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Sample records for aeolian dust transport

  1. Aeolian dust as a transport hazard

    NASA Astrophysics Data System (ADS)

    Baddock, M. C.; Strong, C. L.; Murray, P. S.; McTainsh, G. H.

    2013-06-01

    The effects of blowing dust on transport operations are often mentioned as one of the significant impacts of aeolian processes on human welfare. However, few studies have been presented to demonstrate this impact. This research examined official air traffic incident reports in Australia for inclusively 1969-2010 to characterise the hazard of blowing dust to aviation in the country, the first such study of its kind. For the 42 year record, 61 incidents were identified (mean 1.4 per annum), with the large majority occurring in the first half of the 1970s. Only 20% of incidents occurred from 1984 onwards. Australian dust activity has not decreased over time, and the reduction in incidents is partly explained by improvements in aviation technology. The centralisation of Air Traffic Control operations to major coastal cities may however have reduced pilot reporting of dust-induced aviation incidents. By type of dust activity, dust storms were associated with nearly half of the reported incidents and dust hazes produced around a quarter. Only 5% of incidents resulted in any physical damage to aircraft and only one case involving personal injury was reported. The majority of the adverse effects on aviation due to dust (nearly 60% of reported incidents) were related to difficulties for navigation and completion of scheduled journey. Since aircraft damage and bodily harm were rare, the impact of dust in Australia is mostly that of inconvenience and associated raised economic costs. From 1990, the temporal pattern of incidents does not show any significant increase despite several intensely dusty years associated with recent droughts. This suggests that Australian aviation safety may be relatively resistant to the adverse effects of atmospheric dust as a hazard.

  2. Aeolian transport of biota with dust: A wind tunnel experiment

    NASA Astrophysics Data System (ADS)

    Rivas, J. A., Jr.; Gill, T. E.; Van Pelt, R. S.; Walsh, E.

    2015-12-01

    Ephemeral wetlands are ideal sources for dust emission, as well as repositories for dormant stages of aquatic invertebrates. An important component of invertebrate dispersal and colonization to new areas is the ability to be entrained into the atmosphere. Aquatic invertebrate eggs fall within the size of dust and sand grains (30-600μm), are less dense and aerodynamically shaped. We have shown previously that aquatic invertebrates can be dispersed long distances in dust storms but the extent of transport of taxa based on diapausing egg size/morphology has not been investigated. Here, we control the wind erosion process in a wind tunnel to test entrainment of diapausing stages of brine shrimp, clam shrimp, tadpole shrimp, fairy shrimp, Daphnia, and the rotifers Brachionus plicatilis and B. calyciflorus into the air by saltation. Diapausing eggs were mixed with sterilized wind-erodible soil. The soil/egg mixture was moistened with distilled water and air dried to form a crust. Dust was generated in a wind tunnel by releasing sand grains that act as saltator material similar to wind-entrained natural sands. Maximum wind velocity was 10m/s and entrained particles were sampled through an isokinetic horizontal intake opening. Aeolian sediment was collected from three points in the system; transfer section for coarse sediment, the pan subtending a settling chamber for finer saltation-sized sediment, and two paper filters for suspension-sized sediment. Samples were then passed through 250 and 350 μm sieves to remove abrader sand and rehydrated with various sterile media depending on the type of organism. We retrieved viable brine, fairy, and tadpole shrimp, ostracods, Daphnia, and diapausing eggs of the rotifers after hydration. This experiment demonstrates that resting stages of many invertebrates can be wind-eroded due to size and egg morphology and remain viable under controlled conditions mimicking dust emission.

  3. Aeolian Transport of Invertebrates

    NASA Astrophysics Data System (ADS)

    Gill, T. E.; Walsh, E. J.; Wallace, R. L.; Rojo, L.; Rivas, J. A.

    2012-12-01

    Playas and other ephemeral desert wetlands are preferential terrestrial landforms for dust emission. These sites also are habitat for a diverse assemblage of minute invertebrates. When wetlands desiccate, these invertebrates survive as resting stages (propagules). Thus, playas serve as isolated, ephemeral, biogeographical islands for aquatic invertebrates, but it is unclear how propagules disperse across distances as far as hundreds of kilometers to colonize hydrologically disconnected basins. Aeolian transport (anemochory) may provide the mechanism, especially since many invertebrate propagules are long-lived, aerodynamically shaped, possess low-density, and their size (30-600 μm) falls within the same texture as aeolian dust and sand grains. We are collecting and culturing wind-transported sediment to document its ability to serve in the dispersal of aridland invertebrate propagules. Deposited aeolian sediment was collected from marble-type traps placed on the roof of the Biological Sciences Building at the University of Texas, El Paso, during 19 individual regional-scale Chihuahuan Desert blowing dust/sand events between April 2010 and May 2012. Known source areas for these dust events include playas and ephemeral streams ~40- 150 km upwind. The mean dry grain size of the deposited sediment for each event ranged from 66 to 141 μm. Clean-water rinses of material from each event or standard rehydrations for culturing invertebrates were monitored microscopically for the appearance of organisms. Invertebrates hatched from the sediment of 13 events. Ciliates were detected in each of those samples: gastrotrichs appeared in three samples, nematodes and bdelloid rotifers in two samples, and clam shrimp in one. We have also rehydrated aeolian sediments, collected in standard dust traps, from many dust-emitting playas in Southwest North America and hatched viable organisms including all those previously mentioned as well as branchiopods, fairy shrimp, copepods

  4. Mechanics of aeolian processes: Soil erosion and dust production

    NASA Technical Reports Server (NTRS)

    Mehrabadi, M. M.

    1989-01-01

    Aeolian (wind) processes occur as a result of atmosphere/land-surface system interactions. A thorough understanding of these processes and their physical/mechanical characterization on a global scale is essential to monitoring global change and, hence, is imperative to the fundamental goal of the Earth observing system (Eos) program. Soil erosion and dust production by wind are of consequence mainly in arid and semi arid regions which cover 36 percent of the Earth's land surface. Some recent models of dust production due to wind erosion of agricultural soils and the mechanics of wind erosion in deserts are reviewed and the difficulties of modeling the aeolian transport are discussed.

  5. Detecting Patterns of Aeolian Transport Direction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The magnitude and direction of aeolian transport are of direct interest to those engaged in the study of aeolian processes. Although the magnitude of sediment transport has been studied extensively, the study of aeolian transport direction has garnered less attention. This paper describes the deve...

  6. Geochemical provenance of soils in Kerman urban areas, Iran: Implications for the influx of aeolian dust

    NASA Astrophysics Data System (ADS)

    Dehbandi, Reza; Aftabi, Alijan

    2016-06-01

    The investigation of the interaction of aeolian dust with residual soils has not been fully explored in the Kerman urban areas, Iran. To assess the geochemical influence of aeolian dust on the residual soils of the Kerman urban areas of Iran, 27 samples were studied petrogeochemically. The arid-semi-arid climate of the area together with the southwest-northeast prevailing wind, have deposited aeolian sands over the residual soils. Residual soils reflect similar mineral compositions to that of the underlying bedrock and include mostly calcite and quartz. However, the minor occurrences of pyroxene, amphibole, olivine, plagioclase and volcanic clasts in urban soils and aeolian dust are attributed to volcanogenic inputs transported by aeolian dust. Urban soils and aeolian dust show different geochemical signatures from the local carbonate rocks. All samples contain trace element concentrations that are higher than the carbonate bedrock. Discrimination diagrams indicate that immobile trace elements have geochemical affinity to the detrital ferromagnesian dust inputs and are different from the local carbonate bedrock. Based on the elemental bivariate and ternary diagrams, the soils and aeolian dust are derived from the interaction of carbonate and volcanic rocks. This highlights that the urban soils in the Kerman urban areas have been formed by interactions of the aeolian dust with the primitive residual soils.

  7. Optical properties of Aeolian dusts common to West Texas

    NASA Astrophysics Data System (ADS)

    Ma, Lulu; Zobeck, Ted M.; Hsieh, Daniel H.; Holder, Dean; Morgan, Cristine L. S.; Thompson, Jonathan E.

    2011-11-01

    Both recent models and historical events such as the Dust Bowl and volcanic eruptions have illustrated aerosols can play a significant role in climate change through direct and indirect optical effects. Soil dust aerosols generated by Aeolian processes represent a significant fraction of the total mass burden of atmospheric particles. Central to a better understanding of the climate effects of dust aerosols is knowledge of their optical properties. This research study utilized a dust generator and several instruments to determine certain optical properties of Aeolian dust mimics created by the Amarillo and Pullman soil types native to the panhandle of Texas, USA. Values for the mass-extinction coefficient ranged between 1.74 and 2.97 m 2 g -1 at 522 nm depending on how mass concentration was determined. Single-scatter albedo (SSA) for both soil types ranged from 0.947 to 0.980 at visible wavelengths with SSA increasing at longer wavelengths. Angstrom absorption exponents were measured as 1.73 for Pullman and 2.17 for Amarillo soil. Observed Angstrom extinction exponents were 0.110 and 0.168 for the Pullman and Amarillo soil types. The optical properties reported may be of use for optical based estimates of soil erosion and aid in understanding how regional soil dusts may alter radiative transport presently and during historical events such as the Dust Bowl era.

  8. Changes in soil aggregation and dust emission potential in response to aeolian processes

    NASA Astrophysics Data System (ADS)

    swet, Nitzan; Katra, Itzhak

    2016-04-01

    Aeolian (wind) dust emission has high environmental and socioeconomic significances due to loss of natural soil and air pollution. Dust emission involves complex interactions between the airflow and the soil surface. The soil aggregates were dust particles are held determine the topsoil erodibility in aeolian erosion. Although the key role of soil aggregation in dust emission mechanisms, information on changes in soil aggregate size distribution (ASD) due to aeolian erosion is lucking. This study is focused on quantitative ASD analyses before and after aeolian processes (saltation). Aeolian experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that saltation rates and PM emissions depend on the initial ASD and shear velocity. In all initial soil conditions, the content of aggregates at saltator-sized 63-250 μm was increased by 10-34 % following erosion of macro-aggregates > 500 μm. It revealed that the aggregate-saltator production increases with the shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight the dynamics in soil aggregation in response to aeolian transport and therefore its significance for determining the mechanisms of dust emission from soil aggregates.

  9. A Threshold Continuum for Aeolian Sand Transport

    NASA Astrophysics Data System (ADS)

    Swann, C.; Ewing, R. C.; Sherman, D. J.

    2015-12-01

    The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.

  10. Evaluation of a new model of aeolian transport in the presence of vegetation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation [Okin, 2008]. This approach differs from previou...

  11. Aeolian Sand Transport with Collisional Suspension

    NASA Technical Reports Server (NTRS)

    Jenkins, James T.; Pasini, Jose Miguel; Valance, Alexandre

    2004-01-01

    Aeolian transport is an important mechanism for the transport of sand on Earth and on Mars. Dust and sand storms are common occurrences on Mars and windblown sand is responsible for many of the observed surface features, such as dune fields. A better understanding of Aeolian transport could also lead to improvements in pneumatic conveying of materials to be mined for life support on the surface of the Moon and Mars. The usual view of aeolian sand transport is that for mild winds, saltation is the dominant mechanism, with particles in the bed being dislodged by the impact of other saltating particles, but without in-flight collisions. As the wind becomes stronger, turbulent suspension keeps the particles in the air, allowing much longer trajectories, with the corresponding increase in transport rate. We show here that an important regime exists between these two extremes: for strong winds, but before turbulent suspension becomes dominant, there is a regime in which in-flight collisions dominate over turbulence as a suspension mechanism, yielding transport rates much higher than those for saltation. The theory presented is based on granular kinetic theory, and includes both turbulent suspension and particle-particle collisions. The wind strengths for which the calculated transport rates are relevant are beyond the published strengths of current wind tunnel experiments, so these theoretical results are an invitation to do experiments in the strong-wind regime. In order to make a connection between the regime of saltation and the regime of collisional suspension, it is necessary to better understand the interaction between the bed and the particles that collide with it. This interaction depends on the agitation of the particles of the bed. In mild winds, collisions with the bed are relatively infrequent and the local disturbance associated with a collision can relax before the next nearby collision. However, as the wind speed increases, collision become more frequent

  12. Optical Properties of Aeolian Dusts Common to West Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  13. Lidar measurements of Aeolian dust: Mars and Earth

    NASA Astrophysics Data System (ADS)

    Dickinson, C. S.; Davy, R.; Komguem, L.; Junkermann, W.; Whiteway, J. A.

    2009-12-01

    The Phoenix Lidar system was operated in 2008, beginning in Martian northern spring (L_s = 78) through mid summer (L_s = 147). During this period, nighttime observations of dust indicate both persistent background dust up to heights of approximately 15 km, and enhanced dust loading in the Boundary Layer up to heights of approximately 4 km. The magnitude of the optical extinction was observed to decrease within the Boundary Layer with time following summer solstice. This situation is similar to that observed in the Australian desert: a persistent dust layer up to heights of 6 km, with a daytime Convective Boundary Layer increasing up to heights of 4 km during local dust storm activity, and then decreasing during night. A comparative study was undertaken, with the results being augmented by both in situ measurements of the Australian desert dust, as made by over-flying aircraft, and modeled results of Aeolian dust in both environments.

  14. Aeolian particle flux profiles and transport unsteadiness

    NASA Astrophysics Data System (ADS)

    Bauer, Bernard O.; Davidson-Arnott, Robin G. D.

    2014-07-01

    Vertical profiles of aeolian sediment flux are commonly modeled as an exponential decay of particle (mass) transport with height above the surface. Data from field and wind-tunnel studies provide empirical support for this parameterization, although a large degree of variation in the precise shape of the vertical flux profile has been reported. This paper explores the potential influence of wind unsteadiness and time-varying intensity of transport on the geometry (slope, curvature) of aeolian particle flux profiles. Field evidence from a complex foredune environment demonstrates that (i) the time series of wind and sediment particle flux are often extremely variable with periods of intense transport (referred to herein as sediment "flurries") separated by periods of weak or no transport; (ii) sediment flurries contribute the majority of transport in a minority of the time; (iii) the structure of a flurry includes a "ramp-up" phase lasting a few seconds, a "core" phase lasting a few seconds to many tens of seconds, and a "ramp-down" phase lasting a few seconds during which the system relaxes to a background, low-intensity transport state; and (iv) conditional averaging of flux profiles for flurry and nonflurry periods reveals differences between the geometry of the mean profiles and hence the transport states that produce them. These results caution against the indiscriminate reliance on regression statistics derived from time-averaged sediment flux profiles, especially those with significant flurry and nonflurry periods, when calibrating or assessing the validity of steady state models of aeolian saltation.

  15. The nature and formation of aeolian mineral dust material

    NASA Astrophysics Data System (ADS)

    Smalley, Ian; O'hara-Dhand, Ken; McLaren, Sue

    2013-04-01

    Aeolian dust affects climate and records past climates. It has become a much studied material but there has been a certain lack of emphasis on the actual nature of the dust, and an even greater neglect of actual production mechanisms for dust particles. Huge amounts of dust may be raised from the Bodele depression and other parts of North Africa, and much of it may be carried across the North Atlantic to aid in soil formation in Brazil. But what does it consist of? We know that much of the Bodele dust is diatoms from old Lake Chad, but what of the lithological inorganic mineral content? A very crude division of aeolian dust into large dust(say around 20-50um) and small dust (2-5um)has been proposed. Much of the study of loess has been confused by the failure to make this distinction, and similar problems may arise in the study of the finer fractions of aeolian dust. Much aeolian material is clay-mineral based- formed from clay mineral aggregates(CMA), from lake bottom sediments. This can form large dust particles, as in parna in Australia, but also contributes largely to small long travel aerosolic dust. Another major contributor is the quartz fragment. The large dust for classic loess deposits is mostly quartz silt- and there is considerable discussion about the controls that affect quartz silt. There are some interesting modalities in the world of quartz particle sedimentology which need to be examined. Quartz sand (say 200-500um) is the key initiating material and the formation processes for quartz sand have a down-the-line effect on the formation of smaller particles. The central observation is the action of two processes- a eutectic-like reaction in the proto-rock granite which defines the essential nature of sand particles, and the high-low displacive crystallographic transformation which introduces tensile stresses into the quartz particle systems. The limited range of eutectic particle size means a limited range of tensile stresses. A neat combination of

  16. Granulometric profiling of aeolian dust deposits by automated image analysis

    NASA Astrophysics Data System (ADS)

    Varga, György; Újvári, Gábor; Kovács, János; Jakab, Gergely; Kiss, Klaudia; Szalai, Zoltán

    2016-04-01

    Determination of granulometric parameters is of growing interest in the Earth sciences. Particle size data of sedimentary deposits provide insights into the physicochemical environment of transport, accumulation and post-depositional alterations of sedimentary particles, and are important proxies applied in paleoclimatic reconstructions. It is especially true for aeolian dust deposits with a fairly narrow grain size range as a consequence of the extremely selective nature of wind sediment transport. Therefore, various aspects of aeolian sedimentation (wind strength, distance to source(s), possible secondary source regions and modes of sedimentation and transport) can be reconstructed only from precise grain size data. As terrestrial wind-blown deposits are among the most important archives of past environmental changes, proper explanation of the proxy data is a mandatory issue. Automated imaging provides a unique technique to gather direct information on granulometric characteristics of sedimentary particles. Granulometric data obtained from automatic image analysis of Malvern Morphologi G3-ID is a rarely applied new technique for particle size and shape analyses in sedimentary geology. Size and shape data of several hundred thousand (or even million) individual particles were automatically recorded in this study from 15 loess and paleosoil samples from the captured high-resolution images. Several size (e.g. circle-equivalent diameter, major axis, length, width, area) and shape parameters (e.g. elongation, circularity, convexity) were calculated by the instrument software. At the same time, the mean light intensity after transmission through each particle is automatically collected by the system as a proxy of optical properties of the material. Intensity values are dependent on chemical composition and/or thickness of the particles. The results of the automated imaging were compared to particle size data determined by three different laser diffraction instruments

  17. Identifying sources of aeolian mineral dust: Present and past

    USGS Publications Warehouse

    Muhs, Daniel R; Prospero, Joseph M; Baddock, Matthew C; Gill, Thomas E

    2014-01-01

    Aeolian mineral dust is an important component of the Earth’s environmental systems, playing roles in the planetary radiation balance, as a source of fertilizer for biota in both terrestrial and marine realms and as an archive for understanding atmospheric circulation and paleoclimate in the geologic past. Crucial to understanding all of these roles of dust is the identification of dust sources. Here we review the methods used to identify dust sources active at present and in the past. Contemporary dust sources, produced by both glaciogenic and non-glaciogenic processes, can be readily identified by the use of Earth-orbiting satellites. These data show that present dust sources are concentrated in a global dust belt that encompasses large topographic basins in low-latitude arid and semiarid regions. Geomorphic studies indicate that specific point sources for dust in this zone include dry or ephemeral lakes, intermittent stream courses, dune fields, and some bedrock surfaces. Back-trajectory analyses are also used to identify dust sources, through modeling of wind fields and the movement of air parcels over periods of several days. Identification of dust sources from the past requires novel approaches that are part of the geologic toolbox of provenance studies. Identification of most dust sources of the past requires the use of physical, mineralogical, geochemical, and isotopic analyses of dust deposits. Physical properties include systematic spatial changes in dust deposit thickness and particle size away from a source. Mineralogy and geochemistry can pinpoint dust sources by clay mineral ratios and Sc-Th-La abundances, respectively. The most commonly used isotopic methods utilize isotopes of Nd, Sr, and Pb and have been applied extensively in dust archives of deep-sea cores, ice cores, and loess. All these methods have shown that dust sources have changed over time, with far more abundant dust supplies existing during glacial periods. Greater dust supplies in

  18. Aeolian removal of dust from photovoltaic surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Marabito, Mark

    1990-01-01

    It is well documented that Mars is totally engulfed in huge dust storms nearly each Martian year. Dust elevated in these global dust storms, or in any of the numerous local dust storms could settle on photovoltaic surfaces and seriously hamper photovoltaic power system performance. Using a recently developed technique to uniformly dust simulated photovoltaic surfaces, samples were subjected to Martian-like winds in an attempt to determine whether natural aeolian processes on Mars would sweep off the settled dust. The effects of wind velocity, angle of attack, height off the Martian surface, and surface coating material were investigated. Principles which can help to guide the design of photovoltaic arrays bound for the Martian surface were uncovered. Most importantly, arrays mounted with an angle of attack approaching 45 deg show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required significantly higher wind velocities to clear off the dust. From the perspective of dust-clearing it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by sand if they are set up less than about a meter from the ground. Providing that the surface chemistry of Martian dusts is comparable to our test dust, the materials used for protective coating may be optimized for other considerations such as transparency, and chemical or abrasion resistance. The static threshold velocity is low enough that there are regions on Mars which experience winds strong enough to clear off a photovoltaic array if it is properly oriented. Turbulence fences proved to be an ineffective strategy to keep dust cleared from the photovoltaic surfaces.

  19. Flood Induced Increases in Aeolian Transport Along the Missouri River

    NASA Astrophysics Data System (ADS)

    Benthem, A. J.; Strong, L.; Schenk, E.; Skalak, K.; Hupp, C. R.; Galloway, J.

    2014-12-01

    In 2011, heavy winter snow melt combined with extensive spring rains caused the Missouri River to experience the most extensive flooding since the river was dammed in the 1950s. Large sections of the river banks, islands, and floodplains experienced weeks of prolonged inundation, resulting in extensive sand deposition as up to1 km inland from the established channel. Though locally variable, deposits of up to 3m of loose sand were deposited on the floodplain and extensive areas of shrub, grasslands, and agricultural fields were completely buried or had vegetation washed away in the inundation zone. The flooding also created a number of new unvegetated islands which provide important habitat for endangered species including the Piping Plover (Charadrius melodus). These newly created sand surfaces are unconsolidated and have very little vegetation to prevent aeolian transport. Strong sustained regional winds of up to 20m/s (45mph) cause substantial sediment fluxes which modify landscape topography, shift river morphology, and increase regional dust levels. Our study monitors and quantifies the increase in aeolian transport that occurred following flooding along the Garrison Reach, a 110 km section of free flowing Missouri River in North Dakota. In 2012 and 2013 we measured sand transport and accumulation rates using Leatherman style sand traps and erosion pins to at 9 sites of varying vegetation densities. We apply these flux rates to a high resolution remote sensing vegetation map to estimate the total flux of sand for this segment of the river. We also quantify total available new sand for transport using repeat Light Detection and Ranging (LiDAR) coverage from before and after the flood and examine the relationship between sand deposition and the rate of reestablishment of vegetation. All of these results are used to estimate the scale of flood induced aeolian processes and predict where they may continue to influence the landscape.

  20. Aeolian Removal of Dust Types from Photovoltaic Surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.

    1990-01-01

    Dust elevated in local or global dust storms on the Martian surface could settle on photovoltaic (PV) surfaces and seriously hamper their performance. Using a recently developed technique to apply a uniform dust layer, PV surface materials were subjected to simulated Martian winds in an attempt to determine whether natural aeolian processes on Mars would sweep off the settled dust. Three different types of dust were used. The effects of wind velocity, angle of attack, height above the Martian surface, and surface coating material were investigated. It was found that arrays mounted on an angle of attack approaching 45 deg show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required much higher wind velocities to clear off the dust. From this test it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by soil if they are set up less than about a meter from the ground. Particle size effect appear to dominate over surface chemistry in these experiments, but additional tests are required to confirm this.

  1. Aeolian Removal of Dust Types from Photovoltaic Surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Marabito, Mark

    1990-01-01

    Dust elevated in local or global dust storms on the Martian surface could settle on photovoltaic (PV) surfaces and seriously hamper their performance. Using a recently developed technique to apply a uniform dust layer, PV surface materials were subjected to simulated Martian winds in an attempt to determine whether natural Aeolian processes on Mars would sweep off the settled dust. Three different types of dust were used; an optical polishing powder, basaltic "trap rock", and iron (III) oxide crystals. The effects of wind velocity, angle of attack, height above the Martian surface, and surface coating material were investigated. It was found that arrays mounted with an angle of attack approaching 45 degrees show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required significantly higher wind velocities to clear off the dust. From this test it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by soil if they are set up less than about a meter from the ground. Particle size effects appear to dominate over surface chemistry in these experiments, but additional tests are required to confirm this. Providing that the surface chemistry of Martian dusts is not drastically different from simulated dust and that gravity differences have only minor effects, the materials used for protective coatings for photovoltaic arrays may be optimized for other considerations such as transparency, and chemical or abrasion resistance. The static threshold velocity is low enough that there are regions on Mars which experience winds strong enough to clear off a photovoltaic array if it is properly oriented. Turbulence fences proved to be an ineffective strategy to keep dust cleared from the photovoltaic surfaces.

  2. Dust on Mars: An Aeolian Threat to Human Exploration?

    NASA Technical Reports Server (NTRS)

    Marshall, J.

    1999-01-01

    The NASA HEDS Program is duly concerned for human explorers regarding the potential hazard posed by the ubiquitous dust mantle on Mars. To evaluate properties of dust that could be hazardous to humans, the NMS 2001 Lander payload will include the Mars Environmental Compatibility Assessment (MECA) experiment. This includes optical and atomic-force microscopy to evaluate soil grains for shape and size, wet chemistry to evaluate toxic substances, electrometry to evaluate triboelectric charging, and test-material palets to evaluate electrostatic and magnetic adhesion, and the hardness/abrasiveness of soil grains; these experimental subcomponents are delivered samples by the camera-equipped robotic arm of the lander which will acquire material from depths of 0.5 to 1.0 m in the soil. Data returned by MECA will be of value to both the hEDS and planetary/astrobiology communities. Dust poses a threat to human exploration because the martian system does not hydrologically or chemically remove fine particles that are being continuously generated by thermal, aeolian, and colluvial weathering, and by volcanism and impact over billions of years. The dust is extremely fine-grained, in copious quantities, ubiquitous in distribution, continually mobile, and a source of poorly-grounded static charges -- a suite of characteristics posing a particulate and electrical threat to explorers and their equipment. Dust is mobilized on global and regional scales, but probably also unpredictably and violently at local scales by dust devils. The latter might be expected in great abundance owing to near surface atmospheric instability (dust devils were detected by Pathfinder during its brief lifetime). Preliminary laboratory experiments suggest that space-suit materials subjected to windblown dust may acquire a uniform, highly adhesive dust layer that is also highly cohesive laterally owing to electrostatic forces. This layer will obscure visibility through the helmet visor, penetrate joints

  3. Dust on Mars: An Aeolian Threat to Human Exploration?

    NASA Technical Reports Server (NTRS)

    Marshall, J.

    1999-01-01

    The NASA HEDS Program is duly concerned for human explorers regarding the potential hazard posed by the ubiquitous dust mantle on Mars. To evaluate properties of dust that could be hazardous to humans, the MPS 2001 Lander payload will include the Mars Environmental Compatibility Assessment (MECA) experiment. This includes optical and atomic-force microscopy to evaluate soil grains for shape and size, wet chemistry to evaluate toxic substances, electrometry to evaluate triboelectric charging, and test-material palets to evaluate electrostatic and magnetic adhesion, and the hardness/abrasiveness of soil grains; these experimental subcomponents are delivered samples by the camera-equipped robotic arm of the lander which will acquire material from depths of 0.5 to 1.0 m in the soil. Data returned by MECA will be of value to both the BEDS and planetary/astrobiology communities. Dust poses a threat to human exploration because the martian system does not hydrologically or chemically remove fine particles that are being continuously generated by thermal, aeolian, and colluvial weathering, and by volcanism and impact over billions of years. The dust is extremely fine-grained, in copious quantities, ubiquitous in distribution, continually mobile, and a source of poorly-grounded static charges -- a suite of characteristics posing a particulate and electrical threat to explorers and their equipment. Dust is mobilized on global and regional scales, but probably also unpredictably and violently at local scales by dust devils. The latter might be expected in great abundance owing to near surface atmospheric instability (dust devils were detected by Pathfinder during its brief lifetime). Preliminary laboratory experiments suggest that space-suit materials subjected to windblown dust may acquire a uniform, highly adhesive dust layer that is also highly cohesive laterally owing to electrostatic forces. This layer will obscure visibility through the helmet visor, penetrate joints

  4. Aeolian dust experiment on climate impact: An overview of Japan China joint project ADEC

    NASA Astrophysics Data System (ADS)

    Mikami, M.; Shi, G. Y.; Uno, I.; Yabuki, S.; Iwasaka, Y.; Yasui, M.; Aoki, T.; Tanaka, T. Y.; Kurosaki, Y.; Masuda, K.; Uchiyama, A.; Matsuki, A.; Sakai, T.; Takemi, T.; Nakawo, M.; Seino, N.; Ishizuka, M.; Satake, S.; Fujita, K.; Hara, Y.; Kai, K.; Kanayama, S.; Hayashi, M.; Du, M.; Kanai, Y.; Yamada, Y.; Zhang, X. Y.; Shen, Z.; Zhou, H.; Abe, O.; Nagai, T.; Tsutsumi, Y.; Chiba, M.; Suzuki, J.

    2006-07-01

    The Aeolian Dust Experiment on Climate Impact (ADEC) was initiated in April 2000 as a joint five-year Japan-China project. The goal was to understand the impact of aeolian dust on climate via radiative forcing (RF). Field experiments and numerical simulations were conducted from the source regions in northwestern China to the downwind region in Japan in order to understand wind erosion processes temporal and spatial distribution of dust during their long-range transportation chemical, physical, and optical properties of dust and the direct effect of radiative forcing due to dust. For this, three intensive observation periods (IOP) were conducted from April 2002 to April 2004. The in situ and network observation results are summarized as follows: (1) In situ observations of the wind erosion process revealed that the vertical profile of moving sand has a clear size dependency with height and saltation flux and that threshold wind velocity is dependent on soil moisture. Results also demonstrated that saltation flux is strongly dependent on the parent soil size distribution of the desert surface. (2) Both lidar observations and model simulations revealed a multiple dust layer in East Asia. A numerical simulation of a chemical transport model, CFORS, illustrated the elevated dust layer from the Taklimakan Desert and the lower dust layer from the Gobi Desert. The global-scale dust model, MASINGAR, also simulated the dust layer in the middle to upper free troposphere in East Asia, which originated from North Africa and the Middle East during a dust storm in March 2003. Raman lidar observations at Tsukuba, Japan, found the ice cloud associated with the dust layer at an altitude of 6 to 9 km. Analysis from lidar and the radio-sonde observation suggested that the Asian dust acted as ice nuclei at the ice-saturated region. These results suggest the importance of dust's climate impact via the indirect effect of radiative forcing due to the activation of dust into ice nuclei

  5. Asian Winter Monsoons in the Eocene: Evidence from the Aeolian Dust Series of the Xining Basin

    NASA Astrophysics Data System (ADS)

    Licht, A.; Adriens, R.; Pullen, A. T.; Kapp, P. A.; Abels, H.; van Cappelle, M.; Vandenberghe, J.; Dupont Nivet, G.

    2014-12-01

    The aeolian dust deposits of the Chinese Loess Plateau are attributed to spring and winter monsoonal storms sweeping clastic material from the deserts of the Asian interior into central China and are reported to begin 25-22 million years (Myr) ago. The beginning of aeolian dust sedimentation has been attributed to the onset of central Asia desertification and winter monsoonal circulation, and are commonly linked to development of high topographic relief associated with the Tibetan-Himalayan orogenic system. However, recent papers suggest that the core of the Tibetan Plateau may have reached significant elevation since the earliest phases of the India-Asia collision 55 Myr ago. Here, we extend the sedimentary record of the Chinese Loess Plateau at its western margin to include the late Eocene - late Oligocene deposits of the Xining Basin, which were deposited between 41 and 25 Myr ago based on detailed magnetostratigraphy. The particle size, shape, and surface microtexture of quartz grains in these deposits display textures indicative of prolonged aeolian transport; grain-size distributions show a bimodal distribution similar to Miocene through Quaternary deposits of the Chinese Loess Plateau. The clay mineralogy of the finer fraction and U/Pb zircon ages of the coarser fraction from Xining Loess sediments sampled along three sections spanning the whole studied interval are also similar to those observed in Quaternary and Neogene aeolian deposits of the Chinese Loess Plateau and thus suggest similar sources located in central China. However, slight differences in Eocene U/Pb zircon ages, such as the lack of Cenozoic ages or the scarcity of zircons older than 2000 Myr, suggest that the Tibetan Plateau may have contributed little to the aeolian dust deposition, in favor of sources located further north and west (Kunlun and Tian Shan Ranges). The Xining deposits are thus the first direct evidence that winter monsoonal winds were active 15 Myr earlier than previously

  6. Aeolian dust emissions in Southern Africa: field measurements of dynamics and drivers

    NASA Astrophysics Data System (ADS)

    Wiggs, Giles; Thomas, David; Washington, Richard; King, James; Eckardt, Frank; Bryant, Robert; Nield, Joanna; Dansie, Andrew; Baddock, Matthew; Haustein, Karsten; Engelstaedter, Sebastian; von Holdt, Johannah; Hipondoka, Martin; Seely, Mary

    2016-04-01

    Airborne dust derived from the world's deserts is a critical component of Earth System behaviour, affecting atmospheric, oceanic, biological, and terrestrial processes as well as human health and activities. However, very few data have been collected on the factors that control dust emission from major source areas, or on the characteristics of the dust that is emitted. Such a paucity of data limits the ability of climate models to properly account for the radiative and dynamical impacts triggered by atmospheric dust. This paper presents field data from the DO4 Models (Dust Observations for Models) project that aims to understand the drivers of variability in dust emission processes from major source areas in southern Africa. Data are presented from three field campaigns undertaken between 2011 and 2015. We analysed remote sensing data to identify the key geomorphological units in southern Africa which are responsible for emission of atmospheric dust. These are the Makgadikgadi pans complex in northern Botswana, the ephemeral river valleys of western Namibia, and Etosha Pan in northern Namibia. Etosha Pan is widely recognised as perhaps the most significant source of atmospheric dust in the southern hemisphere. We deployed an array of field equipment within each source region to measure the variability in and dynamics of aeolian erosivity, as well as dust concentration and flux characteristics. This equipment included up to 11 meteorological stations measuring wind shear stress and other standard climatic parameters, Cimel sun photometers, a LiDAR, sediment transport detectors, high-frequency dust concentration monitors, and dust flux samplers. Further data were gathered at each site on the dynamics of surface characteristics and erodibility parameters that impact upon erosion thresholds. These data were augmented by use of a Pi-Swerl portable wind tunnel. Our data represent the first collected at source for these key dust emission areas and highlight the

  7. Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source

    PubMed Central

    Reynolds, Richard; Belnap, Jayne; Reheis, Marith; Lamothe, Paul; Luiszer, Fred

    2001-01-01

    Aeolian dust (windblown silt and clay) is an important component in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to dust-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian dust in arid regions and to evaluate the roles of this dust in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A component of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian dust component is typically as much as 20–30%. Dust inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective dust traps that apparently record a change in dust sources over the past several decades. Some of the recently fallen dust may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt. PMID:11390965

  8. Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source

    USGS Publications Warehouse

    Reynolds, R.; Belnap, Jayne; Lamothe, Paul; Luiszer, Fred

    2001-01-01

    Aeolian dust (windblown silt and clay) is an important component in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to dust-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian dust in arid regions and to evaluate the roles of this dust in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A component of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian dust component is typically as much as 20a??30%. Dust inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective dust traps that apparently record a change in dust sources over the past several decades. Some of the recently fallen dust may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt.

  9. Evaluation of a new model of aeolian transport in the presence of vegetation

    USGS Publications Warehouse

    Li, Junran; Okin, Gregory S.; Herrick, Jeffrey E.; Belnap, Jayne; Miller, Mark E.; Vest, Kimberly; Draut, Amy E.

    2013-01-01

    Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation. This approach differs from previous models by accounting for how vegetation affects the distribution of shear velocity on the surface rather than merely calculating the average effect of vegetation on surface shear velocity or simply using empirical relationships. Vegetation, soil, and meteorological data at 65 field sites with measurements of horizontal aeolian flux were collected from the Western United States. Measured fluxes were tested against modeled values to evaluate model performance, to obtain a set of optimum model parameters, and to estimate the uncertainty in these parameters. The same field data were used to model horizontal aeolian flux using three other schemes. Our results show that the model can predict horizontal aeolian flux with an approximate relative error of 2.1 and that further empirical corrections can reduce the approximate relative error to 1.0. The level of error is within what would be expected given uncertainties in threshold shear velocity and wind speed at our sites. The model outperforms the alternative schemes both in terms of approximate relative error and the number of sites at which threshold shear velocity was exceeded. These results lend support to an understanding of the physics of aeolian transport in which (1) vegetation's impact on transport is dependent upon the distribution of vegetation rather than merely its average lateral cover and (2) vegetation impacts surface shear stress locally by depressing it in the immediate lee of plants rather than by changing the bulk surface's threshold shear velocity. Our results also suggest that threshold shear velocity is exceeded more than might be estimated by single measurements of threshold shear stress and roughness length

  10. Evaluation of a new model of aeolian transport in the presence of vegetation

    NASA Astrophysics Data System (ADS)

    Li, Junran; Okin, Gregory S.; Herrick, Jeffrey E.; Belnap, Jayne; Miller, Mark E.; Vest, Kimberly; Draut, Amy E.

    2013-03-01

    Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation. This approach differs from previous models by accounting for how vegetation affects the distribution of shear velocity on the surface rather than merely calculating the average effect of vegetation on surface shear velocity or simply using empirical relationships. Vegetation, soil, and meteorological data at 65 field sites with measurements of horizontal aeolian flux were collected from the Western United States. Measured fluxes were tested against modeled values to evaluate model performance, to obtain a set of optimum model parameters, and to estimate the uncertainty in these parameters. The same field data were used to model horizontal aeolian flux using three other schemes. Our results show that the model can predict horizontal aeolian flux with an approximate relative error of 2.1 and that further empirical corrections can reduce the approximate relative error to 1.0. The level of error is within what would be expected given uncertainties in threshold shear velocity and wind speed at our sites. The model outperforms the alternative schemes both in terms of approximate relative error and the number of sites at which threshold shear velocity was exceeded. These results lend support to an understanding of the physics of aeolian transport in which (1) vegetation's impact on transport is dependent upon the distribution of vegetation rather than merely its average lateral cover and (2) vegetation impacts surface shear stress locally by depressing it in the immediate lee of plants rather than by changing the bulk surface's threshold shear velocity. Our results also suggest that threshold shear velocity is exceeded more than might be estimated by single measurements of threshold shear stress and roughness length

  11. Global connections between aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Maher, B. A.; Prospero, J. M.; Mackie, D.; Gaiero, D.; Hesse, P. P.; Balkanski, Y.

    2010-04-01

    Palaeo-dust records in sediments and ice cores show that wind-borne mineral aerosol ('dust') is strongly linked with climate state. During glacial climate stages, for example, the world was much dustier, with dust fluxes two to five times greater than in interglacial stages. However, the influence of dust on climate remains a poorly quantified and actively changing element of the Earth's climate system. Dust can influence climate directly, by the scattering and absorption of solar and terrestrial radiation, and indirectly, by modifying cloud properties. Dust transported to the oceans can also affect climate via ocean fertilization in those regions of the world's oceans where macronutrients like nitrate are abundant but primary production and nitrogen fixation are limited by iron scarcity. Dust containing iron, as fine-grained iron oxides/oxyhydroxides and/or within clay minerals, and other essential micronutrients (e.g. silica) may modulate the uptake of carbon in marine ecosystems and, in turn, the atmospheric concentration of CO 2. Here, in order to critically examine past fluxes and possible climate impacts of dust in general and iron-bearing dust in particular, we consider present-day sources and properties of dust, synthesise available records of dust deposition at the last glacial maximum (LGM); evaluate the evidence for changes in ocean palaeo-productivity associated with, and possibly caused by, changes in aeolian flux to the oceans at the LGM; and consider the radiative forcing effects of increased LGM dust loadings.

  12. Measuring aeolian sand transport using acoustic sensors

    NASA Astrophysics Data System (ADS)

    Poortinga, Ate; van Rheenen, Hans; Ellis, Jean T.; Sherman, Douglas J.

    2015-03-01

    Acoustic sensors are frequently used to measure aeolian saltation. Different approaches are used to process the signals from these instruments. The goal of this paper is to describe and discuss a method to measure aeolian saltation with acoustic sensors. In a laboratory experiment, we measured the output from an advanced signal processing scheme on the circuit board of the saltiphone. We use a software implementation of this processing scheme to re-analyse data from four miniphones obtained during a field experiment. It is shown that a set of filters remove background noise outside the frequency spectrum of aeolian saltation (at 8 kHz), whereas signals within this frequency spectrum are amplified. The resulting analogue signal is a proxy of the energy. Using an AC pulse convertor, this signal can be converted into a digital and analogue count signal or an analogue energy signal, using a rectifier and integrator. Spatio-temporal correlation between field deployed miniphones increases by using longer integration times for signal processing. To quantify aeolian grain impact, it is suggested to use the analogue energy output, as this mode is able to detect changes in frequency and amplitude. The analogue and digital count signals are able to detect an increase in frequency, but are not able to detect an increase in signal amplitude. We propose a two-stage calibration scheme consisting of (1) a factory calibration, to set the frequency spectrum of the sensor and (2) a standardized drop-test conducted before and after the experiment to evaluate the response of the sensor.

  13. Compositional trends in aeolian dust along a transect across the southwestern United States

    USGS Publications Warehouse

    Goldstein, H.L.; Reynolds, R.L.; Reheis, M.C.; Yount, J.C.; Neff, J.C.

    2008-01-01

    Aeolian dust strongly influences ecology and landscape geochemistry over large areas that span several desert ecosystems of the southwestern United States. This study evaluates spatial and temporal variations and trends of the physical and chemical properties of dust in the southwestern United States by examining dust deposited in natural depressions on high isolated surfaces along a transect from the Mojave Desert to the central Colorado Plateau. Aeolian dust is recognized in these depressions on the basis of textural, chemical, isotopic, and mineralogical characteristics and comparisons of those characteristics to the underlying bedrock units. Spatial and temporal trends suggest that although local dust sources are important to the accumulated material in these depressions, Mojave Desert dust sources may also contribute. Depth trends in the depressions suggest that Mojave sources may have contributed more dust to the Colorado Plateau recently than in the past. These interpretations point to the important roles of far-traveled aeolian dust for landscape geochemistry and imply future changes to soil geochemistry under changing conditions in far-distant dust source areas. Copyright 2008 by the American Geophysical Union.

  14. Downwind changes in grain size of aeolian dust; examples from marine and terrestrial archives

    NASA Astrophysics Data System (ADS)

    Stuut, Jan-Berend; Prins, Maarten

    2013-04-01

    Aeolian dust in the atmosphere may have a cooling effect when small particles in the high atmosphere block incoming solar energy (e.g., Claquin et al., 2003) but it may also act as a 'greenhouse gas' when larger particles in the lower atmosphere trap energy that was reflected from the Earth's surface (e.g., Otto et al., 2007). Therefore, it is of vital importance to have a good understanding of the particle-size distribution of aeolian dust in space and time. As wind is a very size-selective transport mechanism, the sediments it carries typically have a very-well sorted grain-size distribution, which gradually fines from proximal to distal deposition sites. This fact has been used in numerous paleo-environmental studies to both determine source-to-sink changes in the particle size of aeolian dust (e.g., Weltje and Prins, 2003; Holz et al., 2004; Prins and Vriend, 2007) and to quantify mass-accumulation rates of aeolian dust (e.g., Prins and Weltje 1999; Stuut et al., 2002; Prins et al., 2007; Prins and Vriend, 2007; Stuut et al., 2007; Tjallingii et al., 2008; Prins et al., 2009). Studies on modern wind-blown particles have demonstrated that particle size of dust not only is a function of lateral but also vertical transport distance (e.g., Torres-Padron et al., 2002; Stuut et al., 2005). Nonetheless, there are still many unresolved questions related to the physical properties of wind-blown particles like e.g., the case of "giant" quartz particles found on Hawaii (Betzer et al., 1988) that can only originate from Asia but have a too large size for the distance they travelled through the atmosphere. Here, we present examples of dust particle-size distributions from terrestrial (loess) as well as marine (deep-sea sediments) sedimentary archives and their spatial and temporal changes. With this contribution we hope to provide quantitative data for the modelling community in order to get a better grip on the role of wind-blown particles in the climate system. Cited

  15. 26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Fisher, Adrian; Fink, David; Chappell, John; Melville, Michael

    2014-08-01

    Aeolian dust mantle soils are an important element of many landscapes in south-eastern Australia, though the age of these aeolian deposits has not been radiometrically determined. At Fowlers Gap in western New South Wales, surface cobbles of silcrete and quartz overlie a stone-free, aeolian dust mantle soil, which has a thickness of about 1.6 m. The clay-rich aeolian dust deposit in turn lies upon a buried silcrete and quartz stone layer. Modelling in-situ cosmogenic 26Al and 10Be concentrations measured in both the surface quartz stones and in the buried quartz layer of rocks, reveals that each has experienced a complex exposure-burial history. Due to the absence of quartz stones or sand at intermediate depths, our cosmogenic 26Al and 10Be modelling was not able to determine a definitive mechanism of stone pavement formation and stone burial. Various scenarios of stone formation, transport, burial and exhumation were tested that constrain the age of the deposit to range from 0.9 ± 0.2 Ma to 1.8 ± 0.2 Ma, based largely on different assumptions taken for the time-dependency of the net sedimentation rate. This corresponds with the initiation of the Simpson Desert dune fields and the deflation of lakes in central Australia, which probably responded to the shift to longer-wavelength, larger-amplitude Quaternary glacial cycles at around 1 Ma. Sensitivity analyses were carried out to identify those parameters which better constrained model outputs. Within model errors, which largely are the result of analytical errors in measured 26Al and 10Be concentrations, all three competing theories of colluvial wash, upward displacement of stones, and cumulic pedogenesis are possible mechanisms for the formation of the surface stone pavement.

  16. Aeolian Sediment Transport Pathways and Aerodynamics at Troughs on Mars

    NASA Technical Reports Server (NTRS)

    Bourke, Mary C.; Bullard, Joanna E.; Barnouin-Jha, Olivier S.

