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Sample records for saharan dust episodes

  1. Spatial distribution of PM1 and PM10 during Saharan dust episodes in Athens, Greece

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    G. Ferentinos

    2009-04-01

    Full Text Available The objective of this study is to present and analyse the spatial distribution of PM1 (particulate matter with diameter less than 1 μm and PM10 (particulate matter with diameter less than 10 μm within the greater area of Athens (GAA, Greece, during two extreme Saharan dust episodes in 2006 and 2008. Two portable detectors, based on light scattering method, were used to record the particulate matter concentrations. The samples were collected in the same morning hour of the day which coincided with the peak of vehicles traffic. We analysed the recorded data on normal days and on days with extreme Saharan dust events in order to find out the exceedances of the particulate matter concentrations. Using Kriging method, the spatial patterns of PM1 and PM10 concentrations were constructed for GAA. It is already known that particulate matter represent the main hazard in cardiovascular and respiratory syndromes within the most polluted cities of Europe, which confront high traffic problems, amplified by Saharan dust episodes, which are frequent especially in the Southern Europe, during spring time. The results of the performed analysis showed that during these episodes, PM concentrations over exceed the thresholds set by the European Union, exacerbating the human health in Athens.

  2. Poleward transport of Saharan dust initiated by a Saharan cyclone.

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    Karam Francis, Diana Bou; Chaboureau, Jean-Pierre; Cuesta, Juan

    2016-04-01

    To enhance the understanding of the role of Saharan mineral dust in the Arctic climate system, this study focuses on dust emission and poleward transport associated with an intense Saharan cyclone that occurred over North Africa in early April 2011. Satellites observations at high spatio-temporal resolution are used in this study in order to characterize qualitatively (using MSG-SEVIRI and CALIPSO/CloudSat) and quantitatively (using MODIS and OMI) the dust activity over North Africa associated with the Saharan cyclone as well as the transport of dust toward the northern pole. Beside the observations, a simulation at high resolution is performed using the MesoNh model in order to estimation the dust load transported northward and to evaluate the dust deposition north to 60°N and its impact on the Albedo. In this study, we identify in new and important mechanism for the transport of dust over long distances toward the northern pole: the poleward migration of Saharan cyclones, in which the dust is transported toward the Arctic following a newly identified path; across the Northern Atlantic Ocean around the Icelandic Low. This path is to be added to the two preferable paths mentioned in previous studies i.e. through transport across Northern Europe and across the Atlantic Ocean around the Bermuda High. Key words: Arctic, North Africa, dust storm, dust deposition, surface albedo.

  3. Saharan dust storms: nature and consequences

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    Goudie, A. S.; Middleton, N. J.

    2001-12-01

    This paper reviews recent work on the role of Saharan dust in environmental change, the location and strength of source areas, the transport paths of material away from the desert, the rates of Saharan dust deposition, the nature of that material (including PeriSaharan loess) and the changing rates of dust activity in response to long and short-term climatic changes. The Sahara produces more aeolian soil dust than any other world desert, and Saharan dust has an important impact on climatic processes, nutrient cycles, soil formation and sediment cycles. These influences spread far beyond Africa, thanks to the great distances over which Saharan dust is transported. The precise locations of Saharan dust source areas are not well known, but data from the Total Ozone Mapping Spectrometer (TOMS) suggest two major source areas: the Bodélé depression and an area covering eastern Mauritania, western Mali and southern Algeria. Trajectories of long-distance transport are relatively well documented, but the links between source areas and seasonal Saharan dust pathways are not. However, it is possible that Harmattan dust from the Bodélé depression may not be the source of the prominent winter plume over the tropical North Atlantic, as is often suggested in the literature. Few of the data on particle size characteristics of Saharan dust are derived from major source areas or from Africa itself. Saharan dusts sampled from the Harmattan plume and over Europe are dominated by SiO 2 and Al 2O 3, a characteristic they share with North American and Chinese dusts. The concentrations of these two major elements are similar to those found in world rocks. PeriSaharan loess is conspicuous by its relative absence, considering the Sahara's dominance of the global desert dust cycle both in the contemporary era and through the geological past. In recent decades, the frequency of Saharan dust events has varied markedly in response to climatic factors such as drought and anthropogenic

  4. Saharan dust levels in Greece and received inhalation doses

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    Mitsakou, C.; Kallos, G.; Papantoniou, N.; Spyrou, C.; Solomos, S.; Astitha, M.; Housiadas, C.

    2008-12-01

    The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in the south European Region and especially in urban areas, where there is also significant contribution from anthropogenic sources. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003-2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by more than 20% to the annual number of exceedances - PM10 values greater than EU limits - depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

  5. INVESTIGATION OF SAHARAN DUST TRANSPORT ON THE BASIS OF AEROLOGICAL MEASUREMENTS

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    R. TÓTH

    2016-03-01

    Full Text Available The Sahara Desert is the largest dust source on Earth. Its dust is frequently emitted into the Mediterranean atmosphere and transported by the winds sometimes as far north as Central Europe. The accumulated particles contribute to soil forming processes, while the atmospheric mineral dust has an impact on the radiation budget, cloud forming processes, the pH of precipitation and biogeochemical cycles of marine ecosystems. The PM (particulate matter in ambient air does not contain only primary particles but secondary particles formed in the atmosphere from precursor gases as well. Especially these latter ones have significant negative impacts to human health. There are in average four-five Saharan dust episodes annually in Hungary, sometimes in form of colour precipitation (brown rainfall, red snow. There are several possibilities for providing evidence for the Saharan origin of the dust observed in our country: back-trajectories using NOAA HYSPLIT model, TOMS satellite maps of NASA, maps of aerosol index of Ozone Monitoring Instrument, observations of spectral aerosol optical depth of Aerosol Robotic Network, satellite maps of EUMETSAT, elemental analysis of dust samples. In this study we try to reveal the suitability of the upper-air wind fields in detection of Saharan dust episodes in Central Europe. We deployed the global upper-air data base of the last 41 years that is available by courtesy of College of Engineering and Applied Sciences at University of Wyoming. We apply this method also for tracking air pollution of vegetation fires.

  6. Mixing and Deposition of Saharan Dust during Transatlantic Transport

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    Heinold, Bernd; Schepanski, Kerstin; Gieseler, Daniel; Ulrich, Max

    2017-04-01

    Mineral dust from arid and semi-arid regions plays an important environmental role due to its ability to alter the Earth's energy budget by aerosol-cloud-radiation interactions as well as due to its impact on the biogeochemical cycle and air quality. The Sahara desert is the world's main dust source contributing at least 50% to the global dust load. Large amounts of dust are carried towards the Caribbean within the Saharan Air Layer (SAL), with maximum transport in late boreal spring and early summer. During long-range transport, the dust particles are transformed by aging and mixing, which may have significant but as yet unquantified effects on the dust impact on radiation, cloud properties, and the biogeochemical processes of ecosystems. This study focuses on the important role of mixing and deposition processes on the distribution, lifetime, and particle properties of mineral dust. Regional dust modelling and trajectory analysis are used to investigate the long-range transport of Saharan dust across the Atlantic Ocean towards the Caribbean. Specifically, we address the questions of (1) how the Saharan dust export is influenced by the atmospheric circulation over West Africa and (2) which role the different removal and mixing processes play during long-range transport? Modelling the emission, transport, and deposition of Saharan dust as well as the effect of dust radiative forcing is performed with the regional model COSMO-MUSCAT. The COSMO-MUSCAT simulations are combined with a LAGRANTO trajectory analysis. The consistent dataset is then evaluated to study the boundary layer impact on deposition and dust-cloud interactions along transport paths. The results show that as the source activity, dust deposition is driven by the atmospheric circulation patterns over West Africa. Convective mixing controls dry deposition in the tropics and can explain sporadic deposition events in the subtropics. Overall, this study provides an improved model-based assessment of the

  7. Seasonal transport patterns of intense Saharan dust events at the Mediterranean island of Lampedusa

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    Meloni, D.; di Sarra, A.; Monteleone, F.; Pace, G.; Piacentino, S.; Sferlazzo, D. M.

    2008-05-01

    Saharan dust (SD) episodes occurring at the Mediterranean island of Lampedusa (35.52° N, 12.63° E) from May 1999 to December 2005 have been shown to occur in the 26% of the cloud-free days [Meloni, D., di Sarra, A., Biavati, G., DeLuisi, J.J., Monteleone, F., Pace, G., Piacentino, S., Sferlazzo, D.M., 2007. Seasonal behavior of Saharan dust events at the Mediterranean island of Lampedusa in the period 1999-2005, Atmos. Environ. 41, 3041-3056]. In this paper we focus on intense SD events detected until September 2006, characterized by large values of the Saharan Dust Event Index (SDEI), the sum of the daily average aerosol optical depth at 500 nm, τ, over the duration of the dust episode. The SDEI index provides an indication about the intensity of SD events, due either to a long duration and/or to high dust optical depth. A total of 24 episodes characterized by large values of SDEI are examined. The NCEP-based maps of geopotential height and temperature at 700 mbar are used to identify the main circulation patterns driving SD to the Central Mediterranean and Lampedusa. Dust transport episodes in summer last for several days, and the corresponding SDEI values are the highest of the year. These episodes are mainly governed by two circulation patterns: the trough extending near the Atlantic coast of Europe and the high pressure system present in North Africa, generally above 25° N. This configuration causes strong south-westerly flows from the Sahara towards Southern Italy. The time evolution of τ for these long SD events shows that the largest values (> 0.3) are usually observed when the two patterns are present simultaneously, while low (< 0.3) τ values are measured when the Atlantic trough influence is weak. Moreover, the most probable loading region typically shows a warm kernel in North-Western Sahara, with a tongue extending north-eastward towards Sicily. In spring, moderate to high τ are measured, and SD episodes last as long as 13 days. Two synoptic

  8. Saharan dust detection using multi-sensor satellite measurements

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    Sriharsha Madhavan

    2017-02-01

    Full Text Available Contemporary scientists have vested interest in trying to understand the climatology of the North Atlantic Basin since this region is considered as the genesis for hurricane formation that eventually get shipped to the tropical Atlantic region and the Caribbean. The effects of atmospheric water cycle and the climate of West Africa and the Atlantic basin are hugely impacted by the radiative forcing of Saharan dust. The focus area in this paper would be to improve the dust detection schemes by employing the use of multi sensor measurements in the thermal emissive wavelengths using legacy sensors such as Terra (T and Aqua (A MODerate-resolution Imaging Spectroradiometer (MODIS, fusing with Ozone Monitoring Instrument (OMI. Previous work by Hao and Qu (2007 had considered a limited number of thermal infrared channels which led to a correlation coefficient R2 value of 0.765 between the Aerosol Optical Thickness (AOT at 550 nm and the modeled dust index. In this work, we extend the thermal infrared based dust detection by employing additional channels: the 8.55 μm which has shown high sensitivity to the Saharan dust, along with water vapor channel of 7.1 μm and cloud top channel of 13.1 μm. Also, the dust pixels were clearly identified using the OMI based aerosol types. The dust pixels were cleanly segregated from the other aerosol types such as sulfates, biomass, and other carbonaceous aerosols. These improvements led to a much higher correlation coefficient R2 value of 0.85 between the modified dust index and the AOT in comparison to the previous work. The key limitations from the current AOT products based on MODIS and were put to test by validating the improved dust detection algorithm. Two improvements were noted. First, the dust measurement radiometry using MODIS is significantly improved by at least an order of 2. Second the spatial measurements are enhanced by a factor of at least 10.

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

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

    2016-01-01

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

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

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

    2006-01-01

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

  11. Radioecological impact of Saharan dusts fallout. Case study of a major event on the 21. of february 2004 in south part of France; Impact radioecologique des retombees de poussieres sahariennes. Episode majeur du 21/02/2004 dans le sud de la France

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    Masson, O.; Pourcelot, L.; Gurriaran, R.; Paulat, P

    2005-07-01

    Lithometeors, Sirocco or more commonly 'red mud' are all in fact related to a single phenomenon which affects France every year: the wind transport and deposit of desert particles from the Sahara. On the 21. of February 2004, the southern part of France is swept by a weather event of wind transport of Saharan particles. The recordings of atmospheric dust contamination and the deposit of dust, which results from it, make an episode of exceptional width. In a few hours, the thickness of the deposit exceeds 1 mm (up to 4 mm in Corsica) with a maximum density of surface charge of 50 g.m{sup -2} (50 tons per km{sup 2}). The loads of the PM{sub 10} type particles in the air, recorded by associations of monitoring of the quality of the air, indicate concentrations multiplied to the maximum by 10 and an influence on the ground of the plume ranging between 300 000 and 350 000 km{sup 2}. To the end, 2 million tons are deposited on a portion of the territory located at the south of a line from Nantes to Besancon. This event also had a significant radio-ecological impact, leading to significant {sup 137}Cs, {sup (239+240)}Pu, {sup 241}Am, activity levels of 38 Bq. kg{sup -1} sec, 1 Bq. kg{sup -1} sec and 0,46 Bq. kg{sup -1} sec, respectively. Quality of air monitoring organisations recorded 10-fold increases in the concentration of charged PM{sub 10} {sup 2}type particles within the cloud; ground coverage stretched over a 300 000 km{sup 2} surface area. Across this whole area, the artificial radioactivity deposits are estimated to 37.10{sup 10} Bq. In term of flow of deposit, this episode represents, with him only, i.e. in a few hours, a {sup 137}Cs deposition equivalent to that recorded on average in a cumulated time of one year. Data from this study show that these weather-climatic episodes generate today, environmental samples which on average, present the highest levels and flux of artificial radioactivities, more than those in the sediments of the Rhone river

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

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    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.

  13. Trans-Pacific Transport of Saharan Dust to Western North America: A Case Study

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    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.

  14. The fate of saharan dust across the atlantic and implications for a central american dust barrier

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    E. Nowottnick

    2011-08-01

    Full Text Available 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 Modern Era Retrospective-Analysis for Research and Applications (MERRA meteorological analyses. Compared to observations from MODIS and CALIOP, GEOS-5 reproduces the observed location and magnitude of observed 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 loss 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.

  15. Dust-induced episodic phytoplankton blooms in the Arabian Sea during winter monsoon

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    Banerjee, P.; PrasannaKumar, S.

    to potential iron limitation. Although, all the phytoplankton blooms within CAS were observed following episodic dust events, only four blooms can be attributed to dust depositions. Our work shows that phytoplankton blooms fueled by episodic dust storms...

  16. Dust Episodes in Hong Kong (South China) and their Relationship with the Sharav and Mongolian Cyclones and Jet Streams

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    Lee, Y. C.; Wenig, Mark; Zhang, Zhenxi; Sugimoto, Nobuo; Larko, Dave; Diehl, Thomas

    2012-01-01

    The study presented in this paper analyses two dust episodes in Hong Kong, one occurring in March 2006 and the other on 22 March 2010. The latter is the worst dust episode on Hong Kong record. The focus is on the relationship between the dust episodes and the Sharav/Mongolian cyclones and jet streams. The 16 March 2006 episode is traceable to a continental-scale Saharan dust outbreak of 5-9 March 2006 caused by the cold front of an East Mediterranean Sharav cyclone arriving at north-west Africa on 5 March 2006. The eastward movement of the cyclone along the North African coast is clearly illustrated in the geopotential height contours. Simulations by the chemistry transport model GOCART provide a visible evidence of the transport as well as an estimate of contributions from the Sahara to the aerosol concentration levels in Hong Kong. The transport simulations suggest that the dust is injected to the polar jet north of the Caspian Sea, while it is transported eastward simultaneously by the more southerly subtropical jet. The major source of dust for Hong Kong is usually the Gobi desert. Despite the effect of remote sources, the 16 March 2006 dust episode was still mainly under the influence of the Mongolian cyclone cold fronts. In the recent episode of 22 March 2010, the influence of the Mongolian cyclone predominated as well. It appears that the concurrent influence of the Sharav and Mongolian cyclones on Hong Kong and East Asia is not a common occurrence. Besides transporting dusts from non-East Asian sources to Hong Kong and East Asia, the strong subtropical jet on 21 March 2010 (i.e. 1 day prior to the major dust episode) is believed to have strengthened an easterly monsoon surge to South China causing the transport of voluminous dusts to Taiwan and Hong Kong the following day.

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

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

    2015-07-01

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

  18. Seasonal provenance changes in present-day Saharan dust collected in and off Mauritania

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    Friese, C.A.; van Hateren, J.A.; Vogt, C.; Fischer, G.; Stuut, J.-B.W.

    2017-01-01

    Saharan dust has a crucial influence on the earthclimate system and its emission, transport and deposition areintimately related to, e.g., wind speed, precipitation, temperatureand vegetation cover. The alteration in the physical andchemical properties of Saharan dust due to environmentalchanges is

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

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    V.H Garrison

    2006-12-01

    Full Text Available An international team of scientists from government agencies and universities in the United States, U.S. Virgin Islands (USVI, Trinidad & Tobago, the Republic of Cape Verde, and the Republic of Mali (West Africa is working together to elucidate the role Saharan dust may play in the degradation of Caribbean ecosystems. The first step has been to identify and quantify the persistent organic pollutants (POPs, trace metals, and viable microorganisms in the atmosphere in dust source areas of West Africa, and in dust episodes at downwind sites in the eastern Atlantic (Cape Verde and the Caribbean (USVI and Trinidad & Tobago. Preliminary findings show that air samples from Mali contain a greater number of pesticides, polychlorinated biphenyls (PCBs and polycyclic aromatic hydrocarbons (PAHs and in higher concentrations than the Caribbean sites. Overall, POP concentrations were similar in USVI and Trinidad samples. Trace metal concentrations were found to be similar to crustal composition with slight enrichment of lead in Mali. To date, hundreds of cultureable micro-organisms have been identified from Mali, Cape Verde, USVI, and Trinidad air samples. The sea fan pathogen, Aspergillus sydowii, has been identified in soil from Mali and in air samples from dust events in the Caribbean. We have shown that air samples from a dust-source region contain orders of magnitude more cultureable micro-organisms per volume than air samples from dust events in the Caribbean, which in turn contain 3-to 4-fold more cultureable microbes than during non-dust conditions. Rev. Biol. Trop. 54 (Suppl. 3: 9-21. Epub 2007 Jan. 15.

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

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    K. Schepanski

    2017-09-01

    Full Text Available 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

  1. Tank bromeliads capture Saharan dust in El Yunque National Forest, Puerto Rico

    Science.gov (United States)

    Royer, Dana L.; Moynihan, Kylen M.; Ariori, Carolyn; Bodkin, Gavin; Doria, Gabriela; Enright, Katherine; Hatfield-Gardner, Rémy; Kravet, Emma; Nuttle, C. Miller; Shepard, Lisa; Ku, Timothy C. W.; O'Connell, Suzanne; Resor, Phillip G.

    2018-01-01

    Dust from Saharan Africa commonly blows across the Atlantic Ocean and into the Caribbean. Most methods for measuring this dust either are expensive if collected directly from the atmosphere, or depend on very small concentrations that may be chemically altered if collected from soil. Tank bromeliads in the dwarf forest of El Yunque National Forest, Puerto Rico, have a structure of overlapping leaves used to capture rainwater and other atmospheric inputs. Therefore, it is likely that these bromeliads are collecting in their tanks Saharan dust along with local inputs. Here we analyze the elemental chemistry, including rare earth elements (REEs), of tank contents in order to match their chemical fingerprint to a provenance of the Earth's crust. We find that the tank contents differ from the local soils and bedrock and are more similar to published values of Saharan dust. Our study confirms the feasibility of using bromeliad tanks to trace Saharan dust in the Caribbean.

  2. Saharan dust intrusions in Spain: Health impacts and associated synoptic conditions.

    Science.gov (United States)

    Díaz, Julio; Linares, Cristina; Carmona, Rocío; Russo, Ana; Ortiz, Cristina; Salvador, Pedro; Trigo, Ricardo Machado

    2017-07-01

    A lot of papers have been published about the impact on mortality of Sahara dust intrusions in individual cities. However, there is a lack of studies that analyse the impact on a country and scarcer if in addition the analysis takes into account the meteorological conditions that favour these intrusions. The main aim is to examine the effect of Saharan dust intrusions on daily mortality in different Spanish regions and to characterize the large-scale atmospheric circulation anomalies associated with such dust intrusions. For determination of days with Saharan dust intrusions, we used information supplied by the Ministry of Agriculture, Food & Environment, it divides Spain into 9 main areas. In each of these regions, a representative province was selected. A time series analysis has been performed to analyse the relationship between daily mortality and PM10 levels in the period from 01.01.04 to 31.12.09, using Poisson regression and stratifying the analysis by the presence or absence of Saharan dust advections. The proportion of days on which there are Saharan dust intrusions rises to 30% of days. The synoptic pattern is characterised by an anticyclonic ridge extending from northern Africa to the Iberian Peninsula. Particulate matter (PM) on days with intrusions are associated with daily mortality, something that does not occur on days without intrusions, indicating that Saharan dust may be a risk factor for daily mortality. In other cases, what Saharan dust intrusions do is to change the PM-related mortality behaviour pattern, going from PM2.5. A study such as the one conducted here, in which meteorological analysis of synoptic situations which favour Saharan dust intrusions, is combined with the effect on health at a city level, would seem to be crucial when it comes to analysing the differentiated mortality pattern in situations of Saharan dust intrusions. Copyright © 2017 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

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

    2017-05-01

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

  4. Seasonal provenance changes in present-day Saharan dust collected in and off Mauritania

    Science.gov (United States)

    Friese, Carmen A.; van Hateren, Johannes A.; Vogt, Christoph; Fischer, Gerhard; Stuut, Jan-Berend W.

    2017-08-01

    Saharan dust has a crucial influence on the earth climate system and its emission, transport and deposition are intimately related to, e.g., wind speed, precipitation, temperature and vegetation cover. The alteration in the physical and chemical properties of Saharan dust due to environmental changes is often used to reconstruct the climate of the past. However, to better interpret possible climate changes the dust source regions need to be known. By analysing the mineralogical composition of transported or deposited dust, potential dust source areas can be inferred. Summer dust transport off northwest Africa occurs in the Saharan air layer (SAL). In continental dust source areas, dust is also transported in the SAL; however, the predominant dust input occurs from nearby dust sources with the low-level trade winds. Hence, the source regions and related mineralogical tracers differ with season and sampling location. To test this, dust collected in traps onshore and in oceanic sediment traps off Mauritania during 2013 to 2015 was analysed. Meteorological data, particle-size distributions, back-trajectory and mineralogical analyses were compared to derive the dust provenance and dispersal. For the onshore dust samples, the source regions varied according to the seasonal changes in trade-wind direction. Gibbsite and dolomite indicated a Western Saharan and local source during summer, while chlorite, serpentine and rutile indicated a source in Mauritania and Mali during winter. In contrast, for the samples that were collected offshore, dust sources varied according to the seasonal change in the dust transporting air layer. In summer, dust was transported in the SAL from Mauritania, Mali and Libya as indicated by ferroglaucophane and zeolite. In winter, dust was transported with the trades from Western Sahara as indicated by, e.g., fluellite.

  5. Seasonal provenance changes in present-day Saharan dust collected in and off Mauritania

    Directory of Open Access Journals (Sweden)

    C. A. Friese

    2017-08-01

    Full Text Available Saharan dust has a crucial influence on the earth climate system and its emission, transport and deposition are intimately related to, e.g., wind speed, precipitation, temperature and vegetation cover. The alteration in the physical and chemical properties of Saharan dust due to environmental changes is often used to reconstruct the climate of the past. However, to better interpret possible climate changes the dust source regions need to be known. By analysing the mineralogical composition of transported or deposited dust, potential dust source areas can be inferred. Summer dust transport off northwest Africa occurs in the Saharan air layer (SAL. In continental dust source areas, dust is also transported in the SAL; however, the predominant dust input occurs from nearby dust sources with the low-level trade winds. Hence, the source regions and related mineralogical tracers differ with season and sampling location. To test this, dust collected in traps onshore and in oceanic sediment traps off Mauritania during 2013 to 2015 was analysed. Meteorological data, particle-size distributions, back-trajectory and mineralogical analyses were compared to derive the dust provenance and dispersal. For the onshore dust samples, the source regions varied according to the seasonal changes in trade-wind direction. Gibbsite and dolomite indicated a Western Saharan and local source during summer, while chlorite, serpentine and rutile indicated a source in Mauritania and Mali during winter. In contrast, for the samples that were collected offshore, dust sources varied according to the seasonal change in the dust transporting air layer. In summer, dust was transported in the SAL from Mauritania, Mali and Libya as indicated by ferroglaucophane and zeolite. In winter, dust was transported with the trades from Western Sahara as indicated by, e.g., fluellite.

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

    Science.gov (United States)

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

    2016-01-01

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

  7. Spatial and Temporal Variation of the Extreme Saharan Dust Event over Turkey in March 2016

    Directory of Open Access Journals (Sweden)

    Hakki Baltaci

    2017-02-01

    Full Text Available In this study, the influence of an extraordinary Saharan dust episode over Turkey on 23–24 March 2016 and the atmospheric conditions that triggered this event were evaluated in detail. PM10 (particulate matter less than 10 μm observations from 97 air quality stations, METAR (Meteorological Terminal Aviation Routine Weather Report observations at 64 airports, atmospheric soundings, and satellite products were used for the analysis. To determine the surface and upper levels of atmospheric circulation, National Centers of Environmental Prediction (NCEP/National Center for Atmospheric Research (NCAR Reanalysis data were applied to the extreme dust episodes. On 23 March 2016, high southwesterly winds due to the interaction between surface low- and high-pressure centers over Italy and Levant basin brought thick dust particles from Libya to Turkey. The daily PM10 data from 43 stations exceeded their long-term spring means over Turkey (especially at the northern and western stations. As a consequence of the longitudinal movement of the surface low from Italy to the Balkan Peninsula, and the quasi-stationary conditions of the surface high-pressure center allowed for the penetration of strong south and southwesterly winds to inner parts of the country on the following day. As a consequence, 100%, 90%, 88%, and 87% of the monitoring stations in Marmara (NW Turkey, central Anatolia, western (Aegean and northern (Black Sea regions of Turkey, respectively, exhibited above-normal daily PM10 values. In addition, while strong subsidence at the low levels of the atmosphere plays a significant role in having excessive daily PM10 values in Black Sea, dry atmospheric conditions and thick inversion level near the ground surface of Marmara ensured this region to have peak PM10 values ~00 Local Time (LT.

  8. Estimating the impact of Saharan dust on the year 2001 PM 10 record of Rome, Italy

    Science.gov (United States)

    Gobbi, G. P.; Barnaba, F.; Ammannato, L.

    This paper evaluates the role of Saharan dust advection in the exceeding of the PM 10 thresholds in the city of Rome, Italy. To this purpose, a series of observations and model forecasts recorded in the year 2001 are analysed and discussed. Lidar profiles collected over 168 days of the year are employed to both assess the presence and magnitude of Saharan dust layers over the city and to evaluate the depth of the planetary boundary layer. Backtrajectories are used to verify the Saharan origin of the lidar-sounded air masses. Model predictions of the presence of Saharan dust over the area are employed to fill the time gaps between lidar observations. PM 10 and carbon monoxide records of both a city background (Villa Ada) and a heavy traffic station (Magna Grecia) are cross-analysed with the dust events record and meteorological data. The analysis shows that: (1) Saharan dust was advected over Rome on about 30% of the days of 2001; (2) mean contribution of Saharan dust transport events to daily PM 10 levels was of the order of 20 μg m -3; (3) at the urban background station of Villa Ada, the Saharan contribution caused the surpassing of the maximum number of days in excess of 50 μg m -3 fixed by the current legislation (35 per year). Conversely, at the heavy traffic station of Magna Grecia the Saharan contribution was not determinant at causing the observed large exceeding of that limit, as well as of the maximum yearly average of 40 μg m -3; (4) 25% of the Saharan advection days (of the order of 100/year at Rome) led to a PM 10 increase >30 μg m -3, 4% caused an increase >50 μg m -3, thus leading on their own to surpassing the 50 μg m -3 daily limit.

  9. Millennial-scale fluctuations in Saharan dust supply across the decline of the African Humid Period

    Science.gov (United States)

    Zielhofer, Christoph; von Suchodoletz, Hans; Fletcher, William J.; Schneider, Birgit; Dietze, Elisabeth; Schlegel, Michael; Schepanski, Kerstin; Weninger, Bernhard; Mischke, Steffen; Mikdad, Abdeslam

    2017-09-01

    The Sahara is the world's largest dust source with significant impacts on trans-Atlantic terrestrial and large-scale marine ecosystems. Contested views about a gradual or abrupt onset of Saharan aridity at the end of the African Humid Period dominate the current scientific debate about the Holocene Saharan desiccation. In this study, we present a 19.63 m sediment core sequence from Lake Sidi Ali (Middle Atlas, Morocco) at the North African desert margin. We reconstruct the interaction between Saharan dust supply and Western Mediterranean hydro-climatic variability during the last 12,000 yr based on analyses of lithogenic grain-sizes, XRF geochemistry and stable isotopes of ostracod shells. A robust chronological model based on AMS 14C dated pollen concentrates supports our multi-proxy study. At orbital-scale there is an overall increase in southern dust supply from the Early Holocene to the Late Holocene, but our Northern Saharan dust record indicates that a gradual Saharan desiccation was interrupted by multiple abrupt dust increases before the 'southern dust mode' was finally established at 4.7 cal ka BP. The Sidi Ali record features millennial peaks in Saharan dust increase at about 11.1, 10.2, 9.4, 8.2, 7.3, 6.6, 6.0, and 5.0 cal ka BP. Early Holocene Saharan dust peaks coincide with Western Mediterranean winter rain minima and North Atlantic cooling events. In contrast, Late Holocene dust peaks correspond mostly with prevailing positive phases of the North Atlantic Oscillation. By comparing with other North African records, we suggest that increases in Northern Saharan dust supply do not solely indicate sub-regional to regional aridity in Mediterranean Northwest Africa but might reflect aridity at a trans-Saharan scale. In particular, our findings support major bimillennial phases of trans-Saharan aridity at 10.2, 8.2, 6.0 and 4.2 cal ka BP. These phases coincide with North Atlantic cooling and a weak African monsoon.

  10. Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic

    NARCIS (Netherlands)

    Korte, L.F.; Brummer, G.-J. A.; van der Does, M.; Guerreiro, C.V.; Hennekam, R.; van Hateren, J.A.; Jong, D.; Munday, C.I.; Schouten, S.; Stuut, J-B W.

    2017-01-01

    Massive amounts of Saharan dust are blown fromthe coast of northern Africa across the Atlantic Ocean towardsthe Americas each year. This dust has, depending onits chemistry, direct and indirect effects on global climatewhich include reflection and absorption of solar radiation aswell as transport

  11. Quantifying dust plume formation and aerosol size distribution during the Saharan Mineral Dust Experiment in North Africa

    KAUST Repository

    Khan, Basit Ali

    2015-01-01

    Dust particles mixed in the free troposphere have longer lifetimes than airborne particles near the surface. Their cumulative radiative impact on earth’s meteorological processes and climate might be significant despite their relatively small contribution to total dust abundance. One example is the elevated dust--laden Saharan Air Layer (SAL) over the equatorial North Atlantic, which cools the sea surface and likely suppresses hurricane activity. To understand the formation mechanisms of SAL, we combine model simulations and dust observations collected during the first stage of the Saharan Mineral Dust Experiment (SAMUM--I), which sampled dust events that extended from Morocco to Portugal, and investigated the spatial distribution and the microphysical, optical, chemical, and radiative properties of Saharan mineral dust. We employed the Weather Research Forecast model coupled with the Chemistry/Aerosol module (WRF--Chem) to reproduce the meteorological environment and spatial and size distributions of dust. The experimental domain covers northwest Africa including the southern Sahara, Morocco and part of the Atlantic Ocean with 5 km horizontal grid spacing and 51 vertical layers. The experiments were run from 20 May to 9 June 2006, covering the period of most intensive dust outbreaks. Comparisons of model results with available airborne and ground--based observations show that WRF--Chem reproduces observed meteorological fields as well as aerosol distribution across the entire region and along the airplane’s tracks. We evaluated several aerosol uplift processes and found that orographic lifting, aerosol transport through the land/sea interface with steep gradients of meteorological characteristics, and interaction of sea breezes with the continental outflow are key mechanisms that form a surface--detached aerosol plume over the ocean. Comparisons of simulated dust size distributions with airplane and ground--based observations are generally good, but suggest

  12. Present-day transatlantic Saharan dust deposition across the equatorial North Atlantic Ocean

    Science.gov (United States)

    Korte, Laura; Brummer, Geert-Jan; van der Does, Michelle; Guerreiro, Catarina; Hennekam, Rick; van Hateren, Johannes; Jong, Dirk; Munday, Chris; Schouten, Stefan; Jan-Berend, Stuut

    2017-04-01

    Massive amounts of Saharan dust are blown from the African coast across the Atlantic Ocean towards the Americas each year. This dust has direct and indirect effects on global climate including reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as on land-based dust collectors. The sediment traps were deployed at five sampling sites on a transect between northwest Africa and the Caribbean along 12⁰ N, in a down-wind extension of the land-based dust collectors placed at 19⁰ N on the Mauritanian coast in Iwik. We establish the temporal distribution of the particle fluxes deposited in the Atlantic and compare chemical compositions with the land-based dust collectors propagating to the down-wind sediment trap sites. First-year results show that the total mass fluxes in the ocean are highest at the sampling sites in the East and West, closest to the African continent and the Caribbean, respectively. Element ratios reveal that the lithogenic particles deposited nearest to Africa are most similar in composition to the Saharan dust collected in Iwik. Down-wind Al and Fe contents suggest a downwind change in the mineralogical composition of Saharan dust and indicate an increasing contribution of clay minerals towards the west. In the westernmost Atlantic, gradients suggest admixture of re-suspended clay-sized sediment advected towards the deep sediment trap. Seasonality is most prominent near both continents but generally weak, with mass fluxes dominated by calcium carbonate and clear seasonal maxima of biogenic silica towards the west. See also: www.nioz.nl/dust

  13. Downward particle fluxes of biogenic matter and Saharan dust across the equatorial North Atlantic

    Science.gov (United States)

    Korte, Laura F.; Brummer, Geert-Jan A.; van der Does, Michèlle; Guerreiro, Catarina V.; Hennekam, Rick; van Hateren, Johannes A.; Jong, Dirk; Munday, Chris I.; Schouten, Stefan; Stuut, Jan-Berend W.

    2017-05-01

    Massive amounts of Saharan dust are blown from the coast of northern Africa across the Atlantic Ocean towards the Americas each year. This dust has, depending on its chemistry, direct and indirect effects on global climate which include reflection and absorption of solar radiation as well as transport and deposition of nutrients and metals fertilizing both ocean and land. To determine the temporal and spatial variability of Saharan dust transport and deposition and their marine environmental effects across the equatorial North Atlantic Ocean, we have set up a monitoring experiment using deep-ocean sediment traps as well as land-based dust collectors. The sediment traps were deployed at five ocean sites along a transatlantic transect between north-west Africa and the Caribbean along 12° N, in a downwind extension of the land-based dust collectors placed at 19° N on the Mauritanian coast in Iouîk. In this paper, we lay out the setup of the monitoring experiment and present the particle fluxes from sediment trap sampling over 24 continuous and synchronized intervals from October 2012 through to November 2013. We establish the temporal distribution of the particle fluxes deposited in the Atlantic and compare chemical compositions with the land-based dust collectors propagating to the downwind sediment trap sites, and with satellite observations of Saharan dust outbreaks. First-year results show that the total mass fluxes in the ocean are highest at the sampling sites in the east and west, closest to the African continent and the Caribbean, respectively. Element ratios reveal that the lithogenic particles deposited nearest to Africa are most similar in composition to the Saharan dust collected in Iouîk. Downwind increasing Al, Fe and K contents suggest a downwind change in the mineralogical composition of Saharan dust and indicate an increasing contribution of clay minerals towards the west. In the westernmost Atlantic Ocean, admixture of re-suspended clay

  14. Validation of the Saharan Dust Plume Conceptual Model Using Lidar, Meteosat, and ECMWF Data.

    Science.gov (United States)

    Mohan Karyampudi, V.; Palm, Stephen P.; Reagen, John A.; Fang, Hui; Grant, William B.; Hoff, Raymond M.; Moulin, Cyril; Pierce, Harold F.; Torres, Omar; Browell, Edward V.; Melfi, S. Harvey

    1999-06-01

    Lidar observations collected during the Lidar In-space Technology Experiment experiment in conjunction with the Meteosat and European Centre for Medium-Range Weather Forecasts data have been used not only to validate the Saharan dust plume conceptual model constructed from the GARP (Global Atmospheric Research Programme) Atlantic Tropical Experiment data, but also to examine the vicissitudes of the Saharan aerosol including their optical depths across the west Africa and east Atlantic regions. Optical depths were evaluated from both the Meteosat and lidar data. Back trajectory calculations were also made along selected lidar orbits to verify the characteristic anticyclonic rotation of the dust plume over the eastern Atlantic as well as to trace the origin of a dust outbreak over West Africa.A detailed synoptic analysis including the satellite-derived optical depths, vertical lidar backscattering cross section profiles, and back trajectories of the 16-19 September 1994 Saharan dust outbreak over the eastern Atlantic and its origin over West Africa during the 12-15 September period have been presented. In addition, lidar-derived backscattering profiles and optical depths were objectively analyzed to investigate the general features of the dust plume and its geographical variations in optical thickness. These analyses validated many of the familiar characteristic features of the Saharan dust plume conceptual model such as (i) the lifting of the aerosol over central Sahara and its subsequent transport to the top of the Saharan air layer (SAL), (ii) the westward rise of the dust layer above the gradually deepening marine mixed layer and the sinking of the dust-layer top, (iii) the anticyclonic gyration of the dust pulse between two consecutive trough axes, (iv) the dome-shaped structure of the dust-layer top and bottom, (v) occurrence of a middle-level jet near the southern boundary of the SAL, (vi) transverse-vertical circulations across the SAL front including their

  15. Dust plume formation in the free troposphere and aerosol size distribution during the Saharan Mineral Dust Experiment in North Africa

    KAUST Repository

    Khan, Basit Ali

    2015-11-27

    Dust particles mixed in the free troposphere have longer lifetimes than airborne particles near the surface. Their cumulative radiative impact on earth’s meteorological processes and climate might be significant despite their relatively small contribution to total dust abundance. One example is the elevated dust-laden Saharan Air Layer (SAL) over the tropical and subtropical North Atlantic, which cools the sea surface. To understand the formation mechanisms of a dust layer in the free troposphere, this study combines model simulations and dust observations collected during the first stage of the Saharan Mineral Dust Experiment (SAMUM-I), which sampled dust events that extended from Morocco to Portugal, and investigated the spatial distribution and the microphysical, optical, chemical, and radiative properties of Saharan mineral dust. The Weather Research Forecast model coupled with the Chemistry/Aerosol module (WRF-Chem) is employed to reproduce the meteorological environment and spatial and size distributions of dust. The model domain covers northwest Africa and adjacent water with 5 km horizontal grid spacing and 51 vertical layers. The experiments were run from 20 May to 9 June 2006, covering the period of the most intensive dust outbreaks. Comparisons of model results with available airborne and ground-based observations show that WRF-Chem reproduces observed meteorological fields as well as aerosol distribution across the entire region and along the airplane’s tracks. Several mechanisms that cause aerosol entrainment into the free troposphere are evaluated and it is found that orographic lifting, and interaction of sea breeze with the continental outflow are key mechanisms that form a surface-detached aerosol plume over the ocean. The model dust emission scheme is tuned to simultaneously fit the observed total optical depth and the ratio of aerosol optical depths generated by fine and coarse dust modes. Comparisons of simulated dust size distributions with

  16. Dust plume formation in the free troposphere and aerosol size distribution during the Saharan Mineral Dust Experiment in North Africa

    Directory of Open Access Journals (Sweden)

    Basit Khan

    2015-11-01

    Full Text Available Dust particles mixed in the free troposphere have longer lifetimes than airborne particles near the surface. Their cumulative radiative impact on earth's meteorological processes and climate might be significant despite their relatively small contribution to total dust abundance. One example is the elevated dust-laden Saharan Air Layer (SAL over the tropical and subtropical North Atlantic, which cools the sea surface. To understand the formation mechanisms of a dust layer in the free troposphere, this study combines model simulations and dust observations collected during the first stage of the Saharan Mineral Dust Experiment (SAMUM-I, which sampled dust events that extended from Morocco to Portugal, and investigated the spatial distribution and the microphysical, optical, chemical, and radiative properties of Saharan mineral dust. The Weather Research Forecast model coupled with the Chemistry/Aerosol module (WRF-Chem is employed to reproduce the meteorological environment and spatial and size distributions of dust. The model domain covers northwest Africa and adjacent water with 5 km horizontal grid spacing and 51 vertical layers. The experiments were run from 20 May to 9 June 2006, covering the period of the most intensive dust outbreaks. Comparisons of model results with available airborne and ground-based observations show that WRF-Chem reproduces observed meteorological fields as well as aerosol distribution across the entire region and along the airplane's tracks. Several mechanisms that cause aerosol entrainment into the free troposphere are evaluated and it is found that orographic lifting, and interaction of sea breeze with the continental outflow are key mechanisms that form a surface-detached aerosol plume over the ocean. The model dust emission scheme is tuned to simultaneously fit the observed total optical depth and the ratio of aerosol optical depths generated by fine and coarse dust modes. Comparisons of simulated dust size

  17. Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic

    Directory of Open Access Journals (Sweden)

    M. van der Does

    2016-11-01

    Full Text Available Mineral dust has a large impact on regional and global climate, depending on its particle size. Especially in the Atlantic Ocean downwind of the Sahara, the largest dust source on earth, the effects can be substantial but are poorly understood. This study focuses on seasonal and spatial variations in particle size of Saharan dust deposition across the Atlantic Ocean, using an array of submarine sediment traps moored along a transect at 12° N. We show that the particle size decreases downwind with increased distance from the Saharan source, due to higher gravitational settling velocities of coarse particles in the atmosphere. Modal grain sizes vary between 4 and 32 µm throughout the different seasons and at five locations along the transect. This is much coarser than previously suggested and incorporated into climate models. In addition, seasonal changes are prominent, with coarser dust in summer and finer dust in winter and spring. Such seasonal changes are caused by transport at higher altitudes and at greater wind velocities during summer than in winter. Also, the latitudinal migration of the dust cloud, associated with the Intertropical Convergence Zone, causes seasonal differences in deposition as the summer dust cloud is located more to the north and more directly above the sampled transect. Furthermore, increased precipitation and more frequent dust storms in summer coincide with coarser dust deposition. Our findings contribute to understanding Saharan dust transport and deposition relevant for the interpretation of sedimentary records for climate reconstructions, as well as for global and regional models for improved prediction of future climate.

  18. The transport history of two Saharan dust events archived in an Alpine ice core

    Directory of Open Access Journals (Sweden)

    H. Sodemann

    2006-01-01

    Full Text Available Mineral dust from the Saharan desert can be transported across the Mediterranean towards the Alpine region several times a year. When coinciding with snowfall, the dust can be deposited on Alpine glaciers and then appears as yellow or red layers in ice cores. Two such significant dust events were identified in an ice core drilled at the high-accumulation site Piz Zupó in the Swiss Alps (46°22' N, 9°55' E, 3850 m a.s.l.. From stable oxygen isotopes and major ion concentrations, the events were approximately dated as October and March 2000. In order to link the dust record in the ice core to the meteorological situation that led to the dust events, a novel methodology based on back-trajectory analysis was developed. It allowed the detailed analysis of the specific meteorologic flow evolution that was associated with Saharan dust transport into the Alps, and the identification of dust sources, atmospheric transport paths, and wet deposition periods for both dust events. Differences in the chemical signature of the two dust events were interpreted with respect to contributions from the dust sources and aerosol scavenging during the transport. For the October event, the trajectory analysis indicated that dust deposition took place during 13–15 October 2000. Mobilisation areas of dust were mainly identified in the Algerian and Libyan deserts. A combination of an upper-level potential vorticity streamer and a midlevel jet across Algeria first brought moist Atlantic air and later mixed air from the tropics and Saharan desert across the Mediterranean towards the Alps. The March event consisted of two different deposition phases which took place during 17–19 and 23–25 March 2000. The first phase was associated with an exceptional transport pathway past Iceland and towards the Alps from northerly directions. The second phase was similar to the October event. A significant peak of methanesulphonic acid associated with the March dust event was most

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

    Directory of Open Access Journals (Sweden)

    V.H Garrison

    2006-12-01

    Full Text Available An international team of scientists from government agencies and universities in the United States, U.S. Virgin Islands (USVI, Trinidad & Tobago, the Republic of Cape Verde, and the Republic of Mali (West Africa is working together to elucidate the role Saharan dust may play in the degradation of Caribbean ecosystems. The first step has been to identify and quantify the persistent organic pollutants (POPs, trace metals, and viable microorganisms in the atmosphere in dust source areas of West Africa, and in dust episodes at downwind sites in the eastern Atlantic (Cape Verde and the Caribbean (USVI and Trinidad & Tobago. Preliminary findings show that air samples from Mali contain a greater number of pesticides, polychlorinated biphenyls (PCBs and polycyclic aromatic hydrocarbons (PAHs and in higher concentrations than the Caribbean sites. Overall, POP concentrations were similar in USVI and Trinidad samples. Trace metal concentrations were found to be similar to crustal composition with slight enrichment of lead in Mali. To date, hundreds of cultureable micro-organisms have been identified from Mali, Cape Verde, USVI, and Trinidad air samples. The sea fan pathogen, Aspergillus sydowii, has been identified in soil from Mali and in air samples from dust events in the Caribbean. We have shown that air samples from a dust-source region contain orders of magnitude more cultureable micro-organisms per volume than air samples from dust events in the Caribbean, which in turn contain 3-to 4-fold more cultureable microbes than during non-dust conditions. Rev. Biol. Trop. 54 (Suppl. 3: 9-21. Epub 2007 Jan. 15.Un grupo internacional de agencias gubernamentales y universidades de los Estados Unidos, las Islas Vírgenes (EUA, Trinidad y Tobago, la República de Cabo Verde y la República de Mali (África Oeste, está trabajando en conjunto para elucidar el papel que el polvo del Sahara puede estar jugando en el deterioro de los ecosistemas caribeños. El

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

    Science.gov (United States)

    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

  1. Aetiologies of non-malaria febrile episodes in children under 5 years in sub-Saharan Africa

    NARCIS (Netherlands)

    Kiemde, Francois; Spijker, René; Mens, Petra F.; Tinto, Halidou; Boele, Michael; Schallig, Henk D. F. H.

    2016-01-01

    ObjectivesTo provide an overview of the most frequent aetiologies found in febrile episodes of children under 5 years from sub-Saharan Africa. MethodsMEDLINE and EMBASE were searched for publications in English and French on non-malaria fever episodes in African children under 5 years of age, which

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

    Science.gov (United States)

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

    2006-01-01

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

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

    Science.gov (United States)

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

    2017-05-01

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

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

    Science.gov (United States)

    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.

  5. Saharan and Asian dust: similarities and differences determined by CALIPSO, AERONET, and a coupled climate-aerosol microphysical model

    Directory of Open Access Journals (Sweden)

    L. Su

    2011-04-01

    Full Text Available This study compares the properties of atmospheric dust from the Saharan deserts and the Asian deserts using data from CALIPSO and AERONET during 2006 and 2007 along with simulations using a coupled climate-microphysical sectional model. Saharan deserts are largely south of 30° N, while Asian ones are primarily north of 30° N, hence they experience different meteorological regimes. Saharan dust lifting occurs all year long, primarily due to subtropical weather systems. However, Asian dust is lifted mostly in spring when mid-latitude frontal systems lead to high winds. Rainfall is more abundant over Asia during the dust lifting events, leading to greater local dust removal than over the Sahara. However, most dust removal is due to sedimentation. Despite the different meteorological regimes, the same dust lifting schemes work in models for Asian and Saharan dust. The magnitudes of dust lifted in Africa and Asia differ significantly over the year. In our model the yearly horizontal dust flux just downwind of the African dust source is about 1088 Tg (10° S–40° N, 10° W and from the Asian dust source it is about 355 Tg (25° N–55° N, 105° E in 2007, which is comparable to previous studies. We find the difference in dust flux is mainly due to the larger area over which dust is lifted in Africa than Asia. However, Africa also has stronger winds in some seasons. Once lifted, the Saharan dust layers generally move toward the west and descend in altitude from about 7 km to the surface over several days in the cases studied. Asian dust often has multiple layers (two layers in the cases studied during transport largely to the east. One layer stays well above boundary layer during transport and shows little descent, while the other, lower, layer descends with time. This observation contrasts with studies suggesting the descent of Saharan dust is due to sedimentation of the particles, and suggests instead it is dominated by meteorology. We find the

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

    Science.gov (United States)

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

    2012-04-01

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

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

    Science.gov (United States)

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

    2011-01-01

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

  8. Impacts of Saharan dust on downward irradiance and photosynthetically available radiation in the water column

    Directory of Open Access Journals (Sweden)

    T. Ohde

    2012-09-01

    Full Text Available A semi-empirical approach was used to quantify the modification of the underwater light field in amplitude (magnitude effect and spectral distribution (spectral effect by different atmospheric conditions altering the incident light. The approach based on an optical model in connection with radiation measurements in the area off Northwest Africa. Key inputs of the model were parameterized magnitude and spectral effects. Various atmospheric conditions were considered: clear sky, dusty sky without clouds, cloudy sky without dust and skies with different ratios of dust and clouds. Their impacts were investigated concerning the modification of the downward irradiance and photosynthetically available radiation in the water column. The impact on downward irradiance depended on the wavelength, the water depth, the optical water properties, the dust and cloud properties, and the ratio of clouds to dust. The influence of clouds on the amplitude can be much higher than that of dust. Saharan dust reduced the photosynthetically available radiation in the water column. Ocean regions were more influenced than coastal areas. Compensations of the magnitude and spectral effects were observed at special water depths in ocean regions and at atmospheric conditions with definite cloud to dust ratios.

  9. Characterization of Modern and Fossil Mineral Dust Transported to High Altitude in the Western Alps: Saharan Sources and Transport Patterns

    Directory of Open Access Journals (Sweden)

    Florian Thevenon

    2012-01-01

    Full Text Available Mineral dust aerosols recently collected at the high-altitude Jungfraujoch research station (N, E; 3580 m a.s.l. were compared to mineral dust deposited at the Colle Gnifetti glacier (N, E; 4455 m a.s.l. over the last millennium. Radiogenic isotope signatures and backward trajectories analyses indicate that major dust sources are situated in the north-central to north-western part of the Saharan desert. Less radiogenic Sr isotopic compositions of PM10 aerosols and of mineral particles deposited during periods of low dust transfer likely result from the enhancement of the background chemically-weathered Saharan source. Saharan dust mobilization and transport were relatively reduced during the second part of the Little Ice Age (ca. 1690–1870 except within the greatest Saharan dust event deposited around 1770. After ca. 1870, sustained dust deposition suggests that increased mineral dust transport over the Alps during the last century could be due to stronger spring/summer North Atlantic southwesterlies and drier winters in North Africa. On the other hand, increasing carbonaceous particle emissions from fossil fuel combustion combined to a higher lead enrichment factor point to concomitant anthropogenic sources of particulate pollutants reaching high-altitude European glaciers during the last century.

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

    Science.gov (United States)

    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

  11. Saharan dust event impacts on cloud formation and radiation over Western Europe

    Directory of Open Access Journals (Sweden)

    M. Bangert

    2012-05-01

    Full Text Available 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 −75 W m−2. Including the direct interaction of dust with radiation caused an additional reduction in the incoming short-wave radiation by 40 to 80 W m−2, and the incoming long-wave radiation at the surface was increased significantly in the order of +10 W m−2.

