Science.gov

Sample records for recurrent interannual climate

  1. Recurrent Interannual Climate Modes and Teleconnection Linking North America Warm Season Precipitation Anomalies to Asia Summer Monsoon Variability

    NASA Technical Reports Server (NTRS)

    Lau, K. M.; Weng, H. Y.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    In this paper, we present results showing that summertime precipitation anomalies over North America and East Asia may be linked via pan-Pacific teleconnection patterns, which are components of two dominant recurring global climate modes. The first mode (Mode-1) features an inverse relationship between rainfall anomaly over the US Midwest/central to the eastern/southeastern regions, coupled to a mid-tropospheric high-low pressure system over the northwest and southeast of the US, which regulates low level moisture transport from the Gulf of Mexico to the Midwest. The regional circulation pattern appears to be a part of a global climate mode spanning Eurasia, the North Pacific, North America, and the Atlantic. This mode is associated with coherent fluctuations of jetstream variability over East Asia, and Eurasia, SST in the North Pacific and the North Atlantic. While Mode-1 is moderately correlated with El Nino-Southern Oscillation (ENSO), it appears to be distinct from it, with strong influences from mid-latitude or possibly from higher latitude processes. Results show that Mode-1 not only has an outstanding contribution to the great flood of 1993, it has large contribution to the US precipitation anomalies in other years. Also noted is an apparent increase in influence of Mode-1 on US summertime precipitation in the last two decades since 1977.

  2. Cirrus feedback on interannual climate fluctuations

    SciTech Connect

    Zhou, C.; Dessler, A. E.; Zelinka, M. D.; Yang, P.; Wang, T.

    2014-12-28

    Cirrus clouds are not only important in determining the current climate, but also play an important role in climate change and variability. Analysis of satellite observations shows that the amount and altitude of cirrus clouds (optical depth <3.6, cloud top pressure <440 hPa) increase in response to inter-annual surface warming. Thus, cirrus clouds are likely to act as a positive feedback on short-term climate fluctuations, by reducing the planet’s ability to radiate longwave radiation to space in response to planetary surface warming. Using cirrus cloud radiative kernels, the magnitude of cirrus feedback is estimated to be 0.20±0.21W/m2/°C, which is comparable to the surface albedo feedback. Most of the cirrus feedback comes from increasing cloud amount in the tropical tropopause layer (TTL) and subtropical upper troposphere.

  3. Multi-Wheat-Model Ensemble Responses to Interannual Climate Variability

    NASA Technical Reports Server (NTRS)

    Ruane, Alex C.; Hudson, Nicholas I.; Asseng, Senthold; Camarrano, Davide; Ewert, Frank; Martre, Pierre; Boote, Kenneth J.; Thorburn, Peter J.; Aggarwal, Pramod K.; Angulo, Carlos

    2016-01-01

    We compare 27 wheat models' yield responses to interannual climate variability, analyzed at locations in Argentina, Australia, India, and The Netherlands as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Wheat Pilot. Each model simulated 1981e2010 grain yield, and we evaluate results against the interannual variability of growing season temperature, precipitation, and solar radiation. The amount of information used for calibration has only a minor effect on most models' climate response, and even small multi-model ensembles prove beneficial. Wheat model clusters reveal common characteristics of yield response to climate; however models rarely share the same cluster at all four sites indicating substantial independence. Only a weak relationship (R2 0.24) was found between the models' sensitivities to interannual temperature variability and their response to long-termwarming, suggesting that additional processes differentiate climate change impacts from observed climate variability analogs and motivating continuing analysis and model development efforts.

  4. Communicating uncertainty in seasonal and interannual climate forecasts in Europe.

    PubMed

    Taylor, Andrea L; Dessai, Suraje; de Bruin, Wändi Bruine

    2015-11-28

    Across Europe, organizations in different sectors are sensitive to climate variability and change, at a range of temporal scales from the seasonal to the interannual to the multi-decadal. Climate forecast providers face the challenge of communicating the uncertainty inherent in these forecasts to these decision-makers in a way that is transparent, understandable and does not lead to a false sense of certainty. This article reports the findings of a user-needs survey, conducted with 50 representatives of organizations in Europe from a variety of sectors (e.g. water management, forestry, energy, tourism, health) interested in seasonal and interannual climate forecasts. We find that while many participating organizations perform their own 'in house' risk analysis most require some form of processing and interpretation by forecast providers. However, we also find that while users tend to perceive seasonal and interannual forecasts to be useful, they often find them difficult to understand, highlighting the need for communication formats suitable for both expert and non-expert users. In addition, our results show that people tend to prefer familiar formats for receiving information about uncertainty. The implications of these findings for both the providers and users of climate information are discussed. PMID:26460115

  5. Communicating uncertainty in seasonal and interannual climate forecasts in Europe

    PubMed Central

    Taylor, Andrea L.; Dessai, Suraje; de Bruin, Wändi Bruine

    2015-01-01

    Across Europe, organizations in different sectors are sensitive to climate variability and change, at a range of temporal scales from the seasonal to the interannual to the multi-decadal. Climate forecast providers face the challenge of communicating the uncertainty inherent in these forecasts to these decision-makers in a way that is transparent, understandable and does not lead to a false sense of certainty. This article reports the findings of a user-needs survey, conducted with 50 representatives of organizations in Europe from a variety of sectors (e.g. water management, forestry, energy, tourism, health) interested in seasonal and interannual climate forecasts. We find that while many participating organizations perform their own ‘in house’ risk analysis most require some form of processing and interpretation by forecast providers. However, we also find that while users tend to perceive seasonal and interannual forecasts to be useful, they often find them difficult to understand, highlighting the need for communication formats suitable for both expert and non-expert users. In addition, our results show that people tend to prefer familiar formats for receiving information about uncertainty. The implications of these findings for both the providers and users of climate information are discussed. PMID:26460115

  6. Response of closed basin lakes to interannual climate variability

    NASA Astrophysics Data System (ADS)

    Huybers, Kathleen; Rupper, Summer; Roe, Gerard H.

    2016-06-01

    Lakes are key indicators of a region's hydrological cycle, directly reflecting the basin-wide balance between precipitation and evaporation. Lake-level records are therefore valuable repositories of climate history. However, the interpretation of such records is not necessarily straightforward. Lakes act as integrators of the year-to-year fluctuations in precipitation and evaporation that occur even in a constant climate. Therefore lake levels can exhibit natural, unforced fluctuations that persist on timescales of decades or more. This behavior is important to account for when distinguishing between true climate change and interannual variability as the cause of past lake-level fluctuations. We demonstrate the operation of this general principle for the particular case-study of the Great Salt Lake, which has long historical lake-level and climatological records. We employ both full water-balance and linear models. Both models capture the timing and size of the lake's historical variations. We then model the lake's response to much longer synthetic time series of precipitation and evaporation calibrated to the observations, and compare the magnitude and frequency of the modeled response to the Great Salt Lake's historical record. We find that interannual climate variability alone can explain much of the decadal-to-centennial variations in the lake-level record. Further, analytic solutions to the linear model capture much of the full model's behavior, but fail to predict the most extreme lake-level variations. We then apply the models to other lake geometries, and evaluate how the timing and amplitude of a lake-level response differs with climatic and geometric setting. A lake's response to a true climatic shift can only be understood in the context of these expected persistent lake-level variations. On the basis of these results, we speculate that lake response to interannual climate variability may play an important part in explaining much of Holocene lake

  7. Seasonal and interannual variations of atmospheric CO2 and climate

    USGS Publications Warehouse

    Dettinger, M.D.; Ghil, M.

    1998-01-01

    Interannual variations of atmospheric CO2 concentrations at Mauna Loa are almost masked by the seasonal cycle and a strong trend; at the South Pole, the seasonal cycle is small and is almost lost in the trend and interannual variations. Singular-spectrum analysis (SSA) issued here to isolate and reconstruct interannual signals at both sites and to visualize recent decadal changes in the amplitude and phase of the seasonal cycle. Analysis of the Mauna Loa CO2 series illustrates a hastening of the CO2 seasonal cycle, a close temporal relation between Northern Hemisphere (NH) mean temperature trends and the amplitude of the seasonal CO2 cycle, and tentative ties between the latter and seasonality changes in temperature over the NH continents. Variations of the seasonal CO2 cycle at the South Pole differ from those at Mauna Loa: it is phase changes of the seasonal cycle at the South Pole, rather than amplitude changes, that parallel hemispheric and global temperature trends. The seasonal CO2 cycles exhibit earlier occurrences of the seasons by 7 days at Mauna Loa and 18 days at the South Pole. Interannual CO2 variations are shared at the two locations, appear to respond to tropical processes, and can be decomposed mostly into two periodicities, around (3 years)-1 and (4 years)-1, respectively. Joint SSA analyses of CO2 concentrations and tropical climate indices isolate a shared mode with a quasi-triennial (QT) period in which the CO2 and sea-surface temperature (SST) participation are in phase opposition. The other shared mode has a quasi-quadrennial (QQ) period and CO2 variations are in phase with the corresponding tropical SST variations throughout the tropics. Together these interannual modes exhibit a mean lag between tropical SSTs and CO2 variations of about 6-8 months, with SST leading. Analysis of the QT and QQ signals in global gridded SSTs, joint SSA of CO2 and ??13C isotopic ratios, and SSA of CO2 and NH-land temperatures indicate that the QT variations in

  8. Forcings and chaos in interannual to decadal climate change

    SciTech Connect

    Hansen, J.

    1997-12-31

    We investigate the roles of climate forcings and chaos in climate variability via a series of climate simulations for 1979-95 in which we add forcings one-by-one. Ensembles of simulations are carried out for a given forcing to allow study of predictability, chaos and significance. These experiments suggest that most interannual climate variability in the period 1979-95 at middle and high latitudes is chaotic, i.e., unforced. But observed SST anomalies account for much of the variability over land at low latitudes and a small portion of the variability at high latitudes. The radiative forcings, both natural and anthropogenic, leave clear signatures in the simulated climate change. Pinatubo aerosols warm the stratosphere and cool the surface globally, and in most places cause a tendency for regional surface cooling. Ozone depletion cools the lower stratosphere, troposphere and surface, steepening the temperature lapse rate in the troposphere. But the well-mixed anthropogenic greenhouse gases cause a surface warming which, over the 17 year time scale, more than offsets these cooling mechanisms. Observed stratospheric, tropospheric and surface temperatures reveal evidence of climate response to stratospheric aerosols, ozone depletion, and increasing greenhouse gases.

  9. Intraseasonal and Interannual Variability of Mars Present Climate

    NASA Technical Reports Server (NTRS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1996-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to investigate the nature of intraseasonal and interannual variability of Mars'present climate. We have applied a three-dimensional climate model based on the full hydrostatic primitive equations to determine the spatial, but primarily, the temporal structures of the planet's large-scale circulation as it evolves during a given seasonal advance, and, over multi-annual cycles. The particular climate model applies simplified physical parameterizations and is computationally efficient. It could thus easily be integrated in a perpetual season or advancing season configuration, as well as over many Mars years. We have assessed both high and low-frequency components of the circulation (i.e., motions having periods of Omicron(2-10 days) or greater than Omicron(10 days), respectively). Results from this investigation have explored the basic issue whether Mars' climate system is naturally 'chaotic' associated with nonlinear interactions of the large-scale circulation-regardless of any allowance for year-to-year variations in external forcing mechanisms. Titles of papers presented at scientific conferences and a manuscript to be submitted to the scientific literature are provided. An overview of a areas for further investigation is also presented.

  10. Impacts of Interannual Climate Variability on Agricultural and Marine Ecosystems

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Zebiak, S.; Kaplan, A.; Chen, D.

    2001-01-01

    The El Nino - Southern Oscillation (ENSO) is the dominant mode of global interannual climate variability, and seems to be the only mode for which current prediction methods are more skillful than climatology or persistence. The Zebiak and Cane intermediate coupled ocean-atmosphere model has been in use for ENSO prediction for more than a decade, with notable success. However, the sole dependence of its original initialization scheme and the improved initialization on wind fields derived from merchant ship observations proved to be a liability during 1997/1998 El Nino event: the deficiencies of wind observations prevented the oceanic component of the model from reaching the realistic state during the year prior to the event, and the forecast failed. Our work on the project was concentrated on the use of satellite data for improving various stages of ENSO prediction technology: model initialization, bias correction, and data assimilation. Close collaboration with other teams of the IDS project was maintained throughout.

  11. Effects of interannual climate variability on tropical tree cover

    NASA Astrophysics Data System (ADS)

    Holmgren, Milena; Hirota, Marina; van Nes, Egbert H.; Scheffer, Marten

    2013-08-01

    Climatic warming is substantially intensifying the global water cycle and is projected to increase rainfall variability. Using satellite data, we show that higher climatic variability is associated with reduced tree cover in the wet tropics globally. In contrast, interannual variability in rainfall can have neutral or even positive effects on tree cover in the dry tropics. In South America, tree cover in dry lands is higher in areas with high year-to-year variability in rainfall. This is consistent with evidence from case studies suggesting that in these areas rare wet episodes are essential for opening windows of opportunity where massive tree recruitment can overwhelm disturbance effects, allowing the establishment of extensive woodlands. In Australia, wet extremes have similar effects, but the net effect of rainfall variability is overwhelmed by negative effects of extreme dry years. In Africa, effects of rainfall variability are neutral for dry lands. It is most likely that differences in herbivore communities and fire regimes contribute to regulating tree expansion during wet extremes. Our results illustrate that increasing climatic variability may affect ecosystem services in contrasting, and sometimes surprising, ways. Expansion of dry tropical tree cover during extreme wet events may decrease grassland productivity but enhance carbon sequestration, soil nutrient retention and biodiversity.

  12. Interannual climate variability seen in the Pliocene Model Intercomparison Project

    NASA Astrophysics Data System (ADS)

    Brierley, C. M.

    2014-09-01

    Following proxy observations of weakened temperature gradients along the Equator in the early Pliocene, there has been much speculation about Pliocene climate variability. A major advance for our knowledge about the later Pliocene has been the coordination of modelling efforts through the Pliocene Model Intercomparison Project (PlioMIP). Here the changes in interannual modes of sea surface temperature variability will be presented across PlioMIP. Previously model ensembles have shown little consensus in the response of the El Niño-Southern Oscillation (ENSO) to imposed forcings - either for the past or future. The PlioMIP ensemble, however, shows surprising agreement with eight models simulating reduced variability and only one model indicating no change. The Pliocene's robustly weaker ENSO also saw a shift to lower frequencies. Model ensembles focussed at a wide variety of forcing scenarios have not yet shown this level of coherency. Nonetheless the PlioMIP ensemble does not show a robust response of either ENSO flavour or sea surface temperature variability in the Tropical Indian and North Pacific Oceans. Existing suggestions of ENSO properties linked to changes in zonal temperature gradient, seasonal cycle and the elevation of the Andes Mountains are investigated, yet prove insufficient to explain the coherent response. The reason for this surprisingly coherent signal warrants further investigation.

  13. Interannual climate variability seen in the Pliocene Model Intercomparison Project

    NASA Astrophysics Data System (ADS)

    Brierley, C. M.

    2015-03-01

    Following reconstructions suggesting weakened temperature gradients along the Equator in the early Pliocene, there has been much speculation about Pliocene climate variability. A major advance for our knowledge about the later Pliocene has been the coordination of modelling efforts through the Pliocene Model Intercomparison Project (PlioMIP). Here the changes in interannual modes of sea surface temperature variability will be presented across PlioMIP. Previously, model ensembles have shown little consensus in the response of the El Niño-Southern Oscillation (ENSO) to imposed forcings - either for the past or future. The PlioMIP ensemble, however, shows surprising agreement, with eight models simulating reduced variability and only one model indicating no change. The Pliocene's robustly weaker ENSO also saw a shift to lower frequencies. Model ensembles focussed on a wide variety of forcing scenarios have not yet shown this level of coherency. Nonetheless, the PlioMIP ensemble does not show a robust response of either ENSO flavour or sea surface temperature variability in the tropical Indian and North Pacific oceans. Existing suggestions linking ENSO properties to to changes in zonal temperature gradient, seasonal cycle and the elevation of the Andes Mountains are investigated, yet prove insufficient to explain the consistent response. The reason for this surprisingly coherent signal warrants further investigation.

  14. Interannual climate variability and snowpack in the western United States

    USGS Publications Warehouse

    Cayan, Daniel R.

    1996-01-01

    An important part of the water supply in the western United States is derived from runoff fed by mountain snowmelt Snow accumulation responds to both precipitation and temperature variations, and forms an interesting climatic index, since it integrates these influences over the entire late fall-spring period. Here, effects of cool season climate variability upon snow water equivalent (SWE) over the western part of the conterminous United States are examined. The focus is on measurements on/and 1 April, when snow accumulation is typically greatest. The primary data, from a network of mountainous snow courses, provides a good description of interannual fluctuations in snow accumulations, since many snow courses have records of five decades or more. For any given year, the spring SWE anomaly at a particular snow course is likely to be 25%–60% of its long-term average. Five separate regions of anomalous SWE variability are distinguished, using a rotated principal components analysis. Although effects vary with region and with elevation, in general, the anomalous winter precipitation has the strongest influence on spring SWE fluctuations. Anomalous temperature has a weaker effect overall, but it has great influence in lower elevations such as in the coastal Northwest, and during spring in higher elevations. The regional snow anomaly patterns are associated with precipitation and temperature anomalies in winter and early spring. Patterns of the precipitation, temperature, and snow anomalies extend over broad regional areas, much larger than individual watersheds. These surface anomalies are organized by the atmospheric circulation, with primary anomaly centers over the North Pacific Ocean as well as over western North America. For most of the regions, anomalously low SWE is associated with a winter circulation resembling the PNA pattern. With a strong low in the central North Pacific and high pressure over the Pacific Northwest, this pattern diverts North Pacific

  15. ENSO in a warming world: interannual climate variability in the early Miocene Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Fox, Bethany; Wilson, Gary; Lee, Daphne

    2016-04-01

    The El Niño - Southern Oscillation (ENSO) is the dominant source of interannual variability in the modern-day climate system. ENSO is a quasi-periodic cycle with a recurrence interval of 2-8 years. A major question in modern climatology is how ENSO will respond to increased climatic warmth. ENSO-like (2-8 year) cycles have been detected in many palaeoclimate records for the Holocene. However, the temporal resolution of pre-Quaternary palaeoclimate archives is generally too coarse to investigate ENSO-scale variability. We present a 100-kyr record of ENSO-like variability during the second half of the Oligocene/Miocene Mi-1 event, a period of increasing global temperatures and Antarctic deglaciation (~23.032-2.93 Ma). This record is drawn from an annually laminated lacustrine diatomite from southern New Zealand, a region strongly affected by ENSO in the present day. The diatomite consists of seasonal alternations of light (diatom bloom) and dark (low diatom productivity) layers. Each light-dark couplet represents one year's sedimentation. Light-dark couplet thickness is characterised by ENSO-scale variability. We use high-resolution (sub-annual) measurements of colour spectra to detect couplet thickness variability. Wavelet analysis indicates that absolute values are modulated by orbital cycles. However, when orbital effects are taken into account, ENSO-like variability occurs throughout the entire depositional period, with no clear increase or reduction in relation to Antarctic deglaciation and increasing global warmth.

  16. Application of Infrared Hyperspectral Sounder Data to Climate Research: Interannual Variability and climate trend evaluation.

    NASA Astrophysics Data System (ADS)

    Aumann, H. H.; Gregorich, D. T.

    2007-12-01

    Satellite measurements of the spectrally resolved upwelling infrared radiances have a unique role in the observation of climate and climate change: They give direct insight into the way the Earth Climate System responds to periodic and long term changes in forcing with changes in surface and atmospheric temperatures and changes in large scale atmospheric circulation patterns. The Atmospheric Infrared Sounder (AIRS), the first in a series of hyper-spectral polar orbiting sounders, was launch on the EOS Aqua into a 1:30 pm polar orbit at 705 km altitude in May 2002, with an anticipated lifetime of 12 years. The Infrared Atmospheric Sounding Interferometer (IASI) was launched in October 2006 into a 9:30 AM orbit, to be followed by the Crosstrack InfraRed Sounder (CRIS) in a 2 PM orbit in 2010. The AIRS radiometric stability since 2002 has been verified at the better than 0.01 K/year level. We report on observations of the oceans between 30S and 30N. The 0.05 K/year trend in co2 sensitive channels due to the 2 ppmv/year increase in the co2 column abundance is readily detectable and statistically reliable. The AIRS data show very consistent seasonal modulations of key surface, cloud, water vapor and atmospheric temperatures. After removing the seasonal variation, the anomaly shows interannual rms variability in the monthly means larger than 0.1 K. The rms variability in the monthly means in the mid- tropospheric temperature with peak excursions as large as 0.6 K are observed by the AIRS 2388 cm-1 channel and AMSU channel 5 at 57 GHz. The interannual variability is not obviously correlated with the Multivariate Enso Index (MEI). This variability places limits on the length of time required to measure global warming trends at the 0.1 K/decade level. These limits exceed the expected 12 year lifetime of AIRS and need to be taken into account in the design of space missions and instruments to measure climate change.

  17. What drives interannual variability of hypoxia in Chesapeake Bay: Climate forcing versus nutrient loading?

    NASA Astrophysics Data System (ADS)

    Li, Ming; Lee, Younjoo J.; Testa, Jeremy M.; Li, Yun; Ni, Wenfei; Kemp, W. Michael; Di Toro, Dominic M.

    2016-03-01

    Oxygen depletion in estuaries is a worldwide problem with detrimental effects on many organisms. Although nutrient loading has been stabilized for a number of these systems, seasonal hypoxia persists and displays large year-to-year variations, with larger hypoxic volumes in wetter years and smaller hypoxic volumes in drier years. Data analysis points to climate as a driver of interannual hypoxia variability, but nutrient inputs covary with freshwater flow. Here we report an oxygen budget analysis of Chesapeake Bay to quantify relative contributions of physical and biogeochemical processes. Vertical diffusive flux declines with river discharge, whereas longitudinal advective flux increases with river discharge, such that their total supply of oxygen to bottom water is relatively unchanged. However, water column respiration exhibits large interannual fluctuations and is correlated with primary production and hypoxic volume. Hence, the model results suggest that nutrient loading is the main mechanism driving interannual hypoxia variability in Chesapeake Bay.

  18. Australian Tropical Cyclone Activity: Interannual Prediction and Climate Change

    NASA Astrophysics Data System (ADS)

    Nicholls, N.

    2014-12-01

    It is 35 years since it was first demonstrated that interannual variations in seasonal Australian region tropical cyclone (TC) activity could be predicted using simple indices of the El Niño - Southern Oscillation (ENSO). That demonstration (Nicholls, 1979), which was surprising and unexpected at the time, relied on only 25 years of data (1950-1975), but its later confirmation eventually led to the introduction of operational seasonal tropical cyclone activity. It is worth examining how well the ENSO-TC relationship has performed, over the period since 1975. Changes in observational technology, and even how a tropical cyclone is defined, have affected the empirical relationships between ENSO and seasonal activity, and ways to overcome this in forecasting seasonal activity will be discussed. Such changes also complicate the investigation of long-term trends in cyclone activity. The early work linked cyclone activity to local sea surface temperature thereby leading to the expectation that global warming would result in an increase in cyclone activity. But studies in the 1990s (eg., Nicholls et al., 1998) suggested that such an increase in activity was not occurring, neither in the Australian region nor elsewhere. Trends in Australian tropical cyclone activity will be discussed, and the confounding influence of factors such as changes in observational technologies will be examined. Nicholls, N. 1979. A possible method for predicting seasonal tropical cyclone activity in the Australian region. Mon. Weath. Rev., 107, 1221-1224 Nicholls, N., Landsea, C., and Gill, J., 1998. Recent trends in Australian region tropical cyclone activity. Meteorology and Atmospheric Physics, 65, 197-205.

  19. Intra-annual and interannual ensemble forcing of a regional climate model

    NASA Astrophysics Data System (ADS)

    Dutton, Jan F.; Barron, Eric J.

    2000-12-01

    The use of ensemble modeling within the framework of dynamical downscaling of climate change scenarios derived from global climate model scenarios has not been fully explored. This study uses a six member ensemble of RegCM2 regional climate model simulations forced by the CCM3 global climate model to explore the one-way boundary forcing of regional interannual variability of 500 mbar heights, precipitation, and surface temperature. Anomaly pattern correlations (APCs) between the CCM3 and the RegCM2 500 mbar heights, precipitation, and surface temperature show distinct annual cycles. The January ensemble-averaged APCs for 500 mbar heights, precipitation, and surface temperature are 0.95, 0.65, and 0.90, respectively. The July correlations for the same variables are 0.63, 0.14, and 0.52, respectively. This indicates that the RegCM2 winter interannual variability is strongly dependent on the GCM interannual variability. The summer interannual variability of precipitation is found to contain little GCM-supplied signal. The ensemble run variance of the CCM3 and RegCM2 is also explored. The ratio of RegCM2 to CCM3 500 mbar height normalized ensemble run variance (NERV), a measure of climate reproducibility, is near 1.0 for various regions in the simulated domain. The RegCM2 precipitation NERV is greater than CCM3 NERV, suggesting less reproducibility and therefore less predictability. Certain regions show statistically significant reduced RegCM2 surface temperature NERV, suggesting that greater reproducibility may exist in these regions. The effect of increased topographic resolution in the RegCM2 domain was not found to significantly enhance reproducibility.

  20. Seasonal divergence in the interannual responses of Northern Hemisphere vegetation activity to variations in diurnal climate.

    PubMed

    Wu, Xiuchen; Liu, Hongyan; Li, Xiaoyan; Liang, Eryuan; Beck, Pieter S A; Huang, Yongmei

    2016-01-01

    Seasonal asymmetry in the interannual variations in the daytime and nighttime climate in the Northern Hemisphere (NH) is well documented, but its consequences for vegetation activity remain poorly understood. Here, we investigate the interannual responses of vegetation activity to variations of seasonal mean daytime and nighttime climate in NH (>30 °N) during the past decades using remote sensing retrievals, FLUXNET and tree ring data. Despite a generally significant and positive response of vegetation activity to seasonal mean maximum temperature (Tmax) in ~22-25% of the boreal (>50 °N) NH between spring and autumn, spring-summer progressive water limitations appear to decouple vegetation activity from the mean summer Tmax, particularly in climate zones with dry summers. Drought alleviation during autumn results in vegetation recovery from the marked warming-induced drought limitations observed in spring and summer across 24-26% of the temperate NH. Vegetation activity exhibits a pervasively negative correlation with the autumn mean minimum temperature, which is in contrast to the ambiguous patterns observed in spring and summer. Our findings provide new insights into how seasonal asymmetry in the interannual variations in the mean daytime and nighttime climate interacts with water limitations to produce spatiotemporally variable responses of vegetation growth. PMID:26751166

  1. Seasonal divergence in the interannual responses of Northern Hemisphere vegetation activity to variations in diurnal climate

    PubMed Central

    Wu, Xiuchen; Liu, Hongyan; Li, Xiaoyan; Liang, Eryuan; Beck, Pieter S. A.; Huang, Yongmei

    2016-01-01

    Seasonal asymmetry in the interannual variations in the daytime and nighttime climate in the Northern Hemisphere (NH) is well documented, but its consequences for vegetation activity remain poorly understood. Here, we investigate the interannual responses of vegetation activity to variations of seasonal mean daytime and nighttime climate in NH (>30 °N) during the past decades using remote sensing retrievals, FLUXNET and tree ring data. Despite a generally significant and positive response of vegetation activity to seasonal mean maximum temperature () in ~22–25% of the boreal (>50 °N) NH between spring and autumn, spring-summer progressive water limitations appear to decouple vegetation activity from the mean summer , particularly in climate zones with dry summers. Drought alleviation during autumn results in vegetation recovery from the marked warming-induced drought limitations observed in spring and summer across 24–26% of the temperate NH. Vegetation activity exhibits a pervasively negative correlation with the autumn mean minimum temperature, which is in contrast to the ambiguous patterns observed in spring and summer. Our findings provide new insights into how seasonal asymmetry in the interannual variations in the mean daytime and nighttime climate interacts with water limitations to produce spatiotemporally variable responses of vegetation growth. PMID:26751166

  2. Seasonal divergence in the interannual responses of Northern Hemisphere vegetation activity to variations in diurnal climate

    NASA Astrophysics Data System (ADS)

    Wu, Xiuchen; Liu, Hongyan; Li, Xiaoyan; Liang, Eryuan; Beck, Pieter S. A.; Huang, Yongmei

    2016-01-01

    Seasonal asymmetry in the interannual variations in the daytime and nighttime climate in the Northern Hemisphere (NH) is well documented, but its consequences for vegetation activity remain poorly understood. Here, we investigate the interannual responses of vegetation activity to variations of seasonal mean daytime and nighttime climate in NH (>30 °N) during the past decades using remote sensing retrievals, FLUXNET and tree ring data. Despite a generally significant and positive response of vegetation activity to seasonal mean maximum temperature () in ~22-25% of the boreal (>50 °N) NH between spring and autumn, spring-summer progressive water limitations appear to decouple vegetation activity from the mean summer , particularly in climate zones with dry summers. Drought alleviation during autumn results in vegetation recovery from the marked warming-induced drought limitations observed in spring and summer across 24-26% of the temperate NH. Vegetation activity exhibits a pervasively negative correlation with the autumn mean minimum temperature, which is in contrast to the ambiguous patterns observed in spring and summer. Our findings provide new insights into how seasonal asymmetry in the interannual variations in the mean daytime and nighttime climate interacts with water limitations to produce spatiotemporally variable responses of vegetation growth.

  3. Climatic regulation of seasonal and inter-annual variability in net ecosystem exchange of CO2 on rangelands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Net ecosystem exchange of CO2 (NEE) from terrestrial ecosystems varies seasonally and inter-annually because of temporal variation in climate. If we are predict climate-caused variation in NEE, we must understand how climatic variation influences NEE and its components, CO2 uptake and CO2 loss. ...

  4. Hydrologically Driven Hierarchical Competition-Colonization Model: The Impact of Random Interannual Climate Fluctuations

    NASA Astrophysics Data System (ADS)

    Fernandez-Illescas, C. P.; Rodriguez-Iturbe, I.

    2001-05-01

    While ecologist and hydrologists hace come to recognize the fundamental importance of soil water availability in many ecosystems, much less prgress has been made in understanding the impact of the temporal variability in soil moisture on ecosystem structure. One recent advance in this regard is the analytical treatment of the vegetation-soil-climate system described by Laio et al. (2001) and Porporato et al. (2001) which characterizes the impact of growing season soil moisture variability on vegetation overall condition. Here, this ecohydrological model is linked with the hierarchical competition-colonization model of Tilman (1994) to asses the impact of interannual growing season rainfall variability on vegetation competition and ecosystem biodiversity. Based on climatic and vegetative data from the La Copita Research Area in the Rio Grande Plains of Southern Texas, 10000 year simulations of spatial competition between a herbaceous C4 Paspaleum setaceum species and a woody Prosopis glandulosa (honey mesquite) species are run using the above linked models. Results show that ecosystem structure is quite sensitive to the inclusion of realistic amounts of interannual rainfall fluctuations. This sensitivity exists with respect to the expected magnitude of the fluctuations as well as the degree to which successive fluctuations are correlated. It is also found that markovian models of interannual rainfall variability - which lack long-term persistence- lead to self-affine time series of species abundances which display f-{β } spectral properties. The implications of these effects on ecological modeling are discussed.

  5. Adaptation to Interannual and Interdecadal Climate Variability in Agricultural Production Systems of the Argentine Pampas

    NASA Astrophysics Data System (ADS)

    Podestá, G. P.; Bert, F.; Weber, E.; Laciana, C.; Rajagopalan, B.; Letson, D.

    2007-05-01

    Agricultural ecosystems play a central role in world food production and food security, and involve one of the most climate-sensitive sectors of society-agriculture. We focus on crop production in the Argentine Pampas, one of the world's major agricultural regions. Climate of the Pampas shows marked variability at both interannual and decadal time scales. We explored the scope for adaptive management in response to climate information on interannual scales. We show that different assumptions about what decision makers are trying to achieve (i.e., their objective functions) may change what actions are considered as "optimal" for a given climate context. Optimal actions also were used to estimate the economic value of forecasts of an ENSO phase. Decision constraints (e.g., crop rotations) have critical influence on value of the forecasting system. Gaps in knowledge or misconceptions about climate variability were identified in open-ended "mental model" interviews. Results were used to design educational interventions. A marked increase in precipitation since the 1970s, together with new production technologies, led to major changes in land use patterns in the Pampas. Continuous cropping has widely replaced agriculture-pasture rotations. Nevertheless, production systems that evolved partly in response to increased rainfall may not be viable if climate reverts to a drier epoch. We use historical data to define a range of plausible climate trajectories 20-30 years hence. Regional scenarios are downscaled using semi-parametric weather generators to produce multiple realizations of daily weather consistent with decadal scenarios. Finally, we use the synthetic climate, crop growth models, and realistic models of decision-making under risk to compute risk metrics (e.g., probability of yields or profits being below a threshold). Climatically optimal and marginal locations show differential responses: probabilities of negative economic results are much higher in currently

  6. Exchange of carbon dioxide by a deciduous forest: Response to interannual climate variability

    SciTech Connect

    Goulden, M.L.; Munger, J.W.; Fan, S.M.; Daube, B.C.; Wofsy, S.C.

    1996-03-15

    The annual net uptake of CO{sub 2} by a deciduous forest in New England varied from 1.4 to 2.8 metric tons of carbon per hectare between 1991 and 1995. Carbon sequestration was higher than average in 1991 because of increased photosynthesis and in 1995 because of decreased respiration. Interannual shifts in photosynthesis were associated with the timing of leaf expansion and senescence. Shifts in annual respiration were associated with anomalies in soil temperature, deep snow in winter, and drought in summer. If this ecosystem is typical of northern biomes, interannual climate variations on seasonal time scales may modify annual CO{sub 2} exchange in the Northern Hemisphere by 1 gigaton of carbon or more each year. 26 refs., 4 figs., 1 tab.

  7. Exploring the interannual variability of extreme wave climate in the Northeast Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Izaguirre, Cristina; Menéndez, Melisa; Camus, Paula; Méndez, Fernando J.; Mínguez, Roberto; Losada, Inigo J.

    2012-12-01

    The extreme wave climate is of paramount importance for: (i) off-shore and coastal engineering design, (ii) ship design and maritime transportation, or (iii) analysis of coastal processes. Identifying the synoptic patterns that produce extreme waves is necessary to understand the wave climate for a specific location. Thus, a characterization of these weather patterns may allow the study of the relationships between the magnitude and occurrence of extreme wave events and the climate system. The aim of this paper is to analyze the interannual variability of extreme wave heights. For this purpose, we present a methodological framework and its application to an area over the North East (NE) Atlantic Ocean. The climatology in the NE Atlantic is analyzed using the self-organizing maps (SOMs). The application of this clustering technique to monthly mean sea level pressure fields provides a continuum of synoptic categorizations compared with discrete realizations produced through most traditional methods. The extreme wave climate has been analyzed by means of monthly maxima of the significant wave height (SWH) in several locations over the NE Atlantic. A statistical approach based on a time-dependent generalized extreme value (GEV) distribution has been applied. The seasonal variation was characterized and, afterwards, the interannual variability was studied throughout regional pressure patterns. The anomalies of the 50-year return level estimates of SWH, due to interannual variability have been projected into the weather types of SOM. It provides a comprehensive visual representation, which relates the weather type with the positive or negative contribution to extreme waves over the selected locations.

  8. The Role of Vegetation-Climate Interaction and Interannual Variability in Shaping the African Savanna.

    NASA Astrophysics Data System (ADS)

    Zeng, Ning; Neelin, J. David

    2000-08-01

    Using a coupled atmosphere-land-vegetation model of intermediate complexity, the authors explore how vegetation-climate interaction and internal climate variability might influence the vegetation distribution in Africa. When the model is forced by observed climatological sea surface temperature (SST), positive feedbacks from vegetation changes tend to increase the spatial gradient between desert regions and forest regions at the expense of savanna regions. When interannual variation of SST is included, the climate variability tends to reduce rainfall and vegetation in the wetter regions and to increase them in the drier regions along this gradient, resulting in a smoother desert-forest transition. This effect is most dramatically demonstrated in a model parameter regime for which multiple equilibria (either a desertlike or a forestlike Sahel) can exist when strong vegetation-climate feedbacks are allowed. However, the presence of a variable SST drives the desertlike state and the forestlike state toward an intermediate grasslike state, because of nonlinearities in the coupled system. Both vegetation and interannual variability thus play active roles in shaping the subtropical savanna ecosystem.

  9. Formation mechanism for the amplitude of interannual climate variability in subtropical northern hemisphere: relative contributions from the zonal asymmetric mean state and the interannual variability of SST

    NASA Astrophysics Data System (ADS)

    He, Chao; Lin, Ailan; Gu, Dejun; Li, Chunhui; Zheng, Bin

    2016-04-01

    The Amplitude Interannual climate Variability (AIV) differs among the subtropical northern hemisphere, and the Western North Pacific (WNP) was claimed to exhibit the largest AIV. The robustness of the AIV pattern is investigated in this study with different atmospheric variables from multiple datasets. As consistently shown by the interannual variance patterns of precipitation and circulation, the AIV over subtropical northern hemisphere closely follows the mean state of precipitation, where higher (lower) AIV is located at moister (drier) regions. The largest AIV is seen over the broad area from South Asia to WNP, followed by a secondary local maximum over the Gulf of Mexico. To further investigate the formation mechanism for the AIV pattern, numerical simulations are performed by Community Atmosphere Model version 4 (CAM4). The zonal asymmetry of AIV is reduced if the interannual SST variability is removed, and it almost disappears if the zonal asymmetry of SST mean state is removed. The results suggest that the zonal asymmetric AIV pattern primarily originates from the zonal asymmetric SST mean state, and it is amplified by the interannual SST variability. The atmospheric convection-circulation feedback plays a key role in connecting the AIV with the mean state precipitation. In both observation and CAM4 simulations, stronger (weaker) convection-circulation feedback is seen in moister (drier) regions. By modulating the mean state precipitation and the associated intensity of convection-circulation feedback, the zonal asymmetric SST mean state accounts for the zonal asymmetry of AIV in the subtropical northern hemisphere.

  10. The impact of mean state errors on equatorial Atlantic interannual variability in a climate model

    NASA Astrophysics Data System (ADS)

    Ding, Hui; Keenlyside, Noel; Latif, Mojib; Park, Wonsun; Wahl, Sebastian

    2015-02-01

    Observations show that the Equatorial Atlantic Zonal Mode (ZM) obeys similar physics to the El Niño Southern Oscillation (ENSO): positive Bjerknes and delayed negative feedbacks. This implies the ZM may be predictable on seasonal timescales, but models demonstrate little prediction skill in this region. In this study using different configurations of the Kiel Climate Model (KCM) exhibiting different levels of systematic error, we show that a reasonable simulation of the ZM depends on realistic representation of the mean state, i.e., surface easterlies along the equator, upward sloping thermocline to the east, with an equatorial SST cold tongue in the east. We further attribute the differences in interannual variability among the simulations to the individual components of the positive Bjerknes and delayed negative feedbacks. Differences in the seasonality of the variability are similarly related to the impact of seasonal biases on the Bjerknes feedback. Our results suggest that model physics must be enhanced to enable skillful seasonal predictions in the Tropical Atlantic Sector, although some improvement with regard to the simulation of Equatorial Atlantic interannual variability may be achieved by momentum flux correction. This pertains especially to the seasonal phase locking of interannual SST variability.

  11. Effect of interannual and interdecadal climate oscillations on groundwater in North Carolina

    NASA Astrophysics Data System (ADS)

    Anderson, William P.; Emanuel, Ryan E.

    2008-12-01

    Multi-year climate oscillations such as the El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) affect precipitation and stream discharge rates in the western hemisphere. While inferences may be drawn between these hydroclimatological relationships and groundwater conditions, few studies explicitly link groundwater conditions to these cycles. Here we investigate relationships between winter ENSO, PDO, and lagging baseflow rates in the southeastern United States. We find strong correlation between winter ENSO and lagged baseflow in coastal North Carolina which, coupled with anomalies in mean baseflow, decrease with distance inland from the coast. Our results demonstrate that interannual and interdecadal climate oscillations in the Pacific Ocean have a strong effect on hydrological processes in eastern North America despite filtering by the groundwater flow process. These results have implications for water resource availability in regions where water management is complicated by population growth and climatic uncertainty.

  12. Interannual variability of rainfall over the Sahel based on multiple regional climate models simulations

    NASA Astrophysics Data System (ADS)

    Diallo, Ismaila; Sylla, Mouhamadou B.; Camara, Moctar; Gaye, Amadou T.

    2013-07-01

    We analyse the interannual variability of the averaged summer monsoon rainfall over the Sahel from multiple regional climate models driven by the ERA-interim reanalysis and seek to provide effective information for future modelling work. We find that the majority of the models are able to reproduce the rainfall variability with correlation coefficient exceeding 0.5 compared with observations. This is due to a good representation of the dynamics of the main monsoon features of the West African climate such as the monsoon flux, African Easterly Jet (AEJ) and Tropical Easterly Jet (TEJ). Among the models, only HIRHAM fails to reproduce the rainfall variability exhibiting hence a correlation coefficient of -0.2. This deficiency originates from the fact that HIRHAM does not properly capture the variability of monsoon flow and the relationship between rainfall and the AEJ dynamic. We conclude that a good performance of a regional climate model in simulating the monsoon dynamical features variability is of primary importance for a better representation of the interannual variability of rainfall over the Sahel.

  13. Determinability of inter-annual global and regional climatic changes of the earth radiation budget

    NASA Technical Reports Server (NTRS)

    Ardanuy, P. E.

    1983-01-01

    The degradation characteristics of Earth Radiation Budget (ERB) experiments are examined with reference to the results of recent investigations into the calibration adjustments of the Wide Field of View channels on board the Nimbus 6 and 7 ERB experiments. The mechanisms of degradation are discussed, and changes in the transmissive and reflective properties of radiometers affecting their sensitivities and calibrations are estimated. It is emphasized that in order to observe interannual climate change on a global or a regional scale, calibration adjustments are a necessity.

  14. Structure, inter-annual recurrence, and global-scale connectivity of airborne microbial communities.

    PubMed

    Barberán, Albert; Henley, Jessica; Fierer, Noah; Casamayor, Emilio O

    2014-07-15

    Dust coming from the large deserts on Earth, such as the Sahara, can travel long distances and be dispersed over thousands of square kilometers. Remote dust deposition rates are increasing as a consequence of global change and may represent a mechanism for intercontinental microbial dispersal. Remote oligotrophic alpine lakes are particularly sensitive to dust inputs and can serve as sentinels of airborne microbial transport and the ecological consequences of accelerated intercontinental microbial migration. In this study, we applied high-throughput sequencing techniques (16S rRNA amplicon pyrosequencing) to characterize the microbial communities of atmospheric deposition collected in the Central Pyrenees (NE Spain) along three years. Additionally, bacteria from soils in Mauritania and from the air-water interface of high altitude Pyrenean lakes were also examined. Communities in aerosol deposition varied in time with a strong seasonal component of interannual similarity. Communities from the same season tended to resemble more each other than those from different seasons. Samples from disparate dates, in turn, slightly tended to have more dissimilar microbial assemblages (i.e., temporal distance decay), overall suggesting that atmospheric deposition may influence sink habitats in a temporally predictable manner. The three habitats examined (soil, deposition, and air-water interface) harbored distinct microbial communities, although airborne samples collected in the Pyrenees during Saharan dust outbreaks were closer to Mauritian soil samples than those collected during no Saharan dust episodes. The three habitats shared c.a. 1.4% of the total number of microbial sequences in the dataset. Such successful immigrants were spread in different bacterial classes. Overall, this study suggests that local and regional features may generate global trends in the dynamics and distribution of airborne microbial assemblages, and that the diversity of viable cells in the high

  15. Effect of interannual climate variability on carbon storage in Amazonian ecosystems

    USGS Publications Warehouse

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, David A.; Helfrich, J. V. K., III; Moore, B., III; Vorosmarty, C.J.

