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Sample records for african desert dust

  1. Hf-Nd-Sr isotopic fingerprinting of mineral dust from Asian and North African deserts

    NASA Astrophysics Data System (ADS)

    Ji, J.; Zhao, W.; Balsam, W.

    2015-12-01

    Mineral dust accounts for more than 50% of the atmospheric dust loading and plays an important role in the marine and terrestrial geochemical cycles. The deserts in North Africa, Northern China and Southern Mongolia are the major sources of mineral dust and have been studied intensively over past decades, especially with Sr, Nd and recently Hf isotopes which are seen as powerful tools to identify source areas. However, the isotopic compositions of dust are highly dependent on particle size hindering the ability to accurately identify dust provenance. The clay fraction (<2 μm) comprises about half of all mineral dust and has unique minerals phases dominanted by clay minerals. Once the clay-sized particles are deflated to the upper troposphere, they are transported over long distances and are removed from the atmosphere mainly by wet deposition. Thus, the clay-sized isotopic fingerprints from deserts may be ideal targets not only for tracking the provenance tracing of long-distance transported mineral dust, but also to provide an unparalleled window for understanding the global dust cycle, especially eolian dust preserved in deep-sea sediments and ice cores. In this work we investigate multivariate joint radiogenic Sr, Nd, and Hf isotopic compositions obtained from complete dissolution of clay-sized fractions of surface sediments from Asian and North African deserts. Asian dust source samples included the ten Northern China deserts and sandy lands - the Taklimakan, Gurbantunggut, Qaidam, Badaim Jaran, Tengger and Mu Us deserts, and the Hobq, Hulun Buirm, Onqin Daga and Horqin sandy land - and Mongolian Gobi desert. North African dust samples were from four transects in the Sahara and Sahel from Mali, Togo, Egypt and Morocco . Our results on the clay-sized isotopic measurements of these samples describe (1) the general characteristics of dusts from the Asian with ɛNd from -17.3 to 0.98, ɛHf from -5.95 to 3.68 and 87Sr/86Sr from 0.710113 to 0.73306, and North

  2. The Impact of Desert Dust Aerosol Radiative Forcing on Global and West African Precipitation

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.

    2015-12-01

    Desert dust aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of dust and that neighbors major Sahara Desert dust sources. As such, changes in West African climate due to radiative forcing of desert dust aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net warming of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert dust parameters across models. This presentation will offer quantitative analysis of differences in dust aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.

  3. African and Asian dust: from desert soils to coral reefs

    USGS Publications Warehouse

    Garrison, Virginia H.; Shinn, Eugene A.; Foreman, William T.; Griffin, Dale W.; Holmes, Charles W.; Kellogg, Christina A.; Majewski, Michael S.; Richardson, Laurie L.; Ritchie, Kim B.; Smith, Garriet W.

    2003-01-01

    Many hypotheses have been proposed to explain the decline of coral reefs throughout the world, but none adequately accounts for the lack of recovery of reefs or the wide geographical distribution of coral diseases. The processes driving the decline remain elusive. Hundreds of millions of tons of dust transported annually from Africa and Asia to the Americas may be adversely affecting coral reefs and other downwind ecosystems. Viable microorganisms, macro- and micronutrients, trace metals, and an array of organic contaminants carried in the dust air masses and deposited in the oceans and on land may play important roles in the complex changes occurring on coral reefs worldwide.

  4. African desert dust in the Caribbean atmosphere: Microbiology and public health

    USGS Publications Warehouse

    Griffin, Dale W.; Garrison, V.H.; Herman, J.R.; Shinn, E.A.

    2001-01-01

    Air samples collected on St. John in the U.S. Virgin Islands were screened for the presence of viable bacteria and fungi to determine if the number of cultivatable microbes in the atmosphere differed between "clear atmospheric conditions" and "African dust-events." Results indicate that during "African dust-events," the numbers of cultivatable airborne microorganisms can be 2 to 3 times that found during "clear atmospheric conditions." Direct microbial counts of air samples using an epifluorescent microscopy assay demonstrated that during an "African dust-event," bacteria-like and virus-like particle counts were approximately one log greater than during "clear atmospheric conditions." Bacteria-like particles exhibiting autofluoresence, a trait of phototrophs, were only detected during an "African dust-event.".

  5. Atmospheric transport of mold spores in clouds of desert dust

    USGS Publications Warehouse

    Shinn, E.A.; Griffin, Dale W.; Seba, D.B.

    2003-01-01

    Fungal spores can be transported globally in clouds of desert dust. Many species of fungi (commonly known as molds) and bacteria--including some that are human pathogens--have characteristics suited to long-range atmospheric transport. Dust from the African desert can affect air quality in Africa, Europe, the Middle East, and the Americas. Asian desert dust can affect air quality in Asia, the Arctic, North America, and Europe. Atmospheric exposure to mold-carrying desert dust may affect human health directly through allergic induction of respiratory stress. In addition, mold spores within these dust clouds may seed downwind ecosystems in both outdoor and indoor environments.

  6. Atmospheric transport of mold spores in clouds of desert dust.

    PubMed

    Shinn, Eugene A; Griffin, Dale W; Seba, Douglas B

    2003-08-01

    Fungal spores can be transported globally in clouds of desert dust. Many species of fungi (commonly known as molds) and bacteria--including some that are human pathogens--have characteristics suited to long-range atmospheric transport. Dust from the African desert can affect air quality in Africa, Europe, the Middle East, and the Americas. Asian desert dust can affect air quality in Asia, the Arctic, North America, and Europe. Atmospheric exposure to mold-carrying desert dust may affect human health directly through allergic induction of respiratory stress. In addition, mold spores within these dust clouds may seed downwind ecosystems in both outdoor and indoor environments.

  7. Airborne microorganisms in the African desert dust corridor over the mid-Atlantic ridge, Ocean Drilling Program, Leg 209

    USGS Publications Warehouse

    Griffin, Dale W.; Westphal, Douglas L.; Gray, Michael A.

    2006-01-01

    The objective of this study was to enhance our understanding of the fate and trans-Atlantic transport of dustborne microorganisms from Northern Africa to the Caribbean and Americas, and more specifically to determine if culturable populations could be detected at a mid-ocean site, closer to the source of dust relative to land-based Caribbean sites, during the early summer months of May and June. Between the dates of 22 May and 30 June 2003, daily air samples were collected and evaluated for the presence of culturable bacterial and fungal colony-forming units (CFU). Here we report a statistically significant correlation between daily atmospheric CFU counts at a mid-ocean research site (???15??N, 45??W) and daily desert dust concentrations as determined by the U.S. Navy's Naval Aerosol Analysis and Prediction System (NAAPS) Global Aerosol Model (Honrath et al. (2004). Journal of Geophysical Research, 109; Johnson et al. (2003). Global Biogeochemical Cycles, 17, 1063; Reid et al. (2004). Geophysical Research Letters, 31; Schollaert, Yoder, Westphal, & O'Reilly (2003). Journal of Geophysical Research, 108, 3191). ?? Springer Science+Business Media B.V. 2006.

  8. Desert Dust and Monsoon Rain

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong

    2014-01-01

    For centuries, inhabitants of the Indian subcontinent have know that heavy dust events brought on by strong winds occur frequently in the pre-monsoon season, before the onset of heavy rain. Yet scientists have never seriously considered the possibility that natural dust can affect monsoon rainfall. Up to now, most studies of the impacts of aerosols on Indian monsoon rainfall have focused on anthropogenic aerosols in the context of climate change. However, a few recent studies have show that aerosols from antropogenic and natural sources over the Indian subcontinent may affect the transition from break to active monsoon phases on short timescales of days to weeks. Writing in Nature Geoscience, Vinoj and colleagues describe how they have shown that desert dust aerosols over the Arabian Sea and West Asia can strenghten the summer monsoon over the Indial subcontinent in a matter of days.

  9. Airborne desert dust and aeromicrobiology over the Turkish Mediterranean coastline

    USGS Publications Warehouse

    Griffin, Dale W.; Kubilay, Nilgün; Kocak, Mustafa; Gray, Mike A.; Borden, Timothy C.; Shinn, Eugene A.

    2007-01-01

    Between 18 March and 27 October 2002, 220 air samples were collected on 209 of 224 calendar days, on top of a coastal atmospheric research tower in Erdemli, Turkey. The volume of air filtered for each sample was 340 liters. Two hundred fifty-seven bacterial and 2598 fungal colony forming units (CFU) were enumerated from the samples using a low-nutrient agar. Ground-based dust measurements demonstrated that the region is routinely impacted by dust generated regionally and from North Africa and that the highest combined percent recovery of total CFU and African dust deposition occurred in the month of April (93.4% of CFU recovery and 91.1% of dust deposition occurred during African dust days versus no African dust present, for that month). A statistically significant correlation was observed (peak regional African dust months of March, April and May; rs=0.576, P=0.000) between an increase in the prevalence of microorganisms recovered from atmospheric samples on dust days (regional and African as determined by ground-based dust measurements), versus that observed on non-dust days. Given the prevalence of atmospherically suspended desert dust and microorganisms observed in this study, and that culture-based studies typically only recover a small fraction (

  10. Desert Dust Satellite Retrieval Intercomparison

    NASA Technical Reports Server (NTRS)

    Carboni, E.; Thomas, G. E.; Sayer, A. M.; Siddans, R.; Poulsen, C. A.; Grainger, R. G.; Ahn, C.; Antoine, D.; Bevan, S.; Braak, R.; Brindley, H.; DeSouza-Mchado, S.; Deuze, J. L.; Diner, D.; Ducos, F.; Grey, W.; Hsu, C.; Kalashnikova, O. V.; Kahn, R.; North, P. R. J.; Salustro, C.; Smith, A.; Tanre, D.; Torres, O.; Veihelmann, B.

    2012-01-01

    This work provides a comparison of satellite retrievals of Saharan desert dust aerosol optical depth (AOD) during a strong dust event through March 2006. In this event, a large dust plume was transported over desert, vegetated, and ocean surfaces. The aim is to identify and understand the differences between current algorithms, and hence improve future retrieval algorithms. The satellite instruments considered are AATSR, AIRS, MERIS, MISR, MODIS, OMI, POLDER, and SEVIRI. An interesting aspect is that the different algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. These include multi-angle approaches (MISR, AATSR), polarisation measurements (POLDER), single-view approaches using solar wavelengths (OMI, MODIS), and the thermal infrared spectral region (SEVIRI, AIRS). Differences between instruments, together with the comparison of different retrieval algorithms applied to measurements from the same instrument, provide a unique insight into the performance and characteristics of the various techniques employed. As well as the intercomparison between different satellite products, the AODs have also been compared to co-located AERONET data. Despite the fact that the agreement between satellite and AERONET AODs is reasonably good for all of the datasets, there are significant differences between them when compared to each other, especially over land. These differences are partially due to differences in the algorithms, such as as20 sumptions about aerosol model and surface properties. However, in this comparison of spatially and temporally averaged data, at least as significant as these differences are sampling issues related to the actual footprint of each instrument on the heterogeneous aerosol field, cloud identification and the quality control flags of each dataset.

  11. Desert Dust Properties, Modelling, and Monitoring

    NASA Technical Reports Server (NTRS)

    Kaskaoutis, Dimitris G.; Kahn, Ralph A.; Gupta, Pawan; Jayaraman, Achuthan; Bartzokas, Aristides

    2013-01-01

    This paper is just the three-page introduction to a Special Issue of Advances in Meteorology focusing on desert dust. It provides a paragraph each on 13 accepted papers, most relating to the used of satellite data to assess attributes or distribution of airborne desert dust. As guest Associate Editors of this issue, we organized the papers into a systematic whole, beginning with large-scale transport and seasonal behavior, then to regional dust transport, transport history, and climate impacts, first in the Mediterranean region, then India and central Asia, and finally focusing on transport model assessment and the use of lidar as a technique to constrain dust spatial-temporal distribution.

  12. Wind modeling of Chihuahuan Desert dust outbreaks

    NASA Astrophysics Data System (ADS)

    Rivera Rivera, Nancy I.; Gill, Thomas E.; Gebhart, Kristi A.; Hand, Jennifer L.; Bleiweiss, Max P.; Fitzgerald, Rosa M.

    The Chihuahuan Desert region of North America is a significant source of mineral aerosols in the Western Hemisphere, and Chihuahuan Desert dust storms frequently impact the Paso del Norte (El Paso, USA/Ciudad Juarez, Mexico) metropolitan area. A statistical analysis of HYSPLIT back trajectory residence times evaluated airflow into El Paso on all days and on days with synoptic (non-convective) dust events in 2001-2005. The incremental probability—a measure of the areas most likely to have been traversed by air masses arriving at El Paso during dusty days—was only strongly positively associated with the region west-southwest of the city, a zone of known dust source areas. Focused case studies were made of major dust events on 15 April and 15 December 2003. Trajectories approached the surface and MM5 (NCAR/Penn State Mesoscale Model) wind speeds increased at locations consistent with dust sources observed in satellite imagery on those dates. Back trajectory and model analyses suggested that surface cyclones adjacent to the Chihuahuan Desert were associated with the extreme dust events, consistent with previous studies of dust storms in the Southern High Plains to the northeast. The recognition of these meteorological patterns serves as a forecast aid for prediction of dust events likely to impact the Paso del Norte.

  13. Ice nucleation by soil dust compared to desert dust aerosols

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Steinke, I.; Ullrich, R.; Höhler, K.; Schiebel, T.; Hoose, C.; Funk, R.

    2015-12-01

    A minor fraction of atmospheric aerosol particles, so-called ice-nucleating particles (INPs), initiates the formation of the ice phase in tropospheric clouds and thereby markedly influences the Earth's weather and climate systems. Whether an aerosol particle acts as an INP depends on its size, morphology and chemical compositions. The INP fraction of certain aerosol types also strongly depends on the temperature and the relative humidity. Because both desert dust and soil dust aerosols typically comprise a variety of different particles, it is difficult to assess and predict their contribution to the atmospheric INP abundance. This requires both accurate modelling of the sources and atmospheric distribution of atmospheric dust components and detailed investigations of their ice nucleation activities. The latter can be achieved in laboratory experiments and parameterized for use in weather and climate models as a function of temperature and particle surface area, a parameter called ice-nucleation active site (INAS) density. Concerning ice nucleation activity studies, the soil dust is of particular interest because it contains a significant fraction of organics and biological components, both with the potential for contributing to the atmospheric INP abundance at relatively high temperatures compared to mineral components. First laboratory ice nucleation experiments with a few soil dust samples indicated their INP fraction to be comparable or slightly enhanced to that of desert dust. We have used the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud simulation chamber to study the immersion freezing ability of four different arable soil dusts, sampled in Germany, China and Argentina. For temperatures higher than about -20°C, we found the INP fraction of aerosols generated from these samples by a dry dispersion technique to be significantly higher compared to various desert dust aerosols also investigated in AIDA experiments. In this contribution, we

  14. African Dust Blows over the Caribbean

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Shuttle astronauts frequently track Saharan dust storms as they blow from north Africa across the Atlantic Ocean. Dust palls blowing from Africa take about a week to cross the Atlantic. Recently, researchers have linked Saharan dust to coral disease, allergic reactions in humans, and red tides. The top photograph, a classic image showing African dust over the Caribbean, was taken at a time when few scientists had considered the possibility. The image was taken by Space Shuttle astronauts on July 11, 1994 (STS065-75-47). This photograph looks southwest over the northern edge of a large trans-Atlantic dust plume that blew off the Sahara desert in Africa. In this view, Caicos Island in the Bahamas and the mountainous spines of Haiti are partly obscured by the dust. Closer to the foreground, (about 26 degrees north latitude), the skies are clear. The lower photograph (STS105-723-7) was taken by Space Shuttle astronauts while docked to the International Space Station on August 19, 2001. The spacecraft is over the Atlantic Ocean at roughly 45oN, 60oW. The astronauts were looking obliquely to the south; the boundaries of the dust plumes can be traced visually by the abrupt change from clear to hazy atmosphere-the hazy line marks the northern edge of the dust pall near the Caribbean. Images provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to Astronaut Photography of Earth.

  15. Characterization of aerosolized bacteria and fungi from desert dust events in Mali, West Africa

    USGS Publications Warehouse

    Kellogg, C.A.; Griffin, Dale W.; Garrison, V.H.; Peak, K.K.; Royall, N.; Smith, R.R.; Shinn, E.A.

    2004-01-01

    Millions of metric tons of African desert dust blow across the Atlantic Ocean each year, blanketing the Caribbean and southeastern United States. Previous work in the Caribbean has shown that atmospheric samples collected during dust events contain living microbes, including plant and opportunistic human pathogens. To better understand the potential downwind public health and ecosystem effects of the dust microbes, it is important to characterize the source population. We describe 19 genera of bacteria and 3 genera of fungi isolated from air samples collected in Mali, a known source region for dust storms, and over which large dust storms travel.

  16. Desert dust suppressing precipitation: a possible desertification feedback loop.

    PubMed

    Rosenfeld, D; Rudich, Y; Lahav, R

    2001-05-22

    The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process.

  17. Desert dust suppressing precipitation: A possible desertification feedback loop

    PubMed Central

    Rosenfeld, Daniel; Rudich, Yinon; Lahav, Ronen

    2001-01-01

    The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process. PMID:11353821

  18. Lidar Measurements for Desert Dust Characterization: An Overview

    NASA Technical Reports Server (NTRS)

    Mona, L.; Liu, Z.; Mueller, D.; Omar, A.; Papayannis, A.; Pappalardo, G.; Sugimoto, N.; Vaughan, M.

    2012-01-01

    We provide an overview of light detection and ranging (lidar) capability for describing and characterizing desert dust. This paper summarizes lidar techniques, observations, and fallouts of desert dust lidar measurements. The main objective is to provide the scientific community, including non-practitioners of lidar observations with a reference paper on dust lidar measurements. In particular, it will fill the current gap of communication between research-oriented lidar community and potential desert dust data users, such as air quality monitoring agencies and aviation advisory centers. The current capability of the different lidar techniques for the characterization of aerosol in general and desert dust in particular is presented. Technical aspects and required assumptions of these techniques are discussed, providing readers with the pros and cons of each technique. Information about desert dust collected up to date using lidar techniques is reviewed. Lidar techniques for aerosol characterization have a maturity level appropriate for addressing air quality and transportation issues, as demonstrated by some first results reported in this paper

  19. The past, present and future of African dust.

    PubMed

    Evan, Amato T; Flamant, Cyrille; Gaetani, Marco; Guichard, Françoise

    2016-03-24

    African dust emission and transport exhibits variability on diurnal to decadal timescales and is known to influence processes such as Amazon productivity, Atlantic climate modes, regional atmospheric composition and radiative balance and precipitation in the Sahel. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation, the North Atlantic Oscillation, the meridional position of the intertropical convergence zone, Sahelian rainfall and surface temperatures over the Sahara Desert, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations--in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality and

  20. The past, present and future of African dust.

    PubMed

    Evan, Amato T; Flamant, Cyrille; Gaetani, Marco; Guichard, Françoise

    2016-03-24

    African dust emission and transport exhibits variability on diurnal to decadal timescales and is known to influence processes such as Amazon productivity, Atlantic climate modes, regional atmospheric composition and radiative balance and precipitation in the Sahel. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation, the North Atlantic Oscillation, the meridional position of the intertropical convergence zone, Sahelian rainfall and surface temperatures over the Sahara Desert, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations--in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality and

  1. The past, present and future of African dust

    NASA Astrophysics Data System (ADS)

    Evan, Amato T.; Flamant, Cyrille; Gaetani, Marco; Guichard, Françoise

    2016-03-01

    African dust emission and transport exhibits variability on diurnal to decadal timescales and is known to influence processes such as Amazon productivity, Atlantic climate modes, regional atmospheric composition and radiative balance and precipitation in the Sahel. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation, the North Atlantic Oscillation, the meridional position of the intertropical convergence zone, Sahelian rainfall and surface temperatures over the Sahara Desert, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations—in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality and

  2. Impact and monitoring of dust storms in Taklimakan desert

    NASA Astrophysics Data System (ADS)

    Feng, G. G.; Li, X.; Zheng, Z.

    2012-12-01

    The Taklimakan is China's largest, driest, and warmest desert in total area of 338000km^2 with perimeter of 436 km, it is also known as one of the world's largest shifting-sand deserts. Fully 85 percent of the total area consists of mobile, crescent-shaped sand dunes and are virtually devoid of vegetation. The abundant sand provides material for frequent intense dust storms. The Taklimakan desert fills the expansive Tarim Basin between the Kunlun Mountains and the Tibet Plateau to the south and the Tian Shan Mountains to the north. The Tarim River flows across the basin from west-to-east. In these places, the oases created by fresh surface water support agriculture. Studies outside Xinjiang indicated that 80% dust source of storms was from farmland. Dust storms in the Tarim Basin occur for 20 to 59 days, mainly in spring every year. However, little effort was taken to investigate soil wind erosion and dust emission around the desert. Quantitative understanding of individual dust events in the arid Taklimakan desert, for example, the dust emission rates and the long-range transport, are still incomplete. Therefore, the dust events were observed through routine satellite sensors, lidar instruments, airborne samplers, and surface-based aerosol monitors. Soil wind erosion and suspended particulates emission of four major dust storms from the desert and the typical oasis farmlands at the north rim of the desert were measured using creep sampler, BSNE and TSP at eight heights in 2012. In addition, Aqua satellite AOD data, the NAAPS Global Aeosol model, the CALIPSO satellite products, EPA's AirNow AQI of PM2.5 and HYSPLIT Back Trajectory model were applied to analyze dust transport across the Pacific. Four significant dust storms were observed at the north rim of Taklimakan desert in the spring, 2012. During those events, predominant wind direction ranged from 296 to 334°, wind speed over 7 m/s at 2 m lasted for 471-1074 min, gust wind speed ranged from 11-18m/s. It was

  3. African Dust Aerosols as Atmospheric Ice Nuclei

    NASA Technical Reports Server (NTRS)

    DeMott, Paul J.; Brooks, Sarah D.; Prenni, Anthony J.; Kreidenweis, Sonia M.; Sassen, Kenneth; Poellot, Michael; Rogers, David C.; Baumgardner, Darrel

    2003-01-01

    Measurements of the ice nucleating ability of aerosol particles in air masses over Florida having sources from North Africa support the potential importance of dust aerosols for indirectly affecting cloud properties and climate. The concentrations of ice nuclei within dust layers at particle sizes below 1 pn exceeded 1/cu cm; the highest ever reported with our device at temperatures warmer than homogeneous freezing conditions. These measurements add to previous direct and indirect evidence of the ice nucleation efficiency of desert dust aerosols, but also confirm their contribution to ice nuclei populations at great distances from source regions.

  4. Increase in African dust flux at the onset of commercial agriculture in the Sahel region.

    PubMed

    Mulitza, Stefan; Heslop, David; Pittauerova, Daniela; Fischer, Helmut W; Meyer, Inka; Stuut, Jan-Berend; Zabel, Matthias; Mollenhauer, Gesine; Collins, James A; Kuhnert, Henning; Schulz, Michael

    2010-07-01

    The Sahara Desert is the largest source of mineral dust in the world. Emissions of African dust increased sharply in the early 1970s (ref. 2), a change that has been attributed mainly to drought in the Sahara/Sahel region caused by changes in the global distribution of sea surface temperature. The human contribution to land degradation and dust mobilization in this region remains poorly understood, owing to the paucity of data that would allow the identification of long-term trends in desertification. Direct measurements of airborne African dust concentrations only became available in the mid-1960s from a station on Barbados and subsequently from satellite imagery since the late 1970s: they do not cover the onset of commercial agriculture in the Sahel region approximately 170 years ago. Here we construct a 3,200-year record of dust deposition off northwest Africa by investigating the chemistry and grain-size distribution of terrigenous sediments deposited at a marine site located directly under the West African dust plume. With the help of our dust record and a proxy record for West African precipitation we find that, on the century scale, dust deposition is related to precipitation in tropical West Africa until the seventeenth century. At the beginning of the nineteenth century, a sharp increase in dust deposition parallels the advent of commercial agriculture in the Sahel region. Our findings suggest that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for about 200 years.

  5. Inventory of African desert dust events in the north-central Iberian Peninsula in 2003-2014 based on sun-photometer-AERONET and particulate-mass-EMEP data

    NASA Astrophysics Data System (ADS)

    Cachorro, Victoria E.; Burgos, Maria A.; Mateos, David; Toledano, Carlos; Bennouna, Yasmine; Torres, Benjamín; de Frutos, Ángel M.; Herguedas, Álvaro

    2016-07-01

    A reliable identification of desert dust (DD) episodes over north-central Spain is carried out based on the AErosol RObotic NETwork (AERONET) columnar aerosol sun photometer (aerosol optical depth, AOD, and Ångström exponent, α) and European Monitoring and Evaluation Programme (EMEP) surface particulate-mass concentration (PMx, x = 10, 2.5, and 2.5-10 µm) as the main core data. The impact of DD on background aerosol conditions is detectable by means of aerosol load thresholds and complementary information provided by HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) air mass back trajectories, MODIS (Moderate Resolution Imaging Spectroradiometer) images, forecast aerosol models, and synoptic maps, which have been carefully reviewed by a human observer for each day included in the DD inventory. This identification method allows the detection of low and moderate DD intrusions and also of mixtures of mineral dust with other aerosol types by means of the analysis of α. During the period studied (2003-2014), a total of 152 DD episodes composed of 418 days are identified. Overall, this means ˜ 13 episodes and ˜ 35 days per year with DD intrusion, representing 9.5 % days year-1. During the identified DD intrusions, 19 daily exceedances over 50 µg m-3 are reported at the surface. The occurrence of DD event days during the year peaks in March and June, with a marked minimum in April and lowest occurrence in winter. A large interannual variability is observed showing a statistically significant temporal decreasing trend of ˜ 3 days year-1. The DD impact on the aerosol climatology is addressed by evaluating the DD contribution in magnitude and percent (in brackets) for AOD, PM10, PM2.5, and PM2.5 - 10, obtaining mean values of 0.015 (11.5 %), 1.3 µg m-3 (11.8 %), 0.55 µg m-3 (8.5 %) and 0.79 µg m-3 (16.1 %), respectively. Annual cycles of the DD contribution for AOD and PM10 present two maxima - one in summer (0.03 and 2.4 µg m-3 for AOD in

  6. Comparison of the mixing state of long-range transported Asian and African mineral dust

    NASA Astrophysics Data System (ADS)

    Fitzgerald, Elizabeth; Ault, Andrew P.; Zauscher, Melanie D.; Mayol-Bracero, Olga L.; Prather, Kimberly A.

    2015-08-01

    Mineral dust from arid regions represents the second largest global source of aerosols to the atmosphere. Dust strongly impacts the radiative balance of the earth's atmosphere by directly scattering solar radiation and acting as nuclei for the formation of liquid droplets and ice nuclei within clouds. The climate effects of mineral dust aerosols are poorly understood, however, due to their complex chemical and physical properties, which continuously evolve during atmospheric transport. This work focuses on characterizing atmospheric mineral dust from the two largest global dust sources: the Sahara Desert in Africa and the Gobi and Taklamakan Deserts in Asia. Measurements of individual aerosol particle size and chemical mixing state were made at El Yunque National Forest, Puerto Rico, downwind of the Sahara Desert, and Gosan, South Korea, downwind of the Gobi and Taklamakan Deserts. In general, the chemical characterization of the individual dust particles detected at these two sites reflected the dominant mineralogy of the source regions; aluminosilicate-rich dust was more common at El Yunque (∼91% of El Yunque dust particles vs. ∼69% of Gosan dust particles) and calcium-rich dust was more common at Gosan (∼22% of Gosan dust particles vs. ∼2% of El Yunque dust particles). Furthermore, dust particles from Africa and Asia were subjected to different transport conditions and atmospheric processing; African dust showed evidence of cloud processing, while Asian dust was modified via heterogeneous chemistry and direct condensation of secondary species. A larger fraction of dust detected at El Yunque contained the cloud-processing marker oxalate ion compared to dust detected at Gosan (∼20% vs ∼9%). Additionally, nearly 100% of dust detected at Gosan contained nitrate, showing it was aged via heterogeneous reactions with nitric acid, compared to only ∼60% of African dust. Information on the distinct differences in the chemical composition of mineral dust

  7. Elemental profiles and signatures of fugitive dusts from Chinese deserts.

    PubMed

    Zhang, Rong; Cao, Junji; Tang, Yanrong; Arimoto, Richard; Shen, Zhenxing; Wu, Feng; Han, Yongming; Wang, Gehui; Zhang, Jiaquan; Li, Guohui

    2014-02-15

    Elemental profiles were determined for size-separated fugitive dust particles produced from Chinese desert and gobi soils. Seventeen surface soil samples from six Chinese deserts were collected, composited, resuspended, and sampled through TSP, PM10, and PM2.5 inlets onto Teflon® filters, which were analyzed for twenty-six elements. Two major dust sources could be distinguished based on differences in crustal and enriched elements-the northwestern (NW) region (Taklimakan Desert, Xinjiang Gobi, and Anxinan Gobi) and northern (N) region (Ulan Buh Desert, Central Inner Mongolia Desert, and Erenhot Gobi). The N sources showed lower concentrations of mineral elements (Fe, K, Na, Ti, Mn, Cr, and Rb in PM10, and Fe, K, Ti, Mn, Co, and V in PM2.5) and higher levels of contaminants (S, Zn, Mo, Cu, Cr, Pb, Cd, and As) than the NW ones, especially in PM2.5. Enrichment factors for Cu, Cr, Zn, Pb, As, Mo, and Cd calculated relative to the upper continental crust showed enrichments of one to two orders-of-magnitude, and they were much higher for N sources than NW ones, implying stronger anthropogenic impacts in north China. Aerosol elemental concentrations during dust events at Horqin, Beijing, and Xi'an matched the mass percentages of mineral elements from their presumptive sources better than the alternative ones, validating the differences between the NW and N sources. Additionally, Na/S, Mg/S, Fe/Al, K/Al, Si/Fe, and Na/Al ratios were suggested to differentiate the two dust source regions. The elemental ratios of Ca/Al, K/Al, Fe/Al, and Ti/Fe in the source regions matched those in aerosols collected downwind, and they can be considered as possible source indicators.

  8. The global dispersion of microorganisms and pollutants in clouds of desert dust

    NASA Astrophysics Data System (ADS)

    Griffin, D. W.; Kellogg, C. A.; Garrison, V. H.; Kubilay, N.; Kocak, M.; Shinn, E.

    2003-12-01

    A current estimate of the quantity of dust that is transported some distance in Earth's atmosphere each year is approximately two billion metric tons. Whereas various research projects have been undertaken to understand this planetary process, little has been done to address public and ecosystem health issues. Our research group is currently investigating long-range transport of microorganisms associated with desert dust clouds at various points on the globe via the integration of remote sensing, modeling and microbiological assays. Using a suite of molecular biology techniques, we are identifying cultivable bacteria and fungi and enumerating total bacteria and viruses. Research results indicate that approximately 30% of the microorganisms found in Earth's atmosphere during `African dust events' are species of bacteria or fungi that have previously been identified as disease causing agents in terrestrial plants, trees, and animals. This presentation will cover historical research in this field and the implications of microbial and pollutant \\(metals, pesticides, etc.\\) transport to downwind ecosystems.

  9. Desert dust and human health disorders.

    PubMed

    Goudie, Andrew S

    2014-02-01

    Dust storms may originate in many of the world's drylands and have an effect not only on human health in the drylands themselves but also in downwind environments, including some major urban centres, such as Phoenix, Kano, Athens, Madrid, Dubai, Jedda, Tehran, Jaipur, Beijing, Shanghai, Seoul, Taipei, Tokyo, Sydney, Brisbane and Melbourne. In some parts of the world dust storms occur frequently throughout the year. They can transport particulate material, pollutants, and potential allergens over thousands of km from source. The main sources include the Sahara, central and eastern Asia, the Middle East, and parts of the western USA. In some parts of the world, though not all, the frequency of dust storms is changing in response to land use and climatic changes, and in such locations the health implications may become more severe. Data on the PM10 and P2.5 loadings of dust events are discussed, as are various pollutants (heavy metals, pesticides, etc.) and biological components (spores, fungi, bacteria, etc.). Particulate loadings can far exceed healthy levels. Among the human health effects of dust storms are respiratory disorders (including asthma, tracheitis, pneumonia, allergic rhinitis and silicosis) cardiovascular disorders (including stroke), conjunctivitis, skin irritations, meningococcal meningitis, valley fever, diseases associated with toxic algal blooms and mortality and injuries related to transport accidents.

  10. Aerobiology and the global transport of desert dust

    USGS Publications Warehouse

    Kellogg, Christina A.; Griffin, Dale W.

    2006-01-01

    Desert winds aerosolize several billion tons of soil-derived dust each year, including concentrated seasonal pulses from Africa and Asia. These transoceanic and transcontinental dust events inject a large pulse of microorganisms and pollen into the atmosphere and could therefore have a role in transporting pathogens or expanding the biogeographical range of some organisms by facilitating long-distance dispersal events. As we discuss here, whether such dispersal events are occurring is only now beginning to be investigated. Huge dust events create an atmospheric bridge over land and sea, and the microbiota contained within them could impact downwind ecosystems. Such dispersal is of interest because of the possible health effects of allergens and pathogens that might be carried with the dust.

  11. Satellite Observations of Desert Dust-induced Himalayan Snow Darkening

    NASA Technical Reports Server (NTRS)

    Gautam, Ritesh; Hsu, N. Christina; Lau, William K.-M.; Yasunari, Teppei J.

    2013-01-01

    The optically thick aerosol layer along the southern edge of the Himalaya has been subject of several recent investigations relating to its radiative impacts on the South Asian summer monsoon and regional climate forcing. Prior to the onset of summer monsoon, mineral dust from southwest Asian deserts is transported over the Himalayan foothills on an annual basis. Episodic dust plumes are also advected over the Himalaya, visible as dust-laden snow surface in satellite imagery, particularly in western Himalaya. We examined spectral surface reflectance retrieved from spaceborne MODIS observations that show characteristic reduction in the visible wavelengths (0.47 nm) over western Himalaya, associated with dust-induced solar absorption. Case studies as well as seasonal variations of reflectance indicate a significant gradient across the visible (0.47 nm) to near-infrared (0.86 nm) spectrum (VIS-NIR), during premonsoon period. Enhanced absorption at shorter visible wavelengths and the resulting VIS-NIR gradient is consistent with model calculations of snow reflectance with dust impurity. While the role of black carbon in snow cannot be ruled out, our satellite-based analysis suggests the observed spectral reflectance gradient dominated by dust-induced solar absorption during premonsoon season. From an observational viewpoint, this study underscores the importance of mineral dust deposition toward darkening of the western Himalayan snow cover, with potential implications to accelerated seasonal snowmelt and regional snow albedo feedbacks.

  12. African dust carries microbes across the ocean: are they affecting human and ecosystem health?

    USGS Publications Warehouse

    Kellogg, Christina A.; Griffin, Dale W.

    2003-01-01

    Atmospheric transport of dust from northwest Africa to the western Atlantic Ocean region may be responsible for a number of environmental hazards, including the demise of Caribbean corals; red tides; amphibian diseases; increased occurrence of asthma in humans; and oxygen depletion (eutrophication) in estuaries. Studies of satellite images suggest that hundreds of millions of tons of dust are trans-ported annually at relatively low altitudes across the Atlantic Ocean to the Caribbean Sea and southeastern United States. The dust emanates from the expanding Sahara/Sahel desert region in Africa and carries a wide variety of bacteria and fungi. The U.S. Geological Survey, in collaboration with the NASA/Goddard Spaceflight Center, is conducting a study to identify microbes--bacteria, fungi, viruses--transported across the Atlantic in African soil dust. Each year, millions of tons of desert dust blow off the west African coast and ride the trade winds across the ocean, affecting the entire Caribbean basin, as well as the southeastern United States. Of the dust reaching the U.S., Florida receives about 50 percent, while the rest may range as far north as Maine or as far west as Colorado. The dust storms can be tracked by satellite and take about one week to cross the Atlantic.

  13. Iron mobilization in North African dust.

    SciTech Connect

    Ito, A.; Feng, Y.

    2011-01-01

    Iron is an essential nutrient for phytoplankton. Although iron-containing dust mobilized from arid regions supplies the majority of the iron to the oceans, the key flux in terms of the biogeochemical response to atmospheric deposition is the amount of soluble or bioavailable iron. Atmospheric processing of mineral aerosols by anthropogenic pollutants (e.g. sulfuric acid) may transform insoluble iron into soluble forms. Previous studies have suggested higher iron solubility in smaller particles, as they are subject to more thorough atmospheric processing due to a longer residence time than coarse particles. On the other hand, the specific mineralogy of iron in dust may also influence the particulate iron solubility in size. Compared to mineral dust aerosols, iron from combustion sources could be more soluble, and found more frequently in smaller particles. Internal mixing of alkaline dust with iron-containing minerals could significantly reduce iron dissolution in large dust aerosols due to the buffering effect, which may, in contrast, yield higher solubility in smaller particles externally mixed with alkaline dust (Ito and Feng, 2010). Here, we extend the modeling study of Ito and Feng (2010) to investigate atmospheric processing of mineral aerosols from African dust. In contrast to Asian dust, we used a slower dissolution rate for African dust in the fine mode. We compare simulated fractional iron solubility with observations. The inclusion of alkaline compounds in aqueous chemistry substantially limits the iron dissolution during long-range transport to the Atlantic Ocean: only a small fraction of iron (<0.2%) dissolves from illite in coarsemode dust aerosols with 0.45% soluble iron initially. In contrast, a significant fraction (1-1.5%) dissolves in fine-mode dust aerosols due to the acid mobilization of the iron-containing minerals externally mixed with carbonate minerals. Consequently, the model generally reproduces higher iron solubility in smaller particles

  14. The Modulation of Hurricanes by African Dust

    NASA Astrophysics Data System (ADS)

    Velasco Herrera, Victor Manuel; Perez-Peraza, Jorge Alberto; Velasco Herrera, Graciela

    Here we apply cross-wavelet, the global wavelet spectra and a new wavelet coherency signal-noise method to theavailable data of African Dust for the period 1966-2004 and Database of hurricanes, from the National Weather Service (http:// weather.unisys. com/ hurricane/). Hurricane data was transformed into a series of Pulses Width modulation (PWM) of the type: n = number of hurricanes, 0 no hurricane. We apply the analysis to all categories of tropical cyclones. Results indicate that among the different periodicities common to both series, the more promi-nent is the decadal modulation of dust over hurricanes of category 5, and a annual modulation for all the other categories of Hurricanes. Hurricanes of category 5 develop in the minimums of the decadal variation of African dust, and preferable in areas of deep water of the Atlantic ocean, where the centre of the hurricane has the lowest pressure. If this tendency is sustained , tropical cyclones will not evolve to category 5 up to the next decadal minimum which will take place around the year 2015 2. This is an important result concerning the prediction of floods and for minimizing the human and economical lost provoked for hurricanes of category 5.

  15. High concentrations of regional dust from deserts to plains across the central Rocky Mountains, USA

    NASA Astrophysics Data System (ADS)

    Reynolds, R. L.; Munson, S. M.; Fernandez, D. P.; Neff, J. C.

    2015-12-01

    Regional mineral dust in the American Southwest affects snow-melt rates, biogeochemical cycling, visibility, and public health. We measured total suspended particulates (TSP) across a 500-km-long sampling network of five remote sites in Utah and Colorado, USA, forming a gradient in distance from major dust emitting areas. The two westernmost sites on the Colorado Plateau desert had similar TSP concentrations (2008-2012, daily average=126 μg m-3; max. daily average over a two-week period=700 μg m-3 at Canyonlands National Park, Utah), while the easternmost High Plains site, close to cropped and grazed areas in northeastern Colorado, had an average concentration of 143 μg m-3 in 2011-2012 (max. daily average=656 μg m-3). Such concentrations rank comparably with those of TSP in several African and Asian cities in the paths of frequent dust storms. Dust loadings at the two intervening montane sites decreased from the western slope of the Rocky Mountains (Telluride, daily average=68 μg m-3) to an eastern site (Niwot Ridge, daily average=58 μg m-3). Back-trajectory analyses and satellite retrievals indicated that the three westernmost sites received most dust from large desert-source regions as far as 300 km to their southwest. These sources also sometimes sent dust to the two easternmost sites, which additionally captured dust from sources north and northwest of the central Rocky Mountains as well as locally at the Plains site. The PM10 fraction accounted for <15% of TSP, but most TSP is only slightly larger (typical median size, 15-20 μm) after about 100-800 km transport distances. Correlations between TSP and PM10 values indicate increases in both fractions during regional wind storms, especially related to Pacific frontal systems during late winter to late spring. These measurements and observations indicate that most dust deposition and associated air-quality problems in the interior American West are connected to regional dust sources and not to those in

  16. What is the impact of Harmattan surges on desert dust emission in North Africa?

    NASA Astrophysics Data System (ADS)

    Fiedler, Stephanie; Kaplan, Michael L.; Knippertz, Peter

    2015-04-01

    African dust emission. Regionally, the importance of Harmattan surges for emission is even larger with a contribution of up to 80 % of the emission mass in spring. These maximum contributions are found primarily along the northern fringes of the Sahara, where also the seasonal maxima in total emission and in event occurrence are found. The emission anomalies from Harmattan surges underline the unusually strong emission in March 2004 that has been widely discussed in previous works. The present study underlines the importance of Harmattan surges for North African dust emission. This knowledge helps to prioritize recommendations for model development of meteorological processes for dust emission. The study has been funded by the European Research Council project "Desert Storms" of Prof Peter Knippertz. Tegen, I., Harrison, S., Kohfeld, K., Prentice, I., Coe, M., and Heimann, M.: Impact of vegetation and preferential source areas on global dust aerosols: Results from a model study, J. Geophys. Res., 107, 4576, doi: 10.1029/2001JD000963, 2002.

  17. Atmospheric Movement of Microorganisms in Clouds of Desert Dust and Implications for Human Health

    PubMed Central

    Griffin, Dale W.

    2007-01-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources. PMID:17630335

  18. Atmospheric movement of microorganisms in clouds of desert dust and implications for human health.

    PubMed

    Griffin, Dale W

    2007-07-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

  19. Atmospheric movement of microorganisms in clouds of desert dust and implications for human health

    USGS Publications Warehouse

    Griffin, Dale W.

    2007-01-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

  20. Deciphering the Role of Desert Dust in the Climate Puzzle: The Mediterranean Israeli Dust Experiment (MEIDEX)

    NASA Technical Reports Server (NTRS)

    Levin, Zev; Joseph, Joachim; Mekler, Yuri; Israelevich, Peter; Ganor, Eli; Hilsenrath, Ernest; Janz, Scott

    2002-01-01

    Numerous studies have shown that aerosol particles may be one of the primary agents that can offset the climate warming induced by the increase in the amount of atmospheric greenhouse gases. Desert aerosols are probably the most abundant and massive type of aerosol particles that are present in the atmosphere worldwide. These aerosols are carried over large distances and have various global impacts. They interact with clouds, impact the efficiency of their rain production and change their optical properties. They constitute one of the primary sources of minerals for oceanic life and influence the health of coral reefs. They have direct effects on human health, especially by inducing breathing difficulties in children. It was lately discovered that desert particles carry pathogens from the Sahara desert over the Atlantic Ocean, a fact that may explain the migration of certain types of diseases. Aerosols not only absorb solar radiation but also scatter it, so that their climatic effect is influenced not only by their physical properties and height distribution but also by the reflectivity of the underlying surface. This latter property changes greatly over land and is low over ocean surfaces. Aerosol plumes are emitted from discrete, sporadic sources in the desert areas of the world and are transported worldwide by the atmosphere's wind systems. For example, Saharan dust reaches Mexico City, Florida, Ireland, Switzerland and the Mediterranean region, while Asian dust reaches Alaska, Hawaii and the continental United States. This means that in order to assess its global effects, one must observe dust from space. The Space Shuttle is a unique platform, because it flies over the major deserts of our planet, enabling measurements and remote sensing of the aerosols as they travel from source to sink regions. Such efforts must always be accompanied by in-situ data for validation and calibration, with direct sampling of the airborne particles. MEIDEX is a joint project of

  1. An electrified dust storm over the Negev desert, Israel

    NASA Astrophysics Data System (ADS)

    Yair, Y.; Price, C. G.; Yaniv, R.; Katz, S.

    2015-12-01

    We report on atmospheric electrical measurements conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30035'N, 34045'E) during a massive dust storm that occurred over the Eastern Mediterranean region on 10-11 February 2015. The event transported Saharan dust from Egypt and the Sinai Peninsula in advance of the warm front of a Cyprus low pressure system. Satellite images show the dust plume covering the Negev desert and Southern Israel and moving north. The concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 450 μg m-3 and AOT from the AERONET station in Sde-Boker was 1.5 on the 10th. The gradual intensification of the event reached peak values on February 11th of over 1200 μg m-3 and AOT of 1.8. This was the most severe dust event in a decade. Continuous measurements of the fair weather vertical electric field (Ez) and vertical current density (Jz) were conducted with 1 minute temporal resolution. Meteorological data was also recorded at the site. As the dust was advected over the observation site, we noted very large fluctuations in the electrical parameters. Since the onset of the dust storm, the Ez values changed between +1000 and +8000 V m-1 while the Jz fluctuated between -10 pA m2 and +20 pA m2, both on time-scales of a few minutes. These values are a significant departures from the mean fair-weather values measured at the site, which are -~200 V m-1 and ~2 pA m2. The disturbed episodes lasted for several hours on the 10th and 11th and coincided with local meteorological conditions related to the wind direction, which carried large amounts of dust particles. We interpret the rapid changes as caused by the transport of electrically charged dust. Calculation of the total electrical charge during the dust storm will be presented.

  2. Intercomparison of Desert Dust Optical Depth from Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Carboni, E.; Thomas, G. E.; Sayer, A. M.; Siddans, R.; Poulsen, C. A.; Grainger, R. G.; Ahn, C.; Antoine, D.; Bevan, S.; Braak, R.; Brindley, H.; DeSouza-Machado, S.; Deuze, J. L.; Diner, D.; Ducos, F.; Grey, W.; Hsu, C.; Kalashnikova, O. V.; Kahn, R.; North, P. R. J.; Salustro, C.; Smith, A.; Tanre, D.; Torres, O.; Veihelmann, B,

    2012-01-01

    This work provides a comparison of satellite retrievals of Saharan desert dust aerosol optical depth (AOD) during a strong dust event through March 2006. In this event, a large dust plume was transported over desert, vegetated, and ocean surfaces. The aim is to identify the differences between current datasets. The satellite instruments considered are AATSR, AIRS, MERIS, MISR, MODIS, OMI, POLDER, and SEVIRI. An interesting aspect is that the different algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. These include multi-angle approaches (MISR, AATSR), polarisation measurements (POLDER), single-view approaches using solar wavelengths (OMI, MODIS), and the thermal infrared spectral region (SEVIRI, AIRS). Differences between instruments, together with the comparison of different retrieval algorithms applied to measurements from the same instrument, provide a unique insight into the performance and characteristics of the various techniques employed. As well as the intercomparison between different satellite products, the AODs have also been compared to co-located AERONET data. Despite the fact that the agreement between satellite and AERONET AODs is reasonably good for all of the datasets, there are significant differences between them when compared to each other, especially over land. These differences are partially due to differences in the algorithms, such as assumptions about aerosol model and surface properties. However, in this comparison of spatially and temporally averaged data, it is important to note that differences in sampling, related to the actual footprint of each instrument on the heterogeneous aerosol field, cloud identification and the quality control flags of each dataset can be an important issue.

  3. Health effects of particulate air pollution and airborne desert dust

    NASA Astrophysics Data System (ADS)

    Lelieveld, J.; Pozzer, A.; Giannadaki, D.; Fnais, M.

    2013-12-01

    Air pollution by fine particulate matter (PM2.5) has increased strongly with industrialization and urbanization. In the past decades this increase has taken place at a particularly high pace in South and East Asia. We estimate the premature mortality and the years of human life lost (YLL) caused by anthropogenic PM2.5 and airborne desert dust (DU2.5) on regional and national scales (Giannadaki et al., 2013; Lelieveld et al., 2013). This is based on high-resolution global model calculations that resolve urban and industrial regions in relatively great detail. We apply an epidemiological health impact function and find that especially in large countries with extensive suburban and rural populations, air pollution-induced mortality rates have been underestimated given that previous studies largely focused on the urban environment. We calculate a global premature mortality by anthropogenic aerosols of 2.2 million/year (YLL ≈ 16 million/year) due to lung cancer and cardiopulmonary disease. High mortality rates by PM2.5 are found in China, India, Bangladesh, Pakistan and Indonesia. Desert dust DU2.5 aerosols add about 0.4 million/year (YLL ≈ 3.6 million/year). Particularly significant mortality rates by DU2.5 occur in Pakistan, China and India. The estimated global mean per capita mortality caused by airborne particulates is about 0.1%/year (about two thirds of that caused by tobacco smoking). We show that the highest premature mortality rates are found in the Southeast Asia and Western Pacific regions (about 25% and 46% of the global rate, respectively) where more than a dozen of the most highly polluted megacities are located. References: Giannadaki, D., A. Pozzer, and J. Lelieveld, Modeled global effects of airborne desert dust on air quality and premature mortality, Atmos. Chem. Phys. Discuss. (submitted), 2013. Lelieveld, J., C. Barlas, D. Giannadaki, and A. Pozzer, Model calculated global, regional and megacity premature mortality due to air pollution by ozone

  4. Spatial and temporal variations of blowing dust events in the Taklimakan Desert

    NASA Astrophysics Data System (ADS)

    Yang, Xinghua; Shen, Shuanghe; Yang, Fan; He, Qing; Ali, Mamtimin; Huo, Wen; Liu, Xinchun

    2016-08-01

    The Taklimakan Desert is the source of most blowing dust events in China. However, previous studies of sandstorms in this region have not included data from the inner desert because of the difficulty in making observations in this area. In this study, the spatial and temporal variations of blowing dust events, including sandstorms and blowing sand, and its relations with climatic parameters in the Taklimakan Desert were analyzed using data from ten desert-edge meteorological stations during 1961 to 2010 and two inner-desert meteorological stations during 1988 to 1990, 1996 to 2010, and 1992 to 2010. The results identified two regions (Pishan-Hotan-Minfeng and Xiaotang-Tazhong) where blowing dust events occur on average more than 80 days per year. The regions with the highest occurrence of sandstorms, blowing sand, and blowing dust events were different, with sandstorms centered in the north of the desert (Xiaotang, 46.9 days), whereas the central location for blowing sand (Pishan, 86.4 days) and blowing dust events (Minfeng, 113.5 days) activity was located at the southwestern and southern edges of the desert, respectively. The occurrence of sandstorms generally decreased from 1961 to 2010, while the occurrence of blowing sand increased from 1961 to 1979 and then generally decreased. The temporal variation of blowing dust events was mainly affected by the occurrence of strong wind and daily temperature, with average correlation coefficients of 0.46 and -0.41 for these variables across the whole desert.

  5. Biological effects of desert dust in respiratory epithelial cells and a murine model.

    PubMed

    Ghio, Andrew J; Kummarapurugu, Suryanaren T; Tong, Haiyan; Soukup, Joleen M; Dailey, Lisa A; Boykin, Elizabeth; Ian Gilmour, M; Ingram, Peter; Roggli, Victor L; Goldstein, Harland L; Reynolds, Richard L

    2014-04-01

    As a result of the challenge of recent dust storms to public health, we tested the postulate that desert dust collected in the southwestern United States imparts a biological effect in respiratory epithelial cells and an animal model. Two samples of surface sediment were collected from separate dust sources in northeastern Arizona. Analysis of the PM20 fraction demonstrated that the majority of both dust samples were quartz and clay minerals (total SiO₂ of 52 and 57%). Using respiratory epithelial and monocytic cell lines, the two desert dusts increased oxidant generation, measured by Amplex Red fluorescence, along with carbon black (a control particle), silica, and NIST 1649 (an ambient air pollution particle). Cell oxidant generation was greatest following exposures to silica and the desert dusts. Similarly, changes in RNA for superoxide dismutase-1, heme oxygenase-1, and cyclooxygenase-2 were also greatest after silica and the desert dusts supporting an oxidative stress after cell exposure. Silica, desert dusts, and the ambient air pollution particle NIST 1649 demonstrated a capacity to activate the p38 and ERK1/2 pathways and release pro-inflammatory mediators. Mice, instilled with the same particles, showed the greatest lavage concentrations of pro-inflammatory mediators, neutrophils, and lung injury following silica and desert dusts. We conclude that, comparable to other particles, desert dusts have a capacity to (1) influence oxidative stress and release of pro-inflammatory mediators in respiratory epithelial cells and (2) provoke an inflammatory injury in the lower respiratory tract of an animal model. The biological effects of desert dusts approximated those of silica.

  6. Biological effects of desert dust in respiratory epithelial cells and a murine model

    USGS Publications Warehouse

    Ghio, Andrew J.; Kummarapurugu, Suryanaren T.; Tong, Haiyan; Soukup, Joleen M.; Dailey, Lisa A.; Boykin, Elizabeth; Gilmour, M. Ian; Ingram, Peter; Roggli, Victor L.; Goldstein, Harland L.; Reynolds, Richard L.

    2014-01-01

    As a result of the challenge of recent dust storms to public health, we tested the postulate that desert dust collected in the southwestern United States imparts a biological effect in respiratory epithelial cells and an animal model. Two samples of surface sediment were collected from separate dust sources in northeastern Arizona. Analysis of the PM20 fraction demonstrated that the majority of both dust samples were quartz and clay minerals (total SiO2 of 52 and 57%). Using respiratory epithelial and monocytic cell lines, the two desert dusts increased oxidant generation, measured by Amplex Red fluorescence, along with carbon black (a control particle), silica, and NIST 1649 (an ambient air pollution particle). Cell oxidant generation was greatest following exposures to silica and the desert dusts. Similarly, changes in RNA for superoxide dismutase-1, heme oxygenase-1, and cyclooxygenase-2 were also greatest after silica and the desert dusts supporting an oxidative stress after cell exposure. Silica, desert dusts, and the ambient air pollution particle NIST 1649 demonstrated a capacity to activate the p38 and ERK1/2 pathways and release pro-inflammatory mediators. Mice, instilled with the same particles, showed the greatest lavage concentrations of pro-inflammatory mediators, neutrophils, and lung injury following silica and desert dusts. We conclude that, comparable to other particles, desert dusts have a capacity to (1) influence oxidative stress and release of pro-inflammatory mediators in respiratory epithelial cells and (2) provoke an inflammatory injury in the lower respiratory tract of an animal model. The biological effects of desert dusts approximated those of silica.

  7. An electrified dust storm over the Negev desert, Israel

    NASA Astrophysics Data System (ADS)

    Yair, Yoav; Katz, Shai; Yaniv, Roy; Ziv, Baruch; Price, Colin

    2016-11-01

    We report on atmospheric electrical measurements conducted at the Wise Observatory in Mitzpe-Ramon, Israel (30°35‧N, 34°45‧E) during a large dust storm that occurred over the Eastern Mediterranean region on 10-11 February 2015. The dust was transported from the Sahara, Egypt and the Sinai Peninsula ahead of an approaching Cyprus low. Satellite images show the dust plume covering the Negev desert and Southern Israel and moving north. The concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 450 μg m- 3 and the AOT from the AERONET station in Sde-Boker was 1.5 on February 10th. The gradual intensification of the event reached peak concentrations on February 11th of over 1200 μg m- 3 and an AOT of 1.8. Continuous measurements of the fair weather vertical electric field (Ez) and vertical current density (Jz) were conducted at the Wise Observatory with 1 minute temporal resolution. Meteorological data was also recorded at the site. As the dust was advected over the observatory, very large fluctuations in the electrical parameters were registered. From the onset of the dust storm, the Ez values changed between + 1000 and + 8000 V m- 1 while the current density fluctuated between - 10 pA m2 and + 20 pA m2, both on time-scales of a few minutes. These values are significant departures from the average fair-weather values measured at the site, which are ~- 200 V m- 1 and ~ 2 pA m2. The disturbed episodes lasted for several hours on February 10th and the 11th and coincided with local meteorological conditions related to the wind speed and direction, which carried large amounts of dust particles over our observation station. We interpret the rapid changes as caused by the transport of electrically charged dust, carrying an excess of negative charge at lower altitudes.

  8. Direct radiative effects induced by intense desert dust outbreaks over the broader Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Gkikas, Antonis; Obiso, Vincenzo; Vendrell, Lluis; Basart, Sara; Jorba, Oriol; Pérez Garcia-Pando, Carlos; Hatzianastassiou, Nikos; Gassó, Santiago; Baldasano, Jose Maria

    2016-04-01

    Throughout the year, under favorable conditions, massive loads of mineral particles originating in the northern African and Middle East deserts are transported over the Mediterranean basin. Due to their composition and size, dust aerosols perturb the Earth-Atmosphere system's energy budget interacting directly with the shortwave (SW) and longwave (LW) radiation. The present study aims to compute the Mediterranean dust outbreaks' direct radiative effects (DREs) as well as to assess the effect of including dust DREs in numerical simulations of a regional model. To this aim, 20 intense dust outbreaks have been selected based on their spatial coverage and intensity. Their identification, over the period 2000-2013, has been achieved through an objective and dynamic algorithm which utilizes as inputs daily satellite retrievals derived by the MODIS-Terra, EP-TOMS and OMI-Aura sensors. For each outbreak, two simulations of the NMMB/BSC-Dust model were made for a forecast period of 84 hours, with the model initialized at 00 UTC of the day when the dust outbreak was ignited, activating (RADON) and deactivating (RADOFF) dust-radiation interactions. The simulation domain covers the northern Africa, the Middle East and Europe at 0.25° x 0.25° horizontal resolution, for 40 hybrid sigma pressure levels up to 50 hPa. The instantaneous and regional DREs have been calculated at the top of the atmosphere (TOA), into the atmosphere (ATMAB), and at surface, for the downwelling (SURF) and the absorbed (NETSURF) radiation, for the SW, LW and NET (SW+LW) radiation. The interaction between dust aerosols and NET radiation, locally leads to an atmospheric warming (DREATMAB) by up to 150 Wm-2, a surface cooling (DRENETSURF) by up to 250 Wm-2 and a reduction of the downwelling radiation at the surface (DRESURF) by up to 300 Wm-2. At TOA, DREs are mainly negative (down to -150 Wm-2) indicating a cooling of the Earth-Atmosphere system, although positive values (up to 50 Wm-2) are encountered

  9. Mediterranean desert dust outbreaks and their vertical structure based on remote sensing data

    NASA Astrophysics Data System (ADS)

    Gkikas, A.; Basart, S.; Hatzianastassiou, N.; Marinou, E.; Amiridis, V.; Kazadzis, S.; Pey, J.; Querol, X.; Jorba, O.; Gassó, S.; Baldasano, J. M.

    2015-10-01

    The main aim of the present study is to describe the vertical structure of the intense Mediterranean dust outbreaks, based on the use of satellite and surface-based retrievals/measurements. Strong and extreme desert dust (DD) episodes are identified at 1° × 1° spatial resolution, over the period March 2000-February 2013, through the implementation of an updated objective and dynamic algorithm. According to the algorithm, strong DD episodes occurring at a specific place correspond to cases in which the daily aerosol optical depth at 550 nm (AOD550 nm) exceeds or equals the long-term mean AOD550 nm (Mean) plus two standard deviations (SD) value being smaller than Mean + 4 · SD. Extreme DD episodes correspond to cases in which the daily AOD550 nm value equals or exceeds Mean + 4 · SD. For the identification of DD episodes additional optical properties (Ångström exponent, fine fraction, effective radius and Aerosol Index) derived by the MODIS-Terra & Aqua (also AOD retrievals), OMI-Aura and EP-TOMS databases are used as inputs. According to the algorithm using MODIS-Terra data, over the period March 2000-February 2013, strong DD episodes occur more frequently (up to 9.9 episodes yr-1) over the western Mediterranean while the corresponding frequencies for the extreme ones are smaller (up to 3.3 episodes yr-1, central Mediterranean Sea). In contrast to their frequency, dust episodes are more intense (AODs up to 4.1), over the central and eastern Mediterranean Sea, off the northern African coasts. Slightly lower frequencies and higher intensities are found when the satellite algorithm operates based on MODIS-Aqua retrievals, for the period 2003-2012. The performance of the satellite algorithm is assessed against surface-based daily data from 109 sun-photometric (AERONET) and 22 PM10 stations. The agreement between AERONET and MODIS AOD is satisfactory (R = 0.505 - 0.75) improving considerably when MODIS level 3 retrievals with higher sub-grid spatial

  10. Long-Term Observations of Dust Storms in Sandy Desert Environments

    NASA Astrophysics Data System (ADS)

    Yun, Hye-Won; Kim, Jung-Rack; Choi, Yun-Soo

    2015-04-01

    Mineral dust occupies the largest portion of atmospheric aerosol. Considering the numerous risks that dust poses for socioeconomic and anthropogenic activities, it is crucial to understand sandy desert environments, which frequently generate dust storms and act as a primary source of atmospheric aerosol. To identify mineral aerosol mechanisms, it is essential to monitor desert environmental factors involving dust storm generation in the long term. In this study, we focused on two major environmental factors: local surface roughness and soil moisture. Since installments of ground observation networks in sandy deserts are unfeasible, remote sensing techniques for mining desert environmental factors were employed. The test area was established within the Badain Jaran and Kubuqi Deserts in Inner Mongolia, China, where significant seasonal aeolian processes emit mineral dust that influences all of East Asia. To trace local surface roughness, we employed a multi-angle imaging spectroradiometer (MISR) image sequence to extract multi-angle viewing (MAV) topographic parameters such as normalized difference angular index, which represents characteristics of the target desert topography. The backscattering coefficient from various space-borne SAR and stereotopography were compared with MAV observations to determine calibrated local surface roughness. Soil moisture extraction techniques from InSAR-phase coherence stacks were developed and compiled with advanced scatterometer (ASCAT) soil moisture data. Combined with metrological information such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA interim, correlations between intensity of sand dune activity as a proxy of aeolian processes in desert environments, surface wind conditions, and surface soil moisture were traced. Overall, we have confirmed that tracking sandy desert aeolian environments for long-term observations is feasible with space-borne, multi-sensor observations when combined with

  11. Modeling Optical Properties of Mineral Dust over "The Great Indian Desert"

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Tripathi, S. N.

    2007-12-01

    The Thar desert, sometimes also described as 'The Great Indian Desert', lying in the Northwest part of India with an area of 0.32*106 km2, is known to be the source of natural mineral dust . The mineral dust particles are mostly non-spherical having sharp edges, which show different scattering signature compared to that of equivalent spheres while interacting with the radiation. Furthermore accurate mineralogical information, that governs their refractive indices, is essential for scattering calculations. The radiative impacts of dust particles therefore depend on their morphology and mineralogy. Most of the present satellites consider the particle to be spherical while retrieving their optical properties. Some newly launched spacecraft instruments such as MISR accounts for non spherical nature by including spheroid particles in its retrieval algorithm . Clearly there exits a need for improvement in dust model used in retrieval algorithm to account for their sharp edges together with their index of refraction based on the latest chemical composition at the sensing wavelengths. To the best of our knowledge no such attempt has been made to calculate the optical properties of dust particles over the Thar desert. In this study, the optical properties of mineral dust of the Thar desert has been modeled using T-matrix method with realistic dust shapes based on Scanning Electron Microscope images of the dust over the desert with particle size ranging from 0.1-1.0 ìm at wavelengths spanning from ultraviolet to near infrared (0.38-1.2ìm). Representative dust particles shapes considered are sphere, cylinder, spheroids and chebyshev together with realistic mineral dust composition. Mineralogical analysis of airborne dust over Northwest India has revealed the presence of only basic non-metallic minerals such as Quartz, Feldspar, Mica and Calcite, which posses negligible imaginary part of refractive index at considered wavelength domain, however, the subsequent dust sampling

  12. Urban particle size distributions during two contrasting dust events originating from Taklimakan and Gobi Deserts.

    PubMed

    Zhao, Suping; Yu, Ye; Xia, Dunsheng; Yin, Daiying; He, Jianjun; Liu, Na; Li, Fang

    2015-12-01

    The dust origins of the two events were identified using HYSPLIT trajectory model and MODIS and CALIPSO satellite data to understand the particle size distribution during two contrasting dust events originated from Taklimakan and Gobi deserts. The supermicron particles significantly increased during the dust events. The dust event from Gobi desert affected significantly on the particles larger than 2.5 μm, while that from Taklimakan desert impacted obviously on the particles in 1.0-2.5 μm. It is found that the particle size distributions and their modal parameters such as VMD (volume median diameter) have significant difference for varying dust origins. The dust from Taklimakan desert was finer than that from Gobi desert also probably due to other influencing factors such as mixing between dust and urban emissions. Our findings illustrated the capacity of combining in situ, satellite data and trajectory model to characterize large-scale dust plumes with a variety of aerosol parameters.

  13. African dust outbreaks over the Mediterranean Basin during 2001-2011: concentrations, phenomenology and trends

    NASA Astrophysics Data System (ADS)

    Pey, Jorge; Querol, Xavier; Alastuey, Andres; Forastiere, Franceso; Stafoggia, Massimo

    2013-04-01

    Concentrations, phenomenology and trends of African dust outbreaks over the whole Mediterranean Basin werestudied on an 11-year period (2001-2011). This work has been performed in the context of the MED-PARTICLES (LIFE programme, EU) project, devoted to quantify short-term health effects of particulate matter over the Mediterranean region by distinguishing different particle sizes, chemical components and sources, with emphasis in the effects of African dust. In order to evaluate conduct this investigation, PM10 data from 19 regional and suburban background sites West to East in the Mediterranean area were compiled. After identifying the daily occurrence of African dust outbreaks, a methodology for estimating natural dust contributions on daily PM10 concentrations was applied. Our findings point out that African dust outbreaks are sensibly more frequent in southern sitesacross the Mediterranean, from 30 to 37 % of the annual days, whereas they occur less than 20% of the annual days in northern sites. The central Mediterranean emerges as a transitional area, with slightly higher frequency of dust episodes in its lower extreme when compared to similar latitudinal positions in western and eastern sides of the Basin. A decreasing south to north gradient of African dust contribution to PM10, driven by the latitudinal position of the monitoring sites at least 25°E westwards across the Basin,is patent across the Mediterranean. From 25°E eastwards, higher annual dust contributions are encountered due to the elevated annual occurrence of severe episodesof dust but also because of inputs from Middle Eastern deserts. Concerning seasonality patterns and intensity characteristics, a clear summer prevalence is observed in the western part, with low occurrence of severe episodes (daily dust averages over 100 µg m-3 in PM10); no seasonal trend is detected in the central region, with moderate-intensity episodes; and significantly higher contributions are common in autumn

  14. Observed 20th Century Desert Dust Variability: Impact on Climate and Biogeochemistry

    SciTech Connect

    Mahowald, Natalie; Kloster, Silvia; Engelstaedter, S.; Moore, Jefferson Keith; Mukhopadhyay, S.; McConnell, J. R.; Albani, S.; Doney, Scott C.; Bhattacharya, A.; Curran, M. A. J.; Flanner, Mark G.; Hoffman, Forrest M; Lawrence, David M.; Lindsay, Keith; Mayewski, P. A.; Neff, Jason; Rothenberg, D.; Thomas, E.; Thornton, Peter E; Zender, Charlie S.

    2010-01-01

    Desert dust perturbs climate by directly and indirectly interacting with incoming solar and outgoing long wave radiation, thereby changing precipitation and temperature, in addition to modifying ocean and land biogeochemistry. While we know that desert dust is sensitive to perturbations in climate and human land use, previous studies have been unable to determine whether humans were increasing or decreasing desert dust in the global average. Here we present observational estimates of desert dust based on paleodata proxies showing a doubling of desert dust during the 20th century over much, but not all the globe. Large uncertainties remain in estimates of desert dust variability over 20th century due to limited data. Using these observational estimates of desert dust change in combination with ocean, atmosphere and land models, we calculate the net radiative effect of these observed changes (top of atmosphere) over the 20th century to be -0.14 {+-} 0.11 W/m{sup 2} (1990-1999 vs. 1905-1914). The estimated radiative change due to dust is especially strong between the heavily loaded 1980-1989 and the less heavily loaded 1955-1964 time periods (-0.57 {+-} 0.46 W/m{sup 2}), which model simulations suggest may have reduced the rate of temperature increase between these time periods by 0.11 C. Model simulations also indicate strong regional shifts in precipitation and temperature from desert dust changes, causing 6 ppm (12 PgC) reduction in model carbon uptake by the terrestrial biosphere over the 20th century. Desert dust carries iron, an important micronutrient for ocean biogeochemistry that can modulate ocean carbon storage; here we show that dust deposition trends increase ocean productivity by an estimated 6% over the 20th century, drawing down an additional 4 ppm (8 PgC) of carbon dioxide into the oceans. Thus, perturbations to desert dust over the 20th century inferred from observations are potentially important for climate and biogeochemistry, and our understanding

  15. Disturbance to desert soil ecosystems contributes to dust-mediated impacts at regional scales

    USGS Publications Warehouse

    Pointing, Stephen B.; Belnap, Jayne

    2014-01-01

    This review considers the regional scale of impacts arising from disturbance to desert soil ecosystems. Deserts occupy over one-third of the Earth’s terrestrial surface, and biological soil covers are critical to stabilization of desert soils. Disturbance to these can contribute to massive destabilization and mobilization of dust. This results in dust storms that are transported across inter-continental distances where they have profound negative impacts. Dust deposition at high altitudes causes radiative forcing of snowpack that leads directly to altered hydrological regimes and changes to freshwater biogeochemistry. In marine environments dust deposition impacts phytoplankton diazotrophy, and causes coral reef senescence. Increasingly dust is also recognized as a threat to human health.

  16. Atmospheric microbiology in the northern Caribbean during African dust events

    USGS Publications Warehouse

    Griffin, Dale W.; Kellogg, C.A.; Garrison, V.H.; Lisle, J.T.; Borden, T.C.; Shinn, E.A.

    2003-01-01

    Between July 2000 and August 2001 forty-three air samples were collected in the northern Caribbean: Twenty-six in the US Virgin Islands, and 17 samples aboard ship during two 1-week cruises. Samples were collected during African dust events and non-dust conditions and screened for the presence of culturable bacteria and fungi. A total of 3,652 liters of air were collected during non-dust conditions, with 19 bacteria and 28 fungi being recovered. During dust conditions a total of 2,369 liters of air were screened resulting in the recovery of 171 bacteria and 76 fungi. A statistically significant difference was found between the two data sets. These results support previous African dust research and further demonstrate that dust particles can serve as a vessel for the global dispersion of bacteria and fungi. Dustborne microorganisms may play a significant role in the ecology and health of downwind ecosystems.

  17. Geomorphology of MODIS-Visible Dust Plumes in the Chihuahuan Desert - Preliminary Results

    NASA Astrophysics Data System (ADS)

    Gill, T. E.; Mbuh, M. J.; Dominguez, M. A.; Lee, J. A.; Baddock, M. C.; Lee, C. E.; Whitehead, S. C.; Rivera Rivera, N. I.; Peinado, P.

    2009-12-01

    We identified 28 days since 2001 when blowing dust impacted El Paso, Texas and dust plumes were visible on NASA MODIS Terra/Aqua satellite images in the surrounding Chihuahuan Desert. Initiation points of >270 individual plumes were located on the MODIS images. Land use/land cover for each point was determined by field work, aerial photography, and/or soil/geological maps, and points were assigned to the geomorphic classes proposed by Bullard et al. (this session). Although dust plume identification is subjective (weak plumes, plumes obscured by clouds, and plumes occurring when the satellites are not overhead will be missed), these data provide preliminary information on the relationship between geomorphology and the initiation of major dust storms in the Chihuahuan Desert. Ephemeral lakes and alluvial low-relief non-incised lands are roughly equal producers of satellite-visible dust plumes in the Chihuahuan Desert. Anthropogenic modification of alluvial floodplains for cropping (primarily in the Casas Grandes and Del Carmen river basins) impacts dust generation, since about 2/3 of alluvial low-relief sites show evidence of agriculture. These agricultural fields are generally fallow during the November- April windy season. Not including agricultural lands, playas represent ~2x the number of sources as low-relief alluvial deposits. Aeolian sand deposits (predominantly coppice dunes and sand sheets overlaying alluvial or lacustrine sediments) account for about 1/7 of the points. These sands may act as erosional agents, providing saltating particles for sandblasting and bombardment of other sediments exposed nearby. Edges of ephemeral lakes are proportionally important sources (~10% of the points), likely due to the convergence of saltating sand, fine lacustrine sediments, and low roughness lengths of playa surfaces. Alluvial fans and alluvial uplands are minor dust sources compared to their overall prevalence in the region. Gobi/gibber/stony deposits are known dust

  18. Epifluorescent direct counts of bacteria and viruses from topsoil of various desert dust storm regions

    USGS Publications Warehouse

    Gonzalez-Martin, Cristina; Teigell-Perez, Nuria; Lyles, Mark; Valladares, Basilio; Griffin, Dale W.