    2004-01-01

    Interaction between wind regimes and topography can give rise to complex suites of aeolian landforms. This paper considers aeolian sediment associated wit11 troughs on Mars and identifies a wider range of deposit types than has previously been documented. These include wind streaks, falling dunes, "lateral" dunes, barchan dunes, linear dunes, transverse ridges, sand ramps, climbing dunes, sand streamers, and sand patches. The sediment incorporated into these deposits is supplied by wind streaks and ambient Planitia sources as well as originating within the trough itself, notably from the trough walls and floor. There is also transmission of sediment between dneTsh. e flow dynamics which account for the distribution of aeolian sediment have been modeled using two-dimensional computational fluid dynamics. The model predicts flow separation on the upwind side of the trough followed by reattachment and acceleration at the downwind margin. The inferred patterns of sediment transport compare well with the distribution of aeolian forms. Model data indicate an increase of wind velocity by approx. 30 % at the downwind trough margin. This suggests that the threshold wind speed necessary for sand mobilization on Mars will be more freqentmlye t in these inclined locations.

  17. Sensitivity simulations with direct shortwave radiative forcing by aeolian dust during glacial cycles

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Ganopolski, A.

    2014-07-01

    Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate and dust deposition records suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key elements controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these elements are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters can be reasonably constrained, the simulated dust DRF spans a~wide uncertainty range related to the strong nonlinearity of the Earth system. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several watts per square metre in regions close to major dust sources and negligible values elsewhere. In the case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In the case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods, which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters, dust DRF has the potential to either damp or reinforce glacial-interglacial climate changes.

  18. Sensitivity simulations with direct radiative forcing by aeolian dust during glacial cycles

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Ganopolski, A.

    2014-01-01

    Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate variables and dust deposits suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key factors controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these factors are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters are reasonably constrained by use of these studies, the simulated dust DRF spans a wide uncertainty range related to nonlinear dependencies. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several W m-2 in regions close to major dust sources and negligible values elsewhere. In case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters the DRF has the potential to either damp or reinforce glacial-interglacial climate changes.

  19. Laboratory studies of aeolian sediment transport processes on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Rasmussen, Keld R.; Valance, Alexandre; Merrison, Jonathan

    2015-09-01

    , but not all, older or recent wind tunnel observations. Similarly some measurements performed with uniform sand samples having grain diameters of the order of 0.25-0.40 mm indicate that ripple spacing depends on friction velocity in a similar way as particle jump length. The observations are thus in agreement with a recent ripple model that link the typical jump length to ripple spacing. A possible explanation for contradictory observations in some experiments may be that long observation sequences are required in order to assure that equilibrium exists between ripple geometry and wind flow. Quantitative understanding of saltation characteristics on Mars still lacks important elements. Based upon image analysis and numerical predictions, aeolian ripples have been thought to consist of relatively large grains (diameter > 0.6 mm) and that saltation occurs at high wind speeds (> 26 m/s) involving trajectories that are significantly longer than those on Earth (by a factor of 10-100). However, this is not supported by recent observations from the surface of Mars, which shows that active ripples in their geometry and composition have characteristics compatible with those of terrestrial ripples (Sullivan et al., 2008). Also the highest average wind speeds on Mars have been measured to be < 20 m/s, with even turbulent gusts not exceeding 25 m/s. Electrification is seen as a dominant factor in the transport dynamics of dust on Mars, affecting the structure, adhesive properties and detachment/entrainment mechanisms specifically through the formation of aggregates (Merrison et al., 2012). Conversely for terrestrial conditions electric fields typically observed are not intense enough to significantly affect sand transport rates while little is known in the case of extra-terrestrial environments.

  20. Lower tropospheric aerosol loadings over South Africa: The relative contribution of aeolian dust, industrial emissions, and biomass burning

    NASA Astrophysics Data System (ADS)

    Piketh, S. J.; Annegarn, H. J.; Tyson, P. D.

    1999-01-01

    The southern African haze layer is a ubiquitous subcontinental-scale feature of the lower atmosphere that extends to a depth of ˜5 km(˜500 hPa level) on non rain days, particularly in winter. Aerosols derived from biomass burning are commonly thought to contribute substantially to the total background aerosol loading within the layer. It is shown that in both summer and winter this supposition is without foundation over South Africa. Summer and winter aerosol loadings are derived from gravimetric analysis of stacked filter units and from proton-induced X ray emission (PIXE) analysis of one to four hourly resolved streaker samples. From concentrations of eleven inorganic elements, apportionment into four primary sources, biomass burning particulates, aeolian dust, industrial sulphur aerosols, and marine aerosols, has been effected. It is shown that the background biomass burning component of the total aerosol loading over South Africa in general, and within the plume of material being recirculated over South Africa and from there exported from the subcontinent south of 22°S to the Indian Ocean in particular, is minimal in both summer and winter. Except over coastal and adjacent inland areas, marine aerosols likewise make up a small fraction of the total loading. This is particularly so over the inland plateau areas. Crustally-derived aeolian dust and industrially-produced sulphur aerosols are demonstrated to be the major summer and winter constituents of the haze layer over South Africa and the particulate material being transported to the Indian Ocean region. Sulphur is transported within the aerosol plume exiting southern Africa to the Indian Ocean as agglomerates on aeolian dust nuclei.

  1. Aeolian transport pathways along the transition from Tibetan highlands towards northwestern Chinese deserts

    NASA Astrophysics Data System (ADS)

    Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg

    2014-05-01

    The identification and semi-quantification of aeolian transport pathways enhances the understanding of aeolian sediment archive formation and thus supports reliability and explanatory power concerning palaeoenvironmental reconstructions. Grain size analysis of 279 surface sediment samples from the transition of Tibetan highlands (Qilian Shan) towards northwestern Chinese deserts allows the differentiation of contributing pathways among three types of aeolian sediments: silty loess, sandy loess, and aeolian sands. The study area exhibits a high diversity of geomorphological surfaces due to varieties in relief, elevation and climatic conditions. Therefore, it provides the opportunity to investigate the characteristics of sediments in different geomorphological settings. Using the peaks of grain size frequency's standard deviation of primary loess allows identification of the most sensitive fractions to varying accumulation conditions. mU/fS-ratio (7 - 13 μm / 58 - 84 μm) of primary silty loess relates the far-travelled dust proportion to the locally transported fine sand component. In vicinity to fluvial channels in the foreland mU/fS-values are significantly decreased, whereas mU/fS-values increase with altitude (r2 = 0.74). This indicates higher contribution of long distance transport compared to lower regions. A prominent increase of mU/fS-values above 3000 m asl likely indicates an increasing contribution of fine and medium silt particles transported by Westerlies in higher altitudes. In contrast, lower areas seem to be more strongly influenced by low altitude monsoon currents (NW-Winter- / SE-summer monsoon). The difference in grain size properties is additionally enhanced by the contrasting geomorphologic settings along the mountain declivity: Plain foreland alluvial fans support fine sand supply and availability whereas steep high mountain topography provides only limited potential for fine sand deflation. Similarly, the relatively low relief in intramontane

  2. A conceptual framework for dryland aeolian sediment transport along the grassland-forest continuum: Effects of woody plant canopy cover and disturbance

    USGS Publications Warehouse

    Breshears, D.D.; Whicker, J.J.; Zou, C.B.; Field, J.P.; Allen, C.D.

    2009-01-01

    range of rates in grasslands and associated systems with no woody plants (e.g., agricultural fields), an intermediate range in shrublands, and a relatively small range in woodlands and forests. These trends are consistent with previous observations relating large rates of wind erosion to intermediate values for spatial density of roughness elements. The framework for aeolian sediment transport, which is also relevant to dust fluxes, wind erosion, and related aeolian processes, is applicable to a diverse suite of environmental challenges, including land degradation and desertification, dust storms, contaminant transport, and alterations of the hydrological cycle. ?? 2008 Elsevier B.V.

  3. Effects of particle optical properties on grain size measurements of aeolian dust deposits

    NASA Astrophysics Data System (ADS)

    Varga, György; Újvári, Gábor; Kovács, János; Szalai, Zoltán

    2015-04-01

    Particle size data are holding crucial information on the sedimentary environment at the time the aeolian dust deposits were accumulated. Various aspects of aeolian sedimentation (wind strength, distance to source(s), possible secondary source regions and modes of sedimentation and transport) can be reconstructed from proper grain size distribution data. Laser diffraction methods provide much more accurate and reliable information on the major granulometric properties of wind-blown sediments compared to the sieve and pipette methods. The Fraunhofer and Mie scattering theories are generally used for laser diffraction grain size measurements. () The two different approaches need different 'background' information on the medium measured. During measurements following the Fraunhofer theory, the basic assumption is that parcticles are relatively large (over 25-30 µm) and opaque. The Mie theory could offer more accurate data on smaller fractions (clay and fine silt), assuming that a proper, a'priori knowledge on refraction and absorption indices exists, which is rarely the case for polymineral samples. This study is aimed at determining the effects of different optical parameters on grain size distributions (e.g. clay-content, median, mode). Multiple samples collected from Hungarian red clay and loess-paleosol records have been analysed using a Malvern Mastersizer 3000 laser diffraction particle sizer (with a Hydro LV unit). Additional grain size measurements have been made on a Fritsch Analysette 22 Microtec and a Horiba Partica La-950 v2 instrument to investigate possible effects of the used laser sources with different wavelengths. XRF and XRD measurements have also been undertaken to gain insight into the geochemical/mineralogical compositions of the samples studied. Major findings include that measurements using the Mie theory provide more accurate data on the grain size distribution of aeolian dust deposits, when we use a proper optical setting. Significant

  4. A Japan-Sino joint project, ADEC - Aeolian Dust Experiment on Climate Impact

    NASA Astrophysics Data System (ADS)

    Mikami, M.

    2004-05-01

    In recent years, aeolian dust has been thought to be an important factor of the climate system on the earth by the radiative forcing effect in the atmosphere and by the influence on the carbon dioxide cycle because deposited dust supplies nutrient salts for the phytoplankton on the ocean surface. Among them, radiative forcing direct and/or indirect effects are important factors of the global warming. Nevertheless, the reliability of the evaluation regarding the radiative forcing impact of aeolian dust is very low. [IPCC, 2001]. This is because the understanding and the model representations of dust entrainment, spatial and temporal distribution of dust, and optical properties of dust particles are not so accurate. Based on this background, Aeolian Dust Experiment on Climate Impact (ADEC) was started in April 2000 as a Japan-Sino Joint Project. The goal of this project is to evaluate the global dust supply to the atmosphere and its radiative forcing direct effect. For this purpose, we have made: 1) in situ observations at desert areas in China for wind erosion processes, 2) network observations from China to Japan, ranging from 80 to 140 East, for understanding spatial-size distribution, chemical, and optical properties of dust particles, and 3) numerical simulation by GCM dust model for evaluation of dust impact on the global climate over the past 50 years. This was planned as a five-year project and two intensive observations, IOP-1, April 12-25 2002, and IOP-2, March 15-26 2003, were put into practice. Intensive observations were made at 6 sites in China (Qira, Aksu, Dunhuang, Shapotou, Beijing, and Qingdao) and 4 sites in Japan (Naha, Fukuoka, Nagoya, and Tsukuba). Preliminary results show that 1) saltation flux at a gobi desert monitored by a newly developed sand particle counter was around 10 times larger than that of a sand dune, which will be caused by the difference of the parent soil size distribution of each ground condition, 2) the background of KOSA

  5. Aeolian dust deposition rates in Northern French forests and inputs to their biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Lequy, Émeline; Legout, Arnaud; Conil, Sébastien; Turpault, Marie-Pierre

    2013-12-01

    This study describes the Aeolian dust deposition (ADD) in 4 sites of Northern France. Between December 2009 and March 2012, we sampled (i) Aeolian dust every four weeks, and (ii) 6 episodes of forecasted high atmospheric dust load mainly from the Saharan desert, the largest source of Aeolian dust in the world. These samples were treated with oxygen peroxide to remove organic matter so as to only compare the mineral fraction of the samples in the 4 sampling sites and to analyze their mineralogy. The solid samples contained the hardly soluble part of Aeolian dust (H-ADD). Its deposition was of 1.9 ± 0.3 g m-2 year-1 with a seasonal pattern of high deposition from spring to early autumn and a low deposition in winter. H-ADD deposition during the forecasted episodes of high atmospheric load did not systematically exceed the deposition rate during the rest of the sampling period. This indicates that such episodes little contributed to the annual H-ADD rate. The mineralogy revealed a heterogeneous set of minerals dominated by silicates with a common basis of major types (quartz, feldspars, mica, chlorite, kaolinite and interlayered clay minerals in every sample) with randomly trace minerals (Fe-oxides, sulfates, amphibole, talc, gibbsite and carbonates). The chemistry of H-ADD led to a dominant input of Si (up to 4.4 kg ha-1 year-1), while the nutrients inputs of Ca, K, Mg and P from ADD and the atmospheric organics (APD) in openfield were together of 1.5 ± 0.5 kg ha-1 year-1 with a high contribution of soluble minerals and organic matter of ca. 40% for Mg and K, and of ca. 80% for Ca and P. Nutrient inputs from APD are especially an interesting source of P for forests developed on acidic soils.

  6. An integrated coastal model for aeolian and hydrodynamic sediment transport

    NASA Astrophysics Data System (ADS)

    Baart, F.; den Bieman, J.; van Koningsveld, M.; Luijendijk, A. P.; Parteli, E. J. R.; Plant, N. G.; Roelvink, J. A.; Storms, J. E. A.; de Vries, S.; van Thiel de Vries, J. S. M.; Ye, Q.

    2012-04-01

    Dunes are formed by aeolian and hydrodynamic processes. Over the last decades numerical models were developed that capture our knowledge of the hydrodynamic transport of sediment near the coast. At the same time others have worked on creating numerical models for aeolian-based transport. Here we show a coastal model that integrates three existing numerical models into one online-coupled system. The XBeach model simulates storm-induced erosion (Roelvink et al., 2009). The Delft3D model (Lesser et al., 2004) is used for long term morphology and the Dune model (Durán et al., 2010) is used to simulate the aeolian transport. These three models were adapted to be able to exchange bed updates in real time. The updated models were integrated using the ESMF framework (Hill et al., 2004), a system for composing coupled modeling systems. The goal of this integrated model is to capture the relevant coastal processes at different time and spatial scales. Aeolian transport can be relevant during storms when the strong winds are generating new dunes, but also under relative mild conditions when the dunes are strengthened by transporting sand from the intertidal area to the dunes. Hydrodynamic transport is also relevant during storms, when high water in combination with waves can cause dunes to avalanche and erode. While under normal conditions the hydrodynamic transport can result in an onshore transport of sediment up to the intertidal area. The exchange of sediment in the intertidal area is a dynamic interaction between the hydrodynamic transport and the aeolian transport. This dynamic interaction is particularly important for simulating dune evolution at timescales longer than individual storm events. The main contribution of the integrated model is that it simulates the dynamic exchange of sediment between aeolian and hydrodynamic models in the intertidal area. By integrating the numerical models, we hope to develop a model that has a broader scope and applicability than

  7. Aeolian sand transport: a wind tunnel model

    NASA Astrophysics Data System (ADS)

    Dong, Zhibao; Liu, Xiaoping; Wang, Hongtao; Wang, Xunming

    2003-09-01

    Wind sand transport is an important geological process on earth and some other planets. Formulating the wind sand transport model has been of continuing significance. Majority of the existing models relate sand transport rate to the wind shear velocity based on dynamic analysis. However, the wind shear velocity readapted to blown sand is difficult to determine from the measured wind profiles when sand movement occurs, especially at high wind velocity. Moreover, the effect of grain size on sand transport is open to argument. Detailed wind tunnel tests were carried out with respect to the threshold velocity, threshold shear velocity, and transport rate of differently sized, loose dry sand at different wind velocities to reformulate the transport model. The results suggest that the relationship between threshold shear velocity and grain size basically follow the Bagnold-type equation for the grain size d>0.1 mm. However, the threshold coefficient A in the equation is not constant as suggested by Bagnold, but decreases with the particle Reynolds number. The threshold velocity at the centerline height of the wind tunnel proved to be directly proportional to the square root of grain diameter. Attempts have been made to relate sand transport rate to both the wind velocity and shear velocity readapted to the blown sand movement. The reformulated transport model for loose dry sand follows the modified O'Brien-Rindlaub-type equation: Q= f1( d)(1- Ru) 2( ρ/ g) V3, or the modified Bagnold-type equation: Q= f2( d)(1- Rt) 0.25( ρ/ g) U*3. Where Q is the sand transport rate, the sand flux per unit time and per unit width, in kg m -1 s -1; ρ is the air density, 1.25 kg m -3; g is the acceleration due to gravity, 9.81 m s -2; Ru= Vt/ V; Rt= U*t/ U*; V is the wind velocity at the centerline of the wind tunnel, in m s -1; Vt is the threshold velocity measured at the same height as V, in m s -1; U* is the shear velocity with saltating flux, in m s -1; U*t is threshold shear

  8. Aeolian removal of dust from radiator surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Hotes, Deborah

    1990-01-01

    Simulated radiator surfaces made of arc-textured Cu and Nb-1 percent-Zr and ion beam textured graphite and C-C composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It was found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al2O3 there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10 to 20 percent degradation, and with Fe2O3 a 20 to 40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured Cu and Nb-1 percent Zr was found to be more susceptible to emittance degradation than graphite or C-C composite. The most abrasion occurred at low angles, peaking at the 22.5 deg test samples.

  9. Aeolian removal of dust from radiator surfaces on Mars

    SciTech Connect

    Gaier, J.R.; Perez-Davis, M.E.; Rutledge, S.K.; Hotes, D.

    1994-09-01

    Simulated radiator surfaces made of arc-textured copper and niobium-one percent-zirconium, and ion beam textured graphite and carbon-carbon composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It has been found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al{sub 2}O{sub 3} there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10-20 percent degradation, and with Fe{sub 2}O{sub 3} a 20-40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured copper and Nb-1%Zr was found to be more susceptible to emittance degradation than graphite or carbon-carbon composite. The most abrasion occurred at low angles, peaking at the 22.5{degrees} test samples.

  10. Fluid transport on earth and aeolian transport on Mars

    NASA Technical Reports Server (NTRS)

    Sagan, C.; Bagnold, R. A.

    1975-01-01

    Experimental data on cohesion-free particle transport in fluid beds are applied, via a universal scaling relation, to atmospheric transport of fine grains on Mars. It may be that cohesion due to impact vitrification, vacuum sintering, and adsorbed thin films of water are absent on Mars - in which case the curve of threshold velocity versus grain size may show no turnup to small particle size, and one micron diameter grains may be injected directly by saltation into the Martian atmosphere more readily than 100 micron diameter grains. Curves for threshold and terminal velocities are presented for the full range of Martian pressures and temperatures. Suspension of fine grains is significantly easier at low temperatures and high pressures; late afternoon brightenings of many areas of Mars, and the generation of dust storms in such deep basins as Hellas, may be due to this effect.

  11. A study of the management strategies for river aeolian dust inhibition at the estuary of Zhuo-shui River

    NASA Astrophysics Data System (ADS)

    Tsai, S. F.; Lin, C. Y.

    2014-12-01

    With the characteristics of humidity in summer and drought in winter, there existing lots of bare lands due to the decline of water level cause large amounts of aeolian dust and environmental deterioration during the monsoon seasons in central Taiwan. How to adopt effective measures to inhibit the damage of dust is an essential issue. This study selected the serious dust-affected section of Zhuo-shui river (bridge Zi-qiang to Xi-bin) to delineate the areas of potential aeolian dust occurrence, explore the relationship between elevation and water level determined from return period analysis, submit the countermeasures for dust inhibition at the bare lands and/or cultivated areas, and address the responsibilities of related authority offices for dust prevention by means of literature review. The return period of inundation for the areas of potential aeolian dust occurrence is 1.1 years. Engineering of dust prevention with highly unit price are not recommended due to could be destroyed annually. The deposition sites of a river are usually located at the convex bank, which with silt texture and high salinity are not suitable for cultivation, are delineated as the areas of potential aeolian dust occurrence. Besides technology consideration in dust prevention, this study also examined the related articles of river management to integrate a comprehensive vision for better riverside environment and air quality.

  12. Aeolian dust deposition during the Eocene-Oligocene in central to eastern Asia

    NASA Astrophysics Data System (ADS)

    Vandenberghe, Jef; Abels, Hemmo; van Cappelle, Marijn

    2015-04-01

    Aeolian dust deposition during the Eocene-Oligocene in central to eastern Asia Jef Vandenberghe1, Hemmo Abels2 and Marijn van Cappelle3 1Dept. of Earth Sciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands 2Dept. of Earth Sciences, Universiteit Utrecht, 3584 CD, Utrecht, The Netherlands 3Dept. of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, U.K. The deposition of loess is generally attributed to a monsoonal climate system. Recently it has been shown that such a system existed already at the end of the Eocene on the northeastern Tibetan Plateau (Licht et al., 2014). One of the main arguments to prove the supply of loess by monsoonal winds is the use of grain size properties. The lower part of the Shuiwan section (Eocene) consists of metre-scale alternations of mudstone and gypsum beds; the upper part (Oligocene) is mainly mudstone (Dupont-Nivet et al., 2007; Abels et al., 2010). Sediments are categorized in six grain-size types based on the grain-size distribution and the mode of the silt grain sizes as measured using laser diffraction. Sediments of type 1, the only type with a unimodal grain-size distribution, consist exclusively of clay-sized particles (modal value of 2-2.5 µm). Types 2-6 have a multimodal composition. They contain an additional silt-sized fraction with a modal size of c. 16 µm in type 2; c. 26 µm in type 3 and c. 31 µm in type 4. Type 5 is a mixture of previous types, and type 6 contains in addition a slight amount of sand. Similar bimodal grain-size distributions occur in the Neogene Red Clay and in the Pleistocene loess of the Chinese Loess Plateau. All three silt fractions (with modal sizes 16, 26 and 31 µm) represent typical loess sediments, transported by dust storms in suspension at different altitudes. Their exact grain size depends on wind velocity, source material and transport distance. The 'clay component' may have settled from high suspension clouds in the air down to dry ground or to

  13. Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport

    USGS Publications Warehouse

    Sankey, Joel B.; Law, Darin J.; Breshears, David D.; Munson, Seth M.; Webb, Robert H.

    2013-01-01

    The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages.

  14. The accretion of aeolian dust in soils of the San Juan Mountains, Colorado, USA

    NASA Astrophysics Data System (ADS)

    Lawrence, Corey R.; Neff, Jason C.; Farmer, G. Lang

    2011-06-01

    Recent observations suggest a contemporary aeolian dust flux of at least 5-10 g m-2 yr-1 to high-elevation ecosystems of the San Juan Mountains of southwestern Colorado. To better quantify the influence of dust on San Juan soil geochemistry, we used Sr and Nd isotopic mixing models to estimate the total mass of accreted dust in soils of two alpine basins underlain by bedrocks of different geochemical composition. In order to minimize the potentially confounding effects caused by transient soil pools of Sr and Nd, we implemented a sequential leaching procedure that isolates the residual mineral fraction of soils and their putative parent materials, including local saprolite and exogenous dust inputs. Using this approach, we calculated masses of accreted dust in soils, which were similar across the two isotopic tracers and differing local geologies. Long-term rates of dust accretion were estimated to be slightly higher than contemporary rates of dust deposition. We conclude that dust inputs comprise from 10% to 40% of the total soil mass in these ecosystems. Our observations suggest that dust inputs have exerted a primary control on soil development in the San Juan Mountains and have likely influenced the physical and chemical characteristics of soils in this region.

  15. Reconstructing transport pathways for late Quaternary dust from eastern Australia using the composition of trace elements of long traveled dusts

    NASA Astrophysics Data System (ADS)

    Petherick, Lynda M.; McGowan, Hamish A.; Kamber, Balz S.

    2009-04-01

    The southeast Australian dust transport corridor is the principal pathway through which continental emissions of dust from central and eastern Australia are carried to the oceans by the prevailing mid-latitude westerly circulation. The analysis of trace elements of aeolian dust, preserved in lake sediment on North Stradbroke Island, southeast Queensland, is used to reconstruct variation in the intensity and position of dust transport to the island over the past 25,000 yrs. Separation of local and long traveled dust content of lake sediments is achieved using a unique, four-element (Ga, Ni, Tl and Sc) separation method. The local and continental chronologies of aeolian deposition developed by this study show markedly different records, and indicate varied responses to climate variability on North Stradbroke Island (local aeolian sediment component) and in eastern and central Australia (long traveled dust component). The provenance of the continental component of the record to sub-geologic catchment scales was accomplished using a ternary mixing model in which the chemical identification of dusts extracted, from the lake sediments, was compared to potential chemical characteristics of surface dust from the source areas using 16 trace elements. The results indicate that the position and intensity of dust transport pathways during the late Quaternary varied considerably in response to changing atmospheric circulation patterns as well as to variations in sediment supply to dust source areas, which include the large anabranching river systems of the Lake Eyre and Murray-Darling Basins.

  16. Contemporary research in aeolian geomorphology

    NASA Astrophysics Data System (ADS)

    Bauer, B. O.

    2009-04-01

    The first International Conference on Aeolian Geomorphology (ICAR) was held in 1986, and every four years since then, aeolian geomorphologists from around the world have assembled to discuss their research and to showcase recent advancements in understanding and modeling of aeolian processes. A content analysis of the "Bibliography of Aeolian Research" [Stout, J.E., Warren, A., Gill, T.E., 2009. Publication trends in aeolian research: An analysis of the Bibliography of Aeolian Research. Geomorphology 105, 6-17 (this volume)] shows that the number of publications on aeolian topics has increased exponentially from the mid-20th Century with approximately 50 publications per year to about 500 publications per year when the first ICAR was held, to almost 1000 publications per year currently. Areas of focus have shifted historically from initial concerns with aeolian erosion and dust events as isolated phenomenon of localized curiosity or only regional importance, to comprehensive physically-based investigations and modeling of the mechanics of aeolian transport. Recently, more applied studies have been motivated by the recognition of the importance of aeolian processes to dust emissions into the atmosphere (with relevance for human health and for meteorological conditions and climate change) and within regional management contexts (especially on coasts where impending sea-level rise is of great concern and in arid and semi-arid environments given the dependence of sediment surface stability and remobilization on meteorological and ecological conditions). Aeolian geomorphology is a rapidly growing sub-discipline of Geomorphology that offers rich opportunities for interdisciplinary collaborations with colleagues from the Atmospheric Sciences, Climatology, Sedimentology, Quaternary Geology, Fluid Mechanics, Physics, Mathematics, Computer Science, Physical Geography, Ecology, and Agricultural Sciences, as well as our counterparts in fluvial, coastal, and arid

  17. Predicting aeolian sand transport rates: A reevaluation of models

    NASA Astrophysics Data System (ADS)

    Sherman, Douglas J.; Li, Bailiang

    2012-01-01

    Eight aeolian sand-transport models are evaluated using a field data set and a new approach to estimating shear velocity. The models are those of Bagnold (1937), Kawamura (1951), Zingg (1953), Owen (1964), Kadib (1965), Hsu (1971), Lettau and Lettau (1978) and Sørensen (2004). All of these models predict transport as a function of shear velocity to the third power. Shear velocities are estimated using wind profile data (log-linear slope) with the von Kármán constant and with the apparent von Kármán parameter and the results of the different approaches are evaluated based on comparison of regression statistics and RMS error. The models were not adjusted to account for sediment moisture content or local surface slope effects. All of the models have about the same statistical explanatory power, so evaluations were made by comparing slopes and intercepts of best fit (least-squares) lines and RMSE. From this basis, we conclude that predictions made with the Bagnold (1937) model best match our observations, with the models of Kadib (1965) and Hsu (1971) performing nearly as well. The Lettau and Lettau (1978) and Kawamura (1951) model predictions match observations least.

  18. Aeolian sediment transport on a beach with a varying sediment supply

    NASA Astrophysics Data System (ADS)

    de Vries, S.; Arens, S. M.; de Schipper, M. A.; Ranasinghe, R.

    2014-12-01

    Variability in aeolian sediment transport rates have traditionally been explain by variability in wind speed. Although it is recognised in literature that limitations in sediment supply can influence sediment transport significantly, most models that predict aeolian sediment transport attribute a dominant role to the magnitude of the wind speed. In this paper it is proposed that spatio-temporal variability of aeolian sediment transport on beaches can be dominated by variations in sediment supply rather than variations in wind speed. A new dataset containing wind speed, direction and sediment transport is collected during a 3 day field campaign at Vlugtenburg beach, The Netherlands. During the measurement campaign, aeolian sediment transport varied in time with the tide while wind speed remained constant. During low tide, measured transport was significantly larger than during high tide. Measured spatial gradients in sediment transport at the lower and upper beaches during fairly constant wind conditions suggest that aeolian sediment transport on beaches may be partly governed by the spatial variability in sediment supply, with relatively large supply in the intertidal zone when exposed and small supply on the upper beach due to sorting processes. The measurements support earlier findings that the intertidal zone can be significant source of sediment for sediment transport on beaches. Both a traditional cubic model (with respect to the wind speed) and a newly proposed linear model are fitted to the field data. The fit quality of both types of models are found to be similar.

  19. Asian dust transport during the last century recorded in Lake Suigetsu sediments

    NASA Astrophysics Data System (ADS)

    Nagashima, Kana; Suzuki, Yoshiaki; Irino, Tomohisa; Nakagawa, Takeshi; Tada, Ryuji; Hara, Yukari; Yamada, Kazuyoshi; Kurosaki, Yasunori

    2016-03-01

    Asian dust has a significant impact on the natural environment. Its variability on multiple timescales modulates the ocean biogeochemistry and climate. We demonstrate that temporal changes in the deposition flux of Aeolian dust recorded in sediments from Lake Suigetsu, central Japan, during the last century exhibit a continuous decreasing trend and a decadal-scale decrease in 1952-1974. The former decreasing trend can be explained by a decrease in the dust storm frequency at source regions due to the warming of Mongolia in the twentieth century, suggesting future decrease of Asian dust transport with further warming in Mongolia. Decadal-scale decrease of Aeolian dust is explained by weaker westerlies in lower latitudes in central Japan, reflecting a weaker Aleutian Low during the corresponding period. Decadal-scale westerly change probably causes north-south shifts of the dominant dust transport path, which affects subarctic northern Pacific Ocean biogeochemistry by changing the micronutrient iron supply.

  20. Sand transport by wind, erosion and deposition and the origin of aeolian bedforms

    NASA Astrophysics Data System (ADS)

    Duran Vinent, Orencio

    2014-05-01

    Aeolian processes involve the wind action on a sedimentary substrate, namely erosion, sand transport and deposition. They are responsible for the emergence of aeolian dunes and ripples. Here, we discuss the physics of aeolian sediment transport from a physical point of view. Relevant time and length scales associated to turbulent wind fluctuations are summarized using aerodynamic theory. At the microscopic scale, the main forces acting on the grains are detailed. Sand transport is then studied using two phase numerical simulations based on a discrete element method for particles coupled to a continuum Reynolds averaged description of hydrodynamics. We then introduce the concepts - e.g. saturated flux, saturation length - and the relevant framework for the development of a continuum (macroscopic) quantitative description of transport at the core of our current understanding of aeolian dunes formation. At smaller scales, aeolian ripples arise from the interaction of sediment transport and topography. At larger scales, the nonlinear nature of the interaction between dunes leads to the formation of dune fields.

  1. Aeolian sediment and dust fluxes during predominant “background” wind conditions for unburned and burned semiarid grassland: Interplay between particle size and temporal scale

    NASA Astrophysics Data System (ADS)

    Merino-Martín, Luis; Field, Jason P.; Villegas, Juan Camilo; Whicker, Jeffrey J.; Breshears, David D.; Law, Darin J.; Urgeghe, Anna M.

    2014-09-01

    Monitoring of aeolian transport is needed for assessment and management of human health risks as well as for soil resources. Human health risks are assessed based on duration of exposure as well as concentration. Many aeolian studies focus on periods of high wind speed when concentrations are greatest but few studies focus on “background” conditions when concentrations are likely lower but which represent the most prevalent conditions. Such “background” conditions might be especially important at sites with recent disturbance such as fire. Exposure assessments also require improved understanding relating longer-term (days to weeks) measurements of saltation of larger particles to shorter-term (minutes to hours) measurements of smaller inhalable dust particles. To address these issues, we employed three commonly used instruments for measuring dust emissions for unburned and recently-burned sites: Big Springs Number Eight (BSNE) samplers for larger saltating soil particles (>50 μm) with weekly to monthly sampling resolution, DustTraks for suspended particles (diameters <10 μm) with 1-s sampling resolution, and Total Suspended Particulate (TSP) filter samplers for measuring with hourly to daily sampling resolution. Significant differences in concentrations between burned and unburned sites were detectable in either short (1-s maximum) interval DustTrak PM10 measurements, or in longer term (weekly) BSNE horizontal sediment flux measurements, but not in intermediate-term (daily 5-h means) for either DustTrak PM10 or TSP measurements. The results highlight ongoing dust emissions during less windy periods and provide insight into the complex interplay among particle-size dependent measures and typical time scales measured.

  2. Mass-height profile and total mass transport of wind eroded aeolian sediments from rangelands of the Indian Thar Desert

    NASA Astrophysics Data System (ADS)

    Mertia, R. S.; Santra, Priyabrata; Kandpal, B. K.; Prasad, R.

    2010-11-01

    Wind erosion is an active land degradation process in the Indian Thar Desert and severe dust storm events during hot summer months in the region are very common. Assessment of soil loss due to dust storm events from major land use systems of the Indian Thar Desert is highly essential for proper environmental planning. Characterization of the mass-height profile of wind eroded aeolian sediment is an important step to compute soil loss/mass transport but was not previously studied in the region. In the present study, aeolian mass fluxes (kg m -2) at different heights from soil surface were measured at two major rangelands in the Indian Thar Desert: Overgrazing rangeland at Jaisalmer (26°55'N and 70°57'E), and controlled grazing rangeland at Chandan (27°01'N and 71°01'E). Evaluation of several mass-height profile models revealed that a power decay function [ q( z) = az-b, where q( z) is the measured mass flux at an height of z (m) from soil surface; a and b are parameters of the equation] was best to characterize the mass-height relationship of aeolian sediments from the Indian Thar Desert. The average mass transport rate (kg m -1 day -1) or the total soil loss during hot summer months was significantly higher at the overgrazed rangeland site than at the controlled grazing rangeland site. Therefore, protection of existing rangelands, which comprise about 80% geographical area of the Indian Thar Desert may check the land degradation process due to wind erosion.

  3. Mineral dust transport in the Arctic modelled with FLEXPART

    NASA Astrophysics Data System (ADS)

    Groot Zwaaftink, Christine; Grythe, Henrik; Stohl, Andreas

    2016-04-01

    Aeolian transport of mineral dust is suggested to play an important role in many processes. For instance, mineral aerosols affect the radiation balance of the atmosphere, and mineral deposits influence ice sheet mass balances and terrestrial and ocean ecosystems. While many efforts have been done to model global dust transport, relatively little attention has been given to mineral dust in the Arctic. Even though this region is more remote from the world's major dust sources and dust concentrations may be lower than elsewhere, effects of mineral dust on for instance the radiation balance can be highly relevant. Furthermore, there are substantial local sources of dust in or close to the Arctic (e.g., in Iceland), whose impact on Arctic dust concentrations has not been studied in detail. We therefore aim to estimate contributions of different source regions to mineral dust in the Arctic. We have developed a dust mobilization routine in combination with the Lagrangian dispersion model FLEXPART to make such estimates. The lack of details on soil properties in many areas requires a simple routine for global simulations. However, we have paid special attention to the dust sources on Iceland. The mobilization routine does account for topography, snow cover and soil moisture effects, in addition to meteorological parameters. FLEXPART, driven with operational meteorological data from European Centre for Medium-Range Weather Forecasts, was used to do a three-year global dust simulation for the years 2010 to 2012. We assess the model performance in terms of surface concentration and deposition at several locations spread over the globe. We will discuss how deposition and dust load patterns in the Arctic change throughout seasons based on the source of the dust. Important source regions for mineral dust found in the Arctic are not only the major desert areas, such as the Sahara, but also local bare-soil regions. From our model results, it appears that total dust load in the

  4. Mineral composition of TALDICE aeolian ice core dust by means of synchrotron radiation XAS and XRF techniques

    NASA Astrophysics Data System (ADS)

    Marcelli, A.; Cibin, G.; Sala, M.; Hampai, D.; Maggi, V.; Marino, F.; Delmonte, B.

    2009-04-01

    In this work we present the first accurate non-destructive comparison of the mineral composition of atmospheric dusts contained in a deep ice core from Antarctica using synchrotron radiation. Different mineral assemblages reaching glaciated areas could be correlated to sources areas starting from the knowledge of the dust composition. In this investigation we demonstrate the possibility to characterize with SR the mineral composition of the dust in order to perform its geochemical characterization and to understand the pattern of the transport and the trajectories of the aerosol. This study has been focused on the elemental characterization and the identification of the iron oxidation state of aeolian Antarctic dust by means of synchrotron radiation X-Ray Fluorescence and X-Ray Absorption Spectroscopy. A set of twelve ice samples from the TALDICE (TD, 72˚ 46'S, 159˚ 04'E, 2316 m a.s.l., mean accumulation rate 80 kg*m-2*yr-1) ice core, corresponding to the warm climatic period, Holocene, and to the cold climatic period, Marine Isotopic Stage 3 (MIS 3) have been measured. To obtain both the elemental composition and the iron oxidation state of the mineral dust we performed experiments on specially prepared samples at the Stanford Synchrotron Radiation Lightsource (SSRL) laboratory in the framework of the Proposal N.3082B. Actually, melted ice samples were filtered and then mineral particles were deposited onto Nuclepore polycarbonate membranes in a 1000 class clean room under a 100 class laminar flow bench for both XRF and XAS experiments. A dedicated HV experimental chamber, that allows performing different type of experimental technique on very low absorber concentration samples was developed and tested in Italy. The original experimental setup, including an in-vacuum sample micromanipulator and a special alignment and docking sample system was installed at the beamline 10-2 at SSRL. For the x-ray detection a 7 mm2 high sensitive Silicon Drift Detector was

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

    PubMed

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

    2006-10-01

    The Sahara-Sahel Dust Corridor runs from Chad to Mauritania and expels huge amounts of mineral aerosols into the Atlantic Ocean. Data on samples collected from Algeria, Chad, Niger, and Western Sahara illustrate how corridor dust mineralogy and chemistry relate to geological source and weathering/transport history. Dusts sourced directly from igneous and metamorphic massifs are geochemically immature, retaining soluble cations (e.g., K, Na, Rb, Sr) and accessory minerals containing HFSE (e.g., Zr, Hf, U, Th) and REE. In contrast, silicate dust chemistry in desert basins (e.g., Bodélé Depression) is influenced by a longer history of transport, physical winnowing (e.g., loss of Zr, Hf, Th), chemical leaching (e.g., loss of Na, K, Rb), and mixing with intrabasinal materials such as diatoms and evaporitic salts. Mineral aerosols blown along the corridor by the winter Harmattan winds mix these basinal and basement materials. Dusts blown into the corridor from sub-Saharan Africa during the summer monsoon source from deeply chemically weathered terrains and are therefore likely to be more kaolinitic and stripped of mobile elements (e.g., Na, K, Mg, Ca, LILE), but retain immobile and resistant elements (e.g., Zr, Hf, REE). Finally, dusts blown southwestwards into the corridor from along the Atlantic Coastal Basin will be enriched in carbonate from Mesozoic-Cenozoic marine limestones, depleted in Th, Nb, and Ta, and locally contaminated by uranium-bearing phosphate deposits. PMID:16600327

  6. Rates and environmental controls of aeolian dust accumulation, Athabasca River Valley, Canadian Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Hugenholtz, Chris H.; Wolfe, Stephen A.

    2010-09-01

    Despite an abundance of sedimentary archives of mineral dust (i.e. loess) accumulations from cold, humid environments, the absence of contemporary process investigations limits paleoenvironmental interpretations in these settings. Dust accumulations measured at Jasper Lake, a seasonally-filled reach of the glacially-fed Athabasca River in the Canadian Rocky Mountains, are some of the highest contemporary rates recorded to date. High deposition rates, including a maximum of 27,632 kg ha -1 month -1, occur during river low-flow periods, but even the lowest deposition rates, occurring during bankfull periods, exceed other contemporary rates of deposition. High rates of dust deposition may be attributed to geomorphic and climatic controls affecting sediment supply, availability and transport, and biologic factors affecting accumulation. Localized confinement of the Jasper River by tributary river alluvial fans has caused channel expansion upstream, and formation of the shallow depositional basin known as Jasper Lake. This localized sedimentary basin, coupled with large seasonal water level fluctuations and suitably high wind speeds, favors seasonal dust production. In addition, a dense source-proximal coniferous forest stand encourages high dust accumulation, via increased aerodynamic roughness and airflow deceleration. The forest stand also appears to act as an efficient dust filter, with the interception and storage of dust by the forest canopy playing a significant role with regards to secondary fallout and sediment accumulation. Overall, these results provide new insights on the environmental controls of dust entrainment and accumulation in cold, humid settings, and help clarify controls on the formation of Holocene river-sourced loess deposits.

  7. 2008 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.; Sondossi, Hoda A.; Hazel, Joseph E., Jr.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.; Vanaman, Karen M.

    2009-01-01

    This report presents measurements of weather parameters and aeolian (windblown) sand transport made in 2008 near selected archaeological sites in the Colorado River corridor through Grand Canyon, Ariz. The quantitative methods and data discussed here form a basis for monitoring ecosystem processes that affect archeological-site stability. Combined with forthcoming work to evaluate landscape evolution at nearby archaeological sites, these data can be used to document the relationship between physical processes, including weather and aeolian sand transport, and their effects on the physical integrity of archaeological sites. Data collected in 2008 reveal event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Broad seasonal changes in aeolian sediment flux are also apparent at most study sites. The continuation of monitoring that began in 2007, and installation of equipment at several new sites in early 2008, allowed evaluation of the effects of the March 2008 high-flow experiment (HFE) on aeolian sand transport. At two of the nine sites studied, spring and summer winds reworked 2008 HFE sandbars to form new aeolian dunes, at which sand moved inland toward larger, well-established dune fields. At the other seven study sites, neither dune formation nor enhanced sand transport after the HFE were observed. At several of those sites, dominant wind directions in spring 2008 were not oriented such that much HFE sand would have moved inland; at other sites, lack of increased inland sand flux is attributable to lack of sandbar enlargement near the study sites or to inhibition of sand movement by vegetation or local topography.

  8. New Method for Estimation of Aeolian Sand Transport Rate Using Ceramic Sand Flux Sensor (UD-101)

    PubMed Central

    Udo, Keiko

    2009-01-01

    In this study, a new method for the estimation of aeolian sand transport rate was developed; the method employs a ceramic sand flux sensor (UD-101). UD-101 detects wind-blown sand impacting on its surface. The method was devised by considering the results of wind tunnel experiments that were performed using a vertical sediment trap and the UD-101. Field measurements to evaluate the estimation accuracy during the prevalence of unsteady winds were performed on a flat backshore. The results showed that aeolian sand transport rates estimated using the developed method were of the same order as those estimated using the existing method for high transport rates, i.e., for transport rates greater than 0.01 kg m−1 s−1. PMID:22291553

  9. 2009 weather and aeolian sand-transport data from the Colorado River corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.; Sondossi, Hoda A.; Dealy, Timothy P.; Hazel, Joseph E., Jr.; Fairley, Helen C.; Brown, Christopher R.

    2010-01-01

    This report presents measurements of weather parameters and aeolian sand transport made in 2009 near selected archeological sites in the Colorado River corridor through Grand Canyon, Ariz. The quantitative methods and data discussed here form a basis for monitoring ecosystem processes that affect archeological-site stability. Combined with forthcoming work to evaluate landscape evolution at nearby archeological sites, these data can be used to document the relation between physical processes, including weather and aeolian sand transport, and their effects on the physical integrity of archeological sites. Data collected in 2009 reveal event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Broad seasonal changes in aeolian sediment flux are also apparent at most study sites. Differences in weather patterns between 2008 and 2009 included an earlier spring windy season, greater spring precipitation even though 2009 annual rainfall totals were in general substantially lower than in 2008, and earlier onset of the reduced diurnal barometric-pressure fluctuations commonly associated with summer monsoon conditions. Weather patterns in middle to late 2009 were apparently affected by a transition of the ENSO cycle from a neutral phase to the El Ni?o phase. The continuation of monitoring that began in 2007, and installation of additional equipment at several new sites in early 2008, allowed evaluation of the effects of the March 2008 high-flow experiment (HFE) on aeolian sand transport. As reported earlier, at 2 of the 9 sites studied, spring and summer winds in 2008 reworked the HFE sandbars to form new aeolian dunes, where sand moved inland toward larger, well-established dune fields. Observations in 2009 showed that farther inland migration of the dune at one of those two sites is likely inhibited by vegetation. At the other location, the new aeolian dune form was found to have moved 10 m inland toward older, well

  10. Aeolian processes on Venus

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1989-01-01

    This review assesses the potential aeolian regime on Venus as derived from spacecraft observations, laboratory simulations, and theoretical considerations. The two requirements for aeolian processes (a supply of small, loose particles and winds of sufficient strength to move them) appear to be met on Venus. Venera 9, 10, 13, and 14 images show particles considered to be sand and silt size on the surface. In addition, dust spurts (grains 5 to 50 microns in diameter) observed via lander images and inferred from the Pioneer-Venus nephalometer experiments suggest that the particles are loose and subject to movement. Although data on near surface winds are limited, measurements of 0.3 to 1.2 m/sec from the Venera lander and Pioneer-Venus probes appear to be well within the range required for sand and dust entrainment. Aeolian activity involves the interaction of the atmosphere, lithosphere, and loose particles. Thus, there is the potential for various physical and chemical weathering processes that can effect not only rates of erosion, but changes in the composition of all three components. The Venus Simulator is an apparatus used to simulate weathering under venusian conditions at full pressure (to 112 bars) and temperature (to 800 K). In one series of tests, the physical modifications of windblown particles and rock targets were assessed and it was shown that particles become abraded even when moved by gentle winds. However, little abrasion occurs on the target faces. Thus, compositional signatures for target rocks may be more indicative of the windblown particles than of the bedrock. From these and other considerations, aeolian modifications of the venusian surface may be expected to occur as weathering, erosion, transportation, and deposition of surficial materials. Depending upon global and local wind regimes, there may be distinctive sources and sinks of windblown materials. Radar imaging, especially as potentially supplied via the Magellan mission, may enable the

  11. Aeolian bedforms, yardangs, and indurated surfaces in the Tharsis Montes as seen by the HiRISE Camera: Evidence for dust aggregates

    NASA Astrophysics Data System (ADS)

    Bridges, N. T.; Banks, M. E.; Beyer, R. A.; Chuang, F. C.; Noe Dobrea, E. Z.; Herkenhoff, K. E.; Keszthelyi, L. P.; Fishbaugh, K. E.; McEwen, A. S.; Michaels, T. I.; Thomson, B. J.; Wray, J. J.

