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.

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

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

EXTREME DUST AND SMOKE EVENTS OVER THE U.S. IN 1998

EPA Science Inventory

Dust storms and forest fires are major PM events that occur several times a year over different parts of the US. Such events also originate outside the US, e.g., dust from Sahara and the Asian deserts and smoke from forest fires in Central America and Canada. Such dust and smok...

Characteristics of extreme dust events observed over two urban areas in Iran

NASA Astrophysics Data System (ADS)

Bidokhti, Abbas-Ali A.; Gharaylou, Maryam; Pegahfar, Nafiseh; Sabetghadam, Samaneh; Rezazadeh, Maryam

2016-03-01

Determination of dust loading in the atmosphere is important not only from the public health point of view, but also for regional climate changes. The present study focuses on the characteristics of two major dust events for two urban areas in Iran, Kermanshah and Tehran, over the period of 4 years from 2006 to 2009. To detect extreme dust outbreaks, various datasets including synoptic data, dust concentration, reanalysis data and numerical results of WRF and HYSPLIT models were used. The weather maps demonstrate that for these events dusts are mainly generated when wind velocity is high and humidity is low in the lower troposphere and the region is under the influence of a thermal low. The event lasts until the atmospheric stability prevails and the surface wind speed weakens. The thermal low nature of the synoptic conditions of these major events is also responsible for deep boundary layer development with its thermals affecting the vertical dust flux over the region. Trajectory studies show that the dust events originated from deserts in Iraq and Syria and transported towards Iran. The main distinction between the two types of mobilizations seems to affect the dust concentrations in the Tehran urban area.

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

PubMed Central

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

1992-01-01

Dust exposure and pneumoconiosis were investigated in a South African pottery that manufactured wall tiles and bathroom fittings. This paper describes the objectives of the investigation and presents dust measurement data. x Ray diffraction showed that the clays used by the pottery had a high quartz content (range 58%-23%, mean 38%). Exposure to respirable dust was measured for 43 workers and was highest (6.6 mg/m3) in a bathroom fitting fettler. Quartz concentrations in excess of 0.1 mg/m3 were found in all sections of the manufacturing process from slip production to biscuit firing and sorting. The proportion of quartz in the respirable dust of these sections was 24% to 33%. This is higher than is usually reported in English potteries. Four hundred and six (80%) of the 509 workers employed at the pottery were potentially at risk of occupational lung disease. The finding of large numbers of pottery workers exposed to unacceptable dust concentrations is not surprising as poor dust control was found in all six wall tile and sanitary ware factories surveyed by the National Centre for Occupational Health between 1973 and 1989. Dust related occupational disease can be expected in potters for many years to come. PMID:1637705

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

PubMed

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

1992-07-01

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

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.

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

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

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

Evan, Amato T.; Fiedler, Stephanie; Zhao, Chun

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

Subtropical Dust Storms and Downslope Wind Events

NASA Astrophysics Data System (ADS)

Pokharel, Ashok Kumar; Kaplan, Michael L.; Fiedler, Stephanie

2017-10-01

We performed detailed mesoscale observational analyses and Weather Research and Forecasting (WRF) model simulations to study the terrain-induced downslope winds that generated dust-emitting winds at the beginning of three strong subtropical dust storms in three distinctly different regions of North Africa and the Arabian Peninsula. We revisit the Harmattan dust storm of 2 March 2004, the Saudi dust storm of 9 March 2009, and the Bodélé Depression dust storm of 8 December 2011 and use high-resolution WRF modeling to assess the dynamical processes during the onset of the storms in more depth. Our results highlight the generation of terrain-induced downslope winds in response to the transition of the atmospheric flow from a subcritical to supercritical state in all three cases. These events precede the unbalanced adjustment processes in the lee of the mountain ranges that produced larger-scale dust aerosol mobilization and transport. We see that only the higher-resolution data sets can resolve the mesoscale processes, which are mainly responsible for creating strong low-level terrain-induced downslope winds leading to the initial dust storms.

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.

[Process study on hysteresis of vegetation cover influencing sand-dust events].

PubMed

Xu, Xing-Kui; Wang, Xiao-Tao; Zhang, Feng

2009-02-15

Data analysis from satellite and weather stations during 1982-2000 shows nonlinear relationship between vegetation cover and sand-dust events is present in most part of China. Vegetation cover ratio in summer can impact significantly on the frequency of sand-dust storms from winter to spring in the source regions of sand-dust events. It is not quite clear about the hysteresis that vegetation cover in summer influence sand-dust events during winter and spring. A quasi-geostrophic barotropic model is used under the condition of 3 magnitude of frictional coefficient to investigate the cause of the hysteresis. Wind velocity shows a greatest decline at 90% during 72 h as initial wind velocity is 10 m/s for magnitude of frictional coefficient between atmosphere and water surface, greatest decline at 100% during 18 h for magnitude of frictional coefficient between atmosphere and bare soil and a 100% reduction of wind speed during 1 h for magnitude of frictional coefficient between atmosphere and vegetation cover. Observation and simulation prove that residual root and stem from summervegetation are one of factors to influence sand-dust events happened during winter and spring. Air inhibition from residual root and stem is a most important reason for hysteresis that vegetation cover influence sand-dust events.

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

USGS Publications Warehouse

Kellogg, Christina A.; Griffin, Dale W.

2003-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2015-08-01

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

Monitoring An Intensive Dust Event over Northern China Using Multi-satellite Observation

NASA Astrophysics Data System (ADS)

She, L.; Xue, Y.; Guang, J.; Mei, L.; Che, Y.; Fan, C.; Xie, Y.

2017-12-01

The deserts in western/northern China are one of the major mineral dust source regions of the world. Large amount of dust are emitted and blown east and southeast, especially in spring. An intensive dust event occurred over Northern China during May 3 - 8, 2017. The dust storms came from deserts in China and Mongolia. Due to the long-distance transport, more than ten provinces were affected by this dust event, several provinces occurred strong dust storm. In this study, multi-satellite data were employed to analyse the spatial-temporal evolution and dynamic transport behaviour of the dust plume, especially the geostationary satellite data - Himawari8 Advanced Himawari Imager (AHI) data. AHI data was used to estimate hourly Aerosol Optical Depth (AOD) to monitoring the aerosol distribution as well as the dust plume movements, as the dust storms often characterized by high AOD. A simple dust index was also calculated based on AHI VIS and TIR data to estimate the dust intensity. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data and the Ozone Monitoring Instrument (OMI) Aerosol Index were used as additional data sources to monitor the dust vertical distribution and provide independent information of dust presence. MODIS aerosol product and AERONET aerosol measurements were compared with the AHI retrieved AODs, the comparisons show a good agreement. The dust index was compared with the ground measurements as well as the corresponding RGB image. Simulations from HYSPLIT back-trajectory analysis shows similar temporal variation with the calculated AOD and dust index of the dust plume. Those comparisons with other satellite products and ground measurements suggested both the calculated AOD and dust index well depicted the dust events compared.

A Climatology of Dust-Emission Events over North Africa Based on 27 Years of Surface Observations

NASA Astrophysics Data System (ADS)

Cowie, S.; Knippertz, P.; Schepanski, K.

2012-04-01

The huge quantity of mineral dust emitted annually from North Africa makes this area crucial to the global dust cycle. Once in the atmosphere, dust aerosols have a significant impact on the global radiation budget, clouds, the carbon cycle and can even act as a fertilizer to rain forests in South America. Current model estimates of dust production from North Africa are uncertain. At the heart of this problem is insufficient understanding of key dust emitting processes such as haboobs (cold pools generated through evaporation of convective precipitation), low-level jets (LLJs), and dry convection (dust devils and dust plumes). Scarce observations in this region, in particular in the Sahara, make model evaluation difficult. This work uses long-term surface observations from the MIDAS data set (~120 stations in the arid part of North Africa) to explore the diurnal, seasonal, decadal and geographical variations in dust emission events and their associated wind thresholds. The threshold values are determined from probability density functions of observed 10-minute anemomenter wind speeds. Emission events are defined using the present weather codes (WW) of SYNOP reports. These codes represent events of smaller intensity such as "Dust or sand raised by wind" to severe dust storms. During the 27-year study period (1984-2011) stations are required to have a minimum of 1000 dust observations to be included in the analysis. Dust emission frequency (DEF) is calculated for different time intervals (e.g. monthly, 3-hourly) taking into account the different number of measurements available at each station. North of 25°N a maximum during March-May is evident and relatively consistent over the whole North African region. Wind-speed thresholds for dust emission north of 25°N are higher than south of 25°N in the Sahel, where station-to-station variability is larger, and enhanced DEF activity during February-March is observed. The variability in this region is closely linked to the

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

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

Do Cloud Properties in a Puerto Rican Tropical Montane Cloud Forest Depend on Occurrence of Long-Range Transported African Dust?

NASA Astrophysics Data System (ADS)

Spiegel, Johanna K.; Buchmann, Nina; Mayol-Bracero, Olga L.; Cuadra-Rodriguez, Luis A.; Valle Díaz, Carlos J.; Prather, Kimberly A.; Mertes, Stephan; Eugster, Werner

2014-09-01

We investigated cloud properties of warm clouds in a tropical montane cloud forest at Pico del Este (1,051 m a.s.l.) in the northeastern part of Puerto Rico to address the question of whether cloud properties in the Caribbean could potentially be affected by African dust transported across the Atlantic Ocean. We analyzed data collected during 12 days in July 2011. Cloud droplet size spectra were measured using the FM-100 fog droplet spectrometer that measured droplet size distributions in the range from 2 to 49 µm, primarily during fog events. The droplet size spectra revealed a bimodal structure, with the first peak ( D < 6 µm) being more pronounced in terms of droplet number concentrations, whereas the second peak (10 µm < D < 20 µm) was found to be the one relevant for total liquid water content (LWC) of the cloud. We identified three major clusters of characteristic droplet size spectra by means of hierarchical clustering. All clusters differed significantly from each other in droplet number concentration (), effective diameter (ED), and median volume diameter (MVD). For the cluster comprising the largest droplets and the lowest droplet number concentrations, we found evidence of inhomogeneous mixing in the cloud. Contrastingly, the other two clusters revealed microphysical behavior, which could be expected under homogeneous mixing conditions. For those conditions, an increase in cloud condensation nuclei—e.g., from processed African dust transported to the site—is supposed to lead to an increased droplet concentration. In fact, one of these two clusters showed a clear shift of cloud droplet size spectra towards smaller droplet diameters. Since this cluster occurred during periods with strong evidence for the presence of long-range transported African dust, we hypothesize a link between the observed dust episodes and cloud characteristics in the Caribbean at our site, which is similar to the anthropogenic aerosol indirect effect.

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

USGS Publications Warehouse

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

2007-01-01

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

A parameterization of dust emission (PM10) fluxes of dust events observed at Naiman in Inner Mongolia using the monitored tower data

NASA Astrophysics Data System (ADS)

Park, Soon-Ung; Ju, Jae-Won; Lee, In-Hye; Joo, Seung Jin

2016-09-01

The optimal regression equations for the dust emission flux parameterized with the friction velocity (u*) only, the friction velocity with the threshold friction velocity (u*t) and the friction velocity together with the flux Richardson number (Rf) in the dust source region are derived using the sonic anemometer measured momentum and kinematic heat fluxes at 8 m height and the two-level (3 m and 15 m height) measured PM10 concentrations from a 20-m monitoring tower located at Naiman in the Asian dust source region in China for the period from March 2013 to November 2014. The analysis period is divided into three sub-periods based on the Normalized Difference Vegetation Index (NDVI) to eliminate the effect of vegetation on the dust emission flux. The dust event is identified as a peak half hourly mean dust concentration (PM10) at 3 m height exceeding the sub-period mean dust concentration plus one standard deviation of the sub-period. The total of 317 dust events is identified with the highest number of dust event of 18.8 times a month in summer. The optimal regression equations of the dust emission flux (Fc) for dust events parameterized with u* and Rf are found to simulate quite well the dust emission flux estimated by the observed data at the site for all periods especially for the unstable stratification, suggesting the potential usefulness of these equations parameterized by u* with Rf rather than those by u* only and u* together with u*t for the estimation of the dust emission flux in the Asian dust source region.

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.

Far-Reaching Impacts of African Dust- A Calipso Perspective

NASA Technical Reports Server (NTRS)

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

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

PubMed

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

2015-12-01

The dust origins of the two events were identified using HYSPLIT trajectory model and MODIS and CALIPSO satellite data to understand the particle size distribution during two contrasting dust events originated from Taklimakan and Gobi deserts. The supermicron particles significantly increased during the dust events. The dust event from Gobi desert affected significantly on the particles larger than 2.5 μm, while that from Taklimakan desert impacted obviously on the particles in 1.0-2.5 μm. It is found that the particle size distributions and their modal parameters such as VMD (volume median diameter) have significant difference for varying dust origins. The dust from Taklimakan desert was finer than that from Gobi desert also probably due to other influencing factors such as mixing between dust and urban emissions. Our findings illustrated the capacity of combining in situ, satellite data and trajectory model to characterize large-scale dust plumes with a variety of aerosol parameters. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

USGS Publications Warehouse

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

2010-01-01

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

Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic

NASA Astrophysics Data System (ADS)

Schepanski, Kerstin; Heinold, Bernd; Tegen, Ina

2017-09-01

The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1) the harmattan (trade winds), (2) the Saharan heat low (SHL), and (3) the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August), during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment) field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) flying on board the geostationary Meteosat Second Generation (MSG) satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs) allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are predominantly

Atmospheric dust events in Central Asia: Relationship to wind, soil type, and land use

USDA-ARS?s Scientific Manuscript database

Xinjiang Province is one of the most important source regions of atmospheric dust in China. Spatial-temporal characteristics of dust events in the region were investigated by time series analysis of annual dust event frequency and meteorological data collected at 101 stations in Xinjiang Province fr...

African dust contribution to mean ambient PM10 across the Mediterranean Basin: A quantitative approach to investigate spatial and seasonal patterns

NASA Astrophysics Data System (ADS)

Querol, X.; Pandolfi, M.; Pey, J.; Alastuey, A.; Cusack, M.; Pérez, N.; Amato, F.; Moreno, T.; Viana, M.; Mihalopoulos, N.

2009-04-01

The aim of the present study is quantifying African dust contributions to mean PM10 levels recorded across the Mediterranean basin (2001-2008, 1995-2008 in one case) and evidencing spatial variations and seasonal trends. To this end the same methodology has been applied to a number of data sets on PM levels recorded in aerosol research monitoring sites (Montseny-EUSAAR, Spain, Finokalia-EUSAAR, Greece) and from a number of regional background (RB) monitoring sites from the Co-operative Program for Monitoring and Evaluation of the Long-Range Transmission of Air pollutants in Europe (EMEP) and regional air quality monitoring networks available from Airbase-EEA data set. Around 20 data series spread across the whole Mediterranean and bordering regions have been selected and analyzed in the present study. Once the PM data were obtained the days under the influence of African dust outbreaks were identified (using HYSPLIT, DREAM-BSC, SKIRON and NAAPS tools) for each receptor site. Subsequently, a method (Escudero et al., 2007) based on the statistical data treatment of time series of PM levels, without a need of chemical analysis, was used for the quantification of the daily African PM load during dust outbreaks at each site. Finally, PM speciation data available at MSY and FKL were used to differentiate the local/regional from the African mineral contributions across the Mediterranean Basin. Results show a clear W to E and N to S increasing gradients, both on annual PM levels and annual African dust load. In the Eastern Mediterranean the episodes are more intense and are relatively frequent in spring and summer period. However in the western side of the basin, African dust outbreaks are more frequent in summer and winter. In the N, NW and NE sides of the basin 1-2 µgPM10/m3 of mean annual dust contribution was quantified, whereas in the S, SE, SW this annual contribution ranges from 6 to 10 µgPM10/m3. The number of exceedances of the PM10 daily limit value

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

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

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.

Associations Between Subjective Symptoms and Serum Immunoglobulin E Levels During Asian Dust Events

PubMed Central

Otani, Shinji; Onishi, Kazunari; Mu, Haosheng; Hosoda, Takenobu; Kurozawa, Youichi; Ikeguchi, Masahide

2014-01-01

Asian dust is a seasonal meteorological phenomenon caused by the displacement of atmospheric pollutants from the Mongolian and Chinese deserts. Although the frequency of Asian dust events and atmospheric dust levels have steadily increased in the eastern Asia region, the effects on human health remain poorly understood. In the present study, the impact of Asian dust on human health was determined in terms of allergic reactions. A total of 25 healthy volunteers were tested for a relationship between serum immunoglobulin E (IgE) levels and subjective symptoms during a 3-day Asian dust event recorded in April 2012. They filled daily questionnaires on the severity of nasal, pharyngeal, ocular, respiratory, and skin symptoms by a self-administered visual analog scale. Serum levels of non-specific IgE and 33 allergen-specific IgE molecules were analyzed. Spearman rank-correlation analysis revealed significant positive associations between nasal symptom scores and 2 microbial-specific IgE levels (Penicillium and Cladosporium). Microbes migrate vast distances during Asian dust events by attaching themselves to dust particles. Therefore, some of these symptoms may be associated with type 1 allergic reactions to certain type of microbes. PMID:25075882

Characterization of major pollution events (dust, haze, and two festival events) at Agra, India.

PubMed

Pachauri, Tripti; Singla, Vyoma; Satsangi, Aparna; Lakhani, Anita; Kumari, K Maharaj

2013-08-01

Total suspended particulate (TSP) samples were collected during dust, haze, and two festival events (Holi and Diwali) from February 2009 to June 2010. Pollutant gases (NO2, SO2, and O3) along with the meteorological parameters were also measured during the four pollution events at Agra. The concentration of pollutant gases decreases during dust events (DEs), but the levels of the gases increase during other pollution events indicating the impact of anthropogenic emissions. The mass concentrations were about two times higher during pollution events than normal days (NDs). High TSP concentrations during Holi and Diwali events may be attributed to anthropogenic activities while increased combustion sources in addition to stagnant meteorological conditions contributed to high TSP mass during haze events. On the other hand, long-range transport of atmospheric particles plays a major role during DEs. In the dust samples, Ca(2+), Cl(-), NO3 (-), and SO4 (2-) were the most abundant ions and Ca(2+) alone accounted for 22 % of the total ionic mass, while during haze event, the concentrations of secondary aerosols species, viz., NO3 (-), SO4 (2-), and NH4 (+), were 3.6, 3.3, and 5.1 times higher than the normal days. During Diwali, SO4 (2-) concentration (17.8 μg m(-3)) was highest followed by NO3 (-), K(+), and Cl(-) while the Holi samples were strongly enriched with Cl(-) and K(+) which together made up 32.7 % of the total water-soluble ions. The ion balances indicate that the haze samples were acidic. On the other hand, Holi, Diwali, and DE samples were enriched with cations. The carbonaceous aerosol shows strong variation with the highest concentration during Holi followed by haze, Diwali, DEs, and NDs. However, the secondary organic carbon concentration follows the order haze > DEs > Diwali > Holi > NDs. The scanning electron microscope/EDX results indicate that KCl and carbon-rich particles were more dominant during Holi and haze events while DE samples were enriched

Assessment for the impact of dust events on measles incidence in western China

NASA Astrophysics Data System (ADS)

Ma, Yuxia; Zhou, Jianding; Yang, Sixu; Zhao, Yuxin; Zheng, Xiaodong

2017-05-01

Dust events affect human health in both drylands and downwind environments. In this study, we used county-level data during the period of 1965-2005 to assess the impact of dust events on measles incidence in Gansu province in Western China. We used Fast Fourier Transform (FFT) to set up the cyclical regression model; in particular, we set the model to downwind direction for the typical cities in the Hexi Corridor as well as the capital city Lanzhou. The results showed that Spring measles incidence was the highest in the Hexi Corridor, where dust events occur the most frequently over Gansu province. Measles incidence declined on the pathway of dust storms from west to east due to the weakening of both intensity and duration in dust storms. Measles incidence was positively correlated with monthly wind speed and negatively correlated with rainfall amount, relative humidity, and air pressure. Measles incidence was significantly (p ≤ 0.01) positively correlated with daily coarse particles, e.g., TSP and PM10. According to the cyclical regression model, average monthly excess measles that is related to dust events was 39.1 (ranging from 17.3 to 87.6), 149.9 (ranging from 7.1 to 413.4), and 31.3 (ranging from 20.6 to 63.5) in Zhangye, Lanzhou, and Jiuquan, respectively.

An anomalous African dust event and its impact on aerosol radiative forcing on the Southwest Atlantic coast of Europe in February 2016.

PubMed

Sorribas, M; Adame, J A; Andrews, E; Yela, M

2017-04-01

A desert dust (DD) event that had its origin in North Africa occurred on the 20th-23rd of February 2016. The dust transport phenomenon was exceptional because of its unusual intensity during the coldest season. A historical dataset (2006-2015) of February meteorological scenarios using ECMWF fields, meteorological parameters, aerosol optical properties, surface O 3 and AOD retrieved from MODIS at the El Arenosillo observatory (southwestern Spain) were analysed and compared with the levels during the DD event to highlight its exceptionality. Associated with a low-pressure system in western North Africa, flows transported air from the Sahel to Algeria and consequently increased temperatures from the surface to 700hPa by up to 7-9°C relative to the last decade. These conditions favoured the formation of a Saharan air layer. Dust was transported to the north and reached the Western Mediterranean Basin and the Iberian Peninsula. The arrival of the DD event at El Arenosillo did not affect the surface weather conditions or ozone but did impact the aerosol radiative forcing at the top of atmosphere (RF TOA ). Aerosol radiative properties did not change relative to historical; however, the particle size and the amount of the aerosol were significantly higher. The DD event caused an increase (in absolute terms) of the mean aerosol RF TOA to a value of -8.1Wm -2 (long-term climatological value ~-1.5Wm -2 ). The aerosol RF TOA was not very large relative other DD episodes; however, our analysis of the historical data concluded that the importance of this DD event lay in the month of occurrence. European phenological datasets related to extreme atmospheric events predominantly reflect changes that are probably associated with climate change. This work is an example of this phenomenon, showing an event that occurred in a hotspot, the Saharan desert, and its impact two thousand km away. Copyright © 2017 Elsevier B.V. All rights reserved.

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

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

In order to assess the impact of mineral dust on climate and biogeochemistry, it is paramount to identify the sources of dust emission. In this regard, radiogenic isotopes have recently been used successfully for tracing North African dust provenance and its transport across the tropical Atlantic to the Caribbean. Here we present two time series of radiogenic isotopes (Pb, Sr and Nd) in dusts collected at the Cape Verde Islands and Barbados in order to determine the origin of the dust and examine the seasonality of westerly dust outflow from Northern Africa. Aerosol samples were collected daily during two campaigns - February 2012 (winter) and June-July 2013 (summer) - at the Cape Verde Atmospheric Observatory (CVAO) on the island of São Vicente (16.9°N, 24.9°W). A one-year-long time series of aerosols from Barbados (13.16°N, 59.43°W) - a receptor region in the Caribbean - was sampled at a lower, monthly resolution. Our results resolve a seasonal isotopic signal at Cape Verde shown by daily variations, with a larger radiogenic isotope variability in winter compared to that in summer. This summer signature is also observed over Barbados, indicating similar dust provenance at both locations, despite different sampling years. This constrains the isotope fingerprint of Saharan Air Layer (SAL) dust that is well-mixed during its transport. This result provides unequivocal evidence for a permanent, albeit of variable strength, long-range transport of African dust to the Caribbean and is in full agreement with atmospheric models of North African dust emission and transport across the tropical Atlantic in the SAL. The seasonal isotopic variability is related to changes in the dust source areas - mainly the Sahara and Sahel regions - that are active all-year-round, albeit with variable contributions in summer versus the winter months. Our results provide little support for much dust contributed from the Bodélé Depression in Chad - the "dustiest" place on Earth

Numerical simulation of a dust event in northeastern Germany with a new dust emission scheme in COSMO-ART

USDA-ARS?s Scientific Manuscript database

The dust emission scheme of Shao (2004) has been implemented into the regional atmospheric model COSMO-ART and has been applied to a severe dust event in northeastern Germany on 8th April 2011. The model sensitivity to soil moisture and vegetation cover has been studied. Soil moisture has been found...

African dust and the demise of Caribbean coral reefs

USGS Publications Warehouse

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

2000-01-01

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

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

Mineral dust: observations of emission events and modeling of transport to the upper troposphere

NASA Astrophysics Data System (ADS)

Peter, T.; Wiacek, A.; Taddeo, M.

2009-04-01

The present study explores differences between mineral dust emission events in West African and Asian (Taklimakan) deserts, focusing on the availability of bare mineral dust ice nuclei for interactions with cirrus clouds without previous processing or washout by liquid water clouds. One-week trajectory calculations with high-resolution ECMWF fields are used to track transported (Lagrangian) relative humidities with respect to liquid water and ice, allowing to estimate the formation of liquid, mixed-phase and ice clouds. Transport trajectories can reasonably be assumed to carry dust with them throughout the year, except for the months of December-February, which are quiescent with respect to dust emission in both regions. Practically none of the simulated air parcels reach regions where homogeneous nucleation can take place (T < -35°C) along trajectories that have not experienced water saturation first, i.e. it is very unlikely that mineral dust particles could be a serious competitor for homogeneous nucleation during the formation of high, cold cirrus clouds. For the temperature region between -35°C < T < 0°C, i.e. in air parcels exhibiting necessary conditions for warmer ice clouds at lower altitudes, a small but significant number of air parcels are found to follow trajectories where RHw < 100% and RHi > 100% are simultaneously maintained. However, the potential for such low ice clouds originating from the Taklimakan desert is greater than that of the Sahara by a factor of 4-6. The implication is that although the Sahara is by far the biggest source of dust in the world, the much smaller Taklimakan desert in China's Tarim Basin may be of greater importance as a source of ice nuclei affecting cirrus cloud formation. This is likely the result of several meteorological factors, including the complex regional topography combined with the higher altitude of Taklimakan dust emissions and, on the synoptic scale, the higher altitude of potential temperature levels in

Enhancement and identification of dust events in the south-west region of Iran using satellite observations

NASA Astrophysics Data System (ADS)

Taghavi, F.; Owlad, E.; Ackerman, S. A.

2017-03-01

South-west Asia including the Middle East is one of the most prone regions to dust storm events. In recent years, there was an increase in the occurrence of these environmental and meteorological phenomena. Remote sensing could serve as an applicable method to detect and also characterise these events. In this study, two dust enhancement algorithms were used to investigate the behaviour of dust events using satellite data, compare with numerical model output and other satellite products and finally validate with in-situ measurements. The results show that the use of thermal infrared algorithm enhances dust more accurately. The aerosol optical depth from MODIS and output of a Dust Regional Atmospheric Model (DREAM8b) are applied for comparing the results. Ground-based observations of synoptic stations and sun photometers are used for validating the satellite products. To find the transport direction and the locations of the dust sources and the synoptic situations during these events, model outputs (HYSPLIT and NCEP/NCAR) are presented. Comparing the results with synoptic maps and the model outputs showed that using enhancement algorithms is a more reliable way than any other MODIS products or model outputs to enhance the dust.

Observed characteristics of dust storm events over the western United States using meteorological, satellite, and air quality measurements

NASA Astrophysics Data System (ADS)

Lei, H.; Wang, J. X. L.

2014-08-01

To improve dust storm identification over the western United States, historical dust events measured by air quality and satellite observations are analyzed based on their characteristics in data sets of regular meteorology, satellite-based aerosol optical depth (AOD), and air quality measurements. Based on the prevailing weather conditions associated with dust emission, dust storm events are classified into the following four typical types: (1) The key feature of cold front-induced dust storms is their rapid process with strong dust emissions. (2) Events caused by meso- to small-scale weather systems have the highest levels of emissions. (3) Dust storms caused by tropical disturbances show a stronger air concentration of dust and last longer than those in (1) and (2). (4) Dust storms triggered by cyclogenesis last the longest. In this paper, sample events of each type are selected and examined to explore characteristics observed from in situ and remote-sensing measurements. These characteristics include the lasting period, surface wind speeds, areas affected, average loading on ground-based optical and/or air quality measurements, peak loading on ground-based optical and/or air quality measurements, and loading on satellite-based aerosol optical depth. Based on these analyses, we compare the characteristics of the same dust events captured in different data sets in order to define the dust identification criteria. The analyses show that the variability in mass concentrations captured by in situ measurements is consistent with the variability in AOD from stationary and satellite observations. Our analyses also find that different data sets are capable of identifying certain common characteristics, while each data set also provides specific information about a dust storm event. For example, the meteorological data are good at identifying the lasting period and area impacted by a dust event; the ground-based air quality and optical measurements can capture the peak

Linking Barbados Mineral Dust Aerosols to North African Sources Using Elemental Composition and Radiogenic Sr, Nd, and Pb Isotope Signatures

NASA Astrophysics Data System (ADS)

Bozlaker, Ayse; Prospero, Joseph M.; Price, Jim; Chellam, Shankararaman

2018-01-01

Large quantities of African dust are carried across the Atlantic to the Caribbean Basin and southern United States where it plays an important role in the biogeochemistry of soils and waters and in air quality. Dusts' elemental and isotopic composition was comprehensively characterized in Barbados during the summers of 2013 and 2014, the season of maximum dust transport. Although total suspended insoluble particulate matter (TSIP) mass concentrations varied significantly daily and between the two summers, the abundances (μg element/g TSIP) of 50 elements during "high-dust days" (HDD) were similar. Aerosols were regularly enriched in Na, Cu, Zn, As, Se, Mo, Cd, Sn, Sb, and W relative to the upper continental crust. Enrichment of these elements, many of which are anthropogenically emitted, was significantly reduced during HDD, attributed to mixing and dilution with desert dust over source regions. Generally, Ti/Al, Si/Al, Ca/Al, Ti/Fe, Si/Fe, and Ca/Fe ratios during HDD differed from their respective values in hypothesized North African source regions. Nd isotope composition was relatively invariant for "low-dust days" (LDD) and HDD. In contrast, HDD-aerosols were more radiogenic exhibiting higher 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios compared to LDD. Generally, Barbados aerosols' composition ranged within narrow limits and was much more homogeneous than that of hypothesized African source soils. Our results suggest that summertime Barbados aerosols are dominated by a mixture of particles originating from sources in the Sahara-Sahel regions. The Bodélé Depression, long suspected as a major source, appears to be an insignificant contributor of summertime western Atlantic dust.

Variations in the structure of airborne bacterial communities in Tsogt-Ovoo of Gobi desert area during dust events.

PubMed

Maki, Teruya; Kurosaki, Yasunori; Onishi, Kazunari; Lee, Kevin C; Pointing, Stephen B; Jugder, Dulam; Yamanaka, Norikazu; Hasegawa, Hiroshi; Shinoda, Masato

2017-01-01

Asian dust events transport the airborne bacteria in Chinese desert regions as well as mineral particles and influence downwind area varying biological ecosystems and climate changes. However, the airborne bacterial dynamics were rarely investigated in the Gobi desert area, where dust events are highly frequent. In this study, air samplings were sequentially performed at a 2-m high above the ground at the sampling site located in desert area (Tsogt-Ovoo of Gobi desert; Mongolia 44.2304°N, 105.1700°E). During the dust event days, the bacterial cells and mineral particles increased to more than tenfold of concentrations. MiSeq sequencing targeting 16S ribosomal DNA revealed that the airborne bacteria in desert area mainly belonged to the classes Acidobacteria , Actinobacteria , Bacteroidetes , Chloroflexi , Bacilli , Alpha-proteobacteria , Beta-proteobacteria , and Gamma-proteobacteria. The bacterial community structures were different between dust events and non-dust events. The air samples collected at the dust events indicated high abundance rates of Alpha-proteobacteria , which were reported to dominate on the leaf surfaces of plants or in the saline lake environments. After the dust events, the members of Firmicutes ( Bacilli ) and Bacteroidetes , which are known to form endospore and attach with coarse particles, respectively, increased their relative abundances in the air samples. Presumably, the bacterial compositions and diversities in atmosphere significantly vary during dust events, which carry some particles from grassland (phyllo-sphere), dry lake, and sand surfaces, as well as some bacterial populations such as Firmicutes and Bacteroidetes maintain in the atmosphere for longer time.

Properties of transported African mineral dust aerosols in the Mediterranean region

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

Metagenomic Analysis of Airborne Bacterial Community and Diversity in Seoul, Korea, during December 2014, Asian Dust Event.

PubMed

Cha, Seho; Srinivasan, Sathiyaraj; Jang, Jun Hyeong; Lee, Dongwook; Lim, Sora; Kim, Kyung Sang; Jheong, Weonhwa; Lee, Dong-Won; Park, Eung-Roh; Chung, Hyun-Mi; Choe, Joonho; Kim, Myung Kyum; Seo, Taegun

2017-01-01

Asian dust or yellow sand events in East Asia are a major issue of environmental contamination and human health, causing increasing concern. A high amount of dust particles, especially called as particulate matter 10 (PM10), is transported by the wind from the arid and semi-arid tracks to the Korean peninsula, bringing a bacterial population that alters the terrestrial and atmospheric microbial communities. In this study, we aimed to explore the bacterial populations of Asian dust samples collected during November-December 2014. The dust samples were collected using the impinger method, and the hypervariable regions of the 16S rRNA gene were amplified using PCR followed by pyrosequencing. Analysis of the sequencing data were performed using Mothur software. The data showed that the number of operational taxonomic units and diversity index during Asian dust events were higher than those during non-Asian dust events. At the phylum level, the proportions of Proteobacteria, Actinobacteria, and Firmicutes were different between Asian dust and non-Asian dust samples. At the genus level, the proportions of the genus Bacillus (6.9%), Arthrobacter (3.6%), Blastocatella (2%), Planomicrobium (1.4%) were increased during Asian dust compared to those in non-Asian dust samples. This study showed that the significant relationship between bacterial populations of Asian dust samples and non-Asian dust samples in Korea, which could significantly affect the microbial population in the environment.

Assessing exposure risk for dust storm events-associated lung function decrement in asthmatics and implications for control

NASA Astrophysics Data System (ADS)

Hsieh, Nan-Hung; Liao, Chung-Min

2013-04-01

Asian dust storms (ADS) events are seasonally-based meteorological phenomena that exacerbate chronic respiratory diseases. The purpose of this study was to assess human health risk from airborne dust exposure during ADS events in Taiwan. A probabilistic risk assessment framework was developed based on exposure and experimental data to quantify ADS events induced lung function decrement. The study reanalyzed experimental data from aerosol challenge in asthmatic individuals to construct the dose-response relationship between inhaled dust aerosol dose and decreasing percentage of forced expiratory volume in 1 s (%FEV1). An empirical lung deposition model was used to predict deposition fraction for size specific dust aerosols in pulmonary regions. The toxicokinetic and toxicodynamic models were used to simulate dust aerosols binding kinetics in lung airway in that %FEV1 change was also predicted. The mask respirators were applied to control the inhaled dose under dust aerosols exposure. Our results found that only 2% probability the mild ADS events were likely to cause %FEV1 decrement higher than 5%. There were 50% probability of decreasing %FEV1 exceeding 16.9, 18.9, and 7.1% in north, center, and south Taiwan under severe ADS events, respectively. Our result implicates that the use of activated carbon of mask respirators has the best efficacy for reducing inhaled dust aerosol dose, by which the %FEV1 decrement can be reduced up to less than 1%.