    2013-01-01

    Topsoil from arid regions is the main source of dust clouds that move through the earth's atmosphere, and microbial communities within these soils can survive long-range dispersion. Microbial abundance and chemical composition were analyzed in topsoil from various desert regions. Statistical analyses showed that microbial direct counts were strongly positively correlated with calcium concentrations and negatively correlated with silicon concentrations. While variance between deserts was expected, it was interesting to note differences between sample sites within a given desert region, illustrating the 'patchy' nature of microbial communities in desert environments.

  19. Epifluorescent direct counts of bacteria and viruses from topsoil of various desert dust storm regions.

    PubMed

    Gonzalez-Martin, Cristina; Teigell-Perez, Nuria; Lyles, Mark; Valladares, Basilio; Griffin, Dale W

    2013-01-01

    Topsoil from arid regions is the main source of dust clouds that move through the earth's atmosphere, and microbial communities within these soils can survive long-range dispersion. Microbial abundance and chemical composition were analyzed in topsoil from various desert regions. Statistical analyses showed that microbial direct counts were strongly positively correlated with calcium concentrations and negatively correlated with silicon concentrations. While variance between deserts was expected, it was interesting to note differences between sample sites within a given desert region, illustrating the 'patchy' nature of microbial communities in desert environments.

  20. Epifluorescent direct counts of bacteria and viruses from topsoil of various desert dust storm regions.

    PubMed

    Gonzalez-Martin, Cristina; Teigell-Perez, Nuria; Lyles, Mark; Valladares, Basilio; Griffin, Dale W

    2013-01-01

    Topsoil from arid regions is the main source of dust clouds that move through the earth's atmosphere, and microbial communities within these soils can survive long-range dispersion. Microbial abundance and chemical composition were analyzed in topsoil from various desert regions. Statistical analyses showed that microbial direct counts were strongly positively correlated with calcium concentrations and negatively correlated with silicon concentrations. While variance between deserts was expected, it was interesting to note differences between sample sites within a given desert region, illustrating the 'patchy' nature of microbial communities in desert environments. PMID:22989672

  1. Biological effects of desert dust in respiratory epithelial cells and a murine model.

    EPA Science Inventory

    Abstract As a result of the challenge of recent dust storms to public health, we tested the postulate that desert dust collected in the southwestern United States could impact a biological effect in respiratory epithelial cells and an animal model. Two samples of surface sedime...

  2. Mediterranean intense desert dust outbreaks and their vertical structure based on remote sensing data

    NASA Astrophysics Data System (ADS)

    Gkikas, Antonis; Basart, Sara; Hatzianastassiou, Nikos; Marinou, Eleni; Amiridis, Vassilis; Kazadzis, Stelios; Pey, Jorge; Querol, Xavier; Jorba, Oriol; Gassó, Santiago; Baldasano, José Maria

    2016-07-01

    The main aim of the present study is to describe the vertical structure of the intense Mediterranean dust outbreaks, based on the use of satellite and surface-based retrievals/measurements. Strong and extreme desert dust (DD) episodes are identified at 1° × 1° spatial resolution, over the period March 2000-February 2013, through the implementation of an updated objective and dynamic algorithm. According to the algorithm, strong DD episodes occurring at a specific place correspond to cases in which the daily aerosol optical depth at 550 nm (AOD550 nm) exceeds or equals the long-term mean AOD550 nm (Mean) plus two standard deviations (SD), which is also smaller than Mean+4 × SD. Extreme DD episodes correspond to cases in which the daily AOD550 nm value equals or exceeds Mean+4 × SD. For the identification of DD episodes, additional optical properties (Ångström exponent, fine fraction, effective radius and aerosol index) derived by the MODIS-Terra & Aqua (also AOD retrievals), OMI-Aura and EP-TOMS databases are used as inputs. According to the algorithm using MODIS-Terra data, over the period March 2000-February 2013, strong DD episodes occur more frequently (up to 9.9 episodes year-1) over the western Mediterranean, while the corresponding frequencies for the extreme ones are smaller (up to 3.3 episodes year-1, central Mediterranean Sea). In contrast to their frequency, dust episodes are more intense (AODs up to 4.1), over the central and eastern Mediterranean Sea, off the northern African coasts. Slightly lower frequencies and higher intensities are found when the satellite algorithm operates based on MODIS-Aqua retrievals, for the period 2003-2012. The consistency of the algorithm is successfully tested through the application of an alternative methodology for the determination of DD episodes, which produced similar features of the episodes' frequency and intensity, with just slightly higher frequencies and lower intensities. The performance of the

  3. Mediterranean intense desert dust outbreaks and their vertical structure based on remote sensing data

    NASA Astrophysics Data System (ADS)

    Gkikas, Antonis; Basart, Sara; Hatzianastassiou, Nikos; Marinou, Eleni; Amiridis, Vassilis; Kazadzis, Stelios; Pey, Jorge; Querol, Xavier; Jorba, Oriol; Gassó, Santiago; Baldasano, José Maria

    2016-07-01

    The main aim of the present study is to describe the vertical structure of the intense Mediterranean dust outbreaks, based on the use of satellite and surface-based retrievals/measurements. Strong and extreme desert dust (DD) episodes are identified at 1° × 1° spatial resolution, over the period March 2000-February 2013, through the implementation of an updated objective and dynamic algorithm. According to the algorithm, strong DD episodes occurring at a specific place correspond to cases in which the daily aerosol optical depth at 550 nm (AOD550 nm) exceeds or equals the long-term mean AOD550 nm (Mean) plus two standard deviations (SD), which is also smaller than Mean+4 × SD. Extreme DD episodes correspond to cases in which the daily AOD550 nm value equals or exceeds Mean+4 × SD. For the identification of DD episodes, additional optical properties (Ångström exponent, fine fraction, effective radius and aerosol index) derived by the MODIS-Terra & Aqua (also AOD retrievals), OMI-Aura and EP-TOMS databases are used as inputs. According to the algorithm using MODIS-Terra data, over the period March 2000-February 2013, strong DD episodes occur more frequently (up to 9.9 episodes year-1) over the western Mediterranean, while the corresponding frequencies for the extreme ones are smaller (up to 3.3 episodes year-1, central Mediterranean Sea). In contrast to their frequency, dust episodes are more intense (AODs up to 4.1), over the central and eastern Mediterranean Sea, off the northern African coasts. Slightly lower frequencies and higher intensities are found when the satellite algorithm operates based on MODIS-Aqua retrievals, for the period 2003-2012. The consistency of the algorithm is successfully tested through the application of an alternative methodology for the determination of DD episodes, which produced similar features of the episodes' frequency and intensity, with just slightly higher frequencies and lower intensities. The performance of the

  4. Water uptake of clay and desert dust aerosol particles at sub- and supersaturated water vapor conditions.

    PubMed

    Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona; Gysel, Martin; Weingartner, Ernest; Lohmann, Ulrike; Baltensperger, Urs; Cziczo, Daniel J

    2009-09-28

    Airborne mineral dust particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of warm clouds. It is therefore of atmospheric interest how dust aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation (SS) with respect to liquid water. In this study the subsaturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert dust samples (Saharan dust (SD), Chinese dust (CD) and Arizona test dust (ATD)) were investigated. Aerosols were generated both with a wet and a dry disperser. The water uptake was parameterized via the hygroscopicity parameter kappa. The hygroscopicity of dry generated dust aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived kappa values between 0.00 and 0.02 (the latter corresponds to a particle consisting of 96.7% by volume insoluble material and approximately 3.3% ammonium sulfate). Pure clay aerosols were generally found to be less hygroscopic than natural desert dust particles. The illite and montmorillonite samples had kappa approximately 0.003. The kaolinite samples were less hygroscopic and had kappa=0.001. SD (kappa=0.023) was found to be the most hygroscopic dry-generated desert dust followed by CD (kappa=0.007) and ATD (kappa=0.003). Wet-generated dust showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles. Thus, the generation method is critically important when presenting such data. These results indicate any atmospheric processing of a fresh mineral dust particle which

  5. Water uptake of clay and desert dust aerosol particles at sub- and supersaturated water vapor conditions.

    PubMed

    Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona; Gysel, Martin; Weingartner, Ernest; Lohmann, Ulrike; Baltensperger, Urs; Cziczo, Daniel J

    2009-09-28

    Airborne mineral dust particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of warm clouds. It is therefore of atmospheric interest how dust aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation (SS) with respect to liquid water. In this study the subsaturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert dust samples (Saharan dust (SD), Chinese dust (CD) and Arizona test dust (ATD)) were investigated. Aerosols were generated both with a wet and a dry disperser. The water uptake was parameterized via the hygroscopicity parameter kappa. The hygroscopicity of dry generated dust aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived kappa values between 0.00 and 0.02 (the latter corresponds to a particle consisting of 96.7% by volume insoluble material and approximately 3.3% ammonium sulfate). Pure clay aerosols were generally found to be less hygroscopic than natural desert dust particles. The illite and montmorillonite samples had kappa approximately 0.003. The kaolinite samples were less hygroscopic and had kappa=0.001. SD (kappa=0.023) was found to be the most hygroscopic dry-generated desert dust followed by CD (kappa=0.007) and ATD (kappa=0.003). Wet-generated dust showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles. Thus, the generation method is critically important when presenting such data. These results indicate any atmospheric processing of a fresh mineral dust particle which

  6. Estimated desert-dust ice nuclei profiles from polarization lidar: methodology and case studies

    NASA Astrophysics Data System (ADS)

    Mamouri, R. E.; Ansmann, A.

    2015-03-01

    A lidar method is presented that permits the estimation of height profiles of ice nuclei concentrations (INC) in desert dust layers. The polarization lidar technique is applied to separate dust and non-dust backscatter and extinction coefficients. The desert dust extinction coefficients σd are then converted to aerosol particle number concentrations APC280 which consider particles with radius > 280 nm only. By using profiles of APC280 and ambient temperature T along the laser beam, the profile of INC can be estimated within a factor of 3 by means of APC-T-INC parameterizations from the literature. The observed close relationship between σd at 500 nm and APC280 is of key importance for a successful INC retrieval. We studied this link by means of AERONET (Aerosol Robotic Network) sun/sky photometer observations at Morocco, Cabo Verde, Barbados, and Cyprus during desert dust outbreaks. The new INC retrieval method is applied to lidar observations of dust layers with the spaceborne lidar CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization) during two overpasses over the EARLINET (European Aerosol Research Lidar Network) lidar site of the Cyprus University of Technology (CUT), Limassol (34.7° N, 33° E), Cyprus. The good agreement between the CALIOP and CUT lidar retrievals of σd, APC280, and INC profiles corroborates the potential of CALIOP to provide 3-D global desert dust APC280 and INC data sets.

  7. Observational study of formation mechanism, vertical structure, and dust emission of dust devils over the Taklimakan Desert, China

    NASA Astrophysics Data System (ADS)

    Liu, Chong; Zhao, Tianliang; Yang, Xinghua; Liu, Feng; Han, Yongxiang; Luan, Zhaopeng; He, Qing; Rood, Mark; Yuen, Wangki

    2016-04-01

    A field observation of dust devils was conducted at Xiaotang over the Taklimakan Desert (TD), China, from 7 to 14 July 2014. The measurements of dust devil opacity with the digital optical method and the observed atmospheric boundary layer conditions were applied to investigate the dust devils' formation mechanism, vertical structure, and dust emissions. The critical conditions in the atmospheric boundary layer for dust devil formation were revealed with the land-air surface temperature difference of higher than 15°C, the enhanced momentum flux and sensible heat flux up to 0.54 kg m-1 s-2 and 327 W m-2, respectively, the weak vertical wind shear with the low wind shear index α < 0.10, and the unstable stratification in the lower atmosphere. Based on observed dust opacities, it is identified that a typical dust devil was vertically structured with central updrafts and peripheral downdrafts of dust particles with the asymmetrically horizontal distribution of dust in a rotating dust column. The vertical flux of near-surface dust emissions was also estimated in a range from 5.4 × 10-5 to 9.6 × 10-5 kg m-2 s-1 for a typical dust devil event over TD.

  8. Spatial and temporal variations of dust concentrations in the Gobi Desert of Mongolia

    NASA Astrophysics Data System (ADS)

    Jugder, D.; Shinoda, M.; Sugimoto, N.; Matsui, I.; Nishikawa, M.; Park, S.; Chun, Y.; Park, M.

    2011-12-01

    Dust storms in the extensive Gobi and desert-steppe zones of Mongolia occur frequently and sometimes cause serious disasters. Dust storms progress from source regions to downstream regions. This study was the first to examine dust mass concentrations of PM10 (PM2.5) in the Gobi Desert, Mongolia. The monthly mean concentrations of PM10 (PM2.5) reached yearly maxima in December and January owing to air pollution. Both PM10 and PM2.5 concentrations were enhanced from March to May by dust storms. Large amounts of fine dust particles are emitted to the air during the dust storm period in the Gobi Desert of Mongolia. Daily mean concentrations of PM10 (PM2.5) varied 64~234 (40~115) μg m-3 for dust storms in spring. The highest hourly mean concentration of PM10 was 6626 μg m-3 in the Gobi during a dust storm. Averaged concentrations of PM10 (PM2.5) for more than 4h-duration periods of the dust events varied from 204 (101) μg m-3 to 452 (170) μg m-3. For diurnal variations, the maximum PM10 (PM2.5) concentrations occurred in the morning and evening, coinciding with coal usage in private houses. It is evident that human activities can affect local air quality around urban localities in the Gobi of Mongolia. Afternoon peaks in PM10 (PM2.5) concentrations appear to be due to dust storms. Study results on the temporal and spatial distributions and transportation of dust storms, and elevated dust by using Polarization-sensitive Mie-scattering lidars showed that the maximum height of dusty layers over the Gobi Desert of Mongolia during dust storm periods varied from 0.5 to 5.5 km above ground level. The Mie lidar observations detected the base and top heights of elevated dust layers transported from other source regions to the Gobi Desert. The study results suggest source areas of the elevated dust. The lidar parameters showed annual variation of dust storms with higher frequencies in March to May.

  9. Chemical characterisation of african dust transported to Canary Region

    NASA Astrophysics Data System (ADS)

    Gelado, M. D.; López, P.; Prieto, S.; Collado, C.; Hernández, J. J.

    2009-04-01

    African dust pulses have important effects on the climate conditions and the marine biogeochemistry in the Canary Region. Aerosol samples have been collected at three stations on Gran Canaria Island (Taliarte at sea level, Tafira 269 m a.s.l. and Pico de la Gorra 1930 m a.s.l.) during 2000-2008. Elemental characterisation of the collected mineral aerosol and back trajectories of the air masses are used to distinguish regional African sources of dust. Dust aerosol samples from North Sahara (Morocco, North Algeria and Tunisia), West and Central Sahara (20°-30°N, 18°W-50°E) and Sahel (0°-20°N, 18°W-50°E) have shown different Ca/Ti, Al/Ti and Fe/Al ratios. Ti appears as a better tracer element of specific source of dust than Fe, probably due to a less mineral alteration during the atmospheric transport.

  10. Estimation of desert-dust-related ice nuclei profiles from polarization lidar

    NASA Astrophysics Data System (ADS)

    Mamouri, Rodanthi-Elisavet; Nisantzi, Argyro; Hadjimitsis, Diofantos; Ansmann, Albert

    2015-04-01

    This paper presents a methodology based on the use of active remote sensing techniques for the estimation of ice nuclei concentrations (INC) for desert dust plumes. Although this method can be applied to other aerosol components, in this study we focus on desert dust. The method makes use of the polarization lidar technique for the separation of dust and non-dust contributions to the particle backscatter and extinction coefficients. The profile of the dust extinction coefficient is converted to APC280 (dust particles with radius larger than 280 nm) and, in a second step, APC280 is converted to INC by means of an APC-INC relationship from the literature. The observed close relationship between dust extinction at 500 nm and APC280 is the key to a successful INC retrieval. The correlation between dust extinction coefficient and APC280 is studied by means of AERONET sun/sky photometer at Morocco, Cape Verde, Barbados, and Cyprus, during situations dominated by desert dust outbreaks. In the present study, polarization lidar observations of the EARLINET (European Aerosol Research Lidar Network) lidar at the Cyprus University of Technology (CUT), Limassol (34.7o N, 33o E), Cyprus were used together with spaceborne lidar observations during CALIPSO satellite overpasses to demonstrate the potential of the new INC retrieval method. A good agreement between the CALIOP (Cloud Aerosol Lidar with Orthogonal Polarization) and our CUT lidar observations regarding the retrieval of dust extinction coefficient, APC280, and INC profiles were found and corroborate the potential of CALIOP to provide 3-D global desert-dust-related INC data sets. In the next step, efforts should be undertaken towards the establishment of a global, height-resolved INC climatology for desert dust plumes. Realistic global INC distributions are required for an improved estimation of aerosol effects on cloud formation and the better quantification of the indirect aerosol effect on climate. Acknowledgements

  11. The Impact of African Dust on PM10 Air Quality in the Caribbean Basin

    NASA Astrophysics Data System (ADS)

    Prospero, J. M.

    2015-12-01

    Decades of aerosol measurements on Barbados and Miami have yielded a broad picture of African mineral dust transport to the Caribbean Basin. These measurements show that in summer the aerosol mass is often dominated by dust. At such times over 90% of the dust mass is comprised of particles less than 10 μm aerodynamic diameter and thus fits the EPA criteria for PM10. A number of sites in the Caribbean monitor PM10 using the same instrumentation commonly deployed in European and United States networks. By comparing data from individual islands that have multiple monitoring sites (e.g., Puerto Rico, Martinique, Guadeloupe), it is shown that during dust events PM10 concentrations track very closely and that local sources have a minor impact on PM10 above about 15 to 20 μg m-3. Moreover the PM10 measurements are coherent with the movement of dust clouds over the islands as observed by satellites. In this way dust movement can be tracked at PM10 sites along the Gulf and southeast coasts of the United States. To assess the specific impact of African dust on PM10 in the region, I compare the daily records of dust measurements at Miami and Barbados with concurrent measurements made at proximate PM10 sites. I then use these relationships and the long term dust measurements at Barbados and Miami to assess the long-term variability of PM10 across the region. At Barbados the record goes back 50 years and provides a basis of assessing the effects of climate variability on PM10 transport. This study shows that there is great variability on scales ranging from daily to decadal. The impact of the droughts in the 1970s and 1980s was particularly significant. Across the Caribbean, the rates of exceedances of the WHO PM10 guideline is comparable to those observed in many major urban areas in Europe and the US. The dominance of dust in large PM10 events and the absence of major pollution sources on many islands offers the opportunity to study the health impacts of desert dust in

  12. Impact of the Desert Dust on the Summer Monsoon System over Southwestern North America

    SciTech Connect

    Zhao, Chun; Liu, Xiaohong; Leung, Lai-Yung R.

    2012-04-24

    The radiative forcing of dust emitted from the Southwest United States (US) deserts and its impact on monsoon circulation and precipitation over the North America monsoon (NAM) region are simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem) for 15 years (1995-2009). During the monsoon season, dust has a cooling effect (-0.90 W m{sup -2}) at the surface, a warming effect (0.40 W m{sup -2}) in the atmosphere, and a negative top-of-the-atmosphere (TOA) forcing (-0.50 W m{sup -2}) over the deserts on 24-h average. Most of the dust emitted from the deserts concentrates below 800 hPa and accumulates over the western slope of the Rocky Mountains and Mexican Plateau. The absorption of shortwave radiation by dust heats the lower atmosphere by up to 0.5 K day{sup -1} over the western slope of the Mountains. Model sensitivity simulations with and without dust for 15 summers (June-July-August) show that dust heating of the lower atmosphere over the deserts strengthens the low-level southerly moisture fluxes on both sides of the Sierra Madre Occidental. It also results in an eastward migration of NAM-driven moisture convergence over the western slope of the Mountains. These monsoonal circulation changes lead to a statistically significant increase of precipitation by up to {approx}40% over the eastern slope of the Mountains (Arizona-New Mexico-Texas regions). This study highlights the interaction between dust and the NAM system and motivates further investigation of possible dust feedback on monsoon precipitation under climate change and the megadrought conditions projected for the future.

  13. Desert dust,Ocean spray,Volcanoes,Biomass burning: Pathways of nutrients into Andean rainforests

    NASA Astrophysics Data System (ADS)

    Fabian, P.; Rollenbeck, R.; Spichtinger, N.; Dominguez, G.; Brothers, L.; Thiemens, M.

    2009-04-01

    Regular rain and fogwater sampling in the Podocarpus National Park, along an altitude profile between 1800 and 3185 m, has been carried out since 2002.The research area located in southern Ecuador on the wet eastern slopes of the Andes is dominated by trade winds from easterly directions. The samples, generally accumulated over 1-week intervals, have been analysed for pH,conductivity and major ions(K+,Na+,NH4+,Ca2+,Mg 2+,SO42-,NO3-,PO43). For all components a strong seasonal variation is observed,while the altitudinal gradient is less pronounced. About 35 % of the weekly samples had very low ion contents,at or below the detection limit, with pH generally above 5 and conductivity below 10 uS/cm.10 days back trajectories (FLEXTRA) showed that respective air masses originated in pristine continental areas,with little or no obvious pollution sources. About 65 %,however,were significantly loaded with cations and anions,with pH often as low as 3.5 to 4.0 and conductivity up to 50 uS/cm.Back trajectories showed that respective air masses had passed over areas of intense biomass burning,volcanoes,and the ocean,with even episodic Sahara and/or Namib desert dust interference. Enhanced SO4 2-and NO3- were identified,by combining satellite-based fire pixels with back trajectories,as predominantly resulting from biomass burning. Analyses of oxygen isotopes 16O ,17O ,and 18O of nitrate show that nitrate in fog samples is a product of atmospheric conversion of precursors.For most cases,by using emission inventories, anthropogenic precursor sources other than forest fires could be ruled out,thus leaving biomass burning as the main source of nitrate and sulphate in rain and fogwater. Some SO4 2- ,about 10 % of the total input,could be identified to originate from active volcanoes, whose plumes were sometimes encountered by the respective back trajectories. Enhanced Na +, K + ,and Cl - was found to originate from ocean spray sources.They were associated with strong winds providing

  14. Potential Impacts of Saharan Dust on the African Air Quality

    NASA Astrophysics Data System (ADS)

    Ichoku, C. M.; Petrenko, M.; El-Askary, H. M.; Wang, J.; Yang, Z.; Yue, Y.

    2014-12-01

    The largest dust source in the world is the Sahara desert, which occupies most of the northern half of Africa. A recent international modeling experiment conducted under the auspices of the Aerosol Comparisons between Observations and Models (AEROCOM) initiative estimated that the annual dust generation from the Sahara and its peripheries is in the range of 400 to 2200 Tg yr-1. It is estimated that about 240±80 Tg yr-1 of the dust leaves the western shores of Africa on its way across the Atlantic. Therefore, a majority of the dust emitted from and around the Sahara remains and circulates within Africa, potentially affecting the environment, air quality, and human health, among other effects. Given the apparent scarcity of ground-based air-quality monitoring networks in Africa, we are exploring approaches that utilize satellite measurements and regional models to estimate the air-quality impacts of aerosols (particularly those of biomass burning and dust) in northern Hemisphere Africa. Some of the model simulations evaluated using ground-based and satellite observations show that the regional models deliver a high performance in capturing the mixing and transport of biomass-burning (smoke) and dust aerosols. In this presentation, we will share our preliminary results and future perspectives.

  15. Far-Reaching Impacts of African Dust- A Calipso Perspective

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Prospero, Joseph; Omar, Ali; Remer, Lorraine; Winker, David; Yang, Yuekui; Zhang, Yan; Zhang, Zhibo

    2014-01-01

    African dust can transport across the tropical Atlantic and reach the Amazon basin, exerting far-reaching impacts on climate in downwind regions. The transported dust influences the surface-atmosphere interactions and cloud and precipitation processes through perturbing the surface radiative budget and atmospheric radiative heating and acting as cloud condensation nuclei and ice nuclei. Dust also influences biogeochemical cycle and climate through providing nutrients vital to the productivity of ocean biomass and Amazon forests. Assessing these climate impacts relies on an accurate quantification of dust transport and deposition. Currently model simulations show extremely large diversity, which calls for a need of observational constraints. Kaufman et al. (2005) estimated from MODIS aerosol measurements that about 144 Tg of dust is deposited into the tropical Atlantic and 50 Tg of dust into the Amazon in 2001. This estimated dust import to Amazon is a factor of 3-4 higher than other observations and models. However, several studies have argued that the oversimplified characterization of dust vertical profile in the study would have introduced large uncertainty and very likely a high bias. In this study we quantify the trans-Atlantic dust transport and deposition by using 7 years (2007-2013) observations from CALIPSO lidar. CALIPSO acquires high-resolution aerosol extinction and depolarization profiles in both cloud-free and above-cloud conditions. The unique CALIPSO capability of profiling aerosols above clouds offers an unprecedented opportunity of examining uncertainties associated with the use of MODIS clear-sky data. Dust is separated from other types of aerosols using the depolarization measurements. We estimated that on the basis of 7-year average, 118142 Tg of dust is deposited into the tropical Atlantic and 3860 Tg of dust into the Amazon basin. Substantial interannual variations are observed during the period, with the maximum to minimum ratio of about 1

  16. Dynamic responses of photosystem II in the Namib Desert shrub, Zygophyllum prismatocarpum, during and after foliar deposition of limestone dust.

    PubMed

    van Heerden, P D R; Krüger, G H J; Kilbourn Louw, M

    2007-03-01

    The effects of limestone dust deposition on vegetation in desert ecosystems have not yet been reported. We investigated these effects in a succulent shrub from the Namib Desert at a limestone quarry near Skorpion Zinc mine (Namibia). Effects of limestone dust were determined in Zygophyllum prismatocarpum (dollar bush) plants with heavy, moderate and no visible foliar dust cover by means of chlorophyll a fluorescence measurements. Limestone dust deposition decreased overall plant performance through loss of chlorophyll content, inhibition of CO(2) assimilation, uncoupling of the oxygen-evolving complex and decreased electron transport. Importantly, dynamic recovery occurred after termination of limestone extraction at the quarry. Recovery was accelerated by rainfall, mainly because of dust removal from leaves and stimulation of new growth. These results indicate that limestone dust has severe effects on photosynthesis in desert shrubs, but that recovery is possible and that, in arid environments, this process is modulated by rainfall.

  17. Soil-derived sulfate in atmospheric dust particles at Taklimakan desert

    NASA Astrophysics Data System (ADS)

    Wu, Feng; Zhang, Daizhou; Cao, Junji; Xu, Hongmei; An, Zhisheng

    2012-12-01

    Dust-associated sulfate is believed to be a key species which can alter the physical and chemical properties of dust particles in the atmosphere. Its occurrence in the particles has usually been considered to be the consequence of particles' aging in the air although it is present in some crustal minerals. Our observation at the north and south edge of Taklimakan desert, one of the largest dust sources in the Northern Hemisphere, during a dust episode in April 2008 revealed that sulfate in atmospheric dust samples most likely originated directly from surface soil. Its TSP, PM10 and PM2.5 content was proportional to samples' mass and comprised steadily about 4% in the differently sized samples, the ratio of elemental sulfur to iron was approximately constant 0.3, and no demonstrable influence of pollutants from fossil fuel combustion and biomass burning was detected. These results suggest that sulfate could be substantially derived from surface soil at the desert area and the lack of awareness of this origin may impede accurate results in any investigation of atmospheric sulfur chemistry associated with Taklimakan dust and its subsequent local, regional and global effects on the atmosphere.

  18. Compositions of modern dust and surface sediments in the Desert Southwest, United States

    USGS Publications Warehouse

    Reheis, M.C.; Budahn, J.R.; Lamothe, P.J.; Reynolds, R.L.

    2009-01-01

    Modern dusts across southwestern United States deserts are compositionally similar to dust-rich Av soil horizons (depths of 0-0.5 cm and 1-4 cm at 35 sites) for common crustal elements but distinctly different for some trace elements. Chemical compositions and magnetic properties of the soil samples are similar among sites relative to dust sources, geographic areas, and lithologic substrates. Exceptions are Li, U, and W, enriched in Owens Valley, California, and Mg and Sr, enriched in soils formed on calcareous fan gravel in southeast Nevada. The Av horizons are dominated by dust and reflect limited mixing with substrate sediments. Modern dust samples are also similar across the region, except that Owens Valley dusts are higher in Mg, Ba, and Li and dusts both there and at sites to the north on volcanic substrates are higher in Sb and W. Thus, dust and Av horizons consist of contributions from many different sources that are well mixed before deposition. Modern dusts contain significantly greater amounts of As, Cd, Cr, Cu, Ni, Pb, and Sb than do Av horizons, which record dust additions over hundreds to thousands of years. These results suggest that modern dust compositions are influenced by anthropogenic sources and emissions from Owens (dry) Lake after its artificial desiccation in 1926. Both modern dusts and Av horizons are enriched in As, Ba, Cu, Li, Sb, Th, U, and W relative to average crustal composition, which we interpret to indicate that the geologic sources of dust in the southwestern United States are geochemically distinctive.

  19. The Role of African Easterly Wave on Dust Transport and the Interaction Between Saharan Dust Layer and Atlantic ITCZ During Boreal Summer

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Kim, Kyu-Myong

    2012-01-01

    In this paper, we investigate the relationships among Saharan dust outbreak and transport, African easterly waves (AEW), African easterly jet (AEJ) and associated convective activities of Atlantic Intertropical Convergence Zone (ITCZ) using Cloudsat-Calipso, MODIS and MERRA data. We find that a major Saharan dust outbreak is associated with the formation of a westward propagating strong cyclone around 15-25N over the western part northern Saharan. The strong cyclonic flow mobilizes and lifts the dust from the desert surface to a high elevation. As the cyclone propagate westward, it transports a thick elevated dust layer between 900 -500 hPa from the African continent to the eastern Atlantic. Cloudiness is reduced within the warm, dry dusty layer, but enhanced underneath it, possibly due to the presence of a shallow inversion layer over the marine boundary layer. The dust outbreak is linked to enhanced deep convection in the northern part of Atlantic ITCZ, abutting the southern flank of the dust layer, and a strengthening of the northward flank of the AEJ. As the dust layer spreads westward, it loses elevation and becomes increasing diffused as it reaches the central and western Atlantic. Using band pass filtered EOF analysis of MERRA winds, we find that AEWs propagating westward along two principal tracks, centered at 15-25N and 5-10N respectively. The easterly waves in the northern track are highly correlated with major dust outbreak over North Africa and associated with slower moving systems, with a quasi-periodicity of 6-9 day. On the other hand, easterly waves along the southern track are faster, with quasi-periodicity of 3-5 days. These faster easterly waves are closely tied to rainfall/cloud variations along the Atlantic ITCZ. Dust transport along the southern track by the faster waves generally leads rainfall/cloud anomalies in the same region by one or two days, suggesting the southern tracks of dust outbreak are regions of strong interaction between

  20. Modulation of Saharan dust export by the North African dipole

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Cuevas, E.; Prospero, J. M.; Alastuey, A.; Querol, X.; López-Solano, J.; García, M. I.; Alonso-Pérez, S.

    2015-07-01

    We have studied the relationship between the long-term interannual variability in large-scale meteorology in western North Africa - the largest and most active dust source worldwide - and Saharan dust export in summer, when enhanced dust mobilization in the hyper-arid Sahara results in maximum dust impacts throughout the North Atlantic. We address this issue by analyzing 28 years (1987-2014) of summer averaged dust concentrations at the high-altitude Izaña observatory (~ 2400 m a.s.l.) on Tenerife, and satellite and meteorological reanalysis data. The summer meteorological scenario in North Africa (aloft 850 hPa) is characterized by a high over the the subtropical Sahara and a low over the tropics linked to the monsoon. We measured the variability of this high-low dipole-like pattern in terms of the North African dipole intensity (NAFDI): the difference of geopotential height anomalies averaged over the subtropics (30-32° N, Morocco) and the tropics (10-13° N, Bamako region) close to the Atlantic coast (at 5-8° W). We focused on the 700 hPa standard level due to dust export off the coast of North Africa tending to occur between 1 and 5 km a.s.l. Variability in the NAFDI is associated with displacements of the North African anticyclone over the Sahara and this has implications for wind and dust export. The correlations we found between the 1987-2014 summer mean of NAFDI with dust at Izaña, satellite dust observations and meteorological re-analysis data indicate that increases in the NAFDI (i) result in higher wind speeds at the north of the Inter-Tropical Convergence Zone that are associated with enhanced dust export over the subtropical North Atlantic, (ii) influence the long-term variability of the size distribution of exported dust particles (increasing the load of coarse dust) and (iii) are associated with enhanced rains in the tropical and northern shifts of the tropical rain band that may affect the southern Sahel. Interannual variability in NAFDI is also

  1. African Dust Concentrations in the Caribbean Island of Puerto Rico

    NASA Astrophysics Data System (ADS)

    Mayol-Bracero, O. L.; Morales-Garcia, F.; Santos-Figueroa, G.; Custals, L.; Izaguirre, M.; Prospero, J. M.; McDowell, W. H.

    2015-12-01

    African dust carried to the Tropical Atlantic and Caribbean was measured during the summer months of 2015. Atmospheric particles during dust events were collected at Cape San Juan, Puerto Rico on stacked-filter units and a high-volume sampler for the fine and coarse fractions and on a low-pressure impactor for size-resolved characterization. The filter ash gravimetric method was used to determine bulk dust mass concentrations for the first time in Puerto Rico. The method was validated analyzing same filter portions at CIAM/ACAR University of Puerto Rico and at RSMAS/MAC University of Miami. Filter's extracts were analyzed for ionic species measured by ion chromatography. The water-soluble organic carbon (WSOC) was determined with a total organic carbon (TOC) analyzer. Mineral dust concentrations in Puerto Rico were compared to those reported at Miami during summer periods. Comparison between dust concentration and regional PM10 data and results on size-resolved dust concentration will also be presented.

  2. Radiative Effects of African Dust and Smoke Observed from CERES and CALIOP Data

    NASA Astrophysics Data System (ADS)

    Yorks, J. E.; McGill, M. J.; Rodier, S. D.; Hlavka, D. L.; Vaughan, M. A.; Hu, Y.

    2009-05-01

    Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the Tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the Tropical Atlantic Ocean were analyzed for the month of July for three years (2006-2008) using collocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the CALIPSO and Aqua satellites. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of about 270 W/m2 and thin cirrus clouds had a SW radiative flux of about 208 W/m2. When dust and smoke aerosols interacted with clouds below 5 km, as determined from CALIPSO, the SW radiative flux decreased to as low as roughly 205 W/m2. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics (semi- direct effect). CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system.

  3. The Continuous Monitoring of Desert Dust using an Infrared-based Dust Detection and Retrieval Method

    NASA Technical Reports Server (NTRS)

    Duda, David P.; Minnis, Patrick; Trepte, Qing; Sun-Mack, Sunny

    2006-01-01

    Airborne dust and sand are significant aerosol sources that can impact the atmospheric and surface radiation budgets. Because airborne dust affects visibility and air quality, it is desirable to monitor the location and concentrations of this aerosol for transportation and public health. Although aerosol retrievals have been derived for many years using visible and near-infrared reflectance measurements from satellites, the detection and quantification of dust from these channels is problematic over bright surfaces, or when dust concentrations are large. In addition, aerosol retrievals from polar orbiting satellites lack the ability to monitor the progression and sources of dust storms. As a complement to current aerosol dust retrieval algorithms, multi-spectral thermal infrared (8-12 micron) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Meteosat-8 Spinning Enhanced Visible and Infrared Imager (SEVIRI) are used in the development of a prototype dust detection method and dust property retrieval that can monitor the progress of Saharan dust fields continuously, both night and day. The dust detection method is incorporated into the processing of CERES (Clouds and the Earth s Radiant Energy System) aerosol retrievals to produce dust property retrievals. Both MODIS (from Terra and Aqua) and SEVERI data are used to develop the method.

  4. Dust exposure and pneumoconiosis in a South African pottery. 1. Study objectives and dust exposure.

    PubMed

    Rees, D; Cronje, R; du Toit, R S

    1992-07-01

    Dust exposure and pneumoconiosis were investigated in a South African pottery that manufactured wall tiles and bathroom fittings. This paper describes the objectives of the investigation and presents dust measurement data. x Ray diffraction showed that the clays used by the pottery had a high quartz content (range 58%-23%, mean 38%). Exposure to respirable dust was measured for 43 workers and was highest (6.6 mg/m3) in a bathroom fitting fettler. Quartz concentrations in excess of 0.1 mg/m3 were found in all sections of the manufacturing process from slip production to biscuit firing and sorting. The proportion of quartz in the respirable dust of these sections was 24% to 33%. This is higher than is usually reported in English potteries. Four hundred and six (80%) of the 509 workers employed at the pottery were potentially at risk of occupational lung disease. The finding of large numbers of pottery workers exposed to unacceptable dust concentrations is not surprising as poor dust control was found in all six wall tile and sanitary ware factories surveyed by the National Centre for Occupational Health between 1973 and 1989. Dust related occupational disease can be expected in potters for many years to come.

  5. Stabilization of Desert Surfaces and Accumulation of Dust Under Biological Soil Crusts

    NASA Astrophysics Data System (ADS)

    Finstad, K. M.; Mcnicol, G.; Pfeiffer, M.; Amundson, R.

    2014-12-01

    Biological soil crusts (BSC) are known to play a critical role in the stabilization of desert surfaces by helping to protect sediment from wind and water erosion and aiding in the trapping of airborne particles. The crusts are often composed of cyanobacteria, algae, and fungi, and occupy the upper few cm of a soil. Due to their high tolerance of desiccation and ability to utilize fog and dew sources, BSC are able to exist in environments that may otherwise be too dry for vascular plants. In the hyperarid Atacama Desert, decades or more between measurable precipitation events has created a landscape devoid of macroscopic life. While precipitation is rare, coastal fog occurs regularly and microbial communities capable of utilizing fog and dew water are able to persist. Here we found cyanobacteria and lichen living in association with a thin sulfate and dust crust (~2 cm) covering the surface of 'dust plateaus'. Topographically the region is highly irregular and part of a largely erosional landscape. We hypothesized that these flat-topped plateaus are accretionary features that have been able to maintain dust accumulation for thousands of years as a result of the surface crusts. To test this hypothesis we conducted radiocarbon analysis of crusts and soil profiles at two sites approximately 30 km apart, one in a high fog zone and another in lower fog frequency zone. The radiocarbon analysis shows that sediment has been accumulating in the 'plateaus' for the past 15,000 years and that biological activity and rates of C cycling in the crust increase with increasing fog frequency and intensity. The ages of organic material in the dust decrease monotonically with decreasing soil thickness, suggestive of progressive upward growth by dust accumulation. Our data indicate that the BSC are capable of surviving in hyperarid the Atacama Desert, a Mars analogue, through the utilization of fog water, and that their presence can leave a visible geomorphic imprint on the landscape.

  6. Climatological analysis of dust storms in the area surrounding the Tengger Desert during 1960-2007

    NASA Astrophysics Data System (ADS)

    Guan, Qingyu; Yang, Jing; Zhao, Shilei; Pan, Baotian; Liu, Chenglin; Zhang, Di; Wu, Tao

    2014-09-01

    Based on dust storm records and meteorological data from six stations in the area surrounding the Tengger Desert over the period 1960-2007, the diurnal, monthly and interannual variation of dust storms and severe dust storms, as well as their relation to wind speed, precipitation and temperature, are analyzed and discussed. Statistical analyses demonstrate that such storms occur more frequently from 9:00 to 21:00 local standard time and much more frequently between March and May, especially April. Dust storm frequency (DSF) and severe dust storm frequency (SDSF) show a significant linear decreasing trend from 1960 to 2007. For monthly variability, winds (especially strong ones with speeds 10-20 m/s) are the main factor controlling both dust storm types. Precipitation and temperature have an indirect effect on DSF and SDSF by controlling vegetation growth. For interannual variability, strong wind is still the main control, with precipitation a relatively important cofactor. Temperature has an irregular but somewhat negative relationship with dust storms. Precipitation and especially temperature have likely been important in the increase of DSF since 2000.

  7. Climatological analysis of dust storms in the area surrounding the Tengger Desert during 1960-2007

    NASA Astrophysics Data System (ADS)

    Guan, Qingyu; Yang, Jing; Zhao, Shilei; Pan, Baotian; Liu, Chenglin; Zhang, Di; Wu, Tao

    2015-08-01

    Based on dust storm records and meteorological data from six stations in the area surrounding the Tengger Desert over the period 1960-2007, the diurnal, monthly and interannual variation of dust storms and severe dust storms, as well as their relation to wind speed, precipitation and temperature, are analyzed and discussed. Statistical analyses demonstrate that such storms occur more frequently from 9:00 to 21:00 local standard time and much more frequently between March and May, especially April. Dust storm frequency (DSF) and severe dust storm frequency (SDSF) show a significant linear decreasing trend from 1960 to 2007. For monthly variability, winds (especially strong ones with speeds 10-20 m/s) are the main factor controlling both dust storm types. Precipitation and temperature have an indirect effect on DSF and SDSF by controlling vegetation growth. For interannual variability, strong wind is still the main control, with precipitation a relatively important cofactor. Temperature has an irregular but somewhat negative relationship with dust storms. Precipitation and especially temperature have likely been important in the increase of DSF since 2000.

  8. Dust emission from wet and dry playas in the Mojave Desert, USA

    USGS Publications Warehouse

    Reynolds, R.L.; Yount, J.C.; Reheis, M.; Goldstein, H.; Chavez, P.; Fulton, R.; Whitney, J.; Fuller, C.; Forester, R.M.

    2007-01-01

    The interactions between playa hydrology and playa-surface sediments are important factors that control the type and amount of dust emitted from playas as a result of wind erosion. The production of evaporite minerals during evaporative loss of near-surface ground water results in both the creation and maintenance of several centimeters or more of loose sediment on and near the surfaces of wet playas. Observations that characterize the texture, mineralogic composition and hardness of playa surfaces at Franklin Lake, Soda Lake and West Cronese Lake playas in the Mojave Desert (California), along with imaging of dust emission using automated digital photography, indicate that these kinds of surface sediment are highly susceptible to dust emission. The surfaces of wet playas are dynamic - surface texture and sediment availability to wind erosion change rapidly, primarily in response to fluctuations in water-table depth, rainfall and rates of evaporation. In contrast, dry playas are characterized by ground water at depth. Consequently, dry playas commonly have hard surfaces that produce little or no dust if undisturbed except for transient silt and clay deposited on surfaces by wind and water. Although not the dominant type of global dust, salt-rich dusts from wet playas may be important with respect to radiative properties of dust plumes, atmospheric chemistry, windborne nutrients and human health.

  9. Changes in North African dust deposition: 35 ka through the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Kinsley, C. W.; McGee, D.; Winckler, G.; deMenocal, P. B.; Stuut, J. W.; Bradtmiller, L. I.

    2013-12-01

    Past changes in atmospheric circulation and aridity in the North African region can be explored by examining continuous records of reconstructed eolian dust accumulation in West African margin sediments. Recent high-resolution reconstructions of dust deposition by McGee et al. (2013) from a meridional transect of cores stretching from 27°N to 19°N along the northwest African margin indicate dramatic changes in North African dust emissions over the last 20 ka. Times of high dust emissions were documented during Heinrich Stadial 1 and the Younger Dryas, and lower dust emissions during the African Humid Period. Here we present a continuation of these records, combining grain size endmember modeling with 230Th-normalized fluxes in these cores to document spatial and temporal changes in dust loads and grain size distributions within the North African dust plume from 20 to ~35 ka. Our results provide quantitative estimates of the magnitude of dust flux changes associated with previous Heinrich Stadials, and lend insight to the nature of the North African dust plume through the entirety of the Last Glacial Maximum. References: McGee, D., deMenocal, P.B., Winckler, G., Stuut, J.B.W., Bradtmiller, L.I., 2013. The magnitude, timing and abruptness of changes in North African dust deposition over the last 20,000 yr. Earth And Planetary Science Letters 371-372, 163-176.

  10. Summer African Dust and Florida Thunder Storms: Are CRYSTAL-FACE Anvils Typical of the Subtropics?

    NASA Astrophysics Data System (ADS)

    Sassen, K.; Campbell, J. R.; Prospero, J. M.

    2003-12-01

    The Florida peninsula can be viewed as an outdoor laboratory for the study of the indirect effects of aerosols on the properties of deep convective clouds, and the possible subsequent impact on precipitation. Depending on the seasonal weather patters affecting the area, sources of aerosols can be continental, smoke-produced, oceanic, and, as long known, of Saharan Desert origin. During the recent CRYSTAL-FACE field campaign, a variety of in situ and remote sensing evidence shows that after transport across the mid-Atlantic Ocean, episodes of African dust were widespread in the region. This is a well-known summer-time phenomenon. In one study using aircraft ice nuclei (IN) data and ground-based polarization lidar measurements, the dust was observed to induce the glaciation of a slightly (about -5.0 to -8.0 degrees C) supercooled altocumulus cloud. Extrapolating the finding that African dust particles are especially active IN, it follows that the ingestion of boundary-layer Saharan aerosol could have a strong potential for modifying the microphysical content, dynamics and precipitation of summer thunderstorms in southern Florida. In the current study, we will attempt to identify connections between the characteristics of the intensively-studied thunderstorms and the nature of the dominant aerosols involved in cloud particle formation. As a first step, the near-continuous data record from the Micropulse Lidar, supplemented by Polarization Diversity Lidar data, will be used to monitor aerosol conditions. Backtrack and satellite analyzes, along with the University of Miami surface aerosol sampling record, will identify their source and likely cloud particle forming characteristics. The final stage of this research will search for correlations in in situ-derived cloud microphysical properties such as ice crystal concentration and type. If such connections are found, it must be recognized that the CRYSTAL-FACE dataset may not be representative of subtropical thunderstorms

  11. Using NASA EOS in the Arabian and Saharan Deserts to Examine Dust Particle Size and Spectral Signature of Aerosols

    NASA Astrophysics Data System (ADS)

    Brenton, J. C.; Keeton, T.; Barrick, B.; Cowart, K.; Cooksey, K.; Florence, V.; Herdy, C.; Luvall, J. C.; Vasquez, S.

    2012-12-01

    Exposure to high concentrations of airborne particulate matter can have adverse effects on the human respiratory system. Ground-based studies conducted in Iraq have revealed the presence of potential human pathogens in airborne dust. According to the Environmental Protection Agency (EPA), airborne particulate matter below 2.5μm (PM2.5) can cause long-term damage to the human respiratory system. Given the relatively high incidence of new-onset respiratory disorders experienced by US service members deployed to Iraq, this research offers a new glimpse into how satellite remote sensing can be applied to questions related to human health. NASA's Earth Observing System (EOS) can be used to determine spectral characteristics of dust particles, the depth of dust plumes, as well as dust particle sizes. Comparing dust particle size from the Sahara and Arabian Deserts gives insight into the composition and atmospheric transport characteristics of dust from each desert. With the use of NASA SeaWiFS DeepBlue Aerosol, dust particle sizes were estimated using Angström exponent. Brightness Temperature Difference (BTD) equation was used to determine the distribution of particle sizes, the area of the dust storm, and whether silicate minerals were present in the dust. The Moderate-resolution Imaging Spectroradiometer (MODIS) on Terra satellite was utilized in calculating BTD. Minimal research has been conducted on the spectral characteristics of airborne dust in the Arabian and Sahara Deserts. Mineral composition of a dust storm that occurred 17 April 2008 near Baghdad was determined using imaging spectrometer data from the Jet Propulsion Laboratory Spectral Library and EO-1 Hyperion data. Mineralogy of this dust storm was subsequently compared to that of a dust storm that occurred over the Bodélé Depression in the Sahara Desert on 7 June 2003.

  12. Dust emissions created by low-level rotary-winged aircraft flight over desert surfaces

    NASA Astrophysics Data System (ADS)

    Gillies, J. A.; Etyemezian, V.; Kuhns, H.; McAlpine, J. D.; King, J.; Uppapalli, S.; Nikolich, G.; Engelbrecht, J.

    2010-03-01

    There is a dearth of information on dust emissions from sources that are unique to U.S. Department of Defense testing and training activities. Dust emissions of PM 10 and PM 2.5 from low-level rotary-winged aircraft travelling (rotor-blade ≈7 m above ground level) over two types of desert surfaces (i.e., relatively undisturbed desert pavement and disturbed desert soil surface) were characterized at the Yuma Proving Ground (Yuma, AZ) in May 2007. Fugitive emissions are created by the shear stress of the outflow of high speed air created by the rotor-blade. The strength of the emissions was observed to scale primarily as a function of forward travel speed of the aircraft. Speed affects dust emissions in two ways: 1) as speed increases, peak shear stress at the soil surface was observed to decline proportionally, and 2) as the helicopter's forward speed increases its residence time over any location on the surface diminishes, so the time the downward rotor-generated flow is acting upon that surface must also decrease. The state of the surface over which the travel occurs also affects the scale of the emissions. The disturbed desert test surface produced approximately an order of magnitude greater emission than the undisturbed surface. Based on the measured emission rates for the test aircraft and the established scaling relationships, a rotary-winged aircraft similar to the test aircraft traveling 30 km h -1 over the disturbed surface would need to travel 4 km to produce emissions equivalent to one kilometer of travel by a light wheeled military vehicle also traveling at 30 km h -1 on an unpaved road. As rotary-winged aircraft activity is substantially less than that of off-road vehicle military testing and training activities it is likely that this source is small compared to emissions created by ground-based vehicle movements.

  13. Desert Dust Layers Over Polluted Marine Boundary Layers: ACE-2 Measurements and ACE-Asia Plans

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Schmid, B.; Livingston, J. M.; Redemann, J.; Bergstrom, R. W.; Condon, Estelle P. (Technical Monitor)

    2000-01-01

    Aerosols in ACE-Asia are expected to have some commonalties with those in ACE-2, along with important differences. Among the commonalities are occurrences of desert dust layers over polluted marine boundary layers. Differences include the nature of the dust (yellowish in the East Asia desert outflow, vs. reddish-brown in the Sahara Outflow measured in ACE-2) and the composition of boundary-layer aerosols (e.g., more absorbing, soot and organic aerosol in-the Asian plume, caused by coal and biomass burning, with limited controls). In this paper we present ACE-2 measurements and analyses as a guide to our plans for ACE-2 Asia. The measurements include: (1) Vertical profiles of aerosol optical depth and extinction (380-1558 nm), and of water vapor column and concentration, from the surface through the elevated desert dust, measured by the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14); (2) Comparisons of airborne and shipborne sunphotometer optical depths to satellite-retrieved values, with and without desert dust; (3) Comparisons between airborne Sunphotometer optical depth and extinction spectra and those derived from coincident airborne in situ measurements of aerosol size distribution, scattering and absorption; (4) Comparisons between size distributions measured in situ and retrieved from sunphotometer optical depth spectra; (5) Comparisons between aerosol single scattering albedo values obtained by several techniques, using various combinations of measurements of backscatter, extinction, size distribution, scattering, absorption, and radiative flux. We show how analyses of these data can be used to address questions important to ACE-Asia, such as: (1) How do dust and other absorbing aerosols affect the accuracy of satellite optical depth retrievals? How important are asphericity effects? (2) How important are supermicron dust and seasalt aerosols to overall aerosol optical depth and radiative forcing? How well are these aerosols sampled by aircraft

  14. Effects of dust storms on microwave radiation based on satellite observation and model simulation over the Taklamakan desert

    NASA Astrophysics Data System (ADS)

    Ge, J.; Huang, J.; Weng, F.; Sun, W.

    2008-04-01

    Effects of dust particles on microwave radiation over the Taklamakan desert are studied with use of measurements from the Advanced Microwave Scanning Radiometer (AMSR-E) on the EOS Aqua satellite and a microwave radiation transfer model. Eight observed cases show that the signal from atmospheric dust can be separated from the surface radiation by the fact that the dust particles produce stronger scattering at high frequencies and depolarize the background desert signature. This result of satellite data is consistent with the model simulation.

  15. Effects of dust storms on microwave radiation based on satellite observation and model simulation over the Taklamakan desert

    NASA Astrophysics Data System (ADS)

    Ge, J.; Huang, J.; Weng, F.; Sun, W.

    2008-08-01

    Effects of dust particles on microwave radiation over the Taklamakan desert are studied with use of measurements from the Advanced Microwave Scanning Radiometer (AMSR-E) on the EOS Aqua satellite and a microwave radiation transfer model. Eight observed cases show that the signal from atmospheric dust can be separated from the surface radiation by the fact that the dust particles produce stronger scattering at high frequencies and depolarize the background desert signature. This result of satellite data is consistent with the model simulation.

  16. Possible Influence of Desert Dust on Seedability of Clouds in Israel.

    NASA Astrophysics Data System (ADS)

    Rosenfeld, Daniel; Farbstein, Hanan

    1992-07-01

    Experimental and operational cloud seeding in Israel has been conducted since 1961 by aircraft seeding of silver iodide (AgI) at cloud-base level along a line upwind of target areas. The first experiment, Israeli-1 (1961-67), had a crossover design. Its overall seeding effect was an enhancement of 15% of the rainfall in the target areas, significant at 0.9%. The second experiment, Israeli-2 (1969-75), had a generally similar crossover statistical design to that of Israeli-1 but with some modifications that allowed a separate evaluation of the north target area alone. The seeding effect obtained for the north alone was 13%, significant at 2.8%. Based on this, clouds in northern Israel have been seeded operationally since 1975, while randomized experimental seeding is continuing in the south as Israeli-3.Recent analyses of both targets of the Israeli-2 experiment indicated that rainfall was not enhanced in the south target area. Preliminary and intermediate analyses of Israeli-3 do not indicate rain enhancement in the south either.Reanalyses of the experiments, stratified by observations of dust haze, show an increase of 26% in Israeli-2 north on the 202 `no-dust' days and no effect on the remaining 182 `dust' days. According to Israeli-2 south and Israeli-3, the indicated seeding effects in the south were also more positive by 16% on the `no-dust' days than on the `dust' days.The statistical evidence suggests that dust, blown from the Sahara-Arabian deserts bordering the target area to the south (or something else that is associated with the dust), plays an important role in the natural precipitation processes such that seeding is beneficial only when this dust is absent.

  17. The Challenge of Modeling the Meteorology of Dust Emission: Lessons Learned from the Desert Storms Project

    NASA Astrophysics Data System (ADS)

    Knippertz, P.; Marsham, J. H.; Cowie, S. M.; Fiedler, S.; Heinold, B.; Jemmett-Smith, B. C.; Pantillon, F.; Schepanski, K.; Roberts, A. J.; Pope, R.; Gilkeson, C. A.; Hubel, E.

    2015-12-01

    Mineral dust plays an important role in the Earth system, but a reliable quantification of the global dust budget is still not possible due to a lack of observations and insufficient representation of relevant processes in climate and weather models. Five years ago, the Desert Storms project funded by the European Research Council set out to reduce these uncertainties. Its aims were to (1) improve the understanding of key meteorological mechanisms of peak wind generation in dust emission regions (particularly in northern Africa), (2) assess their relative importance, (3) evaluate their representation in models, (4) determine model sensitivities with respect to resolution and model physics, and (5) explore the usefulness of new approaches for model improvements. Here we give an overview of the most significant findings: (1) The morning breakdown of nocturnal low-level jets is an important emission mechanism, but details depend crucially on nighttime stability, which is often badly handled by models. (2) Convective cold pools are a key control on summertime dust emission over northern Africa, directly and through their influence on the heat low; they are severely misrepresented by models using parameterized convection. A new scheme based on downdraft mass flux has been developed that can mitigate this problem. (3) Mobile cyclones make a relatively unimportant contribution, except for northeastern Africa in spring. (4) A new global climatology of dust devils identifies local hotspots but suggests a minor contribution to the global dust budget in contrast to previous studies. A new dust-devil parameterization based on data from large-eddy simulations will be presented. (5) The lack of sufficient observations and misrepresentation of physical processes lead to a considerable uncertainty and biases in (re)analysis products. (6) Variations in vegetation-related surface roughness create small-scale wind variability and support long-term dust trends in semi-arid areas.

  18. The Challenge of Modelling the Meteorology of Dust Emission: Lessons Learned from the Desert Storms Project

    NASA Astrophysics Data System (ADS)

    Knippertz, Peter; Marsham, John H.; Cowie, Sophie; Fiedler, Stephanie; Heinold, Bernd; Jemmett-Smith, Bradley; Pantillon, Florian; Schepanski, Kerstin; Roberts, Alexander; Pope, Richard; Gilkeson, Carl; Hubel, Eva

    2016-04-01

    Mineral dust plays an important role in the Earth system, but a reliable quantification of the global dust budget is still not possible due to a lack of observations and insufficient representation of relevant processes in climate and weather models. Five years ago, the Desert Storms project funded by the European Research Council set out to reduce these uncertainties. Its aims were to (1) improve the understanding of key meteorological mechanisms of peak wind generation in dust emission regions (particularly in northern Africa), (2) assess their relative importance, (3) evaluate their representation in models, (4) determine model sensitivities with respect to resolution and model physics, and (5) explore the usefulness of new approaches for model improvements. Here we give an overview of the most significant findings: (1) The morning breakdown of nocturnal low-level jets is an important emission mechanism, but details depend crucially on nighttime stability, which is often badly handled by models. (2) Convective cold pools are a key control on summertime dust emission over northern Africa, directly and through their influence on the heat low; they are severely misrepresented by models using parameterized convection. A new scheme based on downdraft mass flux has been developed that can mitigate this problem. (3) Mobile cyclones make a relatively unimportant contribution, except for northeastern Africa in spring. (4) A new global climatology of dust devils identifies local hotspots but suggests a minor contribution to the global dust budget in contrast to previous studies. A new dust-devil parameterization based on data from large-eddy simulations will be presented. (5) The lack of sufficient observations and misrepresentation of physical processes lead to a considerable uncertainty and biases in (re)analysis products. (6) Variations in vegetation-related surface roughness create small-scale wind variability and support long-term dust trends in semi-arid areas.

  19. Inter-annual changes of Biomass Burning and Desert Dust and their impact over East Asia

    NASA Astrophysics Data System (ADS)

    DONG, X.; Fu, J. S.; Huang, K.

    2014-12-01

    Impact of mineral dust and biomass burning aerosols on air quality has been well documented in the last few decades, but the knowledge about their interactions with anthropogenic emission and their impacts on regional climate is very limited (IPCC, 2007). While East Asia is greatly affected by dust storms in spring from Taklamakan and Gobi deserts (Huang et al., 2010; Li et al., 2012), it also suffers from significant biomass burning emission from Southeast Asia during the same season. Observations from both surface monitoring and satellite data indicated that mineral dust and biomass burning aerosols may approach to coastal area of East Asia simultaneously, thus have a very unique impact on the local atmospheric environment and regional climate. In this study, we first investigated the inter-annual variations of biomass burning and dust aerosols emission for 5 consecutive years from 2006-2010 to estimate the upper and lower limits and correlation with meteorology conditions, and then evaluate their impacts with a chemical transport system. Our preliminary results indicated that biomass burning has a strong correlation with precipitation over Southeast Asia, which could drive the emission varying from 542 Tg in 2008 to 945 Tg in 2010, according to FLAMBE emission inventory (Reid et al., 2009). Mineral dust also demonstrated a strong dependence on wind filed. These inter-annual/annual variations will also lead to different findings and impacts on air quality in East Asia. Reference: Huang, K., et al. (2010), Mixing of Asian dust with pollution aerosol and the transformation of aerosol components during the dust storm over China in spring 2007, Journal of Geophysical Research-Atmospheres, 115. IPCC (2007), Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, New York. Li, J., et al. (2012), Mixing of Asian mineral dust with anthropogenic pollutants over East Asia: a model case study of a super-duststorm in

  20. Source Characterization of African Dust Using CCSEM Analysis

    NASA Astrophysics Data System (ADS)

    Rogers, R.; Hunt, A.; Oldfield, F.

    2013-12-01

    A preliminary investigation is underway to determine whether African dust is developed through Pedogenic or Aeolian processes. 85 dust samples were taken from the Sahel and Saharan region of Africa and analyzed using computer controlled scanning electron microscopy (CCSEM). Optimized secondary electron detectors (SED) and back-scattered electron detectors (BSED) with adjustable quadrants was used with a light element Peltier-cooled energy dispersive x-ray spectrometer. A variable pressure system was utilized for the analysis of insulating materials, which eliminated the need for special specimen coating to dissipate charge and remove artifacts. Data from these samples are being used to address two primary questions: (1) Can CCSEM technology accurately describe elemental compounds derived from dust samples and therefore derive mineral content and (2) Are African dusts created through Pedogenic or Aeolian processes. The creation of a 19-point elemental classification system was used to separate and analyze each of the 4000 data points that were taken from 85 samples. Initial findings show large amounts of Fe, Si, and Al-rich minerals. The Al-Si-rich minerals show a close correlation in relative elemental amounts. This is to be expected from clay minerals of the pyroxene group. The Fe, Si-rich minerals trend towards an inverse relationship, which is also consistent with iron oxides of the spinel group that generally consist of magnetite. Other elemental constituents within the samples include varying amounts of Ti, Ca, and K. An initial run of samples, 6 Burkina Soils and 6 Burkina Laterites, show a similarity in chemical composition, leading to the hypothesis that the Burkina Soils originated from the Burkina Laterites. As the experiment progresses we expect to see similar Aeolian processes contributing to the mineral content of other surface dusts. Further research on the effects of these wind driven dusts is needed to assess the potential health impacts and

  1. Technical Note: Optical properties of desert dust with non-spherical particles: data incorporated to OPAC

    NASA Astrophysics Data System (ADS)

    Koepke, P.; Gasteiger, J.; Hess, M.

    2015-02-01

    Mineral desert dust particles in general are no spheres and assuming spherical particles, instead of more realistic shapes, has significant effects on modeled optical dust properties and so on the belonging remote sensing procedures for desert dust and the derived radiative forcing. Thus in a new version of the data base OPAC (Optical Properties of Aerosols and Clouds; Hess et al., 1998), the optical properties of the mineral particles are modeled describing the particles as spheroids with size dependent aspect ratio distributions, but with the size distributions and the spectral refractive indices not changed against the previous version of OPAC. The spheroid assumption strongly improves the scattering functions, but pays regard to the limited knowledge on particle shapes in an actual case. The relative deviations of the phase functions of non-spherical mineral particles from those of spherical particles are up to +60% at scattering angles of about 130° and up to -60% in the backscatter region, but the deviations are generally small for optical properties that are independent of the scattering angle. The improved version of OPAC (4.0) is freely available under http://www.rascin.net/

  2. Sunlight Transmission through Desert Dust and Marine Aerosols: Diffuse Light Corrections to Sun Photometry and Pyrheliometry

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Livingston, J. M.; Dubovik, O.; Ramirez, S. A.; Wang, J.; Redemann, J.; Schmid, B.; Box, M.; Holben, B. N.

    2003-01-01

    Desert dust and marine aerosols are receiving increased scientific attention because of their prevalence on intercontinental scales and their potentially large effects on Earth radiation and climate, as well as on other aerosols, clouds, and precipitation. The relatively large size of desert dust and marine aerosols produces scattering phase functions that are strongly forward- peaked. Hence, Sun photometry and pyrheliometry of these aerosols are more subject to diffuse-light errors than is the case for smaller aerosols. Here we quantify these diffuse-light effects for common Sun photometer and pyrheliometer fields of view (FOV), using a data base on dust and marine aerosols derived from (1) AERONET measurements of sky radiance and solar beam transmission and (2) in situ measurements of aerosol layer size distribution and chemical composition. Accounting for particle non-sphericity is important when deriving dust size distribution from both AERONET and in situ aerodynamic measurements. We express our results in terms of correction factors that can be applied to Sun photometer and pyrheliometer measurements of aerosol optical depth (AOD). We find that the corrections are negligible (less than approximately 1% of AOD) for Sun photometers with narrow FOV (half-angle eta less than degree), but that they can be as large as 10% of AOD at 354 nm wavelength for Sun photometers with eta = 1.85 degrees. For pyrheliometers (which can have eta up to approximately 2.8 degrees), corrections can be as large as 16% at 354 nm. We find that AOD correction factors are well correlated with AOD wavelength dependence (hence Angstrom exponent). We provide best-fit equations for determining correction factors from Angstrom exponents of uncorrected AOD spectra, and we demonstrate their application to vertical profiles of multiwavelength AOD.

  3. Radiative Effects of African Dust and Smoke Observed from CERES and CALIOP Data

    NASA Technical Reports Server (NTRS)

    Yorks, John E.; McGill, Matt; Rodier, Sharon; Vaughan, Mark; Xu, Yongxiang; Hlavka, Dennis

    2009-01-01

    Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the Tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the Tropical Atlantic Ocean were analyzed for the month of July for three years (2006-2008) using collocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth s Radiant Energy System (CERES) instruments on the CALIPSO and Aqua satellites. Aerosol layer height and type can be more accurately determined using CALIOP data, through parameters such as cloud and aerosol layer height, optical depth and depolarization ratio, than data from atmospheric imagers used in previous cloud-aerosol interaction studies. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of 270.2 +/- 16.9 W/sq m and thin cirrus clouds had a SW radiative flux of 208.0 +/- 12.7 W/sq m. When dust aerosols interacted with clouds below 5 km, as determined from CALIPSO, the SW radiative flux decreased to 205.4 +/- 13.0 W/sq m. Similarly, smoke aerosols decreased the SW radiative flux of low clouds to a value of 240.0 +/- 16.6 W/sq m. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics. CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system.

  4. Environmental Sequencing of Biotic Components of Dust in the Chihuahuan Desert

    NASA Astrophysics Data System (ADS)

    Walsh, E.; Gill, T. E.; Rivas, J. A., Jr.; Leung, M. Y.; Mohl, J.

    2015-12-01

    A growing number of studies mark the role of wind in dispersing biota. Most of these approaches have used traditional methods to assess taxonomic diversity. Here we used next generation sequencing to characterize microbiota in dust collected from the Chihuahuan Desert. Atmospheric dust was collected during events during 2011-2014 using dry deposition collectors placed at two sites in El Paso Co., TX. In parallel experiments, we rehydrated subsamples of dust and conducted PCR amplifications using conserved primers for 16S and 18S ribosomal genes. Sequenced reads were de-multiplexed, quality filtered, and processed using QIIME. Taxonomy was assigned based on pairwise identity using BLAST for microbial eukaryotes. All samples were rarefied to a set number of sequences per sample prior to downstream analyses. Bioinformatic analysis of four of the dust samples yielded a diversity of biota, including zooplankton, bacteria, fungi, algae, and protists, but fungi predominate (>90% of both 10K and 3K reads). In our rehydrations of dust samples from the U.S. southwest nematodes, gastrotrichs, tardigrades, monogonont and bdelloid rotifers, branchiopods and numerous ciliates have been recovered. Variability in genetic diversity among samples is based, in part, on the source and extent of the particular dust event. We anticipate the same patterns will be seen in the complete data set. These preliminary results indicate that wind is a major transporter of not only fungi, bacteria and other unicellular organisms but may also be important in shaping the distribution patterns of multi-cellular organisms such as those that inhabit aquatic environments in the arid southwestern US.

  5. Climate change and climate systems influence and control the atmospheric dispersion of desert dust: implications for human health

    USGS Publications Warehouse

    Griffin, Dale W.; Ragaini, Richard C.

    2010-01-01

    The global dispersion of desert dust through Earth’s atmosphere is greatly influenced by temperature. Temporal analyses of ice core data have demonstrated that enhanced dust dispersion occurs during glacial events. This is due to an increase in ice cover, which results in an increase in drier terrestrial cover. A shorter temporal analysis of dust dispersion data over the last 40 years has demonstrated an increase in dust transport. Climate systems or events such as the North Atlantic Oscillation, the Indian Ocean subtropical High, Pacific Decadal Oscillation, and El Nino-Sothern Oscillation are known to influence global short-term dust dispersion occurrence and transport routes. Anthropogenic influences on dust transport include deforestation, harmful use of topsoil for agriculture as observed during the American Dust Bowl period, and the creation of dry seas (Aral Sea) and lakes (Lake Owens in California and Lake Chad in North Africa) through the diversion of source waters (for irrigation and drinking water supplies). Constituents of desert dust both from source regions (pathogenic microorganisms, organic and inorganic toxins) and those scavenged through atmospheric transport (i.e., industrial and agricultural emissions) are known to directly impact human and ecosystem health. This presentation will present a review of global scale dust storms and how these events can be both a detriment and benefit to various organisms in downwind environments.

  6. Impact of desert dust on the biogeochemistry of phosphorus in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Okin, Gregory S.; Mahowald, Natalie; Chadwick, Oliver A.; Artaxo, Paulo

    2004-06-01

    Leaching, biomass removal, and partitioning of phosphorus (P) into reservoirs not available to plants can limit the long-term productivity of terrestrial ecosystems. We evaluate the importance of atmospheric P inputs to the world's soils by estimating the total soil P turnover time with respect to dustborne P additions. Estimated turnover times range from ˜104 to ˜107 years. Our estimates provide a unique perspective on the importance and patterns of aeolian deposition to terrestrial landscapes. Dust source regions are areas of intense soil P cycling on large scales, but are too water-limited for this rapid cycling to have a major influence on ecosystem dynamics. By contrast, semiarid desert margins receive significant aeolian P from neighboring deserts and are likely influenced by dustborne P additions for the long-term maintenance of productivity. This is particularly true for the semiarid steppes of Africa and Eurasia. The prevalence of large dust sources in Africa and Eurasia indicates that these areas may generally be more influenced by dustborne P additions than soils in the Americas. Significant western hemisphere exceptions to this pattern occur on very old landscapes, such as the forests of the southeastern United States and the Amazon Basin. The Amazon Basin is highly dependent on aeolian deposition for the maintenance of long-term productivity. Dust deposition to terrestrial environments has not been constant with time. Variability in past P deposition related to geologically recent climate change may provide the strongest controls on present and future soil P in the Amazon and elsewhere.

  7. Influence of Desert Dust Intrusions on Ground-based and Satellite Derived Ultraviolet Irradiance in Southeastern Spain

    NASA Technical Reports Server (NTRS)

    Krotkov, Nickolay A.; Anton, Manuel; Valenzuela, Antonio; Roman, Roberto; Lyamani, Hassan; Arola, Antti; Olmo, Francisco J.; Alados-Arboledas

    2012-01-01

    The desert dust aerosols strongly affect propagation of solar radiation through the atmosphere, reducing surface irradiance available for photochemistry and photosynthesis. This paper evaluates effects of desert dust on surface UV erythemal irradiance (UVER), as measured by a ground-based broadband UV radiometer and retrieved from the satellite Ozone Monitoring Instrument (OMI) at Granada (southern Spain) from January 2006 to December 2010. The dust effects are characterized by the transmittance ra tio of the measured UVER to the corresponding modeled clear sky value. The transmittance has an exponential dependency on aerosol optical depth (AOD), with minimum values of approximately 0.6 (attenuation of approximately 40%). The OMI UVER algorithm does not account for UV aerosol absorption, which results in overestimation of the ground-based UVER especially during dust episodes with a mean relative difference up to 40%. The application of aerosol absorption post-correction method reduces OMI bias up to approximately 13%. The results highlight great effect of desert dust on the surface UV irradiance in regions like southern Spain, where dust intrusions from Sahara region are very frequent.

