Following Saharan Dust Outbreak Toward The Amazon Basin

NASA Astrophysics Data System (ADS)

Ben Ami, Y.; Koren, I.; Rudich, Y.; Flores, M.

2008-12-01

The role of the Amazon rainforest on earth climatic system is well recognized. To keep forest wellbeing and the fragile balance between the rainforest and the atmosphere, the Amazon must contain a satisfactory amount of nutrients to support the plants. The extensive rain and floods wash most of the soluble nutrients from the rainforest soil, leaving behind acidic kaolinite clay or sandy soil, with limited minerals for plant growth. It was suggested that lack of mineral in the soil may be replenished by deposition of Saharan mineral dust. Using remote sensing data (from the A-train satellites constellation) following with in-situ measurements (as part of the AMazonian Aerosol CharacteriZation Experiment (AMZE) campaign), ground-based data (from AErosol RObotic NETwork (AERONET)) and back trajectory calculations, we analyzed Saharan dust transport toward the Amazon basin during the AMZE period (Feb 7 to Mar 14, 2008). Dust mass, sink, vertical distribution and surface wind speeds were analyzed over the Bodele depression (located in Chad), where most of the dust is emitted, along the Atlantic Ocean and near the Brazilian coastline. Using an integrated data analysis approach we followed dust packages from their emission in the Sahara to their sink in the Amazon forest.

The impact of Saharan Dust on the genesis and evolution of Hurricane Earl (2010)

NASA Astrophysics Data System (ADS)

Pan, B.; Wang, Y.; Hsieh, J. S.; Lin, Y.; Hu, J.; Zhang, R.

2017-12-01

Dust, one of the most abundant natural aerosols, can exert substantial radiative and microphysical effects on the regional climate and has potential impacts on the genesis and intensification of tropical cyclones (TCs). A Weather Research and Forecasting Model and the Regional Oceanic Modeling System coupled model (WRF-ROMS) is used to simulate the evolution of Hurricane Earl (2010), of which Earl was interfered by Saharan dust at the TC genesis stage. A new dust module has been implemented to the TAMU two-moment microphysics scheme in the WRF model. It accounts for both dust as Cloud Condensation Nuclei (CCN) and Ice Nuclei (IN). The hurricane track, intensity and precipitation have been compared to the best track data and TRMM precipitation, respectively. The influences of Saharan dust on Hurricane Earl are investigated with dust-CCN, dust-IN, and dust-free scenarios. The analysis shows that Saharan dust changes the latent heat and moisture distribution, invigorates the convections in the hurricane's eyewall, and suppresses the development of Earl. This finding addresses the importance of accounting dust microphysics effect on hurricane predictions.

Saharan dust nutrients promote Vibrio bloom formation in marine surface waters.

PubMed

Westrich, Jason R; Ebling, Alina M; Landing, William M; Joyner, Jessica L; Kemp, Keri M; Griffin, Dale W; Lipp, Erin K

2016-05-24

Vibrio is a ubiquitous genus of marine bacteria, typically comprising a small fraction of the total microbial community in surface waters, but capable of becoming a dominant taxon in response to poorly characterized factors. Iron (Fe), often restricted by limited bioavailability and low external supply, is an essential micronutrient that can limit Vibrio growth. Vibrio species have robust metabolic capabilities and an array of Fe-acquisition mechanisms, and are able to respond rapidly to nutrient influx, yet Vibrio response to environmental pulses of Fe remains uncharacterized. Here we examined the population growth of Vibrio after natural and simulated pulses of atmospherically transported Saharan dust, an important and episodic source of Fe to tropical marine waters. As a model for opportunistic bacterial heterotrophs, we demonstrated that Vibrio proliferate in response to a broad range of dust-Fe additions at rapid timescales. Within 24 h of exposure, strains of Vibrio cholerae and Vibrio alginolyticus were able to directly use Saharan dust-Fe to support rapid growth. These findings were also confirmed with in situ field studies; arrival of Saharan dust in the Caribbean and subtropical Atlantic coincided with high levels of dissolved Fe, followed by up to a 30-fold increase of culturable Vibrio over background levels within 24 h. The relative abundance of Vibrio increased from ∼1 to ∼20% of the total microbial community. This study, to our knowledge, is the first to describe Vibrio response to Saharan dust nutrients, having implications at the intersection of marine ecology, Fe biogeochemistry, and both human and environmental health.

Saharan dust contributions to PM10 and TSP levels in Southern and Eastern Spain

NASA Astrophysics Data System (ADS)

Rodríguez, S.; Querol, X.; Alastuey, A.; Kallos, G.; Kakaliagou, O.

The analysis of PM10 and TSP levels recorded in rural areas from Southern and Eastern Spain (1996-1999) shows that most of the PM10 and TSP peak events are simultaneously recorded at monitoring stations up to 1000 km apart. The study of the atmospheric dynamics by back-trajectory analysis and simulations with the SKIRON Forecast System show that these high PM10 and TSP events occur when high-dust Saharan air masses are transported over the Iberian Peninsula. In the January-June period, this dust transport is mainly caused by cyclonic activity over the West or South of Portugal, whereas in the summer period this is induced by anticyclonic activity over the East or Southeast Iberian Peninsula. Most of the Saharan intrusions which exert a major influence on the particulate levels occur from May to September (63%) and in January and October. In rural areas in Northeast Spain, where the PM10 annual mean is around 18 μg PM10 m -3, the Saharan dust accounts for 4-7 annual daily exceedances of the forthcoming PM10-EU limit value (50 μg PM10 m -3 daily mean). Higher PM10 background levels are recorded in Southern Spain (30 μg PM10 m -3 as annual mean for rural areas) and very similar values are recorded in industrial and urban areas. In rural areas in Southern Spain, the Saharan dust events accounts for 10-23 annual daily exceedances of the PM10 limit value, a high number when compared with the forthcoming EU standard, which states that the limit value cannot be exceeded more than 7 days per year. The proportion of Sahara-induced exceedances with respect to the total annual exceedances is discussed for rural, urban and industrial sites in Southern Spain.

Modeling of intercontinental Saharan dust transport: What consequences on atmospheric concentrations and deposition fluxes in the Caribbean?

NASA Astrophysics Data System (ADS)

Laurent, Benoit; Formenti, Paola; Desboeufs, Karine; Vincent, Julie; Denjean, Cyrielle; Siour, Guillaume; Mayol-Bracero, Olga L.

2015-04-01

The Dust Aging and Transport from Africa to the Caribbean (Dust-AttaCk) project aims todocument the physical and optical properties of long-range transported African dust to the Caribbean. A comprehensive field campaign was conducted in Cape San Juan, Puerto Rico (18.38°N 65.62°W) during June-July 2012, offering the opportunity to constrain the way Saharan dust are transported from North Africa to the Caribbean by 3D models. Our main objectives are: (i) to discuss the ability of the CHIMERE Eulerian off-line chemistry-transport model to simulate atmospheric Saharan dust loads observed in the Caribbean during the Dust-AttaCk campaign, as well as the altitude of the dust plumes transport over the North Atlantic Ocean up to the Caribbean, (ii) to study the main Saharan dust emission source areas contributing to the dust loads in the Caribbean, (iii) to estimate the Saharan dust deposition in the Caribbean for deposition events observed during the Dust-AttaCk campaign. The dust model outputs are hourly dust concentration fields in µg m-3 for 12 aerosol size bins up to 30 µm and for each of the 15 sigma pressure vertical levels, column integrated dustaerosol optical depth (AOD), and dry and wet deposition fluxes.The simulations performed for the Dust-AttaCk campaign period as well as satellite observations (MODIS AOD, SEVIRI AOD) are used to identify the Saharan emission source regions activated and to study the evolution of the dust plumes tothe Cape San Juan station. In complement, the vertical transport of dust plumes transported from Saharan dust sources and over the North Atlantic Ocean is investigated combining model simulations and CALIOP observations. Aerosol surface concentrations and AOD simulated with CHIMERE are compared with sin-situ observations at Cape San Juan and AERONET stations. Wet deposition measurements performed allow us to constrain dust deposition flux simulated in the Caribbean after long-range transport.

The radiative effects of Saharan dust layer on the marine atmospheric layer

NASA Astrophysics Data System (ADS)

Abed, Mohammed

2017-04-01

The North African Saharan desert is one of the main sources of atmospheric dust. Since dust can be transported by winds for thousands of miles, reaching the Americas and extending across vast expanses of the tropical Atlantic Ocean, it is important to understand the influence that dust has on the radiative properties and the thermodynamic structure of the atmosphere. For climate models it is important that this is represented since the structure of the atmosphere can have important influences downwind on the development of convection, clouds, storms, precipitation and consequently radiative properties. In this study, we aim to understand the dynamic and thermodynamic properties of Saharan dust on the atmospheric structure of marine environment and to investigate the causes of the observed regions of well-mixed potential temperatures of the marine atmosphere in the presence of Saharan dust layers. We compare the influence of dust to other potentially important influences such as wind shear and air mass. To investigate this, we simulated the marine atmosphere in the presence and absence of dust using the UK Met Office Large Eddy Model (LEM) based the BOMEX case-study that is provided with the LEM and updated with observation taken during the FENNEC experiments of June 2011 and 2012. We performed LEM simulations with and without dust heating rates for an eight-hour time period. Data for meteorological profiles were used from the FENNEC aircraft measurements taken over the Atlantic Ocean near the Canary Islands. Our LEM results show that using a stratified (typical of non-dusty) atmosphere and then apply a dust heating rate the profile of potential temperature tends towards a well-mixed layer where the heating rates were applied and consistent with the observational cases. While LEM simulations for wind shear showed very little difference in the potential temperature profile and it was clear the well-mixed layer would not result. LEM simulations using dust heating

Community variability of bacteria in alpine snow (Mont Blanc) containing Saharan dust deposition and their snow colonisation potential.

PubMed

Chuvochina, Maria S; Marie, Dominique; Chevaillier, Servanne; Petit, Jean-Robert; Normand, Philippe; Alekhina, Irina A; Bulat, Sergey A

2011-01-01

Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize high-altitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.

Saharan Dust Particle Size And Concentration Distribution In Central Ghana

NASA Astrophysics Data System (ADS)

Sunnu, A. K.

2010-12-01

A.K. Sunnu*, G. M. Afeti* and F. Resch+ *Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology (KNUST) Kumasi, Ghana. E-mail: albertsunnu@yahoo.com +Laboratoire Lepi, ISITV-Université du Sud Toulon-Var, 83162 La Valette cedex, France E-mail: resch@univ-tln.fr Keywords: Atmospheric aerosol; Saharan dust; Particle size distributions; Particle concentrations. Abstract The Saharan dust that is transported and deposited over many countries in the West African atmospheric environment (5°N), every year, during the months of November to March, known locally as the Harmattan season, have been studied over a 13-year period, between 1996 and 2009, using a location at Kumasi in central Ghana (6° 40'N, 1° 34'W) as the reference geographical point. The suspended Saharan dust particles were sampled by an optical particle counter, and the particle size distributions and concentrations were analysed. The counter gives the total dust loads as number of particles per unit volume of air. The optical particle counter used did not discriminate the smoke fractions (due to spontaneous bush fires during the dry season) from the Saharan dust. Within the particle size range measured (0.5 μm-25 μm.), the average inter-annual mean particle diameter, number and mass concentrations during the northern winter months of January and February were determined. The average daily number concentrations ranged from 15 particles/cm3 to 63 particles/cm3 with an average of 31 particles/cm3. The average daily mass concentrations ranged from 122 μg/m3 to 1344 μg/m3 with an average of 532 μg/m3. The measured particle concentrations outside the winter period were consistently less than 10 cm-3. The overall dust mean particle diameter, analyzed from the peak representative Harmattan periods over the 13-year period, ranged from 0.89 μm to 2.43 μm with an average of 1.5 μm ± 0.5. The particle size distributions exhibited the typical distribution pattern for

PM10 composition during an intense Saharan dust transport event over Athens (Greece).

PubMed

Remoundaki, E; Bourliva, A; Kokkalis, P; Mamouri, R E; Papayannis, A; Grigoratos, T; Samara, C; Tsezos, M

2011-09-15

The influence of Saharan dust on the air quality of Southern European big cities became a priority during the last decade. The present study reports results on PM(10) monitored at an urban site at 14 m above ground level during an intense Saharan dust transport event. The elemental composition was determined by Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF) for 12 elements: Si, Al, Fe, K, Ca, Mg, Ti, S, Ni, Cu, Zn and Mn. PM(10) concentrations exceeded the EU limit (50 μg/m(3)) several times during the sampling period. Simultaneous maxima have been observed for the elements of crustal origin. The concentrations of all the elements presented a common maximum, corresponding to the date where the atmosphere was heavily charged with particulate matter permanently for an interval of about 10h. Sulfur and heavy metal concentrations were also associated to local emissions. Mineral dust represented the largest fraction of PM(10) reaching 79%. Seven days back trajectories have shown that the air masses arriving over Athens, originated from Western Sahara. Scanning Electron Microscopy coupled with Energy Dispersive X-ray analysis (SEM-EDX) revealed that particle agglomerates were abundant, most of them having sizes <2 μm. Aluminosilicates were predominant in dust particles also rich in calcium which was distributed between calcite, dolomite, gypsum and Ca-Si particles. These results were consistent with the origin of the dust particles and the elemental composition results. Sulfur and heavy metals were associated to very fine particles <1 μm. Copyright © 2011 Elsevier B.V. All rights reserved.

Dust emission and transport associated with a Saharan depression: February 2007 case

NASA Astrophysics Data System (ADS)

Bou Karam, Diana; Flamant, Cyrille; Cuesta, Juan; Pelon, Jacques; Williams, Earle

2010-01-01

event over North Africa. Furthermore, the dust was lofted to altitudes as high as 7 km, becoming subject to long-range transport. The model was able to reasonably reproduce the structure, lifetime, and trajectory of the cyclone. Also, comparison with Moderate Resolution Imaging Spectrometer (MODIS) deep blue aerosol optical depths and CALIPSO-CloudSat observations suggests that the model can be reliably used to quantify the dust emissions associated with this event. The mean daily dust loads over the area influenced by the cyclone were simulated to range between 2 and 8 Tg during the lifetime of the Sharav cyclone (i.e., 5 days). This study suggests that dust emissions linked with Saharan cyclones may contribute significantly to the total dust load over West and North Africa observed annually.

Determination of Radiative Forcing of Saharan Dust using Combined TOMS and ERBE Data

NASA Technical Reports Server (NTRS)

Hsu, N. Christina; Herman, Jay R.; Weaver, Clark

1999-01-01

The direct radiative forcing of Saharan dust aerosols has been determined by combining aerosol information derived from Nimbus-7 TOMS with radiation measurements observed at the top of atmosphere (TOA) by NOAA-9 ERBE made during February-July 1985. Cloud parameters and precipitable water derived from the NOAA-9 HIRS2 instrument were used to aid in screening for clouds and water vapor in the analyses. Our results indicate that under "cloud-free" and "dry" conditions there is a good correlation between the ERBE TOA outgoing longwave fluxes and the TOMS aerosol index measurements over both land and ocean in areas under the influence of airborne Saharan dust. The ERBE TOA outgoing shortwave fluxes were also found to correlate well with the dust loading derived from TOMS over ocean. However, the calculated shortwave forcing of Saharan dust aerosols is very weak and noisy over land for the range of solar zenith angle viewed by the NOAA-9 ERBE in 1985. Sensitivity factors of the TOA outgoing fluxes to changes in aerosol index were estimated using a linear regression fit to the ERBE and TOMS measurements. The ratio of the shortwave-to-longwave response to changes in dust loading over the ocean is found to be roughly 2 to 3, but opposite in sign. The monthly averaged "clear-sky" TOA direct forcing of airborne Saharan dust was also calculated by multiplying these sensitivity factors by the TOMS monthly averaged "clear-sky" aerosol index. Both the observational and theoretical analyses indicate that the dust layer height, ambient moisture content as well as the presence of cloud all play an important role in determining the TOA direct radiative forcing due to mineral aerosols.

Saharan dust nutrients promote Vibrio bloom formation in marine surface waters

USGS Publications Warehouse

Westrich, Jason R.; Ebling, Alina M.; Landing, William M.; Joyner, Jessica L.; Kemp, Keri M.; Griffin, Dale W.; Lipp, Erin K.

2016-01-01

Vibrio is a ubiquitous genus of marine bacteria, typically comprising a small fraction of the total microbial community in surface waters, but capable of becoming a dominant taxon in response to poorly characterized factors. Iron (Fe), often restricted by limited bioavailability and low external supply, is an essential micronutrient that can limit Vibrio growth. Vibrio species have robust metabolic capabilities and an array of Fe-acquisition mechanisms, and are able to respond rapidly to nutrient influx, yet Vibrio response to environmental pulses of Fe remains uncharacterized. Here we examined the population growth of Vibrioafter natural and simulated pulses of atmospherically transported Saharan dust, an important and episodic source of Fe to tropical marine waters. As a model for opportunistic bacterial heterotrophs, we demonstrated that Vibrio proliferate in response to a broad range of dust-Fe additions at rapid timescales. Within 24 h of exposure, strains of Vibrio cholerae and Vibrio alginolyticus were able to directly use Saharan dust–Fe to support rapid growth. These findings were also confirmed with in situ field studies; arrival of Saharan dust in the Caribbean and subtropical Atlantic coincided with high levels of dissolved Fe, followed by up to a 30-fold increase of culturable Vibrio over background levels within 24 h. The relative abundance of Vibrio increased from ∼1 to ∼20% of the total microbial community. This study, to our knowledge, is the first to describe Vibrio response to Saharan dust nutrients, having implications at the intersection of marine ecology, Fe biogeochemistry, and both human and environmental health.

Saharan Dust as a Causal Factor of Significant Cloud Cover Along the Saharan Air Layer in the Atlantic Ocean

NASA Technical Reports Server (NTRS)

Kishcha, Pavel; Da Silva, Arlindo M.; Starobinet, Boris; Alpert, Pinhas

2016-01-01

The tropical Atlantic is frequently affected by Saharan dust intrusions. Based on MODIS cloud fraction (CF) data during the ten-year study period, we found that these dust intrusions contribute to significant cloud cover along the Saharan Air Layer (SAL). Below the temperature inversion at the SAL's base, the presence of large amounts of settling dust particles, together with marine aerosols, produces meteorological conditions suitable for the formation of shallow stratocumulus clouds. The significant cloud fraction along the SAL together with clouds over the Atlantic Inter-tropical Convergence Zone contributes to the 20% hemispheric CF asymmetry between the tropical North and South Atlantic. This leads to the imbalance in strong solar radiation, which reaches the sea surface between the tropical North and South Atlantic, and, consequently, affects climate formation in the tropical Atlantic. Therefore, despite the fact that, over the global ocean, there is no noticeable hemispheric asymmetry in cloud fraction, over the significant area such as the tropical Atlantic the hemispheric asymmetry in CF takes place. Saharan dust is also the major contributor to hemispheric aerosol asymmetry over the tropical Atlantic. The NASA GEOS-5 model with aerosol data assimilation was used to extend the MERRA reanalysis with five atmospheric aerosol species (desert dust, sulfates, organic carbon, black carbon, and sea-salt). The obtained ten-year (2002 - 2012) MERRA-driven aerosol reanalysis dataset (aka MERRAero) showed that, over the tropical Atlantic, dust and carbonaceous aerosols were distributed asymmetrically relative to the equator, while other aerosol species were distributed more symmetrically.

Improving Air Pollution Modeling Over The Po Valley Using Saharan Dust Transport Forecasts

NASA Astrophysics Data System (ADS)

Kishcha, P.; Carnevale, C.; Finzi, G.; Pisoni, E.; Volta, M.; Nickovic, S.; Alpert, P.

2012-04-01

Our study shows that Saharan dust can contribute significantly to PM10 concentrations in the Po Valley. This dust contribution should be taken into account when estimating the exceedance of pollution limits. The DREAM dust model has been used for several years for producing operational dust forecasts at Tel-Aviv University, Israel. DREAM has been producing daily forecasts of 3-D distribution of dust concentrations over the Mediterranean region, Middle East, Europe, and over the Atlantic Ocean (http://wind.tau.ac.il/dust8/dust.html). In the current study, DREAM dust forecasts were used to give better model estimates of the contribution of Saharan dust to PM10 concentration over the Po Valley, in Northern Italy. This was carried out by the integration of daily Saharan dust forecasts into a mesoscale Transport Chemical Aerosol Model (TCAM). The Po Valley in Northern Italy is frequently affected by high PM10 concentrations, where both natural and anthropogenic sources play a significant role. Our study of TCAM and DREAM integration was carried out for the period May 15 - June 30, 2007, when four significant dust events were observed. The integrated TCAM-DREAM model performance was evaluated by comparing PM10 measurements with modeled PM10 concentrations. First, Saharan dust impact on TCAM performance was analyzed at eleven remote PM10 sites which had the lowest level of air pollution (PM10 ≤ 14 μg/m3) over the period under consideration. For those remote sites, the observed high PM10 concentrations during dust events stood prominently on the background of low PM10 concentrations. At the remote sites, such a strong deviation from the background level can not be attributed to anthropogenic aerosol emissions because of their distance from anthropogenic sources. The observed maxima in PM10 concentration during dust events is evidence of dust aerosol near the surface in Northern Italy. During all dust events under consideration, the integrated TCAM-DREAM model produced

Characterization of Saharan mineral dust transported to the Colle Gnifetti glacier (Southern Alps, Switzerland) during the last centuries.

NASA Astrophysics Data System (ADS)

Thevenon, Florian; Poté, John; Adatte, Thierry; Chiaradia, Massimo; Hueglin, Christoph; Collaud Coen, Martine

2010-05-01

The Southern Alps act as a barrier to the southwesterly dust-laden winds from the Sahara, and the Colle Gnifetti saddle (45°55'N, 7°52'E, 4455 m asl in the Monte Rosa Massif) satisfactory conserves the history of climatic conditions over the last millennium (Thevenon et al., 2009). Therefore, the Colle Gnifetti glacier is a suitable site for i) studying the composition of past Saharan aeolian dust emissions, and for ii) comparing modern dust emissions with preindustrial emissions. The mineral aerosols entrapped in the ice core have been analyzed for their physical (grain-size by image analysis), mineralogical (by X-ray diffraction), and chemical composition (by ICPMS and by mass spectrometry for Sr and Nd isotopic ratios). The mineral dust characteristics are then compared with present day Saharan dust samples collected at the high altitude research station Jungfraujoch (46°55'N, 7°98E, 3580 asl) and with documented potential dust sources. Results show that i) the increases in atmospheric dustiness correlate with larger mean grain size, and that ii) the dust emissions increase after the industrial revolution, probably as a large-scale atmospheric circulation response to anthropogenic climate forcing (Shindell et al., 2001; Thevenon et al., 2009). However, geochemical variations in aeolian mineral particles also indicate that the source areas of the dust, which are now situated in northern and north-western part of the Saharan desert (Collaud Coen et al., 2004), did not change significantly throughout the past. Therefore, the mineralogy (e.g. illite, kaolinite, chlorite, palygorskite) and the geochemistry of the paleo-dust particles transported to Europe, are relevant to assess past African dust sources. REFERENCES: - Thevenon, F., F. S. Anselmetti, S. M. Bernasconi, and M. Schwikowski (2009). Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over the last millennium. J. Geophys. Res., 114, D17102, doi:10

Persistent organic contaminants in Saharan dust air masses in West Africa, Cape Verde and the eastern Caribbean

USGS Publications Warehouse

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

2014-01-01

Anthropogenic semivolatile organic compounds (SOCs) that persist in the environment, bioaccumulate, are toxic at low concentrations, and undergo long-range atmospheric transport (LRT) were identified and quantified in the atmosphere of a Saharan dust source region (Mali) and during Saharan dust incursions at downwind sites in the eastern Caribbean (U.S. Virgin Islands, Trinidad and Tobago) and Cape Verde. More organochlorine and organophosphate pesticides (OCPPs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyl (PCB) congeners were detected in the Saharan dust region than at downwind sites. Seven of the 13 OCPPs detected occurred at all sites: chlordanes, chlorpyrifos, dacthal, dieldrin, endosulfans, hexachlorobenzene (HCB), and trifluralin. Total SOCs ranged from 1.9–126 ng/m3 (mean = 25 ± 34) at source and 0.05–0.71 ng/m3 (mean = 0.24 ± 0.18) at downwind sites during dust conditions. Most SOC concentrations were 1–3 orders of magnitude higher in source than downwind sites. A Saharan source was confirmed for sampled air masses at downwind sites based on dust particle elemental composition and rare earth ratios, atmospheric back trajectory models, and field observations. SOC concentrations were considerably below existing occupational and/or regulatory limits; however, few regulatory limits exist for these persistent organic compounds. Long-term effects of chronic exposure to low concentrations of SOCs are unknown, as are possible additive or synergistic effects of mixtures of SOCs, biologically active trace metals, and mineral dust particles transported together in Saharan dust air masses.

Exploring records of Saharan dust transport and hurricanes in the Caribbean and Gulf of Mexico over recent millennia

NASA Astrophysics Data System (ADS)

Hayes, C. T.; Wallace, D. J.

2017-12-01

Locations in the northern Caribbean and Gulf of Mexico receive aerosol deposition from the summertime Saharan dust plume that is representative of atmospheric conditions over a very large expanse of the North Atlantic Ocean. A recent reconstruction of stable dust deposition in the Bahamas over the past 2 thousand years contrasts other records from the African continent which were impacted by local anthropogenic emissions. Dust deposition in the Bahamas also appeared relatively insensitive to expected changes in intertropical convergence zone position. Here, we will investigate records of Atlantic hurricane activity and Saharan dust transport, parameters which are anti-correlated today, in the Caribbean and Gulf region over the past few thousand years to further probe possible variations in Saharan dust forcings on Atlantic climate.

Dust emission and transport associated with a Saharan depression: The February 2007 case

NASA Astrophysics Data System (ADS)

Karam, Diana Bou; Flamant, Cyrille; Cuesta, Juan; Pelon, Jacques; Williams, Earle

2010-05-01

. Furthermore, the dust was lofted to altitudes as high as 7 km, becoming subject to long range transport. The model was able to reproduce reasonably the structure, the lifetime and the trajectory of the cyclone. Also comparison with MODIS deep blue AODs and CALIPSO/CloudSat observations suggests that the model can be used reliably to quantify the dust emissions associated with this event. The mean daily dust loads over the area influenced by the cyclone were simulated to range between 2 and 8 Tg during the lifetime of the Sharav cyclone (i.e. 5 days). This study suggests that dust emissions linked with Saharan cyclones may contribute significantly to the total dust load over West and North Africa observed annually.

Microphysical and Optical Properties of Saharan Dust Measured during the ICE-D Aircraft Campaign

NASA Astrophysics Data System (ADS)

Ryder, Claire; Marenco, Franco; Brooke, Jennifer; Cotton, Richard; Taylor, Jonathan

2017-04-01

During August 2015, the UK FAAM BAe146 research aircraft was stationed in Cape Verde off the coast of West Africa. Measurements of Saharan dust, and ice and liquid water clouds, were taken for the ICE-D (Ice in Clouds Experiment - Dust) project - a multidisciplinary project aimed at further understanding aerosol-cloud interactions. Six flights formed part of a sub-project, AER-D, solely focussing on measurements of Saharan dust within the African dust plume. Dust loadings observed during these flights varied (aerosol optical depths of 0.2 to 1.3), as did the vertical structure of the dust, the size distributions and the optical properties. The BAe146 was fully equipped to measure size distributions covering aerosol accumulation, coarse and giant modes. Initial results of size distribution and optical properties of dust from the AER-D flights will be presented, showing that a substantial coarse mode was present, in agreement with previous airborne measurements. Optical properties of dust relating to the measured size distributions will also be presented.

Modeling the Diagnostic Effects of Vegetation, Soil Albedo, and Dust on Mid-Holocene Saharan Climate

NASA Astrophysics Data System (ADS)

Thompson, A.; Poulsen, C. J.; Skinner, C. B.

2017-12-01

Unlike today, the Mid-Holocene (MH, 6,000 BP) African Sahara comprised of mixed vegetation and permanent lakes that supported human settlements. Climate proxies including leaf wax isotope, pollen, and dust flux records suggest that African monsoonal precipitation reached 31°N, compared to 15°N today. Changes in orbital forcing are partly responsible for the intensification of the African monsoon, but alone cannot explain the more humid MH Sahara. Modeling studies have shown that vegetation and soil albedo feedbacks greatly increase Saharan rainfall but still fall short of levels indicated by proxies. A recent study proposed that reduced Saharan dust concentrations due to greater vegetation coverage further increased MH rainfall. However, this study used idealized dust concentrations to improve proxy agreement and did not include the dust aerosol indirect effects in its model physics. Here we use CESM CAM5-chem to quantify the impact of diagnostic changes in Saharan dust, including indirect effects, on MH Saharan climate and compare it to changes in orbital forcing, soil albedo, and vegetation. Consistent with previous studies, a change in MH orbital forcing alone leads to a 20% increase in summer (June-Sept.) precipitation over Northern Africa (0°-30°N, 20°W-30°E) relative to a pre-industrial control, but still fails to reach the northward extent suggested by proxies. Adding MH soil albedo or vegetation increases summer precipitation by 45% and 52%, and shifts the maximum latitudinal rainfall extent 10° and 12° northward, respectively. These increases are 2.28 and 2.64 times greater than the precipitation increase from MH orbital forcing alone. MH soil albedo results in a dust burden increase of 22%, yet MH vegetation results in a 96% reduction. Both MH soil albedo and vegetation combined increase summer precipitation by 56% and 13° northward, an increase 2.84 times greater than the orbital forcing alone, and reduces dust burden by 97%. An additional

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

PubMed

Garrison, V H; Majewski, M S; Konde, L; Wolf, R E; Otto, R D; Tsuneoka, Y

2014-12-01

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. Published by Elsevier B.V.

Impact of Saharan dust events on radionuclide levels in Monaco air and in the water column of the northwest Mediterranean Sea.

PubMed

Pham, Mai Khanh; Chamizo, Elena; Mas Balbuena, José Luis; Miquel, Juan-Carlos; Martín, Jacobo; Osvath, Iolanda; Povinec, Pavel P

2017-01-01

Characterization of atmospheric aerosols collected in Monaco (2004-2008) and in sediment traps at 200 m and 1000 m water depths at the DYFAMED (Dynamics of Atmospheric Fluxes in the Mediterranean Sea) station (2004) was carried out to improve our understanding of the impact of Saharan dust on ground-level air and on the water column. Activity concentrations of natural ( 210 Pb, 210 Po, uranium and radium isotopes) and anthropogenic ( 137 Cs, 239 Pu, 240 Pu, and 239+240 Pu) radionuclides and their isotopic ratios confirmed a Saharan impact on the investigated samples. In association with a large particulate matter deposition event in Monaco on 20 February 2004, the 137 Cs (∼40 Bq kg -1 ) and 239+240 Pu (∼1 Bq kg -1 ) activities were almost a factor of two higher than other Saharan deposition dust events. This single-day particle flux represented 72% of the annual atmospheric deposition in Monaco. The annual deposition of Saharan dust on the sea was 232-407 mBq m -2 for 137 Cs and 6.8-9.8 mBq m -2 for 239+240 Pu and contributed significantly (28-37% for 137 Cs and 34-45% for 239+240 Pu) to the total annual atmospheric input to the northwest Mediterranean Sea. The 137 Cs/ 239+240 Pu activity ratios in dust samples collected during different Saharan dust events confirmed their global fallout origin or mixing with local re-suspended soil particles. In the sediment trap samples the 137 Cs activity varied by a factor of two, while the 239+240 Pu activity was constant, confirming the different behaviors of Cs (dissolved) and Pu (particle reactive) in the water column. The 137 Cs and 239+240 Pu activities of sinking particles during the period of the highest mass flux collected in 20 February 2004 at the 200 m and 1000 m water depths represented about 10% and 15%, respectively, of annual deposition from Saharan dust events. Copyright © 2016 Elsevier Ltd. All rights reserved.

Short-Term Effects of the Particulate Pollutants Contained in Saharan Dust on the Visits of Children to the Emergency Department due to Asthmatic Conditions in Guadeloupe (French Archipelago of the Caribbean)

PubMed Central

Cadelis, Gilbert; Tourres, Rachel; Molinie, Jack

2014-01-01

Background The prevalence of asthma in children is a significant phenomenon in the Caribbean. Among the etiologic factors aggravating asthma in children, environmental pollution is one of the main causes. In Guadeloupe, pollution is primarily transported by Saharan dust including inhalable particles. Methods This study assesses, over one year (2011), the short-term effects of pollutants referred to as PM10 (PM10: particulate matter <10 µm) and PM2.5–10 (PM2.5–10: particulate matter >2.5 µm and <10 µm) contained in Saharan dust, on the visits of children aged between 5 and 15 years for asthma in the health emergency department of the main medical facility of the archipelago of Guadeloupe. A time-stratified case-crossover model was applied and the data were analysed by a conditional logistic regression for all of the children but also for sub-groups corresponding to different age classes and genders. Results The visits for asthma concerned 836 children including 514 boys and 322 girls. The Saharan dust has affected 15% of the days of the study (337 days) and involved an increase in the average daily concentrations of PM10 (49.7 µg/m3 vs. 19.2 µg/m3) and PM 2.5–10 (36.2 µg/m3 vs. 10.3 µg/m3) compared to days without dust. The excess risk percentages (IR%) for visits related to asthma in children aged between 5 and 15 years on days with dust compared to days without dust were, for PM10, ((IR %: 9.1% (CI95%, 7.1%–11.1%) versus 1.1%(CI95%, −5.9%–4.6%)) and for PM2.5–10 (IR%: 4.5%(CI95%, 2.5%–6.5%) versus 1.6% (CI95%, −1.1%–3.4%). There was no statistical difference in the IR% for periods with Saharan dust among different age group of children and between boys and girls for PM10 and PM2.5–10. Conclusion The PM10 and PM2.5–10 pollutants contained in the Saharan dust increased the risk of visiting the health emergency department for children with asthma in Guadeloupe during the study period. PMID:24603899

Impact of the 4 April 2014 Saharan dust outbreak on the photovoltaic power generation in Germany

NASA Astrophysics Data System (ADS)

Rieger, Daniel; Steiner, Andrea; Bachmann, Vanessa; Gasch, Philipp; Förstner, Jochen; Deetz, Konrad; Vogel, Bernhard; Vogel, Heike

2017-11-01

The importance for reliable forecasts of incoming solar radiation is growing rapidly, especially for those countries with an increasing share in photovoltaic (PV) power production. The reliability of solar radiation forecasts depends mainly on the representation of clouds and aerosol particles absorbing and scattering radiation. Especially under extreme aerosol conditions, numerical weather prediction has a systematic bias in the solar radiation forecast. This is caused by the design of numerical weather prediction models, which typically account for the direct impact of aerosol particles on radiation using climatological mean values and the impact on cloud formation assuming spatially and temporally homogeneous aerosol concentrations. These model deficiencies in turn can lead to significant economic losses under extreme aerosol conditions. For Germany, Saharan dust outbreaks occurring 5 to 15 times per year for several days each are prominent examples for conditions, under which numerical weather prediction struggles to forecast solar radiation adequately. We investigate the impact of mineral dust on the PV-power generation during a Saharan dust outbreak over Germany on 4 April 2014 using ICON-ART, which is the current German numerical weather prediction model extended by modules accounting for trace substances and related feedback processes. We find an overall improvement of the PV-power forecast for 65 % of the pyranometer stations in Germany. Of the nine stations with very high differences between forecast and measurement, eight stations show an improvement. Furthermore, we quantify the direct radiative effects and indirect radiative effects of mineral dust. For our study, direct effects account for 64 %, indirect effects for 20 % and synergistic interaction effects for 16 % of the differences between the forecast including mineral dust radiative effects and the forecast neglecting mineral dust.

Analysis of Measurements of Saharan Dust by Airborne and Ground-based Remote Sensing Methods during the Puerto Rico Dust Experiment (PRIDE)

NASA Technical Reports Server (NTRS)

Reid, Jeffrey S.; Kinney, James E.; Westphal, Douglas L.; Holben, Brent N.; Welton, E. Judd; Tsay, Si-Chee; Eleuterio, Daniel P.; Campbell, James; Christopher, Sundar A.; Jonsson, Haflidi H.

2003-01-01

For 26 days in mid-June and July 2000, a research group comprised of U.S. Navy, NASA, and university scientists conducted the Puerto Rico Dust Experiment (PRIDE). In this paper we give a brief overview of mean meteorological conditions during the study. We focus on findings on African dust transported into the Caribbean utilizing Navajo aircraft and AERONET Sun photometer data. During the study midvisible aerosol optical thickness (AOT) in Puerto Rico averaged 0.25, with a maximum less than 0.5 and with clean marine periods of _0.08. Dust AOTs near the coast of Africa (Cape Verde Islands and Dakar) averaged _0.4, 30% less than previous years. By analyzing dust vertical profiles in addition to supplemental meteorology and MPLNET lidar data we found that dust transport cannot be easily categorized into any particular conceptual model. Toward the end of the study period, the vertical distribution of dust was similar to the commonly assumed Saharan Air Layer (SAL) transport. During the early periods of the study, dust had the highest concentrations in the marine and convective boundary layers with only a, weak dust layer in the SAL being present, a state usually associated with wintertime transport patterns. We corroborate the findings of Maring et al. that in most cases, there was an unexpected lack of vertical stratification of dust particle size. We systematically analyze processes which may impact dust vertical distribution and determine and speculate that dust vertical distribution predominately influenced by flow patterns over Africa and differential advection couple with mixing by easterly waves and regional subsidence.

Understanding the Role of the Saharan Heat Low in Modifying Atmospheric Dust Distributions - Observations From Two Research Aircraft Flying Simultaneously Over Western Africa

NASA Astrophysics Data System (ADS)

Engelstaedter, S.; Washington, R.; Allen, C.; Flamant, C.; Chaboureau, J.-P.; Kocha, C.; Lavaysse, C.

2012-04-01

The near-surface low pressure system that develops over western Africa in Boreal summer (know as the Saharan Heat Low) is thought to have a significant influence on regional and global climate due to its links with the Monsoon, the Northern Atlantic and the Mediterranean climate system. The SHL is associated with the deepest atmospheric boundary layer on the planet and is co-located with the highest dust loadings in the world. The processes that link the heat low and dust distribution are only poorly understood. Improving the representation of the heat low and the processes that control the emission and atmospheric distribution of dust in climate and NWP models is crucial if we are to reduce known systematic errors in climate predictions and weather forecasts. In collaboration with European partners, the UK-based consortium project "Fennec - The Saharan Climate System" aims at improving our understanding of this complex climate system by integrating for the first time coordinated ground and aircraft observations from the central Sahara, newly developed satellite products, and the application of regional and global models. On 22 June 2011, two research aircraft operating out of Fuerteventura (Spain) surveyed the Saharan Heat Low centred over Mauritania-Mali border. The aircraft flew simultaneously in the morning and in the afternoon on two different tracks thereby sampling each track four times on that day. Both aircraft were equipped with a downward looking LIDAR for aerosol detection. In total, 51 sondes were dropped during the flights making this the most comprehensive dataset to study the spatio-temporal diurnal evolution of the heat low including the interactions between the atmospheric boundary layer and dust distributions. Combining LIDAR observations, satellite imagery and back-trajectory modelling we show that an aged dust layer was present in the heat low region resulting from previous day's dust activity associated with a south-moving density current from

Enhanced Saharan dust input to the Levant during Heinrich stadials

NASA Astrophysics Data System (ADS)

Torfstein, Adi; Goldstein, Steven L.; Stein, Mordechai

2018-04-01

The history of dust transport to the Levant during the last glacial period is reconstructed using the isotope ratios of Pb, Sr, Nd, and Hf in sediments of Lake Lisan, the last glacial Dead Sea. Exposed marginal sections of the Lisan Formation were sampled near Masada, the Perazim Valley and from a core drilled at the deep floor of the modern lake. Bulk samples and size fractions display unique isotopic fingerprints: the finest detritus fraction (<5 μm) displays higher 87Sr/86Sr and lower εNd values (0.710-0.713 and -7.0 to -9.8, respectively) relative to the coarser fractions (5-20 μm and <20 μm; 0.708-0.710 and -3.4 to -8.3) and the bulk detritus samples (0.709-0.711 and -6 to -7.5). Similarly, the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios (18.26-19.02, 15.634-15.68, and 38.25-38.82, respectively) are systematically higher in the finest detritus fraction relative to corresponding coarser fractions and bulk samples. The 87Sr/86Sr and εNd values of the finest fraction correspond with those of atmospheric dust originating from the Sahara Desert, while those of the coarse fractions are similar to loess deposits exposed in the Sinai and Negev Deserts. Pronounced excursions in the Sr-Nd-Pb isotope ratios toward more Sahara-like values coincide with the Heinrich (H) stadials 6, 5 and 1, reflecting significant increases in Saharan dust fluxes during regionally arid intervals, reflected by sharp lake level drops. Moreover, during H6 the dust came from different Saharan sources than during H1 and H5. While the relatively wet glacial climate in the Levant suppressed the transport of dust to the lake watershed, short-term hyper-arid spells during H-stadial intervals were accompanied by enhanced supply of fine Sahara dust to this region.

Detecting and assessing Saharan dust contribution to PM10 loads: A pilot study within the EU-Life+10 project DIAPASON

NASA Astrophysics Data System (ADS)

Gobbi, Gian Paolo; Barnaba, Francesca; Bolignano, Andrea; Costabile, Francesca; Di Liberto, Luca; Dionisi, Davide; Drewnick, Frank; Lucarelli, Franco; Manigrasso, Maurizio; Nava, Silvia; Sauvage, Laurent; Sozzi, Roberto; Struckmeier, Caroline; Wille, Holger

2015-04-01

The EC LIFE+2010 DIAPASON Project (Desert dust Impact on Air quality through model-Predictions and Advanced Sensors ObservatioNs, www.diapason-life.eu) intends to contribute new methodologies to assess the role of aerosol advections of Saharan dust to the local PM loads recorded in Europe. To this goal, automated Polarization Lidar-Ceilometers (PLCs) were prototyped within DIAPASON to certify the presence of Saharan dust plumes and support evaluating their mass loadings in the lowermost atmosphere. The whole process also involves operational dust forecasts, as well as satellite and in-situ observations. Demonstration of the Project is implemented in the pilot region of Rome (Central Italy) where three networked DIAPASON PLCs started, in October 2013 a year-round, 24h/day monitoring of the altitude-resolved aerosol backscatter and depolarization profiles. Two intensive observational periods (IOPs) involving chemical analysis and detailed physical characterization of aerosol samples have also been carried out in this year-long campaign, namely in Fall 2013 and Spring 2014. These allowed for an extensive interpretation of the PLC observations, highlighting important synergies between the PLC and the in situ data. The presentation will address capabilities of the employed PLCs, observations agreement with model forecasts of dust advections, retrievals of aerosol properties and methodologies developed to detect Saharan advections and to evaluate the relevant mass contribution to PM10. This latter task is intended to provide suggestions on possible improvements to the current EC Guidelines (2011) on this matter. In fact, specific Guidelines are delivered by the European Commission to provide the Member States a common method to asses the Saharan dust contribution to the currently legislated PM-related Air Quality metrics. The DIAPASON experience shows that improvements can be proposed to make the current EC Methodology more robust and flexible. The methodology DIAPASON

The Fate of Saharan Dust Across the Atlantic and Implications for a Central American Dust Barrier

NASA Technical Reports Server (NTRS)

Nowottnick, E.; Colarco, P.; da Silva, A.; Hlavka, D.; McGill, M.

2011-01-01

Saharan dust was observed over the Caribbean basin during the summer 2007 NASA Tropical Composition, Cloud, and Climate Coupling (TC4) field experiment. Airborne Cloud Physics Lidar (CPL) and satellite observations from MODIS suggest a barrier to dust transport across Central America into the eastern Pacific. We use the NASA GEOS-5 atmospheric transport model with online aerosol tracers to perform simulations of the TC4 time period in order to understand the nature of this barrier. Our simulations are driven by the Modem Era Retrospective-Analysis for Research and Applications (MERRA) meteorological analyses. We evaluate our baseline simulated dust distributions using MODIS and CALIOP satellite and ground-based AERONET sun photometer observations. GEOS-5 reproduces the observed location, magnitude, and timing of major dust events, but our baseline simulation does not develop as strong a barrier to dust transport across Central America as observations suggest. Analysis of the dust transport dynamics and lost processes suggest that while both mechanisms play a role in defining the dust transport barrier, loss processes by wet removal of dust are about twice as important as transport. Sensitivity analyses with our model showed that the dust barrier would not exist without convective scavenging over the Caribbean. The best agreement between our model and the observations was obtained when dust wet removal was parameterized to be more aggressive, treating the dust as we do hydrophilic aerosols.

Satellite measurements of physical properties of Saharan dust

NASA Technical Reports Server (NTRS)

Lee, Tae Young; Fraser, Robert S.; Kaufman, Yoram

1986-01-01

The physical properties of Saharan dust obtained from AVHRR and VISSR images are studied. The techniques of Fraser (1976) and Kaufman and Fraser (1985) are used to derive the aerosol optical depth, mass, and single scattering albedo for the region extending from the west coast of Africa to the Barbados Island for the period of June 21-25, 1984. Optical properties measured by satellite are compared to aircraft measurements taken near Barbados Island during the same period. Remote measurement of thermal properties is also discussed.

Tropical storm redistribution of Saharan dust to the upper troposphere and ocean surface

NASA Astrophysics Data System (ADS)

Herbener, Stephen R.; Saleeby, Stephen M.; Heever, Susan C.; Twohy, Cynthia H.

2016-10-01

As a tropical cyclone traverses the Saharan Air Layer (SAL), the storm will spatially redistribute the dust from the SAL. Dust deposited on the surface may affect ocean fertilization, and dust transported to the upper levels of the troposphere may impact radiative forcing. This study explores the relative amounts of dust that are vertically redistributed when a tropical cyclone crosses the SAL. The Regional Atmospheric Modeling System (RAMS) was configured to simulate the passage of Tropical Storm Debby (2006) through the SAL. A dust mass budget approach has been applied, enabled by a novel dust mass tracking capability of the model, to determine the amounts of dust deposited on the ocean surface and transferred aloft. The mass of dust removed to the ocean surface was predicted to be nearly 2 orders of magnitude greater than the amount of dust transported to the upper troposphere.

A Northward Shift of the North Atlantic Ocean Intertropical Convergence Zone in Response to Summertime Saharan Dust Outbreaks

NASA Technical Reports Server (NTRS)

Wilcox, Eric M.; Lau, K. M.; Kim, Kyu-Myong

2010-01-01

The influence on the summertime North Atlantic Ocean inter-tropical convergence zone (ITCZ) of Saharan dust outbreaks is explored using nine years of continuous satellite observations and atmospheric reanalysis products. During dust outbreak events rainfall along the ITCZ shifts northward by 1 to 4 degrees latitude. Dust outbreaks coincide with warmer lower-tropospheric temperatures compared to low dust conditions, which is attributable to advection of the warm Saharan Air Layer, enhanced subtropical subsidence, and radiative heating of dust. The enhanced positive meridional temperature gradient coincident with dust outbreaks is accompanied by an acceleration of the easterly winds on the n011h side of the African Easterly Jet (AEJ). The center of the positive vorticity region south of the AEJ moves north drawing the center of low-level convergence and ITCZ rainfall northward with it. The enhanced precipitation on the north side of the ITCZ occurs in spite of widespread sea surface temperature cooling north of the ITCZ owing to reduced surface solar insolation by dust scattering.

Saharan dust particles in snow samples of Alps and Apennines during an exceptional event of transboundary air pollution.

PubMed

Telloli, Chiara; Chicca, Milvia; Pepi, Salvatore; Vaccaro, Carmela

2017-12-21

Southern European countries are often affected in summer by transboundary air pollution from Saharan dust. However, very few studies deal with Saharan dust pollution at high altitudes in winter. In Italy, the exceptional event occurred on February 19, 2014, colored in red the entire mountain range (Alps and Apennines) and allowed to characterize the particulate matter deposited on snow from a morphological and chemical point of view. Snow samples were collected after this event in four areas in the Alps and one in the Apennines. The particulate matter of the melted snow samples was analyzed by scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) and by inductively coupled plasma mass spectrometry (ICP-MS). These analyses confirmed the presence of Saharan dust particle components in all areas with similar percentages, supported also by the positive correlations between Mg-Ca, Al-Ca, Al-Mg, and Al-K in all samples.

Preliminary Results from an Assimilation of Saharan Dust Using TOMS Radiances and the GOCART Model

NASA Technical Reports Server (NTRS)

Weaver, C. J.; daSilva, Arlindo; Ginoux, Paul; Torres, Omar; Einaudi, Franco (Technical Monitor)

2000-01-01

At NASA Goddard we are developing a global aerosol data assimilation system that combines advances in remote sensing and modeling of atmospheric aerosols. The goal is to provide high resolution, 3-D aerosol distributions to the research community. Our first step is to develop a simple assimilation system for Saharan mineral aerosol. The Goddard Chemistry and Aerosol Radiation model (GOCART) provides accurate 3-D mineral aerosol size distributions. Surface mobilization, wet and dry deposition, convective and long-range transport are all driven by assimilated fields from the Goddard Earth Observing System Data Assimilation System, GEOS-DAS. Our version of GOCART transports sizes from .08-10 microns and only simulates Saharan dust. We draw the assimilation to two observables in this study: the TOMS aerosol index (Al) which is directly related to the ratio of the 340 and 380 radiances and the 380 radiance alone. The forward model that simulates the observables requires the aerosol optical thickness, the single scattering albedo and the height of the aerosol layer from the GOCART fields. The forward model also requires a refractive index for the dust. We test three index values to see which best fits the TOMS observables. These are 1) for Saharan dust reported by Patterson, 2) for a mixture of Saharan dust and a highly reflective material (sea salt or sulfate) and 3) for pure illite. The assimilation works best assuming either pure illite or the dust mixture. Our assimilation cycle first determines values of the aerosol index (Al) and the radiance at 380 nm based on the GOCART aerosol fields. Differences between the observed and GOCART model calculated Al and 380 nm radiance are first analyzed horizontally using the Physical-space Statistical Analysis System (PSAS). A quasi-Newton iteration is then performed to produce analyzed 3D aerosol fields according to parameterized background and observation error covariances. We only assimilate observations into the the GOCART

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.

Geochemical evidence of Saharan dust parent material for soils developed on Quaternary limestones of Caribbean and western Atlantic islands

USGS Publications Warehouse

Muhs, D.R.; Bush, C.A.; Stewart, K.C.; Rowland, T.R.; Crittenden, R.C.

1990-01-01

Most previous workers have regarded the insoluble residues of high-purity Quaternary limestones (coral reefs and oolites) as the most important parent material for well-developed, clay-rich soils on Caribbean and western Atlantic islands, but this genetic mechanism requires unreasonable amounts of limestone solution in Quaternary time. Other possible parent materials from external sources are volcanic ash from the Lesser Antilles island arc and Saharan dust carried across the Atlantic Ocean on the northeast trade winds. Soils on Quaternary coral terraces and carbonate eolianites on Barbados, Jamaica, the Florida Keys (United States), and New Providence Island (Bahamas) were studied to determine which, if either, external source was important. Caribbean volcanic ashes and Saharan dust can be clearly distinguished using ratios of relatively immobile elements ( Al2O3 TiO2, Ti Y, Ti Zr, and Ti Th). Comparison of these ratios in 25 soils, where estimated ages range from 125,000 to about 870,000 yr, shows that Saharan dust is the most important parent material for soils on all islands. These results indicate that the northeast trade winds have been an important component of the regional climatology for much of the Quaterary. Saharan dust may also be an important parent material for Caribbean island bauxites of much greater age. ?? 1990.

The linkage between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

NASA Astrophysics Data System (ADS)

Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

2016-04-01

Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 ka to 5.5 ka ago (deMenocal et al., 2000; McGee et al., 2013). The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. We present simulation results from a recent sensitivity study, where we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface during the Holocene. We have simulated timeslices of he mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6.1-HAM2.1. We prescribe mid-Holocene vegetation cover based on a vegetation reconstruction from pollen data (Hoelzmann et al., 1998) and mid-Holocene lake surface area is determined using a water routing and storage model (Tegen et al., 2002). In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the variation in dust accumulation in marine cores is likely related to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone. Reference: deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., and Yarusinsky, M.: Abrupt onset and termination of the African Humid Period:: rapid climate responses to gradual insolation forcing, Quaternary Science Reviews, 19, 347-361, 2000. Hoelzmann, P., Jolly, D., Harrison, S. P., Laarif, F

Summer variability of Saharan dust transport events in mountain areas north and south of Po basin

NASA Astrophysics Data System (ADS)

Landi, Tony C.; Marinoni, Angela; Cristofanelli, Paolo; Putero, Davide; Duchi, Rocco; Alborghetti, Marcello; Bonafè, Ubaldo; Calzolari, Francescopiero; Pietro Verza, Gian; Bonasoni, Paolo

2013-04-01

Mineral dust intrusions from northern African desert regions have a strong impact on the Mediterranean areas and Italian peninsula as they can cause an anomalous increase of aerosol concentrations in the tropospheric column and often an increase of particulate matter at ground level. The estimate of Saharan dust contribution to aerosols concentrations is therefore a key issue in air quality assessment and policy formulation, since can cause air quality exceedances of the PM10 daily limits (50 μg m-3) set by the European Union (EU/2008/50). This study presents a first identification and characterization of Saharan dust outbreaks observed during summer season at two high mountain stations located both South (Mt. Cimone, 2165 m asl) and North (Rifugio Guasti, Stelvio National Park, 3285 m asl) of Po valley. An estimation of their impact on PM10 concentrations in both sites, and in urban and rural areas of the Po basin is provided. Joining specific measurements (ground and satellite based) and numerical modeling, an investigation into the vertical structure of dust load will be presented. Actually, methodologies conceived for distinguishing dust outbreaks transported above the boundary layer without any impact at the ground level from those causing deposition are currently still lacking. Basically, the approach proposed in this work includes a deep analysis of in-situ measurements starting from long-term observation of Saharan dust carried out at the Mt. Cimone and more recent measurements performed in the framework of SHARE Stelvio Project, as well as the usage of ad hoc model chain (meteorological processor, chemical transport model, and aerosols optical properties calculation) to describe emission, transport and deposition dynamics of mineral dust that - in summertime - often affect the North Italy.

Shape-induced Gravitational Sorting of Saharan Dust During Transatlantic Voyage: Evidence from CALIOP Lidar Depolarization Measurements

NASA Technical Reports Server (NTRS)

Yang, Weidong; Marshak, Alexander; Kostinski, Alexander B.; Varnai, Tamas

2013-01-01

Motivated by the physical picture of shape-dependent air resistance and, consequently, shape-induced differential sedimentation of dust particles, we searched for and found evidence of dust particle asphericity affecting the evolution and distribution of dust-scattered light depolarization ratio (delta). Specifically, we examined a large data set of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations of Saharan dust from June to August 2007. Observing along a typical transatlantic dust track, we find that (1) median delta is uniformly distributed between 2 and 5?km altitudes as the elevated dust leaves the west coast of Africa, thereby indicating uniformly random mixing of particle shapes with height; (2) vertical homogeneity of median delta breaks down during the westward transport: between 2 and 5?km delta increases with altitude and this increase becomes more pronounced with westward progress; (3) delta tends to increase at higher altitude (greater than 4?km) and decrease at lower altitude (less than 4?km) during the westward transport. All these features are captured qualitatively by a minimal model (two shapes only), suggesting that shape-induced differential settling and consequent sorting indeed contribute significantly to the observed temporal evolution and vertical stratification of dust properties. By implicating particle shape as a likely cause of gravitational sorting, these results will affect the estimates of radiative transfer through Saharan dust layers.

