, are preserved. This is the advantage of the stretched-grid approach. The global variable resolution DAS incorporating the stretched-grid GCM has been developed and tested as an efficient tool for producing regional analyses and diagnostics with enhanced mesoscale resolution. The anomalous regional climate events of 1998 that occurred over the U.S., Mexico, South America, China, India, African <span class="hlt">Sahel</span>, and Australia are investigated in both simulation and data assimilation modes. Tree assimilated products are also used, along with gauge precipitation data, for validating the simulation results. The obtained results show that the stretched-grid GCM and DAS are capable of producing realistic high quality simulated and assimilated products at mesoscale resolution for regional climate studies and applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24278203','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24278203"><span>The economic burden of meningitis to households in Kassena-Nankana district of Northern Ghana.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Akweongo, Patricia; Dalaba, Maxwell A; Hayden, Mary H; Awine, Timothy; Nyaaba, Gertrude N; Anaseba, Dominic; Hodgson, Abraham; Forgor, Abdulai A; Pandya, Rajul</p> <p>2013-01-01</p> <p>To estimate the direct and indirect costs of meningitis to households in the Kassena-Nankana District of Ghana. A Cost of illness (COI) survey was conducted between 2010 and 2011. The COI was computed from a retrospective review of 80 meningitis cases answers to questions about direct medical costs, direct non-medical costs incurred and productivity losses due to recent meningitis incident. The average direct and indirect costs of treating meningitis in the district was GH¢152.55 (US$101.7) per household. This is equivalent to about two months minimum wage earned by Ghanaians in unskilled paid jobs in 2009. Households lost 29 days of work per meningitis case and thus those in minimum wage paid jobs lost a monthly minimum wage of GH¢76.85 (US$51.23) due to the illness. Patients who were insured spent an average of GH¢38.5 (US$25.67) in direct medical costs whiles the uninsured patients spent as much as GH¢177.9 (US$118.6) per case. Patients with sequelae incurred additional costs of GH¢22.63 (US$15.08) per case. The least poor were more exposed to meningitis than the poorest. Meningitis is a debilitating but preventable disease that affects people living in the <span class="hlt">Sahel</span> and in poorer conditions. The cost of meningitis treatment may further lead to impoverishment for these households. Widespread mass vaccination will save households' an equivalent of GH¢175.18 (US$117) and impairment due to meningitis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1037505','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1037505"><span>The Fight Against Extremism in the Trans-<span class="hlt">Sahel</span>: The Utilization of Soft Power by the Department of State to Establish, Develop, and Strengthen Potential Partnerships</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2016-02-16</p> <p>34God is great" and armed with guns and throwing grenades stormed into the Radisson Blue Hotel in Mali’s capital Friday morning and seized 170...capacity building programs as well. Nigerian police, customs officials, and immigration officers participated in interagency training to build their...power provides immediate satisfaction and may be required at times, do we as a nation have the wear-with-all to go the long, hard route and maintain</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010536','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010536"><span>Global Scale Attribution of Anthropogenic and Natural Dust Sources and their Emission Rates Based on MODIS Deep Blue Aerosol Products</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ginoux, Paul; Prospero, Joseph M.; Gill, Thomas E.; Hsu, N. Christina; Zhao, Ming</p> <p>2012-01-01</p> <p>Our understanding of the global dust cycle is limited by a dearth of information about dust sources, especially small-scale features which could account for a large fraction of global emissions. Here we present a global-scale high-resolution (0.1 deg) mapping of sources based on Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue estimates of dust optical depth in conjunction with other data sets including land use. We ascribe dust sources to natural and anthropogenic (primarily agricultural) origins, calculate their respective contributions to emissions, and extensively compare these products against literature. Natural dust sources globally account for 75% of emissions; anthropogenic sources account for 25%. North Africa accounts for 55% of global dust emissions with only 8% being anthropogenic, mostly from the <span class="hlt">Sahel</span>. Elsewhere, anthropogenic dust emissions can be much higher (75% in Australia). Hydrologic dust sources (e.g., ephemeral water bodies) account for 31% worldwide; 15% of them are natural while 85% are anthropogenic. Globally, 20% of emissions are from vegetated surfaces, primarily desert shrublands and agricultural lands. Since anthropogenic dust sources are associated with land use and ephemeral water bodies, both in turn linked to the hydrological cycle, their emissions are affected by climate variability. Such changes in dust emissions can impact climate, air quality, and human health. Improved dust emission estimates will require a better mapping of threshold wind velocities, vegetation dynamics, and surface conditions (soil moisture and land use) especially in the sensitive regions identified here, as well as improved ability to address small-scale convective processes producing dust via cold pool (haboob) events frequent in monsoon regimes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.8303M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.8303M"><span>Active folding and thrusting in North Africa: A framework for a seismotectonic model of the Atlas Mountains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meghraoui, Mustapha; Maouche, Said; Timoulali, Youssef; Bouhadad, Youcef; Bouaziz, Samir</p> <p>2013-04-01</p> <p>Large earthquakes in the Atlas Mountains of North Africa are often generated on thrust or reverse faults. For inland faults, surface ruptures and long-term active tectonics appear as a thrust escarpment and fold-related faulting visible in the field and using remote sensing images, or measured using space-borne geodesy (GPS or INSAR). For coastal faults, major uplifts of late Quaternary marine terraces and folding with steplike morphology are exposed indicating the incremental development of coastal active deformation. We have investigated the similarities and differences between different active fault-related folding along the Africa - Eurasia convergent plate boundary. These active structures are seismogenic and the striking case studies are the 1960 Agadir (Mw 5.9), the 1954 Orleansville (Mw 6.7), the 1980 El Asnam (Mw 7.3), the 1992 Gafsa (Mw 5.3), the 1999 Ain Temouchent (Mw 6.0), and the 2003 Zemmouri (Mw 6.8) earthquakes. From paleoseismic investigations the El Asnam active fold shows 0.6 to 1.0 mm/yr uplift rate. West of Algiers on the <span class="hlt">Sahel</span> anticline, the levelling of uplifted successive coastal benches and notches document the incremental folding uplift with ~ 0.84 - 1.2 mm/yr uplift rate in the last 120-140 ka. The relatively fast folding growth during late Pleistocene and Holocene in the Atlas Mountains attests for the significance of earthquake activity and the importance of convergent movements between Africa and Eurasia in the Western Mediterranean. This work is prepared in the framework of the UNESCO (SIDA) - IGCP Project 601 "Seismotectonics and Seismic Hazards in Africa".</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4481G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4481G"><span>Impact of dynamical regionalization on precipitation biases and teleconnections over West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gómara, Iñigo; Mohino, Elsa; Losada, Teresa; Domínguez, Marta; Suárez-Moreno, Roberto; Rodríguez-Fonseca, Belén</p> <p>2018-06-01</p> <p>West African societies are highly dependent on the West African Monsoon (WAM). Thus, a correct representation of the WAM in climate models is of paramount importance. In this article, the ability of 8 CMIP5 historical General Circulation Models (GCMs) and 4 CORDEX-Africa Regional Climate Models (RCMs) to characterize the WAM dynamics and variability is assessed for the period July-August-September 1979-2004. Simulations are compared with observations. Uncertainties in RCM performance and lateral boundary conditions are assessed individually. Results show that both GCMs and RCMs have trouble to simulate the northward migration of the Intertropical Convergence Zone in boreal summer. The greatest bias improvements are obtained after regionalization of the most inaccurate GCM simulations. To assess WAM variability, a Maximum Covariance Analysis is performed between Sea Surface Temperature and precipitation anomalies in observations, GCM and RCM simulations. The assessed variability patterns are: El Niño-Southern Oscillation (ENSO); the eastern Mediterranean (MED); and the Atlantic Equatorial Mode (EM). Evidence is given that regionalization of the ENSO-WAM teleconnection does not provide any added value. Unlike GCMs, RCMs are unable to precisely represent the ENSO impact on air subsidence over West Africa. Contrastingly, the simulation of the MED-WAM teleconnection is improved after regionalization. Humidity advection and convergence over the <span class="hlt">Sahel</span> area are better simulated by RCMs. Finally, no robust conclusions can be determined for the EM-WAM teleconnection, which cannot be isolated for the 1979-2004 period. The novel results in this article will help to select the most appropriate RCM simulations to study WAM teleconnections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002GBioC..16.1046K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002GBioC..16.1046K"><span>Wet deposition of trace elements and radon daughter systematics in the South and equatorial Atlantic atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Guebuem; Church, Thomas M.</p> <p>2002-09-01</p> <p>Atmospheric samples were collected aboard ship in the South and equatorial Atlantic (35°S-10°N) between 19 May and 20 June 1996. We measured 222Rn in air, 210Pb in aerosol, and trace elements (Fe, Mn, Zn, Pb, Cu, Cd, Ni, and Cr), 210Pb, and 210Po in precipitation samples. The large variation of 222Rn in air suggests a significant change in the incursion of continental air with time and latitude in the remote Atlantic. In the equatorial and subtropical Atlantic (20°S-10°N), 222Rn activity was lower but 210Pb/222Rn ratios were higher than those at higher latitudes. The higher 210Pb/222Rn ratios in the equatorial Atlantic appear to be due to prevailing trade easterly winds which transport a supported source of 210Pb in Saharan dust from the African <span class="hlt">Sahel</span>. The enrichment of noncrustal trace elements in precipitation samples from the remote equatorial Atlantic was small on account of the remoteness from the continental emission regions and as a result of dilution with Saharan dust. The wet depositional fluxes of major crustal elements (Fe and Mn) were two- to three-fold higher, while those of Cd and Zn were two- to ten-fold lower, in the South and equatorial Atlantic relative to the western North Atlantic (Bermuda) or North Atlantic coast (Lewes, Delaware). Thus, dominant wet precipitation of Saharan dust in the Intertropical Convergence Zone (ITCZ) areas of the equatorial Atlantic appears to be a large potential source of micronutrients (i.e., Fe) to surface seawater.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28664529','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28664529"><span>Phenology, sterility and inheritance of two environment genic male sterile (EGMS) lines for hybrid rice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>El-Namaky, R; van Oort, P A J</p> <p>2017-12-01</p> <p>There is still limited quantitative understanding of how environmental factors affect sterility of Environment-conditioned genic male sterility (EGMS) lines. A model was developed for this purpose and tested based on experimental data from Ndiaye (Senegal) in 2013-2015. For the two EGMS lines tested here, it was not clear if one or more recessive gene(s) were causing male sterility. This was tested by studying sterility segregation of the F2 populations. Daylength (photoperiod) and minimum temperatures during the period from panicle initiation to flowering had significant effects on male sterility. Results clearly showed that only one recessive gene was involved in causing male sterility. The model was applied to determine the set of sowing dates of two different EGMS lines such that both would flower at the same time the pollen would be completely sterile. In the same time the local popular variety (<span class="hlt">Sahel</span> 108, the male pollen donor) being sufficiently fertile to produce the hybrid seeds. The model was applied to investigate the viability of the two line breeding system in the same location with climate change (+2oC) and in two other potential locations: in M'Be in Ivory Coast and in the Nile delta in Egypt. Apart from giving new insights in the relation between environment and EGMS, this study shows that these insights can be used to assess safe sowing windows and assess the suitability of sterility and fertility period of different environments for a two line hybrid rice production system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080039275&hterms=blue&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dblue','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080039275&hterms=blue&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dblue"><span>SMART-COMMIT