  8. Application of wind-profiling radar data to the analysis of dust weather in the Taklimakan Desert.

    PubMed

    Wang, Minzhong; Wei, Wenshou; Ruan, Zheng; He, Qing; Ge, Runsheng

    2013-06-01

    The Urumqi Institute of Desert Meteorology of the China Meteorological Administration carried out an atmospheric scientific experiment to detect dust weather using a wind-profiling radar in the hinterland of the Taklimakan Desert in April 2010. Based on the wind-profiling data obtained from this experiment, this paper seeks to (a) analyze the characteristics of the horizontal wind field and vertical velocity of a breaking dust weather in a desert hinterland; (b) calculate and give the radar echo intensity and vertical distribution of a dust storm, blowing sand, and floating dust weather; and (c) discuss the atmosphere dust counts/concentration derived from the wind-profiling radar data. Studies show that: (a) A wind-profiling radar is an upper-air atmospheric remote sensing system that effectively detects and monitors dust. It captures the beginning and ending of a dust weather process as well as monitors the sand and dust being transported in the air in terms of height, thickness, and vertical intensity. (b) The echo intensity of a blowing sand and dust storm weather episode in Taklimakan is about -1~10 dBZ while that of floating dust -1~-15 dBZ, indicating that the dust echo intensity is significantly weaker than that of precipitation but stronger than that of clear air. (c) The vertical shear of horizontal wind and the maintenance of low-level east wind are usually dynamic factors causing a dust weather process in Taklimakan. The moment that the low-level horizontal wind field finds a shear over time, it often coincides with the onset of a sand blowing and dust storm weather process. (d) When a blowing sand or dust storm weather event occurs, the atmospheric vertical velocity tends to be of upward motion. This vertical upward movement of the atmosphere supported with a fast horizontal wind and a dry underlying surface carries dust particles from the ground up to the air to form blown sand or a dust storm. PMID:23099859

  9. Application of wind-profiling radar data to the analysis of dust weather in the Taklimakan Desert.

    PubMed

    Wang, Minzhong; Wei, Wenshou; Ruan, Zheng; He, Qing; Ge, Runsheng

    2013-06-01

    The Urumqi Institute of Desert Meteorology of the China Meteorological Administration carried out an atmospheric scientific experiment to detect dust weather using a wind-profiling radar in the hinterland of the Taklimakan Desert in April 2010. Based on the wind-profiling data obtained from this experiment, this paper seeks to (a) analyze the characteristics of the horizontal wind field and vertical velocity of a breaking dust weather in a desert hinterland; (b) calculate and give the radar echo intensity and vertical distribution of a dust storm, blowing sand, and floating dust weather; and (c) discuss the atmosphere dust counts/concentration derived from the wind-profiling radar data. Studies show that: (a) A wind-profiling radar is an upper-air atmospheric remote sensing system that effectively detects and monitors dust. It captures the beginning and ending of a dust weather process as well as monitors the sand and dust being transported in the air in terms of height, thickness, and vertical intensity. (b) The echo intensity of a blowing sand and dust storm weather episode in Taklimakan is about -1~10 dBZ while that of floating dust -1~-15 dBZ, indicating that the dust echo intensity is significantly weaker than that of precipitation but stronger than that of clear air. (c) The vertical shear of horizontal wind and the maintenance of low-level east wind are usually dynamic factors causing a dust weather process in Taklimakan. The moment that the low-level horizontal wind field finds a shear over time, it often coincides with the onset of a sand blowing and dust storm weather process. (d) When a blowing sand or dust storm weather event occurs, the atmospheric vertical velocity tends to be of upward motion. This vertical upward movement of the atmosphere supported with a fast horizontal wind and a dry underlying surface carries dust particles from the ground up to the air to form blown sand or a dust storm.

  10. Potential dust production from wind-erodible soils on the Southern High Plains and Chihuahuan Desert: preliminary figures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Blowing Dust is a common occurrence on the Southern High Plains of West Texas and Eastern New Mexico and the Chihuahuan Desert in southern New Mexico, Far West Texas, and northern Chihuahua, Mexico. We collected sixty two surface soil samples from locations identified on satellite imagery as produci...

  11. Mineralogical, chemical, and optical interrelationships of mineral dusts from desert source regions

    NASA Astrophysics Data System (ADS)

    Engelbrecht, J. P.; Moosmüller, H.; Pincock, S.; Jayanty, J.; Casuccio, G.

    2013-12-01

    The goal of the project was to provide information on the mineralogical, chemical and physical interrelationships of re-suspended mineral dust samples collected from global dust sources. Surface soil samples were previously collected from more than 64 desert sites, including the southwestern USA (12), Mali (3), Chad (3), Morocco (1), Canary Islands (8), Cape Verde (1), Djibouti (1), Afghanistan (3), Iraq (6), Kuwait (5), Qatar (1), UAE (1), Serbia (3), China (5), Namibia (3), Botswana (4), Australia (3), and Chile (1). The < 38 μm sieved fraction of each sample was re-suspended in an entrainment facility, from which the airborne mineral dust could be sampled and analyzed. Instruments integrated into the entrainment facility included two PM10 and two PM2.5 filter samplers, a beta attenuation gauge for the continuous measurement of PM10 and PM2.5 particulate mass fractions, an aerodynamic particle size (APS) analyzer, and a three wavelength (405, 532, 781nm) photoacoustic instrument with integrating reciprocal nephelometer for monitoring aerosol absorption and scattering coefficients during the re-suspension process. Filter sample media included Teflon membrane and quartz fiber filters for chemical analysis (71 species), and Nuclepore filters for individual particle analysis by Scanning Electron Microscopy (SEM). The < 38 μm sieved fractions were also analyzed by X-ray diffraction for their mineral content while the > 38 μm, < 125 μm fractions were further mineralogically characterized by optical microscopy. We will be presenting results on the optical measurements, showing the relationship between single scattering albedo (SSA) at three different wavelengths, and chemical as well as mineralogical content and interrelationships, of the entrained dust samples. Information from this data base will be available for research in global climate, remote sensing, visibility, and health (medical geology).

  12. Long-range transport of North African dust to the eastern United States

    NASA Astrophysics Data System (ADS)

    Perry, Kevin D.; Cahill, Thomas A.; Eldred, Robert A.; Dutcher, Dabrina D.; Gill, Thomas E.

    1997-05-01

    The long-range transport of North African dust to the Middle East, Europe, South America, and the Caribbean has been well documented during the past 25 years. With the advent of routine collection and analysis of fine aerosols at national parks, monuments, and wilderness areas in the continental United States, these North African dust incursions can now be tracked, characterized, and quantified across much of the eastern half of the United States. Identification of the North African source of these dust episodes is confirmed by mass distribution measurements, a characteristic Al/Ca ratio, isentropic backward air mass trajectories, and sequential plots of the spatial distribution of the dust plumes. North African dust incursions into the continental United States persist for ˜10 days and occurred, on average, 3 times per year from 1992 to 1995. Fine soil mass usually exceeds 10 μg m-3 during these dust episodes and dominates local fine soil dust by an order of magnitude or more, even in the so-called "dust bowl" states of the central United States. Size-resolved measurements of elemental composition taken during July 1995 indicate that the mass mean diameter of the transported North African dust is <1 μm. The high mass scattering efficiency and abundant particle surface area associated with these submicron soil aerosols could have important consequences for both the radiative balance of the region and the chemistry of the local aerosols during summer when the long-range transport of North African dust to the United States is most common.

  13. Remote sensing of desert dust aerosols over the Sahel : potential use for health impact studies

    NASA Astrophysics Data System (ADS)

    Deroubaix, A. D.; Martiny, N. M.; Chiapello, I. C.; Marticorena, B. M.

    2012-04-01

    Since the end of the 70's, remote sensing monitors the desert dust aerosols due to their absorption and scattering properties and allows to make long time series which are necessary for air quality or health impact studies. In the Sahel, a huge health problem is the Meningitis Meningococcal (MM) epidemics that occur during the dry season : the dust has been suspected to be crucial to understand their onsets and dynamics. The Aerosol absorption Index (AI) is a semi-quantitative index derived from TOMS and OMI observations in the UV available at a spatial resolution of 1° (1979-2005) and 0.25° (2005-today) respectively. The comparison of the OMI-AI and AERONET Aerosol Optical thickness (AOT) shows a good agreement at a daily time-step (correlation ~0.7). The comparison of the OMI-AI with the Particle Matter (PM) measurement of the Sahelian Dust Transect is lower (~0.4) at a daily time-step but it increases at a weekly time-step (~0.6). The OMI-AI reproduces the dust seasonal cycle over the Sahel and we conclude that the OMI-AI product at a 0.25° spatial resolution is suitable for health impact studies, especially at a weekly epidemiological time-step. Despite the AI is sensitive to the aerosol altitude, it provides a daily spatial information on dust. A preliminary investigation analysis of the link between weekly OMI AI and weekly WHO epidemiological data sets is presented in Mali and Niger, showing a good agreement between the AI and the onset of the MM epidemics with a constant lag (between 1 and 2 week). The next of this study is to analyse a deeper AI time series constituted by TOMS and OMI data sets. Based on the weekly ratios PM/AI at 2 stations of the Sahelian Dust Transect, a spatialized proxy for PM from the AI has been developed. The AI as a proxy for PM and other climate variables such as Temperature (T°), Relative Humidity (RH%) and the wind (intensity and direction) could then be used to analyze the link between those variables and the MM epidemics

  14. A rock-magnetic study of coral skeletons: A record of African dust deposition in the Caribbean

    NASA Astrophysics Data System (ADS)

    Nigro, P. M.; Clement, B. M.; Halley, R.; Helmle, K.; Swart, P.; Dodge, R.

    2008-05-01

    Aeolian African dust from the Saharan-Sahel deserts significantly influences the climate and ecology of the Caribbean region. Large summer dust storms produce mass quantities of air-born, clay-rich material (containing significant iron-oxide components), that are transported over the Atlantic Ocean and deposited in the Caribbean. We present here the results of a rock magnetic study of cores of Scleractinian corals, including a Montastraea annularis collected in Culebra, Puerto Rico on July of 1991, a M. faveolata collected off the coast of St. Vincent (Bequia) on November of 2002, and a Siderastrea radians collected off the coast of Cape Verde on July of 2002. Thin slabs (~5mm) were cut from these cores and x-rayed to reveal annual density banding. Small samples centered over each annual high-density band were cut from the slabs. These samples were then subjected to a series of standard rock magnetic experiments, including Anhysteretic Remanent Magnetization (ARM) acquisition and demagnetization, and Isothermal Remanent Magnetization (IRM) acquisition and demagnetization. Records of both ARMs and IRMs reveal coherent signals that vary with coral age. The IRM acquisition curves demonstrate the presence of two carriers of magnetization in most samples; a low-coercivity component consistent with the presence of magnetite or maghemite and a high-coercivity component consistent with the presence of hematite. Unmixing the IRM acquisition curves differentiates the magnetic components and yields a record of high-coercivity input that we interpret as a record of African dust. Preliminary data from the M. annularis core show a link between high and low variability in the high-coercivity component when compared with the historical record of dust flux to the Caribbean and with the Soudano-Sahel Precipitation Index (SSPI) over a time period of fifty years (1941-1990). High variability is displayed from 1941 through 1950 and 1965 through 1990 whereas low variability is displayed

  15. Optical properties of non-spherical desert dust particles in the terrestrial infrared - An asymptotic approximation approach

    NASA Astrophysics Data System (ADS)

    Klüser, Lars; Di Biagio, Claudia; Kleiber, Paul D.; Formenti, Paola; Grassian, Vicki H.

    2016-07-01

    Optical properties (extinction efficiency, single scattering albedo, asymmetry parameter and scattering phase function) of five different desert dust minerals have been calculated with an asymptotic approximation approach (AAA) for non-spherical particles. The AAA method combines Rayleigh-limit approximations with an asymptotic geometric optics solution in a simple and straightforward formulation. The simulated extinction spectra have been compared with classical Lorenz-Mie calculations as well as with laboratory measurements of dust extinction. This comparison has been done for single minerals and with bulk dust samples collected from desert environments. It is shown that the non-spherical asymptotic approximation improves the spectral extinction pattern, including position of the extinction peaks, compared to the Lorenz-Mie calculations for spherical particles. Squared correlation coefficients from the asymptotic approach range from 0.84 to 0.96 for the mineral components whereas the corresponding numbers for Lorenz-Mie simulations range from 0.54 to 0.85. Moreover the blue shift typically found in Lorenz-Mie results is not present in the AAA simulations. The comparison of spectra simulated with the AAA for different shape assumptions suggests that the differences mainly stem from the assumption of the particle shape and not from the formulation of the method itself. It has been shown that the choice of particle shape strongly impacts the quality of the simulations. Additionally, the comparison of simulated extinction spectra with bulk dust measurements indicates that within airborne dust the composition may be inhomogeneous over the range of dust particle sizes, making the calculation of reliable radiative properties of desert dust even more complex.

  16. Identifying African dust sources that contribute to the seasonal cycles of dust transport to the Caribbean Basin and South America.

    NASA Astrophysics Data System (ADS)

    Prospero, J. M.; Ginoux, P. A.; Molinie, J.

    2014-12-01

    Decades of aerosol measurements on Barbados have yielded a detailed picture of African mineral dust transport to the Caribbean Basin that shows a strong seasonal cycle with a maximum in boreal summer and a minimum in winter. Recently Prospero et al. (Global Biogeochemical Cycles, 2014) presented 10 years (2002 - 2011) of aerosol measurements made at Cayenne, French Guiana, along with concurrent dust measurements on Barbados. The Cayenne study, coupled with satellite products and other evidence, shows that during spring African dust is carried to a broad region of northeastern South America in quantities comparable to, or greater than, those measured at Barbados in summer. Various lines of evidence suggest that the sources that impact on Cayenne in spring are mainly in the Sahel region, including the Bodélé Depression. In summer transport to Barbados is believed to be most affected by emissions that lie in more northerly regions. Thus the record of measurements at Cayenne and Barbados provide a data set that could be used to test the ability of dust transport models to replicate the seasonal shift of dust sources and the consequent impact on transport to these two sites. Here we attempt to link the measurements at Cayenne and Barbados to specific source regions using the GFDL global climate model (Donner et al., 2011) which simulates aerosol mass distributions for dust and other aerosol components. Winds are nudged with the NCEP re-analysis as in Li et al. (2008). The model is run repeatedly over the years 1999-2010, activating dust sources in only one North African country in each run (e.g., Mali, Mauritania, Algeria, Niger, etc.). The model accurately depicts the strong seasonal contrast in dust transport to Barbados and Cayenne and shows the changing impact of African sources over the course of the year. In our presentation we will discuss the model results and compare them to the measurements at the receptor sites. It is notable that during the dust seasons at

  17. A Combined Observational and Modeling Approach to Study Modern Dust Transport from the Patagonia Desert to East Antarctica

    NASA Technical Reports Server (NTRS)

    Gasso, S.; Stein, A.; Marino, F.; Castellano, E.; Udisti, R.; Ceratto, J.

    2010-01-01

    The understanding of present atmospheric transport processes from Southern Hemisphere (SH) landmasses to Antarctica can improve the interpretation of stratigraphic data in Antarctic ice cores. In addition, long range transport can deliver key nutrients normally not available to marine ecosystems in the Southern Ocean and may trigger or enhance primary productivity. However, there is a dearth of observational based studies of dust transport in the SH. This work aims to improve current understanding of dust transport in the SH by showing a characterization of two dust events originating in the Patagonia desert (south end of South America). The approach is based on a combined and complementary use of satellite retrievals (detectors MISR, MODIS, GLAS ,POLDER, OMI,), transport model simulation (HYSPLIT) and surface observations near the sources and aerosol measurements in Antarctica (Neumayer and Concordia sites). Satellite imagery and visibility observations confirm dust emission in a stretch of dry lakes along the coast of the Tierra del Fuego (TdF) island (approx.54deg S) and from the shores of the Colihue Huapi lake in Central Patagonia (approx.46deg S) in February 2005. Model simulations initialized by these observations reproduce the timing of an observed increase in dust concentration at the Concordia Station and some of the observed increases in atmospheric aerosol absorption (here used as a dust proxy) in the Neumayer station. The TdF sources were the largest contributors of dust at both sites. The transit times from TdF to the Neumayer and Concordia sites are 6-7 and 9-10 days respectively. Lidar observations and model outputs coincide in placing most of the dust cloud in the boundary layer and suggest significant de- position over the ocean immediately downwind. Boundary layer dust was detected as far as 1800 km from the source and approx.800 km north of the South Georgia Island over the central sub-Antarctic Atlantic Ocean. Although the analysis suggests the

  18. From dust to varnish: Geochemical constraints on rock varnish formation in the Negev Desert, Israel

    NASA Astrophysics Data System (ADS)

    Goldsmith, Yonaton; Stein, Mordechai; Enzel, Yehouda

    2014-02-01

    Chemical compositions of rock varnish from the Negev Desert of Israel and local settled dust were used to constrain the mechanisms of varnish formation and patterns of Mn enrichment and accumulation in the varnish. Rock varnish was sampled from coeval, undisturbed prehistoric flint artifacts along a south-north climatic transect (˜30-120 mm/yr of rain). Our analyses indicate that Mn, Ba and Pb in the varnish are significantly enriched (˜100×) in respect to the local settling dust and that Mn content systematically fluctuates with depth in the varnish. The varnish and settled dust data combined with basic thermodynamic and kinetic reasoning are used to constrain the following geochemical model of rock varnish formation: dust accumulates in micro-basins on exposed rock surfaces, under pH ˜8 (common Negev value) and during wetting by dew and rain, Mn in the dust is mobilized and leached to a depth of ˜5 μm under the varnish surface where Hollandite Mn-oxides precipitate and are adsorbed onto and between the porous clay minerals that comprise most of the varnish. During its mobile phase Mn-oxide is negatively charged and adsorbs rare earth elements. Once the solution dries abrasion removes the upper, weakly cemented dust sediment, which contains mainly Si, Al and Fe (which are not mobile at pH ˜8). Ca is also removed in large quantities. Mn, Ba, Pb and the REE are deposited at a depth and thus, protected from erosion. Reoccurrences of these processes result in a noticeable accumulation of these elements, but not of Si, Al or Fe. The alternating Mn-rich and Mn-poor laminas form as a result of a competition between the leaching rate of Mn and the adhesion rate of the clay minerals. When moisture is high (low), lamina with high (low) Mn/clay mineral ratio forms. The oxidation states involved in the varnish formation are unknown, therefore, to use Morgan's calculations we must assume, in agreement with the thermodynamic considerations (presented above), that during

  19. From dust to varnish: Geochemical constraints on rock varnish formation in the Negev Desert, Israel

    NASA Astrophysics Data System (ADS)

    Goldsmith, Yonaton; Stein, Mordechai; Enzel, Yehouda

    2014-02-01

    Chemical compositions of rock varnish from the Negev Desert of Israel and local settled dust were used to constrain the mechanisms of varnish formation and patterns of Mn enrichment and accumulation in the varnish. Rock varnish was sampled from coeval, undisturbed prehistoric flint artifacts along a south-north climatic transect (˜30-120 mm/yr of rain). Our analyses indicate that Mn, Ba and Pb in the varnish are significantly enriched (˜100×) in respect to the local settling dust and that Mn content systematically fluctuates with depth in the varnish. The varnish and settled dust data combined with basic thermodynamic and kinetic reasoning are used to constrain the following geochemical model of rock varnish formation: dust accumulates in micro-basins on exposed rock surfaces, under pH ˜8 (common Negev value) and during wetting by dew and rain, Mn in the dust is mobilized and leached to a depth of ˜5 μm under the varnish surface where Hollandite Mn-oxides precipitate and are adsorbed onto and between the porous clay minerals that comprise most of the varnish. During its mobile phase Mn-oxide is negatively charged and adsorbs rare earth elements. Once the solution dries abrasion removes the upper, weakly cemented dust sediment, which contains mainly Si, Al and Fe (which are not mobile at pH ˜8). Ca is also removed in large quantities. Mn, Ba, Pb and the REE are deposited at a depth and thus, protected from erosion. Reoccurrences of these processes result in a noticeable accumulation of these elements, but not of Si, Al or Fe. The alternating Mn-rich and Mn-poor laminas form as a result of a competition between the leaching rate of Mn and the adhesion rate of the clay minerals. When moisture is high (low), lamina with high (low) Mn/clay mineral ratio forms. The oxidation states involved in the varnish formation are unknown, therefore, to use Morgan's calculations we must assume, in agreement with the thermodynamic considerations (presented above), that during

  20. Desert dust and anthropogenic aerosol interactions in the Community Climate System Model coupled-carbon-climate model

    SciTech Connect

    Mahowald, Natalie; Rothenberg, D.; Lindsay, Keith; Doney, Scott C.; Moore, Jefferson Keith; Randerson, James T.; Thornton, Peter E; Jones, C. D.

    2011-02-01

    Coupled-carbon-climate simulations are an essential tool for predicting the impact of human activity onto the climate and biogeochemistry. Here we incorporate prognostic desert dust and anthropogenic aerosols into the CCSM3.1 coupled carbon-climate model and explore the resulting interactions with climate and biogeochemical dynamics through a series of transient anthropogenic simulations (20th and 21st centuries) and sensitivity studies. The inclusion of prognostic aerosols into this model has a small net global cooling effect on climate but does not significantly impact the globally averaged carbon cycle; we argue that this is likely to be because the CCSM3.1 model has a small climate feedback onto the carbon cycle. We propose a mechanism for including desert dust and anthropogenic aerosols into a simple carbon-climate feedback analysis to explain the results of our and previous studies. Inclusion of aerosols has statistically significant impacts on regional climate and biogeochemistry, in particular through the effects on the ocean nitrogen cycle and primary productivity of altered iron inputs from desert dust deposition.

  1. Synergy of multispectral and multisensors satellite observations to evaluate desert aerosol transport and impact of dust deposition on inland waters: study case of Lake Garda

    NASA Astrophysics Data System (ADS)

    Di Nicolantonio, Walter; Cazzaniga, Ilaria; Cacciari, Alessandra; Bresciani, Mariano; Giardino, Claudia

    2015-01-01

    The capabilities of different Earth Observation multispectral satellites are employed for detecting and tracking of desert dust coming from North Africa toward the Northern Italy area and for evaluating the impact of Saharan dust deposition in inland waters, such as those of Lake Garda. Absorbing and scattering spectral optical properties of desert aerosol in the atmospheric windows in the ultraviolet, visible-near-infrared, and infrared spectral ranges are exploited in the dust retrieval performed by OMI/Aura, MODIS/Terra-Aqua, and SEVIRI/MSG satellite sensors. Therefore, the direct link between dust deposition and increase in phytoplankton abundance has been assessed retrieving MERIS-based chlorophyll-a (chl-a) concentration for the desert dust events. Estimates of the increased chl-a in the lake have been derived with values in concentration from 30% to 170%. AERONET sun-photometer measurements, gravimetric particulate matter samplings, in situ chl-a concentration and surface temperature are employed to select events and assess the presence of desert dust and recognize a corresponding increase of the phytoplankton abundance in the analyzed inland waters. The improved observational features that will be provided by the next European Sentinels missions, namely Sentinel-2, 3, 4, 5P, together with MTG-I (Imager) and MTG-S (Sounder) will allow better monitoring atmospheric constituents and studying the environmental impacts of desert dust transport.

  2. Elemental and ionic composition of atmospheric aerosols in the dust storm season in Mongolian Gobi Desert

    NASA Astrophysics Data System (ADS)

    Soyol-Erdene, T. O.; Shagjjamba, D.; Hong, S.; Sarangerel, E.; Byambatsogt, K.

    2014-12-01

    TSP (Total Suspended Particulate) PM10 (particle size smaller than 10 μm) and PM2.5 (particle size smaller than 2.5 μm) aerosol samples in the dust storm session in Mongolian Gobi Desert were collected and their water soluble ionic and elemental composition were elaborated in demonstrating the mixing of mineral aerosol with pollution aerosol. During the sampling period (5-15 April, 2014) the dust storm peaked on 14 April, in which the highest concentrations of PM10 and PM2.5 were 250.1 and 33.4 respectively. The water soluble anions (SO42-, NO3-, Cl- and HCO3- and PO43-) and cations (Na+, K+, NH4+, Ca2+, Mg2+ and Li+) of the samples were determined by ion chromatograph. Elemental composition for 48 elements determined by using X-ray fluorescence analyzer. For the PM2.5 samples, concentrations of V, Ge, As, Se, Br, Ag, Hg, Tl, Bi were less than instrumental detection limit and Cr, Co, Cu, Nb, Mo, Sb, I, Ba, Ce, Hf, W, Au, Pb were determined only in a few samples. Other elements were observed in most samples. For the PM2.5-10 samples, concentrations of Ge, As, Se, Br, Ag, Hf, Tl were less than instrumental detection limit and V, Co, Nb, Mo, I, Ce, W, Pb were determined only small samples. Others are determined in most samples. Aerosol sources, sources fractions (mineral and pollution), and mixing of aerosols from various sources will be investigated by further data analyses.

  3. Remobilization of southern African desert dune systems by twenty-first century global warming.

    PubMed

    Thomas, David S G; Knight, Melanie; Wiggs, Giles F S

    2005-06-30

    Although desert dunes cover 5 per cent of the global land surface and 30 per cent of Africa, the potential impacts of twenty-first century global warming on desert dune systems are not well understood. The inactive Sahel and southern African dune systems, which developed in multiple arid phases since the last interglacial period, are used today by pastoral and agricultural systems that could be disrupted if climate change alters twenty-first century dune dynamics. Empirical data and model simulations have established that the interplay between dune surface erodibility (determined by vegetation cover and moisture availability) and atmospheric erosivity (determined by wind energy) is critical for dunefield dynamics. This relationship between erodibility and erosivity is susceptible to climate-change impacts. Here we use simulations with three global climate models and a range of emission scenarios to assess the potential future activity of three Kalahari dunefields. We determine monthly values of dune activity by modifying and improving an established dune mobility index so that it can account for global climate model data outputs. We find that, regardless of the emission scenario used, significantly enhanced dune activity is simulated in the southern dunefield by 2039, and in the eastern and northern dunefields by 2069. By 2099 all dunefields are highly dynamic, from northern South Africa to Angola and Zambia. Our results suggest that dunefields are likely to be reactivated (the sand will become significantly exposed and move) as a consequence of twenty-first century climate warming.

  4. In situ and Remote Sensing Characterization of California Wildfires and Nevada Desert Dust

    NASA Astrophysics Data System (ADS)

    Air, Dambar S.

    Atmospheric aerosols exert significant influence on the climate and cause problems in human health and ecosystem. This dissertation reports aerosol physical and optical properties obtained from ground based remote sensing instruments, the Multifilter Rotating Shadowband Radiometer (MFRSR) and Cimel sun photometer, and in-situ measurements from photoacoustic (PA) instruments. The measurements were performed during California Rim fire of 2013, desert storm of 2013, and clear sky days. A 2-stream radiation transfer model and Mie theory were used to calculate the retrieved values of solar irradiances and aerosol optical properties. The ground based measurements were also compared with the satellite (Terra MODIS, Aqua MODIS and Deep Blue) measurements. The aerosol optical properties retrieved with the MFRSR show excellent agreement with those obtained with a co-located Cimel sun photometer. However, the comparison with the satellite measurements indicates significant departure from the ground based measurements. The values of the aerosol optical depth (AOD) and Angstrom exponent (AE) during the Rim fire event remained higher than clear sky days due to the presence of smoke particles in the atmosphere. However, the values of AOD during the dust storm were higher but the AE become lower than the clear sky days due to the presence of large particles in the atmosphere. The concentration of the fine mode (diameter less than 1 micron) dominates over the coarse mode (diameter greater than 1 micron) particles during the Rim fire, while coarse particles were more prevalent during dust storm. Back trajectory analysis during the Rim fire indicated that the southerly wind brought the plumes of smoke which originated at California Rim fire toward Reno. Similarly, the back trajectory analysis during the dust storm suggested that the dust was generated from the Humboldt sink and traveled towards Reno. The single scattering albedo (SSA) was found to decrease with wavelength due to the

  5. Optical characteristics of biomass burning and desert dust over the Western Mediterranean during summer: a case study

    NASA Astrophysics Data System (ADS)

    Basart, Sara; Sicart, Michaël; María Baldasano, José; Lane, Diego; Comerón, Adolfo

    2013-04-01

    The present contribution reports on the aerosol vertical distributions in Barcelona (Spain) which were obtained when very high aerosol concentrations were observed on summer 2012. An EARLINET lidar system and AERONET sunphotometer located in Barcelona performed intensive measurements in the framework of the ACTRIS (Aerosols, Clouds, and Trace gases Research InfraStructure Network) project. The data that were collected allow the characterization of the optical properties of the aerosols in this region, benefiting from the synergy of various remote sensing instruments. Due to its location in the Mediterranean basin, Barcelona metropolitan area is influenced by two major aerosol source regions: Europe and the Western Mediterranean Basin, as a major source of anthropogenic pollutants, and North Africa, as a principal source of natural dust. As a result, the composition of atmospheric aerosols in Barcelona station is a mixing of aerosols. During the period between 1 - 2 July, AOD reached high values (~ 0.5). In addition to anthropogenic local contributions, other aerosols long-range transported were also detected. Between 1 - 3 July, strong forest fires occurred in Alicante where advected to Barcelona area. On the other hand, between 28th June and 1st July, the northeastern Iberian Peninsula was affected by the intrusion of Saharan dust. The presence of Saharan dust was successfully forecasted by the BSC-DREAM8b dust regional model. MODIS and AERONET data, as well as air-mass backward trajectories confirmed the existence of biomass burning and desert dust in the case examined. Desert dust was detected between 2 and 4 km (above sea level, a.s.l) with maximum dust concentrations at ~ 4 km a.s.l on 1st June. On the other hand, favourable meteorological conditions made possible that biomass burning from Alicante was southern advected to Barcelona during the study period.

  6. Detection of dust and sandstorms from Taklamakan Desert to Japan by using MODIS mosaic images

    NASA Astrophysics Data System (ADS)

    Kato, Yoshinobu

    2008-12-01

    In recent years, the number of days which dust and sandstorms (DSS) events were observed is increasing in Japan, Korea, China and Mongolia. The Aerosol Vapor Index (AVI) method is a DSS detection method. The AVI is defined as AVI=Tb32-Tb31 for MODIS data of Terra and Aqua satellites, where Tb31 is the brightness temperature of band 31 (10.780-11.280μm) and Tb32 is that of band 32 (11.770-12.270μm). The MODIS mosaic images of true-color, AVI and thermal images are made for the detection of DSS from Taklamakan Desert to Japan. The detection of DSS is possible both at daytime and night, because the AVI method is used. The density of DSS is classified into six levels from 0 (DSS none) to 5 (DSS strong) according to the AVI values. The DSS phenomena during 6-11 April 2006 are analyzed by using the mosaic images of Terra-MODIS. The number of pixels, which is approximately equal to the area of square kilometers, at each level of DSS density is measured. The AVI value at sea is about 0.2-2.3K lower than that at land, because of the influence of water vapor. In daytime, the generation place of DSS hidden under the cloud can be estimated by comparing AVI image with true-color and thermal images.

  7. Derivation of an observation-based map of North African dust emission

    SciTech Connect

    Evan, Amato T.; Fiedler, Stephanie; Zhao, Chun; Menut, Laurent; Schepanski, Kerstin; Flamant, C.; Doherty, Owen

    2015-03-01

    Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodélé depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Aïr and Hoggar Mountains, making this area the second most important region of emission within North Africa.

  8. Effects of an extreme desert dust event on the spectral ultraviolet irradiance at El Arenosillo (Spain)

    NASA Astrophysics Data System (ADS)

    Antón, M.; Sorribas, M.; Bennouna, Y.; Vilaplana, J. M.; Cachorro, V. E.; GröBner, J.; Alados-Arboledas, L.

    2012-02-01

    This paper analyzes the effects of an extreme Saharan dust event detected on 6 September 2007 on spectral UV irradiance recorded at El Arenosillo, South Spain. The intensity of the extreme event was detected using the aerosol optical depth (AOD) and Angström exponent series obtained by a Cimel Sun photometer operated at the study site in the framework of the Aerosol Robotic Network (AERONET). This Saharan dust event is characterized by its strong intensity, with a mean daily AOD value at 440 nm of 1.35 ± 0.40 (1.76 ± 0.03 around 13:00 UT). Additionally, a moderate decrease (˜15 Dobson units (1 DU = 2.69 × 1016 molecules cm-2)) in the total ozone column was recorded with a Brewer spectrophotometer during this episode. The spectral UV irradiance was measured from the transportable Quality Assurance of Spectral Ultraviolet Measurements in Europe (QASUME) through the development of a transportable unit reference spectroradiometer. The relative decrease of the UV irradiance at 320 nm on 6 September is about 50% (40%) with respect to days with low (moderate) aerosol loads. This attenuation slightly decreases with increasing wavelength above 315 nm. The relative differences between QASUME measurements and the spectral UV irradiance derived from the Ozone Monitoring Instrument (OMI) were calculated for the desert dust episode. This satellite instrument strongly overestimates the ground-based UV data recorded on 6 September, with differences between 138% at 305 nm and 72% at 380 nm. Finally, the aerosol forcing efficiency (AFE) is evaluated for UV-B (290-315 nm), UV-A (315-400 nm), and erythemal UV (290-400 nm, weighted by the CIE spectrum), showing a notable decrease (in absolute value) with increasing solar zenith angles (SZAs). For instance, the AFE values for the harmful UV-B irradiance change from -0.41 W/m2 per unit of AOD at 440 nm for a SZA of 30° to -0.21 W/m2 per unit of AOD for a SZA of 50°.

  9. What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions?

    PubMed

    De Longueville, Florence; Hountondji, Yvon-Carmen; Henry, Sabine; Ozer, Pierre

    2010-12-01

    This study aims to compare, on the one hand, the geographical distribution of the desert dust source areas, their contribution to quantities emitted into the atmosphere, the trajectories and the quantities deposited, with on the other hand the areas of research interest focused on the desert dust impacts on air quality and/or human health. Based on a systematic review of the literature using the ISI Web of Knowledge database, we found 231 articles published over the last decade on the desert dust impacts on air quality. Of these, 48% concerned Asian dust and 39% Saharan dust, with the remaining 13% divided between the other dust source areas. However, only one of these studies addressed the worsening air pollution in West Africa, even though it is very close to the Sahara, the greatest contributor to the global dust budget. Moreover, there have been very few studies (41) looking at the direct links between desert dust and human health; in this context too, no interest has been shown in West Africa. Yet this region is also among the areas in which morbidity rates have been noted to be far higher than those found in other regions of the world, and where respiratory infections alone account for more than 20% of the causes of infant mortality. This survey highlights a clear imbalance between those areas most exposed to dust and the most studied areas in terms of dust impacts. Given these findings and the often alarming results published about other regions of the world, we advocate a revival of interest in research on West Africa in order to achieve a better understanding of the desert dust impacts on air quality and health among the populations of this region.

  10. Middle East Health and Air Quality Utilizing NASA EOS in the Saharan and Arabian Deserts to Examine Dust Particle Size and Mineralogy of Aerosols

    NASA Technical Reports Server (NTRS)

    Keeton, Tiffany; Barrick, Bradley; Cooksey, Kirstin; Cowart, Kevin; Florence, Victoria; Herdy, Claire; Padgett-Vasquez, Steve; Luvall, Jeffrey; Molthan, Andrew

    2012-01-01

    Ground-based studies conducted in Iraq have revealed the presence of potential human pathogens in airborne dust. According to the Environmental Protection Agency (EPA), airborne particulate matter below 2.5micron (PM2.5) can cause long-term damage to the human respiratory system. NASA fs Earth Observing System (EOS) can be used to determine spectral characteristics of dust particles and dust particle sizes. Comparing dust particle size from the Sahara and Arabian Deserts gives insight into the composition and atmospheric transport characteristics of dust from each desert. With the use of NASA SeaWiFS DeepBlue Aerosol, dust particle sizes were estimated using Angstrom Exponent. Brightness Temperature Difference (BTD) equation was used to determine the area of the dust storm. The Moderate-resolution Imaging Spectroradiometer (MODIS) on Terra satellite was utilized in calculating BTD. Mineral composition of a dust storm that occurred 17 April 2008 near Baghdad was determined using imaging spectrometer data from the JPL Spectral Library and EO-1 Hyperion data. Mineralogy of this dust storm was subsequently compared to that of a dust storm that occurred over the Bodele Depression in the Sahara Desert on 7 June 2003.

  11. Differences in Fine- Coarse Aerosol Ratios in Convective and Non-Convective Dust Events in a Desert City

    NASA Astrophysics Data System (ADS)

    Gill, T. E.; Rivera Rivera, N. I.; Novlan, D. J.

    2014-12-01

    El Paso, Texas (USA) and Ciudad Juarez, Chihuahua (Mexico) form the Paso del Norte, the largest metropolitan area in North America's Chihuahuan Desert. The cities are subject to frequent dust storms presenting a hazard to local infrastructure and health, including synoptic-scale dust events during winter and spring, and dusty outflows from convective storms (haboobs) primarily during the summer. We evaluate particulate matter (PM2.5 and PM10) concentrations over a decade of convective and non-convective dust events, based on hourly aerosol data collected by Texas Commission on Environmental Quality (TCEQ) continuous air monitors in El Paso cross-referenced to weather observations from the USA National Weather Service. A total of 219 dust events (95 convective and 124 non-convective) events occurred between 2001 and 2010. The PM2.5/PM10 ratio was significantly higher (proportionally greater concentration of fine aerosols) in convective episodes and during summertime events than during non-convective dust events and dust episodes in other seasons, although overall concentrations of both PM2.5 and PM10 were higher in the non-convective events, which were also longer-lasting. These differences in fine/coarse aerosol ratios are likely related to different atmospheric stability conditions, and/or different mechanisms of dust particle entrainment and transport in haboobs versus non-convective dust events. Since visibility degradation and adverse human health effects are known to be exacerbated by to fine aerosol concentrations, thunderstorm-related dust events may present a proportionally greater hazard.

  12. Desert Dust Outbreaks in Southern Europe: Contribution to Daily PM10 Concentrations and Short-Term Associations with Mortality and Hospital Admissions

    PubMed Central

    Stafoggia, Massimo; Zauli-Sajani, Stefano; Pey, Jorge; Samoli, Evangelia; Alessandrini, Ester; Basagaña, Xavier; Cernigliaro, Achille; Chiusolo, Monica; Demaria, Moreno; Díaz, Julio; Faustini, Annunziata; Katsouyanni, Klea; Kelessis, Apostolos G.; Linares, Cristina; Marchesi, Stefano; Medina, Sylvia; Pandolfi, Paolo; Pérez, Noemí; Querol, Xavier; Randi, Giorgia; Ranzi, Andrea; Tobias, Aurelio; Forastiere, Francesco

    2015-01-01

    Background: Evidence on the association between short-term exposure to desert dust and health outcomes is controversial. Objectives: We aimed to estimate the short-term effects of particulate matter ≤ 10 μm (PM10) on mortality and hospital admissions in 13 Southern European cities, distinguishing between PM10 originating from the desert and from other sources. Methods: We identified desert dust advection days in multiple Mediterranean areas for 2001–2010 by combining modeling tools, back-trajectories, and satellite data. For each advection day, we estimated PM10 concentrations originating from desert, and computed PM10 from other sources by difference. We fitted city-specific Poisson regression models to estimate the association between PM from different sources (desert and non-desert) and daily mortality and emergency hospitalizations. Finally, we pooled city-specific results in a random-effects meta-analysis. Results: On average, 15% of days were affected by desert dust at ground level (desert PM10 > 0 μg/m3). Most episodes occurred in spring–summer, with increasing gradient of both frequency and intensity north–south and west–east of the Mediterranean basin. We found significant associations of both PM10 concentrations with mortality. Increases of 10 μg/m3 in non-desert and desert PM10 (lag 0–1 days) were associated with increases in natural mortality of 0.55% (95% CI: 0.24, 0.87%) and 0.65% (95% CI: 0.24, 1.06%), respectively. Similar associations were estimated for cardio-respiratory mortality and hospital admissions. Conclusions: PM10 originating from the desert was positively associated with mortality and hospitalizations in Southern Europe. Policy measures should aim at reducing population exposure to anthropogenic airborne particles even in areas with large contribution from desert dust advections. Citation: Stafoggia M, Zauli-Sajani S, Pey J, Samoli E, Alessandrini E, Basagaña X, Cernigliaro A, Chiusolo M, Demaria M, Díaz J, Faustini A

  13. No change in African dust transport over past 45 years

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-09-01

    The long-distance transport of dust around the planet has important implications for ecosystem stability and global climate dynamics. In some cases, most prominently the vast Amazon rainforest, travelling dust is the primary source of iron and phosphorous to otherwise nutrient-limited regions. Wind-swept sediments can affect the planetary albedo and sully the surface of icy regions driving increased melting. Therefore, understanding how ongoing climate change may affect the wind circulation patterns in major dust-generating regions is particularly important. Unfortunately, hostile environmental conditions in many of the important sources of dust mean that long-term wind speed and direction records from on-the-ground anemometers are nonexistent.

  14. African dust and the demise of Caribbean coral reefs

    USGS Publications Warehouse

    Shinn, E.A.; Smith, G.W.; Prospero, J.M.; Betzer, P.; Hayes, M.L.; Garrison, V.; Barber, R.T.

    2000-01-01

    The vitality of Caribbean coral reefs has undergone a continual state of decline since the late 1970s, a period of time coincidental with large increases in transatlantic dust transport. It is proposed that the hundreds of millions of tons/year of soil dust that have been crossing the Atlantic during the last 25 years could be a significant contributor to coral reef decline and may be affecting other ecosystems. Benchmark events, such as near synchronous Caribbean-wide mortalities of acroporid corals and the urchin Diadema in 1983, and coral bleaching beginning in 1987, correlate with the years of maximum dust flux into the Caribbean. Besides crustal elements, in particular Fe, Si, and aluminosilicate clays, the dust can serve as a substrate for numerous species of viable spores, especially the soil fungus Aspergillus. Aspergillus sydowii, the cause of an ongoing Caribbean-wide seafan disease, has been cultured from Caribbean air samples and used to inoculate sea fans.

  15. Evaluation of coral pathogen growth rates after exposure to atmospheric African dust samples

    USGS Publications Warehouse

    Lisle, John T.; Garrison, Virginia H.; Gray, Michael A.

    2014-01-01

    Laboratory experiments were conducted to assess if exposure to atmospheric African dust stimulates or inhibits the growth of four putative bacterial coral pathogens. Atmospheric dust was collected from a dust-source region (Mali, West Africa) and from Saharan Air Layer masses over downwind sites in the Caribbean [Trinidad and Tobago and St. Croix, U.S. Virgin Islands (USVI)]. Extracts of dust samples were used to dose laboratory-grown cultures of four putative coral pathogens: Aurantimonas coralicida (white plague type II), Serratia marcescens (white pox), Vibrio coralliilyticus, and V. shiloi (bacteria-induced bleaching). Growth of A. coralicida and V. shiloi was slightly stimulated by dust extracts from Mali and USVI, respectively, but unaffected by extracts from the other dust sources. Lag time to the start of log-growth phase was significantly shortened for A. coralicida when dosed with dust extracts from Mali and USVI. Growth of S. marcescens and V. coralliilyticus was neither stimulated nor inhibited by any of the dust extracts. This study demonstrates that constituents from atmospheric dust can alter growth of recognized coral disease pathogens under laboratory conditions.

  16. Composite analysis of dust impacts on African easterly waves in the Moderate Resolution Imaging Spectrometer era

    NASA Astrophysics Data System (ADS)

    Jury, Mark R.; Santiago, Myrna J.

    2010-08-01

    This study examines the synoptic scale impacts of African dust on easterly waves in the tropical northeast Atlantic. Moderate Resolution Imaging Spectrometer aerosol optical depth (AOD), National Oceanic and Atmospheric Administration products, and National Center for Environmental Prediction reanalysis fields in the Atlantic main hurricane development region (MDR) form the basis for statistical analysis of a limited set of cases objectively selected for the 2000-2008 hurricane seasons when thresholds are exceeded for sea surface temperature (SST), easterly wind shear, cyclonic vorticity, and upward motion. After ranking African easterly waves by AOD, the top (dusty) and bottom (clean) cases are studied as composite differences. African dust and subsidence cause temperatures to warm ˜3°C in the 700 hPa layer, while SSTs cause temperatures to cool, stabilizing the atmosphere. Increased AOD and strong (10 m s-1) 600 hPa easterly winds limit cloud efficiency through shear and oversupply of condensation nuclei. Vertical section composites demonstrate that warm dry subsident air coincides with the African dust plume in the latitudes 18°N-30°N. Hurricane reanalysis data indicate that higher AOD in the MDR reduces chances for the intensification of African easterly waves.

  17. Radiative Effect of Saharan Mineral Dust on the Nonlinear Dynamics of African Easterly Waves

    NASA Astrophysics Data System (ADS)

    Grogan, D.; Nathan, T. R.; Chen, S. H.

    2014-12-01

    The radiative effects of Saharan mineral dust aerosols on the nonlinear dynamics of African easterly waves (AEWs) are examined using the Weather Research and Forecasting Dust (WRFD) model. The WRFD model is governed by the Advanced Research WRF dynamical core, and continuity equations for twelve dust particle sizes that represent the spectrum of mineral dust aerosols observed in the atmosphere. To incorporate dust radiative effects in the model, aerosol optical properties (i.e. optical depth, single scattering albedo, and asymmetric parameters) for all dust sizes are inputted into the shortwave and longwave radiation schemes. By choosing zonal-mean distributions of zonal wind and temperature that are consistent with summer over Northwest Africa, idealized dry simulations explore the nonlinear behavior of AEWs in the presence of dust. The initial zonal-mean dust fields are represented as simple distributions that vary in structure and concentration, which are consistent with observed dust events over Africa. Specific AEW features investigated in the simulations include the evolution of wave energy, Eliassen-Palm fluxes, and spatial structures. Among the questions to be addressed are the following: How does the concentration and spatial distribution of the dust field affect the strength and timing of AEW amplitude saturation? What impact will the dust induced wave fluxes have on the horizontal or vertical shear of the zonal-mean AEJ? Does the interaction between the AEJ, AEW and dust affect the timing and location of the AEW trough, and thus the formation of critical latitudes? Answers to these questions will aid in the understanding and forecasting of AEWs, and their possible subsequent development into tropical storms.

  18. A Theoretical Framework for Understanding the Effects of Saharan Mineral Dust Aerosols on African Easterly Waves

    NASA Astrophysics Data System (ADS)

    Nathan, T. R.; Grogan, D.; Chen, S.

    2013-12-01

    Studies have shown that a large fraction of the intense hurricanes observed over the Atlantic Ocean originate as African easterly waves (AEWs). Of the many processes that affect the propagation, growth and structure of AEWs, the effects of Saharan mineral dust aerosols on AEWs remains an outstanding scientific problem. With this in mind, a new theoretical framework is presented that illuminates causal relationships between Saharan dust and the linear dynamics of AEWs. The framework is built on a quasi-geostrophic system governed by coupled equations for potential vorticity, temperature, and dust continuity. The radiative-dust heating rate accounts for both shortwave and longwave radiative transfer. The source of dust is due to surface emission, which depends on surface wind; the sinks of dust are due to sedimentation and dry deposition. A perturbation analysis yields analytical expressions for the propagation and growth characteristics of the model's AEWs. These expressions are functions of vertically and meridionally averaged wave activity, which depends on wave spatial structure, dust-radiative heating, and the background distributions of wind, temperature, and dust mixing ratio. More specifically, the propagation and growth of the AEWs depend on the amount of dust lofted from the surface by the wind, and the meridional and vertical gradients of the basic state dust distribution, which are modulated by the Doppler-shifted frequency. Idealized cases are presented that show the effects of Saharan dust on the propagation, group velocity, growth, structure, and wave fluxes of AEWs. The clarity of the expressions connecting dust aerosols to the linear properties of AEWs provides an important interpretive tool for analyzing results obtained from comprehensive model simulations of AEWs, such as those produced by the Weather Research and Forecasting (WRF) model.

  19. Fertilizing the Amazon and equatorial Atlantic with West African dust

    NASA Astrophysics Data System (ADS)

    Bristow, Charlie S.; Hudson-Edwards, Karen A.; Chappell, Adrian

    2010-07-01

    Atmospheric mineral dust plays a vital role in Earth's climate and biogeochemical cycles. The Bodélé Depression in Chad has been identified as the single biggest source of atmospheric mineral dust on Earth. Dust eroded from the Bodélé is blown across the Atlantic Ocean towards South America. The mineral dust contains micronutrients such as Fe and P that have the potential to act as a fertilizer, increasing primary productivity in the Amazon rain forest as well as the equatorial Atlantic Ocean, and thus leading to N2 fixation and CO2 drawdown. We present the results of chemical analysis of 28 dust samples collected from the source area, which indicate that up to 6.5 Tg of Fe and 0.12 Tg of P are exported from the Bodélé Depression every year. This suggests that the Bodélé may be a more significant micronutrient supplier than previously proposed.

  20. Travertine from Egypt's Western Desert: a terrestrial proxy for North African paleohydrology and paleoclimate during the Quaternary

    NASA Astrophysics Data System (ADS)

    Jimenez, G.; Crossey, L. J.; Karlstrom, K. E.; Polyak, V. J.; Asmerom, Y.

    2013-12-01

    The 'Green Sahara' pluvial phases that overprinted North African aridity during the Pleistocene are well recognized in tropical and Mediterranean marine records. Comparatively few studies have investigated the terrestrial expression of these pluvials, though, in part because of the paucity of paleohydrology archives in the desert. In this study, we show that travertine in Egypt's Western Desert constitutes a unique terrestrial proxy for the North African hydrologic cycle. In the Western Desert, travertine (defined inclusively as chemically-precipitated continental carbonate) deposits in paleo-oasis springs during times of high hydrologic head. Since head increases as meteoric precipitation falls in southern groundwater recharge areas, large-scale travertine accumulations can record pluvial episode durations as well as their geochemical characteristics. We built a database of new and previously-published U/Th ages from five paleo-oasis areas spanning a north-south gradient through the Western Desert. Integrating this geochronology with stable isotope and 87Sr/86Sr geochemistry of travertine samples, we present a terrestrial record of North African pluvial periods for the last ~650 ka. We show that groundwater sources for travertine remain constant through space and time, implying hydrological similarity between pluvial periods. The timing of travertine deposition is inconsistent over shorter (~10 ka) timescales in the various paleo-oases, though, suggesting that local hydrology may obscure the travertine response to pluvials. However, we observe significant travertine deposition across several areas between approximately 100 to 300 ka, and 450 to 600 ka, with a hiatus in between; we interpret these depositional 'peaks' to correspond with maxima in the 400-ka component of eccentricity. Thus, contrary to prior literature, we find that travertine deposition in the Western Desert, and thus pluvial occurrence, responds to orbitally-paced changes in equatorial insolation

  1. The Influence of Precipitation-Driven Annual Plant Growth on Dust Emission in the Mojave Desert, USA

    NASA Astrophysics Data System (ADS)

    Urban, F. E.; Reynolds, R. L.; Fulton, R. E.

    2009-12-01

    Sparsely vegetated drylands are an important source for dust emission. However, little detail is known about dust generation in response to timing of precipitation and the consequent effects on soil and vegetation dynamics in these settings. This deficiency is especially acute at intermediate landscape scales, tens of meters to several hundred meters. It is essential to consider dust emission at this scale, because it links dust generation at scales of grains and wind tunnels with regional-scale dust examined using remotely sensed data from satellites. Three sites of slightly different geomorphic settings in the vicinity of Soda (dry) Lake were instrumented (in 1999) with meteorological and sediment transport sensors to measure wind erosion through saltating particle detection during high winds. Changes in vegetation in close proximity to the instrumented sites were bi-annually documented through measurements of plant type, cover, and repeat photographic imagery. Whereas high wind events are the dominant driver of saltation and dust emission, emissive conditions prevail only when annual plants are sparse or absent. Results show that wind erosion and dust emission at two study sites are highly variable and that such variability is dominantly related to vegetation type and cover as influenced by the amount and timing of antecedent precipitation. Secondary controls on dust emission are availability of new sediment related to flood deposits at the sites and seasonally differential wind strength. At sites where annual plants respond quickly and advantageously to precipitation, emissive conditions typically shut down because of vegetation growth within two to three months. This cover of annual plants, even when dead, persists in the desert landscape as a stabilizing agent for varying amounts of time, ten months to three years depending on the amount and vegetation type and subsequent input of precipitation and further annual plant growth. The lasting stabilization effect

  2. Bulk composition of northern African dust and its source sediments — A compilation

    NASA Astrophysics Data System (ADS)

    Scheuvens, Dirk; Schütz, Lothar; Kandler, Konrad; Ebert, Martin; Weinbruch, Stephan

    2013-01-01

    This paper presents a review of bulk compositional data of northern African dust and its potential source sediments and includes elemental, isotope and mineralogical data. Northern African dust represents about one half of the total global atmospheric mineral dust burden, and its uplift, transport and deposition have strong impacts on climate and various terrestrial and marine ecosystems. The chemical data set shows, that an 'average northern African dust' exhibits comparable Si, Fe and Mn contents with respect to the average composition of the upper continental crust, is slightly depleted in the alkali metals K and Na, and enriched in Ti and P. However, the complete data set yields clear evidence that northern African dust and its source sediments are compositionally heterogeneous on a regional scale and that this heterogeneity can be used to differentiate between major potential source areas on the basis of so-called source markers. An evaluation of these compositional fingerprints shows that the following parameters and especially their combination are effective in the discrimination of the most active source areas in northern Africa: ratio of (Ca + Mg)/Fe [wt.%], calcite (or carbonate) content, palygorskite occurrence and abundance, illite/kaolinite ratio, ?Nd(0) value, and 87Sr/86Sr ratio. For example, the data set corroborates previous ideas, which assign carbonate-, illite- and palygorskite-rich mineral dusts to north(west)ern source regions. Because most of the above listed source markers do not change substantially during transport, even far-traveled dusts may be assigned to specific potential source areas in northern Africa. Some limitations of the presented data set are also discussed. Our compilation reveals some substantial gaps in the knowledge of the composition of source sediments and mineral dusts from important potential source areas that should be filled in the future. The here compiled data set can be used as a reference frame, when

  3. The relationship between gorgonian coral (Cnidaria: Gorgonacea) diseases and African dust storms

    USGS Publications Warehouse

    Weir-Brush, J. R.; Garrison, V.H.; Smith, G.W.; Shinn, E.A.

    2004-01-01

    The number of reports of coral diseases has increased throughout the world in the last 20 years. Aspergillosis, which primarily affects Gorgonia ventalina and G. flabellum, is one of the few diseases to be characterized. This disease is caused by Aspergillus sydowii, a terrestrial fungus with a worldwide distribution. Upon infection, colonies may lose tissue, and ultimately, mortality may occur if the infection is not sequestered. The spores of A. sydowii are <5 ??m, small enough to be easily picked up by winds and dispersed over great distances. Aspergillosis is prevalent in the Caribbean, and it appears that this primarily terrestrial fungus has adapted to a marine environment. It has been proposed that dust storms originating in Africa may be one way in which potential coral pathogens are distributed and deposited into the marine environments of the Caribbean. To test the hypothesis that African dust storms transport and deposit pathogens, we collected air samples from both dust storms and periods of nondust in St. John, U.S. Virgin Islands. Because we focused on fungal pathogens and used A. sydowii as a model, we isolated and cultured fungi on various types of media. Fungi including Aspergillus spp. were isolated from air samples taken from dust events and non-dust events. Twenty-three separate cultures and seven genera were isolated from dust event samples whereas eight cultures from five genera were isolated from non-dust air samples. Three isolates from the Virgin Islands dust event samples morphologically identified as Aspergillus spp. produced signs of aspergillosis in seafans, and the original pathogens were re-isolated from those diseased seafans fulfilling Koch's Postulates. This research supports the hypothesis that African dust storms transport across the Atlantic Ocean and deposit potential coral pathogens in the Caribbean.

  4. Distinct synoptic patterns and air masses responsible for long-range desert dust transport and sea spray in Palermo, Italy

    NASA Astrophysics Data System (ADS)

    Dimitriou, K.; Paschalidou, A. K.; Kassomenos, P. A.

    2016-09-01

    Undoubtedly, anthropogenic emissions carry a large share of the risk posed on public health by particles exposure in urban areas. However, natural emissions, in the form of desert dust and sea spray, are well known to contribute significantly to the PM load recorded in many Mediterranean environments, posing an extra risk burden on public health. In the present paper, we examine the synoptic climatology in a background station in Palermo, Italy, through K-means clustering of the mean sea-level pressure (MSLP) maps, in an attempt to associate distinct synoptic patterns with increased PM10 levels. Four-day backward trajectory analysis is then applied, in order to study the origins and pathways of air masses susceptible of PM10 episodes. It is concluded that a number of atmospheric patterns result in several kind of flows, namely south, west, and slow-moving/stagnant flows, associated with long-range dust transport and sea spray.

  5. Food searches and guiding structures in North African desert ants, Cataglyphis.

    PubMed

    Bolek, Siegfried; Wolf, Harald

    2015-06-01

    North African desert ants, Cataglyphis fortis, use path integration as their primary means of navigation. The ants also use landmarks when these are available to improve navigation accuracy. Extended landmarks, such as walls and channels, may serve further functions, for example, local guidance or triggering of local vectors. The roles of such structures were usually examined in homing animals but not during food searches. When searching for familiar feeding sites, Cataglyphis may show intriguing deviations from expected search performances. These may result from the presence of extended landmarks, namely experimental channels. Here we scrutinise this hypothesis of landmark guidance in food searches. We prevented the ants from seeing the channel walls by covering their eyes, except the dorsal rim area. This experiment was repeated in the open test field with an alley of black cylinders to extend our findings to a more normal foraging environment. Ants with covered eyes did not deviate from expected search performances, whereas ants with normal eyes extended their searches along the axis of the leading structures by 15-20%, in both channels and landmark alleys. This demonstrates that Cataglyphis orients along extended landmarks when searching for familiar food sources and alters its search pattern accordingly.

  6. Sensitivity of desert dust emission modelling to horizontal resolution: the example of the Bodélé Depression

    NASA Astrophysics Data System (ADS)

    Bouet, Christel; Cautenet, Guy; Marticorena, Béatrice; Bergametti, Gilles; Minvielle, Fanny; Schmechtig, Catherine; Laurent, Benoit

    2010-05-01

    Atmospheric aerosols are known to play an important role in the Earth's climate system. However, the quantification of aerosol radiative impact on the Earth's radiative budget is very complex because of the high variability in space and time of aerosol mass and particle number concentrations, and optical properties as well. In many regions, like in desert regions, dust is the largest contribution to aerosol optical thickness [Tegen et al., 1997]. Consequently, it appears fundamental to well represent mineral dust emissions to reduce uncertainties concerning aerosol radiative impact on the Earth's radiative budget. Recently, several studies (e.g. Prospero et al. [2002]) underlined that the Bodélé depression, in northern Chad, is probably the most important source of mineral dust in the world. However many models fail in simulating these large dust emissions. Indeed, dust emission is a threshold phenomenon mainly driven by the intensity of surface wind velocity. Realistic estimates of dust emissions then rely on the quality and accuracy of the surface wind fields. Koren and Kaufman [2004] showed that the reanalysis data (NCEP), which can be used as input data in numerical models, underestimates surface wind velocity in the Bodélé Depression by up to 50%. Such an uncertainty on surface wind velocity cannot allow an accurate simulation of the dust emission. In mesoscale meteorological models, global reanalysis datasets are used to initialize and laterally nudge the models that compute meteorological parameters (like wind velocity) with a finer spatial and temporal resolutions. The question arises concerning the precision of the wind speeds calculated by these models. Using the Regional Atmospheric Modeling System (RAMS, Cotton et al. [2003]) coupled online with the dust production model developed by Marticorena and Bergametti [1995] and recently improved by Laurent et al. [2008] for Africa, the influence of the horizontal resolution of the mesoscale meteorological

  7. The Mid-Holocene West African Monsoon strength modulated by Saharan dust and vegetation

    NASA Astrophysics Data System (ADS)

    Pausata, F. S. R.; Messori, G.; Zhang, Q.

    2015-12-01

    The West African Monsoon (WAM) is crucial for the socio-economic stability of millions of people living in the Sahel. Severe droughts have ravaged the region in the last three decades of the 20th century, highlighting the need for a better understanding of the WAM dynamics. One of the most dramatic changes in the WAM occurred between 15,000-5,000 years BP, when increased summer precipitation led to the so-called "Green Sahara" and to a reduction in dust emissions from the region. Previous studies have shown that variations in vegetation and soil type can have major impacts on precipitation. However, model simulations are still unable to fully reproduce the intensification and geographical expansion of the African monsoon during that period, even when vegetation over the Sahara is simulated. Here, we use a fully coupled simulation for 6000 years BP in which prescribed Saharan vegetation and dust concentrations are changed in turn. A close agreement with proxy records is obtained only when both Saharan vegetation and dust decrease are taken into account (Fig. 1). The dust reduction extends the monsoon's northern limit further than the vegetation-change case only (Fig. 2), by strengthening vegetation-albedo feedbacks and driving a deeper Saharan Heat Low. The dust reduction under vegetated Sahara conditions leads to a northward shift of the WAM extension that is about twice as large as the shift due to the changes in orbital forcing alone. We therefore conclude that accounting for changes in Saharan dust loadings is essential for improving model simulations of the MH WAM. The role of dust is also relevant when looking into the future, since Saharan dust emission may decrease owing to both direct and indirect anthropogenic impacts on land cover.

  8. On the cause of the correlation between West African dust outbreaks and Sahelian rainfall

    NASA Astrophysics Data System (ADS)

    Evan, A. T.; Flamant, C.

    2014-12-01

    A large body of work has shown, using both in-situ data and remote sensing products, that there is a negative correlation between Sahelian rainfall and African dust outbreaks that traverse the tropical Atlantic. One theory for this relationship is that drying out of the Sahel results in the activation of new dust sources. However, there is no direct evidence to support this theory, nor has any modeling study conclusively shown this to be the case. Another theory is that changes in the regional circulation associated with wet and dry periods of the Sahel results in this inverse proportionality between dust and rainfall. A new modeling study has provided compelling evidence to show that this latter theory may be closer to the truth. Here we show that the recent trends in dust from western Africa can be explained by examining changes in surface winds over source regions near the Air, Adrar, and Ouaddai mountains, and the Bodélé depression. Our analysis shows that the recent trends in dust are due to a slow down of the surface winds over the Air and Adrar source regions, and that this is a result of the simultaneous intensification of the low-level circulation of the Sahara Heat Low. Thus, coupling of Sahel rainfall and the Sahara Heat Low results in the correlation between dust and Sahel drought. Furthermore, we estimate future changes in dust from climate models via analysis of modeled changes in wind speeds over these regions. We find that one model in the Fifth Phase Coupled Model Intercomparison Project, the GFDL-CM3, accurately represents historical changes in wind speeds over these key source regions, and that in future scenarios this model shows a large and statistically significant increase in surface windspeeds over the Bodélé, suggesting an increase in African dust emission throughout the 21st Century.

  9. Long-range transport across the Atlantic in summertime does not enhance the hygroscopicity of African mineral dust

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Caquineau, S.; Desboeufs, K.; Laurent, B.; Maille, M.; Quiñones Rosado, M.; Vallejo, P.; Mayol-Bracero, O. L.; Formenti, P.

    2015-09-01

    We present the first direct evidence that the hygroscopic properties of super micron (>1 µm) African dust particles did not change despite undergoing long-range transport across the Atlantic toward the Caribbean. Concurrent measurements of chemical composition show that most of mineral dust was chemically unprocessed and externally mixed. A minor portion of mineral dust was internally mixed with sulfate and chloride (~13-24% by number) or aggregated with sea-salt particles (~3-6%). Only dust particles aggregated with sea salt showed significant hygroscopic growth above 75% relative humidity (RH), resulting in a decrease in extinction mass efficiency by up to a factor 2.2. All other dust particles did not take up significant amounts of water when exposed to up to 94% RH. These results demonstrate that the direct radiative effect of African dust in this region remained independent of RH and an external mixing state could be considered for evaluating the climate effects of dust.

  10. Exploiting quartz spectral signature for the detection of cloud-affected satellite infrared observations over African desert areas.

    PubMed

    Masiello, Guido; Serio, Carmine; Cuomo, Vincenzo

    2004-04-10

    It is shown that IMG (interferometric monitoring of greenhouse gases) spectra recorded over African and Arabian deserts clearly contain the fingerprint of quartz-rich soils. We illustrate how this spectral signature can be exploited to devise a suitable cloud-detection scheme to identify which infrared observations are affected by clouds. As a by-product, the scheme also allows one to identify the most likely underlying emitting surface type and provides a suitable first guess for the surface emissivity to be used, e.g., for the retrieval of geophysical parameters from high-spectral-resolution infrared radiance from space. The analysis has focused on African deserts because of their intrinsic relevance to numerical weather prediction and Earth's climate. Desert areas, like oceans, are poorly covered by the world meteorological radiosonde network and therefore are geographical regions for which the global coverage capability of satellites soundings is expected to provide better initializations for numerical weather prediction than are now available. Application of the cloud-detection scheme to IMG spectra has been considered, which demonstrates the good performance of the method.

  11. Saharan Desert Dust Radiative Impact On The Evolution of The Vertical Thermal Characteristics of The Atmosphere Over The Mediterranean

    NASA Astrophysics Data System (ADS)

    Iori, C.; Liberti, G. L.

    The passage of Saharan dust over the Mediterranean basin, represents the most in- tense and relatively frequent event for what concerns the tropospheric aerosols in that region. Transport of the crustal dusts from the Saharan surface to the mean Mediter- ranean troposphere happens inside air volumes belonging to the superficial layers of the Sahara desert. As a consequence, it is associated with anomalies both in the verti- cal thermodynamic structure as well as in the composition. The first one is due to the avvection of air volumes geographically and vertically belonging to a different region. The second one is due to the composition of the air volumes (water vapour, ozone and aerosol) different from the one of the unperturbed status. Due to the occurence of such anomalies a perturbation in the radiative balance is also expected, because of the in- teraction of water vapour, ozone and aerosol with the atmospheric radiation field and hence with the radiative balance of earth-atmosphere system. This study examine the relative contribution of radiative processes in the evolution of the vertical structure of the atmosphere during the occurence of a desert dust transport event (18-5-1999). In order to do that radiosoundings from a set of stations around the Mediterranean Sea as well as in the source area have been analysed for the spring 1999 to define a mean sta- tus and succesively characterize quantitatively the anomaly associated with the event. In parallel detailed description of vertical properties of the aerosols as well as of the other parameters of interest, available from the PAUR II campaign [Kourtidis et al., 2000], has been employed for computing with the CLIRAD RTM [Chou and Suarez 1999; Chou and Suarez 2001] the heating/cooling rate profiles. Computation have been performed for a day in presence of aerosol as well as for a relatively clear day in order to evaluate the desert dust contribution on the overall radiative effects. A detailed analysis of the

  12. Detection and Preliminary Assessment of Source Areas of the 15 December 2003 Dust Storm in the Chihuahuan Desert, Southwestern North America

    NASA Astrophysics Data System (ADS)

    Rivera Rivera, N. I.; Gill, T. E.; Bleiweiss, M. P.; Hand, J. L.; Dominguez A., M.; Ruiz, A.; Perez, A. E.; Emmert, S. P.; Lee, J. A.; Mulligan, K. R.

    2005-12-01

    Dust storms can disperse large quantities of fine aeolian sediment regionally and even globally. These extreme aerosol events frequently originate with multiple dust plumes developing simultaneously over a large region. Dust outbreaks originating in the southwestern USA and northern Mexico seasonally transport aerosols long distances across continental North America. However, dust sources in this region are not well characterized. Remote sensing data can be used to assess the frequency and magnitude of these dust events for potential impacts on climate, visibility and health-related air quality issues. We applied a technique that consists of examining visible spectral bands, as well as difference "split-window" images for far-infrared (far-IR) channels using a variety of satellite imagery (NOAA/GOES/GVAR/Imager, NOAA/POES/AVHRR and NASA/TERRA/MODIS). This technique was used to locate the origin of multiple dust plumes in the Chihuahuan Desert region of the southwestern United States and northwestern Mexico during a significant dust event that occurred on December 15, 2003. After dust sources were identified, we superimposed their locations on Landsat-7 images to assess surface features of these aeolian "hotspots," and visited many of these sites to determine the geomorphology, soil/sediment properties, and land use associated with these dust sources. Dust plumes in the Chihuahuan Desert on 15 December 2003 emanated from several land types, including saline playas, bare desert soils, disturbed/abandoned lands, and agricultural areas. In Mexico, sources included several sites along the edges of pluvial Lake Palomas near the contacts between sand sheets and lacustrine sediments, small dry lake beds (lagunas secas) and several sites in the Casas Grandes river basin in Chihuahua. In the United States, dust emission hotspots included dry, unvegetated saline playas (the White Sands near the E and SE edges of Lake Lucero, New Mexico, and the northern Salt Basin west of the

  13. Fugitive dust mitigation for PM{sub 10} attainment in the western Mojave Desert: Recommendations on revegetation

    SciTech Connect

    Grantz, D.A.; Vaughn, D.L. |; Roberts, E.

    1997-12-31

    Methods to suppress fugitive dust and associated violations of federal PM{sub 10} standards in the western Mojave Desert, following removal of native vegetation by tillage or overgrazing, have been under investigation by a multi-agency task force for several years. Interim recommendations are now possible for this area of high winds, low rainfall, and mostly arable soil with patchy blowing sand. There can be no guarantee of success in any revegetation program in the desert, but the greatest probability of success in this area can be attained by using the native shrub Atriplex canescens, whether direct seeded or transplanted. No additional nitrogen should be added, and excess nitrogen should be removed if possible, perhaps by a preliminary cropping of barley. This will itself stabilize the soil surface in the short term. Young plants should be protected from herbivory and the harsh elements by using plastic cones. Irrigation is helpful if available. In areas located near native populations of rabbitbrush annual plant cover should be burned but no tillage or other soil disturbance should be imposed, as this facilitates invasion of annual species, including russian thistle, and prevents establishment of rabbitbrush. In sandy areas, seeding with Indian ricegrass may be more effective than with A. canescens. For immediate, short-term, mitigation of blowing dust, furrowing alone and installation of windfences may be effective. Rainfall exhibits high annual variability in arid regions. Absence of fugitive dust emissions in rainy periods, associated with ground cover by annual vegetation, is unlikely to survive several years of low, but normal, rainfall. It is precisely during those periods when rainfall is adequate that long-term revegetation with shrubs has the best chance of success.

  14. Concentrations of Semivolatile Organic Compounds Associated with African Dust Air Masses in Mali, Cape Verde, Trinidad and Tobago, and the U.S. Virgin Islands, 2001-2008

    USGS Publications Warehouse

    Garrison, Virginia H.; Foreman, William T.; Genualdi, Susan A.; Majewski, Michael S.; Mohammed, Azad; Simonich, Staci Massey

    2011-01-01

    Every year, billions of tons of fine particles are eroded from the surface of the Sahara Desert and the Sahel of West Africa, lifted into the atmosphere by convective storms, and transported thousands of kilometers downwind. Most of the dust is carried west to the Americas and the Caribbean in the Saharan Air Layer (SAL). Dust air masses predominately impact northern South America during the Northern Hemisphere winter and the Caribbean and Southeastern United States in summer. Dust concentrations vary considerably temporally and spatially. In a dust source region (Mali), concentrations range from background levels of 575 micrograms per cubic meter (mu/u g per m3) to 13,000 mu/u g per m3 when visibility degrades to a few meters (Gillies and others, 1996). In the Caribbean, concentrations of 200 to 600 mu/u g per m3 in the mid-Atlantic and Barbados (Prospero and others, 1981; Talbot and others, 1986), 3 to 20 mu/u g per m3 in the Caribbean (Prospero and Nees, 1986; Perry and others, 1997); and >100 mu/u g per m3 in the Virgin Islands (this dataset) have been reported during African dust conditions. Mean dust particle size decreases as the SAL traverses from West Africa to the Caribbean and Americas as a result of gravitational settling. Mean particle size reaching the Caribbean is <1 micrometer (mu/u m) (Perry and others, 1997), and even finer particles are carried into Central America, the Southeastern United States, and maritime Canada. Particles less than 2.5 mu/u m diameter (termed PM2.5) can be inhaled deeply into human lungs. A large body of literature has shown that increased PM2.5 concentrations are linked to increased cardiovascular/respiratory morbidity and mortality (for example, Dockery and others, 1993; Penn and others, 2005).