    1998-01-01

    The Amazon Basin contains almost one-half of the world's undisturbed tropical evergreen forest as well as large areas of tropical savanna. The forests account for about 10 per cent of the world's terrestrial primary productivity and for a similar fraction of the carbon stored in land ecosystems, and short-term field measurements suggest that these ecosystems are globally important carbon sinks. But tropical land ecosystems have experienced substantial interannual climate variability owing to frequent El Nino episodes in recent decades. Of particular importance to climate change policy is how such climate variations, coupled with increases in atmospheric CO2 concentration, affect terrestrial carbon storage. Previous model analyses have demonstrated the importance of temperature in controlling carbon storage. Here we use a transient process-based biogeochemical model of terrestrial ecosystems to investigate interannual variations of carbon storage in undisturbed Amazonian ecosystems in response to climate variability and increasing atmospheric CO2 concentration during the period 1980 to 1994. In El Nino years, which bring hot, dry weather to much of the Amazon region, the ecosystems act as a source of carbon to the atmosphere (up to 0.2 petagrams of carbon in 1987 and 1992). In other years, these ecosystems act as a carbon sink (up to 0.7 Pg C in 1981 and 1993). These fluxes are large; they compare to a 0.3 Pg C per year source to the atmosphere associated with deforestation in the Amazon Basin in the early 1990s. Soil moisture, which is affected by both precipitation and temperature, and which affects both plant and soil processes, appears to be an important control on carbon storage.

  16. Interannual to millennial variability of climate extreme indices over Europe: evidence from high resolution proxy data

    NASA Astrophysics Data System (ADS)

    Rimbu, Norel; Ionita, Monica; Lohmann, Gerrit

    2016-04-01

    Interannual to millennial time scale variability of precipitation (R20mm, Rx5day, R95pTOT), cold (TN10p, CSDI and CFD), heat (TX90p and WSDI) and drought (CDD) extreme climate indices is investigated using long-term observational and proxy records. We detect significant correlations between these indices and various high resolution proxy records like lake sediments from southern Germany, stable oxygen isotopes from Greenland ice cores and stable oxygen isotopes from Red Sea corals during observational period. The analysis of long-term reanalysis data in combination with extreme climate indices and proxy data reveals that distinct atmospheric circulation patterns explain most of the identified relationships. In particular, we show that a sediment record from southern Germany (lake Ammersee), which records flood frequency of River Ammer during the last 5500 years, is related to a wave-train atmospheric circulation pattern with a pronounced negative center over western Europe. We show that high frequency of River Ammer floods is related not only to high frequency of extreme precipitation events (R95p) in the Ammer region but also with significant positive anomalies of various extreme temperature indices (TX90p and TXx) over northeastern Europe. Such extreme temperatures are forced by cloudiness anomaly pattern associated with flood related atmospheric circulation pattern. Based on this record we discuss possible interannual to millennial scale variations of extreme precipitation and temperature indices over Europe during the last 5500 years. Coherent variations of extreme precipitation and temperature indices over Europe and stable oxygen isotopes from Greenland ice cores and northern Red Sea corals during observational period are related to atmospheric blocking variability in the North Atlantic region. Possible variations of climate extreme indices during different time slices of the Holocene period and their implications for future extreme climate variability are

  17. Climate-driven interannual variability of water scarcity in food production: a global analysis

    NASA Astrophysics Data System (ADS)

    Kummu, M.; Gerten, D.; Heinke, J.; Konzmann, M.; Varis, O.

    2013-06-01

    Interannual climatic and hydrologic variability has been substantial during the past decades in many regions. While climate variability and its impacts on precipitation and soil moisture have been rather intensively studied, less is known on its impacts on freshwater availability and further implications for global food production. In this paper we quantify effects of hydroclimatic variability on global "green" and "blue" water availability and demand in agriculture. Analysis is based on climate forcing data for the past 30 yr with demography, diet composition and land use fixed to constant reference conditions. We thus assess how observed interannual hydroclimatic variability impacts on the ability of food production units (FPUs) to produce a given diet for their inhabitants, here focused on a benchmark for hunger alleviation (3000 kilocalories per capita per day, with 80% vegetal food and 20% animal products). We applied the LPJmL vegetation and hydrology model to calculate spatially explicitly the variation in green-blue water availability and the water requirements to produce that very diet. An FPU was considered water scarce if its water availability was not sufficient to produce the diet (neglecting trade from elsewhere, i.e. assuming food self-sufficiency). We found that altogether 24% of the global population lives in areas under chronic scarcity (i.e. water is scarce every year) while an additional 19% live under occasional water scarcity (i.e. water is scarce in some years). Of these 2.6 billion people under some degree of scarcity, 55% would have to rely on international trade to reach the reference diet while for 24% domestic trade would be enough (assuming present cropland extent and management). For the remaining 21% of population under scarcity, local food storage and/or intermittent trade would be enough secure the reference diet over the occasional dry years.

  18. Climate-driven interannual variability of water scarcity in food production potential: a global analysis

    NASA Astrophysics Data System (ADS)

    Kummu, M.; Gerten, D.; Heinke, J.; Konzmann, M.; Varis, O.

    2014-02-01

    Interannual climatic and hydrologic variability has been substantial during the past decades in many regions. While climate variability and its impacts on precipitation and soil moisture have been studied intensively, less is known on subsequent implications for global food production. In this paper we quantify effects of hydroclimatic variability on global "green" and "blue" water availability and demand in global agriculture, and thus complement former studies that have focused merely on long-term averages. Moreover, we assess some options to overcome chronic or sporadic water scarcity. The analysis is based on historical climate forcing data sets over the period 1977-2006, while demography, diet composition and land use are fixed to reference conditions (year 2000). In doing so, we isolate the effect of interannual hydroclimatic variability from other factors that drive food production. We analyse the potential of food production units (FPUs) to produce a reference diet for their inhabitants (3000 kcal cap-1 day-1, with 80% vegetal food and 20% animal products). We applied the LPJmL vegetation and hydrology model to calculate the variation in green-blue water availability and the water requirements to produce that very diet. An FPU was considered water scarce if its water availability was not sufficient to produce the diet (i.e. assuming food self-sufficiency to estimate dependency on trade from elsewhere). We found that 24% of the world's population lives in chronically water-scarce FPUs (i.e. water is scarce every year), while an additional 19% live under occasional water scarcity (water is scarce in some years). Among these 2.6 billion people altogether, 55% would have to rely on international trade to reach the reference diet, while for 24% domestic trade would be enough. For the remaining 21% of the population exposed to some degree of water scarcity, local food storage and/or intermittent trade would be enough to secure the reference diet over the

  19. Marine climate influences on interannual variability of tropical cyclones in the eastern Caribbean: 1979-2008

    NASA Astrophysics Data System (ADS)

    Jury, Mark R.

    2015-04-01

    Interannual variability of tropical cyclones (TCs) in the eastern Caribbean is studied using MIT-Hurdat fields during the July-October season from 1979 to 2008. TC intensity shows local climate sensitivity particularly for upper ocean currents, salinity and mixed-layer depth, and 200-850 mb wind shear. Remote influences from the Southern Oscillation, Saharan dust, and the South American monsoon are also identified as important. Ocean currents diminish along the coast of South America, so interbasin transfer between the North Brazil and Caribbean Currents declines in seasons of frequent and intense TCs. This is related to a dipole pattern in the sea surface height formed mainly by reduced trade wind upwelling northeast of Venezuela. A low-salinity plume from the Orinoco River spreads across the eastern Caribbean. It is the weaker currents and shallower mixed layer that conspire with surplus heat to build thermodynamic energy available for TC intensification.

  20. Interannual variability in carbon dioxide fluxes and flux-climate relationships on grazed and ungrazed northern mixed-grass prairie

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The annual carbon (C) budget of grasslands is highly dynamic, dependent on grazing history and on direct and indirect effects of interannual variability (IAV) in climate on carbon dioxide (CO2) fluxes. We measured net ecosystem exchange of CO2 (NEE) and its diurnal components, daytime ecosystem CO2...

  1. Seasonal and interannual variability of climate and vegetation indices across the Amazon

    PubMed Central

    Brando, Paulo M.; Goetz, Scott J.; Baccini, Alessandro; Nepstad, Daniel C.; Beck, Pieter S. A.; Christman, Mary C.

    2010-01-01

    Drought exerts a strong influence on tropical forest metabolism, carbon stocks, and ultimately the flux of carbon to the atmosphere. Satellite-based studies have suggested that Amazon forests green up during droughts because of increased sunlight, whereas field studies have reported increased tree mortality during severe droughts. In an effort to reconcile these apparently conflicting findings, we conducted an analysis of climate data, field measurements, and improved satellite-based measures of forest photosynthetic activity. Wet-season precipitation and plant-available water (PAW) decreased over the Amazon Basin from 1996−2005, and photosynthetically active radiation (PAR) and air dryness (expressed as vapor pressure deficit, VPD) increased from 2002–2005. Using improved enhanced vegetation index (EVI) measurements (2000–2008), we show that gross primary productivity (expressed as EVI) declined with VPD and PAW in regions of sparse canopy cover across a wide range of environments for each year of the study. In densely forested areas, no climatic variable adequately explained the Basin-wide interannual variability of EVI. Based on a site-specific study, we show that monthly EVI was relatively insensitive to leaf area index (LAI) but correlated positively with leaf flushing and PAR measured in the field. These findings suggest that production of new leaves, even when unaccompanied by associated changes in LAI, could play an important role in Basin-wide interannual EVI variability. Because EVI variability was greatest in regions of lower PAW, we hypothesize that drought could increase EVI by synchronizing leaf flushing via its effects on leaf bud development. PMID:20679201

  2. Interannual Variability of Tropical Precipitation: How Well Do Climate Models Agree With Current Satellite Estimates?

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Marshall, Susan; Roads, John; Oglesby, Robert J.; Fitzjarrald, Dan; Goodman, H. Michael (Technical Monitor)

    2001-01-01

    Since the beginning of the World Climate Research Program's Global Precipitation Climatology Project (GPCP) satellite remote sensing of precipitation has made dramatic improvements, particularly for tropical regions. Data from microwave and infrared sensors now form the most critical input to precipitation data sets and can be calibrated with surface gauges to so that the strengths of each data source can be maximized in some statistically optimal sense. Recent availability of the TRMM (Tropical Rainfall Measuring Mission) has further aided in narrowing uncertainties in rainfall over die tropics and subtropics. Although climate modeling efforts have long relied on space-based precipitation estimates for validation, we now are in a position to make more quantitative assessments of model performance, particularly in tropical regions. An integration of the CCM3 using observed SSTs as a lower boundary condition is used to examine how well this model responds to ENSO forcing in terms of anomalous precipitation. An integration of the NCEP spectral model used for the Reanalysis-H effort is also examined. This integration is run with specified SSTs, but with no data assimilation. Our analysis focuses on two aspects of inter-annual variability. First are the spatial anomalies that are indicative of dislocations in Hadley and Walker circulations. Second, we consider the ability of models to replicate observed increases in oceanic precipitation that are noted in satellite observations for large ENSO events. Finally, we consider a slab ocean version of the CCM3 model with prescribed ocean beat transports that mimic upwelling anomalies, but which still allows the surface energy balance to be predicted. This less restrictive experiment is used to understand why model experiments with specified SSTs seem to have noticeably less interannual variability in precipitation than do the satellite observations.

  3. Interannual to Multidecadal Climate Variability and Groundwater Resources of the Western United States

    NASA Astrophysics Data System (ADS)

    Gurdak, J. J.; Kuss, A. M.

    2011-12-01

    Climate variability and change have important implications for groundwater recharge, discharge, contaminant transport, and resource sustainability. Reliable predictions of groundwater sustainability due to climate change will require improved understanding of the effects of global scale atmosphere-ocean climate oscillations on interannual to multidecadal timescales. Climate variability on these timescales partially controls precipitation, air temperature, drought, evapotranspiration, streamflow, recharge, and mobilization of subsurface-chemical reservoirs. Climate variability can augment or diminish human stresses on groundwater, and the responses in storage can be dramatic when different climate cycles lie coincident in a positive or negative phase of variability. Thus, understanding climate variability has particular relevance for management decisions during drought and for water resources close to the limits of sustainability. Major findings will be presented from a national scale study of climate variability on recharge rates and groundwater levels, and will highlight regional aquifers of the western United States, including the Basin and Range (700,000 km2), Central Valley (52,000 km2), High Plains (450,000 km2), and Mississippi Embayment (181,000 km2) aquifer systems. Using singular spectrum analysis, the groundwater pumping signal was removed and natural variations were identified in groundwater levels as partially coincident with the El Niño/Southern Oscillation (ENSO) (2-6 year cycle), North Atlantic Oscillation (3-6 year cycle), Pacific Decadal Oscillation (PDO) (10-25 year cycle), and Atlantic Multidecadal Oscillation (AMO) (50-80 year cycle). The PDO was the most significant contributor to recharge and groundwater level fluctuations in most aquifers. In the Central Valley and the Basin and Range, the PDO contributes to the greatest amount of variance (ranging from 13.6-83%) in all precipitation and groundwater level time series, with moderate to strong

  4. The Role of Global Hydrologic Processes in Interannual and Long-Term Climate Variability

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.

    1997-01-01

    The earth's climate and its variability is linked inextricably with the presence of water on our planet. El Nino / Southern Oscillation-- the major mode of interannual variability-- is characterized by strong perturbations in oceanic evaporation, tropical rainfall, and radiation. On longer time scales, the major feedback mechanism in CO2-induced global warming is actually that due to increased water vapor holding capacity of the atmosphere. The global hydrologic cycle effects on climate are manifested through influence of cloud and water vapor on energy fluxes at the top of atmosphere and at the surface. Surface moisture anomalies retain the "memory" of past precipitation anomalies and subsequently alter the partitioning of latent and sensible heat fluxes at the surface. At the top of atmosphere, water vapor and cloud perturbations alter the net amount of radiation that the earth's climate system receives. These pervasive linkages between water, radiation, and surface processes present major complexities for observing and modeling climate variations. Major uncertainties in the observations include vertical structure of clouds and water vapor, surface energy balance, and transport of water and heat by wind fields. Modeling climate variability and change on a physical basis requires accurate by simplified submodels of radiation, cloud formation, radiative exchange, surface biophysics, and oceanic energy flux. In the past, we m safely say that being "data poor' has limited our depth of understanding and impeded model validation and improvement. Beginning with pre-EOS data sets, many of these barriers are being removed. EOS platforms with the suite of measurements dedicated to specific science questions are part of our most cost effective path to improved understanding and predictive capability. This talk will highlight some of the major questions confronting global hydrology and the prospects for significant progress afforded by EOS-era measurements.

  5. Global analysis of climate-driven interannual variability of food production and related water scarcity

    NASA Astrophysics Data System (ADS)

    Kummu, Matti; Gerten, Dieter; Heinke, Jens; Konzmann, Markus; Varis, Olli

    2014-05-01

    Interannual climatic and hydrologic variability has been substantial during the past decades in many regions. While climate variability and its impacts on precipitation and soil moisture have been studied intensively, less is known on subsequent implications for global food production. In this study we quantify effects of hydroclimatic variability on global "green" and "blue" water availability and demand in global agriculture, and thus complement former studies that have focused merely on long-term averages. We further quantify some options to overcome food deficit due to chronic or sporadic water scarcity. We found that 24% of the world's population lives in chronically water scare food production units (FPUs) (i.e. water is scarce every year), while an additional 19% live under occasional water scarcity (water is scarce in some years). Among these 2.6 billion people altogether, 55% would have to rely on international trade to reach the reference diet, while for 24% domestic trade would be enough. For the remaining 21% of population exposed to some degree of water scarcity, local food storage and/or intermittent trade would be enough to secure the reference diet over the occasional dry years. The analysis is based on historical climate forcing dataset over the period 1977-2007, while demography, diet composition and land use are fixed to reference conditions (year 2000). In so doing, we isolate the effect of interannual hydroclimatic variability from other factors that drive food production. We analyse the potential of FPUs to produce a reference diet for their inhabitants (3,000 kilocalories per capita per day, with 80% vegetal food and 20% animal products). The LPJmL vegetation and hydrology model was used to calculate spatially and explicitly the variation in food production, green-blue water availability and the water requirements to produce that very diet. An FPU was considered water scarce if its water availability was not sufficient to produce the diet (i

  6. Inter-annual climate variability and productivity models for grapevines in Portugal

    NASA Astrophysics Data System (ADS)

    Martinho, M.; Santos, J. A.; Malheiro, A. C.; Pinto, J. G.

    2009-09-01

    Grapevines are a major crop in Portugal, constituting an important source of income for local farmers. The Mediterranean type climate of the country strongly influences the growth and development of this crop, and ultimately the yield. Therefore, for several (9) Portuguese regions over 19 years (1986-2004), the inter-annual variability of grapevine productivity and climate data (mostly temperature and precipitation on a monthly basis) was analyzed in order to define mathematical models based on statistically significant correlations between those variables. One particular region (Vila Real, close to Demarcated Valley of Douro) was studied in more detail using the daily data available. For that purpose, a number of derived indices was calculated (e.g., number of days with positive minimum air temperature or maximum temperature above 25°C, number of days with precipitation higher than 10 mm). Close relationships between temperature, precipitation and relative air humidity were then found to influence productivity. In fact, a high-quality mathematical linear model based on these variables was found for Vila Real. Those analyses also enabled the verification of monthly climatic conditions, which are or not favorable for growth and development of grapevines; results indicate a clear relationship between the vegetative cycle of grapevines and their basic climatic requirements. After validation, this model may be used for predicting future yields in the region and, using data from an atmospheric model, it was also possible to project a future scenario for the productivity in the period (2030-2050), based on an specific emission scenario (A1B). Lastly, in order to isolate the large-scale atmospheric circulation patterns most favorable/unfavorable to wine productivity, years with extremely high (e.g., 1989) and extremely low yields (e.g., 1987) were selected and the corresponding dynamical conditions were analyzed in more detail.

  7. Impacts of Arctic Climate Change on Tundra Fire Regimes at Interannual to Millennial Timescales

    NASA Astrophysics Data System (ADS)

    Hu, F.; Young, A. M.; Chipman, M. L.; Duffy, P.; Higuera, P. E.

    2014-12-01

    Tundra burning is emerging as a key process in the rapidly changing Arctic, and knowledge of tundra fire-regime responses to climate change is essential for projecting Earth system dynamics. This presentation will focus on climate-fire relationships in the Arctic, spatiotemporal patterns of Holocene tundra burning, and the effects of tundra burning on carbon cycling. Analysis of historical records reveals that across the Arctic, tundra burning occurred primarily in areas where mean summer temperature exceeded 9 °C and total summer precipitation was below 115 mm. In Alaska, summer temperature and precipitation explain >90% of the interannual variability in tundra area burned from AD 1950-2009, with thresholds of 10.5 °C and 140 mm. These patterns imply tipping points in tundra fire-regime responses to climate change. The frequency of tundra fires has varied greatly across space and through time. Approximately 1.0% of the circum-Arctic tundra burned from AD 2002-2013, and 4.5% of the Alaskan tundra burned from AD 1950-2009. The latter encompassed ecoregions with fire rotation periods ranging from ~400 to 13,640 years. Charcoal analysis of lake sediments also shows that Arctic tundra can sustain a wide range of fire regimes. Fires were rare on the Alaskan North Slope throughout the Holocene, implying that the climate thresholds evident in the historical records have seldom been crossed. In contrast, in areas of NW Alaska, tundra has burned regularly at 100-250 year intervals during the late Holocene. Tundra burning may cause sudden releases of the enormous amount of Arctic soil C. Charcoal particles from recent burns yielded 14C ages of AD 1952-2006. Thus the C consumed in recent fires may recover through vegetation succession. However, our results suggest that in areas that have burned multiple times in recent decades, old soil C is vulnerable to future fires.

  8. Intraseasonal-to-interannual variability of the Indian Monsoon: the present climate and future projections of climate change

    NASA Astrophysics Data System (ADS)

    Carvalho, L. V.; Jones, C.; Cannon, F.

    2014-12-01

    The Asia Monsoon is among Earth's most intriguing and spectacular phenomena. The Indian Monsoon System (IMS) is a regional manifestation this continental-scale phenomenon with complex characteristics and predictive challenges. India exhibits one of the largest rates of population growth that relies on IMS cycle for water supply. Thus, understanding the temporal variability of the IMS is essential to realistically predict the impacts of climate change on Asia's water resources and food security. Here we investigate intraseasonal-to-interannual variability of the IMS in the climate of the 20th century using the Climate Forecast System Reanalysis (CFSR) and examine future scenarios of climate change using the high spatial resolution models of the Coupled Model Intercomparison Project Phase 5 (CMIP5) project. IMS is characterized with a large-scale index continuous in time and obtained by performing combined EOF analysis (CEOF) of variables that characterize the monsoon cycle: precipitation, low level circulation at 10 m, specific humidity and temperature at 2m. CFSR is used to derive the index (1979-2013). Projections of the CEOF onto the tropical rainfall measuring mission (TRMM) indicate that the first CEOF captures the large-scale features of the South and East Asia Monsoon. The second CEOF is associated with the IMS and its time coefficient is used as large-scale index for the IMS (LIMS). LIMS realistically defines IMS onset and withdrawal, and its amplitude associates with total seasonal precipitation. Moreover, the spectral analysis of the ISMI shows peaks on intraseasonal timescales that are related to IMS's active and break phases. Moreover, we demonstrate that LIMS identifies the interannual variability of IMS and can be used to investigate floods and droughts that have occurred over India. Similar approach is used to investigate the skill of the CMIP5 models in realistically simulating active and break phases of the IMS in the 'historic' run (1951-2005). We

  9. Millennium-Scale Crossdating and Inter-Annual Climate Sensitivities of Standing California Redwoods

    PubMed Central

    Carroll, Allyson L.; Sillett, Stephen C.; Kramer, Russell D.

    2014-01-01

    Extremely decay-resistant wood and fire-resistant bark allow California’s redwoods to accumulate millennia of annual growth rings that can be useful in biological research. Whereas tree rings of Sequoiadendron giganteum (SEGI) helped formalize the study of dendrochronology and the principle of crossdating, those of Sequoia sempervirens (SESE) have proven much more difficult to decipher, greatly limiting dendroclimatic and other investigations of this species. We overcame these problems by climbing standing trees and coring trunks at multiple heights in 14 old-growth forest locations across California. Overall, we sampled 1,466 series with 483,712 annual rings from 120 trees and were able to crossdate 83% of SESE compared to 99% of SEGI rings. Standard and residual tree-ring chronologies spanning up to 1,685 years for SESE and 1,538 years for SEGI were created for each location to evaluate crossdating and to examine correlations between annual growth and climate. We used monthly values of temperature, precipitation, and drought severity as well as summer cloudiness to quantify potential drivers of inter-annual growth variation over century-long time series at each location. SESE chronologies exhibited a latitudinal gradient of climate sensitivities, contrasting cooler northern rainforests and warmer, drier southern forests. Radial growth increased with decreasing summer cloudiness in northern rainforests and a central SESE location. The strongest dendroclimatic relationship occurred in our southernmost SESE location, where radial growth correlated negatively with dry summer conditions and exhibited responses to historic fires. SEGI chronologies showed negative correlations with June temperature and positive correlations with previous October precipitation. More work is needed to understand quantitative relationships between SEGI radial growth and moisture availability, particularly snowmelt. Tree-ring chronologies developed here for both redwood species have

  10. Millennium-scale crossdating and inter-annual climate sensitivities of standing California redwoods.

    PubMed

    Carroll, Allyson L; Sillett, Stephen C; Kramer, Russell D

    2014-01-01

    Extremely decay-resistant wood and fire-resistant bark allow California's redwoods to accumulate millennia of annual growth rings that can be useful in biological research. Whereas tree rings of Sequoiadendron giganteum (SEGI) helped formalize the study of dendrochronology and the principle of crossdating, those of Sequoia sempervirens (SESE) have proven much more difficult to decipher, greatly limiting dendroclimatic and other investigations of this species. We overcame these problems by climbing standing trees and coring trunks at multiple heights in 14 old-growth forest locations across California. Overall, we sampled 1,466 series with 483,712 annual rings from 120 trees and were able to crossdate 83% of SESE compared to 99% of SEGI rings. Standard and residual tree-ring chronologies spanning up to 1,685 years for SESE and 1,538 years for SEGI were created for each location to evaluate crossdating and to examine correlations between annual growth and climate. We used monthly values of temperature, precipitation, and drought severity as well as summer cloudiness to quantify potential drivers of inter-annual growth variation over century-long time series at each location. SESE chronologies exhibited a latitudinal gradient of climate sensitivities, contrasting cooler northern rainforests and warmer, drier southern forests. Radial growth increased with decreasing summer cloudiness in northern rainforests and a central SESE location. The strongest dendroclimatic relationship occurred in our southernmost SESE location, where radial growth correlated negatively with dry summer conditions and exhibited responses to historic fires. SEGI chronologies showed negative correlations with June temperature and positive correlations with previous October precipitation. More work is needed to understand quantitative relationships between SEGI radial growth and moisture availability, particularly snowmelt. Tree-ring chronologies developed here for both redwood species have

  11. Climate extremes dominating seasonal and interannual variations in carbon export from the Mississippi River Basin

    NASA Astrophysics Data System (ADS)

    Tian, Hanqin; Ren, Wei; Yang, Jia; Tao, Bo; Cai, Wei-Jun; Lohrenz, Steven E.; Hopkinson, Charles S.; Liu, Mingliang; Yang, Qichun; Lu, Chaoqun; Zhang, Bowen; Banger, Kamaljit; Pan, Shufen; He, Ruoying; Xue, Zuo

    2015-09-01

    Knowledge about the annual and seasonal patterns of organic and inorganic carbon (C) exports from the major rivers of the world to the coastal ocean is essential for our understanding and potential management of the global C budget so as to limit anthropogenic modification of global climate. Unfortunately our predictive understanding of what controls the timing, magnitude, and quality of C export is still rudimentary. Here we use a process-based coupled hydrologic/ecosystem biogeochemistry model (the Dynamic Land Ecosystem Model) to examine how climate variability and extreme events, changing land use, and atmospheric chemistry have affected the annual and seasonal patterns of C exports from the Mississippi River basin to the Gulf of Mexico. Our process-based simulations estimate that the average annual exports of dissolved organic C (DOC), particulate organic C (POC), and dissolved inorganic C (DIC) in the 2000s were 2.6 ± 0.4 Tg C yr-1, 3.4 ± 0.3 Tg C yr-1, and 18.8 ± 3.4 Tg C yr-1, respectively. Although land use change was the most important agent of change in C export over the past century, climate variability and extreme events (such as flooding and drought) were primarily responsible for seasonal and interannual variations in C export from the basin. The maximum seasonal export of DIC occurred in summer while for DOC and POC the maximum occurred in winter. Relative to the 10 year average (2001-2010), our modeling analysis indicates that the years of maximal and minimal C export cooccurred with wet and dry years (2008: 32% above average and 2006: 32% below average). Given Intergovernmental Panel on Climate Change-predicted changes in climate variability and the severity of rain events and droughts of wet and dry years for the remainder of the 21st century, our modeling results suggest major changes in the riverine link between the terrestrial and oceanic realms, which are likely to have a major impact on C delivery to the coastal ocean.

  12. Inter-annual variability of evapotranspiration in two semiarid ecosystems with different climate patterns

    NASA Astrophysics Data System (ADS)

    Villarreal, S.; Vargas, R.; Yepez, E. A.; Smith, S. V.; Watts, C.; Rodriguez, J.; Garatuza, J.; Martinez, J.; Castro, A.; Lopez, E.

    2012-12-01

    One of the most important climatic characteristics in arid and semiarid environments is the amount and variability of precipitation. This characteristic is important because the variability, magnitude, and number of the precipitation pulses have differing influence on the evapotranspiration flux (ET). We demonstrated this by studying two different semiarid shrublands : one with cool and wet winters (El Mogor), and the other with wet and warm summers (Rayon). We were interested in: a) the behavior of evapotranspiration (ET) when the wet season is in phase with the highest values of net radiation (Rayon), and when these two variables were not in phase (El Mogor); and b) on the interannual transition between dry-wet and wet-dry season. We used six site-years of eddy covariance measurements of ET from 2008-2010 (i.e.,3 years of measurements per site). Preliminary results show that Rayon has a maximum ET during the wet season, while El Mogor has it during the wet-dry transition. We discuss that maximum ET is controlled by precipitation and net radiation, but volumetric water content is a strong environmental control on ET especially during the transition seasons.

  13. Interannual variation in climate-potential net primary productivity relationships in differing ecosystems of California

    SciTech Connect

    Koch, G.W.; Randerson, J.T. )

    1994-06-01

    The seasonality and interannual variation in potential net primary production (NPP) were examined in differing vegetation types in California over three years of contrasting precipitation using co-registered maps of climate, vegetation, and 1km biweekly NDVI derived from high resolution satellite AVHRR data. Differences in seasonality of the vegetation types (annual grassland, chamise chaparral, deciduous oak woodland, and evergreen oak) were clearly evident and corresponded well to patterns observed in field studies. In years and locations having high precipitation the annual peak in NDVI occurred later in all vegetation classes. The annual sum of biweekly NDVI was correlated with annual precipitation in all vegetation types, although the slopes and intercepts of the regressions differed among types. Annual grassland showed the largest increase in sumNDVI per unit increase in total precipitation and most of the variation in grassland sumNDVI was explained by variation in autumn precipitation. In general the ratio of sumNDVI to annual precipitation was dependent on the temporal distribution of precipitation with respect to the long-term average pattern. Published relationships between precipitation and NPP were used to develop equations relating annual NDVI sum to NPP.

  14. Diagnostics of Interannual-to-Interdecadal Climate and Streamflow Variability: Applications to Reservoir Management over NW India

    NASA Astrophysics Data System (ADS)

    Robertson, A. W.; Cook, E. R.; Ghil, M.; Greene, A. M.; Kondrashov, D. A.; Lall, U.; Lu, M.

    2013-12-01

    Multi-year storage reservoirs must be managed in the face of weather and climate variability across time scales ranging from daily weather to interannual climate. While seasonal climate may contain a predictable component associated with the El Nino-Southern Oscillation (ENSO), longer time scales are not yet usefully predictable, nor is the interannual-to-interdecadal power spectrum well estimated from observed data. In addition, climate simulations from general circulation models (GCMs) are often lacking in their ability to generate realistic hydroclimate variability across time scales, especially at small spatial scales. These issues are critical for climate change adaptation planning in water management, where realistic estimates of climate and stream flow variability are required. For the Bhakra reservoir in NW India, we develop estimates of climate and stream flow variability, including the interannual-to-interdecadal power spectrum, based on (1) instrumental stream flow records of the Sutlej river, 1963-2010; (2) tree ring reconstructions of the Sutlej flow back to 1321; and (3) multi-century control simulations of precipitation-minus-evaporation made with several coupled ocean-atmosphere GCMs archived in the IPCC CMIP5 database. By comparing these observed, paleo-proxy, and GCM-based estimates, we shed light on the ability of GCMs to simulate realistic hydroclimate variability over the Indus basin, as well as on the nature of tree-ring based streamflow reconstructions. In addition to these estimates of the variability spectrum, we explore the use of a nonlinear, multi-level stochastic polynomial inverse model to bridge between these different datasets.

  15. Potential impacts of a future Grand Solar Minimum on decadal regional climate change and interannual hemispherical climate variability

    NASA Astrophysics Data System (ADS)

    Spiegl, Tobias; Langematz, Ulrike

    2016-04-01

    Grand Solar Minimum under RCP6.0 conditions. The results obtained were compared to a RCP6.0 simulation that was carried out using the CCMI recommendations for a 21st century solar forcing. We used the ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry-climate model that incorporates interactive ozone chemistry, a high-resolution shortwave radiation scheme, a high model top (0.01 hPa) and is coupled to a 3D ocean general circulation model. We focused on the regional responses to a future Grand Solar Minimum and interannual variability patterns (i.e. the Northern and Southern Annular Mode (NAM/SAM)).

  16. Seasonal and Interannual Variability in Stratification in the Gulf of Maine: Salinity and Temperature Contributions and Climatic Forcing

    NASA Astrophysics Data System (ADS)

    Deese, H. E.; Pettigrew, N. R.; Beard-Tisdale, K.

    2008-12-01

    Seasonality and interannual variability in stratification in the Gulf of Maine impact physical processes, including the connectivity and transport of the coastal current system and isolation of surface waters. These physical processes in turn impact biological processes, such as the spring phytoplankton bloom, growth and transport of eggs and larvae of commercial species, and Harmful Algal Blooms. We use seven years of data from the Gulf of Maine Ocean Observing System (GoMOOS) to describe and explain seasonal and interannual variability in stratification. Results highlight the dominant role of salinity, particularly on the coastal shelf during spring and fall when salinity gradients increase and decrease episodically in geographically irregular and inter-annually varying patterns. As a result, short-term, large amplitude stratification events occur during some years and not others, with likely biological implications. By contrast, the vertical temperature gradients that control surface stratification during summer (June-September) display classical seasonal cycles that vary much less between years and locations. Comparison with oceanic inflows, river inflows, and meteorological data leads to a refined understanding of the relative importance of the physical mechanisms that control the hydrography, particularly salinity and stratification. These insights into seasonal and interannual variability will enhance our ability to predict the Gulf of Maine response to future changes in climatic forcing.

  17. Constructing the reduced dynamical models of interannual climate variability from spatial-distributed time series

    NASA Astrophysics Data System (ADS)

    Mukhin, Dmitry; Gavrilov, Andrey; Loskutov, Evgeny; Feigin, Alexander

    2016-04-01

    We suggest a method for empirical forecast of climate dynamics basing on the reconstruction of reduced dynamical models in a form of random dynamical systems [1,2] derived from observational time series. The construction of proper embedding - the set of variables determining the phase space the model works in - is no doubt the most important step in such a modeling, but this task is non-trivial due to huge dimension of time series of typical climatic fields. Actually, an appropriate expansion of observational time series is needed yielding the number of principal components considered as phase variables, which are to be efficient for the construction of low-dimensional evolution operator. We emphasize two main features the reduced models should have for capturing the main dynamical properties of the system: (i) taking into account time-lagged teleconnections in the atmosphere-ocean system and (ii) reflecting the nonlinear nature of these teleconnections. In accordance to these principles, in this report we present the methodology which includes the combination of a new way for the construction of an embedding by the spatio-temporal data expansion and nonlinear model construction on the basis of artificial neural networks. The methodology is aplied to NCEP/NCAR reanalysis data including fields of sea level pressure, geopotential height, and wind speed, covering Northern Hemisphere. Its efficiency for the interannual forecast of various climate phenomena including ENSO, PDO, NAO and strong blocking event condition over the mid latitudes, is demonstrated. Also, we investigate the ability of the models to reproduce and predict the evolution of qualitative features of the dynamics, such as spectral peaks, critical transitions and statistics of extremes. This research was supported by the Government of the Russian Federation (Agreement No. 14.Z50.31.0033 with the Institute of Applied Physics RAS) [1] Y. I. Molkov, E. M. Loskutov, D. N. Mukhin, and A. M. Feigin, "Random

  18. Seasonal and inter-annual variability in rangeland NEE: Contributions of climatic anomalies and fluctuations in daytime and night-time CO2 fluxes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Net ecosystem exchange of CO2 (NEE) of terrestrial ecosystems varies seasonally and inter-annually partly because of climatic variability. If we are to predict climate-driven variation in NEE, we must understand how climatic anomalies at different temporal scales influence NEE and its components, ...

  19. Interannual to decadal climate variability of sea salt aerosols in the coupled climate model CESM1.0

    NASA Astrophysics Data System (ADS)

    Xu, Li; Pierce, David W.; Russell, Lynn M.; Miller, Arthur J.; Somerville, Richard C. J.; Twohy, Cynthia H.; Ghan, Steven J.; Singh, Balwinder; Yoon, Jin-Ho; Rasch, Philip J.

    2015-02-01

    This study examines multiyear climate variability associated with sea salt aerosols and their contribution to the variability of shortwave cloud forcing (SWCF) using a 150 year simulation for preindustrial conditions of the Community Earth System Model version 1.0. The results suggest that changes in sea salt and related cloud and radiative properties on interannual timescales are dominated by the El Niño-Southern Oscillation cycle. Sea salt variability on longer (interdecadal) timescales is associated with low-frequency variability in the Pacific Ocean similar to the Interdecadal Pacific Oscillation but does not show a statistically significant spectral peak. A multivariate regression suggests that sea salt aerosol variability may contribute to SWCF variability in the tropical Pacific, explaining up to 20-30% of the variance in that region. Elsewhere, there is only a small sea salt aerosol influence on SWCF through modifying cloud droplet number and liquid water path that contributes to the change of cloud effective radius and cloud optical depth (and hence cloud albedo), producing a multiyear aerosol-cloud-wind interaction.

  20. The inter-annual distribution of cloudless days and nights in Abastumani: Coupling with cosmic factors and climate change

    NASA Astrophysics Data System (ADS)

    Didebulidze, G. G.; Todua, M.

    2016-04-01

    We examined inter-annual variations and long-term trends of cloudless days (CD) and cloudless nights (CN) in 1957-1993 from Abastumani (41.75N, 42.82E), at different geomagnetic conditions and corresponding galactic cosmic rays (GCRs) flux changes. It showed possible influence of cosmic factors on cloud covering processes and, thus, climate change. It was demonstrated that (1) the inter-annual distribution of monthly mean values of planetary geomagnetic index Ap (for low and moderate disturbances) at CDs can be described by harmonic function with semiannual (with sharp maxima in March and September) and annual (with maximum in August) periodicities; (2) the inter-annual distribution of Ap index for CN has an additional maximum in June, where the largest decrease of GCR flux is observed. This phenomenon is expressed even stronger during Sudden Storm Commencement (SSC) events and strong geomagnetic disturbances (Ap≥50), when their relative numbers are the greatest and are accompanied by bigger reduction of GCRs flux; (3) the long-term trends of mean annual and mean seasonal values of Ap index and GCRs flux at CD and CN are estimated. It was detected that, for the latitudes of this region, long-term decreases (negative trends) of seasonal GCR flux are different at CD and CN, which could affect the radiative balance at the Earth's surface and, as a result, contribute to the climate change.

  1. Effects of interannual climate variation on phenology and growth of two alpine forbs

    SciTech Connect

    Walker, M.D.; Ingersoll, R.C.; Webber, P.J.

    1995-06-01

    Variations in growth, flowering, and phenology of two forbs, Acomastylis rossii and Bistorta bistortoides, were compared among six years (1983-1988) and five plant communities (fellfield, dry meadow, moist meadow, wet meadow, snowbed) at an alpine site in the Front Range of Colorado. The purpose was to determine the extent to which the phenological patterns of these species varied among plant communities and how interannual climate variability affects phenology and growth. There were significant differences in growth among communities for both species. In B. bistortoides, there were also significant differences among years, due primarily to the influence of a single year (1983) when leaf length increased by {approximately}10% and the average number of B. bistortoides leaves nearly doubled. Key phenological events of both species (initiation of growth, date of maximum leaf length, leaf number, and flower number) were related to snowmelt patterns, resulting in differences among communities. There were also significant differences among years, again primarily related to the single year 1983, the year of a major El Nino Southern Oscillation (ENSO) event that produced high snowfall amounts at the site. The increased leaf length in a high snow year is counterintuitive to the commonly accepted notion that alpine species may be limited by season length. We hypothesize that changes in phenology related to changes in snowfall or snowmelt will cause detectable changes in growth, but that these will not be predicted simply from phenology alone. Rather, the timing of snowmelt in relation to nutrient availability, soil moisture, and air temperature will be critical in determining how individual species respond. 90 refs., 7 figs., 3 tabs.

  2. Interannual climate variations in Arctic as driven by the Global atmosphere oscillation

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Byshev, Vladimir; Neiman, Victor; Sidorova, Alexandra; Sonechkin, Dmitry

    2015-04-01

    The present-day global climate change affects the Arctic basin substantially more because of the sea ice cover extinction and the permafrost melting. But there are essential variations of these effects from year to year. We believe that these variations might be a regional manifestation of a planetary-scale phenomenon named the Global atmospheric oscillation (GAO). GAO includes the well-known El Niño - Southern Oscillation (ENSO) process and similar processes in equatorial Atlantic and Indian Oceans within itself. The goal of this report is to present some arguments to support this point of view. For this goal, we have studied some interrelations between the above-mentioned Arctic anomalies and GAO as seen in global re-analyses of the sea level pressure (SLP) and near surface temperature (NST) for the period of 1920-2013. The mean global fields of SLP and NST have been computed for all El Niño events falling into this time period, and separately, for all and La Niña events. As a result, two (for SLP and NST as well) global fields of the mean El Niño/La Niña difference were obtained. Statistical significance of the non-zero values of these fields, i.e. the reality of GAO, was evaluated with the t-Student's test. It turned out that the main spatial structures of GAO, presented specifically by El Niño and La Niña events in Pacific region, exist at a very high level (up to 99%, t>4) of the significance. Therefore, one can conclude that the interannual-scale dynamics of GAO is actually reflected in the climate features of different regions of the Earth, including the Russian Arctic. In particular, when the boreal winter season coincides with an El Niño event GAO is indicative by a negative anomaly of NST (about -1°C) and a positive anomaly of SLP over the Arctic basin. In contrary, significant (about +1°C) positive anomaly of NST along with reduced SLP over the whole Arctic region is typical for any La Niña event (up to 95%, t>2). To control the reliability

  3. Linkages Between Terrestrial Carbon Uptake and Interannual Climate Variability over the Texas-northern Mexico High Plains

    NASA Astrophysics Data System (ADS)

    Parazoo, N.; Barnes, E. A.; Worden, J.; Harper, A. B.; Bowman, K. W.; Frankenberg, C.

    2014-12-01

    The Texas-northern Mexico high plains experienced record drought conditions in 2011 during strong negative phases of ENSO and the NAO. Given predictions of increased frequency and severity of drought under projected climate change [e.g., Reichstein et al., 2013] and recent findings of CO2 growth rate sensitivity to interannual variability of carbon uptake in semi-arid ecosystems [Poulter et al., 2014], we investigate the response of carbon uptake in the Texas high plains to interannual climate variability with the goal of improved mechanistic understanding of climate-carbon cycle links. Specifically, we examine (1) observed tendencies in regional scale carbon uptake and soil moisture from 2010 to 2011 using satellite observations of gross primary production (GPP) (from plant fluorescence) from GOSAT and soil moisture from SMOS, and (2) the interannual relationship between GPP and ENSO & NAO variability using terrestrial biosphere simulations from 1950-2012. Observations reveal widespread decline of GPP in 2011 (0.42 +/- 0.04 Pg C yr-1) correlated with negative soil moisture tendencies (r = 0.85 +/- 0.21) which leads to corresponding declines in net carbon uptake and transpiration (according to model simulations). Further examination of model results over the period 1950-2012 indicates that negative GPP anomalies are linked systematically to winter and spring precipitation deficits associated with overlapping negative phases of winter NAO and ENSO, with increasing magnitude of negative anomalies in strong La Niña years. Furthermore, the strongest decline of GPP, carbon uptake, and transpiration on record occurred during the 2011 drought and were associated with extreme negative phases of ENSO and NAO, with 2011 being the only year since 1950 that both indices exceeded 1 σ standard deviation.