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

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Saharan Dust on the Move

NASA Image and Video Library

2017-12-08

A piece of Africa—actually lots of them—began to arrive in the Americas in June 2014. On June 23, a lengthy river of dust from western Africa began to push across the Atlantic Ocean on easterly winds. A week later, the influx of dust was affecting air quality as far away as the southeastern United States. This composite image, made with data from the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP, shows dust heading west toward South America and the Gulf of Mexico on June 25, 2014. The dust flowed roughly parallel to a line of clouds in the intertropical convergence zone, an area near the equator where the trade winds come together and rain and clouds are common. In imagery captured by the Moderate Resolution Imaging Spectroradiometer (MODIS), the dust appeared to be streaming from Mauritania, Senegal, and Western Sahara, though some of it may have originated in countries farther to the east. Saharan dust has a range of impacts on ecosystems downwind. Each year, dust events like the one pictured here deliver about 40 million tons of dust from the Sahara to the Amazon River Basin. The minerals in the dust replenish nutrients in rainforest soils, which are continually depleted by drenching, tropical rains. Research focused on peat soils in the Everglades show that African dust has been arriving regularly in South Florida for thousands of years as well. In some instances, the impacts are harmful. Infusion of Saharan dust, for instance, can have a negative impact on air quality in the Americas. And scientists have linked African dust to outbreaks of certain types of toxic algal blooms in the Gulf of Mexico and southern Florida. Read more: 1.usa.gov/1snkzmS NASA images by Norman Kuring, NASA’s Ocean Color web. Caption by Adam Voiland. Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and

SEP events and wake region lunar dust charging with grain radii

NASA Astrophysics Data System (ADS)

Chandran, S. B. Rakesh; Rajesh, S. R.; Abraham, A.; Renuka, G.; Venugopal, Chandu

2017-01-01

Our lunar surface is exposed to all kinds of radiations from the Sun, since it lacks a global magnetic field. Like lunar surface, dust particles are also exposed to plasmas and UV radiation and, consequently they carry electrostatic charges. During Solar Energetic Particle events (SEPs) secondary electron emission plays a vital role in charging of lunar dusts. To study the lunar dust charging during SEPs on lunar wake region, we derived an expression for lunar dust potential and analysed how it varies with different electron temperatures and grain radii. Because of high energetic solar fluxes, secondary yield (δ) values reach up to 2.3 for 0.5 μm dust grain. We got maximum yield at an energy of 550 eV which is in well agreement with lunar sample experimental observation (Anderegg et al., 1972). It is observed that yield value increases with electron energy, reaches to a maximum value and then decreases. During SEPs heavier dust grains show larger yield values because of the geometry of the grains. On the wake region, the dust potential reaches up to -497 V for 0.5 μm dust grain. The electric field of these grains could present a significant threat to manned and unmanned missions to the Moon.

Metagenomic Analysis of Airborne Bacterial Community and Diversity in Seoul, Korea, during December 2014, Asian Dust Event

PubMed Central

Cha, Seho; Srinivasan, Sathiyaraj; Jang, Jun Hyeong; Lee, Dongwook; Lim, Sora; Kim, Kyung Sang; Jheong, Weonhwa; Lee, Dong-Won; Park, Eung-Roh; Chung, Hyun-Mi; Choe, Joonho; Kim, Myung Kyum; Seo, Taegun

2017-01-01

Asian dust or yellow sand events in East Asia are a major issue of environmental contamination and human health, causing increasing concern. A high amount of dust particles, especially called as particulate matter 10 (PM10), is transported by the wind from the arid and semi-arid tracks to the Korean peninsula, bringing a bacterial population that alters the terrestrial and atmospheric microbial communities. In this study, we aimed to explore the bacterial populations of Asian dust samples collected during November–December 2014. The dust samples were collected using the impinger method, and the hypervariable regions of the 16S rRNA gene were amplified using PCR followed by pyrosequencing. Analysis of the sequencing data were performed using Mothur software. The data showed that the number of operational taxonomic units and diversity index during Asian dust events were higher than those during non-Asian dust events. At the phylum level, the proportions of Proteobacteria, Actinobacteria, and Firmicutes were different between Asian dust and non-Asian dust samples. At the genus level, the proportions of the genus Bacillus (6.9%), Arthrobacter (3.6%), Blastocatella (2%), Planomicrobium (1.4%) were increased during Asian dust compared to those in non-Asian dust samples. This study showed that the significant relationship between bacterial populations of Asian dust samples and non-Asian dust samples in Korea, which could significantly affect the microbial population in the environment. PMID:28122054

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

NASA Technical Reports Server (NTRS)

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

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

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

Variations in airborne bacterial communities at high altitudes over the Noto Peninsula (Japan) in response to Asian dust events

NASA Astrophysics Data System (ADS)

Maki, Teruya; Hara, Kazutaka; Iwata, Ayumu; Lee, Kevin C.; Kawai, Kei; Kai, Kenji; Kobayashi, Fumihisa; Pointing, Stephen B.; Archer, Stephen; Hasegawa, Hiroshi; Iwasaka, Yasunobu

2017-10-01

Aerosol particles, including airborne microorganisms, are transported through the free troposphere from the Asian continental area to the downwind area in East Asia and can influence climate changes, ecosystem dynamics, and human health. However, the variations present in airborne bacterial communities in the free troposphere over downwind areas are poorly understood, and there are few studies that provide an in-depth examination of the effects of long-range transport of aerosols (natural and anthropogenic particles) on bacterial variations. In this study, the vertical distributions of airborne bacterial communities at high altitudes were investigated and the bacterial variations were compared between dust events and non-dust events.Aerosols were collected at three altitudes from ground level to the free troposphere (upper level: 3000 or 2500 m; middle level: 1200 or 500 m; and low level: 10 m) during Asian dust events and non-dust events over the Noto Peninsula, Japan, where westerly winds carry aerosols from the Asian continental areas. During Asian dust events, air masses at high altitudes were transported from the Asian continental area by westerly winds, and laser imaging detection and ranging (lidar) data indicated high concentrations of non-spherical particles, suggesting that dust-sand particles were transported from the central desert regions of Asia. The air samples collected during the dust events contained 10-100 times higher concentrations of microscopic fluorescent particles and optical particle counter (OPC) measured particles than in non-dust events. The air masses of non-dust events contained lower amounts of dust-sand particles. Additionally, some air samples showed relatively high levels of black carbon, which were likely transported from the Asian continental coasts. Moreover, during the dust events, microbial particles at altitudes of > 1200 m increased to the concentrations ranging from 1. 2 × 106 to 6. 6 × 106 particles m-3. In contrast

Mineral dust photochemistry induces nucleation events in the presence of SO2

PubMed Central

Dupart, Yoan; King, Stephanie M.; Nekat, Bettina; Nowak, Andreas; Wiedensohler, Alfred; Herrmann, Hartmut; David, Gregory; Thomas, Benjamin; Miffre, Alain; Rairoux, Patrick; D’Anna, Barbara; George, Christian

2012-01-01

Large quantities of mineral dust particles are frequently ejected into the atmosphere through the action of wind. The surface of dust particles acts as a sink for many gases, such as sulfur dioxide. It is well known that under most conditions, sulfur dioxide reacts on dust particle surfaces, leading to the production of sulfate ions. In this report, for specific atmospheric conditions, we provide evidence for an alternate pathway in which a series of reactions under solar UV light produces first gaseous sulfuric acid as an intermediate product before surface-bound sulfate. Metal oxides present in mineral dust act as atmospheric photocatalysts promoting the formation of gaseous OH radicals, which initiate the conversion of SO2 to H2SO4 in the vicinity of dust particles. Under low dust conditions, this process may lead to nucleation events in the atmosphere. The laboratory findings are supported by recent field observations near Beijing, China, and Lyon, France. PMID:23213230

Quantification of the lithogenic carbon pump following a dust deposition event

NASA Astrophysics Data System (ADS)

Bressac, M.; Guieu, C.; Doxaran, D.; Bourrin, F.; Desboeufs, K.; Leblond, N.; Ridame, C.

2013-08-01

Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC-dust association that occurs within the upper ocean is required in order to affine the "ballast hypothesis". In the framework of the DUNE project, two artificial seedings were performed seven days apart within large mesocosms. A suite of optical and biogeochemical measurements were used to quantify surface POC export following simulated dust events within a low-nutrient low-chlorophyll ecosystem. The two successive seedings led to a 2.3-6.7 fold higher POC flux as compared to the POC flux observed in controlled mesocosms. A simple linear regression analysis revealed that the lithogenic fluxes explained more than 85% of the variance in POC fluxes. At the scale of a dust deposition event, we estimated that 42-50% of POC fluxes were strictly associated with lithogenic particles through an aggregation process. Lithogenic ballasting also likely impacted the remaining POC fraction which resulted from the fertilization effect. The observations support the "ballast hypothesis" and provide a quantitative estimation of the surface POC export abiotically triggered by dust deposition. In this work, we demonstrate that the strength of such a "lithogenic carbon pump" depends on the biogeochemical conditions of the water column at the time of deposition. Based on these observations, we suggest that this "lithogenic carbon pump" could represent a major component of the biological pump in oceanic areas subjected to intense atmospheric forcing.

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 (

The influence of an extensive dust event on snow chemistry in the southern Rocky Mountains

Treesearch

Charles Rhoades; Kelly Elder; E. Greene

2010-01-01

In mid-February 2006, windstorms in Arizona, Utah, and western Colorado generated a dust cloud that distributed a layer of dust across the surface of the snowpack throughout much of the Colorado Rockies; it remained visible throughout the winter. We compared the chemical composition of snowfall and snowpack collected during and after the dust deposition event with pre-...

African dust particles and their impact on the solar energy budget in a Caribbean tropical montane cloud forest

NASA Astrophysics Data System (ADS)

Rivera, F. A.; Mayol-Bracero, O. L.; Torres-Delgado, E.

2017-12-01

To understand the impact of aerosols over the atmospheric energy budget it is essential to identify their size and chemical properties. Atmospheric aerosols emitted, for example, from African dust storms, directly affect climate by altering the dynamics of cloud formation and by reducing the amount of radiation reaching vegetation and the soil surface. In this project, we seek to improve our understanding of the variations in the concentrations of African dust and the role it might play in the energy budget at a Tropical Montane Cloud Forest (TMCF). Concentrations of particulate matter with diameters equal or less than 10µm (PM10) and aerosol optical properties (scattering and absorption) for years 2013 and 2014 were studied in northeastern Puerto Rico at the nature reserve of Cabezas de San Juan (CSJ). At CSJ we used an Integrating Nephelometer to measure light scattering at three wavelengths (450, 550 and 700 nm) and calculated the Scattering Angstrom Exponent (SAE), a measure inversely related to the size of the aerosol particle. We also used the Continuous Light Absorption Photometer (CLAP) to measure the light absorption at three wavelengths (450, 550 and 700). Visibility (meters) and radiation (total solar, UV and IR irradiation) were studied at the TMCF of Pico del Este (PE). PM10 data from stations at Cataño, Guaynabo, and Fajardo were also obtained. The PM10 data were used to study the variation in aerosol concentrations during the year and to study whether there was an effect on the incoming solar radiation. The periods under the influence of African dust were identified using the spectral coefficients measured at CSJ and the air mass back trajectories using the HYSPLIT model. During the summer period, an increase in PM10 concentrations, related to African Dust incursions, was observed. Preliminary results suggest that, for 2013 and 2014, in the presence of high concentrations of PM10 and with low SAE, the total radiation at PE decreased. This could be

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

NASA Astrophysics Data System (ADS)

Kalenderski, S.; Stenchikov, G. L.

2015-12-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-07-01

June and PM10 in August) and another in March (0.02 for AOD and 2.2 µg m-3 for PM10) - both displaying a similar evolution with exceptions in July and September. The seasonal cycle of the DD contribution to AOD does not follow the pattern of the total AOD (close to a bell shape), whereas both PM10 cycles (total and DD contribution) are more similar to each other in shape, with an exception in September. The interannual evolution of the DD contribution to AOD and PM10 has evidenced a progressive decrease. This decline in the levels of mineral dust aerosols can explain up to 30 % of the total aerosol load decrease observed in the study area during the period 2003-2014. The relationship between columnar and surface DD contribution shows a correlation coefficient of 0.81 for the interannual averages. Finally, synoptic conditions during DD events are also analysed, observing that the north African thermal low causes most of the events ( ˜ 53 %). The results presented in this study highlight the relevance of the area studied since it can be considered representative of the clean background in the western Mediterranean Basin where DD events have a high impact on aerosol load levels.

Alterations in the airborne bacterial community during Asian dust events occurring between February and March 2015 in South Korea

PubMed Central

Cha, Seho; Lee, Dongwook; Jang, Jun Hyeong; Lim, Sora; Yang, Dahye; Seo, Taegun

2016-01-01

During Asian dust events, a relatively high concentration of particulate matter is transported by wind from arid and semi-arid regions, such as the Gobi and Taklamakan deserts, to nearby countries, including China, Korea, and Japan. The dust particles contain various microorganisms, which can affect human health as well as the environmental microbe population. In the current study, we investigated the characteristics of the airborne bacterial community during Asian dust events between February and March 2015 in South Korea. Bacterial diversity indexes such as operational taxonomic units, Chao1 and Inverse Simpson index were increased, along with total 16S rRNA gene copy number during Asian dust events. The bacterial community structure during Asian dust events was clearly distinguishable from that during non-Asian dust days. The genera Bacillus and Modestobacter were increased 3.9- and 2.7-fold, respectively, while Escherichia-Shigella was decreased by 89.8%. A non-metric multidimensional scaling plot with metadata analysis revealed association of particulate matter concentration, but not temperature, humidity or wind speed, with bacterial community structure, suggesting that the newly transported dust particles contain various microorganisms that influence the airborne bacterial environment. PMID:27849049

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.

Modeling a Typical Winter-time Dust Event over the Arabian Peninsula and the Red Sea

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

Kalenderski, S.; Stenchikov, G.; Zhao, Chun

2013-02-20

We used WRF-Chem, a regional meteorological model coupled with an aerosol-chemistry component, to simulate various aspects of the dust phenomena over the Arabian Peninsula and Red Sea during a typical winter-time dust event that occurred in January 2009. The model predicted that the total amount of emitted dust was 18.3 Tg for the entire dust outburst period and that the two maximum daily rates were ~2.4 Tg/day and ~1.5 Tg/day, corresponding to two periods with the highest aerosol optical depth that were well captured by ground- and satellite-based observations. The model predicted that the dust plume was thick, extensive, andmore » mixed in a deep boundary layer at an altitude of 3-4 km. Its spatial distribution was modeled to be consistent with typical spatial patterns of dust emissions. We utilized MODIS-Aqua and Solar Village AERONET measurements of the aerosol optical depth (AOD) to evaluate the radiative impact of aerosols. Our results clearly indicated that the presence of dust particles in the atmosphere caused a significant reduction in the amount of solar radiation reaching the surface during the dust event. We also found that dust aerosols have significant impact on the energy and nutrient balances of the Red Sea. Our results showed that the simulated cooling under the dust plume reached 100 W/m2, which could have profound effects on both the sea surface temperature and circulation. Further analysis of dust generation and its spatial and temporal variability is extremely important for future projections and for better understanding of the climate and ecological history of the Red Sea.« less

Differential respirable dust related lung function effects between current and former South African coal miners.

PubMed

Naidoo, Rajen N; Robins, Thomas G; Seixas, Noah; Lalloo, Umesh G; Becklake, Margaret

2005-05-01

Dust-related dose-response decrements in lung function among coal miners have been reported in several studies, with varying magnitudes across populations. Few studies have compared differences between current and former coal miners. No studies on dose response relationships with lung function have been conducted in South African coal mines, one of the top three producers of coal internationally. The objectives of this study were (1) to describe the relationship between respirable dust exposure and lung function among current and former South African coal miners and to determine whether differential dust related effects were present between these employment categories; (2) to examine dust related dose response relationships, controlling for potential confounding by smoking and a history of tuberculosis (TB). Six hundred and eighty-four current and 188 ex-miners from three bituminous coal mines in Mpumalanga Province were studied. Interviews assessing work histories, smoking profiles and other risk factors were conducted. Work histories were also obtained from company records. Standardised spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from company-collected sampling and measurements conducted by the researchers. Regression models examined the associations of CDE with per cent predicted FEV(1) and FVC, controlling for smoking, past history of TB and employment status. A statistically significant decline in FEV(1) of 1.1 and 2.2 ml/mg-year/m(3) was found in representative 40-year-old, 1.7-m tall current and former miners, respectively. Significant differences were found between the highest and medium exposure categories. Ex-miners had a lower mean per cent predicted lung function than current miners for each cumulative exposure category, suggesting a "healthy worker" effect. Past history of TB contributed to 21 and 14% declines in per cent predicted FEV(1) and FVC, respectively. Thus, in this

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.

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

USGS Publications Warehouse

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

2012-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Effects of dust storm events on weekly clinic visits related to pulmonary tuberculosis disease in Minqin, China

NASA Astrophysics Data System (ADS)

Wang, Yun; Wang, Ruoyu; Ming, Jing; Liu, Guangxiu; Chen, Tuo; Liu, Xinfeng; Liu, Haixia; Zhen, Yunhe; Cheng, Guodong

2016-02-01

Pulmonary tuberculosis (PTB) is a major public health problem in China. Minqin, a Northwest county of China, has a very high number of annual PTB clinic visits and it is also known for its severe dust storms. The epidemic usually begins in February and ends in July, while the dust storms mainly occur throughout spring and early summer, thereby suggesting that there might be a close link between the causative agent of PTB and dust storms. We investigated the general impact of dust storms on PTB over time by analyzing the variation in weekly clinic visits in Minqin during 2005-2012. We used the Mann-Whitney-Pettitt test and a regression model to determine the seasonal periodicity of PTB and dust storms in a time series, as well as assessing the relationships between meteorological variables and weekly PTB clinic visits. After comparing the number of weekly PTB cases in Gansu province with dust storm events, we detected a clear link between the population dynamics of PTB and climate events, i.e., the onset of epidemics and dust storms (defined by an atmospheric index) occurred in almost the same mean week. Thus, particulate matter might be the cause of PTB outbreaks on dust storm days. It is highly likely that the significant decline in annual clinic visits was closely associated with improvements in the local environment, which prevented desertification and decreased the frequency of dust storm events. To the best of our knowledge, this is the first population-based study to provide clear evidence that a PTB epidemic was affected by dust storms in China, which may give insights into the association between this environmental problem and the evolution of epidemic disease.

Variability of North African hydroclimate during the last two climatic cycles: New insights from dust flux and provenance

NASA Astrophysics Data System (ADS)

Skonieczny, C.; McGee, D.; Bory, A. J. M.; Winckler, G.; Bradtmiller, L.; Bout-Roumazeilles, V.; Perala-Dewey, J.; Delattre, M.; Kinsley, C. W.; Polissar, P. J.; Malaizé, B.

2016-12-01

Every year, several hundred teragrams of dust are emitted from the Sahara and Sahel regions. These mineral particles sensitively track variations in atmospheric circulation and continental aridity. Sediments of the Northeastern Tropical Atlantic Ocean (NETAO) are fed by this intense dust supply and comprise unique long-term archives of past Saharan/Sahelian dust emissions. Past modifications of dust characteristics in these sedimentary archives can provide unique insights into changes in environmental conditions in source areas (aridity, weathering), as well as changes in atmospheric transport (wind direction and strength). Here we document changes in sediment supply to the NETAO using marine sediment core MD03-2705 (18°05N; 21°09W; 3085m water depth). This record is strategically located under the influence of seasonal dust plumes, and marine sediments of this area have revealed that past dust inputs were sensitive to global climate changes over the late Quaternary. We will focus our study on the last two climatic cycles (0-240ka), a period orbitally characterized by changes in the amplitude of both precession (MIS6-5 vs. MIS1-2) and ice volume (MIS 7 vs. MIS5). We will present, for the first time in this area, a continuous high-resolution record of dust, opal, carbonate and organic matter fluxes using 230Th-normalization. The constant flux proxy 230Thxs provides flux data that are not substantially affected by lateral advection or age model errors. These fluxes data will be complemented by grain-size, clay mineralogical and geochemical (major elements) analysis. By pairing dust flux measurements with complementary proxy data reflecting changes in aridity, wind strength and dust source, this study will provide a robust, continuous record of the magnitude and pacing of the North African hydroclimate variability through the last two climatic cycles. In particular, this long-term study will offer the opportunity to compare the well-documented North African climate

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

Spatial variability of excess mortality during prolonged dust events in a high-density city: a time-stratified spatial regression approach.

PubMed

Wong, Man Sing; Ho, Hung Chak; Yang, Lin; Shi, Wenzhong; Yang, Jinxin; Chan, Ta-Chien

2017-07-24

Dust events have long been recognized to be associated with a higher mortality risk. However, no study has investigated how prolonged dust events affect the spatial variability of mortality across districts in a downwind city. In this study, we applied a spatial regression approach to estimate the district-level mortality during two extreme dust events in Hong Kong. We compared spatial and non-spatial models to evaluate the ability of each regression to estimate mortality. We also compared prolonged dust events with non-dust events to determine the influences of community factors on mortality across the city. The density of a built environment (estimated by the sky view factor) had positive association with excess mortality in each district, while socioeconomic deprivation contributed by lower income and lower education induced higher mortality impact in each territory planning unit during a prolonged dust event. Based on the model comparison, spatial error modelling with the 1st order of queen contiguity consistently outperformed other models. The high-risk areas with higher increase in mortality were located in an urban high-density environment with higher socioeconomic deprivation. Our model design shows the ability to predict spatial variability of mortality risk during an extreme weather event that is not able to be estimated based on traditional time-series analysis or ecological studies. Our spatial protocol can be used for public health surveillance, sustainable planning and disaster preparation when relevant data are available.

Observed high aerosol loading during dust events in Delhi

NASA Astrophysics Data System (ADS)

Singh, Khem; Aggarwal, Shankar G.; Jha, Arvind K.; Singh, Nahar; Soni, Daya; Gupta, Prabhat K.

2012-07-01

The present study reports aerosol mass loadings and their chemical property during integrated campaign for aerosol and radiation budget (ICARB) in the month of March to May 2006, at NPL, New Delhi. The Thar Desert in Rajasthan is located on the western end of India and south-west of Delhi is hot and arid region with intense aeolian activity and transport of aerosol by the prevailing southwest-west summer wind. Several dust episodes were observed in Delhi during summer 2006. The dust storm peaked on 29th April, 1 ^{st} and 8 ^{th} May 2006, with very high suspended particulate matter (SPM) concentrations 1986μg/m ^{3}, 1735μg/m ^{3} and 1511μg/m ^{3}, respectively. The average concentration of SPM in the month of March, April and May 2006 was 338 μg/m ^{3}, 698 μg/m ^{3} and 732 μg/m ^{3}, respectively. The SPM filter samples were analysed for water-soluble major cations (Na ^{+}, Ca ^{2+}, K ^{+}, and Mg ^{2+}) by atomic absorption spectrophotometry (AAS). Na ^{+} and Ca ^{2+} contribute about 54% and 20%, respectively of the total identified cation mass, indicating that they were most abundant cations. Strong correlations between Na ^{+}, Ca ^{2+}, K ^{+}, and Mg ^{2+} suggest their soil and dust origin. Such a high particle concentration observed during dust events may also be useful for study the effect of these aerosols on communication medium.

Infrared emission from tidal disruption events - probing the pc-scale dust content around galactic nuclei

NASA Astrophysics Data System (ADS)

Lu, Wenbin; Kumar, Pawan; Evans, Neal J.

2016-05-01

Recent UV-optical surveys have been successful in finding tidal disruption events (TDEs), in which a star is tidally disrupted by a supermassive black hole (BH). These TDEs release a huge amount of radiation energy Erad ˜ 1051-1052 erg into the circum-nuclear medium. If the medium is dusty, most of the radiation energy will be absorbed by dust grains within ˜1 pc from the BH and re-radiated in the infrared. We calculate the dust emission light curve from a 1D radiative transfer model, taking into account the time-dependent heating, cooling and sublimation of dust grains. We show that the dust emission peaks at 3-10 μm and has typical luminosities between 1042 and 1043 erg s-1 (with sky covering factor of dusty clouds ranging from 0.1 to 1). This is detectable by current generation of telescopes. In the near future, James Webb Space Telescope will be able to perform photometric and spectroscopic measurements, in which silicate or polycyclic aromatic hydrocarbon features may be found. Dust grains are non-spherical and may be aligned with the magnetic field, so the dust emission may be significantly polarized. Observations at rest-frame wavelength ≥ 2 μm have only been reported from two TDE candidates, SDSS J0952+2143 and SwiftJ1644+57. Although consistent with the dust emission from TDEs, the mid-infrared fluxes of the two events may be from other sources. Long-term monitoring is needed to draw a firm conclusion. We also point out two nearby TDE candidates (ASASSN-14ae and -14li) where the dust emission may be currently detectable. Detection of dust infrared emission from TDEs would provide information regarding the dust content and its distribution in the central pc of non-active galactic nuclei, which is hard to probe otherwise.

Biopsychosocial Predictors of Fall Events among Older African Americans

PubMed Central

Nicklett, Emily Joy; Taylor, Robert Joseph; Rostant, Ola; Johnson, Kimson E.; Evans, Linnea

2016-01-01

This study identifies risk and protective factors for falls among older, community-dwelling African Americans. Drawing upon the biopsychosocial perspective (Engel, 1997), we conducted a series of sex- and age-adjusted multinomial logistic regression analyses to identify the correlates of fall events among older African Americans. Our sample consisted of 1,442 community-dwelling African Americans aged 65 and older, participating in the 2010-12 rounds of the Health and Retirement Study. Biophysical characteristics associated with greater relative risk of experiencing single and/or multiple falls included greater functional limitations, poorer self-rated health, poorer self-rated vision, chronic illnesses (high blood pressure, diabetes, cancer, lung disease, heart problems, stroke, and arthritis), greater chronic illness comorbidity, older age, and female sex. Physical activity was negatively associated with recurrent falls. Among the examined psychosocial characteristics, greater depressive symptoms were associated with greater relative risk of experiencing single and multiple fall events. Implications for clinicians and future studies are discussed. PMID:28285579

Martian Dust Cycle

NASA Astrophysics Data System (ADS)

Cantor, B. A.; James, P. B.

The Mars Observer Camera (MOC), aboard Mars Global Surveyor (MGS), has completed approximately 3 consecutive Martian years of global monitoring, since entering its mapping orbit on March 9, 1999. MOC observations have shown the important role that dust devils and dust storms play in the Martian dust cycle on time scales ranging from semi-diurnally to interannually. These dust events have been observed across much of the planet from the depths of Hellas basin to the summit of Arsia Mons and range in size from10s of meters across (dust devils) to planet encircling (global dust veils). Though dust devils occur throughout most of the Martian year, each hemisphere has a "dust devil season" that generally follows the subsolar latitude and appears to be repeatable from year-to-year. An exception is NW Amazonis, which has frequent, large dust devils throughout northern spring and summer. MOC observations show no evidence that dust devils cause or lead to dust storms, however, observations do suggest that dust storms can initiate dust devil activity. Dust devils also might play a role in maintaining the low background dust opacity of the Martian atmosphere. Dust storms occur almost daily with few exceptions, with 1000s occurring each year in the present Martian environment, dispelling the notion of a "Classical Dust Storm Season". However, there does appear to be an annual dust storm cycle, with storms developing in specific locations during certain seasons and that some individual storm events are repeatable from year-to-year. The majority of storms develop near the receding seasonal polar cap edge or along the corresponding polar hood boundaries in their respective hemispheres, but they also occur in the northern plains, the windward side of the large shield volcanoes, and in low laying regions such as Hellas, Argyre, and Chryse. The rarest of dust events are the "Great Storms" or "Global Events", of which only 6 (4 "planet encircling" and 2 "global") have been observed

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

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

DeFlorio, Mike; Ghan, Steven J.; Singh, Balwinder

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

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.

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

African Dust Fertilizing the Amazon Rainforest: An Assessment with Seven-year Record of CALIOP Measurements

NASA Astrophysics Data System (ADS)

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

2014-12-01

The productivity of Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of transported African dust in boreal winter and spring is considered an important nutrient input for the Amazon Basin, though its magnitude is not well qunatified. This study provides a remote sensing observation-based estimate of dust deposition in the Amazon Basin using a 7-year (2007-2013) record of three dimensional (3D) distributions of aerosol in both cloud-free and above-cloud conditions from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). It is estimated that the 7-year average of dust deposition into the Amazon Basin amounts to 15.1 ~ 32.1 Tg a-1 (Tg = 1012 g). This imported dust could provide 0.012 ~ 0.025 Tg P a-1 or equivalent to 12 ~ 26 g P ha-1 a-1 to fertilize the Amazon rainforest, which largely compensates the hydrological loss of P. The CLAIOP-based estimate agrees better with estimates from in-situ measurements and model simulations than what has been reported in literature. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3D nature of CALIOP aerosol measurements. The trans-Atlantic transport and deposition of dust shows strong interannual variations that are found to correlate with the North Atlantic Oscillation index in the winter season and anticorrelate with the prior-year Sahel Precipitation Index on an annual basis. Uncertainties associated with the estimate will also be discussed.

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

NASA Astrophysics Data System (ADS)

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

2011-12-01

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

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

USGS Publications Warehouse

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

2010-01-01

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

Performance of distributed bagged stone dust barrier in combating coal-dust explosions

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

Plessis, J.J.L. du; Vassard, P.S.

1999-07-01

The Kloppersbos Research Facility of the CSIR's Division of Mining Technology has developed a new method of building stone dust barriers. The new barrier makes use of a previous concept of containing stone dust in a bag, but incorporates a new method of rupturing the bag. This was achieved by adapting the closing mechanism and by balancing the stone dust content with the void in the bag. The bagged barrier was extensively tested in the 200-m test gallery. During these tests, it became evident that these bags could be made to rupture and spread stone dust when subjected to smallermore » forces than those required for the most commonly used passive barrier, the Polish light barrier. To validate this, as well as to gain international acceptance of this new barrier, tests were conducted in the German experimental mine, DMT Tremonia, Dortmund. The barrier was evaluated against numerous methane-initiated coal-dust explosions. The paper describes the successful inhibition of coal-dust explosions at Kloppersbos and DMT tremonia. The barrier has been proven successfully for static pressures of 44 to 82 kpa, dynamic pressures of 12 to 36 kpa and for flame speeds as low as 23 m/s. This barrier is now accepted by the South African government and has been implemented in numerous South African collieries.« less

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

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

Case study of dust event sources from the Gobi and Taklamakan deserts: An investigation of the horizontal evolution and topographical effect using numerical modeling and remote sensing.

PubMed

Fan, Jin; Yue, Xiaoying; Sun, Qinghua; Wang, Shigong

2017-06-01

A severe dust event occurred from April 23 to April 27, 2014, in East Asia. A state-of-the-art online atmospheric chemistry model, WRF/Chem, was combined with a dust model, GOCART, to better understand the entire process of this event. The natural color images and aerosol optical depth (AOD) over the dust source region are derived from datasets of moderate resolution imaging spectroradiometer (MODIS) loaded on a NASA Aqua satellite to trace the dust variation and to verify the model results. Several meteorological conditions, such as pressure, temperature, wind vectors and relative humidity, are used to analyze meteorological dynamic. The results suggest that the dust emission occurred only on April 23 and 24, although this event lasted for 5days. The Gobi Desert was the main source for this event, and the Taklamakan Desert played no important role. This study also suggested that the landform of the source region could remarkably interfere with a dust event. The Tarim Basin has a topographical effect as a "dust reservoir" and can store unsettled dust, which can be released again as a second source, making a dust event longer and heavier. Copyright © 2016. Published by Elsevier B.V.

Pancam and Microscopic Imager observations of dust on the Spirit Rover: Cleaning events, spectral properties, and aggregates

USGS Publications Warehouse

Vaughan, Alicia F.; Johnson, Jeffrey R.; Herkenhoff, Kenneth E.; Sullivan, Robert; Landis, Geoffrey A.; Goetz, Walter; Madsen, Morten B.

2010-01-01

This work describes dust deposits on the Spirit Rover over 2000 sols through examination of Pancam and Microscopic Imager observations of specific locations on the rover body, including portions of the solar array, Pancam and Mini-TES calibration targets, and the magnets. This data set reveals the three "cleaning events" experienced by Spirit to date, the spectral properties of dust, and the tendency of dust particles to form aggregates 100 um and larger.

The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Bacterial diversity and composition during rain events with and without Saharan dust influence reaching a high mountain lake in the Alps.

PubMed

Peter, Hannes; Hörtnagl, Paul; Reche, Isabel; Sommaruga, Ruben

2014-12-01

The diversity of airborne microorganisms that potentially reach aquatic ecosystems during rain events is poorly explored. Here, we used a culture-independent approach to characterize bacterial assemblages during rain events with and without Saharan dust influence arriving to a high mountain lake in the Austrian Alps. Bacterial assemblage composition differed significantly between samples with and without Saharan dust influence. Although alpha diversity indices were within the same range in both sample categories, rain events with Atlantic or continental origins were dominated by Betaproteobacteria, whereas those with Saharan dust intrusions were dominated by Gammaproteobacteria. The high diversity and evenness observed in all samples suggests that different sources of bacteria contributed to the airborne assemblage collected at the lake shore. During experiments with bacterial assemblages collected during rain events with Saharan dust influence, cell numbers rapidly increased in sterile lake water from initially ∼3 × 103 cell ml-1 to 3.6-11.1 x105 cells ml-1 within 4-5 days, and initially, rare taxa dominated at the end of the experiment. Our study documents the dispersal of viable bacteria associated to Saharan dust intrusions travelling northwards as far as 47° latitude.

Asian Dust Storm Events of 2001 and Associated Pollution Observed in New England by the AIRMAP Monitoring Network

NASA Astrophysics Data System (ADS)

Debell, L. J.; Vozzella, M. E.; Talbot, R. W.; Dibb, J. E.