  15. Effect of the temperature variation between Mediterranean Sea and Syrian deserts on the dust storm occurrence in the western half of Iran

    NASA Astrophysics Data System (ADS)

    Amanollahi, Jamil; Kaboodvandpour, Shahram; Qhavami, Samira; Mohammadi, Bakhtiyar

    2015-03-01

    Recent dust storms have caused crises in western Iran, which necessitate the prediction of these storms a few days before their occurrence. This is the first study of its type that analyzes the effect of temperature differences between the Mediterranean Sea surface and Syrian deserts (creation zone of the dusts storms) on the formation of dust storms in the west of Iran. The study also seeks to identify any changes in the atmospheric temperature created by the extreme dust storm of July 5, 2009 in west of Iran (Sanandaj City). In this study, the MODIS images from 2000 to 2008, and particulate matter data of the Sanandaj station from 2008 to 2012 were utilized to identify the dust storm days. The Mediterranean Sea surface temperature data were extracted from NOAA satellites for dust storm days up to four days preceding them. The web site of world weather was used to obtain the temperature of Damascus, Syria station as the selected land station. According to the results, significant differences were acquired between surface temperatures of Damascus station and the Mediterranean Sea in the dust storm days and up to three days before them. As the dust storm days approached, a rising trend was observed in changes of the temperature difference between land and sea. Thermal map analysis of the atmosphere of the Syrian deserts on July 5, 2009 showed significant decrease in the levels of 1000 hPa and 500 hPa but for the days preceding it no significant changes were observed. It can be concluded that the temperature difference between the Mediterranean Sea surface and the Syrian deserts four days before the dust storm occurrences is the important factor in predicting this event.

  16. Red-ox speciation and mixing state of iron in individual African dust particles

    NASA Astrophysics Data System (ADS)

    Deboudt, Karine; Gloter, Alexandre; Mussi, Alexandre; Flament, Pascal

    2012-06-01

    The Fe distribution in African dust particles collected in Senegal (North-Western Africa) during the African Monsoon Multidisciplinary Analysis Special Observation Period 0 (AMMA-"SOP 0," February 2006) was assessed using individual particle analysis (Scanning and Transmission Electron Microscopy respectively equipped with X-ray Spectrometry (SEM-EDX) and Electron Energy Loss Spectrometry (TEM-EELS)). Senegal is not a dust source area; the chemical composition of collected dusts indicates that they originate primarily in the North-Western Sahara, which is consistent with previous studies of the area. Fe can be present inside dust particles as a substitution element in the crystalline lattice of aluminosilicate, but a high proportion (62%) of aluminosilicate Fe-containing particles are also found as an internal mixture of aluminosilicate with Fe oxide grains (including both oxide and hydroxide species). The 3D structure of such particles obtained by tomography reveals that these Fe-rich inclusions are often found at the surface of aluminosilicate particles but that some are also included inside particles. These Fe oxide grains can result from crustal earth or atmospheric processes during long-range transport. FeIII is dominant in both the aluminosilicate matrix and the Fe oxide grains (FeIII/Σ Fe ratio = 76.8% and 90.0%, respectively, on average), with notable heterogeneities of Fe valence inside grains at a nanometer scale.

  17. Control of Lunar and Martian dust--experimental insights from artificial and natural cyanobacterial and algal crusts in the desert of Inner Mongolia, China.

    PubMed

    Liu, Yongding; Cockell, Charles S; Wang, Gaohong; Hu, Chunxiang; Chen, Lanzhou; De Philippis, Roberto

    2008-02-01

    Studies on the colonization of environmentally extreme ground surfaces were conducted in a Mars-like desert area of Inner Mongolia, People's Republic of China, with microalgae and cyanobacteria. We collected and mass-cultured cyanobacterial strains from these regions and investigated their ability to form desert crusts artificially. These crusts had the capacity to resist sand wind erosion after just 15 days of growth. Similar to the surface of some Chinese deserts, the surface of Mars is characterized by a layer of fine dust, which will challenge future human exploration activities, particularly in confined spaces that will include greenhouses and habitats. We discuss the use of such crusts for the local control of desert sands in enclosed spaces on Mars. These experiments suggest innovative new directions in the applied use of microbe-mineral interactions to advance the human exploration and settlement of space.

  18. Control of Lunar and Martian dust--experimental insights from artificial and natural cyanobacterial and algal crusts in the desert of Inner Mongolia, China.

    PubMed

    Liu, Yongding; Cockell, Charles S; Wang, Gaohong; Hu, Chunxiang; Chen, Lanzhou; De Philippis, Roberto

    2008-02-01

    Studies on the colonization of environmentally extreme ground surfaces were conducted in a Mars-like desert area of Inner Mongolia, People's Republic of China, with microalgae and cyanobacteria. We collected and mass-cultured cyanobacterial strains from these regions and investigated their ability to form desert crusts artificially. These crusts had the capacity to resist sand wind erosion after just 15 days of growth. Similar to the surface of some Chinese deserts, the surface of Mars is characterized by a layer of fine dust, which will challenge future human exploration activities, particularly in confined spaces that will include greenhouses and habitats. We discuss the use of such crusts for the local control of desert sands in enclosed spaces on Mars. These experiments suggest innovative new directions in the applied use of microbe-mineral interactions to advance the human exploration and settlement of space. PMID:18240967

  19. Long-range transport of mineral dust in the global atmosphere: Impact of African dust on the environment of the southeastern United States

    PubMed Central

    Prospero, Joseph M.

    1999-01-01

    Soil dust is a major constituent of airborne particles in the global atmosphere. Dust plumes frequently cover huge areas of the earth; they are one of the most prominent and commonly visible features in satellite imagery. Dust is believed to play a role in many biogeochemical processes, but the importance of dust in these processes is not well understood because of the dearth of information about the global distribution of dust and its physical, chemical, and mineralogical properties. This paper describes some features of the large-scale distribution of dust and identifies some of the geological characteristics of important source areas. The transport of dust from North Africa is presented as an example of possible long-range dust effects, and the impact of African dust on environmental processes in the western North Atlantic and the southeastern United States is assessed. Dust transported over long distances usually has a mass median diameter <10 μm. Small wind-borne soil particles show signs of extensive weathering; consequently, the physical and chemical properties of the particles will greatly depend on the weathering history in the source region and on the subsequent modifications that occur during transit in the atmosphere (typically a period of a week or more). To fully understand the role of dust in the environment and in human health, mineralogists will have to work closely with scientists in other disciplines to characterize the properties of mineral particles as an ensemble and as individual particles especially with regard to surface characteristics. PMID:10097049

  20. Long-Range Transport of Mineral Dust in the Global Atmosphere: Impact of African Dust on the Environment of the Southeastern United States

    NASA Astrophysics Data System (ADS)

    Prospero, Joseph M.

    1999-03-01

    Soil dust is a major constituent of airborne particles in the global atmosphere. Dust plumes frequently cover huge areas of the earth; they are one of the most prominent and commonly visible features in satellite imagery. Dust is believed to play a role in many biogeochemical processes, but the importance of dust in these processes is not well understood because of the dearth of information about the global distribution of dust and its physical, chemical, and mineralogical properties. This paper describes some features of the large-scale distribution of dust and identifies some of the geological characteristics of important source areas. The transport of dust from North Africa is presented as an example of possible long-range dust effects, and the impact of African dust on environmental processes in the western North Atlantic and the southeastern United States is assessed. Dust transported over long distances usually has a mass median diameter <10 μ m Small wind-borne soil particles show signs of extensive weathering; consequently, the physical and chemical properties of the particles will greatly depend on the weathering history in the source region and on the subsequent modifications that occur during transit in the atmosphere (typically a period of a week or more). To fully understand the role of dust in the environment and in human health, mineralogists will have to work closely with scientists in other disciplines to characterize the properties of mineral particles as an ensemble and as individual particles especially with regard to surface characteristics.

  1. Altitude-resolved shortwave and longwave radiative effects of desert dust in the Mediterranean during the GAMARF campaign: Indications of a net daily cooling in the dust layer

    NASA Astrophysics Data System (ADS)

    Meloni, D.; Junkermann, W.; Sarra, A.; Cacciani, M.; De Silvestri, L.; Di Iorio, T.; Estellés, V.; Gómez-Amo, J. L.; Pace, G.; Sferlazzo, D. M.

    2015-04-01

    Desert dust interacts with shortwave (SW) and longwave (LW) radiation, influencing the Earth radiation budget and the atmospheric vertical structure. Uncertainties on the dust role are large in the LW spectral range, where few measurements are available and the dust optical properties are not well constrained. The first airborne measurements of LW irradiance vertical profiles over the Mediterranean were carried out during the Ground-based and Airborne Measurements of Aerosol Radiative Forcing (GAMARF) campaign, which took place in spring 2008 at the island of Lampedusa. The experiment was aimed at estimating the vertical profiles of the SW and LW aerosol direct radiative forcing (ADRF) and heating rates (AHR), taking advantage of vertically resolved measurements of irradiances, meteorological parameters, and aerosol microphysical and optical properties. Two cases, characterized respectively by the presence of a homogeneous dust layer (3 May, with aerosol optical depth, AOD, at 500 nm of 0.59) and by a low aerosol burden (5 May, with AOD of 0.14), are discussed. A radiative transfer model was initialized with the measured vertical profiles and with different aerosol properties, derived from measurements or from the literature. The simulation of the irradiance vertical profiles, in particular, provides the opportunity to constrain model-derived estimates of the AHR. The measured SW and LW irradiances were reproduced when the model was initialized with the measured aerosol size distributions and refractive indices. For the dust case, the instantaneous (solar zenith angle, SZA, of 55.1°) LW-to-SW ADRF ratio was 23% at the surface and 11% at the top of the atmosphere (TOA), with a more significant LW contribution on a daily basis (52% at the surface and 26% at TOA), indicating a relevant reduction of the SW radiative effects. The AHR profiles followed the aerosol extinction profile, with comparable peaks in the SW (0.72 ± 0.11 K d-1) and in the LW (-0.52 ± 0.12 K d-1

  2. Geochemical fingerprint of desert surface sediments and aeolian dust exported from southern South America

    NASA Astrophysics Data System (ADS)

    Gili, S.; Gaiero, D. M.; Jweda, J.; Koestner, E.; Chemale, F.; Kaplan, M. R.; Goldstein, S. L.

    2012-12-01

    Wind-transported dust is a tracer of atmospheric circulation and also provides important information about the climatic conditions prevailing in dust source areas. Understanding the origin of mineral dust deposited in different environments (e.g., continent, ocean, polar ice sheet) and the variability of its concentration and composition, can be used as a proxy for the interpretation of the wind systems characteristics and probable changes in the atmospheric circulation patterns. In order to improve the atmospheric circulation models developed for the Southern Hemisphere, it is necessary to increase the understanding of the characteristics of the South American dust sources. Prospero et al., (2002), showed the existence of three present-day persist dust sources in South America: Patagonia (39°-52°S), central-western Argentina (26°-33°S), and the Puna-Altiplano plateau (19°-26°S). An important question to be addressed is whether these dust sources were also important during the last glacial-interglacial cycles. In most cases, researchers working in the reconstruction of paleo-environments in the Southern Hemisphere have employed sparse geochemical and isotopic data from southern South American samples. As a consequence, there are no regional or systematic studies that define their geochemical "fingerprints" of likely sources. The main goal of this work is to identify the "fingerprints" of materials exported from these areas by means of rare earth elements (REEs) and Sr-Nd-Pb-isotopes measured in surface sediments (topsoils) and mineral dust samples. Samples (n=86) were taken across the "arid diagonal" of southern South America in a N-S transect from Uyuni (20°39'S, 68°11'W, Bolivia) to Bahia Blanca (38°43'S, 62°15'W, Argentina) representing different geomorphologic environments: e.g., ephemeral lakes, lowland areas, edges of salt flats, alluvial fans, dunes, etc. Preliminary data indicate the existence of a heterogeneous chemical/isotopic signature along

  3. Middle East Desert Dust Exposure: Health Risks from Metals and Microbial Pathogens

    NASA Astrophysics Data System (ADS)

    Lyles, M. B.

    2014-12-01

    In the Middle East, dust and sand storms are a persistent problem and can deliver significant amounts of micro-particulates via inhalation into the mouth, nasal pharynx, & lungs due to the fine size and abundance of these micro-particulates. The chronic and acute health risks of this dust inhalation have not been well studied nor has the dust been effectively characterized as to its chemical composition, mineral content, or microbial flora. Scientific experiments were designed to study the Kuwaiti and Iraqi dust as to its physical, chemical, and biological characteristics and for its potential to cause adverse health effects. First, dust samples from different locations were collected and processed and exposure data collected. Initial chemical and physical characterization of each sample including particle size distribution and inorganic analysis was conducted, followed by characterization of biologic flora of the dust, including bacteria, fungi and viruses. Data indicates that the mineralized dust is composed of calcium carbonate over a matrix of metallic silicate nanocrystals containing a variety of trace and heavy metals constituting ~3 % of the PM10 particles by weight, of which ~1% is bioaccessible aluminum and reactive iron, each. The particles also consist of ~1% bioavailable aluminum and reactive iron each. Microbial analysis reveals a significant biodiversity of bacterial, fungi, and viruses of which ~30% are known pathogens. Of the microbes identified, several have hemolytic properties and most have significant antibiotic resistance. Viral analysis indicates a tremendous amount of virons with a large percent of RNA viruses. The level of total suspended particle mass at PM 10 along with environmental & physiological conditions present constitute an excessive exposure to micro-particulates including PM 2.5 and the potential for adverse health effects. Reported data on cell culture and animal studies have indicated a high level of toxicity to these dust

  4. Influence of Asian Desert Dust on Lower Respiratory Tract Symptoms in Patients with Asthma over 4 Years.

    PubMed

    Watanabe, Masanari; Kurai, Jun; Igishi, Tadashi; Yamasaki, Akira; Burioka, Naoto; Takeuchi, Hiromi; Sako, Takanori; Touge, Hirokazu; Nakamoto, Masaki; Hasegawa, Yasuyuki; Chikumi, Hiroki; Matsumoto, Shingo; Yamasaki, Chie; Minato, Sayaka; Ueda, Yutaka; Horasaki, Kazunori; Watanabe, Tetsushi; Shimizu, Eiji

    2012-06-01

    The Asian Dust Storm (ADS) aggravates symptoms and pulmonary dysfunction in adult asthma patients. Our objective was to investigate the association of air pollutants and metals in desert dust with worsening of asthma symptoms during the ADS. A telephone survey was performed to investigate the upper and lower respiratory tract symptoms, ocular symptoms and skin symptoms of asthma patients during the ADS in March between 2007 and 2010. Four surveys were conducted in 46 patients. Two patients noted worsening of lower respiratory tract symptoms in all four surveys, as well as 2 patients in three surveys, 7 patients in two surveys, and 9 patients in one survey. There was no worsening of lower respiratory tract symptoms in 26 patients. In each patient, the influence of the ADS on lower respiratory tract symptoms varied between surveys. In 2010, the level of suspended particulate matter was highest in all four years, but the smallest number of patients noted worsening of lower respiratory tract symptoms. Among pollutants, only the maximum concentration of nitrogen dioxide during the ADS was significantly associated with the worsening of lower respiratory tract symptoms. The influence of the ADS on lower respiratory tract symptoms of adult asthma patients is variable. PMID:24031138

  5. The Dust at Altitude Recovery Technology (DART) System was Developed to Recover Plant, Human, and Animal Pathogens in Asian and African Dust Storms over North America

    NASA Astrophysics Data System (ADS)

    Schuerger, A. C.; Tench, B.; Nehr, A.; Emmons, T.; Valbuena, F.; Palaia, J.; Sugars, C.

    2014-12-01

    Dust emanates year-round from Africa and Asia and impacts air quality in North America. Asian dust plumes deliver up to 64 million tonnes of dust over the NW of the USA, and African dust storms deliver over 50 million tonnes of dust over Florida each year. Several recent studies have demonstrated that human and plant pathogens from Asian [1] African [2] aerosols can be transported to N. America in naturally occurring dust storms. What is unknown is whether these 'presumptive pathogens' impact human, plant, or animal health in the USA. In order to initiate a long-term monitoring program of pathogens in Asian and African dust plumes, we have developed a dust collection system called DART (Dust at Altitude Recovery Technology) (figure). The DART dust sampler can be mounted on a F104 Starfighter jet (figure) and a T6 Texan propeller driven airplane (not shown), and was test flown over FL in Dec. 2013 on the F104 and on the T6 in the summer of 2014. The DART system utilizes a high-volume pump to pass air through 6 separate filtration units where both aerosols and microbial cells are captured. The filtration systems exhibit flow rates from 25-142 L/min depending on the pore size and brand of filters used. Flow rates are directly correlated to increased air speed, and are inversely correlated to increased altitude. Filtration units can be turned on and off individually as required for specific science flight objectives. The DART dust sampler has performed nominally up to 7600 m, 0.92 Mach, and 3.5 +G's. During initial test flights in Dec. 2013, 5 of 8 genera of fungi recovered from the lower atmosphere over FL contained plant pathogens including species in the genera: Acremonium, Aspergillus, Cladosporium, Curvularia, and Fusarium. Numbers of recovered fungi, but not bacteria, increased significantly when 5 or 10 µm filters were used in the DART system compared to filter pore sizes ≤ 1.2 µm. Future sampling programs for both Asian and African dust events will be

  6. Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, François; Laurent, Benoit; Mallet, Marc; Formenti, Paola

    2014-05-01

    The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to

  7. Properties of transported African mineral dust aerosols in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Triquet, Sylvain; Zapf, Pascal; Loisil, Rodrigue; Bourrianne, Thierry; Freney, Evelyn; Dupuy, Regis; Sellegri, Karine; Schwarzenbock, Alfons; Torres, Benjamin; Mallet, Marc; Cassola, Federico; Prati, Paolo; Formenti, Paola

    2015-04-01

    The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), one intensive airborne campaign (ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) has been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport

  8. [Effects of the grain size and thickness of dust deposits on soil water and salt movement in the hinterland of the Taklimakan Desert].

    PubMed

    Sun, Yan-Wei; Li, Sheng-Yu; Xu, Xin-Wen; Zhang, Jian-Guo; Li, Ying

    2009-08-01

    By using mcirolysimeter, a laboratory simulation experiment was conducted to study the effects of the grain size and thickness of dust deposits on the soil water evaporation and salt movement in the hinterland of the Taklimakan Desert. Under the same initial soil water content and deposition thickness condition, finer-textured (<0.063 mm) deposits promoted soil water evaporation, deeper soil desiccation, and surface soil salt accumulation, while coarse-textured (0.063-2 mm) deposits inhibited soil water evaporation and decreased deeper soil water loss and surface soil salt accumulation. The inhibition effect of the grain size of dust deposits on soil water evaporation had an inflection point at the grain size 0.20 mm, i. e., increased with increasing grain size when the grain size was 0.063-0.20 mm but decreased with increasing grain size when the grain size was > 0.20 mm. With the increasing thickness of dust deposits, its inhibition effect on soil water evaporation increased, and there existed a logarithmic relationship between the dust deposits thickness and water evaporation. Surface soil salt accumulation had a negative correlation with dust deposits thickness. In sum, the dust deposits in study area could affect the stability of arid desert ecosystem. PMID:19947210

  9. Using the significant dust deposition event on the glaciers of Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and provenancing of desert dust events recorded in snow pack

    NASA Astrophysics Data System (ADS)

    Shahgedanova, M.; Kutuzov, S.; White, K.; Nosenko, G.

    2012-09-01

    A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution provenancing of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm and the dominant mode of 0.60 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite and oxides of aluminium, manganese, and magnesium. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the provenancing of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives.

  10. Using the significant dust deposition event on the glaciers of Mt.~Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and "provenancing" of desert dust events recorded in snow pack

    NASA Astrophysics Data System (ADS)

    Shahgedanova, M.; Kutuzov, S.; White, K. H.; Nosenko, G.

    2013-02-01

    A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution "provenancing" of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the "provenancing" of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives.

  11. Regional distribution of monsoon and desert dust signals recorded in Asian glaciers

    NASA Astrophysics Data System (ADS)

    Wake, Cameron P.; Mayewski, Paul A.; Xie, Zichu; Wang, Ping; Li, Zhongqin

    1993-07-01

    Short-term (6 months to 17 years) glaciochemical records have been collected from glacier basins throughout the mountains of central Asia. The spatial distribution of snow chemistry in central Asia is controlled predominantly by the influx of dust from the arid and semi-arid regions in central Asia. The glaciochemical data suggests that glaciers which are removed from large source areas of mineral aerosol, such as those in the Himalaya, the Karakoram, and the southeastern Tibetan Plateau, are the ones most likely to contain longer-term glaciochemical records which detail annual to decadal variation in the strength of the Asian monsoon and long-range transport of Asian dust.

  12. Desert dust in rural western US; the influence of dust storms, large particles, and land-use change on aerosol loads

    NASA Astrophysics Data System (ADS)

    Parks, D.; MacDonald, A. E.; Rosen, R. D.; Edmonds, H. N.; Key, E.; Swanberg, N.; Wiseman, W. J.; Sandgathe, S. A.; Neff, J. C.; Fernandez, D.; Munson, S.; Reynolds, R. L.

    2011-12-01

    Atmospheric aerosols are common in urban settings as well as dryland rural environments and are important to both climate and biogeochemical cycling. Most urban and far traveled aerosols are less than 10 micrometers in diameter with many particles in the less than 2.5 or 1 micrometer-size classes. Small aerosols, including many generated by industrial activity, are the focus of federal environmental law and have a major impact on human health. In rural areas of the western US, however, these small industrially derived particles appear to make up a small part of the overall aerosol load. Rather, dust in the rural West is dominated by mineral aerosols including a large amount of particles that range in size from 10 to 40 microns. These particles can travel for hundreds of kilometers, particularly during periods when dust storms are common. In the dusty spring and summer periods in and around Canyonlands and Mesa Verde National Parks, large particles (particles greater than 10 micrometers in diameter) appear to contribute between 50 and 90% to the overall particle load several meters above the ground. During large dust storms, concentrations of total suspended particulates increase by a factor of 8 to 10 while particles less than 10 micrometers in diameter are minimally affected. The presence of large particles in the atmosphere of the rural West is notable for several reasons. First, the majority of the existing aerosol monitoring networks focus on the small particle-size classes of less than 2.5 and 10 microns. Because many aerosol-collection instruments are designed with specific particle-size cutoff criteria, these instruments and the networks that depend on them are effectively blind to the larger particles that can dominate aerosol loads in the West. Second, for large portions of the year including the spring and summer months when dust storms are common, large particles likely play a major role in visibility restrictions across the protected airsheds of the

  13. Back-trajectory analysis of African dust outbreaks at a coastal city in southern Spain: Selection of starting heights and assessment of African and concurrent Mediterranean contributions

    NASA Astrophysics Data System (ADS)

    Cabello, M.; Orza, J. A. G.; Dueñas, C.; Liger, E.; Gordo, E.; Cañete, S.

    2016-09-01

    The present study uses a back-trajectory analysis at multiple heights for better interpretation of the impact of the African dust outbreaks in the coastal Mediterranean city of Málaga (Spain), the southernmost large city in Europe. Throughout a 3-year period, 363 days were identified as dusty days by atmospheric transport models. During these events, PM10, SO2, O3, temperature, AOD and Ångström exponent showed statistically significant differences compared to days with no African dust. It was found that under African dust events, the study site was influenced by Mediterranean air masses at the lowermost heights and by Atlantic advections at high altitudes, while African air masses mostly reached Málaga at intermediate levels. Specifically, the lowest heights at which air masses reached the study site after having resided over Africa are confined into the 1000-2000 m range. The decoupling between the lowest heights and the ones for dust transport may explain the presence of aged air masses at the time of the African outbreak. Additionally, with the aim of studying the influence of the air mass origin and history on air quality, a new procedure based on Principal component analysis (PCA) is proposed to determine which altitudes are best suited as starting points for back-trajectory calculations, as they maximize the differences in residence time over different areas. Its application to Málaga identifies three altitudes (750, 2250 and 4500 m) and a subsequent analysis of back-trajectories for African dust days provided the main source areas over Africa as well as further insight on the Mediterranean contribution.

  14. Effects of Saharan Mineral Dust Aerosols on the Dynamics of an Idealized African Easterly Jet-African Easterly Wave System over North Africa

    NASA Astrophysics Data System (ADS)

    Grogan, Dustin Francis Phillip

    The central objective of this work is to examine the direct radiative effects of Saharan mineral dust aerosols on the dynamics of African easterly waves (AEWs) and the African easterly jet (AEJ). Achieving this objective is built around two tasks that use the Weather Research and Forecasting (WRF) model coupled to an online dust model (WRF-dust model). The first task (Chapter 2) examines the linear dynamics of AEWs; the second task (Chapter 3) examines the nonlinear evolution of AEWs and their interactions with the AEJ. In Chapter 2, the direct radiative effects of dust on the linear dynamics of AEWs are examined analytically and numerically. The analytical analysis combines the thermodynamic equation with a dust continuity equation to form an expression for the generation of eddy available potential energy (APE) by the dust field. The generation of eddy APE is a function of the transmissivity and spatial gradients of the dust, which are modulated by the Doppler-shifted frequency. The expression predicts that for a fixed dust distribution, the wave response will be largest in regions where the dust gradients are maximized and the Doppler-shifted frequency vanishes. The numerical analysis calculates the linear dynamics of AEWs using zonally averaged basic states for wind, temperature and dust consistent with summertime conditions over North Africa. For the fastest growing AEW, the dust increases the growth rate from ~15% to 90% for aerosol optical depths ranging from tau=1.0 to tau=2.5. A local energetics analysis shows that for tau=1.0, the dust increases the maximum barotropic and baroclinic energy conversions by ~50% and ~100%, respectively. The maxima in the generation of APE and conversions of energy are co-located and occur where the meridional dust gradient is maximized near the critical layer, i.e., where the Doppler-shifted frequency is small, in agreement with the prediction from the analytical analysis. In Chapter 3, the direct radiative effects of dust

  15. Aerosol Optical Thickness in the Presence and Absence of African Dust using AERONET and Microtops II Sunphotometers

    NASA Astrophysics Data System (ADS)

    Ruiz, A.; Raizada, S.; Tepley, C. A.; Venero, I.; Zurcher, F.; Mayol-Bracero, O. L.

    2011-12-01

    As part of the Puerto Rico African Dust and Cloud Study (PRADACS) Project, we present a comparison of the aerosol optical thickness (AOT) between the AERONET sunphotometer (CIMEL Electronique 318A) located at Cape San Juan (CSJ, 18° 23' N, 65° 37' E), Puerto Rico, and the radiometers (Microtops II) of the Arecibo Observatory. Data were collected at CSJ during the summer period of 2011, when African dust was present most of the time. Preliminary results showed, for both instruments, AOT values around of 0.4 when there were high concentrations of African dust over the island Puerto Rico. The AOT correlations between the two instruments were very good, with a slope of 0.8 and r2 of 0.9 for all wavelengths. The main differences observed were on the values above 0.6. We will show the temporal behavior of AOT for the two instruments and the spatial differences between them.

  16. Relationship between African dust carried in the Atlantic trade winds and surges in pediatric asthma attendances in the Caribbean

    NASA Astrophysics Data System (ADS)

    Prospero, Joseph M.; Blades, Edmund; Naidu, Raana; Mathison, George; Thani, Haresh; Lavoie, Marc C.

    2008-11-01

    Asthma is epidemic in developed and developing countries including those in the Caribbean where it is widely believed that African dust, transported in high concentrations in the Trade Winds every year, is a major causative factor. The link between asthma and dust in the Caribbean is based largely on anecdotal evidence that associates sharp increases in the occurrence of asthma symptoms with hazy conditions often caused by dust. Here we report on a 2-year study of the relationship between the daily concentrations of dust measured in on-shore Trade Winds at Barbados and pediatric asthma attendance rates at Queen Elizabeth Hospital (QEH). We looked for large increases in QEH daily attendances in relation to daily dust concentrations as previously suggested by anecdotal observations. We could not find any obvious relationship although there may be more subtle linkages between dust and asthma. Our measurements show, however, that the concentration of dust in the size range under 2.5 μm diameter is sufficiently high as to challenge United States Environmental Protection Agency air quality standards for respirable particles. Thus, African dust may constitute a health threat of a different nature, producing symptoms less obvious than those of asthma.

  17. Relationship between African dust carried in the Atlantic trade winds and surges in pediatric asthma attendances in the Caribbean.

    PubMed

    Prospero, Joseph M; Blades, Edmund; Naidu, Raana; Mathison, George; Thani, Haresh; Lavoie, Marc C

    2008-11-01

    Asthma is epidemic in developed and developing countries including those in the Caribbean where it is widely believed that African dust, transported in high concentrations in the Trade Winds every year, is a major causative factor. The link between asthma and dust in the Caribbean is based largely on anecdotal evidence that associates sharp increases in the occurrence of asthma symptoms with hazy conditions often caused by dust. Here we report on a 2-year study of the relationship between the daily concentrations of dust measured in on-shore Trade Winds at Barbados and pediatric asthma attendance rates at Queen Elizabeth Hospital (QEH). We looked for large increases in QEH daily attendances in relation to daily dust concentrations as previously suggested by anecdotal observations. We could not find any obvious relationship although there may be more subtle linkages between dust and asthma. Our measurements show, however, that the concentration of dust in the size range under 2.5 microm diameter is sufficiently high as to challenge United States Environmental Protection Agency air quality standards for respirable particles. Thus, African dust may constitute a health threat of a different nature, producing symptoms less obvious than those of asthma.

  18. Desert speleothems reveal climatic window for African exodus of early modern humans

    NASA Astrophysics Data System (ADS)

    Vaks, Anton; Bar-Matthews, Miryam; Ayalon, Avner; Matthews, Alan; Halicz, Ludwik; Frumkin, Amos

    2007-09-01

    One of the first movements of early modern humans out of Africa occurred 130-100 thousand years ago (ka), when they migrated northward to the Levant region. The climatic conditions that accompanied this migration are still under debate. Using high-precision multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) U-Th methods, we dated carbonate cave deposits (speleothems) from the central and southern Negev Desert of Israel, located at the northeastern margin of the Saharan-Arabian Desert. Speleothems grow only when rainwater enters the unsaturated zone, and this study reveals that a major cluster of wet episodes (the last recorded in the area) occurred between 140 and 110 ka. This episodic wet period coincided with increased monsoonal precipitation in the southern parts of the Saharan-Arabian Desert. The disappearance at this time of the desert barrier between central Africa and the Levant, and particularly in the Sinai-Negev land bridge between Africa and Asia, would have created a climatic “window” for early modern human dispersion to the Levant.

  19. Observed particle sizes and fluxes of Aeolian sediment in the near surface layer during sand-dust storms in the Taklamakan Desert

    NASA Astrophysics Data System (ADS)

    Huo, Wen; He, Qing; Yang, Fan; Yang, Xinghua; Yang, Qing; Zhang, Fuyin; Mamtimin, Ali; Liu, Xinchun; Wang, Mingzhong; Zhao, Yong; Zhi, Xiefei

    2016-08-01

    Monitoring, modeling and predicting the formation and movement of dust storms across the global deserts has drawn great attention in recent decades. Nevertheless, the scarcity of real-time observations of the wind-driven emission, transport and deposition of dusts has severely impeded progress in this area. In this study, we report an observational analysis of sand-dust storm samples collected at seven vertical levels from an 80-m-high flux tower located in the hinterland of the great Taklamakan Desert for ten sand-dust storm events that occurred during 2008-2010. We analyzed the vertical distribution of sandstorm particle grain sizes and horizontal sand-dust sediment fluxes from the near surface up to 80 m high in this extremely harsh but highly representative environment. The results showed that the average sandstorm grain size was in the range of 70 to 85 μm. With the natural presence of sand dunes and valleys, the horizontal dust flux appeared to increase with height within the lower surface layer, but was almost invariant above 32 m. The average flux values varied within the range of 8 to 14 kg m-2 and the vertical distribution was dominated by the wind speed in the boundary layer. The dominant dust particle size was PM100 and below, which on average accounted for 60-80 % of the samples collected, with 0.9-2.5 % for PM0-2.5, 3.5-7.0 % for PM0-10, 5.0-14.0 % for PM0-20 and 20.0-40.0 % for PM0-50. The observations suggested that on average the sand-dust vertical flux potential is about 0.29 kg m-2 from the top of the 80 m tower to the upper planetary boundary layer and free atmosphere through the transport of particles smaller than PM20. Some of our results differed from previous measurements from other desert surfaces and laboratory wind-dust experiments, and therefore provide valuable observations to support further improvement of modeling of sandstorms across different natural environmental conditions.

  20. Composition of aeolian dust in natural traps on isolated surfaces of the central Mojave Desert - Insights to mixing, sources, and nutrient inputs

    USGS Publications Warehouse

    Reynolds, R.L.; Reheis, M.; Yount, J.; Lamothe, P.

    2006-01-01

    The recognition and characterization of aeolian dust in soil contribute to a better understanding of landscape and ecosystem dynamics of drylands. Results of this study show that recently deposited dust, sampled in isolated, mostly high-ground settings, is chemically and mineralogically similar on varied geologic substrates over a large area (15 000 km2) in the Mojave Desert. The silt-plus-clay fraction (fines) on these isolated surfaces is closely alike in magnetic-mineral composition, in contrast to greatly dissimilar magnetic compositions of rock surfaces of vastly different lithologies, on which the fines have accumulated. The fines, thus, are predominantly deposited dust. The amounts of potential nutrients in the sampled dust are much more uniform than might be provided by direct, local weathering of bedrock or by dust locally derived from nearby weathered products. The compositional similarity of the dust on these surfaces is interpreted to result from mixing of fines in the atmosphere as well as in fluvial, alluvial, and lacustrine depositional settings prior to dust emission.

  1. Inhalable desert dust, urban emissions, and potentially biotoxic metals in urban Saharan-Sahelian air

    USGS Publications Warehouse

    Garrison, Virginia H.; Majewski, Michael S.; Konde, Lassana; Wolf, Ruth E.; Otto, Richard D.; Tsuneoka, Yutaka

    2014-01-01

    Saharan dust incursions and particulates emitted from human activities degrade air quality throughout West Africa, especially in the rapidly expanding urban centers in the region. Particulate matter (PM) that can be inhaled is strongly associated with increased incidence of and mortality from cardiovascular and respiratory diseases and cancer. Air samples collected in the capital of a Saharan–Sahelian country (Bamako, Mali) between September 2012 and July 2013 were found to contain inhalable PM concentrations that exceeded World Health Organization (WHO) and US Environmental Protection Agency (USEPA) PM2.5 and PM10 24-h limits 58 – 98% of days and European Union (EU) PM10 24-h limit 98% of days. Mean concentrations were 1.2-to-4.5 fold greater than existing limits. Inhalable PM was enriched in transition metals, known to produce reactive oxygen species and initiate the inflammatory response, and other potentially bioactive and biotoxic metals/metalloids. Eroded mineral dust composed the bulk of inhalable PM, whereas most enriched metals/metalloids were likely emitted from oil combustion, biomass burning, refuse incineration, vehicle traffic, and mining activities. Human exposure to inhalable PM and associated metals/metalloids over 24-h was estimated. The findings indicate that inhalable PM in the Sahara–Sahel region may present a threat to human health, especially in urban areas with greater inhalable PM and transition metal exposure.

  2. Trace-metal concentrations in African dust: effects of long-distance transport and implications for human health

    USGS Publications Warehouse

    Garrison, Virginia; Lamothe, Paul; Morman, Suzette; Plumlee, Geoffrey S.; Gilkes, Robert; Prakongkep, Nattaporn

    2010-01-01

    The Sahara and Sahel lose billions of tons of eroded mineral soils annually to the Americas and Caribbean, Europe and Asia via atmospheric transport. African dust was collected from a dust source region (Mali, West Africa) and from downwind sites in the Caribbean [Trinidad-Tobago (TT) and U.S. Virgin Islands (VI)] and analysed for 32 trace-elements. Elemental composition of African dust samples was similar to that of average upper continental crust (UCC), with some enrichment or depletion of specific trace-elements. Pb enrichment was observed only in dust and dry deposition samples from the source region and was most likely from local use of leaded gasoline. Dust particles transported long-distances (VI and TT) exhibited increased enrichment of Mo and minor depletion of other elements relative to source region samples. This suggests that processes occurring during long-distance transport of dust produce enrichment/depletion of specific elements. Bioaccessibility of trace-metals in samples was tested in simulated human fluids (gastric and lung) and was found to be greater in downwind than source region samples, for some metals (e.g., As). The large surface to volume ratio of the dust particles (<2.5 µm) at downwind sites may be a factor.

  3. Physical and Chemical Characteristics of Desert Dust Deposited on Mt. Elbrus, Caucasus as Documented in Snow Pit and Shallow Core Records

    NASA Astrophysics Data System (ADS)

    Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Ginot, P.; Lavrentiev, I.; Popov, G.

    2013-12-01

    We present a study of dust deposition events and its physical and chemical characteristics in Caucasus Mountains as documented by snow and firn pack at Mt Elbrus. Dust samples were collected from the shallow ice cores and snow pits in 2009-2013 at the western Elbrus plateau (5150 m a.s.l.). Particle size distribution and chemical analysis (major ions, trace elements) were completed for each sample using Coulter Counter Multisizer III, scanning electron microscopy (SEM), IC and ICPMS analysis. It was shown that desert dust deposition occurred in Caucasus 4-8 times a year and originates from the Northern Sahara and the deserts of the Middle East. Analysis of volumetric particle size distributions showed that the modal values ranged between 2 μm and 4 μm although most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm. These values are lower than those obtained from the ice cores in central and southern Asia following the deposition of long-travelled dust and are closer to those reported for the European Alps and the polar ice cores. All samples containing dust have a single mode which is usually interpreted as a single source region. They do not reveal any significant differences between the Saharan and the Middle Eastern sources. The annual average dust mass concentrations were 10-15 mg kg-1 which is higher than the average concentrations reported for other mountain regions and this was strongly affected by dust deposition events. The deposition of dust resulted in elevated concentrations of most ions, especially Ca2+, Mg2+, K+, and sulphates. Dust originated from multiple sources in the Middle East including Mesopotamia or passing over the Middle East was characterised by the elevated concentrations of nitrates and ammonia which is related to a high atmospheric loads of ammonium emitted by agricultural sources and high concentrations of ammonium in dust originating from this region. By contrast, samples of the Saharan dust showed

  4. Large Spatial Scale of the Phenotype-Environment Color Matching in Two Cryptic Species of African Desert Jerboas (Dipodidae: Jaculus)

    PubMed Central

    Boratyński, Zbyszek; Brito, José Carlos; Campos, João Carlos; Karala, Maija; Mappes, Tapio

    2014-01-01

    We tested the camouflage hypothesis, or the linkage between animal (Saharan rodent) and habitat coloration, on the largest geographical scale yet conducted. We aimed to determine whether phenotypic variation is explained by micro-habitat variation and/or genetic polymorphism to determine 1) the strength of linkage between fur color and local substrate color, and 2) the divergence in fur coloration between two genetic clades, representing cryptic species, throughout the complete range of the African desert jerboas (Jaculus jaculus). We used a combination of museum and field-collected specimens, remote sensing tools, satellite and digital photography and molecular genetic and phylogenetic methods to investigate the above hypotheses. Along with showing that the two divergent genetic clades of jerboas occur sympatrically throughout their African distribution, we showed significant covariation between dorsal fur coloration of the animals and the color of their habitat. We also described significant phenotypic divergence in fur color, consistent with genetic divergence between the sympatric clades. The linkage between environment and phenotype supports the idea that the selection promoting cryptic coloration is persistent in contemporary populations of jerboas, however the phenotypic divergence indicates that it has different strengths (or optima) in the two clades. The mosaic distribution of micro-habitats occupied by geographically sympatric clades suggests that it may influence both ecological and evolutionary dynamics between these two cryptic species. PMID:24714509

  5. Birth cohort study on the effects of desert dust exposure on children's health: protocol of an adjunct study of the Japan Environment & Children’s Study

    PubMed Central

    Kanatani, Kumiko T; Adachi, Yuichi; Sugimoto, Nobuo; Noma, Hisashi; Onishi, Kazunari; Hamazaki, Kei; Takahashi, Yoshimitsu; Ito, Isao; Egawa, Miho; Sato, Keiko; Go, Tohshin; Kurozawa, Youichi; Inadera, Hidekuni; Konishi, Ikuo; Nakayama, Takeo

    2014-01-01

    Introduction Desert dust is estimated to constitute about 35% of aerosol in the troposphere. Desertification, climatic variability and global warming all can contribute to increased dust formation. This study aims to examine possible health effects of desert dust exposure on pregnant women and their children. The purpose of this report was to present the study protocol. Methods and analysis This 4-year birth cohort study began in 2011 as an adjunct study of the Japan Environment & Children’s Study (JECS) involving three regions: Kyoto, Toyama and Tottori. The JECS participants of the three regions above who also agreed to participate in this adjunct study were enrolled prior to delivery. Light Detecting and Ranging (LIDAR) with a polarisation analyser, which can distinguish mineral dust particles from other particles, is used for exposure measurements. Outcomes are allergic symptoms for mothers and development of asthma and other allergic or respiratory diseases for their children. Data are acquired in a timely manner by connecting local LIDAR equipment to an online questionnaire system. Participants answer the online questionnaire using mobile phones or personal computers. Ethics and dissemination The study protocol was approved by the ethics committees of Kyoto University, University of Toyama and Tottori University. All participants provided written informed consent. The results of this study will be published in peer-reviewed journals and disseminated to the scientific community and general public. Trial Registration number UMIN000010826. PMID:24958210

  6. Radiative effects of African dust and smoke observed from Clouds and the Earth's Radiant Energy System (CERES) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) data

    NASA Astrophysics Data System (ADS)

    Yorks, John E.; McGill, Matt; Rodier, Sharon; Vaughan, Mark; Hu, Yongxiang; Hlavka, Dennis

    2009-09-01

    Cloud and aerosol effects have a significant impact on the atmospheric radiation budget in the tropical Atlantic because of the spatial and temporal extent of desert dust and smoke from biomass burning in the atmosphere. The influences of African dust and smoke aerosols on cloud radiative properties over the tropical Atlantic Ocean were analyzed for the month of July for 3 years (2006-2008) using colocated data collected by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and Aqua satellites. Aerosol layer height and type can be accurately determined using CALIOP data through directly measured parameters such as optical depth, volume depolarization ratio, attenuated backscatter, and color ratio. On average, clouds below 5 km had a daytime instantaneous shortwave (SW) radiative flux of 270.2 ± 16.9 W/m2 and thin cirrus clouds had a SW radiative flux of 208.0 ± 12.7 W/m2. When dust aerosols interacted with clouds below 5 km, as determined from CALIPSO, the SW radiative flux decreased to 205.4 ± 13.0 W/m2. Similarly, smoke aerosols decreased the SW radiative flux of low clouds to a value of 240.0 ± 16.6 W/m2. These decreases in SW radiative flux were likely attributed to the aerosol layer height and changes in cloud microphysics. CALIOP lidar observations, which more accurately identify aerosol layer height than passive instruments, appear essential for better understanding of cloud-aerosol interactions, a major uncertainty in predicting the climate system.

  7. Three-Dimensional Distribution of a Major Desert Dust Outbreak over East Asia in March 2008 Derived from IASI Satellite Observations

    NASA Technical Reports Server (NTRS)

    Cuesta, Juan; Eremenko, Maxim; Flamant, Cyrille; Dufour, Gaelle; Laurent, Benoît; Bergametti, Gilles; Hopfner, Michael; Orphal, Johannes; Zhou, Daniel

    2015-01-01

    We describe the daily evolution of the three-dimensional (3D) structure of a major dust outbreak initiated by an extratropical cyclone over East Asia in early March 2008, using new aerosol retrievals derived from satellite observations of IASI (Infrared Atmospheric Sounding Interferometer). A novel auto-adaptive Tikhonov-Phillips-type approach called AEROIASI is used to retrieve vertical profiles of dust extinction coefficient at 10 microns for most cloud-free IASI pixels, both over land and ocean. The dust vertical distribution derived from AEROIASI is shown to agree remarkably well with along-track transects of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) spaceborne lidar vertical profiles (mean biases less than 110 meters, correlation of 0.95, and precision of 260 meters for mean altitudes of the dust layers). AEROIASI allows the daily characterization of the 3D transport pathways across East Asia of two dust plumes originating from the Gobi and North Chinese deserts. From AEROIASI retrievals, we provide evidence that (i) both dust plumes are transported over the Beijing region and the Yellow Sea as elevated layers above a shallow boundary layer, (ii) as they progress eastward, the dust layers are lifted up by the ascending motions near the core of the extratropical cyclone, and (iii) when being transported over the warm waters of the Japan Sea, turbulent mixing in the deep marine boundary layer leads to high dust concentrations down to the surface. AEROIASI observations and model simulations also show that the progression of the dust plumes across East Asia is tightly related to the advancing cold front of the extratropical cyclone.

  8. Effects of Prior Precipitation and Source Area Characteristics on Threshold Wind Velocities for Blowing Dust Episodes, Sonoran Desert 1948-78.

    NASA Astrophysics Data System (ADS)

    Holcombe, Troy Leon; Ley, Trevor; Gillette, Dale A.

    1997-09-01

    A better understanding of the effects of precipitation and source area on blowing dust in the Sonoran Desert has been sought through the study of 1190 dust episodes occurring during the 1948-78 time period at Blythe, California, and Yuma, Arizona. Threshold mean hourly wind speeds (MHWSs) increase directly with prior precipitation in proportion to the inhibiting effect of the vegetation canopy, which blooms following periods of increased precipitation. Because of the time required for the vegetation canopy to fully develop and the persistence of the vegetation canopy once developed, correlation between the threshold MHWS and precipitation is highest for 4-6-month windows of total precipitation prior to each dust event at both stations. Many dust events associated with unusually low MHWSs are clustered in time, and these events can be correlated with interstate highway construction and soil preparation for new irrigation projects. Since threshold MHWSs for blowing dust lie well below the recorded MHWSs during most dust events at most times, it is possible to predict that mean annual precipitation could in the future increase to about 8 cm per 6 months without significantly reducing the occurrence of blowing dust episodes. On the other hand, increases in future mean annual precipitation to 10-12 cm per 6 months would raise the threshold MHWS to the point that conditions for blowing dust would be substantially reduced. Many of the infrequently occurring periods of elevated precipitation correlate in time with El Niño-Southern Oscillation events, which typically repeat every 2-8 yr. Average MHWSs, and threshold MHWSs for blowing dust, vary with wind direction at Blythe and Yuma. These variations can be related to variations in the susceptibility of upwind source areas in most instances, but in one or more instances this variation may be related to storm type.

  9. Three-dimensional distribution of a major desert dust outbreak over East Asia in March 2008 derived from IASI satellite observations

    NASA Astrophysics Data System (ADS)

    Cuesta, Juan; Eremenko, Maxim; Flamant, Cyrille; Dufour, Gaëlle; Laurent, Benoît; Bergametti, Gilles; Höpfner, Michael; Orphal, Johannes; Zhou, Daniel

    2015-07-01

    We describe the daily evolution of the three-dimensional (3D) structure of a major dust outbreak initiated by an extratropical cyclone over East Asia in early March 2008, using new aerosol retrievals derived from satellite observations of IASI (Infrared Atmospheric Sounding Interferometer). A novel auto-adaptive Tikhonov-Phillips-type approach called AEROIASI is used to retrieve vertical profiles of dust extinction coefficient at 10 µm for most cloud-free IASI pixels, both over land and ocean. The dust vertical distribution derived from AEROIASI is shown to agree remarkably well with along-track transects of CALIOP spaceborne lidar vertical profiles (mean biases less than 110 m, correlation of 0.95, and precision of 260 m for mean altitudes of the dust layers). AEROIASI allows the daily characterization of the 3D transport pathways across East Asia of two dust plumes originating from the Gobi and North Chinese deserts. From AEROIASI retrievals, we provide evidence that (i) both dust plumes are transported over the Beijing region and the Yellow Sea as elevated layers above a shallow boundary layer, (ii) as they progress eastward, the dust layers are lifted up by the ascending motions near the core of the extratropical cyclone, and (iii) when being transported over the warm waters of the Japan Sea, turbulent mixing in the deep marine boundary layer leads to high dust concentrations down to the surface. AEROIASI observations and model simulations also show that the progression of the dust plumes across East Asia is tightly related to the advancing cold front of the extratropical cyclone.

  10. Geochemical evidence for African dust inputs to soils of western Atlantic islands: Barbados, the Bahamas, and Florida

    NASA Astrophysics Data System (ADS)

    Muhs, Daniel R.; Budahn, James R.; Prospero, Joseph M.; Carey, Steven N.

    2007-06-01

    We studied soils on high-purity limestones of Quaternary age on the western Atlantic Ocean islands of Barbados, the Florida Keys, and the Bahamas. Potential soil parent materials in this region, external to the carbonate substrate, include volcanic ash from the island of St. Vincent (near Barbados), volcanic ash from the islands of Dominica and St. Lucia (somewhat farther from Barbados), the fine-grained component of distal loess from the lower Mississippi River Valley, and wind-transported dust from Africa. These four parent materials can be differentiated using trace elements (Sc, Cr, Th, and Zr) and rare earth elements that have minimal mobility in the soil-forming environment. Barbados soils have compositions that indicate a complex derivation. Volcanic ash from the island of St. Vincent appears to have been the most important influence, but African dust is a significant contributor, and even Mississippi River valley loess may be a very minor contributor to Barbados soils. Soils on the Florida Keys and islands in the Bahamas appear to have developed mostly from African dust, but Mississippi River valley loess may be a significant contributor. Our results indicate that inputs of African dust are more important to the genesis of soils on islands in the western Atlantic Ocean than previously supposed. We hypothesize that African dust may also be a major contributor to soils on other islands of the Caribbean and to soils in northern South America, central America, Mexico, and the southeastern United States. Dust inputs to subtropical and tropical soils in this region increase both nutrient-holding capacity and nutrient status and thus may be critical in sustaining vegetation.

  11. Geochemical evidence for African dust inputs to soils of western Atlantic islands: Barbados, the Bahamas, and Florida

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.R.; Prospero, J.M.; Carey, S.N.

    2007-01-01

    We studied soils on high-purity limestones of Quaternary age on the western Atlantic Ocean islands of Barbados, the Florida Keys, and the Bahamas. Potential soil parent materials in this region, external to the carbonate substrate, include volcanic ash from the island of St. Vincent (near Barbados), volcanic ash from the islands of Dominica and St. Lucia (somewhat farther from Barbados), the fine-grained component of distal loess from the lower Mississippi River Valley, and wind-transported dust from Africa. These four parent materials can be differentiated using trace elements (Sc, Cr, Th, and Zr) and rare earth elements that have minimal mobility in the soil-forming environment. Barbados soils have compositions that indicate a complex derivation. Volcanic ash from the island of St. Vincent appears to have been the most important influence, but African dust is a significant contributor, and even Mississippi River valley loess may be a very minor contributor to Barbados soils. Soils on the Florida Keys and islands in the Bahamas appear to have developed mostly from African dust, but Mississippi River valley loess may be a significant contributor. Our results indicate that inputs of African dust are more important to the genesis of soils on islands in the western Atlantic Ocean than previously supposed. We hypothesize that African dust may also be a major contributor to soils on other islands of the Caribbean and to soils in northern South America, central America, Mexico, and the southeastern United States. Dust inputs to subtropical and tropical soils in this region increase both nutrient-holding capacity and nutrient status and thus may be critical in sustaining vegetation. Copyright 2007 by the American Geophysical Union.

  12. On the decadal scale correlation between African dust and Sahel rainfall: The role of Saharan heat low–forced winds

    PubMed Central

    Wang, Weijie; Evan, Amato T.; Flamant, Cyrille; Lavaysse, Christophe

    2015-01-01

    A large body of work has shown that year-to-year variations in North African dust emission are inversely proportional to previous-year monsoon rainfall in the Sahel, implying that African dust emission is highly sensitive to vegetation changes in this narrow transitional zone. However, such a theory is not supported by field observations or modeling studies, as both suggest that interannual variability in dust is due to changes in wind speeds over the major emitting regions, which lie to the north of the Sahelian vegetated zone. We reconcile this contradiction showing that interannual variability in Sahelian rainfall and surface wind speeds over the Sahara are the result of changes in lower tropospheric air temperatures over the Saharan heat low (SHL). As the SHL warms, an anomalous tropospheric circulation develops that reduces wind speeds over the Sahara and displaces the monsoonal rainfall northward, thus simultaneously increasing Sahelian rainfall and reducing dust emission from the major dust “hotspots” in the Sahara. Our results shed light on why climate models are, to date, unable to reproduce observed historical variability in dust emission and transport from this region. PMID:26601301

  13. Mixing state of aerosols and direct observation of carbonaceous and marine coatings on African dust by individual particle analysis

    NASA Astrophysics Data System (ADS)

    Deboudt, Karine; Flament, Pascal; ChoëL, Marie; Gloter, Alexandre; Sobanska, Sophie; Colliex, Christian

    2010-12-01

    The mixing state of aerosols collected at M'Bour, Senegal, during the Special Observing Period conducted in January-February 2006 (SOP-0) of the African Monsoon Multidisciplinary Analysis project (AMMA), was studied by individual particle analysis. The sampling location on the Atlantic coast is particularly adapted for studying the mixing state of tropospheric aerosols since it is (1) located on the path of Saharan dust plumes transported westward over the northern tropical Atlantic, (2) influenced by biomass burning events particularly frequent from December to March, and (3) strongly influenced by anthropogenic emissions from polluted African cities. Particle size, morphology, and chemical composition were determined for 12,672 particles using scanning electron microscopy (automated SEM-EDX). Complementary analyses were performed using transmission electron microscopy combined with electron energy loss spectrometry (TEM-EELS) and Raman microspectrometry. Mineral dust and carbonaceous and marine compounds were predominantly found externally mixed, i.e., not present together in the same particles. Binary internally mixed particles, i.e., dust/carbonaceous, carbonaceous/marine, and dust/marine mixtures, accounted for a significant fraction of analyzed particles (from 10.5% to 46.5%). Western Sahara was identified as the main source of mineral dust. Two major types of carbonaceous particles were identified: "tar balls" probably coming from biomass burning emissions and soot from anthropogenic emissions. Regarding binary internally mixed particles, marine and carbonaceous compounds generally formed a coating on mineral dust particles. The carbonaceous coating observed at the particle scale on African dust was evidenced by the combined use of elemental and molecular microanalysis techniques, with the identification of an amorphous rather than crystallized carbon structure.

  14. Intercomparison of Satellite Dust Retrieval Products over the West African Sahara During the Fennec Campaign in June 2011

    NASA Technical Reports Server (NTRS)

    Banks, J.R.; Brindley, H. E.; Flamant, C.; Garay, M. J.; Hsu, N. C.; Kalashnikova, O. V.; Klueser, L.; Sayer, A. M.

    2013-01-01

    Dust retrievals over the Sahara Desert during June 2011 from the IASI, MISR, MODIS, and SEVIRI satellite instruments are compared against each other in order to understand the strengths and weaknesses of each retrieval approach. Particular attention is paid to the effects of meteorological conditions, land surface properties, and the magnitude of the dust loading. The period of study corresponds to the time of the first Fennec intensive measurement campaign, which provides new ground-based and aircraft measurements of the dust characteristics and loading. Validation using ground-based AERONET sunphotometer data indicate that of the satellite instruments, SEVIRI is most able to retrieve dust during optically thick dust events, whereas IASI and MODIS perform better at low dust loadings. This may significantly affect observations of dust emission and the mean dust climatology. MISR and MODIS are least sensitive to variations in meteorological conditions, while SEVIRI tends to overestimate the aerosol optical depth (AOD) under moist conditions (with a bias against AERONET of 0.31), especially at low dust loadings where the AOD<1. Further comparisons are made with airborne LIDAR measurements taken during the Fennec campaign, which provide further evidence for the inferences made from the AERONET comparisons. The effect of surface properties on the retrievals is also investigated. Over elevated surfaces IASI retrieves AODs which are most consistent with AERONET observations, while the AODs retrieved by MODIS tend to be biased low. In contrast, over the least emissive surfaces IASI significantly underestimates the AOD (with a bias of -0.41), while MISR and SEVIRI show closest agreement.

  15. Association of Kawasaki disease with tropospheric winds in Central Chile: is wind-borne desert dust a risk factor?

    PubMed

    Jorquera, Héctor; Borzutzky, Arturo; Hoyos-Bachiloglu, Rodrigo; García, Alvaro

    2015-05-01

    It has been found that Kawasaki disease (KD) cases diagnosed in Japan, Hawaii and San Diego, USA increase when tropospheric wind patterns arrive from central Asia, suggesting a common, wind-borne causal agent. We analyzed KD cases hospitalized in Santiago, Chile to look for associations with local, regional and large scale meteorological variables. We compiled monthly data of KD incidence rates, local meteorological variables, large scale wind patterns and several El Niño Southern Oscillation (ENSO) indices for 2001-2010; we considered standardized anomalies in all analyses and used linear time series models to account for data autocorrelation. We found that meteorological variables explain 38% of variance in KD rates. A unit increase in northerly wind at 3 lagged months, temperature at 1 and 3 lagged months and monthly change of ENSO 4 index are associated with changes in KD rates of 0.203 (95% CI 0.049-0.358), 0.181 (95% CI 0.014-0.347), 0.192 (95% CI 0.030-0.353) and -0.307 (95% CI -0.458-0.156), respectively. These results are robust when northerly wind level is changed or when a shorter period (2005-2010) is used to estimate model parameters. We found a statistical association of KD at Santiago, Chile with tropospheric, northerly wind patterns suggesting that dust transported from the Atacama Desert could include a causative agent. A novel result is that ENSO dynamics also explain part of KD variability with a decrease in KD when La Niña is dissipating or El Niño is on the rise; hence climate scale dynamics might be taken into account in future studies worldwide - at least as a potential explanatory variable that may confound KD seasonality on a global scale.

  16. Microbiological fingerprint of African dust deposition in alpine snow pack, Mont Blanc summit

    NASA Astrophysics Data System (ADS)

    Chuvochina, Maria; Alekhina, Irina; Normand, Philippe; Petit, Jean-Robert; Bulat, Sergey

    2010-05-01

    The biogeochemical effect of African dust transport has been reported mostly with respect to nutrient budget change in both terrestrial and aquatic ecosystems and global transport of microorganisms, including pathogens. However, its potential to seed or colonize the remote environments by transported microorganisms is poorly understood. This study has focused on bacterial content and diversity of Saharan dust deposition from 2006, 2008 and 2009 in snow pack of Mont Blanc (MtBl) glacier as well as recognition of bacteria which could be involved in establishing microbiota in this icy environment. Four snow samples recorded Saharan dust events from June 2006 (SDm06/2006 - 3,5 months aged), May and June 2008 (SDm05/2008 and SDm06/2008 - 1 month in between and 1 week aged each) and May 2009 (SDm05/2009 - 1 week aged) were collected at Col du Dome area (4250m a.s.l.). Bacterial community structure was assessed by ribotyping and subsequent sequencing of bacterial 16S rRNA genes. To exclude human-associated and laboratory contamination several controls were run in parallel updating our contaminant library. The obtained phylotypes were tested against this library keeping only those which successfully passed through this exam. Of 176 selected clones from four clone libraries 29.8% were met in our contaminant library. The ‘true' sequences were assigned to 57 phylotypes (>97.5% sequence similarity) originating mostly from soil. The prevalent phylotypes recovered were belonging to different bacterial divisions: Deinococcus-Thermus, Alpha-proteobacteria and CFB groups for SDm06/2006; Actinobacteria, Alpha-proteobacteria and CFB for SDm05/2008 and SDm06/2008; Actinobacteria and chloroplasts/plastids for SDm05/2009. Phylogenetic analysis of all phylotypes showed no shared species amongst all 4 dust layers in MtBl snow pack in 2006, 2008 and 2009. However, two phylotypes (Blastococcus saxobsidens sp. - 99%, Geodermatophilus obscurus sp. - 99%) were shared between 2008 and 2009

  17. High-resolution regional modeling of summertime transport and impact of African dust over the Red Sea and Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Kalenderski, Stoitchko; Stenchikov, Georgiy

    2016-06-01

    Severe dust outbreaks and high dust loading over Eastern Africa and the Red Sea are frequently detected in the summer season. Observations suggest that small-scale dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand these processes, we present here the first high-resolution modeling study of a dust outbreak in June 2012 developed over East Africa, the Red Sea, and the Arabian Peninsula. Using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) component, we identified several dust generating dynamical processes that range from convective to synoptic scales, including synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea, most of the dust transport occurs above 2 km height, whereas across the central and southern parts of the sea; dust is mostly transported below 2 km height. Dust is the dominant contributor (87%) to the aerosol optical depth, producing a domain average cooling effect of -12.1 W m-2 at the surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. Both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. Model results compare well with available ground-based and satellite observations but generally underestimate the observed maximum values of aerosol optical depth. The satellite-retrieved mean optical depth at some locations is underestimated by a factor of 2. A sensitive experiment suggests that these large local differences may result from poor characterization of dust emissions in some areas of the modeled domain. In this case study we successfully simulate the major fine-scale dust generating dynamical processes, explicitly resolving convection and haboob formation. The future

  18. The Fertilizing Role of African Dust in the Amazon Rainforest: A First Multiyear Assessment Based on CALIPSO Lidar Observations

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Remer, Lorraine A.; Prospero, Joseph M.; Omar, Ali; Winker, David; Yang, Yuekui; Zhang, Yan; Zhang, Zhibo; Zhao, Chun

    2015-01-01

    The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three dimensional (3D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8 to approximately 48) Tg a(exp -1) or 29 (8 to approximately 50) kg ha(exp -1) a(exp -1). The dust deposition shows significant interannual variation that is negatively correlated with the prior-year rainfall in the Sahel. The CALIOP-based multi-year mean estimate of dust deposition matches better with estimates from in-situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.0060.037) Tg P of phosphorus per year, equivalent to 23 (7 to approximately 39) g P ha(exp -1) a(exp -1) to fertilize the Amazon rainforest. This out-of-Basin P input largely compensates the hydrological loss of P from the Basin, suggesting an important role of African dust in preventing phosphorus depletion on time scales of decades to centuries.

  19. Impacts of dust reduction on the northward expansion of the African monsoon during the Green Sahara period

    NASA Astrophysics Data System (ADS)

    Pausata, Francesco S. R.; Messori, Gabriele; Zhang, Qiong

    2016-01-01

    The West African Monsoon (WAM) is crucial for the socio-economic stability of millions of people living in the Sahel. Severe droughts have ravaged the region in the last three decades of the 20th century, highlighting the need for a better understanding of the WAM dynamics. One of the most dramatic changes in the West African Monsoon (WAM) occurred between 15000-5000 yr BP, when increased summer rainfall led to the so-called "Green Sahara" and to a reduction in dust emissions from the region. However, model experiments are unable to fully reproduce the intensification and geographical expansion of the WAM during this period, even when vegetation over the Sahara is considered. Here, we use a fully coupled simulation for 6000 yr BP (Mid-Holocene) in which prescribed Saharan vegetation and dust concentrations are changed in turn. A closer agreement with proxy records is obtained only when both the Saharan vegetation changes and dust decrease are taken into account. The dust reduction strengthens the vegetation-albedo feedback, extending the monsoon's northern limit approximately 500 km further than the vegetation-change case only. We therefore conclude that accounting for changes in Saharan dust loadings is essential for improving model simulations of the WAM during the Mid-Holocene.

  20. Improved parameterization of dust emission (PM10) fluxes by the gradient method using the Naiman tower data at the Horqin desert in China.

    PubMed

    Park, Moon-Soo; Park, Soon-Ung; Chun, Youngsin

    2011-12-15

    Dust emission/deposition flux has been estimated using the gradient method with the two-level (3 and 15m high) measured PM(10) concentrations and the sonic anemometer measured momentum and kinematic heat fluxes at 8m high from a 20-m monitoring tower located at Naiman (Horqin desert) in the Asian dust source region in China for the winter of November 2007 to March 2008. The time series of measured PM(10) concentration at 3m high is used to identify the dust event and the non-dust event periods. It is found that the dust emission/deposition flux (F(C)) shows a significant diurnal variation with the maximum emission flux of 5.8 kg km(-2)h(-1) at noon and the minimum of -1.6 kg km(-2)h(-1) in the afternoon for the non-dust event cases. Whereas for the dust event cases, the dust emission flux is found to occur when the prevailing winds are westerlies to northerlies with the maximum flux of 1275 kg km(-2)d(-1), while the maximum dust deposition flux of 148 kg km(-2)d(-1) occurs with the prevailing winds of southerlies to easterlies without any diurnal variation. The optimal regression equation between F(C) and the friction velocity (u(*)) for the dust emission cases is found to be F(C)=9.55 u(*)(3.13) with the R(2) value of 0.73. However, this regression equation can be improved by taking into account the convective velocity (w(*)). The resulting optimal regression equation is found to be F(C)=9.3(u(*)-0.1w(*))(3.19) for the stable stratification (w(*)<0) with the R(2) value of 0.77 and F(C)=10.5(u(*)+0.34w(*))(4.11) for the unstable stratification (w(*)>0) with the R(2) value of 0.78, suggesting the importance of the convective velocity on the dust emission flux.

  1. Observation of low single scattering albedo of aerosols in the downwind of the East Asian desert and urban areas during the inflow of dust aerosols

    NASA Astrophysics Data System (ADS)

    Khatri, Pradeep; Takamura, Tamio; Shimizu, Atsushi; Sugimoto, Nobuo

    2014-01-01

    We analyzed data observed at Fukue-jima (32.752°N, 128.682°E), the downwind of the East Asian desert and urban areas, during the spring season (March-April) of 2008-2011 aiming to understand the light-absorption capacity of Asian dust aerosols, which is a topic of controversy. We observed the decreasing tendency of single-scattering albedo (SSA) with the decrease of Ångström exponent and the increase of the ratio of dust aerosol optical thickness to total aerosol optical thickness, suggesting the important role of coarse-mode dust aerosols on observed low SSAs. The observational data further indicated that the low SSAs during strong dust events were less likely due to the effect of only strong light-absorbing carbonaceous aerosols, such as black carbon (BC), indicating the association of aerosol size distribution on modulating SSA. Such observational results are justified by numerical calculations showing that aerosol size distribution can be the key factor on modulating SSA even without any change in relative amount of light-absorbing aerosol as well as total aerosol optical thickness. Therefore, the observed low SSAs in the downwind regions during dust events could be partially due to the dominance of coarse-mode aerosols over fine-mode aerosols, which are usual in dust events, along with the effect of mixed light-absorbing aerosols. The study further suggests that such effect of aerosol size distribution on SSA can be one of the important reasons for the low SSAs of dust aerosols in the source region as reported by some studies, if coarse-mode aerosols dominate fine-mode aerosols.

  2. The Role of African Dust Particles on Cloud Chemistry and Microphysics in a Tropical Montane Cloud Forest in the Caribbean

    NASA Astrophysics Data System (ADS)

    Torres-Delgado, E.; Valle-Diaz, C. J.; Baumgardner, D.; McDowell, W. H.; Gonzalez, G.; Mayol-Bracero, O. L.

    2015-12-01

    Huge amounts of African dust travels thousands of kilometers from the Sahara and Sahel regions to the Caribbean, northern South America and southern North America. However, not much is understood about how the aging process that takes place during transport changes dust properties, and how it affects cloud's composition and microphysics. In order to improve our understanding of the role of long-range transported African dust (LRTAD) in cloud formation processes we had field campaigns measuring dust physical and chemical properties in summers of 2013, 2014 and 2015, as part of the Puerto Rico African Dust and Cloud Study (PRADACS), and of the Luquillo Critical Zone Observatory (LCZO). Measurements were performed at the tropical montane cloud forest (TMCF) of Pico del Este (PE, 1051 masl) and at the nature reserve of Cabezas de San Juan (CSJ, 60 masl). In both ground stations we monitored meteorological parameters (e.g., temperature, wind speed, wind direction). At CSJ, we measured light absorption and scattering at three wavelengths (467, 528 and 652 nm). At PE we collected cloud and rainwater for chemical analyses and monitored cloud microphysical properties (e.g., liquid water content, droplet size distribution, droplet number concentration, effective diameter and median volume diameter). Summer 2015 was the first attempt to characterize microphysical properties of the summer period (June to August) at PE, where dust is in its higher concentrations of the year. Samples were classified using data from models and satellites together with CSJ measurements as low or high dust influenced. Soluble ions, insoluble trace metals, pH, conductivity, total and dissolved organic carbon and total and dissolved nitrogen were measured for cloud and rainwater. Enrichment factor analysis was used to determine sea and crustal contribution of species by sample, as well as the neutralization factor and fractional acidity. Some preliminary results show cloud water conductivity for low

  3. Rain chemistry and cloud composition and microphysics in a Caribbean tropical montane cloud forest under the influence of African dust

    NASA Astrophysics Data System (ADS)

    Torres-Delgado, Elvis; Valle-Diaz, Carlos J.; Baumgardner, Darrel; McDowell, William H.; González, Grizelle; Mayol-Bracero, Olga L.

    2015-04-01

    It is known that huge amounts of mineral dust travels thousands of kilometers from the Sahara and Sahel regions in Africa over the Atlantic Ocean reaching the Caribbean, northern South America and southern North America; however, not much is understood about how the aging process that takes place during transport changes dust properties, and how the presence of this dust affects cloud's composition and microphysics. This African dust reaches the Caribbean region mostly in the summer time. In order to improve our understanding of the role of long-range transported African dust (LRTAD) in cloud formation processes in a tropical montane cloud forest (TMCF) in the Caribbean region we had field campaigns measuring dust physical and chemical properties in summer 2013, as part of the Puerto Rico African Dust and Cloud Study (PRADACS), and in summer 2014, as a part of the Luquillo Critical Zone Observatory (LCZO) and in collaboration with the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE). Measurements were performed at the TMCF of Pico del Este (PE, 1051 masl) and at the nature reserve of Cabezas de San Juan (CSJ, 60 masl). In both stations we monitored meteorological parameters (e.g., temperature, wind speed, wind direction). At CSJ, we measured light absorption and scattering at three wavelengths (467, 528 and 652 nm). At PE we collected cloud and rainwater and monitored cloud microphysical properties (e.g., liquid water content, droplet size distribution, droplet number concentration, effective diameter and median volume diameter). Data from aerosol models, satellites, and back-trajectories were used together with CSJ measurements to classify air masses and samples collected at PE in the presence or absence of dust. Soluble ions, insoluble trace metals, pH and conductivity were measured for cloud and rainwater. Preliminary results for summer 2013 showed that in the presence of LRTAD (1) the average conductivity of cloud water

  4. Magnetic fabrics and Pan-African structural evolution in the Najd Fault corridor in the Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Abdeen, Mamdouh M.; Greiling, Reinhard O.; Sadek, Mohamed F.; Hamad, Sayed S.

    2014-11-01

    dykes dissecting it, the highest susceptibilities exceed 7 × 10-2 SI units in magnetite-bearing serpentinite. Early orogenic rocks are characterized by relatively high anisotropies (P‧ up to 1.7) and are deformed in numerous shear zones. Most of these shear zones can be related to the Najd Fault System. In contrast, late orogenic sediments and intrusives show mostly low anisotropies. However, magnetic lineations are still distinctly oriented parallel with the Najd Fault trend. The very latest Pan-African intrusives, the broadly N-S trending dykes crosscutting the Kadabora pluton, imply c. E-W directed extension. Such an extension is consistent with the magnetic fabric in some of the dykes. Therefore, the Kadabora dykes mark the end of Najd wrenching and a late stage of extension in this part of the Eastern Desert of Egypt. The other dykes display mostly primary fabrics, related to magma flow during their intrusion and are thus post-deformational with regard to the Pan-African orogeny.

  5. Fungal Spore Concentrations and Ergosterol Content in Aerosol Samples in the Caribbean During African Dust Events

    NASA Astrophysics Data System (ADS)

    Santos-Figueroa, G.; Bolaños-Rosero, B.; Mayol-Bracero, O. L.