Human thermal perception related to Föhn winds due to Saharan dust outbreaks in Crete Island, Greece

NASA Astrophysics Data System (ADS)

Nastos, P. T.; Bleta, A. G.; Matsangouras, I. T.

2017-05-01

Crete Island is located in the southmost border of East Mediterranean basin, facing exacerbating atmospheric conditions (mainly concentrations of particulates) due to Saharan dust outbreaks. It is worth to note that these episodes are more frequent during spring and autumn, when mild biometeorological conditions become intolerable due to the synergy of the so called Föhn winds. Cretan mountains, especially Psiloritis Mt. (summit at 2456 m), are orientated perpendicularly to the southwest air mass flow, generating the Föhn winds. Propagating from the leeward of the mountains, these dry, hot winds have an effect on prevailing biometeorological conditions. While descending to the lowlands on the leeward side of the range, the wind becomes strong, gusty, and desiccating. This wind often lasts less than an hour to several days, with gradual weakening after the first or the second day. Sometimes, it stops very abruptly. In this work, the authors examined and analyzed the abrupt changes of human thermal perception within specific case studies during which Föhn winds appeared in Heraklion city at the leeward of Psiloritis Mt, associated with extreme Saharan dust episodes, observed within the period 2006-2010. In order to verify the development of Föhn winds, Meteorological Terminal Aviation Routine Weather Reports (METARs, meteorological observations every half hour), were acquired from the Heraklion meteorological station installed by the Hellenic National Meteorological Service (HNMS). The biometeorological conditions analyzed are based on human thermal bioclimatic indices such as the Physiologically equivalent temperature (PET) and the Universal Thermal Climate Index (UTCI). METAR recordings of meteorological variables, such as air temperature, vapor pressure, wind speed, and cloudiness, were used as input variables in modeling the aforementioned thermal indices, so that to interpret the grade of the thermo-physiological stress. The PET and UTCI analysis was

Ice Nucleating Particle Properties in the Saharan Air Layer Close to the Dust Source

NASA Astrophysics Data System (ADS)

Boose, Y.; Garcia, I. M.; Rodríguez, S.; Linke, C.; Schnaiter, M.; Nickovic, S.; Lohmann, U.; Kanji, Z. A.; Sierau, B.

2015-12-01

In August 2013 and 2014 measurements of ice nucleating particle (INP) concentrations, aerosol particle size distributions, chemistry and fluorescence were conducted at the Izaña Atmospheric Observatory located at 2373 m asl on Tenerife, west off the African shore. During summer, the observatory is frequently within the Saharan Air Layer and thus often exposed to dust. Absolute INP concentrations and activated fractions at T=-40 to -15°C and RHi=100-150 % were measured. In this study, we discuss the in-situ measured INP properties with respect to changes in the chemical composition, the biological content, the source regions as well as transport pathways and thus aging processes of the dust aerosol. For the first time, ice crystal residues were also analyzed with regard to biological content by means of their autofluorescence signal close to a major dust source region. Airborne dust samples were collected with a cyclone for additional offline analysis in the laboratory under similar conditions as in the field. Both, in-situ and offline dust samples were chemically characterized using single-particle mass spectrometry. The DREAM8 dust model extended with dust mineral fractions was run to simulate meteorological and dust aerosol conditions for ice nucleation. Results show that the background aerosol at Izaña was dominated by carbonaceous particles, which were hardly ice-active under the investigated conditions. When Saharan dust was present, INP concentrations increased by up to two orders of magnitude even at water subsaturated conditions at T≤-25°C. Differences in the ice-activated fraction were found between different dust periods which seem to be linked to variations in the aerosol chemical composition (dust mixed with changing fractions of sea salt and differences in the dust aerosol itself). Furthermore, two biomass burning events in 2014 were identified which led to very low INP concentrations under the investigated temperature and relative humidity

Recent and past Saharan dust deposition in the Carpathian Basin and its possible effects on interglacial soil formation

NASA Astrophysics Data System (ADS)

Varga, György

2016-04-01

Several hundred tons of windblown dust material are transported every year from Saharan dust source areas into direction of Europe, modifying important climatic and other environmental processes of distant areas. North African aerosols have been also identified several times a year in the Carpathian Basin, where under the influence of certain synoptic meteorological conditions Saharan dust accumulation can clearly be observed. Previous satellite based studies were suitable to estimate the frequency and magnitude of Saharan dust episodes in the investigation area, however, the assessment of North African dust deposition can be done with model simulations. In this study, calculations were made by using the data of BSC-DREAM8b (Barcelona Supercomputing Center's Dust REgional Atmospheric Model) v1.0 and v2.0 database. Simulation results of the BSC-DREAM8b v1.0 are available from 1 January 2000 to 31 December 2012, while the results of the updated v2.0 calculations are ready for the period between 1 January 2006 and 31 December 2014. BSC DREAM8b v1.0 model simulations for the period between 2000 and 2012 provided an annual mean of 0.0285 g/m2/y dry and 0.034 g/m2/y wet deposition values in the Carpathian Basin, which is equivalent to a total of 0.0636 g/m2/y. The updated v2.0 version for the period of 2006-2014 gave significantly larger values: 0.133 g/m2/y dry; 0.085 g/m2/y wet and 0.219 g/m2/y total annual dust deposition. By comparing the results of the overlapping period between 2006 and 2012 of the v1.0 and v2.0 simulations, the updated depositional scheme of the newer version provided ˜3.7-fold values in case of dry deposition and ˜1.9-fold increase in results of the wet deposition. Information available from individual events showed that the simulated wet and dry dust deposition rates are significantly underestimated. This is also suggested by previous model calculations which reported values between 5 and 10 g/m2/y for modern dust flux in the investigated area

AEROSE 2004 - An Interdisciplinary Atmosphere-Ocean Saharan Dust Expedition

NASA Astrophysics Data System (ADS)

Clemente-Colón, P.

2004-05-01

The NOAA Center for Atmospheric Sciences (NCAS) is sponsoring a Trans-Atlantic Saharan Dust AERosol and Ocean Science Expedition (AEROSE) aboard the NOAA Ship Ronald H. Brown in March 2004. The fundamental purpose of this aerosol cruise is to study the impacts and microphysical evolution of Saharan dust aerosol as it is transported across the Atlantic Ocean. The mission encompasses both, atmospheric and oceanographic components. Participating institutions include Howard University, NCAS lead institution, the University of Puerto Rico at Mayagüez, the Canary Institute of Marine Sciences, the Spanish Institute of Oceanography, the Laboratory of Atmospheric Physics Siméon Fongang, the University of Miami Rosenstiel School of Marine and Atmospheric Science, the University of Washington Applied Physics Laboratory, NASA Goddard Space Flight Center, the NOAA Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin-Madison, NASA Jet Propulsion Laboratory, and the NOAA/NESDIS Office of Research and Applications. This collaboration provides unique atmospheric and oceanic observations across the North Tropical Atlantic during eastward and westward tracks during a period of nearly one month. Characterization of microphysical properties of Saharan dust aerosol is done trough direct observations of mass, size, and particle number distributions, chemical composition, spatial distributions, and air chemistry. Aerosol radiative properties are studied through a suite of sensors that include a Multi-Angle Absorption Photometer (MAAP), the Marine-Atmosphere Emitted Radiance Interferometer (M-AERI), sunphotometers, and an assortment of other radiometers. Characterization of atmospheric conditions is done through a combination of over 250 radiosonde and ozonesonde launches at 3 to 5 hour intervals during the duration of the cruise and in coordination with satellite overpasses. AEROSE is also supporting the collection of bio-optics and oceanographic

Soluble iron nutrients in Saharan dust over the central Amazon rainforest

NASA Astrophysics Data System (ADS)

Rizzolo, Joana A.; Barbosa, Cybelli G. G.; Borillo, Guilherme C.; Godoi, Ana F. L.; Souza, Rodrigo A. F.; Andreoli, Rita V.; Manzi, Antônio O.; Sá, Marta O.; Alves, Eliane G.; Pöhlker, Christopher; Angelis, Isabella H.; Ditas, Florian; Saturno, Jorge; Moran-Zuloaga, Daniel; Rizzo, Luciana V.; Rosário, Nilton E.; Pauliquevis, Theotonio; Santos, Rosa M. N.; Yamamoto, Carlos I.; Andreae, Meinrat O.; Artaxo, Paulo; Taylor, Philip E.; Godoi, Ricardo H. M.

2017-02-01

The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands. Iron is one of the micronutrients essential for plant growth, and its long-range transport might be an important source for the iron-limited Amazon rainforest. This study assesses the bioavailability of iron Fe(II) and Fe(III) in the particulate matter over the Amazon forest, which was transported from the Sahara desert (for the sake of our discussion, this term also includes the Sahel region). The sampling campaign was carried out above and below the forest canopy at the ATTO site (Amazon Tall Tower Observatory), a near-pristine area in the central Amazon Basin, from March to April 2015. Measurements reached peak concentrations for soluble Fe(III) (48 ng m-3), Fe(II) (16 ng m-3), Na (470 ng m-3), Ca (194 ng m-3), K (65 ng m-3), and Mg (89 ng m-3) during a time period of dust transport from the Sahara, as confirmed by ground-based and satellite remote sensing data and air mass backward trajectories. Dust sampled above the Amazon canopy included primary biological aerosols and other coarse particles up to 12 µm in diameter. Atmospheric transport of weathered Saharan dust, followed by surface deposition, resulted in substantial iron bioavailability across the rainforest canopy. The seasonal deposition of dust, rich in soluble iron, and other minerals is likely to assist both bacteria and fungi within the topsoil and on canopy surfaces, and especially benefit highly bioabsorbent species. In this scenario, Saharan dust can provide essential macronutrients and micronutrients to plant roots, and also directly to plant leaves. The influence of this input on the ecology of the forest canopy and topsoil is discussed, and we argue that this influence would likely be different from that of nutrients from the weathered Amazon bedrock, which otherwise provides the

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.

Profiling of Saharan dust from the Caribbean to western Africa - Part 2: Shipborne lidar measurements versus forecasts

NASA Astrophysics Data System (ADS)

Ansmann, Albert; Rittmeister, Franziska; Engelmann, Ronny; Basart, Sara; Jorba, Oriol; Spyrou, Christos; Remy, Samuel; Skupin, Annett; Baars, Holger; Seifert, Patric; Senf, Fabian; Kanitz, Thomas

2017-12-01

A unique 4-week ship cruise from Guadeloupe to Cabo Verde in April-May 2013 see part 1, Rittmeister et al. (2017) is used for an in-depth comparison of dust profiles observed with a polarization/Raman lidar aboard the German research vessel Meteor over the remote tropical Atlantic and respective dust forecasts of a regional (SKIRON) and two global atmospheric (dust) transport models (NMMB/BSC-Dust, MACC/CAMS). New options of model-observation comparisons are presented. We analyze how well the modeled fine dust (submicrometer particles) and coarse dust contributions to light extinction and mass concentration match respective lidar observations, and to what extent models, adjusted to aerosol optical thickness observations, are able to reproduce the observed layering and mixing of dust and non-dust (mostly marine) aerosol components over the remote tropical Atlantic. Based on the coherent set of dust profiles at well-defined distances from Africa (without any disturbance by anthropogenic aerosol sources over the ocean), we investigate how accurately the models handle dust removal at distances of 1500 km to more than 5000 km west of the Saharan dust source regions. It was found that (a) dust predictions are of acceptable quality for the first several days after dust emission up to 2000 km west of the African continent, (b) the removal of dust from the atmosphere is too strong for large transport paths in the global models, and (c) the simulated fine-to-coarse dust ratio (in terms of mass concentration and light extinction) is too high in the models compared to the observations. This deviation occurs initially close to the dust sources and then increases with distance from Africa and thus points to an overestimation of fine dust emission in the models.

Influence of Atmospheric Processes on the Solubility and Composition of Iron in Saharan Dust.

PubMed

Longo, Amelia F; Feng, Yan; Lai, Barry; Landing, William M; Shelley, Rachel U; Nenes, Athanasios; Mihalopoulos, Nikolaos; Violaki, Kalliopi; Ingall, Ellery D

2016-07-05

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation state became more reduced, and aerosol acidity increased. Atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.

Longwave Radiative Forcing of Saharan Dust Aerosols Estimated from MODIS, MISR and CERES Observations on Terra

NASA Technical Reports Server (NTRS)

Zhang, Jiang-Long; Christopher, Sundar A.

2003-01-01

Using observations from the Multi-angle Imaging Spectroradiometer (MISR), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Clouds and the Earth's Radiant Energy System (CERES) instruments onboard the Terra satellite; we present a new technique for studying longwave (LW) radiative forcing of dust aerosols over the Saharan desert for cloud-free conditions. The monthly-mean LW forcing for September 2000 is 7 W/sq m and the LW forcing efficiency' (LW(sub eff)) is 15 W/sq m. Using radiative transfer calculations, we also show that the vertical distribution of aerosols and water vapor are critical to the understanding of dust aerosol forcing. Using well calibrated, spatially and temporally collocated data sets, we have combined the strengths of three sensors from the same satellite to quantify the LW radiative forcing, and show that dust aerosols have a "warming" effect over the Saharan desert that will counteract the shortwave "cooling effect" of aerosols.

Integrating Saharan dust forecasts into a regional chemical transport model: a case study over Northern Italy.

PubMed

Carnevale, C; Finzi, G; Pisoni, E; Volta, M; Kishcha, P; Alpert, P

2012-02-15

The Po Valley in Northern Italy is frequently affected by high PM10 concentrations, where both natural and anthropogenic sources play a significant role. To improve air pollution modeling, 3D dust fields, produced by means of the DREAM dust forecasts, were integrated as boundary conditions into the mesoscale 3D deterministic Transport Chemical Aerosol Model (TCAM). A case study of the TCAM and DREAM integration was implemented over Northern Italy for the period May 15-June 30, 2007. First, the Saharan dust impact on PM10 concentration was analyzed for eleven remote PM10 sites with the lowest level of air pollution. These remote sites are the most sensitive to Saharan dust intrusions into Northern Italy, because of the absence of intensive industrial pollution. At these remote sites, the observed maxima in PM10 concentration during dust events is evidence of dust aerosol near the surface in Northern Italy. Comparisons between modeled PM10 concentrations and measurements at 230 PM10 sites in Northern Italy, showed that the integrated TCAM-DREAM model more accurately reproduced PM10 concentration than the base TCAM model, both in terms of correlation and mean error. Specifically, the correlation median increased from 0.40 to 0.65, while the normalized mean absolute error median dropped from 0.5 to 0.4. Copyright © 2011 Elsevier B.V. All rights reserved.

Influences of natural emission sources (wildfires and Saharan dust) on the urban organic aerosol in Barcelona (Western Mediterranean Basis) during a PM event.

PubMed

van Drooge, Barend L; Lopez, Jordi F; Grimalt, Joan O

2012-11-01

The urban air quality in Barcelona in the Western Mediterranean Basin is characterized by overall high particulate matter (PM) concentrations, due to intensive local anthropogenic emissions and specific meteorological conditions. Moreover, on several days, especially in summer, natural PM sources, such as long-range transported Saharan dust from Northern Africa or wildfires on the Iberian Peninsula and around the Mediterranean Basin, may influence the levels and composition of the organic aerosol. In the second half of July 2009, daily collected PM(10) filter samples in an urban background site in Barcelona were analyzed on organic tracer compounds representing several emission sources. During this period, an important PM peak event was observed. Individual organic compound concentrations increased two to five times during this event. Although highest increase was observed for the organic tracer of biomass burning, the contribution to the organic aerosol was estimated to be around 6 %. Organic tracers that could be related to Saharan dust showed no correlation with the PM and OC levels, while this was the case for those related to fossil fuel combustion from traffic emissions. Moreover, a change in the meteorological conditions gave way to an overall increase of the urban background contamination. Long-range atmospheric transport of organic compounds from primary emissions sources (i.e., wildfires and Saharan dust) has a relatively moderate impact on the organic aerosol in an urban area where the local emissions are dominating.

Relative Contributions of the Saharan and Sahelian Sources to the Atmospheric Dust Load Over the North Atlantic

NASA Technical Reports Server (NTRS)

Ginoux, Paul; Chin, M.; Torres, O.; Prospero, J.; Dubovik, O.; Holben, B.; Einaudi, Franco (Technical Monitor)

2000-01-01

It has long been recognized that Saharan desert is the major source for long range transport of mineral dust over the Atlantic. The contribution from other natural sources to the dust load over the Atlantic has generally been ignored in previous model studies or been replaced by anthropogenically disturbed soil emissions. Recently, Prospero et.at. have identified the major dust sources over the Earth using TOMS aerosol index. They showed that these sources correspond to dry lakes with layers of sediment deposed in the late Holocene or Pleistocene. One of the most active of these sources seem to be the Bodele depression. Chiapello et al. have analyzed the mineralogical composition of dust on the West coast of Africa. They found that Sahelian dust events are the most intense but are less frequent than Saharan plumes. This suggests that the Bodele depression could contribute significantly to the dust load over the Atlantic. The relative contribution of the Sahel and Sahara dust sources is of importance for marine biogeochemistry or atmospheric radiation, because each source has a distinct mineralogical composition. We present here a model study of the relative contributions of Sahara and Sahel sources to the atmospheric dust aerosols over the North Atlantic. The Georgia Tech/Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model is used to simulate dust distribution in 1996-1997. Dust particles are labeled depending on their sources. In this presentation, we will present the comparison between the model results and observations from ground based measurements (dust concentration, optical thickness and size distribution) and satellite data (TOMS aerosol index). The relative contribution of each source will then be analyzed spatially and temporally.

Influence of atmospheric processes on the solubility and composition of iron in Saharan dust

DOE PAGES

Longo, Amelia F.; Feng, Yan; Lai, Barry; ...

2016-06-10

Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet-chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated the aerosol iron in Mediterranean samples. In Atlantic samples, iron(II and III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation statemore » became more reduced, and aerosol acidity increased. As a result, atmospheric processing including acidic reactions and photoreduction likely influence the form of iron minerals and oxidation state in Saharan dust aerosols and contribute to increases in aerosol-iron solubility.« less

Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact

NASA Astrophysics Data System (ADS)

Longman, Jack; Veres, Daniel; Ersek, Vasile; Salzmann, Ulrich; Hubay, Katalin; Bormann, Marc; Wennrich, Volker; Schäbitz, Frank

2017-07-01

Reconstructions of dust flux have been used to produce valuable global records of changes in atmospheric circulation and aridity. These studies have highlighted the importance of atmospheric dust in marine and terrestrial biogeochemistry and nutrient cycling. By investigating a 10 800-year-long paleoclimate archive from the Eastern Carpathians (Romania) we present the first peat record of changing dust deposition over the Holocene for the Carpathian-Balkan region. Using qualitative (X-ray fluorescence (XRF) core scanning) and quantitative inductively coupled plasma optical emission spectrometer(ICP-OES) measurements of lithogenic (K, Si, Ti) elements, we identify 10 periods of major dust deposition between 9500-9200, 8400-8100, 7720-7250, 6350-5950, 5450-5050, 4130-3770, 3450-2850, 2000-1450, 800-620, and 60 cal yr BP to present. In addition, we used testate amoeba assemblages preserved within the peat to infer local palaeohydroclimatic conditions. Our record highlights several discrepancies between eastern and western European dust depositional records and the impact of highly complex hydrological regimes in the Carpathian region. Since 6100 cal yr BP, we find that the geochemical indicators of dust flux have become uncoupled from the local hydrology. This coincides with the appearance of millennial-scale cycles in the dust input and changes in geochemical composition of dust. We suggest that this is indicative of a shift in dust provenance from local-regional (likely loess-related) to distal (Saharan) sources, which coincide with the end of the African Humid Period and the onset of Saharan desertification.

Satellite Reveals How Much Saharan Dust Feeds Amazon's Plants

NASA Image and Video Library

2015-02-24

What connects Earth's largest, hottest desert to its largest tropical rainforest? The Sahara Desert is a near-uninterrupted brown band of sand and scrub across the northern third of Africa. The Amazon rainforest is a dense green mass of humid jungle that covers northeast South America. But after strong winds sweep across the Sahara, a tan cloud rises in the air, stretches between the continents, and ties together the desert and the jungle. It’s dust. And lots of it. For the first time, a NASA satellite has quantified in three dimensions how much dust makes this trans-Atlantic journey. Scientists have not only measured the volume of dust, they have also calculated how much phosphorus – a natural plant fertilizer present in Saharan sands from part of the desert’s past as a lake bed – gets carried across the ocean from one of the planet’s most desolate places to one of its most fertile. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Intercomparison of observations and model aerosol parameters during two Saharan dust events over the southern United Kingdom

NASA Astrophysics Data System (ADS)

Buxmann, Joelle; Adam, Mariana; Ordonez, Carlos; Tilbee, Marie; Smyth, Tim; Claxton, Bernard; Sugier, Jacqueline; Agnew, Paul

2015-04-01

February 2014 values of 0.07 for 380nm. These high AOD values are attributed to poor surface air quality and elevated Saharan dust levels over much of the UK and Europe. The presence of particles above the boundary layer were observed in the vertical profiles of the attenuated backscatter signal from the LCBR in Exeter. During the evening periods of both days, the Angstrom Exponent (AE) decreased. This effect can be attributed to larger particles, with larger optical depth, indicating dust particles - in agreement with the model predictions of dust. An increase in AOD from below 0.2 at 440nm up to ~0.8 was observed at all sun photometer sites for the second period analyzed starting on 29. March. The AQUM forecasts an AOD of up to 1 at 440nm across the UK, i.e. 20% higher than the observations. The correlations of modelled PM10 with total AOD, PM2.5 with fine mode AOD and PM10-PM2.5 with coarse mode AOD, show an over-estimation of the fine mode particles. The vertical profiles of the LCBR of backscatter and extinction coefficients, plus a comparison of the integrated extinction coefficient, give further insight into the model performance.

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.

Can Transport of Saharan Dust Explain Extensive Clay Deposits in the Amazon Basin? A Test Using Radiogenic Isotopes

NASA Astrophysics Data System (ADS)

Andreae, M. O.; Abouchami, W.; Näthe, K.; Kumar, A.; Galer, S. J.; Jochum, K. P.; Williams, E.; Horbe, A. M.; Rosa, J. W.; Adams, D. K.; Balsam, W. R.

2012-12-01

The Bodélé Depression, located in the Southern Sahara, is a huge source of atmospheric dust and thus an important element in biogeochemical cycles and the radiative budget of Earth's atmosphere. Previous studies have shown that Saharan dust transport across the Atlantic acts as an important source of mineral nutrients to the Amazon rainforest. The Belterra Clay, which outcrops extensively across the Amazon Basin in Brazil, has been proposed to result from dry deposition of African dusts. We have investigated this hypothesis by measuring the radiogenic isotopic composition (Sr, Nd and Pb) of a suite of samples from the Belterra Clay, the Bodélé Depression, dusts deposits collected at various locations along the airmass transport trajectory, as well as loess from the Cape Verde Islands. Radiogenic isotope systems are powerful tracers of provenance and can be used to fingerprint dust sources and atmospheric transport patterns. Our results identify distinct isotopic signatures in the Belterra Clay samples and the African sources. The Belterra Clay display radiogenic Sr and Pb isotope ratios associated with non-radiogenic Nd isotope signatures. In contrast, Bodélé samples and dusts deposits show lower Pb isotope ratios, variable 87Sr/86Sr, and relatively homogeneous Nd isotopic compositions, albeit more radiogenic than those of the Belterra Clay. Our data show unambiguously that the Belterra Clay is not derived from African dust deposition, nor from the Andean chain, as originally suggested by W. Sombroek. Rather, isotopic compositions and Nd model ages are consistent with simple mixing of Archean and younger Proterozoic terranes within the Amazon Basin as a result of weathering and erosion under humid tropical conditions. Whether Saharan dusts contribute to the fertilization in the Amazon Basin cannot be ruled out, however, since the African dust isotopic signature is expected to be entirely overprinted by local sources. Radiogenic isotope data obtained on

Improving Public Health DSSs by Including Saharan Dust Forecasts Through Incorporation of NASA's GOCART Model Results

NASA Technical Reports Server (NTRS)

Berglund, Judith

2007-01-01

Approximately 2-3 billion metric tons of soil dust are estimated to be transported in the Earth's atmosphere each year. Global transport of desert dust is believed to play an important role in many geochemical, climatological, and environmental processes. This dust carries minerals and nutrients, but it has also been shown to carry pollutants and viable microorganisms capable of harming human, animal, plant, and ecosystem health. Saharan dust, which impacts the eastern United States (especially Florida and the southeast) and U.S. Territories in the Caribbean primarily during the summer months, has been linked to increases in respiratory illnesses in this region and has been shown to carry other human, animal, and plant pathogens. For these reasons, this candidate solution recommends integrating Saharan dust distribution and concentration forecasts from the NASA GOCART global dust cycle model into a public health DSS (decision support system), such as the CDC's (Centers for Disease Control and Prevention's) EPHTN (Environmental Public Health Tracking Network), for the eastern United States and Caribbean for early warning purposes regarding potential increases in respiratory illnesses or asthma attacks, potential disease outbreaks, or bioterrorism. This candidate solution pertains to the Public Health National Application but also has direct connections to Air Quality and Homeland Security. In addition, the GOCART model currently uses the NASA MODIS aerosol product as an input and uses meteorological forecasts from the NASA GEOS-DAS (Goddard Earth Observing System Data Assimilation System) GEOS-4 AGCM. In the future, VIIRS aerosol products and perhaps CALIOP aerosol products could be assimilated into the GOCART model to improve the results.

Airborne lidar observations of Saharan dust during FENNEC

NASA Astrophysics Data System (ADS)

Marenco, Franco; Garcia-Carreras, Luis; Rosenberg, Phil; McQuaid, Jim

2013-04-01

In June 2011 and June 2012, the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft took part in the Fennec campaign. The main purpose was to quantify and model boundary layer and aerosol processes over the Saharan "heat low" region, the greatest dust region during summer. Although the central Sahara is extremely remote, the meteorology of this region is vital in driving the West African monsoon, and the dry and dusty air layers are closely related to the formation of Atlantic tropical cyclones. In this presentation, we shall characterise these air layers using data collected with the on-board lidar together with dropsondes. The interpretation of lidar signals in this particular geometry represents a challenge (nadir observations of thick layers), but we shall show that a suitable data inversion framework is possible under certain assumptions. The quality of the lidar data will be assessed using in-situ data from the nephelometer and optical particle counters. Deep air layers containing dust have been observed up to altitude of 5-6 km above mean sea level. The analysis of temperature and dew point profiles are used to identify the boundary layer and residual layer tops, and in conjunction with lidar observations this serves to quantify the dust content of both layers. An aerosol-laden residual layer is usually found during the campaign at an altitude of 2-6 km in the morning hours, with little aerosol below. The aerosol in the boundary layer is seen to develop later when solar heating of the surface induces turbulence until in the late afternoon the top of the boundary layer reaches up to ~ 6 km. Clouds embedded in aerosol layers and aerosol-cloud interactions have also been revealed. Dust aerosol has been observed in most cases, but a thin polluted non-dusty layer has been observed during one flight.

Saharan dust plume charging observed over the UK

NASA Astrophysics Data System (ADS)

Harrison, R. Giles; Nicoll, Keri A.; Marlton, Graeme J.; Ryder, Claire L.; Bennett, Alec J.

2018-05-01

A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cm s‑1 continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (‑8.0 ± 3.3) nC m‑2, which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere’s lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.

Microbial communities established on Mont Blanc summit with Saharan dust deposition

NASA Astrophysics Data System (ADS)

Chuvochina, M.; Alekhina, I.; Normand, P.; Petit, J. R.; Bulat, S.

2009-04-01

Dust originating from the Sahara desert can be uplifted during storms, transported across the Mediterranean towards the Alpine region and deposited during snowfalls. The microbes associated with dust particles can be involved in establishing microbiota in icy environments as well as affect ecosystem and human health. Our objective was to use a culture-free DNA-based approach to assess bacterial content and diversity and furthermore, to identify ‘icy' microbes which could be brought on the Mont Blanc (MtBl) summit with Saharan dust and became living in the snow. Saharan dust fallout on MtBl summit from one event (MB5, event June 2006) vs. control libraries and that from another event (May 2008) were collected in Grenoble (SD, 200 m a.s.l.) and at Col du Dome (MB-SD, 4250 m a.s.l.). Soil from Ksar Ghilane (SS, Saharan desert, Tunisia, March 2008) was taken for overall comparison as a possible source population. Fresh snow falling in Grenoble (85) was collected as example of diversity in this area. To assess the microbial diversity 16S rRNA gene libraries (v3-v5 region) were constructed for corresponding dust-snow samples (MB5, SS, SD, 85 and MB-SD) along with clear snow samples and several controls. For both MB5 and MB-SD samples full-gene technique was evoked in attempt to differentiate reproduced bacteria from damaged DNA. Before sequencing the clones were rybotyped. All clone libraries were distinct in community composition except for some single phylotypes (or closely related groups) overlap. Thus, clone libraries from two different events that were collected at Col du Dome area within 2 year interval (MB5 and MB-SD) were different in community composition except one of the abundant phylotype from MB-SD library (Geodermatophilus sp.) which was shared (98% sequence similarity) with single representative from MB-5 library. These bacteria are pigmented and radiation-resistant, so it could be an indicator of desert origin for our sequences. For MB5 library two

Detection of saharan mineral dust aerosol transport over brazilian northeast through a depolarization lidar

NASA Astrophysics Data System (ADS)

Guedes, Anderson G.; Landulfo, Eduardo; Montilla-Rosero, Elena; Lopes, Fábio J. S.; Hoelzemann, Judith J.; Fernandez, José Henrique; Silva, Marcos P. A.; Santos, Renata S. S.; Guerrero-Rascado, Juan L.; Alados-Arboledas, Lucas

2018-04-01

In this study we present results of linear volume depolarization ratio profiles obtained by a depolarization lidar in operation in Natal, Brazil. The DUSTER system has 4 channels, namely: 1064, 532 s/p and 355 nm. This system is calibrated with a half-wave plate using the Δ90° methodology. The data obtained from this system is correlated with AERONET sunphotometer data, and, when available, CALIPSO satellite data. In addition a trajectory model (HYSPLIT) is used to calculate backward trajectories to assess the origin of the dust polluted air parcels. The objective is to create a transport database of Saharan dust.

The UK particulate matter air pollution episode of March-April 2014: more than Saharan dust

NASA Astrophysics Data System (ADS)

Vieno, M.; Heal, M. R.; Twigg, M. M.; MacKenzie, I. A.; Braban, C. F.; Lingard, J. J. N.; Ritchie, S.; Beck, R. C.; Móring, A.; Ots, R.; Di Marco, C. F.; Nemitz, E.; Sutton, M. A.; Reis, S.

2016-04-01

A period of elevated surface concentrations of airborne particulate matter (PM) in the UK in spring 2014 was widely associated in the UK media with a Saharan dust plume. This might have led to over-emphasis on a natural phenomenon and consequently to a missed opportunity to inform the public and provide robust evidence for policy-makers about the observed characteristics and causes of this pollution event. In this work, the EMEP4UK regional atmospheric chemistry transport model (ACTM) was used in conjunction with speciated PM measurements to investigate the sources and long-range transport (including vertical) processes contributing to the chemical components of the elevated surface PM. It is shown that the elevated PM during this period was mainly driven by ammonium nitrate, much of which was derived from emissions outside the UK. In the early part of the episode, Saharan dust remained aloft above the UK; we show that a significant contribution of Saharan dust at surface level was restricted only to the latter part of the elevated PM period and to a relatively small geographic area in the southern part of the UK. The analyses presented in this paper illustrate the capability of advanced ACTMs, corroborated with chemically-speciated measurements, to identify the underlying causes of complex PM air pollution episodes. Specifically, the analyses highlight the substantial contribution of secondary inorganic ammonium nitrate PM, with agricultural ammonia emissions in continental Europe presenting a major driver. The findings suggest that more emphasis on reducing emissions in Europe would have marked benefits in reducing episodic PM2.5 concentrations in the UK.

Understanding the impact of saharan dust aerosols on tropical cyclones

NASA Astrophysics Data System (ADS)

Naeger, Aaron

Genesis of Tropical Cyclones (TCs) in the main development region for Atlantic hurricanes is tied to convection initiated by African easterly waves (AEWs) during Northern hemisphere summer and fall seasons. The main development region is also impacted by dust aerosols transported from the Sahara. It has been hypothesized that dust aerosols can modulate the development of TCs through aerosol-radiation and aerosol-cloud interaction processes. In this study, we investigate the impact of dust aerosols on TC development using the Weather Research and Forecasting model coupled with chemistry (WRF-Chem). We first develop a technique to constrain the WRF-Chem model with a realistic three-dimensional spatial distribution of dust aerosols. The horizontal distribution of dust is specified using the Moderate Resolution Imaging Spectroradiometer (MODIS) derived aerosol products and output from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model. The vertical distribution of dust is constrained using the Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). We validate our technique through in situ aircraft measurements where both showed aerosol number concentrations from 20-30 cm-3 in the atmosphere for Saharan dust moving over the eastern Atlantic Ocean. Then, we use the satellite data constraint technique to nudge the WRF-Chem aerosol fields throughout the simulation of TC Florence developing over the eastern Atlantic Ocean during September 2006. Three different experiments are conducted where the aerosol-radiation and aerosol-cloud interaction processes are either activated or deactivated in the model while all other model options are identical between the experiments. By comparing the model experiment results, the impact of the aerosol interaction processes on TC development can be understood. The results indicate that dust aerosols can delay or prevent the development of a TC as the minimum sea level pressure of TC Florence was 13 h

Role of clay minerals in the formation of atmospheric aggregates of Saharan dust

NASA Astrophysics Data System (ADS)

Cuadros, Javier; Diaz-Hernandez, José L.; Sanchez-Navas, Antonio; Garcia-Casco, Antonio

2015-11-01

Saharan dust can travel long distances in different directions across the Atlantic and Europe, sometimes in episodes of high dust concentration. In recent years it has been discovered that Saharan dust aerosols can aggregate into large, approximately spherical particles of up to 100 μm generated within raindrops that then evaporate, so that the aggregate deposition takes place most times in dry conditions. These aerosol aggregates are an interesting phenomenon resulting from the interaction of mineral aerosols and atmospheric conditions. They have been termed "iberulites" due to their discovery and description from aerosol deposits in the Iberian Peninsula. Here, these aggregates are further investigated, in particular the role of the clay minerals in the aggregation process of aerosol particles. Iberulites, and common aerosol particles for reference, were studied from the following periods or single dust events and locations: June 1998 in Tenerife, Canary Islands; June 2001 to August 2002, Granada, Spain; 13-20 August 2012, Granada; and 1-6 June 2014, Granada. Their mineralogy, chemistry and texture were analysed using X-ray diffraction, electron microprobe analysis, SEM and TEM. The mineral composition and structure of the iberulites consists of quartz, carbonate and feldspar grains surrounded by a matrix of clay minerals (illite, smectite and kaolinite) that also surrounds the entire aggregate. Minor phases, also distributed homogenously within the iberulites, are sulfates and Fe oxides. Clays are apparently more abundant in the iberulites than in the total aerosol deposit, suggesting that iberulite formation concentrates clays. Details of the structure and composition of iberulites differ from descriptions of previous samples, which indicates dependence on dust sources and atmospheric conditions, possibly including anthropic activity. Iberulites are formed by coalescence of aerosol mineral particles captured by precursor water droplets. The concentration of

Impact of Saharan dust on North Atlantic marine stratocumulus clouds: importance of the semidirect effect

NASA Astrophysics Data System (ADS)

Amiri-Farahani, Anahita; Allen, Robert J.; Neubauer, David; Lohmann, Ulrike

2017-05-01

One component of aerosol-cloud interactions (ACI) involves dust and marine stratocumulus clouds (MSc). Few observational studies have focused on dust-MSc interactions, and thus this effect remains poorly quantified. We use observations from multiple sensors in the NASA A-Train satellite constellation from 2004 to 2012 to obtain estimates of the aerosol-cloud radiative effect, including its uncertainty, of dust aerosol influencing Atlantic MSc off the coast of northern Africa between 45° W and 15° E and between 0 and 35° N. To calculate the aerosol-cloud radiative effect, we use two methods following Quaas et al. (2008) (Method 1) and Chen et al. (2014) (Method 2). These two methods yield similar results of -1.5 ± 1.4 and -1.5 ± 1.6 W m-2, respectively, for the annual mean aerosol-cloud radiative effect. Thus, Saharan dust modifies MSc in a way that acts to cool the planet. There is a strong seasonal variation, with the aerosol-cloud radiative effect switching from significantly negative during the boreal summer to weakly positive during boreal winter. Method 1 (Method 2) yields -3.8 ± 2.5 (-4.3 ± 4.1) during summer and 1 ± 2.9 (0.6 ± 1) W m-2 during winter. In Method 1, the aerosol-cloud radiative effect can be decomposed into two terms, one representing the first aerosol indirect effect and the second representing the combination of the second aerosol indirect effect and the semidirect effect (i.e., changes in liquid water path and cloud fraction in response to changes in absorbing aerosols and local heating). The first aerosol indirect effect is relatively small, varying from -0.7 ± 0.6 in summer to 0.1 ± 0.5 W m-2 in winter. The second term, however, dominates the overall radiative effect, varying from -3.2 ± 2.5 in summer to 0.9 ± 2.9 W m-2 during winter. Studies show that the semidirect effect can result in a negative (i.e., absorbing aerosol lies above low clouds like MSc) or positive (i.e., absorbing aerosol lies within low clouds) aerosol

Using operational active remote sensing devices to detect Saharan dust advections and evaluate their contribution to the PM10 levels: The EU LIFE+ "DIAPASON" project

NASA Astrophysics Data System (ADS)

Gobbi, Gian Paolo; Wille, Holger; Sozzi, Roberto; Barnaba, Francesca; Costabile, Francesca; Angelini, Federico; Frey, Steffen; Bolignano, Andrea; Morelli, Matteo

2013-04-01

The contribution of Saharan-dust advections to both daily and annual PM average mass concentrations can be significant all over Southern Europe. The Directive 2008/50/EC allows subtraction of PM10 exceedances caused by natural contributions from the statistic used to determine air-quality levels in Europe. To this purpose, the Commission Staff Working Paper 6771/11 (EC, 2011) provides specific Guidelines on methods to quantify and subtract the contribution of these sources in the framework of the Air Quality Directive. For Saharan dust, the EC methodology is largely based on a thorough analysis performed over the Iberian Peninsula (Escudero et al, 2007), although revision of the current methodology is in progress. In line with the EC Guidelines, the DIAPASON project ("Desert-dust Impact on Air quality through model-Predictions and Advanced Sensors ObservatioNs"), funded under the EC LIFE+ program, has been formulated to provide a robust, user-oriented, and demonstrated method to assess the presence of desert dust and evaluate its contribution to PM10 levels at the monitoring sites. To this end, in addition to satellite-based data and model forecasts already included in the EC Guidelines, DIAPASON will take advantage, in both the Project implementation and demonstration phase, of innovative and affordable technologies (partly prototyped within the project itself), namely operational Polarization Lidar-Ceilometers (PLC) capable of detecting and profiling dust clouds from the ground up to 10 km altitude. The PLC prototypes have been already finalized during the initial phase of the Project. Three of them will be networked in relevant air quality monitoring stations located in the Rome metropolitan area (Italy) during the DIAPASON observational phase (one-year long field campaign) starting in March 2013. The Rome region was chosen as the DIAPASON pilot scale area since highly impacted by urban pollution and frequently affected by Saharan dust transport events. In fact

Single particle chemical composition and shape of fresh and aged Saharan dust in Morocco and at Cape Verde Islands during SAMUM I and II

NASA Astrophysics Data System (ADS)

Kandler, K.; Lieke, K.; Schütz, L.; Deutscher, C.; Ebert, M.; Jaenicke, R.; Müller-Ebert, D.; Weinbruch, S.

2009-04-01

The Saharan Mineral Dust Experiment (SAMUM) is focussed to the understanding of the radiative effects of mineral dust. During the SAMUM 2006 field campaign at Tinfou, southern Morocco, chemical and mineralogical properties of fresh desert aerosols were measured. The winter campaign of Saharan Mineral Dust Experiment II was based in Praia, Island of Santiago, Cape Verde. This second field campaign was dedicated to the investigation of transported Saharan Mineral Dust. Aerosol particles between 100 nm and 500 μm (Morocco) respectively 50 μm (Cape Verde) in diameter were collected by nozzle and body impactors and in a sedimentation trap. The particles were investigated by electron microscopic single particle analysis and attached energy-dispersive X-ray analysis. Chemical properties as well as size and shape for each particle were recorded. Three size regimes are identified in the aerosol at Tinfou: Smaller than 500 nm in diameter, the aerosol consists of sulfates and mineral dust. Larger than 500 nm up to 50 μm, mineral dust dominates, consisting mainly of silicates, and - to a lesser extent - carbonates and quartz. Larger than 50 μm, approximately half of the particles consist of quartz. Time series of the elemental composition show a moderate temporal variability of the major compounds. Calcium-dominated particles are enhanced during advection from a prominent dust source in Northern Africa (Chott El Djerid and surroundings). At Praia, the boundary layer aerosol consists of a superposition of mineral dust, marine aerosol and ammonium sulfate, soot, and other sulfates as well as mixtures thereof. During low-dust periods, the aerosol is dominated by sea salt. During dust events, mineral dust takes over the majority of the particle mass up to 90 %. Particles smaller 500 nm in diameter always show a significant abundance of ammonium sulfate. The particle aspect ratio was measured for all analyzed particles. Its size dependence reflects that of the chemical

Impacts of Saharan Dust on the Atmospheric Radiative Balance in the Caribbean during SALTRACE 2013

NASA Astrophysics Data System (ADS)

Sauer, D. N.; Weinzierl, B.; Gross, S.; Minikin, A.; Freudenthaler, V.; Gasteiger, J.; Mayer, B. C.

2013-12-01

Direct and indirect aerosol radiative effects represent one of the largest uncertainties in the modeling of the climate system. To better quantify the effects of aerosols on the Earth's radiative balance and understand important physical effects on small scales such as the influence of aerosols on clouds, detailed measurements of aerosol properties are needed to build a globally representative data set. Mineral dust is among the most abundant aerosols and the Sahara Desert constitutes its largest source. During frequent dust outbreaks thick elevated aerosol layers are formed and transported over large distances -often across the Atlantic Ocean into the Caribbean. The Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in June/July 2013 continues the SAMUM field experiments conducted in 2006 and 2008. It aims to study the long-range transport of Saharan mineral dust, the properties of aged mineral dust aerosol, and its impact on radiative quantities and cloud processes. The experiment led to an extensive data set on dust layers from Senegal to the Caribbean using airborne in-situ and remote sensing measurements, complemented with ground-based remote sensing and in-situ measurements on sites in Barbados and Puerto Rico as well as satellite remote sensing data. The airborne data were obtained with an extensive aerosol payload aboard the DLR-operated Falcon 20E research aircraft. The measurements cover the entire size range of atmospheric aerosol with a combination of cabin-operated and wing-mounted instruments. In addition, particle properties such as absorption coefficients and volatility are measured. A nadir-looking 2-μm Doppler-lidar system aboard the aircraft was used for wind measurements and served as a path finder for the selection of representative aerosol in-situ levels. In the Caribbean the dust usually arrives in several layers with distinct properties: the mostly undisturbed pure dust layer in altitudes up to 4-5 km

Environmental factors controlling the seasonal variability in particle size distribution of modern Saharan dust deposited off Cape Blanc

NASA Astrophysics Data System (ADS)

Friese, Carmen A.; van der Does, Michèlle; Merkel, Ute; Iversen, Morten H.; Fischer, Gerhard; Stuut, Jan-Berend W.

2016-09-01

The particle sizes of Saharan dust in marine sediment core records have been used frequently as a proxy for trade-wind speed. However, there are still large uncertainties with respect to the seasonality of the particle sizes of deposited Saharan dust off northwestern Africa and the factors influencing this seasonality. We investigated a three-year time-series of grain-size data from two sediment-trap moorings off Cape Blanc, Mauritania and compared them to observed wind-speed and precipitation as well as satellite images. Our results indicate a clear seasonality in the grain-size distributions: during summer the modal grain sizes were generally larger and the sorting was generally less pronounced compared to the winter season. Gravitational settling was the major deposition process during winter. We conclude that the following two mechanisms control the modal grain size of the collected dust during summer: (1) wet deposition causes increased deposition fluxes resulting in coarser modal grain sizes and (2) the development of cold fronts favors the emission and transport of coarse particles off Cape Blanc. Individual dust-storm events throughout the year could be recognized in the traps as anomalously coarse-grained samples. During winter and spring, intense cyclonic dust-storm events in the dust-source region explained the enhanced emission and transport of a larger component of coarse particles off Cape Blanc. The outcome of our study provides important implications for climate modellers and paleo-climatologists.

The formation and dust lifting processes associated with a large Saharan meso-scale convective system (MCS)

NASA Astrophysics Data System (ADS)

Roberts, Alex; Knippertz, Peter

2013-04-01

This work focusses on the meteorology that produced a large Mesoscale Convective System (MCS) and the dynamics of its associated cold pool. The case occurred between 8th-10th June 2010 and was initiated over the Hoggar and Aïr Mountains in southern Algeria and northern Niger respectively. The dust plume created covered parts of Algeria, Mali and Mauritania and was later deformed the by background flow and transported over the Atlantic and Mediterranean. This study is based on: standard surface observations (where available), ERA-Interim reanalysis, Meteosat imagery, MODIS imagery, Tropical Rainfall Measuring Mission (TRMM) rainfall estimates, Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), CloudSat and a high resolution (3.3km) limited area simulation using the Weather Research and Forecasting (WRF) model. A variety of different processes appear to be important for the generation of this MCS and the spreading of the associated dusty cold pool. These include: the presence of a trough on the subtropical jet, the production of a tropical cloud plume, disruption to the structure of the Saharan heat low and the production of a Libyan high. These features produced moistening of the boundary layer and a convergence zone over the region of MCS initiation. Another important factor appears to have been the production of a smaller MCS and cold pool on the evening of the 7th June. This elevated low-level moisture and encouraged convective initiation the following day. Once triggered on the 8th June some cells grew and merged into a single large system that propagated south westward and produced a large cold pool that emanated from its northern edge. The cells on the northern edge of the system over the Hoggar grew and collapsed producing a haboob that spread over a large area. Cells further south continued to develop into the MCS and actively produce a cold pool over the system's lifetime. This undercut the dusty air from the earlier cold pool and

Extinction-to-Backscatter Ratios of Saharan Dust Layers Derived from In-Situ Measurements and CALIPSO Overflights During NAMMA

NASA Technical Reports Server (NTRS)

Omar, Ali H.; Liu, Zhaoyan; Vaughan, Mark A.; Hu, Yongxiang; Ismail, Syed; Powell, Kathleen A.; Winker, David M.; Trepte, Charles R.; Anderson, Bruce E.

2010-01-01

We determine the aerosol extinction-to-backscatter (Sa) ratios of dust using airborne in-situ measurements of microphysical properties, and CALIPSO observations during the NASA African Monsoon Multidisciplinary Analyses (NAMMA). The NAMMA field experiment was conducted from Sal, Cape Verde during Aug-Sept 2006. Using CALIPSO measurements of the attenuated backscatter of lofted Saharan dust layers, we apply the transmittance technique to estimate dust Sa ratios at 532 nm and a 2-color method to determine the corresponding 1064 nm Sa. Using this method, we found dust Sa ratios of 39.8 plus or minus 1.4 sr and 51.8 plus or minus 3.6 sr at 532 nm and 1064 nm, respectively. Secondly, Sa ratios at both wavelengths is independently calculated using size distributions measured aboard the NASA DC-8 and estimates of Saharan dust complex refractive indices applied in a T-Matrix scheme. We found Sa ratios of 39.1 plus or minus 3.5 sr and 50.0 plus or minus 4 sr at 532 nm and 1064 nm, respectively, using the T-Matrix calculations applied to measured size spectra. Finally, in situ measurements of the total scattering (550 nm) and absorption coefficients (532 nm) are used to generate an extinction profile that is used to constrain the CALIPSO 532 nm extinction profile.

The transition of North Atlantic dust deposition and Saharan landscape during the Holocene

NASA Astrophysics Data System (ADS)

Egerer, S.; Claussen, M.; Stanelle, T.; Reick, C. H.

2017-12-01

The sudden increase in North Atlantic dust deposition about 5 ka BP indicated by sediment records along the West African margin has been associated with an abrupt end of the African Humid Period (AHP). We perform several time slice simulations from 8 ka BP until the pre-industrial era to explore changes in the Holocene dust cycle. To do so, we use the coupled aerosol-climate model ECHAM6-HAM2 including interactive vegetation and dust, whereas ocean conditions and lakes are prescribed. The interactive coupling of vegetation, dust and atmosphere allows to set the dynamics of North Atlantic dust deposition in context to Holocene climate and landscape change in North Africa.In agreement with marine sediment records, we find an abrupt increase in simulated dust deposition at the location of the core sites roughly between 6 and 4 ka BP. Accordingly, dust emission in the North-west Sahara increases rapidly indicating that dust was transported by the same wind systems throughout the Holocene. The sudden increase in dust emission in the North-west Sahara is partly a consequence of a fast decline of vegetation cover from 22°N to 18°N due to vegetation-climate feedbacks and the rapid replacement of shrubs by grasses. Additionally, the prescribed strong but gradual reduction of lake surface area enforces accelerated dust release as former areas covered by lakes turn into highly productive dust sources. Changes in the Saharan landscape and dust emission south of 18°N and in the eastern Sahara as well as changes in atmospheric circulation play a minor role in driving the dynamics of North Atlantic dust deposition at the specific core sites. Our study emphasizes spatial and temporal differences in the transition of North African landscape implying that implications from local data records to large scales have to be treated with caution.

April 2008 Saharan dust event: Its contribution to PM10 concentrations over the Anatolian Peninsula and relation with synoptic conditions.

PubMed

Kabatas, B; Pierce, R B; Unal, A; Rogal, M J; Lenzen, A

2018-08-15

An online-coupled regional Weather Research and Forecasting model with chemistry (WRF-Chem) is utilized incorporating 0.1°×0.1° spatial resolution HTAP (Hemispheric Transport of Air Pollution) anthropogenic emissions to investigate the spatial and temporal distribution of a Saharan dust outbreak, which contributed to high levels (>50μg/m 3 ) of daily PM 10 concentrations over Turkey in April 2008. Aerosol optical depth and cloud optical thickness retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on board of Aqua satellite are used to better analyze the synoptic conditions that generated the dust outbreak in April 2008. A "Sharav" low pressure system, which transports the dust from Saharan source region over Turkey along the cold front, tends to move faster in WRF-Chem simulations than observed. This causes the predicted dust event to arrive earlier than observed leading to an overestimation of surface PM 10 concentrations in WRF-Chem simulation at the beginning of the event. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Dust sources and atmospheric circulation in concert controlling Saharan dust emission and transport towards the Western Mediterranean Basin

NASA Astrophysics Data System (ADS)

Schepanski, Kerstin; Mallet, Marc; Heinold, Bernd; Ulrich, Max

2017-04-01

Dust transported from north African source regions towards Europe is a ubiquitous phenomenon in the Mediterranean region, a geographic region that is in part densely populated. Besides its impacts on the atmospheric radiation budget, dust suspended in the atmosphere results in reduced air quality, which is generally sensed as a reduction in quality of life. Furthermore, the exposure to dust aerosols enhances the prevalence of respiratory diseases, which reduces the general human wellbeing, and ultimately results in an increased loss of working hours due to illness and hospitalization rates. Characteristics of the atmospheric dust life cycle that determine dust transport will be presented with focus on the ChArMEx special observation period in June and July 2013 using the atmosphere-dust model COSMO-MUSCAT (COSMO: Consortium for Small-scale MOdeling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model). Modes of atmospheric circulation were identified from empirical orthogonal function (EOF) analysis of the geopotential height at 850 hPa for summer 2013 and compared to EOFs calculated from 1979-2015 ERA-Interim reanalysis. Generally, two different phases were identified. They are related to the eastward propagation of the subtropical ridge into the Mediterranean basin, the position of the Saharan heat low, and the predominant Iberian heat low. The relation of these centres of action illustrates a dipole pattern for enhanced (reduced) dust emission fluxes, stronger (weaker) meridional dust transport, and consequent increase (decrease) atmospheric dust concentrations and deposition fluxes. In concert, the results from this study aim at illustrating the relevance of knowing the dust source locations in concert with the atmospheric circulation. Ultimately, this study addresses the question of what is finally transported towards the Mediterranean basin and Europe from which source regions - and fostered by which atmospheric circulation pattern. Outcomes from this study

The evolution of Saharan dust input in Lanzarote (Canary Islands): Lower Holocene triggering by human activity in the northwest Sahara?

NASA Astrophysics Data System (ADS)

von Suchodoletz, H.; Oberhänsli, H.; Faust, D.; Zöller, L.; Hambach, U.; Fuchs, M.

2009-04-01

A Holocene increase of Saharan dust input to the area of the Canary islands is accompanied by a strong coarsening of this material during the Early Holocene as recorded in loess-like sediments deposited on Lanzarote. Whereas natural causes can be ruled out for the coarsening that is exceptional during the period of the last 180 ka, it is assumed that anthropogenic activity strongly mobilized dust in an area on the pathway of dust prior to its arrival in Lanzarote comprising parts of Western Sahara and northern Mauritania. Although scarce archaeological data from the coastal area of that region do not point to strong anthropogenic activity during the Early Holocene yet, a high density of unexplored archaeological remains reported from the coastal hinterlands does not exclude this hypothesis. Thus, the results of this study highlight the need of further archaeological investigations in that Saharan region.

Three-dimensional evolution of Saharan dust transport towards Europe based on a 9-year EARLINET-optimized CALIPSO dataset

NASA Astrophysics Data System (ADS)

Marinou, Eleni; Amiridis, Vassilis; Binietoglou, Ioannis; Tsikerdekis, Athanasios; Solomos, Stavros; Proestakis, Emannouil; Konsta, Dimitra; Papagiannopoulos, Nikolaos; Tsekeri, Alexandra; Vlastou, Georgia; Zanis, Prodromos; Balis, Dimitrios; Wandinger, Ulla; Ansmann, Albert

2017-05-01

In this study we use a new dust product developed using CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) observations and EARLINET (European Aerosol Research Lidar Network) measurements and methods to provide a 3-D multiyear analysis on the evolution of Saharan dust over North Africa and Europe. The product uses a CALIPSO L2 backscatter product corrected with a depolarization-based method to separate pure dust in external aerosol mixtures and a Saharan dust lidar ratio (LR) based on long-term EARLINET measurements to calculate the dust extinction profiles. The methodology is applied on a 9-year CALIPSO dataset (2007-2015) and the results are analyzed here to reveal for the first time the 3-D dust evolution and the seasonal patterns of dust over its transportation paths from the Sahara towards the Mediterranean and Continental Europe. During spring, the spatial distribution of dust shows a uniform pattern over the Sahara desert. The dust transport over the Mediterranean Sea results in mean dust optical depth (DOD) values up to 0.1. During summer, the dust activity is mostly shifted to the western part of the desert where mean DOD near the source is up to 0.6. Elevated dust plumes with mean extinction values between 10 and 75 Mm-1 are observed throughout the year at various heights between 2 and 6 km, extending up to latitudes of 40° N. Dust advection is identified even at latitudes of about 60° N, but this is due to rare events of episodic nature. Dust plumes of high DOD are also observed above the Balkans during the winter period and above northwest Europe during autumn at heights between 2 and 4 km, reaching mean extinction values up to 50 Mm-1. The dataset is considered unique with respect to its potential applications, including the evaluation of dust transport models and the estimation of cloud condensation nuclei (CCN) and ice nuclei (IN) concentration profiles. Finally, the product can be used to study dust dynamics during

Saharan Dust Event Impacts on Cloud Formation and Radiation over Western Europe

NASA Technical Reports Server (NTRS)

Bangert, M.; Nenes, A.; Vogel, B.; Vogel, H.; Barahona, D.; Karydis, V. A.; Kumar, P.; Kottmeier, C.; Blahak, U.