  4. A novel method for the detection of persistent and recurrent climatic regimes as almost invariants of the transfer operator

    NASA Astrophysics Data System (ADS)

    Tantet, A.; Dijkstra, H. A.

    2014-12-01

    A novel method and its numerical implementation to find almost invariants of a dynamical system will be presented, with applications to the detection of persistent and recurrent climatic regimes, coherent structures in ocean flows and spatial patterns of climate variability. The method is based on an estimation of the transfer operator of the particular dynamical system. The detection of almost invariants is posed as a Markov reduction problem with a minimization of the relative entropy, here a measure of the distance between the fine-grained system and the reduced Markov chain. It is implemented using a fast-greedy algorithm from complex network theory. Two applications in different domains of climate science are presented. In the first one, two persistent and recurrent atmospheric flow regimes are identified from a simulation of a barotropic model of the northern hemispheric atmosphere with realistic winter forcing. The regimes correspond to the well-known blocked and zonal circulation regimes of the northern hemisphere. Secondly, the algorithm is applied to a correlation network estimated from 140 years of sea surface temperature data to identify spatial patterns of variability. Dominant patterns on interannual to decadal time-scales are found in the tropical Pacific (El Niño-Southern Oscillation), the North Atlantic (the Atlantic Multidecadal Oscillation) and the Indian ocean and West Pacific.

  5. Interannual Variations in Earth's Low-Degree Gravity Field and the Connections With Geophysical/Climatic Changes

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Cox, Christopher M.

    2004-01-01

    Long-wavelength time-variable gravity recently derived from satellite laser ranging (SLR) analysis have focused to a large extent on the effects of the recent (since 1998) large anomalous change in J2, or the Earth's oblateness, and the potential causes. However, it is relatively more difficult to determine whether there are corresponding signals in the shorter wavelength zonal harmonics from the existing SLR-derived time variable gravity results, although it appears that geophysical fluid mass transport is being observed. For example, the recovered J3 time series shows remarkable agreement with NCEP-derived estimates of atmospheric gravity variations. Likewise, some of the non-zonal spherical harmonic components have significant interannual signal that appears to be related to mass transport. The non-zonal degree-2 components show reasonable temporal correlation with atmospheric signals, as well as climatic effects such as El Nino Southern Oscillation. We will present recent updates on the J2 evolution, as well as a look at other low-degree components of the interannual variations of gravity, complete through degree 4. We will examine the possible geophysical and climatic causes of these low-degree time-variable gravity related to oceanic and hydrological mass transports, for example some anomalous but prominent signals found in the extratropic Pacific ocean related to the Pacific Decadal Oscillation.

  6. Predicted changes in interannual water-level fluctuations due to climate change and its implications for the vegetation of the Florida Everglades.

    PubMed

    van der Valk, Arnold G; Volin, John C; Wetzel, Paul R

    2015-04-01

    The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, sloughs, and tree islands) historically and currently found in the Everglades, FL, USA, as with other wetlands with standing water, appears to be primarily a function of the magnitude of interannual water-level fluctuations. Analyses of 40 years of water-depth data were used to estimate the magnitude of contemporary (baseline) water-level fluctuations in undisturbed ridge and slough landscapes. Baseline interannual water-level fluctuations above the soil surface were at least 1.5 m. Predicted changes in interannual water-level fluctuations in 2060 were examined for seven climate change scenarios. When rainfall is predicted to increase by 10 %, the wettest scenario, the interannual range of water-level fluctuation increases to 1.8 m above the soil surface in sloughs. When rainfall is predicted to decrease by 10 % and temperatures to increase by 1.5 °C, the driest scenario, the range of interannual range of water-level fluctuations is predicted to decrease to 1.2 m above the soil surface in sloughs. A change of 25-30 cm in interannual water-level fluctuations is needed to change the number of vegetation types in a wetland. This suggests that the two most extreme climate change scenarios could have a significant impact on the overall structure of wetland vegetation, i.e., the number of vegetation types or zones, found in the Everglades. PMID:25566832

  7. Predicted Changes in Interannual Water-Level Fluctuations Due to Climate Change and Its Implications for the Vegetation of the Florida Everglades

    NASA Astrophysics Data System (ADS)

    van der Valk, Arnold G.; Volin, John C.; Wetzel, Paul R.

    2015-04-01

    The number of dominant vegetation types (wet prairies, sawgrass flats, ridges and sloughs, sloughs, and tree islands) historically and currently found in the Everglades, FL, USA, as with other wetlands with standing water, appears to be primarily a function of the magnitude of interannual water-level fluctuations. Analyses of 40 years of water-depth data were used to estimate the magnitude of contemporary (baseline) water-level fluctuations in undisturbed ridge and slough landscapes. Baseline interannual water-level fluctuations above the soil surface were at least 1.5 m. Predicted changes in interannual water-level fluctuations in 2060 were examined for seven climate change scenarios. When rainfall is predicted to increase by 10 %, the wettest scenario, the interannual range of water-level fluctuation increases to 1.8 m above the soil surface in sloughs. When rainfall is predicted to decrease by 10 % and temperatures to increase by 1.5 °C, the driest scenario, the range of interannual range of water-level fluctuations is predicted to decrease to 1.2 m above the soil surface in sloughs. A change of 25-30 cm in interannual water-level fluctuations is needed to change the number of vegetation types in a wetland. This suggests that the two most extreme climate change scenarios could have a significant impact on the overall structure of wetland vegetation, i.e., the number of vegetation types or zones, found in the Everglades.

  8. Interannual to Decadal Variability of Ocean Evaporation as Viewed from Climate Reanalyses

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Bosilovich, Michael G.; Roberts, Jason B.; Wang, Hailan

    2015-01-01

    Questions we'll address: Given the uncoupled framework of "AMIP" (Atmosphere Model Inter-comparison Project) experiments, what can they tell us regarding evaporation variability? Do Reduced Observations Reanalyses (RedObs) using Surface Fluxes and Clouds (SFC) pressure (and wind) provide a more realistic picture of evaporation variability? What signals of interannual variability (e.g. El Nino/Southern Oscillation (ENSO)) and decadal variability (Interdecadal Pacific Oscillation (IPO)) are detectable with this hierarchy of evaporation estimates?

  9. Changes in interannual climate sensitivities of terrestrial carbon fluxes during the 21st century predicted by CMIP5 Earth System Models

    NASA Astrophysics Data System (ADS)

    Liu, Yongwen; Wang, Tao; Huang, Mengtian; Yao, Yitong; Ciais, Philippe; Piao, Shilong

    2016-03-01

    Terrestrial carbon fluxes are sensitive to climate change, but the interannual climate sensitivity of the land carbon cycle can also change with time. We analyzed the changes in responses of net biome production (NBP), net primary production (NPP), and heterotrophic respiration (Rh) to interannual climate variations over the 21st century in the Earth System Models (ESMs) from the Coupled Model Intercomparison Project 5. Under Representative Concentration Pathway (RCP) 4.5, interannual temperature sensitivities of NBP (γTempNBP), NPP (γTempNPP), and Rh (γTempRh) remain relatively stable at global scale, yet with large differences among ESMs and spatial heterogeneity. Modeled γTempNPP and γTempRh appear to increase in parallel in boreal regions, resulting in unchanged γTempNBP. Tropical γTempNBP decreases in most models, due to decreasing γTempNPP and relatively stable γTempRh. Across models, the changes in γTempNBP can be mainly explained by changes in γTempNPP rather than changes in γTempRh, at both global and regional scales. Interannual precipitation sensitivities of global NBP (γPrecNBP), NPP (γPrecNPP), and Rh (γPrecRh) are predicted not to change significantly, with large differences among ESMs. Across models, the changes in γPrecNBP can be mainly explained by changes in γPrecNPP rather than changes in γPrecRh in temperate regions, but not in other regions. Changes in the interannual climate sensitivities of carbon fluxes are consistent across RCPs 4.5, 6.0, and 8.5 but larger in more intensive scenarios. More effort should be considered to improve terrestrial carbon flux responses to interannual climate variability, e.g., incorporating biogeochemical processes of nutrient limitation, permafrost dynamics, and microbial decomposition.

  10. Feedback of observed interannual vegetation change: a regional climate model analysis for the West African monsoon

    NASA Astrophysics Data System (ADS)

    Klein, Cornelia; Bliefernicht, Jan; Heinzeller, Dominikus; Gessner, Ursula; Klein, Igor; Kunstmann, Harald

    2016-06-01

    West Africa is a hot spot region for land-atmosphere coupling where atmospheric conditions and convective rainfall can strongly depend on surface characteristics. To investigate the effect of natural interannual vegetation changes on the West African monsoon precipitation, we implement satellite-derived dynamical datasets for vegetation fraction (VF), albedo and leaf area index into the Weather Research and Forecasting model. Two sets of 4-member ensembles with dynamic and static land surface description are used to extract vegetation-related changes in the interannual difference between August-September 2009 and 2010. The observed vegetation patterns retain a significant long-term memory of preceding rainfall patterns of at least 2 months. The interannual vegetation changes exhibit the strongest effect on latent heat fluxes and associated surface temperatures. We find a decrease (increase) of rainy hours over regions with higher (lower) VF during the day and the opposite during the night. The probability that maximum precipitation is shifted to nighttime (daytime) over higher (lower) VF is 12 % higher than by chance. We attribute this behaviour to horizontal circulations driven by differential heating. Over more vegetated regions, the divergence of moist air together with lower sensible heat fluxes hinders the initiation of deep convection during the day. During the night, mature convective systems cause an increase in the number of rainy hours over these regions. We identify this feedback in both water- and energy-limited regions of West Africa. The inclusion of observed dynamical surface information improved the spatial distribution of modelled rainfall in the Sahel with respect to observations, illustrating the potential of satellite data as a boundary constraint for atmospheric models.

  11. Effects of Climatic Factors and Ecosystem Responses on the Inter-Annual Variability of Evapotranspiration in a Coniferous Plantation in Subtropical China

    PubMed Central

    Xu, Mingjie; Wen, Xuefa; Wang, Huimin; Zhang, Wenjiang; Dai, Xiaoqin; Song, Jie; Wang, Yidong; Fu, Xiaoli; Liu, Yunfen; Sun, Xiaomin; Yu, Guirui

    2014-01-01

    Because evapotranspiration (ET) is the second largest component of the water cycle and a critical process in terrestrial ecosystems, understanding the inter-annual variability of ET is important in the context of global climate change. Eight years of continuous eddy covariance measurements (2003–2010) in a subtropical coniferous plantation were used to investigate the impacts of climatic factors and ecosystem responses on the inter-annual variability of ET. The mean and standard deviation of annual ET for 2003–2010 were 786.9 and 103.4 mm (with a coefficient of variation of 13.1%), respectively. The inter-annual variability of ET was largely created in three periods: March, May–June, and October, which are the transition periods between seasons. A set of look-up table approaches were used to separate the sources of inter-annual variability of ET. The annual ETs were calculated by assuming that (a) both the climate and ecosystem responses among years are variable (Vcli-eco), (b) the climate is variable but the ecosystem responses are constant (Vcli), and (c) the climate is constant but ecosystem responses are variable (Veco). The ETs that were calculated under the above assumptions suggested that the inter-annual variability of ET was dominated by ecosystem responses and that there was a negative interaction between the effects of climate and ecosystem responses. These results suggested that for long-term predictions of water and energy balance in global climate change projections, the ecosystem responses must be taken into account to better constrain the uncertainties associated with estimation. PMID:24465610

  12. An Assessment of the Potential Predictability of Interannual and Decadal Variability Based on Climate Model Simulations with Specified SST

    NASA Technical Reports Server (NTRS)

    Schubert, Siegfried; Wang, Hailan; Suarez, Max; Koster, Randal

    2009-01-01

    The USCLIVAR working group on drought recently initiated a series of global climate model simulations forced with idealized SST anomaly patterns, designed to address a number of uncertainties regarding the impact of SST forcing and the role of land-atmosphere feedbacks on regional drought. The runs were done with several global atmospheric models including NASA/NSIPP-1, NCEP/GFS, GFDL/AM2, and NCAR CCM3 and CAM3.5. Here we focus on the potential predictability associated with the leading patterns of inter-annual and decadal Pacific SST variability. Specific issues addressed include the nature of the seasonality and regionality of the signal, the noise, and the signal-to-noise ratios, as well as the dependence of the results on the models.

  13. Interannual variations in spring phenology and their response to climate change across the Tibetan Plateau from 1982 to 2013

    NASA Astrophysics Data System (ADS)

    Liu, Lingling; Zhang, Xiaoyang; Donnelly, Alison; Liu, Xinjie

    2016-03-01

    Land surface phenology has been widely used to evaluate the effects of climate change on terrestrial ecosystems in recent decades. Climate warming on the Tibetan Plateau (1960-2010, 0.2 °C/decade) has been found to be greater than the global average (1951-2012, 0.12 °C/decade), which has had a significant impact on the timing of spring greenup. However, the magnitude and direction of change in spring phenology and its response to warming temperature and precipitation are currently under scientific debate. In an attempt to explore this issue further, we detected the onset of greenup based on the time series of daily two-band enhanced vegetation index (EVI2) from the advanced very high resolution radiometer (AVHRR) long-term data record (LTDR; 1982-1999) and Moderate Resolution Imaging Spectroradiometer (MODIS) Climate Modeling Grid (CMG; 2000-2013) using hybrid piecewise logistic models. Further, we examined the temporal trend in greenup onset in both individual pixels and ecoregions across the entire Tibetan Plateau over the following periods: 1982-1999, 2000-2013, and 1982-2013. The interannual variation in greenup onset was linked to the mean temperature and cumulative precipitation in the preceding month, and total precipitation during winter and spring, respectively. Finally, we investigated the relationship between interannual variation in greenup onset dates and temperature and precipitation from 1982 to 2013 at different elevational zones for different ecoregions. The results revealed no significant trend in the onset of greenup from 1982 to 2013 in more than 86 % of the Tibetan Plateau. For each study period, statistically significant earlier greenup trends were observed mainly in the eastern meadow regions while later greenup trends mainly occurred in the southwestern steppe and meadow regions both with areal coverage of less than 8 %. Although spring phenology was negatively correlated with spring temperature and precipitation in the majority of pixels

  14. Groundwater level response in U.S. Principal Aquifers to natural climate variability on interannual to multidecadal timescales

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Gurdak, J. J.; Dickinson, J.; Hanson, R. T.; Ferré, T. P. A.; Maurer, E. P.

    2014-12-01

    Natural climate variability on interannual to multidecadal timescales are important controls on precipitation, drought, evapotranspiration, streamflow, and groundwater recharge. Climate variability can also augment or diminish human stresses on water resources. Thus, understanding climate variability has particular relevance for groundwater management. Findings will be presented from a national scale study of groundwater level response to natural climate variability in principal aquifers (PAs) of the U.S., including the California Coastal Basin, Rio Grande, Coastal Lowlands, Mississippi Embayment, Floridan, and Glacial aquifer systems. We use the U.S. Geological Survey hydroclimatic analysis toolkit HydroClimATe to perform singular spectrum analysis and identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6-12 mo cycle), Pacific/North American oscillation (PNA) (<1-4 yr cycle), El Niño/Southern Oscillation (ENSO) (2-7 yr cycle), North Atlantic Oscillation (NAO) (3-6 yr cycle), Pacific Decadal Oscillation (PDO) (15-30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 yr cycle). Nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. The largest amount of variance in precipitation and groundwater levels was attributed to the PDO, accounting for more than 90% of the variance in many PAs. The next largest amount of variance in precipitation and groundwater levels was attributed to ENSO, accounting for more than 50% of the variance in many PAs. The AMO was the least frequently detected signal in all time series but accounted for as much as 95% of the variance when detected. Thus, climate variability on interannual to multidecadal timescales has a statistically significant and measurable effect on the lagged responses of

  15. The sensitivity of wood production to seasonal and interannual variations in climate in a lowland Amazonian rainforest.

    PubMed

    Rowland, Lucy; Malhi, Y; Silva-Espejo, J E; Farfán-Amézquita, F; Halladay, K; Doughty, C E; Meir, P; Phillips, O L

    2014-01-01

    Understanding climatic controls on tropical forest productivity is key to developing more reliable models for predicting how tropical biomes may respond to climate change. Currently there is no consensus on which factors control seasonal changes in tropical forest tree growth. This study reports the first comprehensive plot-level description of the seasonality of growth in a Peruvian tropical forest. We test whether seasonal and interannual variations in climate are correlated with changes in biomass increment, and whether such relationships differ among trees with different functional traits. We found that biomass increments, measured every 3 months on the two plots, were reduced by between 40 and 55% in the peak dry season (July-September) relative to peak wet season (January-March). The seasonal patterns of biomass accumulation are significantly (p < 0.01) associated with seasonal patterns of rainfall and soil water content; however, this may reflect a synchrony of seasonal cycles rather than direct physiological controls on tree growth rates. The strength of the growth seasonality response among trees is significantly correlated to functional traits: consistent with a hypothesised trade-off between maximum potential growth rate and hydraulic safety, tall and fast-growing trees with broad stems had the most strongly seasonal biomass accumulation, suggesting that they are more productive in the wet season, but more vulnerable to water limitation in the dry season. PMID:24026500

  16. Linking diurnal cycles of river flow to interannual variations in climate

    USGS Publications Warehouse

    Lundquist, Jessica D.; Dettinger, Michael D.

    2003-01-01

    Many rivers in the Western United States have diurnal variations exceeding 10% of their mean flow in the spring and summer months. The shape and timing of the diurnal cycle is influenced by an interplay of the snow, topography, vegetation, and meteorology in a basin, and the measured result differs between wet and dry years. The largest interannual differences occur during the latter half of the melt season, as the snowline retreats to the highest elevations and most shaded slopes in a basin. In most basins, during this period, the hour of peak discharge shifts to later in the day, and the relative amplitude of the diurnal cycle decreases. The magnitude and rate of these changes in the diurnal cycle vary between years and may provide clues about how long- term hydroclimatic variations affect short-term basin dynamics.

  17. Interannual variabilities in tropospheric constituents during 2000-2013 simulated in a chemistry-aerosol coupled climate model

    NASA Astrophysics Data System (ADS)

    Sudo, K.; Ito, A.

    2014-12-01

    Global distributions and abundances of tropospheric constituents (O3, CH4, NOy, CO, VOCs, NHx, SOx and aerosols) interannually change under the influences of meteorology (transport, temperature, water vapor, clouds, rain, etc.) and emissions from anthropogenic/natural sources and biomass burning. Given the importance of climate effects of these species as short-lived climate pollutants (SLCPs), there have been increasing number of studies to project future changes in individual constituents and assess impacts of emission reduction in future. Since chemistry climate model is basically used for such purpose, model validation against the observations and precise interpretation/understanding of changing processes in a model are essentially needed. In this study, we investigate interannual variability of tropospheric constituents during the years 2000 to 2013 in a chemistry-aerosol coupled climate model. The base chemical model used in this study is CHASER (Sudo et al., 2002, 2007) coupled with the aerosol model SPRINTARS (Takemura et al., 2006). The CHASER model, also developed in the framework of the MIROC earth system model (MIROC-ESM-CHEM), simulates detailed chemistry in the troposphere and stratosphere with an on-line aerosol simulation including production of particulate nitrate and SOA. We use the NCEP reanalysis data (FNL) for constraining the model's meteorology. Anthropogenic and biomass burning emissions are specified using the HTAP2 and MAC inventories, respectively. For biogenic VOCs emissions, we employ calculation by the land ecosystem/trace gas emission model VISIT (Ito et al., 2008). Our results show that temporal variability (anomaly) in surface and lower tropospheric ozone very clearly correlates with that in CO especially in NH, indicating principal importance of biomass burning emission in determining near-surface O3 variability; surface PM (PM2.5) in NH also coincides with CO. Changes in middle to upper tropospheric O3, on the other hand

  18. Understanding the influence of global scale climate modes on inter-annual variability of African precipitation using CMIP5 simulations

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, P. S.; Zaitchik, B.

    2013-12-01

    Continental Africa is characterized by considerable spatio-temporal variability of precipitation, which is associated with extreme events such as droughts and floods, that have serious impacts on environment, economy and society. Such variability in precipitation distribution, both in temporal and spatial scale, exerts a profound influence on local and regional water budget and on human and natural systems sensitive to climate variations at timescales of seasons to decades. The present study aims to quantify the large-scale processes that drive rainfall variability over Africa at seasonal and inter-annual timescales. We examine how well these processes are represented in the present generation of climate models for historical conditions and examine projection for mid-21st century. Ten coupled models in Climate Model Intercomparison Project (CMIP5) along with observational datasets of precipitation (Climate Research Unit (CRU)) and Reynolds sea surface temperature (SST) analysis are used to study and compare annual and seasonal variation of precipitation over Africa (between 1960-2005 time period). Principal component and correlation analysis performed on observational datasets show that El Niño/Southern Oscillation (ENSO) variability and global SST have a dominant impact on rainfall variability over Africa. As expected, models performing in CMIP5 vary greatly in their representation of SST variability, including that related to ENSO, as well as in the strength of association between SST variability and precipitation over various regions of Africa. Some models resemble the observed relationships while others associate African precipitation variability with other remote drivers. Under future conditions (RCP8.5 scenario, averaged between 2060-2099), some models project a maintenance or intensification of current associations while others project nonstationary change. We consider the implications of this diversity for climate impact studies and future model

  19. Spectral Kernel Approach to Study Radiative Response of Climate Variables and Interannual Variability of Reflected Solar Spectrum

    NASA Technical Reports Server (NTRS)

    Jin, Zhonghai; Wielicki, Bruce A.; Loukachine, Constantin; Charlock, Thomas P.; Young, David; Noeel, Stefan

    2011-01-01

    The radiative kernel approach provides a simple way to separate the radiative response to different climate parameters and to decompose the feedback into radiative and climate response components. Using CERES/MODIS/Geostationary data, we calculated and analyzed the solar spectral reflectance kernels for various climate parameters on zonal, regional, and global spatial scales. The kernel linearity is tested. Errors in the kernel due to nonlinearity can vary strongly depending on climate parameter, wavelength, surface, and solar elevation; they are large in some absorption bands for some parameters but are negligible in most conditions. The spectral kernels are used to calculate the radiative responses to different climate parameter changes in different latitudes. The results show that the radiative response in high latitudes is sensitive to the coverage of snow and sea ice. The radiative response in low latitudes is contributed mainly by cloud property changes, especially cloud fraction and optical depth. The large cloud height effect is confined to absorption bands, while the cloud particle size effect is found mainly in the near infrared. The kernel approach, which is based on calculations using CERES retrievals, is then tested by direct comparison with spectral measurements from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) (a different instrument on a different spacecraft). The monthly mean interannual variability of spectral reflectance based on the kernel technique is consistent with satellite observations over the ocean, but not over land, where both model and data have large uncertainty. RMS errors in kernel ]derived monthly global mean reflectance over the ocean compared to observations are about 0.001, and the sampling error is likely a major component.

  20. Using Decision Trees to Examine Relationships between Inter-Annual Vegetation Variability, Topographic Attributes, and Climate Signals

    NASA Astrophysics Data System (ADS)

    White, A. B.; Kumar, P.

    2003-12-01

    The objective of this research is to develop KDD (knowledge discovery in databases) techniques for spatio-temporal geo-data, and use these techniques to examine inter-annual vegetation health signals. The underlying hypothesis of the research is that the signatures of inter-annual variability of climate on vegetation dynamics as represented by the statistical descriptors of vegetation index variations depend upon a variety of attributes related to the topography, hydrology, physiography, and climate. NDVI (normalized differential vegetation index) is enlisted to represent vegetation health and relationships between this index and topographic attributes such as elevation, slope, aspect, compound topographic index (CTI), and the proximity to a stream, are analyzed. Several scientific questions related to the identification and characterization of the inter-annual variability ensue as a consequence of our hypothesis. Investigations were performed using 13 years of 1-km resolution NDVI data from the AVHRR instrument on NOAA's POES (polar-orbiting operational environmental satellite) over the continental U.S. Various temporal change indices were used in order to identify anomalous inter-annual behavior in the NDVI index, including maximum absolute and relative deviations from the 13-year mean and positive and negative persistence indices (after Zhou et al., 2001). The KDD technique used in this research is the decision tree, which falls under the classification and prediction division of data mining techniques. The algorithm is similar to c4.5 and id3, but can handle continuous input and output values without binning and is optimized to determine the minimum error. Future work will incorporate clustering algorithms (both distance and density-based) and association rule algorithms (constraint-based) adapted for spatial-temporal data. Investigations will also be performed at smaller spatial scales, integrating higher resolution data. Throughout the growing season

  1. Fluorscence signatures of dissolved organic material in an alpine lake ecosystem: responses to interannual climate variation and nutrient cycling

    NASA Astrophysics Data System (ADS)

    McKnight, Diane; Olivier, Matt; Hell, Katherina

    2016-04-01

    During snowmelt alpine lakes receive lower concentrations of dissolved organic material (DOM) that originates from the surrounding watershed than sub-alpine and montane lakes at lower elevations. Alpine lakes also have a shorter ice-free period that constrains the summer season of phytoplankton growth. Nonetheless, previous study of the reactive transport and production of DOM in an alpine lake in the Colorado Front Range during snowmelt and the summer ice-free season has shown that changes in DOM sources and the influence of biogeochemical processes can be resolved using fluorescence spectroscopy. Here we examine inter-annual variations in DOM fluorescence signatures during the snowmelt and summer periods in comparison to records of climate, residence time and primary production in the lake during the summer. Our analysis shows that variation in chlorophyll a concentration is a driver for variations in the fluorescence index (FI), as well as for specific ultra-violet absorbance. This result supports the predictions from the previous reactive transport modeling. We also conducted mesocosm experiments with nutrient enrichment to explore the role of nitrogen and phosphorus availability in influencing the fluorescence signature of DOM in summer. These results suggest that monitoring of simple spectroscopic properties of DOM can provide a means to track the biogeochemical consequences for alpine lakes of "too much" summer as climate continues to change.

  2. Identifying driving climate factors of wheat and maize yields inter-annual variability in France

    NASA Astrophysics Data System (ADS)

    Ceglar, Andrej; Toreti, Andrea; Lecerf, Remi; Dentener, Frank J.

    2015-04-01

    A canonical powered Partial Least Squares Regression (PLSR) approach is here used to estimate the relationship between meteorological variables and crop (durum wheat and grain maize) yield time series over France. This method combines the advantages of both the Canonical Correlation Analysis (CCA) and the PLSR. The latter is mainly based on the extraction of a subset of latent variables (having the best predictive power) from the full set of predictors. The method is applied to detrended (by using a LOESS approach) time series of crop yields and monthly mean temperature, cumulated precipitation and global solar radiation during the growing seasons from 1990 to 2011. Results show that, overall, temperature has a substantial influence on winter wheat yields in south-western and eastern France, while rainfall plays an important role in the northern and southern parts of the country. Finally, radiation is more important over the southern part of France. Concerning grain maize, the inferred statistical models show relatively low skill over the northern part of France, where inter-annual yield variability is low. Overall, results show that temperature is the most important variable influencing grain maize yields over the southern and eastern parts of France, while rainfall is more important in the central and northern parts of the country. Finally, global radiation is the main meteorological factor over the westernmost part of France.

  3. Dust interannual variability and trend in Central Asia from 2000 to 2014 and their climatic linkages

    NASA Astrophysics Data System (ADS)

    Xi, Xin; Sokolik, Irina N.

    2015-12-01

    We present a comprehensive analysis of the interannual variability and trend of dust aerosol in Central Asia (37°-55°N, 50°-80°E) from 2000 to 2014, based on a set of dust emission simulations using the WRF-Chem-DuMo modeling system, observations of dust frequency derived from surface station synoptic weather records, and dust optical depth (DOD) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) aerosol optical depth (AOD) products. Model simulations reveal that the soil grain size distribution has little impact on the interannual variability of dust fluxes but strongly affects their magnitude. The two physically based dust schemes based on Marticorena and Bergametti (1995) (MB) and Shao et al. (1996) (Shao) produce large differences in the dust flux magnitude and spatiotemporal distributions, largely due to different sensitivities of the threshold friction velocity to vegetation-induced surface roughness. By using a fixed threshold velocity, the dust scheme of Tegen and Fung (1995) (TF) relies on the dynamic dust source function to capture the dust variability associated with vegetation changes. Through a correlation analysis, the simulated dust fluxes show good consistency with the observed dust frequency, whereas only the Shao and TF dust fluxes are consistent with the MODIS Collection 5.1 and SeaWiFS DOD. The dust fluxes, dust frequency, and DOD (except MODIS Collection 6) are highly correlated with the frequency of strong surface winds but show different sensitivities to drought and soil erodibility factors (i.e., precipitation, soil moisture, and vegetation) which are influenced by El Niño-Southern Oscillation (ENSO). In general, La Niña years are associated with reduced precipitation, drier soils, less vegetation, and, consequently, more severe drought and enhanced dust activity in Central Asia. The averaged dust flux of the MB and Shao experiments shows a significant negative trend

  4. The Role of Lightning in Controlling Interannual Variability of Tropical Tropospheric Ozone and OH and its Implications for Climate

    NASA Technical Reports Server (NTRS)

    Murray, Lee T.; Jacob, Daniel J.; Logan, Jennifer A.; Hudman, Rynda C.; Koshak, William J.

    2012-01-01

    Nitrogen oxides (NO(x) = NO + NO2) produced by lightning make a major contribution to the production of the dominant tropospheric oxidants (OH and ozone). These oxidants control the lifetime of many trace gases including long-lived greenhouse gases, and control the source-receptor relationship of inter-hemispheric pollutant transport. Lightning is affected by meteorological variability, and therefore represents a potentially important tropospheric chemistry-climate feedback. Understanding how interannual variability (IAV) in lightning affects IAV in ozone and OH in the recent past is important if we are to predict how oxidant levels may change in a future warmer climate. However, lightning parameterizations for chemical transport models (CTMs) show low skill in reproducing even climatological distributions of flash rates from the Lightning Imaging Sensor (LIS) and the Optical Transient Detector (OTD) satellite instruments. We present an optimized regional scaling algorithm for CTMs that enables sufficient sampling of spatiotemporally sparse satellite lightning data from LIS to constrain the spatial, seasonal, and interannual variability of tropical lightning. We construct a monthly time series of lightning flash rates for 1998-2010 and 35degS-35degN, and find a correlation of IAV in total tropical lightning with El Nino. We use the IAV-constraint to drive a 9-year hindcast (1998-2006) of the GEOS-Chem 3D chemical transport model, and find the increased IAV in LNO(x) drives increased IAV in ozone and OH, improving the model fs ability to simulate both. Although lightning contributes more than any other emission source to IAV in ozone, we find ozone more sensitive to meteorology, particularly convective transport. However, we find IAV in OH to be highly sensitive to lightning NO(x), and the constraint improves the ability of the model to capture the temporal behavior of OH anomalies inferred from observations of methyl chloroform and other gases. The sensitivity of

  5. ASSESSING IMPACT OF SEASONAL AND INTERANNUAL CLIMATE VARIATIONS USING CLIGEN AND WEPP MODELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Physically based response models are useful tools for assessing impacts of climate variations on hydrological and plant growth processes. Most response models require daily weather, which is often synthesized using stochastic daily weather generators. The objectives were to evaluate the ability of...

  6. Assessing Interannual Variation in Growth Response of Big Sagebrush to Climate in Spring Valley, NV

    NASA Astrophysics Data System (ADS)

    Apodaca, L. F.; Devitt, D.; Fenstermaker, L.

    2012-12-01

    An assessment of the growth response of key vegetative species to climatic variability is vital to understanding possible impacts on ecosystems threatened by impending hydrologic change. Big sagebrush (Artemisia tridentata) communities in Spring Valley, NV are predicted to experience changes in water availability brought about by climate change that could result in widespread shifts in community composition, ecotonal boundaries, and plant phenology. The degree and direction of the growth response of sagebrush species to these changes is of great interest to land managers as a decline in growth and plant vigor has implications on the long-term trajectories for community biodiversity and wildfire management practices. To evaluate growth response to past climate variability, an empirical relationship between sagebrush growth ring indices and satellite-derived vegetation indices (NDVI) was examined in the context of historical precipitation. Ring indices were constructed using over one hundred stem cross-sections sampled from thirty-six sagebrush stands located throughout the large, spatially heterogenous 900 km2 Spring Valley study area. Growing season NDVI values were extracted from Landsat scenes collected between 1986 and 2010. Sagebrush early and late wood indices were also compared to seasonal precipitation records in order to examine both the progression of wood development throughout the growing season and the seasonal contribution of spring and summer precipitation to wood growth. The results will allow for a more comprehensive assessment of past vegetative response to climate variation, both temporally and spatially, which can be used in the modeling of growth of an important desert species.

  7. Monitoring climate-driven interannual variability of European Larch phenology in an alpine environment: results of the REPHLEX project

    NASA Astrophysics Data System (ADS)

    Busetto, L.; Migliavacca, M.; Cremonese, E.; Colombo, R.; Galvagno, M.; Morra di Cella, U.; Pari, E.; Siniscalco, C.

    2009-04-01

    In this contribute we present the results of the REPHLEX experiment (REmote sensing of PHenology Larix Experiment), conducted by the Environmental Dynamics Remote Sensing Laboratory of the University of Milano-Bicocca, by the Regional Protection Agency of the Aosta Valley and by Vegetation Biology Department of the University of Torino. The project was aimed at developing appropriate techniques for monitoring the interannual variability of European Larch (Larix decidua Mill.) phenological cycle in the Alpine region of Valle d'Aosta (Northern Italy), and to evaluate its relationships with environmental and climatic drivers. This was achieved by combining field observations, phenological models and satellite remote sensing. Phenological field observations were weekly conducted in 8 test sites during 2005, 2006 and 2007 in order to determine the dates of completion of different phenological phases of the analyzed Larch stands. MODIS 250 16-days composite NDVI data (Product MOD13Q1 - v005) acquired from TERRA platform for the 2000-2007 time period were used to estimate budburst and senescence dates, as well as the length of the growing season. With this aim, NDVI time series were fitted with a double logistic curve, and the dates corresponding to different characteristic points of the curve (maximum of the first derivative and zeroes of the third and fourth derivative) were determined. The comparison between MODIS estimated dates and field data showed that the points of the fitted NDVI curve that allow to better estimate larch phenological dates are the zeroes of its third derivative, which allowed to estimate the start and the end of the growing season with Mean Absolute Errors (MAE) of about 6 and 4 days, respectively. This result is particularly significant since to our knowledge these inflection points have never been used for the estimation of phenological dates in previous studies. Start and end of season were also estimated by applying the Spring Warming and the

  8. Climate Variability and Oceanographic Settings Associated with Interannual Variability in the Initiation of Dinophysis acuminata Blooms

    PubMed Central

    Díaz, Patricio A.; Reguera, Beatriz; Ruiz-Villarreal, Manuel; Pazos, Yolanda; Velo-Suárez, Lourdes; Berger, Henrick; Sourisseau, Marc

    2013-01-01

    In 2012, there were exceptional blooms of D. acuminata in early spring in what appeared to be a mesoscale event affecting Western Iberia and the Bay of Biscay. The objective of this work was to identify common climatic patterns to explain the observed anomalies in two important aquaculture sites, the Galician Rías Baixas (NW Spain) and Arcachon Bay (SW France). Here, we examine climate variability through physical-biological couplings, Sea Surface Temperature (SST) anomalies and time of initiation of the upwelling season and its intensity over several decades. In 2012, the mesoscale features common to the two sites were positive anomalies in SST and unusual wind patterns. These led to an atypical predominance of upwelling in winter in the Galician Rías, and increased haline stratification associated with a southward advection of the Gironde plume in Arcachon Bay. Both scenarios promoted an early phytoplankton growth season and increased stability that enhanced D. acuminata growth. Therefore, a common climate anomaly caused exceptional blooms of D. acuminata in two distant regions through different triggering mechanisms. These results increase our capability to predict intense diarrhetic shellfish poisoning outbreaks in the early spring from observations in the preceding winter. PMID:23959151

  9. Remote sensing of interannual boreal forest NDVI in relation to climatic conditions in interior Alaska

    NASA Astrophysics Data System (ADS)

    Verbyla, David

    2015-12-01

    Climate has warmed substantially in interior Alaska and several remote sensing studies have documented a decadal-scale decline in the normalized difference vegetation index (NDVI) termed a ‘browning trend’. Reduced summer soil moisture due to changing climatic factors such as earlier springs, less snowpack, and summer drought may reduce boreal productivity and NDVI. However, the relative importance of these climatic factors is poorly understood in boreal interior Alaska. In this study, I used the remotely sensed peak summer NDVI as an index of boreal productivity at 250 m pixel size from 2000 to 2014. Maximum summer NDVI was related to last day of spring snow, early spring snow water equivalent (SWE), and a summer moisture index. There was no significant correlation between early spring SWE and peak summer NDVI. There was a significant correlation between the last day of spring snow and peak summer NDVI, but only for a few higher elevation stations. This was likely due to snowmelt occurring later at higher elevations, thus having a greater effect on summer soil moisture relative to lower elevation sites. For most of boreal interior Alaska, summer drought was likely the dominant control on peak summer NDVI and this effect may persist for several years. Peak summer NDVI declined at all 26 stations after the 2004 drought, and the decline persisted for 2 years at all stations. Due to the shallow rooting zone of most boreal plants, even cool and moist sites at lower elevations are likely vulnerable to drought. For example the peak summer NDVI response following the 2004 drought was similar for adjacent cold and warm watershed basins. Thus, if frequent and severe summer droughts continue, moisture stress effects are likely to be widespread and prolonged throughout most of interior boreal Alaska, including relatively cool, moist sites regardless of spring snowpack conditions or spring phenology.

  10. Evaluating Antarctic sea ice predictability at seasonal to interannual timescales in global climate models

    NASA Astrophysics Data System (ADS)

    Marchi, Sylvain; Fichefet, Thierry; Goosse, Hugues; Zunz, Violette; Tietsche, Steffen; Day, Jonny; Hawkins, Ed

    2016-04-01

    Unlike the rapid sea ice losses reported in the Arctic, satellite observations show an overall increase in Antarctic sea ice extent over recent decades. Although many processes have already been suggested to explain this positive trend, it remains the subject of current investigations. Understanding the evolution of the Antarctic sea ice turns out to be more complicated than for the Arctic for two reasons: the lack of observations and the well-known biases of climate models in the Southern Ocean. Irrespective of those issues, another one is to determine whether the positive trend in sea ice extent would have been predictable if adequate observations and models were available some decades ago. This study of Antarctic sea ice predictability is carried out using 6 global climate models (HadGEM1.2, MPI-ESM-LR, GFDL CM3, EC-Earth V2, MIROC 5.2 and ECHAM 6-FESOM) which are all part of the APPOSITE project. These models are used to perform hindcast simulations in a perfect model approach. The predictive skill is estimated thanks to the PPP (Potential Prognostic Predictability) and the ACC (Anomaly Correlation Coefficient). The former is a measure of the uncertainty of the ensemble while the latter assesses the accuracy of the prediction. These two indicators are applied to different variables related to sea ice, in particular the total sea ice extent and the ice edge location. This first model intercomparison study about sea ice predictability in the Southern Ocean aims at giving a general overview of Antarctic sea ice predictability in current global climate models.

  11. Sensitivity of global tropical climate to land surface processes: Mean state and interannual variability

    SciTech Connect

    Ma, Hsi-Yen; Xiao, Heng; Mechoso, C. R.; Xue, Yongkang

    2013-03-01

    This study examines the sensitivity of global tropical climate to land surface processes (LSP) using an atmospheric general circulation model both uncoupled (with prescribed SSTs) and coupled to an oceanic general circulation model. The emphasis is on the interactive soil moisture and vegetation biophysical processes, which have first order influence on the surface energy and water budgets. The sensitivity to those processes is represented by the differences between model simulations, in which two land surface schemes are considered: 1) a simple land scheme that specifies surface albedo and soil moisture availability, and 2) the Simplified Simple Biosphere Model (SSiB), which allows for consideration of interactive soil moisture and vegetation biophysical process. Observational datasets are also employed to assess the reality of model-revealed sensitivity. The mean state sensitivity to different LSP is stronger in the coupled mode, especially in the tropical Pacific. Furthermore, seasonal cycle of SSTs in the equatorial Pacific, as well as ENSO frequency, amplitude, and locking to the seasonal cycle of SSTs are significantly modified and more realistic with SSiB. This outstanding sensitivity of the atmosphere-ocean system develops through changes in the intensity of equatorial Pacific trades modified by convection over land. Our results further demonstrate that the direct impact of land-atmosphere interactions on the tropical climate is modified by feedbacks associated with perturbed oceanic conditions ("indirect effect" of LSP). The magnitude of such indirect effect is strong enough to suggest that comprehensive studies on the importance of LSP on the global climate have to be made in a system that allows for atmosphere-ocean interactions.

  12. Seasonal and Interannual Trends in Largest Cholera Endemic Megacity: Water Sustainability - Climate - Health Challenges in Dhaka, Bangladesh

    NASA Astrophysics Data System (ADS)

    Akanda, Ali S.; Jutla, Antarpreet; Faruque, Abu S. G.; Huq, Anwar; Colwell, Rita R.

    2014-05-01

    The last three decades of surveillance data shows a drastic increase of cholera prevalence in the largest cholera-endemic city in the world - Dhaka, Bangladesh. Emerging megacities in the region, especially those located in coastal areas also remain vulnerable to large scale drivers of cholera outbreaks. However, there has not been any systematic study on linking long-term disease trends with related changes in natural or societal variables. Here, we analyze the 30-year dynamics of urban cholera prevalence in Dhaka with changes in climatic or anthropogenic forcings: regional hydrology, flooding, water usage, changes in distribution systems, population growth and density in urban settlements, as well as shifting climate patterns and frequency of natural disasters. An interesting change is observed in the seasonal trends of cholera prevalence; while an endemic upward trend is seen in the dry season, the post-monsoon trend is epidemic in nature. In addition, the trend in the pre-monsoon dry season is significantly stronger than the post-monsoon wet season; and thus spring is becoming the dominant cholera season of the year. Evidence points to growing urbanization and rising population in unplanned settlements along the city peripheries. The rapid pressure of growth has led to an unsustainable and potentially disastrous situation with negligible-to-poor water and sanitation systems compounded by changing climatic patterns and increasing number of extreme weather events. Growing water scarcity in the dry season and lack of sustainable water and sanitation infrastructure for urban settlements have increased endemicity of cholera outbreaks in spring, while record flood events and prolonged post-monsoon inundation have contributed to increased epidemic outbreaks in fall. We analyze our findings with the World Health Organization recommended guidelines and investigate large scale water sustainability challenges in the context of climatic and anthropogenic changes in the

  13. Climate and socioeconomic influences on interannual variability of cholera in Nigeria.

    PubMed

    Leckebusch, Gregor C; Abdussalam, Auwal F

    2015-07-01

    Cholera is one of the most important climate sensitive diseases in Nigeria that pose a threat to public health because of its fatality and endemic nature. This study aims to investigate the influences of meteorological and socioeconomic factors on the spatiotemporal variability of cholera morbidity and mortality in Nigeria. Stepwise multiple regression and generalised additive models were fitted for individual states as well as for three groups of the states based on annual precipitation. Different meteorological variables were analysed, taking into account socioeconomic factors that are potentially enhancing vulnerability (e.g. absolute poverty, adult literacy, access to pipe borne water). Results quantify the influence of both climate and socioeconomic variables in explaining the spatial and temporal variability of the disease incidence and mortality. Regional importance of different factors is revealed, which will allow further insight into the disease dynamics. Additionally, cross validated models suggest a strong possibility of disease prediction, which will help authorities to put effective control measures in place which depend on prevention, and or efficient response. PMID:25997026

  14. Effects of Interannual Climate Variability in Secondary Forests and Crops Under Traditional and Alternative Shifting Cultivation

    NASA Astrophysics Data System (ADS)

    Sa, T. D.; Guild, L. S.; Carvalho, C. J.; Potter, C. S.; Wickel, A. J.; Brienza, S.; Kato, M. A.; Kato, O.