    2015-12-01

    Fungal spores are a major component of primary biogenic aerosol particles that are emitted to the atmosphere, are ubiquitous, and play an important role in the chemistry and physics of the atmosphere, climate, and public health. Every year, during summer months, African dust (AD) particles are transported to the Caribbean region causing an increase in the concentrations of particulate matter in the atmosphere. AD is one of the most important natural sources of mineral particulate matter at the global scale, and many investigations suggest that it has the ability to transport dust-associated biological particles through long distances. The relationship between AD incursions and the concentration of fungal spores in the Caribbean region is poorly understood. In order to investigate the effects of AD incursions on fungal spore's emissions, fungal spore concentrations were monitored using a Burkard spore trap at the tropical montane cloud forest of Pico del Este at El Yunque National Forest, Puerto Rico. The presence of AD was supported with satellite images of aerosol optical thickness, and with the results from the air masses backward trajectories calculated with the NOAA HYSPLIT model. Basidiospores and Ascospores comprised the major components of the total spore's concentrations, up to a maximum of 98%, during both AD incursions and background days. A considerably decrease in the concentration of fungal spores during AD events was observed. Ergosterol, biomarker for measuring fungal biomass, concentrations were determined in aerosols that were sampled at a marine site, Cabezas de San Juan Nature Reserve, in Fajardo Puerto Rico, and at an urban site, Facundo Bueso building at the University of Puerto Rico. Additional efforts to understand the relationship between the arrival of AD to the Caribbean and a decrease in spore's concentrations are needed in order to investigate changes in local spore's vs the contribution of long-range spores transported within the AD.

  6. Modeling the processing of mineral iron during dust transport

    NASA Astrophysics Data System (ADS)

    Vogelsberg, Ulrike; Wolke, Ralf; Tilgner, Andreas; Tegen, Ina; Herrmann, Hartmut

    2014-05-01

    The Saharan desert and the Gobi desert are the main contributors to Aeolian desert dust, which is a major source of micronutrients to the remote ocean regions. Micronutrients, such as transition metals like iron or copper, are regarded essential for biological processes of different marine species. In this context recent studies have shown that soluble iron, since it is generally the most abundant transition metal in dust particles, has the ability to control marine productivity and thereby likely influence the CO2- budget. Nevertheless, the processing of desert dust leading to the release of soluble iron still lacks sufficient understanding since several factors control the solubilization process. Especially anthropogenic emissions are regarded to significantly add to the amount of soluble iron by acidification of dust particles or by the direct emission of soluble iron comprised, e.g. in coal fly ash. For the investigation of the dissolution process of iron that takes place during dust transportation the spectral air parcel model SPACCIM is used. A mechanism describing the precipitation and dissolution of mineral particles by heterogeneous surface reactions has been implemented. Trajectory properties were derived from COSMO-MUSCAT simulations or from re-analysis data by HYSPLIT. Differences in the chemical composition and the amount of anthropogenic and naturally emitted species on the North African continent and the highly industrialized region of South-East Asia have considerable impact on the acidification of the desert dust. Under this aspect, special cases of dust outbreaks of the Saharan desert and the Gobi desert are investigated and compared with focus on soluble iron produced.

  7. Direct Radiative Effect of Mineral Dust on the Development of African Easterly Waves in Late Summer, 2003-07

    SciTech Connect

    Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong; Matsui, Toshihisa; Arking, Albert

    2012-12-19

    Episodic events of both Saharan dust outbreaks and African easterly waves (AEWs) are observed to move westward over the eastern tropical Atlantic Ocean. The relationship between the warm, dry, and dusty Saharan air layer on the nearby storms has been the subject of considerable debate. In this study, the Weather Research and Forecasting model is used to investigate the radiative effect of dust on the development of AEWs during August and September, the months of maximumtropical cyclone activity, in years 2003–07. The simulations show that dust radiative forcing enhances the convective instability of the environment. As a result, mostAEWsintensify in the presence of a dust layer. The Lorenz energy cycle analysis reveals that the dust radiative forcing enhances the condensational heating, which elevates the zonal and eddy available potential energy. In turn, available potential energy is effectively converted to eddy kinetic energy, in which local convective overturning plays the primary role. The magnitude of the intensification effect depends on the initial environmental conditions, including moisture, baroclinity, and the depth of the boundary layer. The authors conclude that dust radiative forcing, albeit small, serves as a catalyst to promote local convection that facilitates AEW development.

  8. Direct Radiative Effect of Mineral Dust on the Development of African Easterly Wave in Late Summer, 2003-2007

    NASA Technical Reports Server (NTRS)

    Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong; Matsui, Toshihisa; Arking, Albert

    2012-01-01

    Episodic events of both Saharan dust outbreaks and African Easterly Waves (AEWs) are observed to move westward over the eastern tropical Atlantic Ocean. The relationship between the warm, dry, and dusty Saharan Air Layer (SAL) on the nearby storms has been the subject of considerable debate. In this study, the Weather Research and Forecasting (WRF) model is used to investigate the radiative effect of dust on the development of AEWs during August and September, the months of maximum tropical cyclone activity, in years 2003-2007. The simulations show that dust radiative forcing enhances the convective instability of the environment. As a result, most AEWs intensify in the presence of a dust layer. The Lorenz energy cycle analysis reveals that the dust radiative forcing enhances the condensational heating, which elevates the zonal and eddy available potential energy. In turn, available potential energy is effectively converted to eddy kinetic energy, in which local convective overturning plays the primary role. The magnitude of the intensification effect depends on the initial environmental conditions, including moisture, baroclinity, and the depth of the boundary layer. We conclude that dust radiative forcing, albeit small, serves as a catalyst to promote local convection that facilitates AEW development.

  9. Establishing a Functional Link Between African Dust and Region-wide Coral Reef Decline

    NASA Astrophysics Data System (ADS)

    Hayes, M. L.; Barber, R. T.

    2003-12-01

    For nearly thirty years, coral reefs in the Western Atlantic and Caribbean basin have experienced historically unprecedented declines. Algal blooms, mass coral bleaching, disease outbreaks and shifts in the dominance of benthic coral-competitors were first documented in the 1970s and have increased in frequency, intensity, variety and range over the past two decades. Recent studies of decreasing coral cover document regional losses averaging nearly 80% over this period. Here, we provide experimental evidence that increased supplies of iron-rich eolian dust from Africa to typically iron-poor marine environments throughout the region could have played a key role in these profound changes. Atmospheric inputs of "new" micronutrients, especially iron, have the potential to overcome limitations to the growth of opportunistic coral-competitors and the virulence of coral pathogens. Microcosm and mesocosm experiments with a putative bacterial pathogen of stony corals, Aurantimonas coralicida, and a temperate stony coral, Oculina arbuscula, provide a means to test the functional relationship between iron availability, microbial growth and coral health. Iron limitation of A. coralicida growth rates is readily induced by the addition of synthetic chelators such as 2,2' Dipyridyl to bacterial cultures at relatively low concentrations (e.g. 10 μ M). This growth limitation is reversed by 100 nM over-enrichments of pure reagent-grade iron as well as iron-rich "synthetic dust" derived from African lake-bed sediments. The Chrome-azurol S assay demonstrates that A. coralicida also synthesizes high-affinity iron-capture mechanisms (i.e. siderophores) that may serve as critical determinants of virulence. Finally, our experimental mesocosms are based on oligotrophic Mediterranean seawater and permit controlled experimentation under relatively low iron ( ˜5 nM) conditions. Using this system, denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified ribosomal DNA

  10. Relations between albedos and emissivities from MODIS and ASTER data over North African Desert

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Dickinson, R. E.; Ogawa, K.; Tian, Y.; Jin, M.; Schmugge, T.; Tsvetsinskaya, E.

    2003-10-01

    This paper analyzes relations among MODIS surface albedos, ASTER broadband (3-14 μm) emissivities, and a soil taxonomy map over the arid areas of Algeria, Libya, and Tunisia in North Africa at 30 second (about 1 km) and 2 minute (about 4 km) spatial resolutions. The MODIS albedo data are from 7 spectral bands and 3 broadbands during dust-free seasons and the emissivity data are derived from a linear combination of the waveband emissivities of the ASTER five thermal infrared channels. Both albedo and emissivity data in the study region show similar considerable spatial variability, larger than assumed by most climate models, and such variability is related to the surface types (sands, rock, and soil orders). Emissivity over bare soils exhibits statistically significant correlations with albedos at both broadbands and most of spectral bands and decreases linearly with albedos. Albedo and emissivity are more strongly correlated with each other than either is to the surface types, apparently because of their higher resolution either spatially or in surface mineralogy. This paper provides guidance for the possible inclusion of such correlation to specify albedo and emissivity in climate models.

  11. Relations Between Albedos and Emissivities From MODIS and ASTER Data Over North African Desert

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Dickinson, R.; Ogawa, K.; Tian, Y.; Jin, M.; Schmugge, T.; Tsvetsinskaya, E.

    2003-12-01

    This paper analyzes relations among MODIS surface albedos, ASTER broadband (3-14 μ m) emissivities, and a soil taxonomy map over the arid areas of Algeria, Libya, and Tunisia in North Africa at 30 second (about 1 km) and 2 minute (about 4 km) spatial resolutions. The MODIS albedo data are from 7 spectral bands and 3 broadbands during dust-free seasons and the emissivity data are derived from a linear combination of the waveband emissivities of the ASTER five thermal infrared channels. Both albedo and emissivity data in the study region show similar considerable spatial variability, larger than assumed by most climate models, and such variability is related to the surface types (sands, rock, and soil orders). Emissivity over bare soils exhibits statistically significant correlations with albedos at both broadbands and most of spectral bands and decreases linearly with albedos. Albedo and emissivity are more strongly correlated with each other than either is to the surface types, apparently because of their higher resolution either spatially or in surface mineralogy. This paper provides guidance for the possible inclusion of such correlation to specify albedo and emissivity in climate models.

  12. North African dust deposition and hydroclimate over the last 60 ka: A combined view from the east and west of the continent

    NASA Astrophysics Data System (ADS)

    Kinsley, C. W.; McGee, D.; Bradtmiller, L. I.; Tierney, J. E.; Winckler, G.; Stuut, J. B. W.; deMenocal, P. B.

    2014-12-01

    Past changes in atmospheric circulation and hydroclimate over North Africa can be explored by reconstructing eolian dust accumulation in both East and West African margin sediments. Recent high-resolution reconstructions of dust deposition from West Africa (1) indicate dramatic changes in North African dust emissions over the last 20 ka, with comparable results to those found in the terrigenous accumulation rates at nearby ODP Hole 658C (2). A high-resolution record of aridity from East Africa using δDwax indicates dramatic changes in hydroclimate over the past 40 ka (3). The records show similar trends with arid conditions/high dust emissions seen during the Last Glacial Maximum, the Younger Dryas and Heinrich Event 1 (H1), and the wettest conditions of the past 40,000 years with accompanying low dust emissions during the African Humid Period. This study has two goals: 1) Extend the dust flux and terrigeneous accumulation records from West Africa back to 35 ka and 60 ka respectively, to provide quantitative estimates of the magnitude of eolian deposition changes associated with previous Heinrich Stadials (H2 to H6) and summer insolation minima/maxima; 2) Construct a high-resolution record of eolian dust accumulation rates off the East African margin over the past 20 ka using the same sample material as (3) allowing quantitative estimates of the magnitude of dust flux changes associated with abrupt changes in hydroclimate and provide a direct comparison of dust flux and δDwax. The combination of these study areas from both sides of the African continent, and comparison of the dust and leaf wax proxies promises to provide a more complete picture of hydroclimate changes accompanying orbital- and millennial-scale climate changes in North Africa over the last 60,000 years. 1. EPSL 371-372, 163-176. 2. Paleoceanography 21, PA4203. 3. Science 342, 843-846.

  13. High-resolution provenance of desert dust deposited on Mt. Elbrus, Caucasus in 2009-2012 using snow pit and firn core records

    NASA Astrophysics Data System (ADS)

    Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Ginot, P.; Lavrentiev, I.; Kemp, S.

    2013-09-01

    The first record of dust deposition events on Mt. Elbrus, Caucasus Mountains derived from a snow pit and a shallow firn core is presented for the 2009-2012 period. A combination of isotopic analysis, SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analyses of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 20-100 km) resolution. Seventeen dust deposition events were detected; fourteen occurred in March-June, one in February and two in October. Four events originated in the Sahara, predominantly in northeastern Libya and eastern Algeria. Thirteen events originated in the Middle East, in the Syrian Desert and northern Mesopotamia, from a mixture of natural and anthropogenic sources. Dust transportation from Sahara was associated with vigorous Saharan depressions, strong surface winds in the source region and mid-tropospheric southwesterly flow with daily winds speeds of 20-30 m s-1 at 700 hPa level. Although these events were less frequent than those originating in the Middle East, they resulted in higher dust concentrations in snow. Dust transportation from the Middle East was associated with weaker depressions forming over the source region, high pressure centred over or extending towards the Caspian Sea and a weaker southerly or southeasterly flow towards the Caucasus Mountains with daily wind speeds of 12-18 m s-1 at 700 hPa level. Higher concentrations of nitrates and ammonium characterised dust from the Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 μm and 4.16 μm. Most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm and there was no significant difference between dust from the Sahara and the Middle East.

  14. Analyse of direct and indirect effects of Saharan dust on convection and on the African monsoon circulation during the FENNEC project using WRF-CHEM

    NASA Astrophysics Data System (ADS)

    Lavaysse, Christophe; Flamant, Cyrille; Grabowski, Wojciech; Morisson, Hugh; Banks, Jamie

    2013-04-01

    The aim of this study is to analyse the local impacts of dust on convection and on the West African monsoon circulation. Using the regional models WRF-CHEM, different dust schemes have been tested to quantify the impacts of dust on convection and on the main components of the West African monsoon, such as the West African Heat Low (WAHL), African Easterly Waves (AEWs), monsoon and harmatan winds. The specific pre-onset period of the monsoon precipitation over the Sahel has been simulated, in 2011 during the FENNEC project. We have investigated a 15-day period from June 10th to 25th. During this period, high dust concentration over the Sahara has been detected using satellite observations and the WAHL settled in its summer Saharan location. In this study, we have observed that WRF-CHEM is able to reproduce dust outbreaks and transport as detected in the satellite and airborne observations. This study also highlights the two effects of dust on the monsoon circulation over the Sahara: a so-called direct effect associated with dust radiative heating, which increases the WAHL thickness, and a so called indirect effect that modifies mid-level and deep convection over the Sahel.

  15. Dust exposure and pneumoconiosis in a South African pottery. 2. Pneumoconiosis and factors influencing reading of radiological opacities.

    PubMed

    Rees, D; Steinberg, M; Becker, P J; Solomon, A

    1992-07-01

    A cross sectional radiological survey of workers exposed to pottery dust during the manufacture of wall tiles and bathroom fittings was conducted in a South African factory. Roughly one third of workers with 15 or more years of service in high dust sections of the factory had pneumoconiosis. Previously undiagnosed advanced cases, including two with progressive massive fibrosis, were working in dusty occupations. A firm diagnosis of potters' pneumoconiosis was made in 11 of the 358 workers radiographed; all had served more than 10 years suggesting that radiography of workers with more than 10 years service would be a successful case finding strategy in South Africa. A combination of rounded and irregular opacities was the most common radiological finding in the workers with pneumoconiosis (55%). Three readers reported on the chest radiographs, and all found an association between small radiological opacities, which were usually irregular or a combination of irregular and rounded, and exposure to pottery dust. The occurrence of irregular radiological opacities in workers exposed to pottery dust deserves further study. The least experienced reader significantly associated age with small opacities when duration of service (years) was used to measure exposure to dust. Sex was not an important predictor of radiological changes consistent with pneumoconiosis. Breast shadows were not an important cause of false positive readings and participating women did not develop pneumoconiosis after less exposure than men.

  16. Desert Dust Air Mass Mapping in the Western Sahara, using Particle Properties Derived from Space-based Multi-angle Imaging

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph; Petzold, Andreas; Wendisch, Manfred; Bierwirth, Eike; Dinter, Tilman; Fiebig, Marcus; Schladitz, Alexander; von Hoyningen-Huene, Wolfgang

    2008-01-01

    Coincident observations made over the Moroccan desert during the SAhara Mineral dUst experiMent (SAMUM) 2006 field campaign are used both to validate aerosol amount and type retrieved from Multi-angle Imaging SpectroRadiometer (MISR) observations, and to place the sub-orbital aerosol measurements into the satellite's larger regional context. On three moderately dusty days for which coincident observations were made, MISR mid-visible aerosol optical thickness (AOT) agrees with field measurements point-by-point to within 0.05 to 0.1. This is about as well as can be expected given spatial sampling differences; the space-based observations capture AOT trends and variability over an extended region. The field data also validate MISR's ability to distinguish and to map aerosol air masses, from the combination of retrieved constraints on particle size, shape, and single-scattering albedo. For the three study days, the satellite observations (a) highlight regional gradients in the mix of dust and background spherical particles, (b) identify a dust plume most likely part of a density flow, and (c) show an air mass containing a higher proportion of small, spherical particles than the surroundings, that appears to be aerosol pollution transported from several thousand kilometers away.

  17. Soil genesis on the island of Bermuda in the Quaternary: the importance of African dust transport and deposition

    USGS Publications Warehouse

    Muhs, Daniel R.; Budahn, James R.; Prospero, Joseph M.; Skipp, Gary; Herwitz, Stanley R.

    2012-01-01

    The origin of terra rossa, red or reddish-brown, clay-rich soils overlying high-purity carbonate substrates, has intrigued geologists and pedologists for decades. Terra rossa soils can form from accumulation of insoluble residues during dissolution of the host limestones, addition of volcanic ash, or addition of externally derived, long-range-transported (LRT) aeolian particles. We studied soils and paleosols on high-purity, carbonate aeolianites of Quaternary age on Bermuda, where terra rossa origins have been debated for more than a century. Potential soil parent materials on this island include sand-sized fragments of local volcanic bedrock, the LRT, fine-grained (N/YbN, GdN/YbN that can be distinguished from African dust and lower Mississippi River valley loess. Bermuda soils have Sc-Th-La, Cr-Ta-Nd, and Eu/Eu*, LaN/YbN, GdN/YbN that indicate derivation from a combination of LRT dust from Africa and local volcanic bedrock. Our results indicate that soils on islands in a very broad latitudinal belt of the western Atlantic margin have been influenced by African LRT dust inputs over much of the past –500 ka.

  18. Size-Differentiated Chemical Composition of Re-Suspended Soil Dust from the Desert Southwest United States

    EPA Science Inventory

    As part of the Desert Southwest Coarse Particulate Matter Study which characterized the composition of fine and coarse particulate matter in Pinal County, AZ, several source samples were collected from several different soil types to assist in source apportionment analysis of the...

  19. Living in biological soil crust communities of African deserts-Physiological traits of green algal Klebsormidium species (Streptophyta) to cope with desiccation, light and temperature gradients.

    PubMed

    Karsten, Ulf; Herburger, Klaus; Holzinger, Andreas

    2016-05-01

    Green algae of the genus Klebsormidium (Klebsormidiales, Streptophyta) are typical members of biological soil crusts (BSCs) worldwide. The phylogeny and ecophysiology of Klebsormidium has been intensively studied in recent years, and a new lineage called superclade G, which was isolated from BSCs in arid southern Africa and comprising undescribed species, was reported. Three different African strains, that have previously been isolated from hot-desert BSCs and molecular-taxonomically characterized, were comparatively investigated. In addition, Klebsormidium subtilissimum from a cold-desert habitat (Alaska, USA, superclade E) was included in the study as well. Photosynthetic performance was measured under different controlled abiotic conditions, including dehydration and rehydration, as well as under a light and temperature gradient. All Klebsormidium strains exhibited optimum photosynthetic oxygen production at low photon fluence rates, but with no indication of photoinhibition under high light conditions pointing to flexible acclimation mechanisms of the photosynthetic apparatus. Respiration under lower temperatures was generally much less effective than photosynthesis, while the opposite was true for higher temperatures. The Klebsormidium strains tested showed a decrease and inhibition of the effective quantum yield during desiccation, however with different kinetics. While the single celled and small filamentous strains exhibited relatively fast inhibition, the uniserate filament forming isolates desiccated slower. Except one, all other strains fully recovered effective quantum yield after rehydration. The presented data provide an explanation for the regular occurrence of Klebsormidium strains or species in hot and cold deserts, which are characterized by low water availability and other stressful conditions.

  20. Temperature and aridity of the African-Arabian desert belt since 1750 CE reconstructed from Red Sea coral Sr/Ca and δ18O

    NASA Astrophysics Data System (ADS)

    Felis, T.; Rimbu, N.; Ionita, M.; Kölling, M.

    2015-12-01

    Throughout the desert regions of the globe, annually to seasonally resolved proxy records of temperature and aridity that extend the short observational record are sparse. For the African-Arabian desert belt, proxy records of temperature are virtually absent in reconstructions of continental-scale temperature variability during the past millennia. Here we present a new reconstruction of temperature from the African-Arabian desert belt back to 1750 CE, derived from bimonthly analysis of the Sr/Ca-temperature proxy in a northern Red Sea Porites coral (Ras Umm Sidd, Sinai, Egypt). The annual average coral Sr/Ca record is significantly correlated with land surface temperature throughout the eastern Sahara and the Arabian Desert during the last century. The coral Sr/Ca record is also significantly correlated with sea surface temperature (SST) in the Red Sea, Mediterranean Sea and North Atlantic Ocean, but not with Indian Ocean SST. Correlation with sea level pressure (SLP) fields identifies the advection of relatively cold continental air from southeastern Europe toward the Middle East and northeastern Africa as physical mechanism that controls temperature variability at interannual timescales. We combined the Sr/Ca record with a previously reported δ18O record from the same coral, and generated an annually resolved reconstruction of seawater δ18O. Correlation of the annual seawater δ18O reconstruction with SLP and 850 hPa geopotential height fields identifies the advection of relatively dry desert air from the eastern Sahara toward the northern Red Sea as physical mechanism that controls seawater δ18O variability at interannual timescales. This regional mechanism is associated with large-scale SLP anomalies of opposite sign throughout the Northern Hemisphere subtropics and the Arctic. The most striking feature of the seawater δ18O reconstruction is an abrupt regime shift toward fresher conditions in northern Red Sea surface waters between 1850 and 1855 CE. Because

  1. The Relationship between Aerosol Composition and Concentration and Visual Range on Barbados, West Indies: The Impact of African Dust

    NASA Astrophysics Data System (ADS)

    Huang, J.; Prospero, J.; Zhang, C.; Arimoto, R.

    2006-12-01

    Visual Range (VR) measured at Grantley Adams Airport on Barbados shows a very strong annual cycle with the minimum VR values occurring in June or July. This cycle closely matches the annual cycle of African dust concentrations measured in the trade winds at Barbados (13°15'N, 59°30'W) where observations first began in 1965. In winter, monthly mean VR was typically around 30 km or greater while in summer it frequently dipped below 20 km. This same clear signal is observed in the VR records from near-by islands where the same seasonal cycle of dust would be expected: St. Lucia, Martinique and Trinidad and Tobago. We examined the relationship between VR on Barbados and the concentrations of the three major aerosol constituents that we would expect to have the strongest influence on VR: mineral dust, sea salt, and non-sea- salt sulfate (nss-SO4^{=}). We used VR data for the period from 1973, when measurements first began, up to 2006. We found a large discrepancy between the observed VR at the airport and the VR derived from the Koschmieder equation using literature values for the optical properties of the aerosol components; this simple approach would require a much smaller constant than the commonly-used value, 3.912. We further explored the effects of particle size distribution and relative humidity. During boreal summer when VR is lowest, dust is the dominant supramicron aerosol component and it clearly is the major factor in controlling VR. Nonetheless the submicron fraction also has a comparable impact due to its significantly higher light scattering efficiency. During winter, when there is little or no dust, sea salt aerosol and sulfate are dominant. In this report we focus on the various factors that affect visibility on Barbados especially the role of aerosols dominated by supramicrometer particles. We also consider the effects of other factors such as wind speed and precipitation. Finally, we note that the close relationship between summertime VR and dust

  2. The Influence of African Dust on Air Quality in the Caribbean Basin: An Integrated Analysis of Satellite Retrievals, Ground Observations, and Model Simulations

    NASA Astrophysics Data System (ADS)

    Yu, H.; Prospero, J. M.; Chin, M.; Randles, C. A.; da Silva, A.; Bian, H.

    2015-12-01

    Long-term surface measurements in several locations extending from northeastern coast of South America to Miami in Florida have shown that African dust arrives in the Greater Caribbean Basin throughout a year. This long-range transported dust frequently elevates the level of particulate matter (PM) above the WHO guideline for PM10, which raises a concern of possible adverse impact of African dust on human health in the region. There is also concern about how future climate change might affect dust transport and its influence on regional air quality. In this presentation we provide a comprehensive characterization of the influence of African dust on air quality in the Caribbean Basin via integrating the ground observations with satellite retrievals and model simulations. The ground observations are used to validate and evaluate satellite retrievals and model simulations of dust, while satellite measurements and model simulations are used to extend spatial coverage of the ground observations. An analysis of CALIPSO lidar measurements of three-dimensional distribution of aerosols over 2007-2014 yields altitude-resolved dust mass flux into the region. On a basis of 8-year average and integration over the latitude zone of 0°-30°N, a total of 76 Tg dust is imported to the air above the Greater Caribbean Basin, of which 34 Tg (or 45%) is within the lowest 1 km layer and most relevant to air quality concern. The seasonal and interannual variations of the dust import are well correlated with ground observations of dust in Cayenne, Barbados, Puerto Rico, and Miami. We will also show comparisons of the size-resolved dust amount from both NASA GEOS-5 aerosol simulation and MERRA-2 aerosol reanalysis (i.e., column aerosol loading being constrained by satellite measurements of radiance at the top of atmosphere) with the ground observations and satellite measurement.

  3. Increasing trend of African dust, over 49 years, in the eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Ganor, Eliezer; Osetinsky, Isabella; Stupp, Amnon; Alpert, Pinhas

    2010-04-01

    Dust observations in Israel were carried out since 1958. During 1958-2006, 966 dust days were observed. The dust days have been analyzed through their association with the regional eastern Mediterranean synoptic types, as classified by the Tel Aviv University method. Among the synoptic types, the most contributing were winter lows (with 368 days), Red Sea Troughs (214 days), and highs (211 dust days). Association of dust with highs is a new result, not found in the literature to date. Out of the total occurrences of Sharav lows, 36% are associated with dust, out of total winter lows 13%, with a winter low south to Cyprus having a 30% probability to produce a dust day, and of Red Sea Trough days 6% were associated with dust. Annual occurrence of dust days follows the changes in the occurrence of the regional synoptic systems: the number of dust days associated with Red Sea Troughs has increased by 2.3 d/10 yr, and with highs by 0.9 d/10 yr. The total incidence of dust days has increased with an average rate of 2.7 days per decade. This increasing trend in dust storm occurrence fits with previous results for the eastern Mediterranean and south Europe. Since dust storms are a regional phenomenon and reach south, central, and western Europe, this increase has implications for the entire Mediterranean and European regions. The results show potential for statistical forecasting of dust 1 day in advance. Such forecasts are important for public health warnings and for air transportation.

  4. Columnar Aerosol Single-Scattering Albedo and Phase Function Retrieved from Sky Radiance Over the Ocean: Measurements of African Dust

    NASA Technical Reports Server (NTRS)

    Cattrall, Christopher; Carder, Kendall L.; Gordon, Howard R.

    2001-01-01

    The single-scattering albedo and phase function of African mineral dust are retrieved from ground-based measurements of sky radiance collected in the Florida Keys. The retrieval algorithm employs the radiative transfer equation to solve by iteration for these two properties which best reproduce the observed sky radiance using an assumed aerosol vertical structure and measured aerosol optical depth. Thus, no assumptions regarding particle size, shape, or composition are required. The single-scattering albedo, presented at fourteen wavelengths between 380 and 870 nm, displays a spectral shape expected of iron-bearing minerals but is much higher than current dust models allow. This indicates the absorption of light by mineral dust is significantly overestimated in climate studies. Uncertainty in the retrieved albedo is less than 0.02 due to the small uncertainty in the solar-reflectance-based calibration (12.2%) method employed. The phase function retrieved at 860 nm is very robust under simulations of expected experimental errors, indicating retrieved phase functions at this wavelength may be confidently used to describe aerosol scattering characteristics. The phase function retrieved at 443 nm is very sensitive to expected experimental errors and should not be used to describe aerosol scattering. Radiative forcing by aerosol is the greatest source of uncertainty in current climate models. These results will help reduce uncertainty in the absorption of light by mineral dust. Assessment of the radiative impact of aerosol species is a key component to NASA's Earth System Enterprise.

  5. A Comparative Study of Mesoscale Modeling of Smoke and Dust Direct Radiative Effects over Northern Sub-Saharan African Region.

    NASA Astrophysics Data System (ADS)

    Yue, Y.; Wang, J.; Ichoku, C. M.; Zhang, F.

    2014-12-01

    This study aims to investigate the radiative effects of smoke and dust aerosols and of the underlying surface in the Northern Sub-Saharan African (NSSA) region using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). We performed a yearlong (from September 2009 to September 2010) WRF-Chem simulation using hourly emissions from the Fire Energetics and Emissions Research (FEER) emission dataset derived by multiplying emission coefficients based on aerosol and fire observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard Terra and Aqua with fire radiative energy (FRE) measurements from the geostationary Meteosat Spinning Enhanced Visible and Infrared Imager (SEVIRI). The geographic distribution and vertical profiles of simulated dust and smoke aerosols were evaluated with MODIS true color images and Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIPSO) total attenuated backscatter, aerosol extinction coefficient and depolarization data. We found that simulated aerosol vertical concentration profiles are consistent with the above CALIPSO data. Surface albedo and columnar aerosol optical depth (AOD) sensitivity to smoke and dust simulations are performed with WRF-Chem. The simulated surface albedo and AOD were compared with MODIS albedo product (MODIS43) and AOD measurements from the Aerosol Robotic Network (AERONET). The modeled smoke/dust clear-sky and all-sky radiative impacts were analyzed in this study and reveal interesting results that will be discussed.

  6. Cross-shift peak expiratory flow changes are unassociated with respirable coal dust exposure among South African coal miners

    SciTech Connect

    Naidoo, R.N.; Robins, T.G.; Becklake, M.; Seixas, N.; Thompson, M.L.

    2007-12-15

    he objectives of this study were to determine whether cross-shift changes in peak expiratory flow rate (PEFR) were related to respirable dust exposure in South African coalminers. Fifty workers were randomly selected from a cohort of 684 miners from 3 bituminous coal mines in Mpumalanga, South Africa. Peak expiratory efforts were measured prior to the commencement of the shift, and at the end of the shift on at least two occasions separated by at least 2 weeks, with full shift personal dust sampling being conducted on each occasion for each participant. Interviews were conducted, work histories were obtained and cumulative exposure estimates were constructed. Regression models examined the associations of cross-shift changes in PEFR with current and cumulative exposure, controlling for shift, smoking and past history of tuberculosis. There were marginal differences in cross-shift PEFR (ranging from 0.1 to 2 L/min). Linear regression analyses showed no association between cross-shift change in PEFR and current or cumulative exposure. The specific shift worked by participants in the study showed no effect. Our study showed no association between current respirable dust exposure and cross-shift changes in PEFR. There was a non-significant protective effect of cumulative dust exposure on the outcome, suggesting the presence of a 'healthy worker survivor effect' in this data.

  7. Investigation on The Interlink Between Optical Properties of Dusts Over Taiwan and Thar Desert, India Using CALIPSO Data

    NASA Astrophysics Data System (ADS)

    Roja Raman, M.; Chen, Wei-Nai; He, Sin-Jie; Chen, Li-Ting; Hsu, Kai-Hsuan

    2016-06-01

    The optical properties (Angstrom exponent and depolarization) of aerosols are analyzed to characterize the dust particles at different altitudes of the atmosphere using the backscatter signal from the space borne Lidar (CALIPSO) over Asian region with emphasis on Taiwan and Indian regions. The physical and optical properties of dust particles are found different at wet and dry weather conditions. The size distribution of dust particles at different altitudes is estimated. Finally the correlation between the particle depolarization and the angstrom exponent of dust particles at different altitudes is analyzed and the possible reasons are discussed. Further, the spatial inhomogeneity in the correlation coefficient is noticed and the possible relation with regional weather conditions is discussed.

  8. Soil genesis on the island of Bermuda in the Quaternary: The importance of African dust transport and deposition

    NASA Astrophysics Data System (ADS)

    Muhs, Daniel R.; Budahn, James R.; Prospero, Joseph M.; Skipp, Gary; Herwitz, Stanley R.

    2012-09-01

    The origin of terra rossa, red or reddish-brown, clay-rich soils overlying high-purity carbonate substrates, has intrigued geologists and pedologists for decades. Terra rossa soils can form from accumulation of insoluble residues during dissolution of the host limestones, addition of volcanic ash, or addition of externally derived, long-range-transported (LRT) aeolian particles. We studied soils and paleosols on high-purity, carbonate aeolianites of Quaternary age on Bermuda, where terra rossa origins have been debated for more than a century. Potential soil parent materials on this island include sand-sized fragments of local volcanic bedrock, the LRT, fine-grained (<20μm) component of distal loess from the lower Mississippi River Valley, and LRT dust from Africa. These parent materials can be characterized geochemically using trace elements that are immobile in the soil-forming environment. Results indicate that local volcanic bedrock on Bermuda has Sc-Th-La, Cr-Ta-Nd, and Eu/Eu*, LaN/YbN, GdN/YbNthat can be distinguished from African dust and lower Mississippi River valley loess. Bermuda soils have Sc-Th-La, Cr-Ta-Nd, and Eu/Eu*, LaN/YbN, GdN/YbN that indicate derivation from a combination of LRT dust from Africa and local volcanic bedrock. Our results indicate that soils on islands in a very broad latitudinal belt of the western Atlantic margin have been influenced by African LRT dust inputs over much of the past ˜500 ka.

  9. Size distribution and optical properties of African mineral dust after intercontinental transport

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Formenti, Paola; Desboeufs, Karine; Chevaillier, Servanne; Triquet, Sylvain; Maillé, Michel; Cazaunau, Mathieu; Laurent, Benoit; Mayol-Bracero, Olga L.; Vallejo, Pamela; Quiñones, Mariana; Gutierrez-Molina, Ian E.; Cassola, Federico; Prati, Paolo; Andrews, Elisabeth; Ogren, John

    2016-06-01

    The transatlantic transport of mineral dust from Africa is a persistent atmospheric phenomenon, clue for understanding the impacts of dust at the global scale. As part of the DUST Aging and Transport from Africa to the Caribbean (Dust-ATTACk) intensive field campaign, the size distribution and optical properties of mineral dust were measured in June-July 2012 on the east coast of Puerto Rico, more than 5000 km from the west coast of Africa. During the recorded dust events, the PM10 (particulate matter 10 micrometers or less in diameter) concentrations increased from 20 to 70 µg m-3. Remote sensing observations and modeling analysis were used to identify the main source regions, which were found in the Western Sahara, Mauritania, Algeria, Niger, and Mali. The microphysical and optical properties of the dust plumes were almost independent of origin. The size distribution of mineral dust after long-range transport may have modal diameters similar to those on the eastern side of the Atlantic short time after emission, possibly depending on height of transport. Additional submicron particles of anthropogenic absorbing aerosols (likely from regional marine traffic activities) can be mixed within the dust plumes, without affecting in a significant way the PM10 absorption properties of dust observed in Puerto Rico. The Dust-ATTACk experimental data set may be useful for modeling the direct radiative effect of dust. For accurate representation of dust optical properties over the Atlantic remote marine region, we recommend mass extinction efficiency (MEE) and single-scattering albedo values in the range 1.1-1.5 m2 g-1 and 0.97-0.98, respectively, for visible wavelengths.

  10. Mechanisms and Effects of Summertime Transport of African Dust Through the Tokar Mountain Gap to the Red Sea and Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Kalenderski, S.; Stenchikov, G. L.

    2015-12-01

    Very high dust loading over the Red Sea region in summer strongly affects the nutrition balance and thermal and dynamic regimes of the sea. The observations suggest that small-scale local dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand and quantify these processes we present here the first high resolution modeling study of the dust outbreak phenomena in June 2012 over East Africa, the Red Sea, and the Arabian Peninsula using the WRF-Chem model. We identified several dust generating dynamical processes that range from convective to synoptic scales, including: synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea most of the dust transport occurs beyond 2 km above ground level and is strengthened by a pressure gradient formed by low pressure over the eastern Mediterranean and high pressure over the Arabian Peninsula. Across the central and southern parts of the Red Sea dust is mostly transported below 2 km height. During the study period dust is a dominant contributor (87%) to aerosol optical depth (AOD), producing a domain average cooling effect of -12.1 W m-2 at surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. WRF-Chem simulations demonstrate that both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. During the dust outbreak 49.2 Tg of dust deposits within the calculation domain, which is approximately 90% of the total dust emission of 54.5 Tg. Model results compare well with available ground-based and satellite observations but generally underestimate the observed AOD maximum values.

  11. Historical trends and sources of TSP in a Sonoran desert city: Can the North America Monsoon enhance dust emissions?

    NASA Astrophysics Data System (ADS)

    Moreno-Rodríguez, Verónica; Del Rio-Salas, Rafael; Adams, David K.; Ochoa-Landin, Lucas; Zepeda, Joel; Gómez-Alvarez, Agustín; Palafox-Reyes, Juan; Meza-Figueroa, Diana

    2015-06-01

    In this work, the trends of total suspended particulate matter (TSP) were analyzed during a period of 12 years (2000-2012) on the basis of meteorological parameters. The results of historical trends of TSP show that post-monsoon dust emission seems to be connected to rainfall distribution in the urban environment. Particulate matter is dominated by plagioclase, quartz, calcite, and montmorillonite phases with barium sulfate, and particles enriched in Cu, Fe, and Ce. Elemental composition and principal component analysis allow the identification of two major sources for metals incorporated in geogenic dust: cement, and traffic. Geochemical analysis of non-mobile trace elements show a similar signature as local cement brands in TSP filters, but it remains unknown if such a signature is related to cement production, erosion of buildings, or construction activities. La-Ce geochemical tracers show that geogenic dust is an important media of transportation for traffic, and cement-related contaminants. This work highlights the importance of monsoon season precipitation in dust generation in arid urban environments, and it could contribute to regional studies including the southwestern US regarding the dust emission processes and transport of pollutants across the trans-boundary.

  12. Semidirect Dynamical and Radiative Impact of North African Dust Transport on Lower Tropospheric Clouds over the Subtropical North Atlantic in CESM 1.0

    SciTech Connect

    DeFlorio, Mike; Ghan, Steven J.; Singh, Balwinder; Miller, Arthur J.; Cayan, Dan; Russell, Lynn M.; Somerville, Richard C.

    2014-07-16

    This study uses a century length pre-industrial climate simulation by the Community Earth System Model (CESM 1.0) to explore statistical relationships between dust, clouds and atmospheric circulation, and to suggest a dynamical, rather than microphysical, mechanism linking subtropical North Atlantic lower tropospheric cloud cover with North African dust transport. The length of the run allows us to account for interannual variability of dust emissions and transport downstream of North Africa in the model. CESM’s mean climatology and probability distribution of aerosol optical depth in this region agrees well with available AERONET observations. In addition, CESM shows strong seasonal cycles of dust burden and lower tropospheric cloud fraction, with maximum values occurring during boreal summer, when a strong correlation between these two variables exists downstream of North Africa over the subtropical North Atlantic. Calculations of Estimated Inversion Strength (EIS) and composites of EIS on high and low downstream North Africa dust months during boreal summer reveal that dust is likely increasing inversion strength over this region due to both solar absorption and reflection. We find no evidence for a microphysical link between dust and lower tropospheric clouds in this region. These results yield new insight over an extensive period of time into the complex relationship between North African dust and lower tropospheric clouds over the open ocean, which has previously been hindered by spatiotemporal constraints of observations. Our findings lay a framework for future analyses using sub-monthly data over regions with different underlying dynamics.

  13. Does the long-range transport of African mineral dust across the Atlantic enhance their hygroscopicity?

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Caquineau, Sandrine; Desboeufs, Karine; Laurent, Benoit; Quiñones Rosado, Mariana; Vallejo, Pamela; Mayol-Bracero, Olga; Formenti, Paola

    2015-04-01

    Influence of mineral dust on radiation balance is largely dependent on their ability to interact with water. While fresh mineral dusts are highly hydrophobic, various transformation processes (coagulation, heterogeneous chemical reaction) can modify the dust physical and chemical properties during long-range transport, which, in turn, can change the dust hygroscopic properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of dust hygroscopic properties, and their temporal evolution during long-range transport. We present the first direct surface measurements of the hygroscopicity of Saharan dust after long-range transport over the Atlantic Ocean, their relationship with chemical composition, their influence on particle size and shape and implications for optical properties. Particles were collected during the DUST Aging and TransporT from Africa to the Caribbean (Dust-AttaCk) campaign at the Cape San Juan Puerto Rico station in June-July 2012. Environmental scanning electron microscopy (ESEM) was used to analyze the size, shape, chemical composition and hygroscopic properties of individual particles. At different levels of concentrations in summertime, the coarse mode of atmospheric aerosols in Puerto Rico is dominated by Saharan mineral dust. Most of aged dust particles survived atmospheric transport intact with no observed internal mixture with other species and did not show hygroscopic growth up to 94% relative humidity. This is certainly due to the fact that in summertime dust is mostly transported above the marine boundary layer. A minor portion of mineral dust (approximately 19-28% by number) were involved in atmospheric heterogeneous reactions with acidic gases (likely SO2 and HCl) and sea salt aggregation. While sulfate- and chloride-coated dust remained extremely hydrophobic, dust particles in internal mixing with NaCl underwent profound changes in their hygroscopicity, therefore in size and shape. We

  14. A comparison of the physical properties of desert dust retrieved from the sunphotometer observation of major events in the Sahara, Sahel, and Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Masmoudi, Mohamed; Alfaro, Stéphane C.; El Metwally, Mossad

    2015-05-01

    The objective of this work is to assess the variability of the size-distribution, real (n) and imaginary (k) parts of the refractive index, asymmetry parameter (g), and single scattering albedo (SSA) of desert dust events observed in the Sahara, Sahel, and Arabian Peninsula areas. For this we use the level-2 inversions of 14 AERONET sunphotometers representative of the area of study. In the dataset, the dust-dominated events are discriminated on the basis of their large optical depth and low (< 0.3) Ångström exponent (α) calculated between 440 nm and 870 nm. In all the volume size-distributions a coarse mode (CM) of particles is observed but a fine mode (FM) of particles with radii < 0.2 μm is also present. The volume fraction represented by the FM is lower (3%) during the most intense dust storms than during moderate ones (12%). The inter-site variability of the characteristics of the CM-dominated situations is found to be non-significant and at 440, 675, 870, and 1020 nm a common set of values can be adopted for n (1.54 ± 0.03, 1.53 ± 0.02, 1.50 ± 0.02, 1.48 ± 0.02), k (0.0037 ± 0.0007, 0.0012 ± 0.0002, 0.0011 ± 0.0002, 0.0012 ± 0.0002), g (0.77 ± 0.01, 0.74 ± 0.01, 0.73 ± 0.01, 0.74 ± 0.01), and the SSA (0.90 ± 0.02, 0.97 ± 0.01, 0.98 ± 0.01, 0.98 ± 0.01). However; during the less intense dust-events the growing influence of the FM leads to regional differentiation of the dust properties and 2 main areas can be distinguished: 1) the relatively clean central Sahara/Sahel, and 2) the more polluted continuum constituted by the Mediterranean coast and the Arabian Peninsula.

  15. Forecasting the North African dust outbreak towards Europe in April 2011: a model intercomparison

    NASA Astrophysics Data System (ADS)

    Huneeus, N.; Basart, S.; Fiedler, S.; Morcrette, J.-J.; Benedetti, A.; Mulcahy, J.; Terradellas, E.; Pérez García-Pando, C.; Pejanovic, G.; Nickovic, S.; Arsenovic, P.; Schulz, M.; Cuevas, E.; Baldasano, J. M.; Pey, J.; Remy, S.; Cvetkovic, B.

    2015-10-01

    In the framework of the World Meteorological Organisation's Sand and Dust Storm Warning Advisory and Assessment System, we evaluated the predictions of five state-of-the-art dust forecast models during an intense Saharan dust outbreak affecting Western and Northern Europe in April 2011. We assessed the capacity of the models to predict the evolution of the dust cloud with lead-times of up to 72 h using observations of aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS), and dust surface concentrations from a ground-based measurement network. In addition, the predicted vertical dust distribution was evaluated with vertical extinction profiles from the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP). To assess the diversity in forecast capability among the models, the analysis was extended to wind field (both surface and profile), synoptic conditions, emissions and deposition fluxes. Models predict the onset and evolution of the AOD for all analysed lead-times. On average, differences among the models are larger than differences among lead-times for each individual model. In spite of large differences in emission and deposition, the models present comparable skill for AOD. In general, models are better in predicting AOD than near-surface dust concentration over the Iberian Peninsula. Models tend to underestimate the long-range transport towards Northern Europe. Our analysis suggests that this is partly due to difficulties in simulating the vertical distribution dust and horizontal wind. Differences in the size distribution and wet scavenging efficiency may also account for model diversity in long-range transport.

  16. Forecasting the northern African dust outbreak towards Europe in April 2011: A model intercomparison

    DOE PAGES

    Huneeus, N.; Basart, S.; Fiedler, S.; Morcrette, J. -J.; Benedetti, A.; Mulcahy, J.; Terradellas, E.; Garcia-Pando, C. Perez; Pejanovic, G.; Nickovic, S.; et al

    2016-04-21

    In the framework of the World Meteorological Organisation's Sand and Dust Storm Warning Advisory and Assessment System, we evaluated the predictions of five state-of-the-art dust forecast models during an intense Saharan dust outbreak affecting western and northern Europe in April 2011. We assessed the capacity of the models to predict the evolution of the dust cloud with lead times of up to 72 h using observations of aerosol optical depth (AOD) from the AErosol RObotic NETwork (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) and dust surface concentrations from a ground-based measurement network. In addition, the predicted vertical dust distributionmore » was evaluated with vertical extinction profiles from the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP). To assess the diversity in forecast capability among the models, the analysis was extended to wind field (both surface and profile), synoptic conditions, emissions and deposition fluxes. Models predict the onset and evolution of the AOD for all analysed lead times. On average, differences among the models are larger than differences among lead times for each individual model. In spite of large differences in emission and deposition, the models present comparable skill for AOD. In general, models are better in predicting AOD than near-surface dust concentration over the Iberian Peninsula. Models tend to underestimate the long-range transport towards northern Europe. In this paper, our analysis suggests that this is partly due to difficulties in simulating the vertical distribution dust and horizontal wind. Differences in the size distribution and wet scavenging efficiency may also account for model diversity in long-range transport.« less

  17. Forecasting the Northern African Dust Outbreak Towards Europe in April 2011: A Model Intercomparison

    NASA Technical Reports Server (NTRS)

    Huneeus, N.; Basart, S.; Fiedler, S.; Morcrette, J.-J.; Benedetti, A.; Mulcahy, J.; Terradellas, E.; Pérez García-Pando, C.; Pejanovic, G.; Nickovic, S.

    2016-01-01

    In the framework of the World Meteorological Organisation's Sand and Dust Storm Warning Advisory and Assessment System, we evaluated the predictions of five state-of-the-art dust forecast models during an intense Saharan dust outbreak affecting western and northern Europe in April 2011. We assessed the capacity of the models to predict the evolution of the dust cloud with lead times of up to 72 hours using observations of aerosol optical depth (AOD) from the AErosol RObotic NETwork (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) and dust surface concentrations from a ground-based measurement network. In addition, the predicted vertical dust distribution was evaluated with vertical extinction profiles from the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP). To assess the diversity in forecast capability among the models, the analysis was extended to wind field (both surface and profile), synoptic conditions, emissions and deposition fluxes. Models predict the onset and evolution of the AOD for all analysed lead times. On average, differences among the models are larger than differences among lead times for each individual model. In spite of large differences in emission and deposition, the models present comparable skill for AOD. In general, models are better in predicting AOD than near-surface dust concentration over the Iberian Peninsula. Models tend to underestimate the long-range transport towards northern Europe. Our analysis suggests that this is partly due to difficulties in simulating the vertical distribution dust and horizontal wind. Differences in the size distribution and wet scavenging efficiency may also account for model diversity in long-range transport.

  18. Forecasting the northern African dust outbreak towards Europe in April 2011: a model intercomparison

    NASA Astrophysics Data System (ADS)

    Huneeus, N.; Basart, S.; Fiedler, S.; Morcrette, J.-J.; Benedetti, A.; Mulcahy, J.; Terradellas, E.; Pérez García-Pando, C.; Pejanovic, G.; Nickovic, S.; Arsenovic, P.; Schulz, M.; Cuevas, E.; Baldasano, J. M.; Pey, J.; Remy, S.; Cvetkovic, B.

    2016-04-01

    In the framework of the World Meteorological Organisation's Sand and Dust Storm Warning Advisory and Assessment System, we evaluated the predictions of five state-of-the-art dust forecast models during an intense Saharan dust outbreak affecting western and northern Europe in April 2011. We assessed the capacity of the models to predict the evolution of the dust cloud with lead times of up to 72 h using observations of aerosol optical depth (AOD) from the AErosol RObotic NETwork (AERONET) and the Moderate Resolution Imaging Spectroradiometer (MODIS) and dust surface concentrations from a ground-based measurement network. In addition, the predicted vertical dust distribution was evaluated with vertical extinction profiles from the Cloud and Aerosol Lidar with Orthogonal Polarization (CALIOP). To assess the diversity in forecast capability among the models, the analysis was extended to wind field (both surface and profile), synoptic conditions, emissions and deposition fluxes. Models predict the onset and evolution of the AOD for all analysed lead times. On average, differences among the models are larger than differences among lead times for each individual model. In spite of large differences in emission and deposition, the models present comparable skill for AOD. In general, models are better in predicting AOD than near-surface dust concentration over the Iberian Peninsula. Models tend to underestimate the long-range transport towards northern Europe. Our analysis suggests that this is partly due to difficulties in simulating the vertical distribution dust and horizontal wind. Differences in the size distribution and wet scavenging efficiency may also account for model diversity in long-range transport.

  19. Trans boundary transport of pollutants by atmospheric mineral dust.

    PubMed

    Erel, Yigal; Dayan, Uri; Rabi, Reut; Rudich, Yinon; Stein, Mordechai

    2006-05-01

    The transport of anthropogenic pollution by desert dust in the Eastern Mediterranean region was studied by analyzing major and trace element composition, organic species, and Pb isotope ratios in suspended dust samples collected in Jerusalem, Israel. Dust storms in this region are associated with four distinct synoptic conditions (Red Sea Trough (RS), Eastern High (EH), Sharav Cyclone (SC), and Cold Depression (Cyprus low, CD)) that carry dust mostly from North African (SC, CD, EH) and Arabian and Syrian (RS, EH) deserts. Substantial contamination of dust particles by Pb, Cu, Zn, and Ni is observed, while other elements (Na, Ca, Mg, Mn, Sr, Rb, REE, U, and Th) display natural concentrations. Sequential extraction of the abovementioned elements from the dust samples shows that the carbonate and sorbed fractions contain most of the pollution, yet the Al-silicate fraction is also contaminated, implying that soils and sediments in the source terrains of the dust are already polluted. We identified the pollutant sources by using Pb isotopes. It appears that before the beginning of the dust storm, the pollutants in the collected samples are dominated by local sources but with the arrival of dust from North Africa, the proportion of foreign pollutants increases. Organic pollutants exhibit behavior similar and complementary to that of the inorganic tracers, attesting to the importance of anthropogenic-pollutant addition en route of the dust from its remote sources. Pollution of suspended dust is observed under all synoptic conditions, yet it appears that easterly winds carry higher proportions of local pollution and westerly winds carry pollution emitted in the Cairo basin. Therefore, pollution transport by mineral dust should be accounted for in environmental models and in assessing the health-related effects of mineral dust.

  20. Stable isotope ratio measurements of Cu and Zn in mineral dust (bulk and size fractions) from the Taklimakan Desert and the Sahel and in aerosols from the eastern tropical North Atlantic Ocean.

    PubMed

    Dong, Shuofei; Weiss, Dominik J; Strekopytov, Stanislav; Kreissig, Katharina; Sun, Youbin; Baker, Alex R; Formenti, Paola

    2013-09-30

    Accurate characterization of the stable isotope composition of Cu and Zn in major global mineral dust sources and in aerosols is central to the application of these isotope systems to the studies of global geochemical processes and cycles. We test here for the first time Cu and Zn isotope ratios within a well-defined source-receptor setting on the continent-ocean interface and determine the isotope composition of (i) bulk surface soil dust samples from the Sahel region, (ii) individual size fractions of surface dust samples from the Taklimakan Desert, and (iii) aerosols collected in the equatorial eastern North Atlantic region. This is achieved reducing the blank contribution during the ion exchange step using small resin and acid volumes and using a second ion exchange passage to purify the Cu fraction. We find no significant correlation between size fractions and isotope ratios in the two samples analyzed from the Taklimakan Desert. Mass balance calculations suggest that isotope ratios of bulk samples are within the analytical precision of the <4 μm size fraction and can be used to characterize atmospheric long range transport of Cu and Zn in mineral dust from the Taklimakan Desert. The <1 µm size fractions of two aerosol samples collected over the equatorial eastern North Atlantic region have Cu and Zn isotope ratios that are different to Sahel surface soil dust suggesting important non-crustal sources, in line with calculated enrichment factors, and possibly of anthropogenic origin. Using previously reported δ(66)Zn values for anthropogenic emission from Europe, preliminary calculations suggest that up to 55% of Zn arriving at the sampling points in the equatorial eastern North Atlantic region could be of anthropogenic origin.

  1. Mineral dust deposition in Western Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Vincent, Julie; Laurent, Benoit; Bergmatti, Gilles; Losno, Rémi; Bon Nguyen, Elisabeth; Chevaillier, Servanne; Roulet, Pierre; Sauvage, Stéphane; Coddeville, Patrice; Ouboulmane, Noura; Siour, Guillaume; Tovar Sanchez, Antonio; Massanet, Ana; Morales Baquero, Rafael; Di Sarra, Giogio; Sferlazzo, Damiano; Dulac, François; Fornier, Michel; Coursier, Cyril

    2014-05-01

    North African deserts are the world's largest sources of atmospheric mineral dust produced by aeolian erosion. Saharan dust is frequently transported toward Europe over the Mediterranean basin. When deposited in oceanic areas, mineral dust can constitute a key input of nutrients bioavailable for the oceanic biosphere. For instance, Saharan dust deposited in the in the Mediterranean Sea can be a significant source of nutrient like Fe, P and N during summer and autumn. Our objective is to study the deposition Saharan mineral dust in the western Mediterranean basin and to improve how deposition processes are parameterized in 3D regional models. To quantify the deposition flux of Saharan dust in the western Mediterranean region a specific collector (CARAGA) to sample automatically the insoluble atmospheric particle deposition was developed (LISA-ICARE) and a network of CARAGA collectors have been set up. Since 2011, eight CARAGA are then deployed in Frioul, Casset, Montandon and Ersa in France, Mallorca and Granada in Spain, Lampedusa in Italia, and Medenine in Tunisia, along a South-North gradient of almost 2000km from the North African coast to the South of Europe. We observe 10 well identified dust Saharan deposition events at Lampedusa and 6 at Mallorca for a 1-yr sampling period. These dust events are sporadic and the South-North gradient of deposition intensity and frequency is observed (the highest dust mass sampled at the stations are : 2,66 g.m-2 at Lampedusa ; 0,54 g.m-2 at Majorque ; 0,33 g.m-2 at Frioul ; 0,16 g.m-2 at Casset). The ability of the CHIMERE model to reproduce the deposition measurements is tested. The mineral dust plumes simulated over the western Mediterranean basin are also compared to satellite observations (OMI, MODIS) and in-situ measurements performed during the ChArMEx campaign and in the AERONET stations.

  2. Late Pan-African granite emplacement during regional deformation, evidence from magnetic fabric and structural studies in the Hammamat-Atalla area, Central Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Greiling, R. O.; de Wall, H.; Sadek, M. F.; Dietl, C.

    2014-11-01

    Field investigations, microstructural observations, and magnetic fabric analyses revealed a polyphase, late Pan-African deformational evolution in the Um Sheqila-Um Had (595 Ma) composite pluton and in the Hammamat and Atalla areas of the Central Eastern Desert of Egypt in Ediacaran times. Major stages are early shortening (NNW-SSE), subsequent strike-slip (NW-SE shear zones), and late shortening (NW-SE). Strain studies on pebbles and xenoliths together with AMS data show a predominance of shallow, NW-SE trending X axes or magnetic lineations, associated with steep, NW-SE striking magnetic foliations. Magnetic fabrics and microstructures indicate a tectonic fabric in the Um Sheqila-Um Had granitoid plutons, which is dominated by steep NW-SE striking foliations and shallow NW-SE trending lineations, similar to those in the high-angle Atalla Shear Zone. There is a change of lineation directions from ESE-WNW at Um Sheqila (oldest) to NW-SE to Um Had II (youngest). This pattern may indicate an influence of strike-slip and is also consistent with NE-SW compression. This holds also true for the asymmetry of the contact aureole, which is extended towards NW, parallel with the trend of the magnetic lineation. The character and orientation of the deformation pattern in the Um Sheqila-Um Had plutons and the Atalla Shear Zone is thus similar to the pattern of the late shortening phase. The intrusion of the Um Sheqila-Um Had granitoid rocks, therefore, took place before the late shortening stage, but postdates early deformation, which, according to published data, was associated with lithospheric thinning in the Central Eastern Desert. Therefore, these Pan-African plutons do not represent the earliest post-deformational intrusions but a late stage of syn-deformational magmatic activity. At a regional scale, this deformation with steep foliations and shallow lineations may also be related with lateral escape tectonics. The pluton emplacement, the importance of transcurrent

  3. Particle Size Distribution of Airborne Microorganisms and Pathogens during an Intense African Dust Event in the Eastern Mediterranean

    PubMed Central

    Polymenakou, Paraskevi N.; Mandalakis, Manolis; Stephanou, Euripides G.; Tselepides, Anastasios

    2008-01-01

    Background The distribution of microorganisms, and especially pathogens, over airborne particles of different sizes has been ignored to a large extent, but it could have significant implications regarding the dispersion of these microorganisms across the planet, thus affecting human health. Objectives We examined the microbial quality of the aerosols over the eastern Mediterranean region during an African storm to determine the size distribution of microorganisms in the air. Methods We used a five-stage cascade impactor for bioaerosol collection in a coastal city on the eastern Mediterranean Sea during a north African dust storm. Bacterial communities associated with aerosol particles of six different size ranges were characterized following molecular culture–independent methods, regardless of the cell culturability (analysis of 16S rRNA genes). Results All 16S rDNA clone libraries were diverse, including sequences commonly found in soil and marine ecosystems. Spore-forming bacteria such as Firmicutes dominated large particle sizes (> 3.3 μm), whereas clones affiliated with Actinobacteria (found commonly in soil) and Bacteroidetes (widely distributed in the environment) gradually increased their abundance in aerosol particles of reduced size (< 3.3 μm). A large portion of the clones detected at respiratory particle sizes (< 3.3 μm) were phylogenetic neighbors to human pathogens that have been linked to several diseases. Conclusions The presence of aerosolized bacteria in small size particles may have significant implications to human health via intercontinental transportation of pathogens. PMID:18335093

  4. Study of African Dust with Multi-Wavelength Raman Lidar During "Shadow" Campaign in Senegal

    NASA Astrophysics Data System (ADS)

    Veselovskii, Igor; Goloub, Philippe; Podvin, Thierry; Bovchaliuk, Valentyn; Tanre, Didier; Derimian, Yevgeny; Korenskiy, Mikhail; Dubovik, Oleg

    2016-06-01

    West Africa and the adjacent oceanic regions are very important locations for studying dust properties and their influence on weather and climate. The SHADOW (Study of SaHAran Dust Over West Africa) campaign is performing a multi-scale and multi-laboratory study of aerosol properties and dynamics using a set of in situ and remote sensing instruments at an observation site located at IRD (Institute for Research and Development) Center, Mbour, Senegal (14°N, 17°W). In this paper, we present the results of lidar measurements performed during the first phase of SHADOW which occurred in March-April, 2015. The multiwavelength Mie-Raman lidar acquired 3β+2α+1δ measurements during this period. This set of measurements has permitted particle intensive properties such as extinction and backscattering Ångström exponents (BAE) for 355/532 nm wavelengths corresponding lidar ratios and depolarization ratio at 532 nm to be determined. The backscattering Ångström exponent during the dust episodes decreased to ~-0.7, while the extinction Ångström exponent though being negative, was greater than -0.2. Low values of BAE can likely be explained by an increase in the imaginary part of the dust refractive index at 355 nm compared to 532 nm.

  5. The Fertilizing Role of African Dust in the Amazon Rainforest. A First Multiyear Assessment Based on Data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

    SciTech Connect

    Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Remer, L. A.; Prospero, J.; Omar, Ali; Winker, D.; Yang, Yuekui; Zhang, Yan; Zhang, Zhibo; Zhao, Chun

    2015-03-18

    The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three dimensional (3D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8~48) Tg a-1 or 29 (8~50) kg ha-1 a-1. The dust deposition shows significant interannual variation that is negatively correlated with the prior-year rainfall in the Sahel. The CALIOP-based multi-year mean estimate of dust deposition matches better with estimates from in-situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.006~0.037) Tg P of phosphorus per year, equivalent to 23 (7~39) g P ha-1 a-1 to fertilize the Amazon rainforest. This out-of-Basin P input is comparable to the hydrological loss of P from the Basin, suggesting an important role of African dust in preventing phosphorus depletion on time scales of decades to centuries.

  6. Niamey Dust Observations

    DOE Data Explorer

    Flynn, Connor

    2008-10-01

    Niamey aerosol are composed of two main components: dust due to the proximity of the Sahara Desert, and soot from local and regional biomass burning. The purpose of this data product is to identify when the local conditions are dominated by the dust component so that the properties of the dust events can be further studied.

  7. Airborne Sunphotometry of African Dust and Marine Boundary Layer Aerosols in PRIDE

    NASA Technical Reports Server (NTRS)

    Livingston, John M.; Redemann, Jens; Russell, Philip; Schmid, Beat; Reid, Jeff; Pilewskie, Peter; Hipskind, R. Stephen (Technical Monitor)

    2000-01-01

    The Puerto Rico Dust Experiment (PRIDE) was conducted during summer 2000 to study the radiative, microphysical and transport properties of Saharan dust in the Caribbean region. During PRIDE, NASA Ames Research Center's six-channel airborne autotracking sunphotometer (AATS-6) was operated aboard a Piper Navajo airplane based at Roosevelt Roads Naval Station on the northeast coast of Puerto Rico. AATS-6 measurements were taken during 21 science flights off the coast of Puerto Rico in the western Caribbean. Data were acquired within and above the Marine Boundary Layer (MBL) and the Saharan Aerosol Layer (SAL) up to 5.5 km altitude tinder a wide range of dust loadings. Aerosol optical depth (AOD) spectra and columnar water vapor (CWV) values have been calculated from the AATS-6 measurements by using sunphotometer calibration data obtained at Mauna Loa Observatory (3A kin ASL) before (May) and after (October) PRIDE. Mid-visible AOD values measured near the surface during PRIDE ranged from 0.07 on the cleanest day to 0.55 on the most turbid day. Values measured above the MBL were as high as 0.35; values above the SAL were as low as 0.01. The fraction of total column AOD due to Saharan dust cannot be determined precisely from AATS-6 AOD data alone due to the uncertainty in the extent of vertical mixing of the dust down through the MBL. However, analyses of ground-based and airborne in-situ aerosol sampling measurements and ground-based aerosol lidar backscatter data should yield accurate characterization of the vertical mixing that will enable calculation of the Saharan dust AOD component from the sunphotometer data. Examples will be presented showing measured AATS-6 AOD spectra, calculated aerosol extinction and water vapor density vertical profiles, and aerosol size distributions retrieved by inversion of the AOD spectra. Near sea-surface AOD spectra acquired by AATS-6 during horizontal flight legs at 30 m ASL are available for validation of AOD derived from coincident

  8. Geochemical Fingerprinting of Trans-Atlantic African Dust Based on Radiogenic Sr-Nd-Hf Isotopes and Rare Earth Element Anomalies

    NASA Astrophysics Data System (ADS)

    Pourmand, Ali; Prospero, Joseph; Sharifi, Arash

    2015-04-01

    Mineral dust is an important component of Earth's climate system and biogeochemical cycles on a global scale. In order to understand the relationship between climate processes in the source areas and the properties of aerosols at distant receptor sites, we must be able to identify the source provenance of dust. Here we present a multiproxy study that characterizes the temporal variability in the geochemical composition of long-range African dust (LRAD) collected between 2003 and 2011 in the trade winds on the Caribbean island of Barbados. We find systematic differences between Sr-Nd-Hf isotopic composition and rare earth element anomalies of individual dust events and evidence of seasonal shifts in dust source activity and transport. These results indicate that coherent geochemical source signatures of LRAD can be preserved even after transport across thousands of kilometers. We investigated the possibility of identifying the potential source areas through comparisons with literature data. However, these data are almost entirely based on measurements of soil and sediment samples; this could lead to biases because of soil-aerosol particle size and composition differences. Nonetheless, our data suggest that many samples are linked to sources in Mali and sub-Saharan regions. Radiogenic Nd-Hf composition of aerosols can potentially be a useful proxy to study the proximity of mineral dust sources to depositional sites. In order to establish firmer links between LRAD and dust source areas, however, we require much more data on the geochemical composition of aerosols from potential source areas in North Africa.

  9. Geochemical Fingerprinting of Trans-Atlantic African Dust Based on Radiogenic Sr-Nd-Hf Isotopes and Rare Earth Element Anomalies

    NASA Astrophysics Data System (ADS)

    Pourmand, A.; Prospero, J. M.; Sharifi, A.

    2014-12-01

    Mineral dust is an important component of Earth's climate system and biogeochemical cycles on a global scale. In order to understand the relationship between climate processes in the source areas and the properties of aerosols at distant receptor sites, we must be able to identify the source provenance of dust. Here we present a multiproxy study that characterizes the temporal variability in the geochemical composition of long-range African dust (LRAD) collected between 2003 and 2011 in the trade winds on the Caribbean island of Barbados. We find systematic differences between Sr-Nd-Hf isotopic composition and rare earth element anomalies of individual dust events and evidence of seasonal shifts in dust source activity and transport. These results indicate that coherent geochemical source signatures of LRAD can be preserved even after transport across thousands of kilometers. We investigated the possibility of identifying the potential source areas through comparisons with literature data. However, these data are almost entirely based on measurements of soil and sediment samples; this could lead to biases because of soil-aerosol particle size and composition differences. Nonetheless, our data suggest that many samples are linked to sources in Mali and sub-Saharan regions. Radiogenic Nd-Hf composition of aerosols can potentially be a useful proxy to study the proximity of mineral dust sources to depositional sites. In order to establish firmer links between LRAD and dust source areas, however, we require much more data on the geochemical composition of aerosols from potential source areas in North Africa.

  10. Should I stay or should I go? Dispersal and population structure in small, isolated desert populations of West African crocodiles.

    PubMed

    Velo-Antón, Guillermo; Godinho, Raquel; Campos, João Carlos; Brito, José Carlos

    2014-01-01

    The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (FST range: 0.12-0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments. PMID:24740183

  11. Should I stay or should I go? Dispersal and population structure in small, isolated desert populations of West African crocodiles.

    PubMed

    Velo-Antón, Guillermo; Godinho, Raquel; Campos, João Carlos; Brito, José Carlos

    2014-01-01

    The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (FST range: 0.12-0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments.

  12. African dust phosphorus fertilizing the Amazon and the Atlantic Ocean is derived from marine sediments and igneous rocks - no indication for Bodélé diatomite contribution

    NASA Astrophysics Data System (ADS)

    Gross, Avner; Castido, Danilo; Pio, Casimero; Angert, Alon

    2013-04-01

    signatures. The diatomite in the Bodélé depression have lower P concentrations (550-900 µg P g/dust) and fall off the mixing line describe by our samples. These findings implies that the bio-available P delivered by dust from West Africa to the Central Atlantic Ocean and later to the Amazon basin is derived from a mixture of igneous origin and marine sedimentary origin, and that in contrast to previous claims, the Bodélé diatomite is not a major dust-P source. In addition, we found that African dust-P concentrations are between 2 folds to 10 folds higher then generally accounted for in modeling studies.

  13. The Desert Crossings of Mars

    NASA Astrophysics Data System (ADS)

    Cockell, C. S.

    Apart from the polar caps, the Martian volcanoes and the Valles Marineris, ~80% of the martian surface can essentially be classified as `desert'. The methods used to explore Mars, the scientific priorities and the philo- sophical and historical precedents that drive human exploration on Mars will primarily come from our experiences in terrestrial deserts. Here, the methods and approaches used for terrestrial desert expeditions are discussed with reference to Mars. Some of the physical challenges such as low temperature and frost formation will be akin to cold polar desert exploration on Earth. However, some challenges, such as dust storms and lack of liquid water will be akin to hot desert exploration. Expeditions that draw the appropriate lessons from both hot and cold desert terrestrial expeditions will succeed. Examples of major regions on Mars that might be regarded as significant exploratory challenges for expeditions are identified. Key parameters of these expeditions including distance and plausible scientific objectives are provided.

  14. The role of African dust in the formation of Quaternary soils on Mallorca, Spain and implications for the genesis of Red Mediterranean soils

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.; Avila, A.; Skipp, G.; Freeman, J.; Patterson, D.

    2010-01-01

    African dust additions explain the origin of terra rossa soils that are common on the carbonate-platform island of Mallorca, Spain. Mineralogical and geochemical analyses indicate that Quaternary carbonate eolianites on Mallorca have a very high purity, usually composed of more than 90% carbonate minerals (calcite, dolomite, and aragonite). In contrast, terra rossa soils developed on these eolianites have lower carbonate contents and contain higher concentrations of quartz and other silicates. Analyses of immobile trace elements indicate that the non-carbonate fractions of the eolianites have distinctive Zr/Hf, La/Yb, Cr/Sc and Th/Ta values that differ from the superjacent terra rossa soils. These observations indicate that even if sufficient dissolution of the eolianite had taken place to create the soils by residual accumulation, immobile element ratios in the soils require an external source. However, Zr/Hf, La/Yb, Cr/Sc and Th/Ta values in the soils fall within the range of values for these element ratios in African dust collected on Barbados and mainland Spain. We conclude that the silicate fractions of terra rossa soils on Mallorca are derived mainly, though not wholly, from far-traveled African dust, and this process may explain the origin of other terra rossa soils found in southern Europe. ?? 2010.

  15. Linking Endotoxins, African Dust PM10 and Asthma in an Urban and Rural Environment of Puerto Rico

    PubMed Central

    Ortiz-Martínez, Mario G.; Rodríguez-Cotto, Rosa I.; Ortiz-Rivera, Mónica A.; Pluguez-Turull, Cedric W.; Jiménez-Vélez, Braulio D.