2013-01-01

We investigated the impact of mineral dust particles on clouds, radiation and atmospheric state during a strong Saharan dust event over Europe in May 2008, applying a comprehensive online-coupled regional model framework that explicitly treats particle-microphysics and chemical composition. Sophisticated parameterizations for aerosol activation and ice nucleation, together with two-moment cloud microphysics are used to calculate the interaction of the different particles with clouds depending on their physical and chemical properties. The impact of dust on cloud droplet number concentration was found to be low, with just a slight increase in cloud droplet number concentration for both uncoated and coated dust. For temperatures lower than the level of homogeneous freezing, no significant impact of dust on the number and mass concentration of ice crystals was found, though the concentration of frozen dust particles reached up to 100 l-1 during the ice nucleation events. Mineral dust particles were found to have the largest impact on clouds in a temperature range between freezing level and the level of homogeneous freezing, where they determined the number concentration of ice crystals due to efficient heterogeneous freezing of the dust particles and modified the glaciation of mixed phase clouds. Our simulations show that during the dust events, ice crystals concentrations were increased twofold in this temperature range (compared to if dust interactions are neglected). This had a significant impact on the cloud optical properties, causing a reduction in the incoming short-wave radiation at the surface up to -75Wm-2. Including the direct interaction of dust with radiation caused an additional reduction in the incoming short-wave radiation by 40 to 80Wm-2, and the incoming long-wave radiation at the surface was increased significantly in the order of +10Wm-2. The strong radiative forcings associated with dust caused a reduction in surface temperature in the order of -0

Long-range-transported Saharan dust in the Caribbean - an electron microscopy perspective of aerosol composition and modification

NASA Astrophysics Data System (ADS)

Kandler, Konrad; Hartmann, Markus; Ebert, Martin; Weinbruch, Stephan; Weinzierl, Bernadett; Walser, Adrian; Sauer, Daniel; Wadinga Fomba, Khanneh

2015-04-01

From June to July in 2013, the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) was performed in the Caribbean. Airborne aerosol sampling was performed onboard the DLR Falcon aircraft in altitudes between 300 m and 5500 m. Ground-based samples were collected at Ragged Point (Barbados, 13.165 °N, 59.432 °W) and at the Cape Verde Atmospheric Observatory (Sao Vicente, 16.864 °N, 24.868 °W). Different types of impactors and sedimentation samplers were used to collect particles between 0.1 µm and 4 µm (airborne) and between 0.1 µm and 100 µm (ground-based). Particles were analyzed by scanning electron microscopy with attached energy-dispersive X-ray analysis, yielding information on particle size, particle shape and chemical composition for elements heavier than nitrogen. A particle size correction was applied to the chemical data to yield better quantification. A total of approximately 100,000 particles were analyzed. For particles larger than 0.7 µm, the aerosol in the Caribbean during the campaign was a mixture of mineral dust, sea-salt at different aging states, and sulfate. Inside the Saharan dust plume - outside the marine boundary layer (MBL) - the aerosol is absolutely dominated by mineral dust. Inside the upper MBL, sea-salt exists as minor component in the aerosol for particles smaller than 2 µm in diameter, larger ones are practically dust only. When crossing the Soufriere Hills volcano plume with the aircraft, an extremely high abundance of small sulfate particles could be observed. At Ragged Point, in contrast to the airborne measurements, aerosol is frequently dominated by sea-salt particles. Dust relative abundance at Ragged Point has a maximum between 5 µm and 10 µm particles diameter; at larger sizes, sea-salt again prevails due to the sea-spray influence. A significant number of dust particles larger than 20 µm was encountered. The dust component in the Caribbean - airborne as well as ground

Saharan Dust Deposition May Affect Phytoplankton Growth in the Mediterranean Sea at Ecological Time Scales

PubMed Central

Gallisai, Rachele; Peters, Francesc; Volpe, Gianluca; Basart, Sara; Baldasano, José Maria

2014-01-01

The surface waters of the Mediterranean Sea are extremely poor in the nutrients necessary for plankton growth. At the same time, the Mediterranean Sea borders with the largest and most active desert areas in the world and the atmosphere over the basin is subject to frequent injections of mineral dust particles. We describe statistical correlations between dust deposition over the Mediterranean Sea and surface chlorophyll concentrations at ecological time scales. Aerosol deposition of Saharan origin may explain 1 to 10% (average 5%) of seasonally detrended chlorophyll variability in the low nutrient-low chlorophyll Mediterranean. Most of the statistically significant correlations are positive with main effects in spring over the Eastern and Central Mediterranean, conforming to a view of dust events fueling needed nutrients to the planktonic community. Some areas show negative effects of dust deposition on chlorophyll, coinciding with regions under a large influence of aerosols from European origin. The influence of dust deposition on chlorophyll dynamics may become larger in future scenarios of increased aridity and shallowing of the mixed layer. PMID:25333783

A long Saharan dust event over the western Mediterranean: Lidar, Sun photometer observations, and regional dust modeling

NASA Astrophysics Data System (ADS)

PéRez, C.; Nickovic, S.; Baldasano, J. M.; Sicard, M.; Rocadenbosch, F.; Cachorro, V. E.

2006-08-01

A long Saharan dust event affected the western Mediterranean in the period 12-28 June 2002. Dust was present mainly between 1- and 5-km height affecting most parts of the Iberian Peninsula and reaching western/central Europe. Intensive backscatter lidar observations over Barcelona (Spain) and Sun photometer data from two stations (El Arenosillo, Spain, and Avignon, France) are used to evaluate different configurations the Dust Regional Atmospheric Modeling (DREAM) system. DREAM currently operates dust forecasts over the Mediterranean region (http://www.bsc.es/projects/earthscience/DREAM/) considering four particle size bins while only the first two are relevant for long-range transport analysis since their life time is larger than 12 hours. A more detailed bin method is implemented, and two different dust distributions at sources are compared to the operational version. Evaluations are performed at two wavelengths (532 and 1064 nm). The dust horizontal and vertical structure simulated by DREAM shows very good qualitative agreement when compared to SeaWIFS satellite images and lidar height-time displays over Barcelona. When evaluating the modeled aerosol optical depth (AOD) against Sun photometer data, significant improvements are achieved with the use of the new detailed bin method. In general, the model underpredicts the AOD for increasing Ångström exponents because of the influence of anthropogenic pollution in the boundary layer. In fact, the modeled AOD is highly anticorrelated with the observed Ångström exponents. Avignon shows higher influence of small anthropogenic aerosols which explains the better results of the model at the wavelength of 1064 nm over this location. The uncertainties of backscatter lidar inversions (20-30%) are in the same order of magnitude as the differences between the model experiments. Better model results are obtained when comparing to lidar because most of the anthropogenic effect is removed.

Casting Light and Shadows on a Saharan Dust Storm

NASA Technical Reports Server (NTRS)

2003-01-01

On March 2, 2003, near-surface winds carried a large amount of Saharan dust aloft and transported the material westward over the Atlantic Ocean. These observations from the Multi-angle Imaging SpectroRadiometer (MISR) aboard NASA's Terra satellite depict an area near the Cape Verde Islands (situated about 700 kilometers off of Africa's western coast) and provide images of the dust plume along with measurements of its height and motion. Tracking the three-dimensional extent and motion of air masses containing dust or other types of aerosols provides data that can be used to verify and improve computer simulations of particulate transport over large distances, with application to enhancing our understanding of the effects of such particles on meteorology, ocean biological productivity, and human health.

MISR images the Earth by measuring the spatial patterns of reflected sunlight. In the upper panel of the still image pair, the observations are displayed as a natural-color snapshot from MISR's vertical-viewing (nadir) camera. High-altitude cirrus clouds cast shadows on the underlying ocean and dust layer, which are visible in shades of blue and tan, respectively. In the lower panel, heights derived from automated stereoscopic processing of MISR's multi-angle imagery show the cirrus clouds (yellow areas) to be situated about 12 kilometers above sea level. The distinctive spatial patterns of these clouds provide the necessary contrast to enable automated feature matching between images acquired at different view angles. For most of the dust layer, which is spatially much more homogeneous, the stereoscopic approach was unable to retrieve elevation data. However, the edges of shadows cast by the cirrus clouds onto the dust (indicated by blue and cyan pixels) provide sufficient spatial contrast for a retrieval of the dust layer's height, and indicate that the top of layer is only about 2.5 kilometers above sea level.

Motion of the dust and clouds is directly

Saharan dust - A carrier of persistent organic pollutants, metals and microbes to the Caribbean?

USGS Publications Warehouse

Garrison, V.H.; Foreman, W.T.; Genualdi, S.; Griffin, Dale W.; Kellogg, C.A.; Majewski, M.S.; Mohammed, A.; Ramsubhag, A.; Shinn, E.A.; Simonich, S.L.; Smith, G.W.

2006-01-01

An international team of scientists from government agencies and universities in the United States, U.S. Virgin Islands (USVI), Trinidad & Tobago, the Republic of Cape Verde, and the Republic of Mali (West Africa) is working together to elucidate the role Saharan dust may play in the degradation of Caribbean ecosystems. The first step has been to identify and quantify the persistent organic pollutants (POPs), trace metals, and viable microorganisms in the atmosphere in dust source areas of West Africa, and in dust episodes at downwind sites in the eastern Atlantic (Cape Verde) and the Caribbean (USVI and Trinidad & Tobago). Preliminary findings show that air samples from Mali contain a greater number of pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) and in higher concentrations than the Caribbean sites. Overall, POP concentrations were similar in USVI and Trinidad samples. Trace metal concentrations were found to be similar to crustal composition with slight enrichment of lead in Mali. To date, hundreds of cultureable micro-organisms have been identified from Mali, Cape Verde, USVI, and Trinidad air samples. The sea fan pathogen, Aspergillus sydowii, has been identified in soil from Mali and in air samples from dust events in the Caribbean. We have shown that air samples from a dust-source region contain orders of magnitude more cultureable micro-organisms per volume than air samples from dust events in the Caribbean, which in turn contain 3-to 4-fold more cultureable microbes than during non-dust conditions.

Could gradual changes in Holocene Saharan landscape have caused the observed abrupt shift in North Atlantic dust deposition?

NASA Astrophysics Data System (ADS)

Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

2017-09-01

The abrupt change in North Atlantic dust deposition found in sediment records has been associated with a rapid large scale transition of Holocene Saharan landscape. We hypothesize that gradual changes in the landscape may have caused this abrupt shift in dust deposition either because of the non-linearity in dust activation or because of the heterogeneous distribution of major dust sources. To test this hypothesis, we investigate the response of North Atlantic dust deposition to a prescribed 1) gradual and spatially homogeneous decrease and 2) gradual southward retreat of North African vegetation and lakes during the Holocene using the aerosol-climate model ECHAM-HAM. In our simulations, we do not find evidence of an abrupt increase in dust deposition as observed in marine sediment records along the Northwest African margin. We conclude that such gradual changes in landscape are not sufficient to explain the observed abrupt changes in dust accumulation in marine sediment records. Instead, our results point to a rapid large-scale retreat of vegetation and lakes in the area of significant dust sources.

Characterization of Saharan dust properties transported towards Europe in the frame of the FENNEC project: a case study

NASA Astrophysics Data System (ADS)

Marnas, F.; Chazette, P.; Flamant, C.; Royer, P.; Sodemman, H.; Derimian, Y.

2012-04-01

In the framework of the FENNEC experiment (6 to 30 June 2011) an effort has been dedicated to characterize Saharan dust plumes transported towards southern Europe. Hence, a multi instrumented field campaign has been conducted. Ground based nitrogen Raman LIDAR (GBNRL) has been deployed in southern Spain close to Marbella, simultaneously with airborne lidar (AL) performing measurements over both the tropical Atlantic Ocean and the western Africa (from 2 to 23 June). The GBNRL was equipped with co-polar and cross-polar channels to perform continuous measurements of the dust aerosols trapped in the troposphere. It was developed by LSCE with the support of the LEOSPHERE Company. The French FALCON 20 research aircraft operated by SAFIRE (Service des Avions Francais Instrumentés pour la Recherche en Environnement) carried the AL Leandre Nouvelle Generation (LNG) as well as a dropsonde releasing system and radiometers. A major, one week long, dust event has been sampled over Spain from 25 June to 1 July with high optical depth (>0.5 at 355nm) and particular depolarization ratios (15 to 25%). Backtrajectory studies suggest that the dust particles observed were from dust uplifts that occurred in Southern Morocco and Northern Mauritania. The event has been also documented 3 days before by the AL flying over Mauritania. AERONET sunphotometer measurements of aerosol properties, along the dust plume transport path appear to be coherent with both the lidar and the backtrajectory analysis. These analysis exhibit a likely major contribution from the Western Sahara sources to the Southern Europe. Such a contribution may impact the visibility and then the airtrafic, modify the tropospheric chemistry, and add nutrients to both the Mediterranean Sea and the continental surfaces. It can also affect the health of European populations. We will present strategy of the experiment and the case study built from measurements performed at the end of June.

Investigating Sensitivity to Saharan Dust in Tropical Cyclone Formation Using Nasa's Adjoint Model

NASA Technical Reports Server (NTRS)

Holdaway, Daniel

2015-01-01

As tropical cyclones develop from easterly waves coming of the coast of Africa they interact with dust from the Sahara desert. There is a long standing debate over whether this dust inhibits or advances the developing storm and how much influence it has. Dust can surround the storm and absorb incoming solar radiation, cooling the air below. As a result an energy source for the system is potentially diminished, inhibiting growth of the storm. Alternatively dust may interact with clouds through micro-physical processes, for example by causing more moisture to condense, potentially increasing the strength. As a result of climate change, concentrations and amount of dust in the atmosphere will likely change. It it is important to properly understand its effect on tropical storm formation. The adjoint of an atmospheric general circulation model provides a very powerful tool for investigating sensitivity to initial conditions. The National Aeronautics and Space Administration (NASA) has recently developed an adjoint version of the Goddard Earth Observing System version 5 (GEOS-5) dynamical core, convection scheme, cloud model and radiation schemes. This is extended so that the interaction between dust and radiation is also accounted for in the adjoint model. This provides a framework for examining the sensitivity to dust in the initial conditions. Specifically the set up allows for an investigation into the extent to which dust affects cyclone strength through absorption of radiation. In this work we investigate the validity of using an adjoint model for examining sensitivity to dust in hurricane formation. We present sensitivity results for a number of systems that developed during the Atlantic hurricane season of 2006. During this period there was a significant outbreak of Saharan dust and it is has been argued that this outbreak was responsible for the relatively calm season. This period was also covered by an extensive observation campaign. It is shown that the

Investigating sensitivity to Saharan dust in tropical cyclone formation using NASA's adjoint model

NASA Astrophysics Data System (ADS)

Holdaway, Daniel

2015-04-01

As tropical cyclones develop from easterly waves coming off the coast of Africa they interact with dust from the Sahara desert. There is a long standing debate over whether this dust inhibits or advances the developing storm and how much influence it has. Dust can surround the storm and absorb incoming solar radiation, cooling the air below. As a result an energy source for the system is potentially diminished, inhibiting growth of the storm. Alternatively dust may interact with clouds through micro-physical processes, for example by causing more moisture to condense, potentially increasing the strength. As a result of climate change, concentrations and amount of dust in the atmosphere will likely change. It it is important to properly understand its effect on tropical storm formation. The adjoint of an atmospheric general circulation model provides a very powerful tool for investigating sensitivity to initial conditions. The National Aeronautics and Space Administration (NASA) has recently developed an adjoint version of the Goddard Earth Observing System version 5 (GEOS-5) dynamical core, convection scheme, cloud model and radiation schemes. This is extended so that the interaction between dust and radiation is also accounted for in the adjoint model. This provides a framework for examining the sensitivity to dust in the initial conditions. Specifically the set up allows for an investigation into the extent to which dust affects cyclone strength through absorption of radiation. In this work we investigate the validity of using an adjoint model for examining sensitivity to dust in hurricane formation. We present sensitivity results for a number of systems that developed during the Atlantic hurricane season of 2006. During this period there was a significant outbreak of Saharan dust and it is has been argued that this outbreak was responsible for the relatively calm season. This period was also covered by an extensive observation campaign. It is shown that the

Influence of Atmospheric Processes on the Solubility and Composition of Iron in Saharan Dust

NASA Astrophysics Data System (ADS)

Ingall, E. D.; Longo, A.; Feng, Y.; Lai, B.; Landing, W. M.; Shelley, R.; Nenes, A.; Mihalopoulos, N.; Violaki, K.

2016-12-01

Iron is a key micronutrient that is vital for all organisms. The supply of bioavailable, soluble iron controls primary productivity in approximately 30% of the world's oceans. The significant contribution of atmospheric aerosols to the bioavailable iron budget in vast ocean regions, underscores the need to understand the controls and transformations of aerosol iron solubility during atmospheric transport. The Sahara Desert contains the largest and most active sources of aerosol dust globally and can be a key source of nutrients to the Mediterranean Sea, much of the North Atlantic Ocean, and even as far as the Gulf of Mexico. Aerosol iron was examined in Saharan dust plumes using a combination of iron near-edge X-ray absorption spectroscopy and wet chemical techniques. Aerosol samples were collected at three sites located in the Mediterranean, the Atlantic, and Bermuda to characterize iron at different atmospheric transport lengths and time scales. Iron(III) oxides were a component of aerosols at all sampling sites and dominated aerosol iron in Mediterranean samples. In Atlantic samples, iron(II & III) sulfate, iron(III) phosphate, and iron(II) silicates were also contributors to aerosol composition. With increased atmospheric transport time, iron(II) sulfates are found to become more abundant, aerosol iron oxidation state became more reduced, and aerosol acidity increased. Atmospheric processing, including acidic reactions and photo-reduction, likely influence the form of iron minerals and the oxidation state in Saharan dust aerosols and contribute to increases in aerosol iron solubility. Overall, these findings suggest that a combination of factors affects aerosol iron solubility during long-distance atmospheric transport and emphasize the need to consider reductive mechanisms as well as proton-induced solubilization of aerosol iron in modeling studies.

Saharan dust, convective lofting, aerosol enhancement zones, and potential impacts on ice nucleation in the tropical upper troposphere

NASA Astrophysics Data System (ADS)

Twohy, C. H.; Anderson, B. E.; Ferrare, R. A.; Sauter, K. E.; L'Ecuyer, T. S.; van den Heever, S. C.; Heymsfield, A. J.; Ismail, S.; Diskin, G. S.

2017-08-01

Dry aerosol size distributions and scattering coefficients were measured on 10 flights in 32 clear-air regions adjacent to tropical storm anvils over the eastern Atlantic Ocean. Aerosol properties in these regions were compared with those from background air in the upper troposphere at least 40 km from clouds. Median values for aerosol scattering coefficient and particle number concentration >0.3 μm diameter were higher at the anvil edges than in background air, showing that convective clouds loft particles from the lower troposphere to the upper troposphere. These differences are statistically significant. The aerosol enhancement zones extended 10-15 km horizontally and 0.25 km vertically below anvil cloud edges but were not due to hygroscopic growth since particles were measured under dry conditions. Number concentrations of particles >0.3 μm diameter were enhanced more for the cases where Saharan dust layers were identified below the clouds with airborne lidar. Median number concentrations in this size range increased from 100 l-1 in background air to 400 l-1 adjacent to cloud edges with dust below, with larger enhancements for stronger storm systems. Integration with satellite cloud frequency data indicates that this transfer of large particles from low to high altitudes by convection has little impact on dust concentrations within the Saharan Air Layer itself. However, it can lead to substantial enhancement in large dust particles and, therefore, heterogeneous ice nuclei in the upper troposphere over the Atlantic. This may induce a cloud/aerosol feedback effect that could impact cloud properties in the region and downwind.

Identification of mineral dust layers in high alpine snow packs

NASA Astrophysics Data System (ADS)

Greilinger, Marion; Kau, Daniela; Schauer, Gerhard; Kasper-Giebl, Anne

2017-04-01

Deserts serve as a major source for aerosols in the atmosphere with mineral dust as a main contributor to primary aerosol mass. Especially the Sahara, the largest desert in the world, contributes roughly half of the primarily emitted aerosol mass found in the atmosphere [1]. The eroded Saharan dust is episodically transported over thousands of kilometers with synoptic wind patterns towards Europe [2] and reaches Austria about 20 to 30 days per year. Once the Saharan dust is removed from the atmosphere via dry or wet deposition processes, the chemical composition of the precipitation or the affected environment is significantly changed. Saharan dust serves on the one hand as high ionic input leading to an increase of ionic species such as calcium, magnesium or sulfate. On the other hand Saharan dust provides a high alkaline input neutralizing acidic components and causing the pH to increase [3]. Based on these changes in the ion composition, the pH and cross plots of the ion and conductivity balance [4] we tried to develop a method to identify Saharan dust layers in high alpine snow packs. We investigated seasonal snow packs of two high alpine sampling sites situated on the surrounding glaciers of the meteorological Sonnblick observatory serving as a global GAW (Global Atmospheric Watch) station located in the National Park Hohe Tauern in the Austrian Alps. Samples with 10 cm resolution representing the whole winter accumulation period were taken just prior to the start of snow melt at the end of April 2016. In both snow packs two layers with clearly different chemical behavior were observed. In comparison with the aerosol data from the Sonnblick observatory, these layers could be clearly identified as Saharan dust layers. Identified Saharan dust layers in the snow pack allow calculations of the ecological impact of deposited ions, with and without Saharan dust, during snow melt. Furthermore the chemical characteristics for the identification of Saharan dust layers

Intensity of African Humid Periods Estimated from Saharan Dust Fluxes.

PubMed

Ehrmann, Werner; Schmiedl, Gerhard; Beuscher, Sarah; Krüger, Stefan

2017-01-01

North Africa experienced dramatic changes in hydrology and vegetation during the late Quaternary driven by insolation-induced shifts of the tropical rain belt and further modulated by millennial-scale droughts and vegetation-climate feedbacks. While most past proxy and modelling studies concentrated on the temporal and spatial dynamics of the last African humid period, little is known about the intensities and characteristics of pre-Holocene humid periods. Here we present a high-resolution record of fine-grained eastern Saharan dust from the Eastern Mediterranean Sea spanning the last 180 kyr, which is based on the clay mineral composition of the marine sediments, especially the kaolinite/chlorite ratio. Minimum aeolian kaolinite transport occurred during the African Humid Periods because kaolinite deflation was hampered by increased humidity and vegetation cover. Instead, kaolinite weathering from kaolinite-bearing Cenozoic rocks was stored in lake basins, river beds and soils during these periods. During the subsequent dry phases, fine-grained dust was mobilised from the desiccated lakes, rivers and soils resulting in maximum aeolian uptake and transport of kaolinite. The kaolinite transport decreased again when these sediment sources exhausted. We conclude that the amount of clay-sized dust blown out of the Sahara into the Eastern Mediterranean Sea is proportional to the intensity of the kaolinite weathering and accumulation in soils and lake sediments, and thus to the strength of the preceding humid period. These humid periods provided the windows for the migration of modern humans out of Africa, as postulated previously. The strongest humid period occurred during the Eemian and was followed by two weaker phases centred at ca. 100 ka and ca. 80 ka.

Intensity of African Humid Periods Estimated from Saharan Dust Fluxes

PubMed Central

Ehrmann, Werner; Schmiedl, Gerhard; Beuscher, Sarah; Krüger, Stefan

2017-01-01

North Africa experienced dramatic changes in hydrology and vegetation during the late Quaternary driven by insolation-induced shifts of the tropical rain belt and further modulated by millennial-scale droughts and vegetation-climate feedbacks. While most past proxy and modelling studies concentrated on the temporal and spatial dynamics of the last African humid period, little is known about the intensities and characteristics of pre-Holocene humid periods. Here we present a high-resolution record of fine-grained eastern Saharan dust from the Eastern Mediterranean Sea spanning the last 180 kyr, which is based on the clay mineral composition of the marine sediments, especially the kaolinite/chlorite ratio. Minimum aeolian kaolinite transport occurred during the African Humid Periods because kaolinite deflation was hampered by increased humidity and vegetation cover. Instead, kaolinite weathering from kaolinite-bearing Cenozoic rocks was stored in lake basins, river beds and soils during these periods. During the subsequent dry phases, fine-grained dust was mobilised from the desiccated lakes, rivers and soils resulting in maximum aeolian uptake and transport of kaolinite. The kaolinite transport decreased again when these sediment sources exhausted. We conclude that the amount of clay-sized dust blown out of the Sahara into the Eastern Mediterranean Sea is proportional to the intensity of the kaolinite weathering and accumulation in soils and lake sediments, and thus to the strength of the preceding humid period. These humid periods provided the windows for the migration of modern humans out of Africa, as postulated previously. The strongest humid period occurred during the Eemian and was followed by two weaker phases centred at ca. 100 ka and ca. 80 ka. PMID:28129378

Dust altitude and infrared optical depth retrieved from 6 years of AIRS observations : a focus on Saharan dust using A-Train synergy (MODIS, CALIOP)

NASA Astrophysics Data System (ADS)

Peyridieu, S.; Chédin, A.; Capelle, V.; Pierangelo, C.; Lamquin, N.; Armante, R.

2009-04-01

Observation from space, being global and quasi-continuous, is a first importance tool for aerosol studies. Remote sensing in the visible domain has been widely used to obtain better characterization of these particles and their effect on solar radiation. On the opposite, remote sensing of aerosols in the thermal infrared domain still remains marginal. However, knowledge of the effect of aerosols on terrestrial radiation is needed for the evaluation of their total radiative forcing. Infrared remote sensing provides a way to retrieve other aerosol characteristics, including their mean altitude. Moreover, observations are possible at night and day, over ocean and over land. In this context, six years (2003-2008) of the 2nd generation vertical sounder AIRS observations have been processed over the tropical belt (30°N-30°S). Our results of the dust optical depth at 10 µm have been compared to the 0.55 µm Aqua/MODIS optical depth product for this period. The detailed study of Atlantic regions shows a very good agreement between the two products, with a VIS/IR ratio around 0.3-0.5 during the Saharan dust season. Comparing these two AOD products should allow separating different aerosols signals, given that our retrieval algorithm is specifically designed for dust coarse mode whereas MODIS retrieves both accumulation and fine aerosol modes. Mean aerosol layer altitude has also been retrieved from AIRS data and we show global maps and time series of altitude retrieved from space. Altitude retrievals are compared to the CALIOP/Calipso Level-2 product starting June 2006. This comparison, for a region located downwind from the Sahara, again shows a good agreement demonstrating that our algorithm effectively allows retrieving reliable mean dust layer altitude. A global climatology of the dust optical depth at 10 µm and of the aerosol layer mean altitude has also been established. An interesting conclusion is the fact that if the AOD decreases from Africa to the Caribbean

The Evolution and Role of the Saharan Air Layer During Hurricane Helene (2006)

NASA Technical Reports Server (NTRS)

Braun, Scott A.; Sippel, Jason A.; Shie, Chung-Lin; Boller, Ryan A.

2013-01-01

The Saharan air layer (SAL) has received considerable attention in recent years as a potential negative influence on the formation and development of Atlantic tropical cyclones. Observations of substantial Saharan dust in the near environment of Hurricane Helene (2006) during the National Aeronautics and Space Administration (NASA) African Monsoon Multidisciplinary Activities (AMMA) Experiment (NAMMA) field campaign led to suggestions about the suppressing influence of the SAL in this case. In this study, a suite of satellite remote sensing data, global meteorological analyses, and airborne data are used to characterize the evolution of the SAL in the environment of Helene and assess its possible impact on the intensity of the storm. The influence of the SAL on Helene appears to be limited to the earliest stages of development, although the magnitude of that impact is difficult to determine observationally. Saharan dust was observed on the periphery of the storm during the first two days of development after genesis when intensification was slow. Much of the dust was observed to move well westward of the storm thereafter, with little SAL air present during the remainder of the storm's lifetime and with the storm gradually becoming a category-3 strength storm four days later. Dry air observed to wrap around the periphery of Helene was diagnosed to be primarily non-Saharan in origin (the result of subsidence) and appeared to have little impact on storm intensity. The eventual weakening of the storm is suggested to result from an eyewall replacement cycle and substantial reduction of the sea surface temperatures beneath the hurricane as its forward motion decreased.

Retrieval of Saharan desert dust optical depth from thermal infrared measurements by IASI

NASA Astrophysics Data System (ADS)

Vandenbussche, S.; Kochenova, S.; Vandaele, A.-C.; Kumps, N.; De Mazière, M.

2012-04-01

Aerosols are a major actor in the climate system. They are responsible for climate forcing by both direct (by emission, absorption and scattering) and indirect effects (for example, by altering cloud microphysics). A better knowledge of aerosol optical properties, of the atmospheric aerosol load and of aerosol sources and sinks may therefore significantly improve the modeling of climate changes. Aerosol optical depth and other properties are retrieved on an operational basis from daytime measurements in the visible and near infrared spectral range by a number of instruments, like the satellite instruments MODIS, CALIOP, POLDER, MISR and ground-based sunphotometers. Aerosol retrievals from day and night measurements at thermal infrared (TIR) wavelengths (for example, from SEVIRI, AIRS and IASI satellite instruments) are less common, but they receive growing interest in more recent years. Among those TIR measuring instruments, IASI on METOP has one major advantage for aerosol retrievals: its large continuous spectral coverage, allowing to better capture the broadband signature of aerosols. Furthermore, IASI has a high spectral resolution (0.5cm-1 after apodization) which allows retrieving a large number of trace gases at the same time, it will nominally be in orbit for 15 years and offers a quasi global Earth coverage twice a day. Here we will show recently obtained results of desert aerosol properties (concentration, altitude, optical depth) retrieved from IASI TIR measurements, using the ASIMUT software (BIRA-IASB, Belgium) linked to (V)LIDORT (R. Spurr, RTsolutions Inc, US) and to SPHER (M. Mishchenko, NASA GISS, USA). In particular, we will address the case of Saharan desert dust storms, which are a major source of desert dust particles in the atmosphere. Those storms frequently transport sand to Europe, Western Asia or even South America. We will show some test-case comparisons between our retrievals and measurements from other instruments like those listed

Combined use of Satellite and Surface Observations to Infer the Imaginary Part of Refractive Index of Saharan Dust

NASA Technical Reports Server (NTRS)

Sinyuk, Alexander; Torres, Omar; Dubovik, Oleg; Bhartia, P. K. (Technical Monitor)

2002-01-01

We present a method for retrieval of imaginary part of refractive index of desert dust aerosol in UV part of spectrum along with aerosol layer height above the ground. The method uses Total Ozone Mapping Spectrometer' (TOMS) measurements of the top of atmosphere radiances (331 nm, 360 nm) and aerosol optical depth provided by Aerosol Robotic Network (AERONET) (440 nm). Obtained values of imaginary part of refractive index retrieved for Saharan dust aerosol at 360 nm are significantly lower than previously reported values. The average retrieved values vary between 0.0054 and 0.0066 for different geographical locations. Our findings are in good agreement with the results of several recent investigations. The time variability of retrieved values for aerosol layer height is consistent with the predictions of dust transport model.

Impact of a Saharan dust intrusion over southern Spain on DNI estimation with sky cameras

NASA Astrophysics Data System (ADS)

Alonso-Montesinos, J.; Barbero, J.; Polo, J.; López, G.; Ballestrín, J.; Batlles, F. J.

2017-12-01

To operate Central Tower Solar Power (CTSP) plants properly, solar collector systems must be able to work under varied weather conditions. Therefore, knowing the state of the atmosphere, and more specifically the level of incident radiation, is essential operational information to adapt the electricity production system to atmospheric conditions. In this work, we analyze the impact of a strong Saharan dust intrusion on the Direct normal irradiance (DNI) registered at two sites 35 km apart in southeastern Spain: the University of Almería (UAL) and the Plataforma Solar de Almería (PSA). DNI can be inputted into the European Solar Radiation Atlas (ESRA) clear sky procedure to derive Linke turbidity values, which proved to be extremely high at the UAL. By using the Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS) at the PSA site, AERONET data from PSA and assuming dust dominated aerosol, DNI estimations agreed strongly with the measured DNI values. At the UAL site, a SMARTS simulation of the DNI values also seemed to be compatible with dust dominated aerosol.

Sahara Dust

Atmospheric Science Data Center

2013-04-15

article title:  Casting Light and Shadows on a Saharan Dust Storm     ... ocean and dust layer, which are visible in shades of blue and tan, respectively. In the lower panel, heights derived from automated ... cast by the cirrus clouds onto the dust (indicated by blue and cyan pixels) provide sufficient spatial contrast for a retrieval of ...

Extinction-to-Backscatter Ratios of Saharan Dust Layers Derived from In-Situ Measurements and CALIPSO Overflights During NAMMA

NASA Technical Reports Server (NTRS)

Omar, Ali H.; Liu, Zhaoyan; Vaughan, Mark A.; Thornhill, Kenneth L., II; Kittaka, Chieko; Ismail, Syed; Chen, Gao; Powell, Kathleen A.; Winker, David M.; Trepte, Charles R.;

The pulsating nature of large-scale Saharan dust transport as a result of interplays between mid-latitude Rossby waves and the North African Dipole Intensity

NASA Astrophysics Data System (ADS)

Cuevas, E.; Gómez-Peláez, A. J.; Rodríguez, S.; Terradellas, E.; Basart, S.; García, R. D.; García, O. E.; Alonso-Pérez, S.

2017-10-01

It was previously shown that during August the export of Saharan dust to the Atlantic was strongly affected by the difference of the 700-hPa geopotential height anomaly between the subtropics and the tropics over North Africa, which was termed the North African Dipole Intensity (NAFDI). In this work a more comprehensive analysis of the NAFDI is performed, focusing on the entire summer dust season (June-September), and examining the interactions between the mid-latitude Rossby waves (MLRWs) and NAFDI. Widespread and notable aerosol optical depth (AOD) monthly anomalies are found for each NAFDI-phase over the dust corridors off the Sahara, indicating that NAFDI presents intra-seasonal variability and drives dust transport over both the Mediterranean basin and the North Atlantic. Those summer months with the same NAFDI-phase show similar AOD-anomaly patterns. Variations in NAFDI-phase also control the displacement of the Saharan Heat Low (SHL) westwards or eastwards through horizontal advection of temperature over Morocco-Western Sahara or eastern Algeria-Western Libya, respectively. The connection between the SHL and the NAFDI is quantified statistically by introducing two new daily indexes that account for their respective phases (NAFDI daily index -NAFDIDI-, and SHL longitudinal shift index -SHLLSI-) and explained physically using the energy equation of the atmospheric dynamics. The Pearson's correlation coefficient between the one-day-lag SHLLSI and the NAFDIDI for an extended summer season (1980-2013) is 0.78. A positive NAFDI is associated with the West-phase of the SHL, dust sources intensification on central Algeria, and positive AOD anomalies over this region and the Subtropical North Atlantic. A negative NAFDI is associated with the East-phase of the SHL, and positive AOD anomalies over central-eastern Sahara and the central-western Mediterranean Sea. The results point out that the phase changes of NAFDI at intra-seasonal time scale are conducted by those

Combined Use of Satellite and Surface Observations to Infer the Imaginary Part of Refractive Index of Saharan Dust

NASA Technical Reports Server (NTRS)

Sinyuk, Alexander; Torres, Omar; Dubovik, Oleg; Bhartia, P. K. (Technical Monitor)

2002-01-01

We present a method for retrieval of the imaginary part of refractive index of desert dust aerosol in the near UV part of spectrum. The method uses Total Ozone Mapping Spectrometer (TOMS) measurements of the top of the atmosphere radiances at 331 and 360 run and aerosol optical depth provided by the Aerosol Robotic Network (AERONET). Obtained values of imaginary part of refractive index retrieved for Saharan dust aerosol at 360 nm are significantly lower than previously reported values. The average retrieved values vary between 0.0054 and 0.0066 for different geographical locations. Our findings are in good agreement with the results of several recent investigations.

Meteorological and dust aerosol conditions over the western Saharan region observed at Fennec Supersite-2 during the intensive observation period in June 2011

NASA Astrophysics Data System (ADS)

Todd, M. C.; Allen, C. J. T.; Bart, M.; Bechir, M.; Bentefouet, J.; Brooks, B. J.; Cavazos-Guerra, C.; Clovis, T.; Deyane, S.; Dieh, M.; Engelstaedter, S.; Flamant, C.; Garcia-Carreras, L.; Gandega, A.; Gascoyne, M.; Hobby, M.; Kocha, C.; Lavaysse, C.; Marsham, J. H.; Martins, J. V.; McQuaid, J. B.; Ngamini, J. B.; Parker, D. J.; Podvin, T.; Rocha-Lima, A.; Traore, S.; Wang, Y.; Washington, R.

2013-08-01

The climate of the Sahara is relatively poorly observed and understood, leading to errors in forecast model simulations. We describe observations from the Fennec Supersite-2 (SS2) at Zouerate, Mauritania during the June 2011 Fennec Intensive Observation Period. These provide an improved basis for understanding and evaluating processes, models, and remote sensing. Conditions during June 2011 show a marked distinction between: (i) a "Maritime phase" during the early part of the month when the western sector of the Sahara experienced cool northwesterly maritime flow throughout the lower troposphere with shallow daytime boundary layers, very little dust uplift/transport or cloud cover. (ii) A subsequent "heat low" phase which coincided with a marked and rapid westward shift in the Saharan heat low towards its mid-summer climatological position and advection of a deep hot, dusty air layer from the central Sahara (the "Saharan residual layer"). This transition affected the entire western-central Sahara. Dust advected over SS2 was primarily from episodic low-level jet (LLJ)-generated emission in the northeasterly flow around surface troughs. Unlike Fennec SS1, SS2 does not often experience cold pools from moist convection and associated dust emissions. The diurnal evolution at SS2 is strongly influenced by the Atlantic inflow (AI), a northwesterly flow of shallow, cool and moist air propagating overnight from coastal West Africa to reach SS2 in the early hours. The AI cools and moistens the western Saharan and weakens the nocturnal LLJ, limiting its dust-raising potential. We quantify the ventilation and moistening of the western flank of the Sahara by (i) the large-scale flow and (ii) the regular nocturnal AI and LLJ mesoscale processes.

Direct Radiative Forcing from Saharan Mineral Dust Layers from In-situ Measurements and Satellite Retrievals

NASA Astrophysics Data System (ADS)

Sauer, D. N.; Vázquez-Navarro, M.; Gasteiger, J.; Chouza, F.; Weinzierl, B.

2016-12-01

Mineral dust is the major species of airborne particulate matter by mass in the atmosphere. Each year an estimated 200-3000 Tg of dust are emitted from the North African desert and arid regions alone. A large fraction of the dust is lifted into the free troposphere and gets transported in extended dust layers westward over the Atlantic Ocean into the Caribbean Sea. Especially over the dark surface of the ocean, those dust layers exert a significant effect on the atmospheric radiative balance though aerosol-radiation interactions. During the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in summer 2013 airborne in-situ aerosol measurements on both sides of the Atlantic Ocean, near the African coast and the Caribbean were performed. In this study we use data about aerosol microphysical properties acquired between Cabo Verde and Senegal to derive the aerosol optical properties and the resulting radiative forcing using the radiative transfer package libRadtran. We compare the results to values retrieved from MSG/SEVIRI data using the RRUMS algorithm. The RRUMS algorithm can derive shortwave and longwave top-of-atmosphere outgoing fluxes using only information issued from the narrow-band MSG/SEVIRI channels. A specific calibration based on collocated Terra/CERES measurements ensures a correct retrieval of the upwelling flux from the dust covered pixels. The comparison of radiative forcings based on in-situ data to satellite-retrieved values enables us to extend the radiative forcing estimates from small-scale in-situ measurements to large scale satellite coverage over the Atlantic Ocean.

The early summertime Saharan heat low: sensitivity of the radiation budget and atmospheric heating to water vapour and dust aerosol

NASA Astrophysics Data System (ADS)

Alamirew, Netsanet K.; Todd, Martin C.; Ryder, Claire L.; Marsham, John H.; Wang, Yi

2018-01-01

The Saharan heat low (SHL) is a key component of the west African climate system and an important driver of the west African monsoon across a range of timescales of variability. The physical mechanisms driving the variability in the SHL remain uncertain, although water vapour has been implicated as of primary importance. Here, we quantify the independent effects of variability in dust and water vapour on the radiation budget and atmospheric heating of the region using a radiative transfer model configured with observational input data from the Fennec field campaign at the location of Bordj Badji Mokhtar (BBM) in southern Algeria (21.4° N, 0.9° E), close to the SHL core for June 2011. Overall, we find dust aerosol and water vapour to be of similar importance in driving variability in the top-of-atmosphere (TOA) radiation budget and therefore the column-integrated heating over the SHL (˜ 7 W m-2 per standard deviation of dust aerosol optical depth - AOD). As such, we infer that SHL intensity is likely to be similarly enhanced by the effects of dust and water vapour surge events. However, the details of the processes differ. Dust generates substantial radiative cooling at the surface (˜ 11 W m-2 per standard deviation of dust AOD), presumably leading to reduced sensible heat flux in the boundary layer, which is more than compensated by direct radiative heating from shortwave (SW) absorption by dust in the dusty boundary layer. In contrast, water vapour invokes a radiative warming at the surface of ˜ 6 W m-2 per standard deviation of column-integrated water vapour in kg m-2. Net effects involve a pronounced net atmospheric radiative convergence with heating rates on average of 0.5 K day-1 and up to 6 K day-1 during synoptic/mesoscale dust events from monsoon surges and convective cold-pool outflows (haboobs). On this basis, we make inferences on the processes driving variability in the SHL associated with radiative and advective heating/cooling. Depending

Forecasting Dust Storms Using the CARMA-Dust Model and MM5 Weather Data

NASA Astrophysics Data System (ADS)

Barnum, B. H.; Winstead, N. S.; Wesely, J.; Hakola, A.; Colarco, P.; Toon, O. B.; Ginoux, P.; Brooks, G.; Hasselbarth, L. M.; Toth, B.; Sterner, R.

2002-12-01

An operational model for the forecast of dust storms in Northern Africa, the Middle East and Southwest Asia has been developed for the United States Air Force Weather Agency (AFWA). The dust forecast model uses the 5th generation Penn State Mesoscale Meteorology Model (MM5), and a modified version of the Colorado Aerosol and Radiation Model for Atmospheres (CARMA). AFWA conducted a 60 day evaluation of the dust model to look at the model's ability to forecast dust storms for short, medium and long range (72 hour) forecast periods. The study used satellite and ground observations of dust storms to verify the model's effectiveness. Each of the main mesoscale forecast theaters was broken down into smaller sub-regions for detailed analysis. The study found the forecast model was able to forecast dust storms in Saharan Africa and the Sahel region with an average Probability of Detection (POD)exceeding 68%, with a 16% False Alarm Rate (FAR). The Southwest Asian theater had average POD's of 61% with FAR's averaging 10%.

Analysis of two Saharan dust events of North Africa in the Mediterranean region by Using SKIRON/Eta model

NASA Astrophysics Data System (ADS)

Benaouda, D.; Kallos, G.; Azzi, A.; Louka, P.; Benlefki, A.

2009-04-01

As it is well known established that significant ecosystems effects can be produced by pollutants generated many hundreds of kilometres away. Desert is natural laboratories containing valuable mineral deposits that were formed in the arid environment or that were exposed by erosion. Dust is a key species of many biogeochemical. One important effect of the dust cycle is triggering of various biochemical reactions between dust ingredients and the environment. The biogeochemical impact of desert dust also remains a matter of discussion regarding its contribution for different major and minor elements to terrestrial and marine systems and especially its potential fertilising role for remote oceanic areas by supplying micronutrients such as phosphorus and iron. Saharan dust is responsible for the supply of nutrients resulting in the increase of the production of the pelagic system, but competitively may remove phosphorus, through the adsorption on dust particles, contributing to the oligotrophy of the system, in addition, the presence of Si and Fe in the dust deposition may change the phytoplankton communities resulting in fast growth rates leading to blooms. In addition to direct radiative forcing, dust participates in indirect climate forcing through its role as a cloud-condensation nucleus and potential atmospheric CO2 regulator via biospheric nutrient delivery. Scattering and absorption of radiation by dust have impacts on the Earth's radiation budget, the thermal structure of the troposphere, and actinic fluxes, altering dynamical and photochemical processes. Coating of dust particles under polluted conditions can change microphysical properties and promote surface chemical. The Mediterranean Sea is a semi-enclosed basin, which receives substances sporadically from the arid regions of the Sahara desert. In such processes, dust modifies biochemistry of the Mediterranean water, changes features of the terrestrial ecosystems, and neutralises acid rains. Mineral dust

Response of the Water Cycle of West Africa and Atlantic to Radiative Forcing by Saharan Dust

NASA Technical Reports Server (NTRS)

Lau, K. M.; Kim, Kyu-Myong; Sud, Yogesh C.; Walker, Gregory L.

2010-01-01

The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence in support of the "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summer, as a result of large-scale atmospheric feed back triggered by absorbing dust aerosols, rainfall and cloudiness are enhanced over the West Africa/Easter Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean. region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while long wave has the opposite response. The elevated dust layer warms the air over Nest Africa and the eastern Atlantic. The condensation heating associated with the induced deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface energy fluxes, resulting in cooling of the Nest African land and the eastern Atlantic, and a warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at 0.95 or higher.

The contribution of Saharan dust in PM(10) concentration levels in Anatolian Peninsula of Turkey.

PubMed

Kabatas, B; Unal, A; Pierce, R B; Kindap, T; Pozzoli, L

2014-08-01

Sahara-originated dust is the most significant natural source of particulate matter; however, this contribution is still unclear in the Eastern Mediterranean especially in Western Turkey, where significant industrial sources and metropolitan areas are located. The Real-time Air Quality Modeling System (RAQMS) is utilized to explore the possible effects of Saharan dust on high levels of PM10 measured in Turkey. RAQMS model is compared with 118-air quality stations distributed throughout Turkey (81 cities) for April 2008. MODIS aerosol product (MOD04 for Terra and MYD04 for Aqua) is used to see columnar aerosol loading of the atmosphere at 550 nm (Aerosol optical depth (AOD) values found to be between 0.6 and 0.8 during the episode). High-resolution vertical profiles of clouds and aerosols are provided from CALIOP, on board of CALISPO satellite. The results suggest a significant contribution of Sahara dust to high levels of PM10 in Turkey with RAQMS and in situ time series showing similar patterns. The two data sets are found to be in agreement with a correlation of 0.87. Copyright © 2014 Elsevier B.V. All rights reserved.

Modification of Saharan Mineral Dust during Transport across the Atlantic Ocean - Overview and Results from the SALTRACE Field Experiment

NASA Astrophysics Data System (ADS)

Weinzierl, Bernadett; Ansmann, Albert; Reitebuch, Oliver; Freudenthaler, Volker; Müller, Thomas; Kandler, Konrad; Groß, Silke; Sauer, Daniel; Althausen, Dietrich; Toledano, Carlos

2014-05-01

At present one of the largest uncertainties in our understanding of global climate concerns the interaction of aerosols with clouds and atmospheric dynamics. In the climate system, mineral dust aerosol is of key importance, because mineral dust contributes to about half of the global annual particle emissions by mass. Although our understanding of the effects of mineral dust on the atmosphere and the climate improved during the past decade, many questions such as the change of the dust size distribution during transport across the Atlantic Ocean and the associated impact on the radiation budget, the role of wet and dry dust removal mechanisms during transport, and the complex interaction between mineral dust and clouds remain open. The Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE: http://www.pa.op.dlr.de/saltrace) was conducted in June/July 2013 to investigate the transport and transformation of Saharan mineral dust during long-range transport from the Sahara across the Atlantic Ocean into the Caribbean. SALTRACE is a German initiative combining ground-based and airborne in-situ and lidar measurements with meteorological data, long-term measurements, satellite remote sensing and modeling which involved many national and international partners. During SALTRACE, the DLR Falcon research aircraft was based at Sal, Cape Verde, between 11 and 17 June 2013, and at Barbados between 18 June and 11 July 2013. The Falcon was equipped with a suite of in-situ instruments for the measurement of microphysical and optical aerosol properties, with sampling devices for offline particle analysis, with a nadir-looking 2-µm wind lidar, with dropsondes and instruments for standard meteorological parameters. Ground-based lidar and in-situ instruments were deployed in Cape Verde, Barbados and Puerto Rico. During SALTRACE, mineral dust from five dust outbreaks was studied by the Falcon research aircraft between Senegal, the Caribbean and Florida

Principle Component Analysis of the Evolution of the Saharan Air Layer and Dust Transport: Comparisons between a Model Simulation and MODIS Retrievals

NASA Technical Reports Server (NTRS)

Wong, S.; Colarco, P. R.; Dessler, A.

2006-01-01

The onset and evolution of Saharan Air Layer (SAL) episodes during June-September 2002 are diagnosed by applying principal component analysis to the NCEP reanalysis temperature anomalies at 850 hPa, where the largest SAL-induced temperature anomalies are located. The first principal component (PC) represents the onset of SAL episodes, which are associated with large warm anomalies located at the west coast of Africa. The second PC represents two opposite phases of the evolution of the SAL. The positive phase of the second PC corresponds to the southwestward extension of the warm anomalies into the tropical-subtropical North Atlantic Ocean, and the negative phase corresponds to the northwestward extension into the subtropical to mid-latitude North Atlantic Ocean and the southwest Europe. A dust transport model (CARMA) and the MODIS retrievals are used to study the associated effects on dust distribution and deposition. The positive (negative) phase of the second PC corresponds to a strengthening (weakening) of the offshore flows in the lower troposphere around 10deg - 20degN, causing more (less) dust being transported along the tropical to subtropical North Atlantic Ocean. The variation of the offshore flow indicates that the subseasonal variation of African Easterly Jet is associated with the evolution of the SAL. Significant correlation is found between the second PC time series and the daily West African monsoon index, implying a dynamical linkage between West African monsoon and the evolution of the SAL and Saharan dust transport.

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.

Saharan Air Layer Interaction with Hurricane Claudette (2003)

NASA Astrophysics Data System (ADS)

Rothman, G. S.; Gill, T. E.; Chang, C.

2004-12-01

It has long been observed that the Saharan Air Layer (SAL), a large and seasonally-persistent layer of West African aeolian dust suspended over the Atlantic Ocean, may influence the variability and intensity of easterly waves and tropical cyclones in the Atlantic basin. The radiative and conductive properties of the Saharan aerosols may contribute to warming within the dust layer, creating an anomalous baroclinic zone in the tropical North Atlantic. Environmental baroclinic instability is a mechanism for conversion of potential energy to eddy kinetic energy, facilitating wave growth. However, this same baroclinic mechanism, along with the dry properties of the SAL, could also promote asymmetry in a tropical cyclone, limiting its intensity. Detailed investigations of specific cases are necessary to better understand the radiative heating or cooling impact that the Saharan aerosols cause as well as potential influences on cyclone track and intensity stemming from the aeolian dust cloud. Here, we consider the case of Claudette in 2003. On June 29, 2003, an easterly wave embedded near the southern boundary of a broad Saharan dust layer emerged from the West African Coastal Bend region into the Atlantic Ocean. The wave propagated westward, reaching tropical storm intensity as Claudette in the Caribbean and developing into a hurricane just before making landfall on the southern Texas Gulf of Mexico coast on July 15. The SAL propagated in phase with this system throughout almost its entire evolution. Rapid intensification of Claudette into a hurricane in the last 15 hours prior to landfall was concurrent with a decoupling from the Saharan dust intrusion, with the two following separate tracks into North America at the end of the period. We performed an investigation to understand and diagnose the interaction between the Saharan Air Layer and Claudette. HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) along-trajectory potential temperature plots as

Optical-microphysical properties of Saharan dust aerosols and composition relationship using a multi-wavelength Raman lidar, in situ sensors and modelling: a case study analysis

NASA Astrophysics Data System (ADS)

Papayannis, A.; Mamouri, R. E.; Amiridis, V.; Remoundaki, E.; Tsaknakis, G.; Kokkalis, P.; Veselovskii, I.; Kolgotin, A.; Nenes, A.; Fountoukis, C.

2012-05-01

A strong Saharan dust event that occurred over the city of Athens, Greece (37.9° N, 23.6° E) between 27 March and 3 April 2009 was followed by a synergy of three instruments: a 6-wavelength Raman lidar, a CIMEL sun-sky radiometer and the MODIS sensor. The BSC-DREAM model was used to forecast the dust event and to simulate the vertical profiles of the aerosol concentration. Due to mixture of dust particles with low clouds during most of the reported period, the dust event could be followed by the lidar only during the cloud-free day of 2 April 2009. The lidar data obtained were used to retrieve the vertical profile of the optical (extinction and backscatter coefficients) properties of aerosols in the troposphere. The aerosol optical depth (AOD) values derived from the CIMEL ranged from 0.33-0.91 (355 nm) to 0.18-0.60 (532 nm), while the lidar ratio (LR) values retrieved from the Raman lidar ranged within 75-100 sr (355 nm) and 45-75 sr (532 nm). Inside a selected dust layer region, between 1.8 and 3.5 km height, mean LR values were 83 ± 7 and 54 ± 7 sr, at 355 and 532 nm, respectively, while the Ångström-backscatter-related (ABR355/532) and Ångström-extinction-related (AER355/532) were found larger than 1 (1.17 ± 0.08 and 1.11 ± 0.02, respectively), indicating mixing of dust with other particles. Additionally, a retrieval technique representing dust as a mixture of spheres and spheroids was used to derive the mean aerosol microphysical properties (mean and effective radius, number, surface and volume density, and mean refractive index) inside the selected atmospheric layers. Thus, the mean value of the retrieved refractive index was found to be 1.49( ± 0.10) + 0.007( ± 0.007)i, and that of the effective radiuses was 0.30 ± 0.18 μm. The final data set of the aerosol optical and microphysical properties along with the water vapor profiles obtained by Raman lidar were incorporated into the ISORROPIA II model to provide a possible aerosol composition

SMART-COMMIT Observations and Deep-Blue Retrievals of Saharan Dust Properties during NAMMA

NASA Technical Reports Server (NTRS)

Tsay, Si-Chee; Hsu, N. Christina; Ji, Qiang; Jeong, Myeong-Jae

2007-01-01

Monsoon rainfalls sustain the livelihood of more than half of the world's population. The interaction between natural/anthropogenic aerosols, clouds, and precipitation is a critical mechanism that drives the water cycle and fresh water distribution. Analyses of the longterm trend of July-August precipitation anomaly for the last 50 years in the 20" century depict that the largest regional precipitation deficit occurs over the Sahel, where the monsoon water cycle plays an important role. Thus, it is of paramount importance to study how dust aerosols, as well as air pollution and smoke, influence monsoon variability. The NASA African Monsoon Multidisciplinary Activities (NAMMA) was conducted during the international AMMA Special Observation Period (SOP-3) of September 2006 to better comprehend the key attributes of the Saharan Air Layer (SAL) and how they evolve from the source regions to the Atlantic Ocean. The SAL occurs during the late spring through early fall and originates as a result of low-level convergence induced by heat lows over the Sahara that lifts hot, dry, dust laden air aloft into a well mixed layer that extends up to 500mb. This is crucial for understanding the impact of SAL on the key atmospheric processes that determine precipitation over West Africa and tropical cyclogenesis. Results obtained from the synergy of satellite (Deep- Blue) and surface (SMART-COMMIT) observations will be presented and discussed how the physical, optical and radiative properties of the dust in the SAL evolve from the continental to the marine environment.