Observations and Deep-Blue Retrievals of Saharan Dust Properties during NAMMA</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tsay, Si-Chee; Hsu, N. Christina; Ji, Qiang; Jeong, Myeong-Jae</p> <p>2007-01-01</p> <p>Monsoon rainfalls sustain the livelihood of more than half of the world's population. The interaction between natural/anthropogenic aerosols, clouds, and precipitation is a critical mechanism that drives the water cycle and fresh water distribution. Analyses of the longterm trend of July-August precipitation anomaly for the last 50 years in the 20" century depict that the largest regional precipitation deficit occurs over the <span class="hlt">Sahel</span>, where the monsoon water cycle plays an important role. Thus, it is of paramount importance to study how dust aerosols, as well as air pollution and smoke, influence monsoon variability. The NASA African Monsoon Multidisciplinary Activities (NAMMA) was conducted during the international AMMA Special Observation Period (SOP-3) of September 2006 to better comprehend the key attributes of the Saharan Air Layer (SAL) and how they evolve from the source regions to the Atlantic Ocean. The SAL occurs during the late spring through early fall and originates as a result of low-level convergence induced by heat lows over the Sahara that lifts hot, dry, dust laden air aloft into a well mixed layer that extends up to 500mb. This is crucial for understanding the impact of SAL on the key atmospheric processes that determine precipitation over West Africa and tropical cyclogenesis. Results obtained from the synergy of satellite (Deep- Blue) and surface (SMART-COMMIT) observations will be presented and discussed how the physical, optical and radiative properties of the dust in the SAL evolve from the continental to the marine environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.tmp....9A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.tmp....9A"><span>Fuzzy rule-based forecast of meteorological drought in western Niger</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abdourahamane, Zakari Seybou; Acar, Reşat</p> <p>2018-01-01</p> <p>Understanding the causes of rainfall anomalies in the West African <span class="hlt">Sahel</span> to effectively predict drought events remains a challenge. The physical mechanisms that influence precipitation in this region are complex, uncertain, and imprecise in nature. Fuzzy logic techniques are renowned to be highly efficient in modeling such dynamics. This paper attempts to forecast meteorological drought in Western Niger using fuzzy rule-based modeling techniques. The 3-month scale standardized precipitation index (SPI-3) of four rainfall stations was used as predictand. Monthly data of southern oscillation index (SOI), South Atlantic sea surface temperature (SST), relative humidity (RH), and Atlantic sea level pressure (SLP), sourced from the National Oceanic and Atmosphere Administration (NOAA), were used as predictors. Fuzzy rules and membership functions were generated using fuzzy c-means clustering approach, expert decision, and literature review. For a minimum lead time of 1 month, the model has a coefficient of determination R 2 between 0.80 and 0.88, mean square error (MSE) below 0.17, and Nash-Sutcliffe efficiency (NSE) ranging between 0.79 and 0.87. The empirical frequency distributions of the predicted and the observed drought classes are equal at the 99% of confidence level based on two-sample t test. Results also revealed the discrepancy in the influence of SOI and SLP on drought occurrence at the four stations while the effect of SST and RH are space independent, being both significantly correlated (at α < 0.05 level) to the SPI-3. Moreover, the implemented fuzzy model compared to decision tree-based forecast model shows better forecast skills.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A23D2372A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A23D2372A"><span>Sensitivity experiments of a regional climate model to the different convective schemes over Central Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Armand J, K. M.</p> <p>2017-12-01</p> <p>In this study, version 4 of the regional climate model (RegCM4) is used to perform 6 years simulation including one year for spin-up (from January 2001 to December 2006) over Central Africa using four convective schemes: The Emmanuel scheme (MIT), the Grell scheme with Arakawa-Schulbert closure assumption (GAS), the Grell scheme with Fritsch-Chappell closure assumption (GFC) and the Anthes-Kuo scheme (Kuo). We have investigated the ability of the model to simulate precipitation, surface temperature, wind and aerosols optical depth. Emphasis in the model results were made in December-January-February (DJF) and July-August-September (JAS) periods. Two subregions have been identified for more specific analysis namely: zone 1 which corresponds to the <span class="hlt">sahel</span> region mainly classified as desert and steppe and zone 2 which is a region spanning the tropical rain forest and is characterised by a bimodal rain regime. We found that regardless of periods or simulated parameters, MIT scheme generally has a tendency to overestimate. The GAS scheme is more suitable in simulating the aforementioned parameters, as well as the diurnal cycle of precipitations everywhere over the study domain irrespective of the season. In JAS, model results are similar in the representation of regional wind circulation. Apart from the MIT scheme, all the convective schemes give the same trends in aerosols optical depth simulations. Additional experiment reveals that the use of BATS instead of Zeng scheme to calculate ocean flux appears to improve the quality of the model simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27907023','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27907023"><span>Field Trials Reveal Ecotype-Specific Responses to Mycorrhizal Inoculation in Rice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diedhiou, Abdala Gamby; Mbaye, Fatou Kine; Mbodj, Daouda; Faye, Mathieu Ndigue; Pignoly, Sarah; Ndoye, Ibrahima; Djaman, Koffi; Gaye, Souleymane; Kane, Aboubacry; Laplaze, Laurent; Manneh, Baboucarr; Champion, Antony</p> <p>2016-01-01</p> <p>The overuse of agricultural chemicals such as fertilizer and pesticides aimed at increasing crop yield results in environmental damage, particularly in the Sahelian zone where soils are fragile. Crop inoculation with beneficial soil microbes appears as a good alternative for reducing agricultural chemical needs, especially for small farmers. This, however, requires selecting optimal combinations of crop varieties and beneficial microbes tested in field conditions. In this study, we investigated the response of rice plants to inoculation with arbuscular mycorrhizal fungi (AMF) and plant growth promoting bacteria (PGPB) under screenhouse and field conditions in two consecutive seasons in Senegal. Evaluation of single and mixed inoculations with AMF and PGPB was conducted on rice (Oryza sativa) variety <span class="hlt">Sahel</span> 202, on sterile soil under screenhouse conditions. We observed that inoculated plants, especially plants treated with AMF, grew taller, matured earlier and had higher grain yield than the non-inoculated plants. Mixed inoculation trials with two AMF strains were then conducted under irrigated field conditions with four O. sativa varieties, two O. glaberrima varieties and two interspecific NERICA varieties, belonging to 3 ecotypes (upland, irrigated, and rainfed lowland). We observed that the upland varieties had the best responses to inoculation, especially with regards to grain yield, harvest index and spikelet fertility. These results show the potential of using AMF to improve rice production with less chemical fertilizers and present new opportunities for the genetic improvement in rice to transfer the ability of forming beneficial rice-microbe associations into high yielding varieties in order to increase further rice yield potentials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5132163','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5132163"><span>Field Trials Reveal Ecotype-Specific Responses to Mycorrhizal Inoculation in Rice</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Diedhiou, Abdala Gamby; Mbaye, Fatou Kine; Mbodj, Daouda; Faye, Mathieu Ndigue; Pignoly, Sarah; Ndoye, Ibrahima; Djaman, Koffi; Gaye, Souleymane; Kane, Aboubacry; Laplaze, Laurent; Manneh, Baboucarr; Champion, Antony</p> <p>2016-01-01</p> <p>The overuse of agricultural chemicals such as fertilizer and pesticides aimed at increasing crop yield results in environmental damage, particularly in the Sahelian zone where soils are fragile. Crop inoculation with beneficial soil microbes appears as a good alternative for reducing agricultural chemical needs, especially for small farmers. This, however, requires selecting optimal combinations of crop varieties and beneficial microbes tested in field conditions. In this study, we investigated the response of rice plants to inoculation with arbuscular mycorrhizal fungi (AMF) and plant growth promoting bacteria (PGPB) under screenhouse and field conditions in two consecutive seasons in Senegal. Evaluation of single and mixed inoculations with AMF and PGPB was conducted on rice (Oryza sativa) variety <span class="hlt">Sahel</span> 202, on sterile soil under screenhouse conditions. We observed that inoculated plants, especially plants treated with AMF, grew taller, matured earlier and had higher grain yield than the non-inoculated plants. Mixed inoculation trials with two AMF strains were then conducted under irrigated field conditions with four O. sativa varieties, two O. glaberrima varieties and two interspecific NERICA varieties, belonging to 3 ecotypes (upland, irrigated, and rainfed lowland). We observed that the upland varieties had the best responses to inoculation, especially with regards to grain yield, harvest index and spikelet fertility. These results show the potential of using AMF to improve rice production with less chemical fertilizers and present new opportunities for the genetic improvement in rice to transfer the ability of forming beneficial rice-microbe associations into high yielding varieties in order to increase further rice yield potentials. PMID:27907023</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24014154','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24014154"><span>Climate change hotspots in the CMIP5 global climate model ensemble.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diffenbaugh, Noah S; Giorgi, Filippo</p> <p>2012-01-10</p> <p>We use a statistical metric of multi-dimensional climate change to quantify the emergence of global climate change hotspots in the CMIP5 climate model ensemble. Our hotspot metric extends previous work through the inclusion of extreme seasonal temperature and precipitation, which exert critical influence on climate change impacts. The results identify areas of the Amazon, the <span class="hlt">Sahel</span> and tropical West Africa, Indonesia, and the Tibetan Plateau as persistent regional climate change hotspots throughout the 21 st century of the RCP8.5 and RCP4.5 forcing pathways. In addition, areas of southern Africa, the Mediterranean, the Arctic, and Central America/western North America also emerge as prominent regional climate change hotspots in response to intermediate and high levels of forcing. Comparisons of different periods of the two forcing pathways suggest that the pattern of aggregate change is fairly robust to the level of global warming below approximately 2°C of global warming (relative to the late-20 th -century baseline), but not at the higher levels of global warming that occur in the late-21 st -century period of the RCP8.5 pathway, with areas of southern Africa, the Mediterranean, and the Arctic exhibiting particular intensification of relative aggregate climate change in response to high levels of forcing. Although specific impacts will clearly be shaped by the interaction of climate change with human and biological vulnerabilities, our identification of climate change hotspots can help to inform mitigation and adaptation decisions by quantifying the rate, magnitude and causes of the aggregate climate response in different parts of the world.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..121.7819S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..121.7819S"><span>Sources of Sahelian-Sudan moisture: Insights from a moisture-tracing atmospheric model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salih, Abubakr A. M.; Zhang, Qiong; Pausata, Francesco S. R.; Tjernström, Michael</p> <p>2016-07-01</p> <p>The summer rainfall across Sahelian-Sudan is one of the main sources of water for agriculture, human, and animal needs. However, the rainfall is characterized by large interannual variability, which has attracted extensive scientific efforts to understand it. This study attempts to identify the source regions that contribute to the Sahelian-Sudan moisture budget during July through September. We have used an atmospheric general circulation model with an embedded moisture-tracing module (Community Atmosphere Model version 3), forced by observed (1979-2013) sea-surface temperatures. The result suggests that about 40% of the moisture comes with the moisture flow associated with the seasonal migration of the Intertropical Convergence Zone (ITCZ) and originates from Guinea Coast, central Africa, and the Western <span class="hlt">Sahel</span>. The Mediterranean Sea, Arabian Peninsula, and South Indian Ocean regions account for 10.2%, 8.1%, and 6.4%, respectively. Local evaporation and the rest of the globe supply the region with 20.3% and 13.2%, respectively. We also compared the result from this study to a previous analysis that used the Lagrangian model FLEXPART forced by ERA-Interim. The two approaches differ when comparing individual regions, but are in better agreement when neighboring regions of similar atmospheric flow features are grouped together. Interannual variability with the rainfall over the region is highly correlated with contributions from regions that are associated with the ITCZ movement, which is in turn linked to the Atlantic Multidecadal Oscillation. Our result is expected to provide insights for the effort on seasonal forecasting of the rainy season over Sahelian Sudan.