    2002-12-01

    Regenerating forests play an important role in long-term carbon sequestration and sustainable landuse as they act as potentially important carbon and nutrient sinks during the shifting agriculture fallow period. The long-term functioning of secondary forests (capoeira) is increasingly threatened by a shortening fallow period during shifting cultivation due to demographic pressures and associated increased vulnerability to severe climatic events. Declining productivity and functioning of fallow forests of shifting cultivation combined with progressive loss of nutrients by successive burning and cropping activities has resulted in declining agricultural productivity. In addition to the effects of intense land use practices, droughts associated with El Ni¤o events are becoming more frequent and severe in moist tropical forests and negative effects on capoeira productivity could be considerable. In Igarape-Acu (near Belem, Para), we hypothesize that experimental alternative landuse/clearing practices (mulching and fallow vegetation improvement by planting with fast-growing leguminous tree species) may make capoeira and crops more resilient to the effects of agricultural pressures and drought through 1) increased biomass, soil organic matter and associated increase in soil water storage, and nutrient retention and 2) greater rooting depth of trees planted for fallow improvement. This experimental practice (mechanized chop-and-mulch with fallow improvement) has resulted in increased soil moisture during the cropping phase, reduced loss of nutrients and organic matter, and higher rates of secondary-forest biomass accumulation. We present preliminary data on water relations during the dry season of 2001 in capoeira and crops for both traditional slash-and-burn and alternative chop-and-mulch practices. These data will be used to test IKONOS data for the detection of moisture status differences. The principal goal of the research is to determine the extent to which capoeira

  15. Integrating interannual climate variability forecasts into weather-indexed crop insurance. The case of Malawi, Kenya and Tanzania

    NASA Astrophysics Data System (ADS)

    Vicarelli, M.; Giannini, A.; Osgood, D.

    2009-12-01

    possible payouts using historical precipitation data and analyzed the differences between years with different ENSO states from 1961 to 2005; (ii) we applied Monte Carlo methods to simulate precipitation distributions in each location and calculated the mean and variance of payouts associated to different ENSO states. The results obtained from historical precipitation data indicate that more abundant rainfall reduces payouts and the risk of loan default during La Niña in southern Kenya and Malawi, during El Niño in Tanzania. The results of the Monte Carlo simulations confirm our findings. Our results suggest that re-insurance schemes could be successfully designed to exploit the anti-correlation patterns related to interannual climate variability for different regions in Africa. Moreover, the exploratory framework presented can potentially be refined applied to other regions (e.g. Central and Latin America).

  16. Evaluating Inter-Annual Climate Variability of Nitrogen Wet Deposition in the United States Using Wavelet Analysis

    NASA Astrophysics Data System (ADS)

    Nergui, T.; Thomas, N.; Liu, M.; Lamb, B. K.; Adam, J. C.; Chung, S. H.

    2012-12-01

    Human activities, primarily agricultural practices and fossil fuel combustion, have caused a significant increase in nitrogen (N) emissions into the atmosphere over the last 150 years. The increase in emission subsequently leads to elevated ozone concentration, haze, increased acid rain and N deposition at local and regional scales. Many ecosystems in the US are naturally N limited. These regions are highly vulnerable to increased N deposition which can lead to irreversible changes in biodiversity richness and composition of the ecosystems. Through the impact on atmospheric chemistry and scavenging by precipitation, climate variability can play a major role on N deposition rates. The El Niño/Southern Oscillation (ENSO), Northern Annular Mode/Arctic Oscillation (NAM/AO), North Atlantic Oscillation (NAO), and the Pacific-North American Pattern (PNA) indices are the key climate indices that characterize the climate in the contiguous US at inter-annual timescale. Here, we identify dominant periodic components (signal) in the N wet deposition and the climate index timeseries and examine their correlations and coherences using wavelet analysis. Seasonal precipitation and nitrogen (ammonium and nitrate) wet deposition data from the National Atmospheric Deposition Program (NADP), National Trends Network (NTN) for 87 sites across the United States are used for the study. The sites were selected based on data continuity of 21 years or more and NADP criteria for valid precipitation and wet deposition data. Precipitation data from the Parameter-elevation Regressions on Independent Slopes Model (PRISM) are also used to replicate and validate the general features of climate variability effects in different regions of US. Initial analysis reveals nitrate wet deposition has a dominant 1-4 year periodicity while ammonium wet deposition has a shorter periodicity (about 0.5-2 year) during 1979 to 2011. Precipitation and total N wet deposition are most correlated in the Great Plains

  17. Recent, unprecedented, arctic ozone losses: climate change or large interannual variability?

    NASA Astrophysics Data System (ADS)

    Rieder, H. E.; Polvani, L. M.

    2012-04-01

    The record ozone loss over the Arctic in the spring of 2011 [e.g., Manney et al., 2011] highlights the importance of a detailed understanding of the connection between cold polar temperatures, polar stratospheric clouds (PSCs) and column ozone. Several studies have analyzed the empirical relationship between PSC volume (Vpsc) and ozone loss in the Arctic [e.g., Rex et al., 2006], and put forward the hypothesis that the coldest Arctic winters are getting colder and therefore anomalous ozone losses in the Arctic are likely to increase in the coming decades. In the present study we analyze trends and variability in polar temperatures, Vpsc and column ozone, using both reanalysis products (ERA40, MERRA) and numerical model output (from selected models participating in the Chemistry-Climate Model Validation Activity). Beyond considering mean values, we employ a variety of statistical measures for extremes (i.e., high quantiles) in order to identify possible changes in the frequency distribution of polar temperatures and Vpsc, and attempt to determine whether the recent occurrences of record ozone loss are indicative of statistically significant trends or simply a reflection of large natural variability.

  18. Climate and Developmental Plasticity: Interannual Variability in Grapevine Leaf Morphology1[OPEN

    PubMed Central

    Li, Darren Y.; Woodford, Quaneisha L.; Yu, Tommy T.

    2016-01-01

    The shapes of leaves are dynamic, changing over evolutionary time between species, within a single plant producing different shaped leaves at successive nodes, during the development of a single leaf as it allometrically expands, and in response to the environment. Notably, strong correlations between the dissection and size of leaves with temperature and precipitation exist in both the paleorecord and extant populations. Yet, a morphometric model integrating evolutionary, developmental, and environmental effects on leaf shape is lacking. Here, we continue a morphometric analysis of >5,500 leaves representing 270 grapevines of multiple Vitis species between two growing seasons. Leaves are paired one-to-one and vine-to-vine accounting for developmental context, between growing seasons. Linear discriminant analysis reveals shape features that specifically define growing season, regardless of species or developmental context. The shape feature, a more pronounced distal sinus, is associated with the colder, drier growing season, consistent with patterns observed in the paleorecord. We discuss the implications of such plasticity in a long-lived woody perennial, such as grapevine (Vitis spp.), with respect to the evolution and functionality of plant morphology and changes in climate. PMID:26826220

  19. Sensitivity of stream flow droughts, water shortage and water stress events to ENSO driven inter-annual climate variability at the global scale

    NASA Astrophysics Data System (ADS)

    Veldkamp, Ted I. E.; Aerts, Jeroen C. J. H.; Ward, Philip J.

    2014-05-01

    Governments and institutions managing water resources have to adapt constantly to regional drought, water shortage and water stress conditions, being caused by climate change, socio-economic developments and/or climate variability. Taking into account the impact of climate variability is important as in some regions it may outweigh long-term climate change or socio-economic developments, especially on a time scale of a few years up to a few decades. As governments and water management institutions apply planning horizons up to a decade with respect to management of adaptation strategies, inter-annual climate variability is especially relevant. A number of studies have estimated the impacts of climate variability on stream flow droughts on a local, continental or global scale. Others have focused on the role of long term climate change and socio-economic trends on blue water availability, shortage and stress. However, a global assessment of the influence of inter-annual climate variability on stream flow droughts, blue water availability, shortage and stress together has not yet been carried out, despite its importance for adaptation planning. To address this issue, we assessed the influence of ENSO-driven climate variability on stream flow droughts, blue water availability, and shortage and stress events at the global scale. Within this contribution we focused on El Nino Southern Oscillation's (ENSO) impact as ENSO is the most dominant source of inter-annual climate variability, impacting climate and society. We carried out this assessment through the following steps: (1) used daily discharge and run-off time-series (0.5º x 0.5º) of three WATCH forced global hydrological models (WaterGAP, PCR-GLOBWB, and STREAM); (2) in combination with time-series of population counts and monthly water demands we calculated monthly and yearly stream flow drought, water availability, water shortage and water stress per Food Producing Unit (FPU) for the period 1960-2000; and (3

  20. Climate and the Individual: Inter-Annual Variation in the Autumnal Activity of the European Badger (Meles meles)

    PubMed Central

    Noonan, Michael J.; Markham, Andrew; Newman, Chris; Trigoni, Niki; Buesching, Christina D.; Ellwood, Stephen A.; Macdonald, David W.

    2014-01-01

    We establish intra-individual and inter-annual variability in European badger (Meles meles) autumnal nightly activity in relation to fine-scale climatic variables, using tri-axial accelerometry. This contributes further to understanding of causality in the established interaction between weather conditions and population dynamics in this species. Modelling found that measures of daylight, rain/humidity, and soil temperature were the most supported predictors of ACTIVITY, in both years studied. In 2010, the drier year, the most supported model included the SOLAR*RH interaction, RAIN, and30cmTEMP (w = 0.557), while in 2012, a wetter year, the most supported model included the SOLAR*RH interaction, and the RAIN*10cmTEMP (w = 0.999). ACTIVITY also differed significantly between individuals. In the 2012 autumn study period, badgers with the longest per noctem activity subsequently exhibited higher Body Condition Indices (BCI) when recaptured. In contrast, under drier 2010 conditions, badgers in good BCI engaged in less per noctem activity, while badgers with poor BCI were the most active. When compared on the same calendar dates, to control for night length, duration of mean badger nightly activity was longer (9.5 hrs ±3.3 SE) in 2010 than in 2012 (8.3 hrs ±1.9 SE). In the wetter year, increasing nightly activity was associated with net-positive energetic gains (from BCI), likely due to better foraging conditions. In a drier year, with greater potential for net-negative energy returns, individual nutritional state proved crucial in modifying activity regimes; thus we emphasise how a ‘one size fits all’ approach should not be applied to ecological responses. PMID:24465376

  1. O the Interannual Variability of South American Climate and the Southern Oscillation.

    NASA Astrophysics Data System (ADS)

    Aceituno, Patricio

    The functioning of the Southern Oscillation (SO) over South America and the surrounding tropical Atlantic and Eastern Pacific Oceans is studied through analyses of SO-related anomalies in various surface and upper-air fields which reveal the three-dimensional characteristics of the SO in this region. Correlation analyses are complemented by case studies of extreme episodes during the negative and positive SO phases (defined as positive by anomalously high/low pressure at Tahiti/Darwin). Most pronounced is the anomalously low pressure and high SST over the Eastern Pacific during the negative SO phase. The perennially positive SO-pressure correlations over the tropical Eastern Pacific extend eastward into the North Atlantic and Southern South America during the respective winter semester. The anomalously warm waters in the tropical Eastern Pacific during the negative SO phase are consistent with positive 500 and 200 mb departures over the tropics indicating a relatively warm troposphere. During austral winter anomalously abundant rainfall in Central Chile during the negative SO phase appears related to a weak and northward displaced South Pacific subtropical high and enhanced upper-air westerlies. By contrast, relatively dry conditions prevail in the northwestern portion of the continent. These seem related to a southward displaced near-equatorial trough, concomitant with enhanced pressure over the Caribbean. During the austral summer, SO-related climate anomalies grow most pronounced, particularly conspicuous being the following three anomaly regimes of the negative SO phase. (i) The excessive rainfall along the Ecuador -Peru littoral and the adjacent open equatorial Pacific is consistent with an intensified and southward displaced near-equatorial trough. (ii) In the tropical North Atlantic during the latter part of the austral summer, the near -equatorial trough is displaced northward, the meridional pressure gradient is reduced, the Northeast trades are weak, the

  2. Use of the HadGEM2 climate-chemistry model to investigate interannual variability in methane sources

    NASA Astrophysics Data System (ADS)

    Hayman, Garry; O'Connor, Fiona; Clark, Douglas; Huntingford, Chris; Gedney, Nicola

    2013-04-01

    The global mean atmospheric concentration of methane (CH4) has more than doubled during the industrial era [1] and now constitutes ? 20% of the anthropogenic climate forcing by greenhouse gases [2]. The globally-averaged CH4 growth rate, derived from surface measurements, has fallen significantly from a high of 16 ppb yr-1 in the late 1970s/early 1980s and was close to zero between 1999 and 2006 [1]. This overall period of declining or low growth was however interspersed with years of positive growth-rate anomalies (e.g., in 1991-1992, 1998-1999 and 2002-2003). Since 2007, renewed growth has been evident [1, 3], with the largest increases observed over polar northern latitudes and the Southern Hemisphere in 2007 and in the tropics in 2008. The observed inter-annual variability in atmospheric methane concentrations and the associated changes in growth rates have variously been attributed to changes in different methane sources and sinks [1, 4]. In this paper, we report results from runs of the HadGEM2 climate-chemistry model [5] using year- and month-specific emission datasets. The HadGEM2 model includes the comprehensive atmospheric chemistry and aerosol package, the UK Chemistry Aerosol community model (UKCA, http://www.ukca.ac.uk/wiki/index.php). The Standard Tropospheric Chemistry scheme was selected for this work. This chemistry scheme simulates the Ox, HOx and NOx chemical cycles and the oxidation of CO, methane, ethane and propane. Year- and month-specific emission datasets were generated for the period from 1997 to 2009 for the emitted species in the chemistry scheme (CH4, CO, NOx, HCHO, C2H6, C3H8, CH3CHO, CH3CHOCH3). The approach adopted varied depending on the source sector: Anthropogenic: The emissions from anthropogenic sources were based on decadal-averaged emission inventories compiled by [6] for the Coupled Carbon Cycle Climate Model Intercomparison Project (C4MIP). These were then used to derive year-specific emission datasets by scaling the

  3. Evaluation of the inter-annual variability of stratospheric chemical composition in chemistry-climate models using ground-based multi species time series

    NASA Astrophysics Data System (ADS)

    Poulain, V.; Bekki, S.; Marchand, M.; Chipperfield, M. P.; Khodri, M.; Lefèvre, F.; Dhomse, S.; Bodeker, G. E.; Toumi, R.; De Maziere, M.; Pommereau, J.-P.; Pazmino, A.; Goutail, F.; Plummer, D.; Rozanov, E.; Mancini, E.; Akiyoshi, H.; Lamarque, J.-F.; Austin, J.

    2016-07-01

    The variability of stratospheric chemical composition occurs on a broad spectrum of timescales, ranging from day to decades. A large part of the variability appears to be driven by external forcings such as volcanic aerosols, solar activity, halogen loading, levels of greenhouse gases (GHG), and modes of climate variability (quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO)). We estimate the contributions of different external forcings to the interannual variability of stratospheric chemical composition and evaluate how well 3-D chemistry-climate models (CCMs) can reproduce the observed response-forcing relationships. We carry out multivariate regression analyses on long time series of observed and simulated time series of several traces gases in order to estimate the contributions of individual forcings and unforced variability to their internannual variability. The observations are typically decadal time series of ground-based data from the international Network for the Detection of Atmospheric Composition Change (NDACC) and the CCM simulations are taken from the CCMVal-2 REF-B1 simulations database. The chemical species considered are column O3, HCl, NO2, and N2O. We check the consistency between observations and model simulations in terms of the forced and internal components of the total interannual variability (externally forced variability and internal variability) and identify the driving factors in the interannual variations of stratospheric chemical composition over NDACC measurement sites. Overall, there is a reasonably good agreement between regression results from models and observations regarding the externally forced interannual variability. A much larger fraction of the observed and modelled interannual variability is explained by external forcings in the tropics than in the extratropics, notably in polar regions. CCMs are able to reproduce the amplitudes of responses in chemical composition to specific external forcings

  4. Seasonal and Inter-annual Variation in Wood Production in Tropical Trees on Barro Colorado Island, Panama, is Related to Local Climate and Species Functional Traits

    NASA Astrophysics Data System (ADS)

    Cushman, K.; Muller-Landau, H. C.; Kellner, J. R.; Wright, S. J.; Condit, R.; Detto, M.; Tribble, C. M.

    2015-12-01

    Tropical forest carbon budgets play a major role in global carbon dynamics, but the responses of tropical forests to current and future inter-annual climatic variation remains highly uncertain. Better predictions of future tropical forest carbon fluxes require an improved understanding of how different species of tropical trees respond to changes in climate at seasonal and inter-annual temporal scales. We installed dendrometer bands on a size-stratified sample of 2000 trees in old growth forest on Barro Colorado Island, Panama, a moist lowland forest that experiences an annual dry season of approximately four months. Tree diameters were measured at the beginning and end of the rainy season since 2008. Additionally, we recorded the canopy illumination level, canopy intactness, and liana coverage of all trees during each census. We used linear mixed-effects models to evaluate how tree growth was related to seasonal and interannual variation in local climate, tree condition, and species identity, and how species identity effects related to tree functional traits. Climatic variables considered included precipitation, solar radiation, soil moisture, and climatological water deficit, and were all calculated from high-quality on-site measurements. Functional traits considered included wood density, maximum adult stature, deciduousness, and drought tolerance. We found that annual wood production was positively related to water availability, with higher growth in wetter years. Species varied in their response to seasonal water availability, with some species showing more pronounced reduction of growth during the dry season when water availability is limited. Interspecific variation in seasonal and interannual growth patterns was related to life-history strategies and species functional traits. The finding of higher growth in wetter years is consistent with previous tree ring studies conducted on a small subset of species with reliable annual rings. Together with previous

  5. Use of the HadGEM2 climate-chemistry model to investigate interannual variability in methane sources

    NASA Astrophysics Data System (ADS)

    Hayman, Garry; O'Connor, Fiona; Clark, Douglas; Huntingford, Chris; Gedney, Nicola

    2013-04-01

    The global mean atmospheric concentration of methane (CH4) has more than doubled during the industrial era [1] and now constitutes ? 20% of the anthropogenic climate forcing by greenhouse gases [2]. The globally-averaged CH4 growth rate, derived from surface measurements, has fallen significantly from a high of 16 ppb yr-1 in the late 1970s/early 1980s and was close to zero between 1999 and 2006 [1]. This overall period of declining or low growth was however interspersed with years of positive growth-rate anomalies (e.g., in 1991-1992, 1998-1999 and 2002-2003). Since 2007, renewed growth has been evident [1, 3], with the largest increases observed over polar northern latitudes and the Southern Hemisphere in 2007 and in the tropics in 2008. The observed inter-annual variability in atmospheric methane concentrations and the associated changes in growth rates have variously been attributed to changes in different methane sources and sinks [1, 4]. In this paper, we report results from runs of the HadGEM2 climate-chemistry model [5] using year- and month-specific emission datasets. The HadGEM2 model includes the comprehensive atmospheric chemistry and aerosol package, the UK Chemistry Aerosol community model (UKCA, http://www.ukca.ac.uk/wiki/index.php). The Standard Tropospheric Chemistry scheme was selected for this work. This chemistry scheme simulates the Ox, HOx and NOx chemical cycles and the oxidation of CO, methane, ethane and propane. Year- and month-specific emission datasets were generated for the period from 1997 to 2009 for the emitted species in the chemistry scheme (CH4, CO, NOx, HCHO, C2H6, C3H8, CH3CHO, CH3CHOCH3). The approach adopted varied depending on the source sector: Anthropogenic: The emissions from anthropogenic sources were based on decadal-averaged emission inventories compiled by [6] for the Coupled Carbon Cycle Climate Model Intercomparison Project (C4MIP). These were then used to derive year-specific emission datasets by scaling the

  6. Coupled ocean-atmosphere model system for studies of interannual-to-decadal climate variability over the North Pacific Basin and precipitation over the Southwestern United States

    SciTech Connect

    Lai, Chung-Chieng A.

    1997-10-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The ultimate objective of this research project is to make understanding and predicting regional climate easier. The long-term goals of this project are (1) to construct a coupled ocean-atmosphere model (COAM) system, (2) use it to explore the interannual-to-decadal climate variability over the North Pacific Basin, and (3) determine climate effects on the precipitation over the Southwestern United States. During this project life, three major tasks were completed: (1) Mesoscale ocean and atmospheric model; (2) global-coupled ocean and atmospheric modeling: completed the coupling of LANL POP global ocean model with NCAR CCM2+ global atmospheric model; and (3) global nested-grid ocean modeling: designed the boundary interface for the nested-grid ocean models.

  7. Inter-annual variability of stream temperature, micro-climate and heat exchange dynamics: a comparison of forest and moorland environments

    NASA Astrophysics Data System (ADS)

    Garner, G.; Hannah, D. M.; Malcolm, I. A.; Sadler, J. P.

    2012-04-01

    Riparian woodland is recognised as important in moderating stream temperature variability and offers potential to mitigate thermal extremes under a warming climate. Previous research on the heat exchanges determining water column temperature has been often short-term, or seasonally-constrained, with the few long term year-round studies limited to a maximum of two years. This paper addresses these research gaps by comparing inter-annual variability in stream temperature, micro-climate and heat exchange dynamics between stream reaches of contrasting riparian landuse. Automatic weather stations (AWS) were installed in semi-natural woodland and moorland (no trees) reaches of the Girnock Burn, an upland tributary of the Aberdeenshire Dee. Data were collected across all seasons over seven calendar years. This research yields, for the first time, a long-term perspective on temporal differences in river heat exchange processes associated with riparian landuse under a range of hydroclimatological conditions. Results indicate that the presence of a riparian canopy has a persistent effect year-to-year in reducing mean and maximum daily water column temperature under a variety of hydrological and meteorological conditions. Woodland and moorland reaches display similar inter-annual variability in daily water column temperature range during spring and early summer, but in mid-summer and autumn woodland inter-annual variability is reduced greatly compared with moorland. Higher inter-annual variability (indicated by standard deviations) in spring and early summer water temperature ranges at both sites are attributed to increasing day length and solar radiation receipt, which a developing forest canopy at the woodland site is not able to mitigate. Once the full riparian canopy, hence maximum shading potential, is established (mid-summer) inter-annual variability in woodland temperature range is reduced greatly. The magnitude of woodland water temperature range is greater in spring

  8. Statistical modeling of interannual shoreline change driven by North Atlantic climate variability spanning 2000-2014 in the Bay of Biscay

    NASA Astrophysics Data System (ADS)

    Robinet, A.; Castelle, B.; Idier, D.; Le Cozannet, G.; Déqué, M.; Charles, E.

    2016-08-01

    Modeling studies addressing daily to interannual coastal evolution typically relate shoreline change with waves, currents and sediment transport through complex processes and feedbacks. For wave-dominated environments, the main driver (waves) is controlled by the regional atmospheric circulation. Here a simple weather regime-driven shoreline model is developed for a 15-year shoreline dataset (2000-2014) collected at Truc Vert beach, Bay of Biscay, SW France. In all, 16 weather regimes (four per season) are considered. The centroids and occurrences are computed using the ERA-40 and ERA-Interim reanalyses, applying k-means and EOF methods to the anomalies of the 500-hPa geopotential height over the North Atlantic Basin. The weather regime-driven shoreline model explains 70% of the observed interannual shoreline variability. The application of a proven wave-driven equilibrium shoreline model to the same period shows that both models have similar skills at the interannual scale. Relation between the weather regimes and the wave climate in the Bay of Biscay is investigated and the primary weather regimes impacting shoreline change are identified. For instance, the winter zonal regime characterized by a strengthening of the pressure gradient between the Iceland low and the Azores high is associated with high-energy wave conditions and is found to drive an increase in the shoreline erosion rate. The study demonstrates the predictability of interannual shoreline change from a limited number of weather regimes, which opens new perspectives for shoreline change modeling and encourages long-term shoreline monitoring programs.

  9. Interannual Variations In the Low-Degree Components of the Geopotential derived from SLR and the Connections With Geophysical/Climatic Processes

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Cox, Christopher M.; Au, Andrew Y.

    2004-01-01

    Recent Satellite Laser Ranging derived long wavelength gravity time series analysis has focused to a large extent on the effects of the recent large changes in the Earth s 52, and the potential causes. However, it is difficult to determine whether there are corresponding signals in the shorter wavelength zonals from the existing SLR-derived time variable gravity results, although it appears that geophysical fluid transport is being observed. For example, the recovered J3 time series shows remarkable agreement with NCEP-derived estimates of atmospheric gravity variations. Likewise, some of the non-zonal spherical harmonic coefficient series have significant interannual signal that appears to be related to mass transport. The non-zonal degree 2 terms show reasonable correlation with atmospheric signals, as well as climatic effects such as El Nino Southern Oscillation. While the formal uncertainty of these terms is significantly higher than that for J2, it is also clear that there is useful signal to be extracted. Consequently, the SLR time series is being reprocessed to improve the time variable gravity field recovery. We will present recent updates on the J2 evolution, as well as a look at other components of the interannual variations of the gravity field, complete through degree 4, and possible geophysical and climatic causes.

  10. An assessment of the global, seasonal, and interannual spacecraft record of Martian climate in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Liu, Junjun; Richardson, Mark I.; Wilson, R. J.

    2003-08-01

    Intercomparison of thermal infrared data collected by Mariner 9, Viking, and Mars Global Surveyor (MGS) is presented with a specific focus on air temperatures, dust opacities, and water ice opacities. Emphasis is placed on creating a uniform data set to most effectively reduce interinstrument biases and offsets. The annual cycle consistently shows a strong asymmetry about the equinoxes, with northern spring and summer exhibiting relatively low temperatures, very high year-to-year repeatability, and essentially no short-term (tens of days) variability. The globally averaged Martian nighttime air temperatures close annually to within a Kelvin during northern spring and summer. Daytime temperatures show more variability (3-6 K). The difference in repeatability of daytime versus nighttime temperatures is not understood. Viking and MGS air temperatures are essentially indistinguishable for this period, suggesting that the Viking and MGS eras are characterized by essentially the same climatic state. Southern summer is characterized by strong dust storm activity and hence strong year-to-year air temperature variability. Dust opacity shows a remarkable degree of interannual variability in southern spring and summer, associated with the intermittent activity of regional and planet-encircling dust storms, but exhibits high year-to-year repeatability in northern spring and summer. Specifically, late northern spring and early northern summer dust opacities appear to be completely insensitive to the occurrence (or not) of major dust storms in the previous southern spring or summer. We show that both Viking and MGS data sets exhibit significant (and similar) polar cap edge dust storm activity. The origins of the various major dust storms can be identified in the thermal infrared data from Viking and MGS, including the transport of dust from the northern autumn baroclinic zone into the southern hemisphere tropics, which has also been identified in visible imaging. We also note

  11. Large-scale climate control on the occurrence of turbid events on interannual scales in a karstified, heavily exploited karst system in northwestern France

    NASA Astrophysics Data System (ADS)

    Massei, N.; Laignel, B.; Dupont, J. P.

    2015-12-01

    High-amplitude turbid episodes at water supplies can cause significant sanitary issues to populations. Owing to their hydrogeologic specificity, karst ground waters are particularly sensitive to such phenomena, involving either fast infiltration of turbid surface water or resuspension of intra-karstic sediments during flood events. In some regions, such as Upper Normandy (France), soil erosion and karst features in the chalk aquifer are at the origin of major turbid events which may result in interrupted water supply to the local populations. Thanks to a long daily turbidity time series corresponding to measurements at one major karst spring since the mid-80's, we could investigate the large-scale atmospheric circulation control on below- or above-average turbidity periods. The turbidity time-series actually display periods on pluriannual duration during which daily turbid events are more frequent and have higher amplitudes, which can not be seen on daily precipitation records. Comparison was made between annual precipitation amounts, chalk aquifer water table variations and turbidity throughout this approximately 25-year period, which showed interannual recharge periods associated to above-normal turbid conditions. We then studied the linkages between such variations and large-scale atmospheric circulation using a NOAA sea level pressure reanalysis product. A wavelet multiresolution analysis of all hydrological and climatic signals revealed common aperiodic oscillations on interannual scales and allowed identification of the large-scale, interannual-scale atmospheric pattern that was responsible for those above-normal turbid periods; this atmospheric pattern was not necessarily similar to that responsible to any individual short-term turbid event.

  12. Improving interannual prediction skill in a changing climate via the identi cation of compensating coupled model errors

    SciTech Connect

    Tziperman, Eli; MacMartin, Douglas

    2013-08-31

    Significant progress can be made through a truly interdisciplinary effort, combining the expertise from climate dynamics and from engineering control. We believe that this novel approach can make a unique and valuable contribution, and help the climate community deliver improved models for the potential response of the Earth's climate to increased greenhouse gas levels.

  13. Long series relationships between global interannual CO2 increment and climate: evidence for stability and change in role of the tropical and boreal-temperate zones.

    PubMed

    Adams, Jonathan M; Piovesan, Gianluca

    2005-06-01

    Interannual variability in global CO2 increment (averaged from the Mauna Loa and South Pole Stations) shows certain strong spatial relationships to both tropical and temperate temperatures. There is a fairly strong positive year-round correlation between tropical mean annual temperatures (leading by 4 months) and annual CO2 throughout the time series since 1960, agreeing with the generally held view that the tropics play a major role in determining inter-annual variability in CO2 increment, with a major CO2 pulse following a warm year in the tropics. This 'almost no lag' climatic response is very strong during winter and relatively stable in time. However, the correlation with tropical temperature appears to have weakened in the first years of the 1990s in correspondence of the Pinatubo eruption and the positive phase of the AO/NAO. A secondary concurrent temperature signal is linked to summer variations of north temperate belt. Northern summer temperatures in the region 30-60 degrees N-and especially in the land area corresponding to the central east USA-have become relatively more closely correlated with CO2 increment. This trend has become increasingly stronger in recent years, suggesting an increasing role for growing season processes in the northern midlatitudes in affecting global CO2 increment. Once non-lagged annual tropical temperature variations are accounted for, terrestrial ecosystems, especially the temperate-boreal biomes, also show a coherent large scale lagged response. This involves an inverse response to annual temperature of preceding years centered at around 2 years before. This lagged response is most likely linked to internal biogeochemical cycles, in particular N cycling. During the study period north boreal ecosystems show a strengthening of the lagged correlation with temperature in recent years, while the lagged correlation with areas of tropical ecosystems has weakened. Residuals from a multiple correlations based on these climatic

  14. ASSESSING IMPACT OF INTERANNUAL CLIMATE VARIATIONS ON WATER RESOURCES AND CROP PRODUCTIVITY USING CLIGEN AND WEPP MODELS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Physically based hydrological and plant growth models are useful tools for assessing the impact of climate variations. Most response models require daily weather, which is often synthesized using stochastic daily weather generators. The objectives were to evaluate the ability of the CLImate GENera...

  15. Modelling the interannual variability (1979-2012) of the Mediterranean open-sea deep convection using a coupled regional climate system model

    NASA Astrophysics Data System (ADS)

    Somot, Samuel; Testor, Pierre; Durrieu de Madron, Xavier; Houpert, Loic; Herrmann, Marine; Dubois, Clotilde; Sevault, Florence

    2013-04-01

    The North-Western Mediterranean Sea is known as one of the only place in the world where open-sea deep convection occurs (often up to more than 2000m) with the formation of the Western Mediterranean Deep Water (WMDW). This phenomena is mostly driven by local preconditioning of the water column and strong buoyancy losses during Winter. At the event scale, the WMDW formation is characterized by different phases (preconditioning, strong mixing, restratification and spreading), intense air-sea interaction and strong meso-scale activity but, on a longer time scale, it also shows a large interannual variability and may be strongly affected by climate change with impact on the regional biogeochemistry. Therefore simulating and understanding the temporal variability of the North-Western Mediterranean open-sea deep convection is considered as quite a challenging task for the ocean and climate modelling community. Achieving such a goal requires to work with high resolution models for the ocean and the atmosphere interacting freely and to run long-term and temporally homogeneous simulations with a realistic chronology. In agreement with this statement, we developed at Meteo-France / CNRM a Mediterranean Regional Climate System Model (RCSM) that includes high-resolution representation of the regional atmosphere, land surface, rivers and ocean. The various components are respectively ALADIN (50 km), ISBA (50 km), TRIP (50 km) and NEMO-MED8 (10 km). All the components are interactively coupled daily and a simulation over the period 1979-2012 has been performed using the atmosphere ERA-Interim reanalysis and the ocean NEMOVAR1° reanalysis as 3D lateral-boundary conditions. Spectral nudging technique is applied in the atmosphere. We first evaluate the ability of this model to simulate some of the observed WMDW formation events (air-sea flux, timing, water mass characteristics, deep water formation rate) thanks to the large observational efforts recently carried out to better

  16. Inter-annual to inter-decadal streamflow variability in Quebec and Ontario in relation to dominant large-scale climate indices

    NASA Astrophysics Data System (ADS)

    Nalley, D.; Adamowski, J.; Khalil, B.; Biswas, A.

    2016-05-01

    The impacts of large-scale climate oscillations on hydrological systems and their variability have been documented in different parts of the world. Since hydroclimatic data are known to exhibit non-stationary characteristics, spectral analyses such as wavelet transforms are very useful in extracting time-frequency information from such data. As Canadian studies, particularly those of regions east of the Prairies, using wavelet transform-based methods to draw links between relevant climate indices [e.g., the El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the Pacific Decadal Oscillation (PDO)] and streamflow variability are not common, this study aims to analyze such relationships for the southern regions of Quebec and Ontario. Monthly and annual streamflow data with a record length of 55 years were used to capture streamflow variability at intra-annual, inter-annual and inter-decadal scales. The continuous wavelet transform spectra of monthly streamflow data revealed consistent significant 6- and 12-month periodicities, which are likely associated with strong seasonality factors. Its annual counterparts showed four different significant periodicities: up to 4 years, 4-6 years, 6-8 years, and greater than 8 years - all of which occurred after the late 1960s/early 1970s. Wavelet coherence analyses show that the influence of ENSO and NAO at the inter-annual scale occurs at 2-6 year periodicities, and the influence of PDO occur at periodicities up to 8 years and exceeding 16 years. Correlations between these climate indices and streamflow were computed to determine the time delay of streamflow response to the influence of ENSO, NAO, and PDO. The lag times ranged from 6-48 months (for monthly data) and 1-4 years (for annual data). This research contributes to our understanding of streamflow variability over the southern parts of Quebec and Ontario, and the role of ENSO, NAO, and PDO phenomena on this variability. These relationships can

  17. Interannual and seasonal dynamics, and the age, of nonstructural carbohydrate pools in the stemwood of temperate trees across a climatic gradient in New England

    NASA Astrophysics Data System (ADS)

    Richardson, A. D.; Carbone, M. S.; Czimczik, C. I.; Keenan, T. F.; Schaberg, P.; Xu, X.

    2011-12-01

    Like all plants, forest trees accumulate and store surplus mobile carbon (C) compounds as resources to be used to support future growth. This can be viewed as a bet-hedging strategy, providing reserves that the tree can draw on in times of stress-e.g., following disturbance, disease, or extreme climatic events. In the context of climate change, understanding factors influencing the availability of these stored C compounds to support growth and metabolism is essential for predicting the resilience of forests to environmental stress factors. We conducted this study to investigate the role of these stored C pools in the context ecosystem C balance at time scales from days to years. At quarterly intervals over a three year period, we monitored stemwood total nonstructural carbohydrate (TNC) concentrations of the dominant tree species of New England. Work was conducted at three sites along a climatic gradient: an oak-dominated transition hardwood forest (Harvard Forest), a maple-beech-birch northern hardwood forest (Bartlett Experimental Forest), and a spruce-fir forest (Howland Forest). We observed large differences among species both in TNC concentrations, and in how the TNC pool is partitioned to different compounds (starch, sucrose, glucose, fructose, raffinose, xylose and stachyose). Within a species, however, seasonal dynamics were remarkably similar across sites. The interannual variability in maximum TNC concentrations appears to be smaller than interannual variability in annual net ecosystem exchange of CO2. With an additional set of samples, we are using the bomb radiocarbon (14C) spike to estimate the average age of the sugars and starches in the TNC pool, and relating this to factors such as size, age, and recent growth rates of each tree. Initial results suggest that these TNC pools range in age from several years to several decades old. The average ages of starch and sugar pools are related, with the starches generally being older than sugars

  18. Climate Change Decision Making in the Water User Community: Assessment Needs for Projections from Interannual to Multi-Decadal Scales

    NASA Astrophysics Data System (ADS)

    Behar, D.; Adams, A.; Schneiderman, E.; Kaatz, L.

    2012-12-01

    Water managers are increasingly using climate science tools, including model output, in assessing the potential effects of climate change on their operations, infrastructure, and levels of service. The Water Utility Climate Alliance (WUCA), ten large metropolitan utilities providing drinking water to 43 million Americans, has developed relationships individually and collectively across the scientific, agency, and boundary organization communities in pursuit of an understanding of what the current science tells us about the threat of climate change and how to incorporate that understanding into planning. Many WUCA agencies, including those of the authors, have completed or are in the process of completing state-of-the-art assessments using climate model output, expert elicitation, and their own internal modeling tools. A WUCA initiative, Piloting Utility Modeling Applications for Climate Change (PUMA), is facilitating collaboration between five water utilities, four climate science consortiums, and a Modeling Advisory Committee in the preparation of climate change assessments. For WUCA members, and likely others in the adaptation community, the need is for "actionable science," a term WUCA began using in 2008 that was included as an objective in the recently released strategic plan for U.S. Global Change Research Program. Ultimately, assessments feed into existing utility planning processes that look into a future that ranges in scope from years to decades in order to provide guidance on adaptation measures that may be needed. This talk will use WUCA member experiences as case studies to zero in on utility needs for information at these scales, the form of data that best fits with our downstream models (hydrologic, planning), and on the challenges of planning in an atmosphere of uncertainty.

  19. Glacioclimatological study of perennial ice in the Fuji Ice Cave, Japan. Part 2. Interannual variation and relation to climate

    SciTech Connect

    Ohata, Tetsuo; Furukawa, Teruo; Osada, Kazuo )

    1994-08-01

    A glacioclimatological study of the interannual variation of mass of perennial ice in the Fuji Ice Cave at the foot of Mt. Fuji, in central Japan is presented. The cave is a 150-m-long lava tube located in a dense forest area at an altitude of 1120 m. It has a perennial floor ice of areas approximately 3000 m[sup 3] and mean thickness 2.8 m. Mean annual air temperature at the ground surface level is 8.4[degrees]C. Ice surface levels and air temperatures were measured 39 times from July 1984 to December 1992. Mean ice level showed a 15 cm increase from 1984 to 1989 and suddenly started to decrease from 1989 to 1992. In the increase stage, annual net balance (December to November) was similar at various points, but in the decreasing stage, the lowering of the level near the entrance was very large due to intense melting. Air temperature inside the cave at the end of the annual cycle showed a correlation to net balance of the corresponding year. Comparison of yearly net balance with meterological indices at ground level (winter and summer, annual mean air temperature and total precipitation; and number of days with strong precipitation) showed that net balance of a give year has a high correlation with the average winter air temperature anomaly of the preceding 4 yr. This is probably due to the high heat capacity of the cave system. 6 refs., 7 figs., 2 tabs.

  20. Enhanced interannual precipitation variability increases plant functional diversity that in turn ameliorates negative impact on productivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although precipitation interannual variability is projected to increase due to climate change, effects of changes in precipitation variance have received considerable less attention than effects of changes in the mean state of climate. Interannual precipitation variability effects on functional dive...

  1. Seasonal and inter-annual variability of bud development as related to climate in two coexisting Mediterranean Quercus species

    PubMed Central

    Alla, Arben Q.; Camarero, J. Julio; Montserrat-Martí, Gabriel

    2013-01-01

    Background and Aims In trees, bud development is driven by endogenous and exogenous factors such as species and climate, respectively. However, knowledge is scarce on how these factors drive changes in bud size across different time scales. Methods The seasonal patterns of apical bud enlargement are related to primary and secondary growth in two coexisting Mediterranean oaks with contrasting leaf habit (Quercus ilex, evergreen; Quercus faginea, deciduous) over three years. In addition, the climatic factors driving changes in bud size of the two oak species were determined by correlating bud mass with climatic variables at different time scales (from 5 to 30 d) over a 15-year period. Key Results The maximum enlargement rate of buds was reached between late July and mid-August in both species. Moreover, apical bud size increased with minimum air temperatures during the period of maximum bud enlargement rates. Conclusions The forecasted rising minimum air temperatures predicted by climatic models may affect bud size and consequently alter crown architecture differentially in sympatric Mediterranean oaks. However, the involvement of several drivers controlling the final size of buds makes it difficult to predict the changes in bud size as related to ongoing climate warming. PMID:23179859

  2. Satellite-measured interannual variability of turbid river plumes off central-southern Chile: Spatial patterns and the influence of climate variability

    NASA Astrophysics Data System (ADS)

    Saldías, Gonzalo S.; Largier, John L.; Mendes, Renato; Pérez-Santos, Iván; Vargas, Cristian A.; Sobarzo, Marcus

    2016-08-01

    Ocean color imagery from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the Aqua platform is used to characterize the interannual variability of turbid river plumes off central-southern Chile. Emphasis is placed on the influence of climate fluctuations, namely El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Antarctic Oscillation (AAO). Additional satellite data on wind, boat-based hydrographic profiles, and regional climate indices are used to identify the influence of climate variability on the generation of anomalous turbid river plumes. The evolution of salinity at a coastal station on the 90 m isobath between the Itata and Biobío Rivers shows a freshwater surface layer with salinity < 32.5 and 5-10 m thick during major plume events in 2002, 2005 and 2006. Surface salinity minima are correlated with peaks in turbidy from the normalized water leaving radiance at 555 nm (nLw(555)), both representing turbid river plumes. EOF analysis reveals that major turbid plume events occurred primarily during warm phases of the ENSO and PDO, and negative phases of the AAO, when storm tracks are further north. Anomalously large turbid plumes extend long distances offshore (∼ 70-80 km), and individual plumes coalesce into a continuous plume along the coast that covers the entire continental shelf. Season-specific correlation analyses reveal an increased influence of the AAO on river plumes south of Punta Lavapié in spring-summer (negative correlation). North of this major cape, ENSO and PDO indices have a dominant influence on plumes with positive correlations with the nLw(555) signal in winter (and negative in summer). We discuss the biogeochemical implications of plume events and the importance of long-term and high-resolution ocean color observations for studying the temporal evolution of river plumes.

  3. Climatically induced interannual variability in aboveground production in forest-tundra and northern taiga of central Siberia.

    PubMed

    Knorre, Anastasia A; Kirdyanov, Alexander V; Vaganov, Eugene A

    2006-02-01

    To investigate the variability of primary production of boreal forest ecosystems under the current climatic changes, we compared the dynamics of annual increments and productivity of the main components of plant community (trees, shrubs, mosses) at three sites in the north of Siberia (Russia). Annual radial growth of trees and shrubs was mostly defined by summer temperature regime (positive correlation), but climatic response of woody plants was species specific and depends on local conditions. Dynamics of annual increments of mosses were opposite to tree growth. The difference in climatic response of the different vegetation components of the forest ecosystems indicates that these components seem to be adapted to use climatic conditions during the short and severe northern summer, and decreasing in annual production of one component is usually combined with the increase of other component productivity. Average productivity in the northern forest ecosystems varies from 0.05 to 0.14 t ha(-1) year(-1) for trees, from 0.05 to 0.18 t ha(-1) year(-1) for shrubs and from 0.54 to 0.66 t ha(-1) year(-1) for mosses. Higher values of tree productivity combined with lower annual moss productivity were found in sites in northern taiga in comparison with forest-tundra. Different tendencies in the productivity of the dominant species from each vegetation level (trees, shrubs, mosses) were indicated for the last 10 years studied (1990-1999): while productivity of mosses is increasing, productivity of trees is decreasing, but there is no obvious trend in the productivity of shrubs. Our results show that in the long term, the main contribution to changes in annual biomass productivity in forest-tundra and northern taiga ecosystems under the predicted climatic changes will be determined by living ground cover. PMID:16163553

  4. Inter-annual variability of urolithiasis epidemic from semi-arid part of Deccan Volcanic Province, India: climatic and hydrogeochemical perspectives.