    The

  12. Observations and model calculations of trace gas scavenging in a dense Saharan dust plume during MINATROC

    Directory of Open Access Journals (Sweden)

    M. de Reus

    2005-01-01

    Full Text Available An intensive field measurement campaign was performed in July/August 2002 at the Global Atmospheric Watch station Izaña on Tenerife to study the interaction of mineral dust aerosol and tropospheric chemistry (MINATROC. A dense Saharan dust plume, with aerosol masses exceeding 500 µg m-3, persisted for three days. During this dust event strongly reduced mixing ratios of ROx (HO2, CH3O2 and higher organic peroxy radicals, H2O2, NOx (NO and NO2 and O3 were observed. A chemistry boxmodel, constrained by the measurements, has been used to study gas phase and heterogeneous chemistry. It appeared to be difficult to reproduce the observed HCHO mixing ratios with the model, possibly related to the representation of precursor gas concentrations or the absence of dry deposition. The model calculations indicate that the reduced H2O2 mixing ratios in the dust plume can be explained by including the heterogeneous removal reaction of HO2 with an uptake coefficient of 0.2, or by assuming heterogeneous removal of H2O2 with an accommodation coefficient of 5x10-4. However, these heterogeneous reactions cannot explain the low ROx mixing ratios observed during the dust event. Whereas a mean daytime net ozone production rate (NOP of 1.06 ppbv/hr occurred throughout the campaign, the reduced ROx and NOx mixing ratios in the Saharan dust plume contributed to a reduced NOP of 0.14-0.33 ppbv/hr, which likely explains the relatively low ozone mixing ratios observed during this event.

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

    Science.gov (United States)

    Berglund, Judith

    2007-01-01

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

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

    Science.gov (United States)

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

    2017-11-01

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

  15. PM{sub 10} composition during an intense Saharan dust transport event over Athens (Greece)

    Energy Technology Data Exchange (ETDEWEB)

    Remoundaki, E., E-mail: remound@metal.ntua.gr [National Technical University of Athens (NTUA), School of Mining and Metallurgical Engineering, Laboratory of Environmental Science and Engineering, Heroon Polytechniou 9, 15780 Zografou (Greece); Bourliva, A. [Aristotle University of Thessaloniki (AUTH), Department of Geology, 54124 Thessaloniki (Greece); Hellenic Open University, School of Science and Technology, 26335 Patras (Greece); Kokkalis, P.; Mamouri, R.E.; Papayannis, A. [National Technical University of Athens (NTUA), Laser Remote Sensing Laboratory, Heroon Polytechniou 9, 15780 Zografou (Greece); Grigoratos, T.; Samara, C. [Aristotle University of Thessaloniki (AUTH), Department of Chemistry, Environmental Pollution Control Laboratory, 54124 Thessaloniki (Greece); Tsezos, M. [National Technical University of Athens (NTUA), School of Mining and Metallurgical Engineering, Laboratory of Environmental Science and Engineering, Heroon Polytechniou 9, 15780 Zografou (Greece)

    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{sub 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{sub 10} concentrations exceeded the EU limit (50 {mu}g/m{sup 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 10 h. Sulfur and heavy metal concentrations were also associated to local emissions. Mineral dust represented the largest fraction of PM{sub 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 {mu}m. 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 {mu}m. - Highlights: {yields} The paper focuses on the contribution of Saharan dust in PM10 levels at an urban site. {yields} High Ca and Fe, calcite, illite and smectites and poor quartz contents are related to source-regions. {yields} The data sets presented are in very good agreement and are also strongly confirmed by literature. {yields} Dust contribution in PM10 can be of comparable importance for

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

    Science.gov (United States)

    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.

  17. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    Science.gov (United States)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pérez, N.; Pandolfi, M.; de La Rosa, J.

    2011-07-01

    An analysis of chemical composition data of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at the Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, Canary Islands) shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL). The study of this data set with Median Concentrations At Receptor (MCAR) plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate exported to the North Atlantic in the Saharan Air Layer.

  18. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    Directory of Open Access Journals (Sweden)

    S. Rodríguez

    2011-07-01

    Full Text Available An analysis of chemical composition data of particulate matter samples (TSP, PM10 and PM2.5 collected from 2002 to 2008 in the North Atlantic free troposphere at the Izaña Global Atmospheric Watch (GAW observatory (Tenerife, Canary Islands shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL. The study of this data set with Median Concentrations At Receptor (MCAR plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate <10 μm transported from some regions observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90 % of sulphate <10 μm transported from some regions observed in the SAL may be influenced by soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization (PMF2 receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

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

    Science.gov (United States)

    Holdaway, Daniel

    2015-01-01

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

  20. Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study

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    C. Linke

    2006-01-01

    Full Text Available In aerosol chamber experiments optical properties of resuspended mineral dust samples of defined size distributions were measured. Extinction coefficients (bext and mass specific extinction cross sections (σext were determined for Saharan dust samples from different locations. The results for σext were not very sensitive to the type of dust and varied at λ=550 nm between 3.3±0.4 m2 g−1 and 3.7±0.4 m2 g−1. The absorption coefficients (babs and mass specific absorption cross sections (σabs were determined with a novel multi-wavelength photo-acoustic absorption spectrometer (PAS. The single scattering albedo was close to 1 (0.98 to 0.99 at 532 nm and 1064 nm, but significantly lower (0.63 to 0.76 at 266 nm. Additionally the chemical and mineralogical composition of the dust samples were analysed with special regard to the iron oxide phases hematite and goethite. At λ=266 nm the mineral dust sample without any detectable iron oxides showed a significantly higher SSA compared to the sample with a hematite content of 0.6 wt-%.

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

    Science.gov (United States)

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

    2014-01-01

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

  2. Profiling lifetime episodes of upper gastrointestinal bleeding among patients from rural Sub-Saharan Africa where schistosoma mansoni is endemic.

    Science.gov (United States)

    Opio, Christopher Kenneth; Kazibwe, Francis; Ocama, Ponsiano; Rejani, Lalitha; Belousova, Elena Nikolaevna; Ajal, Paul

    2016-01-01

    Severe chronic hepatic schistosomiasis is a common cause of episodes upper gastrointestinal bleeding (UGIB) in sub-Saharan Africa (SSA). However, there is paucity of data on clinical epidemiology of episodes of UGIB from rural Africa despite on going public health interventions to control and eliminate schistosomiasis. Through a cross sectional study we profiled lifetime episodes of upper gastrointestinal bleeding and associated factors at a rural primary health facility in sub-Saharan Africa were schistosomiasis is endemic. The main outcome was number of lifetime episodes of UGIB analyzed as count data. From 107 enrolled participants, 323 lifetime episodes of UGIB were reported. Fifty-seven percent experienced ≥ 2 lifetime episodes of UGIB. Ninety-four percent had severe chronic hepatic schistosomiasis and 80% esophageal varices. Alcohol use and viral hepatitis was infrequent. Eighty-eight percent were previously treated with praziquantel and 70% had a history of blood transfusion. No patient had ever had an endoscopy or treatment for prevention of recurrent variceal bleeding. Multivariable analysis identified a cluster of eight clinical factor variables (age ≥ 40, female sex, history of blood transfusion, abdominal collaterals, esophageal varices, pattern x periportal fibrosis, anemia, and thrombocytopenia) significantly associated (P-value < 0.05) with increased probability of experiencing two or more lifetime episodes of UGIB in our study. Upper gastrointestinal bleeding is a common health problem in this part of rural SSA where schistosomiasis is endemic. The clinical profile described is unique and is important for improved case management, and for future research.

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

    Science.gov (United States)

    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.

  4. Analysis of regional and temporal characteristics of PM10 during an Asian dust episode in Korea.

    Science.gov (United States)

    Lee, Byeong-Kyu; Lee, Haengah Kim; Jun, Na-Young

    2006-05-01

    This study analyzes the regional and temporal distributions of PM10 concentrations observed in major metropolitan cities in Korea before, during and after a recent Asian dust episode in 2002. There were spatial and temporal variations in PM10 concentrations among the mid-western, the southwestern, the southeastern, and the southern parts of Korea during this Asian dust period due to the different air mass movement time and the different wind directions and speeds of prevailing winds in each city or region. The origins of the three-day Asian dust episode were identified by an analysis of two-day backward isentropic air trajectories. The different origins for each day also significantly contributed to the spatial and temporal variations in PM10 concentrations. A significant relationship was found between PM10 concentrations on the day preceding the first peak day and the first peak day of the Asian dust period but only in the mid-western areas. The concentrations of PM10 just after the Asian dust episode were much higher than those just before. There was a significant increase in a coarse fraction, having soil origins, of particles during the Asian dust episode. Concentrations of Mn, Fe, Ni and Cr extracted from the total suspended particulate (TSP) samples collected in 7 cities during the Asian dust episode were much higher when compared with other days in 2001. However, the Asian dust did not consistently increase the concentrations of lead, cadmium and copper as they are influenced by local sources such as local traffic or industrial emissions.

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Science.gov (United States)

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

    2017-05-01

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

  7. Triple-wavelength depolarization-ratio profiling of Saharan dust over Barbados during SALTRACE in 2013 and 2014

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    M. Haarig

    2017-09-01

    Full Text Available Triple-wavelength polarization lidar measurements in Saharan dust layers were performed at Barbados (13.1° N, 59.6° W, 5000–8000 km west of the Saharan dust sources, in the framework of the Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE-1, June–July 2013, SALTRACE-3, June–July 2014. Three case studies are discussed. High quality was achieved by comparing the dust linear depolarization ratio profiles measured at 355, 532, and 1064 nm with respective dual-wavelength (355, 532 nm depolarization ratio profiles measured with a reference lidar. A unique case of long-range transported dust over more than 12 000 km is presented. Saharan dust plumes crossing Barbados were measured with an airborne triple-wavelength polarization lidar over Missouri in the midwestern United States 7 days later. Similar dust optical properties and depolarization features were observed over both sites indicating almost unchanged dust properties within this 1 week of travel from the Caribbean to the United States. The main results of the triple-wavelength polarization lidar observations in the Caribbean in the summer seasons of 2013 and 2014 are summarized. On average, the particle linear depolarization ratios for aged Saharan dust were found to be 0.252 ± 0.030 at 355 nm, 0.280 ± 0.020 at 532 nm, and 0.225 ± 0.022 at 1064 nm after approximately 1 week of transport over the tropical Atlantic. Based on published simulation studies we present an attempt to explain the spectral features of the depolarization ratio of irregularly shaped mineral dust particles, and conclude that most of the irregularly shaped coarse-mode dust particles (particles with diameters > 1 µm have sizes around 1.5–2 µm. The SALTRACE results are also set into the context of the SAMUM-1 (Morocco, 2006 and SAMUM-2 (Cabo Verde, 2008 depolarization ratio studies. Again, only minor changes in the dust depolarization

  8. Vertical profiles, optical and microphysical properties of Saharan dust layers determined by a ship-borne lidar

    Directory of Open Access Journals (Sweden)

    F. Immler

    2003-01-01

    Full Text Available A unique data set of ship-borne lidar measurements of Saharan dust layers above the Atlantic ocean has been collected aboard the research vessel Polarstern with a mobile Aerosol Raman Lidar (MARL during the LIMPIDO-campaign in June 2000. Extended Saharan dust layers have been observed in the region between 8.5º N and 34º N in an altitude range between 2 and 6 km. The continental, North African origin of the probed air masses is confirmed by 8-day backward trajectories. The Saharan dust is characterized by an optical depth in the range of 0.1 and 0.3, a depolarization around 10% and high lidar ratios of 45 sr at 532 nm and 75 sr at 355 nm. The backscattering by the dust particles at the UV-wavelength is relatively weak, resulting in a negative color index. From the measured optical properties the effective radius and the refractive index of the dust particles are derived using a new approach based on Mie Theory and non-spherical scattering calculations. The low backscatter coefficient observed at 355 nm is due to significant absorption which increases with decreasing wavelength. This finding agrees very well with results from satellite and sun photometer measurements. The effective radii decrease from about 3 mm at the base to 0.6 mm at the top of the dust plumes. The non-spherical shapes of the dust particles are responsible for the high values of the lidar ratios.

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

    Science.gov (United States)

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

    2014-01-01

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

  10. The Fate of Saharan Dust Across the Atlantic: An Integrated Modeling and Observational Study of the TC4 Field Campaign

    Science.gov (United States)

    Nowottnick, E.; Colarco, P. R.; daSilva, A.; McGill, M.; Hlavka, D.

    2010-01-01

    During the NASA TC-4 field campaign in July 2007, several Saharan dust events were observed over the Caribbean basin. A-Train observations suggest that these Saharan dust events are confined the Caribbean and rarely transported across Central America to the Pacific Ocean. We investigate the nature of this barrier to dust transport using the NASA GEOS-5 atmospheric general circulation model. Our simulations with GEOS-5 are driven by the Modern Era Retrospective-Analysis for Research and Applications (MERRA) meteorological analyses, and include online simulation of aerosol distributions using a version of the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) model. Simulated dust distributions are evaluated using A-Train observations from MODIS and CALIOP, as well as MISR and ground-based AERONET sun photometers, and show good agreement with the observations in terms of the timing and magnitude of dust events. A component analysis of the dust transport and removal pathways is used to evaluate the relative roles of these processes in establishing the observed dust transport barrier. From this analysis, we show that while both atmospheric dynamics and wet removal contribute towards the Caribbean dust barrier, northward dust transport is the more dominant term. Additional simulations are performed to ascertain the sensitivity of our results to uncertain loss processes (i.e., wet removal) in our model.

  11. Climate change and Saharan dust drive recent cladoceran and primary production changes in remote alpine lakes of Sierra Nevada, Spain.

    Science.gov (United States)

    Jiménez, Laura; Rühland, Kathleen M; Jeziorski, Adam; Smol, John P; Pérez-Martínez, Carmen

    2017-08-22

    Recent anthropogenic climate change and the exponential increase over the past few decades of Saharan dust deposition, containing ecologically important inputs of phosphorus (P) and calcium (Ca), are potentially affecting remote aquatic ecosystems. In this study, we examine changes in cladoceran assemblage composition and chlorophyll-a concentrations over the past ~150 years from high-resolution, well-dated sediment cores retrieved from six remote high mountain lakes in the Sierra Nevada Mountains of Southern Spain, a region affected by Saharan dust deposition. In each lake, marked shifts in cladoceran assemblages and chlorophyll-a concentrations in recent decades indicate a regional-scale response to climate and Saharan dust deposition. Chlorophyll-a concentrations have increased since the 1970s, consistent with a response to rising air temperatures and the intensification of atmospheric deposition of Saharan P. Similar shifts in cladoceran taxa across lakes began over a century ago, but have intensified over the past ~50 years, concurrent with trends in regional air temperature, precipitation, and increased Saharan dust deposition. An abrupt increase in the relative abundance of the benthic cladoceran Alona quadrangularis at the expense of Chydorus sphaericus, and a significant increase in Daphnia pulex gr. was a common trend in these softwater lakes. Differences in the magnitude and timing of these changes are likely due to catchment and lake-specific differences. In contrast with other alpine lakes that are often affected by acid deposition, atmospheric Ca deposition appears to be a significant explanatory factor, among others, for the changes in the lake biota of Sierra Nevada that has not been previously considered. The effects observed in Sierra Nevada are likely occurring in other Mediterranean lake districts, especially in softwater, oligotrophic lakes. The predicted increases in global temperature and Saharan dust deposition in the future will further

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

    Directory of Open Access Journals (Sweden)

    A. Ansmann

    2017-12-01

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

  13. Soluble iron nutrients in Saharan dust over the central Amazon rainforest

    Science.gov (United States)

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

    2017-02-01

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

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

    Science.gov (United States)

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

    2017-12-01

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

  15. Large Saharan dust storms: Implications for chlorophyll dynamics in the Mediterranean Sea

    Science.gov (United States)

    Gallisai, Rachele; Volpe, Gianluca; Peters, Francesc

    2016-11-01

    We investigate the large (LDE) and very large (VLDE) Saharan dust deposition events that occurred between 2000 and 2007 and their short-term impact on the dynamics of marine phytoplankton in the Mediterranean Sea. A total of 153 LDE were identified unevenly distributed over the years. Events were more frequent during winter, in the eastern Mediterranean, and autumn, when they affected both the western and the central Mediterranean. Most of the 31 VLDE occurred during winter and autumn in the central Mediterranean. The dynamics of chlorophyll after VLDE were studied as a proxy for phytoplankton response to atmospheric dust. A significant response of chlorophyll to dust addition was evident; this appeared to be especially true for the western Mediterranean where a chlorophyll increase of up to 345% was recorded, whereas in the central Mediterranean it was up to 146% and in the eastern Mediterranean up to 121%. Chlorophyll response behavior was quite heterogeneous probably as a result of the uniqueness of each VLDE, the differences between Mediterranean areas, the community structure of phytoplankton, and the interaction between bacteria and phytoplankton for new resources. An eastward decreasing trend in chlorophyll response was observed, which is in accordance with the relative importance of bacterial activity with respect to phytoplankton. The increase in mineral aerosols with increased aridity in the region together with the decrease in the depth of the mixed layer of the oceans should boost the importance of aerosols fueling marine production.

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

    Science.gov (United States)

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

    2007-01-01

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

  17. WRF prediction of two winter season Saharan dust events using PM10 concentrations: Boundary versus initial conditions

    Science.gov (United States)

    Jenkins, Gregory S.; Diokhane, Aminita Mbow

    2017-10-01

    During the northern hemisphere winter and spring seasons Saharan dust events overspreading West Africa are frequent and linked to mid-latitude interactions. The dust events have the ability to produce low visibilities, poor air quality and can promote respiratory disease. While a number of case studies have been undertaken, the ability to forecast Saharan dust events is largely unknown. To investigate this matter, we have performed hindcasts using the weather research and forecasting (WRF) model with the Goddard Chemistry Aerosols Radiation Transport (GOCART) module, with 6-h boundary conditions from the NOAA ' National Center for Environmental Prediction (NCEP) final analysis (FNL). We use observed and forecasted PM10 concentrations to evaluate the hindcasts. The hindcasts begin with different conditions 3-8 days before two Saharan dust events where the maximum Particulate matter at 10 microns (PM10) concentrations are observed on 20 January and 7 February 2012 in Dakar, Senegal. The results show that all hindcasts are able to capture the timing of the peak on 20 January but the maximum peak during the second dust event occurs one day prior to the observed peak on 7 February with similar pattern from satellite based aerosol optical depth (AOD) estimates. The hindcasts have positive biases in PM10 concentrations relative to the observations in Dakar Senegal. The hindcasts suggest that WRF model has the potential to effectively forecasts Saharan dust events in real-time forecasts, however, they must be evaluated against additional surface PM10 observations at varying locations, which are currently sparse over West Africa.

  18. Development of the online MM5 tracer model and its applications to air pollution episodes in Istanbul, Turkey and Sahara dust transport

    Science.gov (United States)

    Chen, S.-H.; Dudhia, J.; Kain, J. S.; Kindap, T.; Tan, E.

    2008-06-01

    An online tracer model, based on the fifth-generation Penn State/NCAR Mesoscale model, was developed. The new model includes full representation of processes for advection, boundary layer mixing, subgrid cumulus convective mixing, and sedimentation of tracers. The model was used in two very different applications to document its potential utility. The first application involves pollutant transport to Istanbul, Turkey, focusing on two high-pollution episodes in January 2002. To better maintain large scale features, model simulations were nudged to reanalysis for this application. Using a semi-idealized approach, it was shown that much of the pollution that affected Istanbul during these events may have come from other highly polluted cities located upstream, rather than just local emission sources. Pollutants from upstream sources were trapped in the boundary layer by statically stable low-level conditions and efficient transport to Istanbul was supported by strong northwesterly flow near the surface. The second application involves the transport of dust from the Sahara Desert to the Atlantic Ocean, and the potential role of this dust and the dry, warm Saharan Air Layer (SAL) in the genesis and development of Tropical Storm Chantal in 2001. No nudging was applied to this case study since it may degrade small scale features, which were important to dust saltation. The dust uplifting and transport during the earlier period of Chantal's life cycle were simulated to show a potential link between Sahara dust and Chantal's evolution. Results show strong evidence that Chantal started interacting with SAL and dust at a very early stage of storm development after propagating into the eastern Atlantic Ocean. Moreover, it was found that the peak of the averaged surface dust flux occurred in the early morning right before the mixed boundary layer developed, and the mechanism of dust uptake for this event, nocturnal low-level jets, was different from those previously documented.

  19. On the impact of Saharan dust deposition on the evolution of an alpine snowpack

    Science.gov (United States)

    Tuzet, François; Dumont, Marie; Lafaysse, Matthieu; Missiaen, Anne; Hagenmuller, Pascal; Lejeune, Yves; Joly, Matthieu; Guth, Jonathan; Nabat, Pierre; Picard, Ghislain; Arnaud, Laurent; Morin, Samuel

    2017-04-01

    Alpine snowpacks are frequently affected by Saharan dust outbreaks events resulting in a yellowish or reddish snow layer. These events introduce a strong discontinuity in the vertical profile of light absorbing impurities content within the snowpack. This induces changes in the amount of solar radiation absorbed by the snow and in turn changes in the vertical temperature profile and on snow metamorphism. The impact of such phenomena on snow stability and melt rate is currently not addressed using current snowpack models which either totally ignore impurity-related phenomena are account for them in a very simplistic manner. In this work, we implemented new capabilities within the detailed snow model SURFEX/ISBA-Crocus to account for impurities deposition and evolution within the snowpack. We also refined the original radiative transfer model into a comprehensive spectrally-resolved radiative transfer scheme to explicitly account for their direct and indirect radiative effects. This upgraded model was evaluated against in-situ snow measurements and spectral albedo measurements spanning one winter season at Col de Porte site (French Alps) using two different atmospheric models as inputs for aerosols deposition fluxes. The effect of an observed Saharian dust deposition event on snow temperature, specific surface area and density vertical profiles was numerically investigated with the model and compared to snow observations. The objective is to understand under which snow and meteorological conditions such a deposition event leads to significant modifications of the snowpack physical properties and to the observed decrease in snowpack stability.

  20. Empirical Model for Evaluating PM10 Concentration Caused by River Dust Episodes

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    Chao-Yuan Lin

    2016-06-01

    Full Text Available Around the estuary of the Zhuo-Shui River in Taiwan, the waters recede during the winter, causing an increase in bare land area and exposing a large amount of fine earth and sand particles that were deposited on the riverbed. Observations at the site revealed that when northeastern monsoons blow over bare land without vegetation or water cover, the fine particles are readily lifted by the wind, forming river dust, which greatly endangers the health of nearby residents. Therefore, determining which factors affect river dust and constructing a model to predict river dust concentration are extremely important in the research and development of a prototype warning system for areas at risk of river dust emissions. In this study, the region around the estuary of the Zhuo-Shui River (from the Zi-Qiang Bridge to the Xi-Bin Bridge was selected as the research area. Data from a nearby air quality monitoring station were used to screen for days with river dust episodes. The relationships between PM10 concentration and meteorological factors or bare land area were analyzed at different temporal scales to explore the factors that affect river dust emissions. Study results showed that no single factor alone had adequate power to explain daily average or daily maximum PM10 concentration. Stepwise regression analysis of multiple factors showed that the model could not effectively predict daily average PM10 concentration, but daily maximum PM10 concentration could be predicted by a combination of wind velocity, temperature, and bare land area; the coefficient of determination for this model was 0.67. It was inferred that river dust episodes are caused by the combined effect of multiple factors. In addition, research data also showed a time lag effect between meteorological factors and hourly PM10 concentration. This characteristic was applied to the construction of a prediction model, and can be used in an early warning system for local residents.

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

    Science.gov (United States)

    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

  2. An Investigation of Interaction of Saharan Dust and Atlantic ITCZ Using Cloudsat-Calipso and A-Train Data

    Science.gov (United States)

    Lau, W.; Matsui, Toshi; Kim, Kyu-Myong; Reale, Oreste; Colarco, P.

    2011-01-01

    In this study, we investigate the radiative forcing of Saharan dust, its interactions with the Atlantic Intertropical Convergence Zone (ITCZ), through African easterly waves (AEW), African easterly jets (AEJ), and its impacts in short term numerical forecasts of tropical cyclogenesis using the GOCART-GEOS5 forecast system. Our approach is to develop and use an A-Train satellite simulator (ATSS) to constrain the observed aerosol index of refraction and particle size distribution by finding the values that simultaneously minimize the difference between observed CALIOP, CloudSat, OMI, and MODIS radiances and simulated radiances inverted from atmospheric model output using procedures and physical principles consistent with those used in corresponding retrieval algorithms. We use observations from the A-train and TRMM to determine relationships among the Saharan dust layer, transport by the AEW, and possible responses to dust radiative forcing in developing tropical cyclones in the A-ITCZ. Preliminary model results showing physical processes associated with the generation and transport of the Saharan dust layer, their interactions with the incipient moisture, clouds and rainfall in developing tropical cyclones will be presented. Also presented will be results of a case study of possible radiative impacts on AEW and AEJ during the NAMMA field campaign.

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

    Science.gov (United States)

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

    2017-07-01

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

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

    Directory of Open Access Journals (Sweden)

    J. Longman

    2017-07-01

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

  5. Chemistry and mineralogy of clay minerals in Asian and Saharan dusts and the implications for iron availability

    Science.gov (United States)

    Jeong, G. Y.; Achterberg, E. P.

    2014-06-01

    Mineral dust supplied to remote ocean regions stimulates phytoplankton growth through delivery of micronutrients, notably iron (Fe). Although attention is usually paid to Fe (hydr)oxides as major sources of available Fe, Fe-bearing clay minerals are typically the dominant phase in mineral dust. The mineralogy and chemistry of clay minerals in dust particles, however, are largely unknown. We conducted microscopic identification and chemical analysis of the clay minerals in Asian and Saharan dust particles. Cross-sectional slices of dust particles were prepared by focused ion beam (FIB) techniques and analyzed by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDXS). TEM images of FIB slices revealed that clay minerals occurred as either nano-thin platelets or relatively thick plates. The nano-thin platelets included illite, smectite, illite-smectite mixed layers and their nanoscale mixtures (illite-smectite series clay minerals, ISCMs) which could not be resolved with an electron microbeam. EDXS chemical analysis of the clay mineral grains revealed that the average Fe content was 5.8% in nano-thin ISCM platelets assuming 14% H2O, while the Fe content of illite and chlorite was 2.8 and 14.8%, respectively. In addition, TEM and EDXS analyses were performed on clay mineral grains dispersed and loaded on microgrids. The average Fe content of clay mineral grains was 6.7 and 5.4% in Asian and Saharan dusts, respectively. A comparative X-ray diffraction analysis of bulk dusts showed that Saharan dust was more enriched in clay minerals than in Asian dust, while Asian dust was more enriched in chlorite. The average Fe / Si, Al / Si and Fe / Al molar ratios of the clay minerals, compared to previously reported chemistries of mineral dusts and leached solutions, indicated that dissolved Fe originated from clay minerals. Clay minerals, in particular nanocrystalline ISCMs and Fe-rich chlorite are important sources of available Fe in

  6. Chemistry and mineralogy of clay minerals in Asian and Saharan dusts and the implications for iron supply to the oceans

    Science.gov (United States)

    Jeong, G. Y.; Achterberg, E. P.

    2014-11-01

    Mineral dust supplied to remote ocean regions stimulates phytoplankton growth through delivery of micronutrients, notably iron (Fe). Although attention is usually paid to Fe (hydr)oxides as major sources of available Fe, Fe-bearing clay minerals are typically the dominant phase in mineral dust. The mineralogy and chemistry of clay minerals in dust particles, however, are largely unknown. We conducted microscopic identification and chemical analysis of the clay minerals in Asian and Saharan dust particles. Cross-sectional slices of dust particles were prepared by focused ion beam (FIB) techniques and analyzed by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDXS). TEM images of FIB slices revealed that clay minerals occurred as either nano-thin platelets or relatively thick plates. Chemical compositions and lattice fringes of the nano-thin platelets suggested that they included illite, smectite, illite-smectite mixed layers, and their nanoscale mixtures (illite-smectite series clay minerals, ISCMs) which could not be resolved with an electron microbeam. EDXS chemical analysis of the clay mineral grains revealed that the average Fe content was 5.8% in nano-thin ISCM platelets assuming 14% H2O, while the Fe content of illite and chlorite was 2.8 and 14.8%, respectively. In addition, TEM and EDXS analyses were performed on clay mineral grains dispersed and loaded on micro-grids. The average Fe content of clay mineral grains was 6.7 and 5.4% in Asian and Saharan dusts, respectively. A comparative X-ray diffraction analysis of bulk dusts showed that Saharan dust was more enriched in clay minerals than Asian dust, while Asian dust was more enriched in chlorite. Clay minerals, in particular nanocrystalline ISCMs and Fe-rich chlorite, are probably important sources of Fe to remote marine ecosystems. Further detailed analyses of the mineralogy and chemistry of clay minerals in global mineral dusts are required to evaluate the

  7. Multi-platform in-situ and remote sensing techniques to derive Saharan dust properties during AMISOC-TNF 2013

    Science.gov (United States)

    Córdoba-Jabonero, Carmen; Andrey, Javier; Adame, José Antonio; Sorribas, Mar; Gómez, Laura; Cuevas, Emilio; Gil-Ojeda, Manuel

    2014-10-01

    In the framework of AMISOC (Atmospheric Minor Species relevant to the Ozone Chemistry) project, a multiinstrumented campaign was performed in the Canary Islands area in summer-time from 01 July to 11 August 2013. Both ground-based remote-sensing and airborne in-situ measurements were performed under dust loading conditions. Saharan dusty (DD) conditions were reported during 57% of the overall campaign period. Particular DD cases corresponded to a 2-day period with a progressively arriving Saharan dust intrusion over Tenerife on 31 July (weak incidence) and 01 August (strong incidence). As reference, the non-dusty (ND) situation on 30 July was also examined. Vertical size distributions (SD) for particles within an extended fine-to-coarse (0.16-2.8 μm) mode were provided by using aircraft aerosol PCASP sonde measurements. Extinction profiles and Lidar ratio (LR) values were derived from Micro Pulse Lidar measurements. Despite no MAXDOAS aerosol profiling retrievals were available, the potential of this technique has also been introduced. A good agreement is found between the optical and microphysical properties, showing dust particles confined in a wide layer of around 4.5 km thickness from 1.5 to 6 km height. Dust incidence mostly affected the Free Troposphere (FT). LR ranged between 50 and 55 sr, showing typical values for Saharan dust particles. In general, the dust impact on mass concentration was enhanced due to the increase of larger particles, affecting both the Boundary layer (BL) and FT, but showing differences depending on the dusty case. MAXDOAS profiles are expected to be included in an extended version of this work.

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

    Science.gov (United States)

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

    2010-01-01

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

  9. Saharan dust events at the Jungfraujoch: detection by wavelength dependence of the single scattering albedo and first climatology analysis

    Directory of Open Access Journals (Sweden)

    M. Collaud Coen

    2004-01-01

    Full Text Available Scattering and absorption coefficients have been measured continuously at several wavelengths since March 2001 at the high altitude site Jungfraujoch (3580ma.s.l.. From these data, the wavelength dependences of the Ångström exponent and particularly of the single scattering albedo are determined. While the exponent of the single scattering albedo usually increases with wavelength, it decreases with wavelength during Saharan dust events (SDE due to the greater size of the mineral aerosol particles and their different chemical composition. This change in the sign of the single scattering exponent turns out to be a sensitive means for detecting Saharan dust events. The occurrence of SDE detected by this new method was confirmed by visual inspection of filter colors and by studying long-range back-trajectories. An examination of SDE over a 22-month period shows that SDE are more frequent during the March-June period as well as during October and November. The trajectory analysis indicated a mean traveling time of 96.5h, with the most important source countries situated in the northern and north-western part of the Saharan desert. Most of the SDE do not lead to a detectable increase of the 48-h total suspended particulate matter (TSP concentration at the Jungfraujoch. During Saharan dust events, the average contribution of this dust to hourly TSP at the Jungfraujoch is 16µg/m3, which corresponds to an annual mean of 0.8µg/m3 or 24% of TSP.

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

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    Isabel Marín

    2017-11-01

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

  11. The vertical distribution of aerosols, Saharan dust and cirrus clouds in Rome (Italy in the year 2001

    Directory of Open Access Journals (Sweden)

    G. P. Gobbi

    2004-01-01

    Full Text Available A set of 813 lidar profiles of tropospheric aerosol and cirrus clouds extinction and depolarization observed in Rome, Italy, between February 2001 and February 2002 is analyzed and discussed. The yearly record reveals a meaningful contribution of both cirrus clouds (38% and Saharan dust (12% to the total optical thickness (OT of 0.26, at 532nm. Seasonal analysis shows the planetary boundary layer (PBL aerosols to be confined below 2km in winter and 3.8km in summer, with relevant OT shifting from 0.08 to 0.16, respectively. Cirrus clouds maximise in spring and autumn, in both cases with average OT similar to the PBL aerosols one. With the exception of winter months, Saharan dust is found to represent an important third layer mostly residing between PBL aerosols and cirrus clouds, with yearly average OT0.03. Saharan dust and cirrus clouds were detected in 20% and in 45% of the observational days, respectively. Validation of the lidar OT retrievals against collocated sunphotometer observations show very good agreement. These results represent one of the few yearly records of tropospheric aerosol vertical profiles available in the literature.

  12. Nutrient control of N2 fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events

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    M. Pujo-Pay

    2011-09-01

    Full Text Available A better understanding of the factors controlling N2 fixation is a pre-requisite for improving our knowledge on the contribution of N2 fixation process in the nitrogen cycling. Trace-metal clean nutrient/dust addition bioassays (+P, +PFe, +dust were performed at three stations located in the western, central and eastern Mediterranean Sea, in summer 2008 as part of the BOUM cruise. The main goals were (1 to investigate the nutrient factor(s limiting N2 fixation (uptake of 15N2 and (2 to evaluate the potential impact of a Saharan dust event on this biological process during the stratification period. Initially, surface waters at the three stations were DIP-depleted (2 fixation (from 130 % to 430 %. The highest dust stimulation of N2 fixation was recorded at the station located in the eastern basin. The response of diazotrophic activity to nutrient additions was variable between the sampled stations suggesting a spatial variability of the factor controlling N2 fixation over the whole basin. At all stations, N2 fixation was not limited by Fe nor co-limited by P and Fe. At the western station, N2 fixation was DIP limited while at the eastern one, N2 fixation was first DIP limited, then was limited by one or several chemical element(s released by dust. Our results demonstrated that a Saharan dust input was able to relieve these successive on going limitations. Very interestingly, at the station located in the central basin, N2 fixation was not limited by the availability of P yet it was strongly stimulated by dust addition (x3.1. A chemical element or a combination of several, released by the added dust may have been responsible for the observed stimulations of N2 fixation. These results indicated that Saharan dust pulses to the surface Mediterranean waters, in addition to P and Fe, could be a source of chemical(s element(s that are necessary for metabolic processes and therefore influence rates of N2 fixation.

  13. The impact of Saharan dust on the particulate export in the water column of the North Western Mediterranean Sea

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    E. Ternon

    2010-03-01

    Full Text Available Simultaneous measurements of atmospheric deposition and of sinking particles at 200 and 1000 m depth, were performed in the Ligurian Sea (North-Western Mediterranean between 2003 and 2007, along with phytoplanktonic activity derived from satellite images. Atmospheric deposition of Saharan dust particles was very irregular and confirmed the importance of sporadic high magnitude events over the annual average (11.4 g m−2 yr−1 for the 4 years. The average marine total mass flux was 31 g m−2 yr−1, the larger fraction being the lithogenic one (~37%. The marine total mass flux displayed a seasonal pattern with a maximum in winter, occurring before the onset of the spring bloom. The highest POC fluxes did not occur during the spring bloom nor could they be directly related to any noticeable increase in the surface phytoplanktonic biomass. Over the 4 years of the study, the strongest POC fluxes were concomitant with large increases of the lithogenic marine flux, which had originated from either recent Saharan fallout events (February 2004 and August 2005, from "old" Saharan dust "stored" in the upper water column layer (March 2003 and February 2005, or alternatively from lithogenic material originating from Ligurian riverine flooding (December 2003, Arno, Roya and Var rivers. Those associated export fluxes defined as "lithogenic events", are believed to result from a combination of forcing (winter mixing or Saharan events, in particular extreme ones, biological (zooplankton activity, and also organic-mineral aggregation inducing a ballast effect. By fertilising the surface layer, mixed Saharan dust events were shown to be able to induce "lithogenic events" during the stratification period. These events would be more efficient in transferring POC to the deeper layers than the spring bloom itself. The extreme Saharan event of February 2004 exported ~45% of the total annual POC, compared to an average of

  14. The impact of Saharan dust on the particulate export in the water column of the North Western Mediterranean Sea

    Science.gov (United States)

    Ternon, E.; Guieu, C.; Loã¿E-Pilot, M.-D.; Leblond, N.; Bosc, E.; Gasser, B.; Miquel, J.-C.; Martín, J.

    2010-03-01

    Simultaneous measurements of atmospheric deposition and of sinking particles at 200 and 1000 m depth, were performed in the Ligurian Sea (North-Western Mediterranean) between 2003 and 2007, along with phytoplanktonic activity derived from satellite images. Atmospheric deposition of Saharan dust particles was very irregular and confirmed the importance of sporadic high magnitude events over the annual average (11.4 g m-2 yr-1 for the 4 years). The average marine total mass flux was 31 g m-2 yr-1, the larger fraction being the lithogenic one (~37%). The marine total mass flux displayed a seasonal pattern with a maximum in winter, occurring before the onset of the spring bloom. The highest POC fluxes did not occur during the spring bloom nor could they be directly related to any noticeable increase in the surface phytoplanktonic biomass. Over the 4 years of the study, the strongest POC fluxes were concomitant with large increases of the lithogenic marine flux, which had originated from either recent Saharan fallout events (February 2004 and August 2005), from "old" Saharan dust "stored" in the upper water column layer (March 2003 and February 2005), or alternatively from lithogenic material originating from Ligurian riverine flooding (December 2003, Arno, Roya and Var rivers). Those associated export fluxes defined as "lithogenic events", are believed to result from a combination of forcing (winter mixing or Saharan events, in particular extreme ones), biological (zooplankton) activity, and also organic-mineral aggregation inducing a ballast effect. By fertilising the surface layer, mixed Saharan dust events were shown to be able to induce "lithogenic events" during the stratification period. These events would be more efficient in transferring POC to the deeper layers than the spring bloom itself. The extreme Saharan event of February 2004 exported ~45% of the total annual POC, compared to an average of ~25% for the bloom period. This emphasises the role played by

  15. Defining episodes of diarrhoea: results from a three-country study in Sub Saharan Africa

    CSIR Research Space (South Africa)

    Wright, Jarrad A

    2006-03-01

    Full Text Available The study was conducted to assess the effect of definition of episode on diarrhoeal morbidity and to develop a means of adjusting estimates of morbidity for the definition of episode used. This paper reports on a cohort study of 374 children, aged 9...

  16. Estimation of students' exposure to metal concentrations from river-dust episodes during 1994-2012.

    Science.gov (United States)

    Yang, Hao-Jan; Chen, Szu-Chieh; Hu, Chiung-Wen; Chiang, Yi-Chen; Tsai, Ching-Tsan; Lin, Pin-Yu; Lai, Dian-Jheng; Kuo, Chung-Yih

    2017-02-01

    Two elementary schools (Shiuguang and Fongrong) from Yulin County in Taiwan, near a main area of potential exposure to Aeolian river-dust, were selected to collect outdoor and indoor PM10 aerosols and to measure five metals in PM10 (As, Ni, Cr, Cd, and Mn). Significant relationships (p PM10 concentrations at Lunbei's air quality monitoring station and the two elementary schools. The outdoor PM10 concentrations at the monitoring station and the schools' indoor PM10 concentrations also showed significant correlations. This study also established a relationship between the outdoor and indoor concentrations of PM10 and metals in the schools. Estimations were made regarding students' 8 h of exposure to metal concentrations from river-dust episodes during 1994-2012, based on correlation equations that were shown to be statistically significant.

  17. On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations

    Directory of Open Access Journals (Sweden)

    S. Otto

    2011-05-01

    Full Text Available Realistic size equivalence and shape of Saharan mineral dust particles are derived from in-situ particle, lidar and sun photometer measurements during SAMUM-1 in Morocco (19 May 2006, dealing with measured size- and altitude-resolved axis ratio distributions of assumed spheroidal model particles. The data were applied in optical property, radiative effect, forcing and heating effect simulations to quantify the realistic impact of particle non-sphericity. It turned out that volume-to-surface equivalent spheroids with prolate shape are most realistic: particle non-sphericity only slightly affects single scattering albedo and asymmetry parameter but may enhance extinction coefficient by up to 10 %. At the bottom of the atmosphere (BOA the Saharan mineral dust always leads to a loss of solar radiation, while the sign of the forcing at the top of the atmosphere (TOA depends on surface albedo: solar cooling/warming over a mean ocean/land surface. In the thermal spectral range the dust inhibits the emission of radiation to space and warms the BOA. The most realistic case of particle non-sphericity causes changes of total (solar plus thermal forcing by 55/5 % at the TOA over ocean/land and 15 % at the BOA over both land and ocean and enhances total radiative heating within the dust plume by up to 20 %. Large dust particles significantly contribute to all the radiative effects reported. They strongly enhance the absorbing properties and forward scattering in the solar and increase predominantly, e.g., the total TOA forcing of the dust over land.

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

    Science.gov (United States)

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

    2009-04-01

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

  19. Measurements of Saharan dust aerosols over the Eastern Mediterranean using elastic backscatter-Raman lidar, spectrophotometric and satellite observations in the frame of the EARLINET project

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    A. Papayannis

    2005-01-01

    Full Text Available We report on the vertical distributions of Saharan dust aerosols over the N.E. Mediterranean region, which were obtained during a typical dust outbreak on August 2000, by two lidar systems located in Athens and Thessaloniki, Greece, in the frame of the European EARLINET project. MODIS and ground sun spectrophotometric data, as well as air-mass backward trajectories confirmed the existence of Saharan dust in the case examined, which was also successfully forecasted by the DREAM dust model. The lidar data analysis for the period 2000-2002 made possible, for the first time, an estimation of the vertical extent of free tropospheric dust layers [mean values of the aerosol backscatter and extinction coefficients and the extinction-to-backscatter ratio (lidar ratio, LR at 355 nm], as well as a seasonal distribution of Saharan dust outbreaks over Greece, under cloud-free conditions. A mean value of the lidar ratio at 355 nm was obtained over Athens (53±1 sr and over Thessaloniki (44±2 sr during the Saharan dust outbreaks. The corresponding aerosol optical thickness (AOT at 355 nm, in the altitude range 0-5 km, was 0.69±0.12 and 0.65±0.10 for Athens and Thessaloniki, respectively (within the dust layer the AOT was 0.23 and 0.21, respectively. Air-mass back-trajectory analysis performed in the period 2000-2002 for all Saharan dust outbreaks over the N.E. Mediterranean indicated the main pathways followed by the dust aerosols.

  20. Solar and thermal radiative effects during the 2011 extreme desert dust episode over Portugal

    Science.gov (United States)

    Valenzuela, A.; Costa, M. J.; Guerrero-Rascado, J. L.; Bortoli, D.; Olmo, F. J.

    2017-01-01

    This paper analyses the influence of the extreme Saharan desert dust (DD) event on shortwave (SW) and longwave (LW) radiation at the EARLINET/AERONET Évora station (Southern Portugal) from 4 up to 7 April 2011. There was also some cloud occurrence in the period. In this context, it is essential to quantify the effect of cloud presence on aerosol radiative forcing. A radiative transfer model was initialized with aerosol optical properties, cloud vertical properties and meteorological atmospheric vertical profiles. The intercomparison between the instantaneous TOA shortwave and longwave fluxes derived using CERES and those calculated using SBDART, which was fed with aerosol extinction coefficients derived from the CALIPSO and lidar-PAOLI observations, varying OPAC dataset parameters, was reasonably acceptable within the standard deviations. The dust aerosol type that yields the best fit was found to be the mineral accumulation mode. Therefore, SBDART model constrained with the CERES observations can be used to reliably determine aerosol radiative forcing and heating rates. Aerosol radiative forcings and heating rates were derived in the SW (ARFSw, AHRSw) and LW (ARFLw, AHRLw) spectral ranges, considering a cloud-aerosol free reference atmosphere. We found that AOD at 440 nm increased by a factor of 5 on 6 April with respect to the lower dust load on 4 April. It was responsible by a strong cooling radiative effect pointed out by the ARFSw value (-99 W/m2 for a solar zenith angle of 60°) offset by a warming radiative effect according to ARFLw value (+21.9 W/m2) at the surface. Overall, about 24% and 12% of the dust solar radiative cooling effect is compensated by its longwave warming effect at the surface and at the top of the atmosphere, respectively. Hence, larger aerosol loads could enhance the response between the absorption and re-emission processes increasing the ARFLw with respect to those associated with moderate and low aerosol loads. The unprecedented

  1. Trends of Dust Transport Episodes in Cyprus Using a Classification of Synoptic Types Established with Artificial Neural Networks

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    S. Michaelides

    2013-01-01

    Full Text Available The relationship between dust episodes over Cyprus and specific synoptic patterns has long been considered but also further supported in recent studies by the authors. Having defined a dust episode as a day when the average PM10 measurement exceeds the threshold of 50 mg/(m3 day, the authors have utilized Artificial Neural Networks and synoptic charts, together with satellite and ground measurements, in order to establish a scheme which links specific synoptic patterns with the appearance of dust transport over Cyprus. In an effort to understand better these complicated synoptic-scale phenomena and their associations with dust transport episodes, the authors attempt in the present paper a followup of the previous tasks with the objective to further investigate dust episodes from the point of view of their time trends. The results have shown a tendency for the synoptic situations favoring dust events to increase in the last decades, whereas, the synoptic situations not favoring such events tend to decrease with time.

  2. Informing Reactive Vaccination Strategies for Meningococcal Meningitis in sub-Saharan Africa using Dust and Climate Predictors

    Science.gov (United States)

    Pérez García-Pando, C.; Thomson, M. C.; Stanton, M. C.; Diggle, P. J.; Miller, R. L.; Perlwitz, J. P.; Ceccato, P.

    2014-12-01

    Epidemics of meningococcal meningitis occur in sub-Saharan Africa during the dry season, a period when the region is affected by the Harmattan, a dry and dusty northeasterly trade wind blowing from the Sahara into the Gulf of Guinea. Although the mechanisms remain unclear, the location and seasonality of meningitis epidemics suggest that environmental factors, such as low absolute or relative humidity, high temperatures, and dusty atmospheric conditions play an important role. Using a 20-year time series of meningitis incidence in Niger we examined the potential of statistical models to predict seasonal incidence based on data that would be operationally available, such as climate and dust, population and previous incidence. We used surface dust concentration estimates from a model given the paucity of direct in situ measurements especially at district level. The soil dust aerosol component of the model was thoroughly evaluated with existing satellite and in situ data over the region of interest showing daily aerosol optical depth correlations around 0.6 (p < 0.05). Our results show that wind and dust information along with incidence in the early dry season predict a significant part of the year-to-year variability of the seasonal incidence at both national and district levels. Such a model could provide an early-season alert when wind, dust, and other conditions are conducive to an epidemic. We additionally discuss how this research has focused at "getting science into practice" by engaging with practitioner communities to inform operational decision-making for reactive vaccination.

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

    Science.gov (United States)

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

    2017-08-01

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

  4. Contrasting aerosol optical and radiative properties between dust and urban haze episodes in megacities of Pakistan

    Science.gov (United States)

    Iftikhar, Muhammad; Alam, Khan; Sorooshian, Armin; Syed, Waqar Adil; Bibi, Samina; Bibi, Humera

    2018-01-01

    Satellite and ground based remote sensors provide vital information about aerosol optical and radiative properties. Analysis of aerosol optical and radiative properties during heavy aerosol loading events in Pakistan are limited and, therefore, require in-depth examination. This work examines aerosol properties and radiative forcing during Dust Episodes (DE) and Haze Episodes (HE) between 2010 and 2014 over mega cities of Pakistan (Karachi and Lahore). Episodes having the daily averaged values of Aerosol Optical Depth (AOD) exceeding 1 were selected. DE were associated with high AOD and low Ångström Exponent (AE) over Karachi and Lahore while high AOD and high AE values were associated with HE over Lahore. Aerosol volume size distributions (AVSD) exhibited a bimodal lognormal distribution with a noticeable coarse mode peak at a radius of 2.24 μm during DE, whereas a fine mode peak was prominent at a radius 0.25 μm during HE. The results reveal distinct differences between HE and DE for spectral profiles of several parameters including Single Scattering Albedo (SSA), ASYmmetry parameter (ASY), and the real and imaginary components of refractive index (RRI and IRI). The AOD-AE correlation revealed that dust was the dominant aerosol type during DE and that biomass burning and urban/industrial aerosol types were pronounced during HE. Aerosol radiative forcing (ARF) was estimated using the Santa Barbra DISORT Atmospheric Radiative Transfer (SBDART) model. Calculations revealed a negative ARF at the Top Of the Atmosphere (ARFTOA) and at the Bottom Of the Atmosphere (ARFBOA), with positive ARF within the Atmosphere (ARFATM) during both DE and HE over Karachi and Lahore. Furthermore, estimations of ARFATM by SBDART were shown to be in good agreement with values derived from AERONET data for DE and HE over Karachi and Lahore.

  5. Aetiologies of non-malaria febrile episodes in children under 5 years in sub-Saharan Africa.

    Science.gov (United States)

    Kiemde, Francois; Spijker, René; Mens, Petra F; Tinto, Halidou; Boele, Michael; Schallig, Henk D F H

    2016-08-01

    To provide an overview of the most frequent aetiologies found in febrile episodes of children under 5 years from sub-Saharan Africa. MEDLINE and EMBASE were searched for publications in English and French on non-malaria fever episodes in African children under 5 years of age, which were published between January 1990 and July 2015. Case reports and conference abstracts were excluded. In total, 3851 titles and abstracts were reviewed, and 153 were selected for full screening of which 18 were included in the present review. Bloodstream infection (BSI) was most commonly investigated (nine of 18) followed by urinary tract infection (UTI) (four of 18) and respiratory tract infection (RTI) (two of 18). Few studies investigated BSI and UTI in the same children (two of 18), or BSI and gastrointestinal infection (GII) (one of 18). As for BSI, the most frequently isolated bacteria were E. coli (four of 12), Streptococcus pneumonia (four of 12), Salmonella spp (three of 12) and Staphylococcus aureus (two of 12) with a positive identification rate of 19.7-33.3%, 5.2-27.6%, 11.7-65.4% and 23.5-42.0%, respectively. As for UTI, the main bacteria isolated were E. coli (six of six) and Klebsiella spp (six of six) with a positive rate of 20.0-72.3% and 10.0-28.5%, respectively. No bacterium was isolated in RTI group, but Human influenzae A and B were frequently found, with the highest positive identification rate in Tanzania (75.3%). Dengue virus (two of 12) was the most frequently reported viral infection with a positive identification rate of 16.7-30.8%. Finally, only rotavirus/adenovirus (69.2% positive identification rate) was found in GII and no bacterium was isolated in this group. The high prevalence of treatable causes of non-malaria fever episodes requires a proper diagnosis of the origin of fever followed by an appropriate treatment, thereby reducing the under-5 mortality in sub-Saharan Africa and preventing the overprescription of antibiotics and thus circumventing the

  6. Observations and Modeling of Saharan Dust Interaction with a Tropical Cyclone

    Science.gov (United States)

    Braun, Scott; Shi, Jainn J.; Sippel, Jason A.; Tao, Wei-Kuo

    2015-01-01

    Conflicting views on role of the SAL pre- and post-genesis (Karyampudi and Carlson 1988, Dunion and Velden 2004, Braun 2010, among others). Early dust impact studies claimed negative impacts, but had unrealistic dust distributions. (Zhang et al. 2007, 2009). More recent work with more realistic dust suggest possible positive impacts in some cases (Herbener et al. 2014).