    2015-01-01

    African Dust Events (ADE) are a seasonal phenomenon that has been suggested to exacerbate respiratory and proinflammatory diseases in Puerto Rico (PR). Increases in PM10 concentration and the effects of biological endotoxins (ENX) are critical factors to consider during these storms. ENX promote proinflammatory responses in lungs of susceptible individuals through activation of the Toll-like receptors (TLR2/4) signaling pathways. The objective of the study was to evaluate the toxicological and proinflammatory responses stimulated by ADE PM10 ENX reaching PR using human bronchial epithelial cells. PM10 organic extracts from a rural and urban site in PR (March 2004) were obtained from ADE and non-ADE and compared. A retrospective data analysis (PM10 concentration, aerosol images, and pediatric asthma claims) was performed from 2000 to 2012 with particular emphasis in 2004 to classify PM samples. Urban extracts were highly toxic, proinflammatory (IL-6/IL-8 secretion), and induced higher TLR4 expression and NF-κB activation compared to rural extracts. ENX were found to contribute to cytotoxicity and inflammatory responses provoked by urban ADE PM10 exposure suggesting a synergistic potency of local and natural ENX incoming from ADE. The contribution of ADE PM10 ENX is valuable in order to understand interactions and action mechanisms of airborne pollutants as asthma triggers in PR. PMID:26681839

  16. Microbial hitchhikers on intercontinental dust: catching a lift in Chad

    PubMed Central

    Favet, Jocelyne; Lapanje, Ales; Giongo, Adriana; Kennedy, Suzanne; Aung, Yin-Yin; Cattaneo, Arlette; Davis-Richardson, Austin G; Brown, Christopher T; Kort, Renate; Brumsack, Hans-Jürgen; Schnetger, Bernhard; Chappell, Adrian; Kroijenga, Jaap; Beck, Andreas; Schwibbert, Karin; Mohamed, Ahmed H; Kirchner, Timothy; de Quadros, Patricia Dorr; Triplett, Eric W; Broughton, William J; Gorbushina, Anna A

    2013-01-01

    Ancient mariners knew that dust whipped up from deserts by strong winds travelled long distances, including over oceans. Satellite remote sensing revealed major dust sources across the Sahara. Indeed, the Bodélé Depression in the Republic of Chad has been called the dustiest place on earth. We analysed desert sand from various locations in Chad and dust that had blown to the Cape Verde Islands. High throughput sequencing techniques combined with classical microbiological methods showed that the samples contained a large variety of microbes well adapted to the harsh desert conditions. The most abundant bacterial groupings in four different phyla included: (a) Firmicutes—Bacillaceae, (b) Actinobacteria—Geodermatophilaceae, Nocardiodaceae and Solirubrobacteraceae, (c) Proteobacteria—Oxalobacteraceae, Rhizobiales and Sphingomonadaceae, and (d) Bacteroidetes—Cytophagaceae. Ascomycota was the overwhelmingly dominant fungal group followed by Basidiomycota and traces of Chytridiomycota, Microsporidia and Glomeromycota. Two freshwater algae (Trebouxiophyceae) were isolated. Most predominant taxa are widely distributed land inhabitants that are common in soil and on the surfaces of plants. Examples include Bradyrhizobium spp. that nodulate and fix nitrogen in Acacia species, the predominant trees of the Sahara as well as Herbaspirillum (Oxalobacteraceae), a group of chemoorganotrophic free-living soil inhabitants that fix nitrogen in association with Gramineae roots. Few pathogenic strains were found, suggesting that African dust is not a large threat to public health. PMID:23254516

  17. Microbial hitchhikers on intercontinental dust: catching a lift in Chad.

    PubMed

    Favet, Jocelyne; Lapanje, Ales; Giongo, Adriana; Kennedy, Suzanne; Aung, Yin-Yin; Cattaneo, Arlette; Davis-Richardson, Austin G; Brown, Christopher T; Kort, Renate; Brumsack, Hans-Jürgen; Schnetger, Bernhard; Chappell, Adrian; Kroijenga, Jaap; Beck, Andreas; Schwibbert, Karin; Mohamed, Ahmed H; Kirchner, Timothy; de Quadros, Patricia Dorr; Triplett, Eric W; Broughton, William J; Gorbushina, Anna A

    2013-04-01

    Ancient mariners knew that dust whipped up from deserts by strong winds travelled long distances, including over oceans. Satellite remote sensing revealed major dust sources across the Sahara. Indeed, the Bodélé Depression in the Republic of Chad has been called the dustiest place on earth. We analysed desert sand from various locations in Chad and dust that had blown to the Cape Verde Islands. High throughput sequencing techniques combined with classical microbiological methods showed that the samples contained a large variety of microbes well adapted to the harsh desert conditions. The most abundant bacterial groupings in four different phyla included: (a) Firmicutes-Bacillaceae, (b) Actinobacteria-Geodermatophilaceae, Nocardiodaceae and Solirubrobacteraceae, (c) Proteobacteria-Oxalobacteraceae, Rhizobiales and Sphingomonadaceae, and (d) Bacteroidetes-Cytophagaceae. Ascomycota was the overwhelmingly dominant fungal group followed by Basidiomycota and traces of Chytridiomycota, Microsporidia and Glomeromycota. Two freshwater algae (Trebouxiophyceae) were isolated. Most predominant taxa are widely distributed land inhabitants that are common in soil and on the surfaces of plants. Examples include Bradyrhizobium spp. that nodulate and fix nitrogen in Acacia species, the predominant trees of the Sahara as well as Herbaspirillum (Oxalobacteraceae), a group of chemoorganotrophic free-living soil inhabitants that fix nitrogen in association with Gramineae roots. Few pathogenic strains were found, suggesting that African dust is not a large threat to public health.

  18. Characterizing the annual cycle of African dust transport to the Caribbean Basin and South America and its impact on the environment and air quality

    NASA Astrophysics Data System (ADS)

    Prospero, Joseph M.; Collard, François-Xavier; Molinié, Jack; Jeannot, Alexis

    2014-07-01

    Decades of aerosol measurements on Barbados have yielded a detailed picture of African mineral dust transport to the Caribbean Basin that shows a strong seasonal cycle with a maximum in boreal summer and a minimum in winter. Satellite aerosol products suggest that in spring, there is a comparable transport to northeastern South America. Here we characterize the complete annual cycle of dust transport to the western Atlantic by linking the Barbados record to multiyear records of airborne particulate matter less than 10 µm diameter (PM10) measured in air quality programs at Cayenne (French Guiana) and Guadeloupe. Comparisons of PM10 at these sites with concurrent dust measurements at Barbados demonstrate that high PM10 levels are almost entirely due to dust. Cayenne PM10 peaks in spring in a cycle which is consistent with satellite aerosol optical depth and suggests that the Sahel is the dominant source. The persistent transport of dust during much of the year could impact a wide range of environmental processes over a broad region that extends from the southern United States to the Amazon Basin. Finally, the average 24 h PM10 concentrations at Cayenne and Guadeloupe frequently exceed the World Health Organization air quality guideline. Thus soil dust PM10 could be a significant, but generally unrecognized, health factor at western Atlantic sites and also in other relatively remote regions affected by long-range dust from Africa. Because dust emissions and transport are highly sensitive to climate variability, climate change in coming decades could greatly affect a wide range of biogeochemical processes and human health in this region.

  19. Phylogeny of North African Agama lizards (Reptilia: Agamidae) and the role of the Sahara desert in vertebrate speciation.

    PubMed

    Gonçalves, Duarte V; Brito, José C; Crochet, Pierre-André; Geniez, Philippe; Padial, José M; Harris, D James

    2012-09-01

    The origin of Saharan biodiversity is poorly understood, in part because the geological and paleoclimatic events that presumably shaped species diversity are still controversial, but also because few studies have explored causal explanations for the origin of Saharan diversity using a phylogenetic framework. Here, we use mtDNA (16S and ND4 genes) and nDNA (MC1R and CMOS genes) to infer the relationships and biogeographic history of North African agamas (genus Agama). Agamas are conspicuous, diverse and abundant African lizards that also occur in the Saharan xeric and mesic environments. Our results revealed the presence of three Agama lineages in North Africa: one Afrotropical, one Sahelo-Saharan, and one broadly distributed in North Africa and mainly Saharan. Southern Mauritania contains the highest known diversity, with all three lineages present. Results suggest that agamas colonized the Sahara twice, but only one lineage was able to radiate and diversify there. Species in the Saharan lineage are mostly allopatric, and their splitting, genetic diversity and distribution are greatly explained by mountain ranges. One species in this lineage has colonized the Mediterranean climatic zone (A. impalearis), and another one the Sahel savannah (A. boueti). The other lineage to colonize the Sahara corresponds to A. boulengeri, an eminently Sahelian species that also inhabits Saharan mountain ranges in Mauritania and Mali. Phylogenetic analyses indicate that allopatric montane populations within some currently recognized species are also genetically divergent. Our study therefore concludes that vicariant speciation is a leading motor of species diversification in the area: Inside the Sahara, associated to mountain-ranges isolated by dune seas and bare plains; outside, associated to less harsh climates to the North and South. Paleoclimatic oscillations are suggested as causal explanations of the vicariant distribution and origin of species. Agamas are thought to have

  20. Size-resolved Chemical Composition of Cloud and Rain Water Collected during the Puerto Rico African Dust and Clouds Study (PRADACS) Campaign

    NASA Astrophysics Data System (ADS)

    Torres, E.; Valle Diaz, C. J.; Zurcher, F.; Lee, T.; Collett, J. L.; Fitzgerald, E.; Cuadra, L.; Prather, K. A.; Mayol-Bracero, O. L.

    2011-12-01

    The underlying physico-chemical processes of dust-aerosol interactions are poorly understood; even less understood is how aging impacts cloud properties and climate as the particles travel from Africa to the Caribbean region. Caribbean landmasses have tropical montane cloud forests (TMCFs) that are tightly coupled to the atmospheric hydrologic cycle. Small-scale shifts in temperature and precipitation could have serious ecological consequences. Therefore, this makes TMCFs an interesting ecosystem to see the effects African Dust (AD) might have on cloud formation and precipitation. As part of the Puerto Rico African Dust and Clouds Study (PRADACS) cloud and rain water samples for subsequent chemical analysis were collected at Pico del Este (PE) station in Luquillo, PR (1051 masl) during summer 2011. At PE, two cloud collectors (i.e., single stage (Aluminum version) and 2-stage (Teflon version) Caltech Active Strand Cloudwater Collector (CASCC)), and a rainwater collector were operated. Measurements such as the liquid water content (LWC), pH, conductivity., and composition of single particles using an aerosol time of flight mass spectrometer (ATOFMS) were performed. Preliminary results showed that days with the influence of African dust (AD), had LWC values that ranged from 300 to 500 mg/m3, pH values up to 5.7,, and conductivity up to 180 μS/cm. The ATOFMS showed titanium and iron ions, suggesting the presence of AD as well as, occasionally, sulfate and nitrate ions suggesting the influence of anthropogenic pollution. Results on the chemical composition and the physical properties of cloud, rainwater, and aerosol for the inorganic as well as the organic fraction and how these properties change for the different air masses observed will also be presented.

  1. Climatic controls on the interannual to decadal variability in Saudi Arabian dust activity: Toward the development of a seasonal dust prediction model

    NASA Astrophysics Data System (ADS)

    Yu, Yan; Notaro, Michael; Liu, Zhengyu; Wang, Fuyao; Alkolibi, Fahad; Fadda, Eyad; Bakhrjy, Fawzieh

    2015-03-01

    The observed climatic controls on springtime and summertime Saudi Arabian dust activities during 1975-2012 are analyzed, leading to development of a seasonal dust prediction model. According to empirical orthogonal function analysis, dust storm frequency exhibits a dominantly homogeneous pattern across Saudi Arabia, with distinct interannual and decadal variability. The previously identified positive trend in remotely sensed aerosol optical depth since 2000 is shown to be a segment of the decadal oscillation in dust activity, according to long-duration station record. Regression and correlation analyses reveal that the interannual variability in Saudi Arabian dust storm frequency is regulated by springtime rainfall across the Arabian Peninsula and summertime Shamal wind intensity. The key drivers of Saudi Arabian dust storm variability are identified. Winter-to-spring La Niña enhances subsequent spring dust activity by decreasing rainfall across the country's primary dust source region, the Rub' al Khali Desert. A relatively cool tropical Indian Ocean favors frequent summer dust storms by producing an anomalously anticyclonic circulation over the central Arabian Peninsula, which enhances the Shamal wind. Decadal variability in Saudi Arabian dust storm frequency is associated with North African rainfall and Sahel vegetation, which regulate African dust emissions and transport to Saudi Arabia. Mediterranean sea surface temperatures (SSTs) also regulate decadal dust variability, likely through their influence on Sahel rainfall and Shamal intensity. Using antecedent-accumulated rainfall over the Arabian Peninsula and North Africa, and Mediterranean SSTs, as low-frequency predictors, and tropical eastern Pacific and tropical Indian Ocean SSTs as high-frequency predictors, Saudi Arabia's seasonal dust activity is well predicted.

  2. Multi-stage emerald formation during Pan-African regional metamorphism: The Zabara, Sikait, Umm Kabo deposits, South Eastern desert of Egypt

    NASA Astrophysics Data System (ADS)

    Grundmann, G.; Morteani, G.

    2008-02-01

    The genesis of gem-quality deep green emeralds of Zabara, Sikait and Umm Kabo (South Eastern Desert, Egypt) is to date a controversial topic. The emerald-bearing biotite schists and quartz lenses are interpreted alternatively as a product of (i) thrust-fault-shear zone - controlled large scale alkali-metasomatism driven by post-magmatic fluid flow or of (ii) a large scale interaction between syntectonic pegmatitic magma or hydrothermal fluids with pre-existing basic to ultrabasic rocks, or of (iii) a syn- to post-tectonic regional metamorphism and small scale blackwall metasomatism. Detailed microstructural and chemical analyses of the Egyptian emeralds and their host rocks show that three generations of beryl can be distinguished: a colourless pegmatitic beryl; a pale green Cr-poor beryl crystallized from pegmatite-related hydrothermal fluids; and a deep green Cr- and Mg-rich emerald. The crystallization of the Cr- and Mg-rich emerald was controlled by the very local availability of Cr, Mg and Be-rich metamorphic fluids during the Pan-African tectono-thermal event. Emerald-rich quartz lenses demonstrate that those fluids locally did mobilize quartz, too. The pale green emeralds found within the pegmatites in association with colourless beryl are the product of a mobilization of colourless pegmatitic beryl and/or phenakite by late pegmatitic fluids slightly enriched in Cr by an interaction with the Cr-rich country rocks. The late pegmatitic fluids are typically Na-rich as is demonstrated by the pervasive albitization of the pegmatites. The complex interplay of magmatic and regional metamorphic events during the genesis of the Egyptian emeralds/beryls makes it impossible through stable oxygen isotope data to relate their genesis to the one or the other event.

  3. Assessment of African and local wind-blown dust contributions at three rural sites in SE Spain: aerosol size distribution

    NASA Astrophysics Data System (ADS)

    Orza, J. A. G.; Cabello, M.; Lidón, V.; Martínez, J.

    2009-04-01

    Aerosol number size distribution and meteorological parameters were measured at three rural sites in semiarid southeastern Spain. Number concentrations of suspended particles in 31 size bins between 0.25 and 32 m diameter were continuosly recorded with a GRIMM 190 aerosol spectrometer at: (i) a rural background (RB) location in a perennial tussock grassland, from July to October 2006; (ii) a rural site surrounded by abandoned croplands, and influenced by mineral industries and by a small paved road having a small traffic load located 30 m to the East (RA), from June to December 2007; and (iii) a rural (R) location in an agricultural plot previously cleared and then lightly leveled and compacted for future lemon-tree cultivation, from February to June 2008. Events of long range transport from North Africa to the study area (African dust outbreaks, ADOs) were identified by aerosol transport models, back-trajectories and satellite imagery. There is an increase in the concentration of particles larger than 2 m with increasing wind speed while the concentrations decrease for smaller particles at the RB and R sites. At the RA location, that increase is observed for particles in the range 1.6 - 3.5 m (the precise value depends on the wind speed) when there are West winds. Particulate resuspension is found to occur at all wind speeds, although wind threshold values can be identified by a sharp increase in particle concentrations for a range of particle sizes. Light winds entrain large particles while stronger winds additionally entrain particles of smaller size (down to 2.5 m for the highest winds). The size distributions present maxima at 1.6 and 3 m on days with ADO. Concentration for almost every particle size is higher on ADOs than on days without such events, due in part to the associated meteorological situation. This work was partially supported by the Spanish Ministerio de Educación y Ciencia under grant CGL2004-04419 (RESUSPENSE Project).

  4. Size-resolved Chemical Composition of Cloud and Rain Water Collected during the Puerto Rico African Dust and Clouds Study (PRADACS) Campaign

    NASA Astrophysics Data System (ADS)

    Valle Diaz, C. J.; Mayol-Bracero, O. L.; Zurcher, F.; Gioda, A.; Lee, T.; Collett, J. L.; Pradacs Team

    2010-12-01

    The underlying physico-chemical processes of dust-aerosol interactions are poorly understood; even less understood is how aging impacts cloud properties and climate as the particles travel from Africa to the Caribbean region. Caribbean landmasses have Tropical Montane Cloud Forests (TMCFs) that are tightly coupled to the atmospheric hydrologic cycle. Small-scale shifts in temperature and precipitation could have serious ecological consequences. Therefore, this makes TMCFs an interesting ecosystem to see the effects African Dust (AD) might have on cloud formation and precipitation. The first field measurements of the Puerto Rico African Dust and Clouds Study (PRADACS) were from July 22 to August 12, 2010. Measurements were performed at East Peak (EP) station at Luquillo, PR (1051 masl) and Cape San Juan Station (CSJ), a coastal station at Fajardo, PR (~60 masl). At EP, two cloud collectors (i.e., single stage (Aluminum version) and 2-stage (Teflon version) Caltech Active Strand Cloudwater Collector (CASCC)), and a rainwater collector were operated. Chemical composition (water-soluble ions and carbonaceous, organic nitrogen and metals) and pH were determined for the cloud water and rainwater samples. Here we present preliminary results for EP station. For cloud water and rainwater sampling, pH was 5.5 in average, but during dust events pH values were higher due to the presence of cations that form hydroxides in aqueous solution. Conductivity measurements ranged from 20 to 120 μs/cm; being higher on dust events and lower for rain samples. The values of pH and conductivity in the first stage (large droplets of approximately 15 μm are collected) indicate a higher content of dust than in the second stage (small droplets of approximately 5 μm). This is consistent with the larger sizes of dust particles as well as their lower hygroscopicity which requires more water to serve as Cloud Condensation Nuclei (CCN). Additional results for physical properties and chemical

  5. Respirable coal dust exposure and respiratory symptoms in South-African coal miners: A comparison of current and ex-miners

    SciTech Connect

    Naidoo, R.N.; Robins, T.G.; Seixas, N.; Lalloo, U.G.; Becklake, M.

    2006-06-15

    Dose-response associations between respirable dust exposure and respiratory symptoms and between symptoms and spirometry outcomes among currently employed and formerly employed South-African coal miners were investigated. Work histories, interviews, and spirometry and cumulative exposure were assessed among 684 current and 212 ex-miners. Results: Lower prevalences of symptoms were found among employed compared with ex-miners. Associations with increasing exposure for symptoms of phlegm and past history of tuberculosis were observed, whereas other symptom prevalences were higher in the higher exposure categories. Symptomatic ex-miners exhibited lower lung-function compared to the nonsymptomatic. Compared with published data, symptoms rates were low in current miners but high in ex-miners. Although explanations could include the low prevalence of smoking and/or reporting/selection bias, a 'Survivor' and/or a 'hire' effect is more likely, resulting in an underestimation of the dust-related effect.

  6. Desert dust deposition on Mt. Elbrus, Caucasus Mountains, Russia in 2009-2012 as recorded in snow and shallow ice core: high-resolution "provenancing", transport patterns, physical properties and soluble ionic composition

    NASA Astrophysics Data System (ADS)

    Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Lavrentiev, I.; Kemp, S.

    2013-04-01

    A record of dust deposition events between 2009 and 2012 on Mt. Elbrus, Caucasus Mountains derived from a snow pit and a shallow ice core is presented for the first time for this region. A combination of isotopic analysis, SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (cf. 20-100 km) resolution. Seventeen dust deposition events were detected; fourteen occurred in March-June, one in February and two in October. Four events originated in the Sahara, predominantly in north-eastern Libya and eastern Algeria. Thirteen events originated in the Middle East, in the Syrian Desert and northern Mesopotamia, from a mixture of natural and anthropogenic sources. Dust transportation from Sahara was associated with vigorous Saharan depressions, strong surface winds in the source region and mid-tropospheric south-westerly flow with daily winds speeds of 20-30 m s-1 at 700 hPa level and, although these events were less frequent, they resulted in higher dust concentrations in snow. Dust transportation from the Middle East was associated with weaker depressions forming over the source region, high pressure centered over or extending towards the Caspian Sea and a weaker southerly or south-easterly flow towards the Caucasus Mountains with daily wind speeds of 12-18 m s-1 at 700 hPa level. Higher concentrations of nitrates and ammonium characterise dust from the Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 μm and 4.16 μm. Most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm and there was no significant difference between dust from the Sahara and the Middle East.

  7. Variability of the infrared complex refractive index of African mineral dust: experimental estimation and implications for radiative transfer and satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Di Biagio, C.; Boucher, H.; Caquineau, S.; Chevaillier, S.; Cuesta, J.; Formenti, P.

    2014-10-01

    Experimental estimations of the infrared refractive index of African mineral dust have been retrieved from laboratory measurements of particle transmission spectra in the wavelength range 2.5-25 μm. Five dust samples collected at Banizoumbou (Niger) and Tamanrasset (Algeria) during dust events originated from different Western Saharan and Sahelian areas have been investigated. The real (n) and imaginary (k) parts of the refractive index obtained for the different dust samples vary in the range 1.1-2.7 and 0.05-1.0, respectively, and are strongly sensitive to the mineralogical composition of the particles, especially in the 8-12 and 17-25 μm spectral intervals. Dust absorption is controlled mainly by clays (kaolinite, illite, smectite) and, to a lesser extent, by quartz and calcium-rich minerals (e.g. calcite, gypsum). Significant differences are obtained when comparing our results with existing experimental estimations available in the literature, and with the values of the OPAC (Optical Properties of Aerosols and Clouds) database. The different data sets appear comparable in magnitude, with our values of n and k falling within the range of variability of past studies. However, literature data fail in accurately reproducing the spectral signatures of the main minerals, in particular clays, and they significantly overestimate the contribution of quartz. Furthermore, the real and the imaginary parts of the refractive index from some literature studies are found not to verify the Kramers-Kronig relations, thus being theoretically incorrect. The comparison between our results, from western Africa, and literature data, from different locations in Europe, Africa, and the Caribbean, nonetheless, confirms the expected large variability of the dust infrared refractive index. This highlights the necessity for an extended systematic investigation of dust properties at infrared wavelengths. For the five analysed dust samples, aerosol intensive optical properties relevant to

  8. Loss of lung function associated with exposure to silica dust and with smoking and its relation to disability and mortality in South African gold miners.

    PubMed Central

    Hnizdo, E

    1992-01-01

    The data from a lung function study on 2209 white 45-54 year old South African gold miners in 1968-71 and at a five year follow up examination, were analysed to establish the actual loss of lung function associated with exposure to silica dust and with smoking. Ex-smokers were excluded from the analysis. Of the remaining 1625 subjects, 1249 had the five year follow up test of lung function. The estimated excess loss of lung function for a 50 year old gold miner, associated with 24 years of underground dust exposure of an average respirable dust concentration of 0.30 mg m-3 (14.4 ghm-3) was 236 ml of FEV1 (95% confidence interval (95% CI 134-337) and 217 ml of FVC (95% CI 110-324). By comparison, the effect of smoking one packet of cigarettes a day over 30 years was associated with an estimated loss of 552 ml of FEV1 (95% CI 461-644) and 335 ml of FVC (95% CI 170-500). The cumulative dust exposure was not associated with the longitudinal loss of FEV1 or FVC when the initial FEV1 and FVC were adjusted in the models. According to the predicted values, however, gold miners appear to have a greater loss of lung function from 50 to 55 years of age than that predicted for a general population. PMID:1322158

  9. Mesoscale modeling and satellite observation of transport and mixing of smoke and dust particles over northern sub-Saharan African region

    NASA Astrophysics Data System (ADS)

    Yang, Zhifeng; Wang, Jun; Ichoku, Charles; Hyer, Edward; Zeng, Jing

    2013-11-01

    transport and vertical distribution of smoke and dust aerosols over the northern sub-Saharan African region are simulated in the Weather Research and Forecasting model with Chemistry (WRF-Chem), which uses hourly dynamic smoke emissions from the Fire Locating and Modeling of Burning Emissions database derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) fire products. Model performance for February 2008 is evaluated using MODIS true color images, aerosol optical depth (AOD) measurements from the Aerosol Robotic Network, MODIS AOD retrievals, and the Cloud-Aerosol Lidar data with Orthogonal Polarization (CALIOP) atmospheric backscattering and extinction products. Specification of smoke injection height of 650 m in WRF-Chem yields aerosol vertical profiles that are most consistent with CALIOP observations of aerosol layer height. Between the equator and 10°N, Saharan dust is often mixed with smoke near the surface, and their transport patterns manifest the interplay of trade winds, subtropical highs, precipitation associated with the Intertropical Convergence Zone, and the high mountains located near the Great Rift Valley region. At the 700 hPa level and above, smoke layers spread farther to the north and south and are often above the dust layers over the Sahel region. In some cases, transported smoke can also be mixed with dust over the Saharan region. Statistically, 5% of the CALIOP valid measurements in February 2007-2011 show aerosol layers either above or between the clouds, reinforcing the importance of the aerosol vertical distribution for quantifying aerosol impact on climate in the Sahel region.

  10. Dust storm monitoring: effects on the environment, human health, and potential security conflicts

    NASA Astrophysics Data System (ADS)

    Davara, Fernando; de la Cruz, Antonio

    2004-10-01

    Monitoring dust storms with recently available medium and moderate resolution satellites (Meris, Modis and SeaWiFS) is providing new global information regarding the sources, transportation tracks and affected areas. Saharan dust plumes reach the SE region of the United States and the Caribbean region in summer and the Amazon basin in winter. Generally these Saharan plumes branch off in dust tracks along the North Atlantic reaching Western Europe as far north as the Scandinavian countries. Furthermore, dust storms originating in the Eastern Sahara and Northern African deserts form dust plumes propagated by the Sirocco winds that, after crossing the Mediterranean Sea, affect Southern and Central Europe particularly during spring and summer. Dust storms originating in the Gobi and Taklamakan deserts blow in an easterly direction propagating dust plumes affecting Korea, Japan and reach the United States after crossing the Pacific Ocean. The large amount of cyclic deposition generated by dust storms produces an environmental impact that causes the decay of coral reefs in the Caribbean, the origin and distribution of red tides and the disappearance of sea grasses. The relationship of dust plumes with the increasing number of asthma and allergy cases in the Caribbean correlates well with the appearance of similar cases in Europe and elsewhere during the mid 1980s. The recurrence presence of insecticides in regions where these products were banned long ago, or where they were never used, may be partly due to Saharan dust plumes. The loss of agricultural soil, literally blown away by dust storms in the source areas, creates hardship, hunger and forced-migration. Dust storms should be considered as an important security issue.

  11. Saharan and Arabian Dust Aerosols: A Comparative Case Study of Lidar Ratio

    NASA Astrophysics Data System (ADS)

    Córdoba-Jabonero, Carmen; Sabbah, Ismail; Sorribas, Mar; Adame, José Antonio; Cuevas, Emilio; Sharifi, Faisal Al; Gil-Ojeda, Manuel

    2016-06-01

    This work presents a first comparative study of the Lidar Ratio (LR) values obtained for dust particles in two singular dust-influenced regions: the Canary Islands (Spain, close to the African coast in the North Atlantic Ocean), frequently affected by Saharan dust intrusions, and the Kuwait area (Arabian Peninsula) as usually influenced by Arabian dust storms. Synergetic lidar and sun-photometry measurements are carried out in two stations located in these particular regions for that purpose. Several dusty cases were observed during 2014 in both stations and, just for illustration, two specific dusty case studies have been selected and analyzed to be shown in this work. In general, mean LR values of 54 sr and 40 sr were obtained in these studies cases for Saharan and Arabian dust particles, respectively. Indeed, these results are in agreement with other studies performed for dust particles arriving from similar desert areas. In particular, the disparity found in Saharan and Arabian dust LR values can be based on the singular composition of the suspended dust aerosols over each station. These results can be useful for CALIPSO extinction retrievals, where a single LR value (40 sr) is assumed for pure dust particles independently on the dust source region.

  12. Occurrence, distribution and health risk from polycyclic aromatic compounds (PAHs, oxygenated-PAHs and azaarenes) in street dust from a major West African Metropolis.

    PubMed

    Bandowe, Benjamin A Musa; Nkansah, Marian Asantewah

    2016-05-15

    Scientific evidence suggests that the burden of disease on urban residents of sub-Saharan African Countries is increasing, partly as a result of exposure to elevated concentrations of toxic environmental chemicals. However, characterization of the levels, composition pattern and sources of polycyclic aromatic compounds (PACs) in environmental samples from African cities is still lacking. This study measured the PAHs, oxygenated-PAHs (OPAHs) and azaarene (AZAs) content of street dusts collected from Kumasi, Ghana (a major metropolis located in the tropical forest zone of West Africa). The ∑Alkyl+parent-PAHs, ∑OPAHs and ∑AZAs concentration in street dust averaged 2570 ng g(-1) (range: 181-7600 ng g(-1)), 833 ng g(-1) (57-4200 ng g(-1)) and 73 ng g(-1) (3.3-240 ng g(-1)), respectively. The concentrations of ∑Alkyl+parent-PAHs were strongly correlated (n=25) with ∑OPAHs (r=0.96, p<0.01) and ∑AZAs (r=0.94, p<0.01). The ∑OPAHs concentrations were also strongly correlated with ∑AZAs (r=0.91, p<0.01). Concentrations of individual PAHs in these street dusts were enriched at between 12 and 836 compared to their average concentrations in background soils from same city, demonstrating the high influence of traffic emissions. Several individual OPAHs and AZAs had higher concentrations than their related and often monitored parent-PAHs. The estimated incremental lifetime cancer risks due to the parent-PAHs in street dusts was >10(-6) indicating high risk of contracting cancer from exposure to street dust from Kumasi. The contribution of OPAHs, AZAs, and alkyl-PAHs in street dust to cancer risk could not be quantified because of lack of toxicity equivalency factors for these compounds; however this could be significant because of their high concentration and known higher toxicity of some polar PACs and alkyl-PAHs than their related parent-PAHs.

  13. Holocene dust records from the West African Sahel and their implications for changes in climate and land surface conditions

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Holmes, Jonathan A.; Street-Perrott, F. Alayne; Ficken, Katherine J.

    2014-07-01

    We reconstructed aeolian dust accumulation during the Holocene from two radiocarbon-dated lake-sediment sequences from the Manga Grasslands in northeastern Nigeria in order to investigate long-term changes in the Harmattan dust system over West Africa and evaluate their possible causes. Flux values were low in the early Holocene, decreasing further to a minimum at around 6.2 kyr B.P. after which time they increased, steadily until around 2 kyr B.P. and then more sharply after this time. The long-term variations in dust flux agree broadly with changes in the exposed area of the Lake Chad Basin to the northeast of the study sites, which vary inversely with the volume of Paleolake Megachad. More proximal sources of dust, including the fine fraction of local dune sand and floodplains of nearby rivers, have also made a contribution to the total dust load during times of enhanced dune and fluvial activity. Sharp rises in dust flux over the past century may be related to human activity. Broad patterns of change in dust flux during the Holocene agree with other reconstructions over the same period. However, we see no evidence for a stepped rise during the middle Holocene, as seen at some sites from the northeastern tropical Atlantic, suggesting that controls on the Harmattan dust system have differed from those affecting dust deposition elsewhere across northern Africa.

  14. Radiative forcing of Sahara dust and its impacts on the hydrological cycle in the West African monsoon system

    NASA Astrophysics Data System (ADS)

    Zhao, C.; Liu, X.; Leung, L.; Hagos, S. M.

    2010-12-01

    The WRF-Chem model is applied to simulate the radiative forcing of dust and its impacts on the hydrological cycle during the monsoon season over West Africa (WA). The GOCART dust emission scheme is coupled into two aerosol models (MADE/SORGAM and MOSAIC) in WRF-Chem. During the monsoon season, dust is a dominant contributor to AOD near the dust source regions. Dust heats the atmosphere, and warms the surface in the nighttime through trapping the longwave radiation but cools the surface in the daytime through reducing the shortwave radiation. Dust modifies the surface energy budget through changing radiation, latent heat, and sensible heat fluxes, and results in large surface cooling effect in the afternoon but warming effect in the early morning during the monsoon season over WA. In the standard model configuration, the dust effect on total daily precipitation is small in both strong and weak monsoon years, but is sensitive to the dust absorbing properties. On the other hand, the dust-driven change of the stability of atmosphere significantly reduces the diurnal variation of precipitation during the monsoon season over WA, and improves the model simulation when compared to available observations.

  15. Variability of the infrared complex refractive index of African mineral dust: experimental estimation and implications for radiative transfer and satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Di Biagio, C.; Boucher, H.; Caquineau, S.; Chevaillier, S.; Cuesta, J.; Formenti, P.

    2014-04-01

    Experimental estimations of the infrared refractive index of African mineral dust have been retrieved from laboratory measurements of particle transmission spectra in the wavelength range 2.5-25 μm. Five dust samples collected at Banizoumbou (Niger) and Tamanrasset (Algeria) during dust events originated from different Western Saharan and Sahelian areas have been investigated. The obtained real (n) and imaginary (k) parts of the refractive index for the different dust cases vary in the range 1.1-2.7 and 0.05-1.0, respectively, and appear to be strongly sensitive to the mineralogical composition of the particles, especially in the 8-12 μm and 17-25 μm spectral intervals. Dust absorption is controlled mainly by clays, and, in minor fraction, by quartz and Ca-rich minerals. Size distribution, and the coarse fraction in particular, plays also a role in determining the refractive index. Significant differences are obtained when comparing our results with existing experimental estimations available in the literature, and with the values of the OPAC (Optical Properties of Aerosols and Clouds) database. The different datasets appear comparable in magnitude, with our values of n and k falling in the range of variability of past studies. However, literature data fail in accurately reproducing the spectral signatures of main minerals, in particular clays, and they significantly overestimate the contribution of quartz. We also found that the real and the imaginary parts of the refractive index from part of literature studies do not verify Kramers-Kronig relations, thus resulting theoretically incorrect. The comparison between our results, from Western Africa, and literature data, from different locations in Europe, Africa, and the Caribbean, nonetheless, confirms the expected large variability of the infrared refractive index of dust, thus highlighting the necessity for an extended systematic investigation. Aerosol intensive optical properties relevant to radiative transfer

  16. Geochemical and mineralogical evidence for Sahara and Sahel dust additions to Quaternary soils on Lanzarote, eastern Canary Islands, Spain

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.; Skipp, G.; Prospero, J.M.; Patterson, D.; Bettis, E. Arthur

    2010-01-01

    Africa is the most important source of dust in the world today, and dust storms are frequent on the nearby Canary Islands. Previous workers have inferred that the Sahara is the most important source of dust to Canary Islands soils, with little contribution from the Sahel region. Soils overlying a late Quaternary basalt flow on Lanzarote, Canary Islands, contain, in addition to volcanic minerals, quartz and mica, exotic to the island's bedrock. Kaolinite in the soils also likely has an exotic origin. Trace-element geochemistry shows that the soils are derived from varying proportions of locally derived basalt and African dust. Major-element geochemistry, clay mineralogy and interpretation of satellite imagery suggest that dust additions to the Canary Islands come not only from the Sahara Desert, but also from the Sahel region. ?? Published 2010. This article is a US Government work and is in the public domain in the USA.

  17. Chemistry of serpentine "polymorphs" in the Pan-African serpentinites from the Eastern Desert of Egypt, with an emphasis on the effect of superimposed thermal metamorphism

    NASA Astrophysics Data System (ADS)

    Surour, Adel A.

    2016-08-01

    The present work deals with some Pan-African serpentinites of Neoproterozoic age from five localities in the Eastern Desert of Egypt namely, Abu Fannani, Fawakhir, Barramiya, Ras Shait and Wadi Ghadir that derivedmostly from lherzolite to harzburgite protoliths. The M-value of antigorite is anindicator of the metamorphic grade which is lowest at Fawakhir (greenschist facies) and highest at Abu Fannani (lower amphibolite facies). Antigoritization during progressive regional metamorphism at Fawakhir is limited and its M-value is much higher than 8.52 indicating crystallization temperatures of 220-250 °C whereas it is ≥300 °C in the rest. Antigorite recrystallized at T ≈ 400-450 °C in the contact metamorphic aureoles due to the emplacement of post-orogenic leucogranites at Fawakhir and Gebel Ghadir. Towards the contact with the granites, M-value of antigorite is low (6.48) compared to 8.52 in the least recrystallized antigorite due to the thermal effect. Antigorite that forms in the thermal aureoles is characterized by two types of substitution; Tschermak substitution (Al3+ and Cr3+ for Si4+ in the tetrahedral sites and Mg2+ in the octahedral sites) and non-Tschermak substitutionin the octahedral sites (2R3+ = 3R2+). Generally, both ortho- and clinochrysotiles are common with MgO contents of 41-41.13 wt% and 39.38-40.93 wt%, respectively. In addition to chlorite, high- and low-Al lizardites are present with almost constant total iron (~0.24 cations) as Fe2+(vi) and variable Mg2+. This suggests that significant R3+ in the octahedral sites are mostly occupied by Al3+ and Cr3+ and not iron. In the lizardite structure, there is Tschermak substitution of Si4+ by some trivalent cations in the tetrahedral sites. Using the TEM images, antigorite is distinguishable from chrysotile and they suggest the presence of polyhedral or polygonal serpentine (spherical or circular with alternating sectors of lizardite). Crack-seal microstructures are displayed by chrysotile and

  18. Potential Climate Effects of Dust Aerosols' over West Africa

    NASA Astrophysics Data System (ADS)

    JI, Z.; Wang, G.; Pal, J. S.; Yu, M.

    2014-12-01

    Climate in West Africa is under the influence of the West African monsoon circulation and mineral dust emitted from the Sahara desert (which is the world's largest source of mineral dust emission). Dust aerosols alter the atmospheric radiative fluxes and act as cloud condensation nuclei in the process of emission, transportation and deposition. However, our understanding regarding how dust aerosols influence the present-day and future climate of West Africa is very limited. In this study, a regional climate model RegCM4.3.4-CLM4.5 is used to investigate the potential climatic effects of dust aerosols both in present (1981-2000) and future (2081-2100) periods over WA. First, the model performance and dust climatic effects are evaluated. The contribution of dust climatic effects under RCP8.5 scenario and their confounding effects with land use change are assessed. Our results indicate that the model can reproduce with reasonable accuracy the spatial and temporal distribution of climatology, aerosol optical depth and surface concentration over WA. The shortwave radiative forcing of dust is negative in the surface and positive in the atmosphere, with greater changes in JJA and MAM compared to those in SON and DJF. Over most of West Africa, cooling is the dominant effect on temperature. Their impact on precipitation features a dipole pattern, with decrease in the north and increase in the south of West Africa. Despite the dust-induced decrease of precipitation amount, dusts cause extreme precipitation to increase. To evaluate the uncertainties surrounding our modeling results, sensitivity experiments driven by ICBC from MIROC-ESM and CESM and their dynamic downscaling results are used for comparisons. Results from these sensitivity experiments indicate that the impact of dust aerosols on present and future climate is robust.

  19. Soluble iron dust export in the high altitude Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Ravelo-Pérez, L. M.; Rodríguez, S.; Galindo, L.; García, M. I.; Alastuey, A.; López-Solano, J.

    2016-05-01

    Every summer huge amounts of desert dust particles are exported from the hyperarid subtropical Sahara to the North Atlantic the so-called Saharan Air Layer (SAL), a dry, warm and dust-laden corridor that expands from the North African coast (1-5 km.a.s.l.) to the Americas above the marine boundary layer. Because of the potential impact of the dust deposited on the ocean on marine biogeochemistry and climate, we studied the Fe solubility (in seawater) of atmospheric aerosols samples directly collected in the SAL off the North African coast, i.e. the fresh aerosols recently exported from the Sahara in the SAL. The aerosol sampling was performed at ˜2400 m.a.s.l. in Izaña observatory in Tenerife island. In the total aerosols, we found low Fe concentrations and high fractional Fe solubility (FFS ˜2%) in the North Atlantic free troposphere airflows and high Fe concentrations and low FFS (˜0.7%) within the SAL; the resulting FFS versus total dust (or total Fe) plot shows a hyperbolic trend attributed to the conservative mixing of 'fine combustion aerosols' and 'lithogenic mineral dust'. We then focused on the soluble Fe in the SAL. Our results indicate that ˜70% of soluble Fe is associated with the dissolution of submicron dust particles, probably involving Fe-bearing clays. We found a FFS of submicron dust (˜6%) higher than that typically observed in submicron particles of soil dust samples (<1%). The correlation between FFS and the ammonium-sulphate/dust ratio and the low variability in the Fe/Al ratio in the dust samples, suggests that the increase in the FFS of submicron dust aerosols (with respect to soil dust particles) may be related to the presence of acid pollutants mixed with dust. Previous studies had focused on dust processing and changes of Fe solubility during the trans-Atlantic transport of dust in the SAL. We found that submicron dust exported off the coast of North Africa may have already experienced acid processing over the Sahara, i.e. before

  20. Sources, Sinks, and Transatlantic Transport of North African Dust Aerosol: A Multimodel Analysis and Comparison With Remote Sensing Data

    NASA Technical Reports Server (NTRS)

    Kim, Dongchul; Chin, Mian; Yu, Hongbin; Diehl, Thomas; Tan, Qian; Kahn, Ralph A.; Tsigaridis, Kostas; Bauer, Susanne E.; Takemura, Toshihiko; Pozzoli, Luca; Bellouin, Nicolas; Schulz, Michael; Peyridieu, Sophie; Chedin, Alain; Koffi, Brigitte

    2014-01-01

    This study evaluates model-simulated dust aerosols over North Africa and the North Atlantic from five global models that participated in the Aerosol Comparison between Observations and Models phase II model experiments. The model results are compared with satellite aerosol optical depth (AOD) data from Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging Spectroradiometer (MISR), and Sea-viewing Wide Field-of-view Sensor, dust optical depth (DOD) derived from MODIS and MISR, AOD and coarse-mode AOD (as a proxy of DOD) from ground-based Aerosol Robotic Network Sun photometer measurements, and dust vertical distributions/centroid height from Cloud Aerosol Lidar with Orthogonal Polarization and Atmospheric Infrared Sounder satellite AOD retrievals. We examine the following quantities of AOD and DOD: (1) the magnitudes over land and over ocean in our study domain, (2) the longitudinal gradient from the dust source region over North Africa to the western North Atlantic, (3) seasonal variations at different locations, and (4) the dust vertical profile shape and the AOD centroid height (altitude above or below which half of the AOD is located). The different satellite data show consistent features in most of these aspects; however, the models display large diversity in all of them, with significant differences among the models and between models and observations. By examining dust emission, removal, and mass extinction efficiency in the five models, we also find remarkable differences among the models that all contribute to the discrepancies of model-simulated dust amount and distribution. This study highlights the challenges in simulating the dust physical and optical processes, even in the best known dust environment, and stresses the need for observable quantities to constrain the model processes.

  1. Desert Communities.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides: (1) background information on desert communities, their similarities, and differences; (2) student activities on this topic; and (3) ready-to-copy student pages with pictures of desert animals and plants. Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. (DH)

  2. Dust, Climate, and Human Health

    NASA Technical Reports Server (NTRS)

    Maynard, Nancy G.

    2003-01-01

    Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. Ths paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health.

  3. Dust, Climate, and Human Health

    NASA Technical Reports Server (NTRS)

    Maynard, Nancy G.

    2003-01-01

    Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. This paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health.

  4. Dust, Climate, and Human Health

    NASA Astrophysics Data System (ADS)

    Maynard, N. G.

    2003-12-01

    Air pollution from both natural and anthropogenic causes is considered to be one of the most serious world-wide environment-related health problems, and is expected to become worse with changes in the global climate. Dust storms from the atmospheric transport of desert soil dust that has been lifted and carried by the winds - often over significant distances - have become an increasingly important emerging air quality issue for many populations. Recent studies have shown that the dust storms can cause significant health impacts from the dust itself as well as the accompanying pollutants, pesticides, metals, salt, plant debris, and other inorganic and organic materials, including viable microorganisms (bacteria, viruses and fungi). For example, thousands of tons of Asian desert sediments, some containing pesticides and herbicides from farming regions, are commonly transported into the Arctic during dust storm events. These chemicals have been identified in animal and human tissues among Arctic indigenous populations. Millions of tons of airborne desert dust are being tracked by satellite imagery, which clearly shows the magnitude as well as the temporal and spatial variability of dust storms across the "dust belt" regions of North Africa, the Middle East, and China. This paper summarizes the most recent findings on the effects of airborne desert dust on human health as well as potential climate influences on dust and health

  5. The radiative impact of desert dust on orographic rain in the Cevennes-Vivarais area: a case study from HyMeX

    NASA Astrophysics Data System (ADS)

    Flamant, C.; Chaboureau, J.-P.; Chazette, P.; Di Girolamo, P.; Bourrianne, T.; Totems, J.; Cacciani, M.

    2015-08-01

    The study is focused on Intensive Observation Period (IOP) 14 of the Hydrology Cycle in the Mediterranean Experiment first Special Observing Period (HyMeX SOP 1) that took place from 17 to 19 October and was dedicated to the study of orographic rain in the Cevennes Vivarais (CV) target area. During this IOP a dense dust plume originating from North Africa (Maghreb and Sahara) was observed to be transported over the Balearic Islands towards the south of France. The plume was characterized by an aerosol optical depth between 0.2 and 0.8 at 550 nm, highly variable in time and space over the Western Mediterranean basin. The impact of this dust plume, the biggest event observed during the 2 month long HyMeX SOP 1, on the precipitation over the CV area has been analyzed using high resolution simulations from the convection permitting mesoscale model Meso-NH validated against measurements obtained from numerous instruments deployed specifically during SOP 1 (ground-based/airborne water vapor and aerosol lidars, airborne microphysics probes) as well as space-borne aerosol products. The 4 day simulation reproduced realistically the temporal and spatial variability (incl. vertical distribution) of the dust. The dust radiative impact led to an average 0.6 K heating at the altitude of the dust layer in the CV area (and up to +3 K locally) and an average 100 J kg-1 increase of most unstable convective available potential energy (and up to +900 J kg-1 locally) with respect to a simulation without prescribed dust aerosols. The rainfall amounts and location were only marginally affected by the dust radiative effect, even after 4 days of simulation. The transient nature of this radiative effect in dynamical environments such as those found in the vicinity of heavy precipitation events in the Mediterranean is not sufficient to impact 24 h accumulated rainfall in the dusty simulation.

  6. Background-like nitrate in desert air

    NASA Astrophysics Data System (ADS)

    Wu, Feng; Zhang, Daizhou; Cao, Junji; Zhang, Ting; An, Zhisheng

    2014-02-01

    The atmospheric nitrogen cycle is a key process driving the earth's environmental evolution. Current model studies require knowledge of NOx soil emissions from various land types, but desert emissions remain unquantified or are not addressed with high confidence. Our measurements at two observatories in Taklimakan desert during a dust episode showed an approximately stable and dust-independent nitrate in the air. Its concentration estimated from PM2.5, PM10 and TSP samples under non-dust, floating dust and dust storm conditions was 3.81 ± 1.24 μg m-3, 2.95 ± 0.69 μg m-3, 4.99 ± 1.71 μg m-3, respectively, despite the more-than-one-order difference of dust loading. This concentration was much larger than that in remote marine and tropical forest air. Comprehensive investigation revealed a similar presence of nitrate in other desert air. The nitrate was hypothesized to be the consequence of the conversion of NOx released from desert soils. These results indicate a background-like nitrate and active reactions of nitrogen compounds in desert air.

  7. Application of a PC analysis of remote sensing spectral reflectance data to determine source regions for dust storms.

    NASA Astrophysics Data System (ADS)

    Dickinson, R. E.; Zhou, L.; Sokolik, I.

    2006-12-01

    The source regions of deserts over which dust is lifted into the air occur on relatively small scales and hve been difficult to characterize geographically. The research programs supporting NASA's terra and aqua satellites have pioneered the development of quality controlled climatologies of surface information, that should include features characteristic of dust source regions. With quality satellite data, patterns can be distinguished that are likely to indicate real geophysical features. Zhou et al. (2005) applied a principle component (PC) analysis to the North African desert that revealed intriguing spatial structures. It represents the spatial patterns with a limited number of PC's that maximize the covariances between spectral bands averaged over space. Such analysis acts as a filter of nonphysical information and should highlight commonly occurring small scale features, some of which are likely connected to dust source regions. We present a new such analysis for the Taklamakan desert of China. The first 2 or 3 modes are removed as being of too coarse a spatial scale to represent source regions. Features of the remaining 3 or 4 patterns of significant amplitude are examined for their possible relevancy to dust uplifting. In particular, patterns that show seasonality of vegetation are deemed unlikely to be so relevant. Distinctions in the spectral patterns and MODIS BRDF kernels of remaining terms are examined for their likely indication of a dust source region.

  8. African dust clouds are associated with increased paediatric asthma accident and emergency admissions on the Caribbean island of Trinidad

    NASA Astrophysics Data System (ADS)

    Gyan, K.; Henry, W.; Lacaille, S.; Laloo, A.; Lamsee-Ebanks, C.; McKay, S.; Antoine, R. M.; Monteil, M. A.

    2005-07-01

    A retrospective ecological study of paediatric asthma patients who attended the Accident and Emergency (A&E) department of the Paediatric Priority Care Facility at the Eric Williams Medical Sciences Complex in relation to Saharan dust visibility and other climatic variables for the period 23 May 2001 to 13 May 2002 was undertaken to determine if there is an association between paediatric A&E asthma visits and Saharan dust cloud cover. A Poisson regression model was used to determine the statistical relationship between acute paediatric asthma A&E visits and Saharan dust cover with and without other variables such as climatic parameters and month. During the study period, there were 2,655 A&E visits for acute asthma. There was an association between increased paediatric asthma admissions and increased Saharan dust cover. The best fitting model estimated that in one month, such as June, a deterioration of visibility due to increased Saharan dust cover from no dust (visibility =16 km) to very dusty (visibility =7 km) would increase a daily admission rate of 7.8 patients to 9.25 when climate variables such as barometric pressure and humidity were kept constant.

  9. African dust clouds are associated with increased paediatric asthma accident and emergency admissions on the Caribbean island of Trinidad.

    PubMed

    Gyan, K; Henry, W; Lacaille, S; Laloo, A; Lamsee-Ebanks, C; McKay, S; Antoine, R M; Monteil, M A

    2005-07-01

    A retrospective ecological study of paediatric asthma patients who attended the Accident and Emergency (A and E) department of the Paediatric Priority Care Facility at the Eric Williams Medical Sciences Complex in relation to Saharan dust visibility and other climatic variables for the period 23 May 2001 to 13 May 2002 was undertaken to determine if there is an association between paediatric A and E asthma visits and Saharan dust cloud cover. A Poisson regression model was used to determine the statistical relationship between acute paediatric asthma A and E visits and Saharan dust cover with and without other variables such as climatic parameters and month. During the study period, there were 2,655 A and E visits for acute asthma. There was an association between increased paediatric asthma admissions and increased Saharan dust cover. The best fitting model estimated that in one month, such as June, a deterioration of visibility due to increased Saharan dust cover from no dust (visibility =16 km) to very dusty (visibility =7 km) would increase a daily admission rate of 7.8 patients to 9.25 when climate variables such as barometric pressure and humidity were kept constant.

  10. The radiative impact of desert dust on orographic rain in the Cévennes-Vivarais area: a case study from HyMeX

    NASA Astrophysics Data System (ADS)

    Flamant, C.; Chaboureau, J.-P.; Chazette, P.; Di Girolamo, P.; Bourrianne, T.; Totems, J.; Cacciani, M.

    2015-11-01

    The study is focused on Intensive Observation Period (IOP) 14 of the Hydrological Cycle in the Mediterranean Experiment first Special Observing Period (HyMeX SOP 1) that took place from 17 to 19 October 2012 and was dedicated to the study of orographic rain in the Cévennes-Vivarais (CV) target area. During this IOP a dense dust plume originating from northern Africa (the Maghreb and Sahara) was observed to be transported over the Balearic Islands towards the south of France. The plume was characterized by an aerosol optical depth between 0.2 and 0.8 at 550 nm, highly variable in time and space over the western Mediterranean Basin. The impact of this dust plume, the biggest event observed during the 2-month-long HyMeX SOP 1, on the precipitation over the CV area has been analyzed using high-resolution simulations from the convection permitting mesoscale model Meso-NH (mesoscale non-hydrostatic model) validated against measurements obtained from numerous instruments deployed specifically during SOP 1 (ground-based/airborne water vapor and aerosol lidars, airborne microphysics probes) as well as space-borne aerosol products. The 4-day simulation reproduced realistically the temporal and spatial variability (including the vertical distribution) of the dust. The dust radiative impact led to an average 0.6 K heating at the altitude of the dust layer in the CV area (and up to +3 K locally) and an average 100 J kg-1 increase of most unstable convective available potential energy (and up to +900 J kg-1 locally) with respect to a simulation without prescribed dust aerosols. The rainfall amounts and location were only marginally affected by the dust radiative effect, even after 4 days of simulation. The transient nature of this radiative effect in dynamical environments such as those found in the vicinity of heavy precipitation events in the Mediterranean is not sufficient to impact 24 h of accumulated rainfall in the dust simulation.

  11. Retrieval of optical and physical properties of African dust from multiwavelength Raman lidar measurements during the SHADOW campaign in Senegal

    NASA Astrophysics Data System (ADS)

    Veselovskii, I.; Goloub, P.; Podvin, T.; Bovchaliuk, V.; Derimian, Y.; Augustin, P.; Fourmentin, M.; Tanre, D.; Korenskiy, M.; Whiteman, D. N.; Diallo, A.; Ndiaye, T.; Kolgotin, A.; Dubovik, O.

    2016-06-01

    West Africa and the adjacent oceanic regions are very important locations for studying dust properties and their influence on weather and climate. The SHADOW (study of SaHAran Dust Over West Africa) campaign is performing a multiscale and multilaboratory study of aerosol properties and dynamics using a set of in situ and remote sensing instruments at an observation site located at the IRD (Institute for Research and Development) in Mbour, Senegal (14° N, 17° W). In this paper, we present the results of lidar measurements performed during the first phase of SHADOW (study of SaHAran Dust Over West Africa) which occurred in March-April 2015. The multiwavelength Mie-Raman lidar acquired 3β + 2α + 1δ measurements during this period. This set of measurements has permitted particle-intensive properties, such as extinction and backscattering Ångström exponents (BAE) for 355/532 nm wavelengths' corresponding lidar ratios and depolarization ratio at 532 nm, to be determined. The mean values of dust lidar ratios during the observation period were about 53 sr at both 532 and 355 nm, which agrees with the values observed during the SAMUM-1 and SAMUM-2 campaigns held in Morocco and Cabo Verde in 2006 and 2008. The mean value of the particle depolarization ratio at 532 nm was 30 ± 4.5 %; however, during strong dust episodes this ratio increased to 35 ± 5 %, which is also in agreement with the results of the SAMUM campaigns. The backscattering Ångström exponent during the dust episodes decreased to ˜ -0.7, while the extinction Ångström exponent, though negative, was greater than -0.2. Low values of BAE can likely be explained by an increase in the imaginary part of the dust refractive index at 355 nm compared to 532 nm. The dust extinction and backscattering coefficients at multiple wavelengths were inverted to the particle microphysics using the regularization algorithm and the model of randomly oriented spheroids. The analysis performed has demonstrated that the

  12. Distribution of desert varnish in Arizona

    NASA Technical Reports Server (NTRS)

    Elvidge, Christopher D.

    1989-01-01

    Desert varnish is the dark coat of clay and ferromanganese oxides developed on exposed rock surfaces in arid regions. It forms from the accretion of material from windblown dust. The distribution of desert varnish was mapped in Arizona. It was discovered that desert varnish could be mapped on a regional scale. Well developed desert varnish is common on stable rock surfaces in areas having alkaline soils and less than about 25 cm of annual precipitation. Rock surfaces in areas having more than 40 cm of annual precipitation are generally devoid of desert varnish. An experiment was conducted with varnished desert pavement stone. The stones were broken in half and half was set on a roof in central Illinois from April until October. Removed from the alkaline desert environment, it only took seven months for the varnish to develop an eroded appearance. This experiment graphically illustrates the dependency of desert varnish on alkalinity. In this context, the zones of eroded desert varnish in Arizona indicate that the area of active desert varnish formation has fluctuated, expanding in drier times and contracting/eroding in wetter times.

  13. Thar Desert

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This ASTER sub-scene covers an area of 12 x 15 km in NW India in the Thar Desert. The sand dunes of the Thar Desert constantly shift and take on new shapes. Located in northwestern India and eastern Pakistan, the desert is bounded on the south by a salt marsh known as the Rann of Kutch, and on the west by the Indus River plain. About 800 kilometers long and about 490 kilometers wide, the desert's terrain is mainly rolling sandhills with scattered growths of shrub and rock outcroppings. Only about 12 to 25 centimeters of rain fall on the desert each year, and temperatures rise as high as 52 degrees Celsius. Much of the population is pastoral, raising sheep for their wool. The image is located at 24.4 degrees north latitude and 69.3 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  14. Desert Scrublands

    USGS Publications Warehouse

    Jones, L.L.C.; Halama, K.J.; Lovich, R.E.

    2016-01-01

    Desert scrublands comprise the lower to mid-elevation portions of four different ecosystems including the Chihuahuan, Great Basin, Mojave and Sonoran Deserts. Together the area inside their outer boundaries includes over 8% of the surface area of the United States. Despite significant differences in the flora and fauna of these bioregions they all share the common trait of being arid shrub-steppe ecosystems, receiving, on average, less than 254 mm of rain per year. The austere nature of these landscapes belies their significant biodiversity, the amazing behavioral and physiological adaptations of the biota, and the fragility of the ecosystems to human disturbances. For example, the Mojave Desert alone has at least 250 species of ephemeral plants, mostly winter annuals, and up to 90% are endemic.

  15. Satellite retrieval of aerosol microphysical and optical parameters using neural networks: a new methodology applied to the Sahara desert dust peak

    NASA Astrophysics Data System (ADS)

    Taylor, M.; Kazadzis, S.; Tsekeri, A.; Gkikas, A.; Amiridis, V.

    2014-09-01

    In order to exploit the full-earth viewing potential of satellite instruments to globally characterise aerosols, new algorithms are required to deduce key microphysical parameters like the particle size distribution and optical parameters associated with scattering and absorption from space remote sensing data. Here, a methodology based on neural networks is developed to retrieve such parameters from satellite inputs and to validate them with ground-based remote sensing data. For key combinations of input variables available from the MODerate resolution Imaging Spectro-radiometer (MODIS) and the Ozone Measuring Instrument (OMI) Level 3 data sets, a grid of 100 feed-forward neural network architectures is produced, each having a different number of neurons and training proportion. The networks are trained with principal components accounting for 98% of the variance of the inputs together with principal components formed from 38 AErosol RObotic NETwork (AERONET) Level 2.0 (Version 2) retrieved parameters as outputs. Daily averaged, co-located and synchronous data drawn from a cluster of AERONET sites centred on the peak of dust extinction in Northern Africa is used for network training and validation, and the optimal network architecture for each input parameter combination is identified with reference to the lowest mean squared error. The trained networks are then fed with unseen data at the coastal dust site Dakar to test their simulation performance. A neural network (NN), trained with co-located and synchronous satellite inputs comprising three aerosol optical depth measurements at 470, 550 and 660 nm, plus the columnar water vapour (from MODIS) and the modelled absorption aerosol optical depth at 500 nm (from OMI), was able to simultaneously retrieve the daily averaged size distribution, the coarse mode volume, the imaginary part of the complex refractive index, and the spectral single scattering albedo - with moderate precision: correlation coefficients in the

  16. Desert Survivors!

    ERIC Educational Resources Information Center

    Horton, Jessica; Friedenstab, Steve

    2013-01-01

    This article describes a special third-grade classroom unit based on the reality show "Survivor." The goal of this engaging and interactive unit was to teach students about physical and behavioral adaptations that help animals survive in various desert biomes. The activity combines research, argument, and puppet play over one week of…

  17. Discovering Deserts.

    ERIC Educational Resources Information Center

    Braus, Judy, Ed.

    1985-01-01

    Ranger Rick's NatureScope is a creative education series dedicated to inspiring in children an understanding and appreciation of the natural world while developing the skills they will need to make responsible decisions about the environment. The topic of this issue is "Discovering Deserts." Contents are organized into the following sections: (1)…

  18. A height resolved global view of dust aerosols from the first year CALIPSO lidar measurements

    NASA Astrophysics Data System (ADS)

    Liu, Dong; Wang, Zhien; Liu, Zhaoyan; Winker, Dave; Trepte, Charles

    2008-08-01

    Based on the first year of CALIPSO lidar measurements under cloud-free conditions, a height-resolved global distribution of dust aerosols is presented for the first time. Results indicate that spring is the most active dust season, during which ˜20% and ˜12% of areas between 0 and 60°N are influenced by dust at least 10% and 50% of the time, respectively. In summer within 3-6 km, ˜8.3% of area between 0 and 60°N is impacted by dust at least 50% of the time. Strong seasonal cycles of dust layer vertical extent are observed in major source regions, which are similar to the seasonal variation of the thermally driven boundary layer depth. The arid and semiarid areas in North Africa and the Arabian Peninsula are the most persistent and prolific dust sources. African dust is transported across the Atlantic all yearlong with strong seasonal variation in the transport pathways mainly in the free troposphere in summer and at the low altitudes in winter. However, the trans-Atlantic dust is transported at the low altitudes is important for all seasons, especially transported further cross the ocean. The crossing Atlantic dusty zones are shifted southward from summer to winter, which is accompanied by a similar southward shift of dust-generating areas over North Africa. The Taklimakan and Gobi deserts are two major dust sources in East Asia with long-range transport mainly occurring in spring. The large horizontal and vertical coverage of dust aerosols indicate their importance in the climate system through both direct and indirect aerosol effects.

  19. Organic Extracts from African Dust Storms Stimulate Oxidative Stress and Induce Inflammatory Responses in human lung cells through Nrf2 but not NF-kB

    PubMed Central

    Rodríguez-Cotto, Rosa I.; Ortiz-Martínez, Mario G.; Jiménez-Vélez, Braulio D.

    2015-01-01

    The health impact of the global African dust event (ADE) phenomenon in the Caribbean has been vaguely investigated. Heavy metals in ADE and Non-ADE extracts were evaluated for the formation of reactive oxygen species (ROS) and antioxidant capacity by cells using, deferoxamine mesylate (DF) and N-acetyl-L-cysteine (NAC). Results show that ADE particulate matter 2.5 (PM2.5) induces ROS and stimulates oxidative stress. Pre-treatment with DF reduces ROS in ADE and Non-ADE extracts and in lung cells demonstrating that heavy metals are of utmost importance. Glutathione-S-transferase and Heme Oxygenase 1 mRNA levels are induced with ADE PM and reduced by DF and NAC. ADE extracts induced Nrf2 activity and IL-8 mRNA levels significantly more than Non-ADE. NF-κB activity was not detected in any sample. Trace elements and organic constituents in ADE PM2.5 enrich the local environment load, inducing ROS formation and activating antioxidant-signaling pathways increasing pro-inflammatory mediator expressions in lung cells. PMID:25769104

  20. Decreased Pulmonary Function in School Children in Western Japan after Exposures to Asian Desert Dusts and Its Association with Interleukin-8

    PubMed Central

    Watanabe, Masanari; Kurai, Jun; Sano, Hiroyuki; Saito, Rumiko; Kimura, Yutaka; Aiba, Setsuya; Oshimura, Mitsuo; Yamasaki, Akira; Shimizu, Eiji

    2015-01-01

    The objective of the study was to investigate the influence of Asian dust storms (ADS) on pulmonary function of school children and the relationship of this effect with interleukin-8. Morning peak expiratory flow (PEF) was measured daily in 399 children from April to May 2012 and in 384 of these children from March to May 2013. The data were analyzed for an association between ADS events and PEF by linear mixed models. Interleukin-8 transcriptional activity was assessed in THP-G8 cells stimulated by airborne particles collected on ADS days. Seven ADS days were identified: April 23 and 24, 2012; March 8 to 10, 2013; and March 19 and 20, 2013. Changes in PEF after ADS exposure were −8.17 L/min (95% confidence interval, −11.40 to −4.93) in 2012 and −1.17 L/min (−4.07 to 1.74) in 2013, and there was a significant difference between 2012 and 2013. Interleukin-8 transcriptional activity was significantly higher in 2012 at 10.6 ± 2.9-fold compared to 3.7 ± 0.4 in March 8 to 10, 2013, and 2.3 ± 0.2 in March 19 and 20, 2013. The influence of ADS events on pulmonary function of children differs with each ADS event and may be related to interleukin-8 production. PMID:26060816

  1. Decreased pulmonary function in school children in Western Japan after exposures to Asian desert dusts and its association with interleukin-8.

    PubMed

    Watanabe, Masanari; Noma, Hisashi; Kurai, Jun; Sano, Hiroyuki; Saito, Rumiko; Abe, Satoshi; Kimura, Yutaka; Aiba, Setsuya; Oshimura, Mitsuo; Yamasaki, Akira; Shimizu, Eiji

    2015-01-01

    The objective of the study was to investigate the influence of Asian dust storms (ADS) on pulmonary function of school children and the relationship of this effect with interleukin-8. Morning peak expiratory flow (PEF) was measured daily in 399 children from April to May 2012 and in 384 of these children from March to May 2013. The data were analyzed for an association between ADS events and PEF by linear mixed models. Interleukin-8 transcriptional activity was assessed in THP-G8 cells stimulated by airborne particles collected on ADS days. Seven ADS days were identified: April 23 and 24, 2012; March 8 to 10, 2013; and March 19 and 20, 2013. Changes in PEF after ADS exposure were -8.17 L/min (95% confidence interval, -11.40 to -4.93) in 2012 and -1.17 L/min (-4.07 to 1.74) in 2013, and there was a significant difference between 2012 and 2013. Interleukin-8 transcriptional activity was significantly higher in 2012 at 10.6 ± 2.9-fold compared to 3.7 ± 0.4 in March 8 to 10, 2013, and 2.3 ± 0.2 in March 19 and 20, 2013. The influence of ADS events on pulmonary function of children differs with each ADS event and may be related to interleukin-8 production.

  2. Airborne Dust, "The Good Guy or the Bad Guy": How Much do We Know?

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee

    2010-01-01

    Processes in generating, transporting, and dissipating the airborne dust particles are global phenomena -African dust regularly reaching the Alps; Asian dust seasonally crossing the Pacific into North America, and ultimately the Atlantic into Europe. One of the vital biogeochemical roles dust storms play in Earth's ecosystem is routinely mobilizing mineral dust, as a source of iron, from deserts into oceans for fertilizing the growth of phytoplankton -the basis of the oceanic food chain. Similarly, these dust-laden airs also supply crucial nutrients for the soil of tropical rain forests, the so-called womb of life that hosts 50-90% of the species on Earth. With massive amounts of dust lifted from desert regions and injected into the atmosphere, however, these dust storms often affect daily activities in dramatic ways: pushing grit through windows and doors, forcing people to stay indoors, causing breathing problems, reducing visibility and delaying flights, and by and large creating chaos. Thus, both increasing and decreasing concentrations of doses result in harmful biological effects; so do the airborne dust particles to our Living Earth. Since 1997 NASA has been successfully launching a series of satellites - the Earth Observing System - to intensively study, and gain a better understanding of, the Earth as an integrated system. Through participation in many satellite remote-sensing/retrieval and validation projects over the years, we have gradually developed and refined the SMART (Surface-sensing Measurements for Atmospheric Radiative Transfer) and COMMIT (Chemical, Optical & Microphysical Measurements of In-situ Troposphere) mobile observatories, a suite of surface remote sensing and in-situ instruments that proved to be vital in providing high temporal measurements, which complement the satellite observations. In this talk, we will present SMART-COMMIT which has played key roles, serving as network or supersite, in major international research projects such

  3. Differences in allergic inflammatory responses between urban PM2.5 and fine particle derived from desert-dust in murine lungs.

    PubMed

    He, Miao; Ichinose, Takamichi; Kobayashi, Makoto; Arashidani, Keiichi; Yoshida, Seiichi; Nishikawa, Masataka; Takano, Hirohisa; Sun, Guifan; Shibamoto, Takayuki

    2016-04-15

    The biological and chemical natures of materials adsorbed onto fine particulate matter (PM2.5) vary by origin and passage routes. The exacerbating effects of the two samples-urban PM2.5 (U-PM2.5) collected during the hazy weather in a Chinese city and fine particles (ASD-PM2.5) collected during Asian sand dust (ASD) storm event days in Japan-on murine lung eosinophilia were compared to clarify the role of toxic materials in PM2.5. The amounts of β-glucan and mineral components were higher in ASD-PM2.5 than in U-PM2.5. On the other hand, organic chemicals, including polycyclic aromatic hydrocarbons (PAHs), were higher in U-PM2.5 than in ASD-PM2.5. When BALB/c mice were intratracheally instilled with U-PM2.5 and ASD-PM2.5 (total 0.4 mg/mouse) with or without ovalbumin (OVA), various biological effects were observed, including enhancement of eosinophil recruitment induced by OVA in the submucosa of the airway, goblet cell proliferation in the bronchial epithelium, synergic increase of OVA-induced eosinophil-relevant cytokines and a chemokine in bronchoalveolar lavage fluid, and increase of serum OVA-specific IgG1 and IgE. Data demonstrate that U-PM2.5 and ASD-PM2.5 induced allergic inflammatory changes and caused lung pathology. U-PM2.5 and ASD-PM2.5 increased F4/80(+) CD11b(+) cells, indicating that an influx of inflammatory and exudative macrophages in lung tissue had occurred. The ratio of CD206 positive F4/80(+) CD11b(+) cells (M2 macrophages) in lung tissue was higher in the OVA+ASD-PM2.5 treated mice than in the OVA+U-PM2.5 treated mice. These results suggest that the lung eosinophilia exacerbated by both PM2.5 is due to activation of a Th2-associated immune response along with induced M2 macrophages and the exacerbating effect is greater in microbial element (β-glucan)-rich ASD-PM2.5 than in organic chemical-rich U-PM2.5. PMID:26917405

  4. What Makes a Desert a Desert?

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Presents background information and activities which focus on definition of a desert, locations of deserts, and factors influencing locations. Activities include objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. Two ready-to-copy pages with desert landforms and temperature/rainfall data are…

  5. Desert Research and Technology Studies Exposure of Lotus Coated Electrodynamic Shield Samples

    NASA Technical Reports Server (NTRS)

    Rodriquez, Marcello; Peters, Wanda C.; Straka, Sharon A.; Jones, Craig B.

    2011-01-01

    The Lotus dust mitigation coating and the electrodynamic shield (EDS) are two new technologies currently being developed by NASA as countermeasures for addressing dust accumulation for long-duration human space exploration. These combined technologies were chosen by the Habitation Demonstration Unit (HDU) program for desert dust exposure at the Desert Research and Technologies Studies (D-RaTS) test site in Arizona. Characterization of these samples was performed prior to, during and post D-RaTS exposure.

  6. African Dust Storms Reaching Puerto Rican Coast Stimulate the Secretion of IL-6 and IL-8 and Cause Cytotoxicity to Human Bronchial Epithelial Cells (BEAS-2B).

    PubMed

    Rodríguez-Cotto, Rosa I; Ortiz-Martínez, Mario G; Rivera-Ramírez, Evasomary; Méndez, Loyda B; Dávila, Julio C; Jiménez-Vélez, Braulio D

    2013-10-01

    African dust storm events (ADE) travel across the Atlantic Ocean (ADEAO) and reach the Puerto Rican coast (ADEPRC), potentially impacting air quality and human health. To what extent seasonal variations in atmospheric particulate matter (PM) size fractions, composition and sources trigger respiratory-adverse effects to Puerto Ricans is still unclear. In the present study, we investigated the pro-inflammatory and cytotoxic effects of PM samples harvested during ADEAO (PM10), ADEPRC (PM2.5 and PM10) and Non-ADE (Preand Post-ADEAO and Non-ADEPRC), using BEAS-2B cells. Endotoxins (ENX) in PM2.5 and PM10 extracts and traces of metals (TMET) in PM2.5 extracts were also examined. IL-6 and IL-8 secretion and cytotoxicity were used as endpoints. ADEAO and ADEPRC extracts were found to be more cytotoxic than Non-ADE and ADEAO were more toxic than ADEPRC extracts. PM10 extracts from ADEAO and Post-ADEAO caused significant secretion of IL-8. IL-6 and IL-8 secretion was higher following treatment with PM10 and PM2.5 ADEPRC than with Non-ADEPRC extracts. ENX levels were found to be higher in PM10 ADEAO than in the rest of the samples tested. TMET levels were higher in PM2.5 ADEPRC than in Non-ADEPRC extracts. Deferoxamine significantly reduced cytotoxicity and IL-6 and IL-8 secretion whereas Polymyxin B did not. TMET in PM2.5 fractions is a major determinant in ADEPRC-induced toxicity and work in conjunction with ENX to cause toxicity to lung cells in vitro. ENX and TMET may be responsible, in part, for triggering PM-respiratory adverse responses in susceptible and predisposed individuals. PMID:25002916

  7. Relationship between Rock Varnish and Adjacent Mineral Dust Compositions Using Microanalytical Techniques

    NASA Astrophysics Data System (ADS)

    Macholdt, D.; Jochum, K. P.; Otter, L.; Stoll, B.; Weis, U.; Pöhlker, C.; Müller, M.; Kappl, M.; Weber, B.; Kilcoyne, A. L. D.; Weigand, M.; Al-Amri, A. M.; Andreae, M. O.