A detailed characterization of the Saharan dust collected during the Fennec campaign in 2011: in situ ground-based and laboratory measurements

NASA Astrophysics Data System (ADS)

Rocha-Lima, Adriana; Vanderlei Martins, J.; Remer, Lorraine A.; Todd, Martin; Marsham, John H.; Engelstaedter, Sebastian; Ryder, Claire L.; Cavazos-Guerra, Carolina; Artaxo, Paulo; Colarco, Peter; Washington, Richard

2018-01-01

Millions of tons of mineral dust are lifted by the wind from arid surfaces and transported around the globe every year. The physical and chemical properties of the mineral dust are needed to better constrain remote sensing observations and are of fundamental importance for the understanding of dust atmospheric processes. Ground-based in situ measurements and in situ filter collection of Saharan dust were obtained during the Fennec campaign in the central Sahara in 2011. This paper presents results of the absorption and scattering coefficients, and hence single scattering albedo (SSA), of the Saharan dust measured in real time during the last period of the campaign and subsequent laboratory analysis of the dust samples collected in two supersites, SS1 and SS2, in Algeria and in Mauritania, respectively. The samples were taken to the laboratory, where their size and aspect ratio distributions, mean chemical composition, spectral mass absorption efficiency, and spectral imaginary refractive index were obtained from the ultraviolet (UV) to the near-infrared (NIR) wavelengths. At SS1 in Algeria, the time series of the scattering coefficients during the period of the campaign show dust events exceeding 3500 Mm-1, and a relatively high mean SSA of 0.995 at 670 nm was observed at this site. The laboratory results show for the fine particle size distributions (particles diameter  < 5µm and mode diameter at 2-3 µm) in both sites a spectral dependence of the imaginary part of the refractive index Im(m) with a bow-like shape, with increased absorption in UV as well as in the shortwave infrared. The same signature was not observed, however, in the mixed particle size distribution (particle diameter < 10 µm and mode diameter at 4 µm) in Algeria. Im(m) was found to range from 0.011 to 0.001i for dust collected in Algeria and 0.008 to 0.002i for dust collected in Mauritania over the wavelength range of 350-2500 nm. Differences in the mean elemental

Wet Dust Deposition Across Texas, USA

NASA Astrophysics Data System (ADS)

Collins, J. D., Jr.; Ponette-González, A.; Gill, T. E.; Glass, G. A.; Weathers, K. C.

2016-12-01

Atmospheric dust deposition is of critical importance in terrestrial biogeochemical cycles, supplying essential limiting nutrients, such as calcium and phosphorus as well as pollutants, such as lead, to ecosystems. Dust particles are delivered to terrestrial ecosystems directly as dry deposition or in precipitation (wet deposition) as a result of rainout (particles incorporated into cloud droplets) and washout (particles that collide with raindrops as they fall). Compared to dry deposition, wet dust deposition (dissolved + particulate) is a poorly understood yet potentially significant pathway for dust input, especially in humid regions. We quantified wet dust deposition to two National Atmospheric Deposition Monitoring (NADP) sites across Texas-one in west (Guadalupe Mountains) and one in east (near Houston) Texas-with contrasting climate/dust regimes and land cover. We focused on 2012 during one of the most severe droughts in Texas since 1895. Dust event days (DEDs) were identified using meteorological data for stations within 150 km of the NADP sites where wet deposition was sampled weekly. DEDs were defined using the following criteria: visibility <10 km, <30% relative humidity, and wind speed >50 km, supplemented with other Saharan dust incursion and dust observations. A total of 34 DEDs (20 sample weeks) were identified for the west and 5 DEDs (4 sample weeks) for the east Texas sites. Bulk elemental composition of washout particles is analyzed using Particle Induced X-ray Emission (PIXE) spectroscopy and X-ray Fluorescence (XRF) spectroscopy. Using these data, we will examine differences in the chemical composition of rainwater and aerosol particles filtered from rain samples for dust versus non-dust event days at each study site. Deposition fluxes for dust and non-dust event weeks are also compared. Quantifying the magnitude of wet dust deposition is necessary to improve evaluation of dust impacts on biogeochemical cycles.

Studies of saharan dust intrusions over bucharest using ceilometer's measurements and satellite data

NASA Astrophysics Data System (ADS)

Urlea, Denisa; Boscornea, Andreea; Nicolae Vâjâiac, Sorin; Ţoancă, Florica; Barbu, Nicu; Ştefan, Sabina; Bunescu, Ionuț

2018-04-01

Three case studies of Saharan dust intrusions over southern Romania were performed. For these studies the database from the ceilometers located at Magurele and Strejnic was used. In addition, the meteorological conditions were analyzed using the WLK Catalogue based on the Objektive Wetterlagenklassifikation classification of the weather types [1]. This catalogue uses information from three basic tropospheric levels: 925, 700 and 500 hPa, and information on the precipitable water content over the entire atmosphere column. Geopotential fields at 925hPa and 500hPa are used for establishing the cyclonicity or anticyclonicity, while the U and V components of wind at 700hPa for establishing the dominant direction of the wind flow. For better understanding of the atmospheric parameters we performed HYSPLIT dispersion and trajectories analysis in conjunction with DREAM model output data.

Effect of Dust Storms on the Atmospheric Microbiome in the Eastern Mediterranean.

PubMed

Mazar, Yinon; Cytryn, Eddie; Erel, Yigal; Rudich, Yinon

2016-04-19

We evaluated the impact of Saharan dust storms on the local airborne microbiome in a city in the Eastern Mediterranean area. Samples of particles with diameter less than 10 μm were collected during two spring seasons on both dusty and nondusty days. DNA was extracted, and partial 16S rRNA gene amplicons were sequenced using the Illumina platform. Bioinformatic analysis showed the effect of dust events on the diversity of the atmospheric microbiome. The relative abundance of desert soil-associated bacteria increased during dust events, while the relative abundance of anthropogenic-influenced taxa decreased. Quantitative polymerase chain reaction measurements of selected clinically significant antibiotic resistance genes (ARGs) showed that their relative abundance decreased during dust events. The ARG profiles on dust-free days were similar to those in aerosol collected in a poultry house, suggesting a strong agricultural influence on the local ambient profiles. We conclude that dust storms enrich the ambient airborne microbiome with new soil-derived bacteria that disappear as the dust settles, suggesting that the bacteria are transported attached to the dust particles. Dust storms do not seem to be an important vector for transport of probed ARGs.

Saharan Dust Fertilizing Atlantic Ocean and Amazon Rainforest via Long-range Transport and Deposition: A Perspective from Multiyear Satellite Measurements

NASA Astrophysics Data System (ADS)

Yu, H.; Chin, M.; Yuan, T.; Bian, H.; Remer, L. A.; Prospero, J. M.; Omar, A. H.; Winker, D. M.; Yang, Y.; Zhang, Y.; Zhang, Z.; Zhao, C.

2015-12-01

Massive dust emitted from Sahara desert is carried by trade winds across the tropical Atlantic Ocean, reaching the Amazon Rainforest and Caribbean Sea. Airborne dust degrades air quality and interacts with radiation and clouds. Dust falling to land and ocean adds essential nutrients that could increase the productivity of terrestrial and aquatic ecosystems and modulate the biogeochemical cycles and climate. The resultant climate change will feed back on the production of dust in Sahara desert and its subsequent transport and deposition. Understanding the connections among the remote ecosystems requires an accurate quantification of dust transport and deposition flux on large spatial and temporal scales, in which satellite remote sensing can play an important role. We provide the first multiyear satellite-based estimates of altitude-resolved across-Atlantic dust transport and deposition based on eight-year (2007-2014) record of aerosol three-dimensional distributions from the CALIPSO lidar. On a basis of the 8-year average, 179 Tg (million tons) of dust leaves the coast of North Africa and is transported across Atlantic Ocean, of which 102, 20, and 28 Tg of dust is deposited into the tropical Atlantic Ocean, Caribbean Sea, and Amazon Rainforest, respectively. The dust deposition adds 4.3 Tg of iron and 0.1 Tg of phosphorus to the tropical Atlantic Ocean and Caribbean Sea where the productivity of marine ecosystem depends on the availability of these nutrients. The 28 Tg of dust provides about 0.022 Tg of phosphorus to Amazon Rainforest yearly that replenishes the leak of this plant-essential nutrient by rains and flooding, suggesting an important role of Saharan dust in maintaining the productivity of Amazon rainforest on timescales of decades or centuries. We will also discuss seasonal and interannual variations of the dust transport and deposition, and comparisons of the CALIOP-based estimates with model simulations.

Influence of Saharan dust outbreaks and carbon content on oxidative potential of water-soluble fractions of PM2.5 and PM10

NASA Astrophysics Data System (ADS)

Chirizzi, Daniela; Cesari, Daniela; Guascito, Maria Rachele; Dinoi, Adelaide; Giotta, Livia; Donateo, Antonio; Contini, Daniele

2017-08-01

Exposure to atmospheric particulate matter (PM) leads to adverse health effects although the exact mechanisms of toxicity are still poorly understood. Several studies suggested that a large number of PM health effects could be due to the oxidative potential (OP) of ambient particles leading to high concentrations of reactive oxygen species (ROS). The contribution to OP of specific anthropogenic sources like road traffic, biomass burning, and industrial emissions has been investigated in several sites. However, information about the OP of natural sources are scarce and no data is available regarding the OP during Saharan dust outbreaks (SDO) in Mediterranean regions. This work uses the a-cellular DTT (dithiothreitol) assay to evaluate OP of the water-soluble fraction of PM2.5 and PM10 collected at an urban background site in Southern Italy. OP values in three groups of samples were compared: standard characterised by concentrations similar to the yearly averages; high carbon samples associated to combustion sources (mainly road traffic and biomass burning) and SDO events. DTT activity normalised by sampled air volume (DTTV), representative of personal exposure, and normalised by collected aerosol mass (DTTM), representing source-specific characteristics, were investigated. The DTTV is larger for high PM concentrations. DTTV is well correlated with secondary organic carbon concentration. An increased DTTV response was found for PM2.5 compared to the coarse fraction PM2.5-10. DTTV is larger for high carbon content samples but during SDO events is statistically comparable with that of standard samples. DTTM is larger for PM2.5 compared to PM10 and the relative difference between the two size fractions is maximised during SDO events. This indicates that Saharan dust advection is a natural source of particles having a lower specific OP with respect to the other sources acting on the area (for water-soluble fraction). OP should be taken into account in epidemiological

Nearly a Decade of CALIPSO Observations of Asian and Saharan Dust Properties Near Source and Transport Regions

NASA Technical Reports Server (NTRS)

Omar, Ali H.; Liu, Z.; Tackett, J.; Vaughan, M.; Trepte, C.; Winker, D.; H. Yu,

2015-01-01

The lidar on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, makes robust measurements of dust and has generated a length of record that is significant both seasonally and inter-annually. We exploit this record to determine a multi-year climatology of the properties of Asian and Saharan dust, in particular seasonal optical depths, layer frequencies, and layer heights of dust gridded in accordance with the Level 3 data products protocol, between 2006-2015. The data are screened using standard CALIPSO quality assurance flags, cloud aerosol discrimination (CAD) scores, overlying features and layer properties. To evaluate the effects of transport on the morphology, vertical extent and size of the dust layers, we compare probability distribution functions of the layer integrated volume depolarization ratios, geometric depths and integrated attenuated color ratios near the source to the same distributions in the far field or transport region. CALIPSO is collaboration between NASA and Centre National D'études Spatiales (CNES), was launched in April 2006 to provide vertically resolved measurements of cloud and aerosol distributions. The primary instrument on the CALIPSO satellite is the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), a near-nadir viewing two-wavelength polarization-sensitive instrument. The unique nature of CALIOP measurements make it quite challenging to validate backscatter profiles, aerosol type, and cloud phase, all of which are used to retrieve extinction and optical depth. To evaluate the uncertainty in the lidar ratios, we compare the values computed from dust layers overlying opaque water clouds, considered nominal, with the constant lidar ratio value used in the CALIOP algorithms for dust. We also explore the effects of noise on the CALIOP retrievals at daytime by comparing the distributions of the properties at daytime to the nighttime distributions.

Biological response to coastal upwelling and dust deposition in the area off Northwest Africa

NASA Astrophysics Data System (ADS)

Ohde, T.; Siegel, H.

2010-05-01

Nutrient supply in the area off Northwest Africa is mainly regulated by two processes, coastal upwelling and deposition of Saharan dust. In the present study, both processes were analyzed and evaluated by different methods, including cross-correlation, multiple correlation, and event statistics, using remotely sensed proxies of the period from 2000 to 2008 to investigate their influence on the marine environment. The remotely sensed chlorophyll- a concentration was used as a proxy for the phytoplankton biomass stimulated by nutrient supply into the euphotic zone from deeper water layers and from the atmosphere. Satellite-derived alongshore wind stress and sea-surface temperature were applied as proxies for the strength and reflection of coastal upwelling processes. The westward wind and the dust component of the aerosol optical depth describe the transport direction of atmospheric dust and the atmospheric dust column load. Alongshore wind stress and induced upwelling processes were most significantly responsible for the surface chlorophyll- a variability, accounting for about 24% of the total variance, mainly in the winter and spring due to the strong north-easterly trade winds. The remotely sensed proxies allowed determination of time lags between biological response and its forcing processes. A delay of up to 16 days in the surface chlorophyll- a concentration due to the alongshore wind stress was determined in the northern winter and spring. Although input of atmospheric iron by dust storms can stimulate new phytoplankton production in the study area, only 5% of the surface chlorophyll- a variability could be ascribed to the dust component in the aerosol optical depth. All strong desert storms were identified by an event statistics in the time period from 2000 to 2008. The 57 strong storms were studied in relation to their biological response. Six events were clearly detected in which an increase of chlorophyll- a was caused by Saharan dust input and not by

Depletion of tropospheric ozone associated with mineral dust outbreaks.

PubMed

Soler, Ruben; Nicolás, J F; Caballero, S; Yubero, E; Crespo, J

2016-10-01

From May to September 2012, ozone reductions associated with 15 Saharan dust outbreaks which occurred between May to September 2012 have been evaluated. The campaign was performed at a mountain station located near the eastern coast of the Iberian Peninsula. The study has two main goals: firstly, to analyze the decreasing gradient of ozone concentration during the course of the Saharan episodes. These gradients vary from 0.2 to 0.6 ppb h(-1) with an average value of 0.39 ppb h(-1). The negative correlation between ozone and coarse particles occurs almost simultaneously. Moreover, although the concentration of coarse particles remained high throughout the episode, the time series shows the saturation of the ozone loss. The highest ozone depletion has been obtained during the last hours of the day, from 18:00 to 23:00 UTC. Outbreaks registered during this campaign have been more intense in this time slot. The second objective is to establish from which coarse particle concentration a significant ozone depletion can be observed and to quantify this reduction. In this regard, it has been confirmed that when the hourly particle concentration recorded during the Saharan dust outbreaks is above the hourly particle median values (N > N-median), the ozone concentration reduction obtained is statistically significant. An average ozone reduction of 5.5 % during Saharan events has been recorded. In certain cases, this percentage can reach values of higher than 15 %.

Impact of Dust on Air Quality and Radiative Forcing : AN Episodic Study for the Megacity Istanbul Using RegCM4.1

NASA Astrophysics Data System (ADS)

Agacayak, T.; Kindap, T.; Unal, A.; Mallet, M.; Pozzoli, L.; Karaca, M.; Solmon, F.

2012-04-01

Istanbul is a megacity (with population over 15 million) that has significant levels of Particulate Matter concentrations. It is suspected that long-range transport of Saharan dust is one of the main contributors. The purpose of this study is to investigate the relationship between high PM concentrations and dust transport using atmospheric modeling, satellite data as well as in-situ observations. Measurements of PM10 concentrations at 10 different stations in Istanbul for the period 2004-2010 were provided by the Turkish Ministry of Environment. Daily mean PM10 concentrations exceeding the European standard of 50 µg/m3 were found to be, on average, 49 days for the Spring period, 45 days for the Winter period, and 41 days for the Fall period. DREAM model output (Nickovic et al. 2001; Perez et al. 2006) suggests that high PM10 concentrations correlate highly with mineral dust transport episodes from Saharan desert (i.e., 23% for winter and 58% for spring). In this study, we have utilized RegCM4.1 model to further investigate the Saharan dust transport in the selected episodes. During the period between March 21st and 24th, 2008, observed daily mean of PM10 concentrations reach up to 140 µg/m3 in Istanbul. Simulations conducted by RegCM4.1 provides AOD (350-640 nm model band) values ranging between 0.04 and 0.98during this episode. Central Anatolia is affected from the dust transport on 21 and 22 March 2008, with a daily mean AOD of 0.9. On 23th March 2008, the dust plume reaches the Marmara Sea and AOD increases about 1.0 over the region according to both DREAM and RegCM4.1 model outputs. On the fourth day of the episode, the dust event stops and AOD decreases to 0.5 over the region. Asymmetry parameters can be seen as 0.62 during the dust episode, while single scattering albedo is about 0.93 during the entire dust episode over Istanbul. The effect of the dust episode on the regional radiative budget over Istanbul was also estimated. Model results indicate a daily

Satellite Observations from SEVIRI of Saharan dust over West Africa, within the context of the Fennec project

NASA Astrophysics Data System (ADS)

Banks, J.; Brindley, H.

2012-04-01

During the summer months, the atmosphere over the western half of the Sahara carries some of the highest dust loadings on the planet. This situation develops when intense solar heating over the dry desert creates a deep and hot low pressure system (the Saharan Heat Low, SHL), which allows a strong vertical mixing of dust. The Fennec* consortium project aims to address the deficiency in observations from the sparsely populated western Sahara through the use of field campaign measurements made in June 2011, incorporating observations from ground instruments, aircraft, and from satellite instruments such as SEVIRI, in combination with climate modelling. Fennec aims to study the poorly understood behaviour of the SHL, and the processes which take place within it. Due to their high temporal resolution, observations from SEVIRI can offer new insights into the timing of activation of specific dust sources, and the processes governing their behaviour. Here we employ a multi-year, high time-resolution record of dust detection and aerosol optical depth (AOD) derived from SEVIRI using an algorithm developed at Imperial College to both identify areas of high dust loading and diagnose diurnal patterns in their activation. We will present results from the SEVIRI record alongside results from other satellite instruments such as MODIS, and place these findings in the context of the initial ground-based and in-situ observations available from the Fennec field campaign. We will also identify surface features which can contaminate the dust detection retrieval, due to their emissivities in the 8.7 micron channel. New techniques can be used to filter out these features, based on the difference between the brightness temperatures at 10.8 and 8.7 microns. Using surface visibility measurements and AERONET data, we will evaluate the consequences of this on the dust detection and AOD record. * Fennec is a consortium project which includes groups from the universities of Oxford, Imperial

Contrasting effect of Saharan dust and UVR on autotrophic picoplankton in nearshore versus offshore waters of Mediterranean Sea

NASA Astrophysics Data System (ADS)

González-Olalla, J. M.; Medina-Sánchez, J. M.; Cabrerizo, M. J.; Villar-Argáiz, Manuel; Sánchez-Castillo, Pedro M.; Carrillo, Presentación

2017-08-01

Autotrophic picoplankton (APP) is responsible for the vast majority of primary production in oligotrophic marine areas, such as the Alboran Sea. The increase in atmospheric dust deposition (e.g., from Sahara Desert) associated with global warming, together with the high UV radiation (UVR) on these ecosystems, may generate effects on APP hitherto unknown. We performed an observational study across the Alboran Sea to establish which factors control the abundance and distribution of APP, and we made a microcosm experiment in two distinct areas, nearshore and offshore, to predict the joint UVR × dust impact on APP at midterm scales. Our observational study showed that temperature (T) was the main factor explaining the APP distribution whereas total dissolved nitrogen positively correlated with APP abundance. Our experimental study revealed that Saharan dust inputs reduced or inverted the UVR damage on the photosynthetic quantum yield (ΦPSII) and picoplanktonic primary production (PPP) in the nearshore area but accentuated it in the offshore. This contrasting effect is partially explained by the nonphotochemical quenching, acting as a photorepair mechanism. Picoeukaryotes reflected the observed effects on the physiological and metabolic variables, and Synechococcus was the only picoprokaryotic group that showed a positive response under UVR × dust conditions. Our study highlights a dual sensitivity of nearshore versus offshore picoplankton to dust inputs and UVR fluxes, just at the time in which these two global-change factors show their highest intensities and may recreate a potential future response of the microbial food web under global-change conditions.

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

Raman lidar observations of a Saharan dust outbreak event: Characterization of the dust optical properties and determination of particle size and microphysical parameters

NASA Astrophysics Data System (ADS)

Di Girolamo, Paolo; Summa, Donato; Bhawar, Rohini; Di Iorio, Tatiana; Cacciani, Marco; Veselovskii, Igor; Dubovik, Oleg; Kolgotin, Alexey

2012-04-01

The Raman lidar system BASIL was operational in Achern (Black Forest) between 25 May and 30 August 2007 in the framework of the Convective and Orographically-induced Precipitation Study (COPS). The system performed continuous measurements over a period of approx. 36 h from 06:22 UTC on 1 August to 18:28 UTC on 2 August 2007, capturing the signature of a severe Saharan dust outbreak episode. The data clearly reveal the presence of two almost separate aerosol layers: a lower layer located between 1.5 and 3.5 km above ground level (a.g.l.) and an upper layer extending between 3.0 and 6.0 km a.g.l. The time evolution of the dust cloud is illustrated and discussed in the paper in terms of several optical parameters (particle backscatter ratio at 532 and 1064 nm, the colour ratio and the backscatter Angström parameter). An inversion algorithm was used to retrieve particle size and microphysical parameters, i.e., mean and effective radius, number, surface area, volume concentration, and complex refractive index, as well as the parameters of a bimodal particle size distribution (PSD), from the multi-wavelength lidar data of particle backscattering, extinction and depolarization. The retrieval scheme employs Tikhonov's inversion with regularization and makes use of kernel functions for randomly oriented spheroids. Size and microphysical parameters of dust particles are estimated as a function of altitude at different times during the dust outbreak event. Retrieval results reveal the presence of a fine mode with radii of 0.1-0.2 μm and a coarse mode with radii of 3-5 μm both in the lower and upper dust layers, and the dominance in the upper dust layer of a coarse mode with radii of 4-5 μm. Effective radius varies with altitude in the range 0.1-1.5 μm, while volume concentration is found to not exceed 92 μm3 cm-3. The real and imaginary part of the complex refractive index vary in the range 1.4-1.6 and 0.004-0.008, respectively.

The variation of characteristics and formation mechanisms of aerosols in dust, haze, and clear days in Beijing

NASA Astrophysics Data System (ADS)

Wang, Ying; Zhuang, Guoshun; Sun, Yele; An, Zhisheng

A 4-year campaign from 2001 to 2004 monitoring PM 2.5 and TSP in the spring season in urban Beijing, China was performed to study the variation of characteristics and the different formation mechanisms of aerosols in dust, haze, and clear days. A total of 315 aerosol samples were collected and used in this study. The aerosols were more basic in dust days and more acidic in haze days. The ions presented in the order of SO42->Ca 2+≫ NO3->Cl -> NH4+>Na + in dust days, and of SO42-> NO3-> NH4+≫Cl ->Ca 2+>K + in haze days. Ions has been classified into three groups, "Na +, Mg 2+, Ca 2+", "K +, SO42-, Cl -", and " NO3-, NH4+", representing crust, pollution-crust, and pollution species, respectively. Crust and pollution ions were the main ion fractions in dust and haze days, respectively. The variation of Ca 2+/Al showed that the increase of dust in dust and haze days was from soil and construction, respectively. "CaCO 3, CaSO 4, and (NH 4) 2SO 4" and "(NH 4) 2SO 4, NH 4NO 3, and Ca(NO 3) 2" were the major species in dust and haze days, respectively. The formation of CaSO 4 on airborne soil particles and the formation of (NH 4) 2SO 4 and NH 4NO 3 were the predominant pathways of sulfate and nitrate formations in dust and haze days, respectively. Sulfate might be mainly formed through heterogeneous reactions in the aqueous surface layer on the pre-existing particles, while nitrate mainly through homogeneous gas-phase reactions in the spring season in Beijing. The formation of sulfate and nitrate was accelerated in dust and haze days.

Saharan dust and the impact on adult and elderly allergic patients: the effect of threshold values in the northern sector of Gran Canaria, Spain.

PubMed

Menéndez, Inmaculada; Derbyshire, Edward; Carrillo, Teresa; Caballero, Elena; Engelbrecht, Johann P; Romero, Lidia E; Mayer, Pablo L; Rodríguez de Castro, Felipe; Mangas, José

2017-04-01

Gran Canaria Island is frequently impacted by Saharan dust, a health hazard of particular concern to the island population and health agencies. Airborne mineral dust has the severest impact on the higher age groups of the population, and those with respiratory conditions; despite that, on average, the ambient particulate matter (PM) concentrations fall within international PM guidelines. During 2010 and 2011, an epidemiological survey, in parallel with an air quality study, was conducted at the Dr Negrín hospital in Gran Canaria. This included the quarterly monitoring of outpatients and recording of emergency patients with respiratory diseases, together with the measurement of aerosol, meteorological, and PM-related air quality levels. The finer more toxic particles were collected with PM 2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) aerosol samplers. The filter samples were gravimetrically and chemically analyzed for their elemental, water-soluble ions, carbon, and mineralogical contents. Individual particle morphology was measured by Scanning Electron Microscopy. Statistical analysis of the chemical and clinical data included the analysis of variance and calculation of Spearman correlation coefficients. No statistically significant relations were found between the allergic control group, the emergency room admissions, pulmonary conditions, medication, and elevated Saharan dust levels. However, changing environmental conditions, such as an increase in humidity or a reduction in ambient air temperature made a significant difference to the outcomes recorded on the health statements of the allergic and respiratory illness groups of the Gran Canary population.

Observation of a Saharan dust outbreaks in the frame of the Convective and Orographically-induced Precipitation Study

NASA Astrophysics Data System (ADS)

Di Girolamo, Paolo; Summa, Donato; Bhawar, Rohini; Di Iorio, Tatiana; Caccaini, Marco; Veselovskii, Igor; Kolgotin, Alexey

2009-03-01

The Raman lidar system BASIL was operational in Achern (Supersite R, Lat: 48.64° N, Long: 8.06° E, Elev.: 140 m) in the frame of the Convective and Orographically-induced Precipitation Study. BASIL operated continuously over a period of approx. 36 hours from 06:22 UTC on 1 August to 18:28 UTC on 2 August 2007, to cover IOPs 13 a-b. In this timeframe the signature of a severe Saharan dust outbreak episode was captured. An inversion algorithm was used to retrieve particle size distribution parameters, i.e., mean and effective radius, number, surface area, and volume concentration, and complex refractive index, as well as the parameters of a bimodal particle size distribution, from the multi-wavelength lidar data of particle backscattering and extinction. The inversion method employs Tikhonov's inversion with regularization. Size distribution parameters are estimated as a function of altitude at different times during the dust outbreak event. Retrieval results reveal the dominance in the upper dust layer of a coarse mode with radii 3-4 μm. Number density and volume concentration are in the range 100-800 cm-3 and 5-40 μm3/cm3, respectively, while real and imaginary part of the complex refractive index are in the range 1.41-1.53 and 0.003-0.014, respectively.

Atmospheric aging of dust ice nucleating particles - a combined laboratory and field approach

NASA Astrophysics Data System (ADS)

Boose, Yvonne; Rodríguez, Sergio; García, M. Isabel; Linke, Claudia; Schnaiter, Martin; Zipori, Assaf; Crawford, Ian; Lohmann, Ulrike; Kanji, Zamin A.; Sierau, Berko

2016-04-01

We present INP data measured in-situ at two mostly free tropospheric locations: the High Altitude Research Station Jungfraujoch (JFJ) in the Swiss Alps, located at 3580 m above sea level (asl) and the Izaña observatory on Tenerife, off the West African shore (2373 m asl). INP concentrations were measured online with the Portable Ice Nucleation Chamber, PINC, at the Jungfraujoch in the winters of 2012, 2013 and 2014 and at Izaña in the summers of 2013 and 2014. Each measurement period lasted between 2 to 6 weeks. During summer, Izaña is frequently within the Saharan Air Layer and thus often exposed to Saharan dust events. Saharan dust also reaches the Jungfraujoch mainly during spring. For offline ice nucleation analysis in the laboratory under similar thermodynamic conditions, airborne dust was collected a) at Izaña with a cyclone directly from the air and b) collected from the surface of the Aletsch glacier close to the JFJ after deposition. Supporting measurements of aerosol particle size distributions and fluorescence were conducted at both locations, as well as cloud water isotope analysis at the Jungfraujoch and aerosol chemistry at Izaña. For both locations the origin of the INPs was investigated with a focus on dust and biological particles using back trajectories and chemical signature. Results show that dust aerosol is the dominant INP type at both locations at a temperature of 241 K. In addition to Saharan dust, also more local, basaltic dust is found at the Jungfraujoch. Biological particles are not observed to play a role for ice nucleation in clouds during winter at Jungfraujoch but are enriched in INP compared to the total aerosol at Izaña also during dust events. The comparison of the laboratory and the field measurements at Izaña indicates a good reproducibility of the field data by the collected dust samples. Field and laboratory data of the dust samples from both locations show that the dust arriving at JFJ is less ice nucleation active

Coastal Bacterioplankton Metabolism Is Stimulated Stronger by Anthropogenic Aerosols than Saharan Dust

PubMed Central

Marín, Isabel; Nunes, Sdena; Sánchez-Pérez, Elvia D.; Txurruka, Estibalitz; Antequera, Carolina; Sala, Maria M.; Marrasé, Cèlia; Peters, Francesc

2017-01-01

In oligotrophic regions, such as the Mediterranean Sea, atmospheric deposition has the potential to stimulate heterotrophic prokaryote growth and production in surface waters, especially during the summer stratification period. Previous studies focused on the role of leaching nutrients from mineral particles of Saharan (S) origin, and were restricted to single locations at given times of the year. In this study, we evaluate the effect of atmospheric particles from diverse sources and with a markedly different chemical composition [S dust and anthropogenic (A) aerosols] on marine planktonic communities from three locations of the northwestern Mediterranean with contrasted anthropogenic footprint. Experiments were also carried out at different times of the year, considering diverse initial conditions. We followed the dynamics of the heterotrophic community and a range of biogeochemical and physiological parameters in six experiments. While the effect of aerosols on bacterial abundance was overall low, bacterial heterotrophic production was up to 3.3 and 2.1 times higher in the samples amended with A and S aerosols, respectively, than in the controls. Extracellular enzymatic activities [leu-aminopeptidase (AMA) and β-glucosidase (β-Gl)] were also enhanced with aerosols, especially from A origin. AMA and β-Gl increased up to 7.1 in the samples amended with A aerosols, and up to 1.7 and 2.1 times, respectively, with S dust. The larger stimulation observed with A aerosols might be attributed to their higher content in nitrate. However, the response was variable depending the initial status of the seawater. In addition, we found that both A and S aerosols stimulated bacterial abundance and metabolism significantly more in the absence of competitors and predators. PMID:29187835

A Numerical Estimate of The Impact of The Saharan Dust On Medityerranean Trophic Web

NASA Astrophysics Data System (ADS)

Crise, A.; Crispi, G.

A first estimate of the importance of Saharan dust as input of macronutrients on the phytoplankton standing crop concentration and primary production at basin scale is here presented using a three-dimensional numerical model of the Mediterranean Sea. The numerical scheme adopted is a 1/4 degree resolution 31 levels MOM-based eco- hydrodynamical model with climatological ('perpetual year') forcings coupled on-line with a structure including multi-nutrient, size-fractionated phytoplankton functional groups, herbivores and a parametrized recycling detritus submodel, so to (explicitely or implicitely) include the major energy pathways of the upper layer mediterranean ecosystem. This model takes into account as potential limiting factors, among others, Nitrogen (in its oxidized and reduced forms) and Phosphorus. A gridded data setof (wet and dry) dust deposition over Mediterranean derived from SKIRON operational model is used to identify statistically the areas and the duration/intensity of the events. Starting from this averaging process, experiments are carried out to study the dust induced episodes of release of bioavailable phosphorus which is supposed to be the limiting factor in the oligotrophic waters of the surface layer in Med Sea. The metrics for the evaluation of the impact of deposition have been identified in phyto standing crop, primary and export production and switching in the food web functioning. These global parameters, even if cannot exaust the whealth of the informations provided by the model, can help discriminate the sensitivity of food web to the nutrient pulses induced by the deposition. First results of a scenario analysis of typical atmospheric input events, provide evidence of the response of the upper layer ecosystem to assess the sensitivity of the model predictions to the variability to integrated intensity of external input.

Sahara Dust Cloud

NASA Image and Video Library

2005-07-15

In July of 2005, a continent-sized cloud of hot air and dust originating from the Sahara Desert crossed the Atlantic Ocean and headed towards Florida and the Caribbean, captured by the Atmospheric Infrared Sounder onboard NASA Aqua satellite. A Saharan Air Layer, or SAL, forms when dry air and dust rise from Africa's west coast and ride the trade winds above the Atlantic Ocean. These dust clouds are not uncommon, especially during the months of July and August. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward. http://photojournal.jpl.nasa.gov/catalog/PIA00448

Sahara Dust Cloud

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Dust Particles Click on the image for Quicktime movie from 7/15-7/24

A continent-sized cloud of hot air and dust originating from the Sahara Desert crossed the Atlantic Ocean and headed towards Florida and the Caribbean. A Saharan Air Layer, or SAL, forms when dry air and dust rise from Africa's west coast and ride the trade winds above the Atlantic Ocean.

These dust clouds are not uncommon, especially during the months of July and August. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward.

In a sequence of images created by data acquired by the Earth-orbiting Atmospheric Infrared Sounder ranging from July 15 through July 24, we see the distribution of the cloud in the atmosphere as it swirls off of Africa and heads across the ocean to the west. Using the unique silicate spectral signatures of dust in the thermal infrared, AIRS can detect the presence of dust in the atmosphere day or night. This detection works best if there are no clouds present on top of the dust; when clouds are present, they can interfere with the signal, making it much harder to detect dust as in the case of July 24, 2005.

In the Quicktime movie, the scale at the bottom of the images shows +1 for dust definitely detected, and ranges down to -1 for no dust detected. The plots are averaged over a number of AIRS observations falling within grid boxes, and so it is possible to obtain fractional numbers. [figure removed for brevity, see original site] Total Water Vapor in the Atmosphere Around the Dust Cloud Click on the image for Quicktime movie

The dust cloud is contained within a dry adiabatic layer which originates over the Sahara Desert. This Saharan Air Layer (SAL) advances Westward over the Atlantic Ocean, overriding the cool, moist air nearer the surface. This burst of very dry air is visible in the

Re-Evaluation of Dust Radiative Forcing Using Remote Measurements of Dust Absorption

NASA Technical Reports Server (NTRS)

Kaufman, Yoram J.; Tanre, Didier; Karnieli, Arnon; Remer, Lorraine A.

1998-01-01

Spectral remote observations of dust properties from space and from the ground creates a powerful tool for determination of dust absorption of solar radiation with an unprecedented accuracy. Absorption is a key component in understanding dust impact on climate. We use Landsat spaceborne measurements at 0.47 to 2.2 microns over Senegal with ground based sunphotometers to find that Saharan dust absorption of solar radiation is two to four times smaller than in models. Though dust absorbs in the blue, almost no absorption was found for wavelengths greater 0.6 microns. The new finding increases by 50% recent estimated solar radiative forcing by dust and decreases the estimated dust heating of the lower troposphere. Dust transported from Asia shows slightly higher absorption probably due to the presence of black carbon from populated regions. Large scale application of this method to satellite data from the Earth Observing System can reduce significantly the uncertainty in the dust radiative effects.

A Long-term Record of Saharan Dust Aerosol Properties from TOMS Observations: Optical Depth and Single Scattering Albedo

NASA Technical Reports Server (NTRS)

Torres, Omar; Bhartia, P. K.; Herman, J. R.; Einaudi, Franco (Technical Monitor)

2000-01-01

The interaction between the strong Rayleigh scattering in the near UV spectral region (330-380 nm) and the processes of aerosol absorption and scattering, produce a clear spectral signal in the upwelling radiance at the top of the atmosphere. This interaction is the basis of the TOMS (Total Ozone Mapping Spectrometer) aerosol retrieval technique that can be used for their characterization and to differentiate non-absorbing sulfates from strongly UV-absorbing aerosols such as mineral dust. For absorbing aerosols, the characterization is in terms of the optical depth and single scattering albedo with assumptions about the aerosol plume height. The results for non-absorbing aerosols are not dependent on plume height. Although iron compounds represent only between 5% to 8% of desert dust aerosol mass, hematite (Fe2O3) accounts for most of the near UV absorption. Because of the large ultraviolet absorption characteristic of hematite, the near UV method of aerosol sensing is especially suited for the detection and characterization of desert dust aerosols. Using the combined record of near UV measurements by the Nimbus7 (1978-1992) and Earth Probe (1996-present) TOMS instruments, a global longterm climatology of near UV optical depth and single scattering albedo has been produced. The multi-year long record of mineral aerosol properties over the area of influence of the Saharan desert, will be discussed.

A GCM Study of Responses of the Atmospheric Water Cycle of West Africa and the Atlantic to Saharan Dust Radiative Forcing

NASA Technical Reports Server (NTRS)

Lau, K. M.; Kim, K. M.; Sud, Y. C.; Walker, G. K.

2009-01-01

The responses of the atmospheric water cycle and climate of West Africa and the Atlantic to radiative forcing of Saharan dust are studied using the NASA finite volume general circulation model (fvGCM), coupled to a mixed layer ocean. We find evidence of an "elevated heat pump" (EHP) mechanism that underlines the responses of the atmospheric water cycle to dust forcing as follow. During the boreal summerr, as a result of large-scale atmospheric feedback triggered by absorbing dust aerosols, rainfall and cloudiness are ehanIed over the West Africa/Eastern Atlantic ITCZ, and suppressed over the West Atlantic and Caribbean region. Shortwave radiation absorption by dust warms the atmosphere and cools the surface, while longwave has the opposite response. The elevated dust layer warms the air over West Africa and the eastern Atlantic. As the warm air rises, it spawns a large-scale onshore flow carrying the moist air from the eastern Atlantic and the Gulf of Guinea. The onshore flow in turn enhances the deep convection over West Africa land, and the eastern Atlantic. The condensation heating associated with the ensuing deep convection drives and maintains an anomalous large-scale east-west overturning circulation with rising motion over West Africa/eastern Atlantic, and sinking motion over the Caribbean region. The response also includes a strengthening of the West African monsoon, manifested in a northward shift of the West Africa precipitation over land, increased low-level westerlies flow over West Africa at the southern edge of the dust layer, and a near surface westerly jet underneath the dust layer overr the Sahara. The dust radiative forcing also leads to significant changes in surface energy fluxes, resulting in cooling of the West African land and the eastern Atlantic, and warming in the West Atlantic and Caribbean. The EHP effect is most effective for moderate to highly absorbing dusts, and becomes minimized for reflecting dust with single scattering albedo at0

The Saharan Aerosol Long-range Transport and Aerosol-Cloud Interaction Experiment (SALTRACE 2013) - An overview

NASA Astrophysics Data System (ADS)

Weinzierl, Bernadett; Ansmann, Albert; Reitebuch, Oliver; Freudenthaler, Volker; Müller, Thomas; Kandler, Konrad; Althausen, Dietrich; Chouza, Fernando; Dollner, Maximilian; Farrell, David; Groß, Silke; Heinold, Bernd; Kristensen, Thomas B.; Mayol-Bracero, Olga L.; Omar, Ali; Prospero, Joseph; Sauer, Daniel; Schäfler, Andreas; Toledano, Carlos; Tegen, Ina

2015-04-01

Saharan mineral dust is regularly transported over long distances impacting air quality, health, weather and climate thousands of kilometers downwind of the Sahara. During transport, the properties of mineral dust may be modified thereby changing the associated impact on the radiation budget. Although mineral dust is of key importance for the climate system many questions such as the change of the dust size distribution during long-range transport, the role of wet and dry removal mechanisms, and the complex interaction between mineral dust and clouds remain open. To investigate the aging and modification of Saharan mineral dust during long-range transport across the Atlantic Ocean, the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE: http://www.pa.op.dlr.de/saltrace) was conducted in June/July 2013. SALTRACE was designed as a closure experiment combining ground-based lidar, in-situ and sun photometer instruments deployed on Cape Verde, Barbados and Puerto Rico, with airborne measurements of the DLR research aircraft Falcon, satellite observations and model simulations. During SALTRACE, mineral dust from five dust outbreaks was studied under different atmospheric conditions and a unique data set on the chemical, microphysical and optical properties of aged mineral dust was gathered. For the first time, Lagrangian sampling of a dust plume in the Cape Verde area on 17 June 2013 which was again measured with the same instrumentation on 21 and 22 June 2013 near Barbados was realized. Further highlights of SALTRACE include the formation and evolution of tropical storm Chantal in a dusty environment and the interaction of dust with mixed-phase clouds. In our presentation, we give an overview of the SALTRACE study, discuss the meteorological situation and the dust transport during SALTRACE and highlight selected results from SALTRACE.

Health effects from Sahara dust episodes in Europe: literature review and research gaps.

PubMed

Karanasiou, A; Moreno, N; Moreno, T; Viana, M; de Leeuw, F; Querol, X

2012-10-15

The adverse consequences of particulate matter (PM) on human health have been well documented. Recently, special attention has been given to mineral dust particles, which may be a serious health threat. The main global source of atmospheric mineral dust is the Sahara desert, which produces about half of the annual mineral dust. Sahara dust transport can lead to PM levels that substantially exceed the established limit values. A review was undertaken using the ISI web of knowledge database with the objective to identify all studies presenting results on the potential health impact from Sahara dust particles. The review of the literature shows that the association of fine particles, PM₂.₅, with total or cause-specific daily mortality is not significant during Saharan dust intrusions. However, regarding coarser fractions PM₁₀ and PM₂.₅₋₁₀ an explicit answer cannot be given. Some of the published studies state that they increase mortality during Sahara dust days while other studies find no association between mortality and PM₁₀ or PM₂.₅₋₁₀. The main conclusion of this review is that health impact of Saharan dust outbreaks needs to be further explored. Considering the diverse outcomes for PM₁₀ and PM₂.₅₋₁₀, future studies should focus on the chemical characterization and potential toxicity of coarse particles transported from Sahara desert mixed or not with anthropogenic pollutants. The results of this review may be considered to establish the objectives and strategies of a new European directive on ambient air quality. An implication for public policy in Europe is that to protect public health, anthropogenic sources of particulate pollution need to be more rigorously controlled in areas highly impacted by the Sahara dust. Copyright © 2012 Elsevier Ltd. All rights reserved.

Single particle chemical composition, state of mixing and shape of fresh and aged Saharan dust in Morocco and at Cape Verde Islands during SAMUM I and II

NASA Astrophysics Data System (ADS)

Kandler, Konrad; Emmel, Carmen; Ebert, Martin; Lieke, Kirsten; Müller-Ebert, Dörthe; Schütz, Lothar; Weinbruch, Stephan

2010-05-01

The Saharan Mineral Dust Experiment (SAMUM) is focussed to the understanding of the radiative effects of mineral dust. During the SAMUM 2006 field campaign at Tinfou, southern Morocco, chemical and mineralogical properties of fresh desert aerosol was measured. The winter campaign of Saharan Mineral Dust Experiment II in 2008 was based in Praia, Island of Santiago, Cape Verde. This second field campaign was dedicated to the investigation of transported Saharan Mineral Dust. Ground-based and airborne measurements were performed in the winter season, where mineral dust from the Western Sahara and biomass burning aerosol from the Sahel region occurred. Samples were collected with a miniature impactor system, a sedimentation trap, a free-wing impactor, and a filter sampler. Beryllium discs as well as carbon coated nickel discs, carbon foils, and nuclepore and fiber filters were used as sampling substrates. The size-resolved particle aspect ratio and the chemical composition are determined by scanning electron microscopy and energy-dispersive X-ray microanalysis of single particles. Mineralogical bulk composition is determined by X-ray diffraction analysis. In Morocco, three size regimes are identified in the aerosol: Smaller than 500 nm in diameter, the aerosol consists of sulfates and mineral dust. Larger than 500 nm up to 50 µm, mineral dust dominates, consisting mainly of silicates, and - to a lesser extent - carbonates and quartz. Larger than 50 µm, approximately half of the particles consist of quartz. Time series of the elemental composition show a moderate temporal variability of the major compounds. Calcium-dominated particles are enhanced during advection from a prominent dust source in Northern Africa (Chott El Djerid and surroundings). More detailed results are found in Kandler et al. (2009) At Praia, Cape Verde, the boundary layer aerosol consists of a superposition of mineral dust, marine aerosol and ammonium sulfate, soot, and other sulfates as well as

Mineral dust emission from the Bodélé Depression, northern Chad, during BoDEx 2005

NASA Astrophysics Data System (ADS)

Todd, Martin C.; Washington, Richard; Martins, José Vanderlei; Dubovik, Oleg; Lizcano, Gil; M'bainayel, Samuel; Engelstaedter, Sebastian

2007-03-01

Mineral dust in the atmosphere is an important component of the climate system but is poorly quantified. The Bodélé Depression of northern Chad stands out as the world's greatest source region of mineral dust into the atmosphere. Frequent dust plumes are a distinguishing feature of the region's climate. There is a need for more detailed information on processes of dust emission/transport and dust optical properties to inform model simulations of this source. During the Bodélé Dust Experiment (BoDEx) in 2005, instrumentation was deployed to measure dust properties and boundary layer meteorology. Observations indicate that dust emission events are triggered when near-surface wind speeds exceed 10 ms-1, associated with synoptic-scale variability in the large-scale atmospheric circulation. Dust emission pulses in phase with the diurnal cycle of near-surface winds. Analysis of dust samples shows that the dust consists predominantly of fragments of diatomite sediment. The particle size distribution of this diatomite dust estimated from sun photometer data, using a modified Aeronet retrieval algorithm, indicates a dominant coarse mode (radius centered on 1-2 μm) similar to other Saharan dust observations. Single-scattering albedo values are high, broadly in line with other Saharan dust even though the diatomite composition of dust from the Bodélé is likely to be unusual. The radiative impact of high dust loadings results in a reduction in surface daytime maximum temperature of around 7°C in the Bodélé region. Using optical and physical properties of dust obtained in the field, we estimate the total dust flux emitted from the Bodélé to be 1.18 ± 0.45 Tg per day during a substantial dust event. We speculate that the Bodélé Depression (˜10,800 km2) may be responsible for between 6-18% of global dust emissions, although the uncertainty in both the Bodélé and global estimates remains high.

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.

Dust loading of the normal atmosphere

NASA Astrophysics Data System (ADS)

Hall, F. F., Jr.

1983-01-01

Soil dust can contribute to atmospheric turbidity over most of the globe. The major sources of this dust are in the world's arid regions, where loadings of over 1000 micrograms/cu m can occur during strong winds. Saharan dust transported across the Atlantic can produce loadings up to 100 micrograms/cu m in the Western Hemisphere. Asian sources yield springtime loadings of 5-10 micrograms/cu m at Midway Island. Other important sources of dust are agricultural plowing and vehicular traffic on graded roads. The U.S. air quality standard of 75 micrograms/cu m is often exceeded in rural areas.

CALIPSO Observations of Transatlantic Dust: Vertical Stratification and Effect of Clouds

NASA Technical Reports Server (NTRS)

Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Kalashnikova, Olga V.; Kostinski, Alexander B.

2012-01-01

CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios during the summer of 2007 are used to study transatlantic dust properties downwind of Saharan sources, and to examine the interaction of clouds and dust. We discuss the following findings: (1) while lidar backscatter doesn't change much with altitude in the Saharan Air Layer (SAL), depolarization and color ratios both increase with altitude in the SAL; (2) lidar backscatter and color ratio increase as dust is transported westward in the SAL; (3) the vertical lapse rate of dust depolarization ratio increases within SAL as plumes move westward; (4) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Finally, (5) the odds of CALIOP finding dust below SAL next to clouds are about 2/3 of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dusty volumes lose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

An automatic collector to monitor insoluble atmospheric deposition: application for mineral dust deposition

NASA Astrophysics Data System (ADS)

Laurent, B.; Losno, R.; Chevaillier, S.; Vincent, J.; Roullet, P.; Bon Nguyen, E.; Ouboulmane, N.; Triquet, S.; Fornier, M.; Raimbault, P.; Bergametti, G.

2015-07-01

Deposition is one of the key terms of the mineral dust cycle. However, dust deposition remains poorly constrained in transport models simulating the atmospheric dust cycle. This is mainly due to the limited number of relevant deposition measurements. This paper aims to present an automatic collector (CARAGA), specially developed to sample the total (dry and wet) atmospheric deposition of insoluble dust in remote areas. The autonomy of the CARAGA can range from 25 days to almost 1 year depending on the programmed sampling frequency (from 1 day to 2 weeks respectively). This collector is used to sample atmospheric deposition of Saharan dust on the Frioul islands in the Gulf of Lions in the Western Mediterranean. To quantify the mineral dust mass in deposition samples, a weighing and ignition protocol is applied. Almost 2 years of continuous deposition measurements performed on a weekly sampling basis on Frioul Island are presented and discussed with air mass trajectories and satellite observations of dust. Insoluble mineral deposition measured on Frioul Island was 2.45 g m-2 for February to December 2011 and 3.16 g m-2 for January to October 2012. Nine major mineral deposition events, measured during periods with significant MODIS aerosol optical depths, were associated with air masses coming from the southern Mediterranean Basin and North Africa.

Atmospheric response to Saharan dust deduced from ECMWF reanalysis increments

NASA Astrophysics Data System (ADS)

Kishcha, P.; Alpert, P.; Barkan, J.; Kirchner, I.; Machenhauer, B.

2003-04-01

This study focuses on the atmospheric temperature response to dust deduced from a new source of data - the European Reanalysis (ERA) increments. These increments are the systematic errors of global climate models, generated in reanalysis procedure. The model errors result not only from the lack of desert dust but also from a complex combination of many kinds of model errors. Over the Sahara desert the dust radiative effect is believed to be a predominant model defect which should significantly affect the increments. This dust effect was examined by considering correlation between the increments and remotely-sensed dust. Comparisons were made between April temporal variations of the ERA analysis increments and the variations of the Total Ozone Mapping Spectrometer aerosol index (AI) between 1979 and 1993. The distinctive structure was identified in the distribution of correlation composed of three nested areas with high positive correlation (> 0.5), low correlation, and high negative correlation (<-0.5). The innermost positive correlation area (PCA) is a large area near the center of the Sahara desert. For some local maxima inside this area the correlation even exceeds 0.8. The outermost negative correlation area (NCA) is not uniform. It consists of some areas over the eastern and western parts of North Africa with a relatively small amount of dust. Inside those areas both positive and negative high correlations exist at pressure levels ranging from 850 to 700 hPa, with the peak values near 775 hPa. Dust-forced heating (cooling) inside the PCA (NCA) is accompanied by changes in the static stability of the atmosphere above the dust layer. The reanalysis data of the European Center for Medium Range Weather Forecast(ECMWF) suggests that the PCA (NCA) corresponds mainly to anticyclonic (cyclonic) flow, negative (positive) vorticity, and downward (upward) airflow. These facts indicate an interaction between dust-forced heating /cooling and atmospheric circulation. The

Profiling of Saharan dust from the Caribbean to western Africa - Part 1: Layering structures and optical properties from shipborne polarization/Raman lidar observations

NASA Astrophysics Data System (ADS)

Rittmeister, Franziska; Ansmann, Albert; Engelmann, Ronny; Skupin, Annett; Baars, Holger; Kanitz, Thomas; Kinne, Stefan

2017-11-01

We present final and quality-assured results of multiwavelength polarization/Raman lidar observations of the Saharan air layer (SAL) over the tropical Atlantic. Observations were performed aboard the German research vessel R/V Meteor during the 1-month transatlantic cruise from Guadeloupe to Cabo Verde over 4500 km from 61.5 to 20° W at 14-15° N in April-May 2013. First results of the shipborne lidar measurements, conducted in the framework of SALTRACE (Saharan Aerosol Long-range Transport and Aerosol-Cloud Interaction Experiment), were reported by Kanitz et al.(2014). Here, we present four observational cases representing key stages of the SAL evolution between Africa and the Caribbean in detail in terms of layering structures and optical properties of the mixture of predominantly dust and aged smoke in the SAL. We discuss to what extent the lidar results confirm the validity of the SAL conceptual model which describes the dust long-range transport and removal processes over the tropical Atlantic. Our observations of a clean marine aerosol layer (MAL, layer from the surface to the SAL base) confirm the conceptual model and suggest that the removal of dust from the MAL, below the SAL, is very efficient. However, the removal of dust from the SAL assumed in the conceptual model to be caused by gravitational settling in combination with large-scale subsidence is weaker than expected. To explain the observed homogenous (height-independent) dust optical properties from the SAL base to the SAL top, from the African coast to the Caribbean, we have to assume that the particle sedimentation strength is reduced and dust vertical mixing and upward transport mechanisms must be active in the SAL. Based on lidar observations on 20 nights at different longitudes in May 2013, we found, on average, MAL and SAL layer mean values (at 532 nm) of the extinction-to-backscatter ratio (lidar ratio) of 17±5 sr (MAL) and 43±8 sr (SAL), of the particle linear depolarization ratio of 0

Saharan dust as a causal factor of hemispheric asymmetry in aerosols and cloud cover over the tropical Atlantic Ocean

DOE PAGES

Kishcha, Pavel; Da Sliva, Arlindo; Starobinets, Boris; ...

2015-07-09

Meridional distribution of aerosol optical thickness (AOT) over the tropical Atlantic Ocean (30°N – 30°S) was analyzed to assess seasonal variations of meridional AOT asymmetry. Ten-year MERRA Aerosol Reanalysis (MERRAero) data (July 2002 – June 2012) confirms that the Sahara desert emits a significant amount of dust into the atmosphere over the Atlantic Ocean. Only over the Atlantic Ocean did MERRAero show that desert dust dominates other aerosol species and is responsible for meridional aerosol asymmetry between the tropical North and South Atlantic. Over the 10-year period under consideration, both MISR measurements and MERRAero data showed a pronounced meridional AOTmore » asymmetry. The meridional AOT asymmetry, characterized by the hemispheric ratio (RAOT) of AOT averaged separately over the North and over the South Atlantic, was about 1.7. Seasonally, meridional AOT asymmetry over the Atlantic was the most pronounced between March and July, when dust presence is maximal (RAOT ranged from 2 to 2.4). There was no noticeable meridional aerosol asymmetry in total AOT from September to October. During this period the contribution of carbonaceous aerosols to total AOT in the South Atlantic was comparable to the contribution of dust aerosols to total AOT in the North Atlantic. During the same 10-year period, MODIS cloud fraction (CF) data showed that there was no noticeable asymmetry in meridional CF distribution in different seasons (the hemispheric ratio of CF ranged from 1.0 to 1.2). MODIS CF data illustrated significant cloud cover (CF of 0.7 – 0.9) with limited precipitation ability along the Saharan Air Layer.« less

CALIPSO Observations of Transatlantic Dust: Vertical Stratification and Effect of Clouds

NASA Technical Reports Server (NTRS)

Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Kalashnikova, Olga V.; Kostinski, Alexander B.