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2012-04-01

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

  9. The impact of Saharan dust and black carbon on albedo and long-term mass balance of an Alpine glacier

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    J. Gabbi

    2015-07-01

    Full Text Available Light-absorbing impurities in snow and ice control glacier melt as shortwave radiation represents the main component of the surface energy balance. Here, we investigate the long-term effect of snow impurities, i.e., mineral dust and black carbon (BC, on albedo and glacier mass balance. The analysis was performed over the period 1914–2014 for two sites on Claridenfirn, Swiss Alps, where an outstanding 100-year record of seasonal mass balance measurements is available. Information on atmospheric deposition of mineral dust and BC over the last century was retrieved from two firn/ice cores of high-alpine sites. A combined mass balance and snow/firn layer model was employed to assess the effects of melt and accumulation processes on the impurity concentration at the surface and thus on albedo and glacier mass balance. Compared to pure snow conditions, the presence of Saharan dust and BC lowered the mean annual albedo by 0.04–0.06 depending on the location on the glacier. Consequently, annual melt was increased by 15–19 %, and the mean annual mass balance was reduced by about 280–490 mm w.e. BC clearly dominated absorption which is about 3 times higher than that of mineral dust. The upper site has experienced mainly positive mass balances and impurity layers were continuously buried whereas at the lower site, surface albedo was more strongly influenced by re-exposure of dust and BC-enriched layers due to frequent years with negative mass balances.

  10. Measurements of the Atmospheric Electric Field through a Triangular Array and the Long-range Saharan Dust Electrification in Southern Portugal

    CERN Document Server

    Silva, H G; Pereira, S; Barbosa, S M; Nicoll, K; Pereira, M Collares; Harrison, R G

    2016-01-01

    Atmospheric electric field (AEF) measurements were carried out in three different sites forming a triangular array in Southern Portugal. The campaign was performed during the summer characterized by Saharan dust outbreaks; the 16th-17th July 2014 desert dust event is considered here. Evidence of long-range dust electrification is attributed to the air-Earth electrical current creating a positive space-charge inside of the dust layer. An increase of ~23 V/m is observed in AEF on the day of the dust event corresponding to space-charges of ~20-2 pCm-3 (charge layer thicknesses ~10-100 m). A reduction of AEF is observed after the dust event.

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

    Science.gov (United States)

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

    2000-01-01

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

  12. Impact of mineral dust on cloud formation in a Saharan outflow region

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    L. Smoydzin

    2012-12-01

    Full Text Available We present a numerical modelling study investigating the impact of mineral dust on cloud formation over the Eastern Mediterranean for two case studies: (i 25 September 2008 and (ii 28/29 January 2003. In both cases dust plumes crossed the Mediterranean and interacted with clouds forming along frontal systems. For our investigation we used the fully online coupled model WRF-chem.

    The results show that increased aerosol concentrations due to the presence of mineral dust can enhance the formation of ice crystals. This leads to slight shifts of the spatial and temporal precipitation patterns compared to scenarios where dust was not considered to act as ice nuclei. However, the total amount of precipitation did not change significantly. The only exception occurred when dust entered into an area of orographic ascent, causing glaciation of the clouds, leading to a local enhancement of rainfall. The impact of dust particles acting as giant cloud condensation nuclei on precipitation formation was found to be small. Based on our simulations the contribution of dust to the CCN population is potentially significant only for warm phase clouds. Nevertheless, the dust-induced differences in the microphysical structure of the clouds can contribute to a significant radiative forcing, which is important from a climate perspective.

  13. Observations of Saharan dust microphysical and optical properties from the Eastern Atlantic during NAMMA airborne field campaign

    Directory of Open Access Journals (Sweden)

    G. Chen

    2011-01-01

    Full Text Available As part of the international project entitled "African Monsoon Multidisciplinary Analysis (AMMA", NAMMA (NASA AMMA aimed to gain a better understanding of the relationship between the African Easterly Waves (AEWs, the Sahara Air Layer (SAL, and tropical cyclogenesis. The NAMMA airborne field campaign was based out of the Cape Verde Islands during the peak of the hurricane season, i.e., August and September 2006. Multiple Sahara dust layers were sampled during 62 encounters in the eastern portion of the hurricane main development region, covering both the eastern North Atlantic Ocean and the western Saharan desert (i.e., 5–22° N and 10–35° W. The centers of these layers were located at altitudes between 1.5 and 3.3 km and the layer thickness ranged from 0.5 to 3 km. Detailed dust microphysical and optical properties were characterized using a suite of in-situ instruments aboard the NASA DC-8 that included a particle counter, an Ultra-High Sensitivity Aerosol Spectrometer, an Aerodynamic Particle Sizer, a nephelometer, and a Particle Soot Absorption Photometer. The NAAMA sampling inlet has a size cut (i.e., 50% transmission efficiency size of approximately 4 μm in diameter for dust particles, which limits the representativeness of the NAMMA observational findings. The NAMMA dust observations showed relatively low particle number densities, ranging from 268 to 461 cm−3, but highly elevated volume density with an average at 45 μm3 cm−3. NAMMA dust particle size distributions can be well represented by tri-modal lognormal regressions. The estimated volume median diameter (VMD is averaged at 2.1 μm with a small range of variation regardless of the vertical and geographical sampling locations. The Ångström Exponent assessments exhibited strong wavelength dependence for absorption but a weak one for scattering. The single scattering albedo was estimated at 0.97 ± 0.02. The imaginary part of the refractive

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

    Science.gov (United States)

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

    2017-04-01

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

  15. Disentangling the contribution of Saharan dust and marine aerosol to PM10 levels in the Central Mediterranean

    Science.gov (United States)

    Scerri, Mark M.; Kandler, Konrad; Weinbruch, Stephan

    2016-12-01

    The Għarb rural background station located on the northernmost island in the Maltese archipelago has been used to gather PM10 data since 2008. 224 samples from a monitoring campaign carried out from March 2012 to May 2013, were characterized for various metals and ions by inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography. This speciation data was used in conjunction with the positive matrix factorization (PMF) model in order to determine the contribution of Saharan dust and marine aerosol to PM10 levels at the receptor. PMF managed to isolate two different crustal source contributions: a local crustal component and a trans-boundary component of North African origin. Marine aerosol, secondary nitrate/aged aerosol, and ammonium sulphate were other source contributions, which were isolated by the model. The trans-boundary crustal component (Saharan aerosol) and the marine aerosol are considered to be of natural origin and their joint contribution to PM10 levels at the site was estimated to be 39%. This value is in the upper part of the range derived from previous studies, for natural contributions to PM10 in Europe (0.5%-58%).

  16. Impact of climate change and El Niño episodes on droughts in sub-Saharan Africa

    Science.gov (United States)

    Gizaw, Mesgana Seyoum; Gan, Thian Yew

    2017-07-01

    Various drought prone regions of sub-Saharan Africa (SSAF) have been affected by severe droughts in recent decades and centuries, which had caused catastrophic humanitarian crisis. In this study, the Palmer Drought Severity Index was used to analyse changes in drought characteristics of SSAF during 1971-2000 and the Representative Concentration Pathways (RCP4.5 and RCP8.5) climate projections of selected GCMs (Global Climate Models) for the 2041-2070 (2050s) and 2071-2100 (2080s) periods. The results show that most areas in South Africa (SA) and West Africa (WA) will shift to a drier climate in the 2050 and 2080s. However, some areas in Greater Horn of Africa (GHA) are expected to be relatively wetter in the 2050 and 2080s whereas very little change is projected in the average drought severity of Central Africa (CA). The frequency of short (6-12 months) and long (above 12 months) drought events also increased on average by 5 %. However, a 1-6 % decrease in the average duration of long drought periods was projected during the 2050 and 2080s likely due to the increase in the intensity and frequency of extreme precipitation events in SSAF. An increase in the frequency of El Niño episodes under a warmer twentyfirst century climate is also expected to increase the drought prone regions of WA, SA and particularly GHA while CA still remains virtually unaffected. Overall, the results suggest that SSAF will experience a drier climate in the 2050 and 2080s with an increase in drought prone areas in the four corners of the sub-continent.

  17. Implementation of dust emission and chemistry into the Community Multiscale Air Quality modeling system and initial application to an Asian dust storm episode

    Directory of Open Access Journals (Sweden)

    K. Wang

    2012-11-01

    Full Text Available The US Environmental Protection Agency's (EPA Community Multiscale Air Quality (CMAQ modeling system version 4.7 is further developed to enhance its capability in simulating the photochemical cycles in the presence of dust particles. The new model treatments implemented in CMAQ v4.7 in this work include two online dust emission schemes (i.e., the Zender and Westphal schemes, nine dust-related heterogeneous reactions, an updated aerosol inorganic thermodynamic module ISORROPIA II with an explicit treatment of crustal species, and the interface between ISORROPIA II and the new dust treatments. The resulting improved CMAQ (referred to as CMAQ-Dust, offline-coupled with the Weather Research and Forecast model (WRF, is applied to the April 2001 dust storm episode over the trans-Pacific domain to examine the impact of new model treatments and understand associated uncertainties. WRF/CMAQ-Dust produces reasonable spatial distribution of dust emissions and captures the dust outbreak events, with the total dust emissions of ~111 and 223 Tg when using the Zender scheme with an erodible fraction of 0.5 and 1.0, respectively. The model system can reproduce well observed meteorological and chemical concentrations, with significant improvements for suspended particulate matter (PM, PM with aerodynamic diameter of 10 μm, and aerosol optical depth than the default CMAQ v4.7. The sensitivity studies show that the inclusion of crustal species reduces the concentration of PM with aerodynamic diameter of 2.5 μm (PM2.5 over polluted areas. The heterogeneous chemistry occurring on dust particles acts as a sink for some species (e.g., as a lower limit estimate, reducing O3 by up to 3.8 ppb (~9% and SO2 by up to 0.3 ppb (~27% and as a source for some others (e.g., increasing fine-mode SO42− by up to 1.1 μg m−3 (~12% and PM2.5 by up to 1.4 μg m−3 (~3% over the domain. The

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

    Science.gov (United States)

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

    2016-10-01

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

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

    Directory of Open Access Journals (Sweden)

    M. Ealo

    2016-10-01

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

  20. Particle size traces modern Saharan dust transport and deposition across the equatorial North Atlantic

    NARCIS (Netherlands)

    van der Does, M.; Korte, L.F.; Munday, C.I.; Brummer, G.-J. A.; Stuut, J-B W.

    2016-01-01

    Mineral dust has a large impact on regional andglobal climate, depending on its particle size. Especially inthe Atlantic Ocean downwind of the Sahara, the largest dustsource on earth, the effects can be substantial but are poorlyunderstood. This study focuses on seasonal and spatial variationsin

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

    Science.gov (United States)

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

    2017-04-01

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

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

    Science.gov (United States)

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

    2018-03-01

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

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

    Science.gov (United States)

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

    2015-12-01

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

  4. Genesis of diamond dust, ice fog and thick cloud episodes observed and modelled above Dome C, Antarctica

    Science.gov (United States)

    Ricaud, Philippe; Bazile, Eric; del Guasta, Massimo; Lanconelli, Christian; Grigioni, Paolo; Mahjoub, Achraf

    2017-04-01

    Episodes of thick cloud and diamond dust/ice fog were observed during 15 March to 8 April 2011 and 4 to 5 March 2013 in the atmosphere above Dome C (Concordia station, Antarctica; 75°06' S, 123°21' E; 3233 m a.m.s.l.). The objectives of the paper are mainly to investigate the processes that cause these episodes based on observations and to verify whether operational models can evaluate them. The measurements were obtained from the following instruments: (1) a ground-based microwave radiometer (HAMSTRAD, H2O Antarctica Microwave Stratospheric and Tropospheric Radiometers) installed at Dome C that provided vertical profiles of tropospheric temperature and absolute humidity every 7 min; (2) daily radiosoundings launched at 12:00 UTC at Dome C; (3) a tropospheric aerosol lidar that provides aerosol depolarization ratio along the vertical at Dome C; (4) down- and upward short- and long-wave radiations as provided by the Baseline Surface Radiation Network (BSRN) facilities; (5) an ICE-CAMERA to detect at an hourly rate the size of the ice crystal grains deposited at the surface of the camera; and (6) space-borne aerosol depolarization ratio from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) lidar aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) platform along orbits close to the Dome C station. The time evolution of the atmosphere has also been evaluated by considering the outputs from the mesoscale AROME and the global-scale ARPEGE meteorological models. Thick clouds are detected during the warm and wet periods (24-26 March 2011 and 4 March 2013) with high depolarization ratios (greater than 30 %) from the surface to 5-7 km above the ground associated with precipitation of ice particles and the presence of a supercooled liquid water (depolarization less than 10 %) clouds. Diamond dust and/or ice fog are detected during the cold and dry periods (5 April 2011 and 5 March 2013) with high depolarization ratios (greater

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2018-01-01

    Millions of tons of mineral dust are lifted by the wind from arid surfaces and transported around the globe every year. The physical and chemical properties of the mineral dust are needed to better constrain remote sensing observations and are of fundamental importance for the understanding of dust atmospheric processes. Ground-based in situ measurements and in situ filter collection of Saharan dust were obtained during the Fennec campaign in the central Sahara in 2011. This paper presents results of the absorption and scattering coefficients, and hence single scattering albedo (SSA), of the Saharan dust measured in real time during the last period of the campaign and subsequent laboratory analysis of the dust samples collected in two supersites, SS1 and SS2, in Algeria and in Mauritania, respectively. The samples were taken to the laboratory, where their size and aspect ratio distributions, mean chemical composition, spectral mass absorption efficiency, and spectral imaginary refractive index were obtained from the ultraviolet (UV) to the near-infrared (NIR) wavelengths. At SS1 in Algeria, the time series of the scattering coefficients during the period of the campaign show dust events exceeding 3500 Mm-1, and a relatively high mean SSA of 0.995 at 670 nm was observed at this site. The laboratory results show for the fine particle size distributions (particles diameter  shape, with increased absorption in UV as well as in the shortwave infrared. The same signature was not observed, however, in the mixed particle size distribution (particle diameter particle size distributions were observed from EDXRF measurements, although those differences cannot be used to explain the optical properties variability between the samples. Finally, particles with low-density typically larger than 10 µm in diameter were found in some of the samples collected at the supersite in Mauritania, but these low-density particles were not observed in Algeria.

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

    Science.gov (United States)

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

    2009-01-01

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

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

    Science.gov (United States)

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

    2015-04-01

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

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

    Science.gov (United States)

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

    2013-04-01

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

  11. Vertical mass impact and features of Saharan dust intrusions derived from ground-based remote sensing in synergy with airborne in-situ measurements

    Science.gov (United States)

    Córdoba-Jabonero, Carmen; Andrey-Andrés, Javier; Gómez, Laura; Adame, José Antonio; Sorribas, Mar; Navarro-Comas, Mónica; Puentedura, Olga; Cuevas, Emilio; Gil-Ojeda, Manuel

    2016-10-01

    A study of the vertical mass impact of Saharan dust intrusions is presented in this work. Simultaneous ground-based remote-sensing and airborne in-situ measurements performed during the AMISOC-TNF campaign over the Tenerife area (Canary Islands) in summertime from 01 July to 11 August 2013 were used for that purpose. A particular dusty (DD) case, associated to a progressively arriving dust intrusion lasting for two days on 31 July (weak incidence) and 01 August (strong incidence), is especially investigated. AERONET AOD and AEx values were ranging, respectively, from 0.2 to 1.4 and 0.35 to 0.05 along these two days. Vertical particle size distributions within fine and coarse modes (0.16-2.8 μm range) were obtained from aircraft aerosol spectrometer measurements. Extinction profiles and Lidar Ratio (LR) values were derived from MPLNET/Micro Pulse Lidar observations. MAXDOAS measurements were also used to retrieve the height-resolved aerosol extinction for evaluation purposes in comparison to Lidar-derived profiles. The synergy between Lidar observations and airborne measurements is established in terms of the Mass Extinction Efficiency (MEE) to calculate the vertical mass concentration of Saharan dust particles. Both the optical and microphysical profilings show dust particles mostly confined in a layer of 4.3 km thickness from 1.7 to 6 km height. LR ranged between 50 and 55 sr, typical values for Saharan dust particles. In addition, this 2-day dust event mostly affected the Free Troposphere (FT), being less intense in the Boundary Layer (BL). In particular, rather high Total Mass Concentrations (TMC) were found on the stronger DD day (01 August 2013): 124, 70 and 21 μg m-3 were estimated, respectively, at FT and BL altitudes and on the near-surface level. This dust impact was enhanced due to the increase of large particles affecting the FT, but also the BL, likely due to their gravitational settling. However, the use of an assumed averaged MEE value can be

  12. A new thermal gradient ice nucleation diffusion chamber instrument: design, development and first results using Saharan mineral dust

    Directory of Open Access Journals (Sweden)

    J. B. McQuaid

    2009-06-01

    Full Text Available A new Thermal Gradient ice nucleation Diffusion Chamber (TGDC capable of investigating ice nucleation efficiency of atmospherically important aerosols, termed Ice Nuclei (IN, has been designed, constructed and validated. The TGDC can produce a range of supersaturations with respect to ice (SSi over the temperature range of −10 to −34°C for sufficiently long time needed to observe the ice nucleation by the particles. The novel aspect of this new TGDC is that the chamber is run in static mode with aerosol particles supported on a Teflon substrate, which can be raised and lowered in a controlled way through the SSi profile within the chamber, and nucleation events are directly observed using digital photography. The TGDC consists of two ice coated plates to which a thermal gradient is applied to produce the range of SSi. The design of the TGDC gives the ability to understand time-related ice nucleation event information and to perform experiments at different temperatures and SSi conditions for different IN without changing the thermal gradient within the TGDC. The temperature and SSi conditions of the experimental system are validated by observing (NH42SO4 deliquescence and the results are in good agreement with the literature data. First results are presented of the onset ice nucleation for mineral dust sampled from the Saharan Desert, including images of nucleation and statistical distributions of onset ice nucleation SSi as a function of temperature. This paper illustrates how useful this new TGDC is for process level studies of ice nucleation and more experimental investigations are needed to better quantify the role of ice formation in the atmosphere.

  13. Long-term (2002–2012 investigation of Saharan dust transport events at Mt. Cimone GAW global station, Italy (2165 m a.s.l.

    Directory of Open Access Journals (Sweden)

    Rocco Duchi

    2016-02-01

    Full Text Available Abstract Mineral dust transport from North Africa towards the Mediterranean basin and Europe was monitored over an 11-y period (2002–2012 using the continuous observations made at Mt. Cimone WMO/GAW global station (CMN. CMN is in a strategic position for investigating the impact of mineral dust transported from northern Africa on the atmospheric composition of the Mediterranean basin and southern Europe. The identification of “dusty days” is based on coupling the measured in situ coarse aerosol particle number concentration with an analysis of modeled back trajectories tracing the origin of air masses from North Africa. More than 400 episodes of mineral dust transport were identified, accounting for 15.7% of the investigated period. Our analysis points to a clear seasonal cycle, with the highest frequency from spring to autumn, and a dust-induced variation of the coarse particle number concentration larger than 123% on a seasonal basis. In addition, FLEXTRA 10-d back trajectories showed that northwestern and central Africa are the major mineral dust source regions. Significant inter-annual variability of dust outbreak frequency and related mineral dust loading were detected and during spring the NAO index was positively correlated (R2 = 0.32 with dust outbreak frequency. Lastly, the impact of transported mineral dust on the surface O3 mixing ratio was quantified over the 11-y investigation period. Evidence of a non-linear and negative correlation between mineral dust and ozone concentrations was found, resulting in an average spring and summer decrease of the O3 mixing ratio down to 7%.

  14. Assimilation of MODIS AOD measurements during the Sahara dust episode in April 2016

    Science.gov (United States)

    Scherllin-Pirscher, Barbara; Hirtl, Marcus; Flandorfer, Claudia; Pagowski, Mariusz

    2017-04-01

    In April 2016, an air pollution event with highly elevated surface concentrations of particulate matter (PM) has been observed in Europe. At the Sonnblick observatory (an atmospheric monitoring platform at 3100 m in the Alps in Austria), PM10 surface concentrations were considerably elevated (>100 μg/m3) on April 5, 2016. This event was caused by a Sahara dust storm. In this study we use the WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) model to predict the transport of Sahara dust from northern Africa towards Europe. Simulations were performed from April 1, 2016 to April 8, 2016 using the GOCART (Goddard Chemistry Aerosol Radiation and Transport) aerosol scheme. The GOCART model simulates tropospheric aerosols such as dust and sea salt (both with different size bins), organic carbon (OC), black carbon (BC), and sulfate, enabling the computation of PM2.5 and PM10. Gridpoint statistical interpolation (GSI) is then used to assimilate data of the Moderate Resolution Imaging Spectroradiometer (MODIS) total aerosol optical depth (AOD) retrieval products at a wavelength of 550 nm from the Terra and Aqua satellites. Data assimilation is performed at 12 UTC with an assimilation window of ±3 hours. PM10 analyses are evaluated against PM10 surface measurements provided by EEA (European Environment Agency) and the Austrian Environmental Agency. First results indicate that WRF-Chem underestimates surface concentration of PM10 during the Sahara dust event in April 2016 over Europe but the assimilation of MODIS AOD substantially improves PM10 analyses.

  15. Numerical simulations of windblown dust over complex terrain: the Fiambalá Basin episode in June 2015

    Directory of Open Access Journals (Sweden)

    L. A. Mingari

    2017-06-01

    Full Text Available On 13 June 2015, the London Volcanic Ash Advisory Centre (VAAC warned the Buenos Aires VAAC about a possible volcanic eruption from the Nevados Ojos del Salado volcano (6879 m, located in the Andes mountain range on the border between Chile and Argentina. A volcanic ash cloud was detected by the SEVIRI instrument on board the Meteosat Second Generation (MSG satellites from 14:00 UTC on 13 June. In this paper, we provide the first comprehensive description of this event through observations and numerical simulations. Our results support the hypothesis that the phenomenon was caused by wind remobilization of ancient pyroclastic deposits (ca. 4.5 ka Cerro Blanco eruption from the Bolsón de Fiambalá (Fiambalá Basin in northwestern Argentina. We have investigated the spatiotemporal distribution of aerosols and the emission process over complex terrain to gain insight into the key role played by the orography and the condition that triggered the long-range transport episode. Numerical simulations of windblown dust were performed using the ARW (Advanced Research WRF core of the WRF (Weather Research and Forecasting model (WRF-ARW and FALL3D modeling system with meteorological fields downscaled to a spatial resolution of 2 km in order to resolve the complex orography of the area. Results indicate that favorable conditions to generate dust uplifting occurred in northern Fiambalá Basin, where orographic effects caused strong surface winds. According to short-range numerical simulations, dust particles were confined to near-ground layers around the emission areas. In contrast, dust aerosols were injected up to 5–6 km high in central and southern regions of the Fiambalá Basin, where intense ascending airflows are driven by horizontal convergence. Long-range transport numerical simulations were also performed to model the dust cloud spreading over northern Argentina. Results of simulated vertical particle column mass were compared with the

  16. Numerical simulations of windblown dust over complex terrain: the Fiambalá Basin episode in June 2015

    Science.gov (United States)

    Mingari, Leonardo A.; Collini, Estela A.; Folch, Arnau; Báez, Walter; Bustos, Emilce; Soledad Osores, María; Reckziegel, Florencia; Alexander, Peter; Viramonte, José G.

    2017-06-01

    On 13 June 2015, the London Volcanic Ash Advisory Centre (VAAC) warned the Buenos Aires VAAC about a possible volcanic eruption from the Nevados Ojos del Salado volcano (6879 m), located in the Andes mountain range on the border between Chile and Argentina. A volcanic ash cloud was detected by the SEVIRI instrument on board the Meteosat Second Generation (MSG) satellites from 14:00 UTC on 13 June. In this paper, we provide the first comprehensive description of this event through observations and numerical simulations. Our results support the hypothesis that the phenomenon was caused by wind remobilization of ancient pyroclastic deposits (ca. 4.5 ka Cerro Blanco eruption) from the Bolsón de Fiambalá (Fiambalá Basin) in northwestern Argentina. We have investigated the spatiotemporal distribution of aerosols and the emission process over complex terrain to gain insight into the key role played by the orography and the condition that triggered the long-range transport episode. Numerical simulations of windblown dust were performed using the ARW (Advanced Research WRF) core of the WRF (Weather Research and Forecasting) model (WRF-ARW) and FALL3D modeling system with meteorological fields downscaled to a spatial resolution of 2 km in order to resolve the complex orography of the area. Results indicate that favorable conditions to generate dust uplifting occurred in northern Fiambalá Basin, where orographic effects caused strong surface winds. According to short-range numerical simulations, dust particles were confined to near-ground layers around the emission areas. In contrast, dust aerosols were injected up to 5-6 km high in central and southern regions of the Fiambalá Basin, where intense ascending airflows are driven by horizontal convergence. Long-range transport numerical simulations were also performed to model the dust cloud spreading over northern Argentina. Results of simulated vertical particle column mass were compared with the MSG-SEVIRI retrieval

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

    Science.gov (United States)

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

    2010-05-01

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

  18. The relative importance of water vapour and dust in controlling the variability in radiative heating of the summertime Saharan heat low

    Science.gov (United States)

    Marsham, John H.; Parker, Douglas J.; Todd, Martin C.; Banks, Jamie R.; Brindley, Helen E.; Garcia-Carreras, Luis; Roberts, Alexander J.; Ryder, Claire L.

    2017-04-01

    The summertime Sahara heat low (SHL) is a key component of the West African monsoon (WAM) system but is a key source of uncertainty in global models. There is considerable uncertainty over the relative importance of water vapour and dust concentrations in controlling the radiation budget over the Sahara. This limits our ability to explain the variability and trends in the SHL and WAM systems, and so hampers our ability to reduce model biases. Here we use in situ observations from Fennec supersite-1 in the central Sahara from June 2011 and 2012, as well as satellite retrievals from GERB, to quantify how total column water vapour (TCWV) and dust aerosols control day-to-day variability in the energy balance in observations and ECMWF reanalyses (ERA-I). Results show that the earth-atmosphere system is radiatively heated in June 2011 and 2012. While we are not able to completely disentangle the roles of water vapour, clouds and dust from the observations, the analysis demonstrates that TCWV provides a far stronger control on TOA net radiation, and so the net heating of the earth-atmosphere system, than AOD does. Variations in dust provide a much stronger control on surface heating, but the reduction in surface heating associated with high dust loadings are largely compensated by associated increases in atmospheric heating, and so dust control on net TOA radiation is weak. Dust and TCWV are both important for direct atmospheric heating. ERA-I assimilated radiosondes from the Fennec campaign but uses a monthly dust climatology, and so cannot capture the impact of daily variations in dustiness. Despite this, ERA-I managed to capture the control of TOA net flux by TCWV, with a positive correlation (r = 0.6) between observed and modelled TOA net radiation. Variations in surface net radiation, and so the vertical profile of radiative heating, are not captured in ERA-I, given it does not capture variations in dust. Results show that ventilation of the SHL by cool moist air

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

    Science.gov (United States)

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

    2012-05-01

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

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

    Directory of Open Access Journals (Sweden)

    A. Rocha-Lima

    2018-01-01

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

  1. 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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2017-08-01

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

  3. Episodic therapy for genital herpes in sub-saharan Africa: a pooled analysis from three randomized controlled trials.

    Directory of Open Access Journals (Sweden)

    Helen A Weiss

    Full Text Available BACKGROUND: A randomized controlled trial in South Africa found a beneficial effect of acyclovir on genital ulcer healing, but no effect was seen in trials in Ghana, Central African Republic and Malawi. The aim of this paper is to assess whether the variation in impact of acyclovir on ulcer healing in these trials can be explained by differences in the characteristics of the study populations. METHODOLOGY/PRINCIPAL FINDINGS: Pooled data were analysed to estimate the impact of acyclovir on the proportion of ulcers healed seven days after randomisation by HIV/CD4 status, ulcer aetiology, size and duration before presentation; and impact on lesional HIV-1. Risk ratios (RR were estimated using Poisson regression with robust standard errors. Of 1478 patients with genital ulcer, most (63% had herpetic ulcers (16% first episode HSV-2 ulcers, and a further 3% chancroid, 2% syphilis, 0.7% lymphogranuloma venereum and 31% undetermined aetiology. Over half (58% of patients were HIV-1 seropositive. The median duration of symptoms before presentation was 6 days. Patients on acyclovir were more likely to have a healed ulcer on day 7 (63% vs 57%, RR = 1.08, 95% CI 0.98-1.18, shorter time to healing (p = 0.04 and less lesional HIV-1 RNA (p = 0.03. Small ulcers (<50 mm(2, HSV-2 ulcers, first episode HSV-2 ulcers, and ulcers in HIV-1 seropositive individuals responded best but the better effectiveness in South Africa was not explained by differences in these factors. CONCLUSIONS/SIGNIFICANCE: There may be slight benefit in adding acyclovir to syndromic management in settings where most ulcers are genital herpes. The stronger effect among HIV-1 infected individuals suggests that acyclovir may be beneficial for GUD/HIV-1 co-infected patients. The high prevalence in this population highlights that genital ulceration in patients with unknown HIV status provides a potential entry point for provider-initiated HIV testing.

  4. Impact of dust and smoke mixing on column-integrated aerosol properties from observations during a severe wildfire episode over Valencia (Spain).

    Science.gov (United States)

    Gómez-Amo, J L; Estellés, V; Marcos, C; Segura, S; Esteve, A R; Pedrós, R; Utrillas, M P; Martínez-Lozano, J A

    2017-12-01

    The most destructive wildfire experienced in Spain since 2004 occurred close to Valencia in summer 2012. A total of 48.500ha were affected by two wildfires, which were mostly active during 29-30 June. The fresh smoke plume was detected at the Burjassot measurement station simultaneously to a severe dust episode. We propose an empirical method to evaluate the dust and smoke mixing and its impact on the microphysical and optical properties. For this, we combine direct-sun measurements with a Cimel CE-318 sun-photometer with an inversion methodology, and the Mie theory to derive the column-integrated size distribution, single scattering albedo (SSA) and asymmetry parameter (g). The mixing of dust and smoke greatly increased the aerosol load and modified the background aerosol properties. Mineral dust increased the aerosol optical depth (AOD) up to 1, while the smoke plume caused an extreme AOD peak of 8. The size distribution of the mixture was bimodal, with a fine and coarse modes dominated by the smoke particles and mineral dust, respectively. The SSA and g for the dust-smoke mixture show a marked sensitivity on the smoke mixing-ratio, mainly at longer wavelengths. Mineral dust and smoke share a similar SSA at 440nm (~0.90), but with opposite spectral dependency. A small dust contribution to the total AOD substantially affects the SSA of the mixture, and also SSA at 1020nm increases from 0.87 to 0.95. This leads to a different spectral behaviour of SSA that changes from positive (smoke plume) to negative (dust), depending on the dust and smoke mixing-ratio. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2017-11-01

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

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

    Science.gov (United States)

    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

  8. Bacterial profiling of Saharan dust deposition in the Atlantic Ocean using sediment trap moorings – year one results

    Science.gov (United States)

    Munday, Chris; Brummer, Geert-Jan; van der Does, Michelle; Korte, Laura; Stuut, Jan-Berend

    2015-04-01

    Large quantities of dust are transported from the Sahara Desert across the Atlantic Ocean towards the Caribbean each year, with a large portion of it deposited in the ocean. This dust brings an array of minerals, nutrients and organic matter, both living and dead. This input potentially fertilizes phytoplankton growth, with resulting knock-on effects throughout the food chain. The input of terrestrial microbial life may also have an impact on the marine microbial community. The current multi-year project consists of a transect of floating dust collectors and sub-surface sediment traps placed at 12°N across the Atlantic Ocean. Sediment traps are located 1200m and 3500m below the sea surface and all are synchronized to collect samples for a period of two weeks. The aim is to understand the links between dust input and the bacterial community and how this relates to ocean productivity and the carbon cycle. The first set of sediment trap samples were recovered using the RV Pelagia in November 2013 with promising results. Results from 7 sediment traps (three at 1200m and four at 3500m) were obtained. In general, the total mass flux decreased as distance from the source increased and the upper traps generally held more material than those at 3500m. Denaturing Gradient Gel Electrophoresis (DGGE) was used as a screening technique, revealing highly varied profiles, with the upper (1200m) traps generally showing more variation throughout the year. Several samples have been submitted for high throughput DNA sequencing which will identify the variations in these samples.

  9. Ground-based characterization of aerosol spectral optical properties of haze and Asian dust episodes under Asian continental outflow during winter 2014

    Science.gov (United States)

    Jung, Jinsang; Yu, JeongAh; Lyu, Youngsook; Lee, Minhee; Hwang, Taekyung; Lee, Sangil

    2017-04-01

    Long-range transported (LRT) haze can affect the regional radiation budget and the air quality in areas downwind of the Asian continental outflow. Because in situ observations of spectral aerosol optical properties of the LRT haze are rare, an intensive characterization of aerosol optical properties is needed. This study characterized the spectral optical properties of the LRT haze and Asian dust originating from the Asian continent. Integrated chemical and optical measurements of aerosol particles were carried out in a downwind area of the Asian continental outflow (Daejeon, South Korea) during winter 2014. High concentrations of PM10 (particulate matter with a diameter ≤ 10 µm) and light scattering coefficients at 550 nm, σs, 550, were observed during a long-range transport (LRT) haze episode (PM10 = 163.9 ± 25.0 µg m-3; σs, 550 = 503.4 ± 60.5 Mm-1) and Asian dust episode (PM10 = 211.3 ± 57.5 µg m-3; σs, 550 = 560.9 ± 151 Mm-1). During the LRT haze episode, no significant change in the relative contribution of PM2. 5 (particulate matter with a diameter ≤ 2.5 µm) chemical components was observed as particles accumulated under stagnant atmospheric conditions (13-17 January 2014), suggesting that the increase in PM2. 5 mass concentration was caused mainly by the accumulation of LRT pollutants. On the other hand, a gradual decrease in Ångström exponent (Å) and a gradual increase in single scattering albedo (ω) and mass scattering efficiency (MSE) were observed during the stagnant period, possibly due to an increase in particle size. These results imply that a change in particle size rather than chemical composition during the stagnant period is the dominant factor affecting the aerosol optical properties. During the Asian dust episode, a low PM2. 5 / PM10 ratio and Å(450/700) were observed with average values of 0.59 ± 0.06 and 1.08 ± 0.14, respectively, which were higher than those during the LRT haze episode (0.75 ± 0.06 and 1.39 ± 0

  10. Chemical characteristics of PM2.5-0.3 and PM0.3 and consequence of a dust storm episode at an urban site in Lebanon

    Science.gov (United States)

    Borgie, Mireille; Ledoux, Frédéric; Dagher, Zeina; Verdin, Anthony; Cazier, Fabrice; Courcot, Lucie; Shirali, Pirouz; Greige-Gerges, Hélène; Courcot, Dominique

    2016-11-01

    Located on the eastern side of the Mediterranean Basin at the intersection of air masses circulating between three continents, the agglomeration of Beirut, capital of Lebanon is an important investigating area for air pollution and more studies are needed to elucidate the composition of the smallest particles classified as carcinogenic to humans. PM2.5-0.3 and PM0.3 samples were collected during the spring-summer period in an urban background site of Beirut, after a dust storm episode occurred, and their chemical composition was determined. Our findings showed that components formed by gas to particle conversion (SO42 - and NH4+) and related to combustion processes are mainly found in the PM0.3 fraction. Typical crustal (Ca2+, Fe, Ti, Mg2+), sea-salt (Na+, Cl-, Mg2+, Sr) species, and NO3- are mainly associated with the PM2.5-0.3 fraction. We have also evidenced that the dust episode which occurred in Lebanon in May 2011 originated from the Iraqian and Syrian deserts, which are the least studied, and had a direct influence on the composition of PM2.5-0.3 during the beginning of the first sampling period, and then an indirect and persistent influence by the re-suspension of deposited dust particles. Moreover, PAHs concentrations were much higher in PM0.3 than in PM2.5-0.3 and their composition appeared influenced by diesel (buses, trucks and generator sets) and gasoline (private cars) emissions.

  11. Spatiotemporal drivers of dissolved organic matter in high alpine lakes: Role of Saharan dust inputs and bacterial activity

    Science.gov (United States)

    Mladenov, Natalie; Pulido-Villena, Elvira; Morales-Baquero, Rafael; Ortega-Retuerta, Eva; Sommaruga, Ruben; Reche, Isabel

    2008-06-01

    The effects of many environmental stressors such as UV radiation are mediated by dissolved organic matter (DOM) properties. Therefore, determining the factors shaping spatial and temporal patterns is particularly essential in the most susceptible, low dissolved organic carbon (DOC) lakes. We analyzed spatiotemporal variations in dissolved organic carbon concentration and dissolved organic matter optical properties (absorption and fluorescence) in 11 transparent lakes located above tree line in the Sierra Nevada Mountains (Spain), and we assessed potential external (evaporation and atmospheric deposition) and internal (bacterial abundance, bacterial production, chlorophyll a, and catchment vegetation) drivers of DOM patterns. At spatial and temporal scales, bacteria were related to chromophoric DOM (CDOM). At the temporal scale, water soluble organic carbon (WSOC) in dust deposition and evaporation were found to have a significant influence on DOC and CDOM in two Sierra Nevada lakes studied during the ice-free periods of 2000-2002. DOC concentrations and absorption coefficients at 320 nm were strongly correlated over the spatial scale (n = 11, R2 = 0.86; p < 0.01), but inconsistently correlated over time, indicating seasonal and interannual variability in external factors and a differential response of DOC concentration and CDOM to these factors. At the continental scale, higher mean DOC concentrations and more CDOM in lakes of the Sierra Nevada than in lakes of the Pyrenees and Alps may be due to a combination of more extreme evaporation, and greater atmospheric dust deposition.

  12. Spatiotemporal drivers of dissolved organic matter in high alpine lakes: Role of Saharan dust inputs and bacterial activity.

    Science.gov (United States)

    Mladenov, Natalie; Pulido-Villena, Elvira; Morales-Baquero, Rafael; Ortega-Retuerta, Eva; Sommaruga, Ruben; Reche, Isabel

    2008-01-01

    The effects of many environmental stressors such as UV radiation are mediated by dissolved organic matter (DOM) properties. Therefore, determining the factors shaping spatial and temporal patterns is particularly essential in the most susceptible, low dissolved organic carbon (DOC) lakes. We analyzed spatiotemporal variations in dissolved organic carbon concentration and dissolved organic matter optical properties (absorption and fluorescence) in 11 transparent lakes located above tree line in the Sierra Nevada Mountains (Spain), and we assessed potential external (evaporation and atmospheric deposition) and internal (bacterial abundance, bacterial production, chlorophyll a, and catchment vegetation) drivers of DOM patterns. At spatial and temporal scales, bacteria were related to chromophoric DOM (CDOM). At the temporal scale, water soluble organic carbon (WSOC) in dust deposition and evaporation were found to have a significant influence on DOC and CDOM in two Sierra Nevada lakes studied during the ice-free periods of 2000-2002. DOC concentrations and absorption coefficients at 320 nm were strongly correlated over the spatial scale (n = 11, R(2) = 0.86; p Pyrenees and Alps may be due to a combination of more extreme evaporation, and greater atmospheric dust deposition.

  13. Coccolithophore fluxes in the open tropical North Atlantic: influence of thermocline depth, Amazon water, and Saharan dust

    Science.gov (United States)

    Guerreiro, Catarina V.; Baumann, Karl-Heinz; Brummer, Geert-Jan A.; Fischer, Gerhard; Korte, Laura F.; Merkel, Ute; Sá, Carolina; de Stigter, Henko; Stuut, Jan-Berend W.

    2017-10-01

    Coccolithophores are calcifying phytoplankton and major contributors to both the organic and inorganic oceanic carbon pumps. Their export fluxes, species composition, and seasonal patterns were determined in two sediment trap moorings (M4 at 12° N, 49° W and M2 at 14° N, 37° W) collecting settling particles synchronously from October 2012 to November 2013 at 1200 m of water depth in the open equatorial North Atlantic. The two trap locations showed a similar seasonal pattern in total coccolith export fluxes and a predominantly tropical coccolithophore settling assemblage. Species fluxes were dominated throughout the year by lower photic zone (LPZ) taxa (Florisphaera profunda, Gladiolithus flabellatus) but also included upper photic zone (UPZ) taxa (Umbellosphaera spp., Rhabdosphaera spp., Umbilicosphaera spp., Helicosphaera spp.). The LPZ flora was most abundant during fall 2012, whereas the UPZ flora was more important during summer. In spite of these similarities, the western part of the study area produced persistently higher fluxes, averaging 241×107 ± 76×107 coccoliths m-2 d-1 at station M4 compared to only 66×107 ± 31×107 coccoliths m-2 d-1 at station M2. Higher fluxes at M4 were mainly produced by the LPZ species, favoured by the westward deepening of the thermocline and nutricline. Still, most UPZ species also contributed to higher fluxes, reflecting enhanced productivity in the western equatorial North Atlantic. Such was the case of two marked flux peaks of the more opportunistic species Gephyrocapsa muellerae and Emiliania huxleyi in January and April 2013 at M4, indicating a fast response to the nutrient enrichment of the UPZ, probably by wind-forced mixing. Later, increased fluxes of G. oceanica and E. huxleyi in October-November 2013 coincided with the occurrence of Amazon-River-affected surface waters. Since the spring and fall events of 2013 were also accompanied by two dust flux peaks, we propose a scenario in which atmospheric dust also

  14. Implementation and testing of a desert dust module in a regional climate model

    Directory of Open Access Journals (Sweden)

    A. S. Zakey

    2006-01-01

    Full Text Available In an effort to improve our understanding of aerosol impacts on climate, we implement a desert dust module within a regional climate model (RegCM. The dust module includes emission, transport, gravitational settling, wet and dry removal and calculations of dust optical properties. The coupled RegCM-dust model is used to simulate two dust episodes observed over the Sahara region (a northeastern Africa dust outbreak, and a west Africa-Atlantic dust outbreak observed during the SHADE "Saharan Dust Experiment", as well as a three month simulation over an extended domain covering the Africa-Europe sector. Comparisons with satellite and local aerosol optical depth measurements shows that the model captures the main spatial (both horizontal and vertical and temporal features of the dust distribution. The main model deficiency occurs in the representation of certain dynamical patterns observed during the SHADE case which is associated with an active easterly wave that contributed to the generation of the dust outbreak. The model appears suitable to conduct long term simulations of the effects of Saharan dust on African and European climate.

  15. The representation of dust transport and missing urban sources as major issues for the simulation of PM episodes in a Mediterranean area

    Directory of Open Access Journals (Sweden)

    E. Flaounas

    2009-10-01

    Full Text Available Due to its adverse effects on human health, atmospheric particulate matter (PM constitutes a growing challenge for air quality management. It is also a complex subject of study. The understanding of its atmospheric evolution is indeed made difficult by the wide number of sources and the numerous processes that govern its evolution in the troposphere. As a consequence, the representation of particulate matter in chemistry-transport models needs to be permanently evaluated and enhanced in order to refine our comprehension of PM pollution events and to propose consistent environmental policies. The study presented here focuses on two successive summer particulate pollution episodes that occurred on the French Mediterranean coast. We identify and analyze the constitutive elements of the first and more massive episode and we discuss their representation within a eulerian model.

    The results show that the model fails in reproducing the variability and the amplitude of dust import from western Africa, and that it constitutes a strong bias in PM daily forecasts. We then focus on the lack of diurnal variability in the model, which is attributed to missing urban sources in standard emission inventories, and notably the resuspension of particles by urban road traffic. Through a sensitivity study based on PM and NOx measurements, we assess the sensitivity of PM to local emissions and the need to reconsider road traffic PM sources. In parallel, by coupling the CHIMERE-DUST model outputs to our simulation, we show that the representation of transcontinental dust transport allows a much better representation of atmospheric particles in southern France, and that it is needed in the frame of air quality management for the quantification of the anthropogenic part of particulate matter pollution.

  16. Identification of mineral dust layers in high alpine snow packs

    Science.gov (United States)

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

    2017-04-01

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

  17. Depletion of tropospheric ozone associated with mineral dust outbreaks.

    Science.gov (United States)

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

    2016-10-01

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

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

    Science.gov (United States)

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

    2012-01-01

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

  19. Assimilating MODIS Aerosol Optical Depth Observations to Assess the Impact of Saharan Mineral Dust on the Genesis and Evolution of Hurricane Ernesto (2006)

    Science.gov (United States)

    Earl, K. S.; Chen, S. H.; Liu, Z.; Lin, H. C.

    2016-12-01

    Mineral dust can impact the atmosphere in two primary ways: (1) by directly absorbing, scattering, and emitting short and longwave radiation (radiative effects), and (2) by acting as cloud condensation or ice nuclei, indirectly affecting cloud optical and physical properties as well as precipitation processes (microphysical effects). During boreal summer, mineral dust plumes from North Africa are advected well into the tropical North Atlantic and can regularly be found in close proximity to tropical cyclones (TCs) or their seed disturbances, particularly in the Atlantic Main Development Region, potentially affecting their development and evolution. Many studies indicate that dust radiative effects within African dust plumes alter vertical and horizontal temperature gradients in such a way that may increase mid-level wind shear and static stability in the tropical Atlantic, possibly altering TC development and/or track. The effects of dust microphysics on TCs, on the other hand, are less certain but an increasing body of research suggests that they depend on TC strength, environmental conditions, and how close dust aerosols are to the storm center. Hurricane Ernesto (2006), whose precursor African Easterly Wave disturbance traveled across the Atlantic in close association with a large, persistent dust plume, is one such storm whose development may have been greatly influenced by dust physical processes. The storm developed only after the eventual dissipation of the plume in the eastern Caribbean. In this study, we examine the impact of mineral dust on the genesis and evolution of Hurricane Ernesto with a series of numerical experiments using a modified, dust-capable version of the WRF model and analyses created by assimilating meteorological and MODIS AOD observations within the GSI 3DVAR software framework. The impacts of MODIS AOD assimilation on the simulated dust distribution and forecasts of Ernesto's development are highlighted.

  20. Sensitivity of the dust cycle in a Chemistry-GCM

    Science.gov (United States)

    Gläser, G.; Kerkweg, A.; Wernli, H.

    2010-09-01

    Mineral dust is an important part of the atmospheric aerosol. The export of Saharan dust across the Atlantic Ocean to the South American continent is known to be an important source of nutrition to the rain forest and the sea. Dust mobilisation in deserts and long-range transport occurs in episodic events and is strongly influenced by synoptic-scale flow patterns. The scientific understanding of these processes, the resulting global dust distribution and the climate impact is still low. In this study, the atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC) is used to simulate the mineral dust cycle. We performed free-running 5-year time slice simulations and nudged experiments for selected dust emission episodes. Two different dust emission schemes and four different horizontal resolutions have been used for investigating their influence on the entire dust cycle. The horizontal resolutions T42 (~312 km), T63 (~208 km), T85 (~155 km) and T106 (~125 km) are explored. Independent of the horizontal resolution the "Balkanski" dust emission scheme simulates global maxima of the dust emissions and the dust column mass in the north-western part of India. Various observations indicate that in reality the maximum lies over the Sahara Desert. The "Tegen" dust emission scheme shows a much more realistic distribution. For all horizontal resolutions both schemes simulate dust emissions, total dust load and a dust life time within the range of the 15 GCMs participating in the AEROCOM-project (Aerosol Comparisons between Observations and Models). However, in T42 and T63 the northward transport of dust is too strong leading to unrealistic high column masses in high northern latitudes. The transport and subsequently the global dust distribution in T85 and T106 is much more sensible. The dust emission (total load) is 28 % (16 %) higher in T106 as in T85 which is traced back to higher wind velocities in T106. In addition to these climatological investigations, the

  1. Chemical characteristics of atmospheric fallout in the south of Xi'an during the dust episodes of 2001-2012 (NW China)

    Science.gov (United States)

    Li, Xiaoping; Feng, Linna; Huang, Chunchang; Yan, Xiangyang; Zhang, Xu

    2014-02-01

    Atmospheric fallouts (AFs) were collected in the south of Xi'an, NW China, during the dust episodes of 2001-2012. The chemical characteristics of total 68 AF samples including their chemical compositions, size distribution and magnetic susceptibility were studied. The contamination degree and the source of heavy metals in AF were also explored with enrichment factor method and multivariate statistical analysis. The results showed that the particle mass size distribution of AFs dominated by coarse particles (PM10-50) in dust days. The concentrations of 26 elements associated with AFs determined by wavelength dispersive X-ray fluorescence spectrometry (WDXRF) in studied sites varied from 92.90 to 188.10 mg kg-1 for Cr, 31.40 and 63.00 mg kg-1 for Cu, 16.60 to 167.30 for Pb and 106.60 to 196.80 for Zn. Their average concentrations found in this study were 139.22 ± 29.41 mg kg-1, 46.93 ± 10.56 mg kg-1, 78.42 ± 46.52 mg kg-1 and 150.61 ± 32.84 mg kg-1, respectively, which exceeded their corresponding recommended background values more than two times. While, other elements, such as Br varied from 1.10 to 5.90 with 3.34 ± 1.60 mg kg-1 mean, Cs from 2.90 to 10.90 with mean of 7.23 ± 2.47 mg kg-1, Ga between 6.90 and 20.80 with 15.23 ± 3.59 mg kg-1, Rb in the range of 62.10-124.20 with the average of 80.69 ± 16.89 mg kg-1, Y from 9.90 to 35.00 with 20.43 ± 6.27 mg kg-1 average, La from 29.60 to 54.20 with mean of 37.28 ± 8.28 mg kg-1 and V with average of 81.97 ± 8.93 mg kg-1 in the 57.7-92.10 mg kg-1. Multivariate statistical analysis (principal component analysis and clustering analysis) was suggested that the principal element elements, Al, Fe, Si, K, Ca, Na, Mg, coupled with the trace elements Co, V, Ce, Mn, Ni, Ga, Y, Rb, La, Br, Cs were predominated by crustal material sources, whereas, Cr, Cu, Ba, Sr, As, Pb and Zn were highly influenced by anthropogenic activities. Simultaneously, the water-soluble ions (WS-ions) of NH4+, SO42-, SO32-, NO3-, SiO44-, HSO4

  2. Trace Metals in Saharan Dust: The Use of in Vitro Bioaccessibility Extractions To Assess Potential Health Risks in a Dustier World: Chapter 3

    Science.gov (United States)

    Morman, Suzette A.; Garrison, Virginia H.; Plumlee, Geoffrey S.

    2013-01-01

    Exposure to fine particulate matter (PM) is acknowledged as a risk factor for human morbidity and mortality. Epidemiology and toxicology studies have focused on anthropogenic sources of PM and few consider contributions produced by natural processes (geogenic), or PM produced from natural sources as a result of human activities (geoanthropogenic PM). The focus of this study was to elucidate relationships between human/ecosystem health and dusts produced by a system transitioning from a dominantly natural to a geoanthropogenic PM source. As part of a larger study investigating the relationship between atmospheric transportation of African dust, human health, and coral reef declines, we examined dust samples sourced in Mali, Africa, collected using high-volume samplers from three sites (Mali, Tobago and U.S. Virgin Islands). Inhalation and ingestion exposure pathways were explored by filter extractions using simulated lung and gastric fluids. Bioaccessibility varied by metal and extraction fluid. Although too few samples were analyzed for robust statistics, concentrations for several metals decreased slightly while bioaccessibility increased at downwind sites.

  3. Desert Dust Outbreaks over Mediterranean Basin: A Modeling, Observational, and Synoptic Analysis Approach

    Directory of Open Access Journals (Sweden)

    F. Calastrini

    2012-01-01

    Full Text Available Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB, as they cause an anomalous increase of aerosol concentrations in the tropospheric column and often an increase of particulate matter at the ground level. To estimate the Saharan dust contribution to PM10, a significant dust intrusion event that occurred in June 2006 is investigated, joining numerical simulations and specific measurements. As a first step, a synoptic analysis of this episode is performed. Such analysis, based only on meteorological and aerosol optical thickness observations, does not allow the assessment of exhaustive informations. In fact, it is not possible to distinguish dust outbreaks transported above the boundary layer without any impact at the ground level from those causing deposition. The approach proposed in this work applies an ad hoc model chain to describe emission, transport and deposition dynamics. Furthermore, physical and chemical analyses (PIXE analysis and ion chromatography were used to measure the concentration of all soil-related elements to quantify the contribution of dust particles to PM10. The comparison between simulation results and in-situ measurements show a satisfying agreement, and supports the effectiveness of the model chain to estimate the Saharan dust contribution at ground level.