2002-12-01

The Atmospheric Investigation, Regional Modeling, Analysis and Prediction (AIRMAP) program is operating 4 monitoring sites in New Hampshire, located at Fort Constitution (FC)(43.07oN, 70.71oW, 5m elevation), Thompson Farm (TF) (43.11oN, 70.95oW, 21m elevation), Castle Springs (CS) (43.75oN,71.35oW, 406m elevation) and Mount Washington (MW)(44.267oN, 71.30oW, 1909m elevation). Three chemically distinct, statistically extreme, regional scale dust aerosol events were observed at all four AIRMAP monitoring stations in NH between 4/18/01 and 5/13/01 (UTC). All three events, at all four sites, had days where the 24 hr bulk aerosol samples had Ca2+ concentrations that exceeded at least the 95th percentile of the site-specific, multi-year datasets. NO3- and SO42- were also enhanced above typical levels, ranging from above the 75th to above the 99th percentile. During all three events, mixing ratios of the gas phase pollutants O3 and CO were compared to mixing ratios on either side of the events. During event 1,enhancements above background levels were approximately 130 ppbv for CO and 30 ppbv for O3, very similar to the CO values in apparent Asian dust plumes sampled over Colorado at 6-7 km by aircraft measurements (http://www.cmdl.noaa.gov/info/asiandust.html); enhancements during events 2 and 3 were similar to event 1. The maximum elemental carbon value ever observed at TF, 0.97 μg/m3, occurred during the peak day of event 1. Elemental carbon was not substantially elevated during event 2 and no data were collected during event 3. Elemental ratios, determined by PIXE, on filters from events 1 and 3 were compared pairwise to each other and to published samples attributed to Asian dust storms. The AIRMAP samples collected on the same date at different sites showed good statistical agreement whereas samples collected at the same site on different dates show only moderate correlation. Of 17 published samples of Asian dust storm aerosol, collected well outside of the major

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

NASA Astrophysics Data System (ADS)

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

2006-12-01

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

Quantification of the lithogenic carbon pump following a simulated dust-deposition event in large mesocosms

NASA Astrophysics Data System (ADS)

Bressac, M.; Guieu, C.; Doxaran, D.; Bourrin, F.; Desboeufs, K.; Leblond, N.; Ridame, C.

2014-02-01

Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC-dust association that occurs within the upper ocean is required in order to refine the "ballast hypothesis". In the framework of the DUNE (a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem) project, two artificial seedings were performed seven days apart within large mesocosms. A suite of optical and biogeochemical measurements were used to quantify surface POC export following simulated dust events within a low-nutrient, low-chlorophyll ecosystem. The two successive seedings led to a 2.3-6.7-fold higher POC flux than the POC flux observed in controlled mesocosms. A simple linear regression analysis revealed that the lithogenic fluxes explained more than 85% of the variance in POC fluxes. On the scale of a dust-deposition event, we estimated that 42-50% of POC fluxes were strictly associated with lithogenic particles (through aggregation and most probably sorption processes). Lithogenic ballasting also likely impacted the remaining POC fraction which resulted from the fertilization effect. The observations support the "ballast hypothesis" and provide a quantitative estimation of the surface POC export abiotically triggered by dust deposition. In this work, we demonstrate that the strength of such a "lithogenic carbon pump" depends on the biogeochemical conditions of the water column at the time of deposition. Based on these observations, we suggest that this lithogenic carbon pump could represent a major component of the biological pump in oceanic areas subjected to intense atmospheric forcing.

Dust Cloud, Mid Atlantic Ocean

NASA Technical Reports Server (NTRS)

1991-01-01

This view of a dust cloud from a Sahara Desert, North Africa dust storm was taken over the Mid Atlantic Ocean, some 1700 miles from the African coast (24.5N, 45.0W). Dust, sand and other particulate matter from arid regions is frequently stirred up by fast blowing desert winds and carried aloft to high altitudes where it may be transported great distances, sometimes as much as half way around the world.

Hospital admissions for asthma and acute bronchitis in El Paso, Texas: do age, sex, and insurance status modify the effects of dust and low wind events?

PubMed

Grineski, Sara E; Staniswalis, Joan G; Bulathsinhala, Priyangi; Peng, Yanlei; Gill, Thomas E

2011-11-01

El Paso County (Texas) is prone to still air inversions and is one of the dust "hot spots" in North America. In this context, we examined the sub-lethal effects of airborne dust and low wind events on human respiratory health (i.e., asthma and acute bronchitis) between 2000 and 2003, when 110 dust and 157 low wind events occurred. Because environmental conditions may not affect everyone the same, we explored the effects of dust and low wind within three age groups (children, adults, and the elderly), testing for effect modifications by sex and insurance status, while controlling for weather and air pollutants. We used a case-crossover design using events matched with referent days on the same day-of-the-week, month, and year with conditional logistic regression to estimate the probability of hospital admission, while controlling for apparent temperature (lag 1), nitrogen dioxide, and particulate matter of 2.5μm or less. Children (aged 1-17) were 1.19 (95% confidence interval: 1.00-1.41) times more likely to be hospitalized for asthma three days after a low wind event, and 1.33 (95% CI: 1.01-1.75) times more likely to be hospitalized for acute bronchitis one day after a dust event than on a clear day. Girls were more sensitive to acute bronchitis hospitalizations after dust events (1.83, 95% CI: 1.09-3.08) than boys, but less sensitive than boys to acute bronchitis hospitalizations after low wind events (0.68, 95% CI: 0.46-1.00). We found general trends with regard to dust and low wind events being associated with increased odds of hospitalization for asthma and bronchitis amongst all ages and adults (aged 18-64). Adults covered by Medicaid and adults without health insurance had higher risks of hospitalization for asthma and acute bronchitis after both low wind and dust events. Results suggest that there were respiratory health effects associated with dust and low wind events in El Paso, with stronger impacts among children and poor adults. Girls and boys with

Hospital admissions for asthma and acute bronchitis in El Paso, Texas: Do age, sex, and insurance status modify the effects of dust and low wind events?

PubMed Central

Staniswalis, Joan G.; Bulathsinhala, Priyangi; Peng, Yanlei; Gill, Thomas E.

2013-01-01

Background El Paso County (Texas) is prone to still air inversions and is one of the dust “hot spots” in North America. In this context, we examined the sub-lethal effects of airborne dust and low wind events on human respiratory health (i.e., asthma and acute bronchitis) between 2000 and 2003, when 110 dust and 157 low wind events occurred. Because environmental conditions may not affect everyone the same, we explored the effects of dust and low wind within three age groups (children, adults, and the elderly), testing for effect modifications by sex and insurance status, while controlling for weather and air pollutants. Methods We used a case-crossover design using events matched with referent days on the same day-of-the-week, month, and year with conditional logistic regression to estimate the probability of hospital admission, while controlling for apparent temperature (lag 1), nitrogen dioxide, and particulate matter of 2.5 micrometers or less. Results Children (aged 1–17) were 1.19 (95% confidence interval: 1.00–1.41) times more likely to be hospitalized for asthma three days after a low wind event, and 1.33 (95% CI: 1.01–1.75) times more likely to be hospitalized for acute bronchitis one day after a dust event than on a clear day. Girls were more sensitive to acute bronchitis hospitalizations after dust events (1.83, 95% CI: 1.09–3.08) than boys, but less sensitive than boys to acute bronchitis hospitalizations after low wind events (0.68, 95% CI: 0.46–1.00). We found general trends with regard to dust and low wind events being associated with increased odds of hospitalization for asthma and bronchitis amongst all ages and adults (aged 18–64). Adults covered by Medicaid and adults without health insurance had higher risks of hospitalization for asthma and acute bronchitis after both low wind and dust event Conclusions Results suggest that there were respiratory health effects associated with dust and low wind events in El Paso, with stronger

Sr-Nd-Hf isotopic fingerprinting of transatlantic dust derived from North Africa

NASA Astrophysics Data System (ADS)

Zhao, Wancang; Balsam, William; Williams, Earle; Long, Xiaoyong; Ji, Junfeng

2018-03-01

Long-range transport of African dust plays an important role in understanding dust-climate relationships including dust source areas, dust pathways and associated atmospheric and/or oceanic processes. Clay-sized Sr-Nd-Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust. We investigated the clay-sized Sr-Nd-Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. The transects are from Mali, Niger/Benin/Togo, Egypt and Morocco. Our results show that the Mali transect on the West African Craton (WAC) produces lower εNd (εNd-mean = -16.38) and εHf (εHf-mean = -9.59) values than the other three transects. The Egyptian transect exhibits the lowest 87Sr/86Sr ratios (87Sr/86Srmean = 0.709842), the highest εHf (εHf-mean = -0.34) and εNd values of the four transects. Comparison of the clay-sized Sr-Nd-Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust's provenance is primarily the western Sahel and Sahara as well as the central Sahel. Summer emission dust is derived mainly from the western Sahel and Sahara regions. The source of transatlantic dust in spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd-Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through the spring and into the summer. The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions.

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.

Communication plan for windblown dust.

DOT National Transportation Integrated Search

2015-05-01

Windblown dust events occur in Arizona, and blowing dust has been considered a contributing factor to serious crashes on the : segment of Interstate 10 (I10) between Phoenix and Tucson, as well as on other Arizona roadways. Arizonas dust events...

African Dust Aerosols as Atmospheric Ice Nuclei

NASA Technical Reports Server (NTRS)

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

2003-01-01

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

Identification of dust source regions and dust emission trends across North Africa and the Middle East using MISR satellite observations

NASA Astrophysics Data System (ADS)

Yu, Y.; Kalashnikova, O. V.; Garay, M. J.; Notaro, M.

2017-12-01

Global arid and semi-arid regions supply 1100 to 5000 Tg of Aeolian dust to the atmosphere each year, primarily from North Africa and secondarily from the Middle East. Previous dust source identification methods, based on either remotely-sensed aerosol optical depth (AOD) or dust activity, yield distinct dust source maps, largely due to the limitations in each method and remote-sensing product. Here we apply a novel motion-based method for dust source identification. Dust plume thickness and motion vectors from Multi-angle Imaging SpectroRadiometer (MISR) Cloud Motion Vector Product (CMVP) are examined to identify the regions with high frequency of fast moving-dust plumes, by season. According to MISR CMVP, Bodele depression is the most important dust source across North Africa, consistent with previous studies. Seasonal variability of dust emission across the North Africa is largely driven by climatology of wind and precipitation, featuring the influence of Sharav Cyclone and western African monsoon. In the Middle East, Iraq, Kuwait, and eastern Saudi Arabia are identified as dust source regions, especially during summer months, when the Middle Eastern Shamal wind is active. Furthermore, dust emission trend at each dust source are diagnosed from the motion-based dust source dataset. Increase in dust emission from the Fertile Crescent, Sahel, and eastern African dust sources are identified from MISR CMVP, implying potential contribution from these dust sources to the upward trend in AOD and dust AOD over the Middle East in the 21st century. By comparing with various dust source identification studies, we conclude that the motion-based identification of dust sources is an encouraging alternative and compliment to the AOD-only source identification method.

Tropical cyclone activity enhanced by Sahara greening and reduced dust emissions during the African Humid Period.

PubMed

Pausata, Francesco S R; Emanuel, Kerry A; Chiacchio, Marc; Diro, Gulilat T; Zhang, Qiong; Sushama, Laxmi; Stager, J Curt; Donnelly, Jeffrey P

2017-06-13

Tropical cyclones (TCs) can have devastating socioeconomic impacts. Understanding the nature and causes of their variability is of paramount importance for society. However, historical records of TCs are too short to fully characterize such changes and paleo-sediment archives of Holocene TC activity are temporally and geographically sparse. Thus, it is of interest to apply physical modeling to understanding TC variability under different climate conditions. Here we investigate global TC activity during a warm climate state (mid-Holocene, 6,000 yBP) characterized by increased boreal summer insolation, a vegetated Sahara, and reduced dust emissions. We analyze a set of sensitivity experiments in which not only solar insolation changes are varied but also vegetation and dust concentrations. Our results show that the greening of the Sahara and reduced dust loadings lead to more favorable conditions for tropical cyclone development compared with the orbital forcing alone. In particular, the strengthening of the West African Monsoon induced by the Sahara greening triggers a change in atmospheric circulation that affects the entire tropics. Furthermore, whereas previous studies suggest lower TC activity despite stronger summer insolation and warmer sea surface temperature in the Northern Hemisphere, accounting for the Sahara greening and reduced dust concentrations leads instead to an increase of TC activity in both hemispheres, particularly over the Caribbean basin and East Coast of North America. Our study highlights the importance of regional changes in land cover and dust concentrations in affecting the potential intensity and genesis of past TCs and suggests that both factors may have appreciable influence on TC activity in a future warmer climate.

Tropical cyclone activity enhanced by Sahara greening and reduced dust emissions during the African Humid Period

NASA Astrophysics Data System (ADS)

Pausata, Francesco S. R.; Emanuel, Kerry A.; Chiacchio, Marc; Diro, Gulilat T.; Zhang, Qiong; Sushama, Laxmi; Stager, J. Curt; Donnelly, Jeffrey P.

2017-06-01

Tropical cyclones (TCs) can have devastating socioeconomic impacts. Understanding the nature and causes of their variability is of paramount importance for society. However, historical records of TCs are too short to fully characterize such changes and paleo-sediment archives of Holocene TC activity are temporally and geographically sparse. Thus, it is of interest to apply physical modeling to understanding TC variability under different climate conditions. Here we investigate global TC activity during a warm climate state (mid-Holocene, 6,000 yBP) characterized by increased boreal summer insolation, a vegetated Sahara, and reduced dust emissions. We analyze a set of sensitivity experiments in which not only solar insolation changes are varied but also vegetation and dust concentrations. Our results show that the greening of the Sahara and reduced dust loadings lead to more favorable conditions for tropical cyclone development compared with the orbital forcing alone. In particular, the strengthening of the West African Monsoon induced by the Sahara greening triggers a change in atmospheric circulation that affects the entire tropics. Furthermore, whereas previous studies suggest lower TC activity despite stronger summer insolation and warmer sea surface temperature in the Northern Hemisphere, accounting for the Sahara greening and reduced dust concentrations leads instead to an increase of TC activity in both hemispheres, particularly over the Caribbean basin and East Coast of North America. Our study highlights the importance of regional changes in land cover and dust concentrations in affecting the potential intensity and genesis of past TCs and suggests that both factors may have appreciable influence on TC activity in a future warmer climate.

Enhancing weak transient signals in SEVIRI false colour imagery: application to dust source detection in southern Africa

NASA Astrophysics Data System (ADS)

Murray, Jon E.; Brindley, Helen E.; Bryant, Robert G.; Russell, Jacqui E.; Jenkins, Katherine F.

2013-04-01

Understanding the processes governing the availability and entrainment of mineral dust into the atmosphere requires dust sources to be identified and the evolution of dust events to be monitored. To achieve this aim a wide range of approaches have been developed utilising observations from a variety of different satellite sensors. Global maps of source regions and their relative strengths have been derived from instruments in low Earth orbit (e.g. Total Ozone Monitoring Spectrometer (TOMS) (Prospero et al., 2002), MODerate resolution Imaging Spectrometer (MODIS) (Ginoux et al., 2012)). Instruments such as MODIS can also be used to improve precise source location (Baddock et al., 2009) but the information available is restricted to the satellite overpass times which may not be coincident with active dust emission from the source. Hence, at a regional scale, some of the more successful approaches used to characterise the activity of different sources use high temporal resolution data available from instruments in geostationary orbit. For example, the widely used red-green-blue (RGB) dust scheme developed by Lensky and Rosenfeld (2008) (hereafter LR2008) makes use of observations from selected thermal channels of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) in a false colour rendering scheme in which dust appears pink. This scheme has provided the basis for numerous studies of north African dust sources and factors governing their activation (e.g. Schepanski et al., 2007, 2009, 2012). However, the LR2008 imagery can fail to identify dust events due to the effects of atmospheric moisture, variations in dust layer height and optical properties, and surface conditions (Brindley et al., 2012). Here we introduce a new method designed to circumvent some of these issues and enhance the signature of dust events using observations from SEVIRI. The approach involves the derivation of a composite clear-sky signal for selected channels on an individual time-step and

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.

The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

NASA Astrophysics Data System (ADS)

Wiacek, A.; Peter, T.; Lohmann, U.

2010-02-01

This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳-40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to

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

A simulation of Asian dust events observed from 20 to 29 December 2009 in Korea by using ADAM2

NASA Astrophysics Data System (ADS)

Park, Soon-Ung; Choe, Anna; Park, Moon-Soo

2013-01-01

The Asian dust Aerosol Model 2 (ADAM2) with the MM5 meteorological model has been employed to study long-range transport process of Asian dust and to estimate dust emission, deposition (wet and dry) and concentration over the Asian dust source region and the downwind regions for dust events observed in Korea during the period of 20-29 December 2009, which is one of the dust events chosen by the 3rd Meeting of Working Group for Joint Research on Dust Sand Storm among Mongolia, China, Japan and Korea to study intensively for the development of an early warning system in Asia. It is found that the model simulates quite well the starting and ending times of dust events and the peak dust concentrations with their occurrence times both in the source region and downwind regions. The dust emission in the dust source region is found to be associated with a developing synoptic weather system accompanied with strong surface winds over the source region that usually travels east to southeastward across the source region and then turns to move northeastward toward the north western Pacific Ocean. The dust emitted in the source region is found to be split into two parts: one is transported southeastward to the East China Sea in front of the surface high pressure system and experiencing enhanced deposition due to the sinking motion induced by the southeastward traveling the surface high pressure system whereas, the other moves northeastward toward the surface low pressure system and then lifted upward to form a upper-level high dust concentration layer that results in a favorable condition for the long-range transport of dust. It is also found that the maximum ten-day total dust emission of about 23 t km-2 occurs in the domain Northwestern China (NWC). However, the maximum ten-day total dust deposition of 21 t km-2 with the maximum mean surface concentration of 555 μg m-3 and the column integrated mean concentration of 2.9 g m-2 occurs in the domain Central-northern China (CNC

DASCH ON KU Cyg: A {approx} 5 YEAR DUST ACCRETION EVENT IN {approx} 1900

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

Tang Sumin; Grindlay, Jonathan; Los, Edward

2011-09-01

KU Cyg is an eclipsing binary consisting of an F-type star accreting through a large accretion disk from a K5III red giant. Here we present the discovery of a 5 year dip around 1900 found from its 100 year DASCH light curve. It showed a {approx}0.5 mag slow fading from 1899 to 1903 and brightened back around 1904 on a relatively shorter timescale. The light curve shape of the 1899-1904 fading-brightening event differs from the dust production and dispersion process observed in R Coronae Borealis stars, which usually has a faster fading and slower recovery, and for KU Cyg ismore » probably related to the accretion disk surrounding the F star. The slow fading in KU Cyg is probably caused by increases in dust extinction in the disk, and the subsequent quick brightening may be due to the evaporation of dust transported inward through the disk. The extinction excess which caused the fading may arise from increased mass transfer rate in the system or from dust clump ejections from the K giant.« less

African aerosols and Atlantic tropical cyclone activities

NASA Astrophysics Data System (ADS)

Kafatos, M.; Sun, D.; Sahoo, A.

2006-12-01

Previous studies have shown that the Atlantic basin major hurricane (MH) activity is associated with western Sahelian monsoon rainfall, while rainfall in the Sahel is found to be highly anti-correlated with the African dust storms. So if the Atlantic basin MH activity may be anti-correlated with the African dust aerosols? In order to investigate the relationship between the African dust and the tropical cyclone (including both tropical storms and hurricanes) activities in the Atlantic basin, we explore how the African dust may link to Atlantic TC activity by using the long-term (1982-2005) NCEP Reynolds sea surface temperature (SST) product, and tropical cyclone (TC) data from the National Hurricane Center Best Track Files, and the TOMS aerosol index (AI) data, because the TOMS AI positive values are associated with UV-absorbing aerosols, like dust and smoke. Although no significant negative correlation between the TOMS AI and the Atlantic TC or MH frequency and duration is found, the initial locations of the Atlantic tropical cyclones did occur over the ocean where the aerosol loading was low. Our analysis shows that SST over the north tropical Atlantic ocean is anti-correlated with the TOMS aerosol index. This may be due to the radiative forcing of the aerosols. The effects of the dust aerosols carried across the West African region led to a lowering of SST and therefore inhibited tropical cyclogenesis. During 2005, the aerosol loading along the western African coast was unusually low, while the SST over the main development region (MDR) was abnormally high, and the Atlantic TC/hurricane activities became record strong. We propose future observations to test these results.

Transpacific Transport of Dust to North American High-Elevation Sites: Integrated Dataset and Model Outputs

NASA Astrophysics Data System (ADS)

Kassianov, E.; Pekour, M. S.; Flynn, C. J.; Berg, L. K.; Beranek, J.; Zelenyuk, A.; Zhao, C.; Leung, L. R.; Ma, P. L.; Riihimaki, L.; Fast, J. D.; Barnard, J.; Hallar, G. G.; McCubbin, I.; Eloranta, E. W.; McComiskey, A. C.; Rasch, P. J.

2017-12-01

Understanding the effects of dust on the regional and global climate requires detailed information on particle size distributions and their changes with distance from the source. Awareness is now growing about the tendency of the dust coarse mode with moderate ( 3.5 µm) volume median diameter (VMD) to be rather insensitive to complex removal processes associated with long-range transport of dust from the main sources. Our study, with a focus on the transpacific transport of dust, demonstrates that the impact of coarse mode aerosol (VMD 3µm) is well defined at the high-elevation mountain-top Storm Peak Laboratory (SPL, about 3.2 km MSL) and nearby Atmospheric Radiation Measurement (ARM) Climate Research Facility Mobile Facility (AMF) during March 2011. Significant amounts of coarse mode aerosol are also found at the nearest Aerosol Robotic Network (AERONET) site. Outputs from the high-resolution Weather Research and Forecasting (WRF) Model coupled with chemistry (WRF-Chem) show that the major dust event is likely associated with transpacific transport of Asian and African plumes. Satellite data, including the Moderate Resolution Imaging Spectroradiometer (MODIS) and Multiangle Imaging SpectroRadiometer (MISR) aerosol optical depth (AOD) and plume height from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar data provide the observational support of the WRF-Chem simulations. Our study complements previous findings by indicating that the quasi-static nature of the coarse mode appears to be a reasonable approximation for Asian and African dust despite expected frequent orographic precipitation over mountainous regions in the western United States.

Tropical cyclone activity enhanced by Sahara greening and reduced dust emissions during the African Humid Period

PubMed Central

Pausata, Francesco S. R.; Emanuel, Kerry A.; Chiacchio, Marc; Diro, Gulilat T.; Zhang, Qiong; Sushama, Laxmi; Stager, J. Curt; Donnelly, Jeffrey P.

2017-01-01

Tropical cyclones (TCs) can have devastating socioeconomic impacts. Understanding the nature and causes of their variability is of paramount importance for society. However, historical records of TCs are too short to fully characterize such changes and paleo-sediment archives of Holocene TC activity are temporally and geographically sparse. Thus, it is of interest to apply physical modeling to understanding TC variability under different climate conditions. Here we investigate global TC activity during a warm climate state (mid-Holocene, 6,000 yBP) characterized by increased boreal summer insolation, a vegetated Sahara, and reduced dust emissions. We analyze a set of sensitivity experiments in which not only solar insolation changes are varied but also vegetation and dust concentrations. Our results show that the greening of the Sahara and reduced dust loadings lead to more favorable conditions for tropical cyclone development compared with the orbital forcing alone. In particular, the strengthening of the West African Monsoon induced by the Sahara greening triggers a change in atmospheric circulation that affects the entire tropics. Furthermore, whereas previous studies suggest lower TC activity despite stronger summer insolation and warmer sea surface temperature in the Northern Hemisphere, accounting for the Sahara greening and reduced dust concentrations leads instead to an increase of TC activity in both hemispheres, particularly over the Caribbean basin and East Coast of North America. Our study highlights the importance of regional changes in land cover and dust concentrations in affecting the potential intensity and genesis of past TCs and suggests that both factors may have appreciable influence on TC activity in a future warmer climate. PMID:28559352

Interannual Modulation of Subtropical Atlantic Boreal Summer Dust Variability by ENSO

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

DeFlorio, Mike; Goodwin, Ian D.; Cayan, Dan

2016-01-01

Dust variability in the climate system has been studied for several decades, yet there remains an incomplete understanding of the dynamical mechanisms controlling interannual and decadal variations in dust transport. The sparseness of multi-year observational datasets has limited our understanding of the relationship between climate variations and atmospheric dust. We use available observations and a century-length fully coupled Community Earth System Model (CESM) simulation to show that the El Niño- Southern Oscillation (ENSO) exerts a control on North African dust transport during boreal summer. In CESM, this relationship is stronger over the dusty tropical North Atlantic than near Barbados, onemore » of the few sites having a multi-decadal observed record. During strong La Niña summers in CESM, a statistically significant increase in lower tropospheric easterly wind is associated with an increase in North African dust transport over the Atlantic. Barbados dust and Pacific SST variability are only weakly correlated in both observations and CESM, suggesting that other processes are controlling the crossbasin variability of dust. We also use our CESM simulation to show that the relationship between downstream North African dust transport and ENSO fluctuates on multidecadal timescales and may be modulated by the North Atlantic Oscillation (NAO). Our findings indicate that existing observations of dust over the tropical North Atlantic are not extensive enough to completely describe the variability of dust and dust transport, and demonstrate the importance of global models to supplement and interpret observational records.« less

Injection of mineral dust into the free troposphere during fire events observed with polarization lidar at Limassol, Cyprus

NASA Astrophysics Data System (ADS)

Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Hadjimitsis, D.

2014-11-01

Four-year observations (2010-2014) with EARLINET polarization lidar and AERONET sun/sky photometer at Limassol (34.7° N, 33° E), Cyprus, were used to study the soil dust content in lofted fire smoke plumes advected from Turkey. This first systematic attempt to characterize less than 3-day-old smoke plumes in terms of particle linear depolarization ratio (PDR), measured with lidar, contributes to the more general effort to properly describe the life cycle of free-tropospheric smoke-dust mixtures from the emission event to phases of long-range transport (> 4 days after emission). We found significant PDR differences with values from 9 to 18% in lofted aerosol layers when Turkish fires contributed to the aerosol burden and of 3-13 % when Turkish fires were absent. High Ångström exponents of 1.4-2.2 during all these events with lofted smoke layers, occurring between 1 and 3 km height, suggest the absence of a pronounced particle coarse mode. When plotted vs. travel time (spatial distance between Limassol and last fire area), PDR decreased strongly from initial values around 16-18% (1 day travel) to 4-8% after 4 days of travel caused by deposition processes. This behavior was found to be in close agreement with findings described in the literature. Computation of particle extinction coefficient and mass concentrations, derived from the lidar observations, separately for fine-mode dust, coarse-mode dust, and non-dust aerosol components show extinction-related dust fractions on the order of 10% (for PDR =4%, travel times > 4 days) and 50% (PDR =15%, 1 day travel time) and respective mass-related dust fractions of 25% (PDR =4%) to 80% (PDR =15%). Biomass burning should therefore be considered as another source of free tropospheric soil dust.

Injection of mineral dust into the free troposphere during fire events observed with polarization lidar at Limassol, Cyprus

NASA Astrophysics Data System (ADS)

Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Hadjimitsis, D.

2014-06-01

Four-year observations (2010-2014) with EARLINET polarization lidar and AERONET sun/sky photometer at Limassol (34.7° N, 33° E), Cyprus, were used to study the soil dust content in lofted fire smoke plumes advected from Turkey. This first systematic attempt to characterize less than 3 days old smoke plumes in terms of particle depolarization contributes to the more general effort to properly describe the life cycle of free-tropospheric smoke-dust mixtures from the emission event to phases of long-range transport (>4 days after emission). We found significant differences in the particle depolarization ratio (PDR) with values from 9-18% in lofted aerosol layers when Turkish fires contributed to the aerosol burden and of 3-13% when Turkish fires were absent. High Ångström exponents of 1.4-2.2 during all these events with lofted smoke layers, occuring between 1 and 3 km height, suggest the absence of a pronounced particle coarse mode. When plotted vs. the travel time (spatial distance between Limassol and last fire area), PDR decreased strongly from initial values around 16-18% (one day travel) to 4-8% after 4 days of travel caused by deposition processes. This behavior was found to be in close agreement with the literature. Computation of particle extinction coefficient and mass concentrations, separately for fine-mode dust, coarse-mode dust, and non-dust aerosol components show extinction-related dust fractions of the order of 10% (for PDR = 4%, travel times >4 days) and 50% (PDR = 15%, one day travel time) and mass-related dust fractions of 25% (PDR = 4%) to 80% (PDR = 15%). Biomass burning should be considered as another source of free tropospheric soil dust.

The concentration, source and deposition flux of ammonium and nitrate in atmospheric particles during dust events at a coastal site in northern China

NASA Astrophysics Data System (ADS)

Qi, Jianhua; Liu, Xiaohuan; Yao, Xiaohong; Zhang, Ruifeng; Chen, Xiaojing; Lin, Xuehui; Gao, Huiwang; Liu, Ruhai

2018-01-01

Asian dust has been reported to carry anthropogenic reactive nitrogen during transport from source areas to the oceans. In this study, we attempted to characterize NH4+ and NO3- in atmospheric particles collected at a coastal site in northern China during spring dust events from 2008 to 2011. Based on the mass concentrations of NH4+ and NO3- in each total suspended particle (TSP) sample, the samples can be classified into increasing or decreasing types. In Category 1, the concentrations of NH4+ and NO3- were 20-440 % higher in dust day samples relative to samples collected immediately before or after a dust event. These concentrations decreased by 10-75 % in the dust day samples in Categories 2 and 3. Back trajectory analysis suggested that multiple factors, such as the transport distance prior to the reception site, the mixing layer depth on the transport route and the residence time across highly polluted regions, might affect the concentrations of NH4+ and NO3-. NH4+ in the dust day samples was likely either in the form of ammonium salts existing separately to dust aerosols or as the residual of incomplete reactions between ammonium salts and carbonate salts. NO3- in the dust day samples was attributed to various formation processes during the long-range transport. The positive matrix factorization (PMF) receptor model results showed that the contribution of soil dust increased from 23 to 36 % on dust days, with decreasing contributions from local anthropogenic inputs and associated secondary aerosols. The estimated deposition flux of NNH4++NO3- varied greatly from event to event; e.g., the dry deposition flux of NNH4++NO3- increased by 9-285 % in Category 1 but decreased by 46-73 % in Category 2. In Category 3, the average dry deposition fluxes of particulate nitrate and ammonium decreased by 46 % and increased by 10 %, respectively, leading to 11-48 % decrease in the fluxes of NNH4++NO3-.

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.

Surface Winds and Dust Biases in Climate Models

NASA Astrophysics Data System (ADS)

Evan, A. T.

2018-01-01

An analysis of North African dust from models participating in the Fifth Climate Models Intercomparison Project (CMIP5) suggested that, when forced by observed sea surface temperatures, these models were unable to reproduce any aspects of the observed year-to-year variability in dust from North Africa. Consequently, there would be little reason to have confidence in the models' projections of changes in dust over the 21st century. However, no subsequent study has elucidated the root causes of the disagreement between CMIP5 and observed dust. Here I develop an idealized model of dust emission and then use this model to show that, over North Africa, such biases in CMIP5 models are due to errors in the surface wind fields and not due to the representation of dust emission processes. These results also suggest that because the surface wind field over North Africa is highly spatially autocorrelated, intermodel differences in the spatial structure of dust emission have little effect on the relative change in year-to-year dust emission over the continent. I use these results to show that similar biases in North African dust from the NASA Modern Era Retrospective analysis for Research and Applications (MERRA) version 2 surface wind field biases but that these wind biases were not present in the first version of MERRA.

Younger African American Adults' Use of Religious Songs to Manage Stressful Life Events.

PubMed

Hamilton, Jill B; Stewart, Jennifer M; Thompson, Keitra; Alvarez, Carmen; Best, Nakia C; Amoah, Kevin; Carlton-LaNey, Iris B

2017-02-01

The aim of this study was to explore the use of religious songs in response to stressful life events among young African American adults. Fifty-five young African American adults aged 18-49 participated in a qualitative study involving criterion sampling and open-ended interviews. Data analysis included content analysis and descriptive statistics. Stressful life events were related to work or school; caregiving and death of a family member; and relationships. Religious songs represented five categories: Instructive, Communication with God, Thanksgiving and Praise, Memory of Forefathers, and Life after Death. The tradition of using religious songs in response to stressful life events continues among these young adults. Incorporating religious songs into health-promoting interventions might enhance their cultural relevance to this population.

A Southern California Perspective of the April, 1998 Trans-Pacific Asian Dust Event

NASA Technical Reports Server (NTRS)

Tratt, David M.; Frouin, Robert J.; Westphal, Douglas L.

1999-01-01

The Jet Propulsion Laboratory (JPL) coherent CO2 backscatter lidar has been in almost continuous operation since 1984 and has now accumulated a significant time-series database tracking the long-term and seasonal variability of backscatter from the atmospheric column above the Pasadena, Calif. locale. A particularly noteworthy episode observed by the lidar in 1998 was a particularly extreme instance of incursion by Asian-sourced dust during the closing days of April. Such events are not uncommon during the northern spring, when strong cold fronts and convection over the Asian interior deserts loft crustal material into the mid-troposphere whence it can be transported across the Pacific Ocean, occasionally reaching the continental US. However, the abnormal strength of the initiating storm in this case generated an atypically dense cloud of material which resulted in dramatically reduced visibility along the length of the Western Seaboard. These dust events are now recognized as a potentially significant, non-negligible radiative forcing influence. The progress of the April 1998 dust cloud eastward across the Pacific Ocean was initially observed in satellite imagery and transmitted to the broader atmospheric research community via electronic communications. The use of Internet technology in this way was effective in facilitating a rapid response correlative measurement exercise by numerous atmospheric observation stations throughout the western US and its success has resulted in the subsequent establishment of an ad hoc communications environment, data exchange medium, and mechanism for providing early-warning alert of other significant atmospheric phenomena in the future.

Observing a Severe Dust Storm Event over China using Multiple Satellite Data

NASA Astrophysics Data System (ADS)

Xu, Hui; Xue, Yong; Guang, Jie; Mei, Linlu

2013-04-01

A severe dust storm (SDS) event occurred from 19 to 21 March 2010 in China, originated in western China and Mongolia and propagated into eastern/southern China, affecting human's life in a large area. As reported by National Meteorological Center of CMA (China Meteorological Administration), 16 provinces (cities) of China were hit by the dust storm (Han et al., 2012). Satellites can provide global measurements of desert dust and have particular importance in remote areas where there is a lack of in situ measurements (Carboni et al., 2012). To observe a dust, it is necessary to estimate the spatial and temporal distributions of dust aerosols. An important metric in the characterisation of aerosol distribution is the aerosol optical depth (AOD) (Adhikary et al., 2008). Satellite aerosol retrievals have improved considerably in the last decade, and numerous satellite sensors and algorithms have been generated. Reliable retrievals of dust aerosol over land were made using POLarization and Directionality of the Earth's Reflectance instrument-POLDER (Deuze et al., 2001), Moderate Resolution Imaging Spectroradiometer-MODIS (Kaufman et al., 1997; Hsu et al., 2004), Multiangle Imaging Spectroradiometer-MISR (Martonchik et al., 1998), and Cloud-aerosol Lidar and infrared pathfinder satellite observations (CALIPSO). However, intercomparison exercises (Myhre et al., 2005) have revealed that discrepancies between satellite measurements are particularly large during events of heavy aerosol loading. The reason is that different AOD retrieval algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. For MISR, POLDER and MODIS instrument, the multi-angle approaches, the polarization measurements and single-view approaches were used to retrieval AOD respectively. Combining of multi-sensor AOD data can potentially create a more consistent, reliable and complete picture of the space-time evolution of dust storms (Ehlers, 1991). In order to

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.

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.