    2015-12-01

    Rock varnishes are up to 250 μm thick, Mn- and Fe-rich, dark black to brownish-orange lustrous rock coatings. Water and aeolian dust (60-70%), in combination with biological oxidation or inorganic precipitation processes, or even a combination of both, induce varnish growth rates of a few μm per 1000 a, indicating that element enrichment and aging processes are of major importance for the varnish formation. A combination of 200 nm-fs laser- and 213 nm-ns laser ablation- inductively coupled plasma-mass spectrometry (LA-ICP-MS), focused ion beam (FIB) slicing, and scanning transmission X-ray microscopy-near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) was chosen for high-spatial-resolution analyses. The aim was to identify provenance, chemistry, and dynamics of the varnishes, and their formation over the millennia. To this end, mineral dust and adjacent varnishes were sampled in six arid to semi-arid deserts, in Israel, South Africa, California, and Saudi Arabia. Dust minerals incorporated in the varnishes were examined by STXM-NEXAFS spectroscopic and element mapping at the nm scale. Varnishes from different locations can be distinguished by element ratio plots of Pb/Ni vs. Mn/Ba. A comparison of dust element ratios of particles <50 μm to ratios of adjacent varnishes reveals much lower values for dust. However, the factors between the element ratios of dust and of varnish are similar for four of six regions (Mn/Ba: 6 ± 2; Pb/Ni: 4 ± 3). Two of the six regions diverge, which are South African (Mn/Ba: 20, Pb/Ni: 0.5) and Californian (Anza Borrego Desert: Mn/Ba: 4.5; Pb/Ni: 16.5) varnishes.The results indicate that the enrichment and degradation processes might be similar for most locations, and that Mn and Pb are preferably incorporated and immobilized in most varnishes compared to Ba and Ni. The Pb/Ni ratios of the South African varnishes are indicators for either a preferred incorporation of Ni compared to Pb from available dust, and

  8. The Effect of Dust Storm on Deep Convection over the Tropical North Atlantic

    NASA Astrophysics Data System (ADS)

    Wong, S.; Dessler, A. E.

    2004-12-01

    The effect of the Saharan mineral dust on deep convection over the tropical North Atlantic were investigated by anlayzing Moderate Resolution Imaging Spectroradiometer (MODIS) level-2 retrievals. Brightness temperature at 11 μ m were used to indicate the occurrence of deep convection and the tropospheric aerosol loading was represented by the aerosol optical thickness (AOT) at 0.55 μ m. Probability distribution functions (PDFs) of the brightness temperature were constructed for a region offshore the African west coast for August-September 2002, when dust was frequently blown off the Saharan desert and transported across the North Atlantic. For conditions of high aerosol loading (AOT > 0.8), the frequency of brightness temperatures less than 230 K was reduced by a factor of 5-6 from the value associated with conditions of low aerosol loading (AOT < 0.5). The atmospheric effect of the aerosols lasts at least one day after the passage of the aerosols.

  9. Inverse modeling analysis of soil dust sources over East Asia

    NASA Astrophysics Data System (ADS)

    Ku, Bonyang; Park, Rokjin J.

    2011-10-01

    Soil dust is the dominant aerosol by mass concentration in the troposphere and has considerable effects on air quality and climate. Parts of East Asia, including southern Mongolia, northern China, and the Taklamakan Desert, are important dust source regions. Accurate simulations of dust storm events are crucial for protecting human health and assessing the climatic impacts of dust events. However, even state-of-the-art aerosol models still contain large uncertainties in soil dust simulations, particularly for the dust emissions over East Asia. In this study, we attempted to reduce these uncertainties by using an inverse modeling technique to simulate dust emissions. We used the measured mass concentration of particles less than 10 μm in aerodynamic diameter (PM10) in the surface air over East Asia, in combination with an inverse model, to understand the dust sources. The global three-dimensional GEOS-Chem chemical transport model (CTM) was used as a forward model. The inverse model analysis yielded a 76% decrease in dust emissions from the southern region of the Gobi Desert, relative to the a priori result. The a posteriori dust emissions from the Taklamakan Desert and deserts in eastern and Inner Mongolia were two to three fold higher than the a priori dust emissions. The simulation results with the a posteriori dust sources showed much better agreement with these observations, indicating that the inverse modeling technique can be useful for estimation of the optimized dust emissions from individually sourced regions.

  10. Dust Transport and Deposition Observed from the Terra-MODIS Space Observations

    NASA Technical Reports Server (NTRS)

    Kaufman, Y. J.; Koren, I.; Remer, L. A.; Tanre, D.; Fan, Ginoux; Fan, S.

    2004-01-01

    Meteorological observations, in situ data and satellite images of dust episodes were used already in the 1970s to estimate that 100 tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but deteriorates air quality and caries pathogens as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport and deposition. The Terra spacecraft launched at the dawn of the last millennium provides first systematic well calibrated multispectral measurements from the MODIS instrument, for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and evaluate the African dust column concentration, transport and deposition. We found that 230+/-80 tg of dust are transported annually from Africa to the Atlantic Ocean, 30 tg return to Africa and Europe, 70 tg reach the Caribbean, 45 tg fertilize the Amazon Basin, 4 times as previous estimates thus explaining a paradox regarding the source of nutrition to the Amazon forest, and 120+/-40 tg are deposited in the Atlantic Ocean. The results are compared favorably with dust transport models for particle radius less than or equal to 12 microns. This study is a first example of quantitative use of MODIS aerosol for a geophysical study.

  11. Dust Transport and Deposition Observed from the Terra-Moderate Image Spectrometer (MODIS) Space Observations

    NASA Technical Reports Server (NTRS)

    Kaufman, Y.

    2004-01-01

    Meteorological observations, in situ data and satellite images of dust episodes were used already in the 1970s to estimate that 100 tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but deteriorates air quality and caries pathogens as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport and deposition. The Terra spacecraft launched at the dawn of the last millennium provides first systematic well calibrated multispectral measurements from the MODIS instrument, for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and evaluate the African dust column concentration, transport and deposition. We found that 230 plus or minus 80 tg of dust are transported annually from Africa to the Atlantic Ocean, 30 tg return to Africa and Europe, 70 tg reach the Caribbean, 45 tg fertilize the Amazon Basin, 4 times as previous estimates thus explaining a paradox regarding the source of nutrition to the Amazon forest, and 120 plus or minus 40 tg are deposited in the Atlantic Ocean. The results are compared favorably with dust transport models for particle radius less than or equal to 12 microns. This study is a first example of quantitative use of MODIS aerosol for a geophysical study.

  12. Mineral dust events over the Mediterranean: Multi-platform characterization and comparison with GEOS-Chem simulation

    NASA Astrophysics Data System (ADS)

    Bartlett, K. S.; Luo, G.; Yu, F.; Aerosol Microphysics Research Group

    2011-12-01

    Kevin S. Bartlett, Gan Luo, and Fangqun Yu Atmospheric Sciences Research Center, State University of New York, 251 Fuller Road, Albany, New York 12203, USA Abstract. The Mediterranean Basin (MB) has a population of 210 million with approximately 50% living within the eastern half of the MB where seasonal lows tracking southeastward across Italy transport climate impacting, visibility and air quality reducing mineral dust from North African deserts. Located 1000 km NE of African dust and 400 km SE of Greek population centers, Crete is uniquely located at a crossroads of the seasonal storm track and a mineral dust pathway recording some of the highest average AODs within the region, and is well instrumented to observe this trend. Investigating dust transport using NCEP reanalysis data, surface based METAR, AERONET and SMPS as well as space based MODIS, MISR and CALIPSO observations coupled with nested GEOS-Chem-APM simulations, this study exploits sensor strengths while noting weaknesses to characterize seasonal trends and individual dust events. To verify seasonal trends, METAR, AERONET and NCEP data were collected over Crete from 2003-2010. This 8 year period showed that the majority of large aerosol events occurred during late winter and early spring during passage of transitional low pressure systems. During 2009, newly released, SMPS particle size distribution measurements were acquired from Finokalia. These in situ measurements coupled with the observation collective were key to confirming dust events and for comparing the nested GEOS-Chem's particle size distribution and AOD simulations, which showed some skill capturing dust events as well as the seasonal dust peaks early in the year. In this study we exploited the strengths of the observation collective and model runs to prove seasonal North African dust transport across Crete. We also noted the limitations of surface based: point observations, limited to localized conditions of transport and fallout, where

  13. Original sounding and drifting balloon-borne measurements in the western Mediterranean with the aerosol counter/sizer LOAC during summer ChArMEx campaigns, with a focus on desert dust events

    NASA Astrophysics Data System (ADS)

    Renard, Jean-Baptiste; Dulac, François; Vignelles, Damien; Jeannot, Matthieu; Verdier, Nicolas; Chazette, Patrick; Crenn, Vincent; Sciare, Jean; Totems, Julien; Durand, Pierre; Barret, Brice; Jambert, Corinne; Mallet, Marc; Menut, Laurent; Mailler, Sylvain; Basart, Sara; Baldasano, José Maria

    2015-04-01

    LOAC (Light Optical Aerosol Counter) is a new small optical particle counter/sizer of ~250 grams designed to fly under all kinds of balloons. The measurements are conducted at two scattering angles (12° and 60°), allowing the determination of the aerosol particle concentrations in 19 size classes within a diameter range of ~0.2-100 µm and some identification of the nature of particles dominating different size classes. Following laboratory calibration, the sensor particularly discriminates wet or liquid particles, mineral dust, soot carbon particles and salts. Comparisons with other in situ sensors at the surface and with remote sensing measurements on the vertical were performed to give confidence in measurements. The instrument has been operated at the surface, under all kinds of balloons up to more than 35 km in altitude, including tethered, sounding, open stratospheric and new boundary-layer pressurized drifting balloons (BLPB) from CNES, and was tested on board a small UAV. Operations encompass a variety of environments including the Arctic (Reykjavik, Island, and Kiruna, Sweden), Brazil (Sao Paolo), the western Mediterranean Basin, southwestern France, peri-urban (Ile de France) and urban areas (Paris and Vienna). Presented results are focused on the LOAC balloon-borne measurements performed in the western Mediterranean basin during MISTRALS/ChArMEx campaigns (Mediterranean Integrated Studies aT Regional And Local Scales/the Chemistry-Aerosol Mediterranean Experiment; http://www.mistrals-hjome.org; http://charmex.lsce.ipsl.fr), with a focus on African dust events. Two test flights with a first version of LOAC under sounding balloons were first successfully performed in late June 2012 near Marseille during an intense dust event. In 2013, 19 LOAC flights have been performed under meteorological balloons and 12 under low altitude drifting balloons, most of them from Minorca Island (Spain) in June and early July and others from Levant Island (south of France

  14. Original sounding and drifting balloon-borne measurements in the western Mediterranean with the aerosol counter/sizer LOAC during summer ChArMEx campaigns, with a focus on desert dust events

    NASA Astrophysics Data System (ADS)

    Renard, Jean-Baptiste; Dulac, François; Vignelles, Damien; Jeannot, Matthieu; Verdier, Nicolas; Chazette, Patrick; Crenn, Vincent; Sciare, Jean; Totems, Julien; Durand, Pierre; Barret, Brice; Jambert, Corinne; Mallet, Marc; Menut, Laurent; Mailler, Sylvain; Basart, Sara; Baldasano, José Maria

    2015-04-01

    LOAC (Light Optical Aerosol Counter) is a new small optical particle counter/sizer of ~250 grams designed to fly under all kinds of balloons. The measurements are conducted at two scattering angles (12° and 60°), allowing the determination of the aerosol particle concentrations in 19 size classes within a diameter range of ~0.2-100 µm and some identification of the nature of particles dominating different size classes. Following laboratory calibration, the sensor particularly discriminates wet or liquid particles, mineral dust, soot carbon particles and salts. Comparisons with other in situ sensors at the surface and with remote sensing measurements on the vertical were performed to give confidence in measurements. The instrument has been operated at the surface, under all kinds of balloons up to more than 35 km in altitude, including tethered, sounding, open stratospheric and new boundary-layer pressurized drifting balloons (BLPB) from CNES, and was tested on board a small UAV. Operations encompass a variety of environments including the Arctic (Reykjavik, Island, and Kiruna, Sweden), Brazil (Sao Paolo), the western Mediterranean Basin, southwestern France, peri-urban (Ile de France) and urban areas (Paris and Vienna). Presented results are focused on the LOAC balloon-borne measurements performed in the western Mediterranean basin during MISTRALS/ChArMEx campaigns (Mediterranean Integrated Studies aT Regional And Local Scales/the Chemistry-Aerosol Mediterranean Experiment; http://www.mistrals-hjome.org; http://charmex.lsce.ipsl.fr), with a focus on African dust events. Two test flights with a first version of LOAC under sounding balloons were first successfully performed in late June 2012 near Marseille during an intense dust event. In 2013, 19 LOAC flights have been performed under meteorological balloons and 12 under low altitude drifting balloons, most of them from Minorca Island (Spain) in June and early July and others from Levant Island (south of France

  15. Global dust model intercomparison in AeroCom phase I

    SciTech Connect

    Huneeus, N.; Schulz, M.; Balkanski, Y.; Griesfeller, J.; Prospero, J.; Kinne, S.; Bauer, S.; Boucher, O.; Chin, M.; Dentener, F.; Diehl, T.; Easter, R.; Fillmore, D.; Ghan, S.; Ginoux, P.; Grini, A.; Horowitz, L.; Koch, D.; Krol, M. C.; Landing, W.; Liu, X.; Mahowald, N.; Miller, R.; Morcrette, J. -J.; Myhre, G.; Penner, J.; Perlwitz, J.; Stier, P.; Takemura, T.; Zender, C. S.

    2011-08-01

    This study presents the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations related to desert dust aerosols, their direct radiative effect, and their impact on the biogeochemical cycle, i.e., aerosol optical depth (AOD) and dust deposition. Additional comparisons to Angström exponent (AE), coarse mode AOD and dust surface concentrations are included to extend the assessment of model performance and to identify common biases present in models. These data comprise a benchmark dataset that is proposed for model inspection and future dust model development. There are large differences among the global models that simulate the dust cycle and its impact on climate. In general, models simulate the climatology of vertically integrated parameters (AOD and AE) within a factor of two whereas the total deposition and surface concentration are reproduced within a factor of 10. In addition, smaller mean normalized bias and root mean square errors are obtained for the climatology of AOD and AE than for total deposition and surface concentration. Characteristics of the datasets used and their uncertainties may influence these differences. Large uncertainties still exist with respect to the deposition fluxes in the southern oceans. Further measurements and model studies are necessary to assess the general model performance to reproduce dust deposition in ocean regions sensible to iron contributions. Models overestimate the wet deposition in regions dominated by dry deposition. They generally simulate more realistic surface concentration at stations downwind of the main sources than at remote ones. Most models simulate the gradient in AOD and AE between the different dusty regions. However the seasonality and magnitude of both variables is better simulated at African stations than Middle East ones. The models simulate the offshore transport of West Africa throughout the year but they

  16. Aerosol direct radiative forcing in desert and semi-desert regions of northwestern China

    NASA Astrophysics Data System (ADS)

    Xin, Jinyuan; Gong, Chongshui; Wang, Shigong; Wang, Yuesi

    2016-05-01

    The optical properties of dust aerosols were measured using narrow-band data from a portable sun photometer at four desert and semi-desert stations in northwestern China from 2004 to 2007. Ground-based and satellite observations indicated absorbing dust aerosol loading over the region surrounded by eight large-scale deserts. Radiation forcing was identified by using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The ranges of annual mean aerosol optical depth (AOD), Angström exponents, and single-scattering albedo (SSA) were from 0.25 to 0.35, from - 0.73 to 1.18, and from 0.77 to 0.86, respectively. The ranges of annual mean aerosol direct radiative forcing values at the top of the atmosphere (TOA), mid-atmosphere, and on the surface were from 3.9 to 12.0, from 50.0 to 53.1, and from - 39.1 to - 48.1 W/m2, respectively. The aerosols' optical properties and radiative characteristics showed strong seasonal variations in both the desert and semi-desert regions. Strong winds and relatively low humidity will lead dust aerosols in the atmosphere to an increase, which played greatly affected these optical properties during spring and winter in northwestern China. Based on long-term observations and retrieved data, aerosol direct radiative forcing was confirmed to heat the atmosphere (50-53 W/m2) and cool the surface (- 39 to - 48 W/m2) above the analyzed desert. Radiative forcing in the atmosphere in spring and winter was 18 to 21 W/m2 higher than other two seasons. Based on the dust sources around the sites, the greater the AOD, the more negative the forcing. The annual averaged heating rates for aerosols close to the ground (1 km) were approximately 0.80-0.85 K/day.

  17. 57Fe Mössbauer spectroscopy investigations of iron oxidation states in the Harmattan dust nutrient contribution to West African soils

    NASA Astrophysics Data System (ADS)

    Adetunji, Jacob

    2014-12-01

    A variety of investigations have been carried out on Harmattan dust over many decades demonstrating the continuing importance of the Harmattan dust phenomenon. The investigations have included elemental enrichment factors, mineralogical nutrient input through dust deposition on the soil, meteorological studies, etc. Harmattan dust is important, not only for its impact on radio communication and low visibility in the shipping lanes over the Atlantic, but also on the livelihood and health of people living in countries over which the dust-laden Harmattan wind blows. However, so far, the aspect of nutrient mineral deposition on the soil has not been thoroughly investigated and requires attention, since the majority of people living in West Africa rely heavily on agriculture. It is therefore relevant to know the useful nutrients in the Harmattan dust deposited on soils of the region. This study is therefore aimed at determining the ferric-ferrous ratio of the iron-bearing minerals contained in the Harmattan dust, so their nutritional contribution can be considered. The Mössbauer technique is a powerful tool for studying the ferric-ferrous ratio and has therefore been used, for the first time, to determine the oxidation states of iron in the dust samples. The results of the analysis show that the Harmattan dust is seriously deficient in ferrous iron, which is the more soluble Fe-ion, needed in the soil for healthy crops and plants in general.

  18. Dust Rains Deliver Diverse Assemblages of Microorganisms to the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Itani, Ghida Nouhad; Smith, Colin Andrew

    2016-03-01

    Dust rains may be particularly effective at delivering microorganisms, yet their biodiversities have been seldom examined. During 2011 and 2012 in Beirut, Lebanon, 16 of 21 collected rainfalls appeared dusty. Trajectory modelling of air mass origins was consistent with North African sources and at least one Southwest Asian source. As much as ~4 g particulate matter, ~20 μg DNA, and 50 million colony forming units were found deposited per square meter during rainfalls each lasting less than one day. Sequencing of 93 bacteria and 25 fungi cultured from rain samples revealed diverse bacterial phyla, both Gram positive and negative, and Ascomycota fungi. Denaturing Gradient Gel Electrophoresis of amplified 16S rDNA of 13 rains revealed distinct and diverse assemblages of bacteria. Dust rain 16S libraries yielded 131 sequences matching, in decreasing order of abundance, Betaproteobacteria, Alphaproteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Cyanobacteria, Epsilonproteobacteria, Gammaproteobacteria, and Deltaproteobacteria. Clean rain 16S libraries yielded 33 sequences matching only Betaproteobacteria family Oxalobacteraceae. Microbial composition varied between dust rains, and more diverse and different microbes were found in dust rains than clean rains. These results show that dust rains deliver diverse communities of microorganisms that may be complex products of revived desert soil species and fertilized cloud species.

  19. Dust Rains Deliver Diverse Assemblages of Microorganisms to the Eastern Mediterranean

    PubMed Central

    Itani, Ghida Nouhad; Smith, Colin Andrew

    2016-01-01

    Dust rains may be particularly effective at delivering microorganisms, yet their biodiversities have been seldom examined. During 2011 and 2012 in Beirut, Lebanon, 16 of 21 collected rainfalls appeared dusty. Trajectory modelling of air mass origins was consistent with North African sources and at least one Southwest Asian source. As much as ~4 g particulate matter, ~20 μg DNA, and 50 million colony forming units were found deposited per square meter during rainfalls each lasting less than one day. Sequencing of 93 bacteria and 25 fungi cultured from rain samples revealed diverse bacterial phyla, both Gram positive and negative, and Ascomycota fungi. Denaturing Gradient Gel Electrophoresis of amplified 16S rDNA of 13 rains revealed distinct and diverse assemblages of bacteria. Dust rain 16S libraries yielded 131 sequences matching, in decreasing order of abundance, Betaproteobacteria, Alphaproteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Cyanobacteria, Epsilonproteobacteria, Gammaproteobacteria, and Deltaproteobacteria. Clean rain 16S libraries yielded 33 sequences matching only Betaproteobacteria family Oxalobacteraceae. Microbial composition varied between dust rains, and more diverse and different microbes were found in dust rains than clean rains. These results show that dust rains deliver diverse communities of microorganisms that may be complex products of revived desert soil species and fertilized cloud species. PMID:26939571

  20. Dust Episodes in Hong Kong (South China) and their Relationship with the Sharav and Mongolian Cyclones and Jet Streams

    NASA Technical Reports Server (NTRS)

    Lee, Y. C.; Wenig, Mark; Zhang, Zhenxi; Sugimoto, Nobuo; Larko, Dave; Diehl, Thomas

    2012-01-01

    The study presented in this paper analyses two dust episodes in Hong Kong, one occurring in March 2006 and the other on 22 March 2010. The latter is the worst dust episode on Hong Kong record. The focus is on the relationship between the dust episodes and the Sharav/Mongolian cyclones and jet streams. The 16 March 2006 episode is traceable to a continental-scale Saharan dust outbreak of 5-9 March 2006 caused by the cold front of an East Mediterranean Sharav cyclone arriving at north-west Africa on 5 March 2006. The eastward movement of the cyclone along the North African coast is clearly illustrated in the geopotential height contours. Simulations by the chemistry transport model GOCART provide a visible evidence of the transport as well as an estimate of contributions from the Sahara to the aerosol concentration levels in Hong Kong. The transport simulations suggest that the dust is injected to the polar jet north of the Caspian Sea, while it is transported eastward simultaneously by the more southerly subtropical jet. The major source of dust for Hong Kong is usually the Gobi desert. Despite the effect of remote sources, the 16 March 2006 dust episode was still mainly under the influence of the Mongolian cyclone cold fronts. In the recent episode of 22 March 2010, the influence of the Mongolian cyclone predominated as well. It appears that the concurrent influence of the Sharav and Mongolian cyclones on Hong Kong and East Asia is not a common occurrence. Besides transporting dusts from non-East Asian sources to Hong Kong and East Asia, the strong subtropical jet on 21 March 2010 (i.e. 1 day prior to the major dust episode) is believed to have strengthened an easterly monsoon surge to South China causing the transport of voluminous dusts to Taiwan and Hong Kong the following day.

  1. Physical and Radiative Properties of Aerosol Particles across the Caribbean Basin: A Comparison between Clean and Perturbed African Dust and Volcanic Ash Air Masses

    NASA Astrophysics Data System (ADS)

    Rivera, H.; Ogren, J. A.; Sheridan, P. J.; Mayol-Bracero, O.

    2009-12-01

    Aerosol’s optical and physical properties were measured during year 2007 at Cape San Juan, a ground-based station located at the northeastern tip of Puerto Rico. The three cases investigated were classified according to the origin of the air masses: clean (C), African dust (AD), and volcanic ash (VA). The instrumentation used included a sunphotometer to determine volume size distributions and aerosol optical thickness (AOT), a 3-wavelength nephelometer to determine the scattering coefficient (σsp), and a 3-wavelength particle/soot absorption photometer (PSAP) to measure the absorption coefficient (σap). The average volume size distributions were trimodal for the C (peaks at 0.14, 0.99 and 4.25 µm radius) and AD (peaks at 0.11, 1.30 and 2.00 µm radius) cases and bimodal for the VA (peaks at 0.19 and 2.75 µm radius) case. Fine and coarse modes maxima for AD occurred at radii smaller than for VA, confirming the different origins of those particles. The average values for the total σsp were higher for AD (82.9 Mm-1) and VA (33.7 Mm-1) compared to C (16.6 Mm-1). The same happened for the AOT maximum values at 500 nm with 0.92, 0.30, and 0.06 for AD, VA, and C, respectively. The observed increase in the values of the Angstrom exponent (å) is indicative of a decrease in the size of the particles associated to VA (å= 0.27) and AD (å =0.89) when compared to C (å =0.24). The volume size distributions and thus the mass were dominated by the coarse mode (> 1.0 µm) especially for the AD case. Results have shown that AD as well as VA has a significant impact on the physical and radiative properties across Puerto Rico and the Caribbean. Additional results on the AOT wavelength dependence and on the annual variability of the properties under study will be presented.

  2. Dust aerosol optical properties using ground-based and airborne lidar in the framework of FENNEC

    NASA Astrophysics Data System (ADS)

    Marnas, Fabien; Chazette, Patrick; Flamant, Cyrille; Royer, Philippe; Boytard, Mai-Lan; Genau, Pascal; Doira, Pascal; Bruneau, Didier; Pelon, Jacques; Sanak, Joseph

    2013-04-01

    The FENNEC program aims to improve our knowledge of both the role of the Saharan Heat Low (SHL) on the West African monsoon and the interactions between the African continent and the Mediterranean basin through the Saharan dust transport. The Saharan desert is the major source of mineral dust in the world and may significantly impact the air quality over the Western Europe by increasing the particular matter content. Two lidar systems were operated by the French component of the FENNEC project: an airborne lidar which was flown aboard the French Falcon 20 research aircraft and a ground-based lidar which was located in the southeastern part of Spain, close to Marbella. The presence of dust in the Saharan atmospheric boundary layer has been easily highlighted using the lidars and confirmed by ground-based sunphotometer and observations from both MODIS and SEVIRI spaceborne instruments. The simultaneous use of the sunphotometer-derived Angstrom exponent and the lidar-derived backscatter to extinction ratio is appeared to be a good approach to separate the optical contribution of dust from local aerosols for the coastal site. Over Spain, the dust layer was mainly located above the planetary boundary layer with several kilometers thick. Over the tropical Atlantic Ocean and the Mauritania the airborne lidar shows a high planetary boundary layer (~5 km above the mean sea level) associated to strong aerosol optical thickness (> 0.8 at 532 nm). The airborne lidar data have been inverted using both MODIS and SEVIRI-derived aerosol optical thickness. The differences between dust optical properties close to and remote from the sources will be discussed.

  3. Desert Voices: Southwestern Children's Literature.

    ERIC Educational Resources Information Center

    Polette, Keith

    1997-01-01

    Examines three books with different ways of writing about the desert. Discusses: "Here Is the Southwestern Desert" by Madeline Dunphy, "The Desert Is My Mother" by Pat Mora, and "The Desert Mermaid" by Alberto Blanco. (PA)

  4. Dust events, pulmonary diseases and immune system

    PubMed Central

    Esmaeil, Nafiseh; Gharagozloo, Marjan; Rezaei, Abbas; Grunig, Gabriele

    2014-01-01

    Incidences of sand storms have increased in recent years and there is evidence that these dusts can move across long distances. Sand dusts have different adverse effects on health, but one of the most important of them is pulmonary disease. After inhalation of dust, many dust particles are moved to the airways. Dust particles can be sensed by airways epithelial cells, activate macrophages, dendritic cells and innate immune cells and then initiate responses in various populations of specific immune cells such as T helper cells subsets (Th1, Th2, Th17), T cytotoxic cells and B cells. Initiation of inflammatory immune responses, activation of immune cells and releases of many cytokines, chemokines and other inflammatory molecules, have variable pathologic affects on lung in different respiratory diseases. Unfortunately control of desert dusts is more difficult than control of air pollution. For prevention and treatment of respiratory diseases that are caused by desert dusts, researchers need well-designed epidemiological studies, combined with analysis of the precise composition of sand dusts, and the precise mechanisms of the immune responses. Recognizing the exact cellular and molecular immune mechanisms would be very useful to find new approaches for treatment of desert dust associated pulmonary diseases. PMID:24660118

  5. Ground/satellite observations and atmospheric modeling of dust storms originating in the high Puna-Altiplano deserts (South America): Implications for the interpretation of paleo-climatic archives

    NASA Astrophysics Data System (ADS)

    Gaiero, D. M.; Simonella, L.; Gassó, S.; Gili, S.; Stein, A. F.; Sosa, P.; Becchio, R.; Arce, J.; Marelli, H.

    2013-05-01

    This study provides a detailed description of the sources, transport, dispersion, and deposition of two major dust events originating from the high-altitude subtropical Puna-Altiplano Plateau (15-26°S; 65-69°W) in South America. A long and severe drought provided the right conditions for the onset of both events in July 2009 and 2010. Dust was transported SE and deposited over the Pampas region and was observed to continue to the Atlantic Ocean. Dust monitoring stations located downwind recorded both events, and samples were characterized through chemical and textural analysis. Through a combination of meteorological data and satellite observations (CALIPSO and MODIS detectors), we estimate the emission flux for the 2010 event. This estimate was used to constrain the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) transport model and simulate the dust event. Both satellite imagery and model results agree in the location and extension of the dust cloud. CALIPSO detected dust between ~6000 and ~8500 m a.s.l., which remained at this height during most of its trajectory. The dust cloud mixed with a strong convective system in the region, and the associated precipitation brought down significant amounts of dust to the ground. Dust particle size analysis for both events indicates that near the sources dust samples show median modes of 12.4-14.1 µm, similar to modes observed 1300 km away. Chemical composition of sediments from potential dust sources shows distinct signatures within the Puna-Altiplano Plateau, the Puna sector being clearly different from the Altiplano area. In addition, both sources are markedly different from the Patagonian chemical fingerprint. These results have important implications to improve the interpretation of paleo-environmental archives preserved on the Argentine loess, Antarctic ice cores, and Southern Ocean marine sediments.

  6. Dust storm off Western Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The impacts of Saharan dust storms reach far beyond Africa. Wind-swept deserts spill airborne dust particles out over the Atlantic Ocean where they can enter trade winds bound for Central and North America and the Caribbean. This Moderate Resolution Imaging Spectroradiometer (MODIS) image shows a dust storm casting an opaque cloud of cloud across the Canary Islands and the Atlantic Ocean west of Africa on June 30, 2002. In general it takes between 5 and 7 days for such an event to cross the Atlantic. The dust has been shown to introduce foreign bacteria and fungi that have damaged reef ecosystems and have even been hypothesized as a cause of increasing occurrences of respiratory complaints in places like Florida, where the amount of Saharan dust reaching the state has been increasing over the past 25 years.

  7. Physical impacts of regional climate change in the West African Sahel and the question of desertification

    SciTech Connect

    Nicholson, S.E.; Ba, M.

    1997-11-01

    The question of desertification is examined in the West African Sahel region by considering various physical indicators assumed to accompany this process. The study considers only the past 14 years, since the availability of comprehensive satellite data sets. The physical indicators examined include vegetation cover, surface albedo, soil moisture, wind-borne dust, river flow, lakes, and the ratio of available moisture to vegetation growth. Vegetation cover and albedo are assessed from satellite data. Soil moisture is assessed using a surface hydrologic model. Dust is estimated from visibility measurements. The most important results are that: (1) there is no progressive change in the vegetation cover, (2) an increase of albedo as the region dries up cannot be documented, and (3) there has been a tremendous increase in wind-borne dust over the Sahel. The vegetation cover responds almost directly to rainfall and the movement of the desert boundary corresponds roughly to rainfall fluctuations. The most important meteorological effect of the drought and/or desertification in the Sahel may be the enhanced dust generation, with the region becoming a major global source of atmospheric mineral dust. 5 refs., 7 figs., 1 tab.

  8. The improvement of dust model applying modified soil component of dust source over East Asia.

    NASA Astrophysics Data System (ADS)

    Kwon, D. H.; Koo, Y. S.

    2014-12-01

    The East Asia region is the world's most populous area with a rapidly growing economy resulting in large air pollutant emissions. Asian mineral dust from Gobi Desert, Loess Plateau and barren mixed soil in Northern China and Mongolia has a major impact on the air quality in the Seoul Metropolitan Area. These mineral aerosols PM10 (particulate matter less than 10 um in diameter) concentration frequently exceeds the daily ambient air quality standards of 100μgm-3, and the number of exceedance days of daily PM10 reached about 40 times annually. The PM10 prediction by a regional chemical transport model without the dust emission shows an intrinsic tendency to underestimation according to previous studies in this region, especially for the soil originated coarse PM. This is partially due to the uncertainty of fugitive dust emissions. This study is aim to improve dust model(ADAM2 - Asian Dust Aeorosol Model 2) by changing soil component over source regions using Harmonized World Soil Database. ADAM2 has four dust components of the Gobi Desert, sand dsert, Loess Plateau and barren mixed soil. The soil components, however, should be updated as current and detailed soil components. Therfore, we apply updated dust model with CTM(Chemical Transport Model), CMAQ(Community Multi-scale Air Quality Model) to simulate dust concentration over East Asia. It is found that dust concentration with updated dust model is better agreement with observation during dust event periods, compared with standard dust model.

  9. Validation of SWEEP for creep, saltation, and suspension in a desert-oasis ecotone

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion in the desert-oasis ecotone can accelerate desertification and thus impacts oasis ecological security. Little is known about the susceptibility of the desert-oasis ecotone to wind erosion in the Tarim Basin even though the ecotone is a major source of windblown dust in China. The object...

  10. Exploring the Longwave Radiative Effects of Dust Aerosols

    NASA Technical Reports Server (NTRS)

    Hansell, Richard A., Jr.

    2012-01-01

    Dust aerosols not only affect air quality and visibility where they pose a significant health and safety risk, but they can also play a role in modulating the energy balance of the Earth-atmosphere system by directly interacting with local radiative fields. Consequently, dust aerosols can impact regional climate patterns such as changes in precipitation and the evolution of the hydrological cycle. Assessing the direct effect of dust aerosols at the solar wavelengths is fairly straightforward due in part to the relatively large signal-to-noise ratio in broadband irradiance measurements. The longwave (LW) impacts, on the other hand, are rather difficult to ascertain since the measured dust signal level (10 Wm-2) is on the same order as the instrumental uncertainties. Moreover, compared to the shortwave (SW), limited experimental data on the LW optical properties of dust makes it a difficult challenge for constraining the LW impacts. Owing to the strong absorption features found in many terrestrial minerals (e.g., silicates and clays), the LW effects, although much smaller in magnitude compared to the SW, can still have a sizeable impact on the energetics of the Earth-atmosphere system, which can potentially trigger changes in the heat and moisture surface budgets, and dynamics of the atmosphere. The current endeavor is an integral part of an on-going research study to perform detailed assessments of dust direct aerosol radiative effects (DARE) using comprehensive global datasets from NASA Goddards mobile ground-based facility (cf. http://smartlabs.gsfc.nasa.gov/) during previous field experiments near key dust source regions. Here we examine and compare the results from two of these studies: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years. The former study focused on transported Saharan dust at Sal Island (16.73N, 22.93W), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye China (39

  11. Comparison of horizontal dust fluxes simulated with two dust emission schemes based on field experiments in Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Yang, Xinghua; Yang, Fan; Liu, Xinchun; Huo, Wen; He, Qing; Mamtimin, Ali; Zhang, Qingyu

    2016-10-01

    Horizontal dust fluxes were simulated with two different dust emission schemes developed by Marticorena and Shao (hereinafter referred to as the M scheme, S scheme, and S scheme corrections), based on field experiments over a bare desert surface and a vegetated desert surface from May 19 to June 18, 2010 in Xinjiang, China. The M scheme produced a much higher dust emission than the S schemes over different surface conditions, with the emission being about 4 times larger than that produced by the S schemes over the bare desert, and 3 to 200 times larger over the vegetated surface. Compared to observations, the missing report rate of wind erosion events was about 30 % for the S schemes and about 10 % for the M scheme over the bare desert surface, while all schemes had a false alarm rate of wind erosion events over the vegetated desert surface. The total dust emission from the bare desert surface during the study period was 674.4, 551.5, 595.2, and 2995.8 kg/m for observation, the S scheme, S scheme correction 2, and M scheme, respectively. Total dust emission from the vegetated desert surface was 1.6, 0, 55.5, 0.9, and 227.7 kg/m for observation, the S scheme, S scheme correction 1, S scheme correction 2, and M scheme, respectively.

  12. Global trends in visibility: Implications for dust sources

    USGS Publications Warehouse

    Mahowald, N.M.; Ballantine, J.A.; Feddema, J.; Ramankutty, N.

    2007-01-01

    There is a large uncertainty in the relative roles of human land use, climate change and carbon dioxide fertilization in changing desert dust source strength over the past 100 years, and the overall sign of human impacts on dust is not known. We used visibility data from meteorological stations in dusty regions to assess the anthropogenic impact on long term trends in desert dust emissions. We did this by looking at time series of visibility derived variables and their correlations with precipitation, drought, winds, land use and grazing. Visibility data are available at thousands of stations globally from 1900 to the present, but we focused on 357 stations with more than 30 years of data in regions where mineral aerosols play a dominant role in visibility observations. We evaluated the 1974 to 2003 time period because most of these stations have reliable records only during this time. We first evaluated the visibility data against AERONET aerosol optical depth data, and found that only in dusty regions are the two moderately correlated. Correlation coefficients between visibility-derived variables and AERONET optical depths indicate a moderate correlation (0.47), consistent with capturing about 20% of the variability in optical depths. Two visibility-derived variables appear to compare the best with AERONET observations: the fraction of observations with visibility less than 5 km (VIS5) and the surface extinction (EXT). Regional trends show that in many dusty places, VIS5 and EXT are statistically significantly correlated with the Palmer drought severity index (based on precipitation and temperature) or surface wind speeds, consistent with dust temporal variability being largely driven by meteorology. This is especially true for North African and Chinese dust sources, but less true in the Middle East, Australia or South America, where there are not consistent patterns in the correlations. Climate indices such as El Nino or the North Atlantic Oscillation are not

  13. Global trends in visibility: Implications for dust sources

    USGS Publications Warehouse

    Mahowald, N.M.; Ballantine, J.A.; Feddema, J.; Ramankutty, N.

    2007-01-01

    There is a large uncertainty in the relative roles of human land use, climate change and carbon dioxide fertilization in changing desert dust source strength over the past 100 years, and the overall sign of human impacts on dust is not known. We used visibility data from meteorological stations in dusty regions to assess the anthropogenic impact on long term trends in desert dust emissions. Visibility data are available at thousands of stations globally from 1900 to the present, but we focused on 359 stations with more than 30 years of data in regions where mineral aerosols play a dominant role in visibility observations. We evaluated the 1974 to 2003 time period because most of these stations have reliable records only during this time. We first evaluated the visibility data against AERONET aerosol optical depth data, and found that only in dusty regions are the two moderately correlated. Correlation coefficients between visibility derived variables and AERONET optical depths indicate a moderate correlation (???0.47), consistent with capturing about 20% of the variability in optical depths. Two visibility derived variables appear to compare the best with AERONET observations: the fraction of observations with visibility less than 5 km (VIS5) and the surface extinction (EXT). Regional trends show that in many dusty places, VIS5 and EXT are statistically significantly correlated with the palmer drought severity index (based on precipitation and temperature) or surface wind speeds, consistent with dust temporal variability being largely driven by meteorology. This is especially true for North African and Chinese dust sources, but less true in the Middle East, Australia or South America, where there are not consistent patterns in the correlations. Climate indices such as El Nino or the North Atlantic Oscillation are not correlated with visibility derived variables in this analysis. There are few stations where visibility measures are correlated with cultivation or

  14. Climatic controls of the interannual to decadal variability in Saudi Arabian dust activity: Towards the development of a seasonal prediction tool

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Notaro, M.; Liu, Z.; Alkolibi, F.; Fadda, E.; Bakhrjy, F.

    2013-12-01

    Atmospheric dust significantly influences the climate system, as well as human life in Saudi Arabia. Skillful seasonal prediction of dust activity with climatic variables will help prevent some negative social impacts of dust storms. Yet, the climatic regulators on Saudi Arabian dust activity remain largely unaddressed. Remote sensing and station observations show consistent seasonal cycles in Saudi Arabian dust activity, which peaks in spring and summer. The climatic controls on springtime and summertime Saudi Arabian dust activity during 1975-2010 are studied using observational and reanalysis data. Empirical Orthogonal Function (EOF) of the observed Saudi Arabian dust storm frequency shows a dominant homogeneous pattern across the country, which has distinct interannual and decadal variations, as revealed by the power spectrum. Regression and correlation analyses reveal that Saudi Arabian dust activity is largely tied to precipitation on the Arabian Peninsula in spring and northwesterly (Shamal) wind in summer. On the seasonal-interannual time scale, warm El Niño-Southern Oscillation (ENSO) phase (El Niño) in winter-to-spring inhibits spring dust activity by increasing the precipitation over the Rub'al Khali Desert, a major dust source region on the southern Arabian Peninsula; warm ENSO and warm Indian Ocean Basin Mode (IOBM) in winter-to-spring favor less summer dust activity by producing anomalously low sea-level pressure over eastern north Africa and Arabian Peninsula, which leads to the reduced Shamal wind speed. The decadal variation in dust activity is likely associated with the Atlantic Multidecadal Oscillation (AMO), which impacts Sahel rainfall and North African dust, and likely dust transport to Saudi Arabia. The Pacific Decadal Oscillation (PDO) and tropical Indian Ocean SST also have influence on the decadal variation in Saudi Arabian dust activity, by altering precipitation over the Arabian Peninsula and summer Shamal wind speed. Using eastern

  15. Dust devils as observed by Mars Pathfinder

    NASA Astrophysics Data System (ADS)

    Ferri, Francesca; Smith, Peter H.; Lemmon, Mark; Rennó, Nilton O.

    2003-12-01

    Dust devils are localized meteorological phenomena frequently observed in terrestrial dry lands and desert landscapes as well as on Mars. They are low-pressure, warm core vortices that form at the bottom of convective plumes and loft dust from the surface. They move with the speed of the ambient wind and are tilted by wind shears. The Mars Pathfinder detected dust devils as dust plumes in the Imager for Mars Pathfinder images and as low-pressure convective vortices in the meteorological Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET) experiment data. The Pathfinder data have been analyzed in terms of dust devil size, spatial distribution, and frequency of occurrence. The results show that the Pathfinder imaging and MET observations are consistent with each other and with the observations made by the Viking 1 Orbiter and Mars Global Surveyor. The dust devil's ability to loft dust into the atmosphere has been investigated and a thermodynamic theory for dust devils has been used to calculate their physical parameters relevant to dust transport. The dust devils observed in an active day provide a pumping rate larger than the dust-settling rate derived from the optical obscuration of the Pathfinder rover solar panels. Therefore dust devils are a major factor in transporting dust from the surface to the atmosphere at the Pathfinder site.

  16. Improvisation in West African Musics.

    ERIC Educational Resources Information Center

    Locke, David

    1980-01-01

    Discussed is music of the sub-Sahara. Vocal, instrumental, and dance drumming from the Sudan Desert, the North Coast, East Horn, Central and West Africa, and contrapuntal yodeling of Pygmies is described. For African musicians, the ability to improvise, and creativity, are gifts from God. Includes selected readings and recordings. (KC)

  17. STS-57 OV-105's payload bay (PLB) with Earth observation of Namib Desert

    NASA Technical Reports Server (NTRS)

    1993-01-01

    STS-57 Earth observation taken aboard Endeavour, Orbiter Vehicle (OV) 105, is of the coast of the Namib Desert. This northeast-looking view shows the distinctive yellow, parallel dunes of the Namib Sand Sea in the foreground under OV-105's tail. The largest harbor on the Atlantic coast is Walvis Bay. A small piece of south African territory surrounded by the newly independent country, Walvis Bay is Namibia's major port. On the dune-free flats directly inland from Walvis Bay, large reserves of near-surface uranium have been discovered. The world's largest open-pit uranium mine, the Rossing Mine, has attracted workers from all parts of Namibia. Of special interest for this mission is the unusual occurrence of blowing dust offshore (orange patch over the sea). In what was a mission dominated by episodes of blowing dust, this is another example showing how windy the Earth is at present. This large view from a higher-than-usual altitude includes the large oval patch of the Etosha dry lake n

  18. Spring Dust Storm Smothers Beijing

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A few days earlier than usual, a large, dense plume of dust blew southward and eastward from the desert plains of Mongolia-quite smothering to the residents of Beijing. Citizens of northeastern China call this annual event the 'shachenbao,' or 'dust cloud tempest.' However, the tempest normally occurs during the spring time. The dust storm hit Beijing on Friday night, March 15, and began coating everything with a fine, pale brown layer of grit. The region is quite dry; a problem some believe has been exacerbated by decades of deforestation. According to Chinese government estimates, roughly 1 million tons of desert dust and sand blow into Beijing each year. This true-color image was made using two adjacent swaths (click to see the full image) of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, on March 17, 2002. The massive dust storm (brownish pixels) can easily be distinguished from clouds (bright white pixels) as it blows across northern Japan and eastward toward the open Pacific Ocean. The black regions are gaps between SeaWiFS' viewing swaths and represent areas where no data were collected. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  19. Long-term dust climatology in the western United States reconstructed from routine aerosol ground monitoring

    NASA Astrophysics Data System (ADS)

    Tong, D. Q.; Dan, M.; Wang, T.; Lee, P.

    2012-06-01

    This study introduces an observation-based dust identification approach and applies it to reconstruct long-term dust climatology in the western United States. Long-term dust climatology is important for quantifying the effects of atmospheric aerosols on regional and global climate. Although many routine aerosol monitoring networks exist, it is often difficult to obtain dust records from these networks, because these monitors are either deployed far away from dust active regions (most likely collocated with dense population) or contaminated by anthropogenic sources and other natural sources, such as wildfires and vegetation detritus. Here we propose an approach to identify local dust events relying solely on aerosol mass and composition from general-purpose aerosol measurements. Through analyzing the chemical and physical characteristics of aerosol observations during satellite-detected dust episodes, we select five indicators to be used to identify local dust records: (1) high PM10 concentrations; (2) low PM2.5/PM10 ratio; (3) higher concentrations and percentage of crustal elements; (4) lower percentage of anthropogenic pollutants; and (5) low enrichment factors of anthropogenic elements. After establishing these identification criteria, we conduct hierarchical cluster analysis for all validated aerosol measurement data over 68 IMPROVE sites in the western United States. A total of 182 local dust events were identified over 30 of the 68 locations from 2000 to 2007. These locations are either close to the four US Deserts, namely the Great Basin Desert, the Mojave Desert, the Sonoran Desert, and the Chihuahuan Desert, or in the high wind power region (Colorado). During the eight-year study period, the total number of dust events displays an interesting four-year activity cycle (one in 2000-2003 and the other in 2004-2007). The years of 2003, 2002 and 2007 are the three most active dust periods, with 46, 31 and 24 recorded dust events, respectively, while the years

  20. Fingerprints in the Dust

    NASA Technical Reports Server (NTRS)

    2001-01-01

    These MISR nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a spectacularly dusty spring view from April 7, 2001 (middle). The left-hand and middle images are from Terra orbits 2967 and 6928, respectively, and extend from central Manchuria near the top to portions of North and South Korea at the bottom. They are approximately 380 kilometers in width.

    Asia's desert areas are prone to soil erosion, as underground water tables are lowered by prolonged drought and by industrial and agricultural water use. Heavy winds blowing eastward across the arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the April 2001 storm blew across the Pacific Ocean and were carried as far as North America. The minerals transported in this manner are believed to provide nutrients for both oceanic and land ecosystems.

    According to the Xinhua News Agency in China, nearly one million tons of Gobi Desert dust blow into Beijing each year. During a similar dust outbreak last year, the Associated Press reported that the visibility in Beijing had been reduced the point where buildings were barely visible across city streets, and airline schedules were significantly disrupted. The dust has also been implicated in adverse health effects such as respiratory discomfort and eye irritation.

    The image on the right is a higher resolution MISR nadir-camera view of a portion of the April 7, 2001 dust cloud. It covers an area roughly 250 kilometers wide by 470 kilometers high. When viewed at full magnification, a number of atmospheric wave features, like the ridges and valleys of a fingerprint, are apparent. These are probably induced by surface topography, which can disturb the wind flow. A few small cumulus clouds are also visible, and are casting shadows on the thick lower dust layer.

    Analyses of images such as these constitute one phase of MISR

  1. Characteristics of 14C and 13C of carbonate aerosols in dust storm events in China

    NASA Astrophysics Data System (ADS)

    Chen, Bing; Jie, Dongmei; Shi, Meinan; Gao, Pan; Shen, Zhenxing; Uchida, Masao; Zhou, Liping; Liu, Kexin; Hu, Ke; Kitagawa, Hiroyuki

    2015-10-01

    In contrast with its decrease in western China deserts, the dust storm event in eastern China, Korea, and Japan shows an increase in frequency. Although the drylands in northeastern China have been recognized as an important dust source, the relative contributions of dust transport from the drylands and deserts are inconclusive, thus the quantification of dust storm sources in downwind area remains a challenge. We measured the 14C and 13C contents in carbonates of dust samples from six sites in China, which were collected for the duration of dust storm events in drylands, deserts, and urban areas. The δ13C of the dryland dust samples considerably varied in a range of - 9.7 to - 5.0‰, which partly overlapped the desert dust carbonate δ13C ranges. The 14C content of the dryland dust carbonates showed a narrow range of 60.9 ± 4.0 (as an average and 1 SD of five samples) percent modern carbon (pMC), indicating the enrichment of modern carbonate. Dust samples in desert regions contained relatively aged carbonates with the depleting 14C showing of 28.8 ± 3.3 pMC. After the long-range transport of the western China desert dust plume, the carbonates collected at the southern China remained the depletion of 14C (33.5 ± 5.3 pMC) as in the desert regions. On the other hand, the samples of dust storm events at the urban areas of eastern China showed an enrichment of 14C contents (46.2 ± 5.0 pMC, n = 7), which might be explained by the stronger contribution of modern-carbonate-rich dryland dust.

  2. Trans-Pacific transport of Saharan dust to western North America: A case study

    NASA Astrophysics Data System (ADS)

    McKendry, Ian G.; Strawbridge, Kevin B.; O'Neill, Norman T.; MacDonald, Anne Marie; Liu, Peter S. K.; Leaitch, W. Richard; Anlauf, Kurt G.; Jaegle, Lyatt; Fairlie, T. Duncan; Westphal, Douglas L.

    2007-01-01

    The first documented case of long-range transport of Saharan dust over a pathway spanning Asia and the Pacific to western North America is described. Crustal material generated by North African dust storms during the period 28 February to 3 March 2005 reached western Canada on 13-14 March 2005 and was observed by lidar and sunphotometer in the Vancouver region and by high-altitude aerosol instrumentation at Whistler Peak. Global chemical models (GEOS-Chem and NRL NAAPS) confirm the transport pathway and suggest source attribution was simplified in this case by the distinct, and somewhat unusual, lack of dust activity over Eurasia (Gobi and Takla Makan deserts) at this time. Over western North America the dust layer, although subsiding close to the boundary layer, did not appear to contribute to boundary layer particulate matter concentrations. Furthermore, sunphotometer observations (and associated inversion products) suggest that the dust layer had only subtle optical impact (aerosol optical thickness (τa500) and Ångström exponent (α440-870) were 0.1 and 1.2, respectively) and was dominated by fine particulate matter (modes in aerodynamic diameter at 0.3 and 2.5 μm). High-altitude observations at Whistler, British Columbia, confirm the crustal origin of the layer (rich in Ca++ ions) and the bimodal size distribution. Although a weak event compared to the Asian trans-Pacific dust events of 1998 and 2001, this novel case highlights the possibility that Saharan sources may contribute episodically to the aerosol burden in western North America.

  3. Trans-Pacific Transport of Saharan Dust to Western North America: A Case Study

    NASA Technical Reports Server (NTRS)

    Kendry, Ian G. M.; Strawbridge, Kevin B.; O'Neill, Norman; Macdonald, Anne Marie; Liu, Peter S. K.; Leaitch, W. Richard; Anlauf, Kurt G.; Jaegle, Lyatt; Fairlie, T. Duncan; Westphal, Douglas L.

    2007-01-01

    The first documented case of long range transport of Saharan dust over a pathway spanning Asia and the Pacific to Western North America is described. Crustal material generated by North African dust storms during the period 28 February - 3 March 2005 reached western Canada on 13-14 March 2005 and was observed by lidar and sunphotometer in the Vancouver region and by high altitude aerosol instrumentation at Whistler Peak. Global chemical models (GEOS-CHEM and NRL NAAPS) confirm the transport pathway and suggest source attribution was simplified in this case by the distinct, and somewhat unusual, lack of dust activity over Eurasia (Gobi and Takla Makan deserts) at this time. Over western North America, the dust layer, although subsiding close to the boundary layer, did not appear to contribute to boundary layer particulate matter concentrations. Furthermore, sunphotometer observations (and associated inversion products) suggest that the dust layer had only subtle optical impact (Aerosol Optical Thickness (Tau(sub a500)) and Angstrom exponent (Alpha(sub 440-870) were 0.1 and 1.2 respectively) and was dominated by fine particulate matter (modes in aerodynamic diameter at 0.3 and 2.5microns). High Altitude observations at Whistler BC, confirm the crustal origin of the layer (rich in Ca(++) ions) and the bi-modal size distribution. Although a weak event compared to the Asian Trans-Pacific dust events of 1998 and 2001, this novel case highlights the possibility that Saharan sources may contribute episodically to the aerosol burden in western North America.

  4. Saharan Dust over Senegal

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Airborne African dust regularly reaches northeastern South America and the Caribbean. Westward dust transport from the Sahara across the central Atlantic has been a common occurrence this spring, with major events visible in both satellite images and photographs. Cap Vert, the westernmost point of Senegal, is dimly visible beneath the dust mass (center); the Arquipelago dos Bijagos in Guinea Bissau lies opposite the mouth of the sediment-laden Rio Corubal. This photo (ISS004-E-12080) was taken by the crew of the International Space Station on May 18, 2002, using a digital camera with a 35-mm lens. Image provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to Astronaut Photography of Earth.

  5. Characterization of dust sources in Central Asia using Remote Sensing

    NASA Astrophysics Data System (ADS)

    Nobakht, M.; Shahgedanova, M.; White, K.

    2015-12-01

    Central Asian deserts are a significant source of wind-blown desert dust deposited on snow pack and glaciers of the Tian Shan Mountains, affecting both surface reflectance, and therefore melt and runoff, and geochemistry of snow pack and glacier ice. Detailed knowledge of sources of dust, atmospheric pathways, timing and geography of deposition is of crucial importance. This paper focuses on two aspects of desert dust over Central Asia: (i) seasonal and spatial patterns of aerosol optical depth (AOD) of desert dust and (ii) location and seasonal trends in activity of dust sources. Seasonal and spatial distribution of AOD is investigated using Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue AOD product, acquired over a period of 12 years from January 2003 to December 2014 at 10 km resolution. More detailed maps of dust sources are produced from higher resolution (1km) MODIS dust enhancement products (DEP) which have been modified by the use of additional bands and change in parameterization. The combined use of AOD and DEP enabled us to identify large scale dust emitting areas (through the use of AOD data) and within these areas, identify smaller-scale eroding points (using DEP) thus significantly improving the knowledge of both dust source location and dust entrainment mechanisms including rapid desertification (e.g. Aral Sea) and post-fire wind erosion (e.g. Lake Balkhash basin). Different seasonal patterns of dust emissions were observed in northern, western and southern deserts around the Tian Shan Mountains and their relation to climatological processes in these regions are explored.

  6. Numerical simulations of Asian dust events: A Lagrangian Dust Model and its applications

    NASA Astrophysics Data System (ADS)

    Kim, Cheol-Hee; Lee, Hyo-Jung

    2013-11-01

    An uni-modal Lagrangian Dust Model (LDM) was developed to simulate the dust concentrations and source-receptor (SR) relationships for recent Asian dust events that occurred over the Korean Peninsula. The following dust sources were used for the S-R calculation in this study: S-I) Gurbantunggut desert, S-II) Taklamakan desert, S-III) Tibetan Plateau, S-IV) Mu Us Desert, S-V) Manchuria, and S-VI) Nei Mongol and Gobi Desert. The following two 8-day dust simulation periods were selected for two case studies: (Period A) March 15-22, 2011, and (Period B) April 27-May 4, 2011. During two periods there were highly dense dust onsets observed over a wide area in Korea. Meteorological fields were generated using the WRF (Weather Research and Forecasting) meteorological model, and Lagrangian turbulent properties and dust emission were estimated using FLEXPART model and ADAM2 (Asian Dust Aerosol Model 2), respectively. The simulated dust concentrations are compared with point measurements and Eulerian model outputs. Statistical techniques were also employed to determine the accuracy and uncertainty associated with the model results. The results showed that the LDM compared favorably well with observations for some sites; however, for most sites the model overestimated the observations. Analysis of S-R relationships showed that 38-50% of dust particles originated from Nei Mongol and the Gobi Desert, and 16-25% of dust particles originated from Manchuria, accounting for most of the dust particles in Korea. Because there is no nudging or other artificial forcing included in the LDM, higher error indicators (e.g., root mean square error, absolute gross error) were found for some sites. However, the LDM was able to satisfactorily simulate the maximum timing and starting time of dust events for most sites. Compared with the Eulerian model, ADAM2, the results of LDM found pattern correlations (PCs) equal to 0.78-0.83 and indices of agreement (IOAs) greater than 0.6, suggesting that

  7. Camelid genomes reveal evolution and adaptation to desert environments.

    PubMed

    Wu, Huiguang; Guang, Xuanmin; Al-Fageeh, Mohamed B; Cao, Junwei; Pan, Shengkai; Zhou, Huanmin; Zhang, Li; Abutarboush, Mohammed H; Xing, Yanping; Xie, Zhiyuan; Alshanqeeti, Ali S; Zhang, Yanru; Yao, Qiulin; Al-Shomrani, Badr M; Zhang, Dong; Li, Jiang; Manee, Manee M; Yang, Zili; Yang, Linfeng; Liu, Yiyi; Zhang, Jilin; Altammami, Musaad A; Wang, Shenyuan; Yu, Lili; Zhang, Wenbin; Liu, Sanyang; Ba, La; Liu, Chunxia; Yang, Xukui; Meng, Fanhua; Wang, Shaowei; Li, Lu; Li, Erli; Li, Xueqiong; Wu, Kaifeng; Zhang, Shu; Wang, Junyi; Yin, Ye; Yang, Huanming; Al-Swailem, Abdulaziz M; Wang, Jun

    2014-10-21

    Bactrian camel (Camelus bactrianus), dromedary (Camelus dromedarius) and alpaca (Vicugna pacos) are economically important livestock. Although the Bactrian camel and dromedary are large, typically arid-desert-adapted mammals, alpacas are adapted to plateaus. Here we present high-quality genome sequences of these three species. Our analysis reveals the demographic history of these species since the Tortonian Stage of the Miocene and uncovers a striking correlation between large fluctuations in population size and geological time boundaries. Comparative genomic analysis reveals complex features related to desert adaptations, including fat and water metabolism, stress responses to heat, aridity, intense ultraviolet radiation and choking dust. Transcriptomic analysis of Bactrian camels further reveals unique osmoregulation, osmoprotection and compensatory mechanisms for water reservation underpinned by high blood glucose levels. We hypothesize that these physiological mechanisms represent kidney evolutionary adaptations to the desert environment. This study advances our understanding of camelid evolution and the adaptation of camels to arid-desert environments.

  8. Animals of the Desert.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides background information and student activities on how desert animals have adapted to dryness and heat, how and when animals move on the desert, and nocturnal/diurnal animals. Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. Ready-to-copy pages are included for a…

  9. Chemical coupling between acid gases and water-soluble inorganic ions in size-segregated aerosols during Arabian Dust in Beirut

    NASA Astrophysics Data System (ADS)

    Saliba, Najat; Dada, Lubna; Baalbaki, Rima

    2015-04-01

    In the proximity of the Eastern Mediterranean region, the combination of two large desert areas; Arabian and African, with heavy oil industry and high insolation during summer delineate a unique location of atmospheric processes in the region. Once emitted, dust particles can be transported over long distances and/or remain suspended in the atmosphere for several days. The so-called remnant dust episodes in Beirut originate from both African and Arabian deserts. In this study, the gas and particle transformations and gas-to-particle conversion during Arabian-dust (Ar-D) events are assessed. The increase in primary and secondary gas concentrations during Ar-D days is ascribed to three contributing factors; (i) the regional-long-range transport (LRT), (ii) the drop in the average solar radiation leading to a slow primary-to-secondary conversion and secondary gas photo-degradation, and (iii) the enhancement of the recirculation and accumulation of the main pollutants during dusty days. In parallel, a respective mass increase by 137, 149 and 13% in the coarse (CPM), accumulation (ACC) and ultrafine (UF) fractions was measured and an increase in particle volume distribution was mostly noticed for particles ranging in sizes between 2.25 and 5 μm. This lead to major changes in the inorganic chemical composition of all particle sizes. In particular, the enhanced presence of several types of nitrate and sulfate salts in the accumulation mode confirms that remnant dust episodes offer a favorable environment for gas-to-particle conversion and particle chemical transformations and growth.

  10. Radiative Energetics of Mineral Dust Aerosols from Ground-Based Measurements

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; Hansell, Richard A.

    2011-01-01

    Airborne dust aerosols worldwide contribute a significant part to air quality problems and, to some extent, regional climatic issues (e.g., radiative forcing, hydrological cycle, and primary biological productivity in oceans). Evaluating the direct solar radiative effect of dust aerosols is relatively straightforward due in part to the relatively large SIN ratio in broadband irradiance measurements. The longwave (LW) impact, on the other hand, is rather difficult to ascertain since the measured dust signal level (approx.10 W/sq m) is on the same order as the instrumental uncertainties. Although the magnitude of the LW impact is much smaller than that of the shortwave (SW), it can still have a noticeable influence on the energy distribution of Earth-atmosphere system, particularly due to the strong light-absorptive properties commonly found in many terrestrial minerals. The current effort is part of an ongoing research study to perform a global assessment of dust direct aerosol radiative effects (DARE) during major field deployments of key dust source regions worldwide. In this work we present results stemming from two previous field deployments: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years, both utilizing NASA Goddard's mobile ground-based facility. The former study focused on transported Saharan dust at Sal (16.73degN, 22.93degW), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye (39.082degN, 100.276degE), China near the source between the Taklimakan and Gobi deserts. Due to the compelling variability in spatial and temporal scale of dust properties during field experiments, a deterministic I-D radiative transfer model constrained by local measurements (i.e., spectral photometry/interferometry and lidar for physical/microphysical, mineralogy, and single-scattering properties) is employed to evaluate dust's local instantaneous SW/LW DARE both at the surface and at the top of

  11. Variability of East Asia dust events and their long-term trend

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Huang, Jianping; Ji, Mingxia; Higuchi, Kaz

    In order to examine the decadal variations of the dust events over East Asia, we analyze surface observations from 701 meteorological stations for the period 1960-2004 to obtain spatial and temporal distributions of dust events. Since the Taklamakan Desert in western China and the Gobi Desert in Inner Mongolia are the two major sources of dust storms, we have defined two dust indices, one for the Taklamakan Desert Index (TDI) and one for the Gobi Desert Index (GDI), to characterize the statistical nature of the dust events over these two regions. Both of these indices are well correlated with the Total Ozone Mapping Spectrometer (TOMS) Absorbing Aerosol Index (AAI). TDI and GDI time series exhibit a decreasing trend since the mid-1980s, and is likely caused by an enhanced geopotential height over the Mongolian plateau and the middle Siberian region, as well as by an anomalous shift in the phase and intensity of the stationary wave over.

  12. High resolution mapping of dust sources in Central Asia using MODIS imagery

    NASA Astrophysics Data System (ADS)

    Nobakht, Mohamad; Shahgedanova, Maria; White, Kevin

    2015-04-01

    Dust impacts the energy balance of the Earth via absorption and scattering of radiation in the atmosphere and through the mechanism by which aerosols modify the optical properties of clouds and land surfaces. It is now established that the deposition of mineral dust significantly affects high-altitude environments, including both snow pack and glacier ice. Central Asia is a region where large deserts are located in close proximity to the mountains whose extensive glaciers and snow pack provide runoff supporting agriculture in the densely populated foothills. More than 75% of the territory in Central Asia is desert lowland varying from sandy to stony, salt, and clay deserts. Significant amounts of wind-blown desert dust, originating from these deserts, are deposited on glaciers of Tian Shan Mountains in Central Asia. Satellite remote sensing using optical imagery has provided us with a powerful tool for identification and characterization of dust emission sources. In this study we investigated the spatial distribution and seasonal pattern of dust emissions in surrounding lowlands of the Tian Shan Mountains using Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. Seasonality of dust emission is studied by analyzing MODIS Deep Blue aerosol optical depth, acquired over a period of 12 years from January 2003 to December 2014. We analyzed the spatial distribution and frequency of occurrence of dust optical depth to identify the main dust sources in this region. In order to produce a detailed map of dust emission sources, we also employed a dust enhancement algorithm to obtain high resolution (1km) dust enhancement products from MODIS imageries. The high resolution of MODIS dust enhancement products enabled us to identify several small, eroding point sources within the dust source areas. Different seasonal patterns of dust emissions were observed in northern, western and southern deserts around the Tian Shan Mountains and their relation to climatological

  13. EXTREME DUST AND SMOKE EVENTS OVER THE U.S. IN 1998

    EPA Science Inventory

    Dust storms and forest fires are major PM events that occur several times a year over different parts of the US. Such events also originate outside the US, e.g., dust from Sahara and the Asian deserts and smoke from forest fires in Central America and Canada. Such dust and smok...

  14. Dust Detector

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.

    2001-01-01

    We discuss a recent sounding rocket experiment which found charged dust in the Earth's tropical mesosphere. The dust detector was designed to measure small (5000 - 10000 amu.) charged dust particles, most likely of meteoric origin. A 5 km thick layer of positively charged dust was found at an altitude of 90 km, in the vicinity of an observed sporadic sodium layer and sporadic E layer. The observed dust was positively charged in the bulk of the dust layer, but was negatively charged near the bottom.

  15. Dust storm events over Delhi: verification of dust AOD forecasts with satellite and surface observations

    NASA Astrophysics Data System (ADS)

    Singh, Aditi; Iyengar, Gopal R.; George, John P.

    2016-05-01

    Thar desert located in northwest part of India is considered as one of the major dust source. Dust storms originate in Thar desert during pre-monsoon season, affects large part of Indo-Gangetic plains. High dust loading causes the deterioration of the ambient air quality and degradation in visibility. Present study focuses on the identification of dust events and verification of the forecast of dust events over Delhi and western part of IG Plains, during the pre-monsoon season of 2015. Three dust events have been identified over Delhi during the study period. For all the selected days, Terra-MODIS AOD at 550 nm are found close to 1.0, while AURA-OMI AI shows high values. Dust AOD forecasts from NCMRWF Unified Model (NCUM) for the three selected dust events are verified against satellite (MODIS) and ground based observations (AERONET). Comparison of observed AODs at 550 nm from MODIS with NCUM predicted AODs reveals that NCUM is able to predict the spatial and temporal distribution of dust AOD, in these cases. Good correlation (~0.67) is obtained between the NCUM predicted dust AODs and location specific observations available from AERONET. Model under-predicted the AODs as compared to the AERONET observations. This may be mainly because the model account for only dust and no anthropogenic activities are considered. The results of the present study emphasize the requirement of more realistic representation of local dust emission in the model both of natural and anthropogenic origin, to improve the forecast of dust from NCUM during the dust events.

  16. Are Food Deserts Also Play Deserts?

    PubMed

    Cohen, Deborah A; Hunter, Gerald; Williamson, Stephanie; Dubowitz, Tamara

    2016-04-01

    Although food deserts are areas that lack easy access to food outlets and considered a barrier to a healthy diet and a healthy weight among residents, food deserts typically comprise older urban areas which may have many parks and street configurations that could facilitate more physical activity. However, other conditions may limit the use of available facilities in these areas. This paper assesses the use of parks in two Pittsburgh food desert neighborhoods by using systematic observation. We found that while the local parks were accessible, they were largely underutilized. We surveyed local residents and found that only a minority considered the parks unsafe for use during the day, but a substantial proportion suffered from health limitations that interfered with physical activity. Residents also felt that parks lacked programming and other amenities that could potentially draw more park users. Parks programming and equipment in food desert areas should be addressed to account for local preferences and adjusted to meet the needs and limitations of local residents, especially seniors.

  17. Deserts : geology and resources

    USGS Publications Warehouse

    Walker, Alta S.

    1996-01-01

    Approximately one-third of the Earth's land surface is desert, arid land with meager rainfall that supports only sparse vegetation and a limited population of people and animals. Deserts stark, sometimes mysterious worlds have been portrayed as fascinating environments of adventure and exploration from narratives such as that of Lawrence of Arabia to movies such as "Dune." These arid regions are called deserts because they are dry. They may be hot, they may be cold. They may be regions of sand or vast areas of rocks and gravel peppered with occasional plants. But deserts are always dry. Deserts are natural laboratories in which to study the interactions of wind and sometimes water on the arid surfaces of planets. They contain valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Because deserts are dry, they are ideal places for human artifacts and fossils to be preserved. Deserts are also fragile environments. The misuse of these lands is a serious and growing problem in parts of our world.

  18. Spatial and temporal variations of spring dust emissions in northern China over the last 30 years

    NASA Astrophysics Data System (ADS)

    Song, Hongquan; Zhang, Kesheng; Piao, Shilong; Wan, Shiqiang

    2016-02-01

    Dust emissions caused by wind erosion have significant impacts on land degradation, air quality, and climate change. Dust from the arid and semiarid regions of China is a main contributor to atmospheric dust aerosols in East Asia, and their impacts can stretch far beyond the territory of China. Spatial-temporal patterns of dust emissions in China over the last several decades, however, are still lacking, especially during the spring season. In this study, we simulated the spatial-temporal dynamics of spring dust emissions from 1982 to 2011 in arid and semi-arid areas of China using the Integrated Wind Erosion Modeling System. Results showed that the most severe dust emission events occurred in the Taklimakan Desert, Badain Jaran Desert, Tengger Desert, and Ulan Buh Desert. Over the last three decades, the magnitude of spring dust emissions generally decreased at the regional scale, with an annual spring dust emission of ˜401.10 Tg. Among different vegetation types, the highest annual spring dust emission occurred in the desert steppes (˜163.95 Tg), followed by the deserts (˜103.26 Tg). The dust emission intensity in the desert steppes and the deserts was ˜150.83 kg km-2·yr-1 and ˜205.46 kg km-2·yr-1, respectively. The spatial patterns of the inter-decadal variation are related to climate change and human activities. Mitigation strategies such as returning farmland to grassland, fenced grazing, and adequate grass harvesting, must be taken to prevent further soil losses and grassland degradation in northern China.

  19. An observation-based approach to identify local natural dust events from routine aerosol ground monitoring

    NASA Astrophysics Data System (ADS)

    Tong, D. Q.; Dan, M.; Wang, T.; Lee, P.

    2012-02-01

    Dust is a major component of atmospheric aerosols in many parts of the world. Although there exist many routine aerosol monitoring networks, it is often difficult to obtain dust records from these networks, because these monitors are either deployed far away from dust active regions (most likely collocated with dense population) or contaminated by anthropogenic sources and other natural sources, such as wildfires and vegetation detritus. Here we propose a new approach to identify local dust events relying solely on aerosol mass and composition from general-purpose aerosol measurements. Through analyzing the chemical and physical characteristics of aerosol observations during satellite-detected dust episodes, we select five indicators to be used to identify local dust records: (1) high PM10 concentrations; (2) low PM2.5/PM10 ratio; (3) higher concentrations and percentage of crustal elements; (4) lower percentage of anthropogenic pollutants; and (5) low enrichment factors of anthropogenic elements. After establishing these identification criteria, we conduct hierarchical cluster analysis for all validated aerosol measurement data over 68 IMPROVE sites in the Western United States. A total of 182 local dust events were identified over 30 of the 68 locations from 2000 to 2007. These locations are either close to the four US Deserts, namely the Great Basin Desert, the Mojave Desert, the Sonoran Desert, and the Chihuahuan Desert, or in the high wind power region (Colorado). During the eight-year study period, the total number of dust events displays an interesting four-year activity cycle (one in 2000-2003 and the other in 2004-2007). The years of 2003, 2002 and 2007 are the three most active dust periods, with 46, 31 and 24 recorded dust events, respectively, while the years of 2000, 2004 and 2005 are the calmest periods, all with single digit dust records. Among these deserts, the Chihuahua Desert (59 cases) and the Sonoran Desert (62 cases) are by far the most active

  20. Status and Future of Dust Storm Forecasting

    NASA Astrophysics Data System (ADS)

    Westphal, D. L.