2014-01-01

We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well as particulate retrievals during the summer of 2007 to study transatlantic dust properties downwind of Saharan sources, and to examine the influence of nearby clouds on dust. Our analysis suggests that (1) under clear skies, while lidar backscatter and color ratio do not change much with altitude and longitude in the Saharan Air Layer (SAL), depolarization ratio increases with altitude and decreases westward in the SAL (2) the vertical lapse rate of dust depolarization ratio, introduced here, increases within SAL as plumes move westward (3) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Moreover, the presence of nearby clouds tends to decrease the depolarization of dust volumes within SAL. Finally, (4) the odds of CALIOP finding dust below SAL next to clouds are about of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dust volumes loose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

Impact of Radiatively Interactive Dust Aerosols in the NASA GEOS-5 Climate Model: Sensitivity to Dust Particle Shape and Refractive Index

NASA Technical Reports Server (NTRS)

Colarco, Peter R.; Nowottnick, Edward Paul; Randles, Cynthia A.; Yi, Bingqi; Yang, Ping; Kim, Kyu-Myong; Smith, Jamison A.; Bardeen, Charles D.

2013-01-01

We investigate the radiative effects of dust aerosols in the NASA GEOS-5 atmospheric general circulation model. GEOS-5 is improved with the inclusion of a sectional aerosol and cloud microphysics module, the Community Aerosol and Radiation Model for Atmospheres (CARMA). Into CARMA we introduce treatment of the dust and sea salt aerosol lifecycle, including sources, transport evolution, and sinks. The aerosols are radiatively coupled to GEOS-5, and we perform a series of multi-decade AMIP-style simulations in which dust optical properties (spectral refractive index and particle shape distribution) are varied. Optical properties assuming spherical dust particles are from Mie theory, while those for non-spherical shape distributions are drawn from a recently available database for tri-axial ellipsoids. The climatologies of the various simulations generally compare well to data from the MODIS, MISR, and CALIOP space-based sensors, the ground-based AERONET, and surface measurements of dust deposition and concentration. Focusing on the summertime Saharan dust cycle we show significant variability in our simulations resulting from different choices of dust optical properties. Atmospheric heating due to dust enhances surface winds over important Saharan dust sources, and we find a positive feedback where increased dust absorption leads to increased dust emissions. We further find that increased dust absorption leads to a strengthening of the summertime Hadley cell circulation, increasing dust lofting to higher altitudes and strengthening the African Easterly Jet. This leads to a longer atmospheric residence time, higher altitude, and generally more northward transport of dust in simulations with the most absorbing dust optical properties. We find that particle shape, although important for radiance simulations, is a minor effect compared to choices of refractive index, although total atmospheric forcing is enhanced by greater than 10 percent for simulations incorporating a

Influence of mineral dust transport on the chemical composition and physical properties of the Eastern Mediterranean aerosol

NASA Astrophysics Data System (ADS)

Koçak, M.; Theodosi, C.; Zarmpas, P.; Séguret, M. J. M.; Herut, B.; Kallos, G.; Mihalopoulos, N.; Kubilay, N.; Nimmo, M.

2012-09-01

Bulk aerosol samples were collected from three different coastal rural sites located around the Eastern Mediterranean, (i) Erdemli (ER), Turkey, (ii) Heraklion (HR), Crete, Greece, and (iii) Tel Shikmona (TS), Israel, during two distinct mineral dust periods (October, 2007 and April, 2008) in order to explore the temporal and geographical variability in the aerosol chemical composition. Samples were analyzed for trace elements (Al, Fe, Mn, Ca, Cr, Zn, Cu, V, Ni, Cd, Pb) and water-soluble ions (Cl-, NO3-, SO42-, C2O42-, Na+, NH4+, K+, Mg2+ and Ca2+). The dust events were categorized on the basis of Al concentrations >1000 ng m-3, SKIRON dust forecast model and 3-day back trajectories into three groups namely, Middle East, Mixed and Saharan desert. ER and TS were substantially affected by dust events originating from the Middle East, particularly in October, whilst HR was not influenced by dust transport from the Middle East. Higher AOT values were particularly associated with higher Al concentrations. Contrary to the highest Al concentration: 6300 ng m-3, TS showed relatively lower AI and AOT. Al concentrations at ER were similar for October and April, whilst OMI-AI and AOT values were ˜2 times higher in April. This might be attributed to the weak sensitivity of the TOMS instrument to absorbing aerosols near the ground and optical difference between Middle East and Saharan desert dusts. The lowest enhancement of anthropogenic aerosol species was observed at HR during dust events (nssSO42-/nssCa2+ ˜ 0.13). These species were particularly enhanced when mineral dust arrived at sites after passing through populated and industrialized urban areas.

Modelling supernova line profile asymmetries to determine ejecta dust masses: SN 1987A from days 714 to 3604

NASA Astrophysics Data System (ADS)

Bevan, Antonia; Barlow, M. J.

2016-02-01

The late-time optical and near-IR line profiles of many core-collapse supernovae exhibit a red-blue asymmetry as a result of greater extinction by internal dust of radiation emitted from the receding parts of the supernova ejecta. We present here a new code, DAMOCLES, that models the effects of dust on the line profiles of core-collapse supernovae in order to determine newly formed dust masses. We find that late-time dust-affected line profiles may exhibit an extended red scattering wing (as noted by Lucy et al. 1989) and that they need not be flux-biased towards the blue, although the profile peak will always be blueshifted. We have collated optical spectra of SN 1987A from a variety of archival sources and have modelled the Hα line from days 714 to 3604 and the [O I] 6300,6363 Å doublet between days 714 and 1478. Our line profile fits rule out day 714 dust masses >3 × 10-3 M⊙ for all grain types apart from pure magnesium silicates, for which no more than 0.07 M⊙ can be accommodated. Large grain radii ( ≥ 0.6 μm) are generally required to fit the line profiles even at the earlier epochs. We find that a large dust mass (≥0.1 M⊙) had formed by day 3604 and infer that the majority of the present dust mass must have formed after this epoch. Our findings agree with recent estimates from spectral energy distribution fits for the dust mass evolution of SN 1987A and support the inference that the majority of SN 1987A's dust formed many years after the initial explosion.

Dust Storms and Mortality in the United States, 1995-2005

EPA Science Inventory

Extreme weather events, such as dust storms, are predicted to become more frequent as the global climate warms through the 21st century. The impact of dust storms on human health has been studied extensively in the context of Asian, Saharan, Arabian, and Australian storms, but t...

A Model for Saharan Dust Transport.

NASA Astrophysics Data System (ADS)

D'Almeida, Guillaume A.

1986-07-01

In this paper the source strength and the deposition rate of the dust emerging from the Sahara are assessed. For this purpose a multichannel sunphotometer has been developed and a turbidity network covering 11 stations has been set up in the Sahara, in the Sahel region and the surrounding southern area for a duration of about two years. A correlation analysis connecting observed aerosol turbidity parameters and mineral dust mass concentration has been performed during a four-week field campaign in Agadez (Niger). An appropriate box model including the aerosol turbidity parameters, actual wind field data of the source regions, the general circulation pattern over Africa and dry and wet deposition reveals a total mass production of about 630 × 106 and 710 × 106 t yr1 for all suspended particulate matter, 80 × 106 and 90 × 106 t yr1 for aerosol particles smaller than 5 m radius for the years 1981 and 1982 respectively. About 60% of the mass moves southward to the Gulf of Guinea, 28% westward to the equatorial North Atlantic Ocean and 12% northward to Europe. A considerable part is deposited in the Atlantic Ocean and the Mediterranean forming deep-sea sediments.

Dust Optical Properties Over North Africa and Arabian Peninsula Derived from the AERONET Dataset

NASA Technical Reports Server (NTRS)

Kim, D.; Chin, M.; Yu, H.; Eck, T. F.; Sinyuk, A.; Smirnov, A.; Holben, B. N.

2011-01-01

Dust optical properties over North Africa and the Arabian Peninsula are extracted from the quality assured multi-year datasets obtained at 14 sites of the Aerosol Robotic Network (AERONET). We select the data with (a) large aerosol optical depth (AOD >= 0.4 at 440 nm) and (b) small Angstrom exponent (A(sub ext)<= 0.2) for retaining high accuracy and reducing interference of non-dust aerosols. The result indicates that the major fraction of high aerosol optical depth days are dominated by dust over these sites even though it varies depending on location and time. We have found that the annual mean and standard deviation of single scattering albedo, asymmetry parameter, real refractive index, and imaginary refractive index for Saharan and Arabian desert dust is 0.944 +/- 0.005, 0.752 +/- 0.014, 1.498 +/- 0.032, and 0.0024 +/- 0.0034 at 550 nm wavelength, respectively. Dust aerosol selected by this method is less absorbing than the previously reported values over these sites. The weaker absorption of dust from this study is consistent with the studies using remote sensing techniques from satellite. These results can help to constrain uncertainties in estimating global dust shortwave radiative forcing.

Characterization and quantification of bioaerosols in Saharan dust transported across the Atlantic

NASA Astrophysics Data System (ADS)

Yordanova, Petya; Maier, Stefanie; Rodriguez-Caballero, Emilio; Ditas, Florian; Klimach, Thomas; Prass, Maria; Hrabe de Angelis, Isabella; Blades, Edmund; Holanda, Bruna; Pöhlker, Mira; Maurus, Isabel; Kopper, Gila; Farrell, David; Stevens, Bjorn; Prospero, Joseph M.; Ulrich, Pöschl; Andreae, Meinrat O.; Fröhlich-Nowoisky, Janine; Pöhlker, Christopher; Weber, Bettina

2017-04-01

Primary biological aerosols (bioaerosols), forming a subset of atmospheric particles, are directly released from the biosphere into the atmosphere. They comprise living and dead organisms (e.g., algae, bacteria, archaea), reproduction units (e.g., pollen, seeds, spores) as well as organism fragments and excretions. They play a key role in the dispersal of otherwise mostly sessile organisms (e.g. plants), but also in the spread of pathogens and diseases. Recently, also soil dust has been described to frequently occur in a close connection with biological particles (Conen et al., 2011). Bioaerosols can serve as nuclei for cloud droplets and ice crystals and may influence the radiative properties of the atmosphere, thus influencing the hydrological cycle and climate (Fröhlich-Nowoisky et al., 2016). It has been well described that dust masses are transported across the Atlantic comprising a large variety of bacteria and fungi, but the origin of the biological material remained largely unknown (Prospero et al., 2005). In the present study we aim to accomplish three major tasks, i.e., 1) Thorough identification and quantification of bioaerosol particles, 2) Characterization of ice nucleating (IN) properties of bioaerosols, and 3) Evaluation of similarities between bioaerosols and biological material in source regions of dust. For our field work we utilized filter techniques to collect aerosol samples of transatlantically transported dust at the easternmost site (Ragged Point) on the Caribbean island Barbados. Sampling took place from July to August 2016, when dust transport volumes were expected to reach peak amounts. Total suspended particles were collected ˜30 m above sea level using a high volume sampler (˜ 500 L min-1) and a micro-orifice uniform deposit impactor (MOUDI™) to obtain size-resolved samples. Directly after sampling at different time intervals (i.e. 24-hour, 48-hour, and 7-day samples) the filters were frozen until further analyses. In a

The summer 2012 Saharan dust season in the western Mediterranean with focus on the intense event of late June during the Pre-ChArMEx campaign

NASA Astrophysics Data System (ADS)

Dulac, François; Nicolas, José B.; Sciare, Jean; Mallet, Marc; Léon, Jean-François; Pont, Véronique; Sicard, Michaël; Renard, Jean-Baptiste; Nabat, Pierre; El Amraoui, Laaziz; Jaumouillé, Elodie; Roberts, Greg; Attié, Jean-Luc; Somot, Samuel; Laurent, Benoît; Losno, Rémi; Vincent, Julie; Formenti, Paola; Bergametti, Gilles; Ravetta, François

2013-04-01

Saharan dust is an usual aerosol over the Mediterranean basin that contributes to the high average aerosol load during summer in the western Mediterranean marine environment. Satellite monitoring shows that dust events were numerous during summer 2012. Even though most of the transport of dust particles occurs in altitude, as shown by surface lidars and airborne data, dust events significantly impact surface PM10 concentrations even in urban traffic type of air quality monitoring stations, and background stations are needed to assess the contribution of desert dust. During the pre-ChArMEx field campaign and associated field campaigns TRAQA and VESSAER in the north-western Mediterranean, a large scale African dust event occurred in late June-early July with optical depth levels in the visible up to 0.5-0.7 rather unusual in that area according to long time remote sensing AERONET or satellite series. We have performed measurements in the dust plume for several days with a particularly large variety of both ground-based and airborne (from sounding balloons, an aircraft and an ultra-light aircraft) remote sensing and in situ instruments. In addition to satellite aerosol products including MSG/SEVIRI, which provides the spatial distribution of the aerosol optical depth over the basin up to 4 times per hour, POLDER and CALIOP, this yields a complete set of unusual quantitative constraints for model simulations of this event, combining data on aerosol optical depth, vertical distribution, particle size distribution, chemical, optical and microphysical properties. We shall provide an overview of the data set that includes original measurements of the vertical profile of the aerosol size distribution with a new small balloon borne OPC called LOAC (Light Optical Aerosol Counter) showing large dust particles (up to 30 µm in diameter) within a thick dust layer between 1 and 5 km above south-eastern France, and original network measurement of weekly dust deposition with a new

The Association between Dust Storms and Daily Non ...

EPA Pesticide Factsheets

Background:The impact of dust storms on human health has been studied in the context of Asian,Saharan, Arabian, and Australian storms,but there has been no recent population-level epidemiological research on the dust storms in North America . The relevance of dust storms to public health is likely to increase as extreme weather events are predicted to become more frequent with anticipated changes in climate through the 21st century.Objectives: We examined the association between dust storms and county-level non-accidental mortality in the United States from 1993 through 2005.Methods:Dust storm incidence data, including date and approximate location. are taken from the U.S. National Weather Service storm database. County-level mortality data for the years 1993-2005 were acquired from the National Center for Health Statistics. Distributed lag conditionallogistic regression models under a time-stratified case-crossover design were used to study the relationship between dust storms and daily mortality counts over the whole United States and in Arizona and California specifically. End points included total non-accidental mortality and three mortality subgroups (cardiovascular, respiratory, and other non-acc idental).Results: We estimated that for the United States as a whole, total non-accidental mortality increased by 7.4% (95% Cl: 1.6, 13.5; p = 0.011) and 6.7% (95% Cl: 1.1,12.6; p = 0.018) at 2- and 3-day lags, respectively, and by an average of 2.7% (95% Cl: 0.4,

Dust Storms in the United States are Associated with Increased Cardiovascular Mortality

EPA Science Inventory

Background: Extreme weather events such as dust storms are predicted to become more frequent as the global climate warms through the 21st century. Studies of Asian, Saharan, Arabian, and Australian dust storms have found associations with cardiovascular and total non-accidental...

Far-infrared and dust properties of present-day galaxies in the EAGLE simulations

NASA Astrophysics Data System (ADS)

Camps, Peter; Trayford, James W.; Baes, Maarten; Theuns, Tom; Schaller, Matthieu; Schaye, Joop

2016-10-01

The Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological simulations reproduce the observed galaxy stellar mass function and many galaxy properties. In this work, we study the dust-related properties of present-day EAGLE galaxies through mock observations in the far-infrared and submm wavelength ranges obtained with the 3D dust radiative transfer code SKIRT. To prepare an EAGLE galaxy for radiative transfer processing, we derive a diffuse dust distribution from the gas particles and we re-sample the star-forming gas particles and the youngest star particles into star-forming regions that are assigned dedicated emission templates. We select a set of redshift-zero EAGLE galaxies that matches the K-band luminosity distribution of the galaxies in the Herschel Reference Survey (HRS), a volume-limited sample of about 300 normal galaxies in the Local Universe. We find overall agreement of the EAGLE dust scaling relations with those observed in the HRS, such as the dust-to-stellar mass ratio versus stellar mass and versus NUV-r colour relations. A discrepancy in the f250/f350 versus f350/f500 submm colour-colour relation implies that part of the simulated dust is insufficiently heated, likely because of limitations in our sub-grid model for star-forming regions. We also investigate the effect of adjusting the metal-to-dust ratio and the covering factor of the photodissociation regions surrounding the star-forming cores. We are able to constrain the important dust-related parameters in our method, informing the calculation of dust attenuation for EAGLE galaxies in the UV and optical domain.

Longwave radiative effects of Saharan dust during the ICE-D campaign

NASA Astrophysics Data System (ADS)

Brooke, Jennifer; Havemann, Stephan; Ryder, Claire; O'Sullivan, Debbie

2017-04-01

The Havemann-Taylor Fast Radiative Transfer Code (HT-FRTC) is a fast radiative transfer model based on Principal Components. Scattering has been incorporated into HT-FRTC which allows simulations of aerosol as well as clear-sky atmospheres. This work evaluates the scattering scheme in HT-FRTC and investigates dust-affected brightness temperatures using in-situ observations from Ice in Clouds Experiment - Dust (ICE-D) campaign. The ICE-D campaign occurred during August 2015 and was based from Cape Verde. The ICE-D campaign is a multidisciplinary project which achieved measurements of in-situ mineral dust properties of the dust advected from the Sahara, and on the aerosol-cloud interactions using the FAAM BAe-146 research aircraft. ICE-D encountered a range of low (0.3), intermediate (0.8) and high (1.3) aerosol optical depths, AODs, and therefore provides a range of atmospheric dust loadings in the assessment of dust scattering in HT-FRTC. Spectral radiances in the thermal infrared window region (800 - 1200 cm-1) are sensitive to the presence of mineral dust; mineral dust acts to reduce the upwelling infrared radiation caused by the absorption and re-emission of radiation by the dust layer. ARIES (Airborne Research Interferometer Evaluation System) is a nadir-facing interferometer, measuring infrared radiances between 550 and 3000 cm-1. The ARIES spectral radiances are converted to brightness temperatures by inversion of the Planck function. The mineral dust size distribution is important for radiative transfer applications as it provides a measure of aerosol scattering. The longwave spectral mineral dust optical properties including the mass extinction coefficients, single scattering albedos and the asymmetry parameter have been derived from the mean ICE-D size distribution. HT-FRTC scattering simulations are initialised with vertical mass fractions which can be derived from extinction profiles from the lidar along with the specific extinction coefficient, kext (m2

Ice nucleating particles in the Saharan Air Layer

NASA Astrophysics Data System (ADS)

Boose, Yvonne; Sierau, Berko; García, M. Isabel; Rodríguez, Sergio; Alastuey, Andrés; Linke, Claudia; Schnaiter, Martin; Kupiszewski, Piotr; Kanji, Zamin A.; Lohmann, Ulrike

2016-07-01

This study aims at quantifying the ice nucleation properties of desert dust in the Saharan Air Layer (SAL), the warm, dry and dust-laden layer that expands from North Africa to the Americas. By measuring close to the dust's emission source, before aging processes during the transatlantic advection potentially modify the dust properties, the study fills a gap between in situ measurements of dust ice nucleating particles (INPs) far away from the Sahara and laboratory studies of ground-collected soil. Two months of online INP concentration measurements are presented, which were part of the two CALIMA campaigns at the Izaña observatory in Tenerife, Spain (2373 m a.s.l.), in the summers of 2013 and 2014. INP concentrations were measured in the deposition and condensation mode at temperatures between 233 and 253 K with the Portable Ice Nucleation Chamber (PINC). Additional aerosol information such as bulk chemical composition, concentration of fluorescent biological particles as well as the particle size distribution was used to investigate observed variations in the INP concentration. The concentration of INPs was found to range between 0.2 std L-1 in the deposition mode and up to 2500 std L-1 in the condensation mode at 240 K. It correlates well with the abundance of aluminum, iron, magnesium and manganese (R: 0.43-0.67) and less with that of calcium, sodium or carbonate. These observations are consistent with earlier results from laboratory studies which showed a higher ice nucleation efficiency of certain feldspar and clay minerals compared to other types of mineral dust. We find that an increase of ammonium sulfate, linked to anthropogenic emissions in upwind distant anthropogenic sources, mixed with the desert dust has a small positive effect on the condensation mode INP per dust mass ratio but no effect on the deposition mode INP. Furthermore, the relative abundance of biological particles was found to be significantly higher in INPs compared to the ambient

Possible influence of dust on hurricane genesis

NASA Astrophysics Data System (ADS)

Bretl, Sebastian; Reutter, Philipp; Raible, Christoph C.; Ferrachat, Sylvaine; Lohmann, Ulrike

2014-05-01

Tropical Cyclones (TCs) belong to the most extreme events in nature. In the past decade, the possible impact of dust on Atlantic hurricanes receives growing interest. As mineral dust is able to absorb incoming solar radiation and therefore warm the surrounding air, the presence of dust can lead to a reduction of sea surface temperature (SST) and an increase in atmospheric stability. Furthermore, resulting baroclinic effects and the dry Saharan easterly jet lead to an enhanced vertical shear of the horizontal winds. SST, stability, moisture and vertical wind shear are known to potentially impact hurricane activity. But how Saharan dust influences these prerequisites for hurricane formation is not yet clear. Some dynamical mechanisms induced by the SAL might even strengthen hurricanes. An adequate framework for investigating the possible impact of dust on hurricanes is comparing high resolution simulations (~0.5°x0.5°, 31 vertical levels) with and without radiatively active dust aerosols. To accomplish this task, we are using the general circulation model ECHAM6 coupled to a modified version of the aerosol model HAM, ECHAM6-HAM-Dust. Instead of the five aerosol species HAM normally contains, the modified version takes only insoluble dust into account, but modifies the scavenging parameters in order to have a similar lifetime of dust as in the full ECHAM6-HAM. All remaining aerosols are prescribed. To evaluate the effects of dust on hurricanes, a TC detection and tracking method is applied on the results. ECHAM6-HAM-Dust was used in two configurations, one with radiatively active dust aerosols and one with dust being not radiatively active. For both set-ups, 10 Monte-Carlo simulations of the year 2005 were performed. A statistical method which identifies controlling parameters of hurricane genesis was applied on North Atlantic developing and non-developing disturbances in all simulations, comparing storms in the two sets of simulations. Hereby, dust can be assigned

Advances in understanding mineral dust and boundary layer processes over the Sahara from Fennec aircraft observations

NASA Astrophysics Data System (ADS)

Ryder, C. L.; McQuaid, J. B.; Flamant, C.; Rosenberg, P. D.; Washington, R.; Brindley, H. E.; Highwood, E. J.; Marsham, J. H.; Parker, D. J.; Todd, M. C.; Banks, J. R.; Brooke, J. K.; Engelstaedter, S.; Estelles, V.; Formenti, P.; Garcia-Carreras, L.; Kocha, C.; Marenco, F.; Sodemann, H.; Allen, C. J. T.; Bourdon, A.; Bart, M.; Cavazos-Guerra, C.; Chevaillier, S.; Crosier, J.; Darbyshire, E.; Dean, A. R.; Dorsey, J. R.; Kent, J.; O'Sullivan, D.; Schepanski, K.; Szpek, K.; Trembath, J.; Woolley, A.

2015-07-01

The Fennec climate programme aims to improve understanding of the Saharan climate system through a synergy of observations and modelling. We present a description of the Fennec airborne observations during 2011 and 2012 over the remote Sahara (Mauritania and Mali) and the advances in the understanding of mineral dust and boundary layer processes they have provided. Aircraft instrumentation aboard the UK FAAM BAe146 and French SAFIRE (Service des Avions Français Instrumentés pour la Recherche en Environnement) Falcon 20 is described, with specific focus on instrumentation specially developed for and relevant to Saharan meteorology and dust. Flight locations, aims and associated meteorology are described. Examples and applications of aircraft measurements from the Fennec flights are presented, highlighting new scientific results delivered using a synergy of different instruments and aircraft. These include (1) the first airborne measurement of dust particles sizes of up to 300 microns and associated dust fluxes in the Saharan atmospheric boundary layer (SABL), (2) dust uplift from the breakdown of the nocturnal low-level jet before becoming visible in SEVIRI (Spinning Enhanced Visible Infra-Red Imager) satellite imagery, (3) vertical profiles of the unique vertical structure of turbulent fluxes in the SABL, (4) in situ observations of processes in SABL clouds showing dust acting as cloud condensation nuclei (CCN) and ice nuclei (IN) at -15 °C, (5) dual-aircraft observations of the SABL dynamics, thermodynamics and composition in the Saharan heat low region (SHL), (6) airborne observations of a dust storm associated with a cold pool (haboob) issued from deep convection over the Atlas Mountains, (7) the first airborne chemical composition measurements of dust in the SHL region with differing composition, sources (determined using Lagrangian backward trajectory calculations) and absorption properties between 2011 and 2012, (8) coincident ozone and dust surface area

The Association between Dust Storms and Daily Non-Accidental Mortality in the United States, 1993-2005.

EPA Science Inventory

Background:The impact of dust storms on human health has been studied in the context of Asian,Saharan, Arabian, and Australian storms,but there has been no recent population-level epidemiological research on the dust storms in North America . The relevance of dust storms to publi...

Discernible rhythm in the spatio/temporal distributions of transatlantic dust

NASA Astrophysics Data System (ADS)

Ben-Ami, Y.; Koren, I.; Altaratz, O.; Kostinski, A. B.; Lehahn, Y.

2011-08-01

The differences in North African dust emission regions and transport routes, between the boreal winter and summer are thoroughly documented. Here we re-examine the spatial and temporal characteristics of dust transport over the tropical and subtropical North Atlantic Ocean, using 10 years of satellite data, in order to determine better the different dust transport periods and their characteristics. We see a robust annual triplet: a discernible rhythm of "transatlantic dust weather". The proposed annual partition is composed of two heavy loading periods, associated here with a northern-route period and southern-route period, and one clean, light-loading period, accompanied by unusually low average optical depth of dust. The two dusty periods are quite different in character: their duration, transport routes, characteristic aerosol loading and frequency of pronounced dust episodes. The southern route period lasts about ~4 months, from the end of November to end of March. It is characterized by a relatively steady southern positioning, low frequency of dust events, low background values and high variance in dust loading. The northern-route period lasts ~6.5 months, from the end of March to mid October, and is associated with a steady drift northward of ~0.1 latitude day-1, reaching ~1500 km north of the southern route. The northern period is characterized by higher frequency of dust events, higher (and variable) background and smaller variance in dust loading. It is less episodic than the southern period. Transitions between the periods are brief. Separation between the southern and northern periods is marked by northward latitudinal shift in dust transport and by moderate reduction in the overall dust loading. The second transition between the northern and southern periods commences with an abrupt reduction in dust loading (thereby initiating the clean period) and rapid shift southward of ~0.2 latitude day-1, and 1300 km in total. These rates of northward advance and

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

Hygroscopic properties of large aerosol particles using the example of aged Saharan mineral dust - a semi-automated electron microscopy approach

NASA Astrophysics Data System (ADS)

Hartmann, Markus; Heim, Lars-Oliver; Ebert, Martin; Weinbruch, Stephan; Kandler, Konrad

2015-04-01

Hygroscopic properties of large aerosol particles using the example of aged Saharan mineral dust - a semi-automated electron microscopy approach Markus Hartmann(1), Lars-Oliver Heim(2), Martin Ebert(1), Stephan Weinbruch(1), Konrad Kandler(1) The Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) took place at Barbados from June 10 to July 15 2013. During this period, dust was frequently transported from Africa across the Atlantic Ocean toward the Caribbean. In this study, we investigate the atmospheric aging of the dust aerosol based on its hygroscopicity. Aerosol samples were collected ground-based at Ragged Point (13°9'54.4"N, 59°25'55.7"W) with a single round jet cascade impactor on nickel-substrates. The particles from the stage with a 50% efficiency cutoff size of 1 µm were analyzed with an Environmental Scanning Electron Microscope (ESEM) equipped with an energy-dispersive X-ray detector (EDX) and a cooling stage. In an initial automated run, information on particle size and chemical composition for elements heavier than carbon were gathered. Afterwards, electron microscope images of the same sample areas as before were taken during a stepwise increase of relative humidities (between 50 % and 92%), so that the hygroscopic growth of the droplets could be directly observed. The observed hygroscopic growth can be correlated to the chemical composition of the respective particles. For the automated analysis of several hundred images of droplets an image processing algorithm in Python was developed. The algorithm is based on histogram equalization and watershed segmentation. Since SEM images can only deliver two-dimensional information, but the hygroscopic growth factor usually refers to the volume of a drop, Atomic Force Microscopy (AFM) was used to derive an empirical function for the drop volume depending on the apparent drop diameter in the electron images. Aside from the mineral dust, composed of mostly silicates and

Atmospheric response to Saharan dust deduced from ECMWF reanalysis (ERA) temperature increments

NASA Astrophysics Data System (ADS)

Kishcha, P.; Alpert, P.; Barkan, J.; Kirchner, I.; Machenhauer, B.

2003-09-01

This study focuses on the atmospheric temperature response to dust deduced from a new source of data the European Reanalysis (ERA) increments. These increments are the systematic errors of global climate models, generated in the reanalysis procedure. The model errors result not only from the lack of desert dust but also from a complex combination of many kinds of model errors. Over the Sahara desert the lack of dust radiative effect is believed to be a predominant model defect which should significantly affect the increments. This dust effect was examined by considering correlation between the increments and remotely sensed dust. Comparisons were made between April temporal variations of the ERA analysis increments and the variations of the Total Ozone Mapping Spectrometer aerosol index (AI) between 1979 and 1993. The distinctive structure was identified in the distribution of correlation composed of three nested areas with high positive correlation (>0.5), low correlation and high negative correlation (<-0.5). The innermost positive correlation area (PCA) is a large area near the center of the Sahara desert. For some local maxima inside this area the correlation even exceeds 0.8. The outermost negative correlation area (NCA) is not uniform. It consists of some areas over the eastern and western parts of North Africa with a relatively small amount of dust. Inside those areas both positive and negative high correlations exist at pressure levels ranging from 850 to 700 hPa, with the peak values near 775 hPa. Dust-forced heating (cooling) inside the PCA (NCA) is accompanied by changes in the static instability of the atmosphere above the dust layer. The reanalysis data of the European Center for Medium Range Weather Forecast (ECMWF) suggest that the PCA (NCA) corresponds mainly to anticyclonic (cyclonic) flow, negative (positive) vorticity and downward (upward) airflow. These findings are associated with the interaction between dust-forced heating/cooling and

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

A radiogenic isotope tracer study of transatlantic dust transport from Africa to the Caribbean

NASA Astrophysics Data System (ADS)

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

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

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

NASA Technical Reports Server (NTRS)

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

2016-01-01

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

Atmospheric dust contribution to budget of U-series nuclides in weathering profiles. The Mount Cameroon volcano

NASA Astrophysics Data System (ADS)

Pelt, E.; Chabaux, F. J.; Innocent, C.; Ghaleb, B.

2009-12-01

Analysis of U-series nuclides in weathering profiles is developed today for constraining time scale of soil and weathering profile formation (e.g., Chabaux et al., 2008). These studies require the understanding of U-series nuclides sources and fractionation in weathering systems. For most of these studies the impact of aeolian inputs on U-series nuclides in soils is usually neglected. Here, we propose to discuss such an assumption, i.e., to evaluate the impact of dust deposition on U-series nuclides in soils, by working on present and paleo-soils collected on the Mount Cameroon volcano. Recent Sr, Nd, Pb isotopic analyses performed on these samples have indeed documented significant inputs of Saharan dusts in these soils (Dia et al., 2006). We have therefore analyzed 238U-234U-230Th nuclides in the same samples. Comparison of U-Th isotopic data with Sr-Nd-Pb isotopic data indicates a significant impact of the dust input on the U and Th budget of the soils, around 10% for both U and Th. Using Sr-Nd-Pb isotopic data of Saharan dusts given by Dia et al. (2006) we estimate U-Th concentrations and U-Th isotope ratios of dusts compatible with U-Th data obtained on Saharan dusts collected in Barbados (Rydell H.S. and Prospero J.M., 1972). However, the variations of U/Th ratios along the weathering profiles cannot be explained by a simple mixing scenario between material from basalt and from the defined atmospheric dust pool. A secondary uranium migration associated with chemical weathering has affected the weathering profiles. Mass balance calculation suggests that U in soils from Mount Cameroon is affected at the same order of magnitude by both chemical migration and dust accretion. Nevertheless, the Mount Cameroon is a limit case were large dust inputs from continental crust of Sahara contaminate basaltic terrain from Mount Cameroon volcano. Therefore, this study suggests that in other contexts were dust inputs are lower, or the bedrocks more concentrated in U and Th

CV-Dust: Atmospheric aerosol in the Cape Verde region: carbon and soluble fractions of PM10

NASA Astrophysics Data System (ADS)

Pio, C.; Nunes, T.; Cardoso, J.; Caseiro, A.; Custódio, D.; Cerqueira, M.; Patoilo, D.; Almeida, S. M.; Freitas, M. C.

2012-04-01

Every year, billions of tons of eroded mineral soils from the Saharan Desert and the Sahel region, the largest dust source in the world, cross Mediterranean towards Europe, western Asia and the tropical North Atlantic Ocean as far as the Caribbean and South America. Many aspects of the direct and indirect effects of dust on climate are not well understood and the bulk and surface chemistry of the mineral dust particles determines interactions with gaseous and other particle species. The quantification of the magnitude of warming or cooling remains open because of the strong variability of the atmospheric dust burden and the lack of representative data for the spatial and temporal distribution of the dust composition. CV-Dust is a project that aims at provide a detailed data on the size distribution and the size-resolved chemical and mineralogical composition of dust emitted from North Africa using a natural laboratory like Cape Verde. This archipelago is located in an area of massive dust transport from land to ocean, and is thus ideal to set up sampling devices that are able to characterize and quantify dust transported from Africa. Moreover, Cape Verde's future economic prospects depend heavily on the encouragement of tourism, therefore it is essential to elucidate the role of Saharan dust may play in the degradation of Cape Verde air quality. The main objectives of CV-Dust project are: 1) to characterize the chemical and mineralogical composition of dust transported from Africa by setting up an orchestra of aerosol sampling devices in the strategic archipelago of Cape Verde; 2) to identify the sources of particles in Cape Verde by using receptor models; 3) to elucidate the role Saharan dust may play in the degradation of Cape Verde air quality; 4) to model processes governing dust production, transport, interaction with the radiation field and removal from the atmosphere. Here we present part of the data obtained throughout the last year, involving a set of more

Effective and Accurate Morphology Models for Asian and Saharan Mineral Dust Scattering Properties

NASA Astrophysics Data System (ADS)

Stegmann, P.; Yang, P.

2017-12-01

It is well known that mineral dust particles from desert sources can have a significant influence on the planetary radiation balance. In order to determine the sign and magnitude of the dust radiative forcing effect, complex models have been and continue to be developed. Key factors which influence the single-scattering properties of mineral dust are dust source regions and thus mineralogical composition, and its mixture with water, sea salt, and products of human activity, such as soot. The ensemble of mineral dust scattering particles may then be modeled either as a simple placeholder shape, often ellipsoidal, through the utilization of an appropriate effective medium refractive index scheme. On the other hand, the scattering particles may be represented in a more rigorous manner, such as Voronoi-tessellated aggregates including fractal soot chains. The consequences and differences of either choice are investigated in the project at hand. It will be shown that the effective medium model indicates a drastic dependence of the mineral dust particle composition on the particle size. Thus the refractive index of a dust particle is in fact a function of its size, amongst other factors. Regional differences between African and Asian mineral dust are also of significance.

Dust Storm, Sahara Desert, Algeria/Niger Border, Africa

NASA Image and Video Library

1992-05-16

STS049-92-071 (13 May 1992) --- The STS-49 crew aboard the Earth-orbiting Space Shuttle Endeavour captured this Saharan dust storm on the Algeria-Niger border. The south-looking, late-afternoon view shows one of the best examples in the Shuttle photo data base of a dust storm. A series of gust fronts, caused by dissipating thunderstorms have picked up dust along the outflow boundaries. Small cumulus clouds have formed over the most vigorously ascending parts of the dust front, enhancing the visual effect of the front. The storm is moving roughly north-northwest, at right angles to the most typical path for dust storms in this part of the Sahara (shown by lines of sand on the desert surface in the foreground). Storms such as this can move out into the Atlantic, bringing dust even as far as the Americas on some occasions. A crewmember used a 70mm handheld Hasselblad camera with a 100mm lens to record the frame.

Seasonal radiogenic isotopic variability of the African dust outflow to the tropical Atlantic Ocean and across to the Caribbean

NASA Astrophysics Data System (ADS)

Kumar, Ashwini; Abouchami, W.; Galer, S. J. G.; Singh, Satinder Pal; Fomba, K. W.; Prospero, J. M.; Andreae, M. O.

2018-04-01

- reaching Cape Verde and Barbados during the summer, while contributions during the winter months are likely patchy and minor at most. Importantly, a short-term isotopic excursion is resolved in the Cape Verde winter record during a dust outbreak on 06-08 February 2012. This features a highly radiogenic Pb and Sr and unradiogenic Nd signature, marking a clear shift in dust provenance relative to that of normal days. As the dust storm waned, continuous gradual changes are observed, reflecting mixing and progressive dilution with dust typical of normal days. These inferences from radiogenic isotope tracers are corroborated by both satellite images (CALIPSO and MODIS) and back-trajectory analyses. The radiogenic isotope fingerprinting of these presently-active North African dust sources, and especially the Saharan Air Layer, will prove invaluable in studies of past dust emission from Northern Africa, where imagery and back trajectory analysis are unavailable.

Atmospheric Dust Modeling from Meso to Global Scales with the Online NMMB/BSC-Dust Model Part 2: Experimental Campaigns in Northern Africa

NASA Technical Reports Server (NTRS)

Haustein, K.; Perez, C.; Baldasano, J. M.; Jorba, O.; Basart, S.; Miller, R. L.; Janjic, Z.; Black, T.; Nickovic, S.; Todd, M. C.;

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

Seventeen-year systematic measurements of dust aerosol optical properties using the eole ntua lidar system (2000-2016)

NASA Astrophysics Data System (ADS)

Soupiona, Ourania; Mylonaki, Maria; Papayannis, Alexandros; Argyrouli, Athina; Kokkalis, Panayotis; Tsaknakis, Georgios

2018-04-01

A comprehensive analysis of the seasonal variability of the optical properties of Saharan dust aerosols over Athens, Greece, is presented for a 17-year time period (2000-2016), as derived from multi-wavelength Raman lidar measurements (57 dust events with more than 80 hours of measurements). The profiles of the derived aerosol optical properties (aerosol backscatter and extinction coefficients, lidar ratio and aerosol Ångström exponent) at 355 nm are presented. For these dust events we found a mean value of the lidar ratio of 52±13 sr at 355 nm and of 58±8 sr (not shown) at 532 nm (2-4 km a.s.l. height). For our statistical analysis, presented here, we used monthly-mean values and time periods under cloud-free conditions. The number of dust events was greatest in late spring, summer, and early autumn periods. In this paper we also present a selected case study (04 April 2016) of desert dust long-range transport from the Saharan desert.

Exploring Dust Impacts on Tropical Systems from the NASA HS-3 Field Campaign

NASA Technical Reports Server (NTRS)

Nowottnick, Ed; Colarco, Pete; da Silva, Arlindo; Barahona, Donifan; Hlavka, Dennis

2015-01-01

One of the overall scientific goals of the NASA Hurricane and Severe Storm Sentinel (HS-3) field campaign is to better understand the role of the Saharan Air Layer (SAL) in tropical storm development. During the 2012 HS-3 deployment, the Cloud Physics Lidar (CPL) observed dust within SAL air in close proximity to a developing Nadine (September 11, 2012). Throughout the mission, the NASA GEOS-5 modeling system supported HS-3 by providing 0.25 degrees resolution 5-day global forecasts of aerosols, which were used to support mission planning. The aerosol module was radiatively interactive within the GEOS-5 model, but aerosols were not directly coupled to cloud and precipitation processes. In this study we revisit the aerosol forecasts with an updated version of the GEOS-5 model. For the duration of Hurricane Nadine, we run multiday climate simulations leading up to each respective Global Hawk flight with and without aerosol direct interaction. For each set of simulations, we compare simulated dust mass fluxes to identify differences in SAL entrainment related to the interaction between dust aerosols and the atmosphere. We find that the direct effects of dust induce a low level anticyclonic circulation that temporarily shields Nadine from the intrusion of dry air, leading to a more intense storm.

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.

Classification of Dust Days by Satellite Remotely Sensed Aerosol Products

NASA Technical Reports Server (NTRS)

Sorek-Hammer, M.; Cohen, A.; Levy, Robert C.; Ziv, B.; Broday, D. M.

2013-01-01

Considerable progress in satellite remote sensing (SRS) of dust particles has been seen in the last decade. From an environmental health perspective, such an event detection, after linking it to ground particulate matter (PM) concentrations, can proxy acute exposure to respirable particles of certain properties (i.e. size, composition, and toxicity). Being affected considerably by atmospheric dust, previous studies in the Eastern Mediterranean, and in Israel in particular, have focused on mechanistic and synoptic prediction, classification, and characterization of dust events. In particular, a scheme for identifying dust days (DD) in Israel based on ground PM10 (particulate matter of size smaller than 10 nm) measurements has been suggested, which has been validated by compositional analysis. This scheme requires information regarding ground PM10 levels, which is naturally limited in places with sparse ground-monitoring coverage. In such cases, SRS may be an efficient and cost-effective alternative to ground measurements. This work demonstrates a new model for identifying DD and non-DD (NDD) over Israel based on an integration of aerosol products from different satellite platforms (Moderate Resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI)). Analysis of ground-monitoring data from 2007 to 2008 in southern Israel revealed 67 DD, with more than 88 percent occurring during winter and spring. A Classification and Regression Tree (CART) model that was applied to a database containing ground monitoring (the dependent variable) and SRS aerosol product (the independent variables) records revealed an optimal set of binary variables for the identification of DD. These variables are combinations of the following primary variables: the calendar month, ground-level relative humidity (RH), the aerosol optical depth (AOD) from MODIS, and the aerosol absorbing index (AAI) from OMI. A logistic regression that uses these variables, coded as binary

Providing the Caribbean community with VIIRS-derived weather satellite and dust model output in preparation for African dust impacts

NASA Astrophysics Data System (ADS)

Kuciauskas, A. P.; Xian, P.; Hyer, E. J.; Oyola, M. I.; Campbell, J. R.

2016-12-01

The Naval Research Laboratory Marine Meteorology Division (NRL-MMD) predicts, monitors, and trains Caribbean agencies in preparing for and mitigating unhealthy episodes of Saharan-based dust. Of critical concern is the Saharan Air Layer (SAL), an elevated air mass of hot, dry, and often very dusty conditions that can be environmentally persistent and dangerous to the downstream Caribbean populace, resulting in respiratory illnesses; some of the world's highest asthma rates and associated premature deaths have been documented within the Caribbean islands. The SAL not only impacts the greater Caribbean, but also the Gulf of Mexico, northern South America, and southern and central US. One of the major responsibilities of the National Weather Service forecast office at San Juan, Puerto Rico (NWS-PR) is preparing the public within their area of responsibility for such events. The NRL-MMD has been at the forefront of implementing and demonstrating the positive impact of Suomi-VIIRS during SAL events. In preparation for SAL events, NRL-MMD is currently supporting the NWS-PR with near real time web-based products, primarily from VIIRS datasets. Preliminary studies have shown that VIIRS has demonstrated improvements in the assessment and prediction of dust intensities related to SAL passages. The upcoming launches of JPSS-1 and GOES-R are eagerly anticipated in possibly revolutionizing the R&D related toward further improvements in understanding Saharan dust dynamics and characteristics. Besides NWS-PR, NRL-MMD also collaborates with the Caribbean Institute for Meteorology and Hydrology (CIMH) in both providing and gathering in-situ measurements that stretch from the French Guyana northward through the West Indies island chain. Finally, NRL-MMD is involved with the Caribbean Aerosol Health Network (CAHN),an international network of health and environmental agencies whose mission is to improve the understanding of the impacts (e.g., air quality, health, climate, weather

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.

Interactive Soil Dust Aerosol Model in the GISS GCM. Part 1; Sensitivity of the Soil Dust Cycle to Radiative Properties of Soil Dust Aerosols

NASA Technical Reports Server (NTRS)

Perlwitz, Jan; Tegen, Ina; Miller, Ron L.

2000-01-01

The sensitivity of the soil dust aerosol cycle to the radiative forcing by soil dust aerosols is studied. Four experiments with the NASA/GISS atmospheric general circulation model, which includes a soil dust aerosol model, are compared, all using a prescribed climatological sea surface temperature as lower boundary condition. In one experiment, dust is included as dynamic tracer only (without interacting with radiation), whereas dust interacts with radiation in the other simulations. Although the single scattering albedo of dust particles is prescribed to be globally uniform in the experiments with radiatively active dust, a different single scattering albedo is used in those experiments to estimate whether regional variations in dust optical properties, corresponding to variations in mineralogical composition among different source regions, are important for the soil dust cycle and the climate state. On a global scale, the radiative forcing by dust generally causes a reduction in the atmospheric dust load corresponding to a decreased dust source flux. That is, there is a negative feedback in the climate system due to the radiative effect of dust. The dust source flux and its changes were analyzed in more detail for the main dust source regions. This analysis shows that the reduction varies both with the season and with the single scattering albedo of the dust particles. By examining the correlation with the surface wind, it was found that the dust emission from the Saharan/Sahelian source region and from the Arabian peninsula, along with the sensitivity of the emission to the single scattering albedo of dust particles, are related to large scale circulation patterns, in particular to the trade winds during Northern Hemisphere winter and to the Indian monsoon circulation during summer. In the other regions, such relations to the large scale circulation were not found. There, the dependence of dust deflation to radiative forcing by dust particles is probably

Sensitivity of Sahelian Precipitation to Desert Dust under ENSO variability: a regional modeling study

NASA Astrophysics Data System (ADS)

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

2016-12-01

Mineral dust is estimated to comprise over half the total global aerosol burden, with a majority coming from the Sahara and Sahel region. Bounded by the Sahara Desert to the north and the Sahelian Savannah to the south, the Sahel experiences high interannual rainfall variability and a short rainy season during the boreal summer months. Observation-based data for the past three decades indicates a reduced dust emission trend, together with an increase in greening and surface roughness within the Sahel. Climate models used to study regional precipitation changes due to Saharan dust yield varied results, both in sign convention and magnitude. Inconsistency of model estimates drives future climate projections for the region that are highly varied and uncertain. We use the NASA-Unified Weather Research and Forecasting (NU-WRF) model to quantify the interaction and feedback between desert dust aerosol and Sahelian precipitation. Using nested domains at fine spatial resolution we resolve changes to mesoscale atmospheric circulation patterns due to dust, for representative phases of El Niño-Southern Oscillation (ENSO). The NU-WRF regional earth system model offers both advanced land surface data and resolvable detail of the mechanisms of the impact of Saharan dust. Results are compared to our previous work assessed over the Western Sahel using the Geophysical Fluid Dynamics Laboratory (GFDL) CM2Mc global climate model, and to other previous regional climate model studies. This prompts further research to help explain the dust-precipitation relationship and recent North African dust emission trends. This presentation will offer a quantitative analysis of differences in radiation budget, energy and moisture fluxes, and atmospheric dynamics due to desert dust aerosol over the Sahel.

Cross‐Saharan transport of water vapor via recycled cold pool outflows from moist convection

PubMed Central

Trzeciak, Tomasz M.; Garcia‐Carreras, Luis

2017-01-01

Abstract Very sparse data have previously limited observational studies of meteorological processes in the Sahara. We present an observed case of convectively driven water vapor transport crossing the Sahara over 2.5 days in June 2012, from the Sahel in the south to the Atlas in the north. A daily cycle is observed, with deep convection in the evening generating moist cold pools that fed the next day's convection; the convection then generated new cold pools, providing a vertical recycling of moisture. Trajectories driven by analyses were able to capture the direction of the transport but not its full extent, particularly at night when cold pools are most active, and analyses missed much of the water content of cold pools. The results highlight the importance of cold pools for moisture transport, dust and clouds, and demonstrate the need to include these processes in models in order to improve the representation of Saharan atmosphere. PMID:28344367

The uranium-isotopic composition of Saharan dust collected over the central Atlantic Ocean

NASA Astrophysics Data System (ADS)

Aciego, Sarah M.; Aarons, Sarah M.; Sims, Kenneth W. W.

2015-06-01

Uranium isotopic compositions, (234U/238U)activity , are utilized by earth surface disciplines as chronometers and source tracers, including in soil science where aeolian dust is a significant source to the total nutrient pool. However, the (234U/238U)activity composition of dust is under characterized due to material and analytical constraints. Here we present new uranium isotope data measured by high precision MC-ICP-MS on ten airborne dust samples collected on the M55 trans-Atlantic cruise in 2002. Two pairs of samples are presented with different size fractions, coarse (1-30 μm) and fine (<1 μm), and all samples were processed to separate the water soluble component in order to assess the controls on the (234U/238U)activity of mineral aerosols transported from the Sahara across the Atlantic. Our results indicate (234U/238U)activity above one for both the water soluble (1.13-1.17) and the residual solid (1.06-1.18) fractions of the dust; no significant correlation is found between isotopic composition and travel distance. Residual solids indicate a slight dependance of (234U/238U)activity on particle size. Future modeling work that incorporates dust isotopic compositions into mixing or isotopic fractionation models will need to account for the wide variability in dust (234U/238U)activity .

Relationship between mortality and fine particles during Asian dust, smog-Asian dust, and smog days in Korea.

PubMed

Kim, Hyun-Sun; Kim, Dong-Sik; Kim, Ho; Yi, Seung-Muk

2012-01-01

This study examined the association between all-cause/cardiovascular mortality and PM(2.5) as related to Asian dust (AD), smog-AD, smog, and nonevent days and evaluated the differential risks according to specific events for mortality. The daily records of all-cause/cardiovascular mortality and PM(2.5) from March to May 2003-2006 in Seoul, Korea, were used as independent and dependent variables. Differences in the event effects were assessed using a time-series analysis. Both all-cause and cardiovascular mortalities were significantly associated with PM(2.5) during smog-AD and AD days only. Differences in chemical composition emerging during long-range transport to Korea may explain these observations, especially as regards secondary aerosol, metal-sulfate/or nitrate, and metallic components. These results suggest that exposure to PM(2.5) during specific events is differentially associated with human mortality and that changes in the chemical composition of PM(2.5), occurring during long-range transport, represent important factors in such differential effects on health.

Dust Deposition Events on Mt. Elbrus, Caucasus Mountains in the 21st Century Reconstructed from the Shallow Firn and Ice Cores (Invited)

NASA Astrophysics Data System (ADS)

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

2013-12-01

This paper presents and discusses a record of dust deposition events reconstructed from the shallow firn and ice cores extracted on the Western Plateau, Mt. Elbrus, Caucasus Mountains, Russia. A combination of SEVIRI imagery, HYSPLIT trajectory model, meteorological and atmospheric optical depth data were used to establish timing of deposition events and source regions of dust with very high temporal (hours) and spatial (c. 50-100 km) resolution. The source regions of the desert dust transported to Mt. Elbrus were primarily located in the Middle East, in particular in eastern Syria and in the Syrian Desert at the border between Saudi Arabia, Iraq and Jordan. Northern Sahara, the foothills of the Djebel Akhdar Mountains in eastern Libya and the border region between Libya and Algeria were other important sources of desert dust. Dust sources in the Sahara were natural (e.g. palaeolakes and alluvial deposits in the foothills) while in the Middle East, dust entrainment occurred from both natural (e.g. dry river beds) and anthropogenic (e.g. agricultural fields) sources. The overall majority of dust deposition events occurred between March and June and, less frequently, dust deposition events occurred in February and October. In all cases, dust deposition was associated with depressions causing strong surface wind and dust uplift in the source areas, transportation of dust to the Caucasus with a strong south-westerly flow from the Sahara or southerly flow from the Middle East, merging of the dust clouds with precipitation-bearing weather fronts and precipitation over the Caucasus region. The Saharan depressions were vigorous and associated with stronger daily wind speeds of 20-30 m/s at the 700 hPa level; depressions forming over the Middle East and the associated wind speeds were weaker at 12-15 m/s. The Saharan depressions were less frequent than those carrying dust from the Middle East but higher dust loads were associated with the Saharan depressions. A higher

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

Dust Concentrations and Composition During African Dust Incursions in the Caribbean Region

NASA Astrophysics Data System (ADS)

Mayol-Bracero, O. L.; Santos-Figueroa, G.; Morales-Garcia, F.

2016-12-01

The World Health Organization (WHO) indicates that exposure to PM10 concentrations higher than 50 µg/m³ 24-hour mean in both developed and developing countries could have an adverse impact on public health. Recent studies showed that in the Caribbean region the PM10 concentrations often exceed the WHO guidelines for PM10. These exceedances are largely driven by the presence of African Dust particles that reach the Caribbean region every year during the summer months. These dust particles also influence the Earth's radiative budget directly by scattering solar radiation in the atmosphere and indirectly by affecting cloud formation and, thus, cloud albedo. In order to have a better understanding of the impacts of African Dust on public health and climate, we determine the concentration of dust particles, the carbonaceous fraction (total, elemental and organic carbon: TC, EC, and OC) and water-soluble ions (e.g., Na+, Cl-, Ca+2, NH4+, SO4-2) of aerosol samples in the presence and absence of African Dust. Samples were collected using a Hi-Vol and Stacked-Filter Units for the sampling of total suspended particles (TSP) at two stations in Puerto Rico: a marine site located at Cabezas de San Juan (CSJ) Nature Reserve, in Fajardo, and an urban site located at the University of Puerto Rico, in San Juan. The presence of African Dust was supported with Saharan Air Layer (SAL) imagery and with the results from the air mass backward trajectories calculated with the NOAA Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT). Preliminary results showed that the total mass concentration of aerosols obtained at the urban site is about two times that at the marine site for SFU samples during African Dust incursions. The average dust concentration obtained at CSJ for Hi Vol samples was 22 µg/m³ during the summer 2015. African Dust concentrations, TC, EC, OC, and ionic speciation results for the marine and urban sites will be presented at the conference.

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

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

Ma, Po-Lun; Zhang, Kai; Shi, Jainn Jong

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 inmore » 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.« less

The Association between Dust Storms and Daily Non-Accidental Mortality in the United States, 1993-2005.

PubMed

Crooks, James Lewis; Cascio, Wayne E; Percy, Madelyn S; Reyes, Jeanette; Neas, Lucas M; Hilborn, Elizabeth D

2016-11-01

The impact of dust storms on human health has been studied in the context of Asian, Saharan, Arabian, and Australian storms, but there has been no recent population-level epidemiological research on the dust storms in North America. The relevance of dust storms to public health is likely to increase as extreme weather events are predicted to become more frequent with anticipated changes in climate through the 21st century. We examined the association between dust storms and county-level non-accidental mortality in the United States from 1993 through 2005. Dust storm incidence data, including date and approximate location, are taken from the U.S. National Weather Service storm database. County-level mortality data for the years 1993-2005 were acquired from the National Center for Health Statistics. Distributed lag conditional logistic regression models under a time-stratified case-crossover design were used to study the relationship between dust storms and daily mortality counts over the whole United States and in Arizona and California specifically. End points included total non-accidental mortality and three mortality subgroups (cardiovascular, respiratory, and other non-accidental). We estimated that for the United States as a whole, total non-accidental mortality increased by 7.4% (95% CI: 1.6, 13.5; p = 0.011) and 6.7% (95% CI: 1.1, 12.6; p = 0.018) at 2- and 3-day lags, respectively, and by an average of 2.7% (95% CI: 0.4, 5.1; p = 0.023) over lags 0-5 compared with referent days. Significant associations with non-accidental mortality were estimated for California (lag 2 and 0-5 day) and Arizona (lag 3), for cardiovascular mortality in the United States (lag 2) and Arizona (lag 3), and for other non-accidental mortality in California (lags 1-3 and 0-5). Dust storms are associated with increases in lagged non-accidental and cardiovascular mortality. Citation: Crooks JL, Cascio WE, Percy MS, Reyes J, Neas LM, Hilborn ED. 2016. The association between dust storms

The Association between Dust Storms and Daily Non-Accidental Mortality in the United States, 1993–2005

PubMed Central

Crooks, James Lewis; Cascio, Wayne E.; Percy, Madelyn S.; Reyes, Jeanette; Neas, Lucas M.; Hilborn, Elizabeth D.