  4. The French component of the FENNEC Saharan Climate project 2011 Special Observing Period

    Science.gov (United States)

    Flamant, C.; Chaboureau, J.-P.; Kocha, C.; Lavaysse, C.; Schepanski, K.; Chazette, P.; Bock, O.; Marticorena, B.; Tulet, P.; Pelon, J.; Marnas, F.; Mokhtari, M.; Lafore, J.-P.; Roehrig, R.; Koulali Idrissi, A.; Tsamalis, C.; Chedin, A.

    2012-04-01

    The central Sahara has one of the most extreme climates on Earth. During the northern summer months, a large low pressure system caused by intense solar heating develops over a huge, largely uninhabited expanse of northern Mali, southern Algeria and eastern Mauritania. This Saharan heat low plays a pivotal role in the West African Monsoon. Based on this, the interested French, British and German communities have decided to propose the FENNEC project which aims at (i) characterizing the Saharan atmospheric boundary layer, (ii) evaluating its representation in regional and global models, and (iii) improving "aerosol" products issued from space-borne observations. A key element of this programme was the organization of an international field campaign in June 2011 over the Saharan heat low region, which will include both ground-based and airborne detachments. The Special Observing Period component of FENNEC-France included the implementation of the SAFIRE Falcon 20 to conduct research on the atmospheric boundary layer and the dust cycle of the Sahara, the installation of a remote sensing station in southern Spain, equipped with a backscatter lidar and a sunphotometer, to study the transport of desert dust to Europe, as well as a couple of GPS stations installed in southern Morocco to investigate the moisture inflow from the Atlantic Ocean into the Sahara. For the first time, the ALADIN and AROME models (5 and 24 km grid spacing, respectively) have been implemented operationally to provide forecasts of dust events over the Sahara and parts of the Sahel in June 2011 to assist in planning for airborne operations. This effort was complemented by the forecasts made with the Meso-NH model (5 and 20 km resolution). During the SOP period, the ground-based, airborne and space-borne observations have documented the evolution of dynamic properties of thermodynamic and the atmospheric boundary layer Saharan Africa (Mauritania and Mali) during the installation phase of the Saharan

  5. Characterization of Saharan dust ageing over the western Mediterranean Basin during a multi-intrusion event in June 2013 in the framework of the ADRIMED/ChArMEx campaign

    Science.gov (United States)

    Barragan, Ruben; Sicard, Michaël; Totems, Julien; François Léon, Jean; Baptiste Renard, Jean; Dulac, François; Mallet, Marc; Pelon, Jacques; Alados-Arboledas, Lucas; Amodeo, Aldo; José Granados-Muñoz, María; Boselli, Antonella; Bravo-Aranda, Juan Antonio; Muñoz-Porcar, Constantino; Chazette, Patrick; Comerón, Adolfo; D'Amico, Giuseppe; Wang, Xuan; Mona, Lucia; Pappalardo, Gelsomina

    2015-04-01

    In the framework of the ChArMEx (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/) initiative, a field campaign took place in the western Mediterranean Basin between 10 June and 5 July 2013 within the ADRIMED (Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) project. The scientific objectives of the campaign were the characterization of the different aerosol types found over the Mediterranean Sea and the calculation of their direct radiative forcing (column closure and regional scale). Two super-sites (Ersa, Corsica Island, France, and Lampedusa Island, Italy) were equipped with a complete set of instruments to measure in-situ aerosol physical, chemical and optical properties, as well as aerosol mixing state and vertical distribution and radiative fluxes. Four secondary sites were operated in Granada (Spain), Menorca Island (Spain), Rome (Italy) and Lecce (Italy). All sites were equipped with AERONET sunphotometers. The ground observations were supported by airborne measurements including 2 SAFIRE aircraft (ATR-42 equipped with in situ measurements (10 June - 5 July) and Falcon-20 (17 June - 5 July) with the LNG aerosol lidar) and sounding and drifting balloons launched by CNES from Menorca Island and carrying the LOAC particle counter/sizer (16 June - 4 July). Satellite products from MODIS, MSG/SEVIRI and CALIOP provided additional observations. In several occasions corresponding to aerosol loads of different types, the aircraft flew near EARLINET/ACTRIS (European Aerosol Research Lidar Network / Aerosols, Clouds, and Trace gases Research InfraStructure Network, http://www.actris.net/) lidar stations. This work is focused on a moderate multi-intrusion Saharan dust event occurred over the western Mediterranean Basin (WMB) during the period 14 - 27 June. The dust plumes were detected by the EARLINET stations of Granada, Barcelona, Naples, Potenza, Lecce and Serra la Nave (Sicily) and by the ChArMEx lidar

  6. Fine-scale application of WRF-CAM5 during a dust storm episode over East Asia: Sensitivity to grid resolutions and aerosol activation parameterizations

    Science.gov (United States)

    Wang, Kai; Zhang, Yang; Zhang, Xin; Fan, Jiwen; Leung, L. Ruby; Zheng, Bo; Zhang, Qiang; He, Kebin

    2018-03-01

    An advanced online-coupled meteorology and chemistry model WRF-CAM5 has been applied to East Asia using triple-nested domains at different grid resolutions (i.e., 36-, 12-, and 4-km) to simulate a severe dust storm period in spring 2010. Analyses are performed to evaluate the model performance and investigate model sensitivity to different horizontal grid sizes and aerosol activation parameterizations and to examine aerosol-cloud interactions and their impacts on the air quality. A comprehensive model evaluation of the baseline simulations using the default Abdul-Razzak and Ghan (AG) aerosol activation scheme shows that the model can well predict major meteorological variables such as 2-m temperature (T2), water vapor mixing ratio (Q2), 10-m wind speed (WS10) and wind direction (WD10), and shortwave and longwave radiation across different resolutions with domain-average normalized mean biases typically within ±15%. The baseline simulations also show moderate biases for precipitation and moderate-to-large underpredictions for other major variables associated with aerosol-cloud interactions such as cloud droplet number concentration (CDNC), cloud optical thickness (COT), and cloud liquid water path (LWP) due to uncertainties or limitations in the aerosol-cloud treatments. The model performance is sensitive to grid resolutions, especially for surface meteorological variables such as T2, Q2, WS10, and WD10, with the performance generally improving at finer grid resolutions for those variables. Comparison of the sensitivity simulations with an alternative (i.e., the Fountoukis and Nenes (FN) series scheme) and the default (i.e., AG scheme) aerosol activation scheme shows that the former predicts larger values for cloud variables such as CDNC and COT across all grid resolutions and improves the overall domain-average model performance for many cloud/radiation variables and precipitation. Sensitivity simulations using the FN series scheme also have large impacts on

  7. Atmospheric dust modeling from meso to global scales with the online NMMB/BSC-Dust model – Part 2: Experimental campaigns in Northern Africa

    Directory of Open Access Journals (Sweden)

    K. Haustein

    2012-03-01

    Full Text Available The new NMMB/BSC-Dust model is intended to provide short to medium-range weather and dust forecasts from regional to global scales. It is an online model in which the dust aerosol dynamics and physics are solved at each model time step. The companion paper (Pérez et al., 2011 develops the dust model parameterizations and provides daily to annual evaluations of the model for its global and regional configurations. Modeled aerosol optical depth (AOD was evaluated against AERONET Sun photometers over Northern Africa, Middle East and Europe with correlations around 0.6–0.7 on average without dust data assimilation. In this paper we analyze in detail the behavior of the model using data from the Saharan Mineral dUst experiment (SAMUM-1 in 2006 and the Bodélé Dust Experiment (BoDEx in 2005. AOD from satellites and Sun photometers, vertically resolved extinction coefficients from lidars and particle size distributions at the ground and in the troposphere are used, complemented by wind profile data and surface meteorological measurements. All simulations were performed at the regional scale for the Northern African domain at the expected operational horizontal resolution of 25 km. Model results for SAMUM-1 generally show good agreement with satellite data over the most active Saharan dust sources. The model reproduces the AOD from Sun photometers close to sources and after long-range transport, and the dust size spectra at different height levels. At this resolution, the model is not able to reproduce a large haboob that occurred during the campaign. Some deficiencies are found concerning the vertical dust distribution related to the representation of the mixing height in the atmospheric part of the model. For the BoDEx episode, we found the diurnal temperature cycle to be strongly dependant on the soil moisture, which is underestimated in the NCEP analysis used for model initialization. The low level jet (LLJ and the dust AOD over the Bodélé are

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

    Science.gov (United States)

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

    2012-01-01

    The new NMMB/BSC-Dust model is intended to provide short to medium-range weather and dust forecasts from regional to global scales. It is an online model in which the dust aerosol dynamics and physics are solved at each model time step. The companion paper (Perez et al., 2011) develops the dust model parameterizations and provides daily to annual evaluations of the model for its global and regional configurations. Modeled aerosol optical depth (AOD) was evaluated against AERONET Sun photometers over Northern Africa, Middle East and Europe with correlations around 0.6-0.7 on average without dust data assimilation. In this paper we analyze in detail the behavior of the model using data from the Saharan Mineral dUst experiment (SAMUM-1) in 2006 and the Bodele Dust Experiment (BoDEx) in 2005. AOD from satellites and Sun photometers, vertically resolved extinction coefficients from lidars and particle size distributions at the ground and in the troposphere are used, complemented by wind profile data and surface meteorological measurements. All simulations were performed at the regional scale for the Northern African domain at the expected operational horizontal resolution of 25 km. Model results for SAMUM-1 generally show good agreement with satellite data over the most active Saharan dust sources. The model reproduces the AOD from Sun photometers close to sources and after long-range transport, and the dust size spectra at different height levels. At this resolution, the model is not able to reproduce a large haboob that occurred during the campaign. Some deficiencies are found concerning the vertical dust distribution related to the representation of the mixing height in the atmospheric part of the model. For the BoDEx episode, we found the diurnal temperature cycle to be strongly dependant on the soil moisture, which is underestimated in the NCEP analysis used for model initialization. The low level jet (LLJ) and the dust AOD over the Bodélé are well reproduced

  9. Evaluation of atmospheric dust prediction models using ground-based observations

    Science.gov (United States)

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

    2013-04-01

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

  10. Long-term EARLINET dust observations

    Science.gov (United States)

    Mona, Lucia; Amiridis, Vassilis; Amodeo, Aldo; Binietoglou, Ioannis; D'Amico, Giuseppe; Schwarz, Anja; Papagiannopoulos, Nikolaos; Papayannis, Alexandros; Sicard, Michael; Comeron, Adolfo; Pappalardo, Gelsomina

    2015-04-01

    Systematic observations of Saharan dust events over Europe are performed from May 2000 by EARLINET, the European Aerosol Research LIdar NETwork. EARLINET is a coordinated network of stations that make use of advanced lidar methods for the vertical profiling of aerosols. The backbone of EARLINET network is a common schedule for performing the measurements and the quality assurance of instruments/data. Particular attention is paid to monitoring the Saharan dust intrusions over the European continent. The geographical distribution of the EARLINET stations is particularly appealing for the dust observation, with stations located all around the Mediterranean and in the center of the Mediterranean (Italian stations) where dust intrusions are frequent, and with several stations in the central Europe where dust penetrates occasionally. All aerosol backscatter and extinction profiles related to observations collected during these alerts are grouped in the devoted "Saharan dust" category of the EARLINET database. This category consists of about 4700 files (as of December 2013). Case studies involving several stations around Europe selected from this long-term database have been provided the opportunity to investigate dust modification processes during transport over the continent. More important, the long term EARLINET dust monitoring allows the investigation of the horizontal and vertical extent of dust outbreaks over Europe and the climatological analysis of dust optical intensive and extensive properties at continental scale. This long-term database is also a unique tool for a systematic comparison with dust model outputs and satellite-derived dust products. Because of the relevance for both dust modeling and satellite retrievals improvement, results about desert dust layers extensive properties as a function of season and source regions are investigated and will be presented at the conference. First comparisons with models outputs and CALIPSO dust products will be

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

    Science.gov (United States)

    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

  12. Evaluation of the desert dust effects on global, direct and diffuse spectral ultraviolet irradiance

    Directory of Open Access Journals (Sweden)

    R. Román

    2013-01-01

    Full Text Available This paper presents a study of a strong desert dust episode over the Iberian Peninsula, and its effect on the spectral ultraviolet (UV irradiance in Granada, Spain. Remote sensing measurements, forecast models, and synoptic analysis are used to identify a Saharan desert dust outbreak that affected the Iberian Peninsula starting 20 July 2009. Additionally, a Bentham DMc150 spectroradiometer is employed to obtain global, direct and diffuse spectral UV irradiances every 15 minutes in Granada. The desert dust caused a large attenuation of the direct UV irradiance (up to 55%, while the diffuse UV irradiance increased up to 40% at 400 nm. The UVSPEC/LibRadtran radiative transfer model is used to study the spectral dependence of the experimental UV irradiance ratios (ratios of spectral irradiance for the day with the highest aerosol load to that measured in days with low–moderate load. The spectral increase or decrease of the UV direct irradiance ratios depends on a new parameter: a threshold wavelength. The spectral dependence of the UV diffuse irradiance ratio can be explained because under the influence of the intense dust outbreak, the Mie scattering by aerosols at shorter wavelengths is stronger than the Rayleigh scattering by gases. Finally, the sensitivity analysis of the aerosol absorption properties shows a substantial attenuation of UV spectral irradiance with a weak spectral dependence.

  13. Long-range transport and mixing of aerosol sources during the 2013 North American biomass burning episode: analysis of multiple lidar observations in the western Mediterranean basin

    Directory of Open Access Journals (Sweden)

    G. Ancellet

    2016-04-01

    Full Text Available Long-range transport of biomass burning (BB aerosols between North America and the Mediterranean region took place in June 2013. A large number of ground-based and airborne lidar measurements were deployed in the western Mediterranean during the Chemistry-AeRosol Mediterranean EXperiment (ChArMEx intensive observation period. A detailed analysis of the potential North American aerosol sources is conducted including the assessment of their transport to Europe using forward simulations of the FLEXPART Lagrangian particle dispersion model initialized using satellite observations by MODIS and CALIOP. The three-dimensional structure of the aerosol distribution in the ChArMEx domain observed by the ground-based lidars (Minorca, Barcelona and Lampedusa, a Falcon-20 aircraft flight and three CALIOP tracks, agrees very well with the model simulation of the three major sources considered in this work: Canadian and Colorado fires, a dust storm from western US and the contribution of Saharan dust streamers advected from the North Atlantic trade wind region into the westerlies region. Four aerosol types were identified using the optical properties of the observed aerosol layers (aerosol depolarization ratio, lidar ratio and the transport model analysis of the contribution of each aerosol source: (i pure BB layer, (ii weakly dusty BB, (iii significant mixture of BB and dust transported from the trade wind region, and (iv the outflow of Saharan dust by the subtropical jet and not mixed with BB aerosol. The contribution of the Canadian fires is the major aerosol source during this episode while mixing of dust and BB is only significant at an altitude above 5 km. The mixing corresponds to a 20–30 % dust contribution in the total aerosol backscatter. The comparison with the MODIS aerosol optical depth horizontal distribution during this episode over the western Mediterranean Sea shows that the Canadian fire contributions were as large as the direct

  14. [Amnestic episodes].

    Science.gov (United States)

    Riedmann, G; Lindner, M; Barolin, G S

    1988-12-31

    Amnesic episodes, by no means infrequent occurrences, are likely to trigger off anxiety in the patient and to evade adequate diagnostic interpretation. They consist of an isolated disturbance of short-term memory, manifesting itself as a permanent memory gap. The clinical features may vary from a conspicuous behaviour with stereotype repetition of questions to a completely inconspicuous picture with flawless execution of even highly differentiated behaviour patterns. The vegetative state may either be completely undisturbed or vary from mild impairment with nausea and vertigo to marked vegetative disorder. We are advocating a classification in 3 groups: a) "Genuine" amnesic states as symptoms of impaired blood flow in the basilar system in the absence of other etiological clues. b) "Symptomatic" amnesic episodes with tangible pathogenic factors, such as injury of the head and cervical spine, epilepsy, intoxication with various agents. The "genuine" amnesic states can also be regarded as transitory ischemic attacks of the basilar system. They show the following criteria: preponderance in females beyond middle age, duration of several hours, relatively high frequency of vascular risk factors and degenerative changes in the cervical spine, often triggered off by stress on the cervical spine, low tendency towards recurrence, general clinical benignity. In consequence, we stress the importance of etiological clarification before the onset of therapy. After the diagnosis of "genuine" amnesic state has been established, treatment has to be in accordance with the principles of basilar stroke therapy with subsequent vascular prophylaxis. Nevertheless, because of possible therapeutic or forensic consequences, the "symptomatic" states have to be kept in mind.

  15. Single Particle Analysis by Combined Chemical Imaging to Study Episodic Air Pollution Events in Vienna

    Science.gov (United States)

    Ofner, Johannes; Eitenberger, Elisabeth; Friedbacher, Gernot; Brenner, Florian; Hutter, Herbert; Schauer, Gerhard; Kistler, Magdalena; Greilinger, Marion; Lohninger, Hans; Lendl, Bernhard; Kasper-Giebl, Anne

    2017-04-01

    The aerosol composition of a city like Vienna is characterized by a complex interaction of local emissions and atmospheric input on a regional and continental scale. The identification of major aerosol constituents for basic source appointment and air quality issues needs a high analytical effort. Exceptional episodic air pollution events strongly change the typical aerosol composition of a city like Vienna on a time-scale of few hours to several days. Analyzing the chemistry of particulate matter from these events is often hampered by the sampling time and related sample amount necessary to apply the full range of bulk analytical methods needed for chemical characterization. Additionally, morphological and single particle features are hardly accessible. Chemical Imaging evolved to a powerful tool for image-based chemical analysis of complex samples. As a complementary technique to bulk analytical methods, chemical imaging can address a new access to study air pollution events by obtaining major aerosol constituents with single particle features at high temporal resolutions and small sample volumes. The analysis of the chemical imaging datasets is assisted by multivariate statistics with the benefit of image-based chemical structure determination for direct aerosol source appointment. A novel approach in chemical imaging is combined chemical imaging or so-called multisensor hyperspectral imaging, involving elemental imaging (electron microscopy-based energy dispersive X-ray imaging), vibrational imaging (Raman micro-spectroscopy) and mass spectrometric imaging (Time-of-Flight Secondary Ion Mass Spectrometry) with subsequent combined multivariate analytics. Combined chemical imaging of precipitated aerosol particles will be demonstrated by the following examples of air pollution events in Vienna: Exceptional episodic events like the transformation of Saharan dust by the impact of the city of Vienna will be discussed and compared to samples obtained at a high alpine

  16. Sub-Saharan Africa

    African Journals Online (AJOL)

    Sub-Saharan Africa. Inbound tourism movement has emerged as an important factor in the preva- lence of the disease, after education. Defects of quality of data would not be far fetched, given the lack of logistics and financial resources of most governments for the exercise, possible political manipulations and ideological ...

  17. SUB-SAHARAN AFRICA

    African Journals Online (AJOL)

    (Meade and l'iot, 1993). Such findings which were carried out at different settings of develop' ing countries including Sub-Saharan Africa, appear conflicting and need to be reconciled through a sub-regional survey. Touching on the preventive mechanisms, especially the use of condoms, the educated are more likely to ...

  18. Andromeda's Dust

    OpenAIRE

    Draine, B.T.; Aniano, G.; Krause, Oliver; Groves, Brent; Sandstrom, Karin; Braun, Robert; Leroy, Adam; Klaas, Ulrich; Linz, Hendrik; Rix, Hans-Walter; Schinnerer, Eva; Schmiedeke, Anika; Walter, Fabian

    2013-01-01

    Spitzer Space Telescope and Herschel Space Observatory imaging of M31 is used, with a physical dust model, to construct maps of dust surface density, dust-to-gas ratio, starlight heating intensity, and PAH abundance, out to R=25kpc. The global dust mass is M_d=5.4x10^7Msol, the global dust/H mass ratio is M_d/M_H=0.0081, and the global PAH abundance is =0.039. The dust surface density has an inner ring at R=5.6kpc, a maximum at R=11.2kpc, and an outer ring at R=15.1kpc. The dust/gas ratio var...

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

    Science.gov (United States)

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

  20. PERSPECTIVE: Dust, fertilization and sources

    Science.gov (United States)

    Remer, Lorraine A.

    2006-11-01

    Aerosols, tiny suspended particles in the atmosphere, play an important role in modifying the Earth's energy balance and are essential for the formation of cloud droplets. Suspended dust particles lifted from the world's arid regions by strong winds contain essential minerals that can be transported great distances and deposited into the ocean or on other continents where productivity is limited by lack of usable minerals [1]. Dust can transport pathogens as well as minerals great distance, contributing to the spread of human and agricultural diseases, and a portion of dust can be attributed to human activity suggesting that dust radiative effects should be included in estimates of anthropogenic climate forcing. The greenish and brownish tints in figure 1 show the wide extent of monthly mean mineral dust transport, as viewed by the MODerate resolution Imaging Spectroradiometer (MODIS) satellite sensor. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite Figure 1. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite. The brighter the color, the greater the aerosol loading. Red and reddish tints indicate aerosol dominated by small particles created primarily from combustion processes. Green and brownish tints indicate larger particles created from wind-driven processes, usually transported desert dust. Note the bright green band at the southern edge of the Saharan desert, the reddish band it must cross if transported to the southwest and the long brownish transport path as it crosses the Atlantic to South America. Image courtesy of the NASA Earth Observatory (http://earthobservatory.nasa.gov). Even though qualitatively we recognize the extent and importance of dust transport and the role that it plays in fertilizing nutrient-limited regions, there is much that is still unknown. We are just now beginning to quantify the amount of dust that exits one continental region and the

  1. Sub-Saharan Africa Report

    National Research Council Canada - National Science Library

    1986-01-01

    .... This report contains articles from Sub-Saharan Africa, Angola, Ethiopia, Ghana, Mozambique, Namibia, Sierra Leone, Togo, Zambia, and South Africa, the articles deal mainly with Politics, Sociology...

  2. Sub-Saharan Africa Report

    National Research Council Canada - National Science Library

    1987-01-01

    Partial Contents: Sub Saharan Africa, Military Exercise, Radio Commentary, Stock Exchange, Prime Minister, Economic, Domestic Service, Armed Forces, Health, Organizations, Death, International Service, Foreign Policy...

  3. Sub-Saharan Africa Report

    National Research Council Canada - National Science Library

    1985-01-01

    .... This report from Sub-Saharan Africa, Benin, Botswana, Burkina, Cameroon, Chad, Comoros, Ethiopia, Ghana, Guinea, Kenya, Liberia, Madagascar, Mauritius, Mozambique, Sierra Leone, Somalia, South Africa...

  4. Sub-Saharan Africa Report

    National Research Council Canada - National Science Library

    1985-01-01

    .... This report on Sub-Saharan Africa, Angola, Botswana, Burkina, Cameroon, Ghana, Ivory Coast, Liberia, Madagascar, Malawi, Mali, Mozambique, Namibia, Senegal, South Africa, and Swaziland, contains...

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

    Science.gov (United States)

    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...

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

    Science.gov (United States)

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

  7. Sub-Saharan Africa Report

    National Research Council Canada - National Science Library

    1985-01-01

    This is Sub Saharan Africa Report. It contains the issues with different topics on Inter African Affairs, Angola, Cameroon, Cape Verde, Chad, Congo, Ethiopia, Gambia, Ghana, Guinea, Guinea Bissau, Kenya, madagascar, Mozambique...

  8. WMO SDS-WAS NAMEE Regional Center: Towards continuous evaluation of dust models in Northern Africa

    Science.gov (United States)

    Basart, Sara; García-Castillo, Gerardo; Cuevas, Emilio; Terradellas, Enric

    2016-04-01

    frequently affected by intrusions of Saharan dust. Regional Node are evaluated during two years (2013-2014) with observations recorded in the Sahelian region and Canary Islands. Additionally, since the data sets of weather records have an excellent spatial and temporal coverage, observations of horizontal visibility included in meteorological reports are used as an alternative way to monitor dust events in near-real-time (NRT). Recently, a new visibility product that includes more than 1,500 METAR stations has implemented in the SDS-WAS NAMEE Regional Center. The present contribution also will demonstrate how the visibility can complement the information provided by other observing systems (air quality monitoring stations, sun photometers, vertical profilers or satellite products) and numerical simulations presenting its application in tracking several dust episodes. Otherwise, the vertical distribution of aerosol also influences the radiative effect at the top of the atmosphere, especially when aerosols have strong absorption of shortwave radiation. The free troposphere contribution to aerosol optical depth (AOD) and the altitude of lofted layers are provided thanks to the vertical profiling capability of the lidar/ceilomenter technique. Currently, a lidar located in Dakar (Senegal) and a ceilometer in Santa Cruz de Tenerife (Canary Islands, Spain) provide near-real-time (NRT) vertical profiles of aerosols, which are compared with those simulated by models.

  9. Origin and pathways of the mineral dust transport to two Spanish EARLINET sites: Effect on the observed columnar and range-resolved dust optical properties

    Science.gov (United States)

    Mandija, Florian; Sicard, Michaël; Comerón, Adolfo; Alados-Arboledas, Lucas; Guerrero-Rascado, Juan Luis; Barragan, Ruben; Bravo-Aranda, Juan Antonio; Granados-Muñoz, Maria Jose; Lyamani, Hassan; Muñoz Porcar, Constantino; Rocadenbosch, Francisco; Rodríguez, Alejandro; Valenzuela, Antonio; García Vizcaíno, David

    2017-05-01

    In this paper, is presented a method for estimation of the effect of the transport process to aerosol optical properties. Aerosol optical data retrieved by lidars and sun-photometer measurements, are applied to Saharan dust events observed simultaneously at the two EARLINET/AERONET sites of Barcelona and Granada during the periods of June-September of 2012 and 2013. For this purpose, elastic lidar profiles and sun-photometer columnar retrievals are analyzed together with satellite observations and dust forecast models. Granada presents more than twice Saharan dust outbreaks compared to Barcelona. The scenarios favoring the Saharan dust outbreaks are identified in both places. The mineral dust originating in the Sahara region and arriving at both stations is usually transport wither over the Atlas Mountains or through an Atlantic pathway. Analyses of dust events affecting both stations reveal how differences in the transport process lead to differences in the aerosol optical properties measured at each station. Mean dust related Ångström exponent is 1.8 times higher in Barcelona than in Granada. This difference is a result of the additional contribution of anthropogenic aerosol, mainly in the aerosol fine mode, during the transport of the mineral dust plume over the Iberian Peninsula.

  10. Response of the Eastern Mediterranean microbial ecosystem to dust and dust affected by acid processing in the atmosphere

    Directory of Open Access Journals (Sweden)

    Michael David Krom

    2016-08-01

    Full Text Available Acid processes in the atmosphere, particularly those caused by anthropogenic acid gases, increase the amount of bioavailable P in dust and hence are predicted to increase microbial biomass and primary productivity when supplied to oceanic surface waters. This is likely to be particularly important in the Eastern Mediterranean Sea (EMS, which is P limited during the winter bloom and N&P co-limited for phytoplankton in summer. However, it is not clear how the acid processes acting on Saharan dust will affect the microbial biomass and primary productivity in the EMS. Here, we carried out bioassay manipulations on EMS surface water on which Saharan dust was added as dust (Z, acid treated dust (ZA, dust plus excess N (ZN and acid treated dust with excess N (ZNA during springtime (May 2012 and measured bacterioplankton biomass, metabolic and other relevant chemical and biological parameters. We show that acid treatment of Saharan dust increased the amount of bioavailable P supplied by a factor of ~40 compared to non-acidified dust (18.4 nmoles P mg-1 dust vs. 0.45 nmoles P mg-1 dust, respectively. The increase in chlorophyll, primary and bacterial productivity for treatments Z and ZA were controlled by the amount of N added with the dust while those for treatments ZN and ZNA (in which excessive N was added were controlled by the amount of P added. These results confirm that the surface waters were N&P co-limited for phytoplankton during springtime. However, total chlorophyll and primary productivity in the acid treated dust additions (ZA and ZNA were less than predicted from that calculated from the amount of the potentially limiting nutrient added. This biological inhibition was interpreted as being due to labile trace metals being added with the acidified dust. A probable cause for this biological inhibition was the addition of dissolved Al, which forms potentially toxic Al nanoparticles when added to seawater. Thus, the effect of anthropogenic acid

  11. Dust storms

    OpenAIRE

    Jin, Bihui; Rousseau, Ronald

    2008-01-01

    Dust storms are remarkable natural phenomena. They affect many countries in the Northern Hemisphere and, as such, have become an interesting research topic. We show that nowadays China is the number one publishing country of articles related to their study. On a world scale the number of publications on this topic is increasing exponentially.

  12. Desert dust outbreaks and respiratory morbidity in Athens, Greece.

    Science.gov (United States)

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

    2017-07-01

    Ambient particulate matter (PM) has an adverse effect on respiratory morbidity. Desert dust outbreaks contribute to increased PM levels but the toxicity of desert dust mixed with anthropogenic pollutants needs clarification. We identified 132 days with desert dust episodes and 177 matched days by day of the week, season, temperature and humidity between 2001 and 2006 in Athens, Greece. We collected data on regulated pollutants and daily emergency outpatient visits and admissions for respiratory causes. We applied Poisson regression models adjusting for confounding effects of seasonality, meteorology, holidays and influenza epidemics. We evaluated the sensitivity of our results to co-pollutant exposures and effect modification by age and sex. A 10 μg/m3 increase in PM10 concentration was associated with 1.95% (95% confidence interval (CI): 0.02%, 3.91%) increase in respiratory emergency room visits. No significant interaction with desert dust episodes was observed. Compared with non-dust days, there was a 47% (95% CI: 29%, 68%) increase in visits in dust days not adjusting for PM10. Desert dust days were associated with higher numbers of emergency room visits for asthma, chronic obstructive pulmonary disease and respiratory infections with increases of 38%, 57% and 60%, respectively (p desert dust days and were further confounded by co-pollutants. Desert dust episode days are associated with higher respiratory emergency room visits and hospital admissions. This effect is insufficiently explained by increased PM10 levels.

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

    Science.gov (United States)

    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 O3 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 (RFTOA). 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 RFTOA to a value of -8.1Wm-2 (long-term climatological value ~-1.5Wm-2). The aerosol RFTOA 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.

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

    Science.gov (United States)

    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

  15. Integrated Study of Dust-air Pollution Interaction over the Eastern Mediterranean

    Science.gov (United States)

    Mohamed, A.; Metzger, S. M.; Klingmüller, K.; Mamouri, R. E.; Astitha, M.; Ansmann, A.; Hadjimitsis, D.; Barrie, L. A.; Levin, Z.; Lelieveld, J.

    2015-12-01

    Interactions of desert dust and air pollution over the Eastern Mediterranean (EM) have been studied, focusing on two distinct dust transport events on 22 and 28 September 2011. The atmospheric chemistry-climate model EMAC has been used at about 50 km grid spacing on global scale, applying an online dust emission scheme and calcium as a proxy for dust reactivity. EMAC includes a detailed tropospheric chemistry mechanism, aerosol microphysics and thermodynamics schemes to describe dust "aging''. The model is evaluated using ground-based observations for aerosol concentrations and aerosol optical depth, LIDAR as well as satellite observations. Simulation results and back trajectory analysis show that the development of synoptic disturbances over the EM can enhance dust transport from the Sahara and Arabian deserts in frontal systems that also carry air pollution to the EM. The frontal systems are associated with precipitation that control the dust removal. Our results show the importance of chemical aging of dust, which increases particles size, dust deposition and scavenging efficiency during transport, overall reducing the life-time relative to non-aged dust particles. The relatively long travel periods of Saharan dust result in more sustained aging compared to Arabian dust. Sensitivity simulations indicate three times more dust deposition of aged relative to pristine dust, which significantly decreases the dust lifetime and loading.

  16. Dust Opacities*

    OpenAIRE

    Min Michiel

    2015-01-01

    Dust particles are the dominant source of opacity at (almost) all wavelengths and in (almost) all regions of protoplanetary disks. By this they govern the transport of energy through the disk and thus the thermal structure. Furthermore, their spectral properties determine the low resolution spectral signature observed at infrared wavelengths. The infrared resonances that can be observed using low resolution infrared spectroscopy can be used to identify the composition and size distribution of...

  17. Interstellar Dust

    OpenAIRE

    Compiegne, M.

    2003-01-01

    In the interstellar medium of the Milky Way, certain elements -- e.g., Mg, Si, Al, Ca, Ti, Fe -- reside predominantly in interstellar dust grains. These grains absorb, scatter, and emit electromagnetic radiation, heat the interstellar medium by photoelectric emission, play a role in the ionization balance of the gas, and catalyze the formation of molecules, particularly H2. I review the state of our knowledge of the composition and sizes of interstellar grains, including what we can learn fro...

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

    Science.gov (United States)

    Davara, Fernando; de la Cruz, Antonio

    2004-10-01

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

  19. Genetics Home Reference: episodic ataxia

    Science.gov (United States)

    ... Facebook Twitter Home Health Conditions Episodic ataxia Episodic ataxia Printable PDF Open All Close All Enable Javascript to view the expand/collapse boxes. Description Episodic ataxia is a group of related conditions that affect ...

  20. Dust agglomeration

    Science.gov (United States)

    2000-01-01

    John Marshall, an investigator at Ames Research Center and a principal investigator in the microgravity fluid physics program, is studying the adhesion and cohesion of particles in order to shed light on how granular systems behave. These systems include everything from giant dust clouds that form planets to tiny compressed pellets, such as the ones you swallow as tablets. This knowledge should help us control the grains, dust, and powders that we encounter or use on a daily basis. Marshall investigated electrostatic charge in microgravity on the first and second U.S. Microgravity Laboratory shuttle missions to see how grains aggregate, or stick together. With gravity's effects eliminated on orbit, Marshall found that the grains of sand that behaved ever so freely on Earth now behaved like flour. They would just glom together in clumps and were quite difficult to disperse. That led to an understanding of the prevalence of the electrostatic forces. The granules wanted to aggregate as little chains, like little hairs, and stack end to end. Some of the chains had 20 or 30 grains. This phenomenon indicated that another force, what Marshall believes to be an electrostatic dipole, was at work.(The diagram on the right emphasizes the aggregating particles in the photo on the left, taken during the USML-2 mission in 1995.)

  1. Episodic Aging and End States of Comets

    Science.gov (United States)

    Sekanina, Zdenek

    2008-01-01

    It is known that comets are aging very rapidly on cosmic scales, because they rapidly shed mass. The processes involved are (i) normal activity - sublimation of ices and expulsion of dust from discrete emission sources on and/or below the surface of a comet's nucleus, and (ii) nuclear fragmentation. Both modes are episodic in nature, the latter includes major steps in the comet's life cycle. The role and history of dynamical techniques used are described and results on mass losses due to sublimation and dust expulsion are reviewed. Studies of split comets, Holmes-like exploding comets, and cataclysmically fragmenting comets show that masses of 10 to 100 million tons are involved in the fragmentation process. This and other information is used to investigate the nature of comets' episodic aging. Based on recent advances in understanding the surface morphology of cometary nuclei by close-up imaging, a possible mechanism for large-scale fragmentation events is proposed and shown to be consistent with evidence available from observations. Strongly flattened pancake-like shapes appear to be required for comet fragments by conceptual constraints. Possible end states are briefly examined.

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

    Science.gov (United States)

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

    2010-12-01

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

  3. Perinatal psychiatric episodes

    DEFF Research Database (Denmark)

    Munk-Olsen, Trine; Maegbaek, M L; Johannsen, B M

    2016-01-01

    and childbirth, which suggests differences in the underlying etiology. We further speculate varying treatment incidence and prevalence in pregnancy vs postpartum may indicate that the current Diagnostic and Statistical Manual of Mental Disorders-5 peripartum specifier not adequately describes at-risk periods......Perinatal psychiatric episodes comprise various disorders and symptom severity, which are diagnosed and treated in multiple treatment settings. To date, no studies have quantified the incidence and prevalence of perinatal psychiatric episodes treated in primary and secondary care, which we aimed...... psychiatric facilities, 2.5 births were followed by an episode treated at outpatient psychiatric facility and 12 births by GP-provided pharmacological treatment. We interpret our results the following way: treated severe and moderate psychiatric disorders have different risk patterns in relation to pregnancy...

  4. Sub-Saharan Botanical Collections

    DEFF Research Database (Denmark)

    Demissew, Sebsebe; Beentje, Henk; Cheek, Martin

    2015-01-01

    Many historical specimens from sub-Saharan Africa are only found in European herbaria, but a higher number of newer specimens than widely assumed are kept in African herbaria, with a concentration in eastern and southern parts of the continent. Many of these herbaria were initiated in connection ...... in collaboration between African and European herbaria, and the increasing digitization of herbaria and the general development of relevant services on the Internet, which provides new possibilities for botanical studies in Africa....

  5. Desert Dust Satellite Retrieval Intercomparison

    Science.gov (United States)

    Carboni, E.; Thomas, G. E.; Sayer, A. M.; Siddans, R.; Poulsen, C. A.; Grainger, R. G.; Ahn, C.; Antoine, D.; Bevan, S.; Braak, R.; hide

    2012-01-01

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

  6. Episodic foresight and schizophrenia.

    Science.gov (United States)

    Lyons, Amanda D; Henry, Julie D; Rendell, Peter G; Robinson, Gail; Suddendorf, Thomas

    2016-06-01

    People with schizophrenia have difficulty engaging in specific future-directed thoughts and behaviours, such as generating phenomenological characteristics of future events (a component of episodic foresight), and executing directed preparatory behaviours (a component of prospective memory). However, it remains unclear whether they also exhibit difficulties using episodic foresight to appropriately guide future-directed behaviours. People with schizophrenia and non-clinical controls were administered a behavioural measure that met strict criteria for assessing episodic foresight. In keeping with our focus on the functional application of foresight, this measure required participants to identify a problem, self-generate a resolution, and execute the appropriate future-directed intention. Relative to controls, people with schizophrenia were less likely to spontaneously acquire items that would later allow a problem to be solved, and were also less likely to subsequently use these items to solve the problems. There was no interaction between group and task, indicating that these two components of foresight were disrupted to an equivalent degree. In the clinical (but not the control) group, item acquisition and item use were correlated with general cognitive capacity. No significant associations with clinical variables emerged. The capacity to apply episodic foresight in a functionally adaptive way is disrupted in schizophrenia and may at least partially reflect broader cognitive dysfunction. Future work is now needed to clarify the implications of these difficulties in everyday life, as well as how these difficulties might be remediated. People with schizophrenia have known difficulties with episodic foresight, and it now appears that those difficulties extend to the performance of foresightful preparatory behaviours. Because preparatory behaviours are central to routine and adaptive planning, difficulties with episodic foresight may contribute to or be a result of

  7. Lunar Dust Separation for Toxicology Studies

    Science.gov (United States)

    Cooper, Bonnie L.; McKay, D. S.; Riofrio, L. M.; Taylor, L. A.; Gonzalex, C. P.

    2010-01-01

    During the Apollo missions, crewmembers were briefly exposed to dust in the lunar module, brought in after extravehicular activity. When the lunar ascent module returned to micro-gravity, the dust that had settled on the floor now floated into the air, causing eye discomfort and occasional respiratory symptoms. Because our goal is to set an exposure standard for 6 months of episodic exposure to lunar dust for crew on the lunar surface, these brief exposures of a few days are not conclusive. Based on experience with industrial minerals such as sandblasting quartz, an exposure of several months may cause serious damage, while a short exposure may cause none. The detailed characteristics of sub-micrometer lunar dust are only poorly known, and this is the size range of particles that are of greatest concern. We have developed a method for extracting respirable dust (<2.5 micron) from Apollo lunar soils. This method meets stringent requirements that the soil must be kept dry, exposed only to pure nitrogen, and must conserve and recover the maximum amount of both respirable dust and coarser soil. In addition, we have developed a method for grinding coarser lunar soil to produce sufficient respirable soil for animal toxicity testing while preserving the freshly exposed grain surfaces in a pristine state.

  8. Planktonic Lipidome Responses to Aeolian Dust Input in Low-Biomass Oligotrophic Marine Mesocosms

    Directory of Open Access Journals (Sweden)

    Travis B. Meador

    2017-04-01

    Full Text Available The effect and fate of dry atmospheric deposition on nutrient-starved plankton in the Eastern Mediterranean Sea (EMS; Crete, 2012 was tested by spiking oligotrophic surface seawater mesocosms (3 m3 with Saharan dust (SD; 1.6 g L−1; 23 nmol NOx mg−1; 2.4 nmol PO4 mg−1 or mixed aerosols (A; 1.0 g L−1; 54 nmol NOx mg−1; 3.0 nmol PO4 mg−1 collected from natural and anthropogenic sources. Using high resolution liquid chromatography-mass spectrometry, the concentrations of over 350 individual lipids were measured in suspended particles to track variations in the lipidome associated with dust fertilization. Bacterial and eukaryotic intact polar lipid (IPL biomarkers were categorized into 15 lipid classes based on headgroup identity, including four novel IPL headgroups. Bulk IPL concentrations and archaeal tetraether lipids were uncoupled with the doubling of chlorophyll concentrations that defined the stimulation response of oligotrophic plankton to SD or A amendment. However, molecular level analysis revealed the dynamics of the IPL pool, with significant additions or losses of specific IPLs following dust spikes that were consistent among treatment mesocosms. Multivariate redundancy analysis further demonstrated that the distribution of IPL headgroups and molecular modifications within their alkyl chains were strongly correlated with the temporal evolution of the plankton community and cycling of phosphate. IPLs with phosphatidylcholine, betaine, and an alkylamine-like headgroup increased in the post-stimulated period, when phosphate turnover time had decreased by an order of magnitude and phosphorus uptake was dominated by plankton >2 μm. For most IPL classes, spiking with SD or A yielded significant increases in the length and unsaturation of alkyl chains. A lack of corresponding shifts in the plankton community suggests that the biosynthesis of nitrogenous and phosphatidyl lipids may respond to physiological controls during episodic

  9. Episodes, events, and models

    Directory of Open Access Journals (Sweden)

    Sangeet eKhemlani

    2015-10-01

    Full Text Available We describe a novel computational theory of how individuals segment perceptual information into representations of events. The theory is inspired by recent findings in the cognitive science and cognitive neuroscience of event segmentation. In line with recent theories, it holds that online event segmentation is automatic, and that event segmentation yields mental simulations of events. But it posits two novel principles as well: first, discrete episodic markers track perceptual and conceptual changes, and can be retrieved to construct event models. Second, the process of retrieving and reconstructing those episodic markers is constrained and prioritized. We describe a computational implementation of the theory, as well as a robotic extension of the theory that demonstrates the processes of online event segmentation and event model construction. The theory is the first unified computational account of event segmentation and temporal inference. We conclude by demonstrating now neuroimaging data can constrain and inspire the construction of process-level theories of human reasoning.

  10. Perspectives on Episodic-like and Episodic Memory

    Directory of Open Access Journals (Sweden)

    Bettina M Pause

    2013-04-01

    Full Text Available Episodic memory refers to the conscious recollection of a personal experience that contains information on what has happened and also where and when it happened. Recollection from episodic memory also implies a kind of first-person subjectivity that has been termed autonoetic consciousness. Episodic memory is extremely sensitive to cerebral aging and neurodegenerative diseases. In Alzheimer’s disease deficits in episodic memory function are among the first cognitive symptoms observed. Furthermore, impaired episodic memory function is also observed in a variety of other neuropsychiatric diseases including dissociative disorders, schizophrenia and Parkinson disease. Unfortunately, it is quite difficult to induce and measure episodic memories in the laboratory and it is even more difficult to measure it in clinical populations. Presently, the tests used to assess episodic memory function do not comply with even down-sized definitions of episodic-like memory as a memory for what happened, where and when. They also require sophisticated verbal competences and are difficult to apply to patient populations. In this review, we will summarize the progress made in defining behavioral criteria of episodic-like memory in animals (and humans as well as the perspectives in developing novel tests of human episodic memory which can also account for phenomenological aspects of episodic memory such as autonoetic awareness. We will also define basic behavioral, procedural and phenomenological criteria which might be helpful for the development of a valid and reliable clinical test of human episodic memory.

  11. Perspectives on episodic-like and episodic memory.

    Science.gov (United States)

    Pause, Bettina M; Zlomuzica, Armin; Kinugawa, Kiyoka; Mariani, Jean; Pietrowsky, Reinhard; Dere, Ekrem

    2013-01-01

    Episodic memory refers to the conscious recollection of a personal experience that contains information on what has happened and also where and when it happened. Recollection from episodic memory also implies a kind of first-person subjectivity that has been termed autonoetic consciousness. Episodic memory is extremely sensitive to cerebral aging and neurodegenerative diseases. In Alzheimer's disease deficits in episodic memory function are among the first cognitive symptoms observed. Furthermore, impaired episodic memory function is also observed in a variety of other neuropsychiatric diseases including dissociative disorders, schizophrenia, and Parkinson disease. Unfortunately, it is quite difficult to induce and measure episodic memories in the laboratory and it is even more difficult to measure it in clinical populations. Presently, the tests used to assess episodic memory function do not comply with even down-sized definitions of episodic-like memory as a memory for what happened, where, and when. They also require sophisticated verbal competences and are difficult to apply to patient populations. In this review, we will summarize the progress made in defining behavioral criteria of episodic-like memory in animals (and humans) as well as the perspectives in developing novel tests of human episodic memory which can also account for phenomenological aspects of episodic memory such as autonoetic awareness. We will also define basic behavioral, procedural, and phenomenological criteria which might be helpful for the development of a valid and reliable clinical test of human episodic memory.

  12. The Role of Episodic and Semantic Memory in Episodic Foresight

    Science.gov (United States)

    Martin-Ordas, Gema; Atance, Cristina M.; Louw, Alyssa

    2012-01-01

    In this paper we describe a special form of future thinking, termed "episodic foresight" and its relation with episodic and semantic memory. We outline the methodologies that have largely been developed in the last five years to assess this capacity in young children and non-human animals. Drawing on Tulving's definition of episodic and semantic…

  13. Dust: the latest environmental threat to future coal use

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-01

    A new environmental problem threatens coal which could be more damaging then either acid rain or global warming to its market. The science behind the dust threat is better established than behind either of these others, as dust is a known health hazard. In 1992 it was demonstrated that fine particles below 2.5 microns in diameter caused lung damage, no matter what the materials. Lung and heart problems are exacerbated by fine dust episodes, so emissions of dust are being legislated against. This will affect coal stockyards, handling facilities and combustion plants. Legislation is being introduced in the USA and Europe, but the basis of the legislation differs. An example of dust suppression at a coal stockyard at a Bristol port is given. 3 photos.

  14. LADEE LUNAR DUST EXPERIMENT

    Data.gov (United States)

    National Aeronautics and Space Administration — This archive bundle includes data taken by the Lunar Dust Experiment (LDEX) instrument aboard the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft....

  15. Allergies, asthma, and dust

    Science.gov (United States)

    ... furnace filters frequently. Use high efficiency particulate air (HEPA) filters. When cleaning: Wipe away dust with a damp ... a week. Use a vacuum cleaner with a HEPA filter to help control the dust that vacuuming stirs ...

  16. Construction dust amelioration techniques.

    Science.gov (United States)

    2012-04-01

    Dust produced on seasonal road construction sites in Alaska is both a traffic safety and environmental concern. Dust emanating from : unpaved road surfaces during construction severely reduces visibility and impacts stopping sight distance, and contr...

  17. Potential of polarization/Raman lidar to separate fine dust, coarse dust, maritime, and anthropogenic aerosol profiles

    Science.gov (United States)

    Mamouri, Rodanthi-Elisavet; Ansmann, Albert

    2017-09-01

    We applied the recently introduced polarization lidar-photometer networking (POLIPHON) technique for the first time to triple-wavelength polarization lidar measurements at 355, 532, and 1064 nm. The lidar observations were performed at Barbados during the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE) in the summer of 2014. The POLIPHON method comprises the traditional lidar technique to separate mineral dust and non-dust backscatter contributions and the new, extended approach to separate even the fine and coarse dust backscatter fractions. We show that the traditional and the advanced method are compatible and lead to a consistent set of dust and non-dust profiles at simplified, less complex aerosol layering and mixing conditions as is the case over the remote tropical Atlantic. To derive dust mass concentration profiles from the lidar observations, trustworthy extinction-to-volume conversion factors for fine, coarse, and total dust are needed and obtained from an updated, extended Aerosol Robotic Network sun photometer data analysis of the correlation between the fine, coarse and total dust volume concentration and the respective fine, coarse, and total dust extinction coefficient for all three laser wavelengths. Conversion factors (total volume to extinction) for pure marine aerosol conditions and continental anthropogenic aerosol situations are presented in addition. As a new feature of the POLIPHON data analysis, the Raman lidar method for particle extinction profiling is used to identify the aerosol type (marine or anthropogenic) of the non-dust aerosol fraction. The full POLIPHON methodology was successfully applied to a SALTRACE case and the results are discussed. We conclude that the 532 nm polarization lidar technique has many advantages in comparison to 355 and 1064 nm polarization lidar approaches and leads to the most robust and accurate POLIPHON products.

  18. Dust Transport Across the Atlantic Studied by Airborne Doppler Wind Lidar During the Saltrace Experiment in 2013

    Directory of Open Access Journals (Sweden)

    Chouza Fernando

    2016-01-01

    Full Text Available During the SALTRACE field experiment, conducted during June/July 2013, the Saharan dust transport across the Atlantic was analyzed by a set of ground based, in-situ and airborne instruments, including a 2-μm coherent DWL (Doppler wind lidar mounted onboard the DLR Falcon 20 research aircraft. An overview of the measurements of aerosol backscatter and extinction, horizontal and vertical winds retrieved from the DWL are presented together with a brief description of the applied methods. The retrieved measurements provide direct observation of Saharan dust transport mechanisms across the Atlantic as well as island induced lee waves in the Barbados region.

  19. House-Dust Allergy

    OpenAIRE

    Johnson, C A

    1982-01-01

    House-dust allergy is a common cause of perennial allergic rhinitis and extrinsic asthma. Symptoms tend to be worse when the patient is in bed. A positive skin test properly performed and interpreted confirms the diagnosis. The house-dust mite is the most important antigenic component of house-dust. Treatment consists of environmental control directed at reducing the mite content of bedroom dust, plus control of symptoms with drugs. Immunotherapy is controversial.

  20. Physics of interstellar dust

    CERN Document Server

    Krugel, Endrik

    2002-01-01

    The dielectric permeability; How to evaluate grain cross sections; Very small and very big particles; Case studies of Mie calculus; Particle statistics; The radiative transition probability; Structure and composition of dust; Dust radiation; Dust and its environment; Polarization; Grain alignment; PAHs and spectral features of dust; Radiative transport; Diffuse matter in the Milky Way; Stars and their formation; Emission from young stars. Appendices Mathematical formulae; List of symbols.

  1. Dust-off

    OpenAIRE

    Maycroft, Neil; Cheang, Shu Lea

    2015-01-01

    The fan of a motherboard switches on and off intermittently. It blows household dust, removed from the inside of a computer carcass, into the air. The dust then settles onto the motherboard, to be blown off again. This continual movement of dust is contained in the piece. However, it should remind us that the ceaseless creation and motion of unconfined dust accompanies all stages of the e-waste journey.

  2. CUACE/Dust - an integrated system of observation and modeling systems for operational dust forecasting in Asia

    Science.gov (United States)

    Gong, S. L.; Zhang, X. Y.