    PubMed

    Kale, Sanjay S; Ghole, Vikram Shantaram; Pawar, N J; Jagtap, Deepak V

    2014-01-01

    Semi-arid Karha basin from Deccan Volcanic Province, India was investigated for inter-annual variability of urolithiasis epidemic. The number of reported urolith patient, weather station data and groundwater quality results was used to assess impact of geoenvironment on urolithiasis. Data of 7081 urolith patient were processed for epidemiological study. Gender class, age group, year-wise cases and urolith type were studied in epidemiology. Rainfall, temperature, pan evaporation and sunshine hours were used to correlate urolithiasis. Further, average values of groundwater parameters were correlated with the number of urolith episodes. A total of 52 urolith samples were collected from hospitals and analysed using FTIR technique to identify dominant urolith type in study area. Result shows that male population is more prone, age group of 20-40 is more susceptible and calcium oxalate uroliths are dominant in study area. Year-wise distribution revealed that there is steady increase in urolithiasis with inflation in drought years. In climatic parameters, hot days are significantly correlated with urolithiasis. In groundwater quality, EC, Na and F are convincingly correlated with urolith patients, which concludes the strong relation between geo-environment and urolithiasis. PMID:23869912

  5. The 1994 heat wave in South Korea: mortality impacts and recurrence probability in a changing climate

    NASA Astrophysics Data System (ADS)

    Kysely, J.; Kim, J.

    2010-03-01

    The study deals with mortality impacts of the July-August 1994 heat wave in the population of South Korea, including the megacity of Seoul (with the population exceeding 10 million for the city and 20 million for the metropolitan area), and estimates recurrence probability of the heat wave in a changing climate in terms of simulations of daily temperature series with a stochastic model. The 1994 heat wave is found exceptional with respect to both climatological characteristics and the mortality effects: significantly elevated mortality occurred in all population groups, including children up to 14 years of age, and the total death toll exceeded 3000 in the Korean population, which ranks the 1994 heat wave among the worst weather-related disasters in East Asia. The estimate represents net excess mortality as no mortality displacement effect appeared. A comparison with other documented natural disasters shows that the death toll of the heat wave was much higher than those of the most disastrous floodings and typhoons over Korean Peninsula in the 20th century. The mortality response was stronger in males than females although males are found to be less vulnerable during average heat waves. A climatological analysis reveals that the July-August 1994 heat wave might be considered an extremely rare event with a return period in the order of hundreds of years if stationarity of temperature time series is assumed. However, under a more realistic assumption of gradual warming related to climate change, recurrence probability of an event analogous to the 1994 heat wave sharply rises for near-future time horizons. If warming of 0.04°C/year is assumed over 2001-2060, the recurrence interval of a very long spell of days with temperature exceeding a high threshold (as in the 1994 heat wave) is estimated to decrease to around 40 (10) years in the 2021-2030 (2041-2050) decade. This emphasizes the need for setting up an efficient heat-watch-warning system in this area in order to

  6. Evaluating and Quantifying the Climate-Driven Interannual Variability in Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI3g) at Global Scales

    NASA Technical Reports Server (NTRS)

    Zeng, Fanwei; Collatz, George James; Pinzon, Jorge E.; Ivanoff, Alvaro

    2013-01-01

    Satellite observations of surface reflected solar radiation contain informationabout variability in the absorption of solar radiation by vegetation. Understanding thecauses of variability is important for models that use these data to drive land surface fluxesor for benchmarking prognostic vegetation models. Here we evaluated the interannualvariability in the new 30.5-year long global satellite-derived surface reflectance index data,Global Inventory Modeling and Mapping Studies normalized difference vegetation index(GIMMS NDVI3g). Pearsons correlation and multiple linear stepwise regression analyseswere applied to quantify the NDVI interannual variability driven by climate anomalies, andto evaluate the effects of potential interference (snow, aerosols and clouds) on the NDVIsignal. We found ecologically plausible strong controls on NDVI variability by antecedent precipitation and current monthly temperature with distinct spatial patterns. Precipitation correlations were strongest for temperate to tropical water limited herbaceous systemswhere in some regions and seasons 40 of the NDVI variance could be explained byprecipitation anomalies. Temperature correlations were strongest in northern mid- to-high-latitudes in the spring and early summer where up to 70 of the NDVI variance was explained by temperature anomalies. We find that, in western and central North America,winter-spring precipitation determines early summer growth while more recent precipitation controls NDVI variability in late summer. In contrast, current or prior wetseason precipitation anomalies were correlated with all months of NDVI in sub-tropical herbaceous vegetation. Snow, aerosols and clouds as well as unexplained phenomena still account for part of the NDVI variance despite corrections. Nevertheless, this study demonstrates that GIMMS NDVI3g represents real responses of vegetation to climate variability that are useful for global models.

  7. Exploring the interannual variablitity of the Martian atmosphere with the Mars Climate Database v5.2

    NASA Astrophysics Data System (ADS)

    Millour, Ehouarn; Forget, Francois; Lopez-Valverde, Miguel; Navarro, Thomas; Lefevre, Franck; Gonzalez-Galindo, Francisco; Chaufray, Jean-Yves; Spiga, Aymeric; Lewis, Stephen; Pottier, Alizee; Montabone, Luca

    2016-07-01

    The latest Mars Climate Database (version 5.2) includes synthetic scenarios (namely the "clim" climatology scenario, representative of a standard Mars year without any global dust storm) as well as specific scenarios corresponding to seven actual Mars years, from Mars Year 24 to Mars Year 31. At the COSPAR 2016 scientific assembly, we will address the validation of MCDv5.2 scenarios with available observations from spacecrafts and landers, and discuss more specifically of the obtained multi-annual climatologies and how these deviate over the years.

  8. Influence of soil C stocks and interannual climatic variability on the CO2 and CH4 exchange of maize cultivated on mineral and organic soils in NE Germany

    NASA Astrophysics Data System (ADS)

    Pohl, Madlen; Hagemann, Ulrike; Hoffmann, Mathias; Giebels, Michael; Albiac-Borraz, Elisa; Sommer, Michael; Augustin, Jürgen

    2014-05-01

    Due to its glacially influenced genesis and land use history, the soils of the Great Plain Region of NE-Germany show large differences in groundwater levels and soil carbon (C) stocks over short distances. Although generally featuring a rather dry climate, trace gas exchange at individual sites may be influenced by i) interannual climatic variability, particularly with respect to precipitation; as well as by ii) variability of soil C stocks. However, it is still unclear how these factors affect fluxes of CO2 and CH4, and if there is any positive or negative feedback on the C source or sink function of different soil types. We present measured and modeled CO2 and CH4 fluxes of minerally fertilized grain maize for three sites located near Paulinenaue, within the so-called Rhin-Havelluch, a shallow and drained paludification mire complex in NE Germany. The sites are characterized by a distinct gradient of 0-1 m soil organic C stocks: i) Arenosol (AR: mineral soil/distant groundwater; 8 000 g C m-2), ii) Gleysol (GL: organic soil/groundwater-dependent; 35 000 g C m-2), and iii) Histosol (HS: organic soil/near groundwater; 45 000 g C m-2). CO2 flux measurements of ecosystem respiration (Reco), net ecosystem exchange (NEE) and gross primary production (GPP; calculated as difference between NEE and Reco) were conducted every four weeks using a flow-through non-steady-state closed chamber system. Measurement gaps of Reco and NEE were filled by using temperature or radiation-based models, respectively. CH4 fluxes were measured bi-weekly using a static closed chamber system with interval sampling, with gap filling via linear interpolation. Cumulated fluxes of CO2-C (Reco, GPP, NEE) and CH4-C were calculated for a period of four consecutive years (2007-2010). The intensity of CO2-C fluxes increased with growing soil organic C stocks (AR < GL < HS). Mean annual values of the years 2008-2010 for Reco ranged between 1 500 g C m-2 and 2 000 g C m-2; annual GPP fluxes ranged from

  9. Effects of Interannual Climate Variability on Water Availability and Productivity in Capoeira and Crops Under Traditional and Alternative Shifting Cultivation

    NASA Technical Reports Server (NTRS)

    Guild, Liane S.; Sa, Tatiana D. A.; Carvalho, Claudio J. R.; Potter, Christopher S.; Wickel, Albert J.; Brienza, Silvio, Jr.; Kato, Maria doSocorro A.; Kato, Osvaldo; Brass, James (Technical Monitor)

    2002-01-01

    Regenerating forests play an important role in long-term carbon sequestration and sustainable landuse as they act as potentially important carbon and nutrient sinks during the shifting agriculture fallow period. The long-term functioning of capoeira. is increasingly threatened by a shortening fallow period during shifting cultivation due to demographic pressures and associated increased vulnerability to severe climatic events. Declining productivity and functioning of fallow forests of shifting cultivation combined with progressive loss of nutrients by successive burning and cropping activities has resulted in declining agricultural productivity. In addition to the effects of intense land use practices, droughts associated with El Nino events are becoming more frequent and severe in moist tropical forests and negative effects on capoeira productivity could be considerable. In Igarape-Acu (near Belem, Para), we hypothesize that experimental alternative landuse/clearing practices (mulching and fallow vegetation improvement by planting with fast-growing leguminous tree species) may make capoeira and agriculture more resilient to the effects of agricultural pressures and drought through (1) increased biomass, soil organic matter and associated increase in soil water storage, and nutrient retention and (2) greater rooting depth of trees planted for fallow improvement. This experimental practice (moto mechanized chop-and-mulch with fallow improvement) has resulted increased soil moisture during the cropping phase, reduced loss of nutrients and organic matter, and higher rates of secondary-forest biomass accumulation. We present preliminary data on water relations during the dry season of 2001 in capoeira and crops for both traditional slash-and-burn and alternative chop-and-mulch practices. These data will be used to test IKONOS data for the detection of moisture status differences. The principal goal of the research is to determine the extent to which capoeira and

  10. Detection of Interannual Climate Variability in Secondary Forests and Crops Under Traditional and Alternative Shifting Cultivation Using Ikonos Data

    NASA Astrophysics Data System (ADS)

    Sa, T.; Guild, L.; Carvalho, C.; Wickel, A.; Brienza, S.; Kato, M.; Kato, O.; Leibs, C.

    2004-12-01

    Regenerating forests play an important role in long-term carbon sequestration and sustainable landuse as they act as potentially important carbon and nutrient sinks during the shifting agriculture fallow period. The long-term functioning of secondary forests (capoeira) is increasingly threatened by a shortening fallow period during shifting cultivation due to demographic pressures and associated increased vulnerability to severe climatic events. Declining productivity and functioning of fallow forests of shifting cultivation combined with progressive loss of nutrients by successive burning and cropping activities has resulted in declining agricultural productivity. In addition to the effects of intense land use practices, droughts associated with El Nino events are becoming more frequent and severe in moist tropical forests and negative effects on capoeira productivity could be considerable. The principal goal of the research is to determine the extent to which capoeira and agricultural fields are susceptible to extreme climate events (drought) under contrasting landuse/clearing practices. In Igarape-Açu (near Belem, Para), we hypothesize that experimental alternative landuse/clearing practices (mulching) may make capoeira and crops more resilient to the effects of agricultural pressures and drought through increased biomass, soil organic matter and associated increase in soil water storage, and nutrient retention. This experimental practice (mechanized chop-and-mulch) has resulted in increased soil moisture during the cropping phase, reduced loss of nutrients and organic matter, and higher rates of secondary-forest biomass accumulation. This project aims to measure water availability and it's relation to secondary forest and crop productivity in the Brazilian Amazon. We have conducted field efforts during two dry seasons (August-December). Field data on water relations were collected during the dry season of 2001 and 2002 in capoeira and crops for both

  11. Interannual to Decadal Variability in Climate and the Glacier Mass Balance in Washington, Western Canada, and Alaska*.

    NASA Astrophysics Data System (ADS)

    Bitz, C. M.; Battisti, D. S.

    1999-11-01

    The authors examine the net winter, summer, and annual mass balance of six glaciers along the northwest coast of North America, extending from Washington State to Alaska. The net winter (NWB) and net annual (NAB) mass balance anomalies for the maritime glaciers in the southern group, located in Washington and British Columbia, are shown to be positively correlated with local precipitation anomalies and storminess (defined as the rms of high-passed 500-mb geopotential anomalies) and weakly and negatively correlated with local temperature anomalies. The NWB and NAB of the maritime Wolverine glacier in Alaska are also positively correlated with local precipitation, but they are positively correlated with local winter temperature and negatively correlated with local storminess. Hence, anomalies in mass balance at Wolverine result mainly from the change in moisture that is being advected into the region by anomalies in the averaged wintertime circulation rather than from a change in storminess. The patterns of the wintertime 500-mb circulation and storminess anomalies associated with years of high NWB in the southern glacier group are similar to those associated with low NWB years at the Wolverine glacier, and vice versa.The decadal ENSO-like climate phenomenon discussed by Zhang et al. has a large impact on the NWB and NAB of these maritime glaciers, accounting for up to 35% of the variance in NWB. The 500-mb circulation and storminess anomalies associated with this decadal ENSO-like mode resemble the Pacific-North American pattern, as do 500-mb composites of years of extreme NWB of South Cascade glacier in Washington and of Wolverine glacier in Alaska. Hence, the decadal ENSO-like mode affects precipitation in a crucial way for the NWB of these glaciers. Specifically, the decadal ENSO-like phenomenon strongly affects the storminess over British Columbia and Washington and the moisture transported by the seasonally averaged circulation into maritime Alaska. In contrast

  12. Carbon cycling in a rapidly changing High Arctic: Results from long-term climate experiments and observations of interannual variability in NW Greenland

    NASA Astrophysics Data System (ADS)

    Czimczik, C. I.; Lupascu, M.; Csank, A. Z.; Seibt, U. H.; Maseyk, K. S.; Xu, X.; Welker, J. M.

    2013-12-01

    The High Arctic, a region dominated by polar semi-deserts underlain with continuous permafrost, is experiencing dramatic changes in climate associated with the loss of sea ice, including warming and shifts in precipitation regimes (i.e. wetting and changing snow cover). Here, we present findings from a set of studies that are addressing the sign and strength of the High Arctic's summertime carbon (C) cycle feedback. We explored magnitudes, patterns and sources of C losses through CO2 and CH4 fluxes and via leaching as dissolved organic C (DOC) and particulate organic C (POC) along with measurements of net ecosystem exchange and plant C uptake. From studying long-term summertime experimental warming and/or watering and interannual weather patterns we find that in polar semi-deserts: a) Summer precipitation regime is the key driver of current summertime C budgets. Warming plus wetting results in increased ecosystem C sequestration and reduced losses of older C as CO2, while warming alone decreases C uptake and increases losses of older soil C as CO2. The system is a sink for CH4, but the sink strength will decline with increasing soil moisture. Thus, the High Arctic has the potential to remain a strong summertime C sink even as the rest of the permafrost region transitions to a net C source to the atmosphere as climate continues to warm. b) Old C is diffusing out of the High Arctic landscape into the atmosphere. This C loss is especially evident in the spring before vegetation pumps fresh C into the soil system. Further, loss of older C from the deeper active layer is highly episodic and dominates C emissions during small precipitation events. c) Precipitation regime is also the key driver of that ancient C export from the land surface as DOC, higher precipitation in the later part of the growing season (July-August), when the active layer is deeper, results in a greater fraction of old C transported to the nearshore Arctic Ocean. Collectively these findings

  13. Use of color maps and wavelet coherence to discern seasonal and interannual climate influences on streamflow variability in northern catchments

    NASA Astrophysics Data System (ADS)

    Carey, Sean K.; Tetzlaff, Doerthe; Buttle, Jim; Laudon, Hjalmar; McDonnell, Jeff; McGuire, Kevin; Seibert, Jan; Soulsby, Chris; Shanley, Jamie

    2013-10-01

    The higher midlatitudes of the northern hemisphere are particularly sensitive to change due to the important role the 0°C isotherm plays in the phase of precipitation and intermediate storage as snow. An international intercatchment comparison program called North-Watch seeks to improve our understanding of the sensitivity of northern catchments to change by examining their hydrological and biogeochemical variability and response. Here eight North-Watch catchments located in Sweden (Krycklan), Scotland (Girnock and Strontian), the United States (Sleepers River, Hubbard Brook, and HJ Andrews), and Canada (Dorset and Wolf Creek) with 10 continuous years of daily precipitation and runoff data were selected to assess daily to seasonal coupling of precipitation (P) and runoff (Q) using wavelet coherency, and to explore the patterns and scales of variability in streamflow using color maps. Wavelet coherency revealed that P and Q were decoupled in catchments with cold winters, yet were strongly coupled during and immediately following the spring snowmelt freshet. In all catchments, coupling at shorter time scales occurred during wet periods when the catchment was responsive and storage deficits were small. At longer time scales, coupling reflected coherence between seasonal cycles, being enhanced at sites with enhanced seasonality in P. Color maps were applied as an alternative method to identify patterns and scales of flow variability. Seasonal versus transient flow variability was identified along with the persistence of that variability on influencing the flow regime. While exploratory in nature, this intercomparison exercise highlights the importance of climate and the 0°C isotherm on the functioning of northern catchments.

  14. An assessment of the global, seasonal, and interannual spacecraft record of martian climate in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Liu, J.; Richardson, M.; Wilson, R.

    A comprehensive inter-comparison of thermal infrared data collected by Mariner 9, Viking, and Mars Global Surveyor (MGS) is presented, with a specific focus on air temperatures, dust opacities, and water ice opacities. Emphasis is placed upon creating a uniform data set so as to most effectively reduce inter-instrument biases and offsets. We show that the globally-averaged martian atmosphere undergoes a repeatable annual cycle of air temperature, closing in northern spring and summer to within a Kelvin. The annual cycle shows a strong asymmetry about the equinoxes, with northern summer showing relatively low temperatures and essentially no short-term (tens of days) variability. Viking and MGS air temperatures are essentially indistinguishable, suggesting that the Viking and MGS eras are characterized by exactly the same climatic state. Southern summer is characterized by strong dust storm activity, with the period around Ls=225 has exhibiting regional or global-scale dust storm events in every year observed by spacecraft. Dust opacity shows a highly repeatable annual cycle, closing to essentially the same values each year in northern spring and summer, with Viking and MGS opacities being very similar. We show that both Viking and MGS data sets have significant and similar polar cap edge dust storm activity. The origins of the various major dust storms can be identified in the thermal infrared data from Viking and MGS, including the "flushing" of dust from the northern autumn baroclinic zone into the southern hemisphere tropics, which has also been identified in visible imaging. Water ice opacities have been retrieved from Viking infrared data for the first time and the tropical cloud belt structure and evolution is essentially the same in each of the multiple years observed by Viking and MGS. Polar hood clouds are observed in the Viking and MGS observations with similar timing and extent.

  15. Interannual climate variability and spatially heterogeneous improvement of agricultural management impede detection of a decreasing trend in nitrate pollution in an agricultural catchment

    NASA Astrophysics Data System (ADS)

    Fovet, Ophélie; Dupas, Rémi; Durand, Patrick; Gascuel-Odoux, Chantal; Gruau, Gérard; Hamon, Yannick; Petitjean, Patrice

    2016-04-01

    Despite widespread implementation of the nitrate directive in the European Union since the 1990s, the impact on nitrate concentration in rivers is limited (Bouraoui and Grizzetti, 2011). To assess whether this lack of response is due to the long time lags of nitrate transfer or to inadequate programs of measure, long term river and groundwater monitoring data are necessary. This study analyses 15 years of daily nitrate concentration data at the outlet of an intensively farmed catchment in Western France (Kervidy-Naizin, 5 km²) and quarterly nitrate concentration data in the groundwater of two hillslopes equipped with piezometers (Kerroland and Gueriniec) within the same catchment. In this catchment groundwater contribution to annual stream flow is dominant. The objectives of this study were to i) disentangle the influence of interannual climate variability and improvement of agricultural practices (i.e. reduction in N surplus) in the stream chemistry and ii) discuss the reasons for slow catchment recovery from nitrate pollution by comparing trends in groundwater and stream concentrations. Analysis of stream data showed that flow-weighted mean annual concentration at the outlet of the Kervidy-Naizin catchment has decreased by 1.2 mg NO3- l-1 yr-1 from 1999 to 2015. This decrease was slow but significant (p value < 0.01) even though interannual climate variability (i.e. annual cumulated runoff) added noise to the signal: i) deviation in the linear model of nitrate decrease with time was negatively correlated with annual runoff (r = -0.54, p < 0.01) and ii) local minimums in the nitrate time series were coincident with local maximums in the annual runoff. Thus high runoff during wet years led to dilution of the nitrate originating from groundwater, which added variability to the signal of linear decrease in stream concentration. Analysis of groundwater data showed a significant and sharp decrease in nitrate concentration in the Kerroland piezometer transect (4.0 mg

  16. Inter-annual Tropospheric Aerosol Variability in Late Twentieth Century and its Impact on Tropical Atlantic and West African Climate by Direct and Semi-direct Effects

    SciTech Connect

    Evans, Katherine J; Hack, James J; Truesdale, John; Mahajan, Salil; Lamarque, J-F

    2012-01-01

    A new high-resolution (0.9$^{\\circ}$x1.25$^{\\circ}$ in the horizontal) global tropospheric aerosol dataset with monthly resolution is generated using the finite-volume configuration of Community Atmosphere Model (CAM4) coupled to a bulk aerosol model and forced with recent estimates of surface emissions for the latter part of twentieth century. The surface emissions dataset is constructed from Coupled Model Inter-comparison Project (CMIP5) decadal-resolution surface emissions dataset to include REanalysis of TROpospheric chemical composition (RETRO) wildfire monthly emissions dataset. Experiments forced with the new tropospheric aerosol dataset and conducted using the spectral configuration of CAM4 with a T85 truncation (1.4$^{\\circ}$x1.4$^{\\circ}$) with prescribed twentieth century observed sea surface temperature, sea-ice and greenhouse gases reveal that variations in tropospheric aerosol levels can induce significant regional climate variability on the inter-annual timescales. Regression analyses over tropical Atlantic and Africa reveal that increasing dust aerosols can cool the North African landmass and shift convection southwards from West Africa into the Gulf of Guinea in the spring season in the simulations. Further, we find that increasing carbonaceous aerosols emanating from the southwestern African savannas can cool the region significantly and increase the marine stratocumulus cloud cover over the southeast tropical Atlantic ocean by aerosol-induced diabatic heating of the free troposphere above the low clouds. Experiments conducted with CAM4 coupled to a slab ocean model suggest that present day aerosols can shift the ITCZ southwards over the tropical Atlantic and can reduce the ocean mixed layer temperature beneath the increased marine stratocumulus clouds in the southeastern tropical Atlantic.

  17. Variations of Winter Climate in Association with the Interannual Variability of Atmospheric Mass over Water Oceans, Continents, and Sea Ice-Covered Arctic Region

    NASA Astrophysics Data System (ADS)

    Guan, Z.; Zhang, Q.; Li, M.

    2015-12-01

    Using reanalysis data from NCEP/NCAR, ERA-interim, and HadISST for period 1979-2012, variations of atmospheric mass (AM) over water oceans, continents, and sea-ice-covered arctic region during boreal winter are investigated. It is found that the AM may migrate compensatively among these three types of surfaces on interannual time scales. There are two pairs of strong anti-phase relations. The one is in zonal between Eurasian continent and mid-latitude Pacific (referred to as EPAR), which is a teleconnection pattern characterizing with two strong correlation centers respectively over Eurasia and North Pacific. The other anti-phase relation of AM, referred to as OIAR, is found in meridional between ice-covered Arctic and water oceans including Atlantic and Pacific. In the context of OIAR, two teleconnection patterns are found. One is MANP, which merges as three strong correlation centers respectively over the Mediterranean, Arctic, and North Pacific when AM fluctuates over water oceans. Another is MAEA, which characterizes with three strong correlation centers respectively around the Mediterranean, Arctic, and East Asia when AM fluctuates over the ice-covered Arctic. The MAEA looks largely different from MANP in anomalous surface air pressure over the northwest Pacific. These teleconnections including MANP, MAEA, and EPAR are resulted from thermal contrasts among the three types of surfaces. Rossby waves and vertical circulations play important roles in forming these teleconnection patterns. Interestingly, these teleconnections may significantly influence the winter climate widely in the Northern Hemisphere, especially in regions around the Mediterranean, the northern part of Eurasia, parts of North America, and East Asia.

  18. Interannual variations in atmospheric mass over liquid water oceans, continents, and sea-ice-covered arctic regions and their possible impacts on the boreal winter climate

    NASA Astrophysics Data System (ADS)

    Guan, Zhaoyong; Zhang, Qian; Li, Minggang

    2015-12-01

    Using reanalysis data from National Centers for Environmental Prediction/National Center for Atmospheric Research, ERA-interim, and Hadley Centre Sea Ice and Sea Surface Temperature for the period of 1979-2012, the variations in atmospheric mass (AM) over liquid water oceans, continents, and sea-ice-covered Arctic regions during boreal winter are investigated. It is found that AM may migrate in a compensatory manner among these three types of surfaces on interannual time scales. There are two pairs of strong antiphase relations. One lies in a zonal orientation between the Eurasian continent and the midlatitude Pacific (referred to as Eurasian continent/Pacific antiphase relation) and exhibits a teleconnection pattern characterized by two strong correlation centers, one over Eurasia and one over the North Pacific. The other antiphase AM relation, referred to as ocean/ice-covered Arctic antiphase relation (OIAR), exhibits a meridional orientation between the ice-covered Arctic and liquid water oceans, including the Atlantic and Pacific. In the context of the OIAR, two teleconnection patterns are observed. One features three strong correlation centers, one each over the Mediterranean, Arctic, and North Pacific, and corresponds to AM fluctuations over liquid water oceans. The other is characterized by three strong correlation centers over the Mediterranean, the Arctic, and East Asia, and corresponds to AM fluctuations over the ice-covered Arctic. These teleconnections are the results of thermal contrasts among the three types of surfaces. Rossby waves and vertical circulations play important roles in the formation of these teleconnections. Interestingly, these teleconnections may have significant and widespread influences on the winter climate in the Northern Hemisphere, especially in regions near the Mediterranean, the northern Eurasia, parts of North America, and East Asia.

  19. An assessment of the global, seasonal, and interannual spacecraft record of martian climate in the thermal infrared

    NASA Astrophysics Data System (ADS)

    Liu, J.; Richardson, M. I.; Wilson, R. J.

    2002-09-01

    Comprehensive inter-comparison of thermal infrared data collected by Mariner 9, Viking, and Mars Global Surveyor (MGS) is presented, with a specific focus on air temperatures, dust opacities, and water ice opacities. Emphasis is placed upon creating a uniform data set so as to most effectively reduce inter-instrument biases and offsets. We show that the globally-averaged martian atmosphere executes an exceedingly repeatable annual cycle of air temperature, closing in northern spring and summer to within a Kelvin. The annual cycle shows a strong asymmetry about the equinoxes, with northern summer showing relatively low temperatures and essentially no short-term (tens of days) variability. Viking and MGS air temperatures are essentially indistinguishable, suggesting that the Viking and MGS eras are characterized by exactly the same climatic state. Southern summer is characterized by strong dust storm activity, and we note that the period around Ls=225 is characterized by very high dust opacities associated with dust storm development or decay in every year thus far observed by spacecraft. Dust opacity shows a highly repeatable annual cycle, closing to essentially the same values each year in northern spring and summer, with Viking and MGS opacities being very similar. We show that both Viking and MGS data sets show significant (and similar) polar cap edge dust storm activity. The origins of the various major dust storms can be identified in the thermal infrared data from Viking and MGS, including the "flushing" of dust from the northern autumn baroclinic zone into the southern hemisphere tropics, which has also been identified in visible imaging. Water ice opacities have been retrieved from Viking infrared data for the first time. We show that the cloud belt structure and evolution is essentially the same in each of the multiple years observed by Viking and MGS. Relatively subtle spatial features recur in the cloud belt from year-to-year, suggesting the influence of

  20. Mars dust storms - Interannual variability and chaos

    NASA Technical Reports Server (NTRS)

    Ingersoll, Andrew P.; Lyons, James R.

    1993-01-01

    The hypothesis is that the global climate system, consisting of atmospheric dust interacting with the circulation, produces its own interannual variability when forced at the annual frequency. The model has two time-dependent variables representing the amount of atmospheric dust in the northern and southern hemispheres, respectively. Absorption of sunlight by the dust drives a cross-equatorial Hadley cell that brings more dust into the heated hemisphere. The circulation decays when the dust storm covers the globe. Interannual variability manifests itself either as a periodic solution in which the period is a multiple of the Martian year, or as an aperiodic (chaotic) solution that never repeats. Both kinds of solution are found in the model, lending support to the idea that interannual variability is an intrinsic property of the global climate system. The next step is to develop a hierarchy of dust-circulation models capable of being integrated for many years.

  1. The relationship between interannual and long-term cloud feedbacks

    SciTech Connect

    Zhou, Chen; Zelinka, Mark D.; Dessler, Andrew E.; Klein, Stephen A.

    2015-12-11

    The analyses of Coupled Model Intercomparison Project phase 5 simulations suggest that climate models with more positive cloud feedback in response to interannual climate fluctuations also have more positive cloud feedback in response to long-term global warming. Ensemble mean vertical profiles of cloud change in response to interannual and long-term surface warming are similar, and the ensemble mean cloud feedback is positive on both timescales. However, the average long-term cloud feedback is smaller than the interannual cloud feedback, likely due to differences in surface warming pattern on the two timescales. Low cloud cover (LCC) change in response to interannual and long-term global surface warming is found to be well correlated across models and explains over half of the covariance between interannual and long-term cloud feedback. In conclusion, the intermodel correlation of LCC across timescales likely results from model-specific sensitivities of LCC to sea surface warming.

  2. Ethical Considerations Regarding the Biological Contamination of Climatically Recurrent Special Regions.

    NASA Astrophysics Data System (ADS)

    Clifford, S. M.

    2014-04-01

    years, such as in the Martian polar layered deposits (and other high-latitude, ice-rich environments), at times of high obliquity. Current climate models suggest that, for obliquities > 45°, summertime surface temperatures at polar and near-polar latitudes may approach or exceed the melting point of water for continuous periods of many months (Costard et al., 2001; Jakosky et al., 2003) - conditions that may be repeated annually throughout the maximum obliquity phase of the 105-year obliquity cycle. If so, these icerich, high-latitude environments may be considered climatically recurrent Special Regions - and may be among the most potentially habitable environments on Mars for the survival and growth of terrestrial microorganisms.A significant concern arising from this potential is that, whether by accident or the nominal operation of investigating spacecraft (cleaned to less than Special Region (IVc) standards), we might irreversibly contaminate these sensitive environments. While such contamination may not pose an immediate threat to the integrity of our spacecraft life-detection experiments, its potential impact on the long-term health and ultimate survival of a native Martian biosphere raises significant scientific and ethical concerns, as identified in the NRC report on Preventing the Forward Contamination 0f Mars [4]. Precedents for considering the adoption of planetary protection standards that minimize the potential impact of our exploration efforts on a native biosphere include the NRC report on Preventing the Forward Contamination of Europa, which noted that "future spacecraft missions to Europa must be subject to procedures designed to prevent its contamination by terrestrial organisms. This is necessary to safeguard the scientific integrity of future studies of Europa's biological potential and to protect against potential harm to Europan organisms, if they exist, and is mandated by obligations under the [Outer Space Treaty]" [5]). Virtually identical

  3. Recurrent evolution of herbivory in small, cold-climate lizards: Breaking the ecophysiological rules of reptilian herbivory

    PubMed Central

    Espinoza, Robert E.; Wiens, John J.; Tracy, C. Richard

    2004-01-01

    Herbivory has evolved in many groups of vertebrates, but it is rare among both extinct and extant nonavian reptiles. Among squamate reptiles, (lizards, snakes, and their relatives), <2% of the >7,800 species are considered to be herbivorous, and herbivory is restricted to lizards. Here, we show that within a group of South American lizards (Liolaemidae, ≈170 species), herbivory has evolved more frequently than in all other squamates combined and at a rate estimated to be >65 times faster. Furthermore, in contrast to other herbivorous lizards and to existing theory, most herbivorous liolaemids are small bodied and live in cool climates. Herbivory is generally thought to evolve only in reptile species that are large bodied, live in warm climates, and maintain high body temperatures. These three well known “rules” of herbivory are considered to form the bases of physiological constraints that explain the paucity of herbivorous reptile species. We suggest that the recurrent and paradoxical evolution of herbivory in liolaemids is explained by a combination of environmental conditions (promoting independent origins of herbivory in isolated cool-climate regions), ecophysiological constraints (requiring small body size in cool climates, yet high body temperatures for herbivores), and phylogenetic history. More generally, our study demonstrates how integrating information from ecophysiology and phylogeny can help to explain macroevolutionary trends. PMID:15550549

  4. Effects of Climate Change on Indigenous Livelihoods: The Case of Recurrent Droughts among Nomadic Pastoralist of Southeastern Kenya

    NASA Astrophysics Data System (ADS)

    Mwangi, M. N.; Desanker, P. V.

    2006-12-01

    Drought is the most injurious impact of climate change that decimates lives and hinders socioeconomic development in most rangelands of Kenya. Several scientific evidences indicate that global climate change will increase frequency and intensity of droughts. This will have important ramification for ecosystems and social systems in the rangelands of southeastern Kenya, and correctly so. These rangelands are fragile and degraded; and the inhabitants are mostly poverty-stricken. Nomadic pastoralism is the chief source of livelihood in this region; it relies on local natural pastures. Besides, pressures from land use change constitute an additional exposure, of nomadic pastoralism, to vulnerabilities of this climatic hazard. This region is highly prone to droughts; it is currently recovering from a devastating drought that started in early 2005 and terminated at the start this year. Most important, and like most societies in sub-Saharan Africa, inadequate adaptive capacity among nomadic pastoralists of Kenya, exacerbates deleterious impacts of drought. The livelihood of these pastoralists, therefore, stands to be destabilized. This study presents findings from an on-going research in Kajiado District of southeastern Kenya. Impacts of and adaptation strategies to recurrent and prolonged droughts among the nomadic Maasai pastoralist are presented. The study concludes with possible future scenarios of this form of pastoralism from which climate change actors can draw from.

  5. Changing Climate, Disrupted Livelihoods: The Case of Vulnerability of Nomadic Maasai Pastoralism to Recurrent Droughts in Kajiado District, Kenya

    NASA Astrophysics Data System (ADS)

    Mwangi, M. N.; Desanker, P. V.

    2007-12-01

    Pastoralism is practiced in all arid and semiarid lands (ASALs) of Africa. High interannual rainfall variability and degraded ecosystems characterize these ASALs and limits arable farming. Under these conditions, pastoralism has evolved as the most feasible livelihood system in ASALs, where total annual rainfall correlates with annual net primary productivity, especially grass. Maasai of East Africa are the largest group of nomadic pastoralists in Africa, with about two-thirds living in southern Kenya, mainly in Kajiado and Narok Districts. Maasai people of Kenya subsist by nomadic pastoralism. Nomads migrate with their livestock in search of natural pastures and water as climatic and environmental circumstances mandate. Successful migrations of nomadic pastoralists are being hampered by changing social and ecological factors both at local and broader scales. What is more, increased frequency and duration of drought constitute a major challenge with which the Maasai have to confront. Drought is a slow-developing phenomenon; therefore, it captures delayed attention. Nonetheless, the cumulative impacts of drought are more immense. Drought triggers catastrophic events that diminish adaptive capacity of inhabitants of these ASALs; this is conspicuous in Kajiado District where livestock productivity plummet as resource base erodes. What is more, global climate change is projected to intensify the occurrence, severity and duration of droughts in this region. Frequent droughts are likely to disrupt proper functioning of nomadic Maasai pastoralism. This study presents findings from an integrated research conducted in Kajiado District during the last two years. Spatiotemporal trends of drought, effects of drought on, and possible future of nomadic Maasai pastoralism are presented. This is informative to the Maasai pastoralists, policy makers and other actors in this sector. Most important, the study is contributes toward formulation of informed drought management strategies

  6. Interannual variability of the Arctic freshwater cycle in the second half of the twentieth century in a regionally coupled climate model

    NASA Astrophysics Data System (ADS)

    Niederdrenk, Anne Laura; Sein, Dmitry V.; Mikolajewicz, Uwe

    2016-03-01

    We use a regionally coupled ocean-sea ice-atmosphere-hydrological discharge model to investigate the influence of changes in the atmospheric large-scale circulation on the interannual variability of the Arctic freshwater (FW) components. This model includes all sinks and sources of FW and allows for the analysis of a closed FW cycle in the Arctic. We show that few atmospheric winter modes explain large parts of the interannual variability of the Arctic FW cycle. A strong Icelandic low causing anomalous strong westerlies over the North Atlantic leads to warmer and wetter conditions over Eurasia. The ocean circulation is then characterized by a strong transpolar drift leading to increased export of FW in liquid and solid form into the North Atlantic. In contrast to this, a weaker than usual Icelandic low and a strong Siberian high is associated with a strong Beaufort Gyre and thus an accumulation of FW within the Arctic Ocean. Not only specific winter conditions but also increased precipitation in late spring and summer, caused by enhanced cyclone activity over land, lead to increased Eurasian runoff, which is responsible for most of the variability in Arctic river runoff.

  7. Evaluation of the UK Met Office's HadGEM3-RA and HadRM3P regional climate models within South America-CORDEX simulations: ENSO related interannual precipitation variability

    NASA Astrophysics Data System (ADS)

    Bozkurt, D.; Rojas, M.

    2014-12-01

    This study aims to investigate and compare the ability of the UK Met Office's HadGEM3-RA and HadRM3P regional climate models (RCMs) to simulate mean and interannual variability of precipitation over South America with a special focus on Chile. The HadGEM3-RA is a regional version of the newly developed HadGEM3 global model and the HadRM3P is based on the earlier HadCM3 global model. The RCMs simulations were carried out at 0.44o x 0.44o degree resolution over South America-CORDEX domain for the period 1989-2008. The initial and boundary conditions were provided by ERA-Interim Reanalysis data available at 6-h intervals with a resolution of 1.5o x 1.5o in the horizontal and 37 pressure levels. We compare the results against a number of observational datasets, including gridded dataset of CRU, UDEL, TRMM and GPCP. Moreover, available station data is derived from Direccion General de Aguas (DGA) mainly for Central Chile, which is the heartland of Chile with the highest population and important economic activities. The analysis is mainly focused on evaluating the abilities of the RCMs in simulating spatial pattern and ENSO related precipitation variability in different subregions of South America-CORDEX domain. In general, both RCMs have a good skill in reproducing spatial pattern and annual cycle of observed precipitation in climatically different subregions. However, both RCMs tend to underestimate precipitation in the Amazon Basin, which is more pronounced in the HadRM3P simulations. On the contrary, the RCMs tend to overestimate the precipitation over the Andes and southern Chile. The overestimation could be related to the physical core of the RCMs, but the discrepancies could also arise due to insufficient station network, especially in the mountainous areas, potentially yielding smaller precipitation quantities in the observed data than the true ones. In terms of interannual variability, the models capture ENSO related wet and dry interannual precipitation

  8. Effect of climate, intra and inter-annual variability, on nutrients emission (C,N, P) in stream water: lessons from an agricultural long term observatory of the temperate zone

    NASA Astrophysics Data System (ADS)

    Gascuel-Odoux, Chantal; Remi, Dupas; Patrick, Durand; Ophélie, Fovet; Gerard, Gruau; Anne, Jaffrezic; Guillaume, Humbert; Philippe, Merot; Gu, Sen

    2016-04-01

    Agriculture greatly contributes to modify C, N and P cycles, particularly in animal breeding regions due to high inputs. Climatic conditions, intra and inter-annual variabilities, modify nutrient stream water emissions, acting in time on transfer and transformation, accumulation and mobilization processes, connecting and disconnecting in time different compartments (soil, riparian areas, groundwater). In agricultural catchments, nutrient perturbations are dominated by agricultural land use, and decoupling human activities and climate effects is far from easy. Climate change generally appears as a secondary driver compared to land use. If studied, generally only one nutrient is considered. Only long term, high frequency and multiple element data series can decouple these two drivers. The Kervidy-Naizin watershed belongs to the AgrHyS environmental research observatory (http://www6.inra.fr/ore_agrhys_eng), itself included in RBV (French catchment network of the CZO). On this catchment, 6 years of daily data on DOC, NO3, SRP, TP concentrations allow us to analyze the effect of seasonal and inter-annual climatic variabilities on water quality (C, N, P). Different papers have been published on the effect of climate on nitrate (Molenat et al, 2008), SRP and TP (Dupas et al, 2015) and DOC (Humbert et al, 2015). We will present first results comparing the effect of climate on these three major solute forms of C, N and P. While C and P dynamics are very close and controlled by fluctuation of water table downslope, i.e. in riparian areas, mobilizing C and P in time, nitrate dynamics is controlled by GW dynamics upslope acting as the major N reservoir. As example, the dryness conditions in summer appears a key factor of the C and P emissions in autumn. All the three solute forms interact when anoxic conditions are observed in riparian zones. These basic processes explain how climatic variability can influence and explain interactions between C, N and P emissions in stream

  9. Florida Current: seasonal and interannual variability

    SciTech Connect

    Schott, F.; Zantopp, R.

    1985-01-18

    Annual and interannual variations in the Florida Current, Caribbean and subtropical Atlantic are investigated with the use of historical sea level differences and wind field data. Observational and model evidence suggests that the seasonal transport cycle of the Florida Current is locally forced, either upstream in the Caribbean or downstream over topography. Although at seasonal and shorter periods sea level or bottom pressure fluctuations on the left side of the Florida Current contribute almost all of the variance of sea level difference across the Florida Straits and hence transport, this relation does not seem to apply at interannual time scales. Using results from the Subtropical Atlantic Climate Studies, it is estimated from historical sea level data that interannual transport fluctuations of the Florida Current are only of order 1 x 10/sup 6/ cubic meters per second. Interannual fluctuations in the 2- to 3-year period range in the Florida Straits seem to be correlated with sea level differences across the Caribbean and the subtropical Atlantic but not with Sverdrup transport fluctuations in the subtropical Atlantic. 26 references, 2 figures.

  10. An interannual assessment of the relationship between the stable carbon isotopic composition of ecosystem respiration and climate in a high-elevation subalpine forest

    NASA Astrophysics Data System (ADS)

    Riveros-Iregui, Diego A.; Hu, Jia; Burns, Sean P.; Bowling, David R.; Monson, Russell K.