2016-01-01

Background: The impact of dust storms on human health has been studied in the context of Asian, Saharan, Arabian, and Australian storms, but there has been no recent population-level epidemiological research on the dust storms in North America. The relevance of dust storms to public health is likely to increase as extreme weather events are predicted to become more frequent with anticipated changes in climate through the 21st century. Objectives: We examined the association between dust storms and county-level non-accidental mortality in the United States from 1993 through 2005. Methods: Dust storm incidence data, including date and approximate location, are taken from the U.S. National Weather Service storm database. County-level mortality data for the years 1993–2005 were acquired from the National Center for Health Statistics. Distributed lag conditional logistic regression models under a time-stratified case-crossover design were used to study the relationship between dust storms and daily mortality counts over the whole United States and in Arizona and California specifically. End points included total non-accidental mortality and three mortality subgroups (cardiovascular, respiratory, and other non-accidental). Results: We estimated that for the United States as a whole, total non-accidental mortality increased by 7.4% (95% CI: 1.6, 13.5; p = 0.011) and 6.7% (95% CI: 1.1, 12.6; p = 0.018) at 2- and 3-day lags, respectively, and by an average of 2.7% (95% CI: 0.4, 5.1; p = 0.023) over lags 0–5 compared with referent days. Significant associations with non-accidental mortality were estimated for California (lag 2 and 0–5 day) and Arizona (lag 3), for cardiovascular mortality in the United States (lag 2) and Arizona (lag 3), and for other non-accidental mortality in California (lags 1–3 and 0–5). Conclusions: Dust storms are associated with increases in lagged non-accidental and cardiovascular mortality. Citation: Crooks JL, Cascio WE, Percy MS, Reyes

Linkages between observed, modeled Saharan dust loading and meningitis in Senegal during 2012 and 2013

NASA Astrophysics Data System (ADS)

Diokhane, Aminata Mbow; Jenkins, Gregory S.; Manga, Noel; Drame, Mamadou S.; Mbodji, Boubacar

2016-04-01

The Sahara desert transports large quantities of dust over the Sahelian region during the Northern Hemisphere winter and spring seasons (December-April). In episodic events, high dust concentrations are found at the surface, negatively impacting respiratory health. Bacterial meningitis in particular is known to affect populations that live in the Sahelian zones, which is otherwise known as the meningitis belt. During the winter and spring of 2012, suspected meningitis cases (SMCs) were with three times higher than in 2013. We show higher surface particular matter concentrations at Dakar, Senegal and elevated atmospheric dust loading in Senegal for the period of 1 January-31 May during 2012 relative to 2013. We analyze simulated particulate matter over Senegal from the Weather Research and Forecasting (WRF) model during 2012 and 2013. The results show higher simulated dust concentrations during the winter season of 2012 for Senegal. The WRF model correctly captures the large dust events from 1 January-31 March but has shown less skill during April and May for simulated dust concentrations. The results also show that the boundary conditions are the key feature for correctly simulating large dust events and initial conditions are less important.

Investigating the size, shape and surface roughness dependence of polarization lidars with light-scattering computations on real mineral dust particles: Application to dust particles' external mixtures and dust mass concentration retrievals

NASA Astrophysics Data System (ADS)

Mehri, Tahar; Kemppinen, Osku; David, Grégory; Lindqvist, Hannakaisa; Tyynelä, Jani; Nousiainen, Timo; Rairoux, Patrick; Miffre, Alain

2018-05-01

Our understanding of the contribution of mineral dust to the Earth's radiative budget is limited by the complexity of these particles, which present a wide range of sizes, are highly-irregularly shaped, and are present in the atmosphere in the form of particle mixtures. To address the spatial distribution of mineral dust and atmospheric dust mass concentrations, polarization lidars are nowadays frequently used, with partitioning algorithms allowing to discern the contribution of mineral dust in two or three-component particle external mixtures. In this paper, we investigate the dependence of the retrieved dust backscattering (βd) vertical profiles with the dust particle size and shape. For that, new light-scattering numerical simulations are performed on real atmospheric mineral dust particles, having determined mineralogy (CAL, DOL, AGG, SIL), derived from stereogrammetry (stereo-particles), with potential surface roughness, which are compared to the widely-used spheroidal mathematical shape model. For each dust shape model (smooth stereo-particles, rough stereo-particles, spheroids), the dust depolarization, backscattering Ångström exponent, lidar ratio are computed for two size distributions representative of mineral dust after long-range transport. As an output, two Saharan dust outbreaks involving mineral dust in two, then three-component particle mixtures are studied with Lyon (France) UV-VIS polarization lidar. If the dust size matters most, under certain circumstances, βd can vary by approximately 67% when real dust stereo-particles are used instead of spheroids, corresponding to variations in the dust backscattering coefficient as large as 2 Mm- 1·sr- 1. Moreover, the influence of surface roughness in polarization lidar retrievals is for the first time discussed. Finally, dust mass-extinction conversion factors (ηd) are evaluated for each assigned shape model and dust mass concentrations are retrieved from polarization lidar measurements. From

Experimental evidence of formation of transparent exopolymer particles (TEP) and POC export provoked by dust addition under current and high pCO2 conditions.

PubMed

Louis, Justine; Pedrotti, Maria Luiza; Gazeau, Frédéric; Guieu, Cécile

2017-01-01

The evolution of organic carbon export to the deep ocean, under anthropogenic forcing such as ocean warming and acidification, needs to be investigated in order to evaluate potential positive or negative feedbacks on atmospheric CO2 concentrations, and therefore on climate. As such, modifications of aggregation processes driven by transparent exopolymer particles (TEP) formation have the potential to affect carbon export. The objectives of this study were to experimentally assess the dynamics of organic matter, after the simulation of a Saharan dust deposition event, through the measurement over one week of TEP abundance and size, and to evaluate the effects of ocean acidification on TEP formation and carbon export following a dust deposition event. Three experiments were performed in the laboratory using 300 L tanks filled with filtered seawater collected in the Mediterranean Sea, during two 'no bloom' periods (spring at the start of the stratification period and autumn at the end of this stratification period) and during the winter bloom period. For each experiment, one of the two tanks was acidified to reach pH conditions slightly below values projected for 2100 (~ 7.6-7.8). In both tanks, a dust deposition event of 10 g m-2 was simulated at the surface. Our results suggest that Saharan dust deposition triggered the abiotic formation of TEP, leading to the formation of organic-mineral aggregates. The amount of particulate organic carbon (POC) exported was proportional to the flux of lithogenic particles to the sediment traps. Depending on the season, the POC flux following artificial dust deposition ranged between 38 and 90 mg m-2 over six experimental days. Such variability is likely linked to the seasonal differences in the quality and quantity of TEP-precursors initially present in seawater. Finally, these export fluxes were not significantly different at the completion of the three experiments between the two pH conditions.

Monitoring of Saharan dust fallout on Crete and its contribution to soil formation

NASA Astrophysics Data System (ADS)

Nihlén, Tomas; Mattsson, Jan O.; Rapp, Anders; Gagaoudaki, Chrisoula; Kornaros, Georges; Papageorgiou, John

1995-07-01

A series of 6 dust traps was established in 1988 distributed over the island of Crete (Greece). Eolian dust has been collected in the traps each year and in each season during the 4years of investigation which is still going on. The mean deposition rate for the 6 stations and 4years was calculated as 21.3g m2yr1. Using the highest and lowest values, the deposition can be extrapolated to 6.6-21.4mm for 1000years, which is in agreement with other researchers' findings. The trapped dust shows a homogeneous grain-size distribution. Its mineralogy is similar to what characterizes soil samples from Psiloritis on Crete and source areas in southern Tunisia. In the fine fraction of the soil (particles < 10µm), the contents of the clay mineral kaolinite and of quartz are high. In addition, the oxygen isotope composition of the 3 types of substrate is similar but differs from the weathering products of the limestone bedrock. Statistics of dust episodes covering the period c. 1955-1990 from 10 meteorological stations in Greece revealed that long-distance transport of dust in combination with winds from a southerly sector is common in the Aegean area during spring.

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.

Observations of cross-Saharan transport of water vapour via cycle of cold pools and moist convection

NASA Astrophysics Data System (ADS)

Trzeciak, Tomasz; Garcia-Carreras, Luis; Marsham, John H.

2017-04-01

Very limited observational data has previously limited our ability to study meteorological processes in the Sahara. The Sahara is a key component of the West African monsoon and the world's largest dust source, but its representation is a major uncertainty in global models. Past studies have shown that there is a persistent warm and dry model bias throughout the Sahara, and this has been attributed to the lack of convectively-generated cold pools in the model, which can ventilate the central Sahara from its margins. Here we present an observed case from June 2012 which explains how cold pools are able to transport water vapour across a large area of the Sahara over a period of several days. A daily cycle is found to occur, where deep convection in the evening generates moist cold pools that then feed the next day's convection; the new convection in turn generates new cold pools, providing a vertical recycling of moisture. Trajectories driven by analyses can capture the general direction of transport, but not its full extent, especially at night when cold pools are most active, highlighting the difficulties for models to capture these processes. These results show the importance of cold pools for moisture transport, dust and clouds in the region, and demonstrate the need to include these processes in models to improve the representation of the Saharan atmosphere.

Long-term systematic profiling of dust aerosol optical properties using the EOLE NTUA lidar system over Athens, Greece (2000-2016)

NASA Astrophysics Data System (ADS)

Soupiona, O.; Papayannis, A.; Kokkalis, P.; Mylonaki, M.; Tsaknakis, G.; Argyrouli, A.; Vratolis, S.

2018-06-01

We present a comprehensive analysis of the seasonal variability of the vertical profiles of the optical and geometrical properties of Saharan dust aerosols, observed in the height region between 1000 and 6000 m, over the city of Athens, Greece, from February 2000 to December 2016. These observations were performed by a multi-wavelength (355-387-532-1064 nm) Raman lidar system under cloud-free conditions. The statistical analysis (using aerosol monthly mean values) is based on nighttime vertical Raman measurements of range-resolved aerosol optical properties (backscatter and extinction coefficients, lidar ratio, Ångström exponent) at 355 nm (57 dust events during more than 80 measurement hours). We found that the number of dust events was highest in spring, summer, and early autumn periods and that during spring the dust layers were moved at higher altitudes (∼4500 m) than in other seasons. The number of the forecasted dusty days (on monthly basis) by the BSC-DREAM8b model compared to those of the performed lidar measurements were found to have a quite strong correlation (R2 = 0.81), with a maximum occurrence predicted for the spring season. In the worst case scenario, at least 50% of the model-forecasted dust events can be observed by lidar under cloudless skies over Athens. For the sampled dust plumes we found mean lidar ratios of 52 ± 13 sr at 355 nm in the height range 2000-4000 m a.s.l. Moreover, the dust layers had a mean thickness of 2497 ± 1026 m and a center of mass of 2699 ± 1017 m. An analysis performed regarding the air mass back-trajectories arriving over Athens revealed two main clusters: one pathway from south-west to north-east, with dust emission areas in Tunisia, Algeria and Libya and a second one from south, across the Mediterranean Sea with emission areas over Libya and the remaining part of Algeria and Tunisia. This clustering enabled us to differentiate between the aerosol optical properties between the two clusters, based on their

Vertical distribution of Saharan dust over Rome (Italy): Comparison between 3-year model predictions and lidar soundings

NASA Astrophysics Data System (ADS)

Kishcha, P.; Barnaba, F.; Gobbi, G. P.; Alpert, P.; Shtivelman, A.; Krichak, S. O.; Joseph, J. H.

2005-03-01

Mineral dust particles loaded into the atmosphere from the Sahara desert represent one major factor affecting the Earth's radiative budget. Regular model-based forecasts of 3-D dust fields can be used in order to determine the dust radiative effect in climate models, in spite of the large gaps in observations of dust vertical profiles. In this study, dust forecasts by the Tel Aviv University (TAU) dust prediction system were compared to lidar observations to better evaluate the model's capabilities. The TAU dust model was initially developed at the University of Athens and later modified at Tel Aviv University. Dust forecasts are initialized with the aid of the Total Ozone Mapping Spectrometer aerosol index (TOMS AI) measurements. The lidar soundings employed were collected at the outskirts of Rome, Italy (41.84°N, 12.64°E) during the high-dust activity season from March to June of the years 2001, 2002, and 2003. The lidar vertical profiles collected in the presence of dust were used for obtaining statistically significant reference parameters of dust layers over Rome and for model versus lidar comparison. The Barnaba and Gobbi (2001) approach was used in the current study to derive height-resolved dust volumes from lidar measurements of backscatter. Close inspection of the juxtaposed vertical profiles, obtained from lidar and model data near Rome, indicates that the majority (67%) of the cases under investigation can be classified as good or acceptable forecasts of the dust vertical distribution. A more quantitative comparison shows that the model predictions are mainly accurate in the middle part of dust layers. This is supported by high correlation (0.85) between lidar and model data for forecast dust volumes greater than the threshold of 1 × 10-12 cm3/cm3. In general, however, the model tends to underestimate the lidar-derived dust volume profiles. The effect of clouds in the TOMS detection of AI is supposed to be the main factor responsible for this effect

AERONET-Based Nonspherical Dust Optical Models and Effects on the VIIRS Deep Blue/SOAR Over Water Aerosol Product

NASA Astrophysics Data System (ADS)

Lee, Jaehwa; Hsu, N. Christina; Sayer, Andrew M.; Bettenhausen, Corey; Yang, Ping

2017-10-01

Aerosol Robotic Network (AERONET)-based nonspherical dust optical models are developed and applied to the Satellite Ocean Aerosol Retrieval (SOAR) algorithm as part of the Version 1 Visible Infrared Imaging Radiometer Suite (VIIRS) NASA "Deep Blue" aerosol data product suite. The optical models are created using Version 2 AERONET inversion data at six distinct sites influenced frequently by dust aerosols from different source regions. The same spheroid shape distribution as used in the AERONET inversion algorithm is assumed to account for the nonspherical characteristics of mineral dust, which ensures the consistency between the bulk scattering properties of the developed optical models and the AERONET-retrieved microphysical and optical properties. For the Version 1 SOAR aerosol product, the dust optical model representative for Capo Verde site is used, considering the strong influence of Saharan dust over the global ocean in terms of amount and spatial coverage. Comparisons of the VIIRS-retrieved aerosol optical properties against AERONET direct-Sun observations at five island/coastal sites suggest that the use of nonspherical dust optical models significantly improves the retrievals of aerosol optical depth (AOD) and Ångström exponent by mitigating the well-known artifact of scattering angle dependence of the variables, which is observed when incorrectly assuming spherical dust. The resulting removal of these artifacts results in a more natural spatial pattern of AOD along the transport path of Saharan dust to the Atlantic Ocean; that is, AOD decreases with increasing distance transported, whereas the spherical assumption leads to a strong wave pattern due to the spurious scattering angle dependence of AOD.

Tracing dust provenance in paleoclimate records using mineralogical and isotopic fingerprints: additional clues from present-day studies

NASA Astrophysics Data System (ADS)

Bory, A. J.; Skonieczny, C.; Bout-Roumazeilles, V.; Grousset, F. E.; Biscaye, P. E.

2011-12-01

, despite the fact that these archives are located close to the highest dust-emission areas in the world. Characterization of dust provenance (using mineralogical and isotopic fingerprints) at present, which can be achieved at much higher resolution and benefit from remote sensing data and well-constrained GMC outputs, may provide valuable clues for our understanding of dust provenance in paleoclimate records. We review some investigations carried out in Greenland and Antarctica over the last decade, and present new results from the West African margin. We discuss the extent to which these present-day time series may help us calibrating our paleo-dust provenance proxies, and improving our understanding of dust provenance in paleoclimate records.

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

Satellite and Ground-based Radiometers Reveal Much Lower Dust Absorption of Sunlight than Used in Climate Models

NASA Technical Reports Server (NTRS)

Kaufman, Y. J.; Tanre, D.; Dubovik, O.; Karnieli, A.; Remer, L. A.; Einaudi, Franco (Technical Monitor)

2000-01-01

The ability of dust to absorb solar radiation and heat the atmosphere is one of the main uncertainties in climate modeling and the prediction of climate change. Dust absorption is not well known due to limitations of in situ measurements. New techniques to measure dust absorption are needed in order to assess the impact of dust on climate. Here we report two new independent remote sensing techniques that provide sensitive measurements of dust absorption. Both are based on remote sensing. One uses satellite spectral measurements, the second uses ground based sky measurements from the AERONET network. Both techniques demonstrate that Saharan dust absorption of solar radiation is several times smaller than the current international standards. Dust cooling of the earth system in the solar spectrum is therefore significantly stronger than recent calculations indicate. We shall also address the issue of the effects of dust non-sphericity on the aerosol optical properties.

Analysis of dust storms observed in Mongolia during 1937-1999

NASA Astrophysics Data System (ADS)

Natsagdorj, L.; Jugder, D.; Chung, Y. S.

Climatology of dust storms in Mongolia is compiled based on observational data of 49 meteorological stations from 1960 to 1999 and compared them with data between 1937 and 1989. Three different maps of the distribution of dust storms, drifting dust and the number of dusty days are presented. The results of the analysis show that the number of days with dust storms is <5 days over the Altai, the Khangai and the Khentei mountainous regions and more than 20-37 days in the Gobi Desert and semi-desert area. The greatest occurrence of drifting dust arises around the Mongol Els area of west Mongolia. The number of dusty days, which is derived from the sum of the number of days with dust storms and drifting dust, is <10 days in the mountainous area and 61-127 days in the Gobi Desert and the Great Lakes hollow of west Mongolia. It is found that 61% of dust storms occur in the spring in Mongolia and a dust storm lasts on average from 3.1 to 6.0 h. About 65.5-91.0% of dust storms occur in daytime and 9.0-34.5% at night. Dust storms occur more frequently in the city region and are accompanied by surface wind speeds usually from 6 to 20 ms -1. Dust storms usually occur when soil and air are dry, and 70% of dust storms occur in dry soil conditions. When dust storms occur, relative humidity averages 20-40% in Mongolia. An important outcome of this study is the trend of dusty days between 1960 and 1999. It shows that the number of dusty days has tripled from the 1960s to 1990s and has decreased since 1990.

Evidence of a Weakly Absorbing Intermediate Mode of Aerosols in AERONET Data from Saharan and Sahelian Sites

NASA Technical Reports Server (NTRS)

Gianelli, Scott M.; Lacis, Andrew A.; Carlson, Barbara E.; Hameed, Sultan

2013-01-01

Accurate retrievals of aerosol size distribution are necessary to estimate aerosols' impact on climate and human health. The inversions of the Aerosol Robotic Network (AERONET) usually retrieve bimodal distributions. However, when the inversion is applied to Saharan and Sahelian dust, an additional mode of intermediate size between the coarse and fine modes is sometimes seen. This mode explains peculiarities in the behavior of the Angstrom exponent, along with the fine mode fraction retrieved using the spectral deconvolution algorithm, observed in a March 2006 dust storm. For this study, 15 AERONET sites in northern Africa and on the Atlantic are examined to determine the frequency and properties of the intermediate mode. The mode is observed most frequently at Ilorin in Nigeria. It is also observed at Capo Verde and multiple sites located within the Sahel but much less frequently at sites in the northern Sahara and the Canary Islands. The presence of the intermediate mode coincides with increases in Angstrom exponent, fine mode fraction, single-scattering albedo, and to a lesser extent percent sphericity. The Angstrom exponent decreases with increasing optical depth at most sites when the intermediate mode is present, but the fine mode fraction does not. Single-scattering albedo does not steadily decrease with fine mode fraction when the intermediate mode is present, as it does in typical mixtures of dust and biomass-burning aerosols. Continued investigation is needed to further define the intermediate mode's properties, determine why it differs from most Saharan dust, and identify its climate and health effects.

Observation of Dust Aging Processes During Transport from Africa into the Caribbean - A Lagrangian Case Study

NASA Astrophysics Data System (ADS)

Weinzierl, B.; Sauer, D. N.; Walser, A.; Dollner, M.; Reitebuch, O.; Gross, S.; Chouza, F.; Ansmann, A.; Toledano, C.; Freudenthaler, V.; Kandler, K.; Schäfler, A.; Baumann, R.; Tegen, I.; Heinold, B.

2014-12-01

Aerosol particles are regularly transported over long distances impacting air quality, health, weather and climate thousands of kilometers downwind of the source. During transport, particle properties are modified thereby changing the associated impact on the radiation budget. Although mineral dust is of key importance for the climate system many questions such as the change of the dust size distribution during long-range transport, the role of wet and dry removal mechanisms, and the complex interaction between mineral dust and clouds remain open. In June/July 2013, the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE: http://www.pa.op.dlr.de/saltrace) was conducted to study the transport and transformation of Saharan mineral dust. Besides ground-based lidar and in-situ instruments deployed on Cape Verde, Barbados and Puerto Rico, the DLR research aircraft Falcon was equipped with an extended aerosol in-situ instrumentation, a nadir-looking 2-μm wind lidar and instruments for standard meteorological parameters. During SALTRACE, five large dust outbreaks were studied by ground-based, airborne and satellite measurements between Senegal, Cape Verde, the Caribbean, and Florida. Highlights included the Lagrangian sampling of a dust plume in the Cape Verde area on 17 June which was again measured with the same instrumentation on 21 and 22 June 2013 near Barbados. Between Cape Verde and Barbados, the aerosol optical thickness (500 nm) decreased from 0.54 to 0.26 and the stratification of the dust layers changed significantly from a rather homogenous structure near Africa to a 3-layer structure with embedded cumulus clouds in the Caribbean. In the upper part of the dust layers in the Caribbean, the aerosol properties were similar to the observations near Africa. In contrast, much more variability in the dust properties was observed between 0.7 and 2.5 km altitude probably due to interaction of the mineral dust with clouds. In our

Synoptic conditions favouring the occurrence of dust transport from Africa toward Sardinia Island.

NASA Astrophysics Data System (ADS)

Canu, Annalisa; Pellizzaro, Grazia; Pintus, Gabriella; Duce, Pierpaolo

2016-04-01

Dust events that reach Italy have usually origin in the Sahara and Sahel regions (north-western part of Africa), which represent the dust sources nearest to Italy. In those regions the dust-lifting activity occurs in a remarkable way. Every dust event is different from the others; in fact dust transport and dust concentration in the air can vary remarkably depending on the synoptic situation. In Sardinia, dust events are more frequent in the May-November period, but they can also take place in the December-April period. The main aim of this work was to describe dust outbreaks in Sardinia and to identify the main meteorological scenarios that originate the transport of dust towards the central and western Mediterranean Basin. The evaluation of the geographical dispersion of Saharan dust was performed by using MODIS satellite data and Meteosat imagery combined with SKIRON forecasting model. The origin and the trajectory of the dust carried by winds towards Italy were inferred by the NOAA HYSPLIT model (Hybrid Single Particle Lagrangian Integrated Trajectory Model). In addition, PM10 (particulate matter with a diameter of less than 10 μm) and meteorological data registered by the ARPAS (Regional Environmental Protection Agency of Sardinia) monitoring stations were used to highlight the arrival of African air masses in Sardinia. The study was carried out during the 2014. A total of five events occurred during the year (two in spring and three in autumn) were analyzed. The origin of air masses loaded with dust from North Africa was confirmed by satellite imagery and 3-days air mass backward trajectories calculated by the NOAA HYSPLIT model. The analysis of the PM10 daily pattern registered at northern and southern Sardinia sites showed a rising of values during the dust event. The arrival of air masses from Africa caused the daily mean air temperature to rise whereas relative humidity values decreased. Finally, the results showed that all the event analyzed were

Investigations of Desert Dust and Smoke in the North Atlantic in Support of the TOMS Instrument

NASA Technical Reports Server (NTRS)

Toon, Owen B.

2005-01-01

During the initial period of the work we concentrated on Saharan dust storms and published a sequence of papers (Colarco et a1 2002,2003a,b, Toon, 2004). The U.S. Air Force liked the dust model so well that they appropriated it for operational dust storm forecasting (Barnum et al., 2004). The Air Force has used it for about 5 yrs in the Middle East where dust storms cause significant operational problems. The student working on this project, Peter Colarco, has graduated and is now a civil servant at Goddard where he continues to interact with the TOMS team. This work helped constrain the optical properties of dust at TOMS wavelengths, which is useful for climate simulations and for TOMS retrievals of dust properties such as optical depth. We also used TOMS data to constrain the sources of dust in Africa and the Middle East, to determine the actual paths taken by Saharan dust storms, to learn more about the mechanics of variations in the optical depths, and to learn more about the mechanisms controlling the altitudes of the dust. During the last two years we have been working on smoke from fires. Black carbon aerosols are one of the leading factors in radiative forcing. The US Climate Change Science Program calls this area out for specific study. It has been suggested by Jim Hansen, and Mark Jacobsen among others, that by controlling emissions of black carbon we might reduce greenhouse radiative forcing in a relatively painless manner. However, we need a greatly improved understanding of the amount of black carbon in the atmosphere, where it is located, where it comes from, how it is mixed with other particles, what its actual optical properties are, and how it evolves. In order to learn about these issues we are using a numerical model of smoke. We have applied this model to the SAFARI field program data, and used the TOMS satellite observations in that period (Sept. 2000). Our goal is to constrain source function estimates for black carbon, and smoke optical

Is HIV/AIDS Epidemic Outcome of Poverty in Sub-Saharan Africa?

PubMed Central

Dzimnenani Mbirimtengerenji, Noel

2007-01-01

Undisputable fact is that 14 000 people in Sub-Saharan Africa are being infected daily with HIV and 11 000 are dying every day due to HIV/AIDS related illnesses. In this region more than 60% of the people live below UN poverty line of US$ 1 per day. Some studies have shown that poverty and HIV infection are in correlation, but none has shown whether HIV/AIDS in Sub-Saharan Africa is an outcome of poverty. This article, therefore, shows that HIV is an important outcome of poverty, with sexual trade, migration, polygamy, and teenage marriages as its predictors in the Sub Saharan region. I used the examples of 20 countries with the highest poverty level in the region to demonstrate the gravity of the HIV scourge, using the data from different international databases. PMID:17948947

Using thermal infrared (TIR) data to characterize dust sources, dust fall and the linkage to climate in the Middle East

NASA Astrophysics Data System (ADS)

Mohammad, R.; Ramsey, M.; Scheidt, S. P.

2010-12-01

Prior to mineral dust deposition affecting albedo, aerosols can have direct and indirect effects on local to regional scale climate by changing both the shortwave and longwave radiative forcing. In addition, mineral dust causes health hazards, such as respiratory-related illnesses and deaths, loss of agricultural soil, and safety hazards to aviation and motorists due to reduced visibility. Previous work utilized satellite and ground-based TIR data to describe the direct longwave radiative effect of the Saharan Air Layer (SAL) over the Atlantic Ocean originating from dust storms in the Western Sahara. TIR emission spectroscopy was used to identify the spectral absorption features of that dust. The current research focuses on Kuwait and utilizes a comprehensive set of spatial, analytical and geological tools to characterize dust emissions and its radiative effects. Surface mineral composition maps for the Kuwait region were created using ASTER images and GIS datasets in order to identify the possible sources of wind-blown dust. Backward trajectory analysis using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model suggests the dust source areas were located in Iraq, Syria, Jordan and Saudi Arabia. Samples collected from two dust storms (May and July 2010) were analyzed for their mineral composition and to validate the dust source areas identified by the modeling and remote sensing analysis. These air fall dust samples were collected in glass containers on a 13 meter high rooftop in the suburb of Rumaithiya in Kuwait. Additional samples will be collected to expand the analysis and their chemical compositions will be characterized by a combination of laboratory X-ray fluorescence (XRF), Scanning Electron Microscopy (SEM) and TIR emission spectroscopy. The overarching objective of this ongoing research is to both characterize the effects of mineral dust on climate as well as establish a predictive tool that can identify dust storm sources and

Experimental evidence of formation of transparent exopolymer particles (TEP) and POC export provoked by dust addition under current and high pCO2 conditions

PubMed Central

Pedrotti, Maria Luiza; Gazeau, Frédéric; Guieu, Cécile

2017-01-01

The evolution of organic carbon export to the deep ocean, under anthropogenic forcing such as ocean warming and acidification, needs to be investigated in order to evaluate potential positive or negative feedbacks on atmospheric CO2 concentrations, and therefore on climate. As such, modifications of aggregation processes driven by transparent exopolymer particles (TEP) formation have the potential to affect carbon export. The objectives of this study were to experimentally assess the dynamics of organic matter, after the simulation of a Saharan dust deposition event, through the measurement over one week of TEP abundance and size, and to evaluate the effects of ocean acidification on TEP formation and carbon export following a dust deposition event. Three experiments were performed in the laboratory using 300 L tanks filled with filtered seawater collected in the Mediterranean Sea, during two ‘no bloom’ periods (spring at the start of the stratification period and autumn at the end of this stratification period) and during the winter bloom period. For each experiment, one of the two tanks was acidified to reach pH conditions slightly below values projected for 2100 (~ 7.6–7.8). In both tanks, a dust deposition event of 10 g m-2 was simulated at the surface. Our results suggest that Saharan dust deposition triggered the abiotic formation of TEP, leading to the formation of organic-mineral aggregates. The amount of particulate organic carbon (POC) exported was proportional to the flux of lithogenic particles to the sediment traps. Depending on the season, the POC flux following artificial dust deposition ranged between 38 and 90 mg m-2 over six experimental days. Such variability is likely linked to the seasonal differences in the quality and quantity of TEP-precursors initially present in seawater. Finally, these export fluxes were not significantly different at the completion of the three experiments between the two pH conditions. PMID:28212418

Desert dust outbreaks and respiratory morbidity in Athens, Greece.

PubMed

Trianti, Stavroula-Myrto; Samoli, Evangelia; Rodopoulou, Sophia; Katsouyanni, Klea; Papiris, Spyros A; Karakatsani, Anna

2017-07-01

Ambient particulate matter (PM) has an adverse effect on respiratory morbidity. Desert dust outbreaks contribute to increased PM levels but the toxicity of desert dust mixed with anthropogenic pollutants needs clarification. We identified 132 days with desert dust episodes and 177 matched days by day of the week, season, temperature and humidity between 2001 and 2006 in Athens, Greece. We collected data on regulated pollutants and daily emergency outpatient visits and admissions for respiratory causes. We applied Poisson regression models adjusting for confounding effects of seasonality, meteorology, holidays and influenza epidemics. We evaluated the sensitivity of our results to co-pollutant exposures and effect modification by age and sex. A 10 μg/m 3 increase in PM 10 concentration was associated with 1.95% (95% confidence interval (CI): 0.02%, 3.91%) increase in respiratory emergency room visits. No significant interaction with desert dust episodes was observed. Compared with non-dust days, there was a 47% (95% CI: 29%, 68%) increase in visits in dust days not adjusting for PM 10 . Desert dust days were associated with higher numbers of emergency room visits for asthma, chronic obstructive pulmonary disease and respiratory infections with increases of 38%, 57% and 60%, respectively (p < 0.001 for all comparisons). Analyses of respiratory hospital admissions provided similar results. PM 10 effects decreased when adjusting for desert dust days and were further confounded by co-pollutants. Desert dust episode days are associated with higher respiratory emergency room visits and hospital admissions. This effect is insufficiently explained by increased PM 10 levels.

Detection of Saharan dust and biomass burning events using near-real-time intensive aerosol optical properties in the north-western Mediterranean

NASA Astrophysics Data System (ADS)

Ealo, Marina; Alastuey, Andrés; Ripoll, Anna; Pérez, Noemí; Cruz Minguillón, María; Querol, Xavier; Pandolfi, Marco

2016-10-01

The study of Saharan dust events (SDEs) and biomass burning (BB) emissions are both topics of great scientific interest since they are frequent and important polluting scenarios affecting air quality and climate. The main aim of this work is evaluating the feasibility of using near-real-time in situ aerosol optical measurements for the detection of these atmospheric events in the western Mediterranean Basin (WMB). With this aim, intensive aerosol optical properties (SAE: scattering Ångström exponent, AAE: absorption Ångström exponent, SSAAE: single scattering albedo Ångström exponent and g: asymmetry parameter) were derived from multi-wavelength aerosol light scattering, hemispheric backscattering and absorption measurements performed at regional (Montseny; MSY, 720 m a.s.l.) and continental (Montsec; MSA, 1570 m a.s.l.) background sites in the WMB. A sensitivity study aiming at calibrating the measured intensive optical properties for SDEs and BB detection is presented and discussed. The detection of SDEs by means of the SSAAE parameter and Ångström matrix (made up by SAE and AAE) depended on the altitude of the measurement station and on SDE intensity. At MSA (mountain-top site) SSAAE detected around 85 % of SDEs compared with 50 % at the MSY station, where pollution episodes dominated by fine anthropogenic particles frequently masked the effect of mineral dust on optical properties during less intense SDEs. Furthermore, an interesting feature of SSAAE was its capability to detect the presence of mineral dust after the end of SDEs. Thus, resuspension processes driven by summer regional atmospheric circulations and dry conditions after SDEs favoured the accumulation of mineral dust at regional level having important consequences for air quality. On average, SAE, AAE and g ranged between -0.7 and 1, 1.3 and 2.5 and 0.5 and 0.75 respectively during SDEs. Based on the aethalometer model, BB contribution to equivalent black carbon (BC) accounted for 36 and 40

Long-term variability of dust events in Iceland (1949-2011)

NASA Astrophysics Data System (ADS)

Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

2014-12-01

The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility < 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May-September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March-May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

Impact of aerosols, dust, water vapor and clouds on fair weather PG and implications for the Carnegie curve

NASA Astrophysics Data System (ADS)

Kourtidis, Konstantinos; Georgoulias, Aristeidis

2017-04-01

We studied the impact of anthropogenic aerosols, fine mode natural aerosols, Saharan dust, atmospheric water vapor, cloud fraction, cloud optical depth and cloud top height on the magnitude of fair weather PG at the rural station of Xanthi. Fair weather PG was measured in situ while the other parameters were obtained from the MODIS instrument onboard the Terra and Aqua satellites. All of the above parameteres were found to impact fair weather PG magnitude. Regarding aerosols, the impact was larger for Saharan dust and fine mode natural aerosols whereas regarding clouds the impact was larger for cloud fraction while less than that of aerosols. Water vapour and ice precipitable water were also found to influence fair weather PG. Since aerosols and water are ubiquitous in the atmosphere and exhibit large spatial and temporal variability, we postulate that our understanding of the Carnegie curve might need revision.

Clinical benefits of treatment with SQ house dust mite sublingual tablet in house dust mite allergic rhinitis.

PubMed

Demoly, P; Kleine-Tebbe, J; Rehm, D

2017-10-01

Treatment with SQ (standardised quality) house dust mite sublingual tablet for 1 year resulted in a decreased probability of having an allergic rhinitis (AR) exacerbation day (from 11% [placebo] to 5% [SQ house dust mite sublingual tablet]) and an increased probability of having a mild AR day (from 16% [placebo] to 34% [SQ house dust mite sublingual tablet]). © 2017 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

The Impact of Dry Saharan Air on Tropical Cyclone Intensification

NASA Technical Reports Server (NTRS)

Braun, Scott A.

2012-01-01

The controversial role of the dry Saharan Air Layer (SAL) on tropical storm intensification in the Atlantic will be addressed. The SAL has been argued in previous studies to have potential positive influences on storm development, but most recent studies have argued for a strong suppressing influence on storm intensification as a result of dry air, high stability, increased vertical wind shear, and microphysical impacts of dust. Here, we focus on observations of Hurricane Helene (2006), which occurred during the NASA African Monsoon Multidisciplinary Activities (NAMMA) experiment. Satellite and airborne observations, combined with global meteorological analyses depict the initial environment of Helene as being dominated by the SAL, although with minimal evidence that the SAL air actually penetrated to the core of the disturbance. Over the next several days, the SAL air quickly moved westward and was gradually replaced by a very dry, dust-free layer associated with subsidence. Despite the wrapping of this very dry air around the storm, Helene intensified steadily to a Category 3 hurricane suggesting that the dry air was unable to significantly slow storm intensification. Several uncertainties remain about the role of the SAL in Helene (and in tropical cyclones in general). To better address these uncertainties, NASA will be conducting a three year airborne campaign called the Hurricane and Severe Storm Sentinel (HS3). The HS3 objectives are: To obtain critical measurements in the hurricane environment in order to identify the role of key factors such as large-scale wind systems (troughs, jet streams), Saharan air masses, African Easterly Waves and their embedded critical layers (that help to isolate tropical disturbances from hostile environments). To observe and understand the three-dimensional mesoscale and convective-scale internal structures of tropical disturbances and cyclones and their role in intensity change. The mission objectives will be achieved using

Long-term variability of dust events in Iceland (1949-2011)

NASA Astrophysics Data System (ADS)

Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

2014-06-01

Long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and merged with results obtained from the Northeast Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust. Including codes 04-06 into the criteria for dust observations, the frequency was 135 dust days annually. The Sea Level Pressure (SLP) oscillation controlled whether dust events occurred in NE (16.4 dust days annually) or in southern part of Iceland (about 18 dust days annually). The most dust-frequent decade in S Iceland was the 1960s while the most frequent decade in NE Iceland was the 2000s. A total of 32 severe dust storms (visibility < 500 m) was observed in Iceland with the highest frequency during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm and during summer/autumn (May-September) while the Sub-Arctic dust events (S Iceland) were mainly cold and during winter/spring (March-May). About half of dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between PM10 concentrations and visibility during dust observations at the stations Vik and Storhofdi. This study shows that Iceland is among the dustiest areas of the world and dust is emitted the year-round.

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.

Long-range Transported African Dust in the Caribbean Region: Dust Concentrations and Water-soluble Ions

NASA Astrophysics Data System (ADS)

Santos-Figueroa, G.; Avilés-Piñeiro, G. M.; Mayol-Bracero, O. L.

2017-12-01

Long-range transported African dust (LRTAD) particles reach the Caribbean region every year during the summer months causing an increase in PM10 concentrations and by consequence degradation of air quality. During African dust (AD) incursions at the Caribbean region, PM10 concentration could exceeds the exposure limit of 50 µg/m³ 24-hour mean established by the World Health Organization (WHO). To have a better understanding of the impacts of AD particles to climate and public health at the Caribbean region it is necessary to study and determine the spatial and temporal distribution of dust particles. In order to address this, aerosols samples were collected during and absence of AD incursions during the summer of 2017 using a Hi-Volume (Hi-Vol) sampler for total suspended particles (TSP) at two sampling stations in Puerto Rico. The first station is a marine site located at Cabezas de San Juan (CSJ) Nature Reserve in Fajardo, and the second station is an urban site located at the Facundo Bueso (FB) building at the University of Puerto Rico-Rio Piedras. Aerosol samples were collected using Whatman 41 grade filters from which we determined the concentration of dust particles and the water-soluble ions (e.g., Na+, NH4+, Ca+2, Cl-, SO4-2) in the presence and absence of LRTAD particles. Saharan Air Layer (SAL) imagery, the results from the air mass backward trajectories calculated with the NOAA Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT), and the spectral coefficients from measurements at CSJ were used to monitor and confirm the presence of air masses coming from North Africa. Average dust concentrations using the Stacked-Filter Units (SFUs) at CSJ are around 4 μg/m3. LRTAD concentrations and ionic speciation results using the Hi-Vol for the marine and urban sites will be presented at the conference.

Gusev Dust Devil Movie, Sol 459 (Enhanced)

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 459th martian day, or sol (April 18, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera, and the contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

The images were processed in three steps. All images were calibrated to remove known camera artifacts. The images were then processed to remove stationary objects. The result is a gray scene showing only features that change with time. The final step combined the original image with the image that shows only moving features, showing the martian scene and the enhanced dust devils.

Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface

Gusev Dust Devil Movie, Sol 456 (Enhanced)

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 456th martian day, or sol (April 15, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera, and the contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

The images were processed in three steps. All images were calibrated to remove known camera artifacts. The images were then processed to remove stationary objects. The result is a gray scene showing only features that change with time. The final step combined the original image with the image that shows only moving features, showing the martian scene and the enhanced dust devils.

Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface

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 (

Saharan dust inputs and high UVR levels jointly alter the metabolic balance of marine oligotrophic ecosystems

PubMed Central

Cabrerizo, Marco J.; Medina-Sánchez, Juan Manuel; González-Olalla, Juan Manuel; Villar-Argaiz, Manuel; Carrillo, Presentación

2016-01-01

The metabolic balance of the most extensive bioma on the Earth is a controversial topic of the global-change research. High ultraviolet radiation (UVR) levels by the shoaling of upper mixed layers and increasing atmospheric dust deposition from arid regions may unpredictably alter the metabolic state of marine oligotrophic ecosystems. We performed an observational study across the south-western (SW) Mediterranean Sea to assess the planktonic metabolic balance and a microcosm experiment in two contrasting areas, heterotrophic nearshore and autotrophic open sea, to test whether a combined UVR × dust impact could alter their metabolic balance at mid-term scales. We show that the metabolic state of oligotrophic areas geographically varies and that the joint impact of UVR and dust inputs prompted a strong change towards autotrophic metabolism. We propose that this metabolic response could be accentuated with the global change as remote-sensing evidence shows increasing intensities, frequencies and number of dust events together with variations in the surface UVR fluxes on SW Mediterranean Sea. Overall, these findings suggest that the enhancement of the net carbon budget under a combined UVR and dust inputs impact could contribute to boost the biological pump, reinforcing the role of the oligotrophic marine ecosystems as CO2 sinks. PMID:27775100

Large Contribution of Coarse Mode to Aerosol Microphysical and Optical Properties: Evidence from Ground-Based Observations of a Transpacific Dust Outbreak at a High-Elevation North American Site

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

Kassianov, E.; Pekour, M.; Flynn, C.

Our work is motivated by previous studies of the long-range trans-Atlantic transport of Saharan dust and the observed quasi-static nature of coarse mode aerosol with a volume median diameter (VMD) of approximately 3.5 µm. We examine coarse mode contributions from the trans-Pacific transport of Asian dust to North American aerosol microphysical and optical properties using a dataset collected at the high-elevation, mountain-top Storm Peak Laboratory (SPL, 3.22 km above sea level [ASL]) and the nearby Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF, 2.76 km ASL). Data collected during the SPL Cloud Property Validation Experiment (STORMVEX, March 2011) are complemented bymore » quasi-global high-resolution model simulations coupled with aerosol chemistry. We identify dust event associated mostly with Asian plume (about 70% of dust mass) where the coarse mode with moderate (~4 µm) VMD is distinct and contributes substantially to aerosol microphysical (up to 70% for total volume) and optical (up to 45% for total scattering and aerosol optical depth) properties. Our results, when compared with previous Saharan dust studies, suggest a fairly invariant behavior of coarse mode dust aerosols. If confirmed in additional studies, this invariant behavior may simplify considerably model parameterizations for complex and size-dependent processes associated with dust transport and removal.« less

Dust over Japan

NASA Image and Video Library

2017-12-08

March 24, 2010 - Dust over Japan This image of gray/brown dust being blown over Japan was captured on March 21, 2010 by the MODIS on the Terra satellite. On the left is the Korean peninsula. Japan stretches diagonally across the image, up to the top right corner. The dust is likely from the sandstorm that swept across the China the previous day. The sand and dust originated from the south and east of Inner Mongolia. In this image from March 20, the dust is nearly obscuring the Bohai Sea, which is just west of the Korean peninsula. Here is a handy map. For more information related to this image go to: modis.gsfc.nasa.gov/gallery/individual.php?db_date=2010-0... For more information about Goddard Space Flight Center go here: www.nasa.gov/centers/goddard/home/index.html

Introduction to project DUNE, a DUst experiment in a low Nutrient, low chlorophyll Ecosystem

NASA Astrophysics Data System (ADS)

Guieu, C.; Dulac, F.; Ridame, C.; Pondaven, P.

2014-01-01

analog for wet deposition following evapocondensation with acids for simulating cloud processing by polluted air masses under anthropogenic influence. Using a number of particulate tracers that were followed in the water column and in the sediment traps, it was shown that the dust composition evolves after seeding by total dissolution of these salts. This provided a large source of new dissolved inorganic nitrogen (DIN) in the surface waters. In spite of this dissolution, the typical inter-elemental ratios in the particulate matter, such as Ti / Al or Ba / Al, are not affected during the dust settling, confirming their values as proxies of lithogenic fluxes or of productivity in sediment traps. DUNE experiments have clearly shown the potential for Saharan wet deposition to modify the in situ concentrations of dissolved elements of biogeochemical interest such as Fe and also P and N. Indeed, wet deposition yielded a transient increase in dissolved inorganic phosphorus (DIP) followed by a very rapid return to initial conditions or no return to initial conditions when a second dust seeding followed. By transiently increasing DIP and DIN concentrations in P- and N-starved surface waters of the Mediterranean Sea, wet deposition of Saharan dust can likely relieve the potential P and/or N limitation of biological activity; this has been directly quantified in terms of biological response. Wet deposition of dust strongly stimulated primary production and phytoplanktonic biomass during several days. Small phytoplankton (< 3 μm) was more stimulated after the first dust addition, whereas the larger size class (> 3 μm) significantly increased after the second one, indicating that larger-sized cells need further nutrient supply in order to be able to adjust their physiology and compete for resource acquisition and biomass increase. Among the microorganisms responding to the atmospheric inputs, diazotrophs were stimulated by both wet and dry atmospheric deposition, although N2

Ice nucleation of natural desert dust including organics sourced from nine deserts worldwide

NASA Astrophysics Data System (ADS)

Boose, Yvonne; Welti, André; Atkinson, James; Danielczok, Anja; Bingemer, Heinz; Plötze, Michael; Lohmann, Ulrike; Kanji, Zamin A.

2017-04-01

The extraordinary high ice nucleation (IN) potential of microcline, a K-feldspar mineral, at temperatures (T) above 248 and up to 271 K has been show recently. However, it is unclear if microcline is also found at the surface of airborne mineral dust particles or if chemical and mechanical aging processes lead to its destruction or shielding and thus reduced IN ability in the atmosphere. It is suggested that instead organic material mixed with inorganic minerals is responsible for cloud glaciation at T ≥ 253 K. We collected airborne Saharan dust at 4 locations at different distances from the desert and 11 samples from the surface of 9 of the major deserts worldwide. We studied immersion IN on these samples between 235 - 263 K using the IMCA-ZINC (immersion mode cooling chamber - Zurich ice nucleation chamber) setup and the FRIDGE (Franfurt Ice Nuclei Deposition Freezing Experiment) instrument run in droplet freezing mode. By correlating the results with the bulk mineralogy of the dust samples, determined by X-ray diffraction analysis, we show that at 253 K, K-feldspar indeed predicts best the IN behavior of the samples. At lower T (238 - 245 K) however, quartz and the total feldspar contents correlate best. Furthermore, microcline is only found in one of the airborne Saharan dust samples (3.9 wt%) while in the others the amount is below the detection limit or completely absent. Relative humidity (RH) scans at constant T = 238, 240 and 242 K were additionally performed with the portable ice nucleation counter, PINC. Above and below water saturation a similar prominent role of quartz is found as in the immersion mode. To investigate the role of organic material on the IN ability, we heated some of the samples at 573 K for 10 h and repeated the RH-scans. Furthermore, we performed thermogravimetric analysis of the dusts. The two tested airborne Saharan samples loose between 2.8 and 7.5 % of their mass at T ≤ 573 K, partly due to water release, partly due to

Polluted Dust Classification and Its Optical Properties Analysis Using CALIPSO Data and Simulation

NASA Astrophysics Data System (ADS)

Ding, J.; Yang, P.; Holz, R.; Vaughan, M. A.; Hu, Y.

2015-12-01

In CALIPSO Level 2 aerosol data, dust particles are classified into two subtypes, namely, pure dust and polluted dust based on lidar backscatter, depolarization ratio and surface types. In this research, the polluted dust subtype is found to have two distinct modes in terms of integrated depolarization ratio (IDR) and integrated total color ratio (ICR). Dust with smaller IDR and ICR occurs mainly over areas with strong smoke emissions such as industrial cities. This kind of polluted dust originating from East Asia is also found over the Pacific Ocean. In contrast, the other type originating from the Saharan desert with larger IDR and ICR occurs mainly over the Atlantic Ocean. The disparities of IDR and ICR may result from different pollutants. The polluted dust with smaller ICR and IDR should have stronger absorption of light and may contain black carbon. Other chemical compounds such as sea salts may account for polluted dust with larger ICR and IDR. To further separate the types of polluted dust, cluster analysis is applied to determine the centroid of each type in terms of IDR and ICR. Furthermore, scattering models of dust mixed with various pollutants are constructed to be included in a CALIPSO simulator. The simulated IDR and ICR values are compared with data to retrieve the chemical compositions of polluted dust. The difference of polluted dust over the Pacific and Atlantic Ocean provides new evidence about long-range transport of Asian dust to North America. The distribution of dust polluted by black carbon is determined, which can improve knowledge about the effect of black carbon on the earth's radiation budget.

Dating Saharan dust deposits on Lanzarote (Canary Islands) by luminescence dating techniques and their implication for palaeoclimate reconstruction of NW Africa

NASA Astrophysics Data System (ADS)

von Suchodoletz, H.; Fuchs, M.; ZöLler, L.

2008-02-01

Lava flow dammed valleys (Vegas) on Lanzarote (Canary Islands) represent unique sediment traps, filled with autochthonous volcanic material and allochthonous Saharan dust. These sediments and the intercalated palaeosoil sediments document past environmental change of the last glacial-interglacial cycles, both on Lanzarote and in NW Africa. A reliable chronology must be established to use these sediment archives for palaeoclimate reconstructions. Owing to the lack of organic material and the limiting time range of the 14C-dating method, luminescence dating is the most promising method for these sediments. However, the fluvio-eolian character of these sediments is a major problem for luminescence dating, because these sediments are prone to insufficient resetting of the parent luminescence signal (bleaching) prior to sedimentation. To check for the best age estimates, we compare the bleaching behavior of (1) different grain sizes (coarse- versus fine-grain quartz OSL) and (2) different minerals (fine-grain feldspar IRSL versus fine-grain quartz OSL). The results show that owing to its bleaching characteristics, quartz is the preferable mineral for luminescence dating. On the basis of the fine- and coarse-grain quartz OSL age estimates, a chronostratigraphy up to 100 ka could be established. Beyond this age limit for OSL quartz, the chronostratigraphy could be extended up to 180 ka by correlating the vega sediments with dated marine sediment archives.

Dust devils on Mars

NASA Technical Reports Server (NTRS)

Thomas, P. G.; Gierasch, P.

1985-01-01

Large columns of dust have been discovered rising above plains on Mars. The storms are probably analogous to terrestrial dust devils, but their size indicates that they are more similar to tornadoes in intensity. They occur at locations where the soil has been strongly warmed by the Sun, and there the surface is smooth and fine grained. These are the same conditions that favor dust devils on Earth. Warm gas from the lowest atmospheric layer converges and rises in a thin column, with intense swirl developing at the edge of the column. In one area a mosaic of Viking images shows 97 vortices in a three day period. This represents a density of vortices of about one in each 900 square kilometers. Thus, these dust devils may be important in moving dust or starting over dust storms.

Airborne desert dust and aeromicrobiology over the Turkish Mediterranean coastline

NASA Astrophysics Data System (ADS)

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

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 (<1.0%) of the actual microbial population in any given environment, dust-borne microorganisms and other associated constituents (organic detritus, toxins, etc.) may play a significant role in the regional human and ecosystem health.

Changes in Stratiform Clouds of Mesoscale Convective Complex Introduced by Dust Aerosols

NASA Technical Reports Server (NTRS)

Lin, B.; Min, Q.-L.; Li, R.

2010-01-01

Aerosols influence the earth s climate through direct, indirect, and semi-direct effects. There are large uncertainties in quantifying these effects due to limited measurements and observations of aerosol-cloud-precipitation interactions. As a major terrestrial source of atmospheric aerosols, dusts may serve as a significant climate forcing for the changing climate because of its effect on solar and thermal radiation as well as on clouds and precipitation processes. Latest satellites measurements enable us to determine dust aerosol loadings and cloud distributions and can potentially be used to reduce the uncertainties in the estimations of aerosol effects on climate. This study uses sensors on various satellites to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective complex (MCC). A trans-Atlantic dust outbreak of Saharan origin occurring in early March 2004 is considered. For the observed MCCs under a given convective strength, small hydrometeors were found more prevalent in the dusty stratiform regions than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust regions, particularly at altitudes where heterogeneous nucleation of mineral dust prevails, further supports the observed changes of clouds and precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the size spectrum of precipitation-sized hydrometeors from heavy precipitation to light precipitation and ultimately to suppress precipitation and increase the lifecycle of cloud systems, especially over stratiform areas.

An Assessment of the Surface Longwave Direct Radiative Effect of Airborne Saharan Dust During the NAMMA Field Campaign

NASA Technical Reports Server (NTRS)

Hansell, R. A.; Tsay, S. C.; Ji, Q.; Hsu, N. C.; Jeong, M. J.; Wang, S. H.; Reid, J. S.; Liou, K. N.; Ou, S. C.

2010-01-01

In September 2006, NASA Goddard s mobile ground-based laboratories were deployed to Sal Island in Cape Verde (16.73degN, 22.93degW) to support the NASA African Monsoon Multidisciplinary Analysis (NAMMA) field study. The Atmospheric Emitted Radiance Interferometer (AERI), a key instrument for spectrally characterizing the thermal IR, was used to retrieve the dust IR aerosol optical depths (AOTs) in order to examine the diurnal variability of airborne dust with emphasis on three separate dust events. AERI retrievals of dust AOT are compared with those from the coincident/collocated multifilter rotating shadow-band radiometer (MFRSR), micropulse lidar (MPL), and NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) sensors. The retrieved AOTs are then inputted into the Fu-Liou 1D radiative transfer model to evaluate local instantaneous direct longwave radiative effects (DRE(sub LW)) of dust at the surface in cloud-free atmospheres and its sensitivity to dust microphysical parameters. The top-of-atmosphere DRE(sub LW) and longwave heating rate profiles are also evaluated. Instantaneous surface DRE(sub LW) ranges from 2 to 10 W/sq m and exhibits a strong linear dependence with dust AOT yielding a DRE(sub LW) of 16 W/sq m per unit dust AOT. The DRE(sub LW) is estimated to be approx.42% of the diurnally averaged direct shortwave radiative effect at the surface but of opposite sign, partly compensating for the shortwave losses. Certainly nonnegligible, the authors conclude that DRE(sub LW) can significantly impact the atmospheric energetics, representing an important component in the study of regional climate variation.

Legal immigrants: invasion of alien microbial communities during winter occurring desert dust storms.