    2008-05-01

    An integrated sand and dust storm (SDS) forecasting system - CUACE/Dust (Chinese Unified Atmospheric Chemistry Environment for Dust) has been developed, which consists of a comprehensive dust aerosol module with emission, dry/wet depositions and other atmospheric dynamic processes, and a data assimilation system (DAS) using observational data from the CMA (China Meteorological Administration) ground dust monitoring network and retrieved dust information from a Chinese geostationary satellite - FY-2C. This is the first time that a combination of surface network observations and satellite retrievals of the dust aerosol has been successfully used in the real time operational forecasts in East Asia through a DAS. During its application for the operational SDS forecasts in East Asia for spring 2006, this system captured the major 31 SDS episodes observed by both surface and satellite observations. Analysis shows that the seasonal mean threat score (TS) for 0-24 h forecast over the East Asia in spring 2006 increased from 0.22 to 0.31 by using the DAS, a 41% enhancement. The time series of the forecasted dust concentrations for a number of representative stations for the whole spring 2006 were also evaluated against the surface PM10 monitoring data, showing a very good agreement in terms of the SDS timing and magnitudes near source regions where dust aerosols dominate. This is a summary paper for a special issue of ACP featuring the development and results of the forecasting system.

  3. Episode-Based Evolution Pattern Analysis of Haze Pollution: Method Development and Results from Beijing, China.

    Science.gov (United States)

    Zheng, Guangjie; Duan, Fengkui; Ma, Yongliang; Zhang, Qiang; Huang, Tao; Kimoto, Takashi; Cheng, Yafang; Su, Hang; He, Kebin

    2016-05-03

    Haze episodes occurred in Beijing repeatedly in 2013, resulting in 189 polluted days. These episodes differed in terms of sources, formation processes, and chemical composition and thus required different control policies. Therefore, an overview of the similarities and differences among these episodes is needed. For this purpose, we conducted one-year online observations and developed a program that can simultaneously divide haze episodes and identify their shapes. A total of 73 episodes were identified, and their shapes were linked with synoptic conditions. Pure-haze events dominated in wintertime, whereas mixed haze-dust (PM2.5/PM10 pollution level increased. The only OM-driven episode observed was associated with intensive biomass-burning activities. In comparison, haze evolution generally coincided with increasing sulfur and nitrogen oxidation ratios (SOR and NOR), indicating the enhanced production of secondary inorganic species. Applicability of these conclusions required further tests with simultaneously multisite observations.

  4. Interstellar Dust - A Review

    Science.gov (United States)

    Salama, Farid

    2012-01-01

    The study of the formation and the destruction processes of cosmic dust is essential to understand and to quantify the budget of extraterrestrial organic materials. Although dust with all its components plays an important role in the evolution of interstellar physics and chemistry and in the formation of organic materials, little is known on the formation and destruction processes of carbonaceous dust. Laboratory experiments that are performed under conditions that simulate interstellar and circumstellar environments to provide information on the nature, the size and the structure of interstellar dust particles, the growth and the destruction processes of interstellar dust and the resulting budget of extraterrestrial organic molecules. A review of the properties of dust and of the laboratory experiments that are conducted to study the formation processes of dust grains from molecular precursors will be given.

  5. First-episode psychosis

    DEFF Research Database (Denmark)

    Simonsen, Erik

    2011-01-01

    that two-thirds of the patients had a comorbid personality disorder at two-year follow-up, and schizoid, paranoid and avoidant personality disorder were the most frequent. Schizotypal traits were less prevalent, which in relation to the late follow-up is attributed to uncertainty in differentiating....... Patients with first-episode psychosis had significantly high NEO-PI-R scores for neuroticism and agreeableness, and lower scores for conscientiousness and extroversion. The median time for remission in the total sample was three months. Female gender and better premorbid functioning were predictive of less...... negative symptoms and shorter duration of untreated psychosis (DUP) was predictive for shorter time to remission, stable remission, less severe positive psychotic symptoms, and better social functioning. Female gender, better premorbid social functioning and more education also contributed to a better...

  6. The Mineral Dust Cycle in EMAC 2.40: sensitivity to the spectral resolution and the dust emission scheme

    Directory of Open Access Journals (Sweden)

    G. Gläser

    2012-02-01

    Full Text Available This first detailed analysis of the mineral dust cycle in the ECHAM5/MESSy Atmospheric Chemistry (EMAC model system investigates the performance of two dust emission schemes, following the approach of Balkanski et al. (2004 and Tegen et al. (2002, respectively, and the influence of the horizontal model resolution. Here the spectral resolutions T42, T63, T85, and T106 are investigated. A basic sulphur chemistry, enabling the coating of insoluble dust particles to make them soluble, is employed in order to realistically describe the ageing and wet deposition of mineral dust. Independent of the dust emission scheme the five-year simulations with the horizontal resolutions T42 and T63 produce unrealistically high emissions at some grid points in the Tarim Basin in Central Asia, leading to very high dust loads in polar regions. With these coarse resolutions, dust source grid points in the basin and elevated grid points of the Himalayas with high wind speeds cannot be distinguished, causing this overestimation. In T85 and T106 these regions are well separated and considerably less dust is emitted there. With the chosen model setup, the dust emission scheme by Balkanski et al. (2004 places the global maximum of emissions in the Thar Desert in India. This is unrealistic as the Sahara Desert is known to be the largest dust source in the world. This is the main deficiency of this scheme compared to the one by Tegen et al. (2002, which, based on a qualitative comparison to AEROCOM data, produces a very reasonable distribution of emissions and dust loads in simulations with resolutions T85 and T106. For future climate simulations with EMAC focusing on mineral dust, we recommend to use the dust emission scheme by Tegen et al. (2002 and a model resolution of at least T85. Simulations of two selected episodes and comparison to observational data sets show that in this model configuration EMAC is able to realistically simulate also intense, episodic events of

  7. Moral judgment in episodic amnesia.

    Science.gov (United States)

    Craver, Carl F; Keven, Nazim; Kwan, Donna; Kurczek, Jake; Duff, Melissa C; Rosenbaum, R Shayna

    2016-08-01

    To investigate the role of episodic thought about the past and future in moral judgment, we administered a well-established moral judgment battery to individuals with hippocampal damage and deficits in episodic thought (insert Greene et al. 2001). Healthy controls select deontological answers in high-conflict moral scenarios more frequently when they vividly imagine themselves in the scenarios than when they imagine scenarios abstractly, at some personal remove. If this bias is mediated by episodic thought, individuals with deficits in episodic thought should not exhibit this effect. We report that individuals with deficits in episodic memory and future thought make moral judgments and exhibit the biasing effect of vivid, personal imaginings on moral judgment. These results strongly suggest that the biasing effect of vivid personal imagining on moral judgment is not due to episodic thought about the past and future. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  8. The evolution of episodic memory

    Science.gov (United States)

    Allen, Timothy A.; Fortin, Norbert J.

    2013-01-01

    One prominent view holds that episodic memory emerged recently in humans and lacks a “(neo)Darwinian evolution” [Tulving E (2002) Annu Rev Psychol 53:1–25]. Here, we review evidence supporting the alternative perspective that episodic memory has a long evolutionary history. We show that fundamental features of episodic memory capacity are present in mammals and birds and that the major brain regions responsible for episodic memory in humans have anatomical and functional homologs in other species. We propose that episodic memory capacity depends on a fundamental neural circuit that is similar across mammalian and avian species, suggesting that protoepisodic memory systems exist across amniotes and, possibly, all vertebrates. The implication is that episodic memory in diverse species may primarily be due to a shared underlying neural ancestry, rather than the result of evolutionary convergence. We also discuss potential advantages that episodic memory may offer, as well as species-specific divergences that have developed on top of the fundamental episodic memory architecture. We conclude by identifying possible time points for the emergence of episodic memory in evolution, to help guide further research in this area. PMID:23754432

  9. The Episodic Nature of Episodic-Like Memories

    Science.gov (United States)

    Easton, Alexander; Webster, Lisa A. D.; Eacott, Madeline J.

    2012-01-01

    Studying episodic memory in nonhuman animals has proved difficult because definitions in humans require conscious recollection. Here, we assessed humans' experience of episodic-like recognition memory tasks that have been used with animals. It was found that tasks using contextual information to discriminate events could only be accurately…

  10. Combustibility Determination for Cotton Gin Dust and Almond Huller Dust.

    Science.gov (United States)

    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.

  11. Optical characteristics of desert dust over the East Mediterranean during summer: a case study

    Energy Technology Data Exchange (ETDEWEB)

    Balis, D.; Amiridis, V.; Kazadzis, S. [Lab. of Atmospheric Physics, Aristotle Univ. of Thessaloniki (Greece); Papayannis, A.; Tsaknakis, G.; Tzortzakis, S. [Lab. of Lasers and Applications, National Technical Univ. of Athens (Greece); Kalivitis, N.; Vrekoussis, M.; Kanakidou, M.; Mihalopoulos, N. [Environmental Chemical Processes Lab., Univ. of Crete, Heraklion (Greece); Chourdakis, G. [Raymetries SA, Athens (Greece); Nickovic, S. [Euro-Mediterranean Centre on Insular Coastal Dynamics (ICoD), Univ. of Malta (Malta); World Meteorological Organization, Geneva (Switzerland); Perez, C.; Baldasano, J. [Barcelona Supercomputing Center - Centro Nacional de Supercomputacion (BSC-CNS), Earth Sciences Div., Edificio Nexus II, Barcelona (Spain); Drakakis, M. [FORTH-Crete, Foundation for Research and Technology Hellas, Heraklion, Crete (Greece)

    2006-07-01

    High aerosol optical depth (AOD) values, larger than 0.6, are systematically observed in the ultraviolet (UV) region both by sunphotometers and lidar systems over Greece during summertime. To study in more detail the characteristics and the origin of these high AOD values, a campaign took place in Greece in the frame of the PHOENICS (particles of human origin extinguishing natural solar radiation in climate systems) and EARLINET (European aerosol lidar network) projects during August-September of 2003, which included simultaneous sunphotometric and lidar measurements at three sites covering the north-south axis of Greece: Thessaloniki, Athens and Finokalia, Crete. Several events with high AOD values have been observed over the measuring sites during the campaign period, many of them corresponding to Saharan dust. In this paper we focused on the event of 30 and 31 August 2003, when a dust layer in the height range of 2000-5000 m, progressively affected all three stations. This layer showed a complex behavior concerning its spatial evolution and allowed us to study the changes in the optical properties of the desert dust particles along their transport due to aging and mixing with other types of aerosol. The extinction-to-backscatter ratio determined on the 30 August 2003 at Thessaloniki was approximately 50 sr, characteristic for rather spherical mineral particles, and the measured color index of 0.4 was within the typical range of values for desert dust. Mixing of the desert dust with other sources of aerosols resulted the next day in overall smaller and less absorbing population of particles with a lidar ratio of 20 sr. Mixing of polluted air-masses originating from northern Greece and Crete and Saharan dust result in very high aerosol backscatter values reaching 7 Mm{sup -1}sr{sup -1} over Finokalia. The Saharan dust observed over Athens followed a different spatial evolution and was not mixed with the boundary layer aerosols mainly originating from local

  12. Optical characteristics of desert dust over the East Mediterranean during summer: a case study

    Directory of Open Access Journals (Sweden)

    D. Balis

    2006-05-01

    Full Text Available High aerosol optical depth (AOD values, larger than 0.6, are systematically observed in the Ultraviolet (UV region both by sunphotometers and lidar systems over Greece during summertime. To study in more detail the characteristics and the origin of these high AOD values, a campaign took place in Greece in the frame of the PHOENICS (Particles of Human Origin Extinguishing Natural solar radiation In Climate Systems and EARLINET (European Aerosol Lidar Network projects during August–September of 2003, which included simultaneous sunphotometric and lidar measurements at three sites covering the north-south axis of Greece: Thessaloniki, Athens and Finokalia, Crete. Several events with high AOD values have been observed over the measuring sites during the campaign period, many of them corresponding to Saharan dust. In this paper we focused on the event of 30 and 31 August 2003, when a dust layer in the height range of 2000-5000 m, progressively affected all three stations. This layer showed a complex behavior concerning its spatial evolution and allowed us to study the changes in the optical properties of the desert dust particles along their transport due to aging and mixing with other types of aerosol. The extinction-to-backscatter ratio determined on the 30 August 2003 at Thessaloniki was approximately 50 sr, characteristic for rather spherical mineral particles, and the measured color index of 0.4 was within the typical range of values for desert dust. Mixing of the desert dust with other sources of aerosols resulted the next day in overall smaller and less absorbing population of particles with a lidar ratio of 20 sr. Mixing of polluted air-masses originating from Northern Greece and Crete and Saharan dust result in very high aerosol backscatter values reaching 7 Mm-1 sr-1 over Finokalia. The Saharan dust observed over Athens followed a different spatial evolution and was not mixed with the boundary layer aerosols mainly originating from

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

    Science.gov (United States)

    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.

  14. Episodic Alcohol Consumption by Youths

    OpenAIRE

    Pereverzev, Vladimir Alexeevich

    2015-01-01

    AbstractThis paper presents evidence that even rare episodic alcohol consumption by young people is not harmless. Unsafe rare episodic alcohol consumption by youths (students) was reflected in the reduced attention concentration and lower academic buoyancy, compared to those who completely abstain from alcohol. Key Words: Alcohol, youth, students, attention concentration, academic buoyancy 

  15. Episodic Alcohol Consumption by Youths

    OpenAIRE

    Pereverzev, Vladimir Alexeevich

    2014-01-01

    AbstractThis paper presents evidence that even rare episodic alcohol consumption by young people is not harmless. Unsafe rare episodic alcohol consumption by youths (students) was reflected in the reduced attention concentration and lower academic buoyancy, compared to those who completely abstain from alcohol. Key Words: Alcohol, youth, students, attention concentration, academic buoyancy 

  16. Concentrations and health effects of potash dust.

    Science.gov (United States)

    Markham, J W; Tan, L K

    1981-09-01

    In an investigation of the relationship between atmospheric dust levels and worker health, the respiratory dust exposures of employees at two Saskatchewan potash mines were examined following atmospheric measurements. Some, notably those of the mining crew and the screening operators, were above the Threshold Limit Value 8-hour Time Weighted Average (TLV-TWA) for total nuisance particulates specified by the American Conference of Governmental Industrial Hygienists (ACGIH). Respiratory symptoms were recorded and forced expiratory lung function tests were done among 850 volunteers drawn from an eligible work force of 931. The results were compared between low and higher exposure groups after allowing for personal factors such as age and smoking habits. Symptoms of Grade I chronic phlegm production and mild shortness of breath and chronic cough were more common in the higher exposure groups, but episodes of chest illness were not. Severe respiratory symptoms were rare. There were no statistically significant differences in the proportions performing lung function tests below predicted values.

  17. Communication plan for windblown dust.

    Science.gov (United States)

    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...

  18. The Impact of Dry Saharan Air on Tropical Cyclone Intensification

    Science.gov (United States)

    Braun, Scott A.

    2012-01-01

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

  19. Dust in Space

    Indian Academy of Sciences (India)

    "They cannot look out far·IThey cannot look in deep. I. But when was that ever a bar ITo any watch they keep?" - Robert Frost, (Neither Out Far Nor In Deep'. Dust grains in space, which absorb and redden starlight, were once considered to be a nuisance for astronomers, but the study of dust has be- come important in ...

  20. Respirable dust measured downwind during rock dust application.

    Science.gov (United States)

    Harris, M L; Organiscak, J; Klima, S; Perera, I E

    2017-05-01

    The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducted underground evaluations in an attempt to quantify respirable rock dust generation when using untreated rock dust and rock dust treated with an anticaking additive. Using personal dust monitors, these evaluations measured respirable rock dust levels arising from a flinger-type application of rock dust on rib and roof surfaces. Rock dust with a majority of the respirable component removed was also applied in NIOSH's Bruceton Experimental Mine using a bantam duster. The respirable dust measurements obtained downwind from both of these tests are presented and discussed. This testing did not measure miners' exposure to respirable coal mine dust under acceptable mining practices, but indicates the need for effective continuous administrative controls to be exercised when rock dusting to minimize the measured amount of rock dust in the sampling device.

  1. Respirable dust measured downwind during rock dust application

    Science.gov (United States)

    Harris, M.L.; Organiscak, J.; Klima, S.; Perera, I.E.

    2017-01-01

    The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducted underground evaluations in an attempt to quantify respirable rock dust generation when using untreated rock dust and rock dust treated with an anticaking additive. Using personal dust monitors, these evaluations measured respirable rock dust levels arising from a flinger-type application of rock dust on rib and roof surfaces. Rock dust with a majority of the respirable component removed was also applied in NIOSH’s Bruceton Experimental Mine using a bantam duster. The respirable dust measurements obtained downwind from both of these tests are presented and discussed. This testing did not measure miners’ exposure to respirable coal mine dust under acceptable mining practices, but indicates the need for effective continuous administrative controls to be exercised when rock dusting to minimize the measured amount of rock dust in the sampling device. PMID:28706322

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

    Science.gov (United States)

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

    2013-01-01

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

  3. Imagining the personal past: Episodic counterfactuals compared to episodic memories and episodic future projections.

    Science.gov (United States)

    Özbek, Müge; Bohn, Annette; Berntsen, Dorthe

    2017-04-01

    Episodic counterfactuals are imagined events that could have happened, but did not happen, in a person's past. Such imagined past events are important aspects of mental life, affecting emotions, decisions, and behaviors. However, studies examining their phenomenological characteristics and content have been few. Here we introduced a new method to systematically compare self-generated episodic counterfactuals to self-generated episodic memories and future projections with regard to their phenomenological characteristics (e.g., imagery, emotional valence, and rehearsal) and content (e.g., reference to a cultural life script), and how these were affected by temporal distance (1 month, 1 year, 5+ years). The findings showed that the three types of events differed phenomenologically. First, episodic memories were remembered more easily, with more sensory details, and from a dominantly field perspective, as compared to both future projections and episodic counterfactuals. Second, episodic future projections were more positive, more voluntarily rehearsed, and more central to life story and identity than were both episodic memories and episodic counterfactuals. Third, episodic counterfactuals differed from both episodic memories and future projections by neither having the positivity bias of the future events nor the enhanced sensory details of the past events. Across all three event types, sensory details decreased, whereas importance, reference to a cultural life script, and centrality increased with increasing temporal distance. The findings show that imagined events are phenomenologically different from memories of experienced events, consistent with reality-monitoring theory, and that imagined future events are different from both actual and imagined past events, consistent with some theories of motivation.

  4. The Complexity of Environmental Protection in Sub-Saharan Africa ...

    African Journals Online (AJOL)

    economic development in sub-Saharan Africa. However, there is an implicit determination of the people to protect the human health of the sub-Saharan population and the environment from the adverse effects of pollution and degraded ...

  5. Diagnosis of the Relationship between Dust Storms over the Sahara Desert and Dust Deposit or Coloured Rain in the South Balkans

    Directory of Open Access Journals (Sweden)

    N. G. Prezerakos

    2010-01-01

    Full Text Available The main objects of study in this paper are the synoptic scale atmospheric circulation systems associated with the rather frequent phenomenon of coloured rain and the very rare phenomenon of dust or sand deposits from a Saharan sandstorm triggered by a developing strong depression. Analysis of two such cases revealed that two days before the occurrence of the coloured rain or the dust deposits over Greece a sand storm appeared over the north-western Sahara desert. The flow in the entire troposphere is southerly/south-westerly with an upward vertical motion regime. If the atmospheric conditions over Greece favour rain then this rain contains a part of the dust cloud while the rest is drawn away downstream adopting a light yellow colour. In cases where the atmospheric circulation on the route of the dust cloud trajectories is not intensively anticyclonic dust deposits can occur on the surface long far from the region of the dust origin. Such was the case on 4th April, 1988, when significant synoptic-scale subsidence occurred over Italy and towards Greece. The upper air data, in the form of synoptic maps, illustrate in detail the synoptic-scale atmospheric circulations associated with the emission-transport-deposition and confirm the transportation of dust particles.

  6. The aeolian dust accumulation curve

    NARCIS (Netherlands)

    Goossens, D.

    2001-01-01

    This article presents a simple physical concept of aeolian dust accumulation, based on the behaviour of the subprocesses of dust deposition and dust erosion. The concept is tested in an aeolian dust wind tunnel. The agreement between the accumulation curve predicted by the model and the accumulation

  7. Chemical Characteristics of High PM Episodes Occurring in Spring 2014, Seoul, Korea

    Directory of Open Access Journals (Sweden)

    Hye Jung Shin

    2016-01-01

    Full Text Available This study was conducted for understanding of characteristics of two different high PM episodes occurred during the spring of 2014 in Seoul, Korea. Case 1 was the phenomenon by complex of long range transport and following domestic stagnation. Case 2 was caused by the Asian dust event. During high PM episodes, atmospheric condition became more acidic. The equivalent concentration ratio of nitrate to sulfate decreased to 0.75 and 0.95 in Case 1 and Case 2, respectively, implying that sulfate concentration increase was greater than nitrate concentration increase in high PM episode possibly caused by long range transport. In high PM episodes, SOR and NOR increased with steeper rate for NOR. Considering correlation between temperature and SOR, it was suggested that the homogeneous formation of sulfate was not active in the Korean Peninsula, especially in high PM episodic periods. On the other hand, heterogeneous sulfate formation reaction was dominant for high PM episodes. Considering NOR and its correlation with temperature and humidity, it was suggested that NO2 oxidation was mainly caused by homogeneous oxidation in Case 1. For Case 2, heterogeneous oxidation mainly contributed to forming the nitrate due to the extremely high particle concentrations in Asian dust.

  8. Mechanisms of metal dusting corrosion

    DEFF Research Database (Denmark)

    Hummelshøj, Thomas Strabo

    In this thesis the early stages of metal dusting corrosion is addressed; the development of carbon expanded austenite, C, and the decomposition hereof into carbides. Later stages of metal dusting corrosion are explored by a systematic study of stainless steel foils exposed to metal dusting...... influence of oxygen and carbon on the metal dusting corrosion is explored. The results indicate that exposure to metal dusting conditions have a detrimental effect on the resistance against oxidation and, conversely, that exposure to oxidation has a detrimental effect on the resistance towards metal dusting....... Consequently, a combination of carburizing and oxidizing conditions has a strong mutual catalyzing effect on the metal dusting corrosion....

  9. Vertical distribution of the Saharan Air Layer from 5 years of CALIPSO observations

    Science.gov (United States)

    Tsamalis, C.; Chédin, A.

    2012-04-01

    The Saharan Air Layer (SAL) forms as dry and hot air moves across the Sahara desert. SAL, containing substantial amounts of mineral dust, is a dominant feature that influences the large scale environment from West Africa to eastern tropical America, inhibiting tropical cyclogenesis and Atlantic hurricane formation. Furthermore, SAL dust aerosols have a strong impact on the energy budget through the so-called direct and indirect effects. The SAL has been studied with dedicated campaigns at the two sides of the Atlantic or using space observations due to lack of systematic in situ measurements away from the continents. However the campaigns are restricted in time, while satellite observations of thermodynamic variables are affected by the presence of dust. Moreover, satellite measurements of aerosols, particularly in the visible, mostly provide column integrated properties like the optical depth, without information about the vertical distribution. On the other hand, new generation infrared sounders now bring reliable information on the dust layer mean altitude, but their new established results need further validation. However, the two-wavelength lidar CALIOP, launched on board CALIPSO in April 2006, permits an accurate determination of the aerosol vertical distribution, on a global scale. Thanks to depolarisation at 532 nm, CALIOP is able to discriminate between dust and other types of aerosols, which generally do not depolarize light. Here, the L2 5 km aerosol layer product (version 3.01) is used to calculate the vertical distribution of the dust aerosols above the Atlantic during the last 5 years (June 2006 - May 2011) with a horizontal resolution of 1 degree for the four seasons. More specifically, two classes of aerosols are used from the L2 product: dust and polluted dust, in order to take into account the change of dust aerosols optical properties with transport. Results show the latitudinal displacement of the SAL between winter [-5, 15]°N and summer [10

  10. Dust layer profiling using an aerosol dropsonde

    Science.gov (United States)

    Ulanowski, Zbigniew; Kaye, Paul Henry; Hirst, Edwin; Wieser, Andreas; Stanley, Warren

    2015-04-01

    Technology, which determines standard meteorological variables and GPS position for transmission back to the aircraft. During some of the tests a Saharan dust layer transported over Europe was intercepted and characterized.

  11. Nano Dust Analyzer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to develop a new highly sensitive instrument to confirm the existence of the so-called nano-dust particles, characterize their impact parameters, and...

  12. The Lunar Dust Pendulum

    Science.gov (United States)

    Kuntz, Kip; Collier, Michael R.; Stubbs, Timothy J.; Farrell, William M.

    2011-01-01

    Shadowed regions on the lunar surface acquire a negative potential. In particular, shadowed craters can have a negative potential with respect to the surrounding lunar regolith in sunlight, especially near the terminator regions. Here we analyze the motion of a positively charged lnnar dust grain in the presence of a shadowed crater at a negative potential in vacuum. Previous models describing the transport of charged lunar dust close to the surface have typically been limited to one-dimensional motion in the vertical direction, e.g. electrostatic levitation; however. the electric fields in the vicinity of shadowed craters will also have significant components in the horizontal directions. We propose a model that includes both the horizontal and vertical motion of charged dust grains near shadowed craters. We show that the dust grains execute oscillatory trajectories and present an expression for the period of oscillation drawing an analogy to the motion of a pendulum.

  13. Dust mite (image)

    Science.gov (United States)

    This is a magnified photograph of a dust mite. Mites are carriers (vectors) of many important diseases including typhus (scrub and murine) and rickettsialpox. (Image courtesy of the Centers for Disease ...

  14. Adhesion of Lunar Dust

    Science.gov (United States)

    Walton, Otis R.

    2007-01-01

    This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

  15. Cosmic Dust Catalog

    Data.gov (United States)

    National Aeronautics and Space Administration — Since May 1981, the National Aeronautics and Space Administration (NASA) has used aircraft to collect cosmic dust (CD) particles from Earth's stratosphere. Specially...

  16. [A new assessment for episodic memory. Episodic memory test and caregiver's episodic memory test].

    Science.gov (United States)

    Ojea Ortega, T; González Álvarez de Sotomayor, M M; Pérez González, O; Fernández Fernández, O

    2013-10-01

    The purpose of the episodic memory test and the caregiver's episodic memory test is to evaluate episodic memory according to its definition in a way that is feasible for families and achieves high degrees of sensitivity and specificity. We administered a test consisting of 10 questions about episodic events to 332 subjects, of whom 65 had Alzheimer's disease (AD), 115 had amnestic MCI (aMCI) and 152 showed no cognitive impairment according to Reisberg's global deterioration scale (GDS). We calculated the test's sensitivity and specificity to distinguish AD from episodic aMCI and from normal ageing. The area under the ROC curve for the diagnosis of aMCI was 0.94 and the best cut-off value was 20; for that value, sensitivity was 89% and specificity was 82%. For a diagnosis of AD, the area under the ROC curve was 0.99 and the best cut-off point was 17, with a sensitivity of 98% and a specificity of 91%. A subsequent study using similar methodology yielded similar results when the test was administered directly by the caregiver. The episodic memory test and the caregiver's episodic memory test are useful as brief screening tools for identifying patients with early-stage AD. It is suitable for use by primary care medical staff and in the home, since it can be administered by a caregiver. The test's limitations are that it must be administered by a reliable caregiver and the fact that it measures episodic memory only. Copyright © 2012 Sociedad Española de Neurología. Published by Elsevier Espana. All rights reserved.

  17. Effect of dust size distribution and dust charge fluctuation on dust ion ...

    Indian Academy of Sciences (India)

    The effects of dust size distribution and dust charge fluctuation of dust grains on the small but finite amplitude nonlinear dust ion-acoustic shock waves, in an unmagnetized multi-ion dusty plasma which contains negative ions, positive ions and electrons, are studied in this paper. A Burgers equation and its stationary ...

  18. Selecting baghouse dust collectors

    Energy Technology Data Exchange (ETDEWEB)

    Moore, S.; Rubak, J.; Jolin, M. [Farr Co., El Segundo, CA (United States)]|[Farr Co., Laval, Quebec (Canada)

    1996-10-01

    Control of nuisance or process dusts generated within a plant is a vital concern with today`s growing emphasis on indoor air quality. In the past, many companies simply moved these contaminants away from workers and discharged them into the atmosphere. More stringent pollution control requirements now make this course of action unacceptable. Also, in some cases there is a need to recover high-value dusts, such as chemicals or precious metals. As a result, proper design and selection of a dust collection system are more critical than ever. There are two types of fabric filter dust collection systems commonly used today: baghouses and cartridges. Baghouses were the first collection systems with fabric media (in the form of long tubes, or bags) for removal of contaminants. The versatility of the baghouse--coupled with constant technological refinements--have made it a long-standing favorite among specifiers of pollution control equipment. In fact, baghouses account for more than 80% of all fabric filter dust collection systems in use today. Cartridge dust collectors use rigidly pleated filter elements instead of bags, making it possible to accommodate a large amount of filter surface area in a comparatively small package. Cartridge collectors also offer high efficiency and low pressure drop.

  19. Newton to Einstein - dust to dust

    OpenAIRE

    Kopp, Michael; Uhlemann, Cora; Haugg, Thomas

    2013-01-01

    We investigate the relation between the standard Newtonian equations for a pressureless fluid (dust) and the Einstein equations in a double expansion in small scales and small metric perturbations. We find that parts of the Einstein equations can be rewritten as a closed system of two coupled differential equations for the scalar and transverse vector metric perturbations in Poisson gauge. It is then shown that this system is equivalent to the Newtonian system of continuity and Euler equation...

  20. medication in sub-Saharan Africa

    African Journals Online (AJOL)

    2007-09-04

    Sep 4, 2007 ... In this review article, the issues related to provision of psychotropic drugs in services in sub-Saharan Africa are explored. Problems encountered in procurement of drugs, their safe prescription and practical supply systems are discussed, with possible solutions suggested. The evidence-base for the ...

  1. Ice nucleation properties of mineral dust particles: determination of onset RHi, IN active fraction, nucleation time-lag, and the effect of active sites on contact angles

    Directory of Open Access Journals (Sweden)

    S. Dobbie

    2010-01-01

    Full Text Available A newly developed ice nucleation experimental set up was used to investigate the heterogeneous ice nucleation properties of three Saharan and one Spanish dust particle samples. It was observed that the spread in the onset relative humidities with respect to ice (RHi for Saharan dust particles varied from 104% to 110%, whereas for the Spanish dust from 106% to 110%. The elemental composition analysis shows a prominent Ca feature in the Spanish dust sample which could potentially explain the differences in nucleation threshold. Although the spread in the onset RHi for the three Saharan dust samples were in agreement, the active fractions and nucleation time-lags calculated at various temperature and RHi conditions were found to differ. This could be due to the subtle variation in the elemental composition of the dust samples, and surface irregularities like steps, cracks, cavities etc. A combination of classical nucleation theory and active site theory is used to understand the importance of these surface irregularities on the nucleability parameter, contact angle that is widely used in ice cloud modeling. These calculations show that the surface irregularities can reduce the contact angle by approximately 10 degrees.

  2. Factitious psychogenic nonepileptic paroxysmal episodes

    Directory of Open Access Journals (Sweden)

    Alissa Romano

    2014-01-01

    Full Text Available Mistaking psychogenic nonepileptic paroxysmal episodes (PNEPEs for epileptic seizures (ES is potentially dangerous, and certain features should alert physicians to a possible PNEPE diagnosis. Psychogenic nonepileptic paroxysmal episodes due to factitious seizures carry particularly high risks of morbidity or mortality from nonindicated emergency treatment and, often, high costs in wasted medical treatment expenditures. We report a case of a 28-year-old man with PNEPEs that were misdiagnosed as ES. The patient had been on four antiseizure medications (ASMs with therapeutic serum levels and had had multiple intubations in the past for uncontrolled episodes. He had no episodes for two days of continuous video-EEG monitoring. He then disconnected his EEG cables and had an episode of generalized stiffening and cyanosis, followed by jerking and profuse bleeding from the mouth. The manifestations were unusually similar to those of ES, except that he was clearly startled by spraying water on his face, while he was stiff in all extremities and unresponsive. There were indications that he had sucked blood from his central venous catheter to expel through his mouth during his PNEPEs while consciously holding his breath. Normal video-EEG monitoring; the patient's volitional and deceptive acts to fabricate the appearance of illness, despite pain and personal endangerment; and the absence of reward other than remaining in a sick role were all consistent with a diagnosis of factitious disorder.

  3. Risk of Adverse Health and Performance Effects of Celestial Dust Exposure

    Science.gov (United States)

    Scully, Robert R.; Meyers, Valerie E.

    2015-01-01

    Crew members can be directly exposed to celestial dust in several ways. After crew members perform extravehicular activities (EVAs), they may introduce into the habitat dust that will have collected on spacesuits and boots. Cleaning of the suits between EVAs and changing of the Environmental Control Life Support System filters are other operations that could result in direct exposure to celestial dusts. In addition, if the spacesuits used in exploration missions abrade the skin, as current EVA suits have, then contact with these wounds would provide a source of exposure. Further, if celestial dusts gain access to a suit's interior, as was the case during the Apollo missions, the dust could serve as an additional source of abrasions or enhance suit-induced injuries. When a crew leaves the surface of a celestial body and returns to microgravity, the dust that is introduced into the return vehicle will "float," thus increasing the opportunity for ocular and respiratory injury. Because the features of the respirable fraction of lunar dusts indicate they could be toxic to humans, NASA conducted several studies utilizing lunar dust simulants and authentic lunar dust to determine the unique properties of lunar dust that affect physiology, assess the dermal and ocular irritancy of the dust, and establish a permissible exposure limit for episodic exposure to airborne lunar dust during missions that would involve no more than 6 months stay on the lunar surface. Studies, with authentic lunar soils from both highland (Apollo 16) and mare (Apollo17) regions demonstrated that the lunar soil is highly abrasive to a high fidelity model of human skin. Studies of lunar dust returned during the Apollo 14 mission from an area of the moon in which the soils were comprised of mineral constituents from both major geological regions (highlands and mares regions) demonstrated only minimal ocular irritancy, and pulmonary toxicity that was less than the highly toxic terrestrial crystalline

  4. Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

    Science.gov (United States)

    Vincent, Julie; Laurent, Benoit; Losno, Rémi; Bon Nguyen, Elisabeth; Roullet, Pierre; Sauvage, Stéphane; Chevaillier, Servanne; Coddeville, Patrice; Ouboulmane, Noura; di Sarra, Alcide Giorgio; Tovar-Sánchez, Antonio; Sferlazzo, Damiano; Massanet, Ana; Triquet, Sylvain; Morales Baquero, Rafael; Fornier, Michel; Coursier, Cyril; Desboeufs, Karine; Dulac, François; Bergametti, Gilles

    2016-07-01

    Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French) have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, Frioul and Le Casset (southern French Alps). Deposition measurements are performed on a common weekly period at the five sites. The mean dust deposition fluxes are higher close to the northern African coasts and decrease following a south-north gradient, with values from 7.4 g m-2 year-1 in Lampedusa (35°31' N, 12°37' E) to 1 g m-2 year-1 in Le Casset (44°59' N, 6°28' E). The maximum deposition flux recorded is of 3.2 g m-2 wk-1 in Majorca with only two other events showing more than 1 g m-2 wk-1 in Lampedusa, and a maximum of 0.5 g m-2 wk-1 in Corsica. The maximum value of 2.1 g m-2 year-1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11-14 g m-2 year-1). From the 537 available samples, 98 major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations for the studied period. Despite the large size of African dust plumes detected by satellites, more than 80 % of the major dust deposition events are recorded at only one station, suggesting that the dust

  5. Apathy in first episode psychosis patients

    DEFF Research Database (Denmark)

    Evensen, Julie; Røssberg, Jan Ivar; Barder, Helene

    2012-01-01

    Apathy is a common symptom in first episode psychosis (FEP), and is associated with poor functioning. Prevalence and correlates of apathy 10 years after the first psychotic episode remain unexplored.......Apathy is a common symptom in first episode psychosis (FEP), and is associated with poor functioning. Prevalence and correlates of apathy 10 years after the first psychotic episode remain unexplored....

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

    Science.gov (United States)

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

    2011-01-01

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

  7. Ten-year operational dust forecasting - Recent model development and future plans

    Energy Technology Data Exchange (ETDEWEB)

    Kallos, G; Spyrou, C; Astitha, M; Mitsakou, C; Solomos, S; Kushta, J; Pytharoulis, I; Katsafados, P; Mavromatidis, E; Papantoniou, N; Vlastou, G [University of Athens, School of Physics, Atmospheric Modeling and Weather Forecasting Group - UOA/AM and WFG, University Campus, Bldg. PHYS-V, Athens 15784 (Greece)], E-mail: kallos@mg.uoa.gr

    2009-03-01

    The Sahara desert is one of the major sources of mineral dust on Earth, producing up to 2x10{sup 8} t yr-{sup 1}. A combined effort has been devoted during the last ten years at the University of Athens (UOA) from the Atmospheric Modeling and Weather Forecasting Group (AM and WFG) to the development of an analysis and forecasting tool that will provide early warning of Saharan dust outbreaks. The developed tool is the SKIRON limited-area forecasting system, based on the Eta limited area modeling system with embedded algorithms describing the dust cycle. A new version of the model is currently available, with extra features like eight-size particle bins, radiative transfer corrections, new dust source identification and utilization of rocky soil characterization and incorporation of more accurate deposition schemes. The new version of SKIRON modeling system is coupled with the photochemical model CAMx in order to study processes like the shading effect of dust particles on photochemical processes and the production of second and third generation of aerosols. Moreover, another new development in the AM and WFG is based on the RAMS model, with the incorporation of processes like dust and sea-salt production, gas and aqueous phase chemistry and particle formation. In this study, the major characteristics of the developed (and under development) modeling systems are presented, as well as the spatiotemporal distribution of the transported dust amounts, the interaction with anthropogenically-produced particles and the potential implications on radiative transfer.

  8. Desert dust impacts on human health: an alarming worldwide reality and a need for studies in West Africa

    Science.gov (United States)

    de Longueville, Florence; Ozer, Pierre; Doumbia, Seydou; Henry, Sabine

    2013-01-01

    High desert dust concentrations raise concerns about adverse health effects on human populations. Based on a systematic literature review, this paper aims to learn more about the relationship between desert dust and human health in the world and to analyse the place of West Africa as a study area of interest. Papers focussing on the potential relationship between dust and health and showing quantitative analyses, published between January 1999 and September 2011, were identified using the ISI Web of Knowledge database ( N = 50). A number of adverse health effects, including respiratory, cardiovascular and cardiopulmonary diseases, are associated with dust. This survey highlights obvious dust impacts on human health independently of the study area, health outcomes and method. Moreover, it reveals an imbalance between the areas most exposed to dust and the areas most studied in terms of health effects. None of these studies has been conducted in West Africa, despite the proximity of the Sahara, which produces about half of the yearly global mineral dust. In view of the alarming results in many parts of the world (Asia, Europe, America), this paper concludes by stressing the importance of carrying out impact studies of Saharan dust in West Africa, where dust events are more frequent and intense than anywhere else.

  9. Imagining the personal past: Episodic counterfactuals compared to episodic memories and episodic future projections

    DEFF Research Database (Denmark)

    Özbek, Müge; Bohn, Annette; Berntsen, Dorthe

    2017-01-01

    Episodic counterfactuals are imagined events that could have happened, but did not happen, in a person’s past. Such imagined past events are important aspects of mental life, affecting emotions, decisions, and behaviors. However, studies examining their phenomenological characteristics and content...... are few. Here we introduced a new method to systematically compare self-generated episodic counterfactuals to self-generated episodic memories and future projections with regard to their phenomenological characteristics (e.g., imagery, emotional valence, rehearsal) and content (e.g., reference to cultural...... distance. The findings show that imagined events are phenomenologically different from memories of experienced events, consistent with reality monitoring theory, and that imagined future events are different from both actual and imagined past events, consistent with some theories of motivation....

  10. Dust Storms: Why Are Dust Storms a Concern?

    Science.gov (United States)

    ... Shed Sheep Ranching Shellfishing Shipping Shipyard Storms and Floods Stormwater and Sewage Trash Burning Tree Farm and ... attacks. Exposure to dust in dust storms can cause coughing, wheezing, and runny noses. Breathing a lot ...

  11. Episodic fieldwork, updating, and sociability

    DEFF Research Database (Denmark)

    Whyte, M.

    2013-01-01

    on these relationships. I draw on Simmel's concept of sociability to explore the significance of the recurring updates that are so much a part of long-term and thus episodic fieldwork. Updating suggests participation, positionality, and transformation-as well as play and familiarity. The presumption of familiarity...

  12. Interstellar dust and extinction

    Science.gov (United States)

    Mathis, John S.

    It is noted that the term 'interstellar dust' refers to materials with rather different properties, and that the mean extinction law of Seaton (1979) or Savage and Mathis (1979) should be replaced by the expression given by Cardelli et al. (1989), using the appropriate value of total-to-selective extinction. The older laws were appropriate for the diffuse ISM but dust in clouds differs dramatically in its extinction law. Dust is heavily processed while in the ISM by being included within clouds and cycled back into the diffuse ISM many times during its lifetime. Hence, grains probably reflect only a trace of their origin, although meteoritic inclusions with isotopic anomalies demonstrate that some tiny particles survive intact from a supernova origin to the present.

  13. Selecting baghouse dust collectors

    Energy Technology Data Exchange (ETDEWEB)

    Moore, S.; Rubak, J.; Jolin, M. [Farr Co., El Segundo, CA (United States)]|[Farr Co., Laval, Quebec (Canada)

    1997-04-01

    A thorough analysis of the dust to be captured and determination of specific application requirements are necessary when designing a baghouse collection system. Independent consultants specializing in pollution control equipment and manufacturers with experience in several types of collectors are possible sources of assistance. These experts typically have testing facilities to analyze the dust characteristics. This final article of a two-part series on baghouse design and selection concentrates on application considerations created by the type of dust handled, selecting the best filtration media, selecting the best filtration media, and determining the air-to-cloth (A/C) ratio. The first article discussed bag sizing and cleaning methods and housing and hopper designs.

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

    Science.gov (United States)

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

    2015-10-01

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

  15. Characterization of intense aerosol episodes in the Mediterranean basin from satellite observations

    Science.gov (United States)

    Gkikas, Antonis; Hatzianastassiou, Nikos; Mihalopoulos, Nikolaos

    2014-05-01

    The properties and distribution of aerosols over the broader Mediterranean region are complex since particles of different nature are either produced within its boundaries or transported from other regions. Thus, coarse dust aerosols are transported primarily from Sahara and secondarily from Middle East, while fine polluted aerosols are either produced locally from anthropogenic activities or they are transported from neighbouring or remote European areas. Also during summer biomass aerosols are transported towards the Mediterranean, originating from massive and extended fires occurring in northern Balkans and Eastern Europe and favoured by the prevailing synoptic conditions. In addition, sea-salt aerosols originate from the Mediterranean Sea or the Atlantic Ocean. Occasionally, aerosols are encountered at very high concentrations (aerosol episodes or events) significantly affecting atmospheric dynamics and climate as well as human health. Given the coexistence of different aerosols as internal and external mixtures characterizing and discriminating between the different types of aerosol episodes is a big challenge. A characterization and classification of intense aerosol episodes in the Mediterranean basin (March 2000 - February 2007) is attempted in the present study. This is achieved by implementing an objective and dynamic algorithm which uses daily aerosol optical properties derived from satellite measurements, namely MODIS-Terra, Earth Probe (EP)-TOMS and OMI-Aura. The aerosol episodes are first classified into strong and extreme ones, according to their intensity, by means of aerosol optical depth at 550nm (AOD550nm). Subsequently, they are discriminated into the following aerosol types: (i) biomass/urban-industrial (BU), (ii) desert dust (DD), (iii) sea-salt like (SS), (iv) mixed (MX) and (v) undetermined (UN). The classification is based on aerosol optical properties accounting for the particles' size (Ångström exponent, Effective radius), the

  16. Military Assistance in Sub-Saharan Africa

    Science.gov (United States)

    1994-01-01

    on the wildlife habitats, reduces the animal population through poaching, and reduces another source of income, tourism . 3 Hearing before the...their livestock, and defecate. The roads between Mombassa, Kenya and Goma, Zaire are often litde more than trails of rubble, remnants of what once was...authority of four different unified commands. In sub-Saharan Africa the U.S. Central Command (CENTCOM) is responsible for Djibouti, Kenya , Ethiopia and

  17. Development and evaluation of an operational SDS forecasting system for East Asia: CUACE/DUST

    Science.gov (United States)

    Zhou, C. H.; Gong, S. L.; Zhang, X. Y.; Wang, Y. Q.; Niu, T.; Liu, H. L.; Zhao, T. L.; Yang, Y. Q.; Hou, Q.

    2007-06-01

    CUACE/Dust, an operational sand and dust storm (SDS) forecasting system for East Asia, was developed at CMA (China Meteorological Administration) by integrating a meso-scale dust aerosol model with a 3DVar data assimilation system that uses both surface network observation data and dust intensity data retrieved from the Chinese Geostationary Satellite FY-2C. For spring 2006, CUACE/Dust successfully forecasted most of the 31 SDS episodes in East Asia. A detailed comparison of the modeling predictions for the 8-12 March episode with surface network observations and lidar measurements revealed a robust forecasting ability of the system. The time series of the forecasted dust concentrations for a number of representative stations for the whole spring 2006 were also evaluated against surface PM10 monitoring data, showing a very good agreement in terms of the SDS timing and magnitudes near source regions where dust aerosols dominate. For the entire domain forecasts in spring 2006 (1 March-31 May), a TS (thread score) system evaluated the performance of the system against all available observations and rendered an averaged TS value of 0.31 for 24 h forecasts, 0.23 for 48 h and 0.21 for 72 h forecasts.

  18. Energy Security and Sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Emily Meierding

    2013-02-01

    Full Text Available Published by Palgrave MacmillanOver the last decade the topic of energy security has reappeared on global policy agendas. Most analyses of international energy geopolitics examine the interests and behaviour of powerful energy-importing countries like the US and China. This chapter begins by examining foreign powers’ expanded exploitation of oil and uranium resources in Sub-Saharan Africa. It goes on to examine how energy importers’ efforts to enhance their energy security through Africa are impacting energy security within Africa. It assesses Sub-Saharan states’ attempts to increase consumption of local oil and uranium reserves. Observing the constraints on these efforts, it then outlines some alternative strategies that have been employed to enhance African energy security. It concludes that, while local community-based development projects have improved the well-being of many households, they are not a sufficient guarantor of energy security. Inadequate petroleum access, in particular, remains a development challenge. Foreign powers’ efforts to increase their oil security are undermining the energy security of Sub-Saharan African citizens.

  19. Imagining the personal past: Episodic counterfactuals compared to episodic memories and episodic future projections

    DEFF Research Database (Denmark)

    Özbek, Müge; Bohn, Annette; Berntsen, Dorthe

    2017-01-01

    Episodic counterfactuals are imagined events that could have happened, but did not happen, in a person’s past. Such imagined past events are important aspects of mental life, affecting emotions, decisions, and behaviors. However, studies examining their phenomenological characteristics and content...

  20. Speciation of organic aerosols in the Saharan Air Layer and in the free troposphere westerlies

    Science.gov (United States)

    García, M. Isabel; van Drooge, Barend L.; Rodríguez, Sergio; Alastuey, Andrés

    2017-07-01

    We focused this research on the composition of the organic aerosols transported in the two main airflows of the subtropical North Atlantic free troposphere: (i) the Saharan Air Layer - the warm, dry and dusty airstream that expands from North Africa to the Americas at subtropical and tropical latitudes - and (ii) the westerlies, which flow from North America over the North Atlantic at mid- and subtropical latitudes. We determined the inorganic compounds (secondary inorganic species and elemental composition), elemental carbon and the organic fraction (bulk organic carbon and organic speciation) present in the aerosol collected at Izaña Observatory, ˜ 2400 m a.s.l. on the island of Tenerife. The concentrations of all inorganic and almost all organic compounds were higher in the Saharan Air Layer than in the westerlies, with bulk organic matter concentrations within the range 0.02-4.0 µg m-3. In the Saharan Air Layer, the total aerosol population was by far dominated by dust (93 % of bulk mass), which was mixed with secondary inorganic pollutants ( alkanes, hopanes, polycyclic aromatic hydrocarbons and those formed after oxidation of α-pinene and isoprene, determined by gas chromatography coupled with mass spectrometry) accounted for 15 % of the bulk organic matter (determined by the thermo-optical transmission technique); the most abundant organic compounds were saccharides (associated with surface soils), secondary organic aerosols linked to oxidation of biogenic isoprene (SOA ISO) and dicarboxylic acids (linked to several primary sources and SOA). When the Saharan Air Layer shifted southward, Izaña was within the westerlies stream and organic matter accounted for ˜ 28 % of the bulk mass of aerosols. In the westerlies, the organic aerosol species determined accounted for 64 % of the bulk organic matter, with SOA ISO and dicarboxylic acids being the most abundant; the highest concentration of organic matter (3.6 µg m-3) and of some organic species (e

  1. Speciation of organic aerosols in the Saharan Air Layer and in the free troposphere westerlies

    Directory of Open Access Journals (Sweden)

    M. I. García

    2017-07-01

    Full Text Available We focused this research on the composition of the organic aerosols transported in the two main airflows of the subtropical North Atlantic free troposphere: (i the Saharan Air Layer – the warm, dry and dusty airstream that expands from North Africa to the Americas at subtropical and tropical latitudes – and (ii the westerlies, which flow from North America over the North Atlantic at mid- and subtropical latitudes. We determined the inorganic compounds (secondary inorganic species and elemental composition, elemental carbon and the organic fraction (bulk organic carbon and organic speciation present in the aerosol collected at Izaña Observatory,  ∼  2400 m a.s.l. on the island of Tenerife. The concentrations of all inorganic and almost all organic compounds were higher in the Saharan Air Layer than in the westerlies, with bulk organic matter concentrations within the range 0.02–4.0 µg m−3. In the Saharan Air Layer, the total aerosol population was by far dominated by dust (93 % of bulk mass, which was mixed with secondary inorganic pollutants ( <  5 % and organic matter ( ∼  1.5 %. The chemical speciation of the organic aerosols (levoglucosan, dicarboxylic acids, saccharides, n-alkanes, hopanes, polycyclic aromatic hydrocarbons and those formed after oxidation of α-pinene and isoprene, determined by gas chromatography coupled with mass spectrometry accounted for 15 % of the bulk organic matter (determined by the thermo-optical transmission technique; the most abundant organic compounds were saccharides (associated with surface soils, secondary organic aerosols linked to oxidation of biogenic isoprene (SOA ISO and dicarboxylic acids (linked to several primary sources and SOA. When the Saharan Air Layer shifted southward, Izaña was within the westerlies stream and organic matter accounted for  ∼  28 % of the bulk mass of aerosols. In the westerlies, the organic aerosol species determined

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

    Science.gov (United States)

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

    2002-01-01

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

  3. Identification of the exploatation dust in road dust

    Directory of Open Access Journals (Sweden)

    B. Gajdzik

    2012-01-01

    Full Text Available The aim of this publication is to determine models of explore dust from vehicle brake systems and the presentationof measurement results of the exploitation dust, which is separate from road dust. The following methods and measuring devices were used: T-01M device, screen analysis, analysis of chemical composition with the use of a scanning microscope with Energy Dispersive x-ray Spectroscopy (EDS analyser. The measurements for identifying this type of dust were conducted on marked sections of roads: motorway, city road and mountain road. The explored dust was distinguished in the following car systems: brakes, clutch plates, tyres and catalytic converters.