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC13D1185G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC13D1185G"><span>Assessing climate adaptation options and uncertainties for cereal systems in West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guan, K.; Sultan, B.; Biasutti, M.; Lobell, D. B.</p> <p>2015-12-01</p> <p>The already fragile agriculture production system in West Africa faces further challenges in meeting food security in the coming decades, primarily due to a fast increasing population and risks of climate change. Successful adaptation of agriculture should not only benefit in the current climate but should also reduce negative (or enhance positive) impacts for climate change. Assessment of various possible adaptation options and their uncertainties provides key information for prioritizing adaptation investments. Here, based on the several robust aspects of climate projections in this region (i.e. temperature increases and rainfall pattern shifts), we use two well-validated crop models (i.e. APSIM and SARRA-H) and an ensemble of downscaled climate forcing to assess five possible and realistic adaptation options (late sowing, intensification, thermal time increase, water harvesting and increased resilience to heat stress) in West Africa for the staple crop production of sorghum. We adopt a new assessment framework to account for both the impacts of adaptation options in current climate and their ability to reduce impacts of future climate change, and also consider changes in both mean yield and its variability. Our results reveal that most proposed "adaptation options" are not more beneficial in the future than in the current climate, i.e. not really reduce the climate change impacts. Increased temperature resilience during grain number formation period is the main adaptation that emerges. We also find that changing from the traditional to modern cultivar, and later sowing in West <span class="hlt">Sahel</span> appear to be robust adaptations.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018Geote..52..100G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018Geote..52..100G"><span>Quaternary Activity of the Monastir and Grombalia Fault Systems in the North‒Eastern Tunisia (Seismotectonic Implication)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghribi, R.; Zaatra, D.; Bouaziz, S.</p> <p>2018-01-01</p> <p>The Monastir and Grombalia fault systems consist of three strands that the northern segment corresponds to Hammamet and Grombalia faults. The southern strand represents Monastir Fault also referred to as the Skanes-Khnis Fault. These NW-trends are observed continuously in the major outcropping features of north-eastern Tunisia including both the Cap Bon peninsula and the <span class="hlt">Sahel</span> domain. Along the Hammamet Fault, the north-eastern strand of Grombalia fault system, left lateral drainage offset of amount 220 m is found in Fawara valley. To the South, the left lateral movement is occurred along the Monastir Fault based on 180 m of Tyrrhenian terrace displacement. Field observations supported by satellite images suggest that the Monastir and Grombalia fault systems appear to slip mostly laterally with components of normal dip slip. Assuming the development of the stream networks during the Riss-Würm interglacial (115000-125000 years) and the age of the Tyrrhenian terrace (121 ± 10 ka), the strike slip rates of the Hammamet and Monastir faults are calculated in the range of 1.5-1.8 mm/yr. There vertical slip rates are estimated to be 0.06 and 0.26 mm/yr, respectively. These data are consistent with the displacement rate in the Pelagian shelf (1-2 mm/yr) but they are below the convergence rate of African-Eurasian plates (8 mm/yr). Our seismotectonics study reveals that a maximum earthquake of Mw = 6.5 could occur every 470 years in the Hammamet fault zone and Mw = 6-every 263 years in the Monastir fault zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A23K..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A23K..04M"><span>Online Characterisation of Mineral Dust Aerosol by Single Particle Mass Spectrometry: Mineralogical Signatures of Potential Source Areas in North Africa.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marsden, N. A.; Allan, J. D.; Flynn, M.; Ullrich, R.; Moehler, O.; Coe, H.</p> <p>2017-12-01</p> <p>The mineralogy of individual dust particles is important for atmospheric processes because mineralogy influences optical properties, their potential to act as ice nucleating particles (INP) and geochemical cycling of elements to the ocean. Bulk mineralogy of transported mineral dust has been shown to be a reflection of the source area and size fractionation during transport. Online characterisation of single particle mineralogy is highly desirable as the composition of individual particles can be reported at a temporal resolution that is relevant to atmospheric processes. Single particle mass spectrometry (SPMS) has indentified and characterised the composition of ambient dust particles but is hampered by matrix effects that result in a non-quantatative measurement of composition. The work presented describes a comparison of mass spectral characteristics of sub 2.5μm particle fractions generated from; i) nominally pure samples from the clay mineral society (CMS), ii) soil samples collected from potential source areas in North Africa and iii) ambient measurement of transported African dust made at the Cape Verde Islands. Using a novel approach to analyse the mass spectra, the distinct characteristics of the various dust samples are obtained from the online measurements. Using this technique it was observed that dust generated from sources on the North West Margin of the Sahara Desert have distinct characteristics of illite in contrast to the kaolinitic characteristics of dust generated from sources in the <span class="hlt">Sahel</span>. These methods offer great potential for describing the hourly variation in the source and mineralogy of transported mineral dust and the online differentiation of mineral phase in multi-mineralic dust samples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913780K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913780K"><span>The WASCAL high-resolution climate projection ensemble for West Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kunstmann, Harald; Heinzeller, Dominikus; Dieng, Diarra; Smiatek, Gerhard; Bliefernicht, Jan; Hamann, Ilse; Salack, Seyni</p> <p>2017-04-01</p> <p>With climate change being one of the most severe challenges to rural Africa in the 21st century, West Africa is facing an urgent need to develop effective adaptation and mitigation measures to protect its constantly growing population. We perform ensemble-based regional climate simulations at a high resolution of 12km for West Africa to allow a scientifically sound derivation of climate change adaptation measures. Based on the RCP4.5 scenario, our ensemble consist of three simulation experiments with the Weather Research & Forecasting Tool (WRF) and one additional experiment with the Consortium for Small-scale Modelling Model COSMO in Climate Mode (COSMO-CLM). We discuss the model performance over the validation period 1980-2010, including a novel, station-based precipitation database for West Africa obtained within the WASCAL (West African Science Service Centre for Climate Change and Adapted Land Use) program. Particular attention is paid to the representation of the dynamics of the West African Summer Monsoon and to the added value of our high-resolution models over existing data sets. We further present results on the climate change signal obtained for the two future periods 2020-2050 and 2070-2100 and compare them to current state-of-the-art projections from the CORDEX-Africa project. While the temperature change signal is similar to that obtained within CORDEX-Africa, our simulations predict a wetter future for the Coast of Guinea and the southern Soudano area and a slight drying in the northernmost part of the <span class="hlt">Sahel</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...42.1189K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...42.1189K"><span>Evaluation of the CORDEX-Africa multi-RCM hindcast: systematic model errors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, J.; Waliser, Duane E.; Mattmann, Chris A.; Goodale, Cameron E.; Hart, Andrew F.; Zimdars, Paul A.; Crichton, Daniel J.; Jones, Colin; Nikulin, Grigory; Hewitson, Bruce; Jack, Chris; Lennard, Christopher; Favre, Alice</p> <p>2014-03-01</p> <p>Monthly-mean precipitation, mean (TAVG), maximum (TMAX) and minimum (TMIN) surface air temperatures, and cloudiness from the CORDEX-Africa regional climate model (RCM) hindcast experiment are evaluated for model skill and systematic biases. All RCMs simulate basic climatological features of these variables reasonably, but systematic biases also occur across these models. All RCMs show higher fidelity in simulating precipitation for the west part of Africa than for the east part, and for the tropics than for northern Sahara. Interannual variation in the wet season rainfall is better simulated for the western <span class="hlt">Sahel</span> than for the Ethiopian Highlands. RCM skill is higher for TAVG and TMAX than for TMIN, and regionally, for the subtropics than for the tropics. RCM skill in simulating cloudiness is generally lower than for precipitation or temperatures. For all variables, multi-model ensemble (ENS) generally outperforms individual models included in ENS. An overarching conclusion in this study is that some model biases vary systematically for regions, variables, and metrics, posing difficulties in defining a single representative index to measure model fidelity, especially for constructing ENS. This is an important concern in climate change impact assessment studies because most assessment models are run for specific regions/sectors with forcing data derived from model outputs. Thus, model evaluation and ENS construction must be performed separately for regions, variables, and metrics as required by specific analysis and/or assessments. Evaluations using multiple reference datasets reveal that cross-examination, quality control, and uncertainty estimates of reference data are crucial in model evaluations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.9263C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.9263C"><span>Impact of climate change upon vector born diseases in Europe and Africa using ENSEMBLES Regional Climate Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caminade, Cyril; Morse, Andy</p> <p>2010-05-01</p> <p>Climate variability is an important component in determining the incidence of a number of diseases with significant human/animal health and socioeconomic impacts. The most important diseases affecting health are vector-borne, such as malaria, Rift Valley Fever and including those that are tick borne, with over 3 billion of the world population at risk. Malaria alone is responsible for at least one million deaths annually, with 80% of malaria deaths occurring in sub-Saharan Africa. The climate has a large impact upon the incidence of vector-borne diseases; directly via the development rates and survival of both the pathogen and the vector, and indirectly through changes in the environmental conditions. A large ensemble of regional climate model simulations has been produced within the ENSEMBLES project framework for both the European and African continent. This work will present recent progress in human and animal disease modelling, based on high resolution climate observations and regional climate simulations. Preliminary results will be given as an illustration, including the impact of climate change upon bluetongue (disease affecting the cattle) over Europe and upon malaria and Rift Valley Fever over Africa. Malaria scenarios based on RCM ensemble simulations have been produced for West Africa. These simulations have been carried out using the Liverpool Malaria Model. Future projections highlight that the malaria incidence decreases at the northern edge of the <span class="hlt">Sahel</span> and that the epidemic belt is shifted southward in autumn. This could lead to significant public health problems in the future as the demography is expected to dramatically rise over Africa for the 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29073193','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29073193"><span>Body-size structure of Central Iberian mammal fauna reveals semidesertic conditions during the middle Miocene Global Cooling Event.