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

NASA Technical Reports Server (NTRS)

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

2009-01-01

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

Characterization of PM2.5 chemical composition at the Demokritos suburban station, in Athens Greece. The influence of Saharan dust.

PubMed

Vasilatou, Vasiliki; Diapouli, Evangelia; Abatzoglou, Dimitrios; Bakeas, Evangelos B; Scoullos, Michael; Eleftheriadis, Konstantinos

2017-04-01

The aim of this work is to study the atmospheric concentrations of selected major and trace elements and ions found in PM 2.5 , at a suburban site in Athens, Greece, and discuss on the impact of the different sources. Special focus is given to the influence of Saharan dust episodes. The seasonal variability in the metal and ion concentrations is also examined. The results show that PM 2.5 mass concentrations are significantly influenced by Saharan dust events; it is observed that when the PM 2.5 concentration is higher than 25 μg/m 3 , five out of six times, the air mass crossed North Africa at an altitude within the boundary layer. Fe is found to be the element with the more significant seasonal variability, displaying much higher concentrations during cold period. The frequent Saharan dust intrusions in the cold period of this dataset may explain this result. Mineral dust and secondary aerosol are the main PM 2.5 components (29 and 34%, respectively). During Saharan dust events, the concentration of mineral dust is increased by 35% compared to the days without dust intrusions, while an increase of 68% of the sea salt is also observed. During event days, PM 2.5 concentrations are also increased by 14%. Anthropogenic components do not decrease during those days, while sulfate displays even a slight increase, suggesting enrichment of mineral dust with secondary sulfates. The results indicate that African dust intrusions add a rather significant PM pollution load even in the PM 2.5 fraction, with implication to population exposure and human health.

Extracting lunar dust parameters from image charge signals produced by the Lunar Dust Experiment

NASA Astrophysics Data System (ADS)

Stanley, J.; Kempf, S.; Horanyi, M.; Szalay, J.

2015-12-01

The Lunar Dust Experiment (LDEX) onboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) is an impact ionization dust detector used to characterize the lunar dust exosphere generated by the impacts of large interplanetary particles and meteor streams (Horanyi et al., 2015). In addition to the mass and speed of these lofted particles, LDEX is sensitive to their charge. The resulting signatures of impact events therefore provide valuable information about not only the ambient plasma environment, but also the speed vectors of these dust grains. Here, impact events produced from LDEX's calibration at the Dust Accelerator Laboratory are analyzed using an image charge model derived from the electrostatic simulation program, Coulomb. We show that parameters such as dust grain speed, size, charge, and position of entry into LDEX can be recovered and applied to data collected during LADEE's seven-month mission.

Modeled Downward Transport of a Passive Tracer over Western North America during an Asian Dust Event in April 1998.

NASA Astrophysics Data System (ADS)

Hacker, Joshua P.; McKendry, Ian G.; Stull, Roland B.

2001-09-01

An intense Gobi Desert dust storm in April 1998 loaded the midtroposphere with dust that was transported across the Pacific to western North America. The Mesoscale Compressible Community (MC2) model was used to investigate mechanisms causing downward transport of the midtropospheric dust and to explain the high concentrations of particulate matter of less than 10-m diameter measured in the coastal urban areas of Washington and southern British Columbia. The MC2 was initialized with a thin, horizontally homogeneous layer of passive tracer centered at 650 hPa for a simulation from 0000 UTC 26 April to 0000 UTC 30 April 1998. Model results were in qualitative agreement with observed spatial and temporal patterns of particulate matter, indicating that it captured the important meteorological processes responsible for the horizontal and vertical transport over the last few days of the dust event. A second simulation was performed without topography to isolate the effects of topography on downward transport.Results show that the dust was advected well east of the North American coast in southwesterly midtropospheric flow, with negligible dust concentration reaching the surface initially. Vertically propagating mountain waves formed during this stage, and differences between downward and upward velocities in these waves could account for a rapid descent of dust to terrain height, where the dust was entrained into the turbulent planetary boundary layer. A deepening outflow (easterly) layer near the surface transported the tracer westward and created a zonal-shear layer that further controlled the tracer advection. Later, the shear layer lifted, leading to a downward hydraulic acceleration along the western slopes, as waves generated in the easterly flow amplified below the shear layer that was just above mountain-crest height. Examination of 10 yr of National Centers for Environmental Prediction-National Center for Atmospheric Research reanalyses suggests that such events

Adverse Drug Events and Medication Errors in African Hospitals: A Systematic Review.

PubMed

Mekonnen, Alemayehu B; Alhawassi, Tariq M; McLachlan, Andrew J; Brien, Jo-Anne E

2018-03-01

Medication errors and adverse drug events are universal problems contributing to patient harm but the magnitude of these problems in Africa remains unclear. The objective of this study was to systematically investigate the literature on the extent of medication errors and adverse drug events, and the factors contributing to medication errors in African hospitals. We searched PubMed, MEDLINE, EMBASE, Web of Science and Global Health databases from inception to 31 August, 2017 and hand searched the reference lists of included studies. Original research studies of any design published in English that investigated adverse drug events and/or medication errors in any patient population in the hospital setting in Africa were included. Descriptive statistics including median and interquartile range were presented. Fifty-one studies were included; of these, 33 focused on medication errors, 15 on adverse drug events, and three studies focused on medication errors and adverse drug events. These studies were conducted in nine (of the 54) African countries. In any patient population, the median (interquartile range) percentage of patients reported to have experienced any suspected adverse drug event at hospital admission was 8.4% (4.5-20.1%), while adverse drug events causing admission were reported in 2.8% (0.7-6.4%) of patients but it was reported that a median of 43.5% (20.0-47.0%) of the adverse drug events were deemed preventable. Similarly, the median mortality rate attributed to adverse drug events was reported to be 0.1% (interquartile range 0.0-0.3%). The most commonly reported types of medication errors were prescribing errors, occurring in a median of 57.4% (interquartile range 22.8-72.8%) of all prescriptions and a median of 15.5% (interquartile range 7.5-50.6%) of the prescriptions evaluated had dosing problems. Major contributing factors for medication errors reported in these studies were individual practitioner factors (e.g. fatigue and inadequate knowledge

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

PubMed

Naidoo, Rajen N; Robins, Thomas G; Becklake, Margaret; Seixas, Noah; Thompson, Mary Lou

2007-12-01

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

Niamey Dust Observations

DOE Data Explorer

Flynn, Connor

2008-10-01

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

Characterization of atmospheric bioaerosols along the transport pathway of Asian dust during the Dust-Bioaerosol 2016 Campaign

NASA Astrophysics Data System (ADS)

Tang, Kai; Huang, Zhongwei; Huang, Jianping; Maki, Teruya; Zhang, Shuang; Shimizu, Atsushi; Ma, Xiaojun; Shi, Jinsen; Bi, Jianrong; Zhou, Tian; Wang, Guoyin; Zhang, Lei

2018-05-01

Previous studies have shown that bioaerosols are injected into the atmosphere during dust events. These bioaerosols may affect leeward ecosystems, human health, and agricultural productivity and may even induce climate change. However, bioaerosol dynamics have rarely been investigated along the transport pathway of Asian dust, especially in China where dust events affect huge areas and massive numbers of people. Given this situation, the Dust-Bioaerosol (DuBi) Campaign was carried out over northern China, and the effects of dust events on the amount and diversity of bioaerosols were investigated. The results indicate that the number of bacteria showed remarkable increases during the dust events, and the diversity of the bacterial communities also increased significantly, as determined by means of microscopic observations with 4,6-diamidino-2-phenylindole (DAPI) staining and MiSeq sequencing analysis. These results indicate that dust clouds can carry many bacteria of various types into downwind regions and may have potentially important impacts on ecological environments and climate change. The abundances of DAPI-stained bacteria in the dust samples were 1 to 2 orders of magnitude greater than those in the non-dust samples and reached 105-106 particles m-3. Moreover, the concentration ratios of DAPI-stained bacteria to yellow fluorescent particles increased from 5.1 % ± 6.3 % (non-dust samples) to 9.8 % ± 6.3 % (dust samples). A beta diversity analysis of the bacterial communities demonstrated the distinct clustering of separate prokaryotic communities in the dust and non-dust samples. Actinobacteria, Bacteroidetes, and Proteobacteria remained the dominant phyla in all samples. As for Erenhot, the relative abundances of Acidobacteria and Chloroflexi had a remarkable rise in dust events. In contrast, the relative abundances of Acidobacteria and Chloroflexi in non-dust samples of R-DzToUb were greater than those in dust samples. Alphaproteobacteria made the major

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.

Study of Desert Dust Events over the Southwestern Iberian Peninsula in Year 2000: Two Case Studies

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

Cachorro, V. E.; Vergaz, R.; de Frutos, A. M.

2006-03-07

Strong desert dust events occurring in 2000 over the southwestern Atlantic coast of the Iberian Peninsula are detected and evaluated by means of the TOMS Aerosol Index (A.I.) at three different sites, Funchal (Madeira Island, Portugal), Lisboa (Portugal), and El Arenosillo (Huelva, Spain). At the El Arenosillo station, measurements from an AERONET Cimel sunphotometer allow more retrieval of the spectral AOD and the derived alpha ''angstrom'' coefficient. After using different threshold values of these parameters, we conclude that it is difficult to establish reliable and robust criteria for an automatic estimation of the number of dust episodes and the totalmore » number of dusty days per year. As a result, additional information, such as airmass trajectories, were used to improve the estimation, from which reasonable results were obtained (although some manual editing was still needed). A detailed characterization of two selected desert dust episodes, a strong event in winter and another of less intensity in summer, was carried out using AOD derived from Brewer spectrometer measurements. Size distribution parameters and radiative properties, such as refractive index and the aerosol single scattering albedo derived from Cimel data, were analyzed in detail for one of these two case studies. Although specific to this dust episode, the retrieved range of values of these parameters clearly reflect the characteristics of desert aerosols. Back-trajectory analysis, synoptic weather maps and satellite images were also considered together, as supporting data to assess the aerosol desert characterization in this region of study.« less

The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

NASA Astrophysics Data System (ADS)

Wiacek, A.; Peter, T.; Lohmann, U.

2010-09-01

This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons, without explicitly modelling dust emission and deposition processes. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated dust sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "warm ice clouds" (T≳-40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "warm ice clouds" and the general influence

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

Dust and Smoke

Atmospheric Science Data Center

2014-05-15

...     View Larger Image Desert dust particles tend to be larger in size than aerosols that originate ... for these two events. These MISR results distinguish desert dust, the most common non-spherical aerosol type, from pollution and ...

Characteristics of mineral dust impacting the Persian Gulf

NASA Astrophysics Data System (ADS)

Ahmady-Birgani, Hesam; McQueen, Kenneth G.; Mirnejad, Hassan

2018-02-01

It is generally assumed that severe dust events in western Iran could be responsible for elevated levels of toxic and radioactive elements in the region. Over a period of 5 months, from January 2012 to May 2012, dust particles in the size range PM10 (i.e. <10 μm) were collected at Abadan, a site beside the Persian Gulf. The research aim was to compare chemical compositions of dust and aerosol samples collected during the non-dusty periods and during two severe dust events. Results of ICP-MS analysis of components indicate that during dust events the concentrations of major elements such as Ca, Mg, Al and K increase relative to ambient conditions when Fe and trace elements such as Cu, Cr, Ni, Pb and Zn are in higher proportions. Toxic trace elements that are generally ascribed to human activities, including industrial and urban pollution, are thus proportionately more abundant in the dust under calm conditions than during dust events, when their concentration is diluted by more abundant mineral particles of quartz, calcite and clay. The variability of chemical species during two dust events, noted by tracking the dust plumes in satellite images, was also assessed and the results relate to two different source areas, namely northern Iraq and northwestern Syria.

Lung cancer in relation to exposure to silica dust, silicosis and uranium production in South African gold miners

PubMed Central

Hnizdo, E.; Murray, J.; Klempman, S.

1997-01-01

BACKGROUND: A nested case-control study for lung cancer was performed on a cohort of 2260 South African gold miners in whom an association between exposure to silica dust and risk of lung cancer was previously reported. The objective was to investigate an expanded set of risk factors and also cancer cell type. METHODS: The 78 cases of lung cancer found during the follow up period from 1970 to 1986 were matched with 386 controls. Risk of lung cancer was related to smoking, exposure to silica dust, incidence of silicosis, and uranium production and the uranium content of the mine ore. RESULTS: The risk of lung cancer was associated with tobacco smoking, cumulative dust exposure, duration of underground mining, and with silicosis. The best predictive model included pack years of cigarette consumption (adjusted relative risk (RR) = 1.0 for < 6.5 pack years, 3.5 (95% confidence interval (CI) 0.7 to 16.8) for 6.5-20 pack years, 5.7 (95% CI 1.3 to 25.8) for 21-30 pack years, and 13.2 (95% CI 3.1 to 56.2) for more than 30 pack years) and silicosis (RR = 2.45 (95% CI 1.2 to 5.2)). No association was found with uranium production. The lung tumour cell type distribution was 40.3% small cell carcinoma, 38.8% squamous cell, 16.4% adenocarcinoma, and 4.5% large cell carcinoma. Small and large cell cancer combined were associated with exposure to dust. CONCLUSIONS: The results cannot be interpreted definitively in terms of causal association. Possible interpretations are: (1) subjects with high dust exposure who develop silicosis are at increased risk of lung cancer; (2) high levels of exposure to silica dust on its own is important in the pathogenesis of lung cancer and silicosis is coincidental; and (3) high levels of silica dust exposure may be a surrogate for the exposure to radon daughters. 


 PMID:9093345

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

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.

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.

Evaluating aerosol impacts on Numerical Weather Prediction in two extreme dust and biomass-burning events

NASA Astrophysics Data System (ADS)

Remy, Samuel; Benedetti, Angela; Jones, Luke; Razinger, Miha; Haiden, Thomas

2014-05-01

The WMO-sponsored Working Group on Numerical Experimentation (WGNE) set up a project aimed at understanding the importance of aerosols for numerical weather prediction (NWP). Three cases are being investigated by several NWP centres with aerosol capabilities: a severe dust case that affected Southern Europe in April 2012, a biomass burning case in South America in September 2012, and an extreme pollution event in Beijing (China) which took place in January 2013. At ECMWF these cases are being studied using the MACC-II system with radiatively interactive aerosols. Some preliminary results related to the dust and the fire event will be presented here. A preliminary verification of the impact of the aerosol-radiation direct interaction on surface meteorological parameters such as 2m Temperature and surface winds over the region of interest will be presented. Aerosol optical depth (AOD) verification using AERONET data will also be discussed. For the biomass burning case, the impact of using injection heights estimated by a Plume Rise Model (PRM) for the biomass burning emissions will be presented.

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

NASA Technical Reports Server (NTRS)

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

2013-01-01

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

Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign

NASA Astrophysics Data System (ADS)

Tegen, I.; Heinold, B.; Todd, M.; Helmert, J.; Washington, R.; Dubovik, O.

2006-05-01

We present regional model simulations of the dust emission events during the Bodélé Dust Experiment (BoDEx) that was carried out in February and March 2005 in Chad. A box model version of the dust emission model is used to test different input parameters for the emission model, and to compare the dust emissions computed with observed wind speeds to those calculated with wind speeds from the regional model simulation. While field observations indicate that dust production occurs via self-abrasion of saltating diatomite flakes in the Bodélé, the emission model based on the assumption of dust production by saltation and using observed surface wind speeds as input parameters reproduces observed dust optical thicknesses well. Although the peak wind speeds in the regional model underestimate the highest wind speeds occurring on 10-12 March 2005, the spatio-temporal evolution of the dust cloud can be reasonably well reproduced by this model. Dust aerosol interacts with solar and thermal radiation in the regional model; it is responsible for a decrease in maximum daytime temperatures by about 5 K at the beginning the dust storm on 10 March 2005. This direct radiative effect of dust aerosol accounts for about half of the measured temperature decrease compared to conditions on 8 March. Results from a global dust model suggest that the dust from the Bodélé is an important contributor to dust crossing the African Savannah region towards the Gulf of Guinea and the equatorial Atlantic, where it can contribute up to 40% to the dust optical thickness.

Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign

NASA Astrophysics Data System (ADS)

Tegen, I.; Heinold, B.; Todd, M.; Helmert, J.; Washington, R.; Dubovik, O.

2006-09-01

We present regional model simulations of the dust emission events during the Bodélé Dust Experiment (BoDEx) that was carried out in February and March 2005 in Chad. A box model version of the dust emission model is used to test different input parameters for the emission model, and to compare the dust emissions computed with observed wind speeds to those calculated with wind speeds from the regional model simulation. While field observations indicate that dust production occurs via self-abrasion of saltating diatomite flakes in the Bodélé, the emission model based on the assumption of dust production by saltation and using observed surface wind speeds as input parameters reproduces observed dust optical thicknesses well. Although the peak wind speeds in the regional model underestimate the highest wind speeds occurring on 10-12 March 2005, the spatio-temporal evolution of the dust cloud can be reasonably well reproduced by this model. Dust aerosol interacts with solar and thermal radiation in the regional model; it is responsible for a decrease in maximum daytime temperatures by about 5 K at the beginning the dust storm on 10 March 2005. This direct radiative effect of dust aerosol accounts for about half of the measured temperature decrease compared to conditions on 8 March. Results from a global dust model suggest that the dust from the Bodélé is an important contributor to dust crossing the African Savannah region towards the Gulf of Guinea and the equatorial Atlantic, where it can contribute up to 40% to the dust optical thickness.

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

The dust activity over North Africa associated with the Saharan depression event in February 2007 is investigated by mean of spaceborne observations, ground-based measurements, and mesoscale simulation with Meso-NH. The main characteristics of the cyclone as well as the meteorological conditions during this event are described using the European Centre for Medium-Range Weather Forecasts (ECMWF). The dust storm and cloud cover over North Africa is thoroughly described combining for the first time Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) images for the spatiotemporal evolution and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat observations for the vertical distribution. The Saharan depression formed over Algeria in the lee of the Atlas Mountains on the afternoon of 20 February in response to midlatitude trough intrusion. It migrated eastward with a speed of 11 m s-1 and reached Libya on 22 February before exiting the African continent toward the Mediterranean Sea on 23 February. The horizontal scale of the cyclone at the surface varied between 800 and 1000 km during its lifetime. On the vertical the cyclone extended over 8 km, and a potential vorticity of 2 potential vorticity units (PVU) was reported at its center at 3 km in altitude. The cyclone was characterized by a surface pressure anomaly of about 9 hPa with respect to the environment, a warm front typified at the surface by an increase in surface temperature of 5°C, and a sharp cold front characterized by a drop in surface temperature of 8°C and an increase in 10 m wind speed of 15 m s-1. The cyclone provided dynamical forcing that led to strong near-surface winds and produced a major dust storm over North Africa. The dust was transported all around the cyclone leaving a clear eye at its center and was accompanied by a deep cloud band along the northwestern edge of the cyclone. On the vertical, slanted dust layers were consistently observed during the

Enhancing weak transient signals in SEVIRI false color imagery: Application to dust source detection in southern Africa

NASA Astrophysics Data System (ADS)

Murray, J. E.; Brindley, H. E.; Bryant, R. G.; Russell, J. E.; Jenkins, K. F.; Washington, R.

2016-09-01

A method is described to significantly enhance the signature of dust events using observations from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI). The approach involves the derivation of a composite clear-sky signal for selected channels on an individual time step and pixel basis. These composite signals are subtracted from each observation in the relevant channels to enhance weak transient signals associated with either (a) low levels of dust emission or (b) dust emissions with high salt or low quartz content. Different channel combinations, of the differenced data from the steps above, are then rendered in false color imagery for the purpose of improved identification of dust source locations and activity. We have applied this clear-sky difference (CSD) algorithm over three (globally significant) source regions in southern Africa: the Makgadikgadi Basin, Etosha Pan, and the Namibian and western South African coast. Case study analyses indicate three notable advantages associated with the CSD approach over established image rendering methods: (i) an improved ability to detect dust plumes, (ii) the observation of source activation earlier in the diurnal cycle, and (iii) an improved ability to resolve and pinpoint dust plume source locations.

Low and Mid Level Tropical Atmosphere Characterization during African Dust Outbreaks Using Particle Size Distribution Data Retrieved from ICE-T and PRADACS Field Studies

NASA Astrophysics Data System (ADS)

Martínez-Sánchez, O.; Mayol-Bracero, O. L.; Sepulveda-Vallejo, P.; Heymsfield, A.

2013-12-01

Cloud formation in the tropical atmosphere is difficult to characterize when factors such as the Saharan Air Layer (SAL) play a role influencing the dynamic and thermodynamic processes. In order to characterize particle number size distribution across the Eastern Caribbean with the possible influence of African dust at low and mid levels, data collected during July 2011 from ground-based instruments and an aircraft platform were analyzed. Aerosol measurements from the ocean surface to ~8 km were performed below and in and around clouds by the National Center for Atmospheric Research (NCAR) C130 aircraft during the Ice in Clouds Experiment-Tropical (ICE-T) using the Passive Cavity Aerosol Spectrometer Probe (PCASP), while low-level measurements of aerosols were performed at the University of Puerto Rico-Rio Piedras Campus (UPRRP) during the Puerto Rican African Dust and Cloud Study (PRADACS) using an Optical Particle Counter (OPC) and a Scanning Mobility Particle Sizer (SMPS). Preliminary results using HYSPLIT back trajectories, flight tracks, SAL images and OPC/SMPS/PCASP time series all indicate peaks and troughs in aerosol concentrations at both low and mid levels over time, but the concentration was influenced by how strong the dust outbreak was as well as its horizontal travel speed. These and additional results regarding correlations between wind directions, cloud cover and atmospheric inversions will be presented.

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.

Combustibility Determination for Cotton Gin Dust and Almond Huller Dust.

PubMed

Hughs, Sidney E; Wakelyn, Phillip J

2017-04-26

It has been documented that some dusts generated while processing agricultural products, such as grain and sugar, can constitute combustible dust hazards. After a catastrophic dust explosion in a sugar refinery in 2008, the Occupational Safety and Health Administration (OSHA) initiated action to develop a mandatory standard to comprehensively address the fire and explosion hazards of combustible dusts. Cotton fiber and related materials from cotton ginning, in loose form, can support smoldering combustion if ignited by an outside source. However, dust fires and other more hazardous events, such as dust explosions, are unknown in the cotton ginning industry. Dust material that accumulates inside cotton gins and almond huller plants during normal processing was collected for testing to determine combustibility. Cotton gin dust is composed of greater than 50% inert inorganic mineral dust (ash content), while almond huller dust is composed of at least 7% inert inorganic material. Inorganic mineral dust is not a combustible dust. The collected samples of cotton gin dust and almond huller dust were sieved to a known particle size range for testing to determine combustibility potential. Combustibility testing was conducted on the cotton gin dust and almond huller dust samples using the UN test for combustibility suggested in NFPA 652.. This testing indicated that neither the cotton gin dust nor the almond huller dust should be considered combustible dusts (i.e., not a Division 4.1 flammable hazard per 49 CFR 173.124). Copyright© by the American Society of Agricultural Engineers.

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

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

Naidoo, R.N.; Robins, T.G.; Seixas, N.

2006-06-15

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

Examining the Associations of Racism, Sexism, and Stressful Life Events on Psychological Distress among African American Women

PubMed Central

Stevens-Watkins, Danelle; Perry, Brea; Pullen, Erin; Jewell, Jennifer; Oser, Carrie B.

2013-01-01

African American women may be susceptible to stressful events and adverse health outcomes as a result of their distinct social location at the intersection of gender and race. Here, racism and sexism are examined concurrently using survey data from 204 African American women residing in a southeastern U.S. urban city. Associations between racism, sexism, and stressful events across social roles and contexts (i.e., social network loss, motherhood and childbirth, employment and finances, personal illness and injury, and victimization) are investigated. Then, the relationships among these stressors on psychological distress are compared, and a moderation model is explored. Findings suggest that racism and sexism are a significant source of stress in the lives of African American women, and are correlated both with one another and with other stressful events. Implications for future research and clinical considerations are discussed. PMID:25313434

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.

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

PubMed Central

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

2015-01-01

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

STS-65 Earth observation of Bahama Islands with dust pall, taken from OV-102

NASA Technical Reports Server (NTRS)

1994-01-01

During STS-65 a significant dust pall that originated in western Africa was recorded by a series of low oblique color photographs as it continued its westward trek across the Atlantic Ocean and then the Caribbean Sea and the Gulf of Mexico area. This particular view captures the northern edge of the dust, positioned just slightly north of the Bahama Islands. This major transport of African dust to the western hemisphere has been recorded periodically by other Shuttle astronauts and earlier Shuttle missions. Scientifically, there is evidence that some of this African dust even reaches the Amazon rainforest and serves as a source of airborne nutrients for rainforest vegetation. This photograph was taken aboard Columbia, Orbiter Vehicle (OV) 102.

Time-course monitoring of urban bioaerosol bacterial communities and its use in microbial hazard identification during Asian Dust events in Seoul, Korea

NASA Astrophysics Data System (ADS)

Park, J.

2015-12-01

The microbial communities transported by Asian dust events have attracted much attention as bioaerosols because the transported airborne microbes may strongly influence the downwind ecosystems and potentially human health in East Asia. Bioaerosol study has received relatively little attention and their characterization and risk assessments remain poorly developed. We used high throughput 16S rRNA gene targeted pyrosequencing and real-time quantitative PCR (qPCR) to monitor airborne bacterial communities and assess their potential risk. We monitored microbial communities in bioaerosol in Seoul between 2011 and 2013 using high volume air samplers. Six samples were collected during Asian dust (AD) events and the other 34 samples were urban air collected during non-Asian dust (non-AD) events. According to the qPCR result, the gene copy numbers of 16S rRNA genes were significantly higher during the AD events (P < 0.05) and their abundances were positively correlated with PM10 concentrations and bacterial diversities. The most abundant bacterial members (genus level) in the AD samples were Bacillus, Neisseria and E.coli/Shigella. To identify pathogenic populations, multilocus sequence typing (MLST) and virulence tests were applied using culture methods. 16S rRNA gene sequences of several pathogens were detected and their relative abundances appeared to have increased with increased concentrations of PM10. About 1% of Bacillus isolates were identified as known pathogenic B. cereus, confirming their presence in Asian dust samples. The qPCR detection of bceT gene, which codes for an enterotoxin in B. cereus group, was significantly increased in the AD dust samples over the non-AD samples. The following MLST assessment and virulence test of cultivated Bacillus isolates showed that B. cereus, B. licheniformis and B. mycoides were identified as pathogenic bacteria, and these pathogenic bacteria were usually more abundant during AD events. To assess the possible associations of

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.

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

The dust activity over North Africa associated with the Saharan depression event in February 2007 is investigated by mean of spaceborne observations, ground based measurements and mesoscale simulation with Meso-NH. The main characteristics of the cyclone as well as the meteorological conditions during this event are described using the European Centre for Medium-range Weather Forecasts (ECMWF). The dust storm and cloud cover over North Africa is thoroughly described combining for the first time Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) images for the spatio-temporal evolution and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and CloudSat observations for the vertical distribution. The Saharan depression formed over Algeria in the lee of the Atlas Mountain on the afternoon of February 20 in response to midlatitude trough intrusion. It migrated eastward with a speed of 11 m s-1 and reached Libya on February 22 before exiting the African continent toward the Mediterranean Sea on February 23. The horizontal scale of the cyclone at the surface varied between 800 km and 1000 km during its lifetime. On the vertical the cyclone extended over 8 km and a potential vorticity of 2 PVU was reported on its centre at 3 km in altitude. The cyclone was characterised by a surface pressure anomaly of about 9 hPa with respect to the environment, a warm front typified at the surface by an increase in surface temperature of 5°C, and a sharp cold front characterized by a drop in surface temperature of 8°C and an increase in 10 m wind speed of 15 m s-1. The cyclone provided a dynamical forcing that led to strong near-surface winds and produced a major dust storm over North Africa. The dust was transported all around the cyclone leaving a clear eye on its centre and was accompanied by a deep cloud band along the northwestern edge of the cyclone. On the vertical, slanted dust layers were consistently observed during the event over North Africa

Motion Event Categorisation in a Nativised Variety of South African English

ERIC Educational Resources Information Center

Bylund, Emanuel; Athanasopoulos, Panos

2015-01-01

The present study seeks to expand the current focus on acquisition situations in linguistic relativity research by exploring the effects of nativisation (the process by which a L2 is acquired as a L1) on language-specific cognitive behaviour. Categorisation preferences of goal-oriented motion events were investigated in South African speakers who…

Importance of mineral dust and anthropogenic pollutants mixing during a long-lasting high PM event over East Asia.

PubMed

Wang, Zhe; Pan, Xiaole; Uno, Itsushi; Chen, Xueshun; Yamamoto, Shigekazu; Zheng, Haitao; Li, Jie; Wang, Zifa

2018-03-01

A long-lasting high particulate matter (PM) concentration episode persisted over East Asia from May 24 to June 3, 2014. The Nested Air Quality Prediction Model System (NAQPMS) was used to investigate the mixing of dust and anthropogenic pollutants during this episode. Comparison of observations revealed that the NAQPMS successfully reproduced the time series PM 2.5 and PM 10 concentrations, as well as the nitrate and sulfate concentrations in fine (aerodynamic diameter ≤ 2.5 μm) and coarse mode (2.5 μm < aerodynamic diameter ≤ 10 μm). This episode originated from two dust events that occurred in the inland desert areas of Mongolia and China, and then the long-range transported dust and anthropogenic pollutants were trapped over the downwind region of East Asia for more than one week due to the blocked north Pacific subtropical high-pressure system over the east of Japan. The model results showed that mineral dust accounted for 53-83% of PM 10 , and 39-67% of PM 2.5 over five cities in East Asia during this episode. Sensitivity analysis indicated that the Qingdao and Seoul regions experienced dust and pollution twice, by direct transport from the dust source region and from dust detoured over the Shanghai area. The results of the NAQPMS model confirmed the importance of dust heterogeneous reactions (HRs) over East Asia. Simulated dust NO 3 - concentrations accounted for 75% and 84% of total NO 3 - in fine and coarse mode, respectively, in Fukuoka, Japan. The horizontal distribution of model results revealed that the ratio of dust NO 3 - /dust concentration increased from about 1% over the Chinese land mass to a maximum of 8% and 6% respectively in fine and coarse mode over the ocean to the southeast of Japan, indicating that dust NO 3 - was mainly formed over the Yellow Sea and the East China Sea before reaching Japan. Copyright © 2017 Elsevier Ltd. All rights reserved.

Asian dust exposure triggers acute myocardial infarction.

PubMed

Kojima, Sunao; Michikawa, Takehiro; Ueda, Kayo; Sakamoto, Tetsuo; Matsui, Kunihiko; Kojima, Tomoko; Tsujita, Kenichi; Ogawa, Hisao; Nitta, Hiroshi; Takami, Akinori

2017-11-14

To elucidate whether Asian dust is associated with the incidence of acute myocardial infarction (AMI) and to clarify whether patients who are highly sensitive to Asian dust will develop AMI. Twenty-one participating institutions located throughout Kumamoto Prefecture and capable of performing coronary intervention were included in the study. Data for ground-level observations of Asian dust events were measured at the Kumamoto Local Meteorological Observatory. Data collected between 1 April 2010 and 31 March 2015 were analysed, and 3713 consecutive AMI patients were included. A time-stratified case-crossover design was applied to examine the association between Asian dust exposure and AMI. The occurrence of Asian dust events at 1 day before the onset of AMI was associated with the incidence of AMI [odds ratio (OR), 1.46; 95% confidence interval (CI), 1.09-1.95] and especially, non-ST-segment elevation myocardial infarction was significant (OR 2.03; 95% CI, 1.30-3.15). A significant association between AMI and Asian dust was observed in patients with age ≥75 years, male sex, hypertension, diabetes mellitus, never-smoking status, and chronic kidney disease (CKD). However, Asian dust events had a great impact on AMI onset in patients with CKD (P < 0.01). A scoring system accounting for several AMI risk factors was developed. The occurrence of Asian dust events was found to be significantly associated with AMI incidence among patients with a risk score of 5-6 (OR 2.45; 95% CI: 1.14-5.27). Asian dust events may lead to AMI and have a great impact on its onset in patients with CKD. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Examining the associations of racism, sexism, and stressful life events on psychological distress among African-American women.

PubMed

Stevens-Watkins, Danelle; Perry, Brea; Pullen, Erin; Jewell, Jennifer; Oser, Carrie B

2014-10-01

African-American women may be susceptible to stressful events and adverse health outcomes as a result of their distinct social location at the intersection of gender and race. Here, racism and sexism are examined concurrently using survey data from 204 African-American women residing in a southeastern U.S. urban city. Associations among racism, sexism, and stressful events across social roles and contexts (i.e., social network loss, motherhood and childbirth, employment and finances, personal illness and injury, and victimization) are investigated. Then, the relationships among these stressors on psychological distress are compared, and a moderation model is explored. Findings suggest that racism and sexism are a significant source of stress in the lives of African-American women and are correlated with one another and with other stressful events. Implications for future research and clinical considerations are discussed. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

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

The effect of mineral dust transport on PM10 concentrations and physical properties in Istanbul during 2007-2014

NASA Astrophysics Data System (ADS)

Flores, Rosa M.; Kaya, Nefel; Eşer, Övgü; Saltan, Şehnaz

2017-11-01

Mineral dust is the most significant source of natural particulate matter. In urban regions, where > 50% of the world population is currently living, local emissions of particulate matter are further aggravated by mineral dust loadings from deserts. The megacity of Istanbul is located in an area sensitive to local pollution due to transportation (i.e., private cars, public transportation, aircrafts, ships, heavy diesel trucks, etc.), industrial emissions, residential heating, and long-range transport from Europe, Asia, and deserts. In this work, the effect of desert dust transport on PM10 concentrations and physical properties was investigated for the period of 2007-2014 in the touristic area of Aksaray, Istanbul. The Dust Regional Atmospheric Model (DREAM8b) was used to predict dust loading in Istanbul during dust transport events. Variations on surface PM10 concentrations were investigated according to seasons and during dust transport events. Cluster analysis of air mass backward trajectories was useful to understand frequency analysis and air mass trajectory dependence of PM10 concentrations on dust loadings. The effect of desert dust transport on aerosol optical depths was also investigated. It was observed that PM10 concentrations exceeded the air quality standard of 50 μg m- 3 50% of the time during the study period. The largest number of exceedances in air quality standard occurred during the spring and winter seasons. Approximately 40-60% of the dust loading occurs during the spring. Desert dust and non-desert dust sources contribute to 22-72% and 48-81% of the ground-level PM10 concentrations in Aksaray, Istanbul during the study period. Averaged AOD observed during dust transport events in spring and summer ranged 0.35-0.55. Cluster analysis resolved over 82% the variability of individual air mass backward trajectories into 5 clusters. Overall, air masses arriving to Istanbul at 500 m are equally distributed into northern (52%) and southern (48

Atmospheric Dynamics of Sub-Tropical Dust Storms

NASA Astrophysics Data System (ADS)

Pokharel, Ashok Kumar

Meso-alpha/beta scale observational and meso-beta/gamma scale numerical model analyses were performed to study the atmospheric dynamics responsible for generating Harmattan, Saudi Arabian, and Bodele Depression dust storms. For each dust storm case study, MERRA reanalysis datasets, WRF simulated very high resolution datasets, MODIS/Aqua and Terra images, EUMETSAT images, NAAPS aerosol modelling plots, CALIPSO images, surface observations, and rawinsonde soundings were analyzed. The analysis of each dust storm carried out separately and an in-depth comparison of the events shows some similarities among the three case studies: (1) the presence of a well-organized baroclinic synoptic scale system, (2) small scale dust emission events which occurred prior to the formation of the primary large-scale dust storms, (3) cross mountain flows which produced a strong leeside inversion layer prior to the large scale dust storm, (4) the presence of thermal wind imbalance in the exit region of the mid-tropospheric jet streak in the lee of the mountains shortly after the time of the inversion formation, (5) major dust storm formation was accompanied by large magnitude ageostrophic isallobaric low-level winds as part of the meso-beta scale adjustment process, (6) substantial low-level turbulence kinetic energy (TKE), (7) formation in the lee of nearby mountains, and (8) the emission of the dust occurred initially in narrow meso-beta scale zones parallel to the mountains, and later reached the meso-alpha scale when suspended dust was transported away from the mountains. In addition to this there were additional meso-beta scale and meso-gamma scale adjustment processes resulting in Kelvin waves in the Harmattan and the Bodele Depression cases and the thermally-forced MPS circulation in all of these three cases. The Kelvin wave preceded a cold pool accompanying the air behind the large scale cold front instrumental in the major dust storm. The Kelvin wave organized the major dust

A new approach developed to study variability in North African dust transport routes over the Atlantic during 2001-2015

NASA Astrophysics Data System (ADS)

Meng, L.; Gao, H. W.; Yu, Y.; Yao, X. H.; Gao, Y.; Zhang, C.; Fan, Lei

2017-10-01

We investigated the variability in the North African dust transport routes over the Atlantic (NAD routes) by extracting the dust transport central axis using Moderate Resolution Imaging Spectroradiometer aerosol data for 2001-2015. The results showed that the NAD routes can be classified into two regimes, a southern route centered at the southernmost position of 6.08 ± 1.12°N during November to March and a northern route centered at the northernmost position of 18.21 ± 1.04°N during April to October. In the southern route, large intervariation was correlated with the Intertropical Convergence Zone (ITCZ) and North Atlantic Oscillation (NAO), but the ITCZ and NAO jointly explained only 38% of the variation. In the northern route, the ITCZ alone explained 67% of the intervariation. The extracted trends during 2001-2015 exhibited a northward shift of 1.68° for the southern route and of 0.52° for the northern route. The causes for the shift were also examined.