PubMed

Weil, Tobias; De Filippo, Carlotta; Albanese, Davide; Donati, Claudio; Pindo, Massimo; Pavarini, Lorenzo; Carotenuto, Federico; Pasqui, Massimiliano; Poto, Luisa; Gabrieli, Jacopo; Barbante, Carlo; Sattler, Birgit; Cavalieri, Duccio; Miglietta, Franco

2017-03-10

A critical aspect regarding the global dispersion of pathogenic microorganisms is associated with atmospheric movement of soil particles. Especially, desert dust storms can transport alien microorganisms over continental scales and can deposit them in sensitive sink habitats. In winter 2014, the largest ever recorded Saharan dust event in Italy was efficiently deposited on the Dolomite Alps and was sealed between dust-free snow. This provided us the unique opportunity to overcome difficulties in separating dust associated from "domestic" microbes and thus, to determine with high precision microorganisms transported exclusively by desert dust. Our metagenomic analysis revealed that sandstorms can move not only fractions but rather large parts of entire microbial communities far away from their area of origin and that this microbiota contains several of the most stress-resistant organisms on Earth, including highly destructive fungal and bacterial pathogens. In particular, we provide first evidence that winter-occurring dust depositions can favor a rapid microbial contamination of sensitive sink habitats after snowmelt. Airborne microbial depositions accompanying extreme meteorological events represent a realistic threat for ecosystem and public health. Therefore, monitoring the spread and persistence of storm-travelling alien microbes is a priority while considering future trajectories of climatic anomalies as well as anthropogenically driven changes in land use in the source regions.

Dust Devils in Gusev Crater, Sol 463

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a several dust devils -- whirlwinds that loft dust into the air -- moving across a plain below the hillside vantage point of NASA's Mars Exploration Rover Spirit. Several of the dust devils are visible at once in some of the frames in this sequence. The local solar time was about 2 p.m., when the ground temperature was high enough to cause turbulence that kicks up dust devils as the wind blows across the plain. The number of seconds elapsed since the first frame is indicated at lower left of the images, typically 20 seconds between frames. Spirit's navigation camera took these images on the rover's 463rd martian day, or sol (April 22, 2005.) Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection can trigger dust devils.

Characterisation of nutrients wet deposition under influence of Saharan dust at Puerto-Rico in Caribbean Sea

NASA Astrophysics Data System (ADS)

Desboeufs, Karine; Formenti, Paola; Triquet, Sylvain; Laurent, Benoit; Denjean, Cyrielle; Gutteriez-Moreno, Ian E.; Mayol-Bracero, Olga L.

2015-04-01

Large quantities of African dust are carried across the North Atlantic toward the Caribbean every summer by Trade Winds. Atmospheric deposition of dust aerosols, and in particular wet deposition, is widely acknowledged to be the major delivery pathway for nutrients to ocean ecosystems, as iron, phosphorus and various nitrogen species. The deposition of this dustis so known to have an important impact on biogeochemical processes in the Tropical and Western Atlantic Ocean and Caribbean including Puerto-Rico. However, very few data exists on the chemical composition in nutrients in dusty rain in this region. In the framework of the Dust-ATTAcK project, rainwater was collected at the natural reserve of Cape San Juan (CSJ) (18.38°N, 65.62°W) in Puerto-Ricobetween 20 June 2012 and 12 July 2012 during thedusty period. A total of 7 rainwater events were sampled during various dust plumes. Complementary chemical analyses on aerosols in suspension was also determined during the campaign. The results on dust composition showed that no mixing with anthropogenic material was observed, confirming dust aerosols were the major particles incorporated in rain samples. The partitioning between soluble and particulate nutrients in rain samples showed that phosphorous solubility ranged from 30 and 80%. The average Fe solubility was around 0.5%, in agreement with Fe solubility observed in rains collected in Niger during African monsoon. That means that the high solubility measurements previously observed in Caribbean was probably due to an anthropogenic influence. Atmospheric wet deposition fluxes of soluble and total nutrients (N, P, Si, Fe, Co, Cu, Mn, Ni, Zn) to Caribbean Sea were determined. Atmospheric P and N inputs were strongly depleted relative to the stoichiometry of phytoplankton Fe, N, P and Si requirements.The nitrogen speciation was also determined and showed the predominance of ammonium form. 3-D modeling was used to estimate the spatial extend of these fluxes over the

WRF-Chem model simulations of a dust outbreak over the central Mediterranean and comparison with multi-sensor desert dust observations

NASA Astrophysics Data System (ADS)

Rizza, Umberto; Barnaba, Francesca; Marcello Miglietta, Mario; Mangia, Cristina; Di Liberto, Luca; Dionisi, Davide; Costabile, Francesca; Grasso, Fabio; Gobbi, Gian Paolo

2017-01-01

In this study, the Weather Research and Forecasting model with online coupled chemistry (WRF-Chem) is applied to simulate an intense Saharan dust outbreak event that took place over the Mediterranean in May 2014. Comparison of a simulation using a physics-based desert dust emission scheme with a numerical experiment using a simplified (minimal) emission scheme is included to highlight the advantages of the former. The model was found to reproduce well the synoptic meteorological conditions driving the dust outbreak: an omega-like pressure configuration associated with a cyclogenesis in the Atlantic coasts of Spain. The model performances in reproducing the atmospheric desert dust load were evaluated using a multi-platform observational dataset of aerosol and desert dust properties, including optical properties from satellite and ground-based sun photometers and lidars, plus in situ particulate matter mass concentration (PM) data. This comparison allowed us to investigate the model ability in reproducing both the horizontal and the vertical displacement of the dust plume, as well as its evolution in time. The comparison with satellite (MODIS-Terra) and sun photometers (AERONET) showed that the model is able to reproduce well the horizontal field of the aerosol optical depth (AOD) and its evolution in time (temporal correlation coefficient with AERONET of 0.85). On the vertical scale, the comparison with lidar data at a single site (Rome, Italy) confirms that the desert dust advection occurs in several, superimposed "pulses" as simulated by the model. Cross-analysis of the modeled AOD and desert dust emission fluxes further allowed for the source regions of the observed plumes to be inferred. The vertical displacement of the modeled dust plume was in rather good agreement with the lidar soundings, with correlation coefficients among aerosol extinction profiles up to 1 and mean discrepancy of about 50 %. The model-measurement comparison for PM10 and PM2.5 showed a

Formation of iron nanoparticles and increase in iron reactivity in mineral dust during simulated cloud processing.

PubMed

Shi, Zongbo; Krom, Michael D; Bonneville, Steeve; Baker, Alex R; Jickells, Timothy D; Benning, Liane G

2009-09-01

The formation of iron (Fe) nanoperticles and increase in Fe reactivity in mineral dust during simulated cloud processing was investigated using high-resolution microscopy and chemical extraction methods. Cloud processing of dust was experimentally simulated via an alternation of acidic (pH 2) and circumneutral conditions (pH 5-6) over periods of 24 h each on presieved (<20 microm) Saharan soil and goethite suspensions. Microscopic analyses of the processed soil and goethite samples reveal the neo-formation of Fe-rich nanoparticle aggregates, which were not found initially. Similar Fe-rich nanoparticles were also observed in wet-deposited Saharen dusts from the western Mediterranean but not in dry-deposited dust from the eastern Mediterranean. Sequential Fe extraction of the soil samples indicated an increase in the proportion of chemically reactive Fe extractable by an ascorbate solution after simulated cloud processing. In addition, the sequential extractions on the Mediterranean dust samples revealed a higher content of reactive Fe in the wet-deposited dust compared to that of the dry-deposited dust These results suggestthat large variations of pH commonly reported in aerosol and cloud waters can trigger neo-formation of nanosize Fe particles and an increase in Fe reactivity in the dust

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

NASA Astrophysics Data System (ADS)

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; Sullivan, R. C.; Petters, M. D.; Tobo, Y.; Niemand, M.; Möhler, O.; Snider, J. R.; Wang, Z.; Kreidenweis, S. M.

2014-06-01

Data from both laboratory studies and atmospheric measurements are used to develop a simple parametric description for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken to approximate the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A correction factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this correction factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization to the immersion freezing

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

NASA Astrophysics Data System (ADS)

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; Sullivan, R. C.; Petters, M. D.; Tobo, Y.; Niemand, M.; Möhler, O.; Snider, J. R.; Wang, Z.; Kreidenweis, S. M.

2015-01-01

Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RHw) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RHw of 105% vs. maximum fractions active at higher RHw. Instrumental factors that affect activation behavior vs. RHw in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including calibration

Dust and biological aerosols from the Sahara and Asia influence precipitation in the western U.S.

PubMed

Creamean, Jessie M; Suski, Kaitlyn J; Rosenfeld, Daniel; Cazorla, Alberto; DeMott, Paul J; Sullivan, Ryan C; White, Allen B; Ralph, F Martin; Minnis, Patrick; Comstock, Jennifer M; Tomlinson, Jason M; Prather, Kimberly A

2013-03-29

Winter storms in California's Sierra Nevada increase seasonal snowpack and provide critical water resources and hydropower for the state. Thus, the mechanisms influencing precipitation in this region have been the subject of research for decades. Previous studies suggest Asian dust enhances cloud ice and precipitation, whereas few studies consider biological aerosols as an important global source of ice nuclei (IN). Here, we show that dust and biological aerosols transported from as far as the Sahara were present in glaciated high-altitude clouds coincident with elevated IN concentrations and ice-induced precipitation. This study presents the first direct cloud and precipitation measurements showing that Saharan and Asian dust and biological aerosols probably serve as IN and play an important role in orographic precipitation processes over the western United States.

Reducing float coal dust

PubMed Central

Patts, J.R.; Colinet, J.F.; Janisko, S.J.; Barone, T.L.; Patts, L.D.

2016-01-01

Controlling float coal dust in underground coal mines before dispersal into the general airstream can reduce the risk of mine explosions while potentially achieving a more effective and efficient use of rock dust. A prototype flooded-bed scrubber was evaluated for float coal dust control in the return of a continuous miner section. The scrubber was installed inline between the face ventilation tubing and an exhausting auxiliary fan. Airborne and deposited dust mass measurements were collected over three days at set distances from the fan exhaust to assess changes in float coal dust levels in the return due to operation of the scrubber. Mass-based measurements were collected on a per-cut basis and normalized on the basis of per ton mined by the continuous miner. The results show that average float coal dust levels measured under baseline conditions were reduced by more than 90 percent when operating the scrubber. PMID:28018004

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.

Gusev Dust Devil Movie, Sol 456 (Plain and Isolated)

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 456th martian day, or sol (April 15, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera. Each frame in this movie has the raw image on the top half and a processed version in the lower half that enhances contrast and removes stationary objects, producing an image that is uniformly gray except for features that change from frame to frame.

The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection should trigger dust devils.

Scientists will use the images to study several things. Tracking the dust devils tells which way the wind blows at different times

Gusev Dust Devil Movie, Sol 459 (Plain and Isolated)

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a dust devil scooting across a plain inside Gusev Crater on Mars as seen from the NASA rover Spirit's hillside vantage point during the rover's 459th martian day, or sol (April 18, 2005). The individual images were taken about 20 seconds apart by Spirit's navigation camera. Each frame in this movie has the raw image on the top half and a processed version in the lower half that enhances contrast and removes stationary objects, producing an image that is uniformly gray except for features that change from frame to frame.

The movie results from a new way of watching for dust devils, which are whirlwinds that hoist dust from the surface into the air. Spirit began seeing dust devils in isolated images in March 2005. At first, the rover team relied on luck. It might catch a dust devil in an image or it might miss by a few minutes. Using the new detection strategy, the rover takes a series of 21 images. Spirit sends a few of them to Earth, as well as little thumbnail images of all of them. Team members use the 3 big images and all the small images to decide whether the additional big images have dust devils. For this movie, they specifically told Spirit to send back frames that they knew had dust devils.

Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection should trigger dust devils.

Scientists will use the images to study several things. Tracking the dust devils tells which way the wind blows at different times

Sensitivity of WRF-Chem model to land surface schemes: Assessment in a severe dust outbreak episode in the Central Mediterranean (Apulia Region)

NASA Astrophysics Data System (ADS)

Rizza, Umberto; Miglietta, Mario Marcello; Mangia, Cristina; Ielpo, Pierina; Morichetti, Mauro; Iachini, Chiara; Virgili, Simone; Passerini, Giorgio

2018-03-01

The Weather Research and Forecasting model with online coupled chemistry (WRF-Chem) is applied to simulate a severe Saharan dust outbreak event that took place over Southern Italy in March 2016. Numerical experiments have been performed applying a physics-based dust emission model, with soil properties generated from three different Land Surface Models, namely Noah, RUC and Noah-MP. The model performance in reproducing the severe desert dust outbreak is analysed using an observational dataset of aerosol and desert dust features that includes optical properties from satellite and ground-based sun-photometers, and in-situ particulate matter mass concentration (PM) data. The results reveal that the combination of the dust emission model with the RUC Land Surface Model significantly over-predicts the emitted mineral dust; on the other side, the combination with Noah or Noah-MP Land Surface Model (LSM) gives better results, especially for the daily averaged PM10.

Should precipitation influence dust emission in global dust models?

NASA Astrophysics Data System (ADS)

Okin, Gregory

2016-04-01

Soil moisture modulates the threshold shear stress required to initiate aeolian transport and dust emission. Most of the theoretical and laboratory work that has confirmed the impact of soil moisture has appropriately acknowledged that it is the soil moisture of a surface layer a few grain diameters thick that truly controls threshold shear velocity. Global and regional models of dust emission include the effect of soil moisture on transport threshold, but most ignore the fact that only the moisture of the very topmost "active layer" matters. The soil moisture in the active layer can differ greatly from that integrated through the top 2, 5, 10, or 100 cm (surface layers used by various global models) because the top 2 mm of heavy texture soils dries within ~1/2 day while sandy soils dry within less than 2 hours. Thus, in drylands where dust emission occurs, it is likely that this top layer is drier than the underlying soil in the days and weeks after rain. This paper explores, globally, the time between rain events in relation to the time for the active layer to dry and the timing of high wind events. This analysis is carried out using the same coarse reanalyses used in global dust models and is intended to inform the soil moisture controls in these models. The results of this analysis indicate that the timing between events is, in almost all dust-producing areas, significantly longer than the drying time of the active layer, even when considering soil texture differences. Further, the analysis shows that the probability of a high wind event during the period after a rain where the surface is wet is small. Therefore, in coarse global models, there is little reason to include rain-derived soil moisture in the modeling scheme.

Iceland Polar Vortex 2016 campaign: Winter and high-altitude dust size distributions with the balloon-borne Light Optical Aerosol Counter (LOAC)

NASA Astrophysics Data System (ADS)

Renard, Jean-Baptiste; Dagsson-Waldhauserova, Pavla; Olafsson, Haraldur; Arnalds, Olafur; Vignelles, Damien; Verdier, Nicolas

2017-04-01

particles cm-3 at altitude of 1 km and 60 particles cm-3 at altitude of 5 km, which is at least 5 times higher than during background conditions. The particles were < 3 micrometers in size at altitudes >1 km while largest particles, up to 20 micrometers, were detected close to the ground. Such high number concentrations in several km height were captured by LOAC during a typical Saharan dust plume. On the other hand, aircraft measurements of winter dust storm in 2007 with an aerosol spectrometer (0.1-3 micrometers) detected only 30-50 particles per cm3 in altitude 1900 m. Our results show that fine volcanic glacially reworked dust can reach high altitudes relatively close to the dust source and reside in terms of days under winter atmospheric conditions. The remaining question is the further transport of these high altitude particles outside Iceland.

Four Interstellar Dust Candidates from the Stardust Interstellar Dust Collector

NASA Technical Reports Server (NTRS)

Westphal, A. J.; Allen, C.; Bajt, S.; Bechtel, H. A.; Borg, J.; Brenker, F.; Bridges, J.; Brownlee, D. E.; Burchell, M.; Burghammer, M.;

Gusev Dust Devil, sol 532

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a dust devil seen by NASA's Mars Exploration Rover Spirit during the rover's 532nd martian day, or sol (July 2, 2005). The dust-carrying whirlwind is moving across a plain inside Gusev Crater and viewed from Spirit's vantage point on hills rising from the plain. The clip consists of frames taken by Spirit's navigation camera, processed to enhance contrast for anything in the images that changes from frame to frame. The total elapsed time during the taking of these frames was 8 minutes, 48 seconds.

Spirit began seeing dust devil activity around the beginning of Mars' spring season. Activity increased as spring continued, but fell off again for about two weeks during a dust storm. As the dust storm faded away, dust devil activity came back. In the mid-afternoons as the summer solstice approached, dust devils were a very common occurrence on the floor of Gusev crater. The early-spring dust devils tended to move southwest-to-northeast, across the dust devil streaks in Gusev seen from orbit. Increasingly as the season progresses, the dust devils are seen moving northwest-to-southeast, in the same direction as the streaks. Scientists are watching for the big dust devils that leave those streaks.

Brominated and phosphate flame retardants (FRs) in indoor dust from different microenvironments: Implications for human exposure via dust ingestion and dermal contact.

PubMed

Zheng, Xiaobo; Qiao, Lin; Covaci, Adrian; Sun, Runxia; Guo, Huiying; Zheng, Jing; Luo, Xiaojun; Xie, Qilai; Mai, Bixian

2017-10-01

Indoor dust has been widely used to monitor flame retardants (FRs) in indoor environment, but most studies only focused on floor dust. In the present study, FRs were examined in indoor dust from different locations. Dust from air conditioner (AC) filters, beddings, floor, and windows in bedrooms, and dust from AC filters, printer table surface, computer table surface, floor, and windows in offices were collected, respectively. Polybrominated diphenyl ether congener 209 (BDE 209) and decabromodiphenyl ethane (DBDPE) were the most abundant brominated flame retardants (BFRs), and tris(chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloroisopropyl) phosphate (TDCIPP), and triphenyl phosphate (TPHP) were the most abundant phosphate flame retardants (PFRs). In bedrooms, the AC filter dust had the highest median levels of BDE 209 (536 ng/g) and DBDPE (2720 ng/g), while bed dust had the highest median levels of ΣPFRs (2750 ng/g) among dust samples. In offices, printer table dust had higher median levels of BDE 209 (1330 ng/g), DBDPE (8470 ng/g), and ΣPFRs (11,000 ng/g) than those in other dust samples. The high dust ingestion values of BDE 209, DBDPE, and individual PFR were 0.28, 1.20, and <0.01-0.32 ng/kg bw/day and 7.37, 31.2, and <0.01-4.54 ng/kg bw/day for BDE 209, DBDPE, and individual PFR for adults and toddlers, respectively. The high dermal exposure values of individual PFR during sleeping were <0.01-0.23 and <0.01-0.36 ng/kg bw/day for adults and toddlers, respectively. More human exposure pathways other than dust ingestion should be considered, such as the dermal contact with beddings and furniture. Copyright © 2017 Elsevier Ltd. All rights reserved.

Several Dust Devils in Gusev Crater, Sol 461

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows a several dust devils -- whirlwinds that loft dust into the air -- moving across a plain below the hillside vantage point of NASA's Mars Exploration Rover Spirit. Several of the dust devils are visible at once in some of the 21 frames in this sequence. The local solar time was about 2 p.m., when the ground temperature was high enough to cause turbulence that kicks up dust devils as the wind blows across the plain. The number of seconds elapsed since the first frame is indicated at lower left of the images, typically 20 seconds between frames. Spirit's navigation camera took these images on the rover's 461st martian day, or sol (April 20, 2005.) Contrast has been enhanced for anything in the images that changes from frame to frame, that is, for the dust devil.

Scientists expected dust devils since before Spirit landed. The landing area inside Gusev Crater is filled with dark streaks left behind when dust devils pick dust up from an area. It is also filled with bright 'hollows,' which are dust-filled miniature craters. Dust covers most of the terrain. Winds flow into and out of Gusev crater every day. The Sun heats the surface so that the surface is warm to the touch even though the atmosphere at 2 meters (6 feet) above the surface would be chilly. That temperature contrast causes convection. Mixing the dust, winds, and convection can trigger dust devils.

Multi-decadal and seasonal variability of dust observations in West Greenland.

NASA Astrophysics Data System (ADS)

Bullard, Joanna E.; Mockford, Tom

2017-04-01

Since the early 1900s expedition records from west Greenland have reported local dust storms. The Kangerlussuaq region, near the inland ice, is dry (mean annual precipitation <160 mm) with, on average, 150 snow-free days per year. The main local dust sources are active, proglacial outwash plains although reworking of loess deposits may also be important. This paper presents an analysis of 70-years of dust storm observations (1945-2015) based on WMO weather codes 6 (dust haze), 7 (raised dust or sand) and 9 (distant or past dust storm) and associated wind data. The 70-year average number of dust observations days is 5 per year but variable ranging from 0 observations to 23 observations in 1985. Over the past 7 decades the number of dust days has increased from <30 in 1945-54 to >75 in 1995-2004 and 2005-2015. The seasonality of dust observations has remained consistent throughout most of the period. Dust days occur all year round but are most frequent in May-June and September-October and are associated with minimum snow cover and glacial meltwater-driven sediment supply to the outwash plains during spring and fall flood events. Wind regime is bimodal dominated by katabatic winds from the northeast, which are strongest and most frequent during winter months (Nov-Jan), with less frequent, southwesterly winds generated by Atlantic storms mostly confined to spring (May, June). The southwesterly winds are those most likely to transport dust onto the Greenland ice sheet.

Geochemical variations in aeolian mineral particles from the Sahara-Sahel Dust Corridor.

PubMed

Moreno, Teresa; Querol, Xavier; Castillo, Sonia; Alastuey, Andrés; Cuevas, Emilio; Herrmann, Ludger; Mounkaila, Mohammed; Elvira, Josep; Gibbons, Wes

2006-10-01

The Sahara-Sahel Dust Corridor runs from Chad to Mauritania and expels huge amounts of mineral aerosols into the Atlantic Ocean. Data on samples collected from Algeria, Chad, Niger, and Western Sahara illustrate how corridor dust mineralogy and chemistry relate to geological source and weathering/transport history. Dusts sourced directly from igneous and metamorphic massifs are geochemically immature, retaining soluble cations (e.g., K, Na, Rb, Sr) and accessory minerals containing HFSE (e.g., Zr, Hf, U, Th) and REE. In contrast, silicate dust chemistry in desert basins (e.g., Bodélé Depression) is influenced by a longer history of transport, physical winnowing (e.g., loss of Zr, Hf, Th), chemical leaching (e.g., loss of Na, K, Rb), and mixing with intrabasinal materials such as diatoms and evaporitic salts. Mineral aerosols blown along the corridor by the winter Harmattan winds mix these basinal and basement materials. Dusts blown into the corridor from sub-Saharan Africa during the summer monsoon source from deeply chemically weathered terrains and are therefore likely to be more kaolinitic and stripped of mobile elements (e.g., Na, K, Mg, Ca, LILE), but retain immobile and resistant elements (e.g., Zr, Hf, REE). Finally, dusts blown southwestwards into the corridor from along the Atlantic Coastal Basin will be enriched in carbonate from Mesozoic-Cenozoic marine limestones, depleted in Th, Nb, and Ta, and locally contaminated by uranium-bearing phosphate deposits.

Re-evaluation of Dust Absorption and Radiative Forcing of Climate Using Satellite and Ground Based Remote Sensing

NASA Technical Reports Server (NTRS)

Kaufman, Yoram

1999-01-01

Simultaneous spaceborne and ground based measurements of the scattered solar radiation, create a powerful tool for determination of dust absorption and scattering properties. Absorption of solar radiation is a key component in understanding dust impact on radiative forcing at the top of the atmosphere, on the temperature profile and on cloud formation. We use Landsat spaceborne measurements at seven spectral channels in the range of 0.47 to 2.2 microns over Senegal with corresponding measurements of the aerosol spectral optical thickness by ground based sunphotometers, to find that Saharan dust absorption of solar radiation is two to four times smaller than measured in situ and represented in models. Though dust was found to absorb in the blue (single scattering albedo w = 0.88), almost no absorption, w = 0.98, was found for wavelengths > 0.6 microns. The new finding increases by 50% recently estimated solar radiative forcing by dust at the top of the atmosphere and decreases the estimated dust heating of the lower troposphere due to absorption of solar radiation. Dust transported from Asia shows slightly higher absorption for wavelengths under 1 micron, that can be explained by the presence of black carbon from urban/industrial pollution associated with the submicron size mode. In the talk I shall also discuss recent observation of the impact of dust shape on the dust scattering properties.

Optical properties of mineral dust aerosol in the thermal infrared

NASA Astrophysics Data System (ADS)

Köhler, Claas H.

2017-02-01

The optical properties of mineral dust and biomass burning aerosol in the thermal infrared (TIR) are examined by means of Fourier Transform Infrared Spectrometer (FTIR) measurements and radiative transfer (RT) simulations. The measurements were conducted within the scope of the Saharan Mineral Dust Experiment 2 (SAMUM-2) at Praia (Cape Verde) in January and February 2008. The aerosol radiative effect in the TIR atmospheric window region 800-1200 cm-1 (8-12 µm) is discussed in two case studies. The first case study employs a combination of IASI measurements and RT simulations to investigate a lofted optically thin biomass burning layer with emphasis on its potential influence on sea surface temperature (SST) retrieval. The second case study uses ground based measurements to establish the importance of particle shape and refractive index for benchmark RT simulations of dust optical properties in the TIR domain. Our research confirms earlier studies suggesting that spheroidal model particles lead to a significantly improved agreement between RT simulations and measurements compared to spheres. However, room for improvement remains, as the uncertainty originating from the refractive index data for many aerosol constituents prohibits more conclusive results.

How Saharan Dust Slows River Knickpoints: Coupling Vegetation Canopy, Soils and the Foundation of the Critical Zone

NASA Astrophysics Data System (ADS)

Brocard, G. Y.; Willenbring, J. K.; Harrison, E. J.; Scatena, F. N.

2015-12-01

Forest succession theory maintains that trees drape existing landscapes as passive niche optimizers, but in the Luquillo Mountains in Puerto Rico, the forest exerts a powerful control on erosion. The Luquillo Critical Zone observatory is set in the Luquillo Mountains, an isolated massif at the northeastern tip of Puerto Rico Island which receives up to five meters of rainfall annually. Most of the rainfall received in the mountains is conveyed as quick flow through soil macropores, inhibiting soil erosion by overland flow. Physical erosion is kept low, occurring in the form of infrequent shallow landslides, thus increasing the residence time of minerals in the near-surface environment. The extensive chemical alteration of minerals generates a thick saprolite covered by fine-grained soil. Over the quartz diorite bedrock that characterizes the southern side of the mountains, the weathering process generates saprolite tens of meters deep that is almost completely devoid of weatherable minerals. Soils forming over this saprolite are nutrient-poor, forcing the rainforest to retrieve its nutrients from atmospheric fluxes, such as Saharan dust and marine aerosols. These atmospheric inputs are thus indirectly essential for the forest to be able to maintain slow erosion rates over the mountains. At lower elevation, using cosmogenic nuclide-derived denudation rates, we identified a wave of incision which has been propagating upstream over the past 4 My in the form of very steep and slowly migrating knickpoints. Bedrock abrasion and plucking are infrequent along the knickpoint faces, because the bedrock is massive and because rivers are bedload-starved. This situation is due to the highly weathered upland soils and slow erosion rates and high weathering rate upstream, which acts to reduce bedload grain size and limits bedload fluxes to the knickpoint, respectively. The soils change radically where the wave of erosion has passed and has increased erosion rates. There, nutrient

Synoptic-scale dust transport events in the southern Himalaya

NASA Astrophysics Data System (ADS)

Duchi, R.; Cristofanelli, P.; Marinoni, A.; Bourcier, L.; Laj, P.; Calzolari, F.; Adhikary, B.; Verza, G. P.; Vuillermoz, E.; Bonasoni, P.

2014-06-01

The variability of long-range dust transport events observed in the southern Himalaya and its relation with source areas have been studied thanks to five years’ continuous measurements which were carried out at the “Nepal Climate Observatory-Pyramid” (NCO-P, 27°57‧N, 86°48‧E), the highest Northern Hemisphere GAW-WMO global station sited at 5079 m a.s.l. in the high Khumbu valley (Nepal) on the southern Himalaya. During the period March 2006-February 2011, the analyses of the aerosol particle concentrations and LAGRANTO three-dimensional backward trajectories indicated the occurrence of 275 days affected by synoptic-scale dust transport, which account for 22.2% of the investigated period. The frequency of dust transport days (DTDs) showed a clear seasonal cycle, with the highest seasonal value observed during pre-monsoon season (33.5% of the pre-monsoon’s days are DTDs). Large enhancements in coarse aerosol number concentration N1-10 (average: +689%) and mass PM1-10 (average: +1086%) were observed during the dust transport events as compared to the days without dust (dust-free days, DFDs). In addition, the single scattering albedo (SSA) also showed higher values, ranging from 0.87 to 0.90, during DTDs with respect to DFDs (0.80-0.87). The predominant source of mineral dust reaching the measurement site was identified in the arid regions of the north-western Indian subcontinent (Thar desert), which accounted for 41.6% of the trajectories points associated with DTDs. Seasonal analysis also indicated that the winter season was significantly influenced by far western desert regions, such as North Africa and the Arabic Peninsula.

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.

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

Evaluation of Dust Absorption and Radiative Forcing of Climate Using Satellite and Ground Based Remote Sensing

NASA Technical Reports Server (NTRS)

Kaufman, Yoram J.

1999-01-01

Simultaneous spaceborne and ground based measurements of the scattered solar radiation, create a powerful tool for determination of dust absorption. Absorption of solar radiation is a key component in understanding dust impact on radiative forcing at the top of the atmosphere, on the temperature profile and on cloud formation. We use Landsat spaceborne measurements at seven spectral channels in the range of 0.47 to 2.2 microns over Senegal with corresponding measurements of the aerosol spectral optical thickness by ground based sunphotometers, to find that Saharan dust absorption of solar radiation is two to four times smaller than measured in situ and represented in models. Though dust was found to absorb in the blue (single scattering albedo wo = 0.88), almost no absorption, wo = 0.98, was found for 1 greater than 0.6 microns. The results are in agreement with dust radiative measurements reported in the literature, and explain some previously reported but unexplained dust radiative properties. Therefore, the new finding should be of general relevance. The new finding increases by 50% recently estimated solar radiative forcing by dust at the top of the atmosphere and decreases the estimated dust heating of the lower troposphere due to absorption of solar radiation. Dust transported from Asia shows slightly higher absorption for wavelengths under 1 @im, that can be explained by the presence of black carbon from urban/industrial pollution associated with the submicron size mode.

Computer Model Predicts the Movement of Dust

NASA Technical Reports Server (NTRS)

2002-01-01

A new computer model of the atmosphere can now actually pinpoint where global dust events come from, and can project where they're going. The model may help scientists better evaluate the impact of dust on human health, climate, ocean carbon cycles, ecosystems, and atmospheric chemistry. Also, by seeing where dust originates and where it blows people with respiratory problems can get advanced warning of approaching dust clouds. 'The model is physically more realistic than previous ones,' said Mian Chin, a co-author of the study and an Earth and atmospheric scientist at Georgia Tech and the Goddard Space Flight Center (GSFC) in Greenbelt, Md. 'It is able to reproduce the short term day-to-day variations and long term inter-annual variations of dust concentrations and distributions that are measured from field experiments and observed from satellites.' The above images show both aerosols measured from space (left) and the movement of aerosols predicted by computer model for the same date (right). For more information, read New Computer Model Tracks and Predicts Paths Of Earth's Dust Images courtesy Paul Giroux, Georgia Tech/NASA Goddard Space Flight Center

Mixing of Dust and NH3 Observed Globally over Anthropogenic Dust Sources

NASA Technical Reports Server (NTRS)

Ginoux, P.; Clarisse, L.; Clerbaux, C.; Coheur, P.-F.; Dubovik, O.; Hsu, N. C.; Van Damme, M.

2012-01-01

The global distribution of dust column burden derived from MODIS Deep Blue aerosol products is compared to NH3 column burden retrieved from IASI infrared spectra. We found similarities in their spatial distributions, in particular their hot spots are often collocated over croplands and to a lesser extent pastures. Globally, we found 22% of dust burden collocated with NH3, with only 1% difference between land-use databases. This confirms the importance of anthropogenic dust from agriculture. Regionally, the Indian subcontinent has the highest amount of dust mixed with NH3 (26 %), mostly over cropland and during the pre-monsoon season. North Africa represents 50% of total dust burden but accounts for only 4% of mixed dust, which is found over croplands and pastures in Sahel and the coastal region of the Mediterranean. In order to evaluate the radiative effect of this mixing on dust optical properties, we derive the mass extinction efficiency for various mixtures of dust and NH3, using AERONET sunphotometers data. We found that for dusty days the coarse mode mass extinction efficiency decreases from 0.62 to 0.48 square meters per gram as NH3 burden increases from 0 to 40 milligrams per square meter. The fine mode extinction efficiency, ranging from 4 to 16 square mters per gram, does not appear to depend on NH3 concentration or relative humidity but rather on mineralogical composition and mixing with other aerosols. Our results imply that a significant amount of dust is already mixed with ammonium salt before its long range transport. This in turn will affect dust lifetime, and its interactions with radiation and cloud properties

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.

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

DOE PAGES

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; ...

2014-06-27

Data from both laboratory studies and atmospheric measurements are used to develop a simple parametric description for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RH w) are taken to approximate the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. The parameterizationmore » developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A correction factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RH w of 105% vs. maximum fractions active at higher RH w. Instrumental factors that affect activation behavior vs. RH w in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this correction factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization to the immersion

Integrating laboratory and field data to quantify the immersion freezing ice nucleation activity of mineral dust particles

DOE PAGES

DeMott, P. J.; Prenni, A. J.; McMeeking, G. R.; ...

2015-01-13

Data from both laboratory studies and atmospheric measurements are used to develop an empirical parameterization for the immersion freezing activity of natural mineral dust particles. Measurements made with the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) when processing mineral dust aerosols at a nominal 105% relative humidity with respect to water (RH w) are taken as a measure of the immersion freezing nucleation activity of particles. Ice active frozen fractions vs. temperature for dusts representative of Saharan and Asian desert sources were consistent with similar measurements in atmospheric dust plumes for a limited set of comparisons available. Themore » parameterization developed follows the form of one suggested previously for atmospheric particles of non-specific composition in quantifying ice nucleating particle concentrations as functions of temperature and the total number concentration of particles larger than 0.5 μm diameter. Such an approach does not explicitly account for surface area and time dependencies for ice nucleation, but sufficiently encapsulates the activation properties for potential use in regional and global modeling simulations, and possible application in developing remote sensing retrievals for ice nucleating particles. A calibration factor is introduced to account for the apparent underestimate (by approximately 3, on average) of the immersion freezing fraction of mineral dust particles for CSU CFDC data processed at an RH w of 105% vs. maximum fractions active at higher RH w. Instrumental factors that affect activation behavior vs. RH w in CFDC instruments remain to be fully explored in future studies. Nevertheless, the use of this calibration factor is supported by comparison to ice activation data obtained for the same aerosols from Aerosol Interactions and Dynamics of the Atmosphere (AIDA) expansion chamber cloud parcel experiments. Further comparison of the new parameterization, including

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

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.

Study on the alternative mitigation of cement dust spread by capturing the dust with fogging method

NASA Astrophysics Data System (ADS)

Purwanta, Jaka; Marnoto, Tjukup; Setyono, Prabang; Handono Ramelan, Ari

2017-12-01

The existence of a cement plant impact the lives of people around the factory site. For example the air quality, which is polluted by dust. Cement plant has made various efforts to mitigate the generated dust, but there are still alot of dust fly inground either from the cement factory chimneys or transportation. The purpose of this study was to conduct a review of alternative mitigation of the spread of dust around the cement plant. This study uses research methods such as collecting secondary data which includes data of rain density, the average rains duration, wind speed and direction as well as data of dust intensity quality around PT. Semen Gresik (Persero) Tbk.Tuban plant. A soft Wind rose file is used To determine the wind direction propensity models. The impact on the spread of dust into the environment is determined using secondary data monitoring air quality. Results of the study is that the mitigation of dust around the cement plant is influenced by natural factors, such as the tendency of wind direction, rain fall and rainy days, and the rate of dust emission from the chimney. The alternative means proposed is an environmental friendly fogging dust catcher.

Planetary Dust: Cross-Functional Considerations

NASA Technical Reports Server (NTRS)

Wagner, Sandra

2006-01-01

Apollo astronauts learned first hand how problems with dust impact lunar surface missions. After three days, lunar dust contaminating on EVA suit bearings led to such great difficulty in movement that another EVA would not have been possible. Dust clinging to EVA suits was transported into the Lunar Module. During the return trip to Earth, when microgravity was reestablished, the dust became airborne and floated through the cabin. Crews inhaled the dust and it irritated their eyes. Some mechanical systems aboard the spacecraft were damaged due to dust contamination. Study results obtained by Robotic Martian missions indicate that Martian surface soil is oxidative and reactive. Exposures to the reactive Martian dust will pose an even greater concern to the crew health and the integrity of the mechanical systems. As NASA embarks on planetary surface missions to support its Exploration Vision, the effects of these extraterrestrial dusts must be well understood and systems must be designed to operate reliably and protect the crew in the dusty environments of the Moon and Mars. The AIM Dust Assessment Team was tasked to identify systems that will be affected by the respective dust, how they will be affected, associated risks of dust exposure, requirements that will need to be developed, identified knowledge gaps, and recommended scientific measurements to obtain information needed to develop requirements, and design and manufacture the surface systems that will support crew habitation in the lunar and Martian outposts.

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.;

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

Temporal variations in optical and microphysical properties of mineral dust and biomass burning aerosol derived from daytime Raman lidar observations over Warsaw, Poland

NASA Astrophysics Data System (ADS)

Janicka, Lucja; Stachlewska, Iwona S.; Veselovskii, Igor; Baars, Holger

2017-11-01

In July 2013, favorable weather conditions caused a severe events of advection of biomass burning particles of Canadian forest fires to Europe. The smoke layers were widely observed, especially in Western Europe. An unusual atmospheric aerosol composition was measured at the EARLINET site in Warsaw, Central Poland, during a short event that occurred between 11 and 21 UTC on 10th July 2013. Additionally to the smoke layer, mineral dust was detected in a separate layer. The long-range dust transport pathway followed an uncommon way; originating in Western Sahara, passing above middle Atlantic, and circulating over British Islands, prior to its arrival to Poland. An effective radius of 560 nm was obtained for Saharan dust over Warsaw. This relatively small effective radius is likely due to the long time of the transport. The aerosol-polarization-Raman PollyXT-UW lidar was used for a successful daytime Raman retrieval of the aerosol optical properties at selected times during this short event. The aerosol vertical structure during the inflow over Warsaw in terms of optical properties and depolarization was analyzed, indicating clear distinction of the layers. The microphysical properties were inverted from the lidar derived optical data for selected ranges as representing the smoke and the mineral dust. For smoke, the effective radius was in the range of 0.29-0.36 μm and the complex refractive index 1.36 + 0.008i, on average. For dust, the values of 0.33-0.56 μm and 1.56 + 0.004i were obtained. An evolution of the aerosol composition over Warsaw during the day was analyzed.

[Influence of traffic restriction on road and construction fugitive dust].

PubMed

Tian, Gang; Li, Gang; Qin, Jian-Ping; Fan, Shou-Bin; Huang, Yu-Hu; Nie, Lei

2009-05-15

By monitoring the road and construction dust fall continuously during the "Good Luck Beijing" sport events, the reduction of road and construction dust fall caused by traffic restriction was studied. The contribution rate of road and construction dust to particulate matter of Beijing atmosphere environment, and the emission ratio of it to total local PM10 emission were analyzed. The results show that the traffic restriction reduces road and construction dust fall significantly. The dust fall average value of ring roads was 0.27 g x (m2 x d)(-1) in the "traffic restriction" period, and the values were 0.81 and 0.59 g x (m2 x d)(-1) 1 month and 7 days before. The dust fall average value of major arterial and minor arterial was 0.21 g x (m2 x d)(-1) in the "traffic restriction" period, and the values were 0.54 and 0.58 g x (m2 x d)(-1) 1 month and 7 days before. The roads emission reduced 60%-70% compared with before traffic restriction. The dust fall average values of civil architecture and utility architecture were 0.61 and 1.06 g x (m2 x d)(-1) in the "traffic restriction" period, and the values were 1.15 and 1.55 g x (m2 x d)(-1) 20 days before. The construction dust reduced 30%-47% compared with 20 days before traffic restriction. Road and construction dust emission are the main source of atmosphere particulate matter in Beijing, and its contribution to ambient PM10 concentration is 21%-36%. PM10 emitted from roads and constructions account for 42%-72% and 30%-51% of local emission while the local PM10 account for 50% and 70% of the total emission.

Evaluation of atmospheric dust prediction models using ground-based observations

NASA Astrophysics Data System (ADS)

Terradellas, Enric; María Baldasano, José; Cuevas, Emilio; Basart, Sara; Huneeus, Nicolás; Camino, Carlos; Dundar, Cinhan; Benincasa, Francesco

2013-04-01

April 2011, when several dust episodes where recorded. In regions devoid of air quality stations (as Saharan and Arabian deserts), model forecasts are regularly evaluated for 38 dust-prone sites through the use of an empirical relationship between visibility data (obtained from meteorological reports) and dust surface concentration. Finally, active remote sensing with lidar or ceilometers is the only way to inquire about the dust vertical distribution. Analysis of selected cases comparing model forecasts and lidar observations at Santa Cruz de Tenerife (Canary Islands) yields promising results regarding the identification of the dust plume thickness. From the results of this pilot trial, the convenience of a regular evaluation will be assessed.

Pulmonary toxicity of simulated lunar and Martian dusts in mice: I. Histopathology 7 and 90 days after intratracheal instillation

NASA Technical Reports Server (NTRS)

Lam, Chiu-Wing; James, John T.; McCluskey, Richard; Cowper, Shawn; Balis, John; Muro-Cacho, Carlos

2002-01-01

NASA is contemplating sending humans to Mars and to the moon for further exploration. Volcanic ashes from Arizona and Hawaii with mineral properties similar to those of lunar and Martian soils, respectively, are used to simulate lunar and Martian environments for instrument testing. Martian soil is highly oxidative; this property is not found in Earth's volcanic ashes. NASA is concerned about the health risk from potential exposure of workers in the test facilities. Fine lunar soil simulant (LSS), Martian soil simulant (MSS), titanium dioxide, or quartz in saline was intratracheally instilled into groups of 4 mice (C57BL/6J) at 0.1 mg/mouse (low dose, LD) or 1 mg/mouse (high dose, HD). Separate groups of mice were exposed to ozone (0.5 ppm for 3 h) prior to MSS instillation. Lungs were harvested for histopathological examination 7 or 90 days after the single dust treatment. The lungs of the LSS-LD groups showed no evidence of inflammation, edema, or fibrosis; clumps of particles and an increased number of macrophages were visible after 7 days but not 90 days. In the LSS-HD-7d group, the lungs showed mild to moderate alveolitis, and perivascular and peribronchiolar inflammation. The LSS-HD-90d group showed signs of mild chronic pulmonary inflammation, septal thickening, and some fibrosis. Foci of particle-laden macrophages (PLMs) were still visible. Lung lesions in the MSS-LD-7d group were similar to those observed in the LSS-HD-7d group. The MSS-LD-90d group had PLMs and scattered foci of mild fibrosis in the lungs. The MSS-HD-7d group showed large foci of PLMs, intra-alveolar debris, mild-to-moderate focal alveolitis, and perivascular and peribronchiolar inflammation. The MSS-HD-90d group showed focal chronic mild-to-moderate alveolitis and fibrosis. The findings in the O(3)-MSS-HD-90d group included widespread intra-alveolar debris, focal moderate alveolitis, and fibrosis. Lung lesions in the MSS groups were more severe with the ozone pretreatment. The effects of

Influence of Asian dust storms on air quality in Taiwan.

PubMed

Liu, Chung-Ming; Young, Chea-Yuan; Lee, Yen-Chih

2006-09-15

In each year, dust storms triggered by cold air masses passing through northern China and Mongolia enhance the PM10 concentration over Taiwan region during winter and spring. On average, there are four to five dust events and 6.1 dust days in a year in Taiwan. Each event lasts for 1 day or even longer. A procedure to identify a dust event is rationalized and exercised on data collected during 1994-2005. Also, a ranking method named as the dust intensity rank (DIR) is developed to distinguish the intensity of each event affecting the local air quality. About 86% of dust days belong to ranks 1 and 2. In general, poorer air quality is associated with higher ranks. Ranks 4 and 5 correspond to a PSI (Pollution Standard Index) larger than 100. Linking DIR with the popular PSI is useful for both the public and the official forecasting system. It is also useful for inter-comparison between dust influences on air quality at different downstream regions in Taiwan. Composite analyses of the temporal and spatial variation of the hourly PM10 level indicate that dust particles usually arrive 12 h before the time of the peak PM10 concentration and last for 36 h at northern Taiwan, while the time of the peak concentration at eastern or western Taiwan, due to the evolution of the synoptic weather system, is about 3-12 h later. It is noted that the increase of PM10 level at the western side of Taiwan results from a mixture of upstream Asian dust inputs and local pollutants.

Rapid formation of large dust grains in the luminous supernova 2010jl.

PubMed

Gall, Christa; Hjorth, Jens; Watson, Darach; Dwek, Eli; Maund, Justyn R; Fox, Ori; Leloudas, Giorgos; Malesani, Daniele; Day-Jones, Avril C

2014-07-17

The origin of dust in galaxies is still a mystery. The majority of the refractory elements are produced in supernova explosions, but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming galaxies. The recent detection of 0.1 to 0.5 solar masses of dust in nearby supernova remnants suggests in situ dust formation, while other observations reveal very little dust in supernovae in the first few years after explosion. Observations of the spectral evolution of the bright SN 2010jl have been interpreted as pre-existing dust, dust formation or no dust at all. Here we report the rapid (40 to 240 days) formation of dust in its dense circumstellar medium. The wavelength-dependent extinction of this dust reveals the presence of very large (exceeding one micrometre) grains, which resist destruction. At later times (500 to 900 days), the near-infrared thermal emission shows an accelerated growth in dust mass, marking the transition of the dust source from the circumstellar medium to the ejecta. This provides the link between the early and late dust mass evolution in supernovae with dense circumstellar media.

The footprints of Saharan Air Layer and lightning on the formation of tropical depressions over the eastern Atlantic Ocean

NASA Astrophysics Data System (ADS)

Centeno Delgado, Diana C.

In this study, the results of an observational analysis and a numerical analysis on the role of the Saharan Air Layer during tropical cyclogenesis (TC-genesis) are described. The observational analysis investigates the interaction of dust particles and lightning during the genesis stage of two developed cases (Hurricanes Helene 2006 and Julia 2010). The Weather Research and Forecasting (WRF) and WRF-Chemistry models were used to include and monitor the aerosols and chemical processes that affect TC-genesis. The numerical modeling involved two developed cases (Hurricanes Helene 2006 and Julia 2010) and two non-developed cases (Non-Developed 2011 and Non-Developed 2012). The Aerosol Optical Depth (AOD) and lightning analysis for Hurricane Helene 2006 demonstrated the time-lag connection through their positive contribution to TC-genesis. The observational analyses supported the fact that both systems developed under either strong or weak dust conditions. From the two cases, the location of strong versus weak dust outbreaks in association with lightning was essential interactions that impacted TC-genesis. Furthermore, including dust particles, chemical processes, and aerosol feedback in the simulations with WRF-CHEM provides results closer to observations than regular WRF. The model advantageously shows the location of the dust particles inside of the tropical system. Overall, the results from this study suggest that the SAL is not a determining factor that affects the formation of tropical cyclones.

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

DOE PAGES

Huneeus, N.; Basart, S.; Fiedler, S.; ...

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

The retrieval of the Asian dust depolarization ratio in Korea with the correction of the polarization-dependent transmission

NASA Astrophysics Data System (ADS)

Shin, Sungkyun; Müller, Detlef; Kim, Y. J.; Tatarov, Boyan; Shin, Dongho; Seifert, Patric; Noh, Young Min

2013-01-01

The linear particle depolarization ratios were retrieved from the observation with a multiwavelength Raman lidar at the Gwangju Institute of Science and Technology (GIST), Korea (35.11°N, 126.54°E). The measurements were carried out in spring (March to May) 2011. The transmission ratio measurements were performed to solve problems of the depolarization-dependent transmission at a receiver of the lidar and applied to correct the retrieved depolarization ratio of Asian dust at first time in Korea. The analyzed data from the GIST multiwavelength Raman lidar were classified into three categories according to the linear particle depolarization ratios, which are pure Asian dust on 21 March, the intermediate case which means Asian dust mixed with urban pollution on 13 May, and haze case on 10 April. The measured transmission ratios were applied to these cases respectively. We found that the transmission ratio is needed to be used to retrieve the accurate depolarization ratio of Asian dust and also would be useful to distinguish the mixed dust particles between intermediate case and haze. The particle depolarization ratios of pure Asian dust were approximately 0.25 at 532 nm and 0.14 at 532 nm for the intermediate case. The linear particle depolarization ratios of pure Asian dust observed with the GIST multiwavelength Raman lidar were compared to the linear particle depolarization ratios of Saharan dust observed in Morocco and Asian dust observed both in Japan and China.

Determining the infrared radiative effects of Saharan dust: a radiative transfer modelling study based on vertically resolved measurements at Lampedusa

NASA Astrophysics Data System (ADS)

Meloni, Daniela; di Sarra, Alcide; Brogniez, Gérard; Denjean, Cyrielle; De Silvestri, Lorenzo; Di Iorio, Tatiana; Formenti, Paola; Gómez-Amo, José L.; Gröbner, Julian; Kouremeti, Natalia; Liuzzi, Giuliano; Mallet, Marc; Pace, Giandomenico; Sferlazzo, Damiano M.

2018-03-01

Detailed measurements of radiation, atmospheric and aerosol properties were carried out in summer 2013 during the Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region (ADRIMED) campaign in the framework of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) experiment. This study focusses on the characterization of infrared (IR) optical properties and direct radiative effects of mineral dust, based on three vertical profiles of atmospheric and aerosol properties and IR broadband and narrowband radiation from airborne measurements, made in conjunction with radiosonde and ground-based observations at Lampedusa, in the central Mediterranean. Satellite IR spectra from the Infrared Atmospheric Sounder Interferometer (IASI) are also included in the analysis. The atmospheric and aerosol properties are used as input to a radiative transfer model, and various IR radiation parameters (upward and downward irradiance, nadir and zenith brightness temperature at different altitudes) are calculated and compared with observations. The model calculations are made for different sets of dust particle size distribution (PSD) and refractive index (RI), derived from observations and from the literature. The main results of the analysis are that the IR dust radiative forcing is non-negligible and strongly depends on PSD and RI. When calculations are made using the in situ measured size distribution, it is possible to identify the refractive index that produces the best match with observed IR irradiances and brightness temperatures (BTs). The most appropriate refractive indices correspond to those determined from independent measurements of mineral dust aerosols from the source regions (Tunisia, Algeria, Morocco) of dust transported over Lampedusa, suggesting that differences in the source properties should be taken into account. With the in situ size distribution and the most appropriate refractive index the estimated dust IR radiative forcing

CSM interaction and dust formation in SN 2010jl .

NASA Astrophysics Data System (ADS)

Krafton, K.; Clayton, G. C.

The origin of dust in galaxies >1 Gyr old has remained an unsolved mystery for over a decade. One proposed solution is dust produced by core collapse supernovae (CCSNe). Theorists have shown that 0.1-1 M⊙ of dust must be produced per supernova for this to work as an explanation for the dust in young galaxies. SN 1987A has produced ˜1 M⊙ of dust since its detonation. However, most supernovae have been found to only produce 10-4 - 10-2 M⊙ of dust. The energetic type IIn SN 2010jl is located in UGC 5189, in a dense shell of CSM. As dust condenses in the SN ejecta, we see, (1) a sudden decrease in continuum brightness in the visible due to increased dust extinction, (2) the development of an infrared excess in the SN light curve arising from dust grains absorbing high-energy photons and re-emitting them in the infrared, and (3) the development of asymmetric, blue-shifted emission-line profiles, caused by dust forming in the ejecta, and preferentially extinguishing redshifted emission. A dense circumstellar material (CSM) may increase the dust production by supernovae. We observe signs of strong interaction between the SN ejecta and a dense CSM in SN 2010jl. SN 2010jl has been a source of much debate in the CCSN community, particularly over when and how much dust it formed. The light curve shows strong signs of dust formation after 260 days. Arguments over these subjects have been based on the evolution of the light curve and spectra. We present new optical and IR photometry, as well as optical spectroscopy, of SN 2010jl over 2000 days. We estimate dust masses using the DAMOCLES and MOCASSIN radiative transfer codes.

A quantitative evaluation of the 3-8 July 2009 Shamal dust storm

NASA Astrophysics Data System (ADS)

Hamidi, Mehdi; Kavianpour, Mohammad Reza; Shao, Yaping

2017-02-01

In this paper, a quantitative evaluation of the severe dust storm which occurred in the Middle East during 3-8 July 2009 is presented. The quantification is based on the numerical simulation using the WRF/Chem-D model which has been verified and calibrated for the Middle East region. It is found that, during the 3-8 July 2009 event, more than 9.67 Tg dust were emitted from the study area and the maximum simulated dust emission rate is 540 (μg m-2 s-1). The west of Iraq, east of Syria and northwest of Jordan (Al-Nafud desert and western Euphrates alluvial plain) are found to be the most active areas of dust emission, contributing much to the dust emission from the Middle East region. In this study, more that 60% of dust particles were emitted from these areas and less than 10% were emitted from Iran dust sources. About 21% of the deposited dust was deposited in Iran land, while 79% in other parts of the study area. The dust load in the study area was estimated to be more than 0.3 g m-2. The residence time of dust in the atmosphere was 6.2 days over the study area, 7.8 days over Iran and 6 days over other parts. The simulation results exhibit that Iran contribution in emission rate in the study area is much lower than its contribution in dust deposition and residence time and the conclusion of this study can demonstrate the necessity of forming cooperation for suppressing the severe dust events.

30 CFR 90.100 - Respirable dust standard.

Code of Federal Regulations, 2010 CFR

2010-07-01

... MANDATORY HEALTH STANDARDS-COAL MINERS WHO HAVE EVIDENCE OF THE DEVELOPMENT OF PNEUMOCONIOSIS Dust Standards, Rights of Part 90 Miners § 90.100 Respirable dust standard. After the twentieth calendar day following receipt of notification from MSHA that a Part 90 miner is employed at the mine, the operator shall...

Late Holocene interdecadal climate variability in the Sahel: inferences from a marine dust record offshore Senegal

NASA Astrophysics Data System (ADS)

Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.

2009-04-01

Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid Sahel belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of Sahel climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4

Measuring Dust Emission from the Mojave Desert (USA) by Daily Remote-Camera Observations and Wind-Erosion Measurements: Bearing on "Unseen" Sources and Global Dust Abundance

NASA Astrophysics Data System (ADS)

Reynolds, R. L.; Urban, F.; Goldstein, H. L.; Fulton, R.