  4. Dust Obscures Korea

    Science.gov (United States)

    2002-01-01

    The dust cloud over eastern Asia was so thick on March 21, 2002, that the Korean Peninsula completely disappeared from view in this Sea-viewing Wide Field-of-view Sensor (SeaWiFS) image of the region. Parts of South Korea report that visibility at the surface is less than 50 m (165 feet). Airports throughout the region canceled flights due to the poor visibility. Eyewitnesses in China report that the dust was so thick in Beijing at times that visibility was limited to 100 m (330 feet), while in parts of the Gansu Province visibility was reported at less than 10 m (33 feet). Chinese officials say this is the worst dust storm to hit in more than 10 years. Dust from an earlier event still colors the air to the east of Japan. (The island of Honshu is just peeking out from under the cloud cover in these images.) Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  5. Dust Mite Allergy

    Science.gov (United States)

    ... more likely to develop infections of the sinuses (sinusitis). Asthma. People with asthma and dust mite allergy often have difficulty managing asthma symptoms. They may be at risk of asthma attacks that require immediate medical treatment or emergency care. By Mayo Clinic Staff . Mayo ...

  6. Fingerprints in the Dust

    Science.gov (United States)

    2001-01-01

    These MISR nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a spectacularly dusty spring view from April 7, 2001 (middle). The left-hand and middle images are from Terra orbits 2967 and 6928, respectively, and extend from central Manchuria near the top to portions of North and South Korea at the bottom. They are approximately 380 kilometers in width.Asia's desert areas are prone to soil erosion, as underground water tables are lowered by prolonged drought and by industrial and agricultural water use. Heavy winds blowing eastward across the arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the April 2001 storm blew across the Pacific Ocean and were carried as far as North America. The minerals transported in this manner are believed to provide nutrients for both oceanic and land ecosystems.According to the Xinhua News Agency in China, nearly one million tons of Gobi Desert dust blow into Beijing each year. During a similar dust outbreak last year, the Associated Press reported that the visibility in Beijing had been reduced the point where buildings were barely visible across city streets, and airline schedules were significantly disrupted. The dust has also been implicated in adverse health effects such as respiratory discomfort and eye irritation.The image on the right is a higher resolution MISR nadir-camera view of a portion of the April 7, 2001 dust cloud. It covers an area roughly 250 kilometers wide by 470 kilometers high. When viewed at full magnification, a number of atmospheric wave features, like the ridges and valleys of a fingerprint, are apparent. These are probably induced by surface topography, which can disturb the wind flow. A few small cumulus clouds are also visible, and are casting shadows on the thick lower dust layer.Analyses of images such as these constitute one phase of MISR's participation in the Asian

  7. Understanding the Transport of Patagonian Dust and Its Influence on Marine Biological Activity in the South Atlantic Ocean

    Science.gov (United States)

    Johnson, Matthew; Meskhidze, Nicholas; Kiliyanpilakkil, Praju; Gasso, Santiago

    2010-01-01

    Modeling and remote sensing techniques were applied to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of soluble-iron- laden mineral dust deposition on marine primary productivity in the South Atlantic Ocean (SAO) surface waters. The global chemistry transport model GEOS-Chem, implemented with an iron dissolution scheme, was applied to evaluate the atmospheric transport and deposition of mineral dust and bioavailable iron during two dust outbreaks originating in the source regions of Patagonia. In addition to this "rapidly released" iron, offline calculations were also carried out to estimate the amount of bioavailable iron leached during the residence time of dust in the ocean mixed layer. Model simulations showed that the horizontal and vertical transport pathways of Patagonian dust plumes were largely influenced by the synoptic meteorological patterns of high and low pressure systems. Model-predicted horizontal and vertical transport pathways of Patagonian dust over the SAO were in reasonable agreement with remotely-sensed data. Comparison between remotely-sensed and offline calculated ocean surface chlorophyll-a concentrations indicated that, for the two dust outbreaks examined in this study, the deposition of bioavailable iron in the SAO through atmospheric pathways was insignificant. As the two dust transport episodes examined here represent typical outflows of mineral dust from South American sources, our study suggests that the atmospheric deposition of mineral dust is unlikely to induce large scale marine primary productivity and carbon sequestration in the South Atlantic sector of the Southern Ocean.

  8. Dust and Biological Aerosols from the Sahara and Asia Influence Precipitation in the Western US

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-03-29

    Winter storms in California’s Sierra Nevada increase seasonal snowpack and provide critical water resources for the state. Thus, the mechanisms influencing precipitation in this region have been the subject of research for decades. Previous studies suggest Asian dust enhances cloud ice and precipitation (1), while few studies consider biological aerosols as an important global source of ice nuclei (IN). Here, we show that dust and biological aerosols transported from as far as the Sahara were present in glaciated high-altitude clouds coincident with elevated IN concentrations and ice-induced precipitation. This study presents the first direct cloud and precipitation measurements showing that Saharan and Asian dust and biological aerosols likely serve as IN and play an important role in orographic precipitation processes over the western United States.

  9. Motivation and episodic memory performance

    OpenAIRE

    Ngaosuvan, Leonard

    2004-01-01

    In everyday life, motivation and learning are connected like music and dancing. Many educators realize this and work hard to improve their students' motivation. A motivated student may repeat and self-rehearse the content of a chapter more often, which leads to better learning. However, from a cognitive psychology point of view, it is still uncertain if motivation without differences in repetition or attention, affects episodic memory performance. That is, would a motivated student perform be...

  10. Effect of dust size distribution and dust charge fluctuation on dust ion ...

    Indian Academy of Sciences (India)

    2016-06-17

    Jun 17, 2016 ... Dusty plasma; dust-acoustic shock wave; dust size distribution; adiabatic dust charge variation; negative ions. PACS Nos 52.27.Lw; 52.35.Tc; 52.35.Mw. 1. Introduction ... processes has relation to some phenomena including. Landau damping, collisions between charged particles and neutrals and ...

  11. Application of the Garrlic Algorithm for the Characterization of Dust and Marine Particles Utilizing the Lidar-Sunphotometer Synergy

    Directory of Open Access Journals (Sweden)

    Tsekeri Alexandra

    2016-01-01

    Full Text Available The importance of studying the vertical distribution of aerosol plumes is prominent in regional and climate studies. The new Generalized Aerosol Retrieval from Radiometer and Lidar Combined data algorithm (GARRLiC provides this opportunity combining active and passive ground-based remote sensing from lidar and sunphotometer measurements. Here, we utilize GARRLiC capabilities for the characterization of Saharan dust and marine particles at the Eastern Mediterranean region during the Characterization of Aerosol mixtures of Dust And Marine origin Experiment (CHARADMExp. Two different case studies are presented, a dust-dominated case which we managed to characterize successfully in terms of the particle microphysical properties and their vertical distribution and a case of two separate layers of marine and dust particles for which the characterization proved to be more challenging.

  12. Multiplatform analysis of the radiative effects and heating rates for an intense dust storm on 21 June 2007

    Science.gov (United States)

    Naeger, Aaron R.; Christopher, Sundar A.; Johnson, Ben T.

    2013-08-01

    Dust radiative effects and atmospheric heating rates are investigated for a Saharan dust storm on 21 June 2007 using a combination of multiple satellite data sets and ground and aircraft observations as input into a delta-four stream radiative transfer model (RTM). This combines the strengths of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations and CloudSat satellites and in situ aircraft data to characterize the vertical structure of the dust layers (5 km in height with optical depths between 1.5 and 2.0) and underlying low-level water clouds. These observations were used, along with Aerosol Robotic Network retrievals of aerosol optical properties, as input to the RTM to assess the surface, atmosphere, and top of atmosphere (TOA) shortwave aerosol radiative effects (SWAREs). Our results show that the dust TOA SWARE per unit aerosol optical depth was -56 W m-2 in cloud-free conditions over ocean and +74 W m-2 where the dust overlay low-level clouds, and show heating rates greater than 10 K/d. Additional case studies also confirm the results of the 21 June case. This study shows the importance of identifying clouds beneath dust as they can have a significant impact on the radiative effects of dust, and hence assessments of the role of dust aerosol on the energy budget and climate.

  13. Observation and simulation of dust aerosol cycle and impact on radiative fluxes during the FENNEC campaign in summer 2011

    Science.gov (United States)

    Minvielle, Fanny; Derimian, Yevgeny; Pere, Jean-Christophe; Flamant, Cyrille; Brogniez, Gérard

    2013-04-01

    The Sahara desert is one of the principal worldwide sources of dust aerosol emissions that play significant role in the climatic system. In the framework of the FENNEC campaign, conducted during the summer 2011, we focus on dust radiative effect and impact on the atmospheric dynamics and profile structure. We study the variability of the measured radiative parameters and model atmospheric dynamics during dust plume observations at the FENNEC sites, therefore, trying to understand the link between the Saharan heat low system and dust aerosols. Due to its large size the airborne dust can absorb and scatter not only solar, but also thermal infrared radiation, which requires consideration of both spectral ranges. Analysis of AERONET and other optical observations during the period of intensive campaign in summer 2011 provides information on variability of aerosol optical characteristics and perturbation of solar and TIR flux. We use these observations in conjunction with the meso-scale model RAMS to understand the impact of the dust plumes on the atmospheric dynamics. We also simulate the dust cycle in order to find the contribution of the different emission sources and identify structure of transport over an extended domain. Then, coupling the radiative code (GAME) we calculate the radiative forcing of dust and compare it to the radiative flux observed and computed based on the AERONET observations. Validation of simulations is made using measurements from space-borne CALIOP lidar, SEVIRI and OMI satellites, AERONET ground-based stations and observations acquired onboard the SAFIRE Falcon 20 research aircraft.

  14. Fungal microbiota from rain water and pathogenicity of Fusarium species isolated from atmospheric dust and rainfall dust.

    Science.gov (United States)

    Palmero, D; Rodríguez, J M; de Cara, M; Camacho, F; Iglesias, C; Tello, J C

    2011-01-01

    In order to determine the presence of Fusarium spp. in atmospheric dust and rainfall dust, samples were collected during September 2007, and July, August, and October 2008. The results reveal the prevalence of airborne Fusarium species coming from the atmosphere of the South East coast of Spain. Five different Fusarium species were isolated from the settling dust: Fusarium oxysporum, F. solani, F. equiseti, F. dimerum, and F. proliferatum. Moreover, rainwater samples were obtained during significant rainfall events in January and February 2009. Using the dilution-plate method, 12 fungal genera were identified from these rainwater samples. Specific analyses of the rainwater revealed the presence of three species of Fusarium: F. oxysporum, F. proliferatum and F. equiseti. A total of 57 isolates of Fusarium spp. obtained from both rainwater and atmospheric rainfall dust sampling were inoculated onto melon (Cucumis melo L.) cv. Piñonet and tomato (Lycopersicon esculentum Mill.) cv. San Pedro. These species were chosen because they are the main herbaceous crops in Almeria province. The results presented in this work indicate strongly that spores or propagules of Fusarium are able to cross the continental barrier carried by winds from the Sahara (Africa) to crop or coastal lands in Europe. Results show differences in the pathogenicity of the isolates tested. Both hosts showed root rot when inoculated with different species of Fusarium, although fresh weight measurements did not bring any information about the pathogenicity. The findings presented above are strong indications that long-distance transmission of Fusarium propagules may occur. Diseases caused by species of Fusarium are common in these areas. They were in the past, and are still today, a problem for greenhouses crops in Almería, and many species have been listed as pathogens on agricultural crops in this region. Saharan air masses dominate the Mediterranean regions. The evidence of long distance dispersal

  15. Observations of an 11 September Sahelian Squall Line and Saharan Air Layer Outbreak during NAMMA-06

    Directory of Open Access Journals (Sweden)

    J. W. Smith

    2012-01-01

    Full Text Available The 2006 NASA-African Monsoon Multidisciplinary Analyses (NAMMA-06 field campaign examined a compact, low-level vortex embedded in the trough of an AEW between 9–12 September. The vortex triggered a squall line (SL in southeastern Senegal in the early morning of 11 September and became Tropical Depression 8 on 12 September. During this period, there was a Saharan Air Layer (SAL outbreak in northwestern Senegal and adjacent Atlantic Ocean waters in the proximity of the SL. Increases in aerosol optical thicknesses in Mbour, Senegal, high dewpoint depressions observed in the Kawsara and Dakar rawinsondes, and model back-trajectories suggest the SAL exists. The close proximity of this and SL suggests interaction through dust entrainment and precipitation invigoration.

  16. Early detection of first-episode psychosis

    DEFF Research Database (Denmark)

    Larsen, Tor K; Melle, Ingrid; Auestad, Bjørn

    2006-01-01

    Early intervention is assumed to improve outcome in first-episode psychosis, but this has not been proven.......Early intervention is assumed to improve outcome in first-episode psychosis, but this has not been proven....

  17. Optical properties of mineral dust aerosol in the thermal infrared

    Science.gov (United States)

    Köhler, Claas H.

    2017-02-01

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

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

    Science.gov (United States)

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

    2017-03-10

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

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

    Science.gov (United States)

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

    2006-10-01

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

  20. Shape dependency of the extinction and absorption cross sections of dust aerosols modeled as randomly oriented spheroids

    Directory of Open Access Journals (Sweden)

    R. Wagner

    2011-09-01

    Full Text Available We present computational results on the shape dependency of the extinction and absorption cross sections of dustlike aerosol particles that were modeled as randomly oriented spheroids. Shape dependent variations in the extinction cross sections are largest in the size regime that is governed by the interference structure. Elongated spheroids best fitted measured extinction spectra of re-dispersed Saharan dust samples. For dust particles smaller than 1.5 μm in diameter and low absorption potential, shape effects on the absorption cross sections are very small.

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

    Science.gov (United States)

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

    2017-10-01

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

  2. Spatiotemporal evolution of a severe winter dust event in the western Mediterranean: Aerosol optical and physical properties

    Science.gov (United States)

    Titos, G.; Ealo, M.; Pandolfi, M.; Pérez, N.; Sola, Y.; Sicard, M.; Comerón, A.; Querol, X.; Alastuey, A.

    2017-04-01

    An outstanding Saharan dust event affected the Iberian Peninsula during winter 2016 (20 to 25 February). The impact of this event on ambient PM10 surface levels and its spatial and temporal evolution was investigated by means of data from 250 air quality stations across mainland Spain and the Balearic Islands. The event had a significant impact on surface PM10 levels, and on 22 February, 90% of the air quality monitoring sites registered PM10 concentrations above the EU daily limit value of 50 μg/m3. The study of the attenuated backscattering vertical profiles associated with African dust evidenced a complex structure, with a thick aerosol layer that was at higher altitudes over the pre-Pyrenees compared to the coastal area of Barcelona but closer to the surface than typically observed at both sites. Optical and physical properties of dust particles were investigated at the continental background Global Atmosphere Watch mountain observatory of Montsec (MSA) in the pre-Pyrenees. Good agreement was found between in situ and passive remote sensing methodologies once the aloft dust layer reached the MSA station. Scattering Ångström exponent values decreased to values close to zero (even below zero for surface in situ measurements) indicating the predominance of coarse particles. On the contrary, absorption Ångström exponent values increased during the Saharan dust outbreak denoting an absorption enhancement at shorter wavelengths, characteristic of mineral dust particles. Furthermore, the performance of NMMB/BSC-Dust and BSC-DREAM8b models has been qualitatively evaluated for the dust spatial distribution across Spain and the vertical structure over MSA and Barcelona showing good agreement.

  3. Distribution of dust during two dust storms in Iceland

    Science.gov (United States)

    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.

  4. Trans-Pacific transport of dust aerosols from East Asia: Insights gained from multiple observations and modeling.

    Science.gov (United States)

    Guo, Jianping; Lou, Mengyun; Miao, Yucong; Wang, Yuan; Zeng, Zhaoliang; Liu, Huan; He, Jing; Xu, Hui; Wang, Fu; Min, Min; Zhai, Panmao

    2017-11-01

    East Asia is one of the world's largest sources of dust and anthropogenic pollution. Dust particles originating from East Asia have been recognized to travel across the Pacific to North America and beyond, thereby affecting the radiation incident on the surface as well as clouds aloft in the atmosphere. In this study, integrated analyses are performed focusing on one trans-Pacific dust episode during 12-22 March 2015, based on space-borne, ground-based observations, reanalysis data combined with Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT), and the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem). From the perspective of synoptic patterns, the location and strength of Aleutian low pressure system largely determined the eastward transport of dust plumes towards western North America. Multi-sensor satellite observations reveal that dust aerosols in this episode originated from the Taklimakan and Gobi Deserts. Moreover, the satellite observations suggest that the dust particles can be transformed to polluted particles over the East Asian regions after encountering high concentration of anthropogenic pollutants. In terms of the vertical distribution of polluted dust particles, at the very beginning, they were mainly located in the altitudes ranging from 1 km to 7 km over the source region, then ascended to 2 km-9 km over the Pacific Ocean. The simulations confirm that these elevated dust particles in the lower free troposphere were largely transported along the prevailing westerly jet stream. Overall, observations and modeling demonstrate how a typical springtime dust episode develops and how the dust particles travel over the North Pacific Ocean all the way to North America. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Transport of dust particles in tokamak devices

    Energy Technology Data Exchange (ETDEWEB)

    Pigarov, A.Yu. [University of California at San Diego, La Jolla, CA (United States)]. E-mail: apigarov@uscd.edu; Smirnov, R.D. [University of California at San Diego, La Jolla, CA (United States); Krasheninnikov, S.I. [University of California at San Diego, La Jolla, CA (United States); Rognlien, T.D. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Rosenberg, M. [University of California at San Diego, La Jolla, CA (United States); Soboleva, T.K. [UNAM, Mexico, DistritoFederal (Mexico)

    2007-06-15

    Recent advances in the dust transport modeling in tokamak devices are discussed. Topics include: (1) physical model for dust transport; (2) modeling results on dynamics of dust particles in plasma; (3) conditions necessary for particle growth in plasma; (4) dust spreading over the tokamak; (5) density profiles for dust particles and impurity atoms associated with dust ablation in tokamak plasma; and (6) roles of dust in material/tritium migration.

  6. [House dust mite allergy].

    Science.gov (United States)

    Carrard, A; Pichler, C

    2012-04-01

    House dust mites can be found all over the world where human beings live independent from the climate. Proteins from the gastrointestinal tract- almost all known as enzymes - are the allergens which induce chronic allergic diseases. The inhalation of small amounts of allergens on a regular base all night leads to a slow beginning of the disease with chronically stuffed nose and an exercise induced asthma which later on persists. House dust mites grow well in a humid climate - this can be in well isolated dwellings or in the tropical climate - and nourish from human skin dander. Scales are found in mattresses, upholstered furniture and carpets. The clinical picture with slowly aggravating complaints leads quite often to a delayed diagnosis, which is accidently done on the occasion of a wider spectrum of allergy skin testing. The beginning of a medical therapy with topical steroids as nasal spray or inhalation leads to a fast relief of the complaints. Although discussed in extensive controversies in the literature - at least in Switzerland with the cold winter and dry climate - the recommendation of house dust mite avoidance measures is given to patients with good clinical results. The frequent ventilation of the dwelling with cold air in winter time cause a lower indoor humidity. Covering encasings on mattresses, pillow, and duvets reduces the possibility of chronic contact with mite allergens as well as the weekly changing the bed linen. Another option of therapy is the specific immunotherapy with extracts of house dust mites showing good results in children and adults. Using recombinant allergens will show a better quality in diagnostic as well as in therapeutic specific immunotherapy.

  7. Dust in External Galaxies

    OpenAIRE

    Calzetti, Daniela

    2009-01-01

    Existing (Spitzer Space Telescope) and upcoming (Herschel Space Telescope) facilities are deepening our understanding of the role of dust in tracing the energy budget and chemical evolution of galaxies. The tools we are developing while exploring the local Universe will in turn become pivotal in the interpretation of the high redshift Universe when near--future facilities (the Atacama Large Millimeter Array [ALMA], the Sub--Millimeter Array [SMA], the Large Millimeter Telescope [LMT], the Jam...

  8. Sulfate and nitrate in Asian dust particles observed in desert, coastal and marine air

    Science.gov (United States)

    Zhang, D.; Wu, F.; Junji, C.

    2016-12-01

    Sulfate and nitrate in dust particles are believed to be two key species which can largely alter the physical and chemical properties of the particles in the atmosphere, in particular under humid conditions. Their occurrence in the particles has usually been considered to be the consequence of particles' aging during their long-distance travel in the air although they are present in some crustal minerals. Our observations at two deserts in China during dust episodes revealed that there were soil-derived sulfate and background-like nitrate in atmospheric dust samples. Sulfate in dust samples was proportional to samples' mass and comprised at steady mass percentages in differently sized samples. In contrast, nitrate concentration was approximately stable and independent from dust loading. Our observations at inland and coastal areas of China during dust episodes revealed that sulfate and nitrate were hardly produced on the surface of dust particles that were originated from the deserts areas in northwestern China. This is because the dust particles were in the postfrontal air, where the temperature was low and the relative humidity was small due to the adiabatic properties of the air mass. There are a number studies reporting that sulfate and nitrate had been efficiently produced on mineral particles in inland areas of China. However, those mineral particles were more likely from the local areas rather than from the desert areas. Our observations in the coastal areas of Japan, which is located in the downstream areas of the Asian continent and surrounded by sea areas revealed that dust particles appearing there frequently contained sulfate and nitrate, indicating sulfate and nitrate had been efficiently produced on the surface of the particles when the particles traveled in the marine air between China and Japan.

  9. SAHARAN DUST AND FLORIDA RED TIDES: THE CYANOPHYTE CONNECTION. (R827085)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  10. Soluble iron nutrients in Saharan dust over the central Amazon rainforest

    National Research Council Canada - National Science Library

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

    2017-01-01

      The intercontinental transport of aerosols from the Sahara desert plays a significant role in nutrient cycles in the Amazon rainforest, since it carries many types of minerals to these otherwise low-fertility lands...

  11. Using the significant dust deposition event on the glaciers of Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and

    Directory of Open Access Journals (Sweden)

    G. Nosenko

    2013-02-01

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

  12. Episodic Excessive Blinking in Children.

    Science.gov (United States)

    Mali, Yasmin Poustchi; Simon, John W; Chaudhri, Imran; Zobal-Ratner, Jitka; Barry, Gerard P

    2016-01-01

    Many children present with excessive blinking. Categorization, associated conditions, and prognosis are controversial. All children with excessive blinking were reviewed, excluding those with known uveitis, glaucoma, or obvious eyelid abnormalities. Parents were telephoned for follow-up. No ocular pathology was identified in 31 of 34 children with excessive blinking (91%). Parents were able to report a specific cause of blinking in 7 (21%). In 24 of 34 (71%), parents reported complete resolution of excessive blinking. No new ophthalmologic diagnoses were uncovered on follow-up. Episodes of excessive blinking rarely indicate neurologic disorders and frequently resolve spontaneously. Copyright 2016, SLACK Incorporated.

  13. Dust, Climate, and Human Health

    Science.gov (United States)

    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

  14. Dust, Climate, and Human Health

    Science.gov (United States)

    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.

  15. Chemical characteristics of atmospheric PM2.5 loads during air pollution episodes in Giza, Egypt

    Science.gov (United States)

    Hassan, Salwa K.; Khoder, Mamdouh I.

    2017-02-01

    Several types of pollution episodes, including dust storm (DSs), haze dust (HDs), straw rice combustions (SRCs) are common phenomena and represent severe environmental hazard in Egypt. This study provides the first comprehensive analysis of the chemical characteristics of aerosol during air pollution episodes at an urban area in Giza, Egypt. PM2.5 samples during various PM episodes during 2013-2014 were collected and analyzed. Results indicate that the highest PM2.5 mass concentrations were found during DSs (250 μg/m3), followed by HDs (130 μg/m3) and SRCs (103 μg/m3). Average PM2.5 mass concentrations were 1.91, 3.68 and 1.68 times higher than on normal days (NDs) during HDs, DSs and SRCs, respectively. The highest total water-soluble ions concentration was 61.1 μg/m3 during HDs, followed by SRCs (41.9 μg/m3) and DSs (35.2 μg/m3). SO42- is the most abundant chemical components on the three PM episodes. Secondary inorganic ions (NO3-, SO42-, and NH4+) were enriched during HDs. The total secondary inorganic ions concentrations were 3.17, 1.39 and 1.75 times higher than NDs during HDs days, DSs days and SRCs days, respectively. PM from SRCs showed high K+ and Cl-. SO42-/K+, NO3-/SO42- and Cl-/K+ ratios proved effective as indicators for different pollution episodes. A Ca2+/Al ratio indicates that soil dust was dominant during DSs. Ion balance calculations indicated that PM2.5 from HDs was acidic, while the DSs and SRCs particles were alkaline and the NDs particle's was nearly neutral. The total crustal and anthropogenic metals concentrations were higher in DSs than other PM episodes and normal days. The enrichment factors values in PM episodes and normal days indicate that Fe and Mn in NDs, HDs, DSs and SRCs as well as Cr and Ni in DSs come mainly from crustal sources, whereas Cr, Ni, Co, Cu, Zn, Pb and Cd in PM episodes and NDs are anthropogenic.

  16. Asian dust transport during the springtime of year 2001 and 2002 with a nested version of dust transport model

    Science.gov (United States)

    Uno, I.; Satake, S.; Hara, Y.; Takemura, T.; Wang, Z.; Carmichael, G. R.

    2002-12-01

    Number of yellow sand (Kosa) observation has been surprisingly increasing in Japan and Korea since 2000. Especially extremely high PM10 concentration (exceeding 0.5mg/m3) was observed in Japan several times in 2002, so we have an urgent scientific and political need to forecast/reproduce the detailed dust emission, transport and deposition processes. Intensive modeling studies have already been conducted to examine transport of Sahara dust and its impact on global radiation budget. One of the important differences between the Sahara desert and the Asian desert (mainly Gobi Desert and Takla Makan Desert) is the elevation of the dust source. The averaged elevation of Gobi Desert is approximately 1500 to 2500 m. These deserts are surrounded by high mountains. Furthermore advance of the recent manmade desertification made complicated land use patches for the arid region in Inner Mongolia. Therefore the development of a high horizontal resolution dust model is highly required. In this study, we will report a newly developed nested version of the dust transport model (as a part of Chemical weather FORecasting System; CFORS) in order to have a better understanding of Asian springtime heady dust episode. Here, CFORS is a multi-tracer, on-line, system built within the RAMS mesoscale meteorological model. A unique feature of nested CFORS is that multiple tracers are run on-line in RAMS under the two-way nesting, so that all the fine-scale on-line meteorological information such as 3-D winds, boundary-layer turbulence, surface fluxes and precipitation amount are directly used by the dust emission and transport at every time step. As a result, nested-CFORS produces with high time resolution 3-dimensional fields of dust distributions and major meteorological parameters under the nesting capability of RAMS. In this work, the dust transport model simulation with the nested-CFORS was conducted between March and April of the years 2001 and 2002, respectively. The sensititivy

  17. Parameterizing the interstellar dust temperature

    Science.gov (United States)

    Hocuk, S.; Szűcs, L.; Caselli, P.; Cazaux, S.; Spaans, M.; Esplugues, G. B.

    2017-08-01

    The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction (AV) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths (AV> 20 mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as Td = [ 11 + 5.7 × tanh(0.61 - log 10(AV) ]χuv1/5.9, where χuv is in units of the Draine (1978, ApJS, 36, 595) UV field.

  18. Late Miocene episodic lakes in the arid Tarim Basin, western China.

    Science.gov (United States)

    Liu, Weiguo; Liu, Zhonghui; An, Zhisheng; Sun, Jimin; Chang, Hong; Wang, Ning; Dong, Jibao; Wang, Huanye

    2014-11-18

    The Tibetan Plateau uplift and Cenozoic global cooling are thought to induce enhanced aridification in the Asian interior. Although the onset of Asian desertification is proposed to have started in the earliest Miocene, prevailing desert environment in the Tarim Basin, currently providing much of the Asian eolian dust sources, is only a geologically recent phenomenon. Here we report episodic occurrences of lacustrine environments during the Late Miocene and investigate how the episodic lakes vanished in the basin. Our oxygen isotopic (δ(18)O) record demonstrates that before the prevailing desert environment, episodic changes frequently alternating between lacustrine and fluvial-eolian environments can be linked to orbital variations. Wetter lacustrine phases generally corresponded to periods of high eccentricity and possibly high obliquity, and vice versa, suggesting a temperature control on the regional moisture level on orbital timescales. Boron isotopic (δ(11)B) and δ(18)O records, together with other geochemical indicators, consistently show that the episodic lakes finally dried up at ∼4.9 million years ago (Ma), permanently and irreversibly. Although the episodic occurrences of lakes appear to be linked to orbitally induced global climatic changes, the plateau (Tibetan, Pamir, and Tianshan) uplift was primarily responsible for the final vanishing of the episodic lakes in the Tarim Basin, occurring at a relatively warm, stable climate period.

  19. Late Miocene episodic lakes in the arid Tarim Basin, western China

    Science.gov (United States)

    Liu, Weiguo; Liu, Zhonghui; An, Zhisheng; Sun, Jimin; Chang, Hong; Wang, Ning; Dong, Jibao; Wang, Huanye

    2014-01-01

    The Tibetan Plateau uplift and Cenozoic global cooling are thought to induce enhanced aridification in the Asian interior. Although the onset of Asian desertification is proposed to have started in the earliest Miocene, prevailing desert environment in the Tarim Basin, currently providing much of the Asian eolian dust sources, is only a geologically recent phenomenon. Here we report episodic occurrences of lacustrine environments during the Late Miocene and investigate how the episodic lakes vanished in the basin. Our oxygen isotopic (δ18O) record demonstrates that before the prevailing desert environment, episodic changes frequently alternating between lacustrine and fluvial-eolian environments can be linked to orbital variations. Wetter lacustrine phases generally corresponded to periods of high eccentricity and possibly high obliquity, and vice versa, suggesting a temperature control on the regional moisture level on orbital timescales. Boron isotopic (δ11B) and δ18O records, together with other geochemical indicators, consistently show that the episodic lakes finally dried up at ∼4.9 million years ago (Ma), permanently and irreversibly. Although the episodic occurrences of lakes appear to be linked to orbitally induced global climatic changes, the plateau (Tibetan, Pamir, and Tianshan) uplift was primarily responsible for the final vanishing of the episodic lakes in the Tarim Basin, occurring at a relatively warm, stable climate period. PMID:25368156

  20. Extraction of potential areas of river dust emissions using SPOT imageries

    Science.gov (United States)

    Shu-Fen, Tsai; Chao-Yuan, Lin

    2017-04-01

    During the winter, an increase of exposed bare riverbed at the estuary of Jhuoshuei River in Taiwan often causes river dust episodes which harm the health of nearby residents. This study selected the river section from bridge Ziqiang to bridge Xibin as study area. The SPOT satellite imageries, within 15 days of the aeolian dust event during 2005 - 2014, were obtained to classify the land cover and discuss the relationship of bare land change and aeolian dust emission. Normalized Difference Water Index (NDWI) derived from SPOT imageries can display the spatial distribution of moisture content and particle size in the surface of soil layers. The bare land can be categorized into coarse, medium and fine particles using K-mean cluster analysis, and then combined with the meteorological factors from a nearby air quality monitoring station to explore the contribution to aeolian dust emission. The results show that the bare land with fine particle has a positive correlation with daily average PM10. Therefore, the bare land with fine particle could be the potential zones of river dust emissions. Monitoring the changes of bare riverbed using remote sensing technology is an effective way for river dust episodes prediction.

  1. [Mixed episode: complex recognition and complicated treatment].

    Science.gov (United States)

    Gargoloff, Pedro Rafael

    2003-01-01

    Mixed Episode is a complex syndrome with difficult in its recognition, the most prolonged duration of bipolar episodes, more frequent psychotic profile than Pure Manic Episode, with high suicidality and poor response to drugs. There are evidences of less efficacy with Lithium and Carbamazepine in Manic Episode than mixed states. Valproate improve both, manic and depressive symptoms, and it is proposed to be first choice. Olanzapine has been widely evaluated, showing robust response in acute Mania as well in depressive symptoms during Mixed episode. In the field of clinical practice, there are many patients receiving more than one drug, usually Valproate plus a second generation antipsychotic.

  2. An air quality forecasting system in Beijing--application to the study of dust storm events in China in May 2008.

    Science.gov (United States)

    Zhang, Qijie; Laurent, Benoit; Velay-Lasry, Fanny; Ngo, Richard; Derognat, Claude; Marticorena, Béatrice; Albergel, Armand

    2012-01-01

    An air pollution forecast system, ARIA Regional, was implemented in 2007-2008 at the Beijing Municipality Environmental Monitoring Center, providing daily forecast of main pollutant concentrations. The chemistry-transport model CHIMERE was coupled with the dust emission model MB95 for restituting dust storm events in springtime so as to improve forecast results. Dust storm events were sporadic but could be extremely intense and then control air quality indexes close to the source areas but also far in the Beijing area. A dust episode having occurred at the end of May 2008 was analyzed in this article, and its impact of particulate matter on the Chinese air pollution index (API) was evaluated. Following our estimation, about 23 Tg of dust were emitted from source areas in Mongolia and in the Inner Mongolia of China, transporting towards southeast. This episode of dust storm influenced a large part of North China and East China, and also South Korea. The model result was then evaluated using satellite observations and in situ data. The simulated daily concentrations of total suspended particulate at 6:00 UTC had a similar spatial pattern with respect to OMI satellite aerosol index. Temporal evolution of dust plume was evaluated by comparing dust aerosol optical depth (AOD) calculated from the simulations with AOD derived from MODIS satellite products. Finally, the comparison of reported Chinese API in Beijing with API calculated from the simulation including dust emissions had showed the significant improvement of the model results taking into account mineral dust correctly.

  3. Analysis of urban pollution episodes by inverse modeling

    Science.gov (United States)

    Jorquera, Hector; Castro, Julio

    2010-01-01

    Urban pollution episodes pose two relevant issues: a) was the episode controlled by specific meteorology, a rise of emissions or both? b) Were mitigation measures effective in curbing down pollution? A methodology for answering those questions comes from an inverse modeling approach. In this work we have applied the methodology to the city of Santiago, Chile for which the required input data are available. We use a Kalman filter and ambient observations to constrain sources of tracers such as CO, elemental carbon and suspended street dust. The period analyzed is the week from May 20th till May 26th 2005. We find that a posteriori CO emissions were 76% of the a priori estimates. For suspended street dust a posteriori values are 36% and 21% of the prior values for coarse and fine fractions, respectively. Elemental carbon emissions are underestimated in the prior inventory - we find a correction factor of 1.53 for the whole week. Sensitivity analyses tested the robustness of a posteriori estimates, generating ensembles of simulations for different modeling options. For different initial prior estimates, the ratio of standard deviation to mean values was below 0.20 for 75% of the a posteriori, estimated emissions. For different choices of the error covariance matrices and model errors those ratios were below 0.30 for 75% of a posteriori emissions, which shows the robustness of results for different parameter choices - only a small fraction of results were not significant. The high pollution peaks on May 21st are due to specific meteorological conditions and increased traffic emissions as well. Contingency measures taken on Sunday May 22nd and better dispersion conditions on Monday May 23rd stopped the accumulation of those pollutants, showing the effectiveness of short term strategies such as traffic bans and street sweeping operations in curbing down traffic pollution at Santiago.

  4. Biogas technology research in selected sub-Saharan African countries

    African Journals Online (AJOL)

    This reviews aims to provide an insight and update of the state of biogas technology research in some selected sub-Saharan African countries in peer reviewed literature. This paper also aims to highlight the sub-Saharan countries' strengths and weaknesses in biogas research and development capacity. An attempt is ...

  5. Land-related conflicts in Sub-Saharan Africa

    African Journals Online (AJOL)

    Sub-Saharan Africa has a history of land dispossession and contestation which have resulted in various types of inequalities and a skewed distribution of land resources. Land in Sub-Saharan Africa has been subject to conflict, conquest, expropriation and exploitation thus resulting in the many discrepancies that exist today ...

  6. HIV transmission during paediatric health care in sub- Saharan ...

    African Journals Online (AJOL)

    HIV transmission during paediatric health care in sub- Saharan Africa – risks and evidence. David Gisselquist, John J Potterat, Stuart Brody. Abstract. Health care systems in sub-Saharan Africa are challenged not only to improve care for the increasing number of HIV-infected children, but also to prevent transmission of HIV ...

  7. Factors affecting contraceptive use in Sub-Saharan Africa

    National Research Council Canada - National Science Library

    National Research Council Staff

    1993-01-01

    ...-SAHARAN AFRICA Working Group on Factors Affecting Contraceptive Use Panel on the Population Dynamics of Sub-Saharan Africa Committee on Population Commission on Behavioral and Social Sciences and Education National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1993 Copyrightoriginal retained, the be not from cannot book, paper original howeve...

  8. Empowering Youth for Sub-Saharan Africa's Development | Betchoo ...

    African Journals Online (AJOL)

    At this critical time of development in sub-Saharan Africa where the continent's growth actually makes it a region of great potential, it would be vital to integrate the youth in the development of the youngest continent in the world. Long-time considered as the continent of all worries and social threats, sub-Saharan Africa has ...

  9. Dust and Air Quality Forecasting in the Eastern Caribbean

    Science.gov (United States)

    Sealy, A. M.; Reyes, A.; Farrell, D. A.

    2015-12-01

    Significant amounts of dust travel across the northern tropical Atlantic to the Caribbean every year from the Sahara region. These dust concentrations in the Caribbean often exceed United States Environmental Protection Agency (EPA) standards for particulate matter of 2.5 microns or less (PM 2.5) which could have serious implications for human health in the region. Air pollution has become a major issue in the Caribbean because of urban development, increased vehicle emissions and growing industrialisation. However, the majority of territories in the Caribbean do not have routine air quality monitoring programmes and several do not have or enforce air quality standards for PM2.5 and PM10. As a result, the Caribbean Institute for Meteorology and Hydrology (CIMH) has taken the initiative to provide dust and air quality forecasts for the Eastern Caribbean using the advanced WRF-Chem modeling system. The applications of the WRF-Chem modelling system at CIMH that are currently being focused on are the coupled weather prediction/dispersion model to simulate the release and transport of constituents, especially Saharan dust transport and concentration; and as a coupled weather/dispersion/air quality model with full interaction of chemical species with prediction of particulate matter (PM2.5 and PM10). This will include future applications in the prediction of ozone (O3) and ultraviolet (UV) radiation as well as examining dust radiative forcing and effects on atmospheric precipitation and dynamics. The simulations are currently initialised at 00Z for a seven day forecast and run at 36 km resolution with a planned second domain (at 12 km) for air quality forecasts. Preliminary results from this study will be presented and compared to other dust forecast models currently used in other regions. This work also complements in situ measurements at Ragged Point, Barbados (oldest dust record since 1965), Martinique, Guadeloupe, French Guiana and Puerto Rico. The goal of this study

  10. Episodic memories in anxiety disorders: Clinical implications

    Directory of Open Access Journals (Sweden)

    Armin eZlomuzica

    2014-04-01

    Full Text Available The aim of this review is to summarize research on the emerging role of episodic memories in the context of anxiety disorders (AD. The available literature on explicit-, autobiographical- and episodic memory function in AD including neuroimaging studies is critically discussed. We describe the methodological diversity of episodic memory research in AD and discuss the need for novel tests to measure episodic memory in a clinical setting. We argue that alterations in episodic memory functions might contribute to the etiology of AD. We further explain why future research on the interplay between episodic memory function and emotional disorders as well as its neuroanatomical foundations offers the promise to increase the effectiveness of modern psychological treatments. We conclude that one major task is to develop methods and training programs that might help patients suffering from AD to better understand, interpret and possibly actively use their episodic memories in a way that would support therapeutic interventions and counteract the occurrence of symptoms.

  11. Episodic Memories in Anxiety Disorders: Clinical Implications

    Science.gov (United States)

    Zlomuzica, Armin; Dere, Dorothea; Machulska, Alla; Adolph, Dirk; Dere, Ekrem; Margraf, Jürgen

    2014-01-01

    The aim of this review is to summarize research on the emerging role of episodic memories in the context of anxiety disorders (AD). The available literature on explicit, autobiographical, and episodic memory function in AD including neuroimaging studies is critically discussed. We describe the methodological diversity of episodic memory research in AD and discuss the need for novel tests to measure episodic memory in a clinical setting. We argue that alterations in episodic memory functions might contribute to the etiology of AD. We further explain why future research on the interplay between episodic memory function and emotional disorders as well as its neuroanatomical foundations offers the promise to increase the effectiveness of modern psychological treatments. We conclude that one major task is to develop methods and training programs that might help patients suffering from AD to better understand, interpret, and possibly actively use their episodic memories in a way that would support therapeutic interventions and counteract the occurrence of symptoms. PMID:24795583

  12. Status of dust measurements by the Student Dust Counter

    Science.gov (United States)

    Horanyi, M.; Szalay, J.; Poppe, A.

    2012-04-01

    The Student Dust Counter (SDC) experiment of the New Horizons Mission is an impact dust detector designed to map the spatial and size distribution of dust along the trajectory of the spacecraft across the solar system. The sensors are thin, permanently polarized polyvinylidene fluoride (PVDF) plastic films that generate an electrical signal when dust particles penetrate their surface. SDC is capable of detecting particles with masses m≥ 10-12 g, and it has a total sensitive surface area of about 0.1 m2, pointing most of the time close to the ram direction of the spacecraft. SDC provides the first dust measurements beyond 18 AU, where the Pioneer sensors stopped working. After the Pluto-Charon fly-by, SDC will continue to measure dust on in the Kuiper Belt. These observations will advance our understanding of the origin and evolution of our own solar system, and allow for comparative studies of planet formation in dust disks around other stars. This talk will briefly review the SDC instrument, the most recent data, and the constraints on the dust production rate in the Kuiper Belt, based on SDC observations and Pioneer. We will also make predictions for the Cassini spacecraft for the detection of dust originating from the Kuiper Belt.

  13. Democratic consolidation in sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Ángel Pérez González

    2001-12-01

    Full Text Available The contributions made by theory on democratic consolidation in Eastern Europe are also pertinent to analysis of processes of democratization and democratic consolidation in other areas, such as sub-Saharan Africa. The parameters of analysis highlight the importance of a strong state (organized, with legitimated institutions and a structured society (whether multiethnic or not as necessary conditions for democratization. On the assumption that the colonizing powers basically used two models –the French assimilationist model and the British indirect government model– the study of how these conditions were fulfilled in various sub-Saharan states leads to two conclusions: the first, the possibility of a process of democratization in those states where European (French colonization produced a total assimilation of the colonized society, including above all the colonizer’s political values; and the second, the possibility of processes of democratization in states produced by British colonization where the indigenous structures and those of the metropolis were superimposed, a phenomenon which allowed the application of democratic values by legitimated local institutions.

  14. Youth in sub-Saharan Africa.

    Science.gov (United States)

    Blum, Robert W

    2007-09-01

    Sub-Saharan Africa is going through rapid social, political, and economic transformations that have a profound impact on youth. The present review explores trends and outcomes as they relate to education, family formation and sexual and reproductive health and the interrelationships among these areas. It is based on both published and unpublished reports. Over the past 20 years, school enrollment has increased for much of the subcontinent; although the gender gap has narrowed, females remain educationally disadvantaged. Likewise, marriage is occurring later today than a generation ago, posing new challenges of out-of-wedlock births, clandestine abortions, and an increased likelihood of engaging in premarital sex. So, too, although there has been a slowing of the population growth in much of the region, in many countries of sub-Saharan Africa, the population is doubling every 30 years. Although acquired immunodeficiency syndrome is the predominant cause of death among youth, maternal mortality remains a major risk of death for youth--in some countries 600 times greater than that of peers in the industrialized world.

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

    Science.gov (United States)

    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).

  16. Enhancing global control of alcohol to reduce unsafe sex and HIV in sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Rees Helen V

    2009-11-01

    Full Text Available Abstract Sub-Saharan Africa carries a massive dual burden of HIV and alcohol disease, and these pandemics are inextricably linked. Physiological and behavioural research indicates that alcohol independently affects decision-making concerning sex, and skills for negotiating condoms and their correct use. More than 20 studies in Africa have reported higher occurrence of HIV among people with problem drinking; a finding strongly consistent across studies and similar among women and men. Conflation of HIV and alcohol disease in these setting is not surprising given patterns of heavy-episodic drinking and that drinking contexts are often coterminous with opportunities for sexual encounters. HIV and alcohol also share common ground with sexual violence. Both perpetrators and victims of sexual violence have a high likelihood of having drunk alcohol prior to the incident, as with most forms of violence and injury in sub-Saharan Africa. Reducing alcohol harms necessitates multi-level interventions and should be considered a key component of structural interventions to alleviate the burden of HIV and sexual violence. Brief interventions for people with problem drinking (an important component of primary health care, must incorporate specific discussion of links between alcohol and unsafe sex, and consequences thereof. Interventions to reduce alcohol harm among HIV-infected persons are also an important element in positive-prevention initiatives. Most importantly, implementation of known effective interventions could alleviate a large portion of the alcohol-attributable burden of disease, including its effects on unsafe sex, unintended pregnancy and HIV transmission.

  17. EPISODIC EJECTION FROM ACTIVE ASTEROID 311P/PANSTARRS

    Energy Technology Data Exchange (ETDEWEB)

    Jewitt, David [Department of Earth and Space Sciences, University of California at Los Angeles, 595 Charles Young Drive East, Los Angeles, CA 90095-1567 (United States); Agarwal, Jessica [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Gottingen (Germany); Weaver, Harold [The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Mutchler, Max [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Larson, Stephen, E-mail: jewitt@ucla.edu [Lunar and Planetary Laboratory, University of Arizona, 1629 East University Boulevard, Tucson AZ 85721-0092 (United States)

    2015-01-10

    We examine the development of the active asteroid 311P/PANSTARRS (formerly, 2013 P5) in the period from 2013 September to 2014 February using high resolution images from the Hubble Space Telescope. This multi-tailed object is characterized by a single, reddish nucleus of absolute magnitude H ≥ 18.98 ± 0.10, corresponding to an equal-area sphere of radius ≤200 ± 20 m (for assumed geometric albedo 0.29 ± 0.09). We set an upper limit to the radii of possible companion nuclei at ∼10 m. The nucleus ejected debris in nine discrete episodes, spread irregularly over a nine month interval, each time forming a distinct tail. Particles in the tails range from about 10 μm to at least 80 mm in radius, and were ejected at speeds <1 m s{sup –1}. The ratio of the total ejected dust mass to the nucleus mass is ∼3×10{sup –5}, corresponding to a global surface layer ∼2 mm thick, or to a deeper layer covering a smaller fraction of the surface. The observations are incompatible with an origin of the activity by impact or by the sublimation of entrapped ice. This object appears to be shedding its regolith by rotational (presumably YORP-driven) instability. Long-term fading of the photometry (months) is attributed to gradual dissipation of near-nucleus dust. Photometric variations on short timescales (<0.7 hr) are probably caused by fast rotation of the nucleus. However, because of limited time coverage and dilution of the nucleus signal by near-nucleus dust, we have not been able to determine the rotation period.

  18. Episodic future thinking and episodic counterfactual thinking: intersections between memory and decisions.

    Science.gov (United States)

    Schacter, Daniel L; Benoit, Roland G; De Brigard, Felipe; Szpunar, Karl K

    2015-01-01

    This article considers two recent lines of research concerned with the construction of imagined or simulated events that can provide insight into the relationship between memory and decision making. One line of research concerns episodic future thinking, which involves simulating episodes that might occur in one's personal future, and the other concerns episodic counterfactual thinking, which involves simulating episodes that could have happened in one's personal past. We first review neuroimaging studies that have examined the neural underpinnings of episodic future thinking and episodic counterfactual thinking. We argue that these studies have revealed that the two forms of episodic simulation engage a common core network including medial parietal, prefrontal, and temporal regions that also supports episodic memory. We also note that neuroimaging studies have documented neural differences between episodic future thinking and episodic counterfactual thinking, including differences in hippocampal responses. We next consider behavioral studies that have delineated both similarities and differences between the two kinds of episodic simulation. The evidence indicates that episodic future and counterfactual thinking are characterized by similarly reduced levels of specific detail compared with episodic memory, but that the effects of repeatedly imagining a possible experience have sharply contrasting effects on the perceived plausibility of those events during episodic future thinking versus episodic counterfactual thinking. Finally, we conclude by discussing the functional consequences of future and counterfactual simulations for decisions. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. Episodic future thinking and episodic counterfactual thinking: Intersections between memory and decisions

    Science.gov (United States)

    Schacter, Daniel L.; Benoit, Roland G.; De Brigard, Felipe; Szpunar, Karl K.

    2014-01-01

    This article considers two recent lines of research concerned with the construction of imagined or simulated events that can provide insight into the relationship between memory and decision making. One line of research concerns episodic future thinking, which involves simulating episodes that might occur in one’s personal future, and the other concerns episodic counterfactual thinking, which involves simulating episodes that could have happened in one’s personal past. We first review neuroimaging studies that have examined the neural underpinnings of episodic future thinking and episodic counterfactual thinking. We argue that these studies have revealed that the two forms of episodic simulation engage a common core network including medial parietal, prefrontal, and temporal regions that also supports episodic memory. We also note that neuroimaging studies have documented neural differences between episodic future thinking and episodic counterfactual thinking, including differences in hippocampal responses. We next consider behavioral studies that have delineated both similarities and differences between the two kinds of episodic simulation. The evidence indicates that episodic future and counterfactual thinking are characterized by similarly reduced levels of specific detail compared with episodic memory, but that the effects of repeatedly imagining a possible experience have sharply contrasting effects on the perceived plausibility of those events during episodic future thinking versus episodic counterfactual thinking. Finally, we conclude by discussing the functional consequences of future and counterfactual simulations for decisions. PMID:24373942

  20. Asian dust event observed in Seoul, Korea, during 29-31 May 2008: analysis of transport and vertical distribution of dust particles from lidar and surface measurements.

    Science.gov (United States)

    Kim, Sang-Woo; Yoon, Soon-Chang; Kim, Jiyoung; Kang, Jung-Yoon; Sugimoto, Nobuo

    2010-03-01

    In this study, we investigate the transport of dust particles, its vertical distribution, and the associated meteorological conditions during an Asian dust event that was observed in Seoul, Korea on May 29-31, 2008. This study analyzes data from ground-based and space-borne 2-wavelength polarization lidars, particulate mass concentrations, and synoptic weather data. Surface meteorological station observations of dust phenomena, dust transport model, and weather maps consistently show that the dust particles were transported from the source regions (Inner Mongolia, Man-Ju, and Ordos areas) to Korea via the northeastern part of China. Network observations of the PM(10) concentrations in Korea revealed that a majority of the heavy dust particles traveled across South Korea from the northwest to the southeast direction with a horizontal scale of 250-300km and a traveling speed of approximately 40kmh(-1). This extraordinary dust event, in terms of its intensity and timing during the year, occurred due to the blockage of an unusually intensified low-pressure system in the northeastern part of China as well as high-pressure system centered over the Sea of Okhotsk and the Kuril Islands. The low values of the particle depolarization ratio (delta(532)) (dust period indicate the presence of spherical, non-dust, and relatively small particles. The mean delta(532) value was approximately 0.123+/-0.069 between altitudes of ground approximately 2.8km, and 0.161+/-0.049 for near-surface dust layer (ground approximately 1.2km). This value is quite similar to that obtained during the 3-year SNU-Lidar measurements in Seoul (delta(532) approximately 0.136+/-0.027). The value of delta(532) during the 2nd multilayered dust episode ranged between 0.081 and 0.120 for near-surface dust layers, and between 0.076 and 0.114 for elevated dust layers. The CALIPSO measurements of beta(532), delta(532), and CR also revealed the presence of dense dust aerosols along the transport route.

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

    Directory of Open Access Journals (Sweden)

    N. Huneeus

    2016-04-01

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

  2. Coupled Iron-Phosphorus Cycling in Surface Seawater Mediated by Photoreduction of Fe-rich Dust

    Science.gov (United States)

    Tamburini, F.; Ruttenberg, K. C.