Aerobiology and the global transport of desert dust

USGS Publications Warehouse

Kellogg, Christina A.; Griffin, Dale W.

2006-01-01

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

Evaluation of Demographics and Social Life Events of Asian (Elephas maximus) and African Elephants (Loxodonta africana) in North American Zoos

PubMed Central

Prado-Oviedo, Natalia A.; Bonaparte-Saller, Mary K.; Malloy, Elizabeth J.; Meehan, Cheryl L.; Mench, Joy A.; Carlstead, Kathy; Brown, Janine L.

2016-01-01

This study quantified social life events hypothesized to affect the welfare of zoo African and Asian elephants, focusing on animals that were part of a large multi-disciplinary, multi-institutional elephant welfare study in North America. Age was calculated based on recorded birth dates and an age-based account of life event data for each elephant was compiled. These event histories included facility transfers, births and deaths of offspring, and births and deaths of non-offspring herd mates. Each event was evaluated as a total number of events per elephant, lifetime rate of event exposure, and age at first event exposure. These were then compared across three categories: species (African vs. Asian); sex (male vs. female); and origin (imported vs. captive-born). Mean age distributions differed (p<0.05) between the categories: African elephants were 6 years younger than Asian elephants, males were 12 years younger than females, and captive-born elephants were 20 years younger than imported elephants. Overall, the number of transfers ranged from 0 to 10, with a 33% higher age-adjusted transfer rate for imported African than imported Asian elephants, and 37% lower rate for imported females than males (p<0.05). Other differences (p<0.05) included a 96% higher rate of offspring births for captive-born females than those imported from range countries, a 159% higher rate of birthing event exposures for captive-born males than for their imported counterparts, and Asian elephant females being 4 years younger than African females when they produced their first calf. In summarizing demographic and social life events of elephants in North American zoos, we found both qualitative and quantitative differences in the early lives of imported versus captive-born elephants that could have long-term welfare implications. PMID:27415437

Evaluation of Demographics and Social Life Events of Asian (Elephas maximus) and African Elephants (Loxodonta africana) in North American Zoos.

PubMed

Prado-Oviedo, Natalia A; Bonaparte-Saller, Mary K; Malloy, Elizabeth J; Meehan, Cheryl L; Mench, Joy A; Carlstead, Kathy; Brown, Janine L

2016-01-01

This study quantified social life events hypothesized to affect the welfare of zoo African and Asian elephants, focusing on animals that were part of a large multi-disciplinary, multi-institutional elephant welfare study in North America. Age was calculated based on recorded birth dates and an age-based account of life event data for each elephant was compiled. These event histories included facility transfers, births and deaths of offspring, and births and deaths of non-offspring herd mates. Each event was evaluated as a total number of events per elephant, lifetime rate of event exposure, and age at first event exposure. These were then compared across three categories: species (African vs. Asian); sex (male vs. female); and origin (imported vs. captive-born). Mean age distributions differed (p<0.05) between the categories: African elephants were 6 years younger than Asian elephants, males were 12 years younger than females, and captive-born elephants were 20 years younger than imported elephants. Overall, the number of transfers ranged from 0 to 10, with a 33% higher age-adjusted transfer rate for imported African than imported Asian elephants, and 37% lower rate for imported females than males (p<0.05). Other differences (p<0.05) included a 96% higher rate of offspring births for captive-born females than those imported from range countries, a 159% higher rate of birthing event exposures for captive-born males than for their imported counterparts, and Asian elephant females being 4 years younger than African females when they produced their first calf. In summarizing demographic and social life events of elephants in North American zoos, we found both qualitative and quantitative differences in the early lives of imported versus captive-born elephants that could have long-term welfare implications.

Distribution of dust during two dust storms in Iceland

NASA Astrophysics Data System (ADS)

Ösp Magnúsdóttir, Agnes; Dagsson-Waldhauserova, Pavla; Arnalds, Ólafur; Ólafsson, Haraldur

2017-04-01

Particulate matter mass concentrations and size fractions of PM1, PM2.5, PM4, PM10, and PM15 measured in transversal horizontal profile of two dust storms in southwestern Iceland are presented. Images from a camera network were used to estimate the visibility and spatial extent of measured dust events. Numerical simulations were used to calculate the total dust flux from the sources as 180,000 and 280,000 tons for each storm. The mean PM15 concentrations inside of the dust plumes varied from 10 to 1600 ?g?m?3 (PM10 = 7 to 583 ?g?m?3). The mean PM1 concentrations were 97-241 ?g?m?3 with a maximum of 261 ?g?m?3 for the first storm. The PM1/PM2.5 ratios of >0.9 and PM1/PM10 ratios of 0.34-0.63 show that suspension of volcanic materials in Iceland causes air pollution with extremely high PM1 concentrations, similar to polluted urban areas in Europe or Asia. Icelandic volcanic dust consists of a higher proportion of submicron particles compared to crustal dust. Both dust storms occurred in relatively densely inhabited areas of Iceland. First results on size partitioning of Icelandic dust presented here should challenge health authorities to enhance research in relation to dust and shows the need for public dust warning systems.

Stressful Life Events, Psychological Well-Being, and Parenting in African American Mothers.

ERIC Educational Resources Information Center

Taylor, Ronald

The association of stressful life events with mothers' psychological distress and parenting was examined in 79 African American mothers living in 1- and 2-parent households. Findings reveal that stress in the areas of family disruption and work problems was associated with lower maternal acceptance. Family disruption was also positively associated…

Climatology of atmospheric circulation patterns of Arabian dust in western Iran.

PubMed

Najafi, Mohammad Saeed; Sarraf, B S; Zarrin, A; Rasouli, A A

2017-08-28

Being in vicinity of vast deserts, the west and southwest of Iran are characterized by high levels of dust events, which have adverse consequences on human health, ecosystems, and environment. Using ground based dataset of dust events in western Iran and NCEP/NCAR reanalysis data, the atmospheric circulation patterns of dust events in the Arabian region and west of Iran are identified. The atmospheric circulation patterns which lead to dust events in the Arabian region and western Iran were classified into two main categories: the Shamal dust events that occurs in warm period of year and the frontal dust events as cold period pattern. In frontal dust events, the western trough or blocking pattern at mid-level leads to frontogenesis, instability, and air uplift at lower levels of troposphere in the southwest of Asia. Non-frontal is other pattern of dust event in the cold period and dust generation are due to the regional circulation systems at the lower level of troposphere. In Shamal wind pattern, the Saudi Arabian anticyclone, Turkmenistan anticyclone, and Zagros thermal low play the key roles in formation of this pattern. Summer and transitional patterns are two sub-categories of summer Shamal wind pattern. In summer trough pattern, the mid-tropospheric trough leads to intensify the surface thermal systems in the Middle East and causes instability and rising of wind speed in the region. In synthetic pattern of Shamal wind and summer trough, dust is created by the impact of a trough in mid-levels of troposphere as well as existing the mentioned regional systems which are contributed in formation of summer Shamal wind pattern.

Atmospheric transport of mold spores in clouds of desert dust

USGS Publications Warehouse

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

2003-01-01

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

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

NASA Astrophysics Data System (ADS)

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

2014-07-01

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

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.

[Geochemical characteristics and sources of atmospheric particulates in Shanghai during dust storm event].

PubMed

Qian, Peng; Zheng, Xiang-min; Zhou, Li-min

2013-05-01

Atmospheric particulates were sampled from three sampling sites of Putuo, Minhang and Qingpu Districts in Shanghai between Oct. , 2009 and Oct. , 2010. In addition, particulate samples were also collected from Nantong, Zhengzhou, Xi'an, and Beijing city where dust storm dust transported along during spring. Element compositions of atmospheric particulates were determined by XRF and ICP-MS. The concentrations of major and trace elements in atmospheric particulates from Putuo, Minhang and Qingpu Districts were similar, indicating their common source. The UCC standardization distribution map showed that the major element composition of dust storm samples was similar to that of loess in northwestern China, indicating that the dust storm dust was mainly derived from Western desert and partly from local area. The REE partition patterns of dust storm dusts among different cities along dust transport route were similar to each other, as well as to those of northern loess, which indicates that the dust storm samples may have the same material source as loess, which mainly comes from crust material. However, the REE partition patterns of non-dust storm particulates were different among the studied cities, and different from those of loess, which suggests that the non-dust storm samples may be mixed with non-crust source material, which is different from dust storm dust and loess. The major element composition and REE partition pattern are effective indicators for source tracing of dust storm dust.

Use of Combined A-Train Observations to Validate GEOS Model Simulated Dust Distributions During NAMMA

NASA Technical Reports Server (NTRS)

Nowottnick, E.

2007-01-01

During August 2006, the NASA African Multidisciplinary Analyses Mission (NAMMA) field experiment was conducted to characterize the structure of African Easterly Waves and their evolution into tropical storms. Mineral dust aerosols affect tropical storm development, although their exact role remains to be understood. To better understand the role of dust on tropical cyclogenesis, we have implemented a dust source, transport, and optical model in the NASA Goddard Earth Observing System (GEOS) atmospheric general circulation model and data assimilation system. Our dust source scheme is more physically based scheme than previous incarnations of the model, and we introduce improved dust optical and microphysical processes through inclusion of a detailed microphysical scheme. Here we use A-Train observations from MODIS, OMI, and CALIPSO with NAMMA DC-8 flight data to evaluate the simulated dust distributions and microphysical properties. Our goal is to synthesize the multi-spectral observations from the A-Train sensors to arrive at a consistent set of optical properties for the dust aerosols suitable for direct forcing calculations.

The roles of spirituality in the relationship between traumatic life events, mental health, and drug use among African American women

PubMed Central

Staton-Tindall, Michele; Duvall, Jamieson; Stevens-Watkins, Danelle; Oser, Carrie B.

2013-01-01

This study examines the role of spirituality as a moderator of the relationship between traumatic life experiences, mental health, and drug use in a sample of African American women. It was hypothesized that there would be an inverse relationship overall between spirituality and mental health and drug use among this sample of African American women. Secondly, was expected that spirituality would moderate the relationship between traumatic life events and mental health and drug use. African American women (n=206) were recruited from the community and from probation officers in three urban areas of a southern state, and face-to-face interviews were completed. Findings indicated that there was a main effect for spirituality (as measured by existential well-being on the Spiritual Well-Being Scale) and traumatic life events, mental health, and alcohol use. In addition, spirituality was a significant moderator of the relationship between traumatic life events and cocaine use. Discussion and implications for African American women are included. PMID:24041186

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

Increasing cardiopulmonary emergency visits by long-range transported Asian dust storms in Taiwan.

PubMed

Chan, Chang-Chuan; Chuang, Kai-Jen; Chen, Wen-Jone; Chang, Wei-Tien; Lee, Chung-Te; Peng, Chi-Ming

2008-03-01

This study aims to explore whether Asian dust storms can affect health after 4000 km long-range transport from their origins to downwind areas. Asian dust storms reaching Taipei, Taiwan are tracked by satellite images and confirmed by backward trajectory analysis and ground air pollution monitoring between 1995 and 2002. Our outcome variables include emergency visits for ischaemic heart diseases (ICD-9-CM 410-411, 414), cerebrovascular diseases (ICD-9-CM 430-437), and chronic obstructive pulmonary diseases (COPD) (ICD-9-CM 493, 496) from the National Taiwan University Hospital (NTUH). We use simple paired t-test and Poisson regression models to compare difference in emergency visits, air pollution levels and meteorological conditions for the pairs of Asian dust events and pre-dust periods. There were 39 high dust events with PM(10) greater than 90 microg/m(3) and another 46 low dust events with PM(10) less than 90 microg/m(3). Compared to their pre-dust periods, PM(10) concentrations are significantly increased by 77 microg/m(3) per event for the high dust events. Asian dust storms increase cardiopulmonary emergency visits during storm-affecting periods in Taipei when ambient PM(10) concentrations are above 90 microg/m(3). Compared to their pre-dust periods, emergency visits for ischaemic heart diseases, cerebrovascular diseases, and COPD during high dust events are increased by 0.7 case (35%), 0.7 case (20%), and 0.9 case (20%) per event, respectively, by paired t-tests. By comparing the model-predicted to the observed emergency visits, we find emergency visits for cardiovascular diseases (ICD-9-CM 410-411, 414, 430-437) were significantly increased by 2.9 cases (67%) per event for the 39 high Asian dust events.

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

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

Saharan desert dust lifted by convection over the hot desert surface can reach high altitudes and be transported over great distances. In the UK, Saharan dust episodes occur several times a year, usually during the spring. Dust lifted by cyclonic circulation is often blown into the Atlantic and transported to the UK. This can result in a rapid degradation of air quality due to the increase in the levels of particulate matter (PM). The ability to model the transport and deposition of dust remains an important challenge in order to characterize different pollution events. We present a comparison of observed Aerosol Optical Depth (AOD) with modelled AOD from the Met Office Air Quality Unified Model (AQUM), performed for two dust events in March 2014 (at 380nm, 440nm, 870nm and 1020nm). The observations are derived from five sun photometers located in the southern UK at Exeter, Cardington, Bayfordbury, Chilbolton, and Plymouth. Correlations are investigated between model column integrated PM2.5 and PM10, and observed fine and coarse mode AOD from AERONET. Vertical profiles of attenuated backscatter and extinction from the Jenoptik Nimbus ceilometers part of the Met Office Laser Cloud Base Recorder (LCBR) network are investigated as well (see also session AS3.17/GI2.2 Lidar and Applications). The Met Office air quality model AQUM is an on-line meteorology, chemistry and aerosol modelling system. It runs at a resolution of 12km over a domain covering the UK and north-western Europe. Atmospheric composition modelling employs two-way coupling between aerosol and chemistry evolution, with explicit modelling of sulphate, nitrate, black carbon, organic carbon, biomass burning and wind-blown mineral dust aerosol components. Both the model and observations show an increase in AOD during the first period from 12 -13 March 2014. For example AOD levels of up to 0.52 for the 380nm channel were recorded by the sun photometer in Exeter. This is relatively high compared to average

The impact of lifecourse socioeconomic position on cardiovascular disease events in African Americans: the Jackson Heart Study.

PubMed

Gebreab, Samson Y; Diez Roux, Ana V; Brenner, Allison B; Hickson, DeMarc A; Sims, Mario; Subramanyam, Malavika; Griswold, Michael E; Wyatt, Sharon B; James, Sherman A

2015-05-27

Few studies have examined the impact of lifecourse socioeconomic position (SEP) on cardiovascular disease (CVD) risk among African Americans. We used data from the Jackson Heart Study (JHS) to examine the associations of multiple measures of lifecourse SEP with CVD events in a large cohort of African Americans. During a median of 7.2-year follow-up, 362 new or recurrent CVD events occurred in a sample of 5301 participants aged 21 to 94. Childhood SEP was assessed by using mother's education, parental home ownership, and childhood amenities. Adult SEP was assessed by using education, income, wealth, and public assistance. Adult SEP was more consistently associated with CVD risk in women than in men: age-adjusted hazard ratios for low versus high income (95% CIs), 2.46 (1.19 to 5.09) in women and 1.50 (0.87 to 2.58) in men, P for interaction=0.1244, and hazard ratio for low versus high wealth, 2.14 (1.39 to 3.29) in women and 1.06 (0.62 to 1.81) in men, P for interaction=0.0224. After simultaneous adjustment for all adult SEP measures, wealth remained a significant predictor of CVD events in women (HR=1.73 [1.04, 2.85] for low versus high). Education and public assistance were less consistently associated with CVD. Adult SEP was a stronger predictor of CVD events in younger than in older participants (HR for high versus low summary adult SEP score 3.28 [1.43, 7.53] for participants ≤50 years, and 1.90 (1.36 to 2.66) for participants >50 years, P for interaction 0.0846). Childhood SEP was not associated with CVD risk in women or men. Adult SEP is an important predictor of CVD events in African American women and in younger African Americans. Childhood SEP was not associated with CVD events in this population. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

The Impact of Lifecourse Socioeconomic Position on Cardiovascular Disease Events in African Americans: The Jackson Heart Study

PubMed Central

Gebreab, Samson Y; Diez Roux, Ana V; Brenner, Allison B; Hickson, DeMarc A; Sims, Mario; Subramanyam, Malavika; Griswold, Michael E; Wyatt, Sharon B; James, Sherman A

2015-01-01

Background Few studies have examined the impact of lifecourse socioeconomic position (SEP) on cardiovascular disease (CVD) risk among African Americans. Methods and Results We used data from the Jackson Heart Study (JHS) to examine the associations of multiple measures of lifecourse SEP with CVD events in a large cohort of African Americans. During a median of 7.2-year follow-up, 362 new or recurrent CVD events occurred in a sample of 5301 participants aged 21 to 94. Childhood SEP was assessed by using mother’s education, parental home ownership, and childhood amenities. Adult SEP was assessed by using education, income, wealth, and public assistance. Adult SEP was more consistently associated with CVD risk in women than in men: age-adjusted hazard ratios for low versus high income (95% CIs), 2.46 (1.19 to 5.09) in women and 1.50 (0.87 to 2.58) in men, P for interaction=0.1244, and hazard ratio for low versus high wealth, 2.14 (1.39 to 3.29) in women and 1.06 (0.62 to 1.81) in men, P for interaction=0.0224. After simultaneous adjustment for all adult SEP measures, wealth remained a significant predictor of CVD events in women (HR=1.73 [1.04, 2.85] for low versus high). Education and public assistance were less consistently associated with CVD. Adult SEP was a stronger predictor of CVD events in younger than in older participants (HR for high versus low summary adult SEP score 3.28 [1.43, 7.53] for participants ≤50 years, and 1.90 (1.36 to 2.66) for participants >50 years, P for interaction 0.0846). Childhood SEP was not associated with CVD risk in women or men. Conclusions Adult SEP is an important predictor of CVD events in African American women and in younger African Americans. Childhood SEP was not associated with CVD events in this population. PMID:26019130

Chemical coupling between acid gases and water-soluble inorganic ions in size-segregated aerosols during Arabian Dust in Beirut

NASA Astrophysics Data System (ADS)

Saliba, Najat; Dada, Lubna; Baalbaki, Rima

2015-04-01

In the proximity of the Eastern Mediterranean region, the combination of two large desert areas; Arabian and African, with heavy oil industry and high insolation during summer delineate a unique location of atmospheric processes in the region. Once emitted, dust particles can be transported over long distances and/or remain suspended in the atmosphere for several days. The so-called remnant dust episodes in Beirut originate from both African and Arabian deserts. In this study, the gas and particle transformations and gas-to-particle conversion during Arabian-dust (Ar-D) events are assessed. The increase in primary and secondary gas concentrations during Ar-D days is ascribed to three contributing factors; (i) the regional-long-range transport (LRT), (ii) the drop in the average solar radiation leading to a slow primary-to-secondary conversion and secondary gas photo-degradation, and (iii) the enhancement of the recirculation and accumulation of the main pollutants during dusty days. In parallel, a respective mass increase by 137, 149 and 13% in the coarse (CPM), accumulation (ACC) and ultrafine (UF) fractions was measured and an increase in particle volume distribution was mostly noticed for particles ranging in sizes between 2.25 and 5 μm. This lead to major changes in the inorganic chemical composition of all particle sizes. In particular, the enhanced presence of several types of nitrate and sulfate salts in the accumulation mode confirms that remnant dust episodes offer a favorable environment for gas-to-particle conversion and particle chemical transformations and growth.

Violence and other stressful life events as triggers of depression and anxiety: what psychosocial resources protect African American mothers?

PubMed

Mitchell, Stephanie J; Ronzio, Cynthia R

2011-11-01

Understanding the risk and protective factors related to maternal mental health problems is important for improving the well-being of mothers and children, particularly in African American populations which may be at greater risk for maternal depression and resulting child behavior problems. This study explored whether three psychosocial resources--emotional resilience, social support, and ethnic identity--serve as protective factors in the face of specific stressful events that may trigger African American mothers' depression and anxiety symptoms. Standard self-report measures of depression, anxiety, negative life events, community violence, abuse, emotional resilience, social support, and ethnic identity were administered to African American mothers (N=209) of 2-18 month-old children. Linear regression models revealed main effects of negative life events and abuse on increased depression and anxiety symptoms, while emotional resilience and social support predicted decreased symptoms. There was also a significant interaction revealing a protective-reactive effect of ethnic identity on the associations of witnessed community violence with depression and anxiety symptoms. It is important for primary care providers to screen African American mothers for negative life events and abuse to identify those at increased risk for maternal depression and anxiety symptoms. Treatment programs should target emotional resilience, enhanced social support, and stronger ethnic group affiliation, which may be most effective at preventing mental health problems among mothers exposed to relative lower levels of community violence.

Circumstellar Dust in Symbiotic Novae

NASA Astrophysics Data System (ADS)

Jurkic, T.; Kotnik-Karuza, D.

2015-12-01

We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the near-IR photometry, ISO spectra and mid-IR interferometry. The dust properties were determined using the DUSTY code. A compact circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel shows the presence of an equatorially enhanced dust density during minimum obscuration. Obscuration events are explained by an increase in optical depth caused by the newly condensed dust. The mass loss rates are significantly higher than in intermediate-period single Miras but in agreement with longer-period O-rich AGB stars.

Dust Storm Feature Identification and Tracking from 4D Simulation Data

NASA Astrophysics Data System (ADS)

Yu, M.; Yang, C. P.

2016-12-01

Dust storms cause significant damage to health, property and the environment worldwide every year. To help mitigate the damage, dust forecasting models simulate and predict upcoming dust events, providing valuable information to scientists, decision makers, and the public. Normally, the model simulations are conducted in four-dimensions (i.e., latitude, longitude, elevation and time) and represent three-dimensional (3D), spatial heterogeneous features of the storm and its evolution over space and time. This research investigates and proposes an automatic multi-threshold, region-growing based identification algorithm to identify critical dust storm features, and track the evolution process of dust storm events through space and time. In addition, a spatiotemporal data model is proposed, which can support the characterization and representation of dust storm events and their dynamic patterns. Quantitative and qualitative evaluations for the algorithm are conducted to test the sensitivity, and capability of identify and track dust storm events. This study has the potential to assist a better early warning system for decision-makers and the public, thus making hazard mitigation plans more effective.

Grain dust and respiratory health in South African milling workers.

PubMed Central

Bachmann, M; Myers, J E

1991-01-01

Respiratory health was investigated in 224 grain milling workers. The likelihood of respiratory symptoms and chronic airflow limitation was raised for workers exposed to dust independent of the effects of smoking. Smokers were more likely than non-smokers to respond to a bronchodilator at the end of the working week. Dust was more strongly associated with most abnormal outcomes than was smoking. Subjective categories of exposure to dust were more strongly associated with most abnormal outcomes than were objective categories. The prevalence of all symptoms at the time of a survey conducted at the mill six years before was higher in workers who subsequently left the mill than in those who remained employed although the differences were not significant. PMID:1931723

Recurrent decadal-scale dust events over Holocene western Africa and their control on canyon turbidite activity (Mauritania)

NASA Astrophysics Data System (ADS)

Hanebuth, Till J. J.; Henrich, Rüdiger

2009-02-01

Sediment records from continental shelves and slopes might provide paleoenvironmental information in the highest temporal resolution but are often hampered due to strong erosional and reworking processes. Here, we present a Holocene sedimentary record from an exceptional shelf mud belt depocenter off northern Mauritania, compared to a second sediment core located inside a large canyon system at the adjacent continental slope. Both records are of outstandingly continuous and highest temporal resolution (9 a/cm) and are investigated by sedimentological and geochemical methods. A series of sharply defined, recurrent dust peaks is preserved in the shelf archive. Each event has lasted for a single decade only and seems to coincide with an individual turbidite bed in the canyon. A joint mechanism should, thus, be responsible for both of these deposits and we suggest a regional atmospheric trigger. Only short-lasting Trade wind strengthening would cause such pronounced aridity over western Saharan Africa. The effect would be massive dust export to shelf and slope. Recently developed high resolution aridity and humidity records from western Africa support the existence of these events over the Holocene and identify them as being controlled by the Atlantic system as far south as 19°N.

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

WRF-Chem Model Simulations of Arizona Dust Storms

NASA Astrophysics Data System (ADS)

Mohebbi, A.; Chang, H. I.; Hondula, D.

2017-12-01

The online Weather Research and Forecasting model with coupled chemistry module (WRF-Chem) is applied to simulate the transport, deposition and emission of the dust aerosols in an intense dust outbreak event that took place on July 5th, 2011 over Arizona. Goddard Chemistry Aerosol Radiation and Transport (GOCART), Air Force Weather Agency (AFWA), and University of Cologne (UoC) parameterization schemes for dust emission were evaluated. The model was found to simulate well the synoptic meteorological conditions also widely documented in previous studies. The chemistry module performance in reproducing the atmospheric desert dust load was evaluated using the horizontal field of the Aerosol Optical Depth (AOD) from Moderate Resolution Imaging Spectro (MODIS) radiometer Terra/Aqua and Aerosol Robotic Network (AERONET) satellites employing standard Dark Target (DT) and Deep Blue (DB) algorithms. To assess the temporal variability of the dust storm, Particulate Matter mass concentration data (PM10 and PM2.5) from Arizona Department of Environmental Quality (AZDEQ) ground-based air quality stations were used. The promising performance of WRF-Chem indicate that the model is capable of simulating the right timing and loading of a dust event in the planetary-boundary-layer (PBL) which can be used to forecast approaching severe dust events and to communicate an effective early warning.

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.

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.

Dust Fertilization of the Western Atlantic Biota: a Biochemical Model

NASA Astrophysics Data System (ADS)

Holmes, C. W.

2017-12-01

Every year an estimated 50 million tons of African dust reaches the Western Atlantic. This dust is composed of quartz sand, clay, and a mixture of quartz and clay particles agglutinated with micronutrient enriched ferruginous cement. However, whether it is friend or foe to biochemical systems is a matter of conjecture. Corals are ideal recorders of changing conditions as the layers can be dated so that the record of chemical changes is easily assessed. There is extensive shallow-and deep water coral development bordering the Florida Straits. The changes in trace element chemistry within these corals show a positive relationship with the African dust record. Recently, it has been demonstrated that many of the metals contained within the dust are necessary micronutrients in the fertilization of plankton. Using the results of these studies, a biochemical model has been constructed. This model suggests a path from inorganic dust through microbial transformation to micronutrient enzymes (i.e. Cd-enriched carbonic anahydrase) and carbonate precipitation on the Bahamian Banks. It is estimated that more than ten million metric tons of this fine, metal-rich sediment is formed each year. However, for much of this sediment, its deposition is temporary, as it is transported into the Florida Straits yearly by tropical cyclones. This metal-enriched fine carbonate becomes nutrients for phytoplankton, providing food for the corals, both shallow and deep.

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

aerosol is involved in many important processes in Earth's climate system, with important implications for air quality, climate, atmospheric chemistry, and the biosphere, and different impacts on human health. The relative importance of mineral dust in particulate matter depends on location, season and particle size, mainly concentrated in the coarse fraction. Its impacts on climate and environment have increased years after years and needs to be more understood. In the present work, the relationships between the meteorological conditions and dust transport phenomena from the Saharan regions of north Africa and their transport, deposition in both modes, dry and wet deposition in the Mediterranean region, and the Atlantic Ocean, during two dust events namely: case I (01/03/04 - 06/03/04), case II (29/05/05 - 03/06/05), that have been analysed and their major characteristics have been discussed. This analysis has been performed with the aid of the SKIRON modelling system of the University of Athens. The dust module of SKIRON/Eta model incorporates the state of the art parameterization of all the major phases of the desert dust cycle such as production, diffusion, advection and removal. Model results have been compared with TOMS-AI (Total Ozone Mapping Spectrophotometer Aerosol Index) data for a qualitative comparison of the model. The work has been conducted at the framework of TEMPUS project MADEPODIM.

Chemical Composition Characteristics of Atmospheric Aerosols in Relation to Haze, Asian Dust and Mixed Haze-Asian Dust Episodes at Background Site of Korea in 2013

NASA Astrophysics Data System (ADS)

KO, H.; Song, J. M.; Cha, J. W.; Kang, C. H.; Kim, J.; Ryoo, S. B.

2016-12-01

The PM10 and PM2.5 aerosols were collected at the Gosan site of Jeju Island, Korea in 2013 and analyzed, in order to examine the variation characteristics of chemical compositions in relation to haze, Asian dust, and mixed haze-Asian dust episodes. For the haze event, nitrate concentrations increased highly as 8.8 and 25.1 times for PM10 and PM2.5, respectively, possibly caused by the inflow of air mass stagnated in eastern parts of China into Jeju area. For the Asian dust event, the concentrations of nss-Ca2+, NO3- and nss-SO42- increased 6.0, 1.5, 1.8 times for PM10, and 2.3, 1.3, 1.6 times for PM2.5, respectively. Meanwhile, for the mixed haze-Asian dust event, the concentrations of nss-Ca2+ and NO3- increased 13.4 and 3.2 times for PM10, and 1.8 and 3.4 times for PM2.5, respectively. The NH4NO3 content was higher than that of (NH4)2SO4 during the haze event, however it was relatively low during the mixed haze-Asian dust event. NO3-/nss-SO42- concentration ratios of Asian Dust in PM10 and PM2.5 were 0.4 and 0.2, showing less significant effect from automobile and local pollution sources. The aerosols were acidified mostly by inorganic acids, especially the nitric acid contributed highly to the acidification during both haze and mixed haze-Asian dust events. Meanwhile, the neutralization by ammonia was noticeably high during haze event when the stagnated air mass moved from China.

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.

Assessment of State-of-the-Art Dust Emission Scheme in GEOS

NASA Technical Reports Server (NTRS)

Darmenov, Anton; Liu, Xiaohong; Prigent, Catherine

2017-01-01

The GEOS modeling system has been extended with state of the art parameterization of dust emissions based on the vertical flux formulation described in Kok et al 2014. The new dust scheme was coupled with the GOCART and MAM aerosol models. In the present study we compare dust emissions, aerosol optical depth (AOD) and radiative fluxes from GEOS experiments with the standard and new dust emissions. AOD from the model experiments are also compared with AERONET and satellite based data. Based on this comparative analysis we concluded that the new parameterization improves the GEOS capability to model dust aerosols originating from African sources, however it lead to overestimation of dust emissions from Asian and Arabian sources. Further regional tuning of key parameters controlling the threshold friction velocity may be required in order to achieve more definitive and uniform improvement in the dust modeling skill.

Chemical Speciation of Water Soluble Ions and Metals of Cloud and Rain Water During the Puerto Rico African Dust and Clouds Study (PRADACS) Campaigns

NASA Astrophysics Data System (ADS)

Torres, E.; Valle Diaz, C. J.; Lee, T.; Collett, J. L.; Fitzgerald, E.; Cuadra-Rodriguez, L. A.; Prather, K. A.; Sánchez, M.; McDowell, W. H.; Mayol-Bracero, O. L.

2013-05-01

The underlying physico-chemical processes of dust particles interactions are poorly understood; even less understood is how aging impacts cloud properties and climate as the particles travel from Africa to the Caribbean region. Caribbean landmasses have tropical montane cloud forests (TMCFs) that are tightly coupled to the atmospheric hydrologic cycle. TMCFs are ecosystems to study the effects African Dust (AD) on cloud formation and precipitation as these are very sensitive ecosystems that respond to small changes in climate. As part of the Puerto Rico African Dust and Clouds Study (PRADACS), chemical analyses were performed on cloud and rain water samples collected at Pico del Este (PE) station in Luquillo, PR (1051 masl) during campaigns held from 2010 to 2012. At PE, two cloud collectors (i.e., single stage (Aluminum version), a 2-stage (Teflon version) Caltech Active Strand Cloudwater Collector (CASCC)), a rainwater collector, and anAerosol Time-Of-Flight Mass Spectrometer (ATOFMS) were operated. Chemical analyses performed on collected samples include pH, conductivity, ion chromatography (IC), and inductive coupled plasma (ICP). Results from these campaigns showed that on days that had air masses with the influence of AD, cloud water samples had higher conductivity and pH values on average (up to 5.7 and 180μS/cm, respectively) than those with air masses without AD influence. An increase in the concentrations of water-soluble ions like non-sea salt calcium and magnesium, and metals like magnesium, calcium and aluminum was observed and the appearance of iron was seen on ICP analyses. The ATOFMS, showed an increase on the amount of particles during AD influence with composition of aluminum, silicates, potassium, iron and titanium aerosols. The increase on the aforementioned species was constant in the three years of sampling, which give us confidence in the identification of the chemical species that are present during the influence of AD.