    2010-01-01

    HiRISE images of Mars with ground sampling down to 25 cm/pixel show that the dust-rich mantle covering the surfaces of the Tharsis Montes is organized into ridges whose form and distribution are consistent with formation by aeolian saltation. Other dusty areas near the volcanoes and elsewhere on the planet exhibit a similar morphology. The material composing these "reticulate" bedforms is constrained by their remote sensing properties and the threshold curve combined with the saltation/suspension boundary, both of which vary as a function of elevation (atmospheric pressure), particle size, and particle composition. Considering all of these factors, dust aggregates are the most likely material composing these bedforms. We propose that airfall dust on and near the volcanoes aggregates in situ over time, maybe due to electrostatic charging followed by cementation by salts. The aggregates eventually reach a particle size at which saltation is possible. Aggregates on the flanks are transported downslope by katabatic winds and form linear and "accordion" morphologies. Materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds, forming an interlinked "honeycomb" texture. In many places on and near the volcanoes, light-toned, low thermal inertia yardangs and indurated surfaces are present. These may represent "duststone" formed when aggregates reach a particle size below the threshold curve, such that they become stabilized and subsequently undergo cementation.

  12. Aeolian bedforms, yardangs, and indurated surfaces in the Tharsis Montes as seen by the HiRISE Camera: Evidence for dust aggregates

    USGS Publications Warehouse

    Bridges, N.T.; Banks, M.E.; Beyer, R.A.; Chuang, F.C.; Noe Dobrea, E.Z.; Herkenhoff, K. E.; Keszthelyi, L.P.; Fishbaugh, K.E.; McEwen, A.S.; Michaels, T.I.; Thomson, B.J.; Wray, J.J.

    2010-01-01

    HiRISE images of Mars with ground sampling down to 25 cm/pixel show that the dust-rich mantle covering the surfaces of the Tharsis Montes is organized into ridges whose form and distribution are consistent with formation by aeolian saltation. Other dusty areas near the volcanoes and elsewhere on the planet exhibit a similar morphology. The material composing these "reticulate" bedforms is constrained by their remote sensing properties and the threshold curve combined with the saltation/suspension boundary, both of which vary as a function of elevation (atmospheric pressure), particle size, and particle composition. Considering all of these factors, dust aggregates are the most likely material composing these bedforms. We propose that airfall dust on and near the volcanoes aggregates in situ over time, maybe due to electrostatic charging followed by cementation by salts. The aggregates eventually reach a particle size at which saltation is possible. Aggregates on the flanks are transported downslope by katabatic winds and form linear and "accordion" morphologies. Materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds, forming an interlinked "honeycomb" texture. In many places on and near the volcanoes, light-toned, low thermal inertia yardangs and indurated surfaces are present. These may represent "duststone" formed when aggregates reach a particle size below the threshold curve, such that they become stabilized and subsequently undergo cementation. ?? 2009 Elsevier Inc.

  13. Atmospheric dust in modern soil on aeolian sandstone, Colorado Plateau (USA): Variation with landscape position and contribution to potential plant nutrients

    USGS Publications Warehouse

    Reynolds, R.; Neff, J.; Reheis, M.; Lamothe, P.

    2006-01-01

    Rock-derived nutrients in soils originate from both local bedrock and atmospheric dust, including dust from far-distant sources. Distinction between fine particles derived from local bedrock and from dust provides better understanding of the landscape-scale distribution and abundance of soil nutrients. Sandy surficial deposits over dominantly sandstone substrates, covering vast upland areas of the central Colorado Plateau, typically contain 5-40% silt plus clay, depending on geomorphic setting and slope (excluding drainages and depressions). Aeolian dust in these deposits is indicated by the presence of titanium-bearing magnetite grains that are absent in the sedimentary rocks of the region. Thus, contents of far-traveled aeolian dust can be estimated from magnetic properties that primarily reflect magnetite content, such as isothermal remanent magnetization (IRM). Isothermal remanent magnetization was measured on bulk sediment samples taken along two transects in surficial sediment down gentle slopes away from sandstone headwalls. One transect was in undisturbed surficial sediment, the other in a setting that was grazed by domestic livestock until 1974. Calculation of far-traveled dust contents of the surficial deposits is based on measurements of the magnetic properties of rock, surficial deposits, and modern dust using a binary mixing model. At the undisturbed site, IRM-based calculations show a systematic down-slope increase in aeolian dust (ranging from 2% to 18% of the surface soil mass), similar to the down-slope increase in total fines (18-39% of surface soil mass). A combination of winnowing by wind during the past and down-slope movement of sediment likely accounts for the modern distribution of aeolian dust and associated nutrients. At the previously grazed site, dust also increases down slope (5-11%) in sediment with corresponding abundances of 13-25% fines. Estimates of the contributions of aeolian dust to the total soil nutrients range widely

  14. 2007 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.

    2009-01-01

    Weather data constitute an integral part of ecosystem monitoring in the Colorado River corridor and are particularly valuable for understanding processes of landscape change that contribute to the stability of archeological sites. Data collected in 2007 are reported from nine weather stations in the Colorado River corridor through Grand Canyon, Ariz. The stations were deployed in February and March 2007 to measure wind speed and direction, rainfall, air temperature, relative humidity, and barometric pressure. Sand traps near each weather station collect windblown sand, from which daily aeolian sand-transport rates are calculated. The data reported here were collected as part of an ongoing study to test and evaluate methods for quantifying processes that affect the physical integrity of archeological sites along the river corridor; as such, these data can be used to identify rainfall events capable of causing gully incision and to predict likely transport pathways for aeolian sand, two landscape processes integral to the preservation of archeological sites. Weather data also have widespread applications to other studies of physical, cultural, and biological resources in Grand Canyon. Aeolian sand-transport data reported here, collected in the year before the March 2008 High-Flow Experiment (HFE) at Glen Canyon Dam, represent baseline data against which the effects of the 2008 HFE on windblown sand will be compared in future reports.

  15. Reconstructing pathways of aeolian pollen transport to the marine sediments along the coastline of SW Africa

    NASA Astrophysics Data System (ADS)

    Dupont, Lydie M.; Wyputta, Ulrike

    2003-02-01

    The distribution of pollen in marine sediments is used to reconstruct pathways of terrigenous input to the oceans and provides a record of vegetation change on adjacent continents. The wind transport routes of aeolian pollen is comprehensively illustrated by clusters of trajectories. Isobaric, 4-day backward trajectories are calculated using the modelled wind-field of ECHAM3, and are clustered on a seasonal basis to estimate the main pathways of aeolian particles to sites of marine cores in the south-eastern Atlantic. Trajectories and clusters based on the modelled wind-field of the Last Glacial Maximum hardly differ from those of the present-day. Trajectory clusters show three regional, and two seasonal patterns, determining the pathways of aeolian pollen transport into the south-eastern Atlantic ocean. Mainly, transport out of the continent occurs during austral fall and winter, when easterly and south-easterly winds prevail. South of 25°S, winds blow mostly from the west and southwest, and aeolian terrestrial input is very low. Generally, a good latitudinal correspondence exists between the distribution patterns of pollen in marine surface sediments and the occurrence of the source plants on the adjacent continent. The northern Angola Basin receives pollen and spores from the Congolian and Zambezian forests mainly through river discharge. The Zambezian vegetation zone is the main source area for wind-blown pollen in sediments of the Angola Basin, while the semi-desert and desert areas are the main sources for pollen in sediments of the Walvis Basin and on the Walvis Ridge. A transect of six marine pollen records along the south-western African coast indicates considerable changes in the vegetation of southern Africa between glacial and interglacial periods. Important changes in the vegetation are the decline of forests in equatorial Africa and the north of southern Africa and a northward shift of winter rain vegetation along the western escarpment.

  16. Tracking aeolian transport patterns across a mega-nourishment using video imagery

    NASA Astrophysics Data System (ADS)

    Wijnberg, Kathelijne; van der Weerd, Lianne; Hulscher, Suzanne

    2014-05-01

    Coastal dune areas protect the hinterland from flooding. In order to maintain the safety level provided by the dunes, it may be necessary to artificially supply the beach-dune system with sand. How to best design these shore nourishments, amongst others with respect to optimal dune growth on the long-term (decadal scale), is not yet clear. One reason for this is that current models for aeolian transport on beaches appear to have limited predictive capabilities regarding annual onshore sediment supply. These limited capabilities may be attributed to the lack of appropriate input data, for instance on moisture content of the beach surface, or shortcomings in process understanding. However, it may also be argued that for the long-term prediction of onshore aeolian sand supply from the beach to the dunes, we may need to develop some aggregated-scale transport equations, because the detailed input data required for the application of process-scale transport equations may never be available in reality. A first step towards the development of such new concepts for aggregated-scale transport equations is to increase phenomenological insight into the characteristics and number of aeolian transport events that account for the annual volume changes of the foredunes. This requires high-frequency, long-term data sets to capture the only intermittently occurring aeolian transport events. Automated video image collection seems a promising way to collect such data. In the present study we describe the movement (direction and speed) of sand patches and aeolian bed forms across a nourished site, using video imagery, to characterize aeolian transport pathways and their variability in time. The study site is a mega-nourishment (21 Mm3 of sand) that was recently constructed at the Dutch coast. This mega-nourishment, also referred to as the Sand Motor, is a pilot project that may potentially replace current practice of more frequently applying small scale nourishments. The mega

  17. Aeolian Transport of Ferrous Minerals in the North Polar Region of Mars

    NASA Astrophysics Data System (ADS)

    Horgan, Briony H.; Bell, J. F., III; Noe Dobrea, E. Z.

    2008-09-01

    The north polar region of Mars contains two areally extensive, dark aeolian deposits: (1) the north polar sand seas that encircle the polar cap, and (2) the north polar veneers that drape over the polar cap itself. Both deposits have been previously identified as containing hydrated minerals, and exhibit spectral features consistent with gypsum, a hydrated calcium sulfate. However, it remains unclear whether or not the deposits have exchanged material in the past, and whether any portion of either deposit is active today. In this study, we are investigating the distribution of ferrous minerals in the north polar region using near-infrared spectral data from the Mars Express OMEGA imaging spectrometer. Ferrous minerals, such as olivine and pyroxene, are most readily identified by the presence of a wide absorption band around 1 micron. Observations of changes in the position, depth, and shape of the 1 micron absorption band may be used to track changes in composition. We have identified the presence of a strong 1 micron band in the veneers, the sand sea, and the surrounding plains. Initial results from study regions in Chasma Boreale and Olympia Planum suggest that the position, depth, and shape of the band do vary within the veneers and sand seas. These spectral differences may reflect: (1) compositional variations between the sources of the deposits, (2) the degree of modern activity of the deposits, or (3) changes in mineralogy due to breakdown of softer minerals during aeolian transport over long distances. By extending our observations of these spectral changes to the entire north polar region, we may be able to help identify sources of aeolian material, transport pathways, and the most active regions of modern aeolian activity.

  18. Aeolian sediment transport and landforms in managed coastal systems: A review

    NASA Astrophysics Data System (ADS)

    Jackson, Nancy L.; Nordstrom, Karl F.

    2011-11-01

    Humans modify beaches and dunes and aeolian transport potential by building structures, walking or driving, extracting resources, accommodating recreation, increasing levels of protection, removing storm deposits, or restoring landforms and habitats. The effects of human adjustments are reviewed here in terms of cross-shore zones because humans tend to compartmentalize landforms and habitats through their actions and regulations. Common human modifications in the beach zone include nourishing beaches, constructing shore protection structures and raking to remove litter. Modifications affecting the dune zone include altering the location, size and stability of dunes using sand-trapping fences, vegetation plantings and bulldozers or replacing dunes with shore-parallel structures. Modifications affecting the landward zone include buildings, roads, and parking lots. Landform and habitat resilience requires levels of dynamism and geomorphic complexity not often found in managed systems. Preserving or enhancing dynamism and complexity requires emphasis on innovative designs rooted in geomorphological and aeolian research. Future studies are suggested for: (1) quantifying the effect of small and large scale beach nourishment designs and sediment characteristics on dune initiation, development, and evolution; (2) quantifying the extent to which size and spacing of human structures and landform alterations inhibit sediment transfers alongshore or onshore; (3) identifying the advantages or disadvantages of "niche" dunes formed by structures; (4) providing quantitative data on the effects of raking or driving on the beach; (5) identifying the role of aeolian landforms on private properties; and (6) identifying alternative ways of employing sand fences and vegetation plantings to increase topographic and habitat diversity.

  19. A 37,000-year environmental magnetic record of aeolian dust deposition from Burial Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Dorfman, J. M.; Stoner, J. S.; Finkenbinder, M. S.; Abbott, M. B.; Xuan, C.; St-Onge, G.

    2015-11-01

    Environmental magnetism and radiocarbon dating of Burial Lake sediments constrain the timing and magnitude of regional aeolian deposition for the Noatak region of western Arctic Alaska for the last ˜37,000 years. Burial Lake (68.43°N, 159.17°W, 21.5 m water depth) is optimally located to monitor regional dust deposition because it is perched above local drainage and isolated from glacial processes. Cores collected in the summer of 2010 were studied through the application of magnetizations and progressive alternating field (AF) demagnetization of u-channel samples, with additional data provided by computed tomography (CT) derived density, hysteresis measurements, isothermal remanent magnetization (IRM) acquisition experiments, organic carbon content, biogenic silica, physical grain size, radiocarbon dating of wood, seeds, and plant macrofossils, point source magnetic susceptibility, and X-ray fluorescence (XRF). With similar magnetic properties to regional Alaskan loess deposits, low coercivity, highly magnetic material deposited during the late-Pleistocene contrasts with a high coercivity, weakly magnetic component found throughout the record, consistent with locally-derived detritus. The relative proportion of low coercivity to high coercivity magnetic material, defined by the S-Ratios, is used to reconstruct the regional input of dust to the basin over time. A four-fold decrease in the low coercivity component through the deglacial transition is interpreted to reflect diminished dust input to the region. Comparisons with potential sources of dust show that the timing of deposition in Burial Lake is largely consistent with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. The influence from subaerial exposure of continental shelves cannot be ruled out as a significant far-field source of dust to interior Alaska during the Last Glacial Maximum (LGM), but is unlikely to have been the sole source, or to

  20. The Effect of Particle Density on Aeolian Transport

    NASA Technical Reports Server (NTRS)

    Williams, S. H.; Greeley, R.

    1985-01-01

    A set of experiments using a wide range of particle densities was performed in an open-circuit, terrestrial-atmospheric-pressure wind tunnel at Arizona State University. The results show that saltation flux equations derived for typical geologic material overpredict the flux of low-density particles. Walnut shells (approximately 1.1 g/cc) were used in the experiment and correspond to volcanic ash or ice. Less mass is transported by the wind in the case of low particle density because the style of transport is different. There is a direct, counter-intuitive relationship between particle density and transport height. Measurements of the vertical distribution of material show that the low-density walnut shells travel in a zone within 10 cm of the surface while high-density (approximately 4.5 g/cc) chromite particles travel as 50 cm. Furthermore, the overall saltation rate of the chromite is approximately four times greater than the walnut shells at the same freestream wind speed, even though the wind is much further above threshold for the walnut shells.

  1. The global transport of dust

    USGS Publications Warehouse

    Griffin, Dale W.; Kellogg, C.A.; Garrison, V.H.; Shinn, E.A.

    2002-01-01

    By some estimates as much as two billion metric tons of dust are lifted into the Earth's atmosphere every year. Most of this dust is stirred up by storms, the more dramatic of which are aptly named dust storms. But more than mere dirt is carried aloft. Drifting with the suspended dust particles are soil pollutants such as herbicides and pesticides and a significant number of microorganisms-bacteria, viruses and fungi. We can gain some appreciation of how much microbial life is actually floating in our atmosphere by performing a quick calculation. There are typically about one million bacteria per gram of soil, but let's be conservative and suppose there are only 10,000 bacteria per gram of airborne sediment. Assuming a modest one billion metric tons of sediment in the atmosphere, these numbers translate into a quintillion (1018) sediment-borne bacteria moving around the planet each year-enough to form a microbial bridge between Earth and Jupiter. Here we consider what we've learned about the airborne transport of sediment across the globe, and review some of the remarkable studies in this reemerging field that had it origins more than 100 years ago.

  2. Aeolian sediment transport over gobi: Field studies atop the Mogao Grottoes, China

    NASA Astrophysics Data System (ADS)

    Tan, Lihai; Zhang, Weimin; Qu, Jianjun; Wang, Junzhan; An, Zhishan; Li, Fang

    2016-06-01

    This paper reports on field studies of aeolian sediment transport over a rough surface-gobi atop the Mogao Grottoes, China, in relation to sediment entrainment, saltation mass flux and transport rate prediction. Wind speeds were measured with five cup anemometers at different heights and sediment entrainment and transport measured with horizontal and vertical sediment traps coupled to weighing sensors, where sediment entrainment and transport were measured synchronously with wind speeds. Four sediment transport events, with a measurement duration ranging between 2.5 and 11 h, were studied. The entrainment threshold determined by the horizontal sediment trap varied between 0.28 and 0.33 m s-1, and the effect of non-erodible roughness elements-gravels increased the entrainment threshold approximately by 1.8 times compared to a uniform sand surface. Unlike the non-monotone curve shape of sediment flux density profile over gobi measured in wind tunnels, the flux density profile measured in the field showed an exponential form. Aeolian sediment transport over gobi could be predicted by an Owen-type saltation model: q = Aρ /gu∗ (u∗2 - u∗t2) , where q is sediment transport rate, A is a soil-related dimensionless factor, u∗ is the friction velocity, u∗t is the threshold friction velocity, g is the gravitational acceleration, ρ is the air density. This study indicates that the sediment flux sampling using horizontal and vertical sediment traps coupled to weighing sensors provides a practical method to determine values for A in this model that can provide good estimates of sediment transport rates in gobi areas.

  3. Variation in aeolian environments recorded by the particle size distribution of lacustrine sediments in Ebinur Lake, northwest China.

    PubMed

    Ma, Long; Wu, Jinglu; Abuduwaili, Jilili

    2016-01-01

    Particle size analysis of lacustrine core sediments and atmospheric natural dust were conducted in the drainage area of Ebinur Lake in arid northwest China. Using a combination of (137)Cs and (210)Pb dating, a continuous record of aeolian transportation to the lake sediments and related factors over about the past 150 years was analyzed. Factor analysis revealed the particle-size distributions of riverine and aeolian sediments composed of the terrigenous materials of the lake deposits. Compared with the grain-size distributions of natural dust samples, the results showed that the coarser particle size fraction of lake sediments was mainly derived from the sediments that had experienced aeolian transport to the drainage surface, and the finer sediments came from hydraulic inputs. Then, the method of variations in particle-size standard deviation was used to extract the grain size intervals with the highest variability along a sedimentary sequence. The coarser grain-size populations dominated the variation patterns of the sedimentary sequence. During the last 150 years, strong intensity aeolian transportation occurred during three periods, 1915-1935, 1965-1975 and since the beginning of the 2000s. The climate was dry around 1910s-1930s in this region associated with the appropriate dynamic condition, which provided the enhanced source materials and wind power for the aeolian dust transport. Since 1950s, the climate controlled the foundation of aeolian dust transport, and the aeolian dust transport won't be increased under the humid climate. PMID:27217996

  4. Contemporary geochemical composition and flux of aeolian dust to the San Juan Mountains, Colorado, United States

    NASA Astrophysics Data System (ADS)

    Lawrence, Corey R.; Painter, T. H.; Landry, C. C.; Neff, J. C.

    2010-09-01

    Dust deposition in the Rocky Mountains may be an important biogeochemical flux from upwind ecosystems. Seasonal (winter/spring) dust mass fluxes to the San Juan Mountains during the period from 2004 to 2008 ranged from 5 to 10 g m-2, with individual deposition events reaching as high as 2 g m-2. Dust deposited in the San Juan Mountains was primarily composed of silt- and clay-sized particles, indicating a regional source area. The concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations, whereas trace element concentrations were often enriched. In particular, dust collected from the San Juan Mountain snowpack was characterized by enrichments of heavy metals including As, Cu, Cd, Mo, Pb, and Zn. The mineral composition of dust partially explained dust geochemistry; however, based on results of a sequential leaching procedure it appeared that trace element enrichments were associated with the organic-, and not the mineral-, fraction of dust. Our observations show that the dust-derived fluxes of several nutrients and trace metals are substantial and, because many elements are deposited in a mobile form, could be important controls of vegetation, soil, or surface water chemistry. The flux measurements reported here are useful benchmarks for the characterization of ecosystem biogeochemical cycling in the Rocky Mountains.

  5. Discrete Element Method simulations of the saturation of aeolian sand transport

    NASA Astrophysics Data System (ADS)

    Pähtz, Thomas; Omeradžić, Amir; Carneiro, Marcus V.; Araújo, Nuno A. M.; Herrmann, Hans J.

    2015-03-01

    The saturation length of aeolian sand transport (Ls), characterizing the distance needed by wind-blown sand to adapt to changes in the wind shear, is essential for accurate modeling of the morphodynamics of Earth's sandy landscapes and for explaining the formation and shape of sand dunes. In the last decade, it has become a widely accepted hypothesis that Ls is proportional to the characteristic distance needed by transported particles to reach the wind speed (the "drag length"). Here we challenge this hypothesis. From extensive numerical Discrete Element Method simulations, we find that, for medium and strong winds, Ls∝Vs2/g, where Vs is the saturated value of the average speed of sand particles traveling above the surface and g is the gravitational constant. We show that this proportionality is consistent with a recent analytical model, in which the drag length is just one of four similarly important length scales relevant for sand transport saturation.

  6. Transport of Alaskan Dust into the Gulf of Alaska and Comparison with Similar High-Latitude Dust Environments

    NASA Technical Reports Server (NTRS)

    Crusium, John; Levy, Rob; Wang, Jun; Campbell, Rob; Schroth, Andrew W.

    2012-01-01

    Transport of Alaskan dust into the Gulf of Alaska and comparison with similar high-latitude dust environments. An airborne flux of the micronutrient iron, derived from dust originating from coastal regions may be an important contributor of iron to the Gulf of Alaska's (GoA) oligotrophic waters. Dust blowing off glacier termini and dry riverbeds is a recurring phenomenon in Alaska, usually occurring in the autumn. Since previous studies assumed that dust originating in the deserts of Asia was the largest source of . airborne iron to the GoA, the budget of aeolian deposition of iron needs to be reassessed. Since late 20 I 0, our group has been monitoring dust activity using satellites over the Copper River Delta (CRD) where the most vigorous dust plumes have been observed. Since 2011, sample aerosol concentration and their composition are being collected at Middleton Island (100km off shore of CRD). This presentation will show a summary of the ongoing dust observations and compare with other similar environments (Patagonia, Iceland) by showing case studies. Common features will be highlighted

  7. Dust transport into Martian polar latitudes

    NASA Technical Reports Server (NTRS)

    Murphy, J. R.; Pollack, J. B.

    1992-01-01

    The presence of suspended dust in the Martian atmosphere, and its return to the planet's surface, is implicated in the formation of the polar layered terrain and the dichotomy in perennial CO2 polar cap retention in the two hemispheres. A three dimensional model was used to study Martian global dust storms. The model accounts for the interactive feedbacks between the atmospheric thermal and dynamical states and an evolving radiatively active suspended dust load. Results from dust storm experiments, as well as from simulations in which there is interest in identifying the conditions under which surface dust lifting occurs at various locations and times, indicate that dust transport due to atmospheric eddy motions is likely to be important in the arrival of suspended dust at polar latitudes. The layered terrain in both polar regions of Mars is interpreted as the reality of cyclical episodes of volatile (CO2, H2O) and dust deposition.

  8. Physicochemical Characterization of Aeolian Mine Tailings Dust in the Southwest USA

    NASA Astrophysics Data System (ADS)

    Betterton, E. A.; Barbaris, B.; Conant, W.; Csavina, J.; Gao, S.; Lund, L.; Rheinheimer, P.; Saez, E.; Wonaschutz, A.

    2008-12-01

    Census data reveal that the Southwest is the fastest growing region of the USA, while NOAA GFDL coupled- model results suggest that precipitation is expected to decline in the same region over the coming decades. Besides the obvious impact on water resources, the drier conditions will most likely also result in increased atmospheric dust loads that could impact the health of a rapidly increasing population. This year the US EPA began site assessment and remediation at two mine tailings piles in Arizona contaminated with arsenic, lead, chromium and cadmium. The first is located in the twin towns of Hayden and Winkleman, and the second at the Iron King mine near Humbolt. At a concentration of approximately 0.1 microgram per cubic meter, the level of arsenic in PM10 collected at Hayden/Winkelman sometimes exceeds the Arizona ambient hazardous air pollutant standard (HAPS) by several orders of magnitude. Lead, cadmium and chromium are also sometimes orders of magnitude higher than the HAPS. A top priority is to determine the physicochemical speciation of wind-blown dust as a function of particle diameter because this information can a) help with source apportionment of airborne pollutants (e.g., smelter emissions vs. tailings dust), and b) help to assess the potential health impacts of contaminated dust, since deposition efficiency in human lungs is a strong function of particle diameter. We will present the chemical and physical characteristics of mine tailings dust collected with 10-stage multiple orifice uniform deposit impactors (MOUDI) located at Hayden/Winkleman and Iron King. We will also present scanning mobility particle spectrometer (SMPS) data obtained from the same sites. The MOUDI yields particle composition by size fraction (0.056-18 micrometer aerodynamic diameter) while the SMPS yields particle number by size fraction (0.0025 to 1.0 micrometer diameter). Size selective characteristics such as these have never been previously reported for mine tailings

  9. Dust Charging and Transport on Surfaces

    NASA Astrophysics Data System (ADS)

    Wang, X.; Robertson, S.; Horányi, M.

    2011-11-01

    In this paper, we review laboratory studies of dust transport on surfaces in plasmas, performed for a number of different mechanisms: 1) Dust particles were levitated in plasma sheaths by electrostatic forces balancing the gravitational force. 2) Dust was observed to spread over and lift off a surface that repels electrons in a plasma. 3) Dust was transported on surfaces having different secondary electron yields in plasma with an electron beam as a consequence of differential charging. 4) We also report a mechanism of dust transport by electric fields occurring at electron beam impact/shadow boundaries. These processes are candidates to explain the formation of dust ponds that were recently observed in craters on the asteroid Eros by the NEAR Shoemaker spacecraft.

  10. 2010 weather and aeolian sand-transport data from the Colorado River corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Dealy, Timothy P.; East, Amy E.; Fairley, Helen C.

    2014-01-01

    Measurements of weather parameters and aeolian sand transport were made in 2010 near selected archeological sites in the Colorado River corridor through Grand Canyon, Arizona. Data collected in 2010 indicate event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Differences in weather patterns between 2009 and 2010 included a slightly later spring windy season, greater spring precipitation and annual rainfall totals, and a later onset and length of the reduced diurnal barometric-pressure fluctuations commonly associated with summer monsoon conditions. The increase in spring precipitation was consistent with the 2010 spring El Niño conditions compared to the 2009 spring La Niña conditions, whereas the subsequent transition to an El Niño-Southern Oscillation neutral phase appeared to delay the reduction in diurnal barometric fluctuations.

  11. Temporal Dynamics of Sodic Playa Salt Crust Patterns: Implications for Aeolian Dust Emission Potential

    NASA Astrophysics Data System (ADS)

    Nield, J. M.; King, J.; Bryant, R. G.; Wiggs, G.; Eckardt, F. D.; Thomas, D. S.; Washington, R.

    2013-12-01

    Salt pans (or playas) are common in arid environments and can be major sources of windblown mineral dust, but there are uncertainties associated with their dust emission potential. These landforms typically form crusts which modify both their erosivity and erodibility by limiting sediment availability, modifying surface and aerodynamic roughness and limiting evaporation rates and sediment production. Here we show the relationship between seasonal surface moisture change and crust pattern development based on both remote-sensing and field surface and atmospheric measurements. We use high resolution (sub-cm) terrestrial laser scanning (TLS; ground-based lidar) surveys over weekly, monthly and annual timescales to accurately characterise crustal ridge thrusting and collapse. This can be as much as 2 mm/day on fresh pan areas that have recently been reset by flooding. Over a two month period, this ridge growth can change aerodynamic roughness length values by 6.5 mm. At the same time, crack densities across the surface increase and this raises the availability of erodible fluffy, low density dust source sediment stored below the crust layer. Ridge spaces are defined in the early stages of crust development, as identified by Fourier Transform analysis, but wider wavelengths become more pronounced over time. We present a conceptual model accounting for the driving forces (subsurface, surface and atmospheric moisture) and feedbacks between these and surface shape that lead to crust pattern trajectories between highly emissive degraded surfaces and less emissive ridged or continuous crusts. These findings improve our understanding of temporal changes in dust availability and supply from playa source regions.

  12. Planktonic foraminiferal rare earth elements as a potential new aeolian dust proxy

    NASA Astrophysics Data System (ADS)

    Chou, C.; Liu, Y.; Lo, L.; Wei, K.; Shen, C.

    2012-12-01

    Characteristics of rare earth elements (REEs) have widely been used as important tracers in many fields of earth sciences, including lithosphere research, environmental change, ocean circulation and other natural carbonate materials. Foraminiferal test REE signatures have been suggested to reflect ambient seawater conditions and serve as valuable proxies in the fields of paleoceanography and paleoclimate. Here we present a 60-kyr planktonic foraminifera Globigerinoides ruber (white, 250-300 μm) REE record of a sediment core MD05-2925 (9°20.61'S, 151°27.61'E, water depth 1660 m) from the Solomon Sea. The REE diagram shows two dominant sources of local seawater and nearby terrestrial input. The variability of foraminiferal REE/Ca time series is different from Mg/Ca-inferred sea surface temperature and δ18O records during the past 60-kyr. This inconsistency suggests that planktonic foraminiferal REE content cannot result only from changes in ice volume and temperature. Synchroneity between high planktonic foraminiferal REE content and Antarctic ice core dust amount record implies the same dust sources, probably from Australia or mainland China. Our results suggest that foraminiferal REE can potentially be as a new dust proxy and record dry/humid conditions at the source area.

  13. The Dynamics and Characteristics of Aeolian Dust in Dryland Central Asia: Possible Impacts on Respiratory Health in the Aral Sea Basin

    NASA Astrophysics Data System (ADS)

    Wiggs, G. F.; O'Hara, S.; Wegerdt, J.; van der Meer, J.; Small, I.; Hubbard, R.

    2003-12-01

    Over the last 40 years over 36,000 km2 of the former Aral Sea bed have been exposed creating a potentially significant aeolian dust source. It is widely believed, but little researched, that increased dust storm activity in the region has had a major impact on human health. In this paper we report the findings of a study into the link between dust exposure and respiratory health amongst children in the Autonomous Republic of Karakalpakstan, located on the southern shore of the Aral Sea. Data were collected over a 12 month period at 16 sites located within a broad transect running north to south through Karakalpakstan. At each site monthly measurements of dust deposition were undertaken linked with daily meteorological data at 6 stations. At 3 sites weekly measurements of PM10 were also carried out. Approximately 100 children (aged 7-10 years) were randomly selected within 5 km of each dust trap site and data were collected on their respiratory health and environmental exposures. Lung function data were also collected using a handheld spirometer. A linear regression model was used to predict lung function for the children incorporating variables for Forced Expiratory Volume in one second (FEV1), age, gender, height and weight and we estimated the impact of dust deposition rates on the odds of having abnormal lung function using logistic regression. The findings indicate that dust deposition rates across the region are high with sites located near the former shore of the sea being the worst affected. For these northerly regions the former Aral Sea bed is the most likely source of dust. The situation for the rest of the country seems to be far more complex. In these regions it appears that local sources (agricultural fields, abandoned irrigation grounds, overgrazed dunes, and unpaved roads) and more distant sources to the south and south-west represent significant sediment providers, particularly in the early summer when agricultural fields are ploughed. We found some

  14. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

    NASA Technical Reports Server (NTRS)

    Marshall, J. R.; Borucki, J.; Bratton, C.

    1999-01-01

    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

  15. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

    NASA Technical Reports Server (NTRS)

    Marshall, J. R.; Borucki, J.; Bratton, C.

    1999-01-01

    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

  16. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

    NASA Astrophysics Data System (ADS)

    Marshall, J. R.; Borucki, J.; Bratton, C.

    1999-09-01

    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

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

    USGS Publications Warehouse

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

    2006-01-01

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

  18. Mineral dust transport to the Sierra Nevada, California: Loading rates and potential source areas

    NASA Astrophysics Data System (ADS)

    Vicars, William C.; Sickman, James O.

    2011-03-01

    The transport and deposition of aeolian dust represents an important material input pathway for many marine and terrestrial ecosystems and may be an ecologically significant source of exogenous phosphorus (P) to alpine lakes. In order to assess the abundance and elemental composition of atmospheric mineral dust over the Sierra Nevada of California, we collected size-fractionated atmospheric particulate matter (PM) samples during July 2008 to March 2009 at a mixed conifer site located in Sequoia National Park. PM concentrations were at their highest levels during the dry season, averaging 8.8 ± 3.7 and 11.1 ± 7.5 μg m-3 for the coarse (1 μm < Da < 15 μm) and fine (Da < 1 μm) fractions, respectively, while winter months were characterized by low (<1 μg m-3) PM concentrations in both size fractions. Using Al as a diagnostic tracer for mineral aerosol, we observed a significant and uniform contribution (50-80%) from aeolian dust to the total coarse PM load, whereas submicron particles contained comparatively little crustal material (7-33%). The mass concentrations of elements (Fe, Ca, Mg, P, and V) in the coarse PM fraction were significantly correlated with Al throughout the study, and coarse PM exhibited elemental signatures that were temporally consistent and distinguishable from those of other sites. Conversely, higher elemental enrichments were observed in the fine PM fraction for Fe, V, and P, indicating a greater contribution from anthropogenic emissions to the fine particle load. Fe/Al and Fe/Ca ratios suggest a mixture of mineral dust from regional agricultural activities and long-range transport of mineral dust from Asia. Asian sources comprised 40-90% of mineral dust in July 2008 and then declined to between 10 and 30% in August and early September.

  19. Dust emission from different sol types and geomorphic units in the Sahara - implications for modeling dust emission and transport

    NASA Astrophysics Data System (ADS)

    Crouvi, Onn; Schepanski, Kerstin; Amit, Rivka; Gillespie, Alan; Enzel, Yehouda

    2014-05-01

    Mineral dust plays multiple roles in mediating physical and biogeochemical exchanges among the atmosphere, land and ocean, and thus is an active component of the global climate system. To estimate the past, current, and future impacts of dust on climate, sources of dust and their erodibility should be identified. The Sahara is the major source of dust on Earth. Based on qualitative analysis of remotely sensed data with low temporal resolution, the main sources of dust that have been identified are topographic depressions comprised of dry lake and playa deposits in hyprarid regions. Yet, recent studies cast doubts on these as the major sources and call for a search for others. Moreover, the susceptibility of soils to aeolian erosion (wind land erodibility) in the Sahara is still poorly known. In this study we identify and determine the soil types and geomorphic units most important as Saharan dust sources by correlating between the number of days with dust storms (NDS), derived from remote-sensing data of high temporal resolution, with the distribution of the soil types/geomorphic units. During 2006-8 the source of over 90% of the NDS was sand dunes, leptosols, calcisols, arenosols, and rock debris. Few dust storms originated from dry lake beds and playas. Land erodibility by wind for each soil type/geomorphic unit was estimated by a regression of the NDS and the number of days with high-speed wind events; the regression is relatively high for sand dunes and gypsisols. We use these regressions to differentiate between sources of dust that are supply-limited to those that are transport-limited. We propose that the fracturing of saltating sand and the removal of clay coatings from sand grains through eolian abrasion is the dominant dust-emission mechanism for the sand-rich areas covering large portion of the Sahara. Our results also explain the increased dustiness during the last glacial period, when sand dunes activity has been more common than during the Holocene

  20. Robotic Measurement of Aeolian Processes

    NASA Astrophysics Data System (ADS)

    Roberts, S.; Duperret, J. M.; Jerolmack, D. J.; Lancaster, N.; Nikolich, G.; Shipley, T. F.; Van Pelt, R. S.; Zobeck, T. M.; Koditschek, D. E.

    2015-12-01

    Local and regional measurements of sand transport and dust emission in complex natural settings presently lack spatiotemporal resolution adequate to inform models relevant for land management, climate policy, and the basic science of geomorphology. Deployments of wind, sand and dust sensors sophisticated enough to begin unpacking the complex relations among wind turbulence, surface roughness, sand flux and dust emission remain largely stationary. Aerial observations from satellites, planes and even UAVs help fill in, but none of these modalities offer the hope of "capturing the action" by being at the right place at the right time relative to the highly localized nature of sediment transport during wind storms. We have been developing a legged robot capable of rapidly traversing desert terrain, and are now adapting it to serve as a platform for scientific instrumentation. We aim to field a semi-autonomous, reactive mobile sensory package suited to the needs of aeolian science that can address the limitations of existing alternatives. This presentation reports on early trials in the Jornada LTER and White Sands National Monument aimed at gathering measurements of airflow and rates of sand transport on a dune face, assessing the role of roughness elements such as vegetation in modifying the wind shear stresses incident on the surface, and estimating erosion susceptibility in a natural arid soil. We will solicit ideas from the audience about other potentially interesting and viable measurement targets. Future close collaboration between aeolian, cognitive and robotics scientists such as we hope to promote through this presentation may yield machines with scientifically relevant sensory suites possessing sufficient autonomy to operate in-situ at the most intense episodes of wind and sediment movement under conditions far too uncomfortable and hazardous for human presence.

  1. Mineral dust transport toward Hurricane Helene (2006)

    NASA Astrophysics Data System (ADS)

    Schwendike, Juliane; Jones, Sarah C.; Vogel, Bernhard; Vogel, Heike

    2016-05-01

    This study investigates the transport of mineral dust from its source regions in West Africa toward the developing tropical cyclone Helene (2006) and diagnoses the resulting properties of the air influencing the tropical cyclonegenesis. The model system COSMO-ART (Consortium for Small-Scale Modelling-Aerosols and Reactive Trace gases) in which the emission and transport of mineral dust as well as the radiation feedback are taken into account, was used. The emission of mineral dust between 9 and 14 September 2006 occurred in association with the relatively strong monsoon flow and northeasterly trade winds, with gust fronts of convective systems over land, and with the Atlantic inflow. Additionally, increased surface wind speed was linked to orographical effects at the Algerian Mountains, Atlas Mountains, and the Hoggar. The dust, as part of the Saharan air layer, is transported at low levels by the monsoon flow, the Harmattan, the northeasterly trade winds, and the monsoon trough, and is transported upward in the convergence zone between Harmattan and monsoon flow, in the baroclinic zone along the West African coastline, and by convection. At around 700 hPa the dust is transported by the African easterly jet. Dry and dust-free air is found to the north-northwest of the developing tropical depression due to descent in an anticyclone. Based on the model data, it was possible to distinguish between dry (from the anticyclone), dry and dusty (from the Harmattan and northeasterly trade winds), and dusty and moist air (from the monsoon flow and in the tropical depression due to convection).

  2. Vertical structure of aeolian turbulence in a boundary layer with sand transport

    NASA Astrophysics Data System (ADS)

    Lee, Zoe S.; Baas, Andreas C. W.

    2016-04-01

    originating from the top of the boundary layer, indicating a downwards direction of eddy motion. While directionality of turbulence cannot be definitively determined, our results indicate that the top-down turbulence model is a suitable explanation, further supported by the presence of 'incomplete' eddies which originate at higher elevations but fail to extend to the surface. This provides the first evidence in support of a top down turbulence model as observed in aeolian geomorphology, and we present preliminary findings on its relationship to sand transport activity. Lee, Z.S., Baas, A.C.W. (2016) Variable and conflicting shear stress estimates inside a boundary layer with sediment transport. Earth Surface Processes and Landforms; DOI: 10.1002/esp.3829

  3. Martian aeolian processes, sediments, and features

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Lancaster, Nicholas; Lee, Steven; Thomas, Peter

    1992-01-01

    In this review of the aeolian regime on Mars, consideration is given to the sources and characteristics of the particles that are involved in aeolian processes and the winds that are required to set grains into motion. Dust storms are reviewed and previous observations and the mechanisms of dust-storm generation are assessed. Various aeolian features, including dunes and albedo features, as well as windblown mantle deposits are discussed. In planning for future missions to Mars, aeolian processes must be taken into account. Surface modifications by the wind and windblown deposits can influence remote-sensing observations, affect sampling strategies, and have detrimental effects on manned and unmanned spacecraft on the surface.

  4. Dust Levitation and Transport Near Surfaces

    NASA Astrophysics Data System (ADS)

    Sickafoose, A. A.; Colwell, J. E.; Horanyi, M.; Robertson, S.

    2002-12-01

    There are many examples of active dust transport near surfaces in the solar system: dust grains suspended above the lunar surface, spokes observed in Saturn's rings, and recent images of infilled craters from the NEAR spacecraft at Eros. Electrostatic dust levitation and transport have also been theorized to occur on Mercury, asteroids, and comets. Dusty regoliths are produced by the interplanetary micrometeoroid flux on nearly all airless bodies in the solar system. Therefore, understanding dust charging, levitation, and dynamics above surfaces is important for interpreting remote sensing data and analyzing the evolution of most planetary surfaces. Objects in a plasma, such as planetary bodies in the solar wind, charge to a floating potential determined by the balance between charging currents in the local plasma environment. The primary charging currents are due to collection of electrons and ions from the plasma, photoemission, and secondary electron emission. When photoemission is the dominant charging process, a photoelectron sheath forms near the surface of the object. Positively charged particles released from the surface can levitate above the surface at a height where the gravitational force is balanced by the electric force. In cases where secondary electron emission and photoemission are weak, objects will become negatively charged due to electron collection and will be surrounded by a plasma sheath. Negatively charged dust grains from these surfaces can levitate in the electric field created by the plasma sheath. Dust levitation and transport near surfaces in the solar system is thought to be primarily due to the interaction between charged dust particles and a photoelectron or plasma sheath on the surface. We report the results of experiments on the levitation and transport of dust particles in an argon plasma sheath above a flat, conducting surface. Levitation experiments are performed using monodisperse polystyrene DVB microbeads. Transport

  5. Southeastward Dust Transport during the 16-24 March 2006 Asian Dust Event

    NASA Astrophysics Data System (ADS)

    Tsai, F.; Liu, T.; Hsu, S.; Chen, W.; Tu, J.

    2012-04-01

    Synoptic analyses and regional dust models are applied to analyze the dust measurements obtained during the Asian dust events from 16 to 24 March, 2006, in order to understand the controlling mechanism leading to the dust transport far southeastward of the continent. The southeastward transported dust concentrations measured over Taiwan are traced back to their source areas. By tracing the dust loaded air parcels, the synoptic characteristics of the dust event during generation, transport, and dissipation are inspected and compared with an eastward transported event. It has been found that the synoptic mechanism, rather than the emission intensity, leads to the high dust concentration far southeastward off the continent. Most southeastward moving dust clouds are generated behind the surface front in the descent regions and then transported behind a deep lower-level trough, in which the prevailing northerlies or northwesterlies lead to the southeastward dust transported into the tropics. Without a deep lower-level trough, the dust clouds tend to be transported eastward. Surface lidar observations also show descent of the dust concentrations during their southeastward transport. After moving offshore, the anticyclonic circulation in the leading edge of the surface high circulates the dust parcels ahead of the high-pressure center in a southwestward direction towards the seashore off the Southeast China. With the deceleration of the wind speed, the dust clouds then slowly dissipate over the tropics of the Western Pacific, thus providing nutrients to the marine phytoplanktons.

  6. Modeling aeolian transport in response to succession, disturbance and future climate: Dynamic long-term risk assessment for contaminant redistribution

    NASA Astrophysics Data System (ADS)

    Breshears, David D.; Kirchner, Thomas B.; Whicker, Jeffrey J.; Field, Jason P.; Allen, Craig D.

    2012-01-01

    Aeolian sediment transport is a fundamental process redistributing sediment, nutrients, and contaminants in dryland ecosystems. Over time frames of centuries or longer, horizontal sediment fluxes and associated rates of contaminant transport are likely to be influenced by succession, disturbances, and changes in climate, yet models of horizontal sediment transport that account for these fundamental factors are lacking, precluding in large part accurate assessment of human health risks associated with persistent soil-bound contaminants. We present a simple model based on empirical measurements of horizontal sediment transport (predominantly saltation) to predict potential contaminant transport rates for recently disturbed sites such as a landfill cover. Omnidirectional transport is estimated within vegetation that changes using a simple Markov model that simulates successional trajectory and considers three types of short-term disturbances (surface fire, crown fire, and drought-induced plant mortality) under current and projected climates. The model results highlight that movement of contaminated soil is sensitive to vegetation dynamics and increases substantially (e.g., > fivefold) when disturbance and/or future climate are considered. The time-dependent responses in horizontal sediment fluxes and associated contaminant fluxes were sensitive to variability in the timing of disturbance, with longer intervals between disturbance allowing woody plants to become dominant and crown fire and drought abruptly reducing woody plant cover. Our results, which have direct implications for contaminant transport and landfill management in the specific context of our assessment, also have general relevance because they highlight the need to more fully account for vegetation dynamics, disturbance, and changing climate in aeolian process studies.

  7. Modeling aeolian transport in response to succession, disturbance and future climate: Dynamic long-term risk assessment for contaminant redistribution

    USGS Publications Warehouse

    Breshears, D.D.; Kirchner, T.B.; Whicker, J.J.; Field, J.P.; Allen, C.D.