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Menéndez, Iris; Gómez Cano, Ana R; García Yelo, Blanca A; Domingo, Laura; Domingo, M Soledad; Cantalapiedra, Juan L; Blanco, Fernando; Hernández Fernández, Manuel</p> <p>2017-01-01</p> <p>We developed new quantitative palaeoclimatic inference models based on the body-size structure of mammal faunas from the Old World tropics and applied them to the Somosaguas fossil site (middle Miocene, central Iberian Peninsula). Twenty-six mammal species have been described at this site, including proboscideans, ungulates, carnivores, insectivores, lagomorphs and rodents. Our analyses were based on multivariate and bivariate regression models correlating climatic data and body-size structure of 63 modern mammal assemblages from Sub-Saharan Africa and the Indian subcontinent. The results showed an average temperature of the coldest month higher than 26°C for the Somosaguas fossil site, a mean annual thermal amplitude around 10°C, a drought length of 10 months, and an annual total precipitation greater than 200 mm per year, which are climate conditions typical of an ecotonal zone between the savanna and desert biomes. These results are congruent with the aridity peaks described over the middle Aragonian of Spain and particularly in the local biozone E, which includes Somosaguas. The aridity increase detected in this biozone is associated with the Middle Miocene Global Cooling Event. The environment of Somosaguas around 14 Ma was similar to the current environment in the <span class="hlt">Sahel</span> region of North Africa, the Horn of Africa, the boundary area between the Kalahari and the Namib in Southern Africa, south-central Arabia, or eastern Pakistan and northwestern India. The distribution of modern vegetation in these regions follows a complex mosaic of plant communities, dominated by scattered xerophilous shrublands, semidesert grasslands, and vegetation linked to seasonal watercourses and ponds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24043443','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24043443"><span>Projected impacts of climate change on environmental suitability for malaria transmission in West Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yamana, Teresa K; Eltahir, Elfatih A B</p> <p>2013-10-01</p> <p>Climate change is expected to affect the distribution of environmental suitability for malaria transmission by altering temperature and rainfall patterns; however, the local and global impacts of climate change on malaria transmission are uncertain. We assessed the effect of climate change on malaria transmission in West Africa. We coupled a detailed mechanistic hydrology and entomology model with climate projections from general circulation models (GCMs) to predict changes in vectorial capacity, an indication of the risk of human malaria infections, resulting from changes in the availability of mosquito breeding sites and temperature-dependent development rates. Because there is strong disagreement in climate predictions from different GCMs, we focused on the GCM projections that produced the best and worst conditions for malaria transmission in each zone of the study area. Simulation-based estimates suggest that in the desert fringes of the Sahara, vectorial capacity would increase under the worst-case scenario, but not enough to sustain transmission. In the transitional zone of the <span class="hlt">Sahel</span>, climate change is predicted to decrease vectorial capacity. In the wetter regions to the south, our estimates suggest an increase in vectorial capacity under all scenarios. However, because malaria is already highly endemic among human populations in these regions, we expect that changes in malaria incidence would be small. Our findings highlight the importance of rainfall in shaping the impact of climate change on malaria transmission in future climates. Even under the GCM predictions most conducive to malaria transmission, we do not expect to see a significant increase in malaria prevalence in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5658084','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5658084"><span>Body-size structure of Central Iberian mammal fauna reveals semidesertic conditions during the middle Miocene Global Cooling Event</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gómez Cano, Ana R.; García Yelo, Blanca A.; Domingo, Laura; Domingo, M. Soledad; Cantalapiedra, Juan L.; Blanco, Fernando; Hernández Fernández, Manuel</p> <p>2017-01-01</p> <p>We developed new quantitative palaeoclimatic inference models based on the body-size structure of mammal faunas from the Old World tropics and applied them to the Somosaguas fossil site (middle Miocene, central Iberian Peninsula). Twenty-six mammal species have been described at this site, including proboscideans, ungulates, carnivores, insectivores, lagomorphs and rodents. Our analyses were based on multivariate and bivariate regression models correlating climatic data and body-size structure of 63 modern mammal assemblages from Sub-Saharan Africa and the Indian subcontinent. The results showed an average temperature of the coldest month higher than 26°C for the Somosaguas fossil site, a mean annual thermal amplitude around 10°C, a drought length of 10 months, and an annual total precipitation greater than 200 mm per year, which are climate conditions typical of an ecotonal zone between the savanna and desert biomes. These results are congruent with the aridity peaks described over the middle Aragonian of Spain and particularly in the local biozone E, which includes Somosaguas. The aridity increase detected in this biozone is associated with the Middle Miocene Global Cooling Event. The environment of Somosaguas around 14 Ma was similar to the current environment in the <span class="hlt">Sahel</span> region of North Africa, the Horn of Africa, the boundary area between the Kalahari and the Namib in Southern Africa, south-central Arabia, or eastern Pakistan and northwestern India. The distribution of modern vegetation in these regions follows a complex mosaic of plant communities, dominated by scattered xerophilous shrublands, semidesert grasslands, and vegetation linked to seasonal watercourses and ponds. PMID:29073193</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B51F0352L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B51F0352L"><span>Estimating agricultural yield gap in Africa using MODIS NDVI dataset</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luan, Y.; Zhu, W.; Luo, X.; Liu, J.; Cui, X.</p> <p>2013-12-01</p> <p>Global agriculture has undergone a period of rapid intensification characterized as 'Green Revolution', except for Africa, which is the region most affected by unreliable food access and undernourishment. Increasing crop production will be one of the most challenges and most effectual way to mitigate food insecurity there, as Africa's agricultural yield is on a much lower level comparing to global average. In this study we characterize cropland vegetation phenology in Africa based on MODIS NDVI time series between 2000 and 2012. Cumulated NDVI is a proxy for net primary productivity and used as an indicator for evaluating the potential yield gap in Africa. It is achieved via translating the gap between optimum attainable productivity level in each classification of cropping systems and actual productivity level by the relationship of cumulated NDVI and cereal-equivalent production. The results show most of cropland area in Africa have decreasing trend in cumulated NDVI, distributing in the Nile Delta, Eastern Africa and central of semi-arid to arid savanna area, except significant positive cumulated NDVI trends are mainly found between Senegal and Benin. Using cumulated NDVI and statistics of cereal equivalent production, we find remarkable potential yield gap at the Horn of East Africa (especially in Somalia), Northern Africa (Morocco, Algeria and Tunisia). Meanwhile, countries locating at the savanna area near <span class="hlt">Sahel</span> desert and South Africa also show significant potential, though they already have a relatively high level of productivity. Our results can help provide policy recommendation for local government or NGO to tackle food security problems by identifying zones with high potential of yield improvement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A51M..08G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A51M..08G"><span>Transient Climate Impacts for Scenarios of Aerosol Emissions from Asia: A Story of Coal versus Gas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grandey, B. S.; Cheng, H.; Wang, C.</p> <p>2014-12-01</p> <p>Projections of anthropogenic aerosol emissions are uncertain. In Asia, it is possible that emissions may increase if business continues as usual, with economic growth driving an increase in coal burning. But it is also possible that emissions may decrease rapidly due to the widespread adoption of cleaner technology or a shift towards non-coal fuels, such as natural gas. In this study, the transient climate impacts of three aerosol emissions scenarios are investigated: an RCP4.5 (Representative Concentration Pathway 4.5) control; a scenario with reduced Asian anthropogenic aerosol emissions; and a scenario with enhanced Asian anthropogenic aerosol emissions. A coupled atmosphere-ocean configuration of CESM (Community Earth System Model), including CAM5 (Community Atmosphere Model version 5), is used. Enhanced Asian aerosol emissions are found to delay global mean warming by one decade at the end of the century. Aerosol-induced suppression of the East Asian and South Asian summer monsoon precipitation occurs. The enhanced Asian aerosol emissions also remotely impact precipitation in other parts of the world: over the <span class="hlt">Sahel</span>, West African monsoon precipitation is suppressed; and over Australia, austral summer monsoon precipitation is enhanced. These remote impacts on precipitation are associated with a southward shift of the ITCZ. The aerosol-induced sea surface temperature (SST) response appears to play an important role in the precipitation changes over South Asia and Australia, but not over East Asia. These results indicate that energy production in Asia, through the consequent aerosol emissions and associated radiative effects, might significantly influence future climate both locally and globally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150015972','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150015972"><span>The Fertilizing Role of African Dust in the Amazon Rainforest: A First Multiyear Assessment Based on CALIPSO Lidar Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Remer, Lorraine A.; Prospero, Joseph M.; Omar, Ali; Winker, David; Yang, Yuekui; Zhang, Yan; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20150015972'); toggleEditAbsImage('author_20150015972_show'); toggleEditAbsImage('author_20150015972_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20150015972_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20150015972_hide"></p> <p>2015-01-01</p> <p>The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three dimensional (3D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8 to approximately 48) Tg a(exp -1) or 29 (8 to approximately 50) kg ha(exp -1) a(exp -1). The dust deposition shows significant interannual variation that is negatively correlated with the prior-year rainfall in the <span class="hlt">Sahel</span>. The CALIOP-based multi-year mean estimate of dust deposition matches better with estimates from in-situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.0060.037) Tg P of phosphorus per year, equivalent to 23 (7 to approximately 39) g P ha(exp -1) a(exp -1) to fertilize the Amazon rainforest. This out-of-Basin P input largely compensates the hydrological loss of P from the Basin, suggesting an important role of African dust in preventing phosphorus depletion on time scales of decades to centuries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1225157-fertilizing-role-african-dust-amazon-rainforest-first-multiyear-assessment-based-data-from-cloud-aerosol-lidar-infrared-pathfinder-satellite-observations','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1225157-fertilizing-role-african-dust-amazon-rainforest-first-multiyear-assessment-based-data-from-cloud-aerosol-lidar-infrared-pathfinder-satellite-observations"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Yu, Hongbin; Chin, Mian; Yuan, Tianle</p> <p></p> <p>The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three dimensional (3D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8~48) Tg a -1 or 29 (8~50) kg ha -1 a -1. The dust deposition shows significant interannual variationmore » that is negatively correlated with the prior-year rainfall in the <span class="hlt">Sahel</span>. The CALIOP-based multi-year mean estimate of dust deposition matches better with estimates from in-situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.006~0.037) Tg P of phosphorus per year, equivalent to 23 (7~39) g P ha -1 a -1 to fertilize the Amazon rainforest. This out-of-Basin P input is comparable to the hydrological loss of P from the Basin, suggesting an important role of African dust in preventing phosphorus depletion on time scales of decades to centuries.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A41F3116Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A41F3116Y"><span>African Dust Fertilizing the Amazon Rainforest: An Assessment with Seven-year Record of CALIOP Measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, H.; Chin, M.; Yuan, T.; Bian, H.; Prospero, J. M.; Omar, A. H.; Remer, L. A.; Winker, D. M.; Yang, Y.; Zhang, Y.; Zhang, Z.</p> <p>2014-12-01</p> <p>The productivity of Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of transported African dust in boreal winter and spring is considered an important nutrient input for the Amazon Basin, though its magnitude is not well qunatified. This study provides a remote sensing observation-based estimate of dust deposition in the Amazon Basin using a 7-year (2007-2013) record of three dimensional (3D) distributions of aerosol in both cloud-free and above-cloud conditions from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). It is estimated that the 7-year average of dust deposition into the Amazon Basin amounts to 15.1 ~ 32.1 Tg a-1 (Tg = 1012 g). This imported dust could provide 0.012 ~ 0.025 Tg P a-1 or equivalent to 12 ~ 26 g P ha-1 a-1 to fertilize the Amazon rainforest, which largely compensates the hydrological loss of P. The CLAIOP-based estimate agrees better with estimates from in-situ measurements and model simulations than what has been reported in literature. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The trans-Atlantic transport and deposition of dust shows strong interannual variations that are found to correlate with the North Atlantic Oscillation index in the winter season and anticorrelate with the prior-year <span class="hlt">Sahel</span> Precipitation Index on an annual basis. Uncertainties associated with the estimate will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017667','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017667"><span>Revisiting AVHRR Tropospheric Aerosol Trends Using Principal Component Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.</p> <p>2014-01-01</p> <p>The advanced very high resolution radiometer (AVHRR) satellite instruments provide a nearly 25 year continuous record of global aerosol properties over the ocean. It offers valuable insights into the long-term change in global aerosol loading. However, the AVHRR data record is heavily influenced by two volcanic eruptions, El Chichon on March 1982 and Mount Pinatubo on June 1991. The gradual decay of volcanic aerosols may last years after the eruption, which potentially masks the estimation of aerosol trends in the lower troposphere, especially those of anthropogenic origin. In this study, we show that a principal component analysis approach effectively captures the bulk of the spatial and temporal variability of volcanic aerosols into a single mode. The spatial pattern and time series of this mode provide a good match to the global distribution and decay of volcanic aerosols. We further reconstruct the data set by removing the volcanic aerosol component and reestimate the global and regional aerosol trends. Globally, the reconstructed data set reveals an increase of aerosol optical depth from 1985 to 1990 and decreasing trend from 1994 to 2006. Regionally, in the 1980s, positive trends are observed over the North Atlantic and North Arabian Sea, while negative tendencies are present off the West African coast and North Pacific. During the 1994 to 2006 period, the Gulf of Mexico, North Atlantic close to Europe, and North Africa exhibit negative trends, while the coastal regions of East and South Asia, the <span class="hlt">Sahel</span> region, and South America show positive trends.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51L..03T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51L..03T"><span>Forced and Internal Multi-Decadal Variability in the North Atlantic and their Climate Impacts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ting, M.</p> <p>2017-12-01</p> <p>Atlantic Multidecadal Variability (AMV), a basin-wide North Atlantic sea surface temperature warming or cooling pattern varying on decadal and longer time scales, is one of the most important climate variations in the Atlantic basin. The AMV has shown to be associated with significant climate impacts regionally and globally, from Atlantic hurricane activities, frequency and severity of droughts across North America, as well as rainfall anomalies across the African <span class="hlt">Sahel</span> and northeast Brazil. Despite the important impacts of the AMV, its mechanisms are not completely understood. In particular, it is not clear how much of the historical Atlantic SST fluctuations were forced by anthropogenic sources such as greenhouse warming and aerosol cooling, versus driven internally by changes in the coupled ocean-atmosphere processes in the Atlantic. Using climate models such as the NCAR large ensemble simulations, we were able to successfully separate the forced and internally generated North Atlantic sea surface temperature anomalies through a signal-to-noise maximizing Empirical Orthogonal Function (S/N EOF) analysis method. Two forced modes were identified with one representing a hemispherical symmetric mode and one asymmetric mode. The symmetric mode largely represents the greenhouse forced component while the asymmetric mode resembles the anthropogenic aerosol forcing. When statistically removing both of the forced modes, the residual multidecadal Atlantic SST variability shows a very similar structure as the AMV in the preindustrial simulation. The distinct climate impacts of each of these modes are also identified and the implications and challenges for decadal climate prediction will be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140013336','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140013336"><span>Evidence of a Weakly Absorbing Intermediate Mode of Aerosols in AERONET Data from Saharan and Sahelian Sites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gianelli, Scott M.; Lacis, Andrew A.; Carlson, Barbara E.; Hameed, Sultan</p> <p>2013-01-01</p> <p>Accurate retrievals of aerosol size distribution are necessary to estimate aerosols' impact on climate and human health. The inversions of the Aerosol Robotic Network (AERONET) usually retrieve bimodal distributions. However, when the inversion is applied to Saharan and Sahelian dust, an additional mode of intermediate size between the coarse and fine modes is sometimes seen. This mode explains peculiarities in the behavior of the Angstrom exponent, along with the fine mode fraction retrieved using the spectral deconvolution algorithm, observed in a March 2006 dust storm. For this study, 15 AERONET sites in northern Africa and on the Atlantic are examined to determine the frequency and properties of the intermediate mode. The mode is observed most frequently at Ilorin in Nigeria. It is also observed at Capo Verde and multiple sites located within the <span class="hlt">Sahel</span> but much less frequently at sites in the northern Sahara and the Canary Islands. The presence of the intermediate mode coincides with increases in Angstrom exponent, fine mode fraction, single-scattering albedo, and to a lesser extent percent sphericity. The Angstrom exponent decreases with increasing optical depth at most sites when the intermediate mode is present, but the fine mode fraction does not. Single-scattering albedo does not steadily decrease with fine mode fraction when the intermediate mode is present, as it does in typical mixtures of dust and biomass-burning aerosols. Continued investigation is needed to further define the intermediate mode's properties, determine why it differs from most Saharan dust, and identify its climate and health effects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008WRR....4412445B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008WRR....4412445B"><span>Hydrology of malaria: Model development and application to a Sahelian village</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bomblies, Arne; Duchemin, Jean-Bernard; Eltahir, Elfatih A. B.</p> <p>2008-12-01</p> <p>We present a coupled hydrology and entomology model for the mechanistic simulation of local-scale response of malaria transmission to hydrological and climatological determinants in semiarid, desert fringe environments. The model is applied to the <span class="hlt">Sahel</span> village of Banizoumbou, Niger, to predict interannual variability in malaria vector mosquito populations that lead to variations in malaria transmission. Using a high-resolution, small-scale distributed hydrology model that incorporates remotely sensed data for land cover and topography, we simulate the formation and persistence of the pools constituting the primary breeding habitat of Anopheles gambiae s.l. mosquitoes, the principal regional malaria vector mosquitoes. An agent-based mosquito population model is coupled to the distributed hydrology model, with aquatic-stage and adult-stage components. Through a dependence of aquatic-stage mosquito development and adult emergence on pool persistence, we model small-scale hydrology as a dominant control of mosquito abundance. For each individual adult mosquito, the model tracks attributes relevant to population dynamics and malaria transmission, which are updated as mosquitoes interact with their environment, humans, and animals. Weekly field observations were made in 2005 and 2006. A 16% increase in rainfall between the two years was accompanied by a 132% increase in mosquito abundance between 2005 and 2006. The model reproduces mosquito population variability at seasonal and interannual timescales and highlights individual pool persistence as a dominant control. Future developments of the presented model can be used in the evaluation of impacts of climate change on malaria, as well as the a priori evaluation of environmental management-based interventions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.H11D0826B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.H11D0826B"><span>The Role of Rainfall Patterns in Seasonal Malaria Transmission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bomblies, A.</p> <p>2010-12-01</p> <p>Seasonal total precipitation is well known to affect malaria transmission because Anopheles mosquitoes depend on standing water for breeding habitat. However, the within-season temporal pattern of the rainfall influences persistence of standing water and thus rainfall patterns also affect mosquito population dynamics. In this talk, I show that intraseasonal rainfall pattern describes 40% of the variance in simulated mosquito abundance in a Niger <span class="hlt">Sahel</span> village where malaria is endemic but highly seasonal, demonstrating the necessity for detailed distributed hydrology modeling to explain the variance from this important effect. I apply a field validated, high spatial- and temporal-resolution hydrology model coupled with an entomology model. Using synthetic rainfall time series generated using a stationary first-order Markov Chain model, I hold all variables except hourly rainfall constant, thus isolating the contribution of rainfall pattern to variance in mosquito abundance. I further show the utility of hydrology modeling to assess precipitation effects by analyzing collected water. Time-integrated surface area of pools explains 70% of the variance in mosquito abundance, and time-integrated surface area of pools persisting longer than seven days explains 82% of the variance, showing an improved predictive ability when pool persistence is explicitly modeled at high spatio-temporal resolution. I extend this analysis to investigate the impacts of this effect on malaria vector mosquito populations under climate shift scenarios, holding all climate variables except precipitation constant. In these scenarios, rainfall mean and variance change with climatic change, and the modeling approach evaluates the impact of non-stationarity in rainfall and the associated rainfall patterns on expected mosquito activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThApC.127..197E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThApC.127..197E"><span>On convection and static stability during the AMMA SOP3 campaign</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Embolo Embolo, G. B.; Lenouo, André; Nzeukou, Armand T.; Vondou, Derbetini A.; Kamga, F. Mkankam</p> <p>2017-01-01</p> <p>Using radiosonde dataset from 15 weather stations over West Africa, this paper investigates the contribution of the couple convection-static stability in the framework of the African monsoon multidisciplinary analyses Special Observing Period 3 (AMMA SOP3) experiment. Within this 31-day period, the boundary layer-winds depictions have revealed the West African monsoon's (WAM) depth (around 1500 m) is not thick enough to trigger intense convection. However, the midlevel winds distribution (700-600 hPa) has shown the average African easterly jet core strength (15 m s-1) is sufficient to allow the development of African easterly waves (AEWs) necessary for squall lines activities. In return, in the upper levels (200-100 hPa), the speed (below 18 m s-1) of the mean Tropical easterly jet (TEJ) core cannot favor midlevel updrafts. The free tropospheric humidity (FTH) depiction has indicated convective events are more likely in the western <span class="hlt">Sahel</span> where the highest FTH (FTH >50 %) are recorded. The static stability analysis has testified that convection is stronger in the semi-arid (SA) area during night time (0000 GMT). However, convective activities are inhibited in the wet equatorial (WE) region due to mean low-level stability. We used METEOSAT Second Generation (MSG) infrared (IR10.8) imagery of the 8th September 2006 to confirm that result. Furthermore, a maximum midtropospheric static stability combined with maximum relative humidity (RH) was found on the fringe of the Saharan air layer's (SAL) top (altitude around 5.3 km) in the WE region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002QSRv...21.2047C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002QSRv...21.2047C"><span>Patterns and processes of Late Quaternary environmental change in a montane region of southwestern Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carrión, José S.</p> <p>2002-10-01</p> <p>This paper examines the Late Quaternary (c. 20,300-<505 cal yr BP) environmental history of Siles, a lake situated at 1320 m in the Segura mountains of southern Spain, with the goal of establishing the mechanisms exerting control on vegetation change. Palaeoecological indicators include pollen, microcharcoal, spores of terrestrial plants, fungi, and non-siliceous algae, and other microfossils. The Siles sequence is shown to be sensitive to climatic change, although the control exerted by climate on vegetation is ultimately shaped by disturbances and species interactions, determining the occurrence of century-scale lags and threshold responses. Biotically induced changes of vegetation are also shown at the intrazonal level of variation. The new sequence is placed in the context of two previous records to postulate a picture of Holocene environmental change for the Segura region. The existence of mid-elevation glacial refugia for a number of temperate and Mediterranean trees is shown. A mid-Holocene phase (c. 7500-5200 cal yr BP) emerges regionally as the time of maximum forest development and highest lake levels. The early Holocene occurs as a generally dry, pyrophytic period of pine forests, with grassland scrub in high altitudes, and the late Holocene as a period of protracted vegetation sensitivity, with return to development of pine forests, spread of xerophytic communities, and increased fire activity, under the context of dry spells, localized anthropogenic disturbance, and shallowing and desiccation of lakes. Several events described here correlate with established times of abrupt transitions in the climates of northern Europe, the Mediterranean basin, north Africa, and the <span class="hlt">Sahel</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24952161','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24952161"><span>[Frequency of glucose-6-phosphate dehydrogenase deficiency (A-376/202) in three Malian ethnic groups].