Estimation of respirable dust exposure among coal miners in South Africa.

PubMed

Naidoo, Rajen; Seixas, Noah; Robins, Thomas

2006-06-01

The use of retrospective occupational hygiene data for epidemiologic studies is useful in determining exposure-outcome relationships, but the potential for exposure misclassification is high. Although dust sampling in the South African coal industry has been a legal requirement for several decades, these historical data are not readily adequate for estimating past exposures. This study describes the respirable coal mine dust levels in three South African coal mines over time. Each of the participating mining operations had well-documented dust sampling information that was used to describe historical trends in dust exposure. Investigator-collected personal dust samples were taken using standardized techniques from the face, backbye (underground jobs not at the coal face), and surface from 50 miners at each mine, repeated over three sampling cycles. Job histories and exposure information was obtained from a sample of 684 current miners and 188 ex-miners. Linear models were developed to estimate the exposure levels associated with work in each mine, exposure zone, and over time using a combination of operator-collected historical data and investigator-collected samples. The estimated levels were then combined with work history information to calculate cumulative exposure metrics for the miner cohort. The mean historical and investigator-collected respirable dust levels were within international norms and South African standards. Silica content of the dust samples was also below the 5% regulatory action level. Mean respirable dust concentrations at the face, based on investigator-collected samples, were 0.9 mg/m(3), 1.3 mg/m(3), and 1.9 mg/m(3) at Mines 1, 2, and 3, respectively. The operator-collected samples showed considerable variability across exposure zones, mines, and time, with the annual means at the face ranging from 0.4 mg/m(3) to 2.9 mg/m(3). Statistically significant findings were found between operator- and investigator-collected dust samples. Model

Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

NASA Astrophysics Data System (ADS)

Wittmann, Monika; Dorothea Groot Zwaaftink, Christine; Steffensen Schmidt, Louise; Guðmundsson, Sverrir; Pálsson, Finnur; Arnalds, Olafur; Björnsson, Helgi; Thorsteinsson, Throstur; Stohl, Andreas

2017-03-01

Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ˜ 1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m-2. At the station located higher on the glacier ( ˜ 1525 m a.s.l.), the model produced nine dust events, with one single event causing ˜ 5 g m-2 of dust deposition and a total deposition of ˜ 10 g m-2 yr-1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of

A History of the Martian Dust Storms

NASA Astrophysics Data System (ADS)

McKim, R. J.

2005-08-01

The author reviews historical observations of Martian dust storms from the earliest telescopic records up to the present day (see R.J.McKim, Telescopic Martian Dust Storms: A Narrative and Catalogue, Memoirs of the British Astronomical Association, volume 44, 1999 (166 pp)). The earliest record begins with Maraldi in 1704. The term ``yellow cloud" was coined by Burton (1879). The first event which attracted much attention was the regional dust storm of 1894 October-November. The first planet-encircling event was that of 1909. The daily evolution of dust storms began to be studied in 1911; photography would not help until 1922. Other milestones in our understanding of the phenomenon are illustrated and explained. The telescopic literature is littered with errors of fact and interpretation, and the author describes some of the pitfalls and successes in the analysis of old telescopic records.

A multidisciplinary approach to trace Asian dust storms from source to sink

NASA Astrophysics Data System (ADS)

Yan, Yan; Sun, Youbin; Ma, Long; Long, Xin

2015-03-01

Tracing the source of dust storm (DS) in mega-cities of northern China currently suffers ambiguities from different approaches including source-sink proxy comparison, air mass back trajectory modeling, and satellite image monitoring. By integrating advantages of all three methods, we present a multidisciplinary approach to trace the provenance of dust fall in Xi'an during the spring season (March to May) of 2012. We collected daily dust fall to calculate dust flux variation, and detected eight DS events with remarkable high flux values based on meteorological comparison and extreme detection algorithm. By combining MODIS images and accompanying real-time air mass back trajectories, we attribute four of them as natural DS events and the other four as anthropogenic DS events, suggesting the importance of natural and anthropogenic processes in supplying long-range transported dust. The primary sources of these DS events were constrained to three possible areas, including the northern Chinese deserts, Taklimakan desert, and Gurbantunggut desert. Proxy comparisons based upon the quartz crystallinity index and oxygen isotope further confirmed the source-to-sink linkage between the natural DS events in Xi'an and the dust emissions from the northern Chinese deserts. The integration of geochemical and meteorological tracing approaches favors the dominant contribution of short-distance transportation of modern dust fall on the Chinese Loess Plateau. Our study shows that the multidisciplinary approach could permit a better source identification of modern dust and should be applied properly for tracing the provenance fluctuations of geological dust deposits.

The sensitivity of a general circulation model to Saharan dust heating

NASA Technical Reports Server (NTRS)

Randall, D. A.; Carlson, T.; Mintz, Y.

1984-01-01

During the Northern summer, sporadic outbreaks of wind borne Saharan dust are carried out over the Atlantic by the tropical easterlies. Optical depths due to the dust can reach 3 near the African coast, and the dust cloud can be detected as far west as the Caribbean Sea (Carlson, 1979). In order to obtain insight into the possible effects of Saharan dust on the weather and climate of North Africa and the tropical Atlantic Ocean, simulation experiments have been performed with the Climate Model of the Goddard Laboratory for Atmospheric Sciences. The most recent version of the model is described by Randall (1982). The model produces realistic simulations of many aspects of the observed climate and its seasonal variation.

Can Asian Dust Trigger Phytoplankton Blooms in the Oligotrophic Northern South China Sea?

NASA Technical Reports Server (NTRS)

Wang, Sheng Hsiang; Hsu, Nai-Yung Christina; Tsay, Si-Chee; Lin, Neng-Huei; Sayer, Andrew M.; Huang, Shih-Jen; Lau, William K. M.

2012-01-01

Satellite data estimate a high dust deposition flux (approximately 18 g m(exp-2 a(exp-1) into the northern South China Sea (SCS). However, observational evidence concerning any biological response to dust fertilization is sparse. In this study, we combined long-term aerosol and chlorophyll-a (Chl-a) measurements from satellite sensors (MODIS and SeaWiFS) with a 16-year record of dust events from surface PM10 observations to investigate dust transport, flux, and the changes in Chl-a concentration over the northern SCS. Our result revealed that readily identifiable strong dust events over this region, although relatively rare (6 cases since 1994) and accounting for only a small proportion of the total dust deposition (approximately 0.28 g m(exp-2 a(exp-1), do occur and could significantly enhance phytoplankton blooms. Following such events, the Chl-a concentration increased up to 4-fold, and generally doubled the springtime background value (0.15 mg m(exp-3). We suggest these heavy dust events contain readily bioavailable iron and enhance the phytoplankton growth in the oligotrophic northern SCS.

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

Early-Holocene greening of the Afro-Asian dust belt changed sources of mineral dust in West Asia

NASA Astrophysics Data System (ADS)

Sharifi, Arash; Murphy, Lisa N.; Pourmand, Ali; Clement, Amy C.; Canuel, Elizabeth A.; Naderi Beni, Abdolmajid; Lahijani, Hamid A. K.; Delanghe, Doriane; Ahmady-Birgani, Hesam

2018-01-01

Production, transport and deposition of mineral dust have significant impacts on different components of the Earth systems through time and space. In modern times, dust plumes are associated with their source region(s) using satellite and land-based measurements and trajectory analysis of air masses through time. Reconstruction of past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-dust, and that of their potential source origins. In this contribution, we present a 13,000-yr record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies as well as dust grain size from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in the sources of dust over the interior of West Asia. Our data shows that although the grain size of dust varies in a narrow range through the entire record, the geochemical fingerprint of dust particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from aerosols deposited during high dust flux periods of the Younger Dryas and the mid-late Holocene (6,000-present). Our findings indicate that the composition of mineral dust deposited at the study site changed as a function of prevailing atmospheric circulation regimes and land exposure throughout the last deglacial period and the Holocene. Simulations of atmospheric circulation over the region show the Northern Hemisphere Summer Westerly Jet was displaced poleward across the study area during the early Holocene when Northern Hemisphere insolation was higher due to the Earth's orbital configuration. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia dominating dust export to West Asia during this period. In contrast, the dominant western and

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.

How Early Holocene Greening of the Afro-Asian Dust Belt Changed Sources of Mineral Dust in West Asia

NASA Astrophysics Data System (ADS)

Pourmand, A.; Sharifi, A.; Goes, L. M.; Clement, A. C.; Canuel, E. A.; Naderi Beni, A.; Ahmady-Birgani, H.

2016-12-01

Production, transport and deposition of mineral dust have significant temporal and spatial impacts on different components of the Earth systems. In modern times, dust plumes can be associated with their source origin(s) using satellite and land-based measurements and back-trajectory reconstruction of air masses. Reconstructing past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleo-dust, and their potential source origins. In this contribution, we present a 13,000-year record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in sources of dust over West Asia. The geochemical fingerprint of dust particles deposited during the low-flux, early Holocene period (11,700-6,000 yr BP) is distinctly different from times of high dust fluxes during the Younger Dryas, and that of the mid-late Holocene. This indicates that the composition of mineral dust deposited at the receptor site changed as a function of prevailing atmospheric circulation regimes and land exposure. Simulations of atmospheric circulation over the region show the Northern Hemisphere Westerly Jet (NHWJ) was displaced poleward across the study area during the early Holocene when solar insolation was higher. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia to dominate dust export to West Asia during this period, in contrast to the dominant western and southwest Asian and Eastern African sources that prevail during the modern period.

The effects of transported Asian dust on the composition and concentration of ambient fungi in Taiwan

NASA Astrophysics Data System (ADS)

Chao, H. Jasmine; Chan, Chang-Chuan; Rao, Carol Y.; Lee, Chung-Te; Chuang, Ying-Chih; Chiu, Yueh-Hsiu; Hsu, Hsiao-Hsien; Wu, Yi-Hua

2012-03-01

This study was conducted to evaluate the effects of transported Asian dust and other environmental parameters on the levels and compositions of ambient fungi in the atmosphere of northern Taiwan. We monitored Asian dust events in Taipei County, Taiwan from January 2003 to June 2004. We used duplicate Burkard portable air samplers to collect ambient fungi before, during, and after dust events. Six transported Asian dust events were monitored during the study period. Elevated concentrations of Aspergillus ( A. niger, specifically), Coelomycetes, Rhinocladiella, Sporothrix and Verticillium were noted ( p < 0.05) during Asian dust periods. Botryosporium and Trichothecium were only recovered during dust event days. Multiple regression analysis showed that fungal levels were positively associated with temperature, wind speed, rainfall, non-methane hydrocarbons and particulates with aerodynamic diameters ≤10 μm (PM10), and negatively correlated with relative humidity and ozone. Our results demonstrated that Asian dust events affected ambient fungal concentrations and compositions in northern Taiwan. Ambient fungi also had complex dynamics with air pollutants and meteorological factors. Future studies should explore the health impacts of ambient fungi during Asian dust events, adjusting for the synergistic/antagonistic effects of weather and air pollutants.

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.

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 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.

Dust storms and their impact on ocean and human health: dust in Earth's atmosphere

USGS Publications Warehouse

Griffin, Dale W.; Kellog, Christina A.

2004-01-01

Satellite imagery has greatly influenced our understanding of dust activity on a global scale. A number of different satellites such as NASA's Earth-Probe Total Ozone Mapping Spectrometer (TOMS) and Se-viewing Field-of-view Sensor (SeaWiFS) acquire daily global-scale data used to produce imagery for monitoring dust storm formation and movement. This global-scale imagery has documented the frequent transmission of dust storm-derived soils through Earth's atmosphere and the magnitude of many of these events. While various research projects have been undertaken to understand this normal planetary process, little has been done to address its impact on ocean and human health. This review will address the ability of dust storms to influence marine microbial population densities and transport of soil-associated toxins and pathogenic microorganisms to marine environments. The implications of dust on ocean and human health in this emerging scientific field will be discussed.

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

Temporal and spatial variations in sand and dust storm events in East Asia from 2007 to 2016: Relationships with surface conditions and climate change.

PubMed

An, Linchang; Che, Huizheng; Xue, Min; Zhang, Tianhang; Wang, Hong; Wang, Yaqiang; Zhou, Chunhong; Zhao, Hujia; Gui, Ke; Zheng, Yu; Sun, Tianze; Liang, Yuanxin; Sun, Enwei; Zhang, Hengde; Zhang, Xiaoye

2018-08-15

We analyzed the frequency and intensity of sand and dust storms (SDSs) in East Asia from 2007 to 2016 using observational data from ground stations, numerical modeling, and vegetation indices obtained from both satellite and reanalysis data. The relationships of SDSs with surface conditions and the synoptic circulation pattern were also analyzed. The statistical analyses demonstrated that the number and intensity of SDS events recorded in spring during 2007 to 2016 showed a decreasing trend. The total number of spring SDSs decreased from at least ten events per year before 2011 to less than ten events per year after 2011. The overall average annual variation of the surface dust concentration in the main dust source regions decreased 33.24μg/m 3 (-1.75%) annually. The variation in the temperatures near and below the ground surface and the amount of precipitation and soil moisture all favored an improvement in vegetation coverage, which reduced the intensity and frequency of SDSs. The strong winds accompanying the influx of cold air from high latitudes showed a decreasing trend, leading to a decrease in the number of SDSs and playing a key role in the decadal decrease of SDSs. The decrease in the intensity of the polar vortex during study period was closely related to the decrease in the intensity and frequency of SDSs. Copyright © 2018 Elsevier B.V. All rights reserved.

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.

The impacts of the dust radiative effect on vegetation growth in the Sahel

NASA Astrophysics Data System (ADS)

Evans, S. M.; Shevliakova, E.; Malyshev, S.; Ginoux, P. A.

2017-12-01

Many studies have been conducted on the effects of dust on rainfall in the Sahel, and generally show that African dust weakens the West African Monsoon, drying the region. This drying is often assumed to reduce vegetation cover for the region, providing a positive feedback with dust emission. There are, however, other competing effects of dust that are also important to plant growth, including a reduction in surface temperature, a reduction in downwelling solar radiation, and an increase in the diffuse fraction of that solar radiation. Using the NOAA/GFDL CM3 model coupled to the dynamic vegetation model LM3, we demonstrate that the combined effect of all these processes is to decrease the vegetation coverage and productivity of the Sahel and West Africa. We accomplish this by comparing experiments with radiatively active dust to experiments with radiatively invisible dust. We find that in modern conditions, the dust radiative effect reduces the net primary productivity of West Africa and the Sahel by up to 30% locally, and when summed over the region accounts for a difference of approximately 0.4 GtC per year. Experiments where the vegetation experiences preindustrial rather than modern CO2 levels show that without carbon fertilization, this loss of productivity would be approximately 10% stronger. In contrast, during preindustrial conditions the vegetation response is less than half as strong, despite the dust induced rainfall and temperature anomalies being similar. We interpret this as the vegetation being less susceptible to drought in a less evaporative climate. These changes in vegetation create the possibility of a dust-vegetation feedback loop whose strength varies with the mean state of the climate, and which may grow stronger in the future.

The roles of spirituality in the relationship between traumatic life events, mental health, and drug use among African American women from one southern state.

PubMed

Staton-Tindall, Michele; Duvall, Jamieson; Stevens-Watkins, Danelle; Oser, Carrie B

2013-09-01

This study examines the role of spirituality as a moderator of the relationship between traumatic life experiences, mental health, and drug use in a sample of African American women. It was hypothesized that there would be an inverse relationship overall between spirituality and mental health and drug use among this sample of African American women. Secondly, was expected that spirituality would moderate the relationship between traumatic life events and mental health and drug use. African American women (n = 206) were recruited from the community and from probation officers in three urban areas of a southern state, and face-to-face interviews were completed. Findings indicated that there was a main effect for spirituality (as measured by existential well-being on the Spiritual Well-Being Scale) and traumatic life events, mental health, and alcohol use. In addition, spirituality was a significant moderator of the relationship between traumatic life events and cocaine use. Discussion and implications for African American women are included.

A 16-year record of eolian dust in Southern Nevada and California, USA: Controls on dust generation and accumulation

USGS Publications Warehouse

Reheis, M.C.

2006-01-01

An ongoing project monitors modern dust accumulation in the arid southwestern United States to (1) determine the rate and composition of dust inputs to soils and (2) relate dust accumulation to weather patterns to help predict the effects of climate change on dust production and accumulation. The 16-year records of 35 dust-trap sites in the eastern Mojave Desert and southern Great Basin reveal how generation and accumulation of dust, including the silt-clay, carbonate, and soluble-salt fractions, is affected by the amount and seasonal distribution of rainfall and the behavior of different source types (alluvium, dry playas, and wet playas). Accumulation rates (fluxes) of the silt-clay fraction of dust, including carbonates, range from about 2-20 g/m2/yr. Average rates are higher in the southern part of the study area (south of latitude 36.5??N) and annually fluctuate over a larger range than rates in the northern part of the area. Sites throughout the study area show peaks in dust flux in the 1984-1985 sampling period and again in 1997-1999; northern sites also show increased flux in 1987-1988 and southern sites in 1989-1991. These peaks of dust flux correspond with both La Nina (dry) conditions and with strong El Nino (wet) periods. The accumulation rates of different components of mineral dusts fluctuate differently. For example, soluble-salt flux increases in 1987-1988, coincident with a moderate El Nino event, and increases very strongly in 1997-1999, overlapping with a strong El Nino event. Both of these high-rainfall winters were preceded and accompanied by strong summer rains. In contrast, little or no change in soluble-salt flux occurred during other periods of high winter rainfall but little summer rain, e.g. 1992-1995. The differences between northern vs. southern sites and between sites with playa dust sources vs. alluvial dust sources indicate that regional differences in the response of precipitation and vegetation growth to ENSO influence and

Short-term variability of mineral dust, metals and carbon emission from road dust resuspension

NASA Astrophysics Data System (ADS)

Amato, Fulvio; Schaap, Martijn; Denier van der Gon, Hugo A. C.; Pandolfi, Marco; Alastuey, Andrés; Keuken, Menno; Querol, Xavier

2013-08-01

Particulate matter (PM) pollution in cities has severe impact on morbidity and mortality of their population. In these cities, road dust resuspension contributes largely to PM and airborne heavy metals concentrations. However, the short-term variation of emission through resuspension is not well described in the air quality models, hampering a reliable description of air pollution and related health effects. In this study we experimentally show that the emission strength of resuspension varies widely among road dust components/sources. Our results offer the first experimental evidence of different emission rates for mineral dust, heavy metals and carbon fractions due to traffic-induced resuspension. Also, the same component (or source) recovers differently in a road in Barcelona (Spain) and a road in Utrecht (The Netherlands). This finding has important implications on atmospheric pollution modelling, mostly for mineral dust, heavy metals and carbon species. After rain events, recoveries were generally faster in Barcelona rather than in Utrecht. The largest difference was found for the mineral dust (Al, Si, Ca). Tyre wear particles (organic carbon and zinc) recovered faster than other road dust particles in both cities. The source apportionment of road dust mass provides useful information for air quality management.

Modern dust aerosol availability in northwestern China.

PubMed

Wang, Xunming; Cheng, Hong; Che, Huizheng; Sun, Jimin; Lu, Huayu; Qiang, Mingrui; Hua, Ting; Zhu, Bingqi; Li, Hui; Ma, Wenyong; Lang, Lili; Jiao, Linlin; Li, Danfeng

2017-08-18

The sources of modern dust aerosols and their emission magnitudes are fundamental for linking dust with climate and environment. Using field sample data, wind tunnel experiments and statistical analysis, we determined the contributions of wadis, gobi (stony desert), lakebeds, riverbeds, and interdunes to modern dust aerosol availability in the three important potential dust sources including the Tarim Basin, Qaidam Basin, and Ala Shan Plateau of China. The results show that riverbeds are the dominant landscape for modern dust aerosol availabilities in the Qaidam Basin, while wadis, gobi, and interdunes are the main landscapes over the Ala Shan Plateau and Tarim Basin. The Ala Shan Plateau and Tarim Basin are potential dust sources in northwestern China, while the Qaidam Basin is not a major source of the modern dust aerosols nowadays, and it is not acting in a significant way to the Loess Plateau presently. Moreover, most of modern dust aerosol emissions from China originated from aeolian processes with low intensities rather than from major dust events.

Association between witnessing traumatic events and psychopathology in the South African Stress and Health Study

PubMed Central

Platt, Jonathan; Williams, David R.; Stein, Dan J.; Koenen, Karestan C.

2016-01-01

Background The high burden of witnessing traumatic events has been demonstrated in previous research in South Africa. However, previous work has focused on PTSD rather than a broader range of psychopathological outcomes. This study examined the association between witnessing trauma and multiple outcomes including mood, anxiety, and substance use disorders. Methods Regression models measured the odds of mood, anxiety, and substance use disorders among those who reported witnessing in the South African Stress and Health Study. Discrete-time survival analysis was used to examine whether witnessing was associated with earlier onset of mental disorders. Results Witnessing trauma was more commonly reported among males and those with low-average education. Posttraumatic stress disorder, mood, and anxiety disorders varied significantly with witnessing status, and witnessing was associated with exposure to a higher number of traumatic events compared to other types of traumatic events. Respondents reporting witnessing trauma had elevated odds of mood and anxiety disorders, but not substance use disorders. Conclusion Witnessing trauma is common in the South African population and results in increased risk of mood and anxiety disorders. Interventions aimed at reducing the burden of trauma and its outcomes must now increase their focus on bystanders and other observers, rather than just focusing on those directly affected. PMID:25773525

Association between witnessing traumatic events and psychopathology in the South African Stress and Health Study.

PubMed

Atwoli, Lukoye; Platt, Jonathan; Williams, David R; Stein, Dan J; Koenen, Karestan C

2015-08-01

The high burden of witnessing traumatic events has been demonstrated in previous research in South Africa. However, previous work has focused on PTSD rather than a broader range of psychopathological outcomes. This study examined the association between witnessing trauma and multiple outcomes including mood, anxiety, and substance use disorders. Regression models measured the odds of mood, anxiety, and substance use disorders among those who reported witnessing in the South African Stress and Health Study. Discrete-time survival analysis was used to examine whether witnessing was associated with earlier onset of mental disorders. Witnessing trauma was more commonly reported among males and those with low-average education. Posttraumatic stress disorder, mood, and anxiety disorders varied significantly with witnessing status, and witnessing was associated with exposure to a higher number of traumatic events compared to other types of traumatic events. Respondents reporting witnessing trauma had elevated odds of mood and anxiety disorders, but not substance use disorders. Witnessing trauma is common in the South African population and results in increased risk of mood and anxiety disorders. Interventions aimed at reducing the burden of trauma and its outcomes must now increase their focus on bystanders and other observers, rather than just focusing on those directly affected.

Dust, Climate, and Human Health

NASA Technical Reports Server (NTRS)

Maynard, Nancy G.

2003-01-01

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

Dust, Climate, and Human Health

NASA Technical Reports Server (NTRS)

Maynard, Nancy G.

2003-01-01

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

Dust, Climate, and Human Health

NASA Astrophysics Data System (ADS)

Maynard, N. G.

2003-12-01

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

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

Physico-chemical characterization of African urban aerosols (Bamako in Mali and Dakar in Senegal) and their toxic effects in human bronchial epithelial cells: description of a worrying situation.

PubMed

Val, Stéphanie; Liousse, Cathy; Doumbia, El Hadji Thierno; Galy-Lacaux, Corinne; Cachier, Hélène; Marchand, Nicolas; Badel, Anne; Gardrat, Eric; Sylvestre, Alexandre; Baeza-Squiban, Armelle

2013-04-02

The involvement of particulate matter (PM) in cardiorespiratory diseases is now established in developed countries whereas in developing areas such as Africa with a high level of specific pollution, PM pollution and its effects are poorly studied. Our objective was to characterize the biological reactivity of urban African aerosols on human bronchial epithelial cells in relation to PM physico-chemical properties to identify toxic sources. Size-speciated aerosol chemical composition was analyzed in Bamako (BK, Mali, 2 samples with one having desert dust event BK1) and Dakar (DK; Senegal) for Ultrafine UF, Fine F and Coarse C PM. PM reactivity was studied in human bronchial epithelial cells investigating six biomarkers (oxidative stress responsive genes and pro-inflammatory cytokines). PM mass concentrations were mainly distributed in coarse mode (60%) and were impressive in BK1 due to the desert dust event. BK2 and DK samples showed a high content of total carbon characteristic of urban areas. The DK sample had huge PAH quantities in bulk aerosol compared with BK that had more water soluble organic carbon and metals. Whatever the site, UF and F PM triggered the mRNA expression of the different biomarkers whereas coarse PM had little or no effect. The GM-CSF biomarker was the most discriminating and showed the strongest pro-inflammatory effect of BK2 PM. The analysis of gene expression signature and of their correlation with main PM compounds revealed that PM-induced responses are mainly related to organic compounds. The toxicity of African aerosols is carried by the finest PM as with Parisian aerosols, but when considering PM mass concentrations, the African population is more highly exposed to toxic particulate pollution than French population. Regarding the prevailing sources in each site, aerosol biological impacts are higher for incomplete combustion sources resulting from two-wheel vehicles and domestic fires than from diesel vehicles (Dakar). Desert dust

Martian Dust Devils: 2 Mars Years of MGS MOC Observations

NASA Astrophysics Data System (ADS)

Cantor, B. A.; Edgett, K. S.

2002-12-01

Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) wide and narrow angle images have captured more than 1000 active dust devils over 2 Mars years. In the most recent Mars year, we repeatedly imaged (and are continuing to image) several areas to monitor dust devil occurrence. Some Mars dust devils are as small as a few to 10s of meters across, others are 100s of meters across and over 6 km high. Each Martian hemisphere has a "dust devil season" that generally follows the subsolar latitude. An exception is NW Amazonis, which has frequent, large dust devils throughout northern spring and summer (probably every afternoon; observations are acquired 2-3 times a week). The Amazonis and other MOC observations show no evidence that dust devils cause, lead to, or have a systematic relationship with dust storms. However, dust devils sometimes do occur near small, localized storms; and one specific relation occurred during the onset of the global dust events of 2001: slightly elevated levels of atmospheric dust (an optically thin cloud) triggered a very short period of dust devil activity in NW Amazonis in early northern autumn. The redistribution of dust by the 2001 global events may have also affected subsequent spring and summer dust devil activity in Hellas, where considerably fewer dust devils occurred in 2001-2002 than 1999-2000. In SW Syria, frequent, large dust devils occurred after the 2001 global events and persisted through southern summer. While dust devils have no specific relation to dust storms, they might play a role in the seasonal "wave of darkening" at middle and high latitudes by removing or disrupting thin veneers of dust. Dust devils have been observed to create thin, filamentary streaks. Some streaks are darker than their surroundings, while others are lighter. Some dust devils do not create streaks. At mid-latitudes, surfaces darken in spring as 100s of crisscrossing streaks form on widely-varied terrain. Some rare streaks exhibit cycloidal patterns

African and Asian dust: from desert soils to coral reefs

USGS Publications Warehouse

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

2003-01-01

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

Simulation and analysis of synoptic scale dust storms over the Arabian Peninsula

NASA Astrophysics Data System (ADS)

Beegum, S. Naseema; Gherboudj, Imen; Chaouch, Naira; Temimi, Marouane; Ghedira, Hosni

2018-01-01

Dust storms are among the most severe environmental problems in arid and semi-arid regions of the world. The predictability of seven dust events, viz. D1: April 2-4, 2014; D2: February 23-24, 2015; D3: April 1-3, 2015; D4: March 26-28, 2016; D5: August 3-5, 2016; D6: March 13-14, 2017 and D7:March 19-21, 2017, are investigated over the Arabian Peninsula using a regionally adapted chemistry transport model CHIMERE coupled with the Weather Research and Forecast (WRF) model. The hourly forecast products of particulate matter concentrations (PM10) and aerosol optical depths (AOD) are compared against both satellite-based (MSG/SEVRI RGB dust, MODIS Deep Blue Aerosol Optical Depth: DB-AOD, Ozone Monitoring Instrument observed UV Aerosol Absorption Index: OMI-AI) and ground-based (AERONET AOD) remote sensing products. The spatial pattern and the time series of the simulations show good agreement with the observations in terms of the dust intensity as well as the spatiotemporal distribution. The causative mechanisms of these dust events are identified by the concurrent analyses of the meteorological data. From these seven storms, five are associated with synoptic scale meteorological processes, such as prefrontal storms (D1 and D7), postfrontal storms of short (D2), and long (D3) duration types, and a summer shamal storm (D6). However, the storms D4 and D6 are partly associated with mesoscale convective type dust episodes known as haboobs. The socio-economic impacts of the dust events have been assessed by estimating the horizontal visibility, air quality index (AQI), and the dust deposition flux (DDF) from the forecasted dust concentrations. During the extreme dust events, the horizontal visibility drops to near-zero values co-occurred withhazardous levels of AQI and extremely high dust deposition flux (250 μg cm- 2 day- 1).

Original sounding and drifting balloon-borne measurements in the western Mediterranean with the aerosol counter/sizer LOAC during summer ChArMEx campaigns, with a focus on desert dust events

NASA Astrophysics Data System (ADS)

Renard, Jean-Baptiste; Dulac, François; Vignelles, Damien; Jeannot, Matthieu; Verdier, Nicolas; Chazette, Patrick; Crenn, Vincent; Sciare, Jean; Totems, Julien; Durand, Pierre; Barret, Brice; Jambert, Corinne; Mallet, Marc; Menut, Laurent; Mailler, Sylvain; Basart, Sara; Baldasano, José Maria

2015-04-01

LOAC (Light Optical Aerosol Counter) is a new small optical particle counter/sizer of ~250 grams designed to fly under all kinds of balloons. The measurements are conducted at two scattering angles (12° and 60°), allowing the determination of the aerosol particle concentrations in 19 size classes within a diameter range of ~0.2-100 µm and some identification of the nature of particles dominating different size classes. Following laboratory calibration, the sensor particularly discriminates wet or liquid particles, mineral dust, soot carbon particles and salts. Comparisons with other in situ sensors at the surface and with remote sensing measurements on the vertical were performed to give confidence in measurements. The instrument has been operated at the surface, under all kinds of balloons up to more than 35 km in altitude, including tethered, sounding, open stratospheric and new boundary-layer pressurized drifting balloons (BLPB) from CNES, and was tested on board a small UAV. Operations encompass a variety of environments including the Arctic (Reykjavik, Island, and Kiruna, Sweden), Brazil (Sao Paolo), the western Mediterranean Basin, southwestern France, peri-urban (Ile de France) and urban areas (Paris and Vienna). Presented results are focused on the LOAC balloon-borne measurements performed in the western Mediterranean basin during MISTRALS/ChArMEx campaigns (Mediterranean Integrated Studies aT Regional And Local Scales/the Chemistry-Aerosol Mediterranean Experiment; http://www.mistrals-hjome.org; http://charmex.lsce.ipsl.fr), with a focus on African dust events. Two test flights with a first version of LOAC under sounding balloons were first successfully performed in late June 2012 near Marseille during an intense dust event. In 2013, 19 LOAC flights have been performed under meteorological balloons and 12 under low altitude drifting balloons, most of them from Minorca Island (Spain) in June and early July and others from Levant Island (south of France

Onset of frequent dust storms in northern China at ~AD 1100.

PubMed

He, Yuxin; Zhao, Cheng; Song, Mu; Liu, Weiguo; Chen, Fahu; Zhang, Dian; Liu, Zhonghui

2015-11-26

Dust storms in northern China strongly affect the living and health of people there and the dusts could travel a full circle of the globe in a short time. Historically, more frequent dust storms occurred during cool periods, particularly the Little Ice Age (LIA), generally attributed to the strengthened Siberian High. However, limited by chronological uncertainties in proxy records, this mechanism may not fully reveal the causes of dust storm frequency changes. Here we present a late Holocene dust record from the Qaidam Basin, where hydrological changes were previously reconstructed, and examine dust records from northern China, including the ones from historical documents. The records, being broadly consistent, indicate the onset of frequent dust storms at ~AD 1100. Further, peaked dust storm events occurred at episodes of high total solar irradiance or warm-dry conditions in source regions, superimposed on the high background of frequent dust storms within the cool LIA period. We thus suggest that besides strong wind activities, the centennial-scale dust storm events over the last 1000 years appear to be linked to the increased availability of dust source. With the anticipated global warming and deteriorating vegetation coverage, frequent occurrence of dust storms in northern China would be expected to persist.

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.

Atmospheric bioaerosols transported via dust storms in the western United States

NASA Astrophysics Data System (ADS)

Hallar, A. Gannet; Chirokova, Galina; McCubbin, Ian; Painter, Thomas H.; Wiedinmyer, Christine; Dodson, Craig

2011-09-01

Measurements are presented showing the presence of biological material within frequent dust storms in the western United States. Previous work has indicated that biological particles were enhancing the impact of dust storms on the formation of clouds. This paper presents multiple case studies, between April and May 2010, showing the presence of and quantifying the amount of biological material via an Ultraviolet Aerodynamic Particle Sizer during dust events. All dust storms originated in the Four Corners region in the western Untied States and were measured at Storm Peak Laboratory, a high elevation facility in northwestern Colorado. From an Aerodynamic Particle Sizer, the mean dust particle size during these events was approximately 1 μm, with number concentrations between 6 cm-3 and 12 cm-3. Approximately 0.2% of these dust particles had fluorescence signatures, indicating the presence of biological material.

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.

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

USGS Publications Warehouse

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

2011-01-01

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

The Africanization of honeybees (Apis mellifera L.) of the Yucatan: a study of a massive hybridization event across time.

PubMed

Clarke, Kylea E; Rinderer, Thomas E; Franck, Pierre; Quezada-Euán, Javier G; Oldroyd, Benjamin P

2002-07-01

Until recently, African and European subspecies of the honeybee (Apis mellifera L.) had been geographically separated for around 10,000 years. However, human-assisted introductions have caused the mixing of large populations of African and European subspecies in South and Central America, permitting an unprecedented opportunity to study a large-scale hybridization event using molecular analyses. We obtained reference populations from Europe, Africa, and South America and used these to provide baseline information for a microsatellite and mitochondrial analysis of the process of Africanization of the bees of the Yucatan Peninsula, Mexico. The genetic structure of the Yucatecan population has changed dramatically over time. The pre-Africanized Yucatecan population (1985) comprised bees that were most similar to samples from southeastern Europe and northern and western Europe. Three years after the arrival of Africanized bees (1989), substantial paternal gene flow had occurred from feral Africanized drones into the resident European population, but maternal gene flow from the invading Africanized population into the local population was negligible. However by 1998, there was a radical shift with both African nuclear alleles (65%) and African-derived mitochondria (61%) dominating the genomes of domestic colonies. We suggest that although European mitochondria may eventually be driven to extinction in the feral population, stable introgression of European nuclear alleles has occurred.