2017-12-01

A large gap in understanding the effects of atmospheric dust at all spatial scales is uncertainty about how much and whence dust is emitted annually. Digital recording of dust emission at high spatial and temporal resolution would, together with periodic flux measurements, support improved estimates of local-scale dust flux where infrastructure could support remote internet enabled cameras. Such recording would also elucidate wind-erosion dynamics when combined with meteorological data. Remote camera recording of dust-emitting settings on and around Soda Lake (Mojave Desert) was conducted every 15 minutes during daylight between 10 Nov. 2010 and 31 Dec. 2016 and images uploaded to a web server. Examination of 135,000 images revealed frequent dust events, termed "dust days" when plumes obscured mountains beyond source areas. Such days averaged 68 (sd=10) per year (2011 through 2016). We examined satellite retrievals (MODIS, GOES) for dust events during six cloudless days of highest and longest duration dust emission but none were observed. From Apr. 2000 through May 2013, aeolian sediments collected at three sites were sampled and weighed. Estimates of the emitted mass of silt- and clay-size fractions were made on the basis of measured horizontal mass flux, particle sizes of sediment in collectors, and roughly determined areas of dust generation. Over this period, nearly 4 Tg yr-1 of dust (as particulate matter <63 micrometers) were emitted across the study area. Much higher rates (about 7 Tg yr-1) were estimated for a subset period from Jan. 2011 through May 2013 following a major Mojave River flood in the basin in late Dec. 2010 that deposited flood sediment across the lake basin. Increased emission was likely related to the availability of fresh, unanchored flood sediment. Within the Mojave and Great Basin deserts of North America, many settings akin to those at Soda Lake similarly emit dust that is rarely detected in satellite retrievals. These findings strongly

Aerosol optical properties during firework, biomass burning and dust episodes in Beijing

NASA Astrophysics Data System (ADS)

Yu, Xingna; Shi, Chanzhen; Ma, Jia; Zhu, Bin; Li, Mei; Wang, Jing; Yang, Suying; Kang, Na

2013-12-01

In order to characterize the aerosol optical properties during different pollution episodes that occurred in Beijing, the aerosol loading, scattering, and size distributions are presented using solar and sky radiance measurements from 2001 to 2010 in this paper. A much higher aerosol loading than the background level was observed during the pollution episodes. The average aerosol optical depth (AOD) is largest during dust episodes coupled with the lowest Ångström exponent (α), while higher AOD and lower α were more correlated with firework and biomass burning days. The total mean AOD at 440, 675, 870 and 1020 nm were 0.24, 0.49, 0.64 and 1.38 in the clean, firework display, biomass burning and dust days, respectively. The mean α for dust days was 0.51 and exceeded 1.1 for the remaining episodes. The size distribution of the dusty periods was dominated by the coarse mode, but the coarse mode was similar magnitude to the fine mode during the firework and biomass burning days. The volume concentration of the coarse mode during the dust days increased by a magnitude of more than 2-8 times that derived in the other three aerosol conditions, suggesting that dust is the major contributor of coarse mode particles in Beijing. The single scattering albedo (SSA) values also increased during the pollution episodes. The overall mean SSA at the four wavelengths were 0.865, 0.911, 0.922 and 0.931 in clean, firework display, biomass burning, and dust days in Beijing, respectively. However, in the blue spectral range, the dust aerosols exhibited pronounced absorption.

Dust Measurements by the Student Dust Counter (SDC) onboard the New Horizons Mission

NASA Astrophysics Data System (ADS)

James, David; Horanyi, Mihaly; Poppe, Andrew

The Venetia Burney Student Dust Counter (VSDC) on the New Horizons spacecraft is a dust impact detector designed to map the interplanetary dust distribution along the trajectory of the New Horizons spacecraft as it traverses our solar system. VSDC is the first student built instrument on a deep space mission and is currently operated by a small group of undergraduate and graduate students at the Laboratory for Atmospheric and Space Physics (LASP), University of Colorado. VSDC is based on permanently polarized thin plastic film sensors that generate an electrical signal when an impacting dust particle penetrates them. The total surface area is about 0.1 square meters and the detection threshold is about 1 micron in radius. By the time of this meeting (7/2008), VSDC will have operated for about 500 days, covering an approximate distance of 1.2 to 10.5 AU. In this talk, we will briefly review the VSDC instrument, including the in-flight calibrations and tests. We will report on the measured spatial and size distribution of interplanetary dust particles before and after the New Horizons encounter with Jupiter. These data will also be compared to earlier measurements by Ulysses, Galileo and Cassini.

Global dust model intercomparison in AeroCom phase I

NASA Astrophysics Data System (ADS)

Huneeus, N.; Schulz, M.; Balkanski, Y.; Griesfeller, J.; Kinne, S.; Prospero, J.; 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. E.; Perlwitz, J.; Stier, P.; Takemura, T.; Zender, C.

2010-10-01

Desert dust plays an important role in the climate system through its impact on Earth's radiative budget and its role in the biogeochemical cycle as a source of iron in high-nutrient-low-chlorophyll regions. A large degree of diversity exists between the many global models that simulate the dust cycle to estimate its impact on climate. We present the results of a broad intercomparison of a total of 15 global aerosol models within the AeroCom project. Each model is compared to observations focusing on variables responsible for the uncertainties in estimating the direct radiative effect and the dust 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 concentration are included to extend the assessment of model performance. These datasets form a benchmark data set which is proposed for model inspection and future dust model developments. In general, models perform better in simulating climatology of vertically averaged integrated parameters (AOD and AE) in dusty sites than they do with total deposition and surface concentration. Almost all models overestimate deposition fluxes over Europe, the Indian Ocean, the Atlantic Ocean and ice core data. Differences among the models arise when simulating deposition at remote sites with low fluxes over the Pacific and the Southern Atlantic Ocean. This study also highlights important differences in models ability to reproduce the deposition flux over Antarctica. The cause of this discrepancy could not be identified but different dust regimes at each site and issues with data quality should be considered. Models generally simulate better surface concentration at stations downwind of the main sources than at remote ones. Likewise, they simulate better surface concentration at stations affected by Saharan dust than at stations affected by Asian dust. Most models simulate the gradient in AOD and AE between the

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

Impact of Middle Eastern dust storms on indoor and outdoor composition of bioaerosol

NASA Astrophysics Data System (ADS)

Goudarzi, Gholamreza; Soleimani, Zahra; Sorooshian, Armin; Marzouni, Mohammad Bagherian; Maleki, Heidar

2016-08-01

The presence of microbes in airborne aerosol particles, especially dust, is a major public health concern in desert regions. This study is the first of its kind to examine the effect of dust storms on indoor and outdoor microbial air quality at a hospital on the western side of Iran (city of Ahvaz), which is notorious for being highly vulnerable to dust emissions. Air samples were collected inside and outside of the hospital environment for six months, with the unique advantage of this study being that the region and duration of measurements allow for a clear comparison between dusty and normal days. On normal days, the average concentrations (outdoor/indoor) of bacteria and fungi were 423/329 cfu m-3 and 596/386 cfu m-3, respectively, which increased to 1257/406 cfu m-3 and 1116/550 cfu m-3 on dust event days. Indoor/Outdoor ratios for bacteria and fungi are lower on dust event days (0.26-0.60) versus normal days (0.44-0.95). Bacillus spp., Micrococcus spp., Streptomyces spp., and Staphylococcus spp. were the dominant bacteria both indoors and outdoors on normal and dust event days. Gram positive bacteria exhibited higher concentrations than Gram negative bacteria in both outdoor and indoor air samples as well as during both normal and dust event days. The data suggest that Gram positive bacteria are more resistant to undesirable outdoor conditions (e.g., high incident solar radiation) as compared to Gram negative ones. These results have implications for other populated arid regions where more stringent control of indoor air quality can greatly benefit public health.

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.

Sol 568 Dust Devil in Gusev, Unenhanced

NASA Technical Reports Server (NTRS)

2005-01-01

This movie clip shows several dust devils moving from right to left across a plain inside Mars' Gusev Crater, as seen from the vantage point of NASA's Mars Exploration Rover Spirit in hills rising from the plain. The clip consists of frames taken by Spirit's navigation camera during the rover's 543rd martian day, or sol (July 13, 2005). Unlike some other movie clips of dust devils seen by Spirit, the images in this clip have not been processed to enhance contrast of the dust devils. The total time elapsed during the taking of these frames was 12 minutes, 17 seconds.

Spirit began seeing dust devil activity around the beginning of Mars' spring season. Activity increased as spring continued, but fell off again for about two weeks during a dust storm. As the dust storm faded away, dust devil activity came back. In the mid-afternoons as the summer solstice approached, dust devils were a very common occurrence on the floor of Gusev crater. The early-spring dust devils tended to move southwest-to-northeast, across the dust devil streaks in Gusev seen from orbit. Increasingly as the season progresses, the dust devils are seen moving northwest-to-southeast, in the same direction as the streaks. Scientists are watching for the big dust devils that leave those streaks.

The footprints of Saharan air layer and lightning on the formation of tropical depressions over the eastern Atlantic Ocean

NASA Astrophysics Data System (ADS)

Centeno Delgado, Diana C.; Chiao, Sen

2015-02-01

The roles of the Saharan Air Layer (SAL) and lightning during genesis of Tropical Depression (TD) 8 (2006) and TD 12 (2010) were investigated in relation to the interaction of the dust outbreaks with each system and their surrounding environment. This study applied data collected from the 2006 NASA African Monsoon Multidisciplinary Analysis and 2010 Genesis and Rapid Intensification Processes projects. Satellite observations from METEOSAT and Moderate Resolution Imaging Spectroradiometer (MODIS)—Aerosol Optical Depth (AOD) were also employed for the study of the dust content. Lightning activity data from the Met Office Arrival Time Difference (ATD) system were used as another parameter to correlate moist convective overturning and a sign of cyclone formation. The AOD and lightning analysis for TD 8 demonstrated the time-lag connection through their positive contribution to TC-genesis. TD 12 developed without strong dust outbreak, but with lower wind shear (2 m s-1) and an organized Mesoscale Convective System (MCS). Overall, the results from the combination of various data analyses in this study support the fact that both systems developed under either strong or weak dust conditions. From these two cases, the location (i.e., the target area) of strong versus weak dust outbreaks, in association with lightning, were essential interactions that impacted TC-genesis. While our dust footprints hypothesis applied under strong dust conditions (i.e., TD 8), other factors (e.g., vertical wind shear, pre-existing vortex and trough location, thermodynamics) need to be evaluated as well. The results from this study suggest that the SAL is not a determining factor that affects the formation of tropical cyclones (i.e., TD 8 and TD 12).

[Characteristics of particulate matters and its chemical compositions during the dust episodes in Shanghai in spring, 2011].

PubMed

Li, Gui-Ling; Zhou, Min; Chen, Chang-Hong; Wang, Hong-Li; Wang, Qian; Lou, Sheng-Rong; Qiao, Li-ping; Tang, Xi-bin; Li, Li; Huang, Hai-ying; Chen, Ming-hua; Huang, Cheng; Zhang, Gang-Feng

2014-05-01

A continuous air quality observation was conducted in the urban area of Shanghai from April 28 to May 18 in 2011. The mass concentration of particle matters and main chemical compositions of fine particle were measured and analyzed. The mass concentrations of PM10 and PM2.5 during the dust episode were much higher than those in non-dust episode, with the maximum daily mass concentrations of PM10 and PM2.5 reaching 787.2 microg.gm-3 and 139.5 microgm(-3) , respectively. The average PM2.5 /PM10 ratio was (32.9 +/-14. 6)% (15. 6% -85.1% ). The total water soluble inorganic ions(TWSII ) contributed (27.2 +/- 19. 2)% (4. 8% -80. 8% ) of total PM2.5, and the secondary water soluble ions (SNA) , including SO(2-)4 , NO-(3) and NH(+)(4) , were (76.9 +/- 13.9)% (41.9%-94.2%) in TWSIl. The concentrations of TWSII and SNA in PM2.5 during dust days became lower than those in non-dust days while the trend of the ratio of Ca2+ to PM2.5, increased. The mean OC/EC value in non-dust days was higher than that in the heavy dust pollution episode, but lower than that in weak dust days. In addition, mineral-rich particle in dust period had an acid-buffer effect, making particle alkaline in dust days stronger. In non-dust days, SO(2-)(4) and NO(-)(3) mainly existed in the form of NH4HSO4, (NH4)SO4, and NH4NO3, and combined with other mineral ions during dust days.

Analysis of land surface and synoptic conditions during dust storm events in the Middle East via a new high resolution inventory of mineral dust derived from SEVIRI.

NASA Astrophysics Data System (ADS)

Hennen, Mark

2017-04-01

This paper provides the most up-to-date dust climatology for the Middle East, presenting a new high resolution inventory of over 27,000 dust emission events observed over the Middle East in 2006 - 2013. The inventory was derived from the dust RGB product of the Spinning Enhanced Visual and InfraRed Imager (SEVIRI) on-board Meteosat's second generation satellite (MSG). Mineral dust emissions were derived from visual inspection of the SEVIRI scenes which have 4-5 km2 spatial and 15-minute temporal resolution. The location of every emission event was recorded in a database, along with time and trajectory of dust movement. This is an improvement on previous studies, which derive dust source areas from the daily observations of Aerosol Optical Depth whose maxima do not necessarily coincide with sources of emissions and produces more accurate information on the location of the key dust sources in the region. Results showed that dust sources are constrained to relatively small areas, with 21% of dust emission generated from just 0.9% of total surface area of the Middle East, mainly from eight source regions including the Tigris-Euphrates flood plains of Iraq and Syria, Western and Northern Saudi Arabia and the Sistan Basin in Eastern Iran. The Tigris-Euphrates flood plain was the most active dust region, producing 41% of all dust events with a peak activity in 2009. The southern areas of the Arabian Peninsula recorded very few dust emission observations, in contrast to many previous studies which do not use such high temporal resolution data. The activation and frequency of dust emissions are characterised by strong seasonality developing in response to specific synoptic conditions. To characterise synoptic conditions conducive to the development of dust storms, dust days' emission thresholds, based on number of dust emission events per day / per region and specific to each of the eight main dust emitting regions, were determined. ERA Interim reanalysis data were used to

A Mid-Summer's Dust Devil

NASA Technical Reports Server (NTRS)

2001-01-01

One objective for the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in the Extended Mission is to continue looking for changes and dynamic events taking place on the red planet. The feature shown here elicited gasps of excitement among the MOC Operations Staff when it was received in early April 2001.

The feature is a dust devil. Dust devils are spinning, columnar vortices of wind that move across the landscape, pick up dust, and look somewhat like miniature tornadoes. Dust devils are a common occurrence in dry and desert landscapes on Earth as well as Mars. When this dust devil was spied in Amazonis Planitia on April 10th, the MOC was looking straight down. Usually when the camera is looking down the dust devil will appear as a circular, fuzzy patch with a straight shadow indicating its columnar shape. In this case, however, the dust devil is somewhat curved and kinked--its shape is best seen in the shadow it casts to the right. A thin, light-toned track has been left by the dust devil as it moved eastward across the landscape. Usually, such tracks are darker than the surroundings, in this case the light tone might indicate that the dust being removed by the passing dust devil is darker than the surface underneath the thin veneer of dust.

Dust devils most typically form when the ground heats up during the day, warming the air immediately above the surface. As the warmed air nearest the surface begins to rise, it spins. The spinning column begins to move across the surface and picks up loose dust (if any is present). The dust makes the vortex visible and gives it the 'dust devil' or tornado-like appearance. This dust devil occurred at an optimal time for dust devils whether on Earth or Mars--around 2 p.m. local time in the middle of Northern Hemisphere Summer. North is up, sunlight illuminates the scene from the left (west), and 500 meters is about 547 yards. The shadow cast by the dust devil goes off the edge of the image, but the length shown

A Spitzer Survey for Dust in Type IIn Supernovae

NASA Technical Reports Server (NTRS)

Fox, Ori D.; Chevalier, Roger A.; Skrutskie, Michael F.; Soderberg, Alicia M.; Filippenko, Alexei V.; Ganeshalingam, Mohan; Silverman, Jeffrey M.; Smith, Nathan; Steele, Thea N.

2011-01-01

Recent observations suggest that Type IIn supernovae (SNe IIn) may exhibit late-time (greater than 100 days) infrared (IR) emission from warm dust more than other types of core-collapse SNe. Mid-IR observations, which span the peak of the thermal spectral energy distribution, provide useful constraints on the properties of the dust and, ultimately, the circumstellar environment, explosion mechanism, and progenitor system. Due to the low SN IIn rate (less than 10% of all core-collapse SNe), few IR observations exist for this subclass. The handful of isolated studies, however, show late-time IR emission from warm dust that, in some cases, extends for five or six years post-discovery. While previous Spitzer/IRAC surveys have searched for dust in SNe, none have targeted the Type IIn subclass. This article presents results from a warm Spitzer/IRAC survey of the positions of all 68 known SNe IIn within a distance of 250 Mpc between 1999 and 2008 that have remained unobserved by Spitzer more than 100 days postdiscovery. The detection of late-time emission from ten targets (approximately 15%) nearly doubles the database of existing mid-IR observations of SNe IIn. Although optical spectra show evidence for new dust formation in some cases, the data show that in most cases the likely origin of the mid-IR emission is pre-existing dust, which is continuously heated by optical emission generated by ongoing circumstellar interaction between the forward shock and circumstellar medium. Furthermore, an emerging trend suggests that these SNe decline at approximately 1000-2000 days post-discovery once the forward shock overruns the dust shell. The mass-loss rates associated with these dust shells are consistent with luminous blue variable (LBV) progenitors.

A Spitzer Survey for Dust in Type IIn Supernovae

NASA Technical Reports Server (NTRS)

Fox, Ori D.; Chevalier, Roger A.; Skrutskie, Michael F.; Soderberg, Alicia M.; Filippenko, Alexei V.; Ganeshalingam, Mohan; Silverman, Jeffrey M.; Smith, Nathan; Steele, Thea N

2011-01-01

Recent observations suggest that Type IIn supernovae (SNe IIn) may exhibit late-time (>100 days) infrared (IR) emission from warm dust more than other types of core-collapse SNe. Mid-IR observations, which span the peak of the thermal spectral energy distribution, provide useful constraints on the properties of the dust and, ultimately, the circumstellar environment, explosion mechanism, and progenitor system. Due to the low Type IIn rate (<10% of all core-collapse SNe), few IR observations exist for this subclass. The handful of isolated studies, however, show late-time IR emission from warm dust that, in some cases, extends for five or six years post-discovery. vVhile previous Spitzer/IRAC surveys have searched for dust in SNe, none have targeted the Type IIn subclass. This article presents results from a warm Spitzer/IRAC survey of the positions of all 68 known SNe IIn within a distance of 250 Mpc between 1999 and 2008 that have remained unobserved by Spitzer more than 100 days post-discovery. The detection of late-time emission from ten targets (approx. 15 %) nearly doubles the database of existing mid-IR observations of SNe IIn. Although optical spectra show evidence for new dust formation in some cases, the data show that in most cases the likely origin of the mid-IR emission is pre-existing dust, which is continuously heated by optical emission generated by ongoing circumstellar interaction between the forward shock and circumstellar medium. Furthermore, an emerging trend suggests these SNe "turn off" at " approx. 1000-2000 days post-discovery once the forward shock overruns the dust shell. The mass-loss rates associated with these dust shells are consistent with luminous blue variable (LBV) progenitors having similar mass-loss histories.

The Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment SALTRACE 2013 - Overview and Early Results (Invited)

NASA Astrophysics Data System (ADS)

Weinzierl, B.; Ansmann, A.; Reitebuch, O.; Freudenthaler, V.; Müller, T.; Kandler, K.; Althausen, D.; Busen, R.; Dollner, M.; Dörnbrack, A.; Farrell, D. A.; Gross, S.; Heimerl, K.; Klepel, A.; Kristensen, T. B.; Mayol-Bracero, O. L.; Minikin, A.; Prescod, D.; Prospero, J. M.; Rahm, S.; Rapp, M.; Sauer, D. N.; Schaefler, A.; Toledano, C.; Vaughan, M.; Wiegner, M.

2013-12-01

Mineral dust is an important player in the global climate system. In spite of substantial progress in the past decade, many questions in our understanding of the atmospheric and climate effects of mineral dust remain open such as the change of the dust size distribution during transport across the Atlantic Ocean and the associated impact on the radiation budget, the role of wet and dry dust removal mechanisms during transport, and the complex interaction between mineral dust and clouds. To close gaps in our understanding of mineral dust in the climate system, the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE: http://www.pa.op.dlr.de/saltrace) was conducted in June/July 2013. SALTRACE is a German initiative combining ground-based and airborne in-situ and lidar measurements with meteorological data, long-term measurements, satellite remote sensing and modeling. During SALTRACE, the DLR research aircraft Falcon was based on Sal, Cape Verde, between 11 and 17 June, and on Barbados between 18 June and 11 July 2013. The Falcon was equipped with a suite of in-situ instruments for the measurement of microphysical and optical aerosol properties and with a nadir-looking 2-μm wind lidar. Ground-based lidar and in-situ instruments were deployed in Barbados and Puerto Rico. Mineral dust from several dust outbreaks was measured by the Falcon between Senegal and Florida. On the eastern side of the Atlantic, dust plumes extended up to 6 km altitude, while the dust layers in the Caribbean were mainly below 4.5 km. The aerosol optical thickness of the dust outbreaks studied ranged from 0.2 to 0.6 at 500 nm in Barbados. Highlights during SALTRACE included the sampling of a dust plume in the Cape Verde area on 17 June which was again measured with the same instrumentation on 21 and 22 June near Barbados. The event was also captured by the ground-based lidar and in-situ instrumentation. Another highlight was the formation of tropical storm

VLTI monitoring of the dust formation event of the Nova V1280 Scorpii

NASA Astrophysics Data System (ADS)

Chesneau, O.; Banerjee, D. P. K.; Millour, F.; Nardetto, N.; Sacuto, S.; Spang, A.; Wittkowski, M.; Ashok, N. M.; Das, R. K.; Hummel, C.; Kraus, S.; Lagadec, E.; Morel, S.; Petr-Gotzens, M.; Rantakyro, F.; Schöller, M.

2008-08-01

Context: We present the first high spatial-resolution monitoring of the dust-forming nova V1280 Sco, performed with the Very Large Telescope Interferometer (VLTI). Aims: These observations promise to improve the distance determination of such events and constrain the mechanisms leading to very efficient dust formation under the harsh physical conditions encountered in novae ejecta. Methods: Spectra and visibilities were regularly acquired between the onset of dust formation, 23 days after discovery (or 11 days after maximum), and day 145, using the beam-combiner instruments AMBER (near-IR) and MIDI (mid-IR). These interferometric observations were complemented by near-infrared data from the 1.2 m Mt. Abu Infrared Observatory, India. The observations are initially interpreted in terms of simple uniform models; however more complex models, probably involving a second shell, are required to explain data acquired following t=110 d after outburst. This behavior is in accordance with the light curve of V1280 Sco, which exhibits a secondary peak at about t=106 d, followed by a new, steep decline, suggesting a new dust-forming event. Spherical dust shell models generated with the DUSTY code are used to investigate the parameters of the main dust shell. Results: Using uniform disk models, these observations allow us to determine an apparent linear expansion rate for the dust shell of 0.35 ± 0.03 mas day-1 and the approximate ejection time of the matter in which dust formed of t_ejec = 10.5 ± 7 d, i.e. close to the maximum brightness. This information, combined with the expansion velocity of 500 ± 100 km s-1, implies a distance estimate of 1.6 ± 0.4 kpc. The sparse uv coverage does not enable deviations from spherical symmetry to be clearly discerned. The dust envelope parameters were determined. The dust mass generated was typically 2-8 × 10-9 M_⊙ day-1, with a probable peak in production at about 20 days after the detection of dust and another peak shortly after t

Fennec dust forecast intercomparison over the Sahara in June 2011

NASA Astrophysics Data System (ADS)

Chaboureau, Jean-Pierre; Flamant, Cyrille; Dauhut, Thibaut; Kocha, Cécile; Lafore, Jean-Philippe; Lavaysse, Chistophe; Marnas, Fabien; Mokhtari, Mohamed; Pelon, Jacques; Reinares Martínez, Irene; Schepanski, Kerstin; Tulet, Pierre

2016-06-01

In the framework of the Fennec international programme, a field campaign was conducted in June 2011 over the western Sahara. It led to the first observational data set ever obtained that documents the dynamics, thermodynamics and composition of the Saharan atmospheric boundary layer (SABL) under the influence of the heat low. In support to the aircraft operation, four dust forecasts were run daily at low and high resolutions with convection-parameterizing and convection-permitting models, respectively. The unique airborne and ground-based data sets allowed the first ever intercomparison of dust forecasts over the western Sahara. At monthly scale, large aerosol optical depths (AODs) were forecast over the Sahara, a feature observed by satellite retrievals but with different magnitudes. The AOD intensity was correctly predicted by the high-resolution models, while it was underestimated by the low-resolution models. This was partly because of the generation of strong near-surface wind associated with thunderstorm-related density currents that could only be reproduced by models representing convection explicitly. Such models yield emissions mainly in the afternoon that dominate the total emission over the western fringes of the Adrar des Iforas and the Aïr Mountains in the high-resolution forecasts. Over the western Sahara, where the harmattan contributes up to 80 % of dust emission, all the models were successful in forecasting the deep well-mixed SABL. Some of them, however, missed the large near-surface dust concentration generated by density currents and low-level winds. This feature, observed repeatedly by the airborne lidar, was partly forecast by one high-resolution model only.

Fennec dust forecast intercomparison over the Sahara in June 2011

NASA Astrophysics Data System (ADS)

Chaboureau, J. P.; Flamant, C.; Dauhut, T.; Lafore, J. P.; Lavaysse, C.; Pelon, J.; Schepanski, K.; Tulet, P.

2016-12-01

In the framework of the Fennec international programme, a field campaign was conducted in June 2011 over the western Sahara. It led to the first observational data set ever obtained that documents the dynamics, thermodynam-ics and composition of the Saharan atmospheric boundary layer (SABL) under the influence of the heat low. In support to the aircraft operation, four dust forecasts were run daily at low and high resolutions with convection-parameterizing and convection-permitting models, respectively. The unique airborne and ground-based data sets allowed the first ever intercomparison of dust forecasts over the western Sahara. At monthly scale, large aerosol optical depths (AODs) were forecast over the Sahara, a feature observed by satellite retrievals but with different magnitudes. The AOD intensity was correctly predicted by the high-resolution models, while it was underestimated by the low-resolution models. This was partly because of the generation of strong near-surface wind associated with thunderstorm-related density currents that could only be reproduced by models representing convection explicitly. Such models yield emissions mainly in the afternoon that dominate the total emission over the western fringes of the Adrar des Iforas and the Aïr Mountains in the high-resolution forecasts. Over the western Sahara, where the harmattan contributes up to 80 % of dust emission, all the models were successful in forecasting the deep well-mixed SABL. Some of them, however, missed the large near-surface dust concentration generated by density currents and low-level winds. This feature, observed repeatedly by the airborne lidar, was partly forecast by one high-resolution model only.

Effect of desert dust exposure on allergic symptoms: A natural experiment in Japan.

PubMed

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

2016-05-01

Desert dust originating from arid and semiarid areas is transported to widespread regions, including Japan. Desert dust particles exert adjuvant effects in animals. To examine whether desert dust enhances allergic symptoms in real-life settings and to explore its effect modifiers. We conducted an observational study of 3,327 pregnant women during spring and fall in October 2011 to May 2013 in 3 regions in Japan as an adjunct study of the Japan Environment & Children's Study. We acquired participants' daily symptom scores by sending a questionnaire to their mobile phones on high desert-dust days (>0.07/km) and on some randomly selected other days (control days) for each participant. Pregnant women had an increased risk of allergic symptoms on high desert-dust days (adjusted odds ratio [OR], 1.10; 95% CI, 1.04-1.18). The increased OR was mostly driven by those who showed positive IgE to Japanese cedar pollen when pollen simultaneously dispersed (adjusted OR, 1.25; 95% CI, 1.13-1.38), whereas no clear risk increase was observed in the absence of pollen or for participants with negative IgE to Japanese cedar pollen. The risk elevation was observed from low levels of desert dust in a dose-dependent manner even on control days. Ambient desert dust level was associated with an increased risk of allergic symptoms in pollen-sensitized pregnant women when pollen was present in the air. The risk increase was dose dependent and was observed from low levels of desert dust. These results support a hypothesis that ambient desert dust particles exert adjuvant effects in human in real-life settings. clinicaltrials.gov Identifier: UMIN000010826. Copyright © 2016 American College of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

Particulate matter concentrations during desert dust outbreaks and daily mortality in Nicosia, Cyprus.

PubMed

Neophytou, Andreas M; Yiallouros, Panayiotis; Coull, Brent A; Kleanthous, Savvas; Pavlou, Pavlos; Pashiardis, Stelios; Dockery, Douglas W; Koutrakis, Petros; Laden, Francine

2013-01-01

Ambient particulate matter (PM) has been shown to have short- and long-term effects on cardiorespiratory mortality and morbidity. Most of the risk is associated with fine PM (PM(2.5)); however, recent evidence suggests that desert dust outbreaks are major contributors to coarse PM (PM(10-2.5)) and may be associated with adverse health effects. The objective of this study was to investigate the risk of total, cardiovascular and respiratory mortality associated with PM concentrations during desert dust outbreaks. We used a time-series design to investigate the effects of PM(10) on total non-trauma, cardiovascular and respiratory daily mortality in Cyprus, between 1 January 2004 and 31 December 2007. Separate PM(10) effects for non-dust and dust days were fit in generalized additive Poisson models. We found a 2.43% (95% CI: 0.53, 4.37) increase in daily cardiovascular mortality associated with each 10-μg/m(3) increase in PM(10) concentrations on dust days. Associations for total (0.13% increase, 95% CI: -1.03, 1.30) and respiratory mortality (0.79% decrease, 95% CI: -4.69, 3.28) on dust days and all PM(10) and mortality associations on non-dust days were not significant. Although further study of the exact nature of effects across different affected regions during these events is needed, this study suggests adverse cardiovascular effects associated with desert dust events.

[Dust storms trend in the Capital Circle of China over the past 50 years and its correlation with temperature, precipitation and wind].

PubMed

Chen, Yu-fu; Tang, Hai-ping

2005-01-01

The trends of number of dust storm days of the selected 11 meteorological stations from their established year to 2000 as well as their correlations with temperature, precipitation and wind are revealed. The number of dust storm days of the Capital Circle of China is distinctly variable in space and time. The numbers of dust storm days of the western area are far more than those of the eastern area. The interannual variability of number of dust storm days is remarkable. The number of dust storm days of the following 7 stations, Erlianhaote, Abaga, Xilinhaote, Fengning, Zhangjiakou, Huailai and Beijing, declined along the past decades, but those of the other four stations had no significant upward or downward trends. There is a marked seasonality of the number of dust storm days, and the maximum was in April. The correlation between number of dust storm days and number of days of mean wind velocity > 5 m/s, which is critical wind velocity to entrain sand into the air, was strongest among the three climatic factor. There were significant positive correlations between the number of dust storm days and number of days of mean wind velocity > 5 m/s in 6 stations. The second strongest climatic factor correlated with the number of dust storm days is temperature. There are significant negative correlations between the number of dust storm days and mean annual temperature, mean winter temperature, mean spring temperature in 3 or 4 stations. The correlation between the number of dust storm days and precipitation is weakest. Only one station, Zhurihe, showes significant negative correlation between the number of dust storm days and spring rainfall. There are 4 stations whose number of dust storm days don't significantly correlate with the climate. In the end, the spatial-temporal variability of dust storms and its relation with climate in the Capital Circle of China were discussed thoroughly.

Toxicity of lunar dust assessed in inhalation-exposed rats

PubMed Central

Lam, Chiu-wing; Scully, Robert R.; Zhang, Ye; Renne, Roger A.; Hunter, Robert L.; McCluskey, Richard A.; Chen, Bean T.; Castranova, Vincent; Driscoll, Kevin E.; Gardner, Donald E.; McClellan, Roger O.; Cooper, Bonnie L.; McKay, David S.; Marshall, Linda; James, John T.

2015-01-01

Humans will again set foot on the moon. The moon is covered by a layer of fine dust, which can pose a respiratory hazard. We investigated the pulmonary toxicity of lunar dust in rats exposed to 0, 2.1, 6.8, 20.8 and 60.6 mg/m3 of respirable-size lunar dust for 4 weeks (6 h/day, 5 days/week); the aerosols in the nose-only exposure chambers were generated from a jet-mill ground preparation of a lunar soil collected during the Apollo 14 mission. After 4 weeks of exposure to air or lunar dust, groups of five rats were euthanized 1 day, 1 week, 4 weeks or 13 weeks after the last exposure for assessment of pulmonary toxicity. Biomarkers of toxicity assessed in bronchoalveolar fluids showed concentration-dependent changes; biomarkers that showed treatment effects were total cell and neutrophil counts, total protein concentrations and cellular enzymes (lactate dehydrogenase, glutamyl transferase and aspartate transaminase). No statistically significant differences in these biomarkers were detected between rats exposed to air and those exposed to the two low concentrations of lunar dust. Dose-dependent histopathology, including inflammation, septal thickening, fibrosis and granulomas, in the lung was observed at the two higher exposure concentrations. No lesions were detected in rats exposed to ≤6.8 mg/m3. This 4-week exposure study in rats showed that 6.8 mg/m3 was the highest no-observable-adverse-effect level (NOAEL). These results will be useful for assessing the health risk to humans of exposure to lunar dust, establishing human exposure limits and guiding the design of dust mitigation systems in lunar landers or habitats. PMID:24102467

Solar-Panel Dust Accumulation and Cleanings

NASA Technical Reports Server (NTRS)

2005-01-01

Air-fall dust accumulates on the solar panels of NASA's Mars Exploration Rovers, reducing the amount of sunlight reaching the solar arrays. Pre-launch models predicted steady dust accumulation. However, the rovers have been blessed with occasional wind events that clear significant amounts of dust from the solar panels.

This graph shows the effects of those panel-cleaning events on the amount of electricity generated by Spirit's solar panels. The horizontal scale is the number of Martian days (sols) after Spirit's Jan. 4, 2005, (Universal Time) landing on Mars. The vertical scale indicates output from the rover's solar panels as a fraction of the amount produced when the clean panels first opened. Note that the gradual declines are interrupted by occasional sharp increases, such as a dust-cleaning event on sol 420.

An IR Sounding-Based Analysis of the Saharan Air Layer in North Africa

NASA Technical Reports Server (NTRS)

Nicholls, Stephen D.; Mohr, Karen I.

2018-01-01

Intense daytime surface heating over barren-to-sparsely vegetated surfaces results in dry convective mixing. In the absence of external forcing such as mountain waves, the dry convection can produce a deep, well-mixed, nearly isentropic boundary layer that becomes a well-mixed residual layer in the evening. These well-mixed layers (WML) retain their unique mid-tropospheric thermal and humidity structure for several days. To detect the SAL and characterize its properties, AIRS Level 2 Ver. 6 temperature and humidity products (2003-Present) are evaluated against rawinsondes and compared to model analysis at each of the 55 rawinsonde stations in northern Africa. To distinguish WML from Saharan air layers (WMLs of Saharan origin), the detection involved a two-step process: 1) algorithm-based detection of WMLs in dry environments (less than 7 g per kilogram mixing ratio) 2) identification of Sahara air layers (SAL) by applying Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) back trajectories to determine the history of each WML. WML occurrence rates from AIRS closely resemble that from rawinsondes, yet rates from model analysis were up to 30% higher than observations in the Sahara due to model errors. Despite the overly frequent occurrence of WMLs from model analysis, HYSPLIT trajectory analysis showed that SAL occurrence rates (given a WML exists) from rawinsondes, AIRS, and model analysis were nearly identical. Although the number of WMLs varied among the data sources, the proportion of WMLs which were classified as SAL was nearly the same. The analysis of SAL bulk properties showed that AIRS and model analysis exhibited a slight warm and moist bias relative to rawinsondes in non-Saharan locations, but model analysis was notably warmer than rawinsondes and AIRS within the Sahara. The latter result is likely associated with the dearth of available data assimilated by model analysis in the Sahara. The variability of SAL thicknesses was reasonably

Growth impacts of Saharan dust, mineral nutrients, and CO2 on a planktonic herbivore in southern Mediterranean lakes.

PubMed

Villar-Argaiz, Manuel; Cabrerizo, Marco J; González-Olalla, Juan Manuel; Valiñas, Macarena S; Rajic, Sanja; Carrillo, Presentación

2018-05-17

Rising levels of CO 2 can boost plant biomass but reduce its quality as a food source for herbivores. However, significant uncertainties remain as to the degree to which the effect is modulated by other environmental factors and the underlying processes causing these responses in nature. To address these questions, we carried out CO 2 -manipulation experiments using natural seston from three lakes under nutrient-enriched conditions (mimicking eutrophication and atmospheric dust-input processes) as a food source for the planktonic Daphnia pulicaria. Contrary to expectations, there were no single effects of rising CO 2 on herbivorous growth. Instead, synergistic CO 2  × nutrient interactions indicated that CO 2 did not support higher zooplankton growth rates unless supplemented with dust or inorganic nutrients (nitrogen, N; phosphorus, P) in two of three studied lakes. The overall positive correlation between zooplankton growth and seston carbon (C), but not seston C:P, suggested that this was a food quantity-mediated response. In addition, we found that this correlation improved when the data were grouped according to the nutrient treatments, and that the response was largest for dust. The synergistic CO 2  × nutrient effects reported here imply that the effects of rising CO 2 levels on herbivorous growth may be strongly influenced by eutrophication processes and the increase in dust deposition predicted for the Mediterranean region. Copyright © 2018 Elsevier B.V. All rights reserved.

Characterization of synoptic patterns causing dust outbreaks that affect the Arabian Peninsula

NASA Astrophysics Data System (ADS)

Hermida, L.; Merino, A.; Sánchez, J. L.; Fernández-González, S.; García-Ortega, E.; López, L.

2018-01-01

Dust storms pose serious weather hazards in arid and semiarid regions of the earth. Understanding the main synoptic conditions that give rise to dust outbreaks is important for issuing forecasts and warnings to the public in cases of severe storms. The aim of the present study is to determine synoptic patterns that are associated with or even favor dust outbreaks over the Arabian Peninsula. In this respect, red-green-blue dust composite images from the Meteosat Second Generation (MSG) satellite are used to detect dust outbreaks affecting the Arabian Peninsula, with possible influences in southwestern Asia and northeastern Africa, between 2005 and 2013. The Meteosat imagery yielded a sample of 95 dust storm days. Meteorological fields from NCEP/NCAR reanalysis data of wind fields at 10 m and 250 hPa, mean sea level pressure, and geopotential heights at 850 and 500 hPa were obtained for the dust storm days. Using principal component analysis in T-mode and non-hierarchical k-means clustering, we obtained four major atmospheric circulation patterns associated with dust outbreaks during the study days. Cluster 4 had the largest number of days with dust events, which were constrained to summer, and cluster 3 had the fewest. In clusters 1, 2 and 3, the jet stream favored the entry of a low-pressure area or trough that varied in location between the three clusters. Their most northerly location was found in cluster 4, along with an extensive low-pressure area supporting strong winds over the Arabian Peninsula. The spatial distribution of aerosol optical depth for each cluster obtained was characterized using the Moderate Resolution Imaging Spectroradiometer data. Then, using METAR stations, clusters were also characterized in terms of frequency and visibility.

Characterization of Settled Atmospheric Dust by the DART Experiment

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.; Jenkins, Phillip P.; Baraona, Cosmo

1999-01-01

The DART ("Dust Accumulation and Removal Test") package is an experiment which will fly as part of the MIP experiment on the Mars-2001 Surveyor Lander. Dust deposition could be a significant problem for photovoltaic array operation for long duration emissions on the surface of Mars. Measurements made by Pathfinder showed 0.3% loss of solar array performance per day due to dust obscuration. The DART experiment is designed to quantify dust deposition from the Mars atmosphere, measure the properties of settled dust, measure the effect of dust deposition on the array performance, and test several methods of mitigating the effect of settled dust on a solar array. Although the purpose of DART (along with its sister experiment, MATE) is to gather information critical to the design of future power systems on the surface of Mars, the dust characterization instrumentation on DART will also provide significant scientific data on the properties of settled atmospheric dust.

An 11-year analysis of satellite retrievals of dust aerosol over the Red Sea and the Persian Gulf

NASA Astrophysics Data System (ADS)

Banks, Jamie; Brindley, Helen; Schepanski, Kerstin; Stenchikov, Georgiy

2017-04-01

As enclosed seas bordering two large desert regions, the Saharan and Arabian deserts, the maritime environments of the Red Sea and the Persian Gulf are heavily influenced by the presence of desert dust aerosol. The inter-annual variability of dust presence over the Red Sea is analysed and presented, with respect to the summer-time latitudinal gradient in dust loading, which is at a maximum in the far south of the Red Sea and at a minimum in the far north. Two satellite aerosol optical depth (AOD) products from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) and the MODerate resolution Imaging Spectroradiometer (MODIS) instruments are used to quantify this loading over the region. Over an eleven-year period from 2005-2015 the July mean SEVIRI AODs at 630 nm vary between 0.48 and 1.45 in the southern half of the Sea, while in the north this varies between 0.22 and 0.66. Inter-retrieval offsets are observed to occur at higher dust loadings, with pronounced positive MODIS-SEVIRI AOD offsets at AODs greater than 1, indicating substantial and systematic differences between the retrievals over the Red Sea at high dust loadings. These differences appear to be influenced in part by the differences in scattering angle range of the satellite measurements, implying that assumptions of particle shape introduce more substantial biases at the highest dust loadings.

Source reconciliation of atmospheric dust causing visibility impairment in Class I areas of the western United States

NASA Astrophysics Data System (ADS)

Kavouras, Ilias G.; Etyemezian, Vicken; Dubois, David W.; Xu, Jin; Pitchford, Marc

2009-01-01

Aerosol data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, air mass backward trajectories, land use maps, soil characteristics maps, diagnostic ratios of elemental composition, and multivariate linear regression were utilized as part of a semiquantitative analysis. The purpose of the analysis was to determine the types of dust-causing events that contribute to low visibility at a given site when the sum of extinction from coarse mass (CM) and fine soil (FS) was larger than any other aerosol component and the reconstructed aerosol extinction coefficient was among the 20% highest (calculated on a calendar year basis) for that site. For these "worst dust days," the above tools were used to ascribe the cause of low visibility to one of the following types of events: (1) transcontinental transport of dust originating from Asia; (2) windblown dust events from sources located nearby the site and; (3) transport of windblown dust from sources upwind of the site. Depending on the weight of evidence, a low or high level of confidence was associated with the assignment of one of these three events. Absence of convincing evidence resulted in ascribing the worst dust day to "undetermined events." Of the 610 worst dust days over the 2001-2003 period, 51% were associated with one of the three event types with high confidence and an additional 30% were accounted for with low confidence. Of the 496 worst dust days associated with an event (either low or high confidence), Asian dust was the assigned event on 55 days (for 2001-2002), locally generated windblown dust on 201 days, and transport from upwind source areas susceptible to wind erosion on 240 days. Events associated with windblown episodes from source areas in the United States and Mexico exhibited the highest dust concentrations. Asian dust events were associated with lower dust concentrations and a larger FS-to-CM ratio. Some variations between Asian dust and continental North American

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

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

Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona

2009-11-01

Airborne mineral dust particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of warm clouds. It is therefore of particular interest how dust aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation with respect to liquid water similar to atmospheric conditions. In this study the sub-saturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols was 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 wellmore » as three desert dust samples (Saharan dust (SD), Chinese dust (CD) and Arizona test dust (ATD)) were used. Aerosols were generated both with a wet and a dry disperser and the water uptake was parameterized via the hygroscopicity parameter, κ. The hygroscopicity of dry generated dust aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived κ values between 0.00 and 0.02. The latter value can be idealized as a particle consisting of 96.7% (by volume) insoluble material and ~3.3% ammonium sulfate. Pure clay aerosols were found to be generally less hygroscopic than real desert dust particles. All illite and montmorillonite samples had κ~0.003, kaolinites were least hygroscopic and had κ=0.001. SD (κ=0.023) was found to be the most hygroscopic dry-generated desert dust followed by CD (κ=0.007) and ATD (κ=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 while immersed in an aqueous medium during atomization, thus indicating that specification of the generation method is critically important when presenting such data. Any atmospheric

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

Intense dust episodes in the Mediterranean and possible effects on atmospheric lapse rates

NASA Astrophysics Data System (ADS)

Hatzianastassiou, Nikos; Gkikas, Antonis; Papadimas, Christos D.; Gavrouzou, Maria

2016-04-01

Dust aerosols are major contributor to the atmospheric particulate matter, having significant effects on climate and weather patterns as well as on human health, not to mention others like agriculture or ocean chlorophyll. Moreover, these effects are maximized under conditions of massive dust concentration in the atmosphere, namely dust episodes or events. Such events are caused by uplifting and transport of dust from arid and semi-arid areas under favorable synoptic conditions. The Mediterranean basin, nearby to the greatest world deserts of North Africa and Middle East, frequently undergoes dust episodes. During such Mediterranean episodes, the number and mass concentration of dust is high, due to the proximity of its source areas. The dust episodes, through the direct interaction of dust primarily withthe shortwave but also with longwave radiation can lead to strong local warming in the atmosphere, possibly causing temperature inversion during daytime. The existence of such temperature inversions, associated with intense dust episodes in the Mediterranean, is the focus in this study. The methodology followed to achieve the scientific goal of the study consists in the use of a synergy of different data. This synergy enables: (i) the determination of intense dust episodes over the Mediterranean, (ii) the investigation and specification of temperature lapse rates and inversions during the days of dust episodes and (iii) the identification of vertical distribution of aerosols in the atmosphere over specific locations during the days of the episodes. These objectives are achieved through the use of data from: (i) the AERosol Robotic NETwork (AERONET) network, (ii) the Upper Air Observations (radiosondes) database of the University of Wyoming (UoW) and (iii) the European Aerosol Research Lidar Network (EARLINET) database. The study period spans the years from 2000 to 2013, constrained by the data availability of the databases. A key element of the methodology is the

Challenges in understanding past and present eolian dust dynamics

NASA Astrophysics Data System (ADS)

Stuut, Jan-Berend; Merkel, Ute; Rousseau, Denis-Didier

2012-05-01

Dust Workshop 2011: Processes and Quaternary History of Dust Dynamics; Bremen, Germany, 31 October to 3 November 2011 Mineral dust is now generally recognized as a key element in global climate. However, many open questions need to be addressed to reduce the large uncertainties that still exist regarding the global dust cycle. The Atmospheric Dust During the Last Glacial Cycle: Observations and Modeling initiative (ADOM; see http://www.pages-igbp.org/workinggroups/adom) of the Past Global Changes (PAGES) tackles these questions from both modern and paleo perspectives. A 3-day workshop funded by PAGES and the Center for Marine Environmental Sciences (MARUM) in Germany brought together 50 international experts on marine, terrestrial, and polar dust archives; meteorology; remote sensing; and climate modeling. The workshop aimed to bridge gaps between disciplines and to cover all temporal and spatial scales involved in dust processes.

Dust Storm in Southern California

NASA Technical Reports Server (NTRS)

2007-01-01

Along historic Route 66, just southeast of the little town of Amboy, California, lies a dried-up lake. Dry lakebeds are good sources of two things: salt and dust. In this image, the now-parched Bristol Lake offers up both. On April 12, 2007, dust storms menaced the area around Amboy. To the northwest, near Newberry Springs, California, dust hampered visibility and led to a multi-car collision on Interstate 40, killing two people and injuring several others. The same day, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this image of a dust storm in the dry remains of Bristol Lake. Many small dust clouds boil up from the ground surface, casting their shadows to the northwest. A bright white cloud floating over the dust also throws its shadow onto the ground below. East of the dust storm are salt works that stand out from the surrounding landscape thanks to their straight lines and sharp angles. Dark ground surfaces alternate with mined white salt in a network of stripes. When lakes evaporate, chemicals that had been dissolved in the water stay behind, making dry lake beds an ideal place to find heavy concentrations of minerals, including salt. Besides the salt works, something else appears in stark contrast to this arid place. Lush green fields of irrigated crops appear in the east. Besides their color, their orderly arrangement reveals their human-made origin.

Dust ablation in Pluto's atmosphere

NASA Astrophysics Data System (ADS)

Horanyi, Mihaly; Poppe, Andrew; Sternovsky, Zoltan

2016-04-01

Based on measurements by dust detectors onboard the Pioneer 10/11 and New Horizons spacecraft the total production rate of dust particles born in the Edgeworth Kuiper Belt (EKB) has been be estimated to be on the order of 5 ṡ 103 kg/s in the approximate size range of 1 - 10 μm. Dust particles are produced by collisions between EKB objects and their bombardment by both interplanetary and interstellar dust particles. Dust particles of EKB origin, in general, migrate towards the Sun due to Poynting-Robertson drag but their distributions are further sculpted by mean-motion resonances as they first approach the orbit of Neptune and later the other planets, as well as mutual collisions. Subsequently, Jupiter will eject the vast majority of them before they reach the inner solar system. The expected mass influx into Pluto atmosphere is on the order of 200 kg/day, and the arrival speed of the incoming particles is on the order of 3 - 4 km/s. We have followed the ablation history as function of speed and size of dust particles in Pluto's atmosphere, and found that volatile rich particles can fully sublimate due to drag heating and deposit their mass in narrow layers. This deposition might promote the formation of the haze layers observed by the New Horizons spacecraft. This talk will explore the constraints on the composition of the dust particles by comparing the altitude of the deposition layers to the observed haze layers.

Toxicity of lunar dust assessed in inhalation-exposed rats.

PubMed

Lam, Chiu-wing; Scully, Robert R; Zhang, Ye; Renne, Roger A; Hunter, Robert L; McCluskey, Richard A; Chen, Bean T; Castranova, Vincent; Driscoll, Kevin E; Gardner, Donald E; McClellan, Roger O; Cooper, Bonnie L; McKay, David S; Marshall, Linda; James, John T

2013-10-01

Humans will again set foot on the moon. The moon is covered by a layer of fine dust, which can pose a respiratory hazard. We investigated the pulmonary toxicity of lunar dust in rats exposed to 0, 2.1, 6.8, 20.8 and 60.6 mg/m(3) of respirable-size lunar dust for 4 weeks (6 h/day, 5 days/week); the aerosols in the nose-only exposure chambers were generated from a jet-mill ground preparation of a lunar soil collected during the Apollo 14 mission. After 4 weeks of exposure to air or lunar dust, groups of five rats were euthanized 1 day, 1 week, 4 weeks or 13 weeks after the last exposure for assessment of pulmonary toxicity. Biomarkers of toxicity assessed in bronchoalveolar fluids showed concentration-dependent changes; biomarkers that showed treatment effects were total cell and neutrophil counts, total protein concentrations and cellular enzymes (lactate dehydrogenase, glutamyl transferase and aspartate transaminase). No statistically significant differences in these biomarkers were detected between rats exposed to air and those exposed to the two low concentrations of lunar dust. Dose-dependent histopathology, including inflammation, septal thickening, fibrosis and granulomas, in the lung was observed at the two higher exposure concentrations. No lesions were detected in rats exposed to ≤6.8 mg/m(3). This 4-week exposure study in rats showed that 6.8 mg/m(3) was the highest no-observable-adverse-effect level (NOAEL). These results will be useful for assessing the health risk to humans of exposure to lunar dust, establishing human exposure limits and guiding the design of dust mitigation systems in lunar landers or habitats.

Dust storms and the risk of asthma admissions to hospitals in Kuwait.

PubMed

Thalib, Lukman; Al-Taiar, Abdullah

2012-09-01

Arid areas in the Arabian Peninsula are one of the largest sources of global dust, yet there is no data on the impact of this on human health. This study aimed to investigate the impact of dust storms on hospital admissions due to asthma and all respiratory diseases over a period of 5 years in Kuwait. A population-based retrospective time series study of daily emergency asthma admissions and admissions due to respiratory causes in public hospitals in Kuwait was analyzed in relation to dust storm events. Dust storm days were defined as the mean daily PM(10)>200 μg/m(3) based on measurements obtained from all six monitoring sites in the country. During the five-year study period, 569 (33.6%) days had dust storm events and they were significantly associated with an increased risk of same-day asthma and respiratory admission, adjusted relative risk of 1.07 (95% CI: 1.02-1.12) and 1.06 (95% CI: 1.04-1.08), respectively. This was particularly evident among children. Dust storms have a significant impact on respiratory and asthma admissions. Evidence is more convincing and robust compared to that from other geographical settings which highlights the importance of public health measures to protect people's health during dust storms and reduce the burden on health services due to dust events. Copyright © 2012 Elsevier B.V. All rights reserved.

Characteristics of aerosol and meteorological parameters during major dust storm events (2005 - 2010) over Beijing, China

NASA Astrophysics Data System (ADS)

Zheng, Sheng; Cao, Chunxiang; Singh, Ramesh

Multi satellite sensors are capable in monitoring dust storm, its path and changes in atmospheric parameters. The present paper discusses aerosol optical properties and meteorological parameters during major dust storm events (2005-2010) over Beijing, China. The back trajectory model shows that the dust is transported from the Inner Mongolia and Mongolia to Beijing. High aerosol optical depth (AOD) and low Ångström exponent (AE) values are observed during dusty days, the average AOD (675 nm) and AE (440-870 nm) during dusty days are 2.33 and 0.06, respectively. The aerosol size distribution (ASD) in coarse mode shows a large increase in the volume during dusty days. The single scattering albedo (SSA) increases with higher wavelength on dusty days, and higher compared to non-dusty days, indicating the presence of high scattering particles due to dust storm events. Characteristics of particles during dusty and non-dusty days are also supported by the real and imaginary parts of refractive index (RI). High air pollution index (API) during dusty days represent poor air quality is a serious health hazard at the time of dust events. The CO volume mixing ratio (COVMR) from Atmospheric Infrared Sounder (AIRS) shows decrease on the ground on dusty days, while the relative humidity (RH) and H _{2}0 mass mixing ratio (H _{2}OMMR) enhance. In addition, due to the dust storm in 2005, enhanced level of water vapor (WV) using Moderate Resolution Imaging Spectroradiometer (MODIS) data is observed in and around Beijing over the dust storms track.

Characterization of Dust Properties during ACE-Asia and PRIDE: A Column Satellite-Surface Perspective

NASA Technical Reports Server (NTRS)

Lau, William K. M. (Technical Monitor); Tsay, Si-Chee; Hsu, N. Christina; Herman, Jay R.; Ji, Q. Jack

2002-01-01

Many recent field experiments are designed to study the compelling variability in spatial and temporal scale of both pollution-derived and naturally occurring aerosols, which often exist in high concentration over particular pathways around the globe. For example, the ACE-Asia (Aerosol Characterization Experiment-Asia) was conducted from March-May 2001 in the vicinity of the Taklimakan and Gobi deserts, East Coast of China, Yellow Sea, Korea, and Japan, along the pathway of Kosa (severe events that blanket East Asia with yellow desert dust, peaked in the Spring season). The PRIDE (Puerto RIco Dust Experiment, July 2000) was designed to measure the properties of Saharan dust transported across the Atlantic Ocean to the Caribbean. Dust particles typically originate in desert areas far from polluted urban regions. During transport, dust layers can interact with anthropogenic sulfate and soot aerosols from heavily polluted urban areas. Added to the complex effects of clouds and natural marine aerosols, dust particles reaching the marine environment can have drastically different properties than those from the source. Thus, understanding the unique temporal and spatial variations of dust aerosols is of special importance in regional-to-global climate issues such as radiative forcing, the hydrological cycle, and primary biological productivity in the ocean. During ACE-Asia and PRIDE we had measured aerosol physical/optical/radiative properties, column precipitable water amount, and surface reflectivity over homogeneous areas from ground-based remote sensing. The inclusion of flux measurements permits the determination of aerosol radiative flux in addition to measurements of loading and optical depth. At the time of the Terra/MODIS, SeaWiFS, TOMS and other satellite overpasses, these ground-based observations can provide valuable data to compare with satellite retrievals over land. We will present the results and discuss their implications in regional climatic effects.

Cranial measures and ancient DNA both show greater similarity of Neandertals to recent modern Eurasians than to recent modern sub-Saharan Africans.

PubMed