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dolo, A; Maiga, B; Guindo, A; Diakité, S A S; Diakite, M; Tapily, A; Traoré, M; Sangaré, B; Arama, C; Daou, M; Doumbo, O</p> <p>2014-08-01</p> <p>Erythrocyte G6PD deficiency is the most common worldwide enzymopathy. The aim of this study was to determine erythrocyte G6PD deficiency in 3 ethnic groups of Mali and to investigate whether erythrocyte G6PD deficiency was associated to the observed protection against malaria seen in Fulani ethnic group. The study was conducted in two different areas of Mali: in the <span class="hlt">Sahel</span> region of Mopti where Fulani and Dogon live as sympatric ethnic groups and in the Sudanese savannah area where lives mostly the Malinke ethnic group. The study was conducted in 2007 in Koro and in 2008 in Naguilabougou. It included a total 90 Dogon, 42 Fulani and 80 Malinke ethnic groups. Malaria was diagnosed using microscopic examination after Giemsa-staining of thick and thin blood smear. G6PD deficiency (A-(376/202)) samples were identified using RFLP (Restriction Fragment Length Polymorphism) assay and analysis of PCR-amplified DNA amplicon. G6PD deficiency (A-(376/202)) rate was 11.1%, 2.4%, and 13.3% in Dogon, Fulani, and Malinke ethnic group respectively. Heterozygous state for G6PD (A-(376/202)) was found in 7.8% in Dogon; 2.4% in Fulani and 9.3% in Malinke ethnic groups while hemizygous state was found at the frequency of 2.2% in Dogon and 4% in Malinke. No homozygous state was found in our study population.We conclude that G6PD deficiency is not differing significantly between the three ethnic groups, Fulani, Dogon and Malinke.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6593974-soil-tillage-windbreak-effects-millet-cowpea-wind-speed-evaporation-wind-erosion','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6593974-soil-tillage-windbreak-effects-millet-cowpea-wind-speed-evaporation-wind-erosion"><span>Soil tillage and windbreak effects on millet and cowpea: I. Wind speed, evaporation, and wind erosion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Banzhaf, J.; Leihner, D.E.; Buerkert, A.</p> <p></p> <p>Deforestation, overgrazing, and declining soil regeneration periods have resulted in increased wind erosion problems in dry areas of the West African <span class="hlt">Sahel</span>, but little is known about the bio-physical factors involved. This research was conducted to determine the effects of ridging and four different windbreak spacings on wind erosion, potential evaporation, and soil water reserves. A field trial was conducted from 1985 to 1987 on 12 ha of a Psammentic Paleustalf in Southern Niger. Millet, Pennisetum glaucum (L.), and cowpea, Vigna unguiculata (L.) Walp., were seeded in strips on flat and ridged soil. Windbreaks of savannah vegetation were spaced atmore » 6, 20, 40, and 90 m. The effects of ridging on wind speed, evaporation, and wind erosion were small and mostly non-significant. However, average wind speed at 0.3 m above ground in the center of cowpea and millet strips was significantly reduced from 2.8 to 2.1 m s[sup [minus]1] as windbreak distances narrowed from 90 to 6 m. As a consequence, potential evaporation declined by 15% and the amount of windblown soil particles by 50% in ridged and by 70% in flat treatments. Despite reduced potential evaporation, average subsoil water reserves were 14 mm smaller in the 6- than in the 20-m windbreak spacing indicating excessive water extraction by the windbreak vegetation. Thus, establishing windbreaks with natural savannah vegetation may require a careful consideration of the agronomic benefits and costs to competing crops. 21 refs., 5 figs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=GL-2002-001605&hterms=HAut&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DHAut','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=GL-2002-001605&hterms=HAut&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DHAut"><span>West Africa</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>With its vast expanses of sand, framed by mountain ranges and exposed rock, northwestern Africa makes a pretty picture when viewed from above. This image was acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra spacecraft. The Canary Islands can be seen on the left side of the image just off Africa's Atlantic shore. The light brown expanse running through the northern two thirds of the image is the Sahara Desert. The desert runs up against the dark brown Haut Atlas mountain range of Morocco in the northwest, the Atlantic Ocean to the west and the semi-arid (light brown pixels) Sahelian region in the South. The Sahara, however, isn't staying put. Since the 1960s, the desert has been expanding into the Sahelian region at a rate of up to 6 kilometers per year. In the 1980s this desert expansion, combined with over cultivation of the <span class="hlt">Sahel</span>, caused a major famine across west Africa. Over the summer months, strong winds pick up sands from the Sahara and blow them across the Atlantic as far west as North America, causing air pollution in Miami and damaging coral reefs in the Bahamas and the Florida Keys. The white outlines on the map represent country borders. Starting at the top-most portion of the map and working clockwise, the countries shown are Morocco, Western Sahara, Mauritania, Senegal, Mali, Burkina Fasso, Nigeria, Mali (again), and Algeria. Image by Reto Stockli, Robert Simmon, and Brian Montgomery, NASA Earth Observatory, based on data from MODIS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11584662','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11584662"><span>Malaria prophylaxis in the French armed forces: evolution of concepts.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Touze, J E; Paule, P; Baudon, D; Boutin, J P</p> <p>2001-01-01</p> <p>Malaria is still a serious public health problem in the world and control remains a major priority for the approximately 25.000 French troops deployed, mostly on permanent assignment, in malaria transmission regions. Epidemiological surveillance of malaria provides data necessary to assess morbidity, monitor changing patterns of Plasmodium falciparum drug-sensitivity, and evaluate the efficacy of malaria control measures. About 540 cases were observed in 1999 for an incidence of 4.1 p. 100 men. year. Since 1991, strong emphasis has been placed on prophylaxis. In addition to vector control measures and individual protection against mosquito bites (impregnated bednets, protective clothing, application of repellents, and indoor insecticide spraying), drug prophylaxis has been recommended using a combination of 100 mg of chloroquine and 200 mg of proguanil chlorhydrate (CQ + PG) in a single capsule manufactured by the French Health Army Service. Initially this policy led to a significant decrease in malaria cases among French soldiers. However the incidence of malaria rose in 1995 and 1996. This recrudescence was attributed to poor compliance with chemoprophylaxis and to the declining efficacy of the CQ + PG combination. In response to these problems, a new policy was implemented especially in countries where cycloguanil-resistant Plasmodium falciparum incidence rate is increasing. The new chemoprophylactic regimen calls for a personal prescription of mefloquine. Doxycycline monohydrate is used in case of mefloquine contra-indication or intolerance. Combination of CQ + PG delivered in a single capsule remains a suitable chemoprophylactic regimen in <span class="hlt">Sahel</span> countries as well as Horn of Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ERL....13f5003N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ERL....13f5003N"><span>The effects of 1.5 and 2 degrees of global warming on Africa in the CORDEX ensemble</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikulin, Grigory; Lennard, Chris; Dosio, Alessandro; Kjellström, Erik; Chen, Youmin; Hänsler, Andreas; Kupiainen, Marco; Laprise, René; Mariotti, Laura; Fox Maule, Cathrine; van Meijgaard, Erik; Panitz, Hans-Jürgen; Scinocca, John F.; Somot, Samuel</p> <p>2018-06-01</p> <p>There is a general lack of information about the potential effects of 1.5, 2 or more degrees of global warming on the regional climates within Africa, and most studies that address this use data from coarse resolution global models. Using a large ensemble of CORDEX Africa simulations, we present a pan-African overview of the effects of 1.5 and 2 °C global warming levels (GWLs) on the African climate. The CORDEX simulations, consistent with their driving global models, show a robust regional warming exceeding the mean global one over most of Africa. The highest increase in annual mean temperature is found over the subtropics and the smallest one over many coastal regions. Projected changes in annual mean precipitation have a tendency to wetter conditions in some parts of Africa (e.g. central/eastern <span class="hlt">Sahel</span> and eastern Africa) at both GWLs, but models’ agreement on the sign of change is low. In contrast to mean precipitation, there is a consistent increase in daily precipitation intensity of wet days over a large fraction of tropical Africa emerging already at 1.5 °C GWL and strengthening at 2 °C. A consistent difference between 2 °C and 1.5 °C warmings is also found for projected changes in annual mean temperature and daily precipitation intensity. Our study indicates that a 0.5 °C further warming (from 1.5 °C–2 °C) can indeed produce a robust change in some aspects of the African climate and its extremes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29261678','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29261678"><span>Empirical analysis of vegetation dynamics and the possibility of a catastrophic desertification transition.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weissmann, Haim; Kent, Rafi; Michael, Yaron; Shnerb, Nadav M</p> <p>2017-01-01</p> <p>The process of desertification in the semi-arid climatic zone is considered by many as a catastrophic regime shift, since the positive feedback of vegetation density on growth rates yields a system that admits alternative steady states. Some support to this idea comes from the analysis of static patterns, where peaks of the vegetation density histogram were associated with these alternative states. Here we present a large-scale empirical study of vegetation dynamics, aimed at identifying and quantifying directly the effects of positive feedback. To do that, we have analyzed vegetation density across 2.5 × 106 km2 of the African <span class="hlt">Sahel</span> region, with spatial resolution of 30 × 30 meters, using three consecutive snapshots. The results are mixed. The local vegetation density (measured at a single pixel) moves towards the average of the corresponding rainfall line, indicating a purely negative feedback. On the other hand, the chance of spatial clusters (of many "green" pixels) to expand in the next census is growing with their size, suggesting some positive feedback. We show that these apparently contradicting results emerge naturally in a model with positive feedback and strong demographic stochasticity, a model that allows for a catastrophic shift only in a certain range of parameters. Static patterns, like the double peak in the histogram of vegetation density, are shown to vary between censuses, with no apparent correlation with the actual dynamical features. Our work emphasizes the importance of dynamic response patterns as indicators of the state of the system, while the usefulness of static modality features appears to be quite limited.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Tectp.676..211G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Tectp.676..211G"><span>Neotectonics of coastal Jeffara (southern Tunisia): State of the art</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghedhoui, Rim; Deffontaines, Benoît; Rabia, Mohamed Chedly</p> <p>2016-04-01</p> <p>Helped by the studies and results of previous researchers, we herein study the neotectonic of the coastal Jeffara with the input of numerous 2D reflection seismic profiles onshore, combined with Digital Elevation Model analyses (issued from SRTM) and field works. Acquired and available data were then integrated within a GIS Geodatabase, where Jerba, Zarzis and Jorf appear to be part of a N-S pull-apart basin within a NW-SE transtensive right-lateral major fault zone. Our structural geologic and geomorphologic analyses confirm and prove the presence of NNW-SSE right-lateral en-echelon tension gashes, NW-SE aligned salt diapirs, numerous active folds offsets, en-echelon folds, and so-on… They are associated with this major right-lateral NW-SE transtensive major coastal Jeffara fault zone that affect the Holocene and the Villafranchian deposits. We therefore confirm herein a new structural geodynamic Jeffara model, due to the post Lower Cretaceous northward migration of northern African to the Eurasian plates, this NW-SE transtensive fault zone is interpreted as a part of the southern branch of the eastward <span class="hlt">Sahel</span> block extrusion toward the free Mediterranean Sea boundary. Therefore this geodynamic movement may explain the presence, offshore, of small elongated NW-SE, N-S and NE-SW transtensive basins and grabens with petroleum interest. To conclude, at the regional scale, the structural geomorphologic approach combined with both field work and 2D reflection seismic profile analyses appear to be an excellent tool to prove and confirm the NW-SE right-lateral transtensive extrusion fault zone of the coastal Jeffara.