    2011-06-01

    We measured the carbon isotopic composition (δ13C) of ecosystem respiration (δ13CR) in a subalpine forest across four growing seasons to examine whether patterns in δ13CR were consistent with those expected based on leaf-level gas-exchange theory, and in agreement with past studies of the relation between δ13CR and climate conducted across broad geographic regions. Conventional trends (i.e., less negative δ13CR with increased vapor pressure deficit (VPD) and air temperature (TAIR), and decreased soil moisture (θ)) were observed when we focused on the driest portions of average-wetness years and when δ13CR was positively correlated with nighttime ecosystem respiration (RE). Nonconventional trends (i.e., more negative δ13CR with decreased θ, and increased VPD and TAIR) were observed under specific climatic conditions (e.g., late snowmelt; extreme TAIR late in the growing season), and when δ13CR was negatively correlated with RE. These nonconventional trends were independently corroborated using δ13C of extracted sugars from needles of dominant tree species at the site. Our results clearly demonstrate that the commonly reported relations between δ13CR and climate may break down depending on the interactions among environmental conditions. Efforts to model and predict the variability of δ13CR under changing climatic variables must characterize and parameterize the effects of unique combinations of weather conditions and variable hydrologic regimes, in combination with the susceptibility of photosynthetic isotope discrimination to extreme air temperatures.

  11. Comparing the interannual variability of NDVI of croplands over China and India for the period 1982-2006: socioeconomic versus climatic drivers of change.

    NASA Astrophysics Data System (ADS)

    Milesi, C.; Hashimoto, H.; Ichii, K.; Wang, W.; Michaelis, A.; Melton, F.; Hiatt, S.; Nemani, R.

    2008-12-01

    China and India, holding the world's largest populations, have in the matter of a few decades moved from being among the poorest nations to becoming the fastest growing economies. The broadly similar economic goals of these two countries have been pursued under significantly different governing institutions and policies. Here we compare the effects of the different socio-economic trajectories of China and India on the patterns of vegetation greenness over cropland areas inferred from coarse resolution remote sensing data and their sensitivity to ongoing and future climate changes. For this purpose we analyze 1982-2006 NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) from the GIMMS data set along with climate data and socio-economic statistics. We find that the 1982-2006 NDVI patterns over India are characterized by a strong significant upward trend linked to a recent expansion of minor irrigation projects, which are heavily relying on groundwater exploitation and may now have reached a limit due to exhaustion of resources and increased sensitivity to climate changes. In China, large scale agricultural development preceding the 1980s has brought the NDVI over Chinese cropland to much higher values than over India, reflecting the much higher use of fertilizer and crop yields. After a period of increasing NDVI trends up to the late 1990s, previously documented as the result of a longer growing season due to increased spring temperatures, NDVI has declined, likely reflecting a more recent focus of China on industrial rather than agricultural growth. This study highlights the strong coupling of the socioeconomic and physical environment at scales relevant to ecosystem and climate models.

  12. Interannual variability of photosynthesis across Africa and its attribution

    NASA Astrophysics Data System (ADS)

    Williams, Christopher A.; Hanan, Niall P.; Baker, Ian; Collatz, G. James; Berry, Joseph; Denning, A. Scott

    2008-12-01

    Africa is thought to be a large source of interannual variability in the global carbon cycle, only vaguely attributed to climate fluctuations. This study uses a biophysical model, Simple Biosphere, to examine in detail what specific factors, physiological (acute stress from low soil water, temperature, or low humidity) and biophysical (low vegetation radiation use), are responsible for spatiotemporal patterns of photosynthesis across the African continent during the period 1982-2003. Acute soil water stress emerges as the primary factor driving interannual variability of photosynthesis for most of Africa. Southern savannas and woodlands are a particular hot spot of interannual variability in photosynthesis, owing to high rainfall variability and photosynthetic potential but intermediate annual rainfall. Surprisingly low interannual variability of photosynthesis in much of the Sudano-Sahelian zone derives from relatively low vegetation cover, pronounced humidity stress, and somewhat lower rainfall variability, whereas perennially wet conditions diminish interannual variability in photosynthesis across much of the Congo Basin and coastal West Africa. Though not of focus here, the coefficient of variation in photosynthesis is notably high in drylands and desert margins (i.e., Sahel, Greater Horn, Namib, and Kalahari) having implications for supply of food and fiber. These findings emphasize that when considering impacts of climate change and land surface feedbacks to the atmosphere, it is important to recognize how vegetation, climate, and soil characteristics may conspire to filter or dampen ecosystem responses to hydroclimatic variability.

  13. A 150 year record of inter-annual climate variability and organic carbon burial in Santa Monica and Santa Barbara Basins

    SciTech Connect

    Hagadorn, J.W.; Stott, L.D.; Sinha, A.; Rincon, M. . Dept. of Geological Sciences); Schimmelmann, A. . Scripps Inst. of Oceanography)

    1992-01-01

    Stable isotopic measurements were conducted on total organic carbon (TOC) and fossil planktonic foraminifera in laminated sediments collected from Santa Monica and Santa Barbara Basins, California Borderland, in order to investigate relationships between climatic variability and organic carbon burial. These data currently provide biannual sample resolution back to 1750 AD. During the past 150 years, there has been a positive covariance between the carbon isotopic composition of fossil planktonic foraminifera and of TOC. Periods of increased delta C-13 of TOC and foraminifera correspond to higher organic carbon burial in Santa Monica and Santa Barbara Basins. When combined, these patterns are interpreted as variation in productivity within the basins. Isotopic variability in TOC and planktonic foraminifera is significantly higher prior to 1900 AD. Although spring sea surface temperatures were also significantly more variable during this period, the authors do not recognize a systematic relationship between temperature and organic carbon burial. Spectral analysis of isotopic compositions of fossil foraminifera calcite, TOC, organic carbon burial and lamination frequency in the sediments reveal distinct spectral peaks at 5 and 7.7 years, corresponding to ENSO/El Nino frequencies. Additional spectral peaks occur at 19 and 20 years. Previous time series analyses of tree ring width records indicate similar decadal-scale frequencies and suggest a possible link to solar and/or lunar nodal tidal cycles. While these initial results suggest a relationship between climate-cyclicity, primary productivity and organic carbon burial, the phase relationship cannot be deciphered from this preliminary data set.

  14. Isotopic monitoring (2H, 18O) of the St. Lawrence and Ottawa rivers between 1997 and 2003- Links with interannual climatic variability and hydrological processes in their catchment basins

    NASA Astrophysics Data System (ADS)

    Myre, A.; Hillaire-Marcel, C.

    2004-05-01

    This study based on a water isotope (18O and 2H) monitoring of the St. Lawrence and Ottawa rivers (Canada) is a contribution to the international IAEA project: Isotopes tracing of hydrologic processes in large river basins [Gibson et al., 2002. EOS 83: 613 et p.]. Sampling of the St. Lawrence and Ottawa river waters started in 1997, on a biweekly to weekly basis. Monitoring stations are located at Montreal (i.e., at the outlet of the Great Lakes), Quebec City (the estuary of the St. Lawrence) and at the Carillon hydroelectric dam, near the outlet of a major tributary, the Ottawa River into the St. Lawrence itself. The goal of the study was to examine the seasonal and interannual variability of isotopic signatures of the St. Lawrence and Ottawa rivers, in relation notably with interannual climatic variations, and seasonal hydrologic processes in the watershed (summer evaporation, snowmelt, transit time of precipitation signals into runoff). Waters sampled at the three stations depict distinct isotopic compositions. At Montreal, relatively stable isotopic composition are observed with a mean weighted annual value of -54 % for 2H and -7.1 % for 18O. The Ottawa River water at Carillon also displays stable isotopic compositions but much lighter values (weighted mean annual values: -80 % for 2H and -10.8 % for 18O). Finally, isotopic compositions at Quebec City are intermediate between those of Montreal and Carillon, but show a much larger variability. They reflect mixing between the heavy isotope enriched Great Lakes water, the lighter water from the Ottawa River, and highly variable inputs from smaller tributaries (from the Laurentides and Appalachian mountains). The mean weighted isotopic compositions at Quebec City are -65 % and -8.6 %, respectively for 2H and 18O). Evaporative enrichment, in particular during low water level episodes, seem to be more important in the Ottawa River catchment than in the Great Lakes basin, based on a comparison of isotopic clusters at

  15. Information transfer across the scales of climate variability: The effect of the 7-8 year cycle on the annual and interannual scales

    NASA Astrophysics Data System (ADS)

    Palus, Milan; Jajcay, Nikola; Hlinka, Jaroslav; Kravtsov, Sergey; Tsonis, Anastasios

    2016-04-01

    Complexity of the climate system stems not only from the fact that it is variable over a huge range of spatial and temporal scales, but also from the nonlinear character of the climate system that leads to interactions of dynamics across scales. The dynamical processes on large time scales influence variability on shorter time scales. This nonlinear phenomenon of cross-scale causal interactions can be observed due to the recently introduced methodology [1] which starts with a wavelet decomposition of a multi-scale signal into quasi-oscillatory modes of a limited bandwidth, described using their instantaneous phases and amplitudes. Then their statistical associations are tested in order to search for interactions across time scales. An information-theoretic formulation of the generalized, nonlinear Granger causality [2] uncovers causal influence and information transfer from large-scale modes of climate variability with characteristic time scales from years to almost a decade to regional temperature variability on short time scales. In analyses of air temperature records from various European locations, a quasioscillatory phenomenon with the period around 7-8 years has been identified as the factor influencing variability of surface air temperature (SAT) on shorter time scales. Its influence on the amplitude of the SAT annual cycle was estimated in the range 0.7-1.4 °C and the effect on the overall variability of the SAT anomalies (SATA) leads to the changes 1.5-1.7 °C in the annual SATA means. The strongest effect of the 7-8 year cycle was observed in the winter SATA means where it reaches 4-5 °C in central European station and reanalysis data [3]. This study is supported by the Ministry of Education, Youth and Sports of the Czech Republic within the Program KONTAKT II, Project No. LH14001. [1] M. Palus, Phys. Rev. Lett. 112 078702 (2014) [2] M. Palus, M. Vejmelka, Phys. Rev. E 75, 056211 (2007) [3] N. Jajcay, J. Hlinka, S. Kravtsov, A. A. Tsonis, M. Palus, Time

  16. Interannual and seasonal dynamics, and the age, of nonstructural carbohydrate pools in the stemwood of temperate trees across a climatic gradient in the Northeastern US

    NASA Astrophysics Data System (ADS)

    Richardson, A. D.; Carbone, M. S.; Czimczik, C. I.; Keenan, T. F.; Schaberg, P.; Murakami, P.; Xu, X.

    2012-04-01

    Like all plants, forest trees accumulate and store non-structural carbohydrates (NSC) as resources to be used in the future. This can be viewed as a bet-hedging strategy, providing reserves that the tree can draw on in times of stress—e.g., following disturbance, disease, or extreme climatic events. In the context of climate change, understanding factors influencing the availability of these stored NSC compounds to support growth and metabolism is essential for predicting the resilience of forests to environmental stress factors. We conducted this study to investigate the role of these stored NSC pools in the context of ecosystem C balance at time scales from days to years. At quarterly intervals over a three-year period, we monitored stemwood total NSC concentrations of the dominant tree species of New England. Work was conducted at three sites along a climatic gradient: an oak-dominated transition hardwood forest (Harvard Forest), a maple-beech-birch northern hardwood forest (Bartlett Experimental Forest), and a spruce-fir forest (Howland Forest). We observed large differences among species both in NSC concentrations, and in how the NSC pool is partitioned to different compounds (starch, sucrose, glucose, fructose, raffinose, and stachyose). Within a species, however, seasonal dynamics were remarkably similar across sites. We used the bomb radiocarbon (14C) spike to estimate the average age of the sugars and starches in the NSC pool in a subset of nine maple trees from each site. We found that the age of sugars ranged from 1-24 y and starches from 1-31 y. The ages of sugar and starch pools were highly correlated across all sites, and there was no significant difference in the mean age of the two pools, which was ~11 y. Using a one-pool representation of NSC reserves (similar to the standard approach used in several existing forest C models) our model FöBAAR (FOrest Biomass, Allocation, Assimilation and Respiration) failed to reproduce the seasonal NSC dynamics

  17. Anatomy of the recurrent coastal sediment plume in Lake Michigan and its impacts on light climate, nutrients, and plankton

    NASA Astrophysics Data System (ADS)

    Vanderploeg, H. A.; Johengen, T. H.; Lavrentyev, P. J.; Chen, C.; Lang, G. A.; Agy, M. A.; Bundy, M. H.; Cavaletto, J. F.; Eadie, B. J.; Liebig, J. R.; Miller, G. S.; Ruberg, S. A.; McCormick, M. J.

    2007-03-01

    As part of the Episodic Events Great Lakes Experiment, we sampled total suspended matter (TSM), light climate, nutrients, and plankton along cross-margin transects in southern Lake Michigan during February, March, and April 1998-2000 to capture conditions before, during, and after the occurrence of storm-driven recurrent coastal sediment plumes to define the anatomy of the resuspension events and get insights into their interactions with nutrients and plankton. Variability in timing and strength of winter storms among years led to different timing, intensity, and extent of plumes among years. TSM concentrations in the core of plumes varied between 15 and 30 mg L-1, and photic depth was reduced to ˜1 to 2 m, thus potentially seriously limiting phytoplankton growth in plume areas. Total P concentration was highly correlated with TSM and river influence. Chlorophyll concentrations were lower in plume regions than in adjacent areas, in contrast to the relatively constant chlorophyll concentration across the plume predicted by a coupled hydrodynamic and nutrient-phytoplankton-zooplankton model. Contrary to expectation, protozoan microzooplankton (MZ) biomass was not more abundant in the plume than adjacent waters, but was highest in nearshore areas receiving river inflow. Storms affected horizontal distribution of zooplankton. Because of the lower concentrations of phytoplankton in the plume, the plume over the short term had a negative impact on zooplankton during this food-limiting season. Our results combined with those of other EEGLE studies lead us to conclude that storms and storm-driven plumes had a negative effect on the planktonic food web.

  18. Grape harvest and yield responses to inter-annual changes in temperature and precipitation in an area of north-east Spain with a Mediterranean climate

    NASA Astrophysics Data System (ADS)

    Camps, Josep Odó; Ramos, María Concepción

    2012-09-01

    This study presents an analysis of temperature and precipitation trends and their impact on grape harvests in the Penedès region (NE Spain). It includes analyses of maximum, minimum and mean daily temperatures (for both the growing and ripening seasons) and daily rainfall (for the hydrological year, the growing season and each phenological stage) for three observatories in the immediate area. We analysed a series of factors: beginning and end harvest dates; the day on which a given potential alcoholic degree was reached; and yield for several varieties of grape grown in the area in relation to climatic variables. Maximum temperatures increased at all the observatories, with greater values being recorded in recent years (1996-2009) than in previous decades (1960s-2000s): we observed increases in average growing season temperatures of 0.11°C per year for the period 1996-2009 vs 0.04°C per year for the period 1960-2009 at Vilafranca del Penedès. These temperature changes were due mainly to increases in maximum temperatures and an increase in the incidence of extreme heat (number of days with T > 30°C). Crop evapotranspiration also increased significantly during the same period. The Winkler index also increased, so the study area would correspond to region IV according to that climatic classification. There were no significant trends in annual rainfall but rainfall recorded between bloom and veraison decreased significantly at the three observatories, with the greatest decrease corresponding to the period 1996-2009. The dates on which harvests started and ended showed a continuous advance (of between -0.7 and -1.1 days per year, depending on the variety), which was significantly correlated with the average mean and maximum daily growing season temperatures (up to -7.68 days for 1°C increase). Winegrape yield was influenced by the estimated water deficit (crop evapotranspiration minus precipitation) in the bloom-veraison period; this value increased due to a

  19. Interannual variability of stratospheric trace gases: The role of extratropical wave driving

    NASA Astrophysics Data System (ADS)

    Ma, J.; Waugh, D. W.; Douglass, A. R.; Kawa, S. R.; Newman, P. A.; Pawson, S.; Stolarski, R.; Lin, S. J.

    2004-10-01

    The interannual variability of methane and ozone from a 35-year middle atmosphere climate model simulation with no interannual variations in external forcing or chemistry is examined. The internal dynamics in the model produces large tracer interannual variability, particularly in polar regions. During winter and spring the interannual standard deviation in the polar lower-middle stratosphere is about 30% of the climatological mean for methane and 15% for ozone. Global-scale, coherent interannual variations in temperature, residual circulation, and tracers are correlated with variability in the extratropical wave forcing. Statistically significant positive correlations between wave driving and polar tracer tendencies, including column ozone, occur from autumn to spring in both hemispheres. These positive correlations imply that interannual variations in polar tracers are dominated by variations in the horizontal eddy transport and not by variations in residual mean descent rates.

  20. The relationship between interannual and long-term cloud feedbacks

    DOE PAGESBeta

    Zhou, Chen; Zelinka, Mark D.; Dessler, Andrew E.; Klein, Stephen A.

    2015-12-11

    The analyses of Coupled Model Intercomparison Project phase 5 simulations suggest that climate models with more positive cloud feedback in response to interannual climate fluctuations also have more positive cloud feedback in response to long-term global warming. Ensemble mean vertical profiles of cloud change in response to interannual and long-term surface warming are similar, and the ensemble mean cloud feedback is positive on both timescales. However, the average long-term cloud feedback is smaller than the interannual cloud feedback, likely due to differences in surface warming pattern on the two timescales. Low cloud cover (LCC) change in response to interannual andmore » long-term global surface warming is found to be well correlated across models and explains over half of the covariance between interannual and long-term cloud feedback. In conclusion, the intermodel correlation of LCC across timescales likely results from model-specific sensitivities of LCC to sea surface warming.« less

  1. Comparison of different wind products and buoy wind data with seasonality and interannual climate variability in the southern Bay of Biscay (2000-2009)

    NASA Astrophysics Data System (ADS)

    Alvarez, Inés; Gomez-Gesteira, Moncho; deCastro, Maite; Carvalho, David

    2014-08-01

    Ocean surface winds are essential factors in determining oceanographic and atmospheric processes that can affect ocean circulation and wave generation. Accurate surface wind datasets are needed, therefore, to enable the proper analysis of these processes. Wind data from six databases (National Centers for Environmental Prediction reanalysis (NCEP Reanalysis II), European Centre for Medium-Range Weather Forecasts (ECMWF) re-analysis (ERA-Interim), Modern-Era Retrospective-analysis for Research and Applications (MERRA), NCEP Climate Forecast System Reanalysis (CFSR), QuikSCAT and Cross-Calibrated Multi-Platform (CCMP)) were compared with wind measured in situ by four ocean buoys at the southern limit of the Bay of Biscay. The study covered the period 2000-2009 in such a way that the extent of the time series reduced the margin of error and allowed the disaggregation of the wind data using velocity bins and direction sectors. Statistical results confirmed that datasets with finer spatial resolution (lower than 0.5°×0.5°) gave better results, especially in near-shore areas. A more complete analysis was, therefore, carried out using the finer resolution datasets (QuikSCAT, CCMP and CFSR). This comparison showed that all the datasets were less accurate at low wind speeds (<4 m s-1) and more accurate at moderate wind speeds. The calculated mean wind speed errors were similar for the three datasets, and the lowest value (1.67 m s-1) was from the CCMP dataset. The lowest mean error for wind direction (~37°) was also observed in the CCMP data. The lowest mean wind speed (and direction) bias was obtained from the QuikSCAT data, and the next lowest from the CFSR data. The seasonality for north and east wind components was also determined for the last decade and the results were consistent with forcing for the continental slope current seasonality and winter temperatures or Navidad by wind stress. Correlations between NAO and north and east wind components were low showing

  2. The effect of inter-annual variability of consumption, production, trade and climate on crop-related green and blue water footprints and inter-regional virtual water trade: A study for China (1978-2008).

    PubMed

    Zhuo, La; Mekonnen, Mesfin M; Hoekstra, Arjen Y

    2016-05-01

    Previous studies into the relation between human consumption and indirect water resources use have unveiled the remote connections in virtual water (VW) trade networks, which show how communities externalize their water footprint (WF) to places far beyond their own region, but little has been done to understand variability in time. This study quantifies the effect of inter-annual variability of consumption, production, trade and climate on WF and VW trade, using China over the period 1978-2008 as a case study. Evapotranspiration, crop yields and green and blue WFs of crops are estimated at a 5 × 5 arc-minute resolution for 22 crops, for each year in the study period, thus accounting for climate variability. The results show that crop yield improvements during the study period helped to reduce the national average WF of crop consumption per capita by 23%, with a decreasing contribution to the total from cereals and increasing contribution from oil crops. The total consumptive WFs of national crop consumption and crop production, however, grew by 6% and 7%, respectively. By 2008, 28% of total water consumption in crop fields in China served the production of crops for export to other regions and, on average, 35% of the crop-related WF of a Chinese consumer was outside its own province. Historically, the net VW within China was from the water-rich South to the water-scarce North, but intensifying North-to-South crop trade reversed the net VW flow since 2000, which amounted 6% of North's WF of crop production in 2008. South China thus gradually became dependent on food supply from the water-scarce North. Besides, during the whole study period, China's domestic inter-regional VW flows went dominantly from areas with a relatively large to areas with a relatively small blue WF per unit of crop, which in 2008 resulted in a trade-related blue water loss of 7% of the national total blue WF of crop production. The case of China shows that domestic trade, as governed by

  3. Validation of Interannual Differences of AIRS Monthly Mean Parameters

    NASA Technical Reports Server (NTRS)

    Susskind, Joel; Iredell, Lena; Keita, Fricky; Molnar, Gyula

    2005-01-01

    Monthly mean fields of select geophysical parameters derived from analysis of AIRS/AMSU data, and their interannual differences, are shown and compared with analogous fields derived from other sources. All AIRS fields are derived using the AIRS Science Team Version 4 algorithm. Monthly mean results are shown for January 2004, as are interannual differences between January 2004 and January 2003. AIRS temperature and water vapor profile fields are compared with monthly mean collocated ECMWF 3 hour forecast and monthly mean TOVS Pathfinder Path A data. AIRS Tropospheric and Stratospheric coarse climate indicators are compared with analogous MSU products derived by Spencer and christy and found in the TOVS Pathfinder Path A data set. Total ozone is compared with results produced by TOMS. OLR is compared with OLR derived using CERES data and found in the TOVS Pathfinder Path A data set. AIRS results agree well in all cases, especially in the interannual difference sense.

  4. Clusters of interannual sea ice variability in the northern hemisphere

    NASA Astrophysics Data System (ADS)

    Fučkar, Neven S.; Guemas, Virginie; Johnson, Nathaniel C.; Massonnet, François; Doblas-Reyes, Francisco J.

    2015-11-01

    We determine robust modes of the northern hemisphere (NH) sea ice variability on interannual timescales disentangled from the long-term climate change. This study focuses on sea ice thickness (SIT), reconstructed with an ocean-sea-ice general circulation model, because SIT has a potential to contain most of the interannual memory and predictability of the NH sea ice system. We use the K-means cluster analysis—one of clustering methods that partition data into groups or clusters based on their distances in the physical space without the typical constraints of other unsupervised learning statistical methods such as the widely-used principal component analysis. To adequately filter out climate change signal in the Arctic from 1958 to 2013 we have to approximate it with a 2nd degree polynomial. Using 2nd degree residuals of SIT leads to robust K-means cluster patterns, i.e. invariant to further increase of the polynomial degree. A set of clustering validity indices yields K = 3 as the optimal number of SIT clusters for all considered months and seasons with strong similarities in their cluster patterns. The associated time series of cluster occurrences exhibit predominant interannual persistence with mean timescale of about 2 years. Compositing analysis of the NH surface climate conditions associated with each cluster indicates that wind forcing seem to be the key factor driving the formation of interannual SIT cluster patterns during the winter. Climate memory in SIT with such interannual persistence could lead to increased predictability of the Artic sea ice cover beyond seasonal timescales.

  5. Estimating inter-annual runoff variability from global hydroclimatic data

    NASA Astrophysics Data System (ADS)

    Peel, Murray; McMahon, Thomas; Finlayson, Brian

    2016-04-01

    Inter-annual variability of runoff, measured by the coefficient of variation of annual runoff (RCv), is an important constraint on reservoir yield and storage size for water resources management. For a catchment with a fixed storage capacity, any increase in reservoir inflow RCv translates into reduced reservoir yield for a given reliability of supply. Developing an improved understanding of the physical influences on inter-annual runoff variability around the world and how these may change in future is of vital importance to achieving on-going robust water and catchment management. Here we take a large-scale Comparative Hydrology approach to develop empirical relationships for RCv using a global hydroclimatic data set of 588 catchments. Empirical RCv relationships are developed for the World and catchments experiencing predominantly (≥75% catchment area) tropical, arid, temperate or cold climate types. The RCv relationships are developed specifically using non-streamflow based predictor variables so they can be used for predicting RCv in ungauged basins (the PUB problem - Prediction in Ungauged Basins) and or ungauged climates (the PUC problem - Prediction in Ungauged Climates) if past or future projections of the required predictor variables are available. Empirical relationship predictor variables are based on precipitation, evaporative demand, vegetation and topography. Key variables that contribute to explaining RCv in each relationship will be assessed to identify the dominant drivers of RCv and how the contribution of those drivers varies between regions and climate types, with particular focus on inter-annual climate variability.

  6. Terrestrial Waters and Sea Level Variations on Interannual Time Scale

    NASA Technical Reports Server (NTRS)

    Llovel, W.; Becker, M.; Cazenave, A.; Jevrejeva, S.; Alkama, R.; Decharme, B.; Douville, H.; Ablain, M.; Beckley, B.

    2011-01-01

    On decadal to multi-decadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea level variations. However, modification of the terrestrial water cycle due to climate variability and direct anthropogenic forcing may also affect sea level. For the past decades, variations in land water storage and corresponding effects on sea level cannot be directly estimated from observations because these are almost non-existent at global continental scale. However, global hydrological models developed for atmospheric and climatic studies can be used for estimating total water storage. For the recent years (since mid-2002), terrestrial water storage change can be directly estimated from observations of the GRACE space gravimetry mission. In this study, we analyse the interannual variability of total land water storage, and investigate its contribution to mean sea level variability at interannual time scale. We consider three different periods that, each, depend on data availability: (1) GRACE era (2003-2009), (2) 1993-2003 and (3) 1955-1995. For the GRACE era (period 1), change in land water storage is estimated using different GRACE products over the 33 largest river basins worldwide. For periods 2 and 3, we use outputs from the ISBA-TRIP (Interactions between Soil, Biosphere, and Atmosphere-Total Runoff Integrating Pathways) global hydrological model. For each time span, we compare change in land water storage (expressed in sea level equivalent) to observed mean sea level, either from satellite altimetry (periods 1 and 2) or tide gauge records (period 3). For each data set and each time span, a trend has been removed as we focus on the interannual variability. We show that whatever the period considered, interannual variability of the mean sea level is essentially explained by interannual fluctuations in land water storage, with the largest contributions arising from tropical river basins.

  7. Regional simulation of interannual variability over South America

    NASA Astrophysics Data System (ADS)

    Misra, V.; Dirmeyer, P. A.; Kirtman, B. P.; Juang, H.-M. Henry; Kanamitsu, M.

    2002-08-01

    Three regional climate simulations covering the austral summer season during three contrasting phases of the El Niño-Southern Oscillation cycle were conducted with the Regional Spectral Model (RSM) developed at the National Centers for Environmental Prediction (NCEP). The simulated interannual variability of precipitation over the Amazon River Basin, the Intertropical Convergence Zone, the Pacific and Atlantic Ocean basins, and extratropical South America compare reasonably well with observations. The RSM optimally filters the peturbations about a time-varying base field, thereby enhancing the information content of the global NCEP reanalysis. The model is better than the reanalysis in reproducing the observed interannual variability of outgoing longwave radiation at both high frequencies (3-30 days) and intraseasonal (30-60 days) scales. The low-level jet shows a peak in its speed in 1998 and a minimum in the 1999 simulations. The lag correlation of the jet index with convection over various areas in continental South America indicates that the jet induces precipitation over the Pampas region downstream. A detailed moisture budget was conducted over various subregions. This budget reveals that moisture flux convergence determines most of the interannual variability of precipitation over the Amazon Basin, the Atlantic Intertropical Convergence Zone, and the Nordeste region of Brazil. However, both surface evaporation and surface moisture flux convergence were found to be critical in determining the interannual variability of precipitation over the southern Pampas, Gran Chaco area, and the South Atlantic Convergence Zone.

  8. Caribbean hurricanes: interannual variability and prediction

    NASA Astrophysics Data System (ADS)

    Jury, Mark R.; Rodríguez, Ernesto

    2011-11-01

    Climatic conditions that affect the interannual variability of Caribbean hurricanes are studied. Composite meteorological and oceanographic reanalysis fields are constructed for active and inactive seasons since 1979, and differences are calculated for spring and summer periods to provide guidance in statistical analysis. Predictors are extracted for areas exhibiting high contrast between active and inactive seasons, and intercomparisons are made. Zonal winds north of Venezuela exhibit westerly anomalies prior to active years, so coastal upwelling and the north Brazil current are diminished. Rainfall increases in the Orinoco River basin, creating a fresh warm plume north of Trinidad. The predictor time series are regressed onto an index of Caribbean hurricanes, and multivariate algorithms are formulated. It is found that atmospheric kinematic and convective predictors explain only ˜20% of hurricane variance at 3-5-month lead time. Subsurface ocean predictors offer higher levels of explained hurricane variance (42%) at 3-5-month lead time, using 1-200-m-depth-averaged temperatures in the east Pacific and southern Caribbean. We place the statistical results in a conceptual framework to better understand climatic processes anticipating Caribbean hurricanes.

  9. Recurrent varicocele

    PubMed Central

    Rotker, Katherine; Sigman, Mark

    2016-01-01

    Varicocele recurrence is one of the most common complications associated with varicocele repair. A systematic review was performed to evaluate varicocele recurrence rates, anatomic causes of recurrence, and methods of management of recurrent varicoceles. The PubMed database was evaluated using keywords “recurrent” and “varicocele” as well as MESH criteria “recurrent” and “varicocele.” Articles were not included that were not in English, represented single case reports, focused solely on subclinical varicocele, or focused solely on a pediatric population (age <18). Rates of recurrence vary with the technique of varicocele repair from 0% to 35%. Anatomy of recurrence can be defined by venography. Management of varicocele recurrence can be surgical or via embolization. PMID:26806078

  10. Interannual variability of South American monsoon circulation

    NASA Astrophysics Data System (ADS)

    Alonso Gan, Manoel; Rafaele Araújo Lima, Jeane

    2016-04-01

    The South America Monsoon System (SAMS) is responsible for influencing the atmospheric circulation and precipitation over most of tropical South America (SA) during the summer season. Studies for aiming to understand the temporal variability of this system have great value to the scientific community, because the processes that control the monsoon climate are not totally clear. Thus, the main objective of this research is to investigate the possible large-scale climatic factors and the remote interaction mechanisms, which may be associated with summer season interannual variability focusing on identifying the main differences between dry and wet extremes rainy season in the South-eastern Amazon Basin (SAB), Central-West (WC) and Southeast (SE) of Brazil, which are areas influenced by the summer monsoon regime. For such analyzes, Pearson correlations, quantile method and composite analysis were used during the period from 1979 to 2014. The correlation between precipitation anomaly in SAB and the sea surface temperature anomaly (SSTA) and wind at 850hPa and 300hPa indicate El Niño-Southern Oscillation (ENSO) influence. Precipitation anomalies in WC did not show significant correlation with SSTA. However, a pattern similar to ENSO Modoki type was observed in the composite analysis. At 850 hPa, the presence of an anomalous cyclonic (anticyclonic) circulation was observed over the central region of SA during wet (dry) summers seasons. Over SE region of Brazil, a dipole SSTA pattern over the South Atlantic was identified, as well the presence of anomalous circulations with an equivalent barotropic structure over these SSTA areas. This pattern is more evident in case of dry summer on the SE. At 300 hPa, the wave train between 30°S-60°S was observed presenting a feature curvature from 120°W reaching SA, similar to the Pacific-South American pattern (PSA). Analysis of the summer interannual variability indicated the manifestation of wet summers more frequently than dry

  11. Interannual variability of the spatial distribution of sea ice in the north polar region

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    1991-01-01

    The interannual variability of the monthly average spatial distributions of northern hemisphere sea ice was examined for the 1973-1987 period of the electrically scanning microwave radiometer on the Nimbus 5 satellite and the scanning multichannel microwave radiometer on the Nimbus 7 satellite passive microwave data record. Strong seasonal and spatial contrasts in the amount of interannual variability are mapped and identified. The maps and analyses provide a baseline against which future northern hemisphere sea ice distributions can be compared in the continuing attempt to analyze global climate and to determine whether or not significant climate change is occurring.

  12. Interannual Variability in FPAR and NPP across California's Ecosystems

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Goulden, M. L.; Randerson, J. T.

    2005-12-01

    Quantifying the response of ecosystems to climate is particularly important for understanding California's regional carbon budget because of large year-to-year changes in precipitation and because of large changes in temperature and precipitation that are predicted to occur across the western U.S. during the 21st century. Here, we examined how net primary production (NPP) varies with precipitation and how this ecosystem process contributes to the changes in carbon storage on interannual timescales. We used FPAR derived from NOAA AVHRR satellite observations during 1982-2003 and from MODIS observations during 2000-2005 as inputs to the CASA biogeochemical model. We found that mean annual integrals of NDVI, FPAR, and NPP were closely linked with mean annual precipitation levels across the state. The sensitivity of NPP to interannual variability in precipitation depended on ecosystem type. Desert shrub and grassland ecosystems responded the most to interannual changes in precipitation, whereas forests showed little or no response. In semiarid ecosystems, the site-level temporal sensitivity of NPP to variations in precipitation was found to be lower than the sensitivity of NPP to precipitation derived from a spatial model, suggesting that other constraints such as plant structure or nitrogen availability may limit NPP responses to short-term precipitation transients.

  13. Oceanic Control of Northeast Pacific Hurricane Activity at Interannual Timescales

    SciTech Connect

    Balaguru, Karthik; Leung, Lai-Yung R.; Yoon, Jin-Ho

    2013-10-16

    Despite the strong dependence of the Power Dissipation Index (PDI), which is a measure of the intensity of Tropical Cyclone (TC) activity, on tropical sea-surface temperatures (SSTs), the variations in PDI are not completely explained by SST. Here we show, using an analysis of a string of observational data sets, that the variability of the thermocline depth (TD) in the east Pacific exerts a significant degree of control on the variability of PDI in that region. On average, a deep thermocline with a larger reservoir of heat favors TC intensification by reducing SST cooling while a shallow thermocline with a smaller heat reservoir promotes enhanced SST cooling that contributes to TC decay. At interannual time scales, the variability of basin-mean TD accounts for nearly 30% of the variability in the PDI during the TC season. Also, about 20% of the interannual variability in the east Pacific basin-mean TD is due to the El Niño and the Southern Oscillation (ENSO), a dominant climate signal in this region. This study suggests that a better understanding of the factors governing the interannual variability of the TD conditions in the east Pacific and how they may change over time, may lead to an improved projection of future east Pacific TC activity.

  14. Inter-annual variability influences the eco-evolutionary dynamics of range-shifting

    PubMed Central

    Bocedi, Greta; Dytham, Calvin; Travis, Justin M.J.

    2014-01-01

    Understanding the eco-evolutionary dynamics of species under rapid climate change is vital for both accurate forecasting of biodiversity responses and for developing effective management strategies. Using an individual-based model we demonstrate that the presence and form (colour) of inter-annual variability in environmental conditions can impact the evolution of dispersal during range shifts. Under stable climate, temporal variability typically results in higher dispersal. However, at expanding margins, inter-annual variability actually inhibits the evolution of higher emigration propensities by disrupting the spatial sorting and natural selection processes. These results emphasize the need for future theoretical studies, as well as predictive modelling, to account for the potential impacts of inter-annual variability. PMID:24498572

  15. Cross-tropopause ozone flux: diagnosing methods and interannual variations

    NASA Astrophysics Data System (ADS)

    Tang, Q.; Hess, P. G.; Brown-steiner, B. E.; Kinnison, D. E.

    2012-12-01

    Ozone is a key chemically reactive greenhouse gas in the atmosphere affecting air quality and climate. Cross-tropopause flux is a major source for tropospheric ozone and thus provides an important pathway for chemistry-climate coupling. However, large uncertainties exist in its estimations based on both models and observations. Here we diagnose the global stratosphere-troposphere exchange (STE) flux of ozone using the Whole Atmosphere Community Climate Model (WACCM) simulation with different, but consistent methods, such as ozone budgets in different regions (i.e., troposphere and lower most stratosphere) and fluxes derived from different vertical velocities (e.g., transformed Eulerian mean circulation and diabatic heating). We analyze the differences between different diagnostics, identify the causes, and evaluate their relative accuracy. We examine the sensitivity of STE ozone flux to major factors in WACCM, such as tropopause definition, nudging height to the offline meteorological field, and interannual meteorological variability (e.g. El Niño vs. La Niña). Based on these results, we recognize key processes driving the interannual variability of stratospheric ozone influx.

  16. Evaluation of RegCM4 in simulating the interannual and interdecadal variations of Meiyu rainfall in China

    NASA Astrophysics Data System (ADS)

    Hu, Yijia; Zhong, Zhong; Lu, Wei; Zhang, Yaocun; Sun, Yuan

    2016-05-01

    In this paper, the performance of the regional climate model (RegCM4) in simulating the interannual and interdecadal variation of Meiyu rainfall over lower and middle reaches of Yangtze River (LMRYR) in China is evaluated. The results show that the bias of the simulated Meiyu rainfall exhibits some uncertainties and obvious interdecadal variation similar with that of Meiyu rainfall itself. The rainfall bias and its interdecadal variation have little impact on the simulation of the interannual variation of the Meiyu rainfall. Not only the amplitude but also the phase of the interannual variation of the Meiyu rainfall can be reproduced by the RegCM4. However, the interdecadal variation of the rainfall bias has large impacts on the model's performance in simulating the interdecadal component of the Meiyu rainfall, leading to lower skill of RegCM4 in simulating the interdecadal variation of the Meiyu rainfall than that in simulating the interannual variation. In addition, the interannual signals of the temperature, humidity, and vorticity in the lower troposphere in the large-scale NCEP lateral boundary force are stronger than the interdecadal signals, and the model can respond well to these interannual signals. Therefore, the RegCM4 has better performance in simulating the interannual variation of water vapor budget than the interdecadal variation, which further favors the simulation of the Meiyu rainfall at interannual time scale.

  17. Inter-annual sea level variability in the southern South China Sea

    NASA Astrophysics Data System (ADS)

    Soumya, M.; Vethamony, P.; Tkalich, P.

    2015-10-01

    The South China Sea (SCS) is the largest marginal sea in the western Pacific Basin. Sea level anomalies (SLAs) in the southern South China Sea (SSCS) are assumed to be governed by various phenomena associated with the adjacent parts of the Indian Ocean and the Pacific Ocean. We have used monthly sea level anomalies obtained from 12 tide gauge stations of PSMSL and UHSLC and merged and gridded AVISO products of SLAs (sea level anomalies) derived from satellite altimeter. We find that IOD-influenced inter-annual variations are found only in the southwestern and southeastern coastal regions of SSCS. Our analysis reveals that inter-annual regional sea level drops are associated with positive phase of the IOD, and the rises with negative phase of the IOD. SLA variations at decadal scale in the southeastern and northern Gulf of Thailand correlate with Pacific Decadal Oscillations (PDO). Multiple linear regression analysis of inter-annual SLAs and climate indices shows that IOD induced inter-annual variations dominate in the southwestern SCS and it contributes to about ~ 40% of inter-annual sea level variation. Meanwhile, ENSO contributes to around ~ 30% variation in sea level in the southwestern and ~ 40% variation in the southeastern SSCS. The present study also suggests that inter-annual SLA variations in the SSCS can occur by ENSO and IOD induced changes in wind stress curl and volume transport variations.

  18. Marine and terrestrial influences on interannual CO{sub 2} variations at Mauna Loa and the South Pole

    SciTech Connect

    Dettinger, M.D.; Ghil, M.

    1997-11-01

    Data are presented and very briefly discussed regarding interannual variations of atmospheric carbon dioxide (CO{sub 2}) concentrations. Interannual variations are isolated from monthly concentrations by using singular-spectrum analysis of CO{sub 2} and atmospheric carbon isotopic ratios at Mauna Loa, Hawaii, United States and at the South Pole. Interannual variations are shared at the two sites, and can be used to differentiate between marine and land-surface responses to different interannual climate variations on global scales. Two time-scales are compared: (1) quasi-quadrennial (QQ) and (2) 3-year. Phase relations indicate that QQ variations are dominated by terrestrial influences, whereas the 3-year variations reflect marine (upwelling) influences in the eastern Pacific. The contrasting CO{sub 2} responses on these two time scales thus provide a useful measure of differences in global climate responses, and especially in terrestrial-ecosystem responses to different tropical forcings. 1 fig.

  19. The interannual variability of polar cap recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission

    NASA Technical Reports Server (NTRS)

    Martin, L. J.; James, P. B.

    1992-01-01

    The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets.

  20. The interannual variability of polar CAP recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission

    NASA Astrophysics Data System (ADS)

    Martin, L. J.; James, P. B.

    The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets.

  1. Recurrent vulvovaginitis.

    PubMed

    Powell, Anna M; Nyirjesy, Paul

    2014-10-01

    Vulvovaginitis (VV) is one of the most commonly encountered problems by a gynecologist. Many women frequently self-treat with over-the-counter medications, and may present to their health-care provider after a treatment failure. Vulvovaginal candidiasis, bacterial vaginosis, and trichomoniasis may occur as discreet or recurrent episodes, and have been associated with significant treatment cost and morbidity. We present an update on diagnostic capabilities and treatment modalities that address recurrent and refractory episodes of VV. PMID:25220102

  2. Seasonal hypoxia in eutrophic stratified coastal shelves: mechanisms, sensibilities and interannual variability from the North-Western Black Sea case

    NASA Astrophysics Data System (ADS)

    Capet, A.; Beckers, J.-M.; Grégoire, M.

    2012-12-01

    The Black Sea north-western shelf (NWS) is a~shallow eutrophic area in which seasonal stratification of the water column isolates bottom waters from the atmosphere and prevents ventilation to compensate for the large consumption of oxygen, due to respiration in the bottom waters and in the sediments. A 3-D coupled physical biogeochemical model is used to investigate the dynamics of bottom hypoxia in the Black Sea NWS at different temporal scales from seasonal to interannual (1981-2009) and to differentiate the driving factors (climatic versus eutrophication) of hypoxic conditions in bottom waters. Model skills are evaluated by comparison with 14 500 in-situ oxygen measurements available in the NOAA World Ocean Database and the Black Sea Commission data. The choice of skill metrics and data subselections orientate the validation procedure towards specific aspects of the oxygen dynamics, and prove the model's ability to resolve the seasonal cycle and interannual variability of oxygen concentration as well as the spatial location of the oxygen depleted waters and the specific threshold of hypoxia. During the period 1981-2009, each year exhibits seasonal bottom hypoxia at the end of summer. This phenomenon essentially covers the northern part of the NWS, receiving large inputs of nutrients from the Danube, Dniestr and Dniepr rivers, and extends, during the years of severe hypoxia, towards the Romanian Bay of Constanta. In order to explain the interannual variability of bottom hypoxia and to disentangle its drivers, a statistical model (multiple linear regression) is proposed using the long time series of model results as input variables. This statistical model gives a general relationship that links the intensity of hypoxia to eutrophication and climate related variables. The use of four predictors allows to reproduce 78% of hypoxia interannual variability: the annual nitrate discharge (N), the sea surface temperature in the month preceding stratification (T), the

  3. Recurrent novae

    NASA Technical Reports Server (NTRS)

    Hack, Margherita; Selvelli, Pierluigi

    1993-01-01

    Recurrent novae seem to be a rather inhomogeneous group: T CrB is a binary with a M III companion; U Sco probably has a late dwarf as companion. Three are fast novae; two are slow novae. Some of them appear to have normal chemical composition; others may present He and CNO excess. Some present a mass-loss that is lower by two orders of magnitude than classical novae. However, our sample is too small for saying whether there are several classes of recurrent novae, which may be related to the various classes of classical novae, or whether the low mass-loss is a general property of the class or just a peculiarity of one member of the larger class of classical novae and recurrent novae.