    2012-01-01

    Aeolian sediment transport is a fundamental process redistributing sediment, nutrients, and contaminants in dryland ecosystems. Over time frames of centuries or longer, horizontal sediment fluxes and associated rates of contaminant transport are likely to be influenced by succession, disturbances, and changes in climate, yet models of horizontal sediment transport that account for these fundamental factors are lacking, precluding in large part accurate assessment of human health risks associated with persistent soil-bound contaminants. We present a simple model based on empirical measurements of horizontal sediment transport (predominantly saltation) to predict potential contaminant transport rates for recently disturbed sites such as a landfill cover. Omnidirectional transport is estimated within vegetation that changes using a simple Markov model that simulates successional trajectory and considers three types of short-term disturbances (surface fire, crown fire, and drought-induced plant mortality) under current and projected climates. The model results highlight that movement of contaminated soil is sensitive to vegetation dynamics and increases substantially (e.g., > fivefold) when disturbance and/or future climate are considered. The time-dependent responses in horizontal sediment fluxes and associated contaminant fluxes were sensitive to variability in the timing of disturbance, with longer intervals between disturbance allowing woody plants to become dominant and crown fire and drought abruptly reducing woody plant cover. Our results, which have direct implications for contaminant transport and landfill management in the specific context of our assessment, also have general relevance because they highlight the need to more fully account for vegetation dynamics, disturbance, and changing climate in aeolian process studies. ?? 2011.

  8. Global Dust Transport as Observed by A-Train Satellites

    NASA Astrophysics Data System (ADS)

    Luo, Tao; Wang, Zhien; Zhang, Damao

    2016-06-01

    This paper presented a new height-resolved view of global dust transport based on 2007-2010 A-train observations. First, a new dust identification methodology was developed to improve optically thin dust layer detection. Second a new dust partition methodology was developed and applied to CALIPSO lidar measurements to derive dust partitions in external mixed aerosols. These new approaches allow a new view of global dust distribution from dense dust layers near the strong source regions to the optically thin, but significant dust layers from the point of view of aerosol-cloud interactions, over the weak source regions, the transport areas, and the upper troposphere. The results will not only help us to better understand global dust transport and dust-cloud interactions, but also provide critical information for model evaluations and improvements.

  9. Radiation transport in dust in disk geometry

    NASA Technical Reports Server (NTRS)

    Chun, Ming Leung

    1986-01-01

    The main objective of the research program is twofold: (1) to develop a computer code to solve the problem of scattering, absorption and emission of photons by dust grains in a dusty medium with 2 dimensional disk geometry, and (2) to study the various physical and geometrical effects of 2 dimensional radiation transport on the thermal structure and radiation field. These tasks were accomplished and are briefly summarized. The method for solving the radiation transport problem in disk geometry is a generalization of the quasi-diffusion method (QDM) previously developed by the author.

  10. Aeolian Morphodynamics of Loess Landscapes

    NASA Astrophysics Data System (ADS)

    Mason, J. A.; Hanson, P. R.; Sweeney, M.; Loope, H. M.; Miao, X.; Lu, H.

    2012-12-01

    Striking aeolian landforms characterize loess landscapes of the Great Plains and Upper Mississippi Valley, USA, shaped in Late Pleistocene environments with many characteristics of modern deserts including large active dunefields. Similar aeolian morphodynamics are evident in northern China and the Columbia Basin, USA, and are clearly important for interpreting the paleoenvironmental record of loess. Four zones spanning the upwind margin of thick loess can be defined from landforms and surficial deposits. From upwind to downwind, they are: A) A largely loess-free landscape, with patchy to continuous aeolian sand mantling bedrock. B) Patchy loess deposits, often streamlined and potentially wind-aligned, intermingled with dunes and sand sheets; interbedding of loess and sand may be common. C) Thick, coarse loess with an abrupt upwind edge, with troughs, yardang-like ridges, and/or wind-aligned scarps recording large-scale wind erosion. D) Thinner, finer loess with little evidence of post-depositional wind erosion. The degree of development and spatial scale of these zones varies among the loess regions we studied. To explain this zonation we emphasize controls on re-entrainment of loess by the wind after initial deposition, across gradients of climate and vegetation. The role of saltating sand in dust entrainment through abrasion of fine materials is well known. Using the Portable In situ Wind Erosion Laboratory (PI-SWERL), we recently demonstrated that unvegetated Great Plains loess can also be directly entrained under wind conditions common in the region today (Sweeney et al., 2011, GSA Abstracts with Programs, Vol. 43, No. 5, p. 251). Rainfall-induced crusts largely prevent direct entrainment in fine loess, but appear less effective in coarse loess. We propose that in zone A, any loess deposited was both abraded by saltating sand and directly re-entrained, so none accumulated. Sparse vegetation in this zone was primarily an effect of climate, but the resulting

  11. The Enigma of Lunar Dust Transport

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Stubbs, T. J.; Vondrak, R. R.; Delory, G. T.; Halekas, J. S.

    2011-01-01

    We will review the highly contrasting points of view regarding the ability of fine dust grains to become transported in the near-space lunar environment. While Surveyor and Apollo camera images suggest the presence of a horizon glow that has been provocatively interpreted as levitated and/or lofted dust, there is contrasting geological evidence to indicate that surface regolith has not been moved in a substantial way. While electric forces have been suggested as a driver for grain dynamics, recent detailed modeling of near-surface non-monotonic potentials would suggest grains could not get to large heights. While lofting models require submicron grains to hold/contain 100's of elementary charges, it can be shown analytical1y that a grain residing on a flat surface would have an extremely low probability of having even a single electron on its surface, Can these diametrically opposing viewpoints be reconciled? We will review the pros and cons on both sides. and suggest that the UVS and LDEX instrument on LADEE will provide key new insights on dust transport at the Moon.

  12. The origin of bimodal grain-size distribution for aeolian deposits

    NASA Astrophysics Data System (ADS)

    Lin, Yongchong; Mu, Guijin; Xu, Lishuai; Zhao, Xue

    2016-03-01

    Atmospheric dust deposition is a common phenomenon in arid and semi-arid regions. Bimodal grain size distribution (BGSD) (including the fine component and coarse component) of aeolian deposits has been widely reported. But the origin of this pattern is still debated. Here, we focused on the sedimentary process of modern dust deposition, and analyzed the grain size distribution of modern dust deposition, foliar dust, and aggregation of the aeolian dust collected in Cele Oasis, southern margin of Tarim Basin. The results show that BGSD also appear in a dust deposition. The content of fine components (<20 μm size fraction) change with temporal and spatial variation. Fine component from dust storm is significant less than that from subsequent floating dust. Fine component also varies with altitude. These indicate that modern dust deposition have experienced changing aerodynamic environment and be reworked during transportation and deposition, which is likely the main cause for BGSD. The dusts from different sources once being well-mixed in airflow are hard to form multiple peaks respectively corresponding with different sources. In addition, the dust deposition would appear BGSD whether aggregation or not. Modern dust deposition is the continuation of ancient dust deposition. They both may have the same cause of formation. Therefore, the origin of BGSD should provide a theoretical thinking for reconstructing the palaeo-environmental changes with the indicator of grain size.

  13. Magnetic characteristics of aeolian and fluvial sediments and onset of dust accumulation at Lake Yoa (northern Chad) during the Holocene

    NASA Astrophysics Data System (ADS)

    Just, Janna; Kröpelin, Stefan; Karls, Jens; Rethemeyer, Janet; Melles, Martin

    2014-05-01

    samples will be analyzed using a cryogenic magnetometer. The magnetic grain size will be used to identify the initiation of increased accumulation of aeolian material. By analyzing Isothermal Remanent Magnetization acquisition curves, fluvial and aeolian end-members will be characterized in terms of magnetic mineralogy. Furthermore, a possible climate-induced impact on the formation of pedogenetic magnetic minerals in the source area of fluvial and aeolian sediments will be evaluated by a comparison of the environmental magnetic with organic proxies.

  14. Development of a Global Tropospheric Aerosol Chemical Transport Model MASINGAR and its Application to the Dust Storm Forecasting

    NASA Astrophysics Data System (ADS)

    Tanaka, T. Y.

    2002-12-01

    We are developing a new three-dimensional aerosol chemical transport model coupled with the MRI/JMA98 GCM, named Model of Aerosol Species IN the Global AtmospheRe (MASINGAR), for the study of atmospheric aerosols and related trace species. MASINGAR treats four major aerosol species that include nss-sulfate, carbonaceous, mineral dust, and sea-salt aerosols. The model accounts for large-scale advective transport, subgrid-scale eddy diffusive and convective transport, surface emission and deposition, wet deposition, as well as chemical reactions. The advective transport is calculated using the semi-Lagrangian transport scheme. Parameterization of convective transport is based on the convective mass flux by Arakawa-Schubert scheme. The space and time resolution of the model are variable, with a standard resolution of T42 (2.8ox2.8o) and 30 levels (up to 0.8hPa). In addition, the model has a built-in four-dimensional data assimilation with assimilated meteorological field, which enables the model to perform a realistic simulation on a specific period and short-period forecast of aerosols. The model was applied to the numerical forecasting of dust storm in spring, 2002, when the first intensive observational period of Aeolian Dust Experiment on the Climatic impact (ADEC) project was conducted. The model simulation of mineral dust aerosol suggests that the synoptic scale aerosol events can be simulated by MASINGAR.

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

    USGS Publications Warehouse

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Region-Resolved Global Dust Transport

    NASA Astrophysics Data System (ADS)

    Wagstrom, K.; Lamancusa, C.

    2015-12-01

    Currently the functionality required to directly track the transport of regionally tagged chemical species does not exist in global models as it does in select regional models. While some global models contain adjoint formulations that allow for the concentration sensitivities of a given region to be determined, this method does not show how pollution from a given region impacts all the areas around it. The closest that global models get to directly tracking regionally tagged species have primarily been through brute-force or zero-out applications, which tend to be either very limited in scope or have significant impacts on chemical reaction rates. Specifically the tagged species approach captures both the non-linear behaviors within the model, missed in the brute-force method, and the full scope of the chemical reactions, missed in the zero-out applications. With the ability to easily tag pollutants based on their source region it becomes realistic to estimate the impacts that sub-continent scale regions can have on air pollution levels. Depending on the resolution of both the model and available population data, it is possible to use this functionality to estimate exposure resulting from region specific pollution. In this study we have implemented a module within the GEOS-Chem 3-D atmospheric composition model that will allow for this type of flexible region tagging for non-reactive species as a step towards being able to track species point of origin through chemical reactions. Functionally this module behaves similarly to the Particulate Matter Source Apportionment Technology (PSAT) feature within the Comprehensive Air Quality Model with Extensions (CAMx) which tracks the species utilizing the various fluxes in each grid cell in the model. Utilizing this module we have divided the sub-Saharan into several distinct regions in order to track how dust from each region is transported around the globe. The results are compared to identify regional differences in how

  19. Dust-Particle Transport in Tokamak Edge Plasmas

    SciTech Connect

    Pigarov, A Y; Krasheninnikov, S I; Soboleva, T K; Rognlien, T D

    2005-09-12

    Dust particulates in the size range of 10nm-100{micro}m are found in all fusion devices. Such dust can be generated during tokamak operation due to strong plasma/material-surface interactions. Some recent experiments and theoretical estimates indicate that dust particles can provide an important source of impurities in the tokamak plasma. Moreover, dust can be a serious threat to the safety of next-step fusion devices. In this paper, recent experimental observations on dust in fusion devices are reviewed. A physical model for dust transport simulation, and a newly developed code DUSTT, are discussed. The DUSTT code incorporates both dust dynamics due to comprehensive dust-plasma interactions as well as the effects of dust heating, charging, and evaporation. The code tracks test dust particles in realistic plasma backgrounds as provided by edge-plasma transport codes. Results are presented for dust transport in current and next-step tokamaks. The effect of dust on divertor plasma profiles and core plasma contamination is examined.

  20. Modeling aeolian transport of soil-bound plutonium: considering infrequent but normal environmental disturbances is critical in estimating future dose.

    PubMed

    Michelotti, Erika A; Whicker, Jeffrey J; Eisele, William F; Breshears, David D; Kirchner, Thomas B

    2013-06-01

    Dose assessments typically consider environmental systems as static through time, but environmental disturbances such as drought and fire are normal, albeit infrequent, events that can impact dose-influential attributes of many environmental systems. These phenomena occur over time frames of decades or longer, and are likely to be exacerbated under projected warmer, drier climate. As with other types of dose assessment, the impacts of environmental disturbances are often overlooked when evaluating dose from aeolian transport of radionuclides and other contaminants. Especially lacking are predictions that account for potential changing vegetation cover effects on radionuclide transport over the long time frames required by regulations. A recently developed dynamic wind-transport model that included vegetation succession and environmental disturbance provides more realistic long-term predictability. This study utilized the model to estimate emission rates for aeolian transport, and compare atmospheric dispersion and deposition rates of airborne plutonium-contaminated soil into neighboring areas with and without environmental disturbances. Specifically, the objective of this study was to utilize the model results as input for a widely used dose assessment model (CAP-88). Our case study focused on low levels of residual plutonium found in soils from past operations at Los Alamos National Laboratory (LANL), in Los Alamos, NM, located in the semiarid southwestern USA. Calculations were conducted for different disturbance scenarios based on conditions associated with current climate, and a potential future drier and warmer climate. Known soil and sediment concentrations of plutonium were used to model dispersal and deposition of windblown residual plutonium, as a function of distance and direction. Environmental disturbances that affected vegetation cover included ground fire, crown fire, and drought, with reoccurrence rates for current climate based on site historical

  1. Wind Transport of Radionuclide- Bearing Dust, Peña Blanca, Chihuahua, Mexico

    NASA Astrophysics Data System (ADS)

    Velarde, R.; Goodell, P. C.; Gill, T. E.; Arimoto, R.

    2007-05-01

    This investigation evaluates radionuclide fractionation during wind erosion of high-grade uranium ore storage piles at Peña Blanca (50km north of Chihuahua City), Chihuahua, Mexico. The aridity of the local environment promotes dust resuspension by high winds. Although active operations ceased in 1983, the Peña Blanca mining district is one of Mexico`s most important uranium ore reserves. The study site contains piles of high grade ore, left loose on the surface, and separated by the specific deposits from which they were derived (Margaritas, Nopal I, and Puerto I). Similar locations do not exist in the United States, since uranium mining sites in the USA have been reclaimed. The Peña Blanca site serves as an analog for the Yucca Mountain project. Dust deposition is collected at Peña Blanca with BSNE sediment catchers (Fryrear, 1986) and marble dust traps (Reheis, 1999). These devices capture windblown sediment; subsequently, the sample data will help quantify potentially radioactive short term field sediment loss from the repository surface and determine sediment flux. Aerosols and surface materials will be analyzed and radioactivity levels established utilizing techniques such as gamma spectroscopy. As a result, we will be able to estimate how much radionuclide contaminated dust is being transported or attached geochemically to fine grain soils or minerals (e.g., clays or iron oxides). The high-grade uranium-bearing material is at secular equilibrium, thus the entire decay series is present. Of resulting interest is not only the aeolian transport of uranium, but also of the other daughter products. These studies will improve our understanding of geochemical cycling of radionuclides with respect to sources, transport, and deposition. The results may also have important implications for the geosciences and homeland security, and potential applications to public health. Funding for this project is provided in part via a NSF grant to Arimoto.

  2. Critical issues for modeling dust transport in tokamaks.

    PubMed

    Bacharis, Minas; Coppins, Michael; Allen, John E

    2010-08-01

    Dust produced in tokamaks is an important issue for fusion. Dust particles can introduce health and safety issues when in the same time can have an impact on reactor performance. Apart from the associated problems there are also potential benefits that make the better understanding of their behavior important. In this work the dust transport code Dust in TOKamakS will be used to explore the effect that variations in the plasma background and the physical model, describing the plasma-dust interaction, have on their predicted trajectories. PMID:20866922

  3. Micro-topographic analysis of shell pavements formed by aeolian transport in a wind tunnel simulation

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl; Li, Bailiang; Nash, David

    2012-12-01

    Beach surfaces containing shell materials represent one end-member of a range of environments in which armoring is the primary control on wind erosion. Unlike spheres and cylinders which have formed the basis of theoretical model formulation and much of the early work in wind tunnels, mollusc shells have complex and non-uniform shapes which vary with their orientation. Identification of shell perimeter, height and frontal area relative to the bed area (roughness density) is therefore a formidable task, but nonetheless is essential for modeling sediment entrainment from beach surfaces. A methodology is suggested in this paper for capturing and analyzing these geospatial data, in the context of a wind tunnel simulation designed to improve understanding of the geophysical processes involved in armoring. For deposits where non-erodible shells represent half of the volume of the parent material, the surface appears to be highly stable to wind erosion from the outset, although minor reworking of the intervening, erodible sediment does occur. In comparison, the shell coverage must increase to approximately 30% during wind erosion events in order for any given beach surface to stabilize, especially beach deposits with a low concentration of shells by volume. With suitable calibration, the Raupach shear stress partitioning model can be forced to perform well in predicting the threshold conditions for particle entrainment. However, this approach overlooks the pivotal involvement of particle impact and ricochet in the creation and sculpting of the armored bed. As a case in point, when the shells are removed from digital elevation models of armored beach surfaces formed in aeolian systems, the adjusted topography is not suggestive of the presence of coherent flow structures (e.g., horseshoe vortices and wedge shaped shelter areas) as assumed to exist in the stress partitioning approach for isolated flows. This would suggest that future work on the armoring of natural surfaces

  4. CALIPSO observations of changes in dust properties during transatlantic transport

    NASA Astrophysics Data System (ADS)

    Marshak, A.; Yang, W.; Varnai, T.; Kostinski, A. B.

    2015-12-01

    The vertical distribution of dust shape and size is highly important for understanding and estimating dust radiative forcing. We used CALIPSO nighttime datasets to examine the vertical structure and evolution of Saharan dust during transatlantic transport. The results show that most Saharan dust is lifted to high altitude and descends after traveling thousands of km-s. Initially, the depolarization ratio and color ratio of Saharan dust are uniformly distributed along altitude, suggesting vertically constant particle size and shape distributions. During transport, the depolarization ratio of Saharan dust drops at lower altitudes, suggesting that particle shapes become less irregular; while at relatively high altitudes, the depolarization ratio of dust increases during transport. The changes observed during transport likely come from the effects of gravitational sorting caused by variations in particle shape and size. A simple model with only two shapes qualitatively captures these features and confirms that shape-induced differential settling contribute significantly to the observed vertical stratification of dust properties. In addition, the effect of clouds on dust properties will be also discussed.

  5. The thermal structure of the atmospheric surface boundary layer on Mars as modified by the radiative effect of aeolian dust

    NASA Technical Reports Server (NTRS)

    Pallmann, A. J.

    1983-01-01

    A computational simulation, based on Mariner 9 data, was performed for the thermal characteristics of the Martian atmospheric surface boundary layer in clear and dust-filled conditions. A radiative transfer model consisting of the atmospheric enthalpy rate equation, the radiative flux integrated over the 0.2-50 microns, the solid angle interval, and 0.50 km altitudes, broken into 52 levels. Mariner 9 IR data for CO2 absorption lines were included in the form of a temperture-dependent equation, while the line-widths were interpreted in terms of the pressure dependene as well as temperature. The lines covered the regions from 1-50 microns and varying conditions of dust content in the atmosphere. Attention was given to the thermal coupling between the ground and the atmosphere. It was found that convective heat exchange develops quickly due to radiative heating of the Martian desert surface, but does not cool the surface because of the attenuated atmosphere. The model predictd the 100 K temperature variations in the dusty atmosphere, as observed by the Viking thermal mapper. It is suggested that radiative flux convergence is as important as convection at equivalent efficiencies.

  6. First X-Ray absorption spectroscopy results on Aeolian dust archived in Antarctica and Alpine firn cores

    NASA Astrophysics Data System (ADS)

    Marcelli, A.; Maggi, V.; Cibin, G.; Sala, M.; Marino, F.; Delmonte, B.

    2006-12-01

    We present the first x-ray absorption spectroscopy (XAS) data at the Fe K-edge collected on insoluble mineral dust from Talos Dome firn core (TDC, 159°04'E, 72°46'S, 2316 m a.s.l., mean accumulation rate 8 g cm-2 yr- 1), drilled in the framework of the International Trans Antarctic Scientific Expedition (ITASE), and from a Colle del Lys 2003 firn core (CDL03, 45°92'N, 7°86'E, 4248m a.s.l., mean accumulation rate 134 g cm-2 yr-1, Lys Glacier, Mt. Rosa, Italy). The low concentration of mineral particles, obtained by filtering each firn core melted samples on Nuclepore membranes in a 1000 class clean room, required a specific procedure to prepare the samples necessary to the successful collection of the XAS data. The firn samples were decontaminated in clean room under laminar flow bench by means of a ceramic knife and discarding the external part of the cores. Analyses of the insoluble particle content were performed by particle counter Beckman CounterãMultisizer III in order to defined concentration and size distribution of particles in each samples. A dedicated HV experimental chamber, devoted to the realization of XAS experiments on very low absorber concentration samples, was developed and realized in the framework of the CryoAlp collaboration at IMONT, the Italian National Institute for Mountains. The original experimental setup, thanks to the presence of an in-vacuum sample micromanipulator and special sample alignment and docking system installed for these experiments at the Stanford Synchrotron Radiation Laboratory at the beamline 6-2, allows both normal-incidence X-ray Fluorescence detection using a Ketek SDD detector having an energy resolution of about 150 eV and extremely low energy detection limit, and Total X-ray Reflection Fluorescence and Absorption Spectroscopy measurements. The high quality of the XANES experiments performed, using both normal incidence and Total Reflection XAS measurements, allowed recognizing iron-inclusion mineral fractions

  7. Size-differentiated chemical characteristics of Asian paleo dust: records from aeolian deposition on Chinese Loess Plateau.

    PubMed

    Wu, Feng; Chow, Judith C; An, Zhisheng; Watson, John G; Cao, Junji

    2011-02-01

    The Chinese Loess Plateau (CLP) receives and potentially contributes to Asian dust storms that affect particulate matter (PM) concentrations, visibility, and climate. Loess on the CLP has experienced little weathering effect and is regarded as an ideal record to represent geochemical characteristics of Asian paleo dust. Samples were taken from 2-, 9-, and 15-m depths (representing deposition periods from approximately 12,000 to approximately 200,000 yr ago) in the Xi Feng loess profile on the CLP. The samples were resuspended and then sampled through total suspended particulates (TSP), PM10, PM2.5, and PM1 (PM with aerodynamic diameters < approximately 30, 10, 2.5, and 1 microm, respectively) inlets onto filters for mass, elemental, ionic, and carbon analyses using a Desert Research Institute resuspension chamber. The elements Si, Ca, Al, Fe, K, Mg, water-soluble Ca (Ca2+), organic carbon, and carbonate carbon are the major constituents (> 1%) in loess among the four PM fractions (i.e., TSP, PM10, PM2.5, and PM1). Much of Ca is water soluble and corresponds with measures of carbonate, indicating that most of the calcium is in the form of calcium carbonate rather than other calcium minerals. Most of the K is insoluble, indicating that loess can be separated from biomass burning contributions when K+ is measured. The loess has elemental abundances similar to those of the upper continental crust (UCC) for Mg, Fe, Ti, Mn, V, Cr, and Ni, but substantially different ratios for other elements such as Ca, Co, Cu, As, and Pb. These suggest that the use of UCC as a reference to represent pure or paleo Asian dust needs to be further evaluated. The aerosol samples from the source regions have similar ratios to loess for crustal elements, but substantially different ratios for species from anthropogenic sources (e.g., K, P, V, Cr, Cu, Zn, Ni, and Pb), indicating that the aerosol samples from the geological-source-dominated environment are not a "pure" soil product as compared

  8. Quantifying the effects of European beach grass on aeolian sand transport over the last century: Bodega Marine Reserve, California

    NASA Astrophysics Data System (ADS)

    Cesmat, R.; Werner, S.; Smith, M. E.; Riedel, T.; Best, R.; Olyarnik, S.

    2012-12-01

    Introduction of European beach grass (Ammophila arenaria) to coastal dune systems of western North America induced significant changes to the transport and storage of sediment, and consequently the nesting habitat of the western snowy plover (Charadrius alexandrinus nivosus). At the Bodega Marine Reserve and Sonoma Coast State Park, Ammophila was introduced within the ~0.5 km2 dune area in the 1920's to limit the flux of sand through Bodega Harbor and agricultural land. To assess the potential impact of restoration efforts (Ammophila removal) on aeolian sediment flux, we measured sediment flux as a function of wind speeds and ground cover, and used these measurements to parameterize a spatial model for historical sand deposition Fine- to coarse-grained lithic to sub-lithic sand is delivered to the Bodega dune system from Salmon Creek beach, the down-shore terminus of a littoral system fed by the 3846 km2 Russian River catchment, several small (<100 km2) coastal catchments, and seacliff erosion. Littoral sediment traverses the 1.8 km wide dune system from NW to SE via aeolian transport. Ammophila colonization occurred initially adjacent to the shoreface, inducing deposition of a ~10 meter-high foredune and has subsequently encroached the ~0.5 km2 region between the foredune and Bodega Harbor. Comparison of historical topographic maps via raster subtraction indicates rapid construction of both the foredune and a ~15 meter-high transverse dune (Gaffney ridge) at the edge of the planted region. An average accumulation rate of ~4,000 m3/yr is indicated within the study swath by the preserved sediment volumes. Within the modern dune system, unvegetated areas exhibit 2-3 meter wavelength, ~1/2 meter amplitude mega-ripples, and the uppermost 2-10 cm consists of coarse-sand to granule-sized armor layer. In contrast, grain-sizes in vegetated areas are largely vertically homogenous. Open areas are typically 2-8 meters lower than adjacent vegetated areas, and show evidence for

  9. The physics of wind-blown sand and dust.

    PubMed

    Kok, Jasper F; Parteli, Eric J R; Michaels, Timothy I; Karam, Diana Bou

    2012-10-01

    The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan. PMID:22982806

  10. Lunar dust transport and potential interactions with power system components

    NASA Technical Reports Server (NTRS)

    Katzan, Cynthia M.; Edwards, Jonathan L.

    1991-01-01

    The lunar surface is covered by a thick blanket of fine dust. This dust may be readily suspended from the surface and transported by a variety of mechanisms. As a consequence, lunar dust can accumulate on sensitive power components, such as photovoltaic arrays and radiator surfaces, reducing their performance. In addition to natural mechanisms, human activities on the Moon will disturb significant amounts of lunar dust. Of all the mechanisms identified, the most serious is rocket launch and landing. The return of components from the Surveyor 3 provided a rare opportunity to observe the effects of the nearby landing of the Apollo 12 Lunar Module. The evidence proved that significant dust accumulation occurred on the Surveyor at a distance of 155 m. From available information on particle suspension and transport mechanisms, a series of models was developed to predict dust accumulation as a function of distance from the lunar module. The accumulation distribution was extrapolated to a future Lunar Lander scenario. These models indicate that accumulation is expected to be substantial even as far as 2 km from the landing site. Estimates of the performance penalties associated with lunar dust coverage and photovoltaic arrays are presented. Because of the lunar dust adhesive and cohesive properties, the most practical dust defensive strategy appears to be the protection of sensitive components from the arrival of lunar dust by location, orientation, or barriers.

  11. Lunar dust transport and potential interactions with power system components

    SciTech Connect

    Katzan, C.M.; Edwards, J.L.

    1991-11-01

    The lunar surface is covered by a thick blanket of fine dust. This dust may be readily suspended from the surface and transported by a variety of mechanisms. As a consequence, lunar dust can accumulate on sensitive power components, such as photovoltaic arrays and radiator surfaces, reducing their performance. In addition to natural mechanisms, human activities on the Moon will disturb significant amounts of lunar dust. Of all the mechanisms identified, the most serious is rocket launch and landing. The return of components from the Surveyor III provided a rare opportunity to observe the effects of the nearby landing of the Apollo 12 lunar module. The evidence proved that significant dust accumulation occurred on the Surveyor at a distance of 155 m. From available information on particle suspension and transport mechanisms, a series of models was developed to predict dust accumulation as a function of distance from the lunar module. The accumulation distribution was extrapolated to a future lunar lander scenario. These models indicate that accumulation is expected to be substantial even as far as 2 km from the landing site. Estimates of the performance penalties associated with lunar dust coverage on radiators and photovoltaic arrays are presented. Because of the lunar dust adhesive and cohesive properties, the most practical dust defensive strategy appears to be the protection of sensitive components from the arrival of lunar dust by location, orientation, or barriers.

  12. Seasonal and directional variations of aeolian sediment transport on the coarse-grained zibar surface of the Kumtagh Desert, NW China

    NASA Astrophysics Data System (ADS)

    Qian, Guangqiang; Yang, Zhuanling; Dong, Zhibao; Luo, Wanyin; Zhang, Zhengcai; Lu, Junfeng

    2016-04-01

    The aeolian process over fine to medium sand beds has been thoroughly discussed based on short-term, in-situ observations and wind tunnel tests. However, little is known about the long period variation of aeolian sediment transport as well as the geomorphological significance of saltating process, in particular, on the coarse-grained surface. By means of a segmented, eight-directional sand trap (SEDST) designed by the authors, the aeolian sediment transport on zibar surface was measured in the Kumtagh Desert of NW China. The SEDST has eight sub-traps faced to eight directions, each sub-trap contains a vertical array of samplers with four openings at 0 - 0.1 m, 0.1 - 0.2 m, 0.2 - 0.4 m and 0.4 - 1.0 m, respectively. Each opening is connected with an underground sand chamber. During the 1-yr field observation since May 2014, sediments were collected for six times with an interval of 1 to 3 months depending on the wind strength. The total weight of the captured sediments is 314.76 kg and most of them (54%) were transported within 0.1 m above the ground. The sediment transport rate ranges from 0.43 to 64.47 g/m.min for the six runs, the maximum transport rate occurred during the period of Aug to Oct 2014 with sediments from the north direction. The annual mean transport rate changes between 11.81 and 28.49 g/m.min and the sediments are mainly blown from the N, NE and NW directions. The resultant sediment transport direction (net transport) is SSE (172.92°), which implies the major sediment source direction. The sediment flux profiles can be fitted with the exponential decay function for six runs and all directions. Three groups can be identified from the gradients of the fitting curves, i.e. the N, NE and NW cluster, the S and SE cluster, as well as the E, SE and W cluster. Each cluster represents a particular combination of sediment source features and geomorphological settings that may significantly affect the formation process of zibars. The sediment transport

  13. Spatial and temporal patterns of aeolian sediment transport on an inland parabolic dune, Bigstick Sand Hills, Saskatchewan, Canada

    NASA Astrophysics Data System (ADS)

    Hugenholtz, C. H.; Wolfe, S. A.; Walker, I. J.; Moorman, B. J.

    2009-04-01

    Topographic changes from erosion pins and on-site meteorological data document the spatial and temporal patterns of aeolian sediment transport at monthly to annual timescales across an active parabolic dune within a vegetation-stabilized inland, prairie dune field. Over two years, the sediment budget, calculated from digital elevation models, shows that the total volume of erosion (9890 m 3) is greater than the amount of deposition (6990 m 3), indicating a net loss of 2900 m 3 of sediment (or ˜ 29% of eroded sediment) from the dune. Sediment erosion occurred mainly on the stoss slope (3600 m 3; ˜ 36% of eroded sediment), but also on the south (2100 m 3; ˜ 21%) and north sides of the dune head (1700 m 3; ˜ 17%), the blowouts along the arms (1740 m 3, ˜ 18%) and the crest (650 m 3; ˜ 7%). Erosion from the deflation basin is limited by surface roughness and armoring effects of a gravel lag deposit (100 m 3; ˜ 1%). Thus, the blowouts currently contribute to maintaining dune mobility because no other sediment input occurs from upwind. Sediment deposition onto the dune occurred primarily beyond the brink on the south and southeast lee slopes (5500 m 3; ˜ 80%), coinciding with the southeasterly resultant transport direction for November 2004-05. The net loss of about 2900 m 3 (˜ 29%) may be attributed to sediment carried in suspension over and beyond the dune. Correlation analysis between sediment transport and meteorological variables suggests that monthly to seasonal changes of surface conditions (e.g., vegetation cover, ground freezing, moisture) buffer the relative importance of temperature and precipitation on rates of sediment transport. Conversely, wind correlates well on a monthly to seasonal basis because it is a driver of transport under all types of surface conditions. Seasonal effects produce a complex interaction between wind, climate and surface conditions. This leads to a dynamic range of threshold velocities, which in turn causes spatial and

  14. Assessment of the Forward Contamination Risk of Mars by Clean Room Isolates from Space-Craft Assembly Facilities through Aeolian Transport - a Model Study

    NASA Astrophysics Data System (ADS)

    van Heereveld, Luc; Merrison, Jonathan; Nørnberg, Per; Finster, Kai

    2016-07-01

    The increasing number of missions to Mars also increases the risk of forward contamination. Consequently there is a need for effective protocols to ensure efficient protection of the Martian environment against terrestrial microbiota. Despite the fact of constructing sophisticated clean rooms for spacecraft assembly a 100 % avoidance of contamination appears to be impossible. Recent surveys of these facilities have identified a significant number of microbes belonging to a variety of taxonomic groups that survive the harsh conditions of clean rooms. These microbes may have a strong contamination potential, which needs to be investigate to apply efficient decontamination treatments. In this study we propose a series of tests to evaluate the potential of clean room contaminants to survive the different steps involved in forward contamination. We used Staphylococcus xylosus as model organism to illustrate the different types of stress that potential contaminants will be subjected to on their way from the spacecraft onto the surface of Mars. Staphylococcus xylosus is associated with human skin and commonly found in clean rooms and could therefore contaminate the spacecraft as a result of human activity during the assembling process. The path the cell will take from the surface of the spacecraft onto the surface of Mars was split into steps representing different stresses that include desiccation, freezing, aeolian transport in a Martian-like atmosphere at Martian atmospheric pressure, and UV radiation climate. We assessed the surviving fraction of the cellular population after each step by determining the integrated metabolic activity of the survivor population by measuring their oxygen consumption rate. The largest fraction of the starting culture (around 70 %) was killed during desiccation, while freezing, Martian vacuum and short-term UV radiation only had a minor additional effect on the survivability of Staphylococcus xylosus. The study also included a simulation

  15. Source and transportation of summer dust over the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Jia, Rui; Liu, Yuzhi; Chen, Bin; Zhang, Zhijuan; Huang, Jianping

    2015-12-01

    Satellite observational evidences (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations, CALIPSO) have presented that the Tibetan Plateau (TP) is subject to heavy loading of dust aerosols during summer. Combining back trajectory and weather system analyses, the source and transportation of summer Tibetan dust from 2007 to 2014 were investigated. The Tibetan dust is mainly from the Taklimakan Desert and partially from the Gurbantunggut Desert and Great Indian Thar Desert. Case study indicates that the meteorological conditions together with the topography benefit the dust emission adjacent to the TP and the transport toward the plateau. When a cold advection or front developed by strong cold advection passes, dust particles are emitted into the atmosphere from the Taklimakan and Gurbantunggut deserts and then transported to the northern slope of the TP with northeasterly wind induced by the Altai and Tian Shan mountains. For the period from 2007 to 2014, the correlation coefficient of the monthly frequencies of summer dust events over the TP and cold advection passing the Taklimakan and Gurbantunggut deserts were as high as 0.68 and 0.34, respectively. Differently, although the correlation is limited, much TP dust mobilized from the Great Indian Thar Desert is associated with the passing low-pressure system activity and generally polluted by anthropogenic aerosols. The polluted dust is further transported to the southern slope of the TP by the prevailing westerly wind. Investigations on the source and transportation of summer dust over the TP provide a solid foundation of data that can be used to reveal the role of TP dust in the radiation balance, hydrological cycle, and monsoon cycle in India and East Asia.

  16. Studies in Martian Aeolian Geology

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    2001-01-01

    This report gives the results from the investigation through March 15, 1999 for the first two years of the three year investigation (year 3 runs from March 1, 1999 to February 27, 2000). The investigation included three tasks, all involving windblown dust (particles a few micrometers in diameter) to simulate the aeolian regime on Mars. Experiments were conducted primarily in the Mars Surface Wind Tunnel (MARSWIT) at NASA-Ames Research Center.

  17. Evaluating global atmospheric transport of plutonium with dust aerosols

    NASA Astrophysics Data System (ADS)

    Velarde, R.; Arimoto, R.; Gill, T. E.; Kang, C.; Goodell, P.

    2009-12-01

    The resuspension of soils contaminated with radionuclides from nuclear weapons tests is a mechanism by which plutonium can be re-distributed throughout the environment. To better understand the global atmospheric transport of plutonium, we measured the activity of Pu in aerosol samples from four widely separated sites that receive dust from distant sources in both Asia and Africa. High-volume aerosol samples were collected from Barbados (2005 - 2006); Gosan, South Korea (2005 - 2006); Izaña, Canary Islands (1989 - 1996); and Mauna Loa Observatory, Hawaii (2005 - 2006) to evaluate the relationship between Pu activity and mineral dust concentrations (using crustal elements such as aluminum as a dust proxy). The activity of 239,240Pu (239Pu + 240Pu) in the aerosol samples was determined by alpha spectrometry following a series of chemical separations. Concentrations of other elements were determined by a variety of techniques. Pu activity was below the detection limit in many samples. In those samples where it was detected, the Gosan site had the highest dust concentrations and highest total plutonium activity, while Mauna Loa Observatory had the lowest dust concentrations and lowest 239,240Pu activity. The Izaña samples had the second highest concentrations of dust and plutonium activity, while Barbados had the third highest levels of both crustal aerosols and plutonium activity. The dust concentrations are consistent with previous observations at these remote sites, and we propose that the plutonium (primarily from past atmospheric nuclear weapons testing, much of which took place in arid lands) was deposited on erodible soil surfaces and subsequently transported as part of the overall mineral dust load. The results of this study have implications for the global transport and fate of Pu through its association with dust, the biogeochemical and environmental impacts of other substances associated with dust, and the workings of the dust cycle itself.

  18. Meso-scale aeolian transport of beach sediment via dune blowout pathways within a linear foredune

    NASA Astrophysics Data System (ADS)

    O'Keeffe, Nicholas; Delgado-Fernandez, Irene; Jackson, Derek; Aplin, Paul; Marston, Christopher

    2016-04-01

    The evolution of coastal foredunes is largely controlled by sediment exchanges between the geomorphic sub-units of the nearshore, beach, foredune and dune field. Although blowouts are widely recognised as efficient sediment transport pathways, both event-scale and meso-scale quantification of their utility in transferring beach sediments landwards is limited. Foredunes characterised by multiple blowouts may be more susceptible to coastline retreat through the enhanced landwards transport of beach or foredune sediments. To date, a key constraint for investigations of such scenarios has been the absence of accurate blowout sediment transport records. Here we use the Sefton coast in north-west England as a study area where an unprecedented temporal coverage of LIDAR data is available between 1999 and 2015. Additionally, an extensive set of aerial photography also exists, dating back to 1945 allowing comparison of blowout frequency and magnitude together with the alongshore limits of coastline retreat. Digital terrain models are derived for each year that LIDAR data is available. Informed by LIDAR based topography and areas of bare sand (aerial photos) terrain models have been created containing individual blowouts. Differentials in 'z' values between each terrain model of each available year has identified topographic change and total levels of transport. Preliminary results have confirmed the importance of blowouts in transporting beach or foredune sediment landwards and thus potentially promoting coastline retreat. Repetition of processes across a larger number of blowout topographies will allow better identification of individual blowouts for 'event' scale field investigations to examine spatial and temporal variability of beach sediment transport via blowouts routes.

  19. Aeolian dust event in Korea observed by an EZ Lidar in the frame of global lidar networks.

    NASA Astrophysics Data System (ADS)

    Lolli, Simone

    2010-05-01

    Duststorms and sandstorms regularly devastate Northeast Asia and cause considerable damage to transportation system and public health; further, these events are conceived to be one of the very important indices for estimating the global warming and desertification. Previously, yellow sand events were considered natural phenomena that originate in deserts and arid areas. However, the greater scale and frequency of these events in recent years are considered to be the result of human activities such as overgrazing and over-cultivation. Japan, Korea, Cina and Mongolia are directly concerned to prevent and control these storms and have been able to some extent to provide forecasts and early warnings. In this framework, to improve the accuracy of forecasting , a compact and rugged eye safe lidar, the EZ LIDAR™, developed together by Laboratoire des Sciences du Climat et l'Environnement (LSCE) (CEA-CNRS) and LEOSPHERE (France) to study and investigate structural and optical properties of clouds and aerosols, thanks to the strong know-how of CEA and CNRS in the field of air quality measurements and cloud observation and analysis, was deployed in Seoul, Korea in order to detect and study yellow sand events, thanks to its depolarization channel and scan capabilities. The preliminary results, showed in this paper, of this measurement campaign put in evidence that EZ Lidar, for its capabilities of operating unattended day and night under each atmospheric condition, is mature to be deployed in a global network to study long-range transport, crucial in the forecasting model.

  20. Turbulent flow structures and aeolian sediment transport over a barchan sand dune

    NASA Astrophysics Data System (ADS)

    Wiggs, G. F. S.; Weaver, C. M.

    2012-03-01

    The turbulent structure of airflow over a barchan sand dune is determined using quadrant analysis of wind velocity data derived from sonic anemometers. Results indicate an increased frequency of ejection and sweep events in the toe region of the dune, characteristic of the turbulent bursting process. In contrast, at the crest there was a significant increase in the occurrence of outward interactions. Combined with high frequency saltation data our analyses show that turbulent structures characterised by a positive streamwise fluctuating velocity (+u‧ sweeps at the toe and outward interactions at the crest) have a dominant influence on sand transport on the dune, together accounting for up to 83% and 95% of transporting events at the toe and crest respectively.

  1. Theoretical and measured aeolian sand transport on a barrier island, Louisiana, USA

    USGS Publications Warehouse

    Dingler, J.R.; Hsu, S.A.; Reiss, T.E.

    1992-01-01

    Over the past 100 yr, the Isles Dernieres, a low lying barrier island chain along the coast of central Louisiana, has undergone more than 1km of northward beach face retreat within the loss of 70% of its surface area. The erosion results from a long term relative sea level rise coupled with day to day wind and wave action that ultimately favours erosion over deposition. The theoretical estimate of 1.28 m3 m-1 for the rate of sand transport by the northerly wind compares well with the measured backshore erosion rate of 1.26m3 m-1, which was determined by comparing beach profiles from the start and end of the period of northerly winds. The theoretical estimate of 0.04m3 m-1 for the rate of sand transport by the southerly wind, however, is notably less than the measured rate of 0.45m3 m-1. -from Authors

  2. Aeolian geomorphology from the global perspective

    NASA Technical Reports Server (NTRS)

    Greeley, R.

    1985-01-01

    Any planet or satellite having a dynamic atmosphere and a solid surface has the potential for experiencing aeolian (wind) processes. A survey of the Solar System shows at least four planetary objects which potentially meet these criteria: Earth, Mars, Venus, and possibly Titan, the largest satellite of Saturn. While the basic process is the same among these four objects, the movement of particles by the atmosphere, the aeolian environment is drastically different. It ranges from the hot (730 K), dense atmosphere of Venus to the extremely cold desert (218 K) environment of Mars where the atmospheric surface pressure is only approximately 7.5 mb. In considering aeolian processes in the planetary perspective, all three terrestrial planets share some common areas of attention for research, especially in regard to wind erosion and dust storms. Relevant properties of planetary objects potentially subject to aeolian processes are given in tabular form.

  3. Dust Transport, Deposition and Radiative Effects Observed from MODIS

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  4. PTV measurement of the spanwise component of aeolian transport in steady state

    NASA Astrophysics Data System (ADS)

    O'Brien, Patrick; McKenna Neuman, Cheryl

    2016-03-01

    This paper outlines and validates an improved particle tracking technique (PTV-EPAS) with automated trajectory detection capabilities, and then reports on a novel set of wind tunnel experiments aimed at measuring all three velocity components simultaneously. In order to study a fully adjusted particle cloud, the entire floor of the tunnel was filled with quartz sand (median diameter 550 μm) and the freestream velocity set to 8 ms-1 at an elevation of 0.35 m, above the threshold for particle entrainment at 6.5 ms-1. This produced a friction velocity (u∗) of ∼0.38 ms-1 with u∗/u∗t = 1.3. Measurement of particle trajectories aligned at a spanwise angle (θ) relative to the mean airflow along the center-line of the wind tunnel involved incrementally adjusting the light sheet orientation from 0° to 60°. Three replicate experiments were carried out for each of 13 angles. Only 12% of all 2 × 105 trajectories sampled were strictly aligned with the mean streamwise air flow, while 95% were contained within 45°. As θ increases, a greater proportion of the particle transport consists of slow moving ejecta that ascend from and then impact the bed surface at higher angles than observed for saltation.

  5. Dust particle diffusion in ion beam transport region.

    PubMed

    Miyamoto, N; Okajima, Y; Romero, C F; Kuwata, Y; Kasuya, T; Wada, M

    2016-02-01

    Dust particles of μm size produced by a monoplasmatron ion source are observed by a laser light scattering. The scattered light signal from an incident laser at 532 nm wavelength indicates when and where a particle passes through the ion beam transport region. As the result, dusts with the size more than 10 μm are found to be distributed in the center of the ion beam, while dusts with the size less than 10 μm size are distributed along the edge of the ion beam. Floating potential and electron temperature at beam transport region are measured by an electrostatic probe. This observation can be explained by a charge up model of the dust in the plasma boundary region. PMID:26932116

  6. Dust particle diffusion in ion beam transport region

    NASA Astrophysics Data System (ADS)

    Miyamoto, N.; Okajima, Y.; Romero, C. F.; Kuwata, Y.; Kasuya, T.; Wada, M.

    2016-02-01

    Dust particles of μm size produced by a monoplasmatron ion source are observed by a laser light scattering. The scattered light signal from an incident laser at 532 nm wavelength indicates when and where a particle passes through the ion beam transport region. As the result, dusts with the size more than 10 μm are found to be distributed in the center of the ion beam, while dusts with the size less than 10 μm size are distributed along the edge of the ion beam. Floating potential and electron temperature at beam transport region are measured by an electrostatic probe. This observation can be explained by a charge up model of the dust in the plasma boundary region.