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC34A..07N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC34A..07N"><span>20th-Century Climate Change over Africa: Seasonal Variation in Hydroclimate Trends and Sahara Desert Extent</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nigam, S.; Thomas, N. P.</p> <p>2017-12-01</p> <p>Twentieth-century trends in seasonal temperature and precipitation over the African continent are analyzed from observational data sets and historical climate simulations. Given the agricultural economy of the continent, a seasonal perspective is adopted as it is more pertinent than an annual-average one which can mask off-setting but agriculturally-sensitive seasonal hydroclimate variations. Examination of linear trends in seasonal surface air temperature (SAT) shows that heat stress has increased in several regions, including Sudan and Northern Africa where largest SAT trends occur in the warm season. Broadly speaking, the northern continent has warmed more than the southern one in all seasons. Precipitation trends are varied but notable declining trends are found in the countries along the Gulf of Guinea, especially in the source region of Niger river in West Africa, and in the Congo river basin. Rainfall over the African Great Lakes - one of the largest freshwater repositories - has however increased. We show that the Sahara Desert has expanded significantly over the 20th century - by 12-20% depending on the season. The desert expanded southward in summer, reflecting retreat of the northern edge of the <span class="hlt">Sahel</span> rainfall belt; and to the north in winter, indicating potential impact of the widening of the Tropics. Specific mechanisms driving the expansion in each season are investigated. Finally, this observational analysis is used to evaluate the state-of-the-art climate models from a comparison of the 20th-century hydroclimate trends with those manifest in historical climate simulations. The evaluation shows that modeling regional hydroclimate change over the Africa continent remains challenging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27771460','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27771460"><span>Molecular characterization and phylogenetic analysis of Fasciola gigantica from Nigeria.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ichikawa-Seki, Madoka; Tokashiki, Minami; Opara, Maxwell Nwachukwu; Iroh, Gabriel; Hayashi, Kei; Kumar, Uday Mohanta; Itagaki, Tadashi</p> <p>2017-02-01</p> <p>Fasciola gigantica is considered the major pathogen causing fasciolosis in Africa; however, molecular characterization of this fluke has not been adequately elucidated. It is important to scientifically elucidate the dispersal history of F. gigantica by analyzing its genetic diversity. Fasciola flukes from Nigeria were analyzed using nuclear and mitochondrial DNA markers. A total of 172 Fasciola flukes collected from cattle were identified as F. gigantica because they displayed the F. gigantica fragment pattern in multiplex PCR for the nuclear marker, phosphoenolpyruvate carboxykinase (pepck). In total, 70 haplotypes were detected from Nigerian F. gigantica on the basis of the concatenated sequence of mitochondrial NADH dehydrogenase subunit 1 (nad1) and cytochrome c oxidase 1 (cox1). The index of neutrality (Fu's Fs) suggests rapid expansion of the Nigerian F. gigantica population. Although four haplogroups, Nigeria 1A, 1B, 2A, and 2B, were detected from Nigerian F. gigantica, a climate-specific genetic structure was not observed among F. gigantica populations from three agro-climatic regions (<span class="hlt">Sahel</span>, Savannah, and Forest). This is probably because of the frequent transportation of livestock from one part of the country to the other. Nigeria 1A and 1B had close relationships with the Egyptian population of F. gigantica, whereas Nigeria 2A and 2B were comparatively related to the Zambian population. No haplotype was shared among the three countries, and it therefore is difficult to estimate the dispersal route of F. gigantica within the African continent. Copyright © 2016. Published by Elsevier Ireland Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030054359&hterms=global+issues&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dglobal%2Bissues','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030054359&hterms=global+issues&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dglobal%2Bissues"><span>Dynamics and Properties of Global Aerosol using MODIS, AERONET and GOCART Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kaufman, Yoram; Chin, Mian; Reme, Lorraine; Tanre, Didier; Mattoo, Shana</p> <p>2002-01-01</p> <p>Recently produced daily Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol data for the whole year of 2001 are used to show the concentration and dynamics of aerosol over ocean and large parts of the continents. The data were validated against the Aerosol Robotic Network (AERONET) measurements over land and ocean in a special issue in GRL now in press. Monthly averages and a movie based on the daily data are produced and used to demonstrate the spatial and temporal evolution of aerosol. The MODIS wide spectral range is used to distinguish fine smoke and pollution aerosol from coarse dust and salt. The aerosol is observed above ocean and land. The movie produced from the MODIS data provides a new dimension to aerosol observations by showing the dynamics of the system. For example in February smoke and dust emitted from the <span class="hlt">Sahel</span> and West Africa is shown to travel to the North-East Atlantic. In April heavy dust and pollution from East Asia is shown to travel to North America. In May-June pollution and dust play a dynamical dance in the Arabian Sea and Bay of Bengal. In Aug-September smoke from South Africa and South America is shown to pulsate in tandem and to periodically to be transported to the otherwise pristine Southern part of the Southern Hemisphere. The MODIS data are compared with the Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation Transport (GOCART) model to test and adjust source and sink strengths in the model and to study the effect of clouds on the representation of the satellite data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960016274','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960016274"><span>Radiative transfer in shrub savanna sites in Niger: Preliminary results from HAPEX-<span class="hlt">Sahel</span>. Part 3: Optical dynamics and vegetation index sensitivity to biomass and plant cover</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>vanLeeuwen, W. J. D.; Huete, A. R.; Duncan, J.; Franklin, J.</p> <p>1994-01-01</p> <p>A shrub savannah landscape in Niger was optically characterized utilizing blue, green, red and near-infrared wavelengths. Selected vegetation indices were evaluated for their performance and sensitivity to describe the complex Sahelian soil/vegetation canopies. Bidirectional reflectance factors (BRF) of plants and soils were measured at several view angles, and used as input to various vegetation indices. Both soil and vegetation targets had strong anisotropic reflectance properties, rendering all vegetation index (6) responses to be a direct function of sun and view geometry. Soil background influences were shown to alter the response of most vegetation indices. N-space greenness had the smallest dynamic range in VI response, but the n-space brightness index provided additional useful information. The global environmental monitoring index (GEMI) showed a large 6 dynamic range for bare soils, which was undesirable for a vegetation index. The view angle response of the normalized difference vegetation index (NDVI), atmosphere resistant vegetation index (ARVI) and soil atmosphere resistant vegetation index (SARVI) were asymmetric about nadir for multiple view angles, and were, except for the SARVI, altered seriously by soil moisture and/or soil brightness effects. The soil adjusted vegetation index (SAVI) was least affected by surface soil moisture and was symmetric about nadir for grass vegetation covers. Overall the SAVI, SARVI and the n-space vegetation index performed best under all adverse conditions and were recommended to monitor vegetation growth in the sparsely vegetated Sahelian zone.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25716875','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25716875"><span>Is the WBE model appropriate for semi-arid shrubs subjected to clear cutting?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Issoufou, Hassane Bil-Assanou; Rambal, Serge; Le Dantec, Valérie; Oï, Monique; Laurent, Jean-Paul; Saadou, Mahamane; Seghieri, Josiane</p> <p>2015-02-01</p> <p>It is crucial to understand the adaptive mechanisms of woody plants facing periodic drought to assess their vulnerability to the increasing climate variability predicted in the <span class="hlt">Sahel</span>. Guiera senegalensis J.F.Gmel is a semi-evergreen Combretaceae commonly found in Sahelian rangelands, fallows and crop fields because of its value as an agroforestry species. We compared canopy leafing, and allometric measurements of leaf area, stem area and stem length and their relationships with leaf water potential, stomatal conductance (gs) and soil-to-leaf hydraulic conductance (KS-L), in mature and current-year resprouts of G. senegalensis in Sahelian Niger. In mature shrubs, seasonal drought reduced the ratio of leaf area to cross-sectional stem area (AL : AS), mainly due to leaf shedding. The canopy of the current-year resprouts remained permanently leafed as the shrubs produced leaves and stems continuously, and their AL : AS ratio increased throughout the dry season. Their KS-L increased, whereas gs decreased. West, Brown and Enquist's (WBE) model can thus describe allometric trends in the seasonal life cycle of undisturbed mature shrubs, but not that of resprouts. Annual clear cutting drives allometric scaling relationships away from theoretical WBE predictions in the current-year resprouts, with scaling exponents 2.5 times greater than those of mature shrubs. High KS-L (twice that of mature shrubs) supports this intensive regeneration process. The adaptive strategy described here is probably common to many woody species that have to cope with both severe seasonal drought and regular disturbance over the long term. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRD..123.1384B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRD..123.1384B"><span>Linking Barbados Mineral Dust Aerosols to North African Sources Using Elemental Composition and Radiogenic Sr, Nd, and Pb Isotope Signatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bozlaker, Ayse; Prospero, Joseph M.; Price, Jim; Chellam, Shankararaman</p> <p>2018-01-01</p> <p>Large quantities of African dust are carried across the Atlantic to the Caribbean Basin and southern United States where it plays an important role in the biogeochemistry of soils and waters and in air quality. Dusts' elemental and isotopic composition was comprehensively characterized in Barbados during the summers of 2013 and 2014, the season of maximum dust transport. Although total suspended insoluble particulate matter (TSIP) mass concentrations varied significantly daily and between the two summers, the abundances (μg element/g TSIP) of 50 elements during "high-dust days" (HDD) were similar. Aerosols were regularly enriched in Na, Cu, Zn, As, Se, Mo, Cd, Sn, Sb, and W relative to the upper continental crust. Enrichment of these elements, many of which are anthropogenically emitted, was significantly reduced during HDD, attributed to mixing and dilution with desert dust over source regions. Generally, Ti/Al, Si/Al, Ca/Al, Ti/Fe, Si/Fe, and Ca/Fe ratios during HDD differed from their respective values in hypothesized North African source regions. Nd isotope composition was relatively invariant for "low-dust days" (LDD) and HDD. In contrast, HDD-aerosols were more radiogenic exhibiting higher 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios compared to LDD. Generally, Barbados aerosols' composition ranged within narrow limits and was much more homogeneous than that of hypothesized African source soils. Our results suggest that summertime Barbados aerosols are dominated by a mixture of particles originating from sources in the Sahara-<span class="hlt">Sahel</span> regions. The Bodélé Depression, long suspected as a major source, appears to be an insignificant contributor of summertime western Atlantic dust.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1438003','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1438003"><span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Grandey, Benjamin S.; Cheng, Haiwen; Wang, Chien</p> <p></p> <p>Fuel usage is an important driver of anthropogenic aerosol emissions. In Asia, it is possible that aerosol emissions may increase if business continues as usual, with economic growth driving an increase in coal burning. But it is also possible that emissions may decrease rapidly as a result of the widespread adoption of cleaner technologies or a shift toward noncoal fuels, such as natural gas. In this study, the transient climate impacts of two aerosol emissions scenarios are investigated: a representative concentration pathway 4.5 (RCP4.5) control, which projects a decrease in anthropogenic aerosol emissions, and a scenario with enhanced anthropogenic aerosolmore » emissions from Asia. A coupled atmosphere–ocean configuration of the Community Earth System Model (CESM), including the Community Atmosphere Model, version 5 (CAM5), is used. Three sets of initial conditions are used to produce a three-member ensemble for each scenario. Enhanced Asian aerosol emissions are found to exert a large cooling effect across the Northern Hemisphere, partially offsetting greenhouse gas–induced warming. Aerosol-induced suppression of the East Asian and South Asian summer monsoon precipitation occurs. The enhanced Asian aerosol emissions also remotely impact precipitation in other parts of the world. Over Australia, austral summer monsoon precipitation is enhanced, an effect associated with a southward shift of the intertropical convergence zone, driven by the aerosol-induced cooling of the Northern Hemisphere. Over the <span class="hlt">Sahel</span>, West African monsoon precipitation is suppressed, likely via a weakening of the West African westerly jet. These results indicate that fuel usage in Asia, through the consequent aerosol emissions and associated radiative effects, might significantly influence future climate both locally and globally.