  4. Reduced interannual rainfall variability in East Africa during the last ice age.

    PubMed

    Wolff, Christian; Haug, Gerald H; Timmermann, Axel; Sinninghe Damsté, Jaap S; Brauer, Achim; Sigman, Daniel M; Cane, Mark A; Verschuren, Dirk

    2011-08-01

    Interannual rainfall variations in equatorial East Africa are tightly linked to the El Niño Southern Oscillation (ENSO), with more rain and flooding during El Niño and droughts in La Niña years, both having severe impacts on human habitation and food security. Here we report evidence from an annually laminated lake sediment record from southeastern Kenya for interannual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia and for reductions in both the mean rate and the variability of rainfall in East Africa during the Last Glacial period. Climate model simulations support forward extrapolation from these lake sediment data that future warming will intensify the interannual variability of East Africa's rainfall. PMID:21817050

  5. Interannual variability of tropospheric trace gases and aerosols: The role of biomass burning emissions

    NASA Astrophysics Data System (ADS)

    Voulgarakis, Apostolos; Marlier, Miriam E.; Faluvegi, Greg; Shindell, Drew T.; Tsigaridis, Kostas; Mangeon, Stéphane

    2015-07-01

    Fires are responsible for a range of gaseous and aerosol emissions. However, their influence on the interannual variability of atmospheric trace gases and aerosols has not been systematically investigated from a global perspective. We examine biomass burning emissions as a driver of interannual variability of large-scale abundances of short-lived constituents such as carbon monoxide (CO), hydroxyl radicals (OH), ozone, and aerosols using the Goddard Institute for Space Studies ModelE composition-climate model and a range of observations, with an emphasis on satellite information. Our model captures the observed variability of the constituents examined in most cases, but with substantial underestimates in boreal regions. The strongest interannual variability on a global scale is found for carbon monoxide (~10% for its global annual burden), while the lowest is found for tropospheric ozone (~1% for its global annual burden). Regionally, aerosol optical depth shows the largest variability which exceeds 50%. Areas of strong variability of both aerosols and CO include the tropical land regions (especially Equatorial Asia and South America) and northern high latitudes, while even regions in the northern midlatitudes experience substantial interannual variability of aerosols. Ozone variability peaks over equatorial Asia in boreal autumn, partly due to varying biomass burning emissions, and over the western and central Pacific in the rest of the year, mainly due to meteorological fluctuations. We find that biomass burning emissions are almost entirely responsible for global CO interannual variability, and similarly important for OH variability. The same is true for global and regional aerosol variability, especially when not taking into account dust and sea-salt particles. We show that important implications can arise from such interannual influences for regional climate and air quality.

  6. ENSO Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific.

    PubMed

    Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng

    2015-01-01

    Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other. PMID:26678931

  7. ENSO Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific

    PubMed Central

    Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng

    2015-01-01

    Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other. PMID:26678931

  8. Predictability of large interannual Arctic sea-ice anomalies

    NASA Astrophysics Data System (ADS)

    Tietsche, Steffen; Notz, Dirk; Jungclaus, Johann H.; Marotzke, Jochem

    2013-11-01

    In projections of twenty-first century climate, Arctic sea ice declines and at the same time exhibits strong interannual anomalies. Here, we investigate the potential to predict these strong sea-ice anomalies under a perfect-model assumption, using the Max-Planck-Institute Earth System Model in the same setup as in the Coupled Model Intercomparison Project Phase 5 (CMIP5). We study two cases of strong negative sea-ice anomalies: a 5-year-long anomaly for present-day conditions, and a 10-year-long anomaly for conditions projected for the middle of the twenty-first century. We treat these anomalies in the CMIP5 projections as the truth, and use exactly the same model configuration for predictions of this synthetic truth. We start ensemble predictions at different times during the anomalies, considering lagged-perfect and sea-ice-assimilated initial conditions. We find that the onset and amplitude of the interannual anomalies are not predictable. However, the further deepening of the anomaly can be predicted for typically 1 year lead time if predictions start after the onset but before the maximal amplitude of the anomaly. The magnitude of an extremely low summer sea-ice minimum is hard to predict: the skill of the prediction ensemble is not better than a damped-persistence forecast for lead times of more than a few months, and is not better than a climatology forecast for lead times of two or more years. Predictions of the present-day anomaly are more skillful than predictions of the mid-century anomaly. Predictions using sea-ice-assimilated initial conditions are competitive with those using lagged-perfect initial conditions for lead times of a year or less, but yield degraded skill for longer lead times. The results presented here suggest that there is limited prospect of predicting the large interannual sea-ice anomalies expected to occur throughout the twenty-first century.

  9. Interannual Variability of the Mosaic Land-Surface Model

    NASA Technical Reports Server (NTRS)

    Bosilovich, Michael G.; Houser, Paul R.; Schubert, Siegfried

    1999-01-01

    Recently, NASA Goddard Earth Observing System (GEOS-1) reanalysis data has been used to provide forcing for the Koster and Suarez Mosaic Land-surface Model (LSM). The LSM was integrated off-line at all global land points for the period of 1983 - 1995 by the Off-line Land- surface GEOS Assimilation system (OLGA). Here, we compare the interannual variability of OLGA, GEOS-1 and surface observing stations temperature and moisture. Particular attention is given to the United States because of the extreme seasons of 1988 and 1993. Furthermore, the comparison of OLGA is extended to include the analysis of data on the'tiles' (different surface types) in the Mosaic LSM. Results indicate that the GEOS-1 near-surface temperature and moisture reasonably represents the interannual variability in more normal years. However, OLGA also simulates the extreme drought and floods years well. The analysis of the tile information shows that the "Bare soil" surface type is most sensitive to the climate extremes. Off-line testing has provided valuable information on the performance of the Mosaic LSM prior to its incorporation into the new version of the GEOS Data Assimilation System and the integration of a new long reanalysis.

  10. Interannual variability of Winter Precipitation in Southeast China

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Fraedrich, Klaus; zhu, Xiuhua; Sielmann, Frank

    2014-05-01

    The observed winter (DJF) precipitation in Southeast China (1961-2010) is characterized by a monopole pattern of the three-monthly Standardized Precipitation Index (SPI-3) whose interannual variability is related to the anomalies of East Asian Winter Monsoon (EAWM) systems. Dynamic composites and linear regression analysis indicate that the intensity of EAWM and Siberia High (SH), the position of East Asian Trough (EAT), El Niño events and SST anomalies over South China Sea (SCS) influence different regions of anomalous Southeast China winter precipitation on interannual scales. The circulation indices (EAWM, SH and EAT) mainly affect the winter precipitation in the eastern part of Southeast China. El Niño events affect the South China winter precipitation due to the anticyclone anomalies over Philippines. The effect of SCS SST anomalies on the winter precipitation is mainly in the south part of Yangtze River. And the contributions from all the impact factors do not counteract with one another to generate the Southeast China winter precipitation variability. Thus, a set of circulation regimes, represented by a handful indices, provide the basis for modeling precipitation anomalies or extremes in future climate projections.

  11. Interannual variability of winter precipitation in Southeast China

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Fraedrich, Klaus; Zhu, Xiuhua; Sielmann, Frank; Zhi, Xiefei

    2015-01-01

    The observed winter (DJF) precipitation in Southeast China (1961-2010) is characterized by a monopole pattern of the 3-monthly Standardized Precipitation Index (SPI-3) whose interannual variability is related to the anomalies of East Asian Winter Monsoon (EAWM) systems. Dynamic composites and linear regression analysis indicate that the intensity of EAWM and Siberia High (SH), the position of East Asian Trough (EAT), and El Niño events and sea surface temperature (SST) anomalies over South China Sea (SCS) influence different regions of anomalous Southeast China winter precipitation on interannual scales. The circulation indices (EAWM index, SH index, and EAT index) mainly affect the winter precipitation in the eastern part of Southeast China. El Niño events affect the South China winter precipitation due to the anticyclone anomalies over Philippines. The effect of SCS SST anomalies on the winter precipitation is mainly in the southern part of Yangtze River. Thus, a set of circulation regimes, represented by a handful indices, provide the basis for modeling precipitation anomalies or extremes in future climate projections.

  12. Interannual variability of snow and fluvial regimes in Andorra

    NASA Astrophysics Data System (ADS)

    Pesado, Cristina; Riba, Sergi; Pons, Marc; Lopez-Moreno, Juan Ignacio

    2016-04-01

    Highlands in Andorra are snow-dominated areas during all the winter and most of the spring season. Interannual snow variability in these areas has a strong and straight influence on the amount and seasonality of river regimes at the bottom of the valley where most of the population and water requirements are concentrated. The present study analyzes the temporal and spatial variability of the fluvial regimes in Andorra and seeks to understand the interplay of different topographic and climatic variables on this variability. For example, in mountainous regions temperature determines the state of precipitation and this state can significantly affect runoff formation. The interannual temporal and spatial variability of temperatures, pluviometry and different snow indices such as snow heights and days with snow on the ground has been studied for the last decade and correlated with the fluvial dynamics and its variability using discharge measurements. This study focus especially in the assessment of the role of snow and its seasonality in the fluvial regime dynamics and the influence in the torrential flows and flood hazard. Flood hazard, force to take protection measures, which need information about flood frequency and magnitude. For this, flow instrumental series are used, but usually they do not consider phenomena like snowmelt. This study contributes intends to better understand the interplay between snow and fluvial dynamics and improve the assessment of the availability of water resources as well as the requirements in terms of protection measures.

  13. Interannual variability of deep convection in the Northwestern Mediterranean simulated with a coupled AORCM

    NASA Astrophysics Data System (ADS)

    L'Hévéder, Blandine; Li, Laurent; Sevault, Florence; Somot, Samuel

    2013-08-01

    A hindcast experiment of the Mediterranean present-day climate is performed using a fully-coupled Atmosphere-Ocean Regional Climate Model (AORCM) for the Mediterranean basin. The new model, called LMDz-NEMO-Med, is composed of LMDz4-regional as atmospheric component and of NEMOMED8 as oceanic component. This AORCM equilibrates freely, without any flux adjustment, neither in fresh water nor in heat. At its atmospheric lateral boundary conditions, it is driven by ERA-40 data from 1958 to 2001, after a spin-up of 40 years in coupled configuration. The model performance is assessed and compared with available observational datasets. The model skill in reproducing mean state and inter-annual variability of main atmospheric and oceanic surface fields is in line with that of state-of-the-art AORCMs. Considering the ocean behaviour, the inter-annual variations of the basin-scale heat content are in very good agreement with the observations. The model results concerning salt content could not be adequately validated. High inter-annual variability of deep convection in the Gulf of Lion is simulated, with 53 % of convective winters, representative of the present climate state. The role of different factors influencing the deep convection and its inter-annual variability is examined, including dynamic and hydrostatic ocean preconditioning and atmospheric surface forcing. A conceptual framework is outlined and validated in linking the occurrence of deep convection to the efficiency of the integrated surface buoyancy fluxes along the winter season to mix the initially stratified averaged water column down to the convective threshold depth. This simple framework (based only on 2 independent variables) is able to explain 60 % (resp. 69 %) of inter-annual variability of the deep water formation rate (resp. maximum mixed layer depth) for the West Mediterranean Deep Water (WMDW) formation process.

  14. Interannual Variability of Tropical Rainfall as Seen From TRMM

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.

    2005-01-01

    Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30deg N/S) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Although it is well documented that El Nino-Southern Oscillation (ENSO) events with marked SST changes over the tropical oceans produce significant regional changes in precipitation, water vapor, and radiative fluxes in the tropics, we still cannot yet adequately quantify the associated net integrated changes to water and heat balance over the entire tropical oceanic or land sectors. Resolving this uncertainty is important since precipitation and latent heat release variations over land and ocean sectors are key components of the tropical heat balance in its most aggregated form. Rainfall estimates from the Version 5 Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) averaged over the tropical oceans have not solved this issue and, in fact, show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. In this paper we will focus on findings that uncertainties in microphysical assumptions necessitated by the single-frequency PR measurement pose difficulties for detecting climate-related precipitation signals. Recent work has shown that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees closely with the TMI time series, yet the PR rainfall interannual variability (and attenuation derived predominantly from reflectivity) differs even in sign. We will explore these apparent inconsistencies and examine changes in new TRMM Version 6 retrievals. To place these results in a tropical water balance perspective we also examine interannual variations in evaporation over the tropical oceans made from TRMM and SSM/I (Special Sensor Microwave Imager) measurements of surface

  15. What is the Effect of Interannual Hydroclimatic Variability on Water Supply Reservoir Operations?

    NASA Astrophysics Data System (ADS)

    Galelli, S.; Turner, S. W. D.

    2015-12-01

    Rather than deriving from a single distribution and uniform persistence structure, hydroclimatic data exhibit significant trends and shifts in their mean, variance, and lagged correlation through time. Consequentially, observed and reconstructed streamflow records are often characterized by features of interannual variability, including long-term persistence and prolonged droughts. This study examines the effect of these features on the operating performance of water supply reservoirs. We develop a Stochastic Dynamic Programming (SDP) model that can incorporate a regime-shifting climate variable. We then compare the performance of operating policies—designed with and without climate variable—to quantify the contribution of interannual variability to standard policy sub-optimality. The approach uses a discrete-time Markov chain to partition the reservoir inflow time series into small number of 'hidden' climate states. Each state defines a distinct set of inflow transition probability matrices, which are used by the SDP model to condition the release decisions on the reservoir storage, current-period inflow and hidden climate state. The experimental analysis is carried out on 99 hypothetical water supply reservoirs fed from pristine catchments in Australia—all impacted by the Millennium drought. Results show that interannual hydroclimatic variability is a major cause of sub-optimal hedging decisions. The practical import is that conventional optimization methods may misguide operators, particularly in regions susceptible to multi-year droughts.

  16. Interannual to Synoptic Scale Variability in Intercontinental Transport

    NASA Astrophysics Data System (ADS)

    Gupta, M. L.; Nielsen, J. E.; Douglass, A. R.; Kawa, S. R.; Pawson, S.

    2004-05-01

    Intercontinental transport (ICT) represents pathways of atmospheric flow responsible for dispersion of air pollutants e.g. ozone and aerosols that play vital roles in regional air quality and climate change. Temporal variations in atmospheric dynamics influence behavior of ICT. Here, we investigate interannual to synoptic scale variability in ICT using a source-receptor relationship. We performed a 10-year `online' simulation of eight Rn-like tracers (one global and seven regional) using Finite Volume General Circulation Model. Six-hourly model output archived from this simulation is analyzed for surface concentration, vertical profile and column amount of all tracers on various timescales at 50 regional receptors placed around the globe. We quantified the contributions from the seven source regions to global tracer distribution at these receptors. In addition, we will present a statistical description of tracer distributions and regional contributions representing the 10-year simulation period.

  17. Trends in Rainfall, Streamflow, and Interannual Variability in Palau

    NASA Astrophysics Data System (ADS)

    Gupta, A.

    2008-05-01

    Anecdotal evidence from Palau suggests that streamflow may be declining with time. This research examines trends in rainfall and streamflow and attempts to identify causes of variability. Rainfall for the period of 1953-2002 exhibited a significant declining trend. Rainfall intensity appears to be increasing and interannual variability also shows an increasing trend. Streamflow also exhibited significant decreasing trends for the period of the early 1970s to early 1990s. Precipitation in Palau is only moderately correlated with the PDO, ENSO, and SO indices. Declining rainfall and streamflow conditions have important policy implications for the developing island nation, which is currently exhibiting rapid population growth. A lack of strong correlation with regional climate indices is also problematic when making flood and drought predictions.

  18. Interannual Variability of Ozone and Ultraviolet Exposure

    NASA Technical Reports Server (NTRS)

    Herman, J. R.; Piacentini, R. D.; Ziemke, J.; Celarier, E.; Larko. D.

    1999-01-01

    Annual zonal averages of ozone amounts from Nimbus-7/TOMS (Total Ozone Mapping Spectrometer) (1979 to 1992) are used to estimate the interannual variability of ozone and UVB (290 - 315 nm) irradiance between plus or minus 60 deg. latitude. Clear-sky interannual ozone and UVB changes are mainly caused by the Quasi Biennial Oscillation (QBO) of stratospheric winds, and can amount to plus or minus 15% at 300 nm and plus or minus 5% at 310 nm (or erythemal irradiance) at the equator and at middle latitudes. Near the equator, the interannual variability of ozone amounts and UV irradiance caused by the combination of the 2.3 year QBO and annual cycles implies that there is about a 5-year periodicity in UVB variability. At higher latitudes, the appearance of the interannual UVB maximum is predicted by the QBO, but without the regular periodicity. The 5-year periodic QBO effects on UVB irradiance are larger than the currently evaluated long-term changes caused by the decrease in ozone amounts.

  19. Interannual Variation in Phytoplankton Primary Production at a Global Scale

    NASA Technical Reports Server (NTRS)

    Rousseaux, Cecile Severine; Gregg, Watson W.

    2013-01-01

    We used the NASA Ocean Biogeochemical Model (NOBM) combined with remote sensing data via assimilation to evaluate the contribution of four phytoplankton groups to the total primary production. First, we assessed the contribution of each phytoplankton groups to the total primary production at a global scale for the period 1998-2011. Globally, diatoms contributed the most to the total phytoplankton production ((is)approximately 50%, the equivalent of 20 PgC·y1). Coccolithophores and chlorophytes each contributed approximately 20% ((is) approximately 7 PgC·y1) of the total primary production and cyanobacteria represented about 10% ((is) approximately 4 PgC·y1) of the total primary production. Primary production by diatoms was highest in the high latitudes ((is) greater than 40 deg) and in major upwelling systems (Equatorial Pacific and Benguela system). We then assessed interannual variability of this group-specific primary production over the period 1998-2011. Globally the annual relative contribution of each phytoplankton groups to the total primary production varied by maximum 4% (1-2 PgC·y1). We assessed the effects of climate variability on group-specific primary production using global (i.e., Multivariate El Niño Index, MEI) and "regional" climate indices (e.g., Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO)). Most interannual variability occurred in the Equatorial Pacific and was associated with climate variability as indicated by significant correlation (p (is) less than 0.05) between the MEI and the group-specific primary production from all groups except coccolithophores. In the Atlantic, climate variability as indicated by NAO was significantly correlated to the primary production of 2 out of the 4 groups in the North Central Atlantic (diatoms/cyanobacteria) and in the North Atlantic (chlorophytes and coccolithophores). We found that climate variability as indicated by SAM had only a limited effect

  20. Enhanced interannual precipitation variability increases plant functional diversity that in turn ameliorates negative impact on productivity.

    PubMed

    Gherardi, Laureano A; Sala, Osvaldo E

    2015-12-01

    Although precipitation interannual variability is projected to increase due to climate change, effects of changes in precipitation variance have received considerable less attention than effects of changes in the mean state of climate. Interannual precipitation variability effects on functional diversity and its consequences for ecosystem functioning are assessed here using a 6-year rainfall manipulation experiment. Five precipitation treatments were switched annually resulting in increased levels of precipitation variability while maintaining average precipitation constant. Functional diversity showed a positive response to increased variability due to increased evenness. Dominant grasses decreased and rare plant functional types increased in abundance because grasses showed a hump-shaped response to precipitation with a maximum around modal precipitation, whereas rare species peaked at high precipitation values. Increased functional diversity ameliorated negative effects of precipitation variability on primary production. Rare species buffered the effect of precipitation variability on the variability in total productivity because their variance decreases with increasing precipitation variance. PMID:26437913

  1. Understanding the Role of Interannual Variability and Momentum Transfer on Wind Energy

    NASA Astrophysics Data System (ADS)

    Koerner, S.; Brunsell, N. A.; Miller, L.; Mechem, D. B.

    2014-12-01

    Forecasting realistic wind power potential is essential for wind energy to assist with meeting future energy demands. Current wind power estimates rely on the use of mean climatological wind speeds. This approach to estimating wind power neglects the influence of momentum extraction by the turbines (i.e. turbine-turbine interactions) and interannual variability in windspeed. The present study will use a wind turbine parameterization within the Weather and Research Forecasting (WRF) model to assess the role of interannual and climatic variability on power extraction. The WRF model will be forced by NARR, and run from 1980-2010 to incorporate different climatic conditions over the central United States. Analysis focusses on the role of climate variability on wind power extraction; specifically on the role of drought and wet periods, as well as variability in the Great Plains Low Level Jet. In addition, WRF will be used to assess the impact of wind turbines on each term of the momentum budget. Understanding the impact of interannual variability will improve our understanding of the role that wind power can play in meeting future energy demands.

  2. Interannual variability of the coupled tropical Pacific ocean - atmosphere system associated with the El Nino-southern oscillation

    SciTech Connect

    Zhang, Rong-Hua; Levitus, S.

    1997-06-01

    Upper-ocean temperature and surface marine meteorological observations are used to examine interannual variability of the coupled tropical Pacific climate system. The basinwide structure and evolution of meteorological and oceanographic fields associated with ENSO events are described using composites, empirical orthogonal functions, and a lagged correlation analysis. The analyses reveal well-defined spatial structures and coherent phase relations among various anomaly fields.

  3. Interannual and Interdecadal Variability in Sea Level.

    NASA Astrophysics Data System (ADS)

    Unal, Yurdanur Sezginer

    The observational data set archived by the Permanent Service for Mean Sea Level (PSMSL) consists of monthly means of sea-level heights at 846 stations. 213 of them are suitable for our purposes. We identified two dominant time scales of El Nino-Southern Oscillation (ENSO) signal, as quasi-biennial and low-frequency (LF) at almost all stations, with the highest amplitudes in the equatorial Pacific and along the west coast of North America. Global sea-level rise, after post-glacial rebound corrections, are 1.620.38 mm/yr. Propagation features of the interannual variability are studied along the coastal sea level stations in five regions: eastern, western, and equatorial Pacific; eastern and western Atlantic. Throughout the Pacific, three dominant spatio-temporal oscillatory patterns are found in the time scales of ENSO variability. In the eastern Pacific, the biennial mode and the 6-yr low-frequency mode propagate poleward. In the western Pacific, interannual oscillation propagates southward in the northern hemisphere but no clear propagation is observed in the southern hemisphere. Equatorward propagation of the biennial signal is very clear in each hemisphere. In the equatorial Pacific, both the quasi -quadrannial and quasi-biennial modes at 10^ circN propagate westward. Strong and weak El Nino years are evident in RSLH reconstructed from the biennial and low-frequency modes. Interannual variability with periods of 3 and 4-8 years is detected in the Atlantic RSLH data. In the eastern Atlantic region, we have found slow propagation of both modes northward and southward, away from 40-45^circN. Sufficiently long and continuous RSLH at 81 stations show interdecadal oscillations with the periods of 9-13 and 18 years. 11.6 and 12.8 years of oscillations are found in the eastern and western Atlantic ocean at latitudes 40^circN-70^ circN and 10^circN -50^circN, respectively. The aforementioned features are simulated with a wind driven ocean model for the periods of 1950 and

  4. The Effect of the Interannual Variability of the OH Sink on the Interannual Variability of the Atmospheric Methane Mixing Ratio and Carbon Stable Isotope Composition

    NASA Astrophysics Data System (ADS)

    Guillermo Nuñez Ramirez, Tonatiuh; Houweling, Sander; Marshall, Julia; Williams, Jason; Brailsford, Gordon; Schneising, Oliver; Heimann, Martin

    2013-04-01

    The atmospheric hydroxyl radical concentration (OH) varies due to changes in the incoming UV radiation, in the abundance of atmospheric species involved in the production, recycling and destruction of OH molecules and due to climate variability. Variability in carbon monoxide emissions from biomass burning induced by El Niño Southern Oscillation are particularly important. Although the OH sink accounts for the oxidation of approximately 90% of atmospheric CH4, the effect of the variability in the distribution and strength of the OH sink on the interannual variability of atmospheric methane (CH4) mixing ratio and stable carbon isotope composition (δ13C-CH4) has often been ignored. To show this effect we simulated the atmospheric signals of CH4 in a three-dimensional atmospheric transport model (TM3). ERA Interim reanalysis data provided the atmospheric transport and temperature variability from 1990 to 2010. We performed simulations using time dependent OH concentration estimations from an atmospheric chemistry transport model and an atmospheric chemistry climate model. The models assumed a different set of reactions and algorithms which caused a very different strength and distribution of the OH concentration. Methane emissions were based on published bottom-up estimates including inventories, upscaled estimations and modeled fluxes. The simulations also included modeled concentrations of atomic chlorine (Cl) and excited oxygen atoms (O(1D)). The isotopic signal of the sources and the fractionation factors of the sinks were based on literature values, however the isotopic signal from wetlands and enteric fermentation processes followed a linear relationship with a map of C4 plant fraction. The same set of CH4emissions and stratospheric reactants was used in all simulations. Two simulations were done per OH field: one in which the CH4 sources were allowed to vary interannually, and a second where the sources were climatological. The simulated mixing ratios and

  5. Modelling interannual variation in the spring and autumn land surface phenology of the European forest

    NASA Astrophysics Data System (ADS)

    Rodriguez-Galiano, Victor F.; Sanchez-Castillo, Manuel; Dash, Jadunandan; Atkinson, Peter M.; Ojeda-Zujar, Jose

    2016-06-01

    This research reveals new insights into the weather drivers of interannual variation in land surface phenology (LSP) across the entire European forest, while at the same time establishes a new conceptual framework for predictive modelling of LSP. Specifically, the random-forest (RF) method, a multivariate, spatially non-stationary and non-linear machine learning approach, was introduced for phenological modelling across very large areas and across multiple years simultaneously: the typical case for satellite-observed LSP. The RF model was fitted to the relation between LSP interannual variation and numerous climate predictor variables computed at biologically relevant rather than human-imposed temporal scales. In addition, the legacy effect of an advanced or delayed spring on autumn phenology was explored. The RF models explained 81 and 62 % of the variance in the spring and autumn LSP interannual variation, with relative errors of 10 and 20 %, respectively: a level of precision that has until now been unobtainable at the continental scale. Multivariate linear regression models explained only 36 and 25 %, respectively. It also allowed identification of the main drivers of the interannual variation in LSP through its estimation of variable importance. This research, thus, shows an alternative to the hitherto applied linear regression approaches for modelling LSP and paves the way for further scientific investigation based on machine learning methods.

  6. Interannual and interdecadal variability in United States surface-air temperatures, 1910-87

    USGS Publications Warehouse

    Dettinger, M.D.; Ghil, M.; Keppenne, C.L.

    1995-01-01

    Monthly mean surface-air temperatures at 870 sites in the contiguous United States were analyzed for interannual and interdecadal variability over the time interval 1910-87. The temperatures were analyzed spatially by empirical-orthogonal-function analysis and temporally by singularspectrum analysis (SSA). The dominant modes of spatio-temporal variability are trends and nonperiodic variations with time scales longer than 15 years, decadal-scale oscillations with periods of roughly 7 and 10 years, and interannual oscillations of 2.2 and 3.3 years. Together, these modes contribute about 18% of the slower-than-annual United States temperature variance. Two leading components roughly capture the mean hemispheric temperature trend and represent a long-term warming, largest in the southwest, accompanied by cooling of the domain's southeastern quadrant. The extremes of the 2.2-year interannual oscillation characterize temperature differences between the Northeastern and Southwestern States, whereas the 3.3-year cycle is present mostly in the Western States. The 7- to 10-year oscillations are much less regular and persistent than the interannual oscillations and characterize temperature differences between the western and interior sectors of the United States. These continental- or regional-scale temperature variations may be related to climatic variations with similar periodicities, either global or centered in other regions; such variations include quasi-biennial oscillations over the tropical Pacific or North Atlantic and quasi-triennial oscillations of North Pacific sea-surface temperatures.

  7. Interannual variability of the Adriatic Sea circulation

    NASA Astrophysics Data System (ADS)

    Beg Paklar, Gordana; Sepic, Jadranka; Grbec, Branka; Dzoic, Tomislav; Kovac, Zarko; Ivatek-Sahdan, Stjepan

    2016-04-01

    The Regional Ocean Modeling System (ROMS) was implemented in order to reproduce interannual variability of the Adriatic Sea circulation. Simulations and model result analysis were performed for a three-year period from 1st January 2011 to 31st December 2013. ROMS model run was forced with realistic atmospheric fields obtained from meteorological model Aladin, climatological river discharges, tides and Mediterranean circulation imposed at the southern open boundary. Atmospheric forcing included momentum, heat and water fluxes calculated interactively from the Aladin surface fields during ROMS model simulations. Model results were compared with available CTD and ADCP measurements and discussed in the light of the climatological circulation and thermohaline properties of the Adriatic Sea and its coastal areas. Interannual variability in the Adriatic circulation is related to the prevailing atmospheric conditions, changes in the hydrological conditions and water mass exchange at the Otranto Strait. Basic features of the Adriatic circulation - basin-wide cyclonic circulation with several embedded smaller cyclonic gyres around main pits - are well reproduced by ROMS model. Modelled temperatures and salinities are within corresponding seasonal intervals, although measured profiles generally indicate stronger stratification than modelled ones. Summer circulation in 2011 with current reversal obtained along the eastern Adriatic coast was related to the sampling results of the early fish stages as well as to ARGO drifter movements. Simulated fields from the Adriatic scale model were used to prescribe the initial and open boundary conditions for the interannual simulation in the middle Adriatic coastal domain.

  8. Interannual and interdecadal variability in 335 years of central England temperatures.

    PubMed

    Plaut, G; Ghil, M; Vautard, R

    1995-05-01

    Understanding the natural variability of climate is important for predicting its near-term evolution. Models of the oceans' thermohaline and wind-driven circulation show low-frequency oscillations. Long instrumental records can help validate the oscillatory behavior of these models. Singular spectrum analysis applied to the 335-year-long central England temperature (CET) record has identified climate oscillations with interannual (7- to 8-year) and interdecadal (15- and 25-year) periods, probably related to the North Atlantic's wind-driven and thermohaline circulation, respectively. Statistical prediction of oscillatory variability shows CETs decreasing toward the end of this decade and rising again into the middle of the next. PMID:17832386

  9. Interannual Variability of Snow Water Equivalent (SWE) over Western Himalayas

    NASA Astrophysics Data System (ADS)

    Tiwari, Sarita; Kar, Sarat C.; Bhatla, R.

    2016-04-01

    Considering the importance of snow and glaciers in the Himalayas for understanding the water cycle and for water resource management of the rivers originating from the Himalayan, interannual variability of snow accumulation process over Himalayas and surrounding region has been studied using snow water equivalent (SWE) data. Remote sensing data from National Snow and Ice Data Centre have been used. These data have been compared against ground (in situ) observations of SWE measured at several gauge stations in the Indian part of the Satluj River basin. Accumulated SWE from remote sensing data and ground observations in the Satluj River basin have good and significant correlation. These data have also been compared against the Climate Forecast System Reanalysis and the European Centre for Medium Range Weather Forecast reanalysis-Interim (ERA-I). Upper air and surface data from the reanalyses have also been used to examine the atmospheric conditions when snowfall occurs and snow accumulates for the season. In this study, it is found that there is large interannual variation in SWE over western Himalayas and Satluj River basin (domain of interest). During excess years of snowfall, strong westerly winds are observed at 500 hPa over India. In wind anomaly, a cyclonic circulation is seen over northern parts of India with a deep trough along Pakistan, Rajasthan and Gujarat region. As a consequence of this trough, a moisture convergence zone is established in the region leading to more amount of snowfall. At the same time, during excess snow accumulation years, the air temperature from the surface to 500 hPa is colder than other years enabling the fallen snow to accumulate through the season.

  10. Interannual forcing mechanisms of California Current transports II: Mesoscale eddies

    NASA Astrophysics Data System (ADS)

    Davis, Andrew; Di Lorenzo, Emanuele

    2015-02-01

    Mesoscale eddies exert dominant control of cross-shelf exchanges, yet the forcing dynamics underlying their interannual and decadal variability remain uncertain. Using an ensemble of high-resolution ocean model hindcasts of the central and eastern North Pacific from 1950 to 2010 we diagnose the forcing mechanisms of low-frequency eddy variability in the California Current System (CCS). We quantify eddy activity by developing eddy counts based on closed contours of the Okubo-Weiss parameter and find that the spatial and temporal features of model-derived counts largely reproduce the short AVISO observational record. Comparison of model ensemble members allows us to separate the intrinsic and deterministic fractions of eddy variability in the northern CCS (34.5-50°N) and in the southern CCS (28.5-34.5°N). In the North, a large fraction of low-frequency eddy variability (30% anticyclones, 20% cyclones) is deterministic and shared with satellite observations. We develop a diagnostic model based on indices of the large-scale barotropic and baroclinic states of the CCS which recovers this deterministic variance. This model also strongly correlates with local atmospheric forcing. In contrast to the North, Southern CCS eddy counts exhibit very little deterministic variance, and eddy formation closely resembles a red-noise process. This new understanding of the external forcings of eddy variability allows us to better estimate how climate variability and change impact mesoscale transports in the California Current. The skill of our diagnostic model and its close association with local wind stress curl indicate that local atmospheric forcing is the dominant driver of eddy activity on interannual and decadal time scales north of pt. conception (~33°N).

  11. Projections of Southern Hemisphere atmospheric circulation interannual variability

    NASA Astrophysics Data System (ADS)

    Grainger, Simon; Frederiksen, Carsten S.; Zheng, Xiaogu

    2016-05-01

    An analysis is made of the coherent patterns, or modes, of interannual variability of Southern Hemisphere 500 hPa geopotential height field under current and projected climate change scenarios. Using three separate multi-model ensembles (MMEs) of coupled model intercomparison project phase 5 (CMIP5) models, the interannual variability of the seasonal mean is separated into components related to (1) intraseasonal processes; (2) slowly-varying internal dynamics; and (3) the slowly-varying response to external changes in radiative forcing. In the CMIP5 RCP8.5 and RCP4.5 experiments, there is very little change in the twenty-first century in the intraseasonal component modes, related to the Southern annular mode (SAM) and mid-latitude wave processes. The leading three slowly-varying internal component modes are related to SAM, the El Niño-Southern oscillation (ENSO), and the South Pacific wave (SPW). Structural changes in the slow-internal SAM and ENSO modes do not exceed a qualitative estimate of the spatial sampling error, but there is a consistent increase in the ENSO-related variance. Changes in the SPW mode exceed the sampling error threshold, but cannot be further attributed. Changes in the dominant slowly-varying external mode are related to projected changes in radiative forcing. They reflect thermal expansion of the tropical troposphere and associated changes in the Hadley Cell circulation. Changes in the externally-forced associated variance in the RCP8.5 experiment are an order of magnitude greater than for the internal components, indicating that the SH seasonal mean circulation will be even more dominated by a SAM-like annular structure. Across the three MMEs, there is convergence in the projected response in the slow-external component.

  12. The Caribbean Low-Level Jet Interannual Summer Variability

    NASA Astrophysics Data System (ADS)

    Munoz, E.; Busalacchi, A.

    2006-12-01

    The Caribbean Low-Level Jet (CALLJ) is an intrinsic component of the climate of the Caribbean and Central America region albeit its controls and effects are not well known. The CALLJ is manifested as strong easterly winds in boreal summer at about 925 mb over the Caribbean Sea. Our overarching objectives are: to determine the factors that control the interannual variability of the CALLJ, and to determine the contribution of CALLJ anomalies on summer Caribbean precipitation. An index representing the CALLJ variability is defined as the 925-mb zonal winds averaged over the area: 70°-80° W, 12°-16° N. The summer months corresponding to the upper and lower quartiles of the CALLJ index are chosen from the period 1979-2001 to construct composites. Multivariate principal component analysis is performed with Caribbean 925-mb zonal winds and sea level pressure (SLP) or Caribbean precipitation. It is observed that the main anomalous climate pattern associated with an anomalously strong CALLJ is one with low SLP and warm sea surface temperature (SST) anomalies in the tropical Pacific and high SLP and cool SST anomalies in the tropical Atlantic and the Caribbean. These climate anomalies force remotely the CALLJ through changes in the Caribbean SLP gradients while local feedbacks amplify the effects. Less precipitation over large areas of the Caribbean and Central America is due to stronger vertical wind shear and moisture flux divergence related to a strengthening of the CALLJ. The findings contribute to a better understanding of the climate interactions in the Caribbean region in light of the CALLJ variability and controls.

  13. Climate and developmental plasticity: interannual variability in grapevine leaf morphology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shape of leaves are dynamic, changing over evolutionary time between species, within a single plant producing different shaped leaves at successive nodes, during the development of a single leaf as it allometrically expands, and in response to the environment. Notably, strong correlations betwee...

  14. Interannual to decadal predictability in the North Atlantic Europe region

    NASA Astrophysics Data System (ADS)

    Jouzeau, A.; Terray, L.

    2003-04-01

    A 200-year control experiment is performed with the third version of the ARPEGE-Climat atmospheric model coupled to the ORCALIM2 (ORCA/Louvain Ice Model) sea-ice/ocean model. This study takes place in the framework of the PREDICATE project. The simulation shows low frequency fluctuations (period of 30-50 years) in the Thermohaline Circulation (THC) of about 15% of the mean transport. Two 25-year long ensemble experiments are then conducted, contrasting opposite phases of the THC: the first ensemble starts at a maximum of the intensity of the THC, the second one at a minimum. For each ensemble, the different members (6 members for each ensemble) only differ by infinitesimal perturbations of their initial atmospheric conditions. We use these ensembles to study the potential predictability at interannual to decadal time scales. The preliminary results suggest the existence of predictability up to several years in the THC and SST in the North Atlantic. On the other hand, there seems to be very little predictability (beyond one year) arising from atmospheric variables. These results are obtained using a simple predictability index introduced by Collins and Allen (2001) which measures the rate of spread of the ensembles of simulations against climatology. A cluster analysis will then be performed to investigate the modification of the frequency of occurrence of the main climatic regimes and their links with the THC states.

  15. Global modeling of land water and energy balances. Part III: Interannual variability

    USGS Publications Warehouse

    Shmakin, A.B.; Milly, P.C.D.; Dunne, K.A.

    2002-01-01

    The Land Dynamics (LaD) model is tested by comparison with observations of interannual variations in discharge from 44 large river basins for which relatively accurate time series of monthly precipitation (a primary model input) have recently been computed. When results are pooled across all basins, the model explains 67% of the interannual variance of annual runoff ratio anomalies (i.e., anomalies of annual discharge volume, normalized by long-term mean precipitation volume). The new estimates of basin precipitation appear to offer an improvement over those from a state-of-the-art analysis of global precipitation (the Climate Prediction Center Merged Analysis of Precipitation, CMAP), judging from comparisons of parallel model runs and of analyses of precipitation-discharge correlations. When the new precipitation estimates are used, the performance of the LaD model is comparable to, but not significantly better than, that of a simple, semiempirical water-balance relation that uses only annual totals of surface net radiation and precipitation. This implies that the LaD simulations of interannual runoff variability do not benefit substantially from information on geographical variability of land parameters or seasonal structure of interannual variability of precipitation. The aforementioned analyses necessitated the development of a method for downscaling of long-term monthly precipitation data to the relatively short timescales necessary for running the model. The method merges the long-term data with a reference dataset of 1-yr duration, having high temporal resolution. The success of the method, for the model and data considered here, was demonstrated in a series of model-model comparisons and in the comparisons of modeled and observed interannual variations of basin discharge.

  16. Controls on interannual variability in lightning-caused fire activity in the western US

    NASA Astrophysics Data System (ADS)

    Abatzoglou, John T.; Kolden, Crystal A.; Balch, Jennifer K.; Bradley, Bethany A.

    2016-04-01

    Lightning-caused wildfires account for a majority of burned area across the western United States (US), yet lightning remains among the more unpredictable spatiotemporal aspects of the fire environment and a challenge for both modeling and managing fire activity. A data synthesis of cloud-to-ground lightning strikes, climate and fire data across the western US from 1992 to 2013 was conducted to better understand geographic variability in lightning-caused wildfire and the factors that influence interannual variability in lightning-caused wildfire at regional scales. Distinct geographic variability occurred in the proportion of fires and area burned attributed to lightning, with a majority of fires in the interior western US attributed to lightning. Lightning ignition efficiency was highest across the western portion of the region due to the concomitance of peak lightning frequency and annual nadir in fuel moisture in mid-to-late summer. For most regions the number of total and dry lightning strikes exhibited strong interannual correlation with the number of lightning-caused fires, yet were a poor predictor of area burned at regional scales. Commonality in climate–fire relationships for regional annual area burned by lightning- versus human-ignited fires suggests climate conditions, rather than lightning activity, are the predominant control of interannual variability in area burned by lightning-caused fire across much of the western US.

  17. Pre-onset land surface processes and `internal' interannual variabilities of the Indian summer monsoon

    NASA Astrophysics Data System (ADS)

    Saha, Subodh K.; Halder, Subhadeep; Kumar, K. Krishna; Goswami, B. N.

    2011-06-01

    It is proposed that, land-atmosphere interaction around the time of monsoon onset could modulate the first episode of climatological intraseasonal oscillation (CISO) and may generate significant `internal' interannual variation in the Indian summer monsoon rainfall. The regional climate model RegCM3 is used over Indian monsoon domain for 27 years of control simulation. In order to prove the hypothesis, another two sets of experiment are performed using two different boundary conditions (El Niño year and non-ENSO year). In each of these experiments, a single year of boundary conditions are used repeatedly year after year to generate `internal' interannual monsoon variability. Simulation of monsoon climate in the control model run is found to be in reasonably good agreement with observation. However, large rainfall bias is seen over Arabian Sea and Bay of Bengal. The interannual monsoon rainfall variability are of the same order in two experiments, which suggest that the external influences may not be important on the generation of `internal' monsoon rainfall variability. It is shown that, a dry (wet) pre-onset land-surface condition increases (decreases) rainfall in June which in turn leads to an anomalous increase (decrease) in seasonal (JJAS) rainfall. The phase and amplitude of CISO are modulated during May-June and beyond that the modulation of CISO is quite negligible. Though the pre-onset rainfall is unpredictable, significant modulation of the post-onset monsoon rainfall by it can be exploited to improve predictive skill within the monsoon season.

  18. Long-term trends and interannual variability of fires in South America during 2001-2009

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Randerson, J. T.; Morton, D. M.; Jin, Y.; Giglio, L.; Collatz, G. J.; Kasibhatla, P. S.; van der Werf, G.; Defries, R. S.

    2010-12-01

    Forest and savanna fires in South America have large impacts on ecosystems, air quality, and global climate. In this paper we investigated long-term trends and interannual variability of forest and savanna fires in South America during 2001-2009 based on multiple satellite datasets. We found that fires associated with the deforestation frontier in evergreen forests increased in the first half of the decade, peaked at 2005, and declined thereafter. Fires in deciduous forests in southern Bolivia, northern Argentina and western Paraguay were characterized by a consistent increasing trend. Savanna fires showed smaller interannual variability, except for a high (2007) and a low (2009) year. Time series of fire counts (FC), burned area, and GFED3 emissions demonstrated a moving fire front in the deforestation arc toward the interior of the Amazon. Fire intensity (FI), defined as the ratio of FC to the deforestation area, increased consistently during 2001-2007 and decreased in 2008. Fire persistence (FP), which is linked with high rates of fuel consumption including repeated human aggregation and burning of fuels, decreased at the deforestation frontier after 2004. We explored the possibility of using FP to estimate the FI and the deforestation area. The interannual variability of fire activity was found to be correlated with precipitation with variable time lags in different biomes. Climate variability and drought stress were related to ENSO and the North Atlantic Oscillation.