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

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

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

High Proportions of Sub-micron Particulate Matter in Icelandic Dust Storms in 2015

NASA Astrophysics Data System (ADS)

Dagsson Waldhauserova, Pavla; Arnalds, Olafur; Olafsson, Haraldur; Magnusdottir, Agnes

2017-04-01

Iceland is extremely active dust region and desert areas of over 44,000 km2 acknowledge Iceland as the largest Arctic and European desert. Frequent dust events, up to 135 dust days annually, transport dust particles far distances towards the Arctic and Europe. Satellite MODIS pictures have revealed dust plumes exceeding 1,000 km. The annual dust deposition was calculated as 40.1 million tons yr-1. Two dust storms were measured in transverse horizontal profile about 90 km far from different dust sources in southwestern Iceland in the summer of 2015. Aerosol monitor DustTrak DRX 8533EP was used to measure PM mass concentrations corresponding to PM1, PM2.5, PM4, PM10 and the total PM15 at several places within the dust plume. Images from camera network operated by the Icelandic Road and Coastal Administration were used to estimate the visibility and spatial extent of measured dust events. A numerical simulation of surface winds was carried out with the numerical model HIRLAM with horizontal resolution of 5 km and used to calculate the total dust flux from the sources. The in situ measurements inside the dust plumes showed that aeolian dust can be very fine. The study highlights that suspended volcanic dust in Iceland causes air pollution with extremely high PM1 concentrations comparable to the polluted urban stations in Europe or Asia rather than reported dust event observations from around the world. The PM1/PM2.5 ratios are generally low during dust storms outside of Iceland, much lower than > 0.9 and PM1/PM10 ratios of 0.34-0.63 found in our study. It shows that Icelandic volcanic dust consists of higher proportion of submicron particles compared to crustal dust. The submicron particles are predicted to travel long distances. Moreover, such submicron particles pose considerable health risk because of high potential for entering the lungs. Icelandic volcanic glass has often fine pipe-vesicular structures known from asbestos and high content of heavy metals. Previous

Dust Emission Modeling Incorporating Land Cover Parameterizations in the Chihuahuan Desert and Dissemination of Data Suites

NASA Astrophysics Data System (ADS)

Olgin, J. G.; Pennington, D. D.; Webb, N.

2017-12-01

A variety of models have been developed to better understand dust emissions - from initial erosive event to entrainment to transport through the atmosphere. Many of these models have been used to analyze dust emissions by representing atmospheric and surface variables, such as wind and soil moisture respectively, in a numerical model to determine the resulting dust emissions. Pertinent to modeling these variables, there are three important factors influencing emissions: 1) Friction velocity threshold based on wind interactions with dust, 2) horizontal flux (saltation) of dust and 3) vertical dust flux. While all of the existing models incorporate these processes, additional improvements are needed to yield results reflective of recorded data of dust events. Our investigation focuses on explicitly identifying specific land cover (LC) elements unique to the Chihuahan desert that contribute to aerodynamic roughness length (Zo); a main component to dust emission and key to provide results more representative of known dust events in semi-arid regions. These elements will be formulated into computer model inputs by conducting analysis (e.g. geostatistics) on field and satellite data to ascertain core LC characteristics responsible for affecting wind velocities (e.g. wind shadowing effects), which are conducive to dust emissions. This inputs will be used in a modified program using the Weather and Research Forecast model (WRF) to replicate previously recorded dust events. Results from this study will be presented here.

Cryptic Diversity of African Tigerfish (Genus Hydrocynus) Reveals Palaeogeographic Signatures of Linked Neogene Geotectonic Events

PubMed Central

Goodier, Sarah A. M.; Cotterill, Fenton P. D.; O'Ryan, Colleen; Skelton, Paul H.; de Wit, Maarten J.

2011-01-01

The geobiotic history of landscapes can exhibit controls by tectonics over biotic evolution. This causal relationship positions ecologically specialized species as biotic indicators to decipher details of landscape evolution. Phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, including fishes, can reveal key events of drainage evolution, notably where geochronological resolution is insufficient. Where geochronological resolution is insufficient, phylogeographic statistics that reconstruct spatio-temporal details of evolutionary histories of aquatic species, notably fishes, can reveal key events of drainage evolution. This study evaluates paleo-environmental causes of mitochondrial DNA (mtDNA) based phylogeographic records of tigerfishes, genus Hydrocynus, in order to reconstruct their evolutionary history in relation to landscape evolution across Africa. Strong geographical structuring in a cytochrome b (cyt-b) gene phylogeny confirms the established morphological diversity of Hydrocynus and reveals the existence of five previously unknown lineages, with Hydrocynus tanzaniae sister to a clade comprising three previously unknown lineages (Groups B, C and D) and H. vittatus. The dated phylogeny constrains the principal cladogenic events that have structured Hydrocynus diversity from the late Miocene to the Plio-Pleistocene (ca. 0–16 Ma). Phylogeographic tests reveal that the diversity and distribution of Hydrocynus reflects a complex history of vicariance and dispersals, whereby range expansions in particular species testify to changes to drainage basins. Principal divergence events in Hydrocynus have interfaced closely with evolving drainage systems across tropical Africa. Tigerfish evolution is attributed to dominant control by pulses of geotectonism across the African plate. Phylogenetic relationships and divergence estimates among the ten mtDNA lineages illustrates where and when local tectonic

Effects of Desert Dust on Nutrient Cycling in the San Juan Mountains, Colorado

NASA Astrophysics Data System (ADS)

Neff, J. C.; Farmer, L.; Painter, T. H.; Landry, C.; Reynolds, R.

2005-12-01

The San Juan Mountains of southwestern Colorado lie downwind from several major deserts and experience several dust-deposition events each year. These events appear related to storms that erode soils in the deserts of the western US and then deposit atmospheric dust from these soils during or after snowfall during large late winter and spring deposition events. To evaluate the biogeochemical implications of eolian deposition, we collected dust from distinct layers deposited into the seasonal snowpack. We also sampled soils and lake sediments in a high-elevation catchment in the San Juan Mountains. Atmospheric dust was characterized by measurements of chemical composition, Sr isotopic content and analysis of the organic and inorganic constituents of deposited eolian material. The origins of snowpack dust in the San Juans were analyzed using atmospheric tracer transport modeling. These analyses suggest that many dust events originate in southern Utah and northern Arizona, areas that have undergone substantial land use change through the 20th century and that experience severe wind erosion of soils during periodic severe droughts. Analyses of 87Sr/86Sr isotope ratios dust, soils, bedrock, and sediments suggest that eolian dust may compose as much as 90% of the near-surface soil (top 5 cm). In alpine lake sediments, Sr isotopes suggest a relatively recent (20th century) increase in the fraction of sediments derived from dust (relative to bedrock) and a similarly large contribution of dust to surface sediments. Sediment chemistry in two small alpine tarns show changes in Ca, Mg, Al, and Fe concentrations that imply increasing dust (vs. bedrock) contributions to lake sediments over the past 100-200 years. Increasing loading of Ca, Mg and P to alpine basins may have implications for alpine and sub-alpine biogeochemical cycling including water quality and plant nutrient use.

Spatial distribution of threshold wind speeds for dust outbreaks in northeast Asia

NASA Astrophysics Data System (ADS)

Kimura, Reiji; Shinoda, Masato

2010-01-01

Asian windblown dust events cause human and animal health effects and agricultural damage in dust source areas such as China and Mongolia and cause "yellow sand" events in Japan and Korea. It is desirable to develop an early warning system to help prevent such damage. We used our observations at a Mongolian station together with data from previous studies to model the spatial distribution of threshold wind speeds for dust events in northeast Asia (35°-45°N and 100°-115°E). Using a map of Normalized Difference Vegetation Index (NDVI), we estimated spatial distributions of vegetation cover, roughness length, threshold friction velocity, and threshold wind speed. We also recognized a relationship between NDVI in the dust season and maximum NDVI in the previous year. Thus, it may be possible to predict the threshold wind speed in the next dust season using the maximum NDVI in the previous year.

Saharan Dust, Transport Processes, and Possible Impacts on Hurricane Activities

NASA Technical Reports Server (NTRS)

Lau, William K. M.; Kim, K. M.

2010-01-01

In this paper, we present observational evidence of significant relationships between Saharan dust outbreak, and African Easterly wave activities and hurricane activities. We found two dominant paths of transport of Saharan dust: a northern path, centered at 25degN associated with eastward propagating 6-19 days waves over northern Africa, and a southern path centered at 15degN, associated with the AEW, and the Atlantic ITCZ. Seasons with stronger dust outbreak from the southern path are associated with a drier atmosphere over the Maximum Development Region (MDR) and reduction in tropical cyclone and hurricane activities in the MDR. Seasons with stronger outbreak from the northern path are associated with a cooler N. Atlantic, and suppressed hurricane in the western Atlantic basin.

Trans boundary transport of pollutants by atmospheric mineral dust.

PubMed

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

2006-05-01

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

Early Human Speciation, Brain Expansion and Dispersal Influenced by African Climate Pulses

PubMed Central

Shultz, Susanne; Maslin, Mark

2013-01-01

Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS) lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto) and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration. PMID:24146922

Early human speciation, brain expansion and dispersal influenced by African climate pulses.

PubMed

Shultz, Susanne; Maslin, Mark

2013-01-01

Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS) lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto) and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration.

Development of High-Resolution Dynamic Dust Source Function -A Case Study with a Strong Dust Storm in a Regional Model

PubMed Central

Kim, Dongchul; Chin, Mian; Kemp, Eric M.; Tao, Zhining; Peters-Lidard, Christa D.; Ginoux, Paul

2018-01-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02-03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events. PMID:29632432

Development of High-Resolution Dynamic Dust Source Function -A Case Study with a Strong Dust Storm in a Regional Model.

PubMed

Kim, Dongchul; Chin, Mian; Kemp, Eric M; Tao, Zhining; Peters-Lidard, Christa D; Ginoux, Paul

2017-06-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 02-03 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

Development of High-Resolution Dynamic Dust Source Function - A Case Study with a Strong Dust Storm in a Regional Model

NASA Technical Reports Server (NTRS)

Kim, Dongchul; Chin, Mian; Kemp, Eric M.; Tao, Zhining; Peters-Lidard, Christa D.; Ginoux, Paul

2017-01-01

A high-resolution dynamic dust source has been developed in the NASA Unified-Weather Research and Forecasting (NU-WRF) model to improve the existing coarse static dust source. In the new dust source map, topographic depression is in 1-km resolution and surface bareness is derived using the Normalized Difference Vegetation Index (NDVI) data from Moderate Resolution Imaging Spectroradiometer (MODIS). The new dust source better resolves the complex topographic distribution over the Western United States where its magnitude is higher than the existing, coarser resolution static source. A case study is conducted with an extreme dust storm that occurred in Phoenix, Arizona in 0203 UTC July 6, 2011. The NU-WRF model with the new high-resolution dynamic dust source is able to successfully capture the dust storm, which was not achieved with the old source identification. However the case study also reveals several challenges in reproducing the time evolution of the short-lived, extreme dust storm events.

The Miocene Extraterrestrial Dust Deposition Event Tracked by Helium, Neon, Chromium and Extraterrestrial Insoluble Organic Matter at the Monte Dei Corvi Beach Section

NASA Astrophysics Data System (ADS)

Meier, M. M. M.; Steele, R. C. J.; Schmitz, B.; Piani, L.; Maden, C.; Plant, A. A.; Schönbächler, M.; Busemann, H.

2017-12-01

A temporarily increased flux of extraterrestrial dust to Earth can lead to tell-tale clues in sediments of the same age. A common example is peaks of 3He in sediments, which occur because extraterrestrial material is rich in implanted solar wind that has a high 3He/4He ratio compared to the atmosphere. One of two known 3He-peaks in Cenozoic sediments is found within the Miocene, at an age of about 8 Ma (Tortonian stage). This peak has been tied to the asteroid break-up event which formed the Veritas family (Farley et al., Nature, 2006). The Global Boundary Stratotype Section and Point for the Tortonian is located near Monte Dei Corvi, in Ancona, Italy. It has previously been well characterized using both magneto- and cyclostratigraphy (Hüsing et al., EPSL, 2009), and can thus provide excellent time-constraints on the age of the event, now dated to have started at 8.47±0.05 Ma (Montanari et al., GSA Bulletin, 2017). In this project, we study these sediments with the primary goal of determining the meteoritic type of the extraterrestrial dust. We have been following three different avenues towards that goal: (1) light noble gas (He, Ne) analyses of bulk sediments (Meier et al., Annual Meeting of the Meteoritical Society, 2016), which are used as tracers of dust flux. The measured He vs. Ne allows us to characterize the preservation state of the extraterrestrial noble gases in the sediments (see Chavrit et al., EPSL, 2016); (2) Cr abundance and isotope analysis of bulk sediments and residues, which should allow us to determine the meteoritic type of the deposited dust (e.g., Rotaru et al., Nature, 1992); (3) an attempt to isolate and characterize potentially surviving meteoritic organic matter in the bulk sediments from Monte Dei Corvi. Insoluble organic matter, which contributes 1-2% of the mass in some carbonaceous chondrites (tied to C- and D-type asteroids, like the ones found abundantly in the Veritas family; Ziffer et al., Icarus, 2011) is strongly acid- and

A 3 million year index for North African humidity/aridity and the implication of potential pan-African Humid periods

NASA Astrophysics Data System (ADS)

Grant, Katharine M.; Rohling, Eelco J.; Westerhold, Thomas; Zabel, Matthias; Heslop, David; Konijnendijk, Tiuri; Lourens, Lucas

2017-09-01

Mediterranean sediments are valuable archives of both African monsoon variability and higher-latitude climate processes, and can also be used to provide an environmental context for early human migrations and settlements. However, the long history of Mediterranean palaeoclimate studies largely pre-dates the advent of widespread x-ray fluorescence (XRF) core-scanning, so there are few continuous and high-resolution geochemical records from this key region that extend beyond the last glacial cycle. Here we present XRF core-scanning results for ODP Site 967 (Eastern Mediterranean) that have been fully-calibrated into element concentrations spanning the last 3 million years (My). Comparison with independent geochemical data from conventional XRF highlights disparities for certain element/element ratios, thus suggesting the need for caution when taking ratios of scanning XRF data. Principal component analysis of the calibrated XRF dataset reveals two dominant components: detrital inputs (PC1) and a 'sapropel' (≈monsoon run-off) signal (PC2), which we use to establish a new orbitally-tuned chronology. We observe inverse covariation between PC2 and a previously published aeolian dust record from ODP Site 967 (Larrasoaña et al., 2003), and combine these records to produce a composite index of humidity and aridity for the wider North African region over the past 3 My. We propose that by combining run-off and dust signals in a single metric, our index captures the effects of both strengthening/northward migration (increased run-off) and weakening/southward retreat (increased dust) of the North African monsoon. Comparison of the index with published records of Northwest and East African palaeohumidity suggests that it tracks the timing of ;Green Sahara Periods; throughout the Plio-Pleistocene, and that at least 30 of these intervals coincided with increased humidity across East Africa. We tentatively suggest that these specific episodes may be termed ;pan-African Humid

Dust storm in Alaska

NASA Image and Video Library

2013-11-18

Dust storm in Alaska captured by Aqua/MODIS on Nov. 17, 2013 at 21:45 UTC. When glaciers grind against underlying bedrock, they produce a silty powder with grains finer than sand. Geologists call it “glacial flour” or “rock flour.” This iron- and feldspar-rich substance often finds its ways into rivers and lakes, coloring the water brown, grey, or aqua. When river or lake levels are low, the flour accumulates on drying riverbanks and deltas, leaving raw material for winds to lift into the air and create plumes of dust. Scientists are monitoring Arctic dust for a number of reasons. Dust storms can reduce visibility enough to disrupt air travel, and they can pose health hazards to people on the ground. Dust is also a key source of iron for phytoplankton in regional waters. Finally, there is the possibility that dust events are becoming more frequent and severe due to ongoing recession of glaciers in coastal Alaska. To read more about dust storm in this region go to: earthobservatory.nasa.gov/IOTD/view.php?id=79518 Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team 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

Airborne dust absorption by semi-arid forests reduces PM pollution in nearby urban environments.

PubMed

Uni, Daphna; Katra, Itzhak

2017-11-15

Dust storms are a major source of global atmospheric particulate matter (PM), having significant impacts on air pollution and human health. During dust storms, daily averages of atmospheric PM concentrations can reach high levels above the World Health Organization (WHO) guideline for air quality. The objective of this study was to explore the impact of forests on PM distribution following dust events in a region that is subjected to frequent dust storms (Northern Negev, Israel). Dust was measured in a forest transect including urban environments that are nearby the forest and at a distal location. During a background period, without dust events, the forest with its surrounding areas were characterized by lower monthly average of PM concentrations (38μg/m 3 ) compared with areas that are not affected by the forest (54μg/m 3 ). Such difference can be meaningful for long-term human health exposure. A reduction in PM levels in the forest transect was evident at most measured dust events, depending on the storm intensity and the locations of the protected areas. A significant reduction in PM 2.5 /PM 10 during dust events, indicates the high efficiency of the forest trees to absorb airborne PM 2.5 . Analysis of dust particles absorbed on the foliage revealed a total dust deposits of 8.1-9.2g/m 2 , which is equal to a minimum of 418.2tons removed from the atmosphere per a forest foliage area (30km 2 ). The findings can support environmental strategies to enhance life quality in regions that are subjected to dust storms, or under potential risk of dust-related PM due to land use and/or climate changes. Copyright © 2017 Elsevier B.V. All rights reserved.

Measurements of Dust Devil Lower Structure and Properties, El Dorado Valley, Nevada, June 2002

NASA Astrophysics Data System (ADS)

Towner, M. C.; Ringrose, T. J.; Balme, M.; Greeley, R.; Zarnecki, J. C.

2002-12-01

We report the results of a recent field campaign in Nevada, USA, carried out to investigate the lower structure (less than 2m) and dust lofting mechanisms of terrestrial dust devils. Over several days, an instrumented platform was repeatedly deployed from the back of a pickup truck into the path of oncoming dust devils. Around 40 events were recorded, including core penetrations of large and small dust devils, close misses and periods of ambient background conditions before and after dust devil events, and during periods of dust devil inactivity. The platform deployed consisted of a 2 by 1m base with a 2m mast and carried a total of 24 instruments. The instrument suite consisted of horizontal wind profiling down to 5mm above surface, vertical wind speed and direction, temperature and pressure profiling, airborne and saltating particle recorders, vertical electric field gradient measurements, and upward looking UV sensors. We present preliminary results of profiles for several events, together with details of ambient conditions required for dust devil formation.

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.

Short-cut transport path for Asian dust directly to the Arctic: a case study

NASA Astrophysics Data System (ADS)

Huang, Zhongwei; Huang, Jianping; Hayasaka, Tadahiro; Wang, Shanshan; Zhou, Tian; Jin, Hongchun

2015-11-01

Asian dust can be transported long distances from the Taklimakan or Gobi desert to North America across the Pacific Ocean, and it has been found to have a significant impact on ecosystems, climate, and human health. Although it is well known that Asian dust is transported all over the globe, there are limited observations reporting Asian dust transported to the Arctic. We report a case study of a large-scale heavy dust storm over East Asia on 19 March 2010, as shown by ground-based and space-borne multi-sensor observations, as well as NCEP/NCAR reanalysis data and HYSPLIT trajectories. Our analysis suggests that Asian dust aerosols were transported from northwest China to the Arctic within 5 days, crossing eastern China, Japan and Siberia before reaching the Arctic. The results indicate that Asian dust can be transported for long distances along a previously unreported transport path. Evidence from other dust events over the past decade (2001-2010) also supports our results, indicating that dust from 25.2% of Asian dust events has potentially been transported directly to the Arctic. The transport of Asian dust to the Arctic is due to cyclones and the enhanced East Asia Trough (EAT), which are very common synoptic systems over East Asia. This suggests that many other large dust events would have generated long-range transport of dust to the Arctic along this path in the past. Thus, Asian dust potentially affects the Arctic climate and ecosystem, making climate change in the Arctic much more complex to be fully understood.

The case for a southeastern Australian Dust Bowl, 1895-1945

NASA Astrophysics Data System (ADS)

Cattle, Stephen R.

2016-06-01

Australia has an anecdotal history of severe wind erosion and dust storm activity, but there has been no lasting public perception of periods of extreme dust storm activity in this country, such as that developed in the USA following the Dust Bowl of the 1930s. Newspaper accounts of droughts and dust storms in southeastern (SE) Australia between 1895 and 1945 suggest that, at various times, the scale of these events was comparable to those experienced in the USA Dust Bowl. During this 50-year period, average annual rainfall values in this region were substantially below long-term averages, air temperatures were distinctly warmer, marginal lands were actively cropped and grazed, and rabbits were a burgeoning grazing pest. From the beginning of the Federation Drought of 1895-1902, dust storm activity increased markedly, with the downwind coastal cities of Sydney and Melbourne experiencing dust hazes, dust storms and falls of red rain relatively regularly. Between 1935 and 1945, Sydney and Melbourne received ten and nine long-distance dust events, respectively, with the years of 1938 and 1944/45 being the most intensely dusty. Entire topsoil horizons were blown away, sand drift was extreme, and crops and sheep flocks were destroyed. Although these periods of extreme dust storm activity were not as sustained as those experienced in the USA in the mid-1930s, there is a strong case to support the contention that SE Australia experienced its own extended, somewhat episodic version of a Dust Bowl, with a similar combination of causal factors and landscape effects.

Ecological Restoration Programs Induced Amelioration of the Dust Pollution in North China Plain

NASA Astrophysics Data System (ADS)

Long, X.; Tie, X.; Li, G.; Junji, C.

2017-12-01

With Moderate Resolution Imaging Spectroradiometer (MODIS) land cover product (MCD12Q1), we quantitatively evaluate the ecological restoration programs (ERP) induced land cover change in China by calculating gridded the land use fraction (LUF). We clearly capture two obvious vegetation (grass and forest) protective barriers arise between the dust source region DSR and North China Plain NCP from 2011 to 2013. The WRF-DUST model is applied to investigate the impact of ERPs on dust pollution from 2 to 8 March 2016, corresponding to a national dust storm event over China. Despite some model biases, the WRF-DUST model reasonably reproduced the temporal variations of dust storm event, involving IOA of 0.96 and NMB of 2% for DSR, with IOA of 0.83 and NMB of -15% for downwind area of NCP. Generally, the WRF-DUST model well capture the spatial variations and evolutions of dust storm events with episode-average [PMC] correlation coefficient (R) of 0.77, especially the dust storm outbreak and transport evolution, involving daily average [PMC] R of 0.9 and 0.73 on 4-5 March, respectively. It is found that the ERPs generally reduce the dust pollution in NCP, especially for BTH, involving upper dust pollution control benefits of -15.3% (-21.0 μg m-3) for BTH, and -6.2% (-9.3 μg m-3) for NCP. We are the first to conduct model sensitivity studies to quantitatively evaluate the impacts of the ERPs on the dust pollution in NCP. And our narrative is independently based on first-hand sources, whereas government statistics.

Optical Properties of Aeolian Dusts Common to West Texas

USDA-ARS?s Scientific Manuscript database

Both recent models and historical events such as the Dust Bowl and volcanic eruptions have illustrated aerosols can play a significant role in climate change through direct and indirect optical effects. Soil dust aerosols generated by Aeolian processes represent a significant fraction of the total ...

Microbes and Microstructure: Dust's Role in the Snowpack Evolution

NASA Astrophysics Data System (ADS)

Lieblappen, R.; Courville, Z.; Fegyveresi, J. M.; Barbato, R.; Thurston, A.

2017-12-01

Dust is a primary vehicle for transporting microbial communities to polar and alpine snowpacks both through wind distribution (dry deposition) and snowfall events (wet deposition). The resulting microbial community diversity in the snowpack may then resemble the source material properties rather than its new habitat. Dust also has a strong influence on the microstructural properties of snow, resulting in changes to radiative and mechanical properties. As local reductions in snowpack albedo lead to enhanced melting and a heterogeneous snow surface, the microbial communities are also impacted. Here we study the impact of the changing microstructure in the snowpack, its influence on microbial function, and the fate of dust particles within the snow matrix. We seek to quantify the changes in respiration and water availability with the onset of melt. Polar samples were collected from the McMurdo Ice Shelf, Antarctica in February, 2017, while alpine samples were collected from Silverton, CO from October to May, 2017 as part of the Colorado Dust on Snow (CDOS) network. At each site, coincident meteorological data provides temperature, wind, and radiative measurements. Samples were collected immediately following dust deposition events and after subsequent snowpack evolution. We used x-ray micro-computed tomography to quantify the microstructural evolution of the snow, while also imaging the microstructural distribution of the dust within the snow. The dust was then collected and analyzed for chemical and microbial activity.

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.

Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

2012-01-01

The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation

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.

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.

Circumstellar dust in symbiotic novae

NASA Astrophysics Data System (ADS)

Jurkic, Tomislav; Kotnik-Karuza, Dubravka

2015-08-01

Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding evolution of symbiotic binaries. We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the long-term near-IR photometry, infrared ISO spectra and mid-IR interferometry. Pulsation properties and long-term variabilities were found from the near-IR light curves. The dust properties were determined using the DUSTY code which solves the radiative transfer. No changes in pulsational parameters were found, but a long-term variations with periods of 20-25 years have been detected which cannot be attributed to orbital motion.Circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel showed the presence of an optically thin CS dust envelope and an optically thick dust region outside the line of sight, which was further supported by the detailed modelling using the 2D LELUYA code. Obscuration events in RR Tel were explained by an increase in optical depth caused by the newly condensed dust leading to the formation of a compact dust shell. HM Sge showed permanent obscuration and a presence of a compact dust shell with a variable optical depth. Scattering of the near-IR colours can be understood by a change in sublimation temperature caused by the Mira variability. Presence of large dust grains (up to 4 µm) suggests an increased grain growth in conditions of increased mass loss. The mass loss rates of up to 17·10-6 MSun/yr were significantly higher than in intermediate-period single Miras and in agreement with longer-period O-rich AGB stars.Despite the nova outburst, HM Sge remained enshrouded in dust with no significant dust destruction. The existence of unperturbed dust shell suggests a small influence of the hot component and strong dust shielding from the UV flux. By the use

Airborne Dust in Space Vehicles and Habitats

NASA Technical Reports Server (NTRS)

James, John

2006-01-01

Airborne dust, suspended inside a space vehicle or in future celestial habitats, can present a serious threat to crew health if it is not controlled. During the Apollo missions to the moon, lunar dust brought inside the capsule caused eye irritation and breathing difficulty to the crew when they launched from the moon and re-acquired "microgravity." During Shuttle flights reactive and toxic dusts such as lithium hydroxide have created a risk to crew health, and fine particles from combustion events can be especially worrisome. Under nominal spaceflight conditions, airborne dusts and particles tend to be larger than on earth because of the absence of gravity settling. Aboard the ISS, dusts are effectively managed by HEPA filters, although floating dust in newly-arrived modules can be a nuisance. Future missions to the moon and to Mars will present additional challenges because of the possibility that external dust will enter the breathing atmosphere of the habitat and reach the crew's respiratory system. Testing with simulated lunar and Martian dust has shown that these materials are toxic when placed into the lungs of test animals. Defining and evaluating the physical and chemical properties of Martian dusts through robotic missions will challenge our ability to prepare better dust simulants and to determine the risk to crew health from exposure to such dusts.

Hypervelocity dust particle impacts observed by the Giotto magnetometer and plasma experiments

NASA Technical Reports Server (NTRS)

Neubauer, F. M.; Glassmeier, K.-H.; Coates, A. J.; Goldstein, R.; Acuna, M. H.

1990-01-01

This paper describes 13 very short events in the magnetic field of the inner magnetic pile-up region of Comet Halley observed by the Giotto magnetometer experiment together with simultaneous plasma data obtained by the Johnstone plasma analyzer and the ion mass spectrometer experiments. The events are due to dust impacts in the milligram range on the spacecraft at the relative velocity between the cometary dust and the spacecraft of 68 km/sec. They are generally consistent with dust impact events derived from spacecraft attitude perturbations by the Giotto camera. Their characteristic shape generally involves a sudden decrease in magnetic-field magnitude, a subsequent overshoot beyond initial field values, and an asymptotic approach to the initial field (somewhat reminiscent of the magnetic-field signature after the AMPTE releases in the solar wind). These observations give a new way of analyzing ultra-fast dust particles incident on a spacecraft.

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

Mars Dust and LETKF Data Assimilation of TES Observations

NASA Astrophysics Data System (ADS)

Greybush, S. J.; Hoffman, R. N.; Wilson, R.; Kang, J.; Zhao, Y.; Hoffman, M. J.; Kalnay, E.; Miyoshi, T.

2012-12-01

Simulation and prediction of dust storms remains one of the greatest challenges in Martian meteorology. Large-scale dust storms impact all Mars operations including spacecraft observations. What makes the difference between a regional event and a planet-encircling event? What are the predictability characteristics of these events and of the transition from regional to global? We examine the meteorology, including dustiness, in the Mars reanalysis created with the GFDL Mars Global Climate Model (MGCM) Local Ensemble Transform Kalman Filter (LETKF) data assimilation system (DAS). Characterizing the distribution and temporal evolution of dust in the Martian atmosphere is a considerable challenge. Spacecraft observations are sparse and have limitations in vertical coverage, dust physical properties are not well known, and model parameterizations of surface lifting have limited success in reproducing observed variability. Methods for generating a dust reanalysis begin with satellite inferred dust information in the form of column opacities, dust profile retrievals, or the original radiances. Opacities may be estimated from a formal retrieval of the satellite data or inferred through surface brightness temperatures. The opacities have been ingested via ad hoc adjustments to model tracer fields (Conrath vertical distributions, changes to the boundary layer dust only, etc.), but could also be assimilated by the LETKF or other advanced DAS. We will present dust distributions in the most recent version of the MGCM-LETKF Mars reanalysis. Current results are from two DASs, one assuming a fixed dust distribution and one using TES opacities and updating the boundary layer dust only. In these reanalyses, a full year of Thermal Emission Spectrometer (TES) temperature profiles have been assimilated. Since an accurate characterization of the sources and sinks of dust would greatly improve our understanding of the Martian dust cycle and its representation in numerical weather

Impact and monitoring of dust storms in Taklimakan desert

NASA Astrophysics Data System (ADS)

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

2012-12-01

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

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.

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.

Radiogenic isotope evidence for transatlantic atmospheric dust transport

NASA Astrophysics Data System (ADS)

Kumar, Ashwini; Abouchami, Wafa; Garrison, Virginia H.; Galer, Stephen J. G.; Andreae, Meinrat O.

2013-04-01

Early studies by Prospero and colleagues [1] have shown that African dust reaches all across the Atlantic and into the Caribbean. It may contribute to fertilizing the Amazon rainforest [2,3,4], in addition to enhancing the ocean biological productivity via delivery of iron, a key nutrient element[5]. Radiogenic isotope ratios (Sr, Nd, Pb) are robust tracers of dust sources and can thus provide information on provenance and pathways of dust transport. Here we report Sr, Nd and Pb isotope data on atmospheric aerosols, collected in 2008 on quartz filters, from 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.) to investigate the hypothesis of dust transport across the Atlantic. About 2 cm2 of filter were acid-leached in 0.5 N HBr for selective removal of the anthropogenic labile Pb component (leachate) and possibly the fine soluble particle fraction. The remainder of the filter was subsequently dissolved using a mixture of HF and HNO3 acids, and should be representative of the silicate fraction. Isotopic compositions were measured by TIMS on a ThermoFisher Triton at MPIC, with Pb isotope ratios determined using the triple-spike method. Significant Pb isotope differences between leachates and residues were observed. The variability in Pb isotopic composition among leachates may be attributed to variable and distinct anthropogenic local Pb sources from Africa and South America [6], however, residues are imprinted by filter blank contribution suggesting to avoid the quartz fiber filter for isotopic study of aerosols. The Nd and Sr isotope ratios of aerosol leachates show similar signatures at all three locations investigated. The nearly identical Nd and Sr isotopic compositions in the Mali, Tobago and Virgin islands leachates are comparable to those obtained on samples from the Bodélé depression, Northern Chad [7] and suggest a possible common

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

Dust Transport, Deposition and Radiative Effects Observed from MODIS

NASA Technical Reports Server (NTRS)

Kaufman, Y. J.; Koren, I.; Remer, L. A.; Tanre, D.; Ginoux, P.; Fan, S.

2003-01-01

Carlson (1977) used satellite (AVHRR) observation of dust episodes 3 estimate that 90 tg of dust are emitted from Africa (0-30 N) to the Atlantic Ocean between June and August. MODIS systematic measurements of aerosol optical thickness (AOT) and the fraction of the AOT (f) due to the fine mode (see Remer et al abstract), are used to derive the column concentration, flux and deposition of African dust over the Atlantic Ocean. The main data set is for 2001 but the results are consistent with MODIS measurements from 2002. The analysis first determines the properties of maritime baseline aerosol (AOT=0.06, f=0.5); followed by linear scaling of the dust AOT and the anthropogenic AOT, based on MODIS measured values of the fraction "f" being 0.9 for anthropogenic aerosol and 0.5 for dust. NCEP winds are used in the analysis and are evaluated against observed dust movements between the Terra and Aqua passes (see Koren et al. abstract). Monthly values of dust transport and deposition are calculated. Preliminary results show that 280 tg of dust are emitted annually from Africa to the Atlantic Ocean between 20s and 30N, with 40 tg returning to Africa and Europe between 30N and 50N. 85 tg reach the Americas, with 130-150 tg are deposited in the Atlantic Ocean. The results are compared with dust transport models that indicate 110-230 tg of dust being deposited in the Ocean. It is interesting to note that the early estimates of Carlson (1977) and Carlson & Prosper0 (1972) are very close to our estimate from MODIS of 100 tg for the same latitude range and monthly period.

Social anxiety and post-event processing among African-American individuals.

PubMed

Buckner, Julia D; Dean, Kimberlye E

2017-03-01

Social anxiety is among the most prevalent psychiatric conditions, yet little attention has been paid to whether putative cognitive vulnerability factors related to social anxiety in predominantly White samples are related to social anxiety among historically underrepresented groups. We tested whether one such vulnerability factor, post-event processing (PEP; detailed review of social event that can increase state social anxiety) was related to social anxiety among African-American (AA; n = 127) persons, who comprise one of the largest underrepresented racial groups in the U.S. Secondarily, we tested whether AA participants differed from non-Hispanic White participants (n = 127) on PEP and social anxiety and whether race moderated the relation between PEP and social anxiety. Data were collected online among undergraduates. PEP was positively correlated with social anxiety among AA participants, even after controlling for depression and income, pr = .30, p = .001. AA and White participants did not differ on social anxiety or PEP, β = -1.57, 95% CI: -5.11, 1.96. The relation of PEP to social anxiety did not vary as a function of race, β = 0.00, 95% CI: -0.02, 0.02. PEP may be an important cognitive vulnerability factor related to social anxiety among AA persons suffering from social anxiety.

Interannual similarity in the Martian atmosphere during the dust storm season

NASA Astrophysics Data System (ADS)

Kass, D. M.; Kleinböhl, A.; McCleese, D. J.; Schofield, J. T.; Smith, M. D.