    2002-12-01

    Nutrient concentrations are exceedingly low in the oligotrophic waters of the open ocean. One source of the micronutrient iron (Fe) to these regions is deposition of continentally-derived dust. Photolytic reduction of Fe is believed to be a key process in rendering bioavailable the Fe present in dust particles delivered to surface seawater. Fe(III)-oxyhydroxides, in general, have a strong affinity for sorption of phosphate, and Fe-oxyhydroxides present in dust derived from continental soils can be highly enriched in phosphate. Therefore, solubilization of Fe(III) phases via photoreduction may liberate phosphate to surface seawater. Because biological productivity in oligotrophic regions of the open ocean can be limited by phosphate as well as by iron, this process could be an important avenue for providing two essential, limiting nutrients to support primary productivity in these regions. Alternatively, if Fe-rich dust delivered to surface waters has unsaturated surface sorption sites, dust may actively scavenge phosphate from surface waters, pushing the system further toward phosphate limitation. Depending upon the balance between these two processes, continentally derived dust may either partially alleviate or enhance phosphate limitation in oligotrophic waters. We will present results of experiments designed to determine whether phosphate-containing Fe(III)-oxyhydroxides, subjected to photoreduction, release phosphate to seawater. In a series of incubation experiments, synthetic iron minerals (ferrihydrite, goethite) and natural dust samples (Saharan dust, Chinese loess) are suspended in artificial seawater and exposed to sunlight in the presence/absence of citrate. We observe an increase in both dissolved Fe(II) and Fe(Total) during daylight hours, which we attribute to the photoreduction process. Fe concentrations are at least 5 times higher in the presence of citrate, consistent with other studies exploring the effect of organic ligands on the Fe

  3. Fennec dust forecast intercomparison over the Sahara in June 2011

    Directory of Open Access Journals (Sweden)

    J.-P. Chaboureau

    2016-06-01

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

  4. Exploring the Longwave Radiative Effects of Dust Aerosols

    Science.gov (United States)

    Hansell, Richard A., Jr.

    2012-01-01

    Dust aerosols not only affect air quality and visibility where they pose a significant health and safety risk, but they can also play a role in modulating the energy balance of the Earth-atmosphere system by directly interacting with local radiative fields. Consequently, dust aerosols can impact regional climate patterns such as changes in precipitation and the evolution of the hydrological cycle. Assessing the direct effect of dust aerosols at the solar wavelengths is fairly straightforward due in part to the relatively large signal-to-noise ratio in broadband irradiance measurements. The longwave (LW) impacts, on the other hand, are rather difficult to ascertain since the measured dust signal level (10 Wm-2) is on the same order as the instrumental uncertainties. Moreover, compared to the shortwave (SW), limited experimental data on the LW optical properties of dust makes it a difficult challenge for constraining the LW impacts. Owing to the strong absorption features found in many terrestrial minerals (e.g., silicates and clays), the LW effects, although much smaller in magnitude compared to the SW, can still have a sizeable impact on the energetics of the Earth-atmosphere system, which can potentially trigger changes in the heat and moisture surface budgets, and dynamics of the atmosphere. The current endeavor is an integral part of an on-going research study to perform detailed assessments of dust direct aerosol radiative effects (DARE) using comprehensive global datasets from NASA Goddards mobile ground-based facility (cf. http://smartlabs.gsfc.nasa.gov/) during previous field experiments near key dust source regions. Here we examine and compare the results from two of these studies: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years. The former study focused on transported Saharan dust at Sal Island (16.73N, 22.93W), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye China (39

  5. Mineral Dust Analysis and Application in Refining Source Region Information for the Sahara and East Asia Deserts

    Science.gov (United States)

    Reid, E. A.; Reid, J. S.; Westphal, D.; Cliff, S.; Dunlap, M.

    2002-12-01

    The study of transported mineral dust aerosols relies heavily on simplified dust source region parameters. Source regions are broadly defined by soil class and expected erodibility, factors which continuously changes with land use and climate conditions. Mineral dust particles may undergo numerous cycles of deposition and re-entrainment prior to collection and analysis. Using the Sahara Desert and the East Asia deserts as test cases, we investigate the possibility of retrieving source information from receptor sites through single particle and bulk analyses of collected aerosol particles. In June and July of 2000, Saharan mineral dust aerosols transported across the Atlantic Ocean to Puerto Rico were collected for bulk and single particle chemical and morphological analyses. The Puerto Rico Dust Experiment, (PRIDE), involved sampling aerosols upwind of the islands at various altitudes in the marine boundary layer (MBL) and Saharan Air Layer (SAL) via a Navajo research aircraft. A surface site included a Davis Rotating Drum (DRUM) cascade impactor to size segregate the aerosols into eight stages, from 12 to 0.1 micrometers, with four-hour time resolution. In April of 2001, size segregated Asian mineral dust aerosols were collected by three hour resolution DRUM samplers at surface sites in Cheju, Taiwan, for bulk chemical analysis. The aircraft samples and selected DRUM samples were subjected to single particle analysis by scanning electron microscopy (SEM) for particle morphology, and by Energy Dispersive Analysis with X-rays (EDAX) to derive elemental ratios of key soil elements. The DRUM samples were subjected to X-Ray Fluorescence (XRF) to derive bulk elemental composition for elements Al though Zn. Cluster and principal component analysis of the data derived statistically significant particle groupings. By including particle morphology data, and using ternary analyses, derivation of additional source information was possible. Particle compositions

  6. Gravimetric dust sampling for control purposes and occupational dust sampling.

    CSIR Research Space (South Africa)

    Unsted, AD

    1997-02-01

    Full Text Available Prior to the introduction of gravimetric dust sampling, konimeters had been used for dust sampling, which was largely for control purposes. Whether or not absolute results were achievable was not an issue since relative results were used to evaluate...

  7. Climatology and classification of spring Saharan cyclone tracks

    Energy Technology Data Exchange (ETDEWEB)

    Hannachi, A. [Reading University, Department of Meteorology, PO Box 243, Reading (United Kingdom); Awad, A. [King Abdulaziz University, Department of Meteorology, Jeddah (Saudi Arabia); Ammar, K. [Meteorological Authority, Department of Research, Cairo (Egypt)

    2011-08-15

    Spring Saharan cyclones constitute a dominant feature of the not-well-explored Saharan region. In this manuscript, a climatological analysis and classification of Saharan cyclone tracks are presented using 6-hourly NCEP/NCAR sea level pressure (SLP) reanalyses over the Sahara (10 W-50 E, 20 N-50 N) for the Spring (March-April-May) season over the period 1958-2006. A simple tracking procedure based on following SLP minima is used to construct around 640 Spring Saharan cyclone tracks. Saharan cyclones are found to be short-lived compared to their extratropical counterparts with an e-folding time of about 3 days. The lee side of the west Atlas mountain is found to be the main cyclogenetic region for Spring Saharan cyclones. Central Iraq is identified as the main cyclolytic area. A subjective procedure is used next to classify the cyclone tracks where six clusters are identified. Among these clusters the Western Atlas-Asia Minor is the largest and most stretched, whereas Algerian Sahara-Asia Minor is composed of the most long-lived tracks. Upper level flow associated with the tracks has also been examined and the role of large scale baroclinicity in the growth of Saharan cyclones is discussed. (orig.)

  8. [Diabetes mellitus in sub-saharan Africa].

    Science.gov (United States)

    Sidibe el-H

    1998-01-01

    Diabetes mellitus is becoming more common in African cities, where it may affect up to 7% of the hospital population. It particularly affects poor male patients and 73 to 80% of those affected have non insulin-dependent diabetes. The frequency of non-obese, poorly cetogenic patients is high in Sub-Saharan Africa. This may be due to malnutrition, with a deficit either in protein or in calories. Such malnutrition is a major public health problem affecting children in Sudanese and Sahelian areas and may interact with environmental and genetic factors. In equatorial environments, the toxic effects of alcohol abuse on the pancreas are simply another environmental factor, reducing the endocrine function of the pancreas. These observations are important because: 1) diabetes mellitus has a severe social impact in this area and 2) nutrition has a general effect on the pathogenesis of diabetes mellitus.

  9. Caregiver psychoeducation for first-episode psychosis.

    LENUS (Irish Health Repository)

    McWilliams, Stephen

    2010-01-01

    International best-practice guidelines for the management of first-episode psychosis have recommended the provision of psychoeducation for multifamily groups. While there is ample evidence of their efficacy in multiepisode psychosis, there is a paucity of evidence supporting this approach specifically for first-episode psychosis. We sought to determine whether a six-week caregiver psychoeducation programme geared specifically at first-episode psychosis improves caregiver knowledge and attitudes.

  10. Energy Justice in Sub-Saharan Africa

    Science.gov (United States)

    Buchholz, Kathleen B.

    Sub-Saharan Africa has the lowest rates of electrification and some of the worst education statistics worldwide. In the absence of strong infrastructure for a reliable grid system and quality universal primary schooling, the poor suffer significantly. Though substantial research has been done on both issues separately, the relationship between the two has yet to be explored. This thesis uses social justice theories to introduce the connections between energy poverty and an individual's education capabilities through a case study in Zambia. Case study research was carried out in the urban low-resource settlements of Lusaka, Zambia over a period of two months with Lifeline Energy, using methods of participant observation. Drawing on trends discovered in survey responses, interviews and feedback from a distribution of renewable technologies, this study demonstrates that a lack of modern forms of energy detracts from education. By synthesizing the data with Martha Nussbaum's capabilities approach and Sendhil Mullainathan and Eldar Shafir's scarcity theory, the research reveals that energy poverty hinders an individual's ability to study and gain a quality education and diminishes their available cognitive capacity to learn by tunneling attention to the resource deficit. Furthermore, it supports the claim that energy poverty is not gender neutral. The research concludes that the scarcity caused by energy poverty can be lessened by the investment in and use of small-scale renewable technologies which alleviates some of the daily stress and grind of poverty. This thesis lays the groundwork to recognize energy poverty as an injustice. Keywords: Energy Poverty, Education, Gender, Sub-Saharan Africa, Scarcity, Capabilities Approach..

  11. Of data and dust

    CERN Multimedia

    Stephanie Hills

    2016-01-01

    The traditional image of an archive is one of dusty old boxes, books and papers. When your archive is digital, dust spells disaster. An innovative environmental sensor designed and built by a CERN IT specialist has become an essential element in the Laboratory’s data-preservation strategy.   The novel air particle monitoring sensor designed by CERN's Julien Leduc. CERN’s archive holds more than 130 petabytes of data from past and present high-energy physics experiments. Some of it is 40 years old, most of it needs to be kept forever, and all of it is held on tape cartridges (over 20,000 of them). The cartridges are held inside tape libraries with robotic arms that load them into tape drives where they can be read and written. Tape cartridges have many advantages over other data storage media, notably cost and long-term reliability, but topping the list of drawbacks is their vulnerability to contamination from airborne dust particles; a tiny piece of g...

  12. Dust in planetary nebulae

    Science.gov (United States)

    Sloan, G. C.

    2017-10-01

    Infrared spectra from the Spitzer Space Telescope trace the evolution of carbon-rich dust from the asymptotic giant branch (AGB) to young planetary nebulae (PNe). On the AGB, amorphous carbon dominates the dust, but SiC and MgS also appear. In more evolved systems with warmer central stars, the spectra reveal the unidentified 21 μm feature, features from aliphatic hydrocarbons, and spectra from polycyclic aromatic hydrocarbons (PAHs), often with shifted feature positions indicative of the presence of aliphatics. More evolved systems with hot central stars show more typical PAH spectra, along with fullerenes and/or an emission feature known as the big-11 feature at ~11 μm. This features arises from a combination of SiC and PAHs, and it is usually accompanied by a shoulder at 18 μm, which while unidentified might be from cool silicate grains. The strong emission from MgS and SiC in young PNe probably arises from coatings on carbonaceous grains.

  13. Impact of episodic thinking on altruism

    Science.gov (United States)

    Yi, Richard; Pickover, Alison; Stuppy-Sullivan, Allison M.; Baker, Sydney; Landes, Reid D.

    2016-01-01

    Episodic future thinking, which refers to the use of prospective imagery to concretely imagine oneself in future scenarios, has been shown to reduce delay discounting (enhance self-control). A parallel approach, in which prospective imagery is used to concretely imagine other’s scenarios, may similarly reduce social discounting (i.e., enhance altruism). In study 1, participants engaged in episodic thinking about the self or others, in a repeated-measures design, while completing a social discounting task. Reductions in social discounting were observed as a function of episodic thinking about others, though an interaction with order was also observed. Using an independent-measures design in study 2, the effect of episodic thinking about others was replicated. Study 3 addressed a limitation of studies 1 and 2, the possibility that simply thinking about others decreased social discounting. Capitalizing on Construal Level Theory, which specifies that social distance and time in the future are both dimensions of a common psychological distance, we hypothesized that episodic future thinking should also decrease social discounting. Participants engaged in episodic future thinking or episodic present thinking, in a repeated-measures design, while completing a social discounting task. The pattern of results was similar to study 1, providing support for the notion that episodic thinking about psychologically distant outcomes (for others or in the future) reduces social discounting. Application of similar episodic thinking approaches may enhance altruism. PMID:27821875

  14. Impact of episodic thinking on altruism.

    Science.gov (United States)

    Yi, Richard; Pickover, Alison; Stuppy-Sullivan, Allison M; Baker, Sydney; Landes, Reid D

    2016-07-01

    Episodic future thinking, which refers to the use of prospective imagery to concretely imagine oneself in future scenarios, has been shown to reduce delay discounting (enhance self-control). A parallel approach, in which prospective imagery is used to concretely imagine other's scenarios, may similarly reduce social discounting (i.e., enhance altruism). In study 1, participants engaged in episodic thinking about the self or others, in a repeated-measures design, while completing a social discounting task. Reductions in social discounting were observed as a function of episodic thinking about others, though an interaction with order was also observed. Using an independent-measures design in study 2, the effect of episodic thinking about others was replicated. Study 3 addressed a limitation of studies 1 and 2, the possibility that simply thinking about others decreased social discounting. Capitalizing on Construal Level Theory, which specifies that social distance and time in the future are both dimensions of a common psychological distance, we hypothesized that episodic future thinking should also decrease social discounting. Participants engaged in episodic future thinking or episodic present thinking, in a repeated-measures design, while completing a social discounting task. The pattern of results was similar to study 1, providing support for the notion that episodic thinking about psychologically distant outcomes (for others or in the future) reduces social discounting. Application of similar episodic thinking approaches may enhance altruism.

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

    Science.gov (United States)

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

    2016-07-01

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

  16. Dust and the Sick Building Syndrome

    DEFF Research Database (Denmark)

    Gyntelberg, Finn; Suadicani, Poul; Wohlfahrt Nielsen, Jan

    1994-01-01

    Farmakologi, bacteria, dust, histamine, disease, gram-negative, indoor climate, sick building syndrome......Farmakologi, bacteria, dust, histamine, disease, gram-negative, indoor climate, sick building syndrome...

  17. Dust Migration in Gravitationally Active Protoplanetary Disks

    Science.gov (United States)

    Backus, I.; Quinn, T.

    2017-05-01

    Solid growth and planet formation may require dense regions of dust. I investigate dust migration concentration, in gravitationally active protoplanetary disks using high resolution, 3D SPH simulations.

  18. Dust characterization in FTU tokamak

    Science.gov (United States)

    De Angeli, M.; Maddaluno, G.; Laguardia, L.; Ripamonti, D.; Perelli Cippo, E.; Apicella, M. L.; Conti, C.; Giacomi, G.; Grosso, G.

    2015-08-01

    Dust present in the vessel of FTU has been collected and analysed. Being FTU a device with full metal plasma facing components for the whole life and equipped with a liquid lithium limiter (LLL) make FTU of special interest from a point of view of dust studies. Analyses were conducted by standard dust analysis methods and by dedicated analysis, as X-rays and neutron diffraction, to investigate the presence of lithium compounds due the presence of the LLL in FTU. Dust collected near the LLL presents a different elemental composition, namely Li compounds, compared to the dust collected in the rest of the vessel; in particular LiO2, LiOH, and Li2CO3. On the basis of these results, the formation of Li2CO3 is proposed via a two steps process. Results of fuel retention measured by thermal desorption spectroscopy (TDS) method show that fuel retention should not be an issue for FTU.

  19. High resolution satellite derived erodibility factors for WRF/Chem windblown dust simulations in Argentina

    Science.gov (United States)

    Cremades, Pablo Gabriel; Fernandez, Rafael Pedro; Allend, David; Mulena, Celeste; Puliafito, Salvador Enrique

    2017-04-01

    A proper representation of dust sources is critical to accurately predict atmospheric particle concentrations in regional windblown dust simulations. The Weather Research and Forecasting model with Chemistry (WRF/Chem) includes a topographic-based erodibility map originally conceived for global scale modeling, which fails to identify the geographical location of dust sources in many regions of Argentina. Therefore, this study aims at developing a method to obtain a high-resolution erodibility map suitable for regional or local scale modeling using WRF/Chem. We present two independent approaches based on global methods to estimate soil erodibility using satellite retrievals, i.e. topography from the Shuttle Radar Topography Mission (SRTM) and surface reflectance from the Moderate Resolution Imaging Spectroradiometer (MODIS). Simulation results of a severe Zonda wind episode in the arid central-west Argentina serve as bases for the analysis of these methods. Simulated dust concentration at surface level is compared with particulate matter measurements at one site in Mendoza city. In addition, we use satellite aerosol optical depth (AOD) retrievals to investigate model performance in reproducing spatial distribution of dust emissions. The erodibility map based on surface reflectance from MODIS improves the representation of small scale features, and increases the overall dust aerosol loading with respect to the standard map included by default. Simulated concentrations are in good agreement with measurements as well as satellite derived dust spatial distribution.

  20. Asian dust storm observed at a rural mountain site in southern China: chemical evolution and heterogeneous photochemistry

    Directory of Open Access Journals (Sweden)

    W. Nie

    2012-12-01

    Full Text Available Heterogeneous processes on dust particles are important for understanding the chemistry and radiative balance of the atmosphere. This paper investigates an intense Asian dust storm episode observed at Mount Heng (1269 m a.s.l. in southern China on 24–26 April 2009. A set of aerosol and trace gas data collected during the study was analyzed to investigate their chemical evolution and heterogeneous photochemistry as the dust traveled to southern China. Results show that the mineral dust arriving at Mt. Heng experienced significant modifications during transport, with large enrichments in secondary species (sulfate, nitrate, and ammonium compared with the dust composition collected at an upwind mountain top site (Mount Hua. A photochemical age "clock" (−Log10(NOx/NOy was employed to quantify the atmospheric processing time. The result indicates an obvious increase in the abundance of secondary water-soluble ions in dust particles with the air mass atmospheric processing time. Based on the observations, a 4-stage evolution process is proposed for carbonate-containing Asian dust, starting from fresh dust to particles coated with hydrophilic and acidic materials. Daytime-enhanced nitrite formation on the dust particles was also observed, which indicates the recent laboratory result of the TiO2 photocatalysis of NO2 as a potential source of nitrite and nitrous acid.

  1. Dust in protoplanetary disks: observations*

    Directory of Open Access Journals (Sweden)

    Waters L.B.F.M.

    2015-01-01

    Full Text Available Solid particles, usually referred to as dust, are a crucial component of interstellar matter and of planet forming disks surrounding young stars. Despite the relatively small mass fraction of ≈1% (in the solar neighborhood of our galaxy; this number may differ substantially in other galaxies that interstellar grains represent of the total mass budget of interstellar matter, dust grains play an important role in the physics and chemistry of interstellar matter. This is because of the opacity dust grains at short (optical, UV wavelengths, and the surface they provide for chemical reactions. In addition, dust grains play a pivotal role in the planet formation process: in the core accretion model of planet formation, the growth of dust grains from the microscopic size range to large, cm-sized or larger grains is the first step in planet formation. Not only the grain size distribution is affected by planet formation. Chemical and physical processes alter the structure and chemical composition of dust grains as they enter the protoplanetary disk and move closer to the forming star. Therefore, a lot can be learned about the way stars and planets are formed by observations of dust in protoplanetary disks. Ideally, one would like to measure the dust mass, the grain size distribution, grain structure (porosity, fluffiness, the chemical composition, and all of these as a function of position in the disk. Fortunately, several observational diagnostics are available to derive constrains on these quantities. In combination with rapidly increasing quality of the data (spatial and spectral resolution, a lot of progress has been made in our understanding of dust evolution in protoplanetary disks. An excellent review of dust evolution in protoplanetary disks can be found in Testi et al. (2014.

  2. COAL DUST EMISSION PROBLEM

    Directory of Open Access Journals (Sweden)

    M. M. Biliaiev

    2016-12-01

    Full Text Available Purpose. The article aims to develop 2D numerical models for the prediction of atmospheric pollution during transportation of coal in the railway car, as well as the ways to protect the environment and the areas near to the mainline from the dust emission due to the air injection installation. Methodology. To solve this problem there were developed numerical models based on the use of the equations of motion of an inviscid incompressible fluid and mass transfer. For the numerical integration of the transport equation of the pollutant the implicit alternating-triangular difference scheme was used. For numerical integration of the 2D equation for the velocity potential the method of total approximation was used. The developed numerical models are the basis of established software package. On the basis of the constructed numerical models it was carried out a computational experiment to assess the level of air pollution when transporting bulk cargo by rail when the railway car has the air injection. Findings. 2D numerical models that belong to the class «diagnostic models» were developed. These models take into account the main physical factors affecting the process of dispersion of dust pollution in the atmosphere during transportation of bulk cargo. The developed numerical models make it possible to calculate the dust loss process, taking into account the use of the air injection of the car. They require a small cost of the computer time during practical realization at the low and medium power machines. There were submitted computational calculations to determine pollutant concentrations and the formation of the zone of pollution near the train with bulk cargo in «microscale» scale taking into account the air curtains. Originality. 2D numerical models taking into account the relevant factors influencing the process of dispersion of pollutants in the atmosphere, and the formation of the zone of pollution during transportation of bulk cargo by

  3. Episodic plate tectonics on Venus

    Science.gov (United States)

    Turcotte, Donald

    1992-01-01

    Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the Moon, Earth, and Mars indicate a mean surface age of 0.5 +/- 0.3 Ga. Another important observation is that 52 percent of the craters are slightly fractured and only 4.5 percent are embayed by lava flows. These observations led researchers to hypothesize that a pervasive resurfacing event occurred about 500 m.y. ago and that relatively little surface volcanism has occurred since. Other researchers have pointed out that a global resurfacing event that ceased about 500 MYBP is consistent with the results given by a recent study. These authors carried out a series of numerical calculations of mantle convection in Venus yielding thermal evolution results. Their model considered crustal recycling and gave rapid planetary cooling. They, in fact, suggested that prior to 500 MYBP plate tectonics was active in Venus and since 500 MYBP the lithosphere has stabilized and only hot-spot volcanism has reached the surface. We propose an alternative hypothesis for the inferred cessation of surface volcanism on Venus. We hypothesize that plate tectonics on Venus is episodic. Periods of rapid plate tectonics result in high rates of subduction that cool the interior resulting in more sluggish mantle convection.

  4. Characterization of Dust Properties during ACE-Asia and PRIDE: A Column Satellite-Surface Perspective

    Science.gov (United States)

    Lau, William K. M. (Technical Monitor); Tsay, Si-Chee; Hsu, N. Christina; Herman, Jay R.; Ji, Q. Jack

    2002-01-01

    Many recent field experiments are designed to study the compelling variability in spatial and temporal scale of both pollution-derived and naturally occurring aerosols, which often exist in high concentration over particular pathways around the globe. For example, the ACE-Asia (Aerosol Characterization Experiment-Asia) was conducted from March-May 2001 in the vicinity of the Taklimakan and Gobi deserts, East Coast of China, Yellow Sea, Korea, and Japan, along the pathway of Kosa (severe events that blanket East Asia with yellow desert dust, peaked in the Spring season). The PRIDE (Puerto RIco Dust Experiment, July 2000) was designed to measure the properties of Saharan dust transported across the Atlantic Ocean to the Caribbean. Dust particles typically originate in desert areas far from polluted urban regions. During transport, dust layers can interact with anthropogenic sulfate and soot aerosols from heavily polluted urban areas. Added to the complex effects of clouds and natural marine aerosols, dust particles reaching the marine environment can have drastically different properties than those from the source. Thus, understanding the unique temporal and spatial variations of dust aerosols is of special importance in regional-to-global climate issues such as radiative forcing, the hydrological cycle, and primary biological productivity in the ocean. During ACE-Asia and PRIDE we had measured aerosol physical/optical/radiative properties, column precipitable water amount, and surface reflectivity over homogeneous areas from ground-based remote sensing. The inclusion of flux measurements permits the determination of aerosol radiative flux in addition to measurements of loading and optical depth. At the time of the Terra/MODIS, SeaWiFS, TOMS and other satellite overpasses, these ground-based observations can provide valuable data to compare with satellite retrievals over land. We will present the results and discuss their implications in regional climatic effects.

  5. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    Directory of Open Access Journals (Sweden)

    C. Denjean

    2016-02-01

    Full Text Available This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco, time of transport (1–5 days and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l. than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling

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

    Science.gov (United States)

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

    2013-03-29

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

  7. Dust interferometers in plasmas

    CERN Document Server

    Chaudhuri, M; Thomas, H M

    2016-01-01

    An interferometric imaging technique has been proposed to instantly measure the diameter of individual spherical dust particles suspended in a gas discharge plasma. The technique is based on the defocused image analysis of both spherical particles and their binary agglomerates. Above a critical diameter, the defocused images of spherical particles contain stationary interference fringe patterns and the fringe number increases with particle diameters. Below this critical diameter, the particle size has been measured using the rotational interference fringe patterns which appear only on the defocused images of binary agglomerates. In this case, a lower cut-off limit of particle diameter has been predicted, below which no such rotational fringe patterns are observed for the binary agglomerates. The method can be useful as a diagnostics for complex plasma experiments on earth as well as under microgravity condition.

  8. Competition and mobile penetration in sub-Saharan Africa | Belayeh ...

    African Journals Online (AJOL)

    Saharan African (SSA) countries between 2000 and 2006. We examine both the impact of introducing competition and the role of intensity of competition on mobile penetration in these countries. Different specifications with different measures of ...

  9. Identification of a new strain of Actinomadura isolated from Saharan ...

    African Journals Online (AJOL)

    Identification of a new strain of Actinomadura isolated from Saharan soil and ... soil, with strong antifungal activity against pathogenic and toxinogenic fungi, was ... The butanolic extract contained four bioactive spots detected on thin layer ...

  10. Episodic accretion on to strongly magnetic stars

    NARCIS (Netherlands)

    D'Angelo, C.R.; Spruit, H.C.

    2010-01-01

    Some accreting neutron stars and young stars show unexplained episodic flares in the form of quasi-periodic oscillations or recurrent outbursts. In a series of two papers, we present new work on an instability that can lead to episodic outbursts when the accretion disc is truncated by the star's

  11. Intrusions in Episodic Memory: Reconsolidation or Interference?

    Science.gov (United States)

    Klingmüller, Angela; Caplan, Jeremy B.; Sommer, Tobias

    2017-01-01

    It would be profoundly important if reconsolidation research in animals and other memory domains generalized to human episodic memory. A 3-d-list-discrimination procedure, based on free recall of objects, with a contextual reminder cue (the testing room), has been thought to demonstrate reconsolidation of human episodic memory (as noted in a…

  12. Episodic memory and the witness trump card.

    Science.gov (United States)

    Henry, Jeremy; Craver, Carl

    2018-01-01

    We accept Mahr & Csibra's (M&C's) causal claim that episodic memory provides humans with the means for evaluating the veracity of reports about non-occurrent events. We reject their evolutionary argument that this is the proper function of episodic memory. We explore three intriguing implications of the causal claim, for cognitive neuropsychology, comparative psychology, and philosophy.

  13. Tracking the Construction of Episodic Future Thoughts

    Science.gov (United States)

    D'Argembeau, Arnaud; Mathy, Arnaud

    2011-01-01

    The ability to mentally simulate possible futures ("episodic future thinking") is of fundamental importance for various aspects of human cognition and behavior, but precisely how humans construct mental representations of future events is still essentially unknown. We suggest that episodic future thoughts consist of transitory patterns…

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

    Energy Technology Data Exchange (ETDEWEB)

    Kassianov, E. [Pacific Northwest National Laboratory, Richland, Washington; Pekour, M. [Pacific Northwest National Laboratory, Richland, Washington; Flynn, C. [Pacific Northwest National Laboratory, Richland, Washington; Berg, L. K. [Pacific Northwest National Laboratory, Richland, Washington; Beranek, J. [Pacific Northwest National Laboratory, Richland, Washington; Zelenyuk, A. [Pacific Northwest National Laboratory, Richland, Washington; Zhao, C. [Pacific Northwest National Laboratory, Richland, Washington; Leung, L. R. [Pacific Northwest National Laboratory, Richland, Washington; Ma, P. L. [Pacific Northwest National Laboratory, Richland, Washington; Riihimaki, L. [Pacific Northwest National Laboratory, Richland, Washington; Fast, J. D. [Pacific Northwest National Laboratory, Richland, Washington; Barnard, J. [University of Nevada, Reno, Nevada; Hallar, A. G. [Storm Peak Laboratory, Desert Research Institute, Steamboat Springs, Colorado; McCubbin, I. B. [Storm Peak Laboratory, Desert Research Institute, Steamboat Springs, Colorado; Eloranta, E. W. [University of Wisconsin–Madison, Madison, Wisconsin; McComiskey, A. [National Oceanic and Atmospheric Administration, Boulder, Colorado; Rasch, P. J. [Pacific Northwest National Laboratory, Richland, Washington

    2017-05-01

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

  15. What Explains Economic Underdevelopment in Sub-Saharan Africa

    Science.gov (United States)

    2015-12-01

    climate causes undue harm to the human body. Such tropical diseases as malaria only compound the problem. Infant mortality is high due in part to...is unlimited 12b. DISTRIBUTION CODE 2 13. ABSTRACT (maximum 200 words) This thesis examines the causes of slow economic growth in Sub-Saharan...LEFT BLANK v ABSTRACT This thesis examines the causes of slow economic growth in Sub-Saharan Africa. In particular, it attempts to identify the

  16. Gender Inequality in Education in sub-Saharan Africa

    OpenAIRE

    Victor Ombati; Ombati Mokua

    2012-01-01

    This paper examines the issue of gender inequality in education in sub-Saharan Africa. It argues that in sub-Saharan African countries, the provision of education for boys and girls is uneven, and biased through gender, location, class and region- resulting to high illiteracy rates for girls and women. The paper concludes that political instability and violence, poverty and economical challenges, negative cultural values, female genital mutilation, early marriage, and sexual harassment are so...

  17. Divergent thinking and constructing episodic simulations.

    Science.gov (United States)

    Addis, Donna Rose; Pan, Ling; Musicaro, Regina; Schacter, Daniel L

    2016-01-01

    Divergent thinking likely plays an important role in simulating autobiographical events. We investigated whether divergent thinking is differentially associated with the ability to construct detailed imagined future and imagined past events as opposed to recalling past events. We also examined whether age differences in divergent thinking might underlie the reduced episodic detail generated by older adults. The richness of episodic detail comprising autobiographical events in young and older adults was assessed using the Autobiographical Interview. Divergent thinking abilities were measured using the Alternative Uses Task. Divergent thinking was significantly associated with the amount of episodic detail for imagined future events. Moreover, while age was significantly associated with imagined episodic detail, this effect was strongly related to age-related changes in episodic retrieval rather than divergent thinking.

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

    Science.gov (United States)

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

    2010-05-01

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

  19. Observations of mesoscale and boundary-layer scale circulations affecting dust transport and uplift over the Sahara

    Directory of Open Access Journals (Sweden)

    J. H. Marsham

    2008-12-01

    Full Text Available Observations of the Saharan boundary layer, made during the GERBILS field campaign, show that mesoscale land surface temperature variations (which were related to albedo variations induced mesoscale circulations. With weak winds along the aircraft track, land surface temperature anomalies with scales of greater than 10 km are shown to significantly affect boundary-layer temperatures and winds. Such anomalies are expected to affect the vertical mixing of the dusty and weakly stratified Saharan Residual Layer (SRL. Mesoscale variations in winds are also shown to affect dust loadings in the boundary layer.

    Using the aircraft observations and data from the COSMO model, a region of local dust uplift, with strong along-track winds, was identified in one low-level flight. Large eddy model (LEM simulations based on this location showed linearly organised boundary-layer convection. Calculating dust uplift rates from the LEM wind field showed that the boundary-layer convection increased uplift by approximately 30%, compared with the uplift rate calculated neglecting the convection. The modelled effects of boundary-layer convection on uplift are shown to be larger when the boundary-layer wind is decreased, and most significant when the mean wind is below the threshold for dust uplift and the boundary-layer convection leads to uplift which would not otherwise occur.

    Both the coupling of albedo features to the atmosphere on the mesoscale, and the enhancement of dust uplift by boundary-layer convection are unrepresented in many climate models, but may have significant impacts on the vertical transport and uplift of desert dust. Mesoscale effects in particular tend to be difficult to parametrise.

  20. The heterogeneous chemical kinetics of N2O5 on CaCO3 and other atmospheric mineral dust surrogates

    Directory of Open Access Journals (Sweden)

    F. Karagulian

    2006-01-01

    Full Text Available Uptake experiments of N2O5 on several mineral dust powder samples were carried out under continuous molecular flow conditions at 298±2 K. At [N2O5]0=(4.0±1.0×1011 cm−3 we have found γss values ranging from (3.5±1.1×10−2 for CaCO3 to (0.20±0.05 for Saharan Dust with γss decreasing as [N2O5]0 increased. The uptake coefficients reported in this work are to be regarded as upper limiting values owing to the fact that they are based on the geometric (projected surface area of the mineral dust sample. We have observed delayed production of HNO3 upon uptake of N2O5 for every investigated sample owing to hydrolysis of N2O5 with surface-adsorbed H2O. Arizona Test Dust and Kaolinite turned out to be the samples that generated the largest amount of gas phase HNO3 with respect to N2O5 taken up. In contrast, the yield of HNO3 for Saharan Dust and CaCO3 is lower. On CaCO3 the disappearance of N2O5 was also accompanied by the formation of CO2. For CaCO3 sample masses ranging from 0.33 to 2.0 g, the yield of CO2 was approximately 42–50% with respect to the total number of N2O5 molecules taken up. The reaction of N2O5 with mineral dust and the subsequent production of gas phase HNO3 lead to a decrease in [NOx] which may have a significant effect on global ozone.

  1. Dust lattice waves in Debye binary dust chain

    Science.gov (United States)

    He, Kerong; Chen, Hui; Liu, Sanqiu

    2017-12-01

    The dust lattice waves in a one-dimensional Debye binary dust chain consisting of two distinct dust particle species with different charges and masses are investigated. It is found that there are two branches for both longitudinal and transverse modes, namely the optical mode of high frequency and the acoustic mode of low frequency, which will be merged into one ordinary longitudinal (transverse) mode of single dust chain. The influence of the parameters, i.e., the dimensionless lattice parameter α, the mass ratio σ, and the charge ratio ɛ of the two particles, on the dispersion relation of longitudinal and transverse waves is discussed. Furthermore, the branching and the merging of longitudinal and transverse waves are discussed in detail.

  2. Large clean mesocosms and simulated dust deposition: a new methodology to investigate responses of marine oligotrophic ecosystems to atmospheric inputs

    Science.gov (United States)

    Guieu, C.; Dulac, F.; Desboeufs, K.; Wagener, T.; Pulido-Villena, E.; Grisoni, J.-M.; Louis, F.; Ridame, C.; Blain, S.; Brunet, C.; Bon Nguyen, E.; Tran, S.; Labiadh, M.; Dominici, J.-M.

    2010-09-01

    Intense Saharan dust deposition occurs over large oligotrophic areas in the Mediterranean Sea and in the Tropical Atlantic, and its impact on the biogeochemical functioning of such oligotrophic ecosystems needs to be understood. However, due to the logistical difficulties of investigating in situ natural dust events, and due to the inherent limitations of microcosm laboratory experiments, new experimental approaches need to be developed. In this paper, we present a new experimental setup based on large, clean mesocoms deployed in the frame of the DUNE (a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem) project. We demonstrate that these tools are highly relevant and provide a powerful new strategy to in situ studies of the response of an oligotrophic ecosystem to chemical forcing by atmospheric deposition of African dust. First, we describe how to cope with the large amount of dust aerosol needed to conduct the seeding experiments by producing an analogue from soil collected in a source area and by performing subsequent appropriate physico-chemical treatments in the laboratory, including an eventual processing by simulated cloud water. The comparison of the physico-chemical characteristics of produced dust analogues with the literature confirms that our experimental simulations are representative of dust, aging during atmospheric transport, and subsequent deposition to the Mediterranean. Second, we demonstrate the feasibility in coastal areas to installing, in situ, a series of large (6 × 52 m3) mesocosms without perturbing the local ecosystem. The setup, containing no metallic parts and with the least possible induced perturbation during the sampling sequence, provides an approach for working with the required conditions for biogeochemical studies in oligotrophic environments, where nutrient and micronutrients are at nano- or subnano-molar levels. Two, distinct "seeding experiments" were conducted by deploying three mesocosms serving as controls

  3. Dust emissions in the West African heat trough. The role of the diurnal cycle and of extratropical disturbances

    Energy Technology Data Exchange (ETDEWEB)

    Knippertz, P. [Inst. fuer Physik der Atmosphaere, Johannes Gutenberg-Univ. Mainz (Germany)

    2008-10-15

    The summertime West African heat trough (HT) is one of the most active dust sources in the world. A detailed case study during May/June 2006 based upon analyses from the European Centre for Medium-Range Weather Forecasts and a new Meteosat dust product illustrates two important mechanisms of dust emissions in this region: (1) The dry continental-scale HT circulation exhibits a strong diurnal cycle characterized by nocturnal low-level jets and downward mixing of momentum to the surface during the build-up of the planetary boundary layer in the morning. This leads to strong gusty surface winds and dust emission, mostly along the northern side of the HT, but also within the southerly monsoon flow. Transports lead to an accumulation of dust near the axis of the HT. (2) Triggered by a lee cyclogenesis south of the Atlas Mountains, the Intertropical Discontinuity that separates dry Saharan and moist monsoonal air shifts northward and allows deep moist convection to penetrate into the Sahara. The evaporation of precipitation in the dry desert air also generates strong gusty winds and dust emissions. This study helps to clarify the physical mechanisms for a previously discovered relation between the annual cycles of dustiness on one hand and near-surface convergence and gustiness on the other hand. (orig.)

  4. [Causation, prevention and treatment of dust explosion].

    Science.gov (United States)

    Dong, Maolong; Jia, Wenbin; Wang, Hongtao; Han, Fei; Li, Xiao-Qiang; Hu, Dahai

    2014-10-01

    With the development of industrial technology, dust explosion accidents have increased, causing serious losses of people's lives and property. With the development of economy, we should lay further emphasis on causation, prevention, and treatment of dust explosion. This article summarizes the background, mechanism, prevention, and treatment of dust explosion, which may provide some professional knowledge and reference for the treatment of dust explosion.

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

    Directory of Open Access Journals (Sweden)

    A. Gkikas

    2016-07-01

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

  6. Can sub-Saharan Africa feed itself?

    Science.gov (United States)

    van Ittersum, Martin K; van Bussel, Lenny G J; Wolf, Joost; Grassini, Patricio; van Wart, Justin; Guilpart, Nicolas; Claessens, Lieven; de Groot, Hugo; Wiebe, Keith; Mason-D'Croz, Daniel; Yang, Haishun; Boogaard, Hendrik; van Oort, Pepijn A J; van Loon, Marloes P; Saito, Kazuki; Adimo, Ochieng; Adjei-Nsiah, Samuel; Agali, Alhassane; Bala, Abdullahi; Chikowo, Regis; Kaizzi, Kayuki; Kouressy, Mamoutou; Makoi, Joachim H J R; Ouattara, Korodjouma; Tesfaye, Kindie; Cassman, Kenneth G

    2016-12-27

    Although global food demand is expected to increase 60% by 2050 compared with 2005/2007, the rise will be much greater in sub-Saharan Africa (SSA). Indeed, SSA is the region at greatest food security risk because by 2050 its population will increase 2.5-fold and demand for cereals approximately triple, whereas current levels of cereal consumption already depend on substantial imports. At issue is whether SSA can meet this vast increase in cereal demand without greater reliance on cereal imports or major expansion of agricultural area and associated biodiversity loss and greenhouse gas emissions. Recent studies indicate that the global increase in food demand by 2050 can be met through closing the gap between current farm yield and yield potential on existing cropland. Here, however, we estimate it will not be feasible to meet future SSA cereal demand on existing production area by yield gap closure alone. Our agronomically robust yield gap analysis for 10 countries in SSA using location-specific data and a spatial upscaling approach reveals that, in addition to yield gap closure, other more complex and uncertain components of intensification are also needed, i.e., increasing cropping intensity (the number of crops grown per 12 mo on the same field) and sustainable expansion of irrigated production area. If intensification is not successful and massive cropland land expansion is to be avoided, SSA will depend much more on imports of cereals than it does today.

  7. Paediatric challenges in Sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Robert Hilliard

    2016-01-01

    Full Text Available The United Nations Millennium Development Goals (MDGs project is coming to an end in 2015 and is being replaced by ambitious and aspirational Sustainable Development Goals (SDGs. Although the MDGs have been nearly achieved, this is not true in Sub-Saharan Africa where there is still unnecessarily high infant and childhood mortality and where there are many challenges to providing modern child health care. To achieve the SDGs in the next fifteen years, in low-income countries, national ministries of health and community health leaders will need to set reasonable goals and quality improvement projects. Attention needs to paid to economical, evidence-based effective health care; to education of children and youth and of health professional; health promotion and prevention of illness; a balance between expensive health care in large urban hospitals and community health projects; and most importantly to the social determinants of health. But the SDGs are achievable with coordinated and sustained national commitments and increased financial commitments from Western countries.

  8. Diet, malnutrition in sub-Saharan Africa.

    Science.gov (United States)

    Serdula, M

    1988-12-01

    This study analyzes the association of protein energy malnutrition and mortality in preschool (non-emergency) children in Sub-Saharan Africa. 2 functional consequences of malnutrition are discussed: retarded physical growth (anthropometry) and mortality. The anthropometric measures used to assess malnutrition are weight-for-age, weight for height, and mid-upper arm circumference. The major factors associated with malnutrition and mortality include dietary intake, severity and frequency of infections, social, demographic, economic and cultural factors (area of residence, seasonality, socioeconomic status, mother's age and educational level, family support and cohesiveness, birth order of index child and birth interval between children and number of children under 5 in the family, maternal nutritional status and health and adequacy of breast milk volume and composition for young infants. Understanding these factors will identify children-at-risk for malnutrition and target them for intervention programs. The article focuses on the association of malnutrition with mortality in relation to: 1) breastfeeding and weaning practice; 2) vitamin A and 3) infection. Reviews of African and Asian studies on the subject demonstrated that higher mortality rates were associated with malnutrition, however, the causal associations remain unclear. Since malnourished children are at higher risk for illness, short-term interventions should include growth monitoring, nutrition education, prevention and treatment of infections, food supplementation, hospital rehabilitation, home gardens and improved agricultural practices; while long-term interventions should include improvement in the economic and environmental conditions. (author's modified).

  9. Electroencephalographic slow waves prior to sleepwalking episodes.

    Science.gov (United States)

    Perrault, Rosemarie; Carrier, Julie; Desautels, Alex; Montplaisir, Jacques; Zadra, Antonio

    2014-12-01

    Recent studies have suggested that the onset of sleepwalking episodes may be preceded by fluctuations in slow-wave sleep electroencephalographic characteristics. However, whether or not such fluctuations are specific to sleepwalking episodes or generalized to all sleep-wake transitions in sleepwalkers remains unknown. The goal of this study was to compare spectral power for delta (1-4 Hz) and slow delta (0.5-1 Hz) as well as slow oscillation density before the onset of somnambulistic episodes versus non-behavioral awakenings recorded from the same group of sleepwalkers. A secondary aim was to describe the time course of observed changes in slow-wave activity and slow oscillations during the 3 min immediately preceding the occurrence of somnambulistic episodes. Twelve adult sleepwalkers were investigated polysomnographically during the course of one night. Slow-wave activity and slow oscillation density were significantly greater prior to patients' somnambulistic episodes as compared with non-behavioral awakenings. However, there was no evidence for a gradual increase over the 3 min preceding the episodes. Increased slow-wave activity and slow oscillation density appear to be specific to sleepwalking episodes rather than generalized to all sleep-wake transitions in sleepwalkers. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Surface System Dust Mitigation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed effort will perform a detailed examination of dust mitigation and tolerance strategies for connections and mechanisms to be employed on the lunar...

  11. Regarding Electrified Martian Dust Storms

    Science.gov (United States)

    Farrell, W. M.

    2017-06-01

    We examine the dynamic competition between dust devil/storm charging currents and dissipating atmospheric currents. A question: Can high-current lightning be a dissipation product of this competition? Most likely not but there are exceptions.

  12. Loess and Eolian Dust Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Records of past environment derived from Loess and Eolian dust (silt-sized material deposited on the Earth surface by the surface winds. Parameter keywords describe...

  13. Radiative Energetics of Mineral Dust Aerosols from Ground-Based Measurements

    Science.gov (United States)

    Tsay, Si-Chee; Hansell, Richard A.

    2011-01-01

    Airborne dust aerosols worldwide contribute a significant part to air quality problems and, to some extent, regional climatic issues (e.g., radiative forcing, hydrological cycle, and primary biological productivity in oceans). Evaluating the direct solar radiative effect of dust aerosols is relatively straightforward due in part to the relatively large SIN ratio in broadband irradiance measurements. The longwave (LW) impact, on the other hand, is rather difficult to ascertain since the measured dust signal level (approx.10 W/sq m) is on the same order as the instrumental uncertainties. Although the magnitude of the LW impact is much smaller than that of the shortwave (SW), it can still have a noticeable influence on the energy distribution of Earth-atmosphere system, particularly due to the strong light-absorptive properties commonly found in many terrestrial minerals. The current effort is part of an ongoing research study to perform a global assessment of dust direct aerosol radiative effects (DARE) during major field deployments of key dust source regions worldwide. In this work we present results stemming from two previous field deployments: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years, both utilizing NASA Goddard's mobile ground-based facility. The former study focused on transported Saharan dust at Sal (16.73degN, 22.93degW), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye (39.082degN, 100.276degE), China near the source between the Taklimakan and Gobi deserts. Due to the compelling variability in spatial and temporal scale of dust properties during field experiments, a deterministic I-D radiative transfer model constrained by local measurements (i.e., spectral photometry/interferometry and lidar for physical/microphysical, mineralogy, and single-scattering properties) is employed to evaluate dust's local instantaneous SW/LW DARE both at the surface and at the top of

  14. Iron dissolution kinetics of mineral dust at low pH during simulated atmospheric processing

    Directory of Open Access Journals (Sweden)

    Z. Shi

    2011-02-01

    Full Text Available We investigated the iron (Fe dissolution kinetics of African (Tibesti and Asian (Beijing dust samples at acidic pH with the aim of reproducing the low pH conditions in atmospheric aerosols. The Beijing dust and three size fractions of the Tibesti dust (<20 μm: PM20; <10 μm: PM10; and <2.5 μm: PM2.5 were dissolved at pH 1, 2 and/or 3 for up to 1000 h. In the first 10 min, all dust samples underwent an extremely fast Fe solubilisation. Subsequently, the Fe dissolution proceeded at a much slower rate before reaching a stable dissolution plateau. The time-dependant Fe dissolution datasets were best described by a model comprising three acid-extractable Fe pools each dissolving according to first-order kinetics. The dissolution rate constant k (h−1 of each pool was independent of the source (Saharan or Asian and the size (PM20, PM10 or PM2.5 of the dust but highly dependent on pH. The "fast" Fe pool had a k (25 h−1 at pH = 1 of a similar magnitude to "dry" ferrihydrite nanoparticles and/or poorly crystalline Fe(III oxyhydroxide, while the "intermediate" and "slow" Fe pools had k values respectively 50–60 times and 3000–4000 times smaller than the "fast" pool. The "slow" Fe pool was likely to consist of both crystalline Fe oxide phases (i.e., goethite and/or hematite and Fe contained in the clay minerals. The initial mass of the "fast", "intermediate" and "slow" Fe pools represented respectively about 0.5–2%, 1–3% and 15–40% of the total Fe in the dust samples. Furthermore, we showed that in systems with low dust/liquid ratios, Fe can be dissolved from all three pools, whereas at high dust/liquid ratios (e.g., in aerosols, sufficient Fe may be solubilised from the "fast" phase to dominate the Fe dissolved and to suppress the dissolution of Fe from the other Fe pools. These data demonstrated that dust/liquid ratio and pH are

  15. Autobiographical Memory and Episodic Future Thinking

    DEFF Research Database (Denmark)

    Rasmussen, Katrine; Berntsen, Dorthe

    the construction of specific events during episodic future thinking remain largely unexplored. In this study, we examined whether episodic future thoughts depend on executive processes and are affected by cue imageability to the same extent as autobiographical remembering of past events. Results showed...... that autobiographical memory and episodic future thinking were affected similarly by cue imageability, suggesting that retrieval strategy can be manipulated in similar ways for both temporal directions. Furthermore, executive control processes (as measured by verbal fluency) was correlated with fluency and number...... of details in both memories and future thoughts, indicating the involvement of some common component processes in autobiographical memory and future thinking....

  16. Variability of mineral dust deposition in the western Mediterranean basin and south-east of France

    Directory of Open Access Journals (Sweden)

    J. Vincent

    2016-07-01

    Full Text Available Previous studies have provided some insight into the Saharan dust deposition at a few specific locations from observations over long time periods or intensive field campaigns. However, no assessment of the dust deposition temporal variability in connection with its regional spatial distribution has been achieved so far from network observations over more than 1 year. To investigate dust deposition dynamics at the regional scale, five automatic deposition collectors named CARAGA (Collecteur Automatique de Retombées Atmosphériques insolubles à Grande Autonomie in French have been deployed in the western Mediterranean region during 1 to 3 years depending on the station. The sites include, from south to north, Lampedusa, Majorca, Corsica, Frioul and Le Casset (southern French Alps. Deposition measurements are performed on a common weekly period at the five sites. The mean dust deposition fluxes are higher close to the northern African coasts and decrease following a south–north gradient, with values from 7.4 g m−2 year−1 in Lampedusa (35°31′ N, 12°37′ E to 1 g m−2 year−1 in Le Casset (44°59′ N, 6°28′ E. The maximum deposition flux recorded is of 3.2 g m−2 wk−1 in Majorca with only two other events showing more than 1 g m−2 wk−1 in Lampedusa, and a maximum of 0.5 g m−2 wk−1 in Corsica. The maximum value of 2.1 g m−2 year−1 observed in Corsica in 2013 is much lower than existing records in the area over the 3 previous decades (11–14 g m−2 year−1. From the 537 available samples, 98 major Saharan dust deposition events have been identified in the records between 2011 and 2013. Complementary observations provided by both satellite and air mass trajectories are used to identify the dust provenance areas and the transport pathways from the Sahara to the stations for the studied period. Despite the large size of African dust plumes detected by satellites, more

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

    Science.gov (United States)

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

    2015-01-01

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

  18. Dry Mars: Parched Rocks and Fallen Dust

    Science.gov (United States)

    Treiman, Allan H.

    2001-01-01

    While "following the water" to find life on Mars, it is easy to overlook evidence that Mars is harshly dry, and to neglect ideas that do not invoke water. Direct evidence for a dry Mars comes from the ALH 84001 meteorite, which has seen little or no liquid water during its last 3.9 billion years on Mars. Its aridity is difficult to reconcile with a Mars of abundant near-surface surface water or with episodes of warm wet climate. Alternative scenarios are also possible, even likely, for the martian gullies and debris flows that have been cited as evidence of liquid water. It is reasonable that the gullies flows are the remnants of massive dust avalanches, comparable to large climax snow avalanches seen on Earth. Mars' surface is now desiccated, and at least part of it has been equally desiccated for the past 3.9 billion years. With this background, and the wealth of atmospheric, imaging, and chemical data available from Mars, one must be very cautious in evaluating claims for liquid water recently at or near Mars' surface. Additional information is contained in the original extended abstract.