  7. Levitation and Transport of Charged Dust Over Surfaces in Space

    NASA Astrophysics Data System (ADS)

    Colwell, Joshua E.; Horányi, Mihály; Robertson, Scott; Sickafoose, Amanda A.

    2002-12-01

    Dust in planetary regoliths may become charged and levitated in plasma sheaths and photoelectron sheaths near the surface [1,2]. This provides an explanation for the observations of the lunar horizon glow [3]. Horizontal electric fields or inhomogeneities in the sheath may lead to net transport of dust on the surface. Electrostatic levitation of dust may also explain observations of regolith deposits in craters on the asteroid 433 Eros by the NEAR spacecraft [4]. We present the results of a simple model of dust transport in a photoelectron sheath across a surface with simple topographical forms. We find a net deposition of particles launched in random directions at photoelectron sheath boundaries such as might occur in the terminator region. Topographic boundaries such as blocks and craters provide an additional sink for particles moving horizontally across the surface in a sheath.

  8. Global transport of Asian dust revealed by NASA/CALIPSO and a global aerosol transport model

    NASA Astrophysics Data System (ADS)

    Eguchi, K.; Yumimoto, K.; Uno, I.; Takemura, T.

    2009-12-01

    Trans-Pacific transport of mineral dust and air pollutants originating from Asia to North America is well known. Eguchi et al. (2009, ACP) pointed out that the Taklimakan Desert supplies mineral dust for upper troposphere and can play an important role in intercontinental-scale dust transport. Asian dust is also detected from ice cores on Greenland and French Alps. The effects of Asian dust on cloud systems and the associated radiative forcing can extend over the Northern Hemisphere. In this study, we report the detailed structure of Asian dust during the global transport using integrated analysis of observations by CALIOP on-boarded NASA/CALIPSO satellite and a glocal aerosol transport model. We used the CALIOP Level 1B data products (ver. 2.01), containing the total attenuated backscatter coefficients at 532/1064 nm and the volume depolarization ratio at 532 nm. Dust extinction coefficients are then derived from the Fernald’s inversion method by setting the lidar ratio to S1=50 sr. As for a global aerosol transport model, we used the Spectral Radiation Transport Model for the Aerosol Species (SPRINTARS; Takemura et al., 2005, JGR). We performed a sensitivity experiment that aims at an analysis specified for a single dust event originating from the Taklimakan. The simulation was performed over May 2007. A sever dust storm occurred on 8-9 May 2007 in Taklimakan Desert. Dust cloud emitted during this dust storm is uplifted to altitude of 8-10 km and starts the travel of full circuit around the globe. It has a meridional width of 100-200 km. About one tenth of the original uplifted dust mass (8.1 Gg) is encircling the globe taking about 2 weeks. Because of its high transport height, the dust cloud almost unaffected by wet removal so that the decay of its concentration level is small. Over the western North Pacific of 2nd circuit, the dust cloud pulls down to the lower troposphere by anticyclonic down draft, and finally it settles on North Pacific because of wet

  9. Synoptic-scale dust transport events in the southern Himalaya

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  10. Simulation of Martian surface conditions and dust transport

    NASA Astrophysics Data System (ADS)

    Nørnberg, P.; Merrison, J. P.; Finster, K.; Folkmann, F.; Gunnlaugsson, H. P.; Hansen, A.; Jensen, J.; Kinch, K.; Lomstein, B. Aa.; Mugford, R.

    2002-11-01

    The suspended atmospheric dust which is also found deposited over most of the Martian globe plays an important (possibly vital) role in shaping the surface environment. It affects the weather (solar flux), water transport and possibly also the electrical properties at the surface. The simulation facilities at Aarhus provide excellent tools for studying the properties of this Martian environment. Much can be learned from such simulations, supporting and often inspiring new investigations of the planet. Electrical charging of a Mars analogue dust is being studied within a wind tunnel simulation aerosol. Here electric fields are used to extract dust from suspension. Although preliminary the results indicate that a large fraction of the dust is charged to a high degree, sufficient to dominate adhesion/cohesion processes. A Mars analogue dust layer has been shown to be an excellent trap for moisture, causing increased humidity in the soil below. This allows the possibility for liquid water to be stable close to the surface (less than 10 cm). This is being investigated in an environment simulator where heat and moisture transport can be studied through layers of Mars analogue dust.

  11. Lunar dust transport by photoelectric charging at sunset

    NASA Technical Reports Server (NTRS)

    Pelizzari, M. A.; Criswell, D. R.

    1978-01-01

    The motion of dust grains from a photoelectrically charged object at the moon's sunset terminator is studied with the aid of a simple model. It is shown that sunlit objects ranging in size from less than 0.01 cm to 5 cm in radius are responsible for the levitation of dust grains to heights of observed horizon glow. The transverse displacement of these grains is observed to be at least twice their maximum altitude, so that fitting the latter to horizon glow implies horizontal particle ranges typically 6 to 60 cm. Detachment of these grains from the sunlit areas takes place mainly along the contracting sunlight boundaries as the areas shrink during sunset. A high ratio of intergrain adhesion force to dust-grain weight is essential for the occurrence of horizon glow and significant dust transport from the subcentimeter sized sunlit areas.

  12. Dust charging and transport on airless planetary bodies

    NASA Astrophysics Data System (ADS)

    Wang, X.; Schwan, J.; Hsu, H.-W.; Grün, E.; Horányi, M.

    2016-06-01

    We report on laboratory experiments to shed light on dust charging and transport that have been suggested to explain a variety of unusual phenomena on the surfaces of airless planetary bodies. We have recorded micron-sized insulating dust particles jumping to several centimeters high with an initial speed of ~0.6 m/s under ultraviolet illumination or exposure to plasmas, resulting in an equivalent height of ~0.11 m on the lunar surface that is comparable to the height of the so-called lunar horizon glow. Lofted large aggregates and surface mobilization are related to many space observations. We experimentally show that the emission and re-absorption of photoelectron and/or secondary electron at the walls of microcavities formed between neighboring dust particles below the surface are responsible for generating unexpectedly large negative charges and intense particle-particle repulsive forces to mobilize and lift off dust particles.

  13. Electrostatic dust transport on the surfaces of airless bodies

    NASA Astrophysics Data System (ADS)

    Wang, X.; Schwan, J.; Hsu, H. W.; Horanyi, M.

    2015-12-01

    The surfaces of airless bodies are charged due to the exposure to solar wind plasma and UV radiation. Dust particles on the regolith of these surfaces can become charged, and may move and even get lofted due to electrostatic force. Electrostatic dust transport has been a long-standing problem that may be related to many observed phenomena on the surfaces of airless planetary bodies, including the lunar horizon glow, the dust ponds on asteroid Eros, the spokes in Saturn's rings, and more recently, the collection of dust particles ejected off Comet 67P, observed by Rosetta. In order to resolve these puzzles, a handful of laboratory experiments have been performed in the past and demonstrated that dust indeed moves and lifts from surfaces exposed to plasma. However, the exact mechanisms for the mobilization of dust particles still remain a mystery. Current charging models, including the so-called "shared charge model" and the charge fluctuation theory, will be discussed. It is found that neither of these models can explain the results from either laboratory experiments or in-situ observations. Recently, single dust trajectories were captured with our new dust experiments, enabling novel micro-scale investigations. The particles' initial launch speeds and size distributions are analyzed, and a new so-called "patched charge model" is proposed to explain our findings. We identify the role of plasma micro-cavities that are formed in-between neighboring dust particles. The emitted secondary or photo- electrons are proposed to be absorbed inside the micro-cavities, resulting in significant charge accumulation on the exposed patches of the surfaces of neighboring particles. The resulting enhanced Coulomb force (repulsion) between particles is likely the dominant force to mobilize and lift them off the surface. The role of other properties, including surface morphology, cohesion and photoelectron charging, will also be discussed.

  14. Long-range transport of giant particles in Asian dust identified by physical, mineralogical, and meteorological analysis

    NASA Astrophysics Data System (ADS)

    Jeong, G. Y.; Kim, J. Y.; Seo, J.; Kim, G. M.; Jin, H. C.; Chun, Y.

    2014-01-01

    Giant particles transported over long distances are generally of limited concern in atmospheric studies due to their low number concentrations in mineral dust and possible local origin. However, they can play an important role in regional circulation of earth materials due to their enormous volume concentration. Asian dust laden with giant particles was observed in Korea on 31 March 2012, after a migration of about 2000 km across the Yellow Sea from the Gobi Desert. Scanning electron microscopy (SEM) revealed that 20% of the particles exceeded 10 μm in equivalent sphere diameter, with a maximum of 60 μm. The median diameter from the number distribution was 5.7 μm, which was larger than the diameters recorded of 2.5 and 2.9 μm in Asian dust storms in 2010 and 2011, respectively, and was consistent with independent optical particle counter data. Giant particles (>10 μm) contributed about 89% of the volume of the dust in the 2012 storm. Illite-smectite series clay minerals were the major mineral group followed by quartz, plagioclase, K-feldspar, and calcite. The total phyllosilicate content was ~52%. The direct long-range transport of giant particles was confirmed by calcite nanofibers closely associated with clays in a submicron scale identified by high-resolution SEM and transmission electron microscopy. Since giant particles consisted of clay agglomerates and clay-coated quartz, feldspars, and micas, the mineral composition varied little throughout the fine (<5 μm), coarse (5-10 μm), giant-S (10-20 μm), and giant-L (>20 μm) size bins. Analysis of the synoptic conditions of the 2012 dust event and its migration indicated that the mid-tropospheric strong wind belt directly stretching to Korea induced rapid transport of the dust, delivering giant particles. Giant dust particles with high settling velocity would be the major input into the terrestrial and marine sedimentary and ecological systems of East Asia and the western Pacific. Analysis of ancient

  15. Long-range transport of giant particles in Asian dust identified by physical, mineralogical, and meteorological analysis

    NASA Astrophysics Data System (ADS)

    Jeong, G. Y.; Kim, J. Y.; Seo, J.; Kim, G. M.; Jin, H. C.; Chun, Y.

    2013-08-01

    Giant particles transported over long distances are generally of limited concern in atmospheric studies due to their low number concentrations in mineral dust and possible local origin. However, they can play an important role in regional circulation of earth materials due to their enormous volume concentration. Asian dust laden with giant particles was observed in Korea on 31 March 2012, after a migration of about 2000 km across the Yellow Sea from the Gobi Desert. Scanning electron microscopy (SEM) revealed that 20% of the particles exceeded 10 μm in equivalent sphere diameter, with a maximum of 60 μm. The median diameter from the number distribution was 5.7 μm, which was larger than the diameters recorded of 2.5 and 2.9 μm in Asian dust storms in 2010 and 2011, respectively, and was consistent with independent optical particle counter data. Giant particles (> 10 μm) contributed about 89% of the volume of the dust in the 2012 storm. Illite-smectite series clay minerals were the major mineral group followed by quartz, plagioclase, K-feldspar, and calcite. The total phyllosilicate content was ~ 52%. The direct long-range transport of giant particles was confirmed by calcite nanofibers closely associated with clays in a submicron scale identified by high-resolution SEM and transmission electron microscopy. Since giant particles consisted of clay agglomerates and clay-coated quartz, feldspars, and micas, the mineral composition varied little throughout the fine (< 5 μm), coarse (5-10 μm), giant-S (10-20 μm), and giant-L (> 20 μm) size bins. Analysis of the synoptic conditions of the 2012 dust event and its migration indicated that the mid-tropospheric strong wind belt directly stretching to Korea induced rapid transport of the dust, delivering giant particles. Giant dust particles with high settling velocity would be the major input into the terrestrial and marine sedimentary and ecological systems of East Asia and the western Pacific. Analysis of ancient

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

    USGS Publications Warehouse

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

    2012-01-01

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

  17. Global transport of thermophilic bacteria in atmospheric dust.

    PubMed

    Perfumo, Amedea; Marchant, Roger

    2010-04-01

    Aerosols from dust storms generated in the Sahara-Sahel desert area of Africa are transported north over Europe and periodically result in dry dust precipitation in the Mediterranean region. Samples of dust collected in Turkey and Greece following two distinct desert storm events contained viable thermophilic organisms of the genus Geobacillus, namely G. thermoglucosidasius and G. thermodenitrificans, and the recently reclassified Aeribacillus pallidus (formerly Geobacillus pallidus). We present here evidence that African dust storms create an atmospheric bridge between distant geographical regions and that they are also probably the source of thermophilic geobacilli later deposited over northern Europe by rainfall or dust plumes themselves. The same organisms (99% similarity in the 16S rDNA sequence) were found in dust collected in the Mediterranean region and inhabiting cool soils in Northern Ireland. This study also contributes new insights to the taxonomic identification of Geobacillus sp. Attempts to identify these organisms using 16S rRNA gene sequences have revealed that they contain multiple and diverse copies of the ribosomal RNA operon (up to 10 copies with nine different sequences), which dictates care in interpreting data about the systematics of this genus. PMID:23766086

  18. Quiescence of Asian dust events in South Korea and Japan during 2012 spring: Dust outbreaks and transports

    NASA Astrophysics Data System (ADS)

    Lee, Yun Gon; Ho, Chang-Hoi; Kim, Joo-Hong; Kim, Jhoon

    2015-08-01

    This study examined the quiescence of Asian dust events in South Korea and Japan during the spring of 2012, presenting a synoptic characterization and suggesting possible causes. Synoptic observation reports from the two countries confirmed that spring 2012 had the lowest number of dust events in 2000-2012. The monthly dust frequency (DF) in March 2012 over the dust source regions, i.e., deserts in northern China and Mongolia, indicated a significant decrease compared to the 12 year (2000-2011) March climatology. The DF in April 2012 was comparable to the 12 year climatology values, but in May 2012 it was slightly lower. The daily Ozone Monitoring Instrument Aerosol Index and the Navy Aerosol Analysis and Prediction System simulations revealed stagnant dust movement in March and May 2012. Anomalous anticyclones north of the source regions decreased the dust outbreaks and enhanced the southeasterly winds, resulting in few dust events over the downwind countries (i.e., South Korea and Japan). By contrast, in April 2012, a strong anomalous cyclone east of Lake Baikal slightly increased the dust outbreaks over northeastern China. However, the major dust outbreaks were not transported downwind because of exceptional dust pathways, i.e., the southeastward pathway of dust transport was unusually blocked by the expansion of an anomalous anticyclonic circulation over the Sea of Okhotsk, with dust being transported northeast.

  19. Persistent Aeolian Activity at Endeavour Crater, Mars

    NASA Astrophysics Data System (ADS)

    Chojnacki, M.; Michaels, T. I.; Fenton, L. K.

    2013-12-01

    Long-term monitoring of sites that are known to have active dunes and ripples is generally limited to 3 Mars-Years (MY). Here, we discuss new results of dune activity and albedo change in Endeavour crater (EC), Meridiani Planum (MP) that record eight MY of aeolian activity. MP dune fields often show large yearly variations in albedo; EC darkened by ~12% in TES albedo between MY 24 and 26 (from 0.14 to 0.12). THEMIS VIS albedo of dunes did not change significantly from MY 26 to 29, but did decrease notably (~15 %) in MY 30. These darkening events are most likely related to aeolian-driven dust cleaning (e.g., removal by saltating sand, dust devils). For example, the Opportunity rover (poised on the western rim of EC) observed evidence for a MY 31 dune field dust-clearing event. HiRISE monitoring of MP has shown it be one of the most active regions outside of north polar latitudes. Paired images of western EC taken 3 MY apart show clear evidence for dune modification that include: ripple migration, change in dune perimeters, exposure of previously buried light-toned rock, and/or burial of rock by sand (Fig. 1a-1b). Dune slip face movement is evident for most dunes, where crests and aprons advanced (2-7 m) in the downwind direction (to the SSE) at rates of 0.7-2.3 m per MY. Small dome dunes in the eastern EC were found to have a large degree of aeolian activity (e.g., deflation and/or translation) by an earlier study that used MGS-MRO images (MY 24-30). New MY 31 images validate earlier observations, showing clear evidence for bedform deflation where dunes often occupy less area (~50%) than in earlier MY 29 images (Fig. 1c-1d). Areal removal rates are on par with earlier estimates. Bedform modification and sand streamer orientation appear to be caused by a NNW wind regime, consistent with earlier observations, mesoscale modeling, and the transport direction of barchans to the west. Dunes in EC are now known to be periodically (consistently?) active from over a decade

  20. Publication trends in aeolian research: An analysis of the Bibliography of Aeolian Research

    NASA Astrophysics Data System (ADS)

    Stout, John E.; Warren, Andrew; Gill, Thomas E.

    2009-04-01

    An analysis of the Bibliography of Aeolian Research has provided information regarding publication trends in aeolian research. Results suggest that there has been a significant increase in the number of publications per year since the first aeolian-research publication appeared in 1646. Rates of publication have increased from only three publications in the 17th Century to nearly three publications per day in the 21st Century. The temporal distribution of publications follows a complex pattern that is influenced by many factors. In the 17th and 18th Centuries, publications appear as isolated clusters indicating limited interest in aeolian research and limited opportunities for individuals to contribute to scientific literature. With time, many new scientific societies are formed and many new scientific journals are established, opening new opportunities for scientists to contribute to scientific discourse. Landmark publications open up new research areas and define new directions for aeolian research. General advances in science and technology provide new techniques for sampling blowing sand and dust. In addition, clear signs exist that publication rates respond to major environmental and climatic events, especially large-scale disasters that focus attention on wind erosion and blowing dust. The Sirocco dust events of 1901-1903, the North American Dust Bowl of the1930s, and the recent sand and dust storm problems in China have all led to significant increases in the number of publications in aeolian research. Rates of publication are negatively influenced by major political and social upheavals, especially global conflicts such as World Wars I and II. Sudden shifts in government structure and support can also influence publication rates. A good example is the increased publication rates in China following the end of the Cultural Revolution, a trend that continues today.

  1. Asian dust: seasonal transport to the hawaiian islands.

    PubMed

    Parrington, J R; Zoller, W H; Aras, N K

    1983-04-01

    Analyses of atmospheric particles collected at Mauna Loa Observatory in Hawaii from February 1979 through September 1982 reveal strong influxes of Asian dust in the spring of each year. Concentrations of a typical crustal element, aluminum, are more than an order of magnitude greater between February and June than during the remainder of the year (71 +/- 51 versus 6.7 +/- 2.3 nanograms per cubic meter). The mass of crustal material transported during the relatively short dust episodes accounts for an average of 80 percent of the total yearly mass of atmospheric particles at 3400 meters on Mauna Loa. PMID:17795828

  2. Asian dust: seasonal transport to the Hawaiian Islands

    SciTech Connect

    Parrington, J.R.; Zoller, W.H.; Aras, N.K.

    1983-04-08

    Analyses of atmospheric particles collected at Mauna Loa Observatory in Hawaii from February 1979 through September 1982 reveal strong influxes of Asian dust in the spring of each year. Concentrations of a typical crustal element, aluminum, are more than an order of magnitude greater between February and June than during the remainder of the year (71 +/- 51 versus 6.7 +/- 2.3 nanograms per cubic meter). The mass of crustal material transported during the relatively short dust episodes accounts for an average of 80 percent of the total yearly mass of atmospheric particles at 3400 meters on Mauna Loa.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  4. Representation of Vegetation and Other Nonerodible Elements in Aeolian Shear Stress Partitioning Models for Predicting Transport Threshold

    NASA Technical Reports Server (NTRS)

    King, James; Nickling, William G.; Gillies, John A.

    2005-01-01

    The presence of nonerodible elements is well understood to be a reducing factor for soil erosion by wind, but the limits of its protection of the surface and erosion threshold prediction are complicated by the varying geometry, spatial organization, and density of the elements. The predictive capabilities of the most recent models for estimating wind driven particle fluxes are reduced because of the poor representation of the effectiveness of vegetation to reduce wind erosion. Two approaches have been taken to account for roughness effects on sediment transport thresholds. Marticorena and Bergametti (1995) in their dust emission model parameterize the effect of roughness on threshold with the assumption that there is a relationship between roughness density and the aerodynamic roughness length of a surface. Raupach et al. (1993) offer a different approach based on physical modeling of wake development behind individual roughness elements and the partition of the surface stress and the total stress over a roughened surface. A comparison between the models shows the partitioning approach to be a good framework to explain the effect of roughness on entrainment of sediment by wind. Both models provided very good agreement for wind tunnel experiments using solid objects on a nonerodible surface. However, the Marticorena and Bergametti (1995) approach displays a scaling dependency when the difference between the roughness length of the surface and the overall roughness length is too great, while the Raupach et al. (1993) model's predictions perform better owing to the incorporation of the roughness geometry and the alterations to the flow they can cause.

  5. Late Pleistocene aeolian dust provenances and wind direction changes reconstructed by heavy mineral analysis of the sediments of the Dehner dry maar (Eifel Mountains, Germany)

    NASA Astrophysics Data System (ADS)

    Lehmkuhl, Frank; Römer, Wolfgang; Sirocko, Frank

    2016-04-01

    The study presents the results of a heavy mineral analysis from a 38 m long record of aeolian sediments from a core section of the Dehner dry maar (Eifel Mountains, Germany). The record encompasses the period from 30 to about 12.5 ka. Heavy-mineral analysis of the silt fraction has been performed at a sampling interval of 1 m. Statistical analyses enabled the distinction of local and regional source areas of aeolian material and revealed pronounced changes in the amounts of different heavy mineral species and corresponding changes in the grain size index (GSI). The results indicate that during the early stages of MIS 2 (40 to 30m depth) aeolian sediments were supplied mostly from local sources. This period is characterized by a low GSI ratio resulting from a reduced mobility of material due to a vegetation cover. The climax of the LGM is characterized by a higher supply of heavy minerals from regional and more distant sources. Changes in the provenance areas are indicated in inverse relationships between zircon, rutile, tourmaline (ZRT) and carbonate particles. Shifts in the wind direction are documented in pronounced peaks of carbonate particles indicating easterly winds that have crossed the limestone basins in the Eifeler North South Zone. ZRT-group minerals on the other hand suggest a westerly source area and a supply from areas consisting of Paleozoic clastic sedimentary rocks. In the periods following the LGM the analyses indicate an increasing degree of mixing of heavy minerals from various provinces. This suggests the existence of a presumably incomplete, thin cover of deflatable loessic sediments that has been repeatedly reworked on the elevated surfaces of the Eifel.

  6. Field Evidence for Differences in Post-Fire Aeolian Transport Related to Vegetation Type in Semi-Arid Grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Disturbances such as wildfires, which cause a temporary reduction in vegetation cover, can greatly accelerate soil erosion by wind and promote dust emissions. Enhanced erosion leads to a reduction in soil fertility and the post-fire mobilization of soil and associated emissions of dust represent a s...

  7. Aeolian Processes at the Mars Exploration Rover Opportunity Landing Site

    NASA Technical Reports Server (NTRS)

    Sullivan, R.; Bell, J. F., III; Calvin, W.; Fike, D.; Golombek, M.; Greeley, R.; Grotzinger, J.; Herkenhoff, K.; Jerolmack, D.; Malin, M.

    2005-01-01

    The traverse of the Mars Exploration Rover Opportunity across its Meridiani Planum landing site has shown that wind has affected regolith by creating drifts, dunes, and ubiquitous ripples, by sorting grains during aeolian transport, by forming bright wind streaks downwind from craters seen from orbit, and by eroding rock with abrading, wind-blown material. Pre-landing orbiter observations showed bright and dark streaks tapering away from craters on the Meridiani plains. Further analysis of orbiter images shows that major dust storms can cause bright streak orientations in the area to alternate between NW and SE, implying bright wind streak materials encountered by Opportunity are transient, potentially mobilized deposits. Opportunity performed the first in situ investigation of a martian wind streak, focusing on a bright patch of material just outside the rim of Eagle crater. Data from Pancam, the Miniature Thermal Emission Spectrometer (Mini-TES), the Alpha-Particle X-Ray Spectrometer (APXS), and the Mossbauer spectrometer either are consistent with or permit an air fall dust interpretation. We conclude that air fall dust, deposited in the partial wind shadow of Eagle crater, is responsible for the bright streak seen from orbit, consistent with models involving patchy, discontinuous deposits of air fall dust distributed behind obstacles during periods of atmospheric thermal stability during major dust storms.

  8. Modeling Aeolian Transport of Contaminated Sediments at Los Alamos National Laboratory, Technical Area 54, Area G: Sensitivities to Succession, Disturbance, and Future Climate

    SciTech Connect

    Whicker, Jeffrey J.; Kirchner, Thomas B.; Breshears, David D.; Field, Jason P.

    2012-03-27

    succession and environmental disturbance. Aeolian, or wind-driven, sediment transport drives soil erosion, affects biogeochemical cycles, and can lead to the transport of contaminants. Rates of aeolian sediment transport depend in large part on the type, amount, and spatial pattern of vegetation. In particular, the amount of cover from trees and shrubs, which act as roughness elements, alters rates of aeolian sediment transport. The degree to which the understory is disturbed and the associated spacing of bare soil gaps further influence sediment transport rates. Changes in vegetation structure and patterns over periods of years to centuries may have profound impacts on rates of wind-driven transport. For recently disturbed areas, succession is likely to occur through a series of vegetation communities. Area G currently exhibits a mosaic of vegetation cover, with patches of grass and forbs over closed disposal units, and bare ground in heavily used portions of the site. These areas are surrounded by less disturbed regions of shrubland and pinon-juniper woodland; some ponderosa pine forest is also visible in the canyon along the road. The successional trajectory for the disturbed portions of Area G is expected to proceed from grasses and forbs (which would be established during site closure), to shrubs such as chamisa, to a climax community of pinon-juniper woodland. Although unlikely under current conditions, a ponderosa pine forest could develop over the site if the future climate is wetter. In many ecosystems, substantial and often periodic disturbances such as fire or severe drought can rapidly alter vegetation patterns. Such disturbances are likely to increase in the southwestern US where projections call for a warmer and drier climate. With respect to Area G, the 3 most likely disturbance types are surface fire, crown fire, and drought-induced tree mortality. Each type of disturbance has a different frequency or likelihood of occurrence, but all 3 tend to reset the

  9. Survivability of dust in tokamaks: Dust transport in the divertor sheath

    SciTech Connect

    Delzanno, Gian Luca; Tang, Xianzhu

    2014-02-15

    The survivability of dust being transported in the magnetized sheath near the divertor plate of a tokamak and its impact on the desired balance of erosion and redeposition for a steady-state reactor are investigated. Two different divertor scenarios are considered. The first is characterized by an energy flux perpendicular to the plate q{sub 0}≃1 MW/m{sup 2} typical of current short-pulse tokamaks. The second has q{sub 0}≃10 MW/m{sup 2} and is relevant to long-pulse machines like ITER or Demonstration Power Plant. It is shown that micrometer dust particles can survive rather easily near the plates of a divertor plasma with q{sub 0}≃1 MW/m{sup 2} because thermal radiation provides adequate cooling for the dust particle. On the other hand, the survivability of micrometer dust particles near the divertor plates is drastically reduced when q{sub 0}≃10 MW/m{sup 2}. Micrometer dust particles redeposit their material non-locally, leading to a net poloidal mass migration across the divertor. Smaller particles (with radius ∼0.1 μm) cannot survive near the divertor and redeposit their material locally. Bigger particle (with radius ∼10 μm) can instead survive partially and move outside the divertor strike points, thus causing a net loss of divertor material to dust accumulation inside the chamber and some non-local redeposition. The implications of these results for ITER are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  11. Towards a phoenix phase in aeolian research: shifting geophysical perspectives from fluvial dominance

    SciTech Connect

    Whicker, Jeffrey J; Field, Jason P; Breshears, David D

    2008-01-01

    Aeolian processes are a fundamental driver of earth surface dynamics, yet the importance of aeolian processes in a broader geosciences context may be overshadowed by an unbalanced emphasis on fluvial processes. Here we wish to highlight that aeolian and fluvial processes need to be considered in concert relative to total erosion and to potential interactions, that relative dominance and sensitivity to disturbance vary with mean annual precipitation, and that there are important scale-dependencies associated with aeolian-fluvial interactions. We build on previous literature to present relevant conceptual syntheses highlighting these issues. We then highlight the relative investments that have been made in aeolian research on dust emission and management relative to that in fluvial research on sediment production. Literature searches highlight that aeolian processes are greatly understudied relative to fluvial processes when considering total erosion in different environmental settings. Notably, within the USA, aeolian research was triggered by the Dust Bowl catastrophe of the 1930s, but the resultant research agencies have shifted to almost completely focusing on fluvial processes, based on number of remaining research stations and on monetary investments in control measures. However, numerous research issues associated with intensification of land use and climate change impacts require a rapid ramping up in aeolian research that improves information about aeolian processes relative to fluvial processes, which could herald a post-Dust Bowl Phoenix phase in which aeolian processes are recognized as broadly critical to geo- and environmental sciences.

  12. Transpacific transport and evolution of the optical properties of Asian dust

    NASA Astrophysics Data System (ADS)

    Liu, Zhaoyan; Fairlie, T. Duncan; Uno, Itsushi; Huang, Jingfeng; Wu, Dong; Omar, Ali; Kar, Jayanta; Vaughan, Mark; Rogers, Raymond; Winker, David; Trepte, Charles; Hu, Yongxiang; Sun, Wenbo; Lin, Bing; Cheng, Anning

    2013-02-01

    Five years of CALIPSO lidar layer products are used to study transpacific transport of Asian dust. We focus on possible changes to dust intrinsic optical properties during the course of transport, with specific emphasis on changes to particulate depolarization ratio (PDR). PDR distributions for Asian dust transported across the Pacific are compared to previously reported PDR distributions for African dust transported across the Atlantic. African dust shows a slight decreasing trend in PDR during westward transport across the Atlantic during its most active long-range transport season in summer. Asian dust, on the other hand, shows some spatial variability in PDR over the Pacific during its most active long-range transport season in spring. The dust PDR is generally smaller over the ocean than over the Tarim basin and nearby downwind regions. PDR also shows a decreasing trend with latitude moving northward toward the Arctic, together with an increasing trend in the dust aerosol optical depth (AOD) when passing over polluted Asian regions. Possible explanations include (i) the mixing of dust externally or internally with other types of aerosol over the heavily developed industrial regions in East Asia, and (ii) the downstream mixing of dust plumes from different source regions (i.e., Tarim and Gobi). Dust from different source regions exhibits relatively large differences in PDR, with mean values of 0.34±0.07, 0.28±0.06, and 0.30±0.08, respectively, over the Tarim basin, Gobi Desert and Northwest African source regions. Different transport mechanisms are seen for African dust and Asian dust. Asian dust transport is originated by cold fronts and driven by westerly jets. In contrast, summer African transatlantic dust transport is driven by trade winds and is generally well confined in altitude in the free troposphere throughout the tropics and subtropics.

  13. Aeolian processes and the bioshpere: Interactions and feedback loops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aeolian processes affect landform evolution, biogeochemical cycles, regional climate, human health, and desertification. The entrainment, transport and deposition of aeolian sediments are recognized as major drivers in the dynamics of the earth system and there is a growing interest in the scientif...

  14. Studies of dust transport in long pulse plasma discharges in the large helical device

    NASA Astrophysics Data System (ADS)

    Shoji, M.; Kasahara, H.; Tokitani, M.; Seki, T.; Saito, K.; Kamio, S.; Seki, R.; Tanaka, Y.; Pigarov, A.; Smirnov, R.; Kawamura, G.; Tanaka, H.; Masuzaki, S.; Uesugi, Y.; Mutoh, T.; The LHD Experiment Group

    2015-05-01

    Three-dimensional trajectories of incandescent dust particles in plasmas were observed with stereoscopic fast framing cameras in a large helical device. It proved that the dust is located in the peripheral plasma and most of the dust moves along the magnetic field lines with acceleration in the direction that corresponds to the plasma flow. ICRF heated long pulse plasma discharges were terminated with the release of large amounts of dust from a closed divertor region. After the experimental campaign, the traces of exfoliation of carbon rich mixed-material deposition layers were found in the divertor region. Transport of carbon dust is investigated using a modified dust transport simulation code, which can explain the observed dust trajectories. It also shows that controlling the radius of the dust particles to less than 1 mm is necessary to prevent the plasma termination by penetration of dust for the long pulse discharges. Dust transport simulation including heavy metal dust particles demonstrates that high heating power operation is effective for shielding the main plasma from dust penetration by an enhanced plasma flow effect and a high heat load onto the dust particles in the peripheral plasma. It shows a more powerful penetration characteristic of tungsten dust particles compared to that of carbon and iron dust particles.

  15. Beyond Orbital-Motion-Limited theory effects for dust transport in tokamaks

    SciTech Connect

    Delzanno, Gian Luca; Tang, Xianzhu

    2015-05-29

    Dust transport in tokamaks is very important for ITER. Can many kilograms of dust really accumulate in the device? Can the dust survive? The conventional dust transport model is based on Orbital-Motion-Limited theory (OML). But OML can break in the limit where the dust grain becomes positively charged due to electron emission processes because it overestimates the dust collected power. An OML+ approximation of the emitted electrons trapped/passing boundary is shown to be in good agreement with PIC simulations.

  16. Numerical simulations of dust transport into northern high latitudes during a Martian polar warming

    NASA Technical Reports Server (NTRS)

    Barnes, J. R.; Hollingsworth, J. L.

    1987-01-01

    The formation and evolution of the polar laminated terrain depends on rates of dust transport to the polar caps. A simplified dynamical model is shown similar to models used to simulate terrestrial stratospheric polar warmings could simulate certain observed features of the circulation during Martian global dust storms. Model simulations of dust transport showed that substantial quantities of dust, enough to produce optical depths of approx. 1, could reach the pole during these storms.

  17. Introducing a New International Society of Aeolian Research

    NASA Astrophysics Data System (ADS)

    Zobeck, T. M.; Lee, J.; Lancaster, N.; Bullard, J. E.

    2008-12-01

    Aeolian research is a long-standing and rapidly growing area of geological study where scientists of many disciplines meet to investigate the effects of wind on the surface of the Earth and other planetary bodies such as Mars and Titan. Fields of study in aeolian research cover a broad spectrum ranging from developing a basic scientific understanding of the fundamental physical processes of grain motion to the effects of soil erosion on landscape health and environmental sustainability. Aeolian research also includes studies of the effects of aeolian particles on global climate, air quality, and human health, coastal sand transport processes, land degradation, dune migration, the formation of sand seas, and much more. A growing number of international conferences have been organized to focus specifically on aeolian phenomena and a vast number of scholarly publications have been produced to support the science. One popular bibliography includes over 30,000 citations and hundreds of peer-reviewed papers are published each year. Until very recently, no scientific society specifically dealing with aeolian research has been available. The new International Society of Aeolian Research (ISAR) that has been organized to bring together aeolian scientists from around the world. The new society was created to promote contacts among researchers in aeolian processes and related subjects for discussion and comparison of research, to initiate conferences (such as the International Conference on Aeolian Research), to organize excursions, and support the publication of a peer-reviewed scientific journal. The International Society of Aeolian Research sponsors the new Elsevier journal Aeolian Research in support of these activities. This paper will provide further details about the new society and the journal. Please see www.aeolianresearch.org for details.

  18. Studies in Aeolian geology

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1988-01-01

    The objective of the research was to assess the significance of aeolian (windblown) processes in the evolution of planetary surfaces. The approach was to use wind tunnel simulations, field studies of possible analogs, and analyses of spacecraft data.

  19. Electrostatic Transport and Manipulation of Lunar Soil and Dust

    SciTech Connect

    Kawamoto, Hiroyuki

    2008-01-21

    Transport and manipulation technologies of lunar soil and dust are under development utilizing the electrostatic force. Transport of particles is realized by an electrostatic conveyer consisting of parallel electrodes. Four-phase traveling electrostatic wave was applied to the electrodes to transport particles upon the conveyer and it was demonstrated that particles were efficiently transported under conditions of low frequency, high voltage, and the application of rectangular wave. Not only linear but also curved and closed transport was demonstrated. Numerical investigation was carried out with a three-dimensional hard-sphere model of the Distinct Element Method to clarify the mechanism of the transport and to predict performances in the lunar environment. This technology is expected to be utilized not only for the transport of bulk soil but also for the cleaning of a solar panel and an optical lens. Another technology is an electrostatic manipulation system to manipulate single particle. A manipulator consisted of two parallel pin electrodes. When voltage was applied between the electrodes, electrophoresis force generated in non-uniform electrostatic field was applied to the particle near the tip of the electrode. The particle was captured by the application of the voltage and released from the manipulator by turning off the voltage. It was possible to manipulate not only insulative but also conductive particles. Three-dimensional electrostatic field calculation was conducted to calculate the electrophoresis force and the Coulomb force.

  20. Geochemical investigation of dry- and wet-deposited dust during the same dust-storm event in Harbin, China: Constraint on provenance and implications for formation of aeolian loess

    NASA Astrophysics Data System (ADS)

    Xie, Yuanyun; Chi, Yunping

    2016-04-01

    A strong dust-storm event occurred in Harbin, China on May 11, 2011. The dry- and wet-deposited dust depositions in this dust-storm event, together with the surface sediments from the potential sources, were collected to study grain size distributions, carbonate content and carbon isotopic composition of carbonate, major element, trace element and rare earth elements (REE), and Sr-Nd isotopic compositions. The results indicate as follows. The dry-deposited dusts are characterized by bimodal grain-size distributions with a fine mode at 3.6 μm and a coarse mode at 28 μm whereas the wet-deposited dusts are indicative of unimodal grain-size modes with a fine mode at 6 μm. The dust-storm depositions are influenced to a certain extent by sedimentary sorting and are of a derivation from the recycled sediments. Based on identifying the immobility of element pairs before constraining sources of dust-storm deposits using geochemical elements, in conjunction with REE and especially Sr-Nd isotopic compositions, the primary and strengthening sources for the dust-storm event were detected, respectively. The Hunsandake Sandy Land as the primary source and the Horqin Sandy Land as the strengthening source were together responsible for the derivation of dust depositions during dust-storm event. The Hunsandake Sandy Land, however, contributes less dust to the dust-storm event in Harbin compared to the Horqin Sandy Land, and the Hulun Buir Sandy Land is undoubtedly excluded from being one of the sources for dust-storm depositions in Harbin. There are not notable differences in geochemical (especially Sr-Nd isotopic) compositions between dry- and wet-deposited dusts, indicating that the wet-deposited dust is of identical derivation to the dry-deposited dust. Based on our observations, it is of interest to suggest that fine and coarse particles in the CLP (Chinese Loess Plateau) loess possibly have the same sources.

  1. The aeolian sedimentary system in the northern Qilian Shan and Hexi Corridor (N-China) - geomorphologic, sedimentologic and climatic drivers

    NASA Astrophysics Data System (ADS)

    Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg

    2015-04-01

    The formation of aeolian deposits depends on the influence of climatic factors but also on non-climatic controls, such as local geomorphological setting and tectonic activity. Unravelling the environmental history needs a careful consideration of a set of sections to capture spatial variability and a detailed investigation of depositing processes and chronology. Along the northern margin of the Qilian Shan mountain range 22 OSL-dated loess and aeolian sand sections and additional surface samples reveal the interactions between climatic, geomorphologic and sedimentologic factors. Thin loess covers (~1-2 m) occur in elevations of 2000 to 3800 m asl, which were mainly accumulated during the Holocene. End-member modelling of loess grain size data exhibits three dominant aeolian transport pathways representing local transport from fluvial storages, dust storm contribution and background dust deposition. Their relative contributions show a clear dependence on geomorphological setting, and additionally, synchronous trends throughout the Holocene. Their relative changes allow conclusions about Holocene environmental conditions. Discontinuous archives (aeolian sand, lacustrine, and alluvial deposition) in the lower forelands of the Qilian Shan show a distinct spatial pattern contrasting western and eastern forelands. The comparison of OSL ages exhibits high sediment accumulation (~2 m/ka) in the drier western part during the Late Glacial, while the lack of Holocene ages indicates sediment discharge / deflation. In contrast, moister areas in the eastern foreland yield scattered Holocene ages. This indicates high sediment dynamics, benefiting from fluvial reworking and thus provided sediment availability. Fluvial sediment supply plays an important role in sediment recycling. Meanwhile, western forelands lack efficient sand sources and fluvial reworking agents. The study exemplifies the complex sedimentary systems acting along mountain to foreland transects which often host

  2. MECA Worksop on Dust on Mars 2

    NASA Technical Reports Server (NTRS)

    Lee, Steven (Editor)

    1986-01-01

    Topics addressed include: sedimentary debris; mineralogy; Martian dust cycles; Mariner 9 mission; Viking observations; Mars Observer; atmospheric circulation; aeolian features; aerosols; and landslides.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  4. Atmospheric Fate and Transport of Agricultural Dust and Ammonia

    NASA Astrophysics Data System (ADS)

    Hiranuma, N.; Brooks, S. D.; Thornton, D. C.; Auvermann, B. W.; Fitz, D. R.

    2008-12-01

    Agricultural fugitive dust and odor are significant sources of localized air pollution in the semi-arid southern Great Plains. Daily episodes of ground-level fugitive dust emissions from the cattle feedlots associated with increased cattle activity in the early evenings are routinely observed, while consistently high ammonia is observed throughout the day. Here we present measurements of aerosol size distributions and concentrations of gas and particulate phase ammonia species collected at a feedlot in Texas during summers of 2006, 2007 and 2008. A GRIMM sequential mobility particle sizer and GRIMM 1.108 aerosol spectrometer were used to determine aerosol size distributions in the range of 10 nm to 20 µm aerodynamic diameter at the downwind and upwind edges of the facility. Using aqueous scrubbers, simultaneous measurements of both gas phase and total ammonia species present in the gas and particle phases were also collected. In addition to the continuous measurements at the edges of the facility, coincident aerosol and ammonia measurements were obtain at an additional site further downwind (~3.5 km). Taken together our measurements will be used to quantify aerosol and ammonia dispersion and transport. Relationships between the fate and transport of the aerosols and ammonia will be discussed.

  5. Lunar Swirls: Plasma Magnetic Field Interaction and Dust Transport

    NASA Astrophysics Data System (ADS)

    Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin; Hyde, Truell

    2013-10-01

    In close collaboration between the Center for Astrophysics, Space Physics and Engineering Research (CASPER) at Baylor University, Texas, and the Institute of Space Systems (IRS) at the University of Stuttgart, Germany, two plasma facilities have been established using the Inductively heated Plasma Generator 6 (IPG6), based on proven IRS designs. A wide range of applications is currently under consideration for both test and research facilities. Basic investigations in the area of plasma radiation and catalysis, simulation of certain parameters of fusion divertors and space applications are planned. In this paper, the facility at Baylor University (IPG6-B) will be used for simulation of mini-magnetospheres on the Moon. The interaction of the solar wind with magnetic fields leads to the formation of electric fields, which can influence the incoming solar wind ion flux and affect dust transport processes on the lunar surface. Both effects may be partially responsible for the occurrence of lunar swirls. Interactions of the solar wind with such mini-magnetospheres will be simulated in the IPG6-B by observing the interaction between a plasma jet and a permanent magnet. The resulting data should lead to better models of dust transport processes and solar wind deflection on the moon.

  6. Radiogenic isotope evidence for transatlantic atmospheric dust transport

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Early studies by Prospero and colleagues [1] have shown that African dust reaches all across the Atlantic and into the Caribbean. It may contribute to fertilizing the Amazon rainforest [2,3,4], in addition to enhancing the ocean biological productivity via delivery of iron, a key nutrient element[5]. Radiogenic isotope ratios (Sr, Nd, Pb) are robust tracers of dust sources and can thus provide information on provenance and pathways of dust transport. Here we report Sr, Nd and Pb isotope data on atmospheric aerosols, collected in 2008 on quartz filters, from three different locations in Mali (12.6° N, 8.0° W; 555 m a.s.l.), Tobago (11.3° N, 60.5° W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7° N, 64.6° W; 27 m a.s.l.) to investigate the hypothesis of dust transport across the Atlantic. About 2 cm2 of filter were acid-leached in 0.5 N HBr for selective removal of the anthropogenic labile Pb component (leachate) and possibly the fine soluble particle fraction. The remainder of the filter was subsequently dissolved using a mixture of HF and HNO3 acids, and should be representative of the silicate fraction. Isotopic compositions were measured by TIMS on a ThermoFisher Triton at MPIC, with Pb isotope ratios determined using the triple-spike method. Significant Pb isotope differences between leachates and residues were observed. The variability in Pb isotopic composition among leachates may be attributed to variable and distinct anthropogenic local Pb sources from Africa and South America [6], however, residues are imprinted by filter blank contribution suggesting to avoid the quartz fiber filter for isotopic study of aerosols. The Nd and Sr isotope ratios of aerosol leachates show similar signatures at all three locations investigated. The nearly identical Nd and Sr isotopic compositions in the Mali, Tobago and Virgin islands leachates are comparable to those obtained on samples from the Bodélé depression, Northern Chad [7] and suggest a possible common

  7. Modeling of particulate matter transport in atmospheric boundary layer following dust emission from source areas

    NASA Astrophysics Data System (ADS)

    Katra, Itzhak; Elperin, Tov; Fominykh, Andrew; Krasovitov, Boris; Yizhaq, Hezi

    2016-03-01

    A two-dimensional model for particulate matter (PM) dispersion due to dust emission from soils is presented. Field experiments were performed at a dust source site (Negev loess soil) with a portable boundary layer wind tunnel to determine the emitted PM fluxes for different wind speeds and varying soil conditions. The numerical model is formulated using parameterizations based on the aeolian experiments. The wind velocity profiles used in the simulations were fitted from data obtained in field measurements. Size distribution of the emitted dust particles in the numerical simulations was taken into account using a Monte Carlo method. The PM concentration distributions at a distance of several kilometers from the dust source under specific shear velocities and PM fluxes from the soil were determined numerically by solving advection-diffusion equation. The obtained PM10 concentrations under typical wind and soil conditions are supported by PM data recorded over time in a standard environmental monitoring station. The model enhances our capacity of quantification of dust processes to support climate models as well as health risk assessment.

  8. Roughness configuration matters for aeolian sediment flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The parameterisation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Roughness effects are typically represented by bulk drag-partitioning schemes that scale the threshold friction velocity (u*t) for soil entrainment by the ratio of s...