  19. Dynamics of the Chesapeake Bay outflow plume: Realistic plume simulation and its seasonal and interannual variability

    NASA Astrophysics Data System (ADS)

    Jiang, Long; Xia, Meng

    2016-02-01

    The three-dimensional unstructured-grid Finite Volume Coastal Ocean Model (FVCOM) was implemented for Chesapeake Bay and its adjacent coastal ocean to delineate the realistic Chesapeake Bay outflow plume (CBOP) as well as its seasonal and interannual variability. Applying the appropriate horizontal and vertical resolution, the model exhibited relatively high skill in matching the observational water level, temperature, and salinity from 2003 to 2012. The simulated surface plume structure was verified by comparing output to the HF radar current measurements, earlier field observations, and the MODIS and AVHRR satellite imagery. According to the orientation, shape, and size of the CBOP from both model snapshots and satellite images, five types of real-time plume behavior were detected, which implied strong regulation by wind and river discharge. In addition to the episodic plume modulation, horizontal and vertical structure of the CBOP exhibited variations on seasonal and interannual temporal scales. Seasonally, river discharge with a 1 month lag was primarily responsible for the surface plume area variation, while the plume thickness was mainly correlated to wind magnitude. On the interannual scale, river discharge was the predominant source of variability in both surface plume area and depth; however, the southerly winds also influenced the offshore plume depth. In addition, large-scale climate variability, such as the North Atlantic Oscillation, could potentially affect the plume signature in the long term by altering wind and upwelling dynamics, underlining the need to understand the impacts of climate change on buoyant plumes, such as the CBOP.

  20. Effects of Uncertainty in TRMM Precipitation Radar Path Integrated Attenuation on Interannual Variations of Tropical Oceanic Rainfall

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.; Fitzjarrald, Dan E.; Kummerow, Christian D.; Arnold, James E. (Technical Monitor)

    2002-01-01

    Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30 deg N/S) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Time series of rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM Precipitation Radar (PR) over the tropical oceans show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. We show that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees closely with the TMI time series. Further analysis of the frequency distribution of PR (2A25 product) rain rates suggests that the algorithm incorporates the attenuation measurement in a very conservative fashion so as to optimize the instantaneous rain rates. Such an optimization appears to come at the expense of monitoring interannual climate variability.

  1. Analysis of the Relationship Between Climate and NDVI Variability at Global Scales

    NASA Technical Reports Server (NTRS)

    Zeng, Fan-Wei; Collatz, G. James; Pinzon, Jorge; Ivanoff, Alvaro

    2011-01-01

    interannual variability in modeled (CASA) C flux is in part caused by interannual variability in Normalized Difference Vegetation Index (NDVI) Fraction of Photosynthetically Active Radiation (FPAR). This study confirms a mechanism producing variability in modeled NPP: -- NDVI (FPAR) interannual variability is strongly driven by climate; -- The climate driven variability in NDVI (FPAR) can lead to much larger fluctuation in NPP vs. the NPP computed from FPAR climatology

  2. The Elastic Response of the Earth to Interannual Variations in Antarctic Precipitation

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.; Conrad, Clinton P.

    1995-01-01

    Measurements of elastic displacements of the bedrock surrounding large ice sheets have been proposed as a means to detect mass changes in these ice sheets. However, accumulation of glacial mass on the ice sheets is a noisy process, subject to large spatial and temporal variations in precipitation. We simulated the response of the Antarctic continent to a stochastic model of interannual precipitation variations and found that interannual variations in the elastic response of the earth are large when compared to the long-term mean of displacements produced by an assumed average ice mass imbalance of 10%. If, as some scientists predict, Antarctic ice mass changes in the future become dramatic, the long-term signal should be large enough to be detected by a few years of geodetic measurements, despite climatic noise.

  3. Interannual growth dynamics of vegetation in the Kuparuk River watershed, Alaska based on the Normalized Difference Vegetation Index

    USGS Publications Warehouse

    Hope, A.S.; Boynton, W.L.; Stow, D.A.; Douglas, D.C.

    2003-01-01

    Interannual above-ground production patterns are characterized for three tundra ecosystems in the Kuparuk River watershed of Alaska using NOAA-AVHRR Normalized Difference Vegetation Index (NDVI) data. NDVI values integrated over each growing season (SINDVI) were used to represent seasonal production patterns between 1989 and 1996. Spatial differences in ecosystem production were expected to follow north-south climatic and soil gradients, while interannual differences in production were expected to vary with variations in seasonal precipitation and temperature. It was hypothesized that the increased vegetation growth in high latitudes between 1981 and 1991 previously reported would continue through the period of investigation for the study watershed. Zonal differences in vegetation production were confirmed but interannual variations did not covary with seasonal precipitation or temperature totals. A sharp reduction in the SINDVI in 1992 followed by a consistent increase up to 1996 led to a further hypothesis that the interannual variations in SINDVI were associated with variations in stratospheric optical depth. Using published stratospheric optical depth values derived from the SAGE and SAGE-II satellites, it is demonstrated that variations in these depths are likely the primary cause of SINDVI interannual variability.

  4. Modeling Interannual Variations of Summer Monsoons.

    NASA Astrophysics Data System (ADS)

    Palmer, T. N.; Brankovi, .; Viterbo, P.; Miller, M. J.

    1992-05-01

    Results from a set of 90-day integrations, made with a T42 version of the ECMWF model and forced with a variety of specified sea surface temperature (SST) datasets, are discussed. Most of the integrations started from data for 1 June 1987 and 1 June 1988. During the summer of 1987, both the Indian and African monsoons were weak, in contrast with the summer of 1988 when both monsoons were much stronger. With observed SSTs, the model is able to simulate the interannual variations in the global-scale velocity potential and stream-function fields on seasonal time scales. On a regional basis, rainfall over the Sahel and, to a lesser extent, India showed the correct sense of interannual variation, though in absolute terms the model appears to have an overall dry bias in these areas.Additional integrations were made to study the impact of the observed SST anomalies in individual oceans. Much of the interannual variation in both Indian and African rainfall can be accounted for by the remote effect of the tropical Pacific SST anomalies only. By comparison with the effect of the Pacific, interannual variability in Indian Ocean, tropical Atlantic Ocean, or extratropical SSTs had a relatively modest influence on tropical large-scale flow or rainfall in the areas studied.Integrations run with identical SSTs but different initial conditions indicated that for large-scale circulation diagnostics, the impact of anomalous ocean forcing dominated the possible impact of variations in initial conditions. In terms of local rainfall amounts, on the other hand, the impact of initial conditions is comparable with that of SST anomaly over parts of India and Southeast Asia, less so over the Sahel. While this may suggest that a nonnegligible fraction of the variance of month-to-seasonal mean rainfall on the regional scale in the tropics may not be dynanamically predictable, it is also quite possible that the disparity in the apparent predictability of rainfall and circulation anomalies is a

  5. Interannual and Decadal Variability of Summer Rainfall over South America

    NASA Technical Reports Server (NTRS)

    Zhou, Jiayu; Lau, K.-M.

    1999-01-01

    Using the CPC (Climate Prediction Center) Merged Analysis of Precipitation product along with the Goddard Earth Observing System reanalysis and the Climate Analysis Center sea surface temperature (SST) data, we conduct a diagnostic study of the interannual and decadal scale variability of summer rainfall over South America. Results show three leading modes of rainfall variation identified with interannual, decadal, and long-term trend variability. Together, these modes explain more than half the total variance. The first mode is highly correlated with El Nino/southern oscillation (ENSO), showing severe drought over Northeast Brazil and copious rainfall over the Ecuador coast and the area of Uruguay-Southern Brazil in El Nino years. This pattern is attributed to the large scale zonal shift of the Walker circulation and local Hadley cell anomaly induced by positive (negative) SST anomaly over the eastern (western) equatorial Pacific. In El Nino years, two convective belts indicated by upper tropospheric velocity potential trough and mid-tropospheric rising motion, which are somewhat symmetric about the equator, extend toward the northeast and the southeast into the tropical North and South Atlantic respectively. Sandwiched between the ascent is a region of descending motion over Northeast Brazil. The southern branch of the anomalous Hadley cell is dynamically linked to the increase of rainfall over Uruguay-Southern Brazil. The regional response of anomalous circulation shows a stronger South American summer monsoon and an enhanced (weakened) subtropical high over the South Atlantic (South Pacific) Ocean. The decadal variation displays a meridional shift of the Intertropical Convergence Zone (ITCZ), which is tie to the anomalous cross-equatorial SST gradient over the Atlantic and the eastern Pacific. In conjunction with this mode is a large scale mass swing between the polar regions and midlatitudes in both hemispheres. Over the South Atlantic and the South Pacific

  6. Marginal Lands Gross Primary Production Dominate Atmospheric CO2 Interannual Variations

    NASA Astrophysics Data System (ADS)

    Ahlström, A.; Raupach, M. R.; Schurgers, G.; Arneth, A.; Jung, M.; Reichstein, M.; Smith, B.

    2014-12-01

    Since the 1960s terrestrial ecosystems have acted as a substantial sink for atmospheric CO2, sequestering about one quarter of anthropogenic emissions in an average year. Variations in this land carbon sink are also responsible for most of the large interannual variability in atmospheric CO2 concentrations. While most evidence places the majority of the sink in highly productive forests and at high latitudes experiencing warmer and longer growing seasons, the location and the processes governing the interannual variations are still not well characterised. Here we evaluate the hypothesis that the long-term trend and the variability in the land CO2 sink are respectively dominated by geographically distinct regions: the sink by highly productive lands, mainly forests, and the variability by semi-arid or "marginal" lands where vegetation activity is strongly limited by water and therefore responds strongly to climate variability. Using novel analysis methods and data from both upscaled flux-tower measurements and a dynamic global vegetation model, we show that (1) the interannual variability in the terrestrial CO2 sink arises mainly from variability in terrestrial gross primary production (GPP); (2) most of the interannual variability in GPP arises in tropical and subtropical marginal lands, where negative anomalies are driven mainly by warm, dry conditions and positive anomalies by cool, wet conditions; (3) the variability in the GPP of high-latitude marginal lands (tundra and shrublands) is instead controlled by temperature and light, with warm bright conditions resulting in positive anomalies. The influence of ENSO (El Niño-Southern Oscillation) on the growth rate of atmospheric CO2 concentrations is mediated primarily through climatic effects on GPP in marginal lands, with opposite signs in subtropical and higher-latitude regions. Our results show that the land sink of CO2 (dominated by forests) and its interannual variability (dominated by marginal lands) are

  7. The Arctic Predictability and Prediction on Seasonal-to-Interannual TimEscales (APPOSITE) data set version 1

    NASA Astrophysics Data System (ADS)

    Day, Jonathan J.; Tietsche, Steffen; Collins, Mat; Goessling, Helge F.; Guemas, Virginie; Guillory, Anabelle; Hurlin, William J.; Ishii, Masayoshi; Keeley, Sarah P. E.; Matei, Daniela; Msadek, Rym; Sigmond, Michael; Tatebe, Hiroaki; Hawkins, Ed

    2016-06-01

    Recent decades have seen significant developments in climate prediction capabilities at seasonal-to-interannual timescales. However, until recently the potential of such systems to predict Arctic climate had rarely been assessed. This paper describes a multi-model predictability experiment which was run as part of the Arctic Predictability and Prediction On Seasonal to Interannual Timescales (APPOSITE) project. The main goal of APPOSITE was to quantify the timescales on which Arctic climate is predictable. In order to achieve this, a coordinated set of idealised initial-value predictability experiments, with seven general circulation models, was conducted. This was the first model intercomparison project designed to quantify the predictability of Arctic climate on seasonal to interannual timescales. Here we present a description of the archived data set (which is available at the British Atmospheric Data Centre), an assessment of Arctic sea ice extent and volume predictability estimates in these models, and an investigation into to what extent predictability is dependent on the initial state. The inclusion of additional models expands the range of sea ice volume and extent predictability estimates, demonstrating that there is model diversity in the potential to make seasonal-to-interannual timescale predictions. We also investigate whether sea ice forecasts started from extreme high and low sea ice initial states exhibit higher levels of potential predictability than forecasts started from close to the models' mean state, and find that the result depends on the metric. Although designed to address Arctic predictability, we describe the archived data here so that others can use this data set to assess the predictability of other regions and modes of climate variability on these timescales, such as the El Niño-Southern Oscillation.

  8. Future changes of interannual variation of the Asian summer monsoon precipitation using the CMIP5

    NASA Astrophysics Data System (ADS)

    Kamizawa, Nozomi; Takahashi, Hiroshi G.

    2015-04-01

    The Asian summer monsoon (ASM) region is one of the most populated areas in the world. Since the life of people who live in the region and the industry are strongly dependent on the ASM precipitation, it is interested that how it would change under the circumstance of global warming. Many studies have reported that the mean ASM precipitation would increase by comparing the CMIP models' climatology. Although the changes in mean climate are important, the long-term changes of interannual variability in precipitation are also significant. This study investigated the long-term trend of interannual precipitation variation over the ASM region by using 22 CMIP5 models. The RCP4.5 scenario was used. To investigate the long-term trend of the interannual variation of the ASM precipitation, each model data was recreated to 2.5 degree resolution and a running standard deviation for 21 years of June-July-August (JJA) precipitation were calculated. Next, we created the coefficient variation (CV) by dividing the running standard deviation by the mean JJA precipitation. Then we run a Mann-Kendall test for the CV at each grid. There were more areas which were indicated a statistically significant increasing trend than a decreasing trend in the ASM region. 40.6% of the region indicated an increasing trend in the future. On the other hand, 16.8% of the area was indicated to have a decreasing trend. It was also common in the global scale that the there were more areas that indicated an increasing trend than a decreasing trend. We also divided the area into three groups: land, shore and open ocean. In the ASM region, the shore areas particularly had an increasing CV trend. To investigate the long-term changes of the interannual variability of the precipitation and the atmospheric circulation over the ASM region, we conducted a composite analysis for the five wettest and driest years for two periods: the early 21st century (2007-2031) and the late 21st century (2076-2100). The special

  9. Interannual variability of the Mediterranean trophic regimes from ocean color satellites

    NASA Astrophysics Data System (ADS)

    Mayot, Nicolas; D'Ortenzio, Fabrizio; Ribera d'Alcalà, Maurizio; Lavigne, Héloïse; Claustre, Hervé

    2016-03-01

    D'Ortenzio and Ribera d'Alcalà (2009, DR09 hereafter) divided the Mediterranean Sea into "bioregions" based on the climatological seasonality (phenology) of phytoplankton. Here we investigate the interannual variability of this bioregionalization. Using 16 years of available ocean color observations (i.e., SeaWiFS and MODIS), we analyzed the spatial distribution of the DR09 trophic regimes on an annual basis. Additionally, we identified new trophic regimes, exhibiting seasonal cycles of phytoplankton biomass different from the DR09 climatological description and named "Anomalous". Overall, the classification of the Mediterranean phytoplankton phenology proposed by DR09 (i.e., "No Bloom", "Intermittently", "Bloom" and "Coastal"), is confirmed to be representative of most of the Mediterranean phytoplankton phenologies. The mean spatial distribution of these trophic regimes (i.e., bioregions) over the 16 years studied is also similar to the one proposed by DR09, although some annual variations were observed at regional scale. Discrepancies with the DR09 study were related to interannual variability in the sub-basin forcing: winter deep convection events, frontal instabilities, inflow of Atlantic or Black Sea Waters and river run-off. The large assortment of phytoplankton phenologies identified in the Mediterranean Sea is thus verified at the interannual scale, further supporting the "sentinel" role of this basin for detecting the impact of climate changes on the pelagic environment.

  10. The Interannual Stability of Cumulative Frequency Distributions for Convective System Size and Intensity

    NASA Technical Reports Server (NTRS)

    Mohr, Karen I.; Molinari, John; Thorncroft, Chris D,

    2010-01-01

    The characteristics of convective system populations in West Africa and the western Pacific tropical cyclone basin were analyzed to investigate whether interannual variability in convective activity in tropical continental and oceanic environments is driven by variations in the number of events during the wet season or by favoring large and/or intense convective systems. Convective systems were defined from TRMM data as a cluster of pixels with an 85 GHz polarization-corrected brightness temperature below 255 K and with an area at least 64 km 2. The study database consisted of convective systems in West Africa from May Sep for 1998-2007 and in the western Pacific from May Nov 1998-2007. Annual cumulative frequency distributions for system minimum brightness temperature and system area were constructed for both regions. For both regions, there were no statistically significant differences among the annual curves for system minimum brightness temperature. There were two groups of system area curves, split by the TRMM altitude boost in 2001. Within each set, there was no statistically significant interannual variability. Sub-setting the database revealed some sensitivity in distribution shape to the size of the sampling area, length of sample period, and climate zone. From a regional perspective, the stability of the cumulative frequency distributions implied that the probability that a convective system would attain a particular size or intensity does not change interannually. Variability in the number of convective events appeared to be more important in determining whether a year is wetter or drier than normal.

  11. Sole larval supply to coastal nurseries: Interannual variability and connectivity at interregional and interpopulation scales

    NASA Astrophysics Data System (ADS)

    Savina, M.; Lunghi, M.; Archambault, B.; Baulier, L.; Huret, M.; Le Pape, O.

    2016-05-01

    Simulating fish larval drift helps assess the sensitivity of recruitment variability to early life history. An individual-based model (IBM) coupled to a hydrodynamic model was used to simulate common sole larval supply from spawning areas to coastal and estuarine nursery grounds at the meta-population scale (4 assessed stocks), from the southern North Sea to the Bay of Biscay (Western Europe) on a 26-yr time series, from 1982 to 2007. The IBM allowed each particle released to be transported by currents, to grow depending on temperature, to migrate vertically depending on development stage, to die along pelagic stages or to settle on a nursery, representing the life history from spawning to metamorphosis. The model outputs were analysed to explore interannual patterns in the amounts of settled sole larvae at the population scale; they suggested: (i) a low connectivity between populations at the larval stage, (ii) a moderate influence of interannual variation in the spawning biomass, (iii) dramatic consequences of life history on the abundance of settling larvae and (iv) the effects of climate variability on the interannual variability of the larvae settlement success.

  12. Mechanisms of Interannual Variations of the Meridional Overturning Circulation of the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Cabanes, Cecile; Lee, Tong; Fu, Lee-Lueng

    2008-01-01

    The authors investigate the nature of the interannual variability of the meridional overturning circulation (MOC) of the North Atlantic Ocean using an Estimating the Circulation and Climate of the Ocean (ECCO) assimilation product for the period of 1993-2003. The time series of the first empirical orthogonal function of the MOC is found to be correlated with the North Atlantic Oscillation (NAO) index, while the associated circulation anomalies correspond to cells extending over the full ocean depth. Model sensitivity experiments suggest that the wind is responsible for most of this interannual variability, at least south of 40(deg)N. A dynamical decomposition of the meridional streamfunction allows a further look into the mechanisms. In particular, the contributions associated with 1) the Ekman flow and its depth-independent compensation, 2) the vertical shear flow, and 3) the barotropic gyre flowing over zonally varying topography are examined. Ekman processes are found to dominate the shorter time scales (1.5-3 yr), while for longer time scales (3-10 yr) the MOC variations associated with vertical shear flow are of greater importance. The latter is primarily caused by heaving of the pycnocline in the western subtropics associated with the stronger wind forcing. Finally, how these changes in the MOC affect the meridional heat transport (MHT) is examined. It is found that overall, Ekman processes explain a larger part of interannual variability (3-10 yr) for MHT (57%) than for the MOC (33%).

  13. Feedback Attributions to the Interannual Variation of the Dominant Modes of the East Asian Winter Monsoon

    NASA Astrophysics Data System (ADS)

    Li, Yana; Yang, Song

    2016-04-01

    This study investigates the interannual variation and feedback attributions of the East Asian Winter Monsoon for the period of 1979-2013. The variations of winter mean surface air temperature are dominated by two distinct principal modes, which account for 70.9% of the total variance. The interannual variation of the northern mode features high correlations with the variations of the Arctic Oscillation, the Siberia High, and the tropoical Indian Ocean Dipole, while the southern mode is strongly linked to the East Asia trough and the atmospheric circulation over the northwestern Pacific. To find the main factors which affect the two different modes, this study decomposes the surface air temperature interannual variation into various feedback attributions by applying a climate feedback-response analysis method. The results indicate that the surface cooling associated with the northern mode is mainly contributed by the feedback processes of atmospheric dynamics, cloud, and sensible heating. For the southern mode, the surface cooling is mainly attributed to the atmospheric dynamic process, sensible heating, and water vapor, while the oceanic dynamics and heat storage process induces a negative effect that warms the surface.

  14. The Seasonal and Interannual Variability of the Budgets of N2O and CCl3F

    NASA Technical Reports Server (NTRS)

    Wong, Sun; Prather, Michael J.; Rind, David H.

    1999-01-01

    The 6-year wind archives from the Goddard Institute for Space Studies/Global Climate-Middle Atmosphere Model (GISS/GCMAM) were in- put to the GISS/Harvard/Irvine Chemical Transport Model (G/H/I CTM) to study the seasonal and interannual variability of the budgets and distributions of nitrous oxide (N2O) and trichlorofluoromethane (CCl3F), with the corresponding chemical loss frequencies recycled and boundary conditions kept unchanged from year to year. The effects of ozone feedback and quasi-biennial oscillation (QBO) were not included. However, the role of circulation variation in driving the lifetime variability is investigated. It was found that the global loss rates of these tracers are related to the extratropical planetary wave activity, which drives the tropical upward mass flux. For N2O, a semiannual signal in the loss rate variation is associated with the interhemispheric asymmetry in the upper stratospheric wave activity. For CCl3F, the semiannual signal is weaker, associated with the comparatively uniform wave episodes in the lower stratosphere. The loss rates lag behind the wave activity by about 1-2 months. The interannual variation of the GCM generated winds drives the interannual variation of the annually averaged lifetime. The year-to-year variations of the annually averaged lifetimes can be about 3% for N2O and 4% for CCl3F.

  15. Interannual variation of global net radiation flux as measured from space

    NASA Astrophysics Data System (ADS)

    Zhu, Ping; Wild, Martin; Ruymbeke, Michel; Thuillier, Gérard; Meftah, Mustapha; Karatekin, Ozgur

    2016-06-01

    The global net radiation flux (NRF) in and out of the climate system at the top of the atmosphere (TOA) varies at interannual time scales, reflecting the complexity of the processes responsible for attaining global energy equilibrium. These processes are investigated in this study using the previously unexplored data acquired by a bolometric type sensor installed in the PICARD microsatellite. The obtained anomalies in the NRF (PICARD-NRF) are compared to the global NRF changes at the TOA measured by the Clouds and Earth's Radiant Energy System mission (CERES-NRF). The interanual PICARD-NRF is strongly correlated with the matching period CERES-NRF; the bootstrapped correlation at the 95%(+0.85 and +0.97) confidence intervals is +0.93. Consistency in the interannual variability in the NRF derived by two completely independent measurement systems enhances confidence in the estimated magnitude of these variations. To reveal the possible drivers of the NRF interannual variability, the NRF values were compared with the multivariate El Niño-Southern Oscillation index.

  16. Seasonal and interannual changes in cirrus

    NASA Technical Reports Server (NTRS)

    Wylie, Donald P.

    1990-01-01

    Statistics on cirrus clouds using the multispectral data from the GOES/VAS satellite have been collected since 1985. The method used to diagnose cirrus clouds and a summary of the first two years of data was given in Wylie and Menzel (1989) and at the 1988 FIRE meeting in Vail, CO. This study was expanded to three years of data which allows a more detailed discussion of the geographical and seasonal changes in cloud cover. Interannual changes in cloud cover also were studied. GOES/VAS cloud retrievals also were compared to atmospheric dynamic parameters and to radiative attenuation data taken by a lidar. Some of the highlights of these studies are discussed.

  17. Interannual variability: a crucial component of space use at the territory level.

    PubMed

    Uboni, Alessia; Vucetich, John A; Stahler, Daniel R; Smith, Douglas W

    2015-01-01

    Interannual variability in space use and how that variation is influenced by density-dependent and density-independent factors are important processes in population ecology. Nevertheless, interannual variability has been neglected by the majority of space use studies. We assessed that variation for wolves living in 15 different packs within Yellowstone National Park during a 13-year period (1996-2008). We estimated utilization distributions to quantify the intensity of space use within each pack's territory each year in summer and winter. Then, we used the volume of intersection index (VI) to quantify the extent to which space use varied from year to year. This index accounts for both the area of overlap and differences in the intensity of use throughout a territory and ranges between 0 and 1. The mean VI index was 0.49, and varied considerably, with approximately 20% of observations (n = 230) being <0.3 or >0.7. In summer, 42% of the variation was attributable to differences between packs. These differences can be attributable to learned behaviors and had never been thought to have such an influence on space use. In winter, 34% of the variation in overlap between years was attributable to interannual differences in precipitation and pack size. This result reveals the strong influence of climate on predator space use and underlies the importance of understanding how climatic factors are going to affect predator populations in the occurrence of climate change. We did not find any significant association between overlap and variables representing density-dependent processes (elk and wolf densities) or intraspecific competition (ratio of wolves to elk). This last result poses a challenge to the classic view of predator-prey systems. On a small spatial scale, predator space use may be driven by factors other than prey distribution. PMID:26236891

  18. Interannual Variability of Boreal Summer Rainfall in the Equatorial Atlantic

    NASA Technical Reports Server (NTRS)

    Gu, Guojun; Adler, Robert F.

    2007-01-01

    Tropical Atlantic rainfall patterns and variation during boreal summer [June-July-August (JJA)] are quantified by means of a 28-year (1979-2006) monthly precipitation dataset from the Global Precipitation Climatology Project (GPCP). Rainfall variability during boreal spring [March-April-May (MAM)] is also examined for comparison in that the most intense interannual variability is usually observed during this season. Comparable variabilities in the Intertropical Convergence Zone (ITCZ) strength and the basin-mean rainfall are found during both seasons. Interannual variations in the ITCZ's latitudinal location during JJA however are generally negligible, in contrasting to intense year-to-year fluctuations during MAM. Sea surface temperature (SST) oscillations along the equatorial region (usually called the Atlantic Nino events) and in the tropical north Atlantic (TNA) are shown to be the two major local factors modulating the tropical Atlantic climate during both seasons. During MAM, both SST modes tend to contribute to the formation of an evident interhemispheric SST gradient, thus inducing anomalous shifting of the ITCZ and then forcing a dipolar structure of rainfall anomalies across the equator primarily in the western basin. During JJA the impacts however are primarily on the ITCZ strength likely due to negligible changes in the ITCZ latitudinal location. The Atlantic Nino reaches its peak in JJA, while much weaker SST anomalies appear north of the equator in JJA than in MAM, showing decaying of the interhemispheric SST mode. SST anomalies in the tropical central-eastern Pacific (the El Nino events) have a strong impact on tropical Atlantic including both the tropical north Atlantic and the equatorial-southern Atlantic. However, anomalous warming in the tropical north Atlantic following positive SST anomalies in the tropical Pacific disappears during JJA because of seasonal changes in the large-scale circulation cutting off the ENSO influence passing through the

  19. Understanding inter-annual displacements associated to loading in Southern Europe using geodetic techniques

    NASA Astrophysics Data System (ADS)

    Valty, P.; de Viron, O.; Panet, I.

    2012-12-01

    Over the last decades, the number and diversity of geodetic measurements has kept growing, now providing long time series of precise and independent measurements. Since 2002, the GRACE mission has been measuring the Earth's gravity field temporal variations, which are dominated by mass transfers associated to the water cycle. These water mass variations also cause the Earth's surface to deform, impacting the time series of horizontal or vertical displacements measured by GPS. Because they sense the total water content, from the surface to the depth, over long time spans, geodetic data provide unique information, that can improve our understanding of the water resources variations and how they are influenced by climate variations. In this context, we analyze the inter-annual variability common to GRACE, GPS and the loading models over Southern Europe, where a dense network of GPS permanent stations is available. First, we convert the GRACE geoids into their associated displacements and then, we isolate common inter-annual variability modes with the GPS data and the loading models by applying a Singular Value Decomposition (SVD). When analysing the spatial and temporal characteristics of these modes, we evidence the signature of extreme climatic events like the heatwaves of 2003 and 2007. We finally discuss these results in terms of hydrological signal and investigate the specific signature of the noticed critic climatic events in the geodetic time series.

  20. Impacts of absorbing aerosols on interannual and intraseasonal variability of the South Asian monsoon

    NASA Astrophysics Data System (ADS)

    Lau, W. K. M.; Kim, K. M.; Shi, J. J.; Tao, W. K.

    2015-12-01

    Aerosol-monsoon interactions on the interannual and intraseasonal variability of the South Asian monsoon are investigated from observations and modeling. On interannual time scales, we found from observations, and confirm with coupled ocean-atmosphere climate modeling, that absorbing aerosols (mainly desert dust and BC), can significantly amplifying the ENSO impact on the Indian monsoon, through precipitation and circulation feedback induced by the EHP effect. On intraseasonal time scales, modeling studies with the high-resolution WRF regional climate model demonstrated that EHP combined with the semi-direct and microphysics effects, associated with enhanced desert dust transported from the Middle East deserts across the Arabian Sea to the Indian subcontinent, may alter the moisture transport pathways, suppress the development of monsoon depression over northeastern India, resulting in development of intense convective cells, and extreme heavy rain along the Himalayan foothills in central and northwestern India. The implications of these feedback processes on climate change in the South Asian monsoon region will be discussed.

  1. Links between tropical Pacific seasonal, interannual and orbital variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Cobb, K. M.; Carré, M.; Braconnot, P.; Leloup, J.; Zhou, Y.; Harrison, S. P.; Corrège, T.; McGregor, H. V.; Collins, M.; Driscoll, R.; Elliot, M.; Schneider, B.; Tudhope, A.

    2016-02-01

    The El Niño/Southern Oscillation (ENSO) is the leading mode of interannual climate variability. However, it is unclear how ENSO has responded to external forcing, particularly orbitally induced changes in the amplitude of the seasonal cycle during the Holocene. Here we present a reconstruction of seasonal and interannual surface conditions in the tropical Pacific Ocean from a network of high-resolution coral and mollusc records that span discrete intervals of the Holocene. We identify several intervals of reduced variance in the 2 to 7 yr ENSO band that are not in phase with orbital changes in equatorial insolation, with a notable 64% reduction between 5,000 and 3,000 years ago. We compare the reconstructed ENSO variance and seasonal cycle with that simulated by nine climate models that include orbital forcing, and find that the models do not capture the timing or amplitude of ENSO variability, nor the mid-Holocene increase in seasonality seen in the observations; moreover, a simulated inverse relationship between the amplitude of the seasonal cycle and ENSO-related variance in sea surface temperatures is not found in our reconstructions. We conclude that the tropical Pacific climate is highly variable and subject to millennial scale quiescent periods. These periods harbour no simple link to orbital forcing, and are not adequately simulated by the current generation of models.

  2. Improved Water and Energy Management Utilizing Seasonal to Interannual Hydroclimatic Forecasts

    NASA Astrophysics Data System (ADS)

    Arumugam, S.; Lall, U.

    2014-12-01

    Seasonal to interannual climate forecasts provide valuable information for improving water and energy management. Given that the climatic attributes over these time periods are typically expressed as probabilistic information, we propose an adaptive water and energy management framework that uses probabilistic inflow forecasts to allocate water for uses with pre-specified reliabilities. To ensure that the system needs are not compromised due to forecast uncertainty, we propose uncertainty reduction using model combination and based on a probabilistic constraint in meeting the target storage. The talk will present findings from recent studies from various basins that include (a) role of multimodel combination in reducing the uncertainty in allocation (b) relevant system characteristics that improve the utility of forecasts, (c) significance of streamflow forecasts in promoting interbasin transfers and (d) scope for developing power demand forecasts utilizing temperature forecasts. Potential for developing seasonal nutrient forecasts using climate forecasts for supporting water quality trading will also be presented. Findings and synthesis from the panel discussion from the recently concluded AGU chapman conference on "Seaonal to Interannual Hydroclimatic Forecasts and Water Management" will also be summarized.

  3. Interannual variability in biochemistry of partially mixed estuaries: Dissolved silicate cycles in northern San Francisco Bay

    USGS Publications Warehouse

    Peterson, David H.; Cayan, Daniel R.; Festa, John F.

    1986-01-01

    Much of the interannual variability in partially mixed estuaries in dissolved inorganic nutrient and dissolved oxygen patterns results from an enhancement or reduction of their annual cycle (generally via climatic forcing). In northern San Francisco Bay estuary the annual cycle of dissolved silicate supply peaks in spring and the effect of phytoplankton removal peaks in fall. Because riverine silicate sources are enhanced in wet years and reduced in dry years, the annual silicate cycle is modified accordingly. Effects of phytoplankton removal are reduced and delayed in wet years and enhanced and advanced (seen earlier) in dry years. Similar reasoning can apply to interpreting and understanding other mechanisms and rates.

  4. Interannual Variability of the Tropical Water Cycle: Capabilities in the TRMM Era and Challenges for GPM

    NASA Technical Reports Server (NTRS)

    Robertson, Franklin R.

    2003-01-01

    Considerable uncertainty surrounds the issue of whether precipitation over the tropical oceans (30" NE) systematically changes with interannual sea-surface temperature (SST) anomalies that accompany El Nino (warm) and La Nina (cold) events. Although it is well documented that El Nino-Southern Oscillation (ENSO) events with marked SST changes over the tropical oceans, produce significant regional changes in precipitation, water vapor, and radiative fluxes in the tropics, we still cannot yet adequately quantify the associated net integrated changes to water and heat balance over the entire tropical oceanic or land sectors. Robertson et al., [2001 GRL] for example, showed that substantial disagreement exists among contemporary satellite estimates of interannual variations in tropical rainfall that are associated with SST changes. Berg et al., [2002 J. Climate] have documented the distinct differences between precipitation structure over the eastern and western Pacific ITCZ and noted how various satellite precipitation algorithms may respond quite differently to ENSO modulations of these precipitation regimes. Resolving this uncertainty is important since precipitation and latent heat release variations over land and ocean sectors are key components of the tropical heat balance in its most aggregated form. Rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) averaged over the tropical oceans have not solved this issue and, in fact, show marked differences with estimates from two TRMM Microwave Imager (TMI) passive microwave algorithms. In this paper we will focus on findings that uncertainties in microphysical assumptions necessitated by the single-frequency PR measurement pose difficulties for detecting climate-related precipitation signals. Recent work has shown that path-integrated attenuation derived from the effects of precipitation on the radar return from the ocean surface exhibits interannual variability that agrees

  5. Northern Hemispheric Interannual Teleconnection Patterns and Their Changes Due to the Greenhouse Effect.

    NASA Astrophysics Data System (ADS)

    Liang, Xin-Zhong; Wang, Wei-Chyung; Dudek, Michael P.

    1996-02-01

    Observed and general circulation climate model (GCM) simulated interannual teleconnection patterns in the Northern Hemisphere are compared on a monthly basis. The study was based on 1946-1991 observations and two separate 100-year simulations corresponding to the present climate and a greenhouse warming climate. The teleconnection patterns are characterized by action centers and composite extreme anomaly (CEA) distributions. The definition and comparison of observed and simulated patterns include examination of time persistence, spatial coherence as well as consistent signatures between 500-mb height, sea level pressure, and surface air temperature.For the present climate simulation, the GCM reproduces observed spatial and temporal variations of the action centers of four principal teleconnection patterns: the North Atlantic oscillation, the North Pacific oscillation, the Pacific/North American pattern, and the Eurasian pattern. Substantial model biases exist in the magnitude, regional structure as well as monthly transition of anomalies. The CEA regional characteristics are better simulated over land than over the oceans. For example, the model most accurately simulates the Eurasian pattern, which has its dominant action centers over Eurasia. In addition, all three climate variables exhibit substantial anomalies for each land-based action center. In contrast, over the oceans, the model systematically underestimates sea level pressure and 500-mb height CEAs, while it produces small surface temperature responses. It is suggested that atmospheric dynamics associated with flow instability is likely to be the dominant mechanism that generates these teleconnections, while the lack of interactive ocean dynamics may be responsible for small responses over the oceans.In the greenhouse warming climate, the GCM continues to simulate the four interannual teleconnection patterns. Systematic changes, however, are found for the Pacific/North American and Eurasian patterns in

  6. Interannual Variations in Global Vegetation Phenology Derived from a Long Term AVHRR and MODIS Data Record

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Friedl, M. A.; Yu, Y.

    2013-12-01

    Land surface phenology metrics are widely retrieved from satellite observations at regional and global scales, and have been shown to be valuable for monitoring terrestrial ecosystem dynamics in response to extreme climate events and predicting biological responses to future climate scenarios. While the response of spring vegetation greenup to climate warming at mid-to-high latitudes is well-documented, understanding of diverse phenological responses to climate change over entire growing cycles and at broad geographic scales is incomplete. Many studies assume that the timing of individual phenological indicators in responses to climate forcing is independent of phenological events that occur at other times during the growing season. In this paper we use a different strategy. Specifically, we hypothesize that integrating sequences of key phenological indicators across growing seasons provides a more effective way to capture long-term variation in phenology in response to climate change. To explore this hypothesis we use global land surface phenology metrics derived from the Version 3 Long Term Vegetation Index Products from Multiple Satellite Data Records data set to examine interannual variations and trends in global land surface phenology from 1982-2010. Using daily enhanced vegetation index (EVI) data at a spatial resolution of 0.05 degrees, we model the phenological trajectory for each individual pixel using piecewise logistic models. The modeled trajectories were then used to detect phenological indicators including the onset of greenness increase, the onset of greenness maximum, the onset of greenness decrease, the onset of greenness minimum, and the growing season length, among others at global scale. The quality of land surface phenology detection for individual pixels was calculated based on metrics that characterize the EVI quality and model fits in annual time series at each pixel. Phenological indicators characterized as having good quality were then

  7. Codominant water control on global interannual variability and trends in land surface phenology and greenness.

    PubMed

    Forkel, Matthias; Migliavacca, Mirco; Thonicke, Kirsten; Reichstein, Markus; Schaphoff, Sibyll; Weber, Ulrich; Carvalhais, Nuno

    2015-09-01

    Identifying the relative importance of climatic and other environmental controls on the interannual variability and trends in global land surface phenology and greenness is challenging. Firstly, quantifications of land surface phenology and greenness dynamics are impaired by differences between satellite data sets and phenology detection methods. Secondly, dynamic global vegetation models (DGVMs) that can be used to diagnose controls still reveal structural limitations and contrasting sensitivities to environmental drivers. Thus, we assessed the performance of a new developed phenology module within the LPJmL (Lund-Potsdam-Jena managed Lands) DGVM with a comprehensive ensemble of three satellite data sets of vegetation greenness and ten phenology detection methods, thereby thoroughly accounting for observational uncertainties. The improved and tested model allows us quantifying the relative importance of environmental controls on interannual variability and trends of land surface phenology and greenness at regional and global scales. We found that start of growing season interannual variability and trends are in addition to cold temperature mainly controlled by incoming radiation and water availability in temperate and boreal forests. Warming-induced prolongations of the growing season in high latitudes are dampened by a limited availability of light. For peak greenness, interannual variability and trends are dominantly controlled by water availability and land-use and land-cover change (LULCC) in all regions. Stronger greening trends in boreal forests of Siberia than in North America are associated with a stronger increase in water availability from melting permafrost soils. Our findings emphasize that in addition to cold temperatures, water availability is a codominant control for start of growing season and peak greenness trends at the global scale. PMID:25882036

  8. Influence of interannual variations in transport on summertime abundances of ozone over the Middle East

    NASA Astrophysics Data System (ADS)

    Liu, Jane J.; Jones, Dylan B. A.; Zhang, Shunli; Kar, Jay

    2011-10-01

    We used the GEOS-Chem model to investigate the impact of interannual variations in transport on summertime ozone abundances (between 1987 and 2006) in the middle troposphere over the Middle East. We found that ozone abundances fluctuated interannually by about ±7% (or ±6 ppbv from the 20-year mean of ˜80 ppbv). In the 20-year mean, ozone transported from Asia and ozone produced locally were the dominant sources of ozone, accounting for 31% and 23%, respectively, of ozone abundances over the Middle East, with an interannual variability of ±30% and ±15%, respectively. We found that the interannual variations in the Asian and local sources were related to the strengths of the South Asian High and the Arabian anticyclone, respectively. In years when the Asian influence was weaker in the region, transport from other areas, such as North America, was enhanced. Consequently, variations in ozone transported from Asia were strongly anti-correlated with variations in ozone transported from North America, for example, with a correlation coefficient of r = -0.75. This trade-off between transport from Asia and other regions was found to be linked to the position and strength of the subtropical westerly jet over central Asia. When the westerly jet is displaced poleward, transport of ozone from Asia is enhanced and transport from North America and other regions in the Northern Hemisphere is diminished. In contrast, when the jet is displaced equatorward, transport of ozone from Asia is diminished and transport from North America and other regions in the Northern Hemisphere is enhanced. These results suggest that climate-related changes in the position of the westerly jet will have implications for the transport of pollution into the Middle East.

  9. Interannual Variability in Global Soil Respiration on a 0.5 Degree Grid Cell Basis (1980-1994)

    SciTech Connect

    Raich, J.W.

    2003-09-15

    We used a climate-driven regression model to develop spatially resolved estimates of soil-CO{sub 2} emissions from the terrestrial land surface for each month from January 1980 to December 1994, to evaluate the effects of interannual variations in climate on global soil-to-atmosphere CO{sub 2} fluxes. The mean annual global soil-CO{sub 2} flux over this 15-y period was estimated to be 80.4 (range 79.3-81.8) Pg C. Monthly variations in global soil-CO{sub 2} emissions followed closely the mean temperature cycle of the Northern Hemisphere. Globally, soil-CO{sub 2} emissions reached their minima in February and peaked in July and August. Tropical and subtropical evergreen broad-leaved forests contributed more soil-derived CO{sub 2} to the atmosphere than did any other vegetation type ({approx}30% of the total) and exhibited a biannual cycle in their emissions. Soil-CO{sub 2} emissions in other biomes exhibited a single annual cycle that paralleled the seasonal temperature cycle. Interannual variability in estimated global soil-CO{sub 2} production is substantially less than is variability in net carbon uptake by plants (i.e., net primary productivity). Thus, soils appear to buffer atmospheric CO{sub 2} concentrations against far more dramatic seasonal and interannual differences in plant growth. Within seasonally dry biomes (savannas, bushlands, and deserts), interannual variability in soil-CO{sub 2} emissions correlated significantly with interannual differences in precipitation. At the global scale, however, annual soil-CO{sub 2} fluxes correlated with mean annual temperature, with a slope of 3.3 PgCY{sup -1} per degree Celsius. Although the distribution of precipitation influences seasonal and spatial patterns of soil-CO{sub 2} emissions, global warming is likely to stimulate CO{sub 2} emissions from soils.

  10. Recurrent Preterm Birth

    PubMed Central

    Mazaki-Tovi, Shali; Romero, Roberto; Kusanovic, Juan Pedro; Erez, Offer; Pineles, Beth L.; Gotsch, Francesca; Mittal, Pooja; Than, Nandor Gabor

    2012-01-01

    Recurrent preterm birth is frequently defined as two or more deliveries before 37 completed weeks of gestation. The recurrence rate varies as a function of the antecedent for preterm birth: spontaneous versus indicated. Spontaneous preterm birth is the result of either preterm labor with intact membranes or preterm prelabor rupture of the membranes. This article reviews the body of literature describing the risk of recurrence of spontaneous and indicated preterm birth. Also discussed are the factors which modify the risk for recurrent spontaneous preterm birth (a short sonographic cervical length and a positive cervicovaginal fetal fibronectin test). Patients with a history of an indicated preterm birth are at risk not only for recurrence of this subtype, but also for spontaneous preterm birth. Individuals of African-American origin have a higher rate of recurrent preterm birth. The potential roles of genetic and environmental factors in recurrent preterm birth are considered. PMID:17531896