  19. Sub-Saharan Africa thirty years hence.

    Science.gov (United States)

    Wheeler, J

    1986-11-01

    By the year 2015, Sub-Saharan Africa's population will probably rise from a 1985 level of about 460 million to about 1.1 billion. Today Africa's population is growing at a rate of roughly 3% a year, with exceptionally high growth rates in some countries. The leaders of Africa, and those who wish to help Africa, confront difficult and urgent problems of drought, political and military conflict, accumulated debt, lower commodity prices, and other factors of immediate and important concern. Africa has given education a high priority and should be as well known for its success in increasing school enrollment as it is for its relative failures in other areas. A projected population of 1.1 billion people and a fertility rate down to 30/1000 by the year 2015 suggests that the number of children old enough to enter primary school will be of the order of 30 million a year at this time. The working-age population will grow from 235 million now to perhaps 600 million in 30 years. The urban population has been growing at about 6% a year--twice the pace of population increase. All of these situations will have an effect on environment, water, and health. Coping with Africa's burgeoning population in terms of children in school, the demand on health systems, the need for jobs, achieving an adequate diet, the provision of basic urban services, and all the rest, is an extraordinary challenge. While the government's role is critical, success at the sectoral level almost always means cost recovery, administration decentralized to the community or to the private sector, and program implementation that does not burden the budget.

  20. [Torsades de pointes: analysis of 105 episodes].

    Science.gov (United States)

    Maia, I G; Sá, R; Alves, P A; Ribeiro, J C; Fernandes, P H; Guarçoni, O; Bassan, R; Dohmann, H F

    1993-02-01

    To analyze episodes of Torsades de Pointes (TP), in search of its electrocardiographic characteristics. We analyzed 105 episodes of TP, in 4 patients using quinidine and diuretics, recorded by 24-hour Holter monitoring. The following parameters were studied; ventricular repolarization out of TP, rhythm disturbances before TP; ECG characteristics of the onset, the bouts and the end of the TP. Ventricular repolarization, out of the TP, was abnormal, with the presence of U-waves at the end of the T-waves, resulting in prolongation of the QT (QU) interval. The U-wave voltage was noted to be cycle-length dependent. Ventricular bigeminy preceded TP in 100 episodes (95%) and the mean interval between both parameters was 18 +/- 16 min. The onset of the TP episodes showed the "short/long/short cycle rule", hereby called "pre-pause cycle", "preparing cycle" and "trigger cycle" respectively. The rotatory QRS-T morphology around the baseline, was seen in 75% of episodes, at the beginning or throughout the bout. Monomorphic ventricular tachycardia pattern was seen in the other 25% of episodes. Termination of bouts was sudden in all cases, and persistent ventricular bigeminy led to another bout in 90 episodes (85%). In TP patients, there is enlargement of QT intervals mostly due to U-waves appearance. The U-waves seen in these cases, probably have an important role in the genesis of TP and are probably related to ventricular after-potentials (triggered activity). Ventricular bigeminy is a premonitory sign of TP in patients using class 1A antiarrhythmic drugs. Persistent ventricular bigeminy post-TP episodes is a strong indicator of another bout of TP. The onset of TP is more important than its morphology for the correct diagnosis of this arrhythmia.

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

    Science.gov (United States)

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

    2013-06-01

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

  2. Clinical care management and workflow by episodes.

    Science.gov (United States)

    Claus, P L; Carpenter, P C; Chute, C G; Mohr, D N; Gibbons, P S

    1997-01-01

    This paper describes the implementation of clinically defined episodes of care and the introduction of an episode-based summary list of patient problems across Mayo Clinic Rochester in 1996 and 1997. Although Mayo's traditional paper-based system has always relied on a type of 'episode of care' (called the "registration") for patient and history management, a new, more clinically relevant definition of episode of care was put into practice in November 1996. This was done to improve care management and operational processes and to provide a basic construct for the electronic medical record. Also since November 1996, a computer-generated summary list of patient problems, the "Master Sheet Summary Report," organized by episode, has been placed in all patient histories. In the third quarter of 1997, the ability to view the episode-based problem summary online was made available to the 3000+ EMR-capable workstations deployed across the Mayo Rochester campus. In addition, the clinically oriented problem summarization process produces an improved basic "package" of clinical information expected to lead to improved analytic decision support, outcomes analysis and epidemiological research.

  3. Interplanetary Dust Particles

    Science.gov (United States)

    Bradley, J. P.

    2003-12-01

    One of the fundamental goals of the study of meteorites is to understand how the solar system and planetary systems around other stars formed. It is known that the solar system formed from pre-existing (presolar) interstellar dust grains and gas. The grains originally formed in the circumstellar outflows of other stars. They were modified to various degrees, ranging from negligible modification to complete destruction and reformation during their ˜108 yr lifetimes in the interstellar medium (ISM) (Seab, 1987; Mathis, 1993). Finally, they were incorporated into the solar system. Submicrometer-sized silicates and carbonaceous material are believed to be the most common grains in the ISM ( Mathis, 1993; Sandford, 1996), but it is not known how much of this presolar particulate matter was incorporated into the solar system, to what extent it has survived, and how it might be distinguished from solar system grains. In order to better understand the process of solar system formation, it is important to identify and analyze these solid grains. Since all of the alteration processes that modified solids in the solar nebula presumably had strong radial gradients, the logical place to find presolar grains is in small primitive bodies like comets and asteroids that have undergone little, if any, parent-body alteration.Trace quantities of refractory presolar grains (e.g., SiC and Al2O3) survive in the matrices of the most primitive carbon-rich chondritic meteorites (Anders and Zinner, 1993; Bernatowicz and Zinner, 1996; Bernatowicz and Walker, 1997; Hoppe and Zinner, 2000; see Chapter 1.02). Chondritic meteorites are believed to be from the asteroid belt, a narrow region between 2.5 and 3.5 astronomical units (AU) that marks the transition from the terrestrial planets to the giant gas-rich planets. The spectral properties of the asteroids suggest a gradation in properties with some inner and main belt C and S asteroids (the source region of most meteorites and polar

  4. 2002 Kuiper prize lecture: Dust Astronomy

    Science.gov (United States)

    Grün, Eberhard; Srama, Ralf; Krüger, Harald; Kempf, Sascha; Dikarev, Valeri; Helfert, Stefan; Moragas-Klostermeyer, Georg

    2005-03-01

    Dust particles, like photons, carry information from remote sites in space and time. From knowledge of the dust particles' birthplace and their bulk properties, we can learn about the remote environment out of which the particles were formed. This approach is called "Dust Astronomy" which is carried out by means of a dust telescope on a Dust Observatory in space. Targets for a dust telescope are the local interstellar medium and nearby star forming regions, as well as comets and asteroids. Dust from interstellar and interplanetary sources is distinguished by accurately sensing their trajectories. Trajectory sensors may use the electric charge signals that are induced when charged grains fly through the detector. Modern in-situ dust impact detectors are capable of providing mass, speed, physical and chemical information of dust grains in space. A Dust Observatory mission is feasible with state-of-the-art technology. It will (1) provide the distinction between interstellar dust and interplanetary dust of cometary and asteroidal origin, (2) determine the elemental composition of impacting dust particles, and (3) monitor the fluxes of various dust components as a function of direction and particle masses.

  5. Theoretical aspects of Dust in fusion devices

    Energy Technology Data Exchange (ETDEWEB)

    Pigarov, A.Yu.; Smirnov, R.D. [University of California at San Diego, La Jolla, CA (United States); Soboleva, T.K. [ICN, Universidad Nacional Autonoma de Mexico, Mexico D. F. (Mexico); Krasheninnikov, S.I.

    2010-05-15

    It is known that micro-particles (dust) exist in fusion devices. However, an impact of dust on plasma contamination, material migration, and performance of fusion devices is still under debate. In burning plasma experiments like ITER dust can also pose safety problems related to it's chemical activity, toxicity, tritium retention, and radioactive content. In order to address all these issues we need to understand the physics of dust generation, dynamics, and transport. In this paper, the results of recent theoretical studies of dust in fusion plasmas are reviewed. Different aspects of the physics of dust in fusion plasmas, including the processes of dust generation, charging, heating, destruction, spinning, forces acting on dust, dust collision with material walls, etc are discussed. The numerical models of these processes have been incorporated into the dust transport code DUSTT, which is capable of tracking of dust particles in fusion devices in 3D geometry. The results of the simulations of dust particle dynamics, transport, and the impact on edge plasma performance are considered. The latest results on nonlinear interactions of dust grain with tokamak plasma as well as remaining gaps in the understanding of physics of dust in fusion devices are discussed (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Modelling of a strong dust event in the complex terrain of the Dead Sea valley during the passage of a gust front

    Directory of Open Access Journals (Sweden)

    Pavel Kishcha

    2016-02-01

    Full Text Available The area of the Dead Sea valley and the adjacent regions are often affected by mineral dust. This study focuses on an extreme dust episode occurring on 22 March 2013, where near-surface dust concentrations of up to 7000 µg m−3 were encountered in the Dead Sea region. This episode is of great interest as it was accompanied by high wind speeds and a gust front that rapidly passed the Judean Mountains. Wind was even accelerated on the lee side of the Judean Mountains leading to a severe downslope wind. We simulated this situation with the comprehensive online-coupled weather forecast model COSMO-ART. Fair agreement was found between the simulated meteorological variables and the observations. The model was capable of producing a reasonable spatiotemporal distribution of near-surface dust concentration, consistent with available measurements in this area. With respect to the time of the maximum near-surface dust concentration in the Dead Sea valley, the model captured it almost perfectly compared to the observed total suspended particle (TSP concentrations. COSMO-ART showed that the high near-surface dust concentration in the Dead Sea valley was mainly determined by local emissions. These emissions were caused by strong winds on the lee side of the Judean Mts. The model showed that an ascending airflow in the Dead Sea valley lifted dust particles, originating mainly from the upwind side of the Judean Mts., up to approximately 7 km. These dust particles contributed to the pronounced maximum in modelled dust aerosol optical depth (AOD over the valley. Here we highlight the important point that the simulated maximum dust AOD was reached in the eastern part of the Dead Sea valley, while the maximum near-surface dust concentration was reached in the western part of the valley.

  7. Estimation of the variability of dust aerosol optical depth over several European regions based on the forecast model data

    Science.gov (United States)

    Mandija, Florian; Chávez Pérez, Victor; Gimeno Presa, Luis; Nieto, Raquel; Añel Cabanelas, Juan Antonio

    2017-04-01

    The main goal of this work is to determine the patterns of the variability of dust aerosol optical depth (AOD) over the European continent for a 9-years period. This aerosol parameter is an important indicator of the presence of dust plumes over the investigated area. Saharan and Arabic deserts are the two major dust sources which affect the European continent. The model used in this study is BSC-DREAM8b_v2.0 (Atmospheric Dust Forecast System), which provided AOD550 data from January 2006 up to December 2014. The investigation of the dust event climatology was realized dividing the affected area (European continent) and dust source area (two main deserts) into several distinct sectors. The European continent is divided into 8 sectors and the two deserts are divided into 4 sectors. The threshold of sector-averaged AOD550 in the cases of dust events is chosen 0.10. Overall results indicate that the dust events affect more the three southern sectors, especially the central one. Meanwhile, the two northern sectors are less affected. It was observed also a dependence of AOD also on the longitude. Central sectors have higher average AOD, while the west ones have the lowest. Highest AOD are observed during late spring and early summer at central and eastern sectors, and during summer at western sector. More than 67% of all daily-averaged AOD data, which overpass the threshold, at all sectors, are lower than 0.2. Sector-averaged AOD at three southern sectors was 0.02-0.04, while at the northern sectors this value falls down to 0.002-0.001. Moreover, no clear inter-annual trends are identified. The yearly cycles of AOD over the European sectors were more evident at southern sectors, especially at the regions of Apennine and Balkan peninsulas.

  8. Dust characterization in FTU tokamak

    Energy Technology Data Exchange (ETDEWEB)

    De Angeli, M., E-mail: deangeli@ifp.cnr.it [Istituto di Fisica del Plasma – Consiglio Nazionale delle Ricerche, Milan (Italy); Maddaluno, G. [ENEA Unità Tecnica Fusione, C.R. ENEA Frascati, CP65, 00044 Frascati (Italy); Laguardia, L. [Istituto di Fisica del Plasma – Consiglio Nazionale delle Ricerche, Milan (Italy); Ripamonti, D. [Istituto per l’Energetica e le Interfasi – Consiglio Nazionale delle Ricerche, Milan (Italy); Perelli Cippo, E. [Istituto di Fisica del Plasma – Consiglio Nazionale delle Ricerche, Milan (Italy); Apicella, M.L. [ENEA Unità Tecnica Fusione, C.R. ENEA Frascati, CP65, 00044 Frascati (Italy); Conti, C. [Istituto per la Conservazione e la Valorizzazione dei Beni Culturali – CNR, Milan (Italy); Giacomi, G. [ENEA Unità Tecnica Fusione, C.R. ENEA Frascati, CP65, 00044 Frascati (Italy); Grosso, G. [Istituto di Fisica del Plasma – Consiglio Nazionale delle Ricerche, Milan (Italy)

    2015-08-15

    Dust present in the vessel of FTU has been collected and analysed. Being FTU a device with full metal plasma facing components for the whole life and equipped with a liquid lithium limiter (LLL) make FTU of special interest from a point of view of dust studies. Analyses were conducted by standard dust analysis methods and by dedicated analysis, as X-rays and neutron diffraction, to investigate the presence of lithium compounds due the presence of the LLL in FTU. Dust collected near the LLL presents a different elemental composition, namely Li compounds, compared to the dust collected in the rest of the vessel; in particular LiO{sub 2}, LiOH, and Li{sub 2}CO{sub 3}. On the basis of these results, the formation of Li{sub 2}CO{sub 3} is proposed via a two steps process. Results of fuel retention measured by thermal desorption spectroscopy (TDS) method show that fuel retention should not be an issue for FTU.

  9. Men's Attitudes Towards Contraception in Sub-Saharan Africa.

    Science.gov (United States)

    Bietsch, Kristin E

    2015-09-01

    This paper examines male attitudes towards family planning in Sub-Saharan Africa. Studying attitudes is ideal as they can be calculated for all men, at any point in their lives, regardless of marital status, sexual activity, or fertility desires. We find that positive attitudes towards family planning have increased across Sub-Saharan Africa in the last two decades. We analyze both the association of positive attitudes with a variety of demographic characteristics (age, marital status, education, and religion) and the relationships with multiple forms of discussion about family planning (radio, television, friends, and partners). We find higher approval at older ages and higher levels of education, and lower levels of approval among Muslims compared to Christians. Interactions between characteristics and discussion of family planning. demonstrate that hearing or talking about contraception has different associations for different groups. This paper offers a new way to explore fertility and reproductive health in Sub-Saharan Africa.

  10. Boundary Layer Dust Occurrence III Atmospheric Dust Over Russia

    Science.gov (United States)

    1977-05-01

    valley of the Syr - Darya , near easily-blown sands. Conditions analogous to Takhiatash and, consequently, a number of 358 dust storm days exceeding an...1 AD Reports Control Syr OSD-1366 ECOM DR 75-2 pt.3 c.l RESEARCH AND DEVELOPMENT TECHNICAL REPORT ECOM-DR-77-2 t.ND AFB, N. M...dust stream was 60 and even 100 units in the lower Don region and in the eastern and northern Azov region, 30 to 40 units in the Don and Volga delta

  11. Impact of human schistosomiasis in sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Abiola Fatimah Adenowo

    Full Text Available Schistosomiasis, a neglected tropical disease of poverty ranks second among the most widespread parasitic disease in various nations in sub-Saharan Africa. Neglected tropical diseases are causes of about 534,000 deaths annually in sub-Saharan Africa and an estimated 57 million disability-adjusted life-years are lost annually due to the neglected tropical diseases. The neglected tropical diseases exert great health, social and financial burden on economies of households and governments. Schistosomiasis has profound negative effects on child development, outcome of pregnancy, and agricultural productivity, thus a key reason why the "bottom 500 million" inhabitants of sub-Saharan Africa continue to live in poverty. In 2008, 17.5 million people were treated globally for schistosomiasis, 11.7 million of those treated were from sub-Saharan Africa. This enervating disease has been successfully eradicated in Japan, as well as in Tunisia. Morocco and some Caribbean Island countries have made significant progress on control and management of this disease. Brazil, China and Egypt are taking steps towards elimination of the disease, while most sub-Saharan countries are still groaning under the burden of the disease. Various factors are responsible for the continuous and persistent transmission of schistosomiasis in sub-Saharan Africa. These include climatic changes and global warming, proximity to water bodies, irrigation and dam construction as well as socio-economic factors such as occupational activities and poverty. The morbidity and mortality caused by this disease cannot be overemphasized. This review is an exposition of human schistosomiasis as it affects the inhabitants of various communities in sub-Sahara African countries. It is hoped this will bring a re-awakening towards efforts to combat this impoverishing disease in terms of vaccines development, alternative drug design, as well as new point-of-care diagnostics.

  12. Impact of human schistosomiasis in sub-Saharan Africa.

    Science.gov (United States)

    Adenowo, Abiola Fatimah; Oyinloye, Babatunji Emmanuel; Ogunyinka, Bolajoko Idiat; Kappo, Abidemi Paul

    2015-01-01

    Schistosomiasis, a neglected tropical disease of poverty ranks second among the most widespread parasitic disease in various nations in sub-Saharan Africa. Neglected tropical diseases are causes of about 534,000 deaths annually in sub-Saharan Africa and an estimated 57 million disability-adjusted life-years are lost annually due to the neglected tropical diseases. The neglected tropical diseases exert great health, social and financial burden on economies of households and governments. Schistosomiasis has profound negative effects on child development, outcome of pregnancy, and agricultural productivity, thus a key reason why the "bottom 500 million" inhabitants of sub-Saharan Africa continue to live in poverty. In 2008, 17.5 million people were treated globally for schistosomiasis, 11.7 million of those treated were from sub-Saharan Africa. This enervating disease has been successfully eradicated in Japan, as well as in Tunisia. Morocco and some Caribbean Island countries have made significant progress on control and management of this disease. Brazil, China and Egypt are taking steps towards elimination of the disease, while most sub-Saharan countries are still groaning under the burden of the disease. Various factors are responsible for the continuous and persistent transmission of schistosomiasis in sub-Saharan Africa. These include climatic changes and global warming, proximity to water bodies, irrigation and dam construction as well as socio-economic factors such as occupational activities and poverty. The morbidity and mortality caused by this disease cannot be overemphasized. This review is an exposition of human schistosomiasis as it affects the inhabitants of various communities in sub-Sahara African countries. It is hoped this will bring a re-awakening towards efforts to combat this impoverishing disease in terms of vaccines development, alternative drug design, as well as new point-of-care diagnostics. Copyright © 2015 Elsevier Editora Ltda. All rights

  13. Impact of human schistosomiasis in sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Abiola Fatimah Adenowo

    2015-03-01

    Full Text Available Schistosomiasis, a neglected tropical disease of poverty ranks second among the most widespread parasitic disease in various nations in sub-Saharan Africa. Neglected tropical diseases are causes of about 534,000 deaths annually in sub-Saharan Africa and an estimated 57 million disability-adjusted life-years are lost annually due to the neglected tropical diseases. The neglected tropical diseases exert great health, social and financial burden on economies of households and governments. Schistosomiasis has profound negative effects on child development, outcome of pregnancy, and agricultural productivity, thus a key reason why the “bottom 500 million” inhabitants of sub-Saharan Africa continue to live in poverty. In 2008, 17.5 million people were treated globally for schistosomiasis, 11.7 million of those treated were from sub-Saharan Africa. This enervating disease has been successfully eradicated in Japan, as well as in Tunisia. Morocco and some Caribbean Island countries have made significant progress on control and management of this disease. Brazil, China and Egypt are taking steps towards elimination of the disease, while most sub-Saharan countries are still groaning under the burden of the disease. Various factors are responsible for the continuous and persistent transmission of schistosomiasis in sub-Saharan Africa. These include climatic changes and global warming, proximity to water bodies, irrigation and dam construction as well as socio-economic factors such as occupational activities and poverty. The morbidity and mortality caused by this disease cannot be overemphasized. This review is an exposition of human schistosomiasis as it affects the inhabitants of various communities in sub-Sahara African countries. It is hoped this will bring a re-awakening towards efforts to combat this impoverishing disease in terms of vaccines development, alternative drug design, as well as new point-of-care diagnostics.

  14. Emigration dynamics in Sub-Saharan Africa.

    Science.gov (United States)

    Adepoju, A

    1995-01-01

    The introduction to this description of emigration dynamics in sub-Saharan Africa notes that the region is characterized by intensive migration caused by such factors as population growth, negative economic growth, ethnic conflict, and human rights abuses. The second section of the report discusses the fragmentary and incomplete nature of data on international migration in the region, especially data on conventional migration. Section 3 looks at demographic factors such as high population growth, illiteracy levels, HIV seroprevalence, and urbanization which lead to high unemployment and emigration. The fourth section considers the effects of the rapid expansion of education which is outstripping the absorptive capacity of the economies of many countries. Unemployment is a serious problem which is projected to become worse as increases in employment opportunities continue to lag behind increases in output. Sections five, six, and seven of the report describe relevant economic factors such as per capita income, income distribution, the economic resource base, and economic development; poverty; and the effects of economic adjustment programs, especially on employment opportunities and wages in the public and private sectors. The next section is devoted to sociocultural factors influencing migration both on the micro- and the macro-levels, including the influence of ethnicity and ethnic conflicts as well as the domination of leadership positions by members of minority groups. The political factors discussed in section 9 include women's status, repressive regimes, political instability which leads to underdevelopment, and the policies of the Organization of African Unity which broadened the definition of refugees and set inviolable borders of member states identical to those inherited upon independence. Section 10 outlines ecological factors contributing to migration, including the decline in acreage of arable land, soil deterioration, poor land management, and the

  15. Desert Dust and Monsoon Rain

    Science.gov (United States)

    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.

  16. Dust remobilization in fusion plasmas

    CERN Document Server

    Tolias, P; De Angeli, M; De Temmerman, G; Ripamonti, D; Riva, G; Bykov, I; Shalpegin, A; Vignitchouk, L; Brochard, F; Bystrov, K; Bardin, S; Litnovsky, A

    2016-01-01

    The first combined experimental and theoretical studies of dust remobilization by plasma forces are reported. The main theoretical aspects of remobilization are analyzed. In particular, the dominant role of adhesive forces is highlighted and generic remobilization conditions - detachment, sliding, rolling - are formulated. A novel experimental technique is proposed, based on controlled adhesion of dust grains on tungsten samples combined with detailed mapping of the dust deposition profile prior and post plasma exposure. Proof-of-principle experiments in the TEXTOR tokamak and the EXTRAP-T2R reversed-field pinch are presented. The versatile environment of the linear device Pilot-PSI allowed for experiments with different magnetic field topologies and varying plasma conditions that were complemented with camera observations.

  17. Iron cycling in a late Paleozoic dust bowl

    Science.gov (United States)

    Owens, J. D.; Soreghan, G. S.; Gerhardt, A.; Sur, S.; Lyons, T. W.

    2009-12-01

    The late Paleozoic glaciation (~300 million years ago) marks the last major, pre-Cenozoic icehouse climate. In addition, emerging research suggests that this was a particularly dusty time, evinced by abundant dust (loessite) deposits throughout western equatorial Pangaea. Delivery of reactive Fe-rich eolian particles to the nutrient-depleted open ocean potentially stimulates primary production during glacial intervals, yet the details remain unclear for recent glaciations and completely unknown for the ancient. Bioavailable Fe is a limiting nutrient in high nitrate, low chlorophyll portions of the open ocean. Because primary abundances of the most labile forms of Fe are not easily assessed in ancient sediments, we use highly reactive Fe (FeHR) (mostly crystalline oxides, some or most of which might have been more soluble precursors at the time of deposition) as determined by a well-calibrated sequential extraction scheme as a proxy for bioavailable Fe. Here we present data from multiple Pennsylvanian-Permian loess and intercalated paleosol (ancient soil) deposits, as well as a modern dust site. We also compare ratios of total Fe (FeT) to Al to ratios of FeHR to FeT to assess whether increased Fe reactivity in dust reflects a net Fe addition or internal mineral repartitioning. We are finding that these paired proxies may provide a unique fingerprint of source relationships. Modern arid Saharan soil dust deposited in the Turks and Caicos Islands has high FeT/Al ratios (0.75 versus ~0.5 for average continental crust), with corresponding FeHR/FeT enrichments (0.48 compared to ~0.38 for typical riverine input). The ancient loessite samples do not show a similar pattern, instead suggesting an antithetic relationship between FeT/Al and FeHR/FeT. Therefore, FeHR was enriched and, by inference, bioavailable despite net Fe loss reflected in sub-crustal FeT/Al ratios. Most work to date has presumed an arid soil source for most bioavailable Fe. However, in light of our work

  18. Cloud ice caused by atmospheric mineral dust - Part 1: Parameterization of ice nuclei concentration in the NMME-DREAM model

    Science.gov (United States)

    Nickovic, Slobodan; Cvetkovic, Bojan; Madonna, Fabio; Rosoldi, Marco; Pejanovic, Goran; Petkovic, Slavko; Nikolic, Jugoslav

    2016-09-01

    Dust aerosols are very efficient ice nuclei, important for heterogeneous cloud glaciation even in regions distant from desert sources. A new generation of ice nucleation parameterizations, including dust as an ice nucleation agent, opens the way towards a more accurate treatment of cold cloud formation in atmospheric models. Using such parameterizations, we have developed a regional dust-atmospheric modelling system capable of predicting, in real time, dust-induced ice nucleation. We executed the model with the added ice nucleation component over the Mediterranean region, exposed to moderate Saharan dust transport, over two periods lasting 15 and 9 days, respectively. The model results were compared against satellite and ground-based cloud-ice-related measurements, provided by SEVIRI (Spinning Enhanced Visible and InfraRed Imager) and the CNR-IMAA Atmospheric Observatory (CIAO) in Potenza, southern Italy. The predicted ice nuclei concentration showed a reasonable level of agreement when compared against the observed spatial and temporal patterns of cloud ice water. The developed methodology permits the use of ice nuclei as input into the cloud microphysics schemes of atmospheric models, assuming that this approach could improve the predictions of cloud formation and associated precipitation.

  19. [Dust lung or dust-induced lung disease ( discussion on chronic dust-induced lung disease)].

    Science.gov (United States)

    Kosarev, V V

    1989-01-01

    The comment on the article by D. M. Zislin (Occupational Hygiene and Industrial Diseases, 1988, N 10) is presented. Proceeding from the author's own experience and literary data, the main statement of D. M. Zislin disputing the concept of dust pulmonary disease (DPD) in the modern occupational pulmonology, is analyzed. The common cause of pneumoconiosis and dust bronchitis has been identified as fibrogenic dust, allergic, carcinogenic and toxic characteristics of which can be only condition affecting the disease clinical character. The article shows that neither generality, nor the differences in the functional changes of external respiration can serve as a convincing argument for or against the existence of the concept of DPD. Modern histomorphologic studies give evidence that low-fibrogenic dusts practically simultaneously cause the onset of the pathologic process both in the interstitial tissue and in the bronchi, the outcome of the process being diffuse pneumosclerosis. The concept of DPD caused by low-fibrogenic dusts has been substantiated on the basis of common etiology and similar pathogenetic, clinical and functional manifestations.

  20. [Thyroid diseases in sub-Saharan Africa].

    Science.gov (United States)

    Sidibé, El Hassane

    2007-01-01

    Thyroid gland diseases vary according to the environment. In sub-Saharan Africa, they are also influenced by population isolation and the absence of food self-sufficiency, both factors affecting the onset and persistence of iodine-deficiency goiters. More cosmopolitan diseases are now added to these thyroid disorders. Women are mainly affected (94.2%), most often with euthyroid goiters (54.7%), followed by Graves disease (13.1%), hypothyroidism (8.8%), thyroiditis (6.6%), toxic multinodular goiters (6.6 %) and unclassified goiters (10%) [Gabon]. The paucity of laboratories specializing in endocrinology and of nuclear medicine facilities, the delay in diagnosis that results in compressive or recurrent goiters, and endemic goiters are all typical in Africa. In children and adolescents, death rates increase with congenital or acquired thyroiditis as with delayed physical or mental development. In this environment, thyroiditis can also be pregnancy-related. Very recent surveys show a prevalence of endemic goiters of 28.6% in the community of Sekota, Ethiopia, 64-70% in Sahel-Sudan (population aged 10-20 years), 20-29% in KwaZulu-Natal (school children), 14.3-30.2% in Namibia (school children), 0.21% (congenital hypothyroidism or cretinism) in Plateau State, Nigeria, 55.2% at Zitenga, Burkina Faso (210 persons 0-45 years), and 10% in Hararé and Wedza, Zimbabwe (newborn TSH >10.1 microIU/mL). The prevalence of goiters is 43.6% in children emigrating from Ethiopia to Israel. Millet from semi-arid zones contains apigenin at a concentration of 150 mg/kg and luteolin at 350 mg/kg, both of which can interfere with thyroid function. The harmful effects of cassava (also known as manioc) are better known: milling cassava reduces its goitrogenic potential. In addition to iodine deficiency, selenium deficiency, and the effect of the thiocyanates in cassava, ion concentrations in soil and drinking water appear to play a role. The proportion of thyroid surgery indicated for

  1. Maternity health care: The experiences of Sub-Saharan African women in Sub-Saharan Africa and Australia.

    Science.gov (United States)

    Mohale, Hlengiwe; Sweet, Linda; Graham, Kristen

    2017-08-01

    Increasing global migration is resulting in a culturally diverse population in the receiving countries. In Australia, it is estimated that at least four thousand Sub-Saharan African women give birth each year. To respond appropriately to the needs of these women, it is important to understand their experiences of maternity care. The study aimed to examine the maternity experiences of Sub-Saharan African women who had given birth in both Sub-Saharan Africa and in Australia. Using a qualitative approach, 14 semi-structured interviews with Sub-Saharan African women now living in Australia were conducted. Data was analysed using Braun and Clark's approach to thematic analysis. Four themes were identified; access to services including health education; birth environment and support; pain management; and perceptions of care. The participants experienced issues with access to maternity care whether they were located in Sub-Saharan Africa or Australia. The study draws on an existing conceptual framework on access to care to discuss the findings on how these women experienced maternity care. The study provides an understanding of Sub-Saharan African women's experiences of maternity care across countries. The findings indicate that these women have maternity health needs shaped by their sociocultural norms and beliefs related to pregnancy and childbirth. It is therefore arguable that enhancing maternity care can be achieved by improving women's health literacy through health education, having an affordable health care system, providing respectful and high quality midwifery care, using effective communication, and showing cultural sensitivity including family support for labouring women. Copyright © 2016 Australian College of Midwives. Published by Elsevier Ltd. All rights reserved.

  2. Durable Dust Repellent Coating for Metals Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Durable Dust Repellent Coating (DDRC) consists of nano-phase silica, titania, or other oxide coatings to repel dust in a vacuum environment over a wide range of...

  3. Dust/Regolith for Surface Exploration

    Science.gov (United States)

    Peters, Benjamin

    2017-01-01

    System-wide dust protection is a key design driver for xEMUsurface operations, and development of dust proof mechanisms, bearings, materials, and coatings coupled with specific operations and surface architecture development is critical for success.

  4. Dust Mitigation for the Lunar Surface Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The lunar surface is to a large extent covered with a dust layer several meters thick. Known as lunar regolith, it poses a hazard in the form of dust clouds being...

  5. Characterization of alluvial dust sources and their temporal development - a multi-sensor approach for the Aïr Massif, Niger

    Science.gov (United States)

    Feuerstein, Stefanie; Schepanski, Kerstin

    2017-04-01

    One of the world's largest sources of atmospheric dust is the Sahara. It is said that 55% of the total global dust emission can be linked to the desert in northern Africa. Thus, understanding the Saharan dust sources is of great importance to estimate the total global dust load and its variability. Especially one type of dust sources has gained attention in dust research in recent years: The emission of dust from sediments formed by hydrologic processes, so called alluvial dust sources. These sediments were either formed in the past under the influences of a more humid paleoclimate or are deposited recently, e.g. during strong precipitation events when surficial runoff leads to the activation of wadi systems or to the occurrence of flash floods. Especially the latter phenomenon is able to deliver a huge amount of potentially erodible sediments. The research presented here focuses on the characterization of these alluvial dust sources with special attention on their temporal variability in relation to wet and dry phases. A study area covering the Aïr Massif in Niger is analysed over a four years time span from January 2013 to December 2016. The whole cycle from sediment formation to dust emission is illustrated by using data of various satellite sensors that are able to capture the processes taking place at the land surface as well as in the atmosphere: (1) The rainfall distribution for the study area is shown by time series of the TRMM precipitation estimates. A catchment analysis of the area helps to estimate the amount of surficial runoff and to detect areas of potential sediment accumulation. (2) Changes in the sediment structure of the land surface are analysed using atmospherically corrected time series of NASA's Landsat-8 OLI satellite. A land cover classification shows the distribution of alluvial sediments over the area; fresh layers of alluvial deposits are detected. Furthermore, the evolution of the vegetation cover, which inhibits dust emission, is

  6. Dust investigations in TEXTOR: Impact of dust on plasma–wall interactions and on plasma performance

    NARCIS (Netherlands)

    Litnovsky, A.; Rudakov, D. L.; Bozhenkov, S.; Smirnov, R. D.; Ratynskaia, S.; H. Bergsåker,; I. Bykov,; Ashikawa, N.; De Temmerman, G.; Xu, Y.; S.I. Krasheninnikov,; Biel, W.; Brezinsek, S.; Coenen, J. W.; Kreter, A.; Kantor, M.; H.T. Lambertz,; Philipps, V.; Pospieszczyk, A.; Samm, U.; Sergienko, G.; Schmitz, O.; Stoschus, H.

    2013-01-01

    Dust will have severe impact on ITER performance since the accumulation of tritium in dust represents a safety issue, a possible reaction of dust with air and steam imposes an explosion hazard and the penetration of dust in core plasmas may degrade plasma performance by increasing radiative losses.

  7. A climatology of Northeast Asian dust events

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Y. [City Univ. of Hong Kong, Kowloon (China). Dept. of Physics and Materials Science; Wang, J. [Academy of Meteorological Sciences, Beijing, BJ (China). State Meteorological Administration, National Meteorological Centre

    2003-08-01

    In this paper, the synoptic features of Northeast Asian dust events in spring are studied. Using surface meteorological records for March, April and May of 2000, 2001 and 2002, the distribution of dust-event frequencies, possible dust-source regions and the synoptic conditions responsible for dust activities are examined. Four regions of frequent dust events are found in the domain of analysis. These are the Tarim Basin, the southern Mongolia and the Inner Mongolia Autonomous Region of China, the Hexi (Yellow River West) Corridor and the northern part of the Indian Subcontinent. The Tarim Basin has the highest dust-event frequency, with most of the events being weak ones (classified as dust-in-suspension). Dust events occur less frequently in the Gobi Desert, but they are often severe and widespread. Dust concentrations in the Tarim and the Gobi regions are found to be of similar order of magnitude with (averaged) maximum values reaching 1 mg m{sup -3}. In different regions, dust events are generated by different synoptic systems. Over the Gobi, almost all dust events arise from the strong northwesterly winds associated with low-pressure systems. In the Tarim Basin, dust events are mostly associated with light winds. Strong northeasterly winds may affect the eastern and southeastern parts of the basin, generating dust storms. It is shown that topography plays a significant role in the transport of dust particles. A preferred route of dust transport is found to exist along the northeastern boundary, and another along the southern boundary, of the Tibetan Plateau. It is suggested the mechanisms for dust emission in the Tarim Basin requires further investigation. (orig.)

  8. PM(10) episodes in Greece: Local sources versus long-range transport-observations and model simulations.

    Science.gov (United States)

    Matthaios, Vasileios N; Triantafyllou, Athanasios G; Koutrakis, Petros

    2017-01-01

    Periods of abnormally high concentrations of atmospheric pollutants, defined as air pollution episodes, can cause adverse health effects. Southern European countries experience high particulate matter (PM) levels originating from local and distant sources. In this study, we investigated the occurrence and nature of extreme PM10 (PM with an aerodynamic diameter ≤10 μm) pollution episodes in Greece. We examined PM10 concentration data from 18 monitoring stations located at five sites across the country: (1) an industrial area in northwestern Greece (Western Macedonia Lignite Area, WMLA), which includes sources such as lignite mining operations and lignite power plants that generate a high percentage of the energy in Greece; (2) the greater Athens area, the most populated area of the country; and (3) Thessaloniki, (4) Patra, and (5) Volos, three large cities in Greece. We defined extreme PM10 pollution episodes (EEs) as days during which PM10 concentrations at all five sites exceeded the European Union (EU) 24-hr PM10 standards. For each EE, we identified the corresponding prevailing synoptic and local meteorological conditions, including wind surface data, for the period from January 2009 through December 2011. We also analyzed data from remote sensing and model simulations. We recorded 14 EEs that occurred over 49 days and could be grouped into two categories: (1) Local Source Impact (LSI; 26 days, 53%) and (2) African Dust Impact (ADI; 23 days, 47%). Our analysis suggested that the contribution of local sources to ADI EEs was relatively small. LSI EEs were observed only in the cold season, whereas ADI EEs occurred throughout the year, with a higher frequency during the cold season. The EEs with the highest intensity were recorded during African dust intrusions. ADI episodes were found to contribute more than local sources in Greece, with ADI and LSI fraction contribution ranging from 1.1 to 3.10. The EE contribution during ADI fluctuated from 41 to 83 μg/m3

  9. On dust in tokamak edge plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Krasheninnikov, S.I. [Jacobs School of Engineering, Department of Mechanical and Aerospace Engineering, University of California at San Diego, Engineering Building II, room 474, 9500 Gilman Drive, La Jolla, CA 92093-0411 (United States)]. E-mail: skrash@mae.ucsd.edu; Soboleva, T.K. [UNAM, Mexico, DF (Mexico); Kurchatov Institute, Moscow (Russian Federation); Tomita, Y. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan); Smirnov, R.D. [Graduate University for Advanced Studies, Toki, Gifu 509-5292 (Japan); Janev, R.K. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

    2005-03-01

    We study the dust particle dynamics in tokamak edge plasmas, with special emphasis on dust particle transport in the sheath and plasma recycling regions. The characteristics of this transport have been examined for both smooth and corrugated wall surfaces. The implications of dust particle transport in the divertor region on the core plasma contamination with impurities have also been examined.

  10. 29 CFR 1910.1043 - Cotton dust.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 6 2010-07-01 2010-07-01 false Cotton dust. 1910.1043 Section 1910.1043 Labor Regulations...) OCCUPATIONAL SAFETY AND HEALTH STANDARDS (CONTINUED) Toxic and Hazardous Substances § 1910.1043 Cotton dust. (a... cotton dust in all workplaces where employees engage in yarn manufacturing, engage in slashing and...

  11. Radio frequency discharge with dust particles

    NARCIS (Netherlands)

    Chutov, Y. I.; W. J. Goedheer,; Kravchenko, O. Y.; Zuz, V. M.; Yan, M.; Martins, R.; Ferreira, I.; Fortunato, E.; Kroesen, G.

    2000-01-01

    A 1D PIC/MCC method has been developed for computer simulations of low-pressure RF discharges with dust particles using the method for dust-free discharges. A RF discharge in argon with dust particles distributed uniformly in the interelectrode gap is simulated at parameters providing a possibility

  12. Thirteen years of Aeolian dust dynamics in a desert region (Negev desert, Israel): analysis of horizontal and vertical dust flux, vertical dust distribution and dust grain size

    NARCIS (Netherlands)

    Offer, Z.Y.; Goossens, D.

    2004-01-01

    At Sede Boqer (northern Negev desert, Israel), aeolian dust dynamics have been measured during the period 1988–2000. This study focuses on temporal records of the vertical and horizontal dust flux, the vertical distribution of the dust particles in the atmosphere, and the grain size of the

  13. Information flows in sub-Saharan Africa

    Directory of Open Access Journals (Sweden)

    Chris Paterson

    2013-04-01

    Full Text Available The state of research into media and information flows in sub-Saharan Africa describes a situation marked by rapid growth of a wide range of media and distinctive geo-linguistic mediaspheres. This article focuses on two revolutions in information flow in the region: first, an expansion since the 1990s of traditional media, facilitated by satellite broadcasting and related technologies; secondly, since about 2000, the ongoing embrace of mobile telephony. It describes these developments in Lusophone, Francophone and Anglophone mediaspheres. Building on the author’s own previous research, and that of others, the article highlights the shift from asymmetrical, elite dominated communications concerning the major public affairs of the day toward increasingly symmetrical and participatory electronic communications. L’état de la recherche portant sur les flux d’information en Afrique sub-saharienne implique un contexte marqué par la croissance rapide d’un vaste panel de médias et d’espaces médiatiques géolinguistiques spécifiques. Le présent article porte sur deux révolutions liées au flux de l’information dans la région : en premier lieu l’expansion des médias traditionnels depuis les années 90, facilitée par la diffusion satellitaire et les technologies qu’elle implique ; en second lieu, l’intérêt actuel pour la téléphonie mobile qui se développe depuis les années 2000. L’article analyse ces évolutions au sein des espaces médiatiques lusophones, francophones et anglophones. Dans la continuité de notre précédente recherche, et celle développée par d’autres à ce sujet, cet article souligne le déplacement de communications asymétriques et dominées par l’élite, sur les affaires publiques majeures, vers des communications électroniques de plus en plus symétriques et participatives. O estado da pesquisa sobre o fluxo da informação na África subsaariana remete a um contexto marcado pelo r

  14. On the visibility of airborne volcanic ash and mineral dust

    Science.gov (United States)

    Weinzierl, B.; Sauer, D. N.; Minikin, A.; Reitebuch, O.; Dahlkötter, F.; Mayer, B. C.; Emde, C.; Tegen, I.; Gasteiger, J.; Petzold, A.; Veira, A.; Kueppers, U.; Schumann, U.

    2012-12-01

    After the eruption of the Eyjafjalla volcano (Iceland) in April 2010 which caused the most extensive restrictions of the airspace over Europe since the end of World War II, the aviation safety concept of avoiding "visible ash", i.e. volcanic ash that can be seen by the human eye, was recommended. However so far, no clear definition of "visible ash" and no relation between the visibility of an aerosol layer and related aerosol mass concentrations are available. The goal of our study is to assess whether it is possible from the pilot's perspective in flight to detect the presence of volcanic ash and to distinguish between volcanic ash and other aerosol layers just by sight. In our presentation, we focus the comparison with other aerosols on aerosol types impacting aviation: Besides volcanic ash, dust storms are known to be avoided by aircraft. We use in-situ and lidar data as well photographs taken onboard the DLR research aircraft Falcon during the Saharan Mineral Dust Experiments (SAMUM) in 2006 and 2008 and during the Eyjafjalla volcanic eruption in April/May 2010. We complement this analysis with numerical modelling, using idealized radiative transfer simulations with the 3D Monte Carlo radiative transfer code MYSTIC for a variety of selected viewing geometries. Both aerosol types, Saharan mineral dust and volcanic ash, show an enhanced coarse mode (> 1 μm) aerosol concentration, but volcanic ash aerosol additionally contains a significant number of Aitken mode particles (Volcanic ash is slightly more absorbing than mineral dust, and the spectral behaviour of the refractive index is slightly different. According to our simulations, these differences are not detectable just by human eye. Furthermore, our data show, that it is difficult to define a lower threshold for the visibility of an aerosol layer because the visual detectability depends on many parameters, including the thickness of the aerosol layer, the brightness and color contrast between the airborne

  15. Major episodes in the geologic history of western Promethei Terra, Mars

    Science.gov (United States)

    Ivanov, M. A.; Korteniemi, J.; Kostama, V.-P.; Raitala, J.; Törmänen, T.; Neukum, G.

    2010-03-01

    Geologic evolution of the western portion of Promethei Terra (40-50°S, 90-105°E) consists of two major episodes. The first was the formation of a late Noachian-early Hesperian volcanic province. During this episode a kilometer-thick suite (≈0.3 × 106 km3) of lavas accumulated to the south of Reull and Harmakhis Valles within a regional depression that probably was formed earlier in a massive erosion. A topographic barrier of the cratered terrains separates the volcanic western Promethei plateau from Hesperia Planum. Thus, the lavas could not originate from Hesperia Planum. The topographic position of western Promethei Terra excludes a possible lava feeding from Hadriaca Patera. Dikes from Tyrrhena Patera potentially could be the lava source. The massive erosion before formation of the lava plateau in western Promethei Terra is poorly consistent, however, with the hypothesis that the distal dikes served as the source and favors emplacement of sills or a local source for the lavas. The second episode after the lava plateau emplacement was surface modification by glacial, fluvial, and aeolian processes. The time of the episode is poorly known, and it could continue from the late Hesperian and through the entire Amazonian epoch. Mesas, channels, and esker-like ridges suggest that at the earlier stages of this episode (late Hesperian-early Amazonian) a glacier or ice dust deposits covered the western Promethei Terra area studied. The 50-60 × 103 km3 formation could contain 15-18 to 40-50 × 103 km3 of ice. This is comparable with the ice involved into of lobate apron formation (5-13 × 103 km3) at the later Amazonian stages of western Promethei Terra. Because of the uncertainties in the ice volume estimates, the total amount of water in the earlier glacier and later aprons was approximately the same.

  16. Development and poverty in sub-Saharan Africa

    DEFF Research Database (Denmark)

    Addison, Tony; Pikkarainen, Ville; Rönkkö, Risto

    2017-01-01

    This paper puts sub-Saharan Africa’s economic development into perspective. While much did not go as hoped for at independence, much of the region has been on a more promising development trajectory since the mid-1990s, as we illustrate using growth, poverty, and human development indicators. We...

  17. Democratic Governance in Sub-Saharan Africa | Eberlei | Ghana ...

    African Journals Online (AJOL)

    Twenty years into sub-Saharan Africa's democratic renewal, an understanding of democratic governance has become established among political actors in the region. Democratic governance is characterised by: legitimation of governmental power through elections, legitimation of governmental politics through ...

  18. Boosting food security in sub-Saharan Africa through cassava ...

    African Journals Online (AJOL)

    It is further argues that this can only be achievable if certain factors that can help to strengthen the expansion of cassava production as a food security crop in Nigeria in particular and Sub-Saharan Africa in general are put into adequate consideration. Some of these are proper implementation of cassava initiative ...

  19. Men's Attitudes Towards Contraception in Sub-Saharan Africa

    African Journals Online (AJOL)

    AJRH Managing Editor

    Methods. Data for this paper are from the Demographic and. Health Surveys conducted in Sub-Saharan Africa. DHS has conducted surveys of men, independent of marital status, in the region since 1991. Inclusions of questions regarding attitudes towards and communication about family planning vary across surveys.

  20. science granting councils initiative in sub-saharan africa ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Dorine Odongo

    Briefly describe your organization, its vision and mission, its interest in STI issues, and its interest in forging long-term relationships with Science Granting Councils in Sub-Saharan Africa (SSA).1 Which regions (Eastern, Southern, Central or West Africa) and countries has your organization worked in? 1 The Initiative is keen ...

  1. Abortion and Contraceptive Use in Sub-Saharan Africa: How ...

    African Journals Online (AJOL)

    Erah

    Based on available evidence, this review article posits that contemporary use of abortion in sub-Saharan Africa often substitutes for and sometimes surpasses modern contraceptive practice. Some studies and some data sets indicate that this occurs not only among adolescents but also within older age groups. In several ...

  2. Capabilities, innovation and entrepreneurship in sub-Saharan Africa

    NARCIS (Netherlands)

    Kroesen, J.O.; Romijn, H

    2015-01-01

    This paper takes a capability approach to analyze the role of entrepreneurship in the socio-economic development of present-day Sub Saharan Africa. The paper zooms in on the nature of the capabilities that are built through the development of entrepreneurship; the key challenges to the development

  3. Workable Social Health Insurance Systems in Sub-Saharan Africa ...

    African Journals Online (AJOL)

    One of the major barriers to access to healthcare in most sub-Saharan African countries is financial constraints. The need therefore arises for African states to put in place workable social health insurance schemes, as is the practice in most developed countries. This article assesses the peculiar characteristics of ...

  4. Neonatal hypothermia in sub-Saharan Africa: A review | Onalo ...

    African Journals Online (AJOL)

    Pertinent books and monographs were accessed. Data in formats inaccessible to the reviewer were excluded. Result and Conclusion: Neonatal hypothermia is a major condition of public health importance in countries of sub- Saharan Africa. Awareness of the burden of the disease is still low in some communities.

  5. Constraints to Agricultural Mechanization in Sub-Saharan Africa

    African Journals Online (AJOL)

    Adeyinka Odunsi

    Email : 1fekkumi@gmail.com ... factors responsible for the present abysmally low level of agricultural mechanization in the Sub-‐Saharan Africa .... Apart from Egypt,. Tunisia, Morocco and South Africa, the level of mechanization is very low in all other parts of the continent which puts the future food security in much danger ...

  6. Soyabean response to rhizobium inoculation across sub-Saharan Africa

    NARCIS (Netherlands)

    Heerwaarden, van Joost; Baijukya, Frederick; Kyei-Boahen, Stephen; Adjei-nsiah, Samuel; Ebanyat, Peter; Kamai, Nkeki; Wolde-Meskel, Endalkachew; Kanampiu, Fred; Vanlauwe, Bernard; Giller, Ken

    2017-01-01

    Improving bacterial nitrogen fixation in grain legumes is central to sustainable intensification of agriculture in sub-Saharan Africa. In the case of soyabean, two main approaches have been pursued: first, promiscuous varieties were developed to form effective symbiosis with locally abundant

  7. Is urbanization in Sub-Saharan Africa different ?

    OpenAIRE

    Henderson, J. Vernon; Roberts, Mark; Storeygard, Adam

    2013-01-01

    In the past dozen years, a literature has developed arguing that urbanization has unfolded differently in post-independence Sub-Saharan Africa than in the rest of the developing world, with implications for African economic growth overall. While African countries are more urbanized than other countries at comparable levels of income, it is well-recognized that total and sector gross domest...

  8. Climate change impacts in Sub-Saharan Africa

    NARCIS (Netherlands)

    Serdeczny, Olivia; Adams, Sophie; Baarsch, Florent; Coumou, Dim; Robinson, Alexander; Hare, William; Schaeffer, Michiel; Perrette, Mahé; Reinhardt, Julia

    2017-01-01

    The repercussions of climate change will be felt in various ways throughout both natural and human systems in Sub-Saharan Africa. Climate change projections for this region point to a warming trend, particularly in the inland subtropics; frequent occurrence of extreme heat events; increasing

  9. Kinship Structures and Social Justice in Sub-Saharan Africa ...

    African Journals Online (AJOL)

    A major obstacle to the development of sustainable democratic systems of government in contemporary sub-Saharan African states is the difficulty in articulating an adequate conception of social justice to serve as a guiding principle in these polities. This difficulty is a consequence of the ethnically heterogeneous character ...

  10. Therapeutic misconception and clinical trials in sub-saharan Africa ...

    African Journals Online (AJOL)

    Objectives: To identify possible existence of therapeutic misconception and its effects on clinical trials in sub-Saharan Africa. Data source: Original research findings and reviews published in the English literature and author's professional experience with clinical trials in some East, Central and West African countries.

  11. Sub-Saharan Africa | IDRC - International Development Research ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Over the years, sub-Saharan Africa has experienced a prolonged development crisis, fuelled by complex ethnic, social, and political realities. The region suffers from weak governments, corruption, and mismanagement of resources. Its overburdened water systems are under increasing stress from fast-growing urban areas, ...

  12. Managing Endometriosis in sub-Saharan Africa: Emerging Concepts ...

    African Journals Online (AJOL)

    AJRH Managing Editor

    Endometriosis is a gynaecological disorder that is characterized by the growth of endometrial tissue outside the uterine cavity1.