    2002-12-01

    In recent years, increased attention has been given to the large amounts of airborne dust derived from the deserts and desertified areas of the world and transported over scales ranging from local to global. This dust can have positive and negative impacts on human activities and the environment, including modifying cloud formation, fertilizing the ocean, degrading air quality, reducing visibility, transporting pathogens, and inducing respiratory problems. The atmospheric radiative forcing by the dust has implications for global climate change and presently is one of the largest unknowns in climate models. These uncertainties have lead to much of the funding for research into the sources, properties, and fate of atmospheric dust. As a result of advances in numerical weather prediction over the past decades and the recent climate research, we are now in a position to produce operational dust storm forecasts. International organizations and national agencies are developing programs for dust forecasting. The approaches and applications of dust detection and forecasting are as varied as the nations that are developing the models. The basic components of a dust forecasting system include atmospheric forcing, dust production, and dust microphysics. The forecasting applications include air and auto traffic safety, shipping, health, national security, climate and weather. This presentation will summarize the methods of dust storm forecasting and illustrate the various applications. The major remaining uncertainties (e.g. sources and initialization) will be discussed as well as approaches for solving those problems.

  1. Dust Storm

    Atmospheric Science Data Center

    2013-04-16

    article title:  Massive Dust Storm over Australia     View ... at JPL September 22, 2009 - Massive dust storm over Australia. project:  MISR category:  ... Sep 22, 2009 Images:  Dust Storm location:  Australia and New Zealand ...

  2. Geomorphometirc Segmentation of Shield Deserts by Self-Organizing Maps

    NASA Astrophysics Data System (ADS)

    Foroutan, M.; Kompanizare, M.; Ehsani, A. H.

    2015-12-01

    Shield deserts have developed on ancient crystalline bedrocks and mainly composed of folded and faulted rocks hardened by heat and pressure over millions of years. They were unearthed by erosion and form steep-sided hills and basins filled with sediments. The Sahara, Arabian, southern African, central Kavir and Australian deserts are in this group. Their ranges usually supply groundwater resources or in some regions contain huge oil reservoirs. Geomorphological segmentation of shield deserts is one of the fundamental tools in their land use or site investigation planning as well as in their surface water and groundwater management. In many studies the morphology of shield deserts has been investigated by limited qualitative and subjective methods using limited number of simple parameters such as surface elevation and slope. However the importance of these regions supports the need for their accurate and quantitative morphologic classification. The present study attempts to implement a quantitative method, Self-Organizing Map (SOM), for geomorphological classification of a typical shield desert within Kavir Desert, Iran. The area is tectonically stable and characterized by flat clay pans, playas, well-developed pediments around scattered and low elevation ranges. Twenty-two multi-scale morphometric parameters were derived from the first- to third-orders partial derivatives of the surface elevation. Seven optimized parameters with their proper scales were selected by Artificial Neural Networks, Optimum Index Factor, Davies-Bouldin Index and statistic models. Finally, the area was segmented to seven homogeneous areas by SOM algorithm. The results revealed the most distinguishing parameter set (MDPS) for morphologic segmentation of shield deserts. The same segmentation results through using MDPS for another shield deserts in Australia proves the applicability of MDPS for shield deserts segmentation.

  3. PERSPECTIVE: Dust, fertilization and sources

    NASA Astrophysics Data System (ADS)

    Remer, Lorraine A.

    2006-11-01

    Aerosols, tiny suspended particles in the atmosphere, play an important role in modifying the Earth's energy balance and are essential for the formation of cloud droplets. Suspended dust particles lifted from the world's arid regions by strong winds contain essential minerals that can be transported great distances and deposited into the ocean or on other continents where productivity is limited by lack of usable minerals [1]. Dust can transport pathogens as well as minerals great distance, contributing to the spread of human and agricultural diseases, and a portion of dust can be attributed to human activity suggesting that dust radiative effects should be included in estimates of anthropogenic climate forcing. The greenish and brownish tints in figure 1 show the wide extent of monthly mean mineral dust transport, as viewed by the MODerate resolution Imaging Spectroradiometer (MODIS) satellite sensor. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite Figure 1. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite. The brighter the color, the greater the aerosol loading. Red and reddish tints indicate aerosol dominated by small particles created primarily from combustion processes. Green and brownish tints indicate larger particles created from wind-driven processes, usually transported desert dust. Note the bright green band at the southern edge of the Saharan desert, the reddish band it must cross if transported to the southwest and the long brownish transport path as it crosses the Atlantic to South America. Image courtesy of the NASA Earth Observatory (http://earthobservatory.nasa.gov). Even though qualitatively we recognize the extent and importance of dust transport and the role that it plays in fertilizing nutrient-limited regions, there is much that is still unknown. We are just now beginning to quantify the amount of dust that exits one continental region and the

  4. What is Desert RATS?

    NASA Video Gallery

    The mission manager and test coordinators for the 2011 mission explain why Desert RATS was started 14 years ago, questions being studied in this year's activities, technologies being tested and the...

  5. Long-term EARLINET dust observations

    NASA Astrophysics Data System (ADS)

    Mona, Lucia; Amiridis, Vassilis; Amodeo, Aldo; Binietoglou, Ioannis; D'Amico, Giuseppe; Schwarz, Anja; Papagiannopoulos, Nikolaos; Papayannis, Alexandros; Sicard, Michael; Comeron, Adolfo; Pappalardo, Gelsomina

    2015-04-01

    Systematic observations of Saharan dust events over Europe are performed from May 2000 by EARLINET, the European Aerosol Research LIdar NETwork. EARLINET is a coordinated network of stations that make use of advanced lidar methods for the vertical profiling of aerosols. The backbone of EARLINET network is a common schedule for performing the measurements and the quality assurance of instruments/data. Particular attention is paid to monitoring the Saharan dust intrusions over the European continent. The geographical distribution of the EARLINET stations is particularly appealing for the dust observation, with stations located all around the Mediterranean and in the center of the Mediterranean (Italian stations) where dust intrusions are frequent, and with several stations in the central Europe where dust penetrates occasionally. All aerosol backscatter and extinction profiles related to observations collected during these alerts are grouped in the devoted "Saharan dust" category of the EARLINET database. This category consists of about 4700 files (as of December 2013). Case studies involving several stations around Europe selected from this long-term database have been provided the opportunity to investigate dust modification processes during transport over the continent. More important, the long term EARLINET dust monitoring allows the investigation of the horizontal and vertical extent of dust outbreaks over Europe and the climatological analysis of dust optical intensive and extensive properties at continental scale. This long-term database is also a unique tool for a systematic comparison with dust model outputs and satellite-derived dust products. Because of the relevance for both dust modeling and satellite retrievals improvement, results about desert dust layers extensive properties as a function of season and source regions are investigated and will be presented at the conference. First comparisons with models outputs and CALIPSO dust products will be

  6. Concentration, size-distribution and deposition of mineral aerosol over Chinese desert regions

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao Y.; Arimoto, R.; Zhu, G. H.; Chen, T.; Zhang, G. Y.

    1998-09-01

    The mass-particle size distributions (MSDs) of 9 elements in ground-based aerosol samples from dust storm (DS) and non-dust storm (N-DS) periods were determined for 12 sites in 9 major desert regions in northern China. The masses of the 9 elements (Al, Fe, K, Mg, Mn, Sc, Si, Sr and Ti) in the atmosphere were dominated by local mineral dust that averaged 270μg m-3, and the MSDs for the elements were approximately log-normal. On the basis of Al data, the<10μm particles account for ~84% of the total dust mass over the deserts. Model-calculated ("100-step" method) dry deposition velocities (Vd) for the 9 dust-derived elements during N-DS periods ranged from 4.4 to 6.8cms-1, with a median value of 5.6cms-1. On the basis of a statistical relationship between D99% (the dust particle diameter corresponding to the uppermost 1% of the cumulative mass distribution) and Vd, one can also predict dry velocities, especially when D99% ranges from 30 to 70μm. This provides a simple way to reconstruct Vd for dust deposits (like aeolian loess sediments in the Loess Plateau). The estimated daily dry deposition fluxes were higher during DS vs. N-DS periods, but in most cases, the monthly averaged fluxes were mainly attributable to N-DS dust. Two regions with high dust loading and fluxes are identified: the "Western High-Dust Desert" and the "Northern High-Dust Desert", with Taklimakan Desert and Badain Juran Desert as their respective centers. These are energetic regions in which desert-air is actively exchanged, and these apparently are the major source areas for Asian dust.

  7. Geochemical evidence for African dust and volcanic ash inputs to terra rossa soils on carbonate reef terraces, northern Jamaica, West Indies

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.R.

    2009-01-01

    The origin of red or reddish-brown, clay-rich, "terra rossa" soils on limestone has been debated for decades. A traditional qualitative explanation for their formation has been the accumulation of insoluble residues as the limestone is progressively dissolved over time. However, this mode of formation often requires unrealistic or impossible amounts of carbonate dissolution. Therefore, where this mechanism is not viable and where local fluvial or colluvial inputs can be ruled out, an external source or sources must be involved in soil formation. On the north coast of the Caribbean island of Jamaica, we studied a sequence of terra rossa soils developed on emergent limestones thought to be of Quaternary age. The soils become progressively thicker, redder, more Fe- and Al-rich and Si-poor with elevation. Furthermore, although kaolinite is found in all the soils, the highest and oldest soils also contain boehmite. Major and trace element geochemistry shows that the host limestones and local igneous rocks are not likely source materials for the soils. Other trace elements, including the rare earth elements (REE), show that tephra from Central American volcanoes is not a likely source either. However, trace element geochemistry shows that airborne dust from Africa plus tephra from the Lesser Antilles island arc are possible source materials for the clay-rich soils. A third, as yet unidentified, source may also contribute to the soils. We hypothesize that older, more chemically mature Jamaican bauxites may have had a similar origin. The results add to the growing body of evidence of the importance of multiple parent materials, including far-traveled dust, to soil genesis.

  8. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, Dániel; Lauretta, Dante S.

    2010-01-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  9. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, D.´niel; Lauretta, Dante S.

    2014-02-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  10. A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

    USGS Publications Warehouse

    Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

    2014-01-01

    Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and

  11. Intergalactic Dust

    NASA Astrophysics Data System (ADS)

    Li, A.

    2002-12-01

    We study the composition and sizes of intergalactic dust based on the expulsion of interstellar dust from the galactic disk. Interstellar grains in the Galactic disk are modelled as a mixture of amorphous silicate dust and carbonaceous dust consisting of polycyclic aromatic hydrocarbon (PAH) molecules and larger graphitic grains (Li & Draine 2001) with size distributions like those of the Milky Way dust (Weingartner & Draine 2001). We model their dynamic evolution in terms of the collective effects caused by (1) radiative acceleration, (2) gravitational attraction, (3) gas drag, (4) thermal sputtering, and (5) Lorenz force from the galactic magnetic field (Ferrara et al. 1991). Radiation pressure from the stellar disk exerts an upward force on dust grains and may ultimately expel them out of the entire galaxy. Gravitational force from the stellar, dust and gas disk as well as the dark matter halo exerts a downward force. Thermal sputtering erodes all grains to some degree but more efficiently destroys small grains. This, together with the fact that (1) very small grains (with small radiation pressure efficiencies) are not well coupled to starlight; (2) for large grains the radiative force to the gravitational force is approximately inversely proportional to grain size, acts as a size ``filter'' for dust leaking into the intergalactic space. Since the radiation pressure efficiency and the grain destruction rate are sensitive to dust composition, the relative importance of carbon dust compared to silicate dust expelled into the intergalactic space differs from that in the galactic plane. We derive the size distributions of both silicate and carbonaceous dust finally getting into the intergalactic space and obtain an intergalactic extinction curve. The predicted intergalactic infrared emission spectrum is calculated. References: Ferrara, A., Ferrini, F., Franco, J., & Barsella, B. 1991, ApJ, 381, 137 Li, A., & Draine, B.T. 2001, ApJ, 554, 778 Weingartner, J

  12. Distribution of calcium carbonate in desert soils: A model

    SciTech Connect

    Mayer, L.; McFadden, L.D.; Harden, J.W.

    1988-04-01

    A model that describes the distribution of calcium carbonate in desert soils as a function of dust flux, time, climate, and other soil-forming factors shows which factors most strongly influence the accumulation of carbonate and can be used to evaluate carbonate-based soil age estimates or paleoclimatic reconstructions. Models for late Holocene soils have produced carbonate distributions that are very similar to those of well-dated soils in New Mexico and southern California. These results suggest that (1) present climate is a fair representation of late Holocene climate, (2) carbonate dust flux can be approximated by its Holocene rate, and (3) changes in climate and/or dust flux at the end of the Pleistocene effected profound and complex changes in soil carbonate distributions. Both higher carbonate dust flux and greater effective precipitation are required during the latest Pleistocene-early Holocene to explain carbonate distributions in latest Pleistocene soils. 21 refs., 4 figs., 1 tab.

  13. Desert Pathfinder at Work

    NASA Astrophysics Data System (ADS)

    2005-09-01

    The Atacama Pathfinder Experiment (APEX) project celebrates the inauguration of its outstanding 12-m telescope, located on the 5100m high Chajnantor plateau in the Atacama Desert (Chile). The APEX telescope, designed to work at sub-millimetre wavelengths, in the 0.2 to 1.5 mm range, passed successfully its Science Verification phase in July, and since then is performing regular science observations. This new front-line facility provides access to the "Cold Universe" with unprecedented sensitivity and image quality. After months of careful efforts to set up the telescope to work at the best possible technical level, those involved in the project are looking with satisfaction at the fruit of their labour: APEX is not only fully operational, it has already provided important scientific results. "The superb sensitivity of our detectors together with the excellence of the site allow fantastic observations that would not be possible with any other telescope in the world," said Karl Menten, Director of the group for Millimeter and Sub-Millimeter Astronomy at the Max-Planck-Institute for Radio Astronomy (MPIfR) and Principal Investigator of the APEX project. ESO PR Photo 30/05 ESO PR Photo 30/05 Sub-Millimetre Image of a Stellar Cradle [Preview - JPEG: 400 x 627 pix - 200k] [Normal - JPEG: 800 x 1254 pix - 503k] [Full Res - JPEG: 1539 x 2413 pix - 1.3M] Caption: ESO PR Photo 30/05 is an image of the giant molecular cloud G327 taken with APEX. More than 5000 spectra were taken in the J=3-2 line of the carbon monoxide molecule (CO), one of the best tracers of molecular clouds, in which star formation takes place. The bright peak in the north of the cloud is an evolved star forming region, where the gas is heated by a cluster of new stars. The most interesting region in the image is totally inconspicuous in CO: the G327 hot core, as seen in methanol contours. It is a truly exceptional source, and is one of the richest sources of emission from complex organic molecules in the

  14. Investigations of the March 2006 African dust storm using ground-based column-integrated high spectral resolution infrared (8-13 μm) and visible aerosol optical thickness measurements: 1. Measurement procedures and results

    NASA Astrophysics Data System (ADS)

    Thomas, M.; Gautier, C.; Ricchiazzi, P.

    2009-06-01

    The infrared (IR) aerosol optical thickness (AOT) spectra of Saharan dust measured during the Portable Infrared Aerosol Transmission Experiment (PIRATE) are reported. Saharan dust optical thickness (extinction) spectra from 8 to 13 μm were obtained using column-integrated solar transmission measurements in Puerto Rico in July 2005 and Senegal in January and March 2006 (during a dust plume) using a Fourier transform infrared (FTIR) spectrometer. The FTIR measured the solar spectral irradiance in the IR in the presence of Saharan dust, and the AOT was determined by comparing the measured spectra to modeled downwelling spectra without dust for the same atmospheric temperature profile, solar zenith angle, water vapor, and ozone concentrations. The modeled dust-free spectra are generated using the Santa Barbara Disort Atmospheric Radiative Transfer (SBDART) program. The measured dust AOT is compared with modeled AOT spectra obtained using Mie theory with dust indices of refraction from Volz and Fouquart with assumed lognormal size distributions. When the visible AOT values from nearby Aerosol Robotic Network (AERONET) sensors are compared to the IR AOT values, results from various dust loadings show that the IR dust AOT at 9.5 μm is typically only one third that of the visible (670 nm) dust AOT, but there is some evidence that this ratio could increase for larger dust size distributions. The surface IR dust forcing is determined to be about -0.4 W/m2 by summing the dusty and clear irradiance differences.

  15. Dust storm simulation over Iran using HYSPLIT.

    PubMed

    Ashrafi, Khosro; Shafiepour-Motlagh, Majid; Aslemand, Alireza; Ghader, Sarmad

    2014-01-01

    Particulate matters have detrimental effects on human health, environment and economic. This pollutant may emit from anthropogenic or natural sources. On global scale, main proportion of natural particulate matter release to the atmosphere because of wind erosion from arid and semi-arid regions. Recently, the amount of dust coming from Arabian countries has dramatically increased, especially dust storms that are affecting western and even central parts of Iran. This phenomenon has caused a lot of environmental problems. Dust source identification and trajectory simulation using numerical techniques are the main aims of this study. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model dust module and trajectory simulation are utilized in this research and two case studies are investigated (in May and June 2010). The base of the HYSPLIT dust module is the PM10 dust storm emission algorithm for desert land use. This methodology is applied to estimate hotspots and trajectories. Due to the results, dust storms started on May 17th and June 7th because of high wind shear (>8.5 m/s) from the western Syrian Desert. The source region limited to 32.50 °N to 33.80 °N and 38.00 °E to 38.80 °E coordinates. Dust plumes lifted and dispersed towards the east and southeast of the sources and reached Ahvaz on May 18th and June 8th. The average of PM10 concentration in these dates reached 625 and 494 μgm3 on Ahvaz monitoring stations, respectively. Moreover, the results gained from the model for dust motion simulation are similar to the MODIS satellite images. PMID:24397928

  16. Dust storm simulation over Iran using HYSPLIT

    PubMed Central

    2014-01-01

    Particulate matters have detrimental effects on human health, environment and economic. This pollutant may emit from anthropogenic or natural sources. On global scale, main proportion of natural particulate matter release to the atmosphere because of wind erosion from arid and semi-arid regions. Recently, the amount of dust coming from Arabian countries has dramatically increased, especially dust storms that are affecting western and even central parts of Iran. This phenomenon has caused a lot of environmental problems. Dust source identification and trajectory simulation using numerical techniques are the main aims of this study. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model dust module and trajectory simulation are utilized in this research and two case studies are investigated (in May and June 2010). The base of the HYSPLIT dust module is the PM10 dust storm emission algorithm for desert land use. This methodology is applied to estimate hotspots and trajectories. Due to the results, dust storms started on May 17th and June 7th because of high wind shear (>8.5 m/s) from the western Syrian Desert. The source region limited to 32.50 °N to 33.80 °N and 38.00 °E to 38.80 °E coordinates. Dust plumes lifted and dispersed towards the east and southeast of the sources and reached Ahvaz on May 18th and June 8th. The average of PM10 concentration in these dates reached 625 and 494 μgm3 on Ahvaz monitoring stations, respectively. Moreover, the results gained from the model for dust motion simulation are similar to the MODIS satellite images. PMID:24397928

  17. Dust storm simulation over Iran using HYSPLIT.

    PubMed

    Ashrafi, Khosro; Shafiepour-Motlagh, Majid; Aslemand, Alireza; Ghader, Sarmad

    2014-01-07

    Particulate matters have detrimental effects on human health, environment and economic. This pollutant may emit from anthropogenic or natural sources. On global scale, main proportion of natural particulate matter release to the atmosphere because of wind erosion from arid and semi-arid regions. Recently, the amount of dust coming from Arabian countries has dramatically increased, especially dust storms that are affecting western and even central parts of Iran. This phenomenon has caused a lot of environmental problems. Dust source identification and trajectory simulation using numerical techniques are the main aims of this study. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) model dust module and trajectory simulation are utilized in this research and two case studies are investigated (in May and June 2010). The base of the HYSPLIT dust module is the PM10 dust storm emission algorithm for desert land use. This methodology is applied to estimate hotspots and trajectories. Due to the results, dust storms started on May 17th and June 7th because of high wind shear (>8.5 m/s) from the western Syrian Desert. The source region limited to 32.50 °N to 33.80 °N and 38.00 °E to 38.80 °E coordinates. Dust plumes lifted and dispersed towards the east and southeast of the sources and reached Ahvaz on May 18th and June 8th. The average of PM10 concentration in these dates reached 625 and 494 μgm3 on Ahvaz monitoring stations, respectively. Moreover, the results gained from the model for dust motion simulation are similar to the MODIS satellite images.

  18. China Dust

    Atmospheric Science Data Center

    2013-04-16

    ... SpectroRadiometer (MISR) nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a ... arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the ...

  19. Dust Storm

    Atmospheric Science Data Center

    2013-04-16

    ... April 11, 2004 (top panels) contrast strongly with the dust storm that swept across Iraq and Saudi Arabia on May 13, 2004 (bottom panels). ... Apr 11 and May 13, 2004 Images:  Dust Storm location:  Middle East thumbnail:  ...

  20. Transport of dusts from East Asian and non-East Asian sources to Hong Kong during dust storm related events 1996-2007

    NASA Astrophysics Data System (ADS)

    Lee, Y. C.; Yang, Xun; Wenig, Mark

    2010-09-01

    Over a twelve year period from 1996 to 2007, 76 dust storm related events (as days) in Hong Kong were selected for study, based on Aluminium and Calcium concentrations in PM 10. Four of the 76 events reach episodic levels with exceedances of the Hong Kong air quality standards. The purpose of the study is to identify and characterize dust sources impacting Hong Kong. Global distribution of aerosols in NASA's daily aerosol index images from TOMS and OMI, are compared to plots generated by NRL(US)'s Navy Aerosol Analysis and Prediction System. Possible source areas are assigned by computing air parcel backward trajectories to Hong Kong using the NOAA HYSPLIT model. PM 10 and elemental data are analyzed for crustal mass concentrations and element mass ratios. Our analysis reveals that 73 out of the 76 dust events (96%) involve non-East Asian sources-the Thar, Central/West Asian, Arabian and Sahara deserts (Saharan influence is found in 63 events), which are previously not known to affect Hong Kong. The Gobi desert is the most frequent origin of dust, affecting 68 dust events while the Taklamakan desert impacts only 30 of the dust events. The impact of the Gobi desert in March and December is apparently associated with the northeast monsoon in East Asia. Our results also show a seasonal pattern in dust impact from both East Asian and more remote sources, with a maximum in March. Dust event occurrences are conspicuously absent from summer. Dust transport to Hong Kong is commonly associated with the passage of frontal low-pressure systems. The coarse size fraction of PM 10 concentrations were, as indicated by Al, Ca and Fe concentrations, about 4-8 times higher during dust events. The mean Ca/Al ratios of sources involving the Taklamakan desert are notably higher than those for non-East Asian sources owing to a higher Ca content of most of the East Asian deserts. The Fe/Al ratios follow a similar trend. Contributions from the desert sources are grossly estimated where

  1. A critical evaluation of the ability of SEVIRI thermal IR RGB rendering to identify mineral dust outbreaks

    NASA Astrophysics Data System (ADS)

    Brindley, H.

    2011-12-01

    Imagery derived from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard the Meteosat Second Generation series of geostationary satellites is routinely exploited for a wide variety of forecasting and hazard monitoring applications. By selectively combining the information from different wavelength channels, red-green-blue (RGB) composites can be produced which offer the potential to identify specific features, while the high temporal resolution of SEVIRI allows these features to be tracked forwards or backwards in time. Amongst the various rendering schemes is one designed to identify and monitor desert dust events using the information content within three thermal IR channels. Imagery produced using this rendering has been widely used by the scientific community as a tool to: identify dust sources and activation; assist with field campaign planning, including aircraft in-flight routing; as a visual tool to probe particular dust generation mechanisms and transport; and to qualitatively assess dust forecast model performance. Since the SEVIRI field of view extends across approximately 70°N to 70°S and 70°E to 70°W the instrument is ideally placed to monitor events originating from both African and Arabian dust sources. Nevertheless, interpretation of the imagery is subjective, and the rendering may fail to produce an unambiguous dust signal under certain conditions. Particular candidates which may confound the identification of a dust signature include high levels of atmospheric water vapour, a strong near-surface temperature inversion, the height of the dust layer, the characteristics of the underlying surface, variability in the dust mineralogical composition and in the size of the dust particles. In this paper a quantitative analysis of the ability of the SEVIRI dust RGB imagery to identify dust presence will be presented. This work is partly motivated by the findings of previous studies, but also by ongoing projects such as the UK-led Fennec

  2. Atmospheric delivery of anthropogenic bioavailable iron from mineral dust to the ocean

    NASA Astrophysics Data System (ADS)

    Ito, A.; Shi, Z.

    2015-12-01

    Atmospheric deposition of anthropogenic soluble iron (Fe) to the ocean has been suggested to modulate primary ocean productivity and thus indirectly affect the climate. A key process contributing to anthropogenic sources of soluble Fe is associated with air pollution, which acidifies Fe-containing mineral aerosols during their transport and leads to Fe transformation from insoluble to soluble forms. However, there is large uncertainty in our estimate of this anthropogenic soluble Fe. Here, we interactively combined laboratory kinetic experiments with global aerosol modeling to more accurately quantify anthropogenic soluble Fe due to air pollution. We firstly examined Fe dissolution kinetics of African dust samples at acidic pH values with and without ionic species commonly found in aerosol water (i.e., sulfate and oxalate). We then constructed a new empirical scheme for Fe release from mineral dust due to inorganic and organic anions in aerosol water, by using acidity as a master variable. We implemented this new scheme and applied an updated mineralogical emission database in a global atmospheric chemistry transport model to estimate the atmospheric concentration and deposition flux of soluble Fe under preindustrial and modern conditions. Our improved model successfully captured the inverse relationship of Fe solubility and total Fe loading measured over the North Atlantic Ocean. However, our modeled Fe solubility was significantly lower than that deduced from observations over the South Atlantic east downwind from the Patagonian dust source regions. Our modeled Fe solubility for dry deposition over the Atlantic is in good agreement the measurement, while that for wet deposition is significantly lower than the measurement. Our model results suggest that human activities contribute to about half of the soluble Fe supply to a significant portion of the oceans in the Northern Hemisphere, while their contribution to oceans in the high latitude remains highly uncertain

  3. Plants of the Desert.

    ERIC Educational Resources Information Center

    NatureScope, 1985

    1985-01-01

    Provides background information and student activities on plants of the desert, including various adaptations for life with limited water supplies. Each activity includes objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. A ready-to-copy student worksheet is included. (DH)

  4. How desert varnish forms?

    NASA Astrophysics Data System (ADS)

    Perry, Randall S.; Kolb, Vera M.; Lynne, Bridget Y.; Sephton, Mark A.; Mcloughlin, Nicola; Engel, Michael H.; Olendzenski, Lorraine; Brasier, Martin; Staley, James T., Jr.

    2005-09-01

    Desert varnish is a black, manganese-rich rock coating that is widespread on Earth. The mechanism underlying its formation, however, has remained unresolved. We present here new data and an associated model for how desert varnish forms, which substantively challenges previously accepted models. We tested both inorganic processes (e.g. clays and oxides cementing coatings) and microbial methods of formation. Techniques used in this preliminary study include SEM-EDAX with backscatter, HRTEM of focused ion beam prepared (FIB) wafers and several other methods including XRPD, Raman spectroscopy, XPS and Tof-SIMS. The only hypothesis capable of explaining a high water content, the presence of organic compounds, an amorphous silica phase (opal-A) and lesser quantities of clays than previously reported, is a mechanism involving the mobilization and redistribution of silica. The discovery of silica in desert varnish suggests labile organics are preserved by interaction with condensing silicic acid. Organisms are not needed for desert varnish formation but Bacteria, Archaea, Eukarya, and other organic compounds are passively incorporated and preserved as organominerals. The rock coatings thus provide useful records of past environments on Earth and possibly other planets. Additionally this model also helps to explain the origin of key varnish and rock glaze features, including their hardness, the nature of the "glue" that binds heterogeneous components together, its layered botryoidal morphology, and its slow rate of formation.

  5. Enrichment of Mineral Dust Storm Particles with Sea Salt Elements - Using bulk and Single Particle Analyses

    NASA Astrophysics Data System (ADS)

    Mamane, Y.; Perrino, C.; Yossef, O.

    2009-12-01

    Mineral aerosol emitted from African and Asian deserts plays an important role in the atmosphere. During their long-range transport, the physical and chemical properties of mineral dust particles change due to heterogeneous reactions with trace gases, coagulation with other particles, and in-cloud processing. These processes affect the optical and hygroscopic properties of dust particles, and in general influencing the physics and chemistry of the atmosphere. Four African and Arabian dust storm episodes affecting the East Mediterranean Coast in the spring of 2006 have been characterized, to determine if atmospheric natural dust particles are enriched with sea salt and anthropogenic pollution. Particle samplers included PM10 and manual dichotomous sampler that collected fine and coarse particles. Three sets of filters were used: Teflon filters for gravimetric, elemental and ionic analyses; Pre-fired Quartz-fiber filters for elemental and organic carbon; and Nuclepore filters for scanning electron microscopy analysis. Computer-controlled scanning electron microscopy (Philips XL 30 ESEM) was used to analyze single particle, for morphology, size and chemistry of selected filter samples. A detailed chemical and microscopical characterization has been performed for the particles collected during dust event days and during clear days. The Saharan and Arabian air masses increased significantly the daily mass concentrations of the coarse and the fine particle fractions. Carbonates, mostly as soil calcites mixed with dolomites, and silicates are the major components of the coarse fraction, followed by sea salt particles. In addition, the levels of anthropogenic heavy metals and sea salt elements registered during the dust episode were considerably higher than levels recorded during clear days. Sea salt elements contain Na and Cl, and smaller amounts of Mg, K, S and Br. Cl ranges from 300 to 5500 ng/m3 and Na from 100 to almost 2400 ng/m3. The Cl to Na ratio on dusty days in

  6. Volatiles in the Desert: Subtle Remote-sensing Signatures of the Dakhleh Oasis Catastrophic Event, Western Desert, Egypt

    NASA Technical Reports Server (NTRS)

    Haldemann, A. F. C.; Kleindienst, M. R.; Churcher, C. S.; Smith, J. R.; Schwarcz, H. P.; Osinski, G.

    2005-01-01

    Over the past decade members of the Dakhleh Oasis Project have studied enigmatic signatures in the Pleistocene geologic record of portions of the Dakhleh oasis and palaeo-oasis in Egypt's Western Desert [1,2]. In particular, Si-Ca-Al rich glass melt (Dakhleh Glass, Fig. 1) points to a catastrophic event between c.100,000-200,000 years ago [3] in this well-studied African savannah and freshwater lake Middle Stone Age environment [4,5].

  7. Long-term variability of dust-storms in Iceland

    NASA Astrophysics Data System (ADS)

    Dagsson-Waldhauserová, Pavla; Ólafsson, Haraldur; Arnalds, Ólafur

    2013-04-01

    Iceland is a volcanic island in the North Atlantic Ocean with maritime climate. In spite of moist climate, large areas are with limited vegetation cover where >40% of Iceland is classified with considerable to very severe erosion and 21% of Iceland are volcanic sandy deserts. Natural emissions from these sources influenced by strong winds affect not only regional air quality in Iceland ("Reykjavik haze") but dust particles are transported over the Atlantic ocean and Arctic Ocean > 1000 km at times. The study places Icelandic dust production area into international perspective, present long term frequency of dust storm events in NE Iceland, and estimate dust aerosol concentrations during reported dust events. Meteorological observations with dust presence codes and related visibility were used to identify the frequency and the long-term changes in dust production in NE Iceland. There were annually 16.4 days on average with reported dust observations on weather stations within the NE erosion area, indicating extreme dust plume activity and erosion within the NE deserts, even though the area is covered with snow during the major part of winter. During the 2000s the highest occurrence of dust events in six decades was reported. We have measured saltation and aeolian transport during dust/volcanic ash storms in Iceland which give some of the most intense wind erosion events ever measured. Icelandic dust affects the ecosystems over much of Iceland and causes regional haze. It is likely to affect the ecosystems of the oceans around Iceland, and it brings dust that lowers the albedo of the Icelandic glaciers, increasing melt-off due to global warming. The study indicates that Icelandic dust is not only a substantial source for regional air pollution, but may be considered to contribute to the Arctic haze phenomena and Arctic air pollution.

  8. Dust storms and cyclone tracks over the arid regions in east Asia in spring

    NASA Astrophysics Data System (ADS)

    Takemi, Tetsuya; Seino, Naoko

    2005-09-01

    It has been argued that frequent dust storm developments in east Asia in spring are closely related to midlatitude synoptic-scale cyclone activity. This study investigates the relationship of springtime dust storms and other dust-related phenomena in east Asia to the tracks and locations of synoptic-scale cyclones by conducting statistical analyses of surface weather data, cyclone track data, and satellite data. Through these analyses, we discuss the role of cyclone activity on dust weather phenomena in east Asia. In the Gobi Desert and northeast China regions, strong cyclonic winds associated with strong cyclones are responsible for the dust weather developments, and the dust weather preferably occurs in the southwestern sector of the cyclone, where frontal activity and cold air action are significant. Despite the extremely dry climate, the formation of frontal cloud systems is evident particularly over the Gobi Desert, which will contribute to the higher frequency of severer dust weather. On the other hand, in the Taklamakan Desert severe dust weather (i.e., dust storm) is not so much affected by synoptic-scale cyclones, but weaker dust phenomena such as dust haze occur around the centers of cyclones that do not propagate farther eastward out of the Taklamakan region.

  9. Global potential of dust devil occurrence

    NASA Astrophysics Data System (ADS)

    Jemmett-Smith, Bradley; Marsham, John; Knippertz, Peter; Gilkeson, Carl

    2014-05-01

    Mineral dust is a key constituent in the climate system. Airborne mineral dust forms the largest component of the global aerosol budget by mass and subsequently affects climate, weather and biogeochemical processes. There remains large uncertainty in the quantitative estimates of the dust cycle. Dry boundary-layer convection serves as an effective mechanism for dust uplift, typically through a combination of rotating dust devils and non-rotating larger and longer-lived convective plumes. These microscale dry-convective processes occur over length scales of several hundred metres or less. They are difficult to observe and model, and therefore their contribution to the global dust budget is highly uncertain. Using an analytical approach to extrapolate limited observations, Koch and Renno (2006) suggest that dust devils and plumes could contribute as much as 35%. Here, we use a new method for quantifying the potential of dust devil occurrence to provide an alternative perspective on this estimate. Observations have shown that dust devil and convective plume occurrence is favoured in hot arid regions under relatively weak background winds, large ground-to-air temperature gradients and deep dry convection. By applying such known constraints to operational analyses from the European Centre for Medium Range Weather Forecasts (ECMWF), we provide, to the best of the authors' knowledge, the first hourly estimates of dust devil occurrence including an analysis of sensitivity to chosen threshold uplift. The results show the expected diurnal variation and allow an examination of the seasonal cycle and day-to-day variations in the conditions required for dust devil formation. They confirm that desert regions are expected to have by far the highest frequency of dry convective vortices, with winds capable of dust uplift. This approach is used to test the findings of Koch and Renno (2006). Koch J., Renno N. (2006). The role of convective plumes and vortices on the global aerosol

  10. Sensitivity of surface characteristics on the simulation of wind-blown-dust source in North America

    NASA Astrophysics Data System (ADS)

    Park, S. H.; Gong, S. L.; Gong, W.; Makar, P. A.; Moran, M. D.; Stroud, C. A.; Zhang, J.

    Recently, a wind-blown-dust-emission module has been built based on a state-of-the-art wind erosion theory and evaluated in a regional air-quality model to simulate a North American dust storm episode in April 2001 (see Park, S.H., Gong, S.L., Zhao, T.L., Vet, R.J., Bouchet, V.S., Gong, W., Makar, P.A., Moran, M.D., Stroud, C., Zhang, J. 2007. Simulation of entrainment and transport of dust particles within North America in April 2001 ("Red Dust episode"). J. Geophys. Res. 112, D20209, doi:10.1029/2007JD008443). A satisfactorily detailed assessment of that module, however, was not possible because of a lack of information on some module inputs, especially soil moisture content. In this paper, the wind-blown-dust emission was evaluated for two additional dust storms using improved soil moisture inputs. The surface characteristics of the wind-blown-dust source areas in southwestern North America were also investigated, focusing on their implications for wind-blown-dust emissions. The improved soil moisture inputs enabled the sensitivity of other important surface characteristics, the soil grain size distribution and the land-cover, to dust emission to be investigated with more confidence. Simulations of the two 2003 dust storm episodes suggested that wind-blown-dust emissions from the desert areas in southwestern North America are dominated by emissions from dry playas covered with accumulated alluvial deposits whose particle size is much smaller than usual desert sands. As well, the source areas in the northwestern Texas region were indicated to be not desert but rather agricultural lands that were "activated" as a wind-blown-dust sources after harvest. This finding calls for revisions to the current wind-blown-dust-emission module, in which "desert" is designated to be the only land-cover category that can emit wind-blown dust.

  11. A study of Desert Dermatoses in the Thar Desert Region

    PubMed Central

    Chatterjee, Manas; Vasudevan, Biju

    2015-01-01

    Introduction: Desert dermatology describes the cutaneous changes and the diseases affecting those living in the desert. Diurnal variation in temperature is high and is characteristic of the deserts. The lack of water affects daily activities and impacts dermatological conditions. Adaptation to the desert is therefore important to survival. This original article focuses on dermatoses occurring in a population in the Thar desert of India, predominantly located in Rajasthan. Materials and Methods: This is a descriptive study involving various dermatoses seen in patients residing in the Thar desert region over a duration of 3 years. Results: Infections were the most common condition seen among this population and among them fungal infections were the most common. The high incidence of these infections would be accounted for by the poor hygienic conditions due to lack of bathing facilities due to scarcity of water and the consequent sweat retention and overgrowth of cutaneous infective organisms. Pigmentary disorders, photodermatoses, leishmaniasis and skin tumors were found to be more prevalent in this region. Desert sweat dermatitis was another specific condition found to have an increased incidence. Conclusion: The environment of the desert provides for a wide variety of dermatoses that can result in these regions with few of these dermatoses found in much higher incidence than in other regions. The concept of desert dermatology needs to be understood in more details to provide better care to those suffering from desert dermatoses and this article is a step forward in this regard. PMID:25657392

  12. Airborne Dust Models in Valley Fever Research

    NASA Astrophysics Data System (ADS)

    Sprigg, W. A.; Galgiani, J. N.; Vujadinovic, M.; Pejanovic, G.; Vukovic, A. J.; Prasad, A. K.; Djurdjevic, V.; Nickovic, S.

    2011-12-01

    Dust storms (haboobs) struck Phoenix, Arizona, in 2011 on July 5th and again on July 18th. One potential consequence: an estimated 3,600 new cases of Valley Fever in Maricopa County from the first storm alone. The fungi, Coccidioides immitis, the cause of the respiratory infection, Valley Fever, lives in the dry desert soils of the American southwest and southward through Mexico, Central America and South America. The fungi become part of the dust storm and, a few weeks after inhalation, symptoms of Valley Fever may appear, including pneumonia-like illness, rashes, and severe fatigue. Some fatalities occur. Our airborne dust forecast system predicted the timing and extent of the storm, as it has done with other, often different, dust events. Atmosphere/land surface models can be part of public health services to reduce risk of Valley Fever and exacerbation of other respiratory and cardiovascular illness.

  13. Identification of debris-flow hazards in warm deserts through analyzing past occurrences: Case study in South Mountain, Sonoran Desert, USA

    NASA Astrophysics Data System (ADS)

    Dorn, Ronald I.

    2016-11-01

    After recognition that debris flows co-occur with human activities, the next step in a hazards analysis involves estimating debris-flow probability. Prior research published in this journal in 2010 used varnish microlamination (VML) dating to determine a minimum occurrence of 5 flows per century over the last 8100 years in a small mountain range of South Mountain adjacent to neighborhoods of Phoenix, Arizona. This analysis led to the conclusion that debris flows originating in small mountain ranges in arid regions like the Sonoran Desert could pose a hazard. Two major precipitation events in the summer of 2014 generated 35 debris flows in the same study area of South Mountain-providing support for the importance of probability analysis as a key step in a hazards analysis in warm desert settings. Two distinct mechanisms generated the 2014 debris flows: intense precipitation on steep slopes in the first storm; and a firehose effect whereby runoff from the second storm was funneled rapidly by cleaned-out debris-flow chutes to remobilize Pleistocene debris-flow deposits. When compared to a global database on debris flows, the 2014 storms were among the most intense to generate desert debris flows - indicating that storms of lesser intensity are capable of generating debris flows in warm desert settings. The 87Sr/86Sr analyses of fines and clasts in South Mountain debris flows of different ages reveal that desert dust supplies the fines. Thus, wetter climatic periods of intense rock decay are not needed to resupply desert slopes with fines; instead, a combination of dust deposition supplying fines and dirt cracking generating coarse clasts can re-arm chutes in a warm desert setting with abundant dust.

  14. Sahara Dust

    Atmospheric Science Data Center

    2013-04-15

    article title:  Casting Light and Shadows on a Saharan Dust Storm   ... CA, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed by NASA's Goddard Space Flight Center, ...

  15. Physico-chemical characterization of African urban aerosols (Bamako in Mali and Dakar in Senegal) and their toxic effects in human bronchial epithelial cells: description of a worrying situation

    PubMed Central

    2013-01-01

    Background The involvement of particulate matter (PM) in cardiorespiratory diseases is now established in developed countries whereas in developing areas such as Africa with a high level of specific pollution, PM pollution and its effects are poorly studied. Our objective was to characterize the biological reactivity of urban African aerosols on human bronchial epithelial cells in relation to PM physico-chemical properties to identify toxic sources. Methods Size-speciated aerosol chemical composition was analyzed in Bamako (BK, Mali, 2 samples with one having desert dust event BK1) and Dakar (DK; Senegal) for Ultrafine UF, Fine F and Coarse C PM. PM reactivity was studied in human bronchial epithelial cells investigating six biomarkers (oxidative stress responsive genes and pro-inflammatory cytokines). Results PM mass concentrations were mainly distributed in coarse mode (60%) and were impressive in BK1 due to the desert dust event. BK2 and DK samples showed a high content of total carbon characteristic of urban areas. The DK sample had huge PAH quantities in bulk aerosol compared with BK that had more water soluble organic carbon and metals. Whatever the site, UF and F PM triggered the mRNA expression of the different biomarkers whereas coarse PM had little or no effect. The GM-CSF biomarker was the most discriminating and showed the strongest pro-inflammatory effect of BK2 PM. The analysis of gene expression signature and of their correlation with main PM compounds revealed that PM-induced responses are mainly related to organic compounds. The toxicity of African aerosols is carried by the finest PM as with Parisian aerosols, but when considering PM mass concentrations, the African population is more highly exposed to toxic particulate pollution than French population. Regarding the prevailing sources in each site, aerosol biological impacts are higher for incomplete combustion sources resulting from two-wheel vehicles and domestic fires than from diesel

  16. Dust Plume off the Coast of Egypt

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Dwarfing the Nile, a river of dust flowed out of the deserts of northern Egypt on May 19, 2007. As the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite passed overhead at 12:05 p.m. local time in Cairo, the sensor captured this image of the dust spreading northward over the Mediterranean Sea from the sandy deserts that span the country. At the margins of the plume, ribbons and ripples of dust are translucent, allowing a glimpse of the desert and water beneath, but in the center, the cloud is opaque, revealing nothing of the surface below. The part of north-central Egypt hidden by the dust plume is the Qattara Depression, the country's lowest point. Dipping down to 133 meters below sea level (436 feet), the depression is home to sandy deserts and dry lake beds that occasionally flood. The sand and fine, lake bed sediments are easily lofted into the air by strong winds that scour the area in late winter and early spring. In the eastern (right-hand) part of the image, the Nile River is lined by narrow ribbons of dull green vegetation. The fan-shaped delta is dotted with tan-colored spots, marking the location of cities and towns. The Nile Valley and Delta make up only a small fraction of the country's total land area, yet they support almost the entire population. The large image provided above has a spatial resolution (level of detail) of 250 meters per pixel. The MODIS Rapid Response Team provides this image in additional resolutions. The Earth Observatory also provides a 250-meter-resolution KMZ file of this image for use with Google Earth.

  17. Preferential dust sources: A geomorphological classification designed for use in global dust-cycle models

    NASA Astrophysics Data System (ADS)

    Bullard, Joanna E.; Harrison, Sandy P.; Baddock, Matthew C.; Drake, Nick; Gill, Thomas E.; McTainsh, Grant; Sun, Youbin

    2011-12-01

    We present a simple theoretical land-surface classification that can be used to determine the location and temporal behavior of preferential sources of terrestrial dust emissions. The classification also provides information about the likely nature of the sediments, their erodibility and the likelihood that they will generate emissions under given conditions. The scheme is based on the dual notions of geomorphic type and connectivity between geomorphic units. We demonstrate that the scheme can be used to map potential modern-day dust sources in the Chihuahuan Desert, the Lake Eyre Basin and the Taklamakan. Through comparison with observed dust emissions, we show that the scheme provides a reasonable prediction of areas of emission in the Chihuahuan Desert and in the Lake Eyre Basin. The classification is also applied to point source data from the Western Sahara to enable comparison of the relative importance of different land surfaces for dust emissions. We indicate how the scheme could be used to provide an improved characterization of preferential dust sources in global dust-cycle models.

  18. Dust emission: small-scale processes with global consequences

    USGS Publications Warehouse

    Okin, Gregory S.; Bullard, Joanna E.; Reynolds, Richard L.; Ballantine, John-Andrew C.; Schepanski, Kerstin; Todd, Martin C.; Belnap, Jayne; Baddock, Matthew C.; Gill, Thomas E.; Miller, Mark E.

    2011-01-01

    Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored.

  19. Dust: Small-scale processes with global consequences

    USGS Publications Warehouse

    Okin, G.S.; Bullard, J.E.; Reynolds, R.L.; Ballantine, J.-A.C.; Schepanski, K.; Todd, M.C.; Belnap, J.; Baddock, M.C.; Gill, T.E.; Miller, M.E.

    2011-01-01

    Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored. ?? Author(s) 2011.

  20. Dust: Small-scale processes with global consequences

    NASA Astrophysics Data System (ADS)

    Okin, Gregory S.; Bullard, Joanna E.; Reynolds, Richard L.; Ballantine, John-Andrew C.; Schepanski, Kerstin; Todd, Martin C.; Belnap, Jayne; Baddock, Matthew C.; Gill, Thomas E.; Miller, Mark E.

    2011-07-01

    Desert dust, both modern and ancient, is a critical component of the Earth system. Atmospheric dust has important effects on climate by changing the atmospheric radiation budget, while deposited dust influences biogeochemical cycles in the oceans and on land. Dust deposited on snow and ice decreases its albedo, allowing more light to be trapped at the surface, thus increasing the rate of melt and influencing energy budgets and river discharge. In the human realm, dust contributes to the transport of allergens and pathogens and when inhaled can cause or aggravate respiratory diseases. Dust storms also represent a significant hazard to road and air travel. Because it affects so many Earth processes, dust is studied from a variety of perspectives and at multiple scales, with various disciplines examining emissions for different purposes using disparate strategies. Thus, the range of objectives in studying dust, as well as experimental approaches and results, has not yet been systematically integrated. Key research questions surrounding the production and sources of dust could benefit from improved collaboration among different research communities. These questions involve the origins of dust, factors that influence dust production and emission, and methods through which dust can be monitored.

  1. Deserts of China

    USGS Publications Warehouse

    Walker, Alta S.

    1982-01-01

    Improving arid land quality requires an understanding of the original state of the land and its relationship to wind, water, and plant regimes, as well as understanding of interactions within the present ecosystem.  Chinese scientists and local residents have made significant advances in improving arid environments in gobi and sandy deserts and in less arid sandy lands.  Wind patterns are being changed by planting forest belts to protect oases and sandy lands, and on a smaller scale by planting grasses and shrubs or constructing straw grids.  Research on reclamation of deserts is now focusing on how sand-fixing plants may be adapted to local environments, and how the resources of grazing land and water may be effectively exploited without being overused.

  2. Southwestern desert resources

    USGS Publications Warehouse

    Halvorson, William L.; van Riper, Charles; Schwalbe, Cecil R.

    2010-01-01

    The southwestern deserts stretch from southeastern California to west Texas and then south to central Mexico. The landscape of this region is known as basin and range topography featuring to "sky islands" of forest rising from the desert lowlands which creates a uniquely diverse ecology. The region is further complicated by an international border, where governments have caused difficulties for many animal populations. This book puts a spotlight on individual research projects which are specific examples of work being done in the area and when they are all brought together, to shed a general light of understanding the biological and cultural resources of this vast region so that those same resources can be managed as effectively and efficiently as possible. The intent is to show that collaborative efforts among federal, state agency, university, and private sector researchers working with land managers, provides better science and better management than when scientists and land managers work independently.

  3. Namib Desert, Namibia, Africa

    NASA Technical Reports Server (NTRS)

    1990-01-01

    One of the driest regions on Earth, the Namib Desert, Namibia, Africa (23.0N, 15.0E) lies adjacent to the Atlantic coast but the upwelling oceanic water causes a very stable rainless atmosphere. The few local inland rivers do not reach the sea but instead, appear as long indentations where they penetrate the dune fields and end as small dry lakes. The vast dune fields are the result of sands deposited over millions of years by the stream flow.

  4. Namib Desert, Namibia, Africa

    NASA Technical Reports Server (NTRS)

    1990-01-01

    One of the driest regions on Earth, the Namib Desert, Namibia, Africa (23.0N, 15.0E) lies adjacent to the Atlantic coast but upwelling oceanic water causes a very stable rainless atmosphere. The few local inland rivers do not reach the sea but instead appear as long indentations where rivers penetrate the dune fields and end as small dry lakes. The vast dune fields are the result of sands deposited over millions of years by the stream flow.

  5. Detection of anthropogenic dust using CALIPSO lidar measurements

    NASA Astrophysics Data System (ADS)

    Huang, J. P.; Liu, J. J.; Chen, B.; Nasiri, S. L.

    2015-10-01

    Anthropogenic dusts are those produced by human activities on disturbed soils, which are mainly cropland, pastureland, and urbanized regions, and are a subset of the total dust load which includes natural sources from desert regions. Our knowledge of anthropogenic dusts is still very limited due to a lack of data. To understand the contribution of anthropogenic dust to the total global dust load, it is important to identify it apart from total dust. In this study, a new technique for distinguishing anthropogenic dust from natural dust is proposed by using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) dust and planetary boundary layer (PBL) height retrievals along with a land use data set. Using this technique, the global distribution of dust is analyzed and the relative contribution of anthropogenic and natural dust sources to regional and global emissions are estimated. Results reveal that local anthropogenic dust aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25 % of the global continental dust load. Of these anthropogenic dust aerosols, more than 53 % come from semi-arid and semi-wet regions. Annual mean anthropogenic dust column burden (DCB) values range from 0.42 g m-2, with a maximum in India, to 0.12 g m-2, with a minimum in North America. A better understanding of anthropogenic dust emission will enable us to focus on human activities in these critical regions and with such knowledge we will be more able to improve global dust models and to explore the effects of anthropogenic emission on radiative forcing, climate change, and air quality in the future.

  6. Detection of anthropogenic dust using CALIPSO lidar measurements

    NASA Astrophysics Data System (ADS)

    Huang, J.; Liu, J.; Chen, B.; Nasiri, S. L.

    2015-04-01

    Anthropogenic dusts are those produced by human activities on disturbed soils, which are mainly cropland, pasture, and urbanized regions and are a subset of the total dust load which includes natural sources from desert regions. Our knowledge of anthropogenic dusts is still very limited due to a lack of data on source distribution and magnitude, and on their effect on radiative forcing which may be comparable to other anthropogenic aerosols. To understand the contribution of anthropogenic dust to the total global dust load and its effect on radiative transfer and climate, it is important to identify them from total dust. In this study, a new technique for distinguishing anthropogenic dust from natural dust is proposed by using Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) dust and planetary boundary layer (PBL) height retrievals along with a land use dataset. Using this technique, the global distribution of dust is analyzed and the relative contribution of anthropogenic and natural dust sources to regional and global emissions are estimated. Results reveal that local anthropogenic dust aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25% of the global continental dust load. Of these anthropogenic dust aerosols, more than 53% come from semi-arid and semi-wet regions. Annual mean anthropogenic dust column burden (DCB) values range from 0.42 g m-2 with a maximum in India to 0.12 g m-2 with a minimum in North America. A better understanding of anthropogenic dust emission will enable us to focus on human activities in these critical regions and with such knowledge we will be better able to improve global dust models and to explore the effects of anthropogenic emission on radiative forcing, climate change and air quality in the future.

  7. Numerical Modeling of 1997-2006 Asian Dust and Mass Budget Analysis in East Asia and West Pacific

    NASA Astrophysics Data System (ADS)

    Liu, M.; Westphal, D. L.

    2006-12-01

    East Asia has two of the Earth's major natural dust sources: the Taklamakan Desert in west China and the Gobi Desert in Mongolia and northwest China. Desertification has increased dust-erodible areas surrounding the deserts so the dust storm frequency has increased in the last few decades. Severe dust storms not only impact East Asia, but also can reach far beyond the continent, as did the dust clouds of April 1998, 2001 and 2005 that drifted over the Pacific Ocean and to North America. The US Navy's operational Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS) is used to simulate the dust events for the springs of 1997 through 2006 at a resolution of one quarter of degree with multiple size bins. We use the modeled data to investigate the spatial and temporal dependence of dust emission, transport and deposition, and estimate the impacts of dust on environment. The distribution of dust plumes in area coverage and vertical depth is studied, as is the inter-annual variation of dust patterns from the different deserts of China and Mongolia, and the fluxes across the Pacific. It is found that PM10 is the dominant fraction particles over the continent and near the ocean, while PM2.5 becomes dominant in the boundary outflow along 170E. The details of analyzed model results will be presented at the meeting.

  8. Aquaporins in desert rodent physiology.

    PubMed

    Pannabecker, Thomas L

    2015-08-01

    Desert rodents face a sizeable challenge in maintaining salt and water homeostasis due to their life in an arid environment. A number of their organ systems exhibit functional characteristics that limit water loss above that which occurs in non-desert species under similar conditions. These systems include renal, pulmonary, gastrointestinal, nasal, and skin epithelia. The desert rodent kidney preserves body water by producing a highly concentrated urine that reaches a maximum osmolality nearly three times that of the common laboratory rat. The precise mechanism by which urine is concentrated in any mammal is unknown. Insights into the process may be more apparent in species that produce highly concentrated urine. Aquaporin water channels play a fundamental role in water transport in several desert rodent organ systems. The role of aquaporins in facilitating highly effective water preservation in desert rodents is only beginning to be explored. The organ systems of desert rodents and their associated AQPs are described.

  9. Quiescence of Asian dust events in South Korea and Japan during 2012 spring: Dust outbreaks and transports

    NASA Astrophysics Data System (ADS)

    Lee, Yun Gon; Ho, Chang-Hoi; Kim, Joo-Hong; Kim, Jhoon

    2015-08-01

    This study examined the quiescence of Asian dust events in South Korea and Japan during the spring of 2012, presenting a synoptic characterization and suggesting possible causes. Synoptic observation reports from the two countries confirmed that spring 2012 had the lowest number of dust events in 2000-2012. The monthly dust frequency (DF) in March 2012 over the dust source regions, i.e., deserts in northern China and Mongolia, indicated a significant decrease compared to the 12 year (2000-2011) March climatology. The DF in April 2012 was comparable to the 12 year climatology values, but in May 2012 it was slightly lower. The daily Ozone Monitoring Instrument Aerosol Index and the Navy Aerosol Analysis and Prediction System simulations revealed stagnant dust movement in March and May 2012. Anomalous anticyclones north of the source regions decreased the dust outbreaks and enhanced the southeasterly winds, resulting in few dust events over the downwind countries (i.e., South Korea and Japan). By contrast, in April 2012, a strong anomalous cyclone east of Lake Baikal slightly increased the dust outbreaks over northeastern China. However, the major dust outbreaks were not transported downwind because of exceptional dust pathways, i.e., the southeastward pathway of dust transport was unusually blocked by the expansion of an anomalous anticyclonic circulation over the Sea of Okhotsk, with dust being transported northeast.

  10. Pan-African adakitic rocks of the north Arabian-Nubian Shield: petrological and geochemical constraints on the evolution of the Dokhan volcanics in the north Eastern Desert of Egypt

    NASA Astrophysics Data System (ADS)

    Obeid, Mohamed A.; Azer, Mokhles K.

    2015-04-01

    The Precambrian basement of Egypt is part of the Red Sea Mountains and represents the north-western part of the Arabian-Nubian Shield (ANS). Five volcanic sections are exposed in the Egyptian basement complex, namely El Kharaza, Monqul, Abu Had, Mellaha and Abu Marwa. They are located in the north Eastern Desert (ED) of Egypt and were selected for petrological and geochemical studies as they represent the Dokhan volcanics. The volcanics divide into two main pulses, and each pulse was frequently accompanied by deposition of immature molasse type sediments, which represent a thick sequence of the Hammamat group in the north ED. Compositionally, the rocks form a continuum from basaltic andesite, andesite, dacite (lower succession) to rhyodacite and rhyolite (upper succession), with no apparent compositional gaps. These high-K calc-alkaline rocks have strong affinities to subduction-related rocks with enriched LILEs (Rb, Ba, K, Th, Ce) relative to high field strength elements (Nb, Zr, P, Ti) and negative Nb anomalies relative to NMORB. The lower succession displays geochemical characteristics of adakitic rocks with SiO2 >53 wt%, Al2O3 >15 wt%, MgO >2.5 wt%, Mg# >49, Sr >650 ppm, Y <17 ppm, Yb <2 ppm, Ni >25 ppm, Cr >50 ppm and Sr/Y >42.4. They also have low Nb, Rb and Zr compared to the coexisting calc-alkaline rhyodacites and rhyolites. The highly fractionated rhyolitic rocks have strong negative Eu anomalies and possess the geochemical characteristics of A-type suites. Trace element geochemical signatures indicate a magma source consistent with post-collisional suites that retain destructive plate signatures associated with subduction zones. The adakitic rocks in the northern ANS are generated through partial melting of delaminated mafic lower crust interacting with overlying mantle-derived magma. The Dokhan volcanics were likely generated by a combination of processes, including partial melting, crystal fractionation and assimilation.

  11. Provenances of atmospheric dust over Korea from Sr-Nd isotopes and rare earth elements in early 2006

    NASA Astrophysics Data System (ADS)

    Lee, Min Kyung; Lee, Yong Il; Yi, Hi-Il

    2010-07-01

    Sr and Nd isotopic composition of pre- and syn-Asian dust (Hwangsa) particles collected from three different water depths at two different offshore sites, western Korea and rare earth elemental composition of syn-Asian dust particles collected from three islands around the Korean Peninsula in late April 2006 were analyzed to interpret their provenance. The dust Sr-Nd isotopic compositions vary spatiotemporally, but they show specific values when the Hwangsa event occurred. Satellite images, airmass backward trajectory modeling, and comparison with Sr-Nd isotopic ratios and rare earth elements compositions of soils and desert sands of northern China all suggest the major source of dust particles for the late April 2006 Hwangsa event to be the Mu Us Desert in northern China. Dust particles of the pre-Hwangsa period include both background dusts and the previous Hwangsa event dust particles, and they are interpreted to have been originated from various arid regions of China such as the Hobq Desert, the Mu Us Desert, and the Taklamakan Desert in different times. Different background dust sources during pre-Hwangsa period in early 2006 resulted from the changing route of the westerlies.

  12. Jeeps Penetrating a Hostile Desert

    ERIC Educational Resources Information Center

    Bailey, Herb

    2009-01-01

    Several jeeps are poised at base camp on the edge of a desert aiming to escort one of them as far as possible into the desert, while the others return to camp. They all have full tanks of gas and share their fuel to maximize penetration. In a friendly desert it is best to leave caches of fuel along the way to help returning jeeps. We solve the…

  13. Microbial origin of desert varnish.

    PubMed

    Dorn, R I; Oberlander, T M

    1981-09-11

    Scanning electron microscopy and energy dispersive x-ray analyses of desert varnish reveal that microorganisms concentrate ambient manganese that becomes greatly enhanced in brown to black varnish. Specific characteristics of desert varnish and of varnish bacteria support a microbial origin for manganese-rich films. Varnish microbes can be cultured and produce laboratory manganese films. Accordingly, natural desert varnish and also manganese-rich rock varnishes in nondesert environments appear to be a product of microbial activity. PMID:17744757

  14. Microbial origin of desert varnish.

    PubMed

    Dorn, R I; Oberlander, T M

    1981-09-11

    Scanning electron microscopy and energy dispersive x-ray analyses of desert varnish reveal that microorganisms concentrate ambient manganese that becomes greatly enhanced in brown to black varnish. Specific characteristics of desert varnish and of varnish bacteria support a microbial origin for manganese-rich films. Varnish microbes can be cultured and produce laboratory manganese films. Accordingly, natural desert varnish and also manganese-rich rock varnishes in nondesert environments appear to be a product of microbial activity.

  15. Rock Varnish: Recorder of Desert Wetness?

    NASA Astrophysics Data System (ADS)

    Broecker, W. S.; Liu, T.

    2001-12-01

    Rock varnish is a thin coating (<200 μ m) of a cocktail rich in Mn, Fe, and clay minerals that is ubiquitous in desert regions. It has become the center of a contentious controversy revolving around its use to date geomorphic surfaces and/or to evaluate past climate conditions. We observe pronounced temporal variations in Mn and Ba concentration that are similar over large regions and that likely relate to variations in paleo-wetness. The mode of formation of varnish remains uncertain, but anthropogenic Pb concentrated in outermost varnish layers indicates its continued formation, and experiments using cosmogenic Be suggest that, while precipitation is a primary control, dust, dew, and aerosols may also be important in delivering the ingredients of varnish. We suggest several steps that may lead to rejuvenation and future breakthrough in varnish studies.

  16. Fine and coarse dust separation with polarization lidar

    NASA Astrophysics Data System (ADS)

    Mamouri, R. E.; Ansmann, A.

    2014-05-01

    The polarization-lidar photometer networking (POLIPHON) method for separating dust and non-dust aerosol backscatter and extinction, volume, and mass concentration is extended to allow for a height-resolved separation of fine-mode and coarse-mode dust properties in addition. The method is applied to a period with complex aerosol layering of fine-mode background dust from Turkey and Arabian desert dust from Syria. The observation was performed at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, in September 2011. The dust profiling methodology and case studies are presented. Consistency between the column-integrated optical properties obtained with sun/sky photometer and the respective results derived by means of the new lidar-based method corroborate the applicability of the extended POLIPHON version.

  17. Fine and coarse dust separation with polarization lidar

    NASA Astrophysics Data System (ADS)

    Mamouri, R. E.; Ansmann, A.

    2014-11-01

    The polarization-lidar photometer networking (POLIPHON) method for separating dust and non-dust aerosol backscatter and extinction, volume, and mass concentration is extended to allow for a height-resolved separation of fine-mode and coarse-mode dust properties in addition. The method is applied to a period with complex aerosol layering of fine-mode background dust from Turkey and Arabian desert dust from Syria. The observation was performed at the combined European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) site of Limassol (34.7° N, 33° E), Cyprus, in September 2011. The dust profiling methodology and case studies are presented. Consistency between the column-integrated optical properties obtained with sun/sky photometer and the respective results derived by means of the new lidar-based method corroborate the applicability of the extended POLIPHON version.

  18. NMMB/BSC-DUST: model validation at regional scale in Northern Africa

    NASA Astrophysics Data System (ADS)

    Haustein, Karsten; Pérez, Carlos; Jorba, Oriol; María Baldasano, José; Janjic, Zavisa; Black, Tom; Slobodan, Nickovic; Prigent, Catherine; Laurent, Benoit

    2010-05-01

    While mineral dust distribution and effects are important at global scales, they strongly depend on dust emissions that are controlled on small spatial and temporal scales. Indeed, the accuracy of surface wind speed used in dust models is crucial. Due to the cubic higher-order power dependency on wind friction velocity and the threshold behaviour of dust emissions, small errors on surface wind speed lead to large dust emission errors. Most global dust models use prescribed wind fields provided by meteorological centres (e.g., NCEP and ECMWF) and their spatial resolution is currently never better than about 1°×1°. Such wind speeds tend to be strongly underestimated over large arid and semi-arid areas and do not account for reflect mesoscale character of systems responsible for a significant fraction of dust emissions regionally and globally. Other Another strong uncertainties in dust emissions from such approaches are related to the missrepresentation originates from of coarse representation of high subgrid-scale spatial heterogeneity in soil and vegetation boundary conditions, mainly in semi-arid areas. With the development of the new model NMMB-BSC/DUST [Pérez et al., 2008], we are now focusing on the evalution of the model sensitivity to several processes related to dust emissions. The results presented here are an intermediate step to provide global dust forecasts up to 7 days at sub-synoptic resolutions in the near future. NMMB-BSC/DUST is coupled online with the NOAA/NCEP/EMC global/regional NMMB atmospheric model [Janjic, 2005] extending from meso to global scales an being fully embedded into the Earth System Modeling Framework (ESMF). We performed regional simulations for the Northern African domain, including the Arabian peninsula and southern/central Europe (0 to 65°N and 25°W to 55°E) at 1/3°x1/3° and 1/6x1/6° horizontal resolution with 64 vertical layers. The model is initialized with 6-hourly updated NCEP 1x1° analysis data with a dust spin

  19. Desert winds; monitoring wind-related surface processes in Arizona, New Mexico, and California

    USGS Publications Warehouse

    Breed, Carol S.; Reheis, Marith C.

    1999-01-01

    The 18-year Desert Winds Project established instrumented field sites in the five major regions of the North American Desert to obtain meteorological, geological, and vegetation data for natural desert sites affected by wind erosion. The eight chapters in this volume describe the settings and operation of the stations and summarize eolian-related research to date around the stations. The report includes studies of the sand-moving effectiveness of storm winds, wind-erosion susceptibility of different ground-surface types, relations of dust storms to meteorological conditions, mediation of wind erosion by vegetation, remote sensing to detect vegetation changes related to climate change, and comparison of regional dust deposition to that near Owens (dry) Lake.

  20. New approaches to dust mitigation in the Antelope Valley

    SciTech Connect

    Farber, R.J.; Kim, B.M.; Grantz, D.A.; Vaughn, D.L.; Zink, T.; Skadberg, K.; Cowherd, C.; Grelinger, M.A.; Campbell, R.; De Salvio, A.; VanCuren, T.; Bort, J.

    1999-07-01

    The arid deserts of the southwestern US experience a frequent dust problem which can lead to PM10 violations. Blowing dust is also one of the major air quality problems of the arid deserts. From 1992 through the present, a group of research scientists have been investigating new techniques for mitigating the windblown dust in the Mojave Desert and more specifically the Antelope Valley near Palmdale and Lancaster, CA. This paper summarizes the progress made toward dust suppression in the Antelope Valley during the initial research phase from 1992 through 1996. During this period, there were both successes and failures. Stabilizing disturbed desert lands in a water-starved environment is challenging. The initial attempts focused on revegetation of native plants by seedings. There were mixed results depending on both the magnitude and timing of the rainfall. Various types of windfences were also erected and their effectiveness was studied using BSNE's. In the present program, the objectives have been broadened to include mitigating dust from all types of disturbed lands, not only abandoned farmlands. Techniques include new approaches to revegetation using seedlings, varying water treatments and soil amendments. An array of chemical suppressants are also being evaluated for cost-effectiveness as a function of longevity. Various geometries of wind fences have also been erected in blow sand areas and are being evaluated for cost-effectiveness using an interesting evaluation scheme. This portion of the paper provides a progress report of these latest dust mitigation techniques. This current research program is due to conclude about 2002. The end product of this decade research program will be a cookbook of dust mitigation solutions for various users including regulatory agencies, the USDA NRCS, farmers and construction interests.

  1. High Latitude Dust in the Earth System

    NASA Technical Reports Server (NTRS)

    Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; McKenna-Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

    2016-01-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

  2. Lunar Dust-Tolerant Electrical Connector

    NASA Technical Reports Server (NTRS)

    Herman, Jason; Sadick, Shazad; Roberts, Dustyn

    2010-01-01

    An electrical connector was developed that is tolerant of the presence of lunar dust. Novel features of the connector include the use of a permeable membrane to act both as a dust barrier and as a wiper to limit the amount of dust that makes its way into the internal chamber of the connector. The development focused on the Constellation lunar extravehicular activity (EVA) spacesuit s portable life support system (PLSS) battery recharge connector; however, continued research is applying this technology to other lunar surface systems such as lunar rover subsystems and cryogenic fluid transfer connections for in-situ resource utilization (ISRU) applications. Lunar dust has been identified as a significant and present challenge in future exploration missions. In addition to posing contamination and health risks for human explorers, the interlocking, angular nature of lunar dust and its broad grain size distribution make it particularly harmful to mechanisms with which it may come into contact. All Apollo lunar missions experienced some degree of equipment failure because of dust, and it appears that dust accumulation on exposed material is unavoidable and difficult to reverse. Both human EVA and ISRU activities are on the mission horizon and are paramount to the establishment of a permanent human base on the Moon. Reusable and dust-tolerant connection mechanisms are a critical component for mission success. The need for dust-tolerant solutions is also seen in utility work and repair, mass transit applications, construction, mining, arctic and marine environments, diving (search and rescue), and various operations in deserts, where dust or sand clogging and coating different mechanisms and connections may render them difficult to operate or entirely inoperable.

  3. Global dust Detection Index (GDDI); a new remotely sensed methodology for dust storms detection.

    PubMed

    Samadi, Mehdi; Darvishi Boloorani, Ali; Alavipanah, Seyed Kazem; Mohamadi, Hossein; Najafi, Mohamad Saeed

    2014-01-01

    Dust storm occurs frequently in arid and semi-arid areas of the world. This natural phenomenon, which is the result of stormy winds, raises a lot of dust from desert surfaces and decreases visibility to less than 1 km. In recent years the temporal frequency of occurrences and their spatial extents has been dramatically increased. West of Iran, especially in spring and summer, suffers from significant increases of these events which cause several social and economic problems. Detecting and recognizing the extent of dust storms is very important issue in designing warning systems, management and decreasing the risk of this phenomenon. As the process of monitoring and prediction are related to detection of this phenomenon and it's separation from other atmospheric phenomena such as cloud, so the main aim of this research is establishing an automated process for detection of dust masses. In this study 20 events of dust happened in western part of Iran during 2000-2011 have been recognized and studied. To the aim of detecting dust events we used satellite images of MODIS sensor. Finally a model based on reflectance and thermal infrared bands has been developed. The efficiency of this method has been checked using dust events. Results show that the model has a good performance in all cases. It also has the ability and robustness to be used in any dust storm forecasting and warning system. PMID:24406015

  4. Effects of aerosols and surface shadowing on bidirectional reflectance measurements of deserts

    NASA Technical Reports Server (NTRS)

    Bowker, David E.; Davis, Richard E.

    1987-01-01

    Desert surfaces are probably one of the most stable of the Earth's natural targets for remote sensing. The bidirectional reflectance properties of the Saudi Arabian desert was investigated during the Summer Monsoon Experiment (Summer Monex). A comparison of high-altitude with near-surface measurements of the White Sands desert showed significant differences. These discrepancies have been attributed to forward scattering of the dust-laden atmosphere prevalent during Summer Monex. This paper is concerned in general with modeling the effects of atmospheric aerosols and surface shadowing on the remote sensing of bidirectional reflectance factors of desert targets, and in particular with comparing the results of these models with flight results. Although it is possible to approximate the latter, it is felt that a surface reflectance model with a smaller specular component would have permitted using a more realistic set of atmospheric conditions in the simulations.

  5. Libyan Desert, Libya, Africa

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Desert landscapes such as this part of the northern Sahara (27.0N, 11.0E) may be analogous to other planets which have no soil or plant growth. The dark rocks in this view are probably volcanic in origin and have many stream beds leading into the dune areas. These stream beds carry sediments