2016-06-01

We find that during the dusty season on Mars (southern spring and summer) of years without a global dust storm there are three large regional-scale dust storms. The storms are labeled A, B, and C in seasonal order. This classification is based on examining the zonal mean 50 Pa (˜25 km) daytime temperature retrievals from TES/MGS and MCS/MRO over 6 Mars Years. Regional-scale storms are defined as events where the temperature exceeds 200 K. Examining the MCS dust field at 50 Pa indicates that warming in the Southern Hemisphere is dominated by direct heating, while northern high latitude warming is a dynamical response. A storms are springtime planet encircling Southern Hemisphere events. B storms are southern polar events that begin near perihelion and last through the solstice. C storms are southern summertime events starting well after the end of the B storm. C storms show the most interannual variability.

Interannual Similarity in the Martian Atmosphere During the Dust Storm Season

NASA Technical Reports Server (NTRS)

Kass, D. M.; Kleinboehl, A.; McCleese, D. J.; Schofield, J. T.; Smith, M. D.

2016-01-01

We find that during the dusty season on Mars (southern spring and summer) of years without a global dust storm there are three large regional-scale dust storms. The storms are labeled A, B, and C in seasonal order. This classification is based on examining the zonal mean 50 Pa (approximately 25 km) daytime temperature retrievals from TES/MGS and MCS/MRO over 6 Mars Years. Regional-scale storms are defined as events where the temperature exceeds 200 K. Examining the MCS dust field at 50 Pa indicates that warming in the Southern Hemisphere is dominated by direct heating, while northern high latitude warming is a dynamical response. A storms are springtime planet encircling Southern Hemisphere events. B storms are southern polar events that begin near perihelion and last through the solstice. C storms are southern summertime events starting well after the end of the B storm. C storms show the most interannual variability.

Classifying and Tracking Dust Plumes from Passive Remote Sensing

NASA Astrophysics Data System (ADS)

Bachl, Fabian E.; Garbe, Christoph S.

2012-03-01

Recent studies emphasize the role mineral dust aerosols play in terms of the earth's climate system, its radiation budget and microbial nutrition cycles. In order to gain further insight into the genesis and long term characteristics of dust events, processing setellite imagery is inevitable. We propose a fully Bayesian multispectral classification method that significantly facilitates this task. Using MSG-SEVIRI imagery we show that our technique allows to extract dust activity well enough to pave the way for a tracking scheme. Based on this procedure we derive an approach to identify regions that are likely to be the origin of emerging dust plumes.

Simulation of African dust properties and radiative effects during the 2015 SHADOW campaign in Senegal

NASA Astrophysics Data System (ADS)

Péré, J.-C.; Rivellini, L.; Crumeyrolle, S.; Chiapello, I.; Minvielle, F.; Thieuleux, F.; Choël, M.; Popovici, I.

2018-01-01

The aim of this work is to estimate optical and radiative properties of dust aerosols and their potential feedbacks on atmospheric properties over Western Africa for the period 20 March-28 April 2015, by using numerical simulations and different sets of remote-sensing and in-situ measurements. Comparisons of simulations made by the on-line coupled meteorological-chemistry model WRF-CHEM with MODIS, AERONET and in-situ observations result in a general agreement for the spatio-temporal variations of aerosol extinction at both local and regional scales. Simulated SSA reached elevated values between 0.88 and 0.96 along the visible/near-infrared in close agreement with AERONET inversions, suggesting the predominance of dust over Western Africa during this specific period. This predominance of dust is confirmed by in-situ measurements of the aerosol size distribution, fitting well with the aerosols size distribution simulated by WRF-CHEM. The impact of this large dust load on the radiative fluxes leads to large modifications of the shortwave and longwave radiative budget both at the ground and at the top of the atmosphere. In return, the response of the atmosphere to these dust-induced radiative changes is the alteration of the surface air temperature and wind fields, with non-negligible impact on the dust emission and transport.

Desert dust hazards: A global review

NASA Astrophysics Data System (ADS)

Middleton, N. J.

2017-02-01

Dust storms originate in many of the world's drylands and frequently present hazards to human society, both within the drylands themselves but also outside drylands due to long-range transport of aeolian sediments. Major sources of desert dust include the Sahara, the Middle East, central and eastern Asia, and parts of Australia, but dust-raising occurs all across the global drylands and, on occasion, beyond. Dust storms occur throughout the year and they vary in frequency and intensity over a number of timescales. Long-range transport of desert dust typically takes place along seasonal transport paths. Desert dust hazards are here reviewed according to the three phases of the wind erosion system: where dust is entrained, during the transport phase, and on deposition. This paper presents a synthesis of these hazards. It draws on empirical examples in physical geography, medical geology and geomorphology to discuss case studies from all over the world and in various fields. These include accelerated soil erosion in agricultural zones - where dust storms represent a severe form of accelerated soil erosion - the health effects of air pollution caused by desert aerosols via their physical, chemical and biological properties, transport accidents caused by poor visibility during desert dust events, and impacts on electricity generation and distribution. Given the importance of desert dust as a hazard to human societies, it is surprising to note that there have been relatively few attempts to assess their impact in economic terms. Existing studies in this regard are also reviewed, but the wide range of impacts discussed in this paper indicates that desert dust storms deserve more attention in this respect.

Microbiological and meteorological analysis of two Australian dust storms in April 2009.

PubMed

Lim, Natalie; Munday, Chris I; Allison, Gwen E; O'Loingsigh, Tadhg; De Deckker, Patrick; Tapper, Nigel J

2011-12-15

Dust is an important source of bioaerosols including bacteria. In this study, the microbiology and meteorology of specific dust storms in Australia were investigated. The samples were collected from two dust events in April 2009 that were characterised by intense cold fronts that entrained dust from the highly erodible and drought-stricken Mallee and Riverina regions of Victoria and central NSW. In the first storm, the dust travelled eastward over Canberra and Sydney, and in the second storm, the dust travelled east/southeastward over Canberra and Melbourne. Rain fell on both cities during the second dust storm. Dust and rain samples were collected, cultured, and the composition compared using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Multiple bands were evident on DGGE indicative of a diverse microflora, and identification of several bands confirmed the presence of multiple genera and species representing three phyla. Numerous bands represented Bacillus species, and these were present in multiple dust samples collected from both Canberra and Melbourne. Interestingly, the microflora present in rain samples collected in Canberra during the second dust storm was quite different and the DGGE banding patterns from these samples clustered separately to most dust samples collected at the same time. Identification of several DGGE bands and PCR products from these rain samples indicated the presence of Pseudomonas species. These results indicate that Australian dust and rain have a diverse microflora and highlights the contribution of dust events to the distribution of microbes in the environment. Copyright © 2011 Elsevier B.V. All rights reserved.

Climatology of dust distribution over West Asia from homogenized remote sensing data

NASA Astrophysics Data System (ADS)

Nabavi, Seyed Omid; Haimberger, Leopold; Samimi, Cyrus

2016-06-01

In the past decade, West Asia has witnessed more frequent and intensified dust storms affecting Iran and Persian Gulf countries. Employing a varying threshold that takes into account systematic differences between TOMS and OMI data, TOMS-OMI Aerosol Index data are used to identify long-term changes in the horizontal distribution of dust storms in West Asia from 1980 to present. The northwest of Iraq and east of Syria are identified as emerging dusty areas, whereas east of Saudi Arabia and southeast of Iraq are identified as permanent dusty areas, including both dust sources and affected areas. Whereas the frequency of dust events increased slightly in the permanent dusty areas, it increased markedly in the emerging dusty areas. As expected, the frequency of dust events is highest in June and July. The dust source areas are identified as the Iraq-Saudi Arabia boundary region and (recently) the northwest of Iraq, using MODIS deep blue aerosol optical depth data. Subsequently, a lagged correlation was implemented between identified dust sources and whole West Asia to determine the main paths and receptors of intense dust storms. Accordingly, southwest of Iran and Persian Gulf countries were determined as main receptors of summertime dust storms in West Asia. During spring, dust storms mostly hit the northern half of the region and reach to the Caspian Sea. Analyzing atmospheric patterns, Shamal and Frontal patterns were found as dominant atmospheric circulations simultaneous with summertime and springtime dust storms, respectively.

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.

Vulnerability Assessment of Dust Storms in the United States under a Changing Climate Scenario

EPA Science Inventory

Severe weather events, such as flooding, drought, forest fires, and dust storms can have a serious impact on human health. Dust storm events are not well predicted in the United States, however they are expected to become more frequent as global climate warms through the 21st cen...

A synoptic climatology of desert dust deposition to the alpine snowpack in the San Juan Mountains, Colorado, U.S.A.

NASA Astrophysics Data System (ADS)

McBride, K.; Painter, T.; Landry, C.

2005-12-01

Currently, collaborative research is underway in the San Juan Mountains to study the radiative and hydrologic effects of desert dust deposits in alpine snow. The component described here will present preliminary results of the development of a synoptic climatology for winter and spring dust deposition to the alpine snowpack in the San Juan Mountains of southwest Colorado. An understanding of the climatology of dust deposition events will improve our capacity to infer the temporal persistence and magnitude of dust deposition and ultimately its effect on hydrologic and ecological processes in the San Juan Mountains. We use the Stochastic Time-Inverted Lagrangian Transport (STILT) model to determine back and forward trajectories of air parcels. The input data were collected at the Putney Data site (3757 m) which has been in use for over 30 years and provides 'free air' wind data as well as ridge crest air temperatures and humidity. Putney lies 2 km SE of the Swamp Angel Study Plot, east of US Highway 550 at Red Mountain Pass. The Swamp Angel Study Plot is one of two extensively instrumented energy balance and radiation sites used in the study and operated by the Center for Snow and Avalanche Studies (CSAS). STILT outputs 3-dimensional probability distributions that describe the potential source regions for air parcels reaching the San Juan Mountains at known times of dust deposition. We analyze 11 dust deposition events that have been documented in snow in the San Juan Mountains or Elk Range of Colorado. One isolated dust event was documented in 1999 in the Elk Range. Subsequently, we have documented the dust deposition events in winters and springs of 2003, 2004, and 2005 in the San Juan Mountains. 2003 and 2004 experienced 3 dust events each but in 2003 the events came in February and April, whereas in 2004 the events came in late April and mid-May. In 2005, of the 4 dust events, the first came in late March, the second and third in early April, and the fourth in

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

Peach leaf responses to soil and cement dust pollution.

PubMed

Maletsika, Persefoni A; Nanos, George D; Stavroulakis, George G

2015-10-01

Dust pollution can negatively affect plant productivity in hot, dry and with high irradiance areas during summer. Soil or cement dust were applied on peach trees growing in a Mediterranean area with the above climatic characteristics. Soil and cement dust accumulation onto the leaves decreased the photosynthetically active radiation (PAR) available to the leaves without causing any shade effect. Soil and mainly cement dust deposition onto the leaves decreased stomatal conductance, photosynthetic and transpiration rates, and water use efficiency due possibly to stomatal blockage and other leaf cellular effects. In early autumn, rain events removed soil dust and leaf functions partly recovered, while cement dust created a crust partially remaining onto the leaves and causing more permanent stress. Leaf characteristics were differentially affected by the two dusts studied due to their different hydraulic properties. Leaf total chlorophyll decreased and total phenol content increased with dust accumulation late in the summer compared to control leaves due to intense oxidative stress. The two dusts did not cause serious metal imbalances to the leaves, except of lower leaf K content.

Iridium enrichment in volcanic dust from blue ice fields, Antarctica, and possible relevance to the K/T boundary event

NASA Technical Reports Server (NTRS)

Koeberl, Christian

1989-01-01

The analysis of samples of volcanic ash dust layers from the Lewis Cliff/Beardmore Glacier in Antarctica shows that some of the samples contain Ir concentrations up to 7.5 ppb. It is shown that the Ir is positively correlated with Se, As, Sb, and other volcanogenic elements. The results show that Ir may be present in some volcanic ash deposits, suggesting that the Ir in the K/T boundary clays is not necessarily of cosmic origin, but may have originated from mantle reservoirs tapped during extensive volcanic eruptions possibly triggered by impact events.

An Extensive Study on Dynamical aspects of Dust Storm over the United Arab Emirates during 18-20 March 2012

NASA Astrophysics Data System (ADS)

Basha, Ghouse; Phanikumar, Devulapalli V.; Ouarda, Taha B. M. J.

2015-04-01

On 18 March 2012, a super dust storm event occurred over Middle East (ME) and lasted for several hours. Following to this, another dust storm occurred on early morning of 20 March 2012 with almost higher intensity. Both these storms reduced the horizontal visibility to few hundreds of meters and represented as one of the most intense and long duration dust storms over United Arab Emirates (UAE) in recent times. These storms also reduced the air quality in most parts of the ME implying the shutdown of Airports, schools and hundreds of people were hospitalized with respirational problems. In the context of the above, we have made a detailed study on the dynamical processes leading to triggering of dust storm over UAE and neighboring regions. We have also analyzed its impact on surface, and vertical profiles of background parameters and aerosols during the dust storm period by using ground-based, space borne, dust forecasting model, and reanalysis data sets. The synoptic and dynamic conditions responsible for the occurrence of the dust storm are discussed extensively by using European Centre for Medium-Range Weather Forecasts (ECMWF) ERA interim reanalysis data sets. The Impact of dust storm on surface and upper air radiosonde measurements and aerosol optical properties are also investigated before, during and after the dust storm event. During the dust storm, surface temperature decreased by 15oC when compared to before and after the event. PM10 values significantly increased maximum of about 1600µg/m3. Spatial variation of Aerosol Optical Depth (AOD) from Moderate-resolution Imaging Spectroradiometer (MODIS) and Ozone Monitoring Instrument (OMI) aerosol index (AI) exhibited very high values during the event and source region can be identified of dust transport to our region with this figure. The total attenuated backscatter at 550nm from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite shows the vertical extent of dust up to 8km. The dynamics of this event is

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

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.

Young Stellar Variability of GM Cephei by Circumstellar Dust Clumps

NASA Astrophysics Data System (ADS)

Huang, Po-Chieh; Chen, Wen-Ping; Hu, Chia-Ling; Burkhonov, Otabek; Ehgamberdiev, Shuhrat; Liu, Jinzhong; Naito, Hiroyuki; Pakstiene, Erika; Qvam, Jan Kare Trandem; Rätz, Stefanie; Semkov, Evgeni

2018-04-01

UX Orionis stars are a sub-type of Herbig Ae/be or T Tauri stars exhibiting sporadic extinction of stellar light due to circumstellar dust obscuration. GM Cep is such an UX Orionis star in the young (∼ 4 Myr) open cluster Trumpler 37 at ∼ 900 pc, showing a prominent infrared access, H-alpha emission, and flare activity. Our multi-color photometric monitoring from 2009 to 2016 showed (i) sporadic brightening on a time scale of days due to young stellar accretion, (ii) cyclic, but not strictly periodical, occultation events, each lasting for a couple months, with a probable recurrence time of about two years, (iii) normal dust reddening as the star became redder when dimmer, (iv) the unusual "blueing" phenomena near the brightness minima, during which the star appeared bluer when dimmer, and (v) a noticeable polarization, from 3 to 9 percent in g', r', and i' -bands. The occultation events may be caused by dust clumps, signifying the density inhomogeneity in a young stellar disk from grain coagulation to planetesimal formation. The level of polarization was anti-correlated with the brightness in the bright state, when the dust clump backscattered stellar light. We discussed two potential hypotheses: orbiting dust clumps versus dust clumps along a spiral arm structure.

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...

Relationship between Rock Varnish and Adjacent Mineral Dust Compositions Using Microanalytical Techniques

NASA Astrophysics Data System (ADS)

Macholdt, D.; Jochum, K. P.; Otter, L.; Stoll, B.; Weis, U.; Pöhlker, C.; Müller, M.; Kappl, M.; Weber, B.; Kilcoyne, A. L. D.; Weigand, M.; Al-Amri, A. M.; Andreae, M. O.

2015-12-01

Rock varnishes are up to 250 μm thick, Mn- and Fe-rich, dark black to brownish-orange lustrous rock coatings. Water and aeolian dust (60-70%), in combination with biological oxidation or inorganic precipitation processes, or even a combination of both, induce varnish growth rates of a few μm per 1000 a, indicating that element enrichment and aging processes are of major importance for the varnish formation. A combination of 200 nm-fs laser- and 213 nm-ns laser ablation- inductively coupled plasma-mass spectrometry (LA-ICP-MS), focused ion beam (FIB) slicing, and scanning transmission X-ray microscopy-near edge X-ray absorption fine structure spectroscopy (STXM-NEXAFS) was chosen for high-spatial-resolution analyses. The aim was to identify provenance, chemistry, and dynamics of the varnishes, and their formation over the millennia. To this end, mineral dust and adjacent varnishes were sampled in six arid to semi-arid deserts, in Israel, South Africa, California, and Saudi Arabia. Dust minerals incorporated in the varnishes were examined by STXM-NEXAFS spectroscopic and element mapping at the nm scale. Varnishes from different locations can be distinguished by element ratio plots of Pb/Ni vs. Mn/Ba. A comparison of dust element ratios of particles <50 μm to ratios of adjacent varnishes reveals much lower values for dust. However, the factors between the element ratios of dust and of varnish are similar for four of six regions (Mn/Ba: 6 ± 2; Pb/Ni: 4 ± 3). Two of the six regions diverge, which are South African (Mn/Ba: 20, Pb/Ni: 0.5) and Californian (Anza Borrego Desert: Mn/Ba: 4.5; Pb/Ni: 16.5) varnishes.The results indicate that the enrichment and degradation processes might be similar for most locations, and that Mn and Pb are preferably incorporated and immobilized in most varnishes compared to Ba and Ni. The Pb/Ni ratios of the South African varnishes are indicators for either a preferred incorporation of Ni compared to Pb from available dust, and

Significant impacts of heterogeneous reactions on the chemical composition and mixing state of dust particles: A case study during dust events over northern China

NASA Astrophysics Data System (ADS)

Wang, Zhe; Pan, Xiaole; Uno, Itsushi; Li, Jie; Wang, Zifa; Chen, Xueshun; Fu, Pingqing; Yang, Ting; Kobayashi, Hiroshi; Shimizu, Atsushi; Sugimoto, Nobuo; Yamamoto, Shigekazu

2017-06-01

The impact of heterogeneous reactions on the chemical components and mixing state of dust particles are investigated by observations and an air quality model over northern China between March 27, 2015 and April 2, 2015. Synergetic observations were conducted using a polarization optical particle counter (POPC), a depolarized two-wavelength Lidar and filter samples in Beijing. During this period, dust plume passed through Beijing on March 28, and flew back on March 29 because of synoptic weather changes. Mineral dust mixed with anthropogenic pollutants was simulated using the Nested Air Quality Prediction Modeling System (NAQPMS) to examine the role of heterogeneous processes on the dust. A comparison of observations shows that the NAQPMS successfully reproduces the time series of the vertical profile, particulate matter concentration, and chemical components of fine mode (diameter ≤ 2.5 μm) and coarse mode (2.5 μm < diameter ≤ 10 μm) particles. After considering the heterogeneous reactions, the simulated nitrate, ammonium, and sulfate are in better agreement with the observed values during this period. The modeling results with observations show that heterogeneous reactions are the major mechanisms producing nitrate reaching 19 μg/m3, and sulfate reaching 7 μg/m3, on coarse mode dust particles, which were almost 100% of the coarse mode nitrate and sulfate. The heterogeneous reactions are also important for fine mode secondary aerosols, for producing 17% of nitrate and 11% of sulfate on fine mode dust particles, with maximum mass concentrations of 6 μg/m3 and 4 μg/m3. In contrast, due to uptake of acid gases (e.g. HNO3 and SO2) by dust particles, the fine mode anthropogenic ammonium nitrate and ammonium sulfate decreased. As a result, the total fine mode nitrate decreased with a maximum of 14 μg/m3, while the total fine mode sulfate increased with a maximum of 2 μg/m3. Because of heterogeneous reactions, 15% of fine mode secondary inorganic aerosols and

Dust Storm over the Red Sea

NASA Technical Reports Server (NTRS)

2002-01-01

In the summer months in the Northern Hemisphere, dust storms originating in the deserts around the Arabian Peninsula have a significant impact on the amount of solar radiation that reaches the surface. Winds sweep desert sands into the air and transport them eastward toward India and Asia with the seasonal monsoon. These airborne particles absorb and deflect incoming radiation and can produce a cooling effect as far away as North America. According to calculations performed by the NASA Goddard Institute for Space Studies (GISS), the terrain surrounding the southern portions of the Red Sea is one of the areas most dramatically cooled by the presence of summertime dust storms. That region is shown experiencing a dust storm in this true-color image from the Moderate Resolution Imaging Spectroradiometer (MODIS) acquired on July 11, 2002. The GISS model simulations indicate that between June and August, the temperatures would be as much as 2 degrees Celsius warmer than they are if it weren't for the dust in the air-a cooling equivalent to the passage of a rain cloud overhead. The image shows the African countries of Sudan (top left), Ethiopia (bottom left), with Eritrea nestled between them along the western coast of the Red Sea. Toward the right side of the image are Saudi Arabia (top) and Yemen (bottom) on the Arabian Peninsula. Overlooking the Red Sea, a long escarpment runs along the western edge of the Arabian Peninsula, and in this image appears to be blocking the full eastward expansion of the dust storm. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

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.

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.

Atmospheric Electricity Effects of Eastern Mediterranean Dust Storms

NASA Astrophysics Data System (ADS)

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

2016-04-01

We present atmospheric electrical measurements conducted at the Wise Observatory (WO) in Mizpe-Ramon (30035'N, 34045'E) and Mt. Hermon (30024'N, 35051'E), Israel, during two massive and unique dust storms that occurred over the Eastern Mediterranean region on February 10-11 and September 08-12, 2015. The first event transported Saharan dust from Egypt and the Sinai Peninsula in advance of a warm front of a Cyprus low pressure system. In the second event, dust particles were transported from the Syrian desert, which dominates the north-east border with Iraq, through flow associated with a shallow Persian trough system. In both events the concentrations of PM10 particles measured by the air-quality monitoring network of the Israeli Ministry of the Environment in Beer-Sheba reached values > 2200 μg m-3. Aerosol Optical Thickness (AOT) obtained from the AERONET station in Sde-Boker reached values up to 4.0. The gradual intensification of the first event reached peak values on the February 11th > 1200 μg m-3 and an AOT ~ 1.8, while the second dust storm commenced on September 8th with a sharp increase reaching peak values of 2225 μg m-3 and AOT of 4.0. Measurements of the fair weather vertical electric field (Ez) and of the vertical current density (Jz) were conducted continuously with a 1 minute temporal resolution. During the February event, very large fluctuations in the electrical parameters were measured at the WO. The Ez values changed between +1000 and +8000 V m-1 while the Jz fluctuated between -10 and +20 pA m-2 (this is an order of magnitude larger compared to the fair weather current density of ~2 pA m-2. In contrast, during the September event, Ez values registered at WO were between -430 and +10 V m-1 while the Jz fluctuated between -6 and +3 pA m2. For the September event the Hermon site showed Ez and Jz values fluctuating between -460 and +570 V m-1 and -14.5 and +18 pA m-2 respectively. The electric field and current variability, amplitude and the

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

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.

Surface Properties Associated With Dust Storm Plume's Point-Source Locations In The Border Region Of The US And Mexico

NASA Astrophysics Data System (ADS)

Bleiweiss, M. P.; DuBois, D. W.; Flores, M. I.

2013-12-01

Dust storms in the border region of the Southwest US and Northern Mexico are a serious problem for air quality (PM10 exceedances), health (Valley Fever is pandemic in the region) and transportation (road closures and deadly traffic accidents). In order to better understand the phenomena, we are attempting to identify critical characteristics of dust storm sources so that, possibly, one can perform more accurate predictions of events and, thus, mitigate some of the deleterious effects. Besides the emission mechanisms for dust storm production that are tied to atmospheric dynamics, one must know those locations whose source characteristics can be tied to dust production and, therefore, identify locations where a dust storm is eminent under favorable atmospheric dynamics. During the past 13 years, we have observed, on satellite imagery, more than 500 dust events in the region and are in the process of identifying the source regions for the dust plumes that make up an event. Where satellite imagery exists with high spatial resolution (less than or equal to 250m), dust 'plumes' appear to be made up of individual and merged plumes that are emitted from a 'point source' (smaller than the resolution of the imagery). In particular, we have observed events from the ASTER sensor whose spatial resolution is 15m as well as Landsat whose spatial resolution is 30m. Tying these source locations to surface properties such as NDVI, albedo, and soil properties (percent sand, silt, clay, and gravel; soil moisture; etc.) will identify regions with enhanced capability to produce a dust storm. This, along with atmospheric dynamics, will allow the forecast of dust events. The analysis of 10 events from the period 2004-2013, for which we have identified 1124 individual plumes, will be presented.

The Relations of Stressful Events and Nonacademic Future Expectations in African American Adolescents: Gender Differences in Parental Monitoring

ERIC Educational Resources Information Center

Cunningham, Michael; Mars, Dustin E.; Burns, Lateela J.

2012-01-01

Urban African American high school students (N = 206) completed a study to examine gender differences in parental monitoring and the effect on the relationship between exposure to stressful life events and nonacademic future expectations. Participant's ages range from 13 to 18 (M = 15.78, SD = 1.19). Participants reported high exposure to…

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

Adjoint Sensitivity Analyses Of Sand And Dust Storms In East Asia

NASA Astrophysics Data System (ADS)

Kay, J.; Kim, H.

2008-12-01

Sand and Dust Storm (SDS) in East Asia, so called Asian dust, is a seasonal meteorological phenomenon. Mostly in spring, dust particles blown into atmosphere in the arid area over northern China desert and Manchuria are transported to East Asia by prevailing flows. Three SDS events in East Asia from 2005 to 2008 are chosen to investigate how sensitive the SDS forecasts to the initial condition uncertainties and thence to suggest the sensitive regions for adaptive observations of the SDS events. Adaptive observations are additional observations in sensitive regions where the observations may have the most impact on the forecast by decreasing the forecast error. Three SDS events are chosen to represent different transport passes from the dust source regions to the Korean peninsula. To investigate the sensitivities to the initial condition, adjoint sensitivities that calculate gradient of the forecast aspect (i.e., response function) with respect to the initial condition are used. The forecast aspects relevant to the SDS transport are forecast error of the surface pressure, surface pressure perturbation, and steering vector of winds in the lower troposphere. Because the surface low pressure system usually plays an important role for SDS transport, the forecast error of the surface pressure and the surface pressure perturbation are chosen as the response function of the adjoint calculation. Another response function relevant to SDS transport is the steering flow over the downstream region (i.e., Korean peninsula) because direction and intensity of the prevailing winds usually determine the intensity and occurrence of the SDS events at the destination. The results show that the sensitive regions for the forecast error of the surface pressure and surface pressure perturbation are initially located in the vicinity of the trough and then propagate eastward as the low system moves eastward. The vertical structures of the adjoint sensitivities are upshear tilted structures

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

Dust Aerosol Particle Size at the Mars Science Laboratory Landing Site

NASA Astrophysics Data System (ADS)

Vicente-Retortillo, Alvaro; Martínez, Germán; Renno, Nilton; Lemmon, Mark; de la Torre-Juárez, Manuel

2017-04-01

We have developed a new methodology to retrieve dust aerosol particle size from Mars Science Laboratory (MSL) observations [1]. We use photodiode output currents measured by the Rover Environmental Monitoring Station (REMS) UV sensor (UVS), ancillary data records (ADR) containing the geometry of the rover and the Sun, and values of the atmospheric opacity retrieved from Mastcam measurements. In particular, we analyze REMS UVS measurements when the Sun is blocked by the masthead and the mast of the rover since the behavior of the output currents during these shadow events depends on the dust phase function, which depends on particle size. The retrieved dust effective radii show a significant seasonal variability, ranging from 0.6 μm during the low opacity season (Ls = 60° - 140°) to 2 μm during the high opacity season (Ls = 180° - 360°). The relationship between atmospheric opacity and dust particle size indicates that dust-lifting events originate at various distances from Gale Crater. The external origin of high dust content events is consistent with the strong and persistent northerly and northwesterly winds at Gale Crater during the perihelion season centered around Ls = 270° [2]. From an interannual perspective, the general behavior of the particle size evolution in MY 31-32 is similar to that in MY 32-33, although some differences are noted. During the low opacity season (Ls = 60° - 140°), the retrieved dust effective radii in MY 33 are significantly lower than in MY 32. A larger contribution of water ice clouds to the total atmospheric opacity during the aphelion season of MY 33 can partially explain such a departure. Differences during the perihelion season are caused by interannual variability of enhanced opacity events. The determination of dust aerosol particle size is important to improve the accuracy of models in simulating the UV environment at the surface [3] and in predicting heating rates, which affect the atmospheric thermal and dynamical

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.

Spring Dust Storm Smothers Beijing

NASA Technical Reports Server (NTRS)

2002-01-01

A few days earlier than usual, a large, dense plume of dust blew southward and eastward from the desert plains of Mongolia-quite smothering to the residents of Beijing. Citizens of northeastern China call this annual event the 'shachenbao,' or 'dust cloud tempest.' However, the tempest normally occurs during the spring time. The dust storm hit Beijing on Friday night, March 15, and began coating everything with a fine, pale brown layer of grit. The region is quite dry; a problem some believe has been exacerbated by decades of deforestation. According to Chinese government estimates, roughly 1 million tons of desert dust and sand blow into Beijing each year. This true-color image was made using two adjacent swaths (click to see the full image) of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, on March 17, 2002. The massive dust storm (brownish pixels) can easily be distinguished from clouds (bright white pixels) as it blows across northern Japan and eastward toward the open Pacific Ocean. The black regions are gaps between SeaWiFS' viewing swaths and represent areas where no data were collected. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

Dust transport and deposition observed from the Terra-MODIS space observations

NASA Astrophysics Data System (ADS)

Kaufman, Y. J.; Koren, I.; Tanre, D.; Fan, S.; Remer, L.; Ginoux, P.

2003-12-01

Meteorological observations, in situ data and satellite images of dust episodes were used already in the 1970s to estimate that 100 tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but deteriorates air quality and caries pathogens as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport and deposition. The Terra spacecraft launched at the dawn of the last millennium provides first systematic well calibrated multispectral measurements from the MODIS instrument, for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and evaluate the African dust column concentration, transport and deposition. We found that 230 80 tg of dust are transported annually from Africa to the Atlantic Ocean, 30 tg return to Africa and Europe, 70 tg reach the Caribbean, 45 tg fertilize the Amazon Basin, 4 times as previous estimates thus explaining a paradox regarding the source of nutrition to the Amazon forest, and 120 40 tg are deposited in the Atlantic Ocean. The results are compared favorably with dust transport models for particle radius * 12 m. This study is a first example of quantitative use of MODIS aerosol for a geophysical study.

Dust Transport and Deposition Observed from the Terra-MODIS Space Observations

NASA Technical Reports Server (NTRS)

Kaufman, Y. J.; Koren, I.; Remer, L. A.; Tanre, D.; Fan, Ginoux; Fan, S.

2004-01-01

Meteorological observations, in situ data and satellite images of dust episodes were used already in the 1970s to estimate that 100 tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but deteriorates air quality and caries pathogens as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport and deposition. The Terra spacecraft launched at the dawn of the last millennium provides first systematic well calibrated multispectral measurements from the MODIS instrument, for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and evaluate the African dust column concentration, transport and deposition. We found that 230+/-80 tg of dust are transported annually from Africa to the Atlantic Ocean, 30 tg return to Africa and Europe, 70 tg reach the Caribbean, 45 tg fertilize the Amazon Basin, 4 times as previous estimates thus explaining a paradox regarding the source of nutrition to the Amazon forest, and 120+/-40 tg are deposited in the Atlantic Ocean. The results are compared favorably with dust transport models for particle radius less than or equal to 12 microns. This study is a first example of quantitative use of MODIS aerosol for a geophysical study.

Looking for Dust-Scattering Light Echoes

NASA Astrophysics Data System (ADS)

Mills, Brianna; Heinz, Sebastian; Corrales, Lia

2018-01-01

Galactic X-ray transient sources such as neutron stars or black holes sometimes undergo an outburst in X-rays. Ring structures have been observed around three such sources, produced by the X-ray photons being scattered by interstellar dust grains along our line of sight. These dust-scattering light echoes have proven to be a useful tool for measuring and constraining Galactic distances, mapping the dust structure of the Milky Way, and determining the dust composition in the clouds producing the echo. Detectable light echoes require a sufficient quantity of dust along our line of sight, as well as bright, short-lived Galactic X-ray flares. Using data from the Monitor of All-Sky X-ray Image (MAXI) on-board the International Space Station, we ran a peak finding algorithm in Python to look for characteristic flare events. Each flare was characterized by its fluence, the integrated flux of the flare over time. We measured the distribution of flare fluences to show how many observably bright flares were recorded by MAXI. This work provides a parent set for dust echo searches in archival X-ray data and will inform observing strategies with current and future X-ray missions such as Athena and Lynx.

The Tranisiting Dust of Boyajian's Star

NASA Astrophysics Data System (ADS)

Bodman, Eva; Ellis, Tyler G.; Boyajian, Tabetha S.; Wright, Jason

2018-06-01

From May to October of 2017, Boyajian's Star displayed four days-long dips in observed flux, which are referred to as “Elsie,” “Celeste,” “Skara Brae,” and “Angkor” (Boyajian et al. 2018). This Elsie family dip event was monitored with the Las Cumbres Observatory in three bands, B, r', and i'. Looking at each dip individually, we analyze the multi-band photometry for wavelength dependency in dip depth to constrain properties of the transiting material. We find that all of the dips show non-grey extinction and are consistent with optically thin dust. Interpreting the dips as transiting dust clouds, we constrain the properties of the dust grains and find that the average grain radius is <1 micron, assuming silicate composition. This wavelength dependency and grain size is inconsistent with observed properties of the long-term “secular” dimming (Meng et al. 2017), suggesting that the dust causing the dips is from a separate population.

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

The Martian Dust Cycle: Observations and Modeling

NASA Technical Reports Server (NTRS)

Kahre, Melinda A.

2013-01-01

The dust cycle is critically important for Mars' current climate system. Suspended atmospheric dust affects the radiative balance of the atmosphere, and thus greatly influences the thermal and dynamical state of the atmosphere. Evidence for the presence of dust in the Martian atmosphere can be traced back to yellow clouds telescopically observed as early as the early 19th century. The Mariner 9 orbiter arrived at Mars in November of 1971 to find a planet completely enshrouded in airborne dust. Since that time, the exchange of dust between the planet's surface and atmosphere and the role of airborne dust on Mars' weather and climate has been studied using observations and numerical models. The goal of this talk is to give an overview of the observations and to discuss the successes and challenges associated with modeling the dust cycle. Dust raising events on Mars range in size from meters to hundreds of kilometers. During some years, regional storms merge to produce hemispheric or planet encircling dust clouds that obscure the surface and raise atmospheric temperatures by tens of kelvin. The interannual variability of planet encircling dust storms is poorly understood. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. A low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading are generally observed: one peak occurs before northern winter solstice and one peak occurs after northern winter solstice. Numerical modeling studies attempting to interactively simulate the Martian dust cycle with general circulation models (GCMs) include the lifting, transport, and sedimentation of radiatively active dust. Two dust lifting processes are commonly represented in