  9. The aeolian wind tunnel

    NASA Technical Reports Server (NTRS)

    Iversen, J. D.

    1991-01-01

    The aeolian wind tunnel is a special case of a larger subset of the wind tunnel family which is designed to simulate the atmospheric surface layer winds to small scale (a member of this larger subset is usually called an atmospheric boundary layer wind tunnel or environmental wind tunnel). The atmospheric boundary layer wind tunnel is designed to simulate, as closely as possible, the mean velocity and turbulence that occur naturally in the atmospheric boundary layer (defined as the lowest portion of the atmosphere, of the order of 500 m, in which the winds are most greatly affected by surface roughness and topography). The aeolian wind tunnel is used for two purposes: to simulate the physics of the saltation process and to model at small scale the erosional and depositional processes associated with topographic surface features. For purposes of studying aeolian effects on the surface of Mars and Venus as well as on Earth, the aeolian wind tunnel continues to prove to be a useful tool for estimating wind speeds necessary to move small particles on the three planets as well as to determine the effects of topography on the evolution of aeolian features such as wind streaks and dune patterns.

  10. Quantifying the Impact of Mineral Dust and Dissolved Iron Deposition on Marine Biological Activity

    NASA Astrophysics Data System (ADS)

    Johnson, M. S.; Meskhidze, N.; Gassó, S.; Solmon, F.

    2009-12-01

    Aeolian dust deposition has proven to be a critical source of iron (Fe) to remote oceanic regions where it can play an important role in regulating marine ecosystem productivity. Increases in marine biological activity have been suggested to reduce atmospheric carbon dioxide (CO2) and enhance oceanic emissions of marine primary organic aerosols and biologically produced trace gases leading to secondary aerosol formation. These mechanisms can affect climate directly by enhancing carbon sequestration rates, and through organic aerosols influencing incoming solar radiation or modulating shallow marine cloud properties. Due to dust emissions and transport also being dependent upon climatic conditions, the relationship between aeolian dust deposition and oceanic emissions (e.g., primary organic matter, dimethylsulphide, halocarbons, and several types of non-methane hydrocarbons) presents a possible ocean-atmosphere feedback cycle. The Southern Ocean (SO) is characterized as being the largest oceanic region with marine primary productivity that is limited by the micronutrient Fe. Despite the potentially important role of dust laden-Fe in this region, few studies exist that can help to constrain the impact of dust-laden Fe fluxes on biological productivity in the Atlantic sector of the SO. Patagonia has been estimated to supply the majority of aeolian-Fe deposited to the South Atlantic Ocean (SAO). Thus, the focus of this study is to quantify the influence of Patagonian dust storms on marine primary productivity in the SAO and assess the potential climatic effect of variability in aeolian dust deposition. In this work we use the global chemistry transport model GEOS-Chem, implemented with a prognostic Fe dissolution scheme (GEOS-Chem/DFeS), to evaluate the deposition of Patagonian dust and associated dissolved iron (DFe) fluxes to the SAO. Model predicted fluxes of DFe were then used to quantify the impact of Patagonian dust on marine primary productivity in the surface

  11. From Desert to Dessert: Why Australian Dust Matters.

    NASA Astrophysics Data System (ADS)

    Hunter, K. A.; Mackie, D. S.; Boyd, P. W.; McTainsh, G. H.

    2006-12-01

    The growth of some types of phytoplankton in several parts of the world ocean, including much of the Southern Ocean, is limited by the supply of iron. Large Australian dust storms uplift, transport and abrade soils, to produce aeolian dust that is a significant source iron to the Southern Ocean. Atmospheric processes that enhance the dissolution of iron from aeolian dusts are of interest and have been studied for material from major dust producing regions like the Sahara, Gobi and Australian deserts; the reported solubility of iron from aeolian dusts ranges from <0.01% to 80%. The characteristic red soils, sands and dusts from Australia are generally believed to consist of quartz grains with a coating of fine grains and crystals of iron oxides, primarily hematite and goethite. The precise mineralogy of soil and dust grain coatings is poorly understood and it also not well known how the coatings are altered during uplift and transport to the ocean. Current models to understand the processes operating during the transport and atmospheric processing of dust include some generalisations and simplifications that are not always warranted and our work has shown the overlooked complexity of the system. Models for aeolian-iron dissolution based on Northern Hemisphere data commonly include the pollutants SOx and NOx. The modern Southern Hemisphere is less polluted and thus resembles past environmental systems. The dissolution of iron from soils of the Saharan, Gobi and Australian deserts in the presence of protons only (i.e. without SOx and NOx) occurs in two phases. The first, faster phase, representing up to 20% of total iron is via a surface-controlled mechanism. The rate determining variable is the exposed surface area of the iron oxides and not the size of the underlying quartz grain. The second, slower, phase of dissolution occurs via the transport-controlled formation of a leached layer. During the simulated aeolian abrasion of Australian soils from dust producing

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

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2016-02-01

    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 studies and satellite retrievals

  13. Prevailing Dust-transport Directions on Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Kramer, Tobias; Noack, Matthias

    2015-11-01

    Dust transport and deposition behind larger boulders on the comet 67P/Churyumov-Gerasimenko (67P/C-G) have been observed by the Rosetta mission. We present a mechanism for dust-transport vectors based on a homogeneous surface activity model incorporating in detail the topography of 67P/C-G. The combination of gravitation, gas drag, and Coriolis force leads to specific dust transfer pathways, which for higher dust velocities fuel the near-nucleus coma. By distributing dust sources homogeneously across the whole cometary surface, we derive a global dust-transport map of 67P/C-G. The transport vectors are in agreement with the reported wind-tail directions in the Philae descent area.

  14. Dust Long-Range Transport and the Dust-Radiation Effects on the Modification of the SAL Environment

    NASA Astrophysics Data System (ADS)

    Chen, S.; Wang, S.; Waylonis, M.; Sc

    2010-12-01

    A tracer model based on the Weather Research and Forecast model was developed to simulate dust long-range transport for a dust outbreak event that occurred during July 18-20, 2005. Two numerical experiments were conducted with (ON) and without (OFF) the dust-radiation effects. Simulations were compared with the Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectrometer (MODIS) and results were very reasonable. The influence of dust-radiation effects on the modification of Saharan Air Layer (SAL), which can have a substantial influence on Tropical Cyclone (TC) activities over the eastern Atlantic Ocean, was also investigated. Suspended dust was able to reduce the net downward shortwave radiation by more than 300 W m-2 on the surface. The modification of temperature profiles due to dust-radiation effects resulted in the adjustment of the vertical shear. The dust-radiation effects also modified the dust distribution, which can have a feedback to the heating profile and the vertical shear.

  15. Investigation of dust transport on the lunar surface in laboratory plasmas

    NASA Astrophysics Data System (ADS)

    Wang, X.; Horanyi, M.; Robertson, S. H.

    2009-12-01

    There has been much evidence indicating dust levitation and transport on or near the lunar surface. Dust mobilization is likely to be caused by electrostatic forces acting on small lunar dust particles that are charged by UV radiation and solar wind plasma. To learn about the basic physical process, we investigated the dynamics of dust grains on a conducting surface in laboratory plasmas. The first experiment was conducted with a dust pile (JSC-Mars-1) sitting on a negatively biased surface in plasma. The dust pile spread and formed a diffusing dust ring. Dust hopping was confirmed by noticing grains on protruding surfaces. The electrostatic potential distributions measured above the dust pile show an outward pointing electrostatic force and a non-monotonic sheath above the dust pile, indicating a localized upward electrostatic force responsible for lifting dust off the surface. The second experiment was conducted with a dust pile sitting on an electrically floating conducting surface in plasma with an electron beam. Potential measurements show a horizontal electric field at the dust/surface boundary and an enhanced vertical electric field in the sheath above the dust pile when the electron beam current is set to be comparable to the Bohm ion current. Secondary electrons emitted from the surfaces play an important role in this case.

  16. Mega-ripples in Iran: A new analog for transverse aeolian ridges on Mars

    NASA Astrophysics Data System (ADS)

    Foroutan, M.; Zimbelman, J. R.

    2016-08-01

    A new terrestrial analog site for transverse aeolian ridges (TARs) is described in this study. The Lut desert of Iran hosts large ripple-like aeolian bedforms, with the same horizontal length scales and patterns of TARs on Mars. Different classes of TARs and different types of other aeolian features such as sand dunes, zibars, dust devil tracks and yardangs can be found in this area, which signify an active aeolian region. This area represents a unique site to study the formation and evolution of these enigmatic features, with potential relevance toward a better understanding of TARs on Mars.

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

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2015-08-01

    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 tranport (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 higher concentration of pollution particles at intermediate altitude (1-3 km) than at elevated altitude (> 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. 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 light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. 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 assimilated to those of native dust in radiative transfer simulations, modeling studies and

  18. A Fractal Model for the Capacitance of Lunar Dust and Lunar Dust Aggregates

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Stubbs, Timothy J.; Keller, John W.; Farrell, William M.; Marshall, John; Richard, Denis Thomas

    2011-01-01

    Lunar dust grains and dust aggregates exhibit clumping, with an uneven mass distribution, as well as features that span many spatial scales. It has been observed that these aggregates display an almost fractal repetition of geometry with scale. Furthermore, lunar dust grains typically have sharp protrusions and jagged features that result from the lack of aeolian weathering (as opposed to space weathering) on the Moon. A perfectly spherical geometry, frequently used as a model for lunar dust grains, has none of these characteristics (although a sphere may be a reasonable proxy for the very smallest grains and some glasses). We present a fractal model for a lunar dust grain or aggregate of grains that reproduces (1) the irregular clumpy nature of lunar dust, (2) the presence of sharp points, and (3) dust features that span multiple scale lengths. We calculate the capacitance of the fractal lunar dust analytically assuming fixed dust mass (i.e. volume) for an arbitrary number of fractal levels and compare the capacitance to that of a non-fractal object with the same volume, surface area, and characteristic width. The fractal capacitance is larger than that of the equivalent non-fractal object suggesting that for a given potential, electrostatic forces on lunar dust grains and aggregates are greater than one might infer from assuming dust grains are sphericaL Consequently, electrostatic transport of lunar dust grains, for example lofting, appears more plausible than might be inferred by calculations based on less realistic assumptions about dust shape and associated capacitance.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  20. The Origin of Transverse Aeolian Ridges on Mars

    NASA Astrophysics Data System (ADS)

    Geissler, P.

    2015-12-01

    Transverse aeolian ridges, or TARs, are found throughout the tropics of Mars and typically appear as rows of bright ripples that are several meters tall and spaced semi-regularly several tens of meters apart. The origin of these features remained mysterious for decades after their discovery in Viking and Mars Global Surveyor images. A new hypothesis (Geissler, 2014, 10.1002-2014JE004633) suggests that TARs might be deposits left behind by dusty turbidity currents in the Martian atmosphere. The hypothesis assumes that the micron-sized dust particles are transported in suspension in turbulent flows, driven both by the winds and by gravity. The dust is concentrated near the surface, much like turbidity currents on Earth. Because of the difference in density, however, the dust clouds behave as a fluid distinct from the clear sky above. In particular, waves can appear at the surface of the dense "fluid" when the flows encounter topographic obstacles along their paths. Such gravity waves travel at speeds that are determined by gravity and the thickness of the flow, much like waves in shallow water on Earth. When the wave propagation speed matches the speed of the flow, stationary waves are produced that persist in fixed locations. The bedforms deposited by such stationary waves are called "antidunes" (Gilbert, 1914, USGS Prof. Paper 86) because, unlike dunes, they can migrate upstream in a supercritical flow. Antidunes are commonly seen in shallow, high energy fluvial deposits on Earth. They are usually destroyed as quickly as they form, and are rarely preserved. The Martian TARs survive because the dust is sticky; TARs are deposited by currents that are much slower than the wind speeds needed to lift the dust again. Subaerial antidunes are much rarer on Earth and less well studied, and so the giant subaerial stationary antidunes of Mars, if that is what the TARs turn out to be, may teach us much about a geological process that is poorly known on our planet.

  1. Dust Devil Sediment Transport: From Lab to Field to Global Impact

    NASA Astrophysics Data System (ADS)

    Klose, Martina; Jemmett-Smith, Bradley C.; Kahanpää, Henrik; Kahre, Melinda; Knippertz, Peter; Lemmon, Mark T.; Lewis, Stephen R.; Lorenz, Ralph D.; Neakrase, Lynn D. V.; Newman, Claire; Patel, Manish R.; Reiss, Dennis; Spiga, Aymeric; Whelley, Patrick L.

    2016-07-01

    The impact of dust aerosols on the climate and environment of Earth and Mars is complex and forms a major area of research. A difficulty arises in estimating the contribution of small-scale dust devils to the total dust aerosol. This difficulty is due to uncertainties in the amount of dust lifted by individual dust devils, the frequency of dust devil occurrence, and the lack of statistical generality of individual experiments and observations. In this paper, we review results of observational, laboratory, and modeling studies and provide an overview of dust devil dust transport on various spatio-temporal scales as obtained with the different research approaches. Methods used for the investigation of dust devils on Earth and Mars vary. For example, while the use of imagery for the investigation of dust devil occurrence frequency is common practice for Mars, this is less so the case for Earth. Modeling approaches for Earth and Mars are similar in that they are based on the same underlying theory, but they are applied in different ways. Insights into the benefits and limitations of each approach suggest potential future research focuses, which can further reduce the uncertainty associated with dust devil dust entrainment. The potential impacts of dust devils on the climates of Earth and Mars are discussed on the basis of the presented research results.

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  3. The transatlantic dust transport from North Africa to the Americas—Its characteristics and source regions

    NASA Astrophysics Data System (ADS)

    Gläser, Gregor; Wernli, Heini; Kerkweg, Astrid; Teubler, Franziska

    2015-11-01

    Transport of Saharan dust over the Atlantic to the Americas is a relevant process since dust is a nutrient for marine and terrestrial ecosystems. It is therefore important to better quantify the frequency and amount of transatlantic dust transport, its preferred altitude and duration, and the regions of dust origin. This study uses a novel combination of Eulerian and Lagrangian diagnostics, applied to a previously validated 5 year simulation of the fifth generation European Centre for Medium Range Weather Forecast-Hamburg-model (ECHAM5)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry model, to quantify these dust transport characteristics and their seasonal variations. Results confirm the previously found preferred transatlantic dust pathways: in boreal winter and spring, African dust is mainly transported below 800 hPa toward South America, whereas in summer and autumn the preferred pathway is to the Caribbean and occurs in a layer up to 500 hPa. The averaged transport duration from dust emission to deposition is 10 days in winter for deposition in the Amazon region and almost 12 days in summer for deposition in the Caribbean. These estimates were obtained by combining correlation analyses of Eulerian dust fluxes and trajectory calculations. The latter were also essential to identify the main source regions of transatlantic dust transport, which were found in all seasons in northwestern Africa (Algeria, Mali, and Mauritania) but not farther east, e.g., in the Bodélé Depression. A specific Lagrangian analysis for this dust emission hot spot suggests that wet deposition associated with the Intertropical Convergence Zone in winter and the African monsoon in summer inhibits Bodélé dust to leave the African continent.

  4. Threshold wind velocity dynamics as a driver of aeolian sediment mas flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Horizontal (saltation) mass flux is a key driver of aeolian dust emission. Estimates of the horizontal mass flux underpin assessments of the global dust budget and influence our understanding of the dust cycle and its interactions. Current equations for predicting horizontal mass flux are based on l...

  5. Extreme detached dust layers near Martian volcanoes: Evidence for dust transport by mesoscale circulations forced by high topography

    NASA Astrophysics Data System (ADS)

    Heavens, N. G.; Cantor, B. A.; Hayne, P. O.; Kass, D. M.; Kleinböhl, A.; McCleese, D. J.; Piqueux, S.; Schofield, J. T.; Shirley, J. H.

    2015-05-01

    Modeling suggests that thermal circulations over Mars's highest volcanoes transport water vapor and dust from the surface into the middle atmosphere, forming detached layers in these constituents. Intense vertical mixing also takes place in regional and global dust storms, which can generate detached layers that are extreme in both altitude and magnitude. Here we employ observations by the Mars Climate Sounder (MCS) on board Mars Reconnaissance Orbiter, taking advantage of improved vertical coverage in MCS's aerosol retrievals, to discover a new class of extreme detached dust layers (EDDLs). Observed during minimal dust storm activity and furthermore distinguished by their potentially large and measurable horizontal extent (>1000 km), these EDDLs cluster near Olympus Mons and the Tharsis Montes, from which they likely originate. The existence of these EDDLs suggests that vertical mixing by topographic circulations can be much stronger than previously modeled and more frequent than previously observed.

  6. Saharan Dust Export towards the Caribbean: Transport, Mixing and Deposition Processes over the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Heinold, Bernd; Schepanski, Kerstin; Haarig, Moritz; Ansmann, Albert; Groß, Silke; Schäfler, Andreas; Weinzierl, Bernadett; Tegen, Ina

    2015-04-01

    Large amounts of Saharan 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. Here, we investigate the long-range transport of Saharan dust across the Atlantic Ocean by means of transport modelling that has been performed within the framework of the SALTRACE (Saharan Aerosol Long-Range Transport and Aerosol-Cloud Interaction Experiment) project. The emission, transport, dry and wet deposition of Saharan dust as well as the effect of dust radiative forcing are simulated with the regional model COSMO-MUSCAT. The model results are evaluated against the various ground and airborne observations from the SALTRACE field measurements at Barbados Island in June and July 2013. The dust simulations, in turn, help to interpret the observations, in particular from a Lagrangian flight experiment, by providing a spatiotemporal context. Specifically, this study addresses the questions of (a) how the Saharan dust export towards the Caribbean is influenced by the atmospheric circulation over West Africa, (b) which role the different removal and mixing processes play during long-range transport, and (c) what is the impact of dust forcing on the vertical structure of the SAL? In addition, the Saharan dust simulations with COSMO-MUSCAT are combined with trajectory analysis to study particle aging and dust-cloud interactions.

  7. Dust Emissions, Transport, and Deposition Simulated with the NASA Finite-Volume General Circulation Model

    NASA Technical Reports Server (NTRS)

    Colarco, Peter; daSilva, Arlindo; Ginoux, Paul; Chin, Mian; Lin, S.-J.

    2003-01-01

    Mineral dust aerosols have radiative impacts on Earth's atmosphere, have been implicated in local and regional air quality issues, and have been identified as vectors for transporting disease pathogens and bringing mineral nutrients to terrestrial and oceanic ecosystems. We present for the first time dust simulations using online transport and meteorological analysis in the NASA Finite-Volume General Circulation Model (FVGCM). Our dust formulation follows the formulation in the offline Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport Model (GOCART) using a topographical source for dust emissions. We compare results of the FVGCM simulations with GOCART, as well as with in situ and remotely sensed observations. Additionally, we estimate budgets of dust emission and transport into various regions.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  9. Aeolian processes in Proctor Crater on Mars: Sedimentary history as analyzed from multiple data sets

    USGS Publications Warehouse

    Fenton, L.K.; Bandfield, J.L.; Ward, A.W.

    2003-01-01

    , rather than by the passage of dust devils. Spectral deconvolution indicates that the dark dunes have infrared spectra consistent with basalt-like materials. The average thermal inertia calculated from Thermal Emission Spectrometer bolometric temperatures is 277 ?? 17 J m-2 s-0.5 K-1, leading to an effective grain size of 740 ?? 170 ??m, which is consistent with coarse sand and within the range expected for Martian sand. The coarse sand that composes the large dune field may have originated from outside the crater, saltating in from the southwest. Most of the transport pathway that delivered this sand to the dune field has since been eroded away or buried. The sand was transported to the east center of the crater floor, where beneath the present-day dunes a 50 m high mound of sand has accumulated. Dune slip faces indicate a wind regime consisting of three opposing winds. Some of these wind directions are correlated with the orientations of dust devil tracks and bright bed forms. The combination of a tall mound of sand and three opposing winds is consistent with a convergent wind regime, which produces the large reversing transverse and star dunes that dominate the dune field. The dark dunes have both active slip faces and seemingly inactive slip faces, suggesting that the dunes vary spatially in their relative activity. Nevertheless, the aeolian activity that has dominated the history of Proctor Crater still continues today. Copyright 2003 by the American Geophysical Union.

  10. Lagrangian dust model simulations for a case of moist convective dust emission and transport in the western Sahara region during Fennec/LADUNEX

    NASA Astrophysics Data System (ADS)

    Sodemann, H.; Lai, T. M.; Marenco, F.; Ryder, C. L.; Flamant, C.; Knippertz, P.; Rosenberg, P.; Bart, M.; McQuaid, J. B.

    2015-06-01

    Due to the harshness and inaccessibility of desert regions, the uncertainties concerning the processes of dust mobilization at the surface, airborne transport, and sedimentation are still considerable, limiting the ability to perform model simulations. In June 2011, a comprehensive data set of ground-based and airborne in situ measurements and remote sensing observations was acquired within the Fennec/Lagrangian Dust Source Inversion Experiment (LADUNEX) field campaign in the western Sahara region. Here we evaluate the ability of the state-of-the-art Lagrangian particle dispersion model FLEXPART, newly fitted with a dust mobilization capability, to simulate dust transport in this region. We investigate a case where a large mesoscale convective system (MCS) triggered dust emissions in central Mali, which subsequently moved as a large cold pool dust front toward northern Mauritania. Specifying dust mobilization for this case is shown to be an important obstacle to simulating dust transport during this event, since neither the MCS nor the associated cold pool-causing dust emission is represented in the meteorological analysis. Obtaining a realistic dust transport simulation for this case therefore requires an inversion approach using a manual specification of the dust sources supported by satellite imagery. When compared to in situ and remote sensing data from two aircraft, the Lagrangian dust transport simulations represent the overall shape and evolution of the dust plume well. While accumulation and coarse mode dust are well represented in the simulation, giant mode particles are considerably underestimated. Our results re-emphasize that dust emission associated with deep moist convection remains a key issue for reliable dust model simulations in northern Africa.

  11. Mass transport by Aeolian saltation on Earth, Mars and Venus: The effects of full saltation cloud development and choking

    NASA Technical Reports Server (NTRS)

    Williams, S. H.; Greeley, R.

    1987-01-01

    Wind tunnel tests were conducted to study the characteristics of particle motion and the quantity transported by wind under a variety of planetary environmental conditions. Analysis of the results indicates that, on Earth, saltation fully develops at near-threshold wind speeds and rarely chokes (retarding of saltation due to high particle concentration and subsequent increase of mid-air collisions). On Mars, saltation becomes fully developed only at favorable locations and at wind speeds well above threshold. The Martian saltation cloud has an insufficient particle concentration to cause choking, particularly over a partially rocky surface. On Venus, full saltation occurs at wind speeds very near threshold, but saltation flux increases less rapidly than expected at relatively modest wind speeds due to choking.

  12. Potential source regions of dust accumulated in northern Africa

    NASA Astrophysics Data System (ADS)

    Wasowska, S.; Woronko, B.

    2012-04-01

    Sahara is the largest source of the dust in the world. The material sampled from dust storms in Tunisia (Nefta Oasis, El Kantoui Harbor), north Egypt (Alexandria) and Morocco (Mhamid Oasis) (March 2001, March and April 2009) was taken to identify the potential sources of dust accumulation and transport paths in North Africa. The samples were analyzed on grain size, micromorphology of silt grain surfaces in Scanning Electron Microscope (SEM), elemental composition of grains and their surface crusts, loss on ignition, mineralogical composition of samples and carbonate content. Additionally the meteorological situation was analyzed during the dust storm occurrences and preceding periods. The results of grain size analyses show that all studied sediments belong to the small dust type, and dust accumulated in Mhamid is the clay mineral agglomerated (CMA) dust. The source of the CMA are the old dry lake beds. Dust particles are mobilized as aggregates of clay minerals, what is controlled by structure (particle packing) of the original lake sediment, and accumulation is dry and wet as well. The results of the analysis of the quartz grain surface micromorphology, the elemental composition and loss on ignition indicate that dust accumulated in Morocco originated from a relatively homogenous sediment source and, on the other hand, dust found in Alexandria comes from a diversified source. Dust sampled in Tunisia is characterized by the highest content of carbonates and organic matter which suggests the intensive dispelling acting on the weathered material from carbonate rocks and local Mediterranean soil covers rich in CaCO3. The analyses of meteorological conditions during the dust storms and the analyses of the textural characteristics of deposits show that it is highly probable that analysed aeolian dust was transported both for shorter and longer distances. Hypothetic source areas of dust accumulated in Mhamid could be the old ergs, some located 300-500 km away like

  13. Modelling the aeolian transport of ammonia emitted from poultry farms and its deposition to a coastal waterbody

    NASA Astrophysics Data System (ADS)

    Wiegand, Aaron N.; Menzel, Sarah; King, Rob; Tindale, Neil

    2011-10-01

    In response to the absence of monitoring data, the Air Pollution Model (TAPM), a 3D prognostic model that predicts both meteorology and air pollution concentrations, was used to investigate the transport of ammonia across part of the Sunshine Coast region (South East Queensland, Australia), following its emission to the atmosphere from 41 poultry farms (egg and broiler) in the district, which cumulatively house approximately 9.8 million fowl. The study estimated the total amount of ammonia that is deposited directly into the Pumicestone Passage waterbody (63 km2) and onto the surrounding catchment (1184 km2), through both wet and dry deposition processes over a twelve-month period. The results indicate that wet deposition is the dominant deposition process into the waterbody (89%) and catchment area (94%). Most of the ammonia deposition is predicted to occur within a relatively short distance from the farms, due to higher concentrations at these locations. In the base case simulation, the estimated 1823 tonnes of annual ammonia emissions were predicted to result in the direct deposition of approximately 2.3 tonnes of ammonia into the Pumicestone Passage waterbody and approximately 53.5 tonnes onto the Pumicestone Passage catchment land surface, where there was potential for its subsequent run-off into the waterbody. This annual loading into the waterbody is not insignificant and is likely to contribute to the formation of algal blooms. The fate of the remaining 91% of the ammonia estimated to be emitted from the farms was not accounted for in the deposition totals. This ammonia most likely remains suspended in the atmosphere and is transported outside of the simulation study area.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  15. Vertical transport of dust in convective boundary layer

    NASA Astrophysics Data System (ADS)

    Kurgansky, Michael

    2015-04-01

    A model is proposed that relates the vertical mass flux of sand (dust) Q to the number density N of convective elements (including vortices), the friction velocity u* and the buoyancy flux B. It is inferred that the flux Q is proportional to the product of the square root of B and the sixth power of u*. This does not contradict to empirical dependencies Q(u*) reported in the literature. Two methods of determination of the number density N are discussed when the dust lifting is mainly due to (terrestrial and Martian) dust devils. The first method is based on optical observations of dust devils produced from a fixed point on the ground and on analysis of dust devil angular size-frequency distribution. The second method uses dust devil close encounters with a fixed array of meteorological stations.

  16. Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

    NASA Technical Reports Server (NTRS)

    Marshall, John R.

    1999-01-01

    Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 um-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a

  17. Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

    NASA Technical Reports Server (NTRS)

    Marshall, John R.

    1999-01-01

    Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a

  18. Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

    NASA Astrophysics Data System (ADS)

    Marshall, John R.

    1999-09-01

    Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 um-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a

  19. Unique Aeolian Transport Mechanisms on Mars: Respective Roles of Percussive and Repercussive Grain Populations in the Sediment Load

    NASA Astrophysics Data System (ADS)

    Marshall, John R.

    1999-09-01

    Experiments show that when sand-size grains impact a sediment surface with energy levels commensurate for Mars, small craters are formed by the ejection of several hundred grains from the bed. The experiments were conducted with a modified crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism. Individual grains of sand could be fired at loose sand targets to observe ballistic effects unhindered by aerodynamic mobilization of the bed. Impact trajectories simulated the saltation process on dune surfaces. Impact craters were not elongated despite glancing (15 deg.) bed impact; the craters were very close to being circular. High-speed photography showed them to grow in both diameter and depth after the impactor had ricochetted from the crater site. The delayed response of the bed was "explosive" in nature, and created a miniature ejecta curtain spreading upward and outward for many centimeters for impact of 100-300 micron-diameter grains into similar material. This behavior is explained by deposition of elastic energy in the bed by the "percussive" grain. Impact creates a subsurface stress regime or "quasi-Boussinesq" compression field. Elastic recovery of the bed occurs by dilatancy; shear stresses suddenly convert the grains to open packing and they consequently become forcefully ejected from the site. Random jostling of the grains causes radial homogenization of stress vectors and a resulting circular crater. A stress model based on repercussive bed dilatancy and interparticle adhesive forces (for smaller grains) predicts, to first order, the observed crater volumes for various impact conditions. On earth, only a few grains are mobilized by a percussive saltating grain; some grains are "knudged" along the ground, and some are partly expelled on short trajectories. These motions constitute reptation transport. On Mars, saltation and reptation become indistinct: secondary or "repercussive" trajectories have sufficient vertical impulse to create a

  20. Particle production and aeolian transport from a ``supply-limited'' source area in the Chihuahuan desert, New Mexico, United States

    NASA Astrophysics Data System (ADS)

    Gillette, Dale A.; Chen, Weinan

    2001-03-01

    Wind erosion mechanisms were investigated for the "scrape site" at the Jornada Experimental Range near Las Cruces, New Mexico, in the Chihuahuan desert. The scrape site was denuded of vegetation and scraped flat in 1991. We adopted the site in 1994 because it offered an opportunity to study wind erosion mechanisms for a large area of unprotected sandy and crusted soil in an otherwise natural setting and over a period of several years. We installed and operated the following instrumentation for a period of 35 months: three meteorological towers, each 2 m in height, with wind speed sensors at 0.2, 0.5, 1.0, and 2.0 m above ground; air temperature at 0.2 and 2 m height; rain gauge; seven sets of particle collectors at 0.1, 0.5, and 1.0 m heights; and three fast-response particle mass flux sensors at 0.02, 0.1, 0.2, and 0.5 m heights; all along a transect crossing the site and parallel to the predominant southwesterly wind direction. The minimum threshold friction velocity for the scrape site with a thin layer of loose material was 25 cm s-1. This minimum threshold velocity increased to as high as 100 cm s-1 depending on the degree of particle depletion and the site's status which varied between supply unlimited just after a high wind episode and supply limited which was more typical for the rest of the time. The dominant mechanism producing fresh sediment for transport was sandblasting of the surface crust. The measurements showed that supply and availability of loose, fine particles on the surface is a strong control of rates of erosion rather than wind energy alone.

  1. Laboratory study of PCB transport from primary sources to settled dust

    EPA Science Inventory

    Transport of house dust and Arizona Test Dust on polychlorinated biphenyl (PCB)-containing panels and PCB-free panels was investigated in a 30-m3 stainless steel chamber. The PCB-containing panels were aluminum sheets coated with a PCB-spiked, oil-based primer or two-part polysul...

  2. Bursts in discontinuous Aeolian saltation.

    PubMed

    Carneiro, M V; Rasmussen, K R; Herrmann, H J

    2015-01-01

    Close to the onset of Aeolian particle transport through saltation we find in wind tunnel experiments a regime of discontinuous flux characterized by bursts of activity. Scaling laws are observed in the time delay between each burst and in the measurements of the wind fluctuations at the fluid threshold Shields number θc. The time delay between each burst decreases on average with the increase of the Shields number until sand flux becomes continuous. A numerical model for saltation including the wind-entrainment from the turbulent fluctuations can reproduce these observations and gives insight about their origin. We present here also for the first time measurements showing that with feeding it becomes possible to sustain discontinuous flux even below the fluid threshold. PMID:26073305

  3. Bursts in discontinuous Aeolian saltation

    PubMed Central

    Carneiro, M. V.; Rasmussen, K. R.; Herrmann, H. J.

    2015-01-01

    Close to the onset of Aeolian particle transport through saltation we find in wind tunnel experiments a regime of discontinuous flux characterized by bursts of activity. Scaling laws are observed in the time delay between each burst and in the measurements of the wind fluctuations at the fluid threshold Shields number θc. The time delay between each burst decreases on average with the increase of the Shields number until sand flux becomes continuous. A numerical model for saltation including the wind-entrainment from the turbulent fluctuations can reproduce these observations and gives insight about their origin. We present here also for the first time measurements showing that with feeding it becomes possible to sustain discontinuous flux even below the fluid threshold. PMID:26073305

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  5. Threshold wind velocity dynamics as a driver of aeolian sediment mass flux

    NASA Astrophysics Data System (ADS)

    Webb, Nicholas P.; Galloza, Magda S.; Zobeck, Ted M.; Herrick, Jeffrey E.

    2016-03-01

    Horizontal (saltation) mass flux is a key driver of aeolian dust emission. Estimates of the horizontal mass flux underpin assessments of the global dust budget and influence our understanding of the dust cycle and its interactions. Current equations for predicting horizontal mass flux are based on limited field data and are constrained to representing transport-limited equilibrium saltation, driven by the wind momentum flux in excess of an entrainment threshold. This can result in large overestimation of the sediment mass flux. Here we compare measurements of the soil entrainment threshold, horizontal mass flux, and their temporal variability for five undisturbed dryland soils to explore the role of threshold in controlling the magnitude of mass flux. Average and median entrainment threshold showed relatively small variability among sites and relatively small variability between seasons, despite significant differences in soil surface conditions. Physical and biological soil crusts had little effect on the threshold value, and threshold appeared to play a minor role in determining the magnitude of sediment transport. Our results suggest that horizontal mass flux was controlled more by the supply limitation and abrasion efficiency of saltators present as loose erodible material or originating from neighboring soil sources. The omission of sediment supply and explicit representation of saltation bombardment from horizontal flux equations is inconsistent with the process representation in dust emission schemes and contributes to uncertainty in model predictions. This uncertainty can be reduced by developing greater process fidelity in models to predict horizontal mass flux under both supply- and transport-limited conditions.

  6. Environmental history recorded in aeolian deposits under stone pavements, Mojave Desert, USA

    NASA Astrophysics Data System (ADS)

    Dietze, Michael; Dietze, Elisabeth; Lomax, Johanna; Fuchs, Markus; Kleber, Arno; Wells, Stephen G.

    2016-01-01

    Reconstructing the evolution of arid landscapes is challenged by limited availability of appropriate environmental archives. A widespread surface feature - stone pavement - traps aeolian fines and forms a special accretionary archive. Seven stone pavement-covered sections on basalt flows in the eastern Mojave Desert are condensed into a composite section, comprising five sedimentological units supported by an OSL-based chronology. Three of the units are of accretionary nature and each is covered by a stone pavement. They were deposited > 50.9-36.6 ka, < 36.6-14.2 ka and < 14.2 ka, and they are intimately coupled with the history of nearby Lake Mojave, which advances the current understanding of regional aeolian activity. End-member modeling analysis of grain-size distributions yielded seven sediment transport regimes. The accretionary system operates in two modes: A) episodic formation of a stone pavement by lateral processes once a vesicular horizon has formed on a barren surface; and B) accretion of dust and eventual burial of the clast layer. These findings improve current concepts about stone pavement evolution and their environmental proxy function in arid landscapes. Stone pavement-covered accretionary deposits are a new key archive that allows quantifying the relative importance of dust accretion, slope processes, soil formation and vegetation cover.

  7. Modeling of mineral dust in the atmosphere: Sources, transport, and optical thickness

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Fung, Inez

    1994-01-01

    A global three-dimensional model of the atmospheric mineral dust cycle is developed for the study of its impact on the radiative balance of the atmosphere. The model includes four size classes of minearl dust, whose source distributions are based on the distributions of vegetation, soil texture and soil moisture. Uplift and deposition are parameterized using analyzed winds and rainfall statistics that resolve high-frequency events. Dust transport in the atmosphere is simulated with the tracer transport model of the Goddard Institute for Space Studies. The simulated seasonal variations of dust concentrations show general reasonable agreement with the observed distributions, as do the size distributions at several observing sites. The discrepancies between the simulated and the observed dust concentrations point to regions of significant land surface modification. Monthly distribution of aerosol optical depths are calculated from the distribution of dust particle sizes. The maximum optical depth due to dust is 0.4-0.5 in the seasonal mean. The main uncertainties, about a factor of 3-5, in calculating optical thicknesses arise from the crude resolution of soil particle sizes, from insufficient constraint by the total dust loading in the atmosphere, and from our ignorance about adhesion, agglomeration, uplift, and size distributions of fine dust particles (less than 1 micrometer).

  8. 3D Structure of Saharan Dust Transport Towards Europe as Seen by CALIPSO

    NASA Astrophysics Data System (ADS)

    Marinou, Eleni; Amiridis, Vassilis; Tsekeri, Alexandra; Solomos, Stavros; Kokkalis, Panos; Proestakis, Emmanouil; Kottas, Michael; Binietoglou, Ioannis; Zanis, Prodromos; Kazadzis, Stelios; Wandinger, Ulla; Ansmann, Albert

    2016-06-01

    We present a 3D multi-year monthly mean climatology of Saharan dust advection over Europe using an area-optimized pure dust CALIPSO product. The product has been developed by applying EARLINET-measured dust lidar ratios and depolarization-based dust discrimination methods and it is shown to have a very good agreement in terms of AOD when compared to AERONET over Europe/North Africa and MODIS over Mediterranean. The processing of such purely observational data reveals the certain seasonal patterns of dust transportation towards Europe and the Atlantic Ocean. The physical and optical properties of the dust layer are identified for several areas near the Saharan sources, over the Mediterranean and over continental Europe.

  9. Impact of Long-Range Dust Transport on Northern California in Spring 2002

    SciTech Connect

    Cameron-Smith, P; Bergmann, D; Chuang, C; Bench, G; Cliff, S; Kelly, P; Perry, K; VanCuren, T

    2005-02-10

    It has been well documented that spectacular dust storms in Asia (e.g. the events in 1998 and 2001) can affect the USA through long-range transport of dust across the Pacific. However, our observations and modeling show that the majority of dust at sites in Lassen National Park and Trinity Alps (Northern California) in spring 2002 (a year with no spectacular Asian dust events) is still from long-range intercontinental transport across the Pacific. We implemented the interactive dust emission algorithm of Ginoux et al. (2004) into the LLNL 3-D global atmospheric chemistry and aerosol transport model (IMPACT), then ran the model using a separate tracer for each dust emission region, using hi-resolution (1 x 1 degree) meteorological data from the NASA GMAO GEOS-3 assimilation system for 2001 and 2002. We also experimentally analyzed size- and time-resolved aerosol samples at Lassen National Park and Trinity Alps in the spring of 2002, which were taken as part of NOAA's ITCT 2k2 measurement campaign. The model-predicted time-series of soil dust over Northern California agrees remarkably well with our measurements, with a strong temporal correlation between the observations and intercontinental transport of dust across the Pacific in the model. Hence, we conclude that the majority of dust we sampled in Northern California in spring 2002, with aerodynamic diameters of 0.56-5 microns, is from long-range intercontinental transport across the Pacific. The strong correlations also strongly validate atmospheric transport in the IMPACT model over the Northern Pacific in spring.

  10. Observation of the simultaneous transport of Asian mineral dust aerosols with anthropogenic pollutants using a POPC during a long-lasting dust event in late spring 2014

    NASA Astrophysics Data System (ADS)

    Pan, Xiaole; Uno, Itsushi; Hara, Yukari; Kuribayashi, Masatoshi; Kobayashi, Hiroshi; Sugimoto, Nobuo; Yamamoto, Shigekazu; Shimohara, Takaaki; Wang, Zifa

    2015-03-01

    We observed a long-lasting dust event from 25 May to 2 June 2014, using a polarization optical particle counter (POPC). The transport of dust plumes over East Asia was verified on the basis of observations of Moderate Resolution Imaging Spectroradiometer, a lidar network, and surface synoptic observation stations. Mixing of dust and anthropogenic pollutants was investigated according to the variation in the depolarization ratio as a function of particle size. The nonsphericity of dust particles varied due to the impact of anthropogenic pollutants on their pathway. In the coarse mode, dust particles always had a clear nonspherical configuration, although large amounts of nitrate were also present. Supermicron particles are occasionally present in a spherical configuration, possibly due to the complex mixing of natural dust and anthropogenic particles. Statistically, ~64% of the total nitrate mass was deemed to be transported from outside of Japan due to a trapping effect in the dust plume.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  13. Dust Transport and Deposition Observed from the Terra-Moderate Image Spectrometer (MODIS) Space Observations

    NASA Technical Reports Server (NTRS)

    Kaufman, Y.

    2004-01-01

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

  14. Trends in African dust transport to the Caribbean: African sources, changing climate, and future scenarios

    NASA Astrophysics Data System (ADS)

    Prospero, J. M.

    2012-12-01

    Aerosol studies were begun on Barbados in 1965 and in Miami in 1974 and they continue to this day. This continuous record of daily measurements shows great variability in dust concentrations on time scales ranging from days to decades. Most notable was the great increase in dust concentrations in the early 1970s, apparently in response to drought in West Africa. Increased dust could impact a number of climate processes and human health in the Caribbean Basin. Indeed, in recent decades the dust concentrations over the Caribbean often exceed the US EPA standards for respirable particles. Thus there is concern over possible health impacts in the present day and how these might change in the future in response to climate change in Africa. It is logical to link of increased dust with drought. Indeed, over much of the Barbados record there was a strong negative correlation between dust concentrations and rainfall in the Sahel-Soudano (SS) region of North Africa. However, in retrospect this correlation was largely driven by three distinct periods in the early record: the period of high rainfall and low dust transport in the mid-to-late 1960s; the first drought in the early 1970s; and the extremely intense drought of the early 1980s. During this period, there seemed to be promising relationships between transport and various climate indices: e.g., El Niño, NAO, AMO. However, since the early 1990s there have been large year-to-year changes in SS rainfall but there is no consistent relationship to dust on Barbados or between dust and common climate indices. Furthermore, over the entire record there is a strong shift in seasonal dust transport, most notably, a great increase in winter and spring transport compared to the pre-drought and early drought period. These trends seem to suggest that there have been profound long-term changes in dust emissions and transport. A possible contributing factor could be increased population and land use in the SS region where over the past

  15. Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

    USGS Publications Warehouse

    Draut, Amy E.

    2012-01-01

    Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow- and sediment-limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble–Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial–aeolian coupling is common globally, it is likely that similar sediment-transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

  16. Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

    NASA Astrophysics Data System (ADS)

    Draut, Amy E.

    2012-06-01

    Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow- and sediment-limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble-Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial-aeolian coupling is common globally, it is likely that similar sediment-transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

  17. Aircraft Measurements of Saharan dust properties and impact of atmospheric transport during Fennec

    NASA Astrophysics Data System (ADS)

    Ryder, Claire; Highwood, Ellie; Rosenberg, Phil; Trembath, Jamie; Brooke, Jennifer; Bart, Mark; Dean, Angela; Dorsey, James; Crosier, Jonny; McQuaid, Jim; Brindley, Helen; Banks, James; Marsham, John; Sodemann, Harald; Washington, Richard

    2013-04-01

    Measurements of Saharan dust from recent airborne campaigns have found variations in size distributions and optical properties across Saharan and sub-Saharan Africa. These variations have an impact on radiation and thus weather and climate, and are important to characterise and understand, in particular, to understand how they vary with time after dust uplift, transport, and height in the atmosphere. New in-situ aircraft measurements from the Fennec 2011 aircraft campaign over a remote part of the Sahara Desert and the Atlantic Ocean will be presented and compared to previous airborne measurements. Size distributions extending to 300 μm will be shown, representing measurements extending further into the coarse mode than previously published for Saharan dust. The dust sampled by the aircraft covered a wide variety of loadings, dust source regions (Mali, Mauritania and Algeria) and dust ages (from fresh uplift to several days old). A significant coarse mode was present in the size distribution measurements with effective diameter up to 23 μm, and the mean size distribution showed greater concentrations of coarse mode than previous aircraft measurements. Single scattering albedo (SSA) values at 550nm calculated from these size distributions revealed high absorption from 0.77 to 0.95, with a mean of 0.85. Directly measured SSA values were higher (0.91 to 0.99) but new instrumentation revealed that these direct measurements, behind Rosemount inlets, overestimate the SSA by 0.02 to 0.20 depending on the concentration of coarse particles present. This is caused by inlet inefficiencies and pipe losses. Previous measurements of SSA from aircraft measurements may also have been overestimates for this reason. This has a significant impact on atmospheric heating rates. The largest dust particles were encountered closest to the ground, and were most abundant in cases where dust was freshly uplifted. Number concentration, mass loading and extinction coefficient showed inverse

  18. Aeolian Slipface Processes on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Cornwall, Carin; Jackson, Derek; Bourke, Mary; Cooper, Andrew

    2016-04-01

    The surface of Mars is dominated by aeolian features and many locations show ripple and dune migration over the past decade with some sediment fluxes comparable to terrestrial dunes. One of the leading goals in investigating aeolian processes on Mars is to explore the boundary conditions of sediment transport, accumulation, and dune mor-phology in relation to wind regime as well as to quantify migration rates and sediment flux. We combine terrestrial field observations, 3D computational fluid dynamics (CFD) modeling and remote sensing data to investigate com-plex, small scale wind patterns and grainflow processes on terrestrial and martian dunes. We aim to constrain grain flow magnitudes and frequencies that occur on slipface slopes of dunes in order to improve estimates of martian dune field migration and sediment flux related to wind velocity and flow patterns. A series of ground-based, high resolution laser scans have been collected in the Maspalomas dune field in Gran Canaria, Spain to investigate grainflow frequency, morphology and slipface advancement. Analysis of these laser scans and simultaneous video recordings have revealed a variety of slipface activity. We identify 6 different grain-flow morphologies including, hourglass shape (classic alcove formation with deposit fan below), superficial flow (thin lenses), narrow trough (vertical lines cm in width), sheet, column (vertical alcove walls), and complex (combi-nation of morphologies triggered simultaneously in the same location). Hourglass grainflow morphologies were the most common and occurred regularly. The superficial and narrow trough morphologies were the second most com-mon and frequently occurred in between large grain flows. Sheet grainflows were rare and unpredictable. These flows involved large portions of the slipface (metres across) and mobilized a substantial amount of sediment in one event. We have compared these grainflow morphologies from Maspalomas to those in martian dune fields and

  19. Australian dust deposits: modern processes and the Quaternary record

    NASA Astrophysics Data System (ADS)

    Hesse, Paul P.; McTainsh, Grant H.

    2003-09-01

    Dust raising and transport are common and important processes in Australia today. The aridity of the Australian continent and high climatic variability result in widespread dust raising in the arid and semi-arid areas and transport to the humid margins and surrounding oceans. The supply of erodible particles appears to be the greatest limitation on total flux of transported dust. Dust raising is greatest in the Lake Eyre Basin, including the Simpson Desert, and Murray-Darling Basin where internal drainage renews supplies of fine particles to the arid zone. In the west and northwest dust entrainment is low, despite considerable aridity. The marine record of dust flux shows at least a threefold increase in dust flux, compared with the Holocene, in the last glacial maximum in both tropical and temperate Australia, driven by weakened Australian monsoon rains and drier westerly circulation, respectively. Despite the widespread confirmation of aeolian dust deposits in southeastern and southwestern Australia, dated or quantified records are extremely rare. The dominant model of Australian dust deposits, the clay-rich 'parna', is shown to be poorly substantiated while modern and ancient dust deposits examined in detail are shown to bear a strong similarity to conventional definitions of loess.

  20. Biogeochemical Impact of Long-Range Transported Dust over Northern South China Sea

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; Wang, S. H.; Hsu, N. C.

    2011-01-01

    Transpacific transport and impact of Asian dust aerosols have been well documented (e.g., results from ACE-Asia and regional follow-on campaigns), but little is known about dust invasion to the South China Sea (SCS). On 19-21 March 2010, a fierce Asian dust storm affected large areas from the Gobi deserts to the West Pacific, including Taiwan and Hong Kong. As a pilot study of the 7-SEAS (Seven South East Asian Studies) in the northern SCS, detailed characteristics of long-range transported dust aerosols were first observed by a comprehensive set of ground-based instruments deployed at the Dongsha islands (20deg42'52" N, 116deg43'51" E). Aerosol measurements such as particle mass concentrations, size distribution, optical properties, hygroscopicity, and vertical profiles help illustrate the evolution of this dust outbreak. Our results indicate that these dust particles were mixed with anthropogenic and marine aerosols, and transported near the surface. Satellite assessment of biogeochemical impact of dust deposition into open oceans is hindered by our current inability in retrieving areal dust properties and ocean colors over an extensive period of time, particularly under the influence of cloudy conditions. In this paper, we analyze the changes of retrieved Chlorophyll-a (Chl-a) concentration over the northern SCS, considered as oligotophic waters in the spring, from long-term SeaWiFS measurements since 1997. Over the past decade, six long-range transported dust events are identified based on spatiotemporal evolutions of PM10 measurements from regional monitoring stations, with the aid of trajectory analysis. Multi-year composites of Chl-a imagery for dust event and non-dust background during March-April are applied to overcome insufficient retrievals of Chl-a due to cloudy environment. Due to anthropogenic modification within a shallow boundary layer off the densely populated and industrial southeast coast of China, the iron ion activation of deliquescent dust

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

    PubMed

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

    2012-03-01

    This study was conducted to evaluate the effects of transported Asian dust and other environmental parameters on the levels and compositions of ambient fungi in the atmosphere of northern Taiwan. We monitored Asian dust events in Taipei County, Taiwan from January 2003 to June 2004. We used duplicate Burkard portable air samplers to collect ambient fungi before, during, and after dust events. Six transported Asian dust events were monitored during the study period. Elevated concentrations of Aspergillus (A. niger, specifically), Coelomycetes, Rhinocladiella, Sporothrix and Verticillium were noted (p < 0.05) during Asian dust periods. Botryosporium and Trichothecium were only recovered during dust event days. Multiple regression analysis showed that fungal levels were positively associated with temperature, wind speed, rainfall, non-methane hydrocarbons and particulates with aerodynamic diameters ≤10 μm (PM(10)), and negatively correlated with relative humidity and ozone. Our results demonstrated that Asian dust events affected ambient fungal concentrations and compositions in northern Taiwan. Ambient fungi also had complex dynamics with air pollutants and meteorological factors. Future studies should explore the health impacts of ambient fungi during Asian dust events, adjusting for the synergistic/antagonistic effects of weather and air pollutants. PMID:21328007

  2. Transport and trapping of dust particles in a potential well created by inductively coupled diffused plasmas.

    PubMed

    Choudhary, Mangilal; Mukherjee, S; Bandyopadhyay, P

    2016-05-01

    A versatile linear dusty (complex) plasma device is designed to study the transport and dynamical behavior of dust particles in a large volume. Diffused inductively coupled plasma is generated in the background of argon gas. A novel technique is used to introduce the dust particles in the main plasma by striking a secondary direct current glow discharge. These dust particles are found to get trapped in an electrostatic potential well, which is formed due to the combination of the ambipolar electric field caused by diffusive plasma and the field produced by the charged glass wall of the vacuum chamber. According to the requirements, the volume of the dust cloud can be controlled very precisely by tuning the plasma and discharge parameters. The present device can be used to address the underlying physics behind the transport of dust particles, self-excited dust acoustic waves, and instabilities. The detailed design of this device, plasma production and characterization, trapping and transport of the dust particle, and some of the preliminary experimental results are presented. PMID:27250421

  3. Transport and trapping of dust particles in a potential well created by inductively coupled diffused plasmas

    NASA Astrophysics Data System (ADS)

    Choudhary, Mangilal; Mukherjee, S.; Bandyopadhyay, P.

    2016-05-01

    A versatile linear dusty (complex) plasma device is designed to study the transport and dynamical behavior of dust particles in a large volume. Diffused inductively coupled plasma is generated in the background of argon gas. A novel technique is used to introduce the dust particles in the main plasma by striking a secondary direct current glow discharge. These dust particles are found to get trapped in an electrostatic potential well, which is formed due to the combination of the ambipolar electric field caused by diffusive plasma and the field produced by the charged glass wall of the vacuum chamber. According to the requirements, the volume of the dust cloud can be controlled very precisely by tuning the plasma and discharge parameters. The present device can be used to address the underlying physics behind the transport of dust particles, self-excited dust acoustic waves, and instabilities. The detailed design of this device, plasma production and characterization, trapping and transport of the dust particle, and some of the preliminary experimental results are presented.

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

    PubMed Central

    Prospero, Joseph M.

    1999-01-01

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

  5. A synoptic characterization of the dust transport in the Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Gaetani, Marco; Pasqui, Massimiliano; Crisci, Alfonso; Guarnieri, Francesca

    2013-04-01

    In this work the daily dust transport over the Mediterranean basin is characterized through circulation type classification (CTC) methods. The dust loads are estimated through the aerosol optical depth (AOD) simulated by the GOCART model in the period 2000-2007 and remote-sensed by the MODIS in the period 2001-2010. The dust transport from the Sahara is identified linking the AOD anomalies to the thermal anomalies into the Mediterranean, studying the covariance modes of AOD and air temperature at 850 hPa from the MERRA dataset. The time series of the expansion coefficients associated to the first two covariance modes allow to describe the dust transport in the eastern, western and central Mediterranean sub-basins. The circulation types are classified using the MERRA geopotential height at 700 hPa in the period 1979-2010, the performance of the CTC methods in the characterization of the dust anomalies is evaluated and the best method is selected. Results show that a T-mode PCA method with 14 classes allows the characterization of dust transport and thermal anomalies in the eastern and western Mediterranean, while the variability in the central Mediterranean is well characterized by a S-mode PCA method with 10 classes. Moreover, extreme dust events over the western, central and eastern Mediterranean are identified, and the associated synoptic circulation patterns evolution is studied. Extreme dust events in the western Mediterranean are associated with high-pressure conditions limiting the development of lows to the western North Africa, while the eastward evolution of cyclones over the central Mediterranean and Northern Africa accompanies dust events in the central and eastern Mediterranean.

  6. The Icelandic volcanic aeolian environment: Processes and impacts - A review

    NASA Astrophysics Data System (ADS)

    Arnalds, Olafur; Dagsson-Waldhauserova, Pavla; Olafsson, Haraldur

    2016-03-01

    Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland's location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust production is on the order of 30-40 million tons annually, some traveling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust storms. They are more frequent in the wake of volcanic eruptions, such as after the Eyjafjallajökull 2010 eruption. Airborne dust affects human health, with negative effects enhanced by the tubular morphology of the grains, and the basaltic composition with its high metal content. Dust deposition on snow and glaciers intensifies melting. Moreover, the dust production probably also influences atmospheric conditions and parameters that affect climate change.

  7. Modeling study on the transport of summer dust and anthropogenic aerosols over the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Sato, Y.; Jia, R.; Xie, Y.; Huang, J.; Nakajima, T.

    2015-11-01

    The Tibetan Plateau (TP) is located at the juncture of several important natural and anthropogenic aerosol sources. Satellites have observed substantial dust and anthropogenic aerosols in the atmosphere during summer over the TP. These aerosols have distinct effects on the earth's energy balance, microphysical cloud properties, and precipitation rates. To investigate the transport of summer dust and anthropogenic aerosols over the TP, we combined the Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS) with a non-hydrostatic regional model (NHM). The model simulation shows heavily loaded dust aerosols over the northern slope and anthropogenic aerosols over the southern slope and the east of the TP. The dust aerosols are primarily mobilized around the Taklimakan Desert, where a portion of the aerosols are transported eastward due to the northwesterly current; simultaneously, a portion of the particles are transported southward when a second northwesterly current becomes northeasterly because of the topographic blocking of the northern slope of the TP. Because of the strong upward current, dust plumes can extend upward to approximately 7-8 km a.s.l. over the northern slope of the TP. When a dust event occurs, anthropogenic aerosols that entrained into the southwesterly current via the Indian summer monsoon are transported from India to the southern slope of the TP. Simultaneously, a large amount of anthropogenic aerosol is also transported from eastern China to the east of the TP by easterly winds. An investigation on the transport of dust and anthropogenic aerosols over the plateau may provide the basis for determining aerosol impacts on summer monsoons and climate systems.

  8. Modeling study on the transport of summer dust and anthropogenic aerosols over the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Sato, Y.; Jia, R.; Xie, Y.; Huang, J.; Nakajima, T.

    2015-05-01

    The Tibetan Plateau (TP) is located at the juncture of several important natural and anthropogenic aerosol sources. Satellites have observed substantial dust and anthropogenic aerosols in the atmosphere during summer over the TP. These aerosols have distinct effects on the earth's energy balance, microphysical cloud properties, and precipitation rates. To investigate the transport of summer dust and anthropogenic aerosols over the TP, we combined the Spectral Radiation-Transport Model for Aerosol Species (SPRINTARS) with a non-hydrostatic regional model (NHM). The model simulation shows heavily loaded dust aerosols over the northern slope and anthropogenic aerosols over the southern slope and to the east of the TP. The dust aerosols are primarily mobilized around the Taklimakan Desert, where a portion of the aerosols are transported eastward due to the northwesterly current; simultaneously, a portion of the particles are transported northward when a second northwesterly current becomes northeasterly because of the topographic blocking of the northern slope of the TP. Because of the strong upward current, dust plumes can extend upward to approximately 7-8 km a.s.l. over the northern slope of the TP. When a dust event occurs, anthropogenic aerosols that entrain into the southwesterly current via the Indian summer monsoon are transported from India to the southern slope of the TP. Simultaneously, a large amount of anthropogenic aerosols is also transported from eastern China to east of the TP by easterly winds. An investigation on the transport of dust and anthropogenic aerosols over the plateau may provide the basis for determining aerosol impacts on summer monsoons and climate systems.

  9. Post-disturbance dust emissions in dry lands: the role of anthropogenic and climatic factors

    NASA Astrophysics Data System (ADS)

    Ravi, S.; Zobeck, T. M.; Sankey, J. B.

    2012-12-01

    Disturbances, which cause a temporary reduction in vegetation cover, can greatly accelerate soil erosion by wind and subsequent dust emissions from desert grasslands and shrublands. These ecosystems worldwide are threatened by contemporary shifts in vegetation composition (e.g. encroachment by shrubs, invasion by exotic grasses) and climatic changes (e.g. increase in aridity, droughts), which alter the frequency and intensity of disturbances and dust emissions. Considering the deleterious impact of dust-borne contaminants on regional air quality and human health, accelerated post-disturbance aeolian transport is an increasingly serious concern for ecosystem management and risk assessment. Here, using extensive wind tunnel studies, field experiments (in grasslands and shrublands of North America) and modeling, we investigated the role of disturbances (fires, grazing) and changes in hydroclimatic factors (air humidity, soil moisture) in altering aeolian processes in desert grassland and shrublands. Our results indicate that the degree of post-disturbance aeolian transport and its attenuation with time was found to be strongly affected by the antecedent vegetation type and post-disturbance climatic conditions. The interactions among sediment transport processes, disturbances and hydroclimatic factors are explored from patch to landscape scales and their roles in dust emissions and land degradation are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  13. Long-range transport of Saharan dust and chemical transformations over the Eastern Mediterranean

    NASA Astrophysics Data System (ADS)

    Athanasopoulou, E.; Protonotariou, A.; Papangelis, G.; Tombrou, M.; Mihalopoulos, N.; Gerasopoulos, E.

    2016-09-01

    Three recent Saharan dust outbreaks during different seasons (4-6 days in winter of 2009, late autumn of 2010 and summer of 2011) are selected in order to study the chemical footprint and aging processes of dust intrusions over the Eastern Mediterranean (EM). The applied model system (PMCAMx, WRF and GEOS-CHEM) and methodology are found competent to reproduce dust production, long-range transport and chemical transformations over the EM, with the synergistic use of synoptic patterns analysis, optical depth retrievals, back-trajectories, surface and satellite aerosol measurements. The dust loads were high during the cold period events and much lighter during summertime, when transport was mainly in the free troposphere. In all cases, dust originated from the northwest and/or west Saharan desert and reached the EM from the west/southwest. Sensitivity runs underlie the effect of dust transport on the chemical constituents of aerosols over the EM and show a large impact on calcium (70-90% of maximum daily values 2-5 μg m-3), with its gradient at surface level being around -10% per 100 km along the dust pathway. For the cold period cases, this value can also be considered analogous to the dust dissipation ratio, because the plume is vertically extended down to the surface layers. Interestingly, the surface particulate nitrate concentrations over the EM are reversely affected by the approaching dust loads, exhibiting the highest values (up to 6 μg m-3) and the largest dust fraction (ca. 70%) during summertime. This is attributed to the enhanced nitric acid formation under high atmospheric temperature and insolation, its uptake onto the carbonate dust particles, and their effective accumulation, due to low deposition rates over the sea and scarce precipitation. Sulfate formation onto dust particles is found insignificant (rapid reaction with ammonia and/or sea-salt), while the influence of dust and sea-salt on sodium, when spatio-temporal averages are calculated, is

  14. Review of dust transport and mitigation technologies in lunar and Martian atmospheres

    NASA Astrophysics Data System (ADS)

    Afshar-Mohajer, Nima; Wu, Chang-Yu; Curtis, Jennifer Sinclair; Gaier, James R.

    2015-09-01

    Dust resuspension and deposition is a ubiquitous phenomenon in all lunar and Martian missions. The near-term plans to return to the Moon as a stepping stone to further exploration of Mars and beyond bring scientists' attention to development and evaluation of lunar and Martian dust mitigation technologies. In this paper, different lunar and Martian dust transport mechanisms are presented, followed by a review of previously developed dust mitigation technologies including fluidal, mechanical, electrical and passive self-cleaning methods for lunar/Martian installed surfaces along with filtration for dust control inside cabins. Key factors in choosing the most effective dust mitigation technology are recognized to be the dust transport mechanism, energy consumption, environment, type of surface materials, area of the surface and surface functionality. While electrical methods operating at higher voltages are identified to be suitable for small but light sensitive surfaces, pre-treatment of the surface is effective for cleaning thermal control surfaces, and mechanical methods are appropriate for surfaces with no concerns of light blockage, surface abrasion and 100% cleaning efficiency. Findings from this paper can help choose proper surface protection/cleaning for future space explorations. Hybrid techniques combining the advantages of different methods are recommended.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. AP-42 ADDITIONS AND REVISIONS - TRANSPORTABILITY FACTORS FOR FUGITIVE DUST

    EPA Science Inventory

    The product is a table of factors, one for each county in the US, reflecting the portion of fugitive dust removed very close to the source via impaction on vegetation and similar mechanisms. Factors were based on land cover in area (county or grid cell) A praft final product was...

  17. Modeling and Satellite Observation of Dust Emission and Transport over the Taklimakan Desert

    NASA Astrophysics Data System (ADS)

    Su, J.; Xu, C.; Huang, J.

    2014-12-01

    Taklimakan Desert is one of the world's largest deserts and the most intense dust source of Asia. It is located in the Tarim Basin (average elevation: 1.1 km) in northwest China and surrounded by high mountains and plateaus (average elevation over 4.5 km). The Taklimakan Desert is a particularly interesting area not only because a large amount of dust particles is emitted into the atmosphere from this region every year, but also due to the very unique orography and the prevailing wind direction in lower troposphere, dust particles can be lofted above 5 km into upper troposphere. In this study, we found that dust particles from the Taklimakan Desert can be vertically transported to Tibetan Plateau (TP) during spring and summer seasons while suspend within boundary layer in autumn and winter by using multi-year Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations. We investigated the relationship between dust aerosol optical depth (AOD) and surface wind speeds by using multi-angle imaging spectro radiometer (MISR) observations and ERA-Interim data, and further modified the EROD map in the default Weather Research and Forecasting model with chemistry (WRF-Chem) according this relationship in order to ensure realistic simulations of dust emissions. Cases study shown that the simulated dust horizontal and vertical distributions compares well with satellites observations, and dust particles from the Tarim Basin can be blown up to the TP within one day.

  18. Regional modeling of natural dust in the United State: Source emission, transport, and photochemical impact

    NASA Astrophysics Data System (ADS)

    Tong, D. Q.; Mathur, R.; Mobley, D.; Wong, D.; Yu, S.

    2008-12-01

    We developed a dust emission module to estimate the wind-blown dust emissions from dessert and agricultural land using local wind speed, threshold wind speed to initiate erosion, soil texture and moisture, land use type, and vegetation coverage. The estimated dust is then partitioned to create a fraction of the total sediment mobilized by the wind for vertical transport and subsequent regional circulation. This dust module also included detailed chemical speciation and size distribution, and a geographic filter to eliminate unrealistic emission sources (e.g., mountain peaks with dry soil and strong winds). We then couple the dust module with a regional air quality model CMAQ to: (1) study if the WRF-CMAQ national air quality forecasting system can accurately predict major dust storms occurring in the United States; 2) estimate the annual budget of natural dust emissions from agricultural and dessert lands and their relative importance for total PM2.5 over different U.S. regions; and 3) examine the effects of dust emissions on photolysis rates and consequently on levels of tropospheric O3 and atmospheric oxidants.

  19. Evaluation of long-range transport and deposition of desert dust with the CTM MOCAGE

    NASA Astrophysics Data System (ADS)

    Martet, M.; Peuch, V.-H.; Laurent, B.; Marticorena, B.; Bergametti, G.

    2009-04-01

    Desert dust modelling and forecasting attract growing interest, due to the numerous impacts of dusts on climate, numerical weather prediction, health, ecosystems, transportation, as well as on many industrial activities. The validation of numerical tools is a very important activity in this context, and we present here an example of such an effort, combining in situ (horizontal visibility in SYNOP messages, IMPROVE database) and remote-sensing data (satellite imagery, AERONET aerosol optical thickness data). Interestingly, these measurements are available routinely, and not only in the context of dedicated measurements campaign; thus, they can be used in an operational context to monitor the performances of operational forecasting systems. MOCAGE is the chemistry-transport model of Météo-France, used operationally to forecast the three-dimensional transport of dusts and their deposition. Two very long-range transport episodes of dust have been studied: one case of Saharan dust transported to East America through Asia and Pacific observed in November 2004 and one case of Saharan dust transported from West Africa to Caribbean Islands in May 2007. Episodes of geographical extension had seldom been studied, and they provide a very selective reference to compare the modelled desert dusts with. The representation of dusts in MOCAGE appears to be realistic in these two very different cases. In turn, the model simulations are used to make the link between the complementary information provided by the different measurements tools, providing a fully consistent picture of the entire episodes. The evolution of the aerosol size distribution during the episodes has also been studied. With no surprise, our study underlines that deposition processes are very sensitive to the size of dust particles. If the atmospheric cycle, in terms of mass, is very much under the influence of larger particles (some micrometres and above), only the finer particles actually travel over thousands

  20. Potential transport pathways of dust emanating from the playa of Ebinur Lake, Xinjiang, in arid northwest China

    NASA Astrophysics Data System (ADS)

    Ge, Yongxiao; Abuduwaili, Jilili; Ma, Long; Wu, Na; Liu, Dongwei

    2016-09-01

    In this paper, the HYSPLIT model, driven with reanalysis meteorological data from 1978 to 2013, was used to understand the potential transport characteristics of dust and salt dust emanating from the playa of Ebinur Lake in arid northwest China. Daily air parcel trajectories were computed forward for 8 days from an origin centered over Ebinur Lake at 100 m above ground level. Air parcel trajectory density plots were mapped for seven levels: 0-100 m agl., 100-500 m agl., 500-1000 m agl., 1000-1500 m agl., 1500-2000 m agl., 2000-3000 m agl., and 3000-5000 m agl. These show that potential dust transport pathways have clear seasonal differentiation. The potential transport distance of dust and salt dust is greatest in spring and summer. In autumn and winter, the potential transport of the high-density air trajectory is below 1000 m traveling a shorter distance. Potential dust transport pathways showed notifying directivity in different seasons and heights. Southeast in spring and summer, and north to northeast in autumn and winter are the two main potential transport channels of dust and salt dust. Accordingly, dust and salt dust from the playa of Ebinur Lake may influence the atmospheric processes and biogeochemical cycles of a vast region. The main area of influence of dust and salt dust is close to the source area, and will significantly accelerate the melting of snow and ice in the Tianshan Mountains. This highlights the urgent need to combine remote sensing, isotope and other methods to further research the transport characteristics of dust and salt dust from the playa of the Ebinur Lake.

  1. Impact of Lunar Dust on the Exploration Initiative

    NASA Technical Reports Server (NTRS)

    Stubbs, T. J.; Vondrak, R. R.; Farrell, W. M.

    2005-01-01

    From the Apollo era it is known that dust on the Moon can cause serious problems for exploration activities. Such problems include adhering to clothing and equipment, reducing external visibility on landings, and causing difficulty to breathing and vision within the spacecraft. An important step in dealing with dust-related problems is to understand how dust grains behave in the lunar environment. All astronauts who walked on the Moon reported difficulties with lunar dust. Eugene Cernan, commander of Apollo 17, stated that one of the most aggravating, restricting facets of lunar surface exploration is the dust and its adherence to everything no matter what kind of material, whether it be skin, suit material, metal, no matter what it be and it's restrictive friction-like action to everything it gets on. Dust has also been highlighted as a priority by the Mars Exploration Program Assessment Group (MEPAG): 1A. Characterize both aeolian dust and particulates that would be kicked up from the martian regolith by surface operations of a human mission with fidelity sufficient to establish credible engineering simulation labs and/or software codes on Earth. We shall briefly describe the properties of lunar dust and its impact on the Apollo astronauts, and then summarize three main problems areas for understanding its behavior: Dust Adhesion and Abrasion, Surface Electric Fields and Dust Transport. These issues are all inter-related and must be well understood in order to minimize the impact of dust on lunar surface exploration.

  2. Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model

    PubMed Central

    Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P.; Russell, MacKenzie R.; Jones, Robert M.; King, Matt; Betterton, Eric A.; Sáez, A. Eduardo

    2014-01-01

    Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition. PMID:25621085

  3. Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model

    NASA Astrophysics Data System (ADS)

    Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P.; Russell, MacKenzie R.; Jones, Robert M.; King, Matt; Betterton, Eric A.; Sáez, A. Eduardo

    2014-09-01

    Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition.

  4. Aeolian sand ripples around plants.

    PubMed

    Zhang, Qian-Hua; Miao, Tian-De

    2003-05-01

    Plants in the desert may locally change the aeolian process, and hence the pattern of sand ripples traveling nearby. The effect of plants on ripples is investigated using a coupled map lattice model with nonuniform coupling coefficients. PMID:12786143

  5. Dust-storm dynamics over Sistan region, Iran: Seasonality, transport characteristics and affected areas

    NASA Astrophysics Data System (ADS)

    Rashki, A.; Kaskaoutis, D. G.; Francois, P.; Kosmopoulos, P. G.; Legrand, M.

    2015-03-01

    The present work examines the seasonality, dust-plume altitudinal variation and affected areas for dust storms originated from the Sistan region, southeastern Iran during the summer (June-September) months of the period 2001-2012 synthesizing local meteorological records, satellite observations (TOMS, OMI, METEOSAT, MODIS) and HYSPLIT forward trajectories. Dust-storm days (356 in total) are associated with visibility below 1 km at Zabol, Iran meteorological station with higher frequency and intensity in June and July. Monthly-mean composite maps of TOMS and OMI AI show high (>3-3.5) values over Sistan and nearby downwind areas. HYSPLIT forward-trajectory analysis at 500 m for air masses originated from Sistan on the dust-storm days shows that they usually follow an anti-clockwise transport direction at elevations usually below 2 km, initially moving southwards and then shifting to east-northeast when they are approaching the Arabian Sea coast. This is the result of the influence of the local topography and formation of thermal low-pressure systems over the arid lands. It is found that in few cases the dust storms from Sistan affect central/south Arabian Sea and India, while they control the aerosol loading over northernmost Arabian Sea. The Infrared Difference Dust Index (IDDI) images, which represent brightness temperature reduction due to dust presence over land, are used at specific periods of persistent dust storms over Sistan, confirming the main pathways of the dust plumes and illustrating the importance of the region as one of the most active dust sources in southwest Asia.

  6. Element geochemical analysis of the contribution of aeolian sand to suspended sediment in desert stream flash floods.

    PubMed

    Jia, Xiaopeng; Wang, Haibing

    2014-01-01

    The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream. PMID:25089295

  7. Element Geochemical Analysis of the Contribution of Aeolian Sand to Suspended Sediment in Desert Stream Flash Floods

    PubMed Central

    Wang, Haibing

    2014-01-01

    The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream. PMID:25089295

  8. Radar-aeolian roughness project

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Dobrovolskis, A.; Gaddis, L.; Iversen, J. D.; Lancaster, N.; Leach, Rodman N.; Rasnussen, K.; Saunders, S.; Vanzyl, J.; Wall, S.

    1991-01-01

    The objective is to establish an empirical relationship between measurements of radar, aeolian, and surface roughness on a variety of natural surfaces and to understand the underlying physical causes. This relationship will form the basis for developing a predictive equation to derive aeolian roughness from radar backscatter. Results are given from investigations carried out in 1989 on the principal elements of the project, with separate sections on field studies, radar data analysis, laboratory simulations, and development of theory for planetary applications.

  9. Sensitivity Study of Cross-Atlantic Dust Transport to Dust Emissions, Chemical Aging and Removal Processes and Comparison with Ground and Satellite Data

    NASA Astrophysics Data System (ADS)

    Mohamed, A.; Metzger, S. M.; Klingmüller, K.; Lelieveld, J.

    2015-12-01

    Representing trans-Atlantic dust transport is one of the challenges in climate modeling and of key importance, because of its large impact on the Earth's radiation budget. Desert dust, emitted from the Sahara, is regularly transported westwards across the Atlantic Ocean towards the Caribbean. The balance between emissions and removal processes, as well as the manifold chemical reactions control the impact of dust on the atmospheric composition and the interaction of dust with climate change. During trans-Atlantic transport, dust undergoes chemical aging, which involves various heterogeneous reactions that strongly depend on the mineral composition of dust (alkalinity), the surface chemistry and the associated aerosol water uptake. In this study, different parameters affecting the long-range dust transport are studied with the atmospheric chemistry-climate model EMAC. We consider chemical speciation of primary sea salt and dust particles and account for major cations (Na+, K+, Mg2+, Ca2) and anions (Cl-, SO42-, HSO4-), calculated online with meteorology, i.e., feeding back onto precipitation and changing surface wind speed and roughness. We resolve the chemical aging of primary particles through explicit neutralization reactions of the cations and anions with major oxidation products (H2SO4, HNO3, HCl, NH3) from natural and anthropogenic air pollution sources, which can condense on the particles surface during long-range transport and undergo gas-liquid-solid aerosol partitioning, depending on the concentration level of emissions and the transport processes of the primary and secondary aerosols and their precursor gases. Comprehensive analysis of the different parameters affecting the long-range transport, which include the emission flux and particle size distributions, aging mechanism, convection scheme, wet and dry scavenging, show a strong dependence of the dust concentration and optical properties over the Caribbean mainly on the chemical aging of dust during

  10. Sensitivity Study of Cross-Atlantic Dust Transport to Dust Emissions, Chemical Aging and Removal Processes and Comparison with Ground and Satellite Data

    NASA Astrophysics Data System (ADS)

    Abdelkader, Mohamed; Metzger, Swen; Klingmüller, Klaus; Steil, Benedikt; Lelieveld, Jos

    2016-04-01

    Representing transatlantic dust transport is one of the challenges in climate modeling and of key importance, because of its large impact on the Earth's radiation budget. Desert dust, emitted from the Sahara, is regularly transported westwards across the Atlantic Ocean towards the Caribbean. The balance between emissions and removal processes, as well as the manifold chemical reactions control the impact of dust on the atmospheric composition and the interaction of dust with climate change. During transatlantic transport, dust undergoes chemical aging, which involves various heterogeneous reactions that strongly depend on the mineral composition of dust (alkalinity), the surface chemistry and the associated aerosol water uptake. In this study, different parameters affecting the long-range dust transport are studied with the atmospheric chemistry-climate model EMAC. We consider chemical speciation of primary sea salt and dust particles and account for major cations (Na+, K+, Mg2+, Ca2) and anions (Cl-, SO42-, HSO4-), calculated online with meteorology, i.e., feeding back onto precipitation and changing surface wind speed and roughness. We resolve the chemical aging of primary particles through explicit neutralization reactions of the cations and anions with major oxidation products (H2SO4, HNO3, HCl, NH3) from natural and anthropogenic air pollution sources, which can condense on the particles surface during long-range transport and undergo gas-liquid-solid aerosol partitioning, depending on the concentration level of emissions and the transport processes of the primary and secondary aerosols and their precursor gases. Comprehensive analysis of the different parameters affecting the long-range transport, which include the emission flux and particle size distributions, aging mechanism, convection scheme, wet and dry scavenging, show a strong dependence of the dust concentration and optical properties over the Caribbean mainly on the chemical aging of dust during long

  11. Mars sampling strategy and aeolian processes

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1988-01-01

    It is critical that the geological context of planetary samples (both in situ analyses and return samples) be well known and documented. Apollo experience showed that this goal is often difficult to achieve even for a planet on which surficial processes are relatively restricted. On Mars, the variety of present and past surface processes is much greater than on the Moon and establishing the geological context of samples will be much more difficult. In addition to impact hardening, Mars has been modified by running water, periglacial activity, wind, and other processes, all of which have the potential for profoundly affecting the geological integrity of potential samples. Aeolian, or wind, processes are ubiquitous on Mars. In the absence of liquid water on the surface, aeolian activity dominates the present surface as documented by frequent dust storms (both local and global), landforms such as dunes, and variable features, i.e., albedo patterns which change their size, shape, and position with time in response to the wind.

  12. Mixing of dust with pollution on the transport path of Asian dust--revealed from the aerosol over Yulin, the north edge of Loess Plateau.

    PubMed

    Wang, Qiongzhen; Zhuang, Guoshun; Li, Juan; Huang, Kan; Zhang, Rong; Jiang, Yilun; Lin, Yanfen; Fu, Joshua S

    2011-01-01

    Both PM(2.5) and TSP were monitored in the spring from 2006 to 2008 in an intensive ground monitoring network of five sites (Tazhong, Yulin, Duolun, Beijing, and Shanghai) along the pathway of Asian dust storm across China to investigate the mixing of dust with pollution on the pathway of the long-range transport of Asian dust. Mineral was found to be the most loading component of aerosols both in dust event days and non-dust days. The concentrations of those pollution elements, As, Cd, Pb, Zn, and S in aerosol were much higher than their mean abundances in the crust even in dust event days. The high concentration of SO(4)(2-) could be from both sources: one from the transformation of the local emitted SO(2) and the other from the sulfate that existed in primary dust, which was transported to Yulin. Na(+), Ca(2+), and Mg(2+) were mainly from the crustal source, while NO(3)(-) and NH(4)(+) were from the local pollution sources. The mixing of dust with pollution aerosol over Yulin in dust event day was found to be ubiquitous, and the mixing extent could be expressed by the ratio of NO(3)(-)/Al in dust aerosol. The ratio of Ca/Al was used as a tracer to study the dust source. The comparison of the ratios of Ca/Al together with back trajectory analysis indicated that the sources of the dust aerosol that invaded Yulin could be from the northwestern desert in China and Mongolia Gobi. PMID:21075425

  13. Effects of Multi-Decadal Variation of SST and Dust Radiative Forcing on Rainfall and Dust Transport over West Africa and Northern Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Kim, K. M.; Lau, W. K. M.; Colarco, P. R.

    2014-12-01

    The effects of multi-decadal variations of sea surface temperature (SST) and dust radiative forcing on the West African monsoon rainfall and circulation, and consequent change in dust emission and transport are examined based on model experiments with the NASA GEOS-5 GCM with prescribed SST. SST patterns representing the 1950s and 1980s are obtained based on Singular Value Decomposition (SVD) between Sahel rainfall and global SST distribution, and prescribed for 7-year simulations for each period. Results show that the subtropical high is strengthened and expanded southwestward associated with colder northern Atlantic Ocean SST in 1980s. As a result, the rain band in the tropical Atlantic Ocean and Sahel moves southward and rainfall is reduced over the Sahel. Stronger surface winds associated with strong surface temperature gradients increase dust emission in the southern Saharan desert and northern Sahel. Combined with circulation changes induced by strengthening the subtropical high and reduced wet deposition, dust transport is increased in the deep tropics (10-20N), but reduced in the northern path (20-30N)To examine the effect of aerosol radiative forcing, additional experiments are conducted after dust radiative feedback is turned off. Without aerosol radiative feedback, model still simulate aforementioned contrast between 1980s and 1950s, but the anomalies of Sahel drought and dust transports are a lot weaker. Preliminary results indicate that atmospheric heating due to shortwave absorption by dust provides additional buoyance and lifts dust particles to higher altitudes. Dust radiative forcing also increases meridional temperature gradients and strengthens the African Easterly Jet, resulting in an increased residence time of dust and farther westward transport.

  14. Transport control of dust particles via the electrical asymmetry effect: experiment, simulation and modelling

    NASA Astrophysics Data System (ADS)

    Iwashita, Shinya; Schüngel, Edmund; Schulze, Julian; Hartmann, Peter; Donkó, Zoltán; Uchida, Giichiro; Koga, Kazunori; Shiratani, Masaharu; Czarnetzki, Uwe

    2013-06-01

    The control of the spatial distribution of micrometre-sized dust particles in capacitively coupled radio frequency discharges is relevant for research and applications. Typically, dust particles in plasmas form a layer located at the sheath edge adjacent to the bottom electrode. Here, a method of manipulating this distribution by the application of a specific excitation waveform, i.e. two consecutive harmonics, is discussed. Tuning the phase angle θ between the two harmonics allows one to adjust the discharge symmetry via the electrical asymmetry effect (EAE). An adiabatic (continuous) phase shift leaves the dust particles at an equilibrium position close to the lower sheath edge. Their levitation can be correlated with the electric field profile. By applying an abrupt phase shift the dust particles are transported between both sheaths through the plasma bulk and partially reside at an equilibrium position close to the upper sheath edge. Hence, the potential profile in the bulk region is probed by the dust particles providing indirect information on plasma properties. The respective motion is understood by an analytical model, showing both the limitations and possible ways of optimizing this sheath-to-sheath transport. A classification of the transport depending on the change in the dc self-bias is provided, and the pressure dependence is discussed.

  15. DUST TRANSPORT IN PROTOSTELLAR DISKS THROUGH TURBULENCE AND SETTLING

    SciTech Connect

    Turner, N. J.; Carballido, A.; Sano, T.

    2010-01-01

    We apply ionization balance and magnetohydrodynamical (MHD) calculations to investigate whether magnetic activity moderated by recombination on dust grains can account for the mass accretion rates and the mid-infrared spectra and variability of protostellar disks. The MHD calculations use the stratified shearing-box approach and include grain settling and the feedback from the changing dust abundance on the resistivity of the gas. The two-decade spread in accretion rates among solar-mass T Tauri stars is too large to result solely from variations in the grain size and stellar X-ray luminosity, but can plausibly be produced by varying these parameters together with the disk magnetic flux. The diverse shapes and strengths of the mid-infrared silicate bands can come from the coupling of grain settling to the distribution of the magnetorotational turbulence, through the following three effects. First, recombination on grains 1 mum or smaller yields a magnetically inactive dead zone extending more than two scale heights from the midplane, while turbulent motions in the magnetically active disk atmosphere overshoot the dead zone boundary by only about one scale height. Second, grains deep in the dead zone oscillate vertically in wave motions driven by the turbulent layer above, but on average settle at the rates found in laminar flow, so that the interior of the dead zone is a particle sink and the disk atmosphere will become dust-depleted unless resupplied from elsewhere. Third, with sufficient depletion, the dead zone is thinner and mixing dredges grains off the midplane. The last of these processes enables evolutionary signatures such as the degree of settling to sometimes decrease with age. The MHD results also show that the magnetic activity intermittently lifts clouds of small grains into the atmosphere. Consequently the photosphere height changes by up to one-third over timescales of a few orbits, while the extinction along lines of sight grazing the disk surface

  16. Characteristics of the long-range transport dust events in Chengdu, Southwest China

    NASA Astrophysics Data System (ADS)

    Chen, Yuan; Luo, Bin; Xie, Shao-dong

    2015-12-01

    Chengdu is an inland megacity in the Sichuan Basin, where dust influence remained an open question. During a one-year haze campaign, two dust events were identified in March 2013, indicating that desert dust can be transported to Chengdu and impacted local air quality strongly. The suggested low SO2/PM10, NO2/PM10 and PM2.5/PM10 ratios of 0.15, 0.27 and 0.40 could be used as immediate indicators for dust days. On typical dust day of March 12, PM10 was as high as 359.1 μg m-3, and crustal matter contributed 80.5% to total PM2.5 mass (106.6 μg m-3). Enrichment factors of most elements have decreased due to the dilution effect except for Ca and Mg. The dust was mainly from western and northern dust regions in China, including the "Northerly Mongolia Path", "Western Desert Path" and "Northwestern Desert Path". Due to the obstruction of Qinghai-Tibet Plateau on the west, the dust air to Chengdu was mostly from the northeastward direction after passing over Qinling Mountain. Moreover, the air experienced obvious elevation from its source regions driven by the cold front synoptic pattern. The spatial distribution of high AOD (Aerosol Optical Depth) values over 1.2 but low Ångström exponent of 0.5-0.6 around Chengdu verified the coarse pollution patterns. However, the dust pollution was not serious in nearby Chongqing and Guizhou and exhibited weak regional feature, a result different from those in Beijing and Shanghai.

  17. Size distribution and optical properties of long-range transported African dust

    NASA Astrophysics Data System (ADS)

    Formenti, Paola; Denjean, Cyrielle; Deboeufs, Karine; Laurent, Benoit; Chevaillier, Servanne; Maillé, Michel; Cazaunau, Mathieu; Vallejo, Pamela; Quinones, Mariana; Gutierrez-Molina, Ian; Cassola, Federico; Prati, Paolo; Andrews, Elisabeth; Ogren, John; Mayol-Bracero, Olga

    2015-04-01

    In the framework of the Dust Aging and Transport from Africa to the Caribbean (Dust-ATTAcK) project, a ground-based field campaign has been conducted at the Cape San Juan aerosol station in Puerto Rico, USA, (18.38°N 65.62°W) during June-July 2012. The aim of the field study was to document the physical and optical properties of long-range transported African dust, in order to reduce uncertainties on its effects on radiation and clouds. Several episodes of long-range transport of mineral dust lasting one-to-three days were observed almost every second day. Dust mostly generated from sources in Mauritania, Western Sahara and Algeria, and remained airborne for approximately seven days before being sampled. The number size distribution of mineral dust, measured between 10 nm and 20 µm by a combination of Scanning Mobility Particle Sizer and an optical particle counter, showed that dust was generally characterized by three modes in the ultrafine, accumulation and coarse mode. Whereas their amplitude changed, their modal diameter remained constant with time.. The particle fraction below 100 nm showed the highest variability as a consequence of mixing which anthropogenic pollution which occurred any time the trade winds blown from the south east before reaching the sampling site. Mass scattering and absorption efficiency, and single scattering albedo have been calculated based on measurements of scattering and absorption coefficients and mass concentrations. For particles in the PM10 fraction, the mass scattering efficiency at 450 nm was of the order of 1.4 m2 g-1 and the mass absorption efficiency at 467 nm of the order of 0.05 m2 g-1. The single scattering albedo at 450 nm was of the order of 0.96.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  19. Recent Aeolian Dune Change on Mars

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.; Edgett, K. S.; Cantor, B. A.

    2007-01-01

    Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or position. Here, we show dome dunes in the north polar region that shrank and then disappeared over a period of 3.04 Mars years (5.7 Earth years), while larger, neighboring dunes showed no erosion or movement. The removal of sand from these dunes indicates that not only is the threshold wind speed for saltation exceeded under present conditions on Mars, but that any sand that is available for transport is likely to be moved. Dunes that show no evidence of change could be crusted, indurated. or subject to infrequent episodes of movement.

  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.

    PubMed

    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

  1. Modeling the emission, transport and deposition of contaminated dust from a mine tailing site.

    PubMed

    Stovern, Michael; Betterton, Eric A; Sáez, A Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P; Russell, Mackenzie R; King, Matt

    2014-01-01

    Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations. PMID:24552963

  2. Agriculture as a source of Aeolian sediment affecting air quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aeolian processes on agricultural lands have been examined for the past several decades on nearly every continent and has led to a better understanding of detachment, entrainment, transport, and deposition. Relatively little is known concerning the effect of these processes on air quality. In fact, ...

  3. The transport of sand and dust on Mars, its importance to science and exploration.

    NASA Astrophysics Data System (ADS)

    Merrison, J. P.; Gunnlaugsson, H. P.; Nørnberg, P.; Rasmussen, K. R.

    2009-04-01

    The transport of particulate matter across a planets surface is a powerful erosion mechanism and a significant factor affecting atmospheric dynamics by the creation of particulate aerosols. In this sense Mars is a test bed for the study of dust aerosols since it lacks the active circulation of water through the atmosphere, as we see on earth. Dust transport has therefore become the dominant process on Mars for both atmospheric contamination and evolution of the surface. Laboratory simulations have shown that dust electrification and aggregation is crucial to the transport of dust on Mars [1,2]. Similarly, on earth electric fields and electrification can play an important role in sand and dust circulation. Even on airless bodies such as the lunar surface dust sized particulates can be emitted and suspended by electrification processes. Granular electrification is being studied in detail in all of these environments, though is still far from being understood [3]. Recently observations by the NASA MER mission have revealed, for the first time, active transport of sand on the surface (saltation). It is becoming clear that, although such sand transport is periodic and at a low rate, it may be an extremely important process for the properties of the surface with regard to bacterial survival and habitation. Similarly with regard to exploration it is clear that a deeper understanding of how dust behaves at the Martian (and lunar) surface, especially under the influence of humans/robots, is essential. New laser and optoelectronic instrumentation is being developed in the study of particulate transport on Mars, specifically for the ESA ExoMars mission [4]. These technologies have potential application on earth, the moon and other solar system environments where granular material may be transported. References: [1] Merrison, J.P. et al., Planet. Space. Sci., (2008) 56, 426-437 [2] Merrison J.P., et al., Icarus, (2007), 191, 568 [3] Merrison J.P., et al., Planet. Space. Sci

  4. Dust transport from glacierized rivers of southern Alaska to the Gulf of Alaska: Interannual variability in magnitude and sources

    NASA Astrophysics Data System (ADS)

    Crusius, J.; Schroth, A. W.; Campbell, R. W.; Resing, J.; Gasso, S.

    2014-12-01

    Dust from high latitudes is underappreciated and little studied. We recently identified new sites of dust formation, and a new dust generation mechanism, from the southern AK coastline, in Crusius et al, 2011. Dust is generated each autumn from glacierized river valleys as river levels and discharge decrease following summer peak glacier melt. The most prominent such river is the Copper River, the single largest freshwater source to the Gulf of Alaska. Each autumn the exposed river floodplains contain abundant, fine glacial flour and represent a large dust source region, prior to significant snowfall. Strong katabatic winds channeled down mountain river valleys generate dust from the fine glacial flour, which is transported as much as several hundred kilometers into the ocean. This dust is an important source of Fe to the Gulf of Alaska, where phytoplankton growth is limited by available Fe (a micronutrient). Glaciers are rapidly losing mass in this region, so there is an increasing supply of fine glacial flour during the summer melt season, and possibly increased deposition of fine glacial flour in the dust source regions. We initiated continuous, year-round time-series measurements of dust concentration, and its geochemical composition, in August of 2011 on Middleton Island, AK, which lies in the path of the dust plume extending from the Copper River valley. Dust is clearly generated from other glacierized river valleys along the southern coast of AK, as well. We will discuss results from our continuous record spanning three dust seasons, which prominently shows these events each autumn, and displays substantial interannual variability. Dust appears to remain in the boundary layer, but is transported hundreds of kilometers into the ocean, into Fe-limited waters. It is also possible that some of this dust is redeposited on snow or glacier surfaces, enhancing melting. This dust source is not accounted for in typical global dust models.

  5. Transatlantic transport and deposition of Saharan dust and its effects on the marine environment

    NASA Astrophysics Data System (ADS)

    Stuut, Jan-Berend W.; Korte, Laura; van der Does, Michèlle; Mundy, Chris

    2015-04-01

    Massive amounts of Northwest African dust are transported westward over the Atlantic Ocean towards the Americas each year. These dust particles are thought to feed back on climate through a number of mechanisms including reflection of solar energy at the top of the atmosphere, absorption of energy that was reflected at the Earth's surface in the lower atmosphere, changes of the Earth's albedo, and fertilisation of both terrestrial and marine ecosystems. We are monitoring Saharan dust transport and deposition using an array of instruments that was deployed along a transect between Northwest Africa and the Caribbean at 12°N. In October 2012, we deployed five moorings along this transect between 23°W and 57°W with sediment traps that collect all material settling down through the water column on a temporal resolution of about two weeks. In November 2013, we added three dust-collecting buoys to the transect. The instruments on these buoys filter air to collect the dust particles that are suspended in the air just above sea level. In this presentation, we will introduce the projects in the framework of which this study is carried out, and present preliminary data on grain-size trends as well as marine-environmental observations.

  6. DUSTTRAFFIC: Transatlantic Transport and Deposition of Saharan Dust and its Effects on the Marine Environment

    NASA Astrophysics Data System (ADS)

    Stuut, J. B. W.; Guerreiro, C. V.; Munday, C. I.; Brummer, G. J. A.; Korte, L.; Van der Does, M.

    2015-12-01

    Massive amounts of Northwest African dust are transported westward over the Atlantic Ocean towards the Americas each year. These dust particles are thought to feed back on climate through a number of mechanisms including reflection of solar energy at the top of the atmosphere, absorption of energy that was reflected at the Earth's surface in the lower atmosphere, changes of the Earth's albedo, and fertilisation of both terrestrial and marine ecosystems. We are monitoring Saharan dust transport and deposition using an array of instruments that was deployed along a transect between Northwest Africa and the Caribbean at 12°N. In October 2012, we deployed five moorings along this transect between 23°W and 57°W with sediment traps that collect all material settling down through the water column on a temporal resolution of about two weeks. In November 2013, we added three dust-collecting buoys to the transect. The instruments on these buoys filter air to collect the dust particles that are suspended in the air just above sea level. In January 2015, the instruments were recovered and re-deployed for the third time, so that two years of sampling can help us understand the temporal and spatial variability of Saharan-dust deposition and its marine environmental effects. In this presentation, we will introduce the projects in the framework of which this study is carried out, and present preliminary data on grain-size trends as well as marine-environmental observations. See: www.nioz.nl/dust

  7. Saharan dust storms: nature and consequences

    NASA Astrophysics Data System (ADS)

    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

  8. Laboratory Simulations of Martian and Venusian Aeolian Processes

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1999-01-01

    With the flyby of the Neptune system by Voyager, the preliminary exploration of the Solar System was accomplished. Data have been returned for all major planets and satellites except the Pluto system. Results show that the surfaces of terrestrial planets and satellites have been subjected to a wide variety of geological processes. On solid- surface planetary objects having an atmosphere, aeolian processes are important in modifying their surfaces through the redistribution of fine-grained material by the wind. Bedrock may be eroded to produce particles and the particles transported by wind for deposition in other areas. This process operates on Earth today and is evident throughout the geological record. Aeolian processes also occur on Mars, Venus, and possibly Titan and Triton, both of which are outer planet satellites that have atmospheres. Mariner 9 and Viking results show abundant wind-related landforms on Mars, including dune fields and yardangs (wind-eroded hills). On Venus, measurements made by the Soviet Venera and Vega spacecraft and extrapolations from the Pioneer Venus atmospheric probes show that surface winds are capable of transporting particulate materials and suggest that aeolian processes may operate on that planet as well. Magellan radar images of Venus show abundant wind streaks in some areas, as well as dune fields and a zone of possible yardangs. The study of planetary aeolian processes must take into account diverse environments, from the cold, low-density atmosphere of Mars to the extremely hot, high- density Venusian atmosphere. Factors such as threshold wind speeds (minimum wind velocity needed to move particles), rates of erosion and deposition, trajectories of windblown particles, and aeolian flow fields over various landforms are all important aspects of the problem. In addition, study of aeolian terrains on Earth using data analogous to planetary data-collection systems is critical to the interpretation of spacecraft information and

  9. A Simulated Climatology of Asian Dust Aerosol and Its Trans-Pacific Transport. Part I: Mean Climate and Validation.

    NASA Astrophysics Data System (ADS)

    Zhao, T. L.; Gong, S. L.; Zhang, X. Y.; Blanchet, J.-P.; McKendry, I. G.; Zhou, Z. J.

    2006-01-01

    The Northern Aerosol Regional Climate Model (NARCM) was used to construct a 44-yr climatology of spring Asian dust aerosol emission, column loading, deposition, trans-Pacific transport routes, and budgets during 1960 2003. Comparisons with available ground dust observations and Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI) measurements verified that NARCM captured most of the climatological characteristics of the spatial and temporal distributions, as well as the interannual and daily variations of Asian dust aerosol during those 44 yr. Results demonstrated again that the deserts in Mongolia and in western and northern China (mainly the Taklimakan and Badain Juran, respectively) were the major sources of Asian dust aerosol in East Asia. The dust storms in spring occurred most frequently from early April to early May with a daily averaged dust emission (diameter d < 41 μm) of 1.58 Mt in April and 1.36 Mt in May. Asian dust aerosol contributed most of the dust aerosol loading in the troposphere over the midlatitude regions from East Asia to western North America during springtime. Climatologically, dry deposition was a dominant dust removal process near the source areas, while the removal of dust particles by precipitation was the major process over the trans-Pacific transport pathway (where wet deposition exceeded dry deposition up to a factor of 20). The regional transport of Asian dust aerosol over the Asian subcontinent was entrained to an elevation of <3 km. The frontal cyclone in Mongolia and northern China uplifted dust aerosol in the free troposphere for trans-Pacific transport. Trans-Pacific dust transport peaked between 3 and 10 km in the troposphere along a zonal transport axis around 40°N. Based on the 44-yr-averaged dust budgets for the modeling domain from East Asia to western North America, it was estimated that of the average spring dust aerosol (diameter d < 41 μm) emission of 120 Mt from Asian source regions, about 51% was

  10. Changes in the Airborne Bacterial Community in Outdoor Environments following Asian Dust Events

    PubMed Central

    Yamaguchi, Nobuyasu; Park, Jonguk; Kodama, Makiko; Ichijo, Tomoaki; Baba, Takashi; Nasu, Masao

    2014-01-01

    Bacterial abundance and community compositions have been examined in aeolian dust in order to clarify their possible impacts on public health and ecosystems. The influence of transcontinentally transported bacterial cells on microbial communities in the outdoor environments of downwind areas should be determined because the rapid influx of a large amount of bacterial cells can disturb indigenous microbial ecosystems. In the present study, we analyzed bacteria in air samples (approximately 100 m3 d−1) that were collected on both Asian dust days and non-Asian dust days over 2 years (between November 2010 and July 2012). Changes in bacterial abundance and community composition were investigated based on their 16S rRNA gene amount and sequence diversity. Seasonal monitoring revealed that airborne bacterial abundance was more than 10-fold higher on severe dust days, while moderate dust events did not affect airborne bacterial abundance. A comparison of bacterial community compositions revealed that bacteria in Asian dust did not immediately disturb the airborne microbial community in areas 3,000–5,000 km downwind of dust source regions, even when a large amount of bacterial cells were transported by the atmospheric event. However, microbes in aeolian dust may have a greater impact on indigenous microbial communities in downwind areas near the dust source. Continuous temporal and spatial analyses from dust source regions to downwind regions (e.g., from the Gobi desert to China, Korea, Japan, and North America) will assist in estimating the impact of atmospherically transported bacteria on indigenous microbial ecosystems in downwind areas. PMID:24553107

  11. The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water

    NASA Astrophysics Data System (ADS)

    Kahre, Melinda A.; Haberle, Robert M.; Hollingsworth, Jeffery L.; Brecht, Amanda S.; Urata, Richard A.

    2015-11-01

    The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

  12. The Coupled Mars Dust and Water Cycles: Understanding How Clouds Affect the Vertical Distribution and Meridional Transport of Dust and Water.

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.

    2015-01-01

    The dust and water cycles are crucial to the current Martian climate, and they are coupled through cloud formation. Dust strongly impacts the thermal structure of the atmosphere and thus greatly affects atmospheric circulation, while clouds provide radiative forcing and control the hemispheric exchange of water through the modification of the vertical distributions of water and dust. Recent improvements in the quality and sophistication of both observations and climate models allow for a more comprehensive understanding of how the interaction between the dust and water cycles (through cloud formation) affects the dust and water cycles individually. We focus here on the effects of clouds on the vertical distribution of dust and water, and how those vertical distributions control the net meridional transport of water. For this study, we utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) combined with the NASA ARC Mars Global Climate Model (MGCM). We demonstrate that the magnitude and nature of the net meridional transport of water between the northern and southern hemispheres during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. We further examine how clouds influence the atmospheric thermal structure and thus the vertical structure of the cloud belt. Our goal is to identify and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

  13. Transport Properties of the Dust Components in Weakly Ionized Plasma

    SciTech Connect

    Vaulina, O. S.; Adamovich, X. G.; Petrov, O. F.; Fortov, V. E.

    2008-09-07

    The experimental study of transport processes are presented for the dusty plasma in radio-frequency (RF-) capacitive discharge. Validity of the Langevin and Green-Kubo equations for the description of dynamics of dusty grains is verified. Experimental examination of the Einstein-Stokes relation between the viscosity and diffusion constants is carried out.

  14. Dust transport and abrasion assessment within simulated standing vegetation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crop residues are useful in protecting the top soil from depletion and abrasion due to wind erosion. A wind tunnel study was done to measure sand transport and abrasion energies within the simulated artificial standing vegetation. Wind profiles, relative abrasion energies and rates of sand dischar...

  15. Understanding the transport of Patagonian dust and its influence on marine biological activity in the South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Johnson, M. S.; Meskhidze, N.; Kiliyanpilakkil, V. P.; Gassó, S.

    2011-03-01

    The supply of bioavailable iron to the high-nitrate low-chlorophyll (HNLC) waters of the Southern Ocean through atmospheric pathways could stimulate phytoplankton blooms and have major implications for the global carbon cycle. In this study, model results and remotely-sensed data are analyzed to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of iron-laden mineral dust deposition on marine biological productivity in the surface waters of the South Atlantic Ocean (SAO). Model simulations for the atmospheric transport and deposition of mineral dust and bioavailable iron are carried out for two large dust outbreaks originated at the source regions of northern Patagonia during the austral summer of 2009. Model-simulated horizontal and vertical transport pathways of Patagonian dust plumes are in reasonable agreement with remotely-sensed data. Simulations indicate that the synoptic meteorological patterns of high and low pressure systems are largely accountable for dust transport trajectories over the SAO. According to model results and retrievals from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), synoptic flows caused by opposing pressure systems (a high pressure system located to the east or north-east of a low pressure system) elevate the South American dust plumes well above the marine boundary layer. Under such conditions, the bulk concentration of mineral dust can quickly be transported around the low pressure system in a clockwise manner, follow the southeasterly advection pathway, and reach the HNLC waters of the SAO and Antarctica in ~3-4 days after emission from the source regions of northern Patagonia. Two different mechanisms for dust-iron mobilization into a bioavailable form are considered in this study. A global 3-D chemical transport model (GEOS-Chem), implemented with an iron dissolution scheme, is employed to estimate the atmospheric fluxes of soluble iron, while a

  16. Understanding the transport of Patagonian dust and its influence on marine biological activity in the South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Johnson, M. S.; Meskhidze, N.; Kiliyanpilakkil, V. P.; Gassó, S.

    2010-11-01

    The supply of bioavailable iron to the high-nitrate low-chlorophyll (HNLC) waters of the Southern Ocean through atmospheric pathways could stimulate phytoplankton blooms and have major implications for the global carbon cycle. In this study, model results and remotely-sensed data are analyzed to examine the horizontal and vertical transport pathways of Patagonian dust and quantify the effect of iron-laden mineral dust deposition on marine biological productivity in the surface waters of the South Atlantic Ocean (SAO). Model simulations for the atmospheric transport and deposition of mineral dust and bioavailable iron are carried out for two large dust outbreaks originated at the source regions of Northern Patagonia during the austral summer of 2009. Model-simulated horizontal and vertical transport pathways of Patagonian dust plumes are in reasonable agreement with remotely-sensed data. Simulations indicate that the synoptic meteorological patterns of high and low pressure systems are largely accountable for dust transport trajectories over the SAO. According to model results and retrievals from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), synoptic flows caused by opposing pressure systems (a high pressure system located to the east or north-east of a low pressure system) elevate the South American dust plumes well above the marine boundary layer. Under such conditions, the bulk concentration of mineral dust can quickly be transported around the low pressure system in a clockwise manner, follow the southeasterly advection pathway, and reach the HNLC waters of the SAO and Antarctica in ~3-4 days after emission from the source regions of Northern Patagonia. Two different mechanisms for dust-iron mobilization into a bioavailable form are considered in this study. A global 3-D chemical transport model (GEOS-Chem), implemented with an iron dissolution scheme, is employed to estimate the atmospheric fluxes of soluble iron, while a

  17. Evidence of Long Range Transport of Dust From Southwest Asia to the United States

    NASA Astrophysics Data System (ADS)

    Bucholtz, A.; Jonsson, H. H.; Liu, M.; Reid, E. A.; Reid, J. S.; Walker, A. L.; Westphal, D. L.

    2005-12-01

    On March 25, 26 and 27 2003, strong dust storms occurred in Iraq and Saudi Arabia at the start of Operation Iraqi Freedom that severely impaired visibility throughout the region. Evidence will be presented here that indicates this dust was carried westward by prevailing winds and transported halfway around the world to the west coast of the United States. A combination of transport modeling, surface and airborne measurements, and compositional analysis will be used to argue the case. A regional mesoscale weather model, the Navy's Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPSTM), and a global tropospheric aerosol model, the Navy Aerosol Analysis and Prediction System (NAAPS), will be used to illustrate the lofting and transport pathways of the dust, and the favorable meteorological conditions for such long range transport. In addition, surface meteorological observations in Asia will be used to show the lack of any significant dust generation in that region during the same time period. Serendipitously, a surface and airborne field study to investigate the properties and effects of the natural and anthropogenic Asian aerosols transported to the west coast of the United States in the springtime began operation in April 2003. Based out of Monterey on the central coast of California, the Asian Dust Above Monterey (ADAM) field study consisted of surface and airborne measurements of the radiative, microphysical, and morphological properties of the aerosols in the region. The surface observations included MPLNET lidar measurements and AERONET sun photometer measurements as part of the Naval Research Laboratory's Mobile Atmospheric Aerosol and Radiation Characterization Observatory (MAARCO), while the airborne observations included bulk filter samplers, and in situ particle number and size samplers on board the Naval Postgraduate School's Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. The first flight of the Twin

  18. Gully annealing by aeolian sediment: field and remote-sensing investigation of aeolian-hillslope-fluvial interactions, Colorado River corridor, Arizona, USA

    NASA Astrophysics Data System (ADS)

    Sankey, Joel B.; Draut, Amy E.

    2014-09-01

    Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This study of gully annealing by aeolian sediment, spanning 95 km along the Colorado River corridor in Glen, Marble, and Grand Canyon, Arizona, USA, employed field and remote sensing observations, including digital topographic modelling. Results indicate that aeolian sediment activity can be locally effective at counteracting gully erosion. Gullies are less prevalent in areas where surficial sediment undergoes active aeolian transport, and have a greater tendency to terminate in active aeolian sand. Although not common, examples exist in the record of historical imagery of gullies that underwent infilling by aeolian sediment in past decades and evidently were effectively annealed. We thus provide new evidence for a potentially important interaction of aeolian-hillslope-fluvial processes, which could affect dryland regions substantially in ways not widely recognized. Moreover, because the biologic soil crust plays an important role in determining aeolian sand activity, and so in turn the extent of gully development, this study highlights a critical role of geomorphic-ecologic interactions in determining arid-landscape evolution.

  19. Transport, Evolution and Entrainment of Asian Dust/Pollution into the Pacific Marine Boundary

    NASA Astrophysics Data System (ADS)

    Clarke, A. D.; McNaughton, C. S.; Kapustin, V.; Vetter, O.; Dibb, J. E.; Anderson, B. E.; Browell, E. V.; Carmichael, G.; Landing, B.

    2007-05-01

    Various airborne and ship based studies over the past several years have allowed us to measure Asian dust and pollution aerosol from near its source to locations up to 10,000km downwind where it was entrained into the marine boundary layer (MBL). Dust was found to accumulate up to half of the soluble species such as sulfate and nitrate during passage through pollution regions in Asia before being lofted into the free troposphere near Japan. At times, transport in the free troposphere included regions of subsidence in high pressure regions that brought these "rivers" of dust and pollution down to the top of the MBL. Shipboard measurements and lidar data indicated both clear air entrainment and convective activity, associated with the passage of low pressure systems, facilitated dust transport through the inversion. High temperature volatilization of particles in the MBL up to 900C was used to remove most sulfates, nitrates, carbon and sea-salt to leave only dust measured and sized by an optical particle counter. These shipboard data and concurrent chemical measurements revealed the relation between entrainment of pollution and dust into the MBL associated with passage of high pressure systems. Subsequent passage of low pressure systems also revealed scavenging and removal of aerosol through precipitation to the ocean surface. This process appears to be a common removal pathway for dust over the Pacific and a mechanism for supplying the ocean surface with soluble iron and aluminum to the ocean surface. Measurements in the free troposphere and MBL also captured various aspects of these processes. Airborne missions flown north of Hawaii during the NASA PEM-Tropics and IMPEX missions characterized the vertical structure of subsiding dust and pollution. In-flight mapping of the dust/pollution layers and structure using the NASA Langley DIAL LIDAR show a sloping, subsiding Asian air-mass entraining into the marine boundary layer (MBL). In-situ measurements of the aerosol

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Kendry, Ian G. M.; Strawbridge, Kevin B.; O'Neill, Norman; Macdonald, Anne Marie; Liu, Peter S. K.; Leaitch, W. Richard; Anlauf, Kurt G.; Jaegle, Lyatt; Fairlie, T. Duncan; Westphal, Douglas L.

    2007-01-01

    The first documented case of long range transport of Saharan dust over a pathway spanning Asia and the Pacific to Western North America is described. Crustal material generated by North African dust storms during the period 28 February - 3 March 2005 reached western Canada on 13-14 March 2005 and was observed by lidar and sunphotometer in the Vancouver region and by high altitude aerosol instrumentation at Whistler Peak. Global chemical models (GEOS-CHEM and NRL NAAPS) confirm the transport pathway and suggest source attribution was simplified in this case by the distinct, and somewhat unusual, lack of dust activity over Eurasia (Gobi and Takla Makan deserts) at this time. Over western North America, the dust layer, although subsiding close to the boundary layer, did not appear to contribute to boundary layer particulate matter concentrations. Furthermore, sunphotometer observations (and associated inversion products) suggest that the dust layer had only subtle optical impact (Aerosol Optical Thickness (Tau(sub a500)) and Angstrom exponent (Alpha(sub 440-870) were 0.1 and 1.2 respectively) and was dominated by fine particulate matter (modes in aerodynamic diameter at 0.3 and 2.5microns). High Altitude observations at Whistler BC, confirm the crustal origin of the layer (rich in Ca(++) ions) and the bi-modal size distribution. Although a weak event compared to the Asian Trans-Pacific dust events of 1998 and 2001, this novel case highlights the possibility that Saharan sources may contribute episodically to the aerosol burden in western North America.

  2. Evidence for the Convective Transport of Dust Aerosol During DC-3

    NASA Astrophysics Data System (ADS)

    Corr, C.; Ziemba, L. D.; Beyersdorf, A. J.; Moore, R.; Winstead, E.; Thornhill, K. L., II; Shook, M.; Anderson, B. E.; Lawson, P.; Froyd, K. D.; Ryerson, T. B.; Peischl, J.; Pollack, I. B.; Scheuer, E. M.; Dibb, J. E.

    2014-12-01

    Bulk aerosol composition and aerosol volume size distributions measured aboard the NASA DC-8 during the NCAR DC-3 (Deep Convective Clouds and Chemistry Experiment) mission in May/June 2012 were used to investigate the transport of mineral dust through twelve storms encountered over Colorado and Oklahoma. Measurements made at low altitudes (< 5 km) in the storm inflow region were compared to those made in the outflow in and around storm cirrus anvils (altitude > 9 km). Total coarse (1 μm < diameter < 5 μm) aerosol volume (Vc) and Ca2+ measured in both storm inflow and outflow were highly correlated, thus dust was assumed to dominate the aerosol coarse volume. Mean outflow Ca2+ concentrations were comparable to mean inflow values as demonstrated by average outflow/inflow Ca2+ ratios near unity. Vc outflow/inflow ratios were also high (>> 0.5) for most storms, suggesting coarse mode dust was efficiently transported through the CO and OK storms. Comparisons between inflow aerosol number concentration (Nc) calculated over a size range characteristic of dust ice nuclei (0.5 μm < diameter < 5 μm) and ice particle concentrations in storm anvils further suggested interstitial coarse mode dust was present in these cirrus anvils. For over half the storms, mean inflow Nc exceeded mean anvil ice particle concentrations implying ice nucleation mechanisms may be sensitive to complex dust characteristics beyond size. Possible artifacts associated with shattered ice crystals were examined via 1) closure calculations for observations from different instrumentation and independent aircraft inlets, and 2) assessment of relationships with cloud microphysical observations. Initial results indicate minimal influence of ice shatter on aerosol measurements, but effects vary for individual storms with different cloud microphysical characteristics.

  3. Dust transport and palaeoclimate during the Oldest Dryas in Central Europe - implications from varves (Lake Constance)

    SciTech Connect

    Niessen, F.; Lister, G.; Giovanoli, F.

    1992-10-01

    This paper evaluates evidence for seasonal loess deposits in peri-Alpine Lake Constance at the end of the last Glacial (Oldest Dryas chronozone). The sedimentology of laminated couplets comprising yellow and grey silts evaluates the couplets as varves comprising alternations of loess and glacial silt and clay. The laminae, less than 1 mm thick, include from bottom to top: (1) a matrix of well-sorted, non-graded fine yellow silt with sand-size intraclasts, (2) coarsening-upward grey silt with a cap of fining-upward silt to clay. This is typical and reflects summer and winter deposits (silt and clay, respectively). The authors propose that the lack of grading and the matrix supported fabric is indicative of aeolian transport and interpret the yellow laminae as loess deposits. Volcanic glass intraclasts in the loess layers are probably derived from volcanic terrain to the west of the lake, indicating an easterly palaeowind direction. Deposition of loess in the lake occurred regularly at the beginning of each annual cycle, suggesting the palaeowinds were associated with winter and/or spring conditions. Two transport scenarios are suggested to explain the sand grains scattered in this deep-water lacustrine record. 1. The grains may have been transported as bedload over the annual winter ice-cover of the lake under moderate wind strengths, frozen into the ice, and released for deposition during spring melt. 2. The sand grains were blown directly out onto the lake water by very strong winds during spring. The first scenario is contrary to the general view that loess was transported during summer, and that loess deposits thus reflect summer conditions only. Loess input to the lake shows a transitional decrease after ca. 14.3 kyr BP and cessation at ca. 14 kyr BP, probably as a result of a change of wind behaviour, increased humidity and/or vegetational changes during the Oldest Dryas in central Europe. 62 refs., 8 figs.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    Saharan dust outbreaks not only transport large amount of dust to the northern Atlantic Ocean, but also alter African easterly jet and wave activities along the jet by changing north-south temperature gradient. Recent modeling and observational studies show that during periods of enhance outbreaks, rainfall on the northern part of ITCZ increases in conjunction with a northward shift of ITCZ toward the dust layer. In this paper, we study the radiative forcing of Saharan dust and its interactions with the Atlantic Inter-tropical Convergence Zone (ITCZ), through African easterly waves (AEW), African easterly jet (AEJ), using the Terra/Aqua observations as well as MERRA data. Using band pass filtered EOF analysis, we find that African easterly waves propagating westward along two principal tracks, centered at 15-25N and 5-10N respectively. The easterly waves in the northern track are slower, with propagation speed of 9 ms-1, and highly correlated with major dust outbreak over North Africa. On the other hand, easterly waves along the southern track are faster with propagating speed of 10 ms-1, and are closely tied to rainfall/cloud variations along the Atlantic ITCZ. Dust transport along the southern track leads rainfall/cloud anomalies in the same region by one or two days, suggesting the southern tracks of dust outbreak are regions of strong interaction between Saharan dust layer and Atlantic ITCZ. Possible linkage between two tracks of easterly waves, as well as the long-term change of easterly wave activities and dust outbreaks, are also discussed.

  5. The National Wind Erosion Research Network: Building a standardized long-term data resource for aeolian research, modeling and land management

    NASA Astrophysics Data System (ADS)

    Webb, Nicholas P.; Herrick, Jeffrey E.; Van Zee, Justin W.; Courtright, Ericha M.; Hugenholtz, Christopher H.; Zobeck, Ted M.; Okin, Gregory S.; Barchyn, Thomas E.; Billings, Benjamin J.; Boyd, Robert; Clingan, Scott D.; Cooper, Brad F.; Duniway, Michael C.; Derner, Justin D.; Fox, Fred A.; Havstad, Kris M.; Heilman, Philip; LaPlante, Valerie; Ludwig, Noel A.; Metz, Loretta J.; Nearing, Mark A.; Norfleet, M. Lee; Pierson, Frederick B.; Sanderson, Matt A.; Sharratt, Brenton S.; Steiner, Jean L.; Tatarko, John; Tedela, Negussie H.; Toledo, David; Unnasch, Robert S.; Van Pelt, R. Scott; Wagner, Larry

    2016-09-01

    The National Wind Erosion Research Network was established in 2014 as a collaborative effort led by the United States Department of Agriculture's Agricultural Research Service and Natural Resources Conservation Service, and the United States Department of the Interior's Bureau of Land Management, to address the need for a long-term research program to meet critical challenges in wind erosion research and management in the United States. The Network has three aims: (1) provide data to support understanding of basic aeolian processes across land use types, land cover types, and management practices, (2) support development and application of models to assess wind erosion and dust emission and their impacts on human and environmental systems, and (3) encourage collaboration among the aeolian research community and resource managers for the transfer of wind erosion technologies. The Network currently consists of thirteen intensively instrumented sites providing measurements of aeolian sediment transport rates, meteorological conditions, and soil and vegetation properties that influence wind erosion. Network sites are located across rangelands, croplands, and deserts of the western US.

  6. Dust transport in a magnetized radio-frequency discharge under microgravity conditions.

    PubMed

    Land, V; Goedheer, W J; Akdim, M R

    2005-10-01

    Dust is found in plasmas used in industrial applications, such as microelectronics and solar cell manufacturing, in fusion plasmas, where it is usually the result of plasma-wall interactions, and in plasmas in space, such as planetary atmospheres, cometary tails, planetary rings, interstellar molecular clouds, and star and planet formation regions. In plasma applications, magnetic fields are occasionally used, mainly to confine the plasma. In space, however, magnetic fields are very often present and they may strongly influence the behavior of dusty plasma, for instance in the formation of stars and planets. We extended a fully self-consistent two-dimensional fluid model for radio-frequency discharges by adding a homogeneous axial magnetic field and the effect it has on the transport of plasma species in a low-temperature dusty discharge. We show that the magnetic field has an important effect on the (ambipolar) diffusion of ions and electrons in the bulk of the discharge. This causes an important change in the force balance of the dust particles and in the time scales of the formation of a dust-free void. Finally, we compare the parameters of the modeled discharge with the parameters of a planet formation region around a young stellar object (YSO). We conclude that a magnetic field in both low-temperature rf discharges under micro-gravity conditions and dusty plasmas around YSO's has an important effect on the transport of dust and must be important for the formation of planets and stars. PMID:16383541

  7. Intercontinental transport of pollution and dust aerosols: implications for regional air quality

    NASA Astrophysics Data System (ADS)

    Chin, Mian; Diehl, T.; Ginoux, P.; Malm, W.

    2007-06-01

    We use the global model GOCART to examine the impact of pollution and dust aerosols emitted from their major sources on surface fine particulate matter concentrations at regional and hemispheric scales. Focusing on the North America region in 2001, we use measurements from the IMPROVE network in the United States to evaluate the model-simulated surface concentrations of the "reconstructed fine mass" (RCFM) and its components of ammonium sulfate, black carbon (BC), organic matter (OM), and fine mode dust. We then quantify the RCFM budget in terms of the RCFM composition, type, and origin to find that in the eastern U.S., ammonium sulfate is the dominant RCFM component (~60%) whereas in the western U.S., dust and OM are just as important as sulfate but have considerable seasonal variations, especially in the NW. On an annual average, North America regional pollution accounts for nearly 30-40% of the surface RCFM in the western U.S., and for a much higher proportion of 65-70% in the eastern U.S. By contrast, pollution from outside of North America contributes to just 2-6% (~0.2 μg m-3) of the total RCFM over the U.S. on an annual average. In comparison, long-range transport of dust is more efficient than that of pollution, which brings 3 to 4 times more fine particles to the U.S. (0.5-0.8 μg m-3 on an annual average) with a maximum influence in spring and over the NW. Of the major pollution regions, Europe has the largest potential to affect the surface aerosol concentrations in other continents due to its shorter distance from receptor continents and its larger fraction of sulfate-producing precursor gas in the outflow. With the IPCC emission scenario for the year 2000, we find that European emissions increase levels of ammonium sulfate by 1-5 μg m-3 over the surface of northern Africa and western Asia, and its contribution to eastern Asia (≥0.2 μg m-3) is twice as much as the Asian contribution to North America. Asia and North America pollution emissions exert

  8. Mineral dust deposition in Western Mediterranean basin

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  9. Use of radar to assess aeolian processes

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Lancaster, N.; Gaddis, L.; Blumberg, D.; Debrovolskis, A.; Saunders, R. S.; Wall, S.; Iversen, J. D.; White, B.; Rasmussen, K. R.

    1991-01-01

    The interaction between wind and desert surfaces has important implications for sediment transport on Earth, Mars, and Venus, and for understanding the relationship between radar backscatter and aerodynamic roughness. Here, researchers report results from measurements of atmospheric boundary layer profiles, assessment of radar backscatter at P, L, and C wavelengths, and surface roughness in Death Valley, the Mojave Desert, and Lunar Lake, NV, and discuss the implications for aeolian process. The sites include playas, gravel and sand regs, alluvial fans, and lava flows. Boundary layer wind profiles were measured using anemometers at heights of 0.75, 1.25, 2.07, 3.44, 5.72, and 9.5 m; temperature sensors at heights of 1.3 and 9.6 m; and wind vanes at 9.7 and 1.5 m. Microtopographic measurements were made using a template and a laser-photo device to obtain RMS height. This study demonstrates that radar backscatter coefficients obtained from airborne and perhaps orbiting instruments could permit the derivation of aerodynamic roughness values for large areas. Such values, when combined with wind frequency data, could enable assessment of aeolian processes on a regional scale.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  11. The Impact of Projected Changes in Monsoon Season Circulation and African Easterly Waves on Saharan Dust Transport

    NASA Astrophysics Data System (ADS)

    Skinner, C. B.; Diffenbaugh, N. S.

    2013-12-01

    The Sahara is the largest source region of mineral dust in the world. Each year, an estimated 100 to 700 million tons of dust are transported from the Sahara through atmospheric processes. Roughly 30 - 50% of this dust travels westward into the North Atlantic where it impacts the regional radiative balance, atmospheric dynamics, and biogeochemical cycles. During the boreal summer season, dust emissions and dust transport over North Africa are largely controlled by westward propagating synoptic-scale and mesoscale systems such as African easterly waves (AEWs) and mesoscale convective systems (MCSs). In particular, strong low-level winds, vertical motion, and convection associated with these systems drive dust mobilization and vertical mixing throughout the atmosphere. In this work we utilize the CMIP5 ensemble of general circulation models to explore the projected impact of enhanced radiative forcing, consistent with a high emissions scenario (RCP8.5), on atmospheric processes that may influence the emission and transport of dust over West Africa. In particular we focus on the simulation of AEWs during the months of the West African monsoon (June - September). Results from the CMIP5 ensemble indicate a robust increase in low-level (850mb) AEW activity along the Sahel/Sahara border in response to increasing greenhouse gas concentrations by the end of the 21st century. Across the CMIP5 ensemble, AEWs exhibit the strongest increase in low-level winds directly over the observed prolific dust sources within Mali, Mauritania and Algeria in the western Sahara. Enhanced AEW activity in this region is consistent with projected increases in low-level baroclinicity and increased ascent associated with a deepening Saharan Heat Low and stronger convergence along the Intertropical Front. We use a variety of observed and modeled relationships between atmospheric processes and dust as well as output from the available CMIP5 dust modules to explore the impact of the projected

  12. Dust in the wind: long range transport of dust in the atmosphere and its implications for global public and ecosystem health

    USGS Publications Warehouse

    Griffin, Dale W.; Kellogg, Christina A.; Shinn, Eugene A.

    2001-01-01

    Movement of soil particles in atmospheres is a normal planetary process. Images of Martian dust devils (wind-spouts) and dust storms captured by NASA's Pathfinder have demonstrated the significant role that storm activity plays in creating the red atmospheric haze of Mars. On Earth, desert soils moving in the atmosphere are responsible for the orange hues in brilliant sunrises and sunsets. In severe dust storm events, millions of tons of soil may be moved across great expanses of land and ocean. An emerging scientific interest in the process of soil transport in the Earth's atmosphere is in the field of public and ecosystem health. This article will address the benefits and the potential hazards associated with exposure to particle fallout as clouds of desert dust traverse the globe.

  13. A combined observational and modeling approach to study modern dust transport from the Patagonia desert to East Antarctica

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  15. Airborne dust transport to the eastern Pacific Ocean off southern California: Evidence from San Clemente Island

    NASA Astrophysics Data System (ADS)

    Muhs, Daniel R.; Budahn, James; Reheis, Marith; Beann, Jossh; Skipp, Gary; Fisher, Eric

    2007-07-01

    Islands are natural dust traps, and San Clemente Island, California, is a good example. Soils on marine terraces cut into Miocene andesite on this island are clay-rich Vertisols or Alfisols with vertic properties. These soils are overlain by silt-rich mantles, 5-20 cm thick, that contrast sharply with the underlying clay-rich subsoils. The silt mantles have a mineralogy that is distinct from the island bedrock. Silt mantles are rich in quartz, which is rare in the island andesite. The clay fraction of the silt mantles is dominated by mica, also absent from local andesite, and contrasts with the subsoils, dominated by smectite. Ternary plots of immobile trace elements (Sc-Th-La and Ta-Nd-Cr) show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust. In contrast, the silt and, to a lesser extent, clay fractions of the silt mantles have compositions closer to average upper continental crust. The silt mantles have particle size distributions similar to loess and Mojave Desert dust, but are coarser than long-range-transported Asian dust. We infer from these observations that the silt mantles are derived from airborne dust from the North American mainland, probably river valleys in the coastal mountains of southern California and/or the Mojave Desert. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. Examination of satellite imagery shows that easterly Santa Ana winds carry abundant dust to the eastern Pacific Ocean and the California Channel Islands. Airborne dust from mainland North America may be an important component of the offshore sediment budget in the easternmost Pacific Ocean, a finding of potential biogeochemical and climatic significance.

  16. Airborne dust transport to the eastern Pacific Ocean off southern California: Evidence from San Clemente Island

    USGS Publications Warehouse

    Muhs, D.R.; Budahn, J.; Reheis, M.; Beann, J.; Skipp, G.; Fisher, E.

    2007-01-01

    Islands are natural dust traps, and San Clemente Island, California, is a good example. Soils on marine terraces cut into Miocene andesite on this island are clay-rich Vertisols or Alfisols with vertic properties. These soils are overlain by silt-rich mantles, 5-20 cm thick, that contrast sharply with the underlying clay-rich subsoils. The silt mantles have a mineralogy that is distinct from the island bedrock. Silt mantles are rich in quartz, which is rare in the island andesite. The clay fraction of the silt mantles is dominated by mica, also absent from local andesite, and contrasts with the subsoils, dominated by smectite. Ternary plots of immobile trace elements (Sc-Th-La and Ta-Nd-Cr) show that the island andesite has a composition intermediate between average upper continental crust and average oceanic crust. In contrast, the silt and, to a lesser extent, clay fractions of the silt mantles have compositions closer to average upper continental crust. The silt mantles have particle size distributions similar to loess and Mojave Desert dust, but are coarser than long-range-transported Asian dust. We infer from these observations that the silt mantles are derived from airborne dust from the North American mainland, probably river valleys in the coastal mountains of southern California and/or the Mojave Desert. Although average winds are from the northwest in coastal California, easterly winds occur numerous times of the year when "Santa Ana" conditions prevail, caused by a high-pressure cell centered over the Great Basin. Examination of satellite imagery shows that easterly Santa Ana winds carry abundant dust to the eastern Pacific Ocean and the California Channel Islands. Airborne dust from mainland North America may be an important component of the offshore sediment budget in the easternmost Pacific Ocean, a finding of potential biogeochemical and climatic significance.

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

    USGS Publications Warehouse

    Kumar, A.; Abouchami, W.; Galer, S.J.G.; Garrison, V.H.; Williams, E.; Andreae, M.O.

    2014-01-01

    Many studies have suggested that long-range transport of African desert dusts across the Atlantic Ocean occurs, delivering key nutrients and contributing to fertilization of the Amazon rainforest. Here we utilize radiogenic isotope tracers – Sr, Nd and Pb – to derive the provenance, local or remote, and pathways of dust transport from Africa to the Caribbean. Atmospheric total suspended particulate (TSP) matter was collected in 2008 on quartz fibre filters, from both sides of the Atlantic Ocean at three different locations: in Mali (12.6°N, 8.0°W; 555 m a.s.l.), Tobago (11.3°N, 60.5°W; 329 m a.s.l.) and the U.S. Virgin Islands (17.7°N, 64.6°W; 27 m a.s.l.). Both the labile phase, representative of the anthropogenic signal, and the refractory detrital silicate fraction were analysed. Dust deposits and soils from around the sampling sites were measured as well to assess the potential contribution from local sources to the mineral dust collected. The contribution from anthropogenic sources of Pb was predominant in the labile, leachate phase. The overall similarity in Pb isotope signatures found in the leachates is attributed to a common African source of anthropogenic Pb, with minor inputs from other sources, such as from Central and South America. The Pb, Sr and Nd isotopic compositions in the silicate fraction were found to be systematically more radiogenic than those in the corresponding labile phases. In contrast, Nd and Sr isotopic compositions from Mali, Tobago, and the Virgin Islands are virtually identical in both leachates and residues. Comparison with existing literature data on Saharan and Sahelian sources constrains the origin of summer dust transported to the Caribbean to mainly originate from the Sahel region, with some contribution from northern Saharan sources. The source regions derived from the isotope data are consistent with 7-day back-trajectory analyses, demonstrating the usefulness of radiogenic isotopes in tracing dust provenance and

  18. Multi-year model simulations of mineral dust distribution and transport over the Indian subcontinent during summer monsoon seasons

    NASA Astrophysics Data System (ADS)

    Sijikumar, S.; Aneesh, S.; Rajeev, K.

    2015-12-01

    Aerosol distribution over the Arabian Sea and the Indian subcontinent during the northern hemispheric summer is dominated by mineral dust transport from the West Asian desert regions. The radiative impact of these dust plumes is expected to have a prominent role in regulating the Asian Summer Monsoon circulation. While satellite observations have provided information in the spatial distribution of aerosols over the oceanic regions during the season, their utility over the land is rather limited. This study examines the transport of mineral dust over the West Asian desert, the Indian subcontinent and the surrounding oceanic regions during the summer monsoon season with the help of a regional scale model, WRF-Chem. Geographical locations of prominent dust sources, altitude ranges of mineral dust transport and their inter-annual variations are examined in detail. Multi-year model simulations were carried out during 2007 to 2012 with a model integration from 15 May to 31 August of each year. Six-year seasonal mean (June to August) vertically integrated dust amount from 1000 to 300 hPa level shows prominent dust loading over the eastern parts of Arabian desert and the northwestern part of India which are identified as two major sources of dust production. Large latitudinal gradient in dust amount is observed over the Arabian Sea with the largest dust concentration over the northwestern part and is primarily caused by the prevailing northwesterly wind at 925 hPa level from the Arabian desert. The model simulations clearly show that most of the dust distributed over the Indo-Gangetic plane originates from the Rajasthan desert located in the northwestern part of India, whereas dust observed over the central and south peninsular India and over the Arabian Sea are mainly transported from the Arabian desert. Abnormal dust loading is observed over the north Arabian Sea during June 2008. This has been produced as a result of the low pressure system (associated with the onset of

  19. Multi-year model simulations of mineral dust distribution and transport over the Indian subcontinent during summer monsoon seasons

    NASA Astrophysics Data System (ADS)

    Sijikumar, S.; Aneesh, S.; Rajeev, K.

    2016-08-01

    Aerosol distribution over the Arabian Sea and the Indian subcontinent during the northern hemispheric summer is dominated by mineral dust transport from the West Asian desert regions. The radiative impact of these dust plumes is expected to have a prominent role in regulating the Asian Summer Monsoon circulation. While satellite observations have provided information in the spatial distribution of aerosols over the oceanic regions during the season, their utility over the land is rather limited. This study examines the transport of mineral dust over the West Asian desert, the Indian subcontinent and the surrounding oceanic regions during the summer monsoon season with the help of a regional scale model, WRF-Chem. Geographical locations of prominent dust sources, altitude ranges of mineral dust transport and their inter-annual variations are examined in detail. Multi-year model simulations were carried out during 2007 to 2012 with a model integration from 15 May to 31 August of each year. Six-year seasonal mean (June to August) vertically integrated dust amount from 1000 to 300 hPa level shows prominent dust loading over the eastern parts of Arabian desert and the northwestern part of India which are identified as two major sources of dust production. Large latitudinal gradient in dust amount is observed over the Arabian Sea with the largest dust concentration over the northwestern part and is primarily caused by the prevailing northwesterly wind at 925 hPa level from the Arabian desert. The model simulations clearly show that most of the dust distributed over the Indo-Gangetic plane originates from the Rajasthan desert located in the northwestern part of India, whereas dust observed over the central and south peninsular India and over the Arabian Sea are mainly transported from the Arabian desert. Abnormal dust loading is observed over the north Arabian Sea during June 2008. This has been produced as a result of the low pressure system (associated with the onset of

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

    NASA Astrophysics Data System (ADS)

    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 <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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  2. Mapping of Fugitive Dust Generation, Transport, and Deposition in the Nogales, Arizona Region Using Enhanced Thematic Mapper Plus (ETM+) Data

    NASA Astrophysics Data System (ADS)

    Stefanov, W. L.; Stefanov, W. L.; Ramsey, M. S.; Christensen, P. R.

    2001-05-01

    Urban centers located along the U.S.-Mexico border represent significant sources of fugitive (airborne) dust. This dust, which can lead to adverse health effects, arises from several factors including construction activities related to land use conversion (i.e., agricultural to residential), unpaved roadways, agricultural activities, and human disturbance of the soil. Fundamental baseline data needed for modeling and monitoring of particulate generation and transport are accurate regional classification of land cover, degree of disturbance, and a metric of land cover change. Identification and delineation of fugitive dust source regions using a purely field-based approach is time and labor intensive and can lead to errors over time as land use changes. Further, restrictions on access to specific areas (such as private lands and reservations) may impede or prevent site investigations in these areas. Remotely gathered information can be used to circumvent these difficulties and provide rapid dust source region identification with quantitative area measurements required in transport models. Landsat ETM+ data was used to identify and delineate surficial materials that were either potential fugitive dust source regions or were important factors in dust transport and deposition. Using a knowledge-based system, land cover was classified into three generalized types: natural and disturbed soils (dust generation sites); asphalt, concrete, and urban materials (dust transport areas); and vegetated areas (dust deposition sites). Accuracy of the land cover classification was assessed using field verification, comparison of field and image reflectance spectra, and digital aerial orthophotographs. Results of image classification and field verification for Landsat data acquired during the winter of 2000 show a strong correlation, and will be used with data collected during the summer dry season for change detection analysis. The digital format of the classified data is optimal for

  3. Oxidant enhancement in martian dust devils and storms: storm electric fields and electron dissociative attachment.

    PubMed

    Delory, Gregory T; Farrell, William M; Atreya, Sushil K; Renno, Nilton O; Wong, Ah-San; Cummer, Steven A; Sentman, Davis D; Marshall, John R; Rafkin, Scot C R; Catling, David C

    2006-06-01

    Laboratory studies, numerical simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity." In convective structures such as dust devils and dust storms, grain stratification leads to macroscopic charge separations and gives rise to an overall electric dipole moment in the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous numerical simulations indicate that these storm electric fields on Mars can approach the ambient breakdown field strength of approximately 25 kV/m. In terrestrial dust phenomena, potentials ranging from approximately 20 to 160 kV/m have been directly measured. The large electrostatic fields predicted in martian dust devils and storms can energize electrons in the low pressure martian atmosphere to values exceeding the electron dissociative attachment energy of both CO2 and H2O, which results in the formation of the new chemical products CO/O- and OH/H-, respectively. Using a collisional plasma physics model, we present calculations of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach the breakdown value of approximately 25 kV/m. The dissociation of H2O into OH/H- provides a key ingredient for the generation of oxidants; thus electrically charged dust may significantly impact the habitability of Mars. PMID:16805701

  4. Comparing dust flux records from the Subarctic North Pacific and Greenland: Implications for atmospheric transport to Greenland and for the application of dust as a chronostratigraphic tool

    NASA Astrophysics Data System (ADS)

    Serno, Sascha; Winckler, Gisela; Anderson, Robert F.; Maier, Edith; Ren, Haojia; Gersonde, Rainer; Haug, Gerald H.

    2015-06-01

    We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27,000 years based on a core from the Detroit Seamount. Comparing the SNP dust record to the North Greenland Ice Core Project (NGRIP) ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the 230Th-normalized 4He flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745 ± 140 years at 11,653 year B.P., 680 ± 228 years at 14,630 year B.P., and 790 ± 498 years at 23,290 year B.P. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    SciTech Connect

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

    2015-03-01

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

  7. Saharan dust deposition in the Carpathian Basin and its possible effects on interglacial soil formation

    NASA Astrophysics Data System (ADS)

    Varga, György; Cserháti, Csaba; Kovács, János; Szalai, Zoltán

    2016-09-01

    Several hundred tons of windblown dust material are lifted into the atmosphere and are transported every year from Saharan dust source areas towards Europe having an important climatic and other environmental effect also on distant areas. According to the systematic observations