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24692268','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24692268"><span>Livestock and food security: vulnerability to population growth and climate change.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Godber, Olivia F; Wall, Richard</p> <p>2014-10-01</p> <p>Livestock production is an important contributor to sustainable food security for many nations, particularly in low-income areas and marginal habitats that are unsuitable for crop production. Animal products account for approximately one-third of global human protein consumption. Here, a range of indicators, derived from FAOSTAT and World Bank statistics, are used to model the relative vulnerability of nations at the global scale to predicted climate and population changes, which are likely to impact on their use of grazing livestock for food. Vulnerability analysis has been widely used in global change science to predict impacts on food security and famine. It is a tool that is useful to inform policy decision making and direct the targeting of interventions. The model developed shows that nations within sub-Saharan Africa, particularly in the <span class="hlt">Sahel</span> region, and some Asian nations are likely to be the most vulnerable. Livestock-based food security is already compromised in many areas on these continents and suffers constraints from current climate in addition to the lack of economic and technical support allowing mitigation of predicted climate change impacts. Governance is shown to be a highly influential factor and, paradoxically, it is suggested that current self-sufficiency may increase future potential vulnerability because trade networks are poorly developed. This may be relieved through freer trade of food products, which is also associated with improved governance. Policy decisions, support and interventions will need to be targeted at the most vulnerable nations, but given the strong influence of governance, to be effective, any implementation will require considerable care in the management of underlying structural reform. © 2014 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1438003-transient-climate-impacts-scenarios-aerosol-emissions-from-asia-story-coal-versus-gas','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1438003-transient-climate-impacts-scenarios-aerosol-emissions-from-asia-story-coal-versus-gas"><span>Transient Climate Impacts for Scenarios of Aerosol Emissions from Asia: A Story of Coal versus Gas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Grandey, Benjamin S.; Cheng, Haiwen; Wang, Chien</p> <p>2016-04-06</p> <p>Fuel usage is an important driver of anthropogenic aerosol emissions. In Asia, it is possible that aerosol emissions may increase if business continues as usual, with economic growth driving an increase in coal burning. But it is also possible that emissions may decrease rapidly as a result of the widespread adoption of cleaner technologies or a shift toward noncoal fuels, such as natural gas. In this study, the transient climate impacts of two aerosol emissions scenarios are investigated: a representative concentration pathway 4.5 (RCP4.5) control, which projects a decrease in anthropogenic aerosol emissions, and a scenario with enhanced anthropogenic aerosolmore » emissions from Asia. A coupled atmosphere–ocean configuration of the Community Earth System Model (CESM), including the Community Atmosphere Model, version 5 (CAM5), is used. Three sets of initial conditions are used to produce a three-member ensemble for each scenario. Enhanced Asian aerosol emissions are found to exert a large cooling effect across the Northern Hemisphere, partially offsetting greenhouse gas–induced warming. Aerosol-induced suppression of the East Asian and South Asian summer monsoon precipitation occurs. The enhanced Asian aerosol emissions also remotely impact precipitation in other parts of the world. Over Australia, austral summer monsoon precipitation is enhanced, an effect associated with a southward shift of the intertropical convergence zone, driven by the aerosol-induced cooling of the Northern Hemisphere. Over the <span class="hlt">Sahel</span>, West African monsoon precipitation is suppressed, likely via a weakening of the West African westerly jet. These results indicate that fuel usage in Asia, through the consequent aerosol emissions and associated radiative effects, might significantly influence future climate both locally and globally.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24992942','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24992942"><span>Agent-based modeling of malaria vectors: the importance of spatial simulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bomblies, Arne</p> <p>2014-07-03</p> <p>The modeling of malaria vector mosquito populations yields great insight into drivers of malaria transmission at the village scale. Simulation of individual mosquitoes as "agents" in a distributed, dynamic model domain may be greatly beneficial for simulation of spatial relationships of vectors and hosts. In this study, an agent-based model is used to simulate the life cycle and movement of individual malaria vector mosquitoes in a Niger <span class="hlt">Sahel</span> village, with individual simulated mosquitoes interacting with their physical environment as well as humans. Various processes that are known to be epidemiologically important, such as the dependence of parity on flight distance between developmental habitat and blood meal hosts and therefore spatial relationships of pools and houses, are readily simulated using this modeling paradigm. Impacts of perturbations can be evaluated on the basis of vectorial capacity, because the interactions between individuals that make up the population- scale metric vectorial capacity can be easily tracked for simulated mosquitoes and human blood meal hosts, without the need to estimate vectorial capacity parameters. As expected, model results show pronounced impacts of pool source reduction from larvicide application and draining, but with varying degrees of impact depending on the spatial relationship between pools and human habitation. Results highlight the importance of spatially-explicit simulation that can model individuals such as in an agent-based model. The impacts of perturbations on village scale malaria transmission depend on spatial locations of individual mosquitoes, as well as the tracking of relevant life cycle events and characteristics of individual mosquitoes. This study demonstrates advantages of using an agent-based approach for village-scale mosquito simulation to address questions in which spatial relationships are known to be important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/54338-dynamical-basis-asian-summer-monsoon-rainfall-el-nino-relationship','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/54338-dynamical-basis-asian-summer-monsoon-rainfall-el-nino-relationship"><span>On the dynamical basis for the Asian summer monsoon rainfall-El Nino relationship</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Nigam, S.</p> <p></p> <p>The dynamical basis for the Asian summer monsoon rainfall-El Nino linkage is explored through diagnostic calculations with a linear steady-state multilayer primitive equation model. The contrasting monsoon circulation during recent El Nino (1987) and La Nina (1988) years is first simulated using orography and the residually diagnosed heating (from the thermodynamic equation and the uninitialized, but mass-balanced, ECMWF analysis) as forcings, and then analyzed to provide insight into the importance of various regional forcings, such as the El Nino-related heating anomalies over the tropical Indian and Pacific Oceans. The striking simulation of the June-August (1987-1988) near-surface and upper-air tropical circulationmore » anomalies indicates that tropical anomaly dynamics during northern summer is essentially linear even at the 150-mb level. The vertical structure of the residually diagnosed heating anomaly that contributes to this striking simulation differs significantly from the specified canonical vertical structure (used in generating 3D heating from OLR/precipitation distributions) near the tropical tropopause. The dynamical diagnostic analysis of the anomalous circulation during 1987 and 1988 March-May and June-August periods shows the orographically forced circulation anomaly (due to changes in the zonally averaged basic-state flow) to be quite dominant in modulating the low-level moisture-flux convergence and hence monsoon rainfall over Indochina. The El Nino-related persistent (spring-to-summer) heating anomalies over the tropical Pacific and Indian Ocean basins, on the other hand, mostly regulate the low-level westerly monsoon flow intensity over equatorial Africa and the northern Indian Ocean and, thereby, the large-scale moisture flux into <span class="hlt">Sahel</span> and Indochina. 38 refs., 12 figs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5737887','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5737887"><span>Empirical analysis of vegetation dynamics and the possibility of a catastrophic desertification transition</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kent, Rafi; Michael, Yaron; Shnerb, Nadav M.</p> <p>2017-01-01</p> <p>The process of desertification in the semi-arid climatic zone is considered by many as a catastrophic regime shift, since the positive feedback of vegetation density on growth rates yields a system that admits alternative steady states. Some support to this idea comes from the analysis of static patterns, where peaks of the vegetation density histogram were associated with these alternative states. Here we present a large-scale empirical study of vegetation dynamics, aimed at identifying and quantifying directly the effects of positive feedback. To do that, we have analyzed vegetation density across 2.5 × 106 km2 of the African <span class="hlt">Sahel</span> region, with spatial resolution of 30 × 30 meters, using three consecutive snapshots. The results are mixed. The local vegetation density (measured at a single pixel) moves towards the average of the corresponding rainfall line, indicating a purely negative feedback. On the other hand, the chance of spatial clusters (of many “green” pixels) to expand in the next census is growing with their size, suggesting some positive feedback. We show that these apparently contradicting results emerge naturally in a model with positive feedback and strong demographic stochasticity, a model that allows for a catastrophic shift only in a certain range of parameters. Static patterns, like the double peak in the histogram of vegetation density, are shown to vary between censuses, with no apparent correlation with the actual dynamical features. Our work emphasizes the importance of dynamic response patterns as indicators of the state of the system, while the usefulness of static modality features appears to be quite limited. PMID:29261678</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018HESS...22.3275P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018HESS...22.3275P"><span>Regional co-variability of spatial and temporal soil moisture-precipitation coupling in North Africa: an observational perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrova, Irina Y.; van Heerwaarden, Chiel C.; Hohenegger, Cathy; Guichard, Françoise</p> <p>2018-06-01</p> <p>The magnitude and sign of soil moisture-precipitation coupling (SMPC) is investigated using a probability-based approach and 10 years of daily microwave satellite data across North Africa at a 1° horizontal scale. Specifically, the co-existence and co-variability of spatial (i.e. using soil moisture gradients) and temporal (i.e. using soil moisture anomaly) soil moisture effects on afternoon rainfall is explored. The analysis shows that in the semi-arid environment of the <span class="hlt">Sahel</span>, the negative spatial and the negative temporal coupling relationships do not only co-exist, but are also dependent on one another. Hence, if afternoon rain falls over temporally drier soils, it is likely to be surrounded by a wetter environment. Two regions are identified as SMPC <q>hot spots</q>. These are the south-western part of the domain (7-15° N, 10° W-7° E), with the most robust negative SMPC signal, and the South Sudanese region (5-13° N, 24-34° E). The sign and significance of the coupling in the latter region is found to be largely modulated by the presence of wetlands and is susceptible to the number of long-lived propagating convective systems. The presence of wetlands and an irrigated land area is found to account for about 30 % of strong and significant spatial SMPC in the North African domain. This study provides the first insight into regional variability of SMPC in North Africa, and supports the potential relevance of mechanisms associated with enhanced sensible heat flux and mesoscale variability in surface soil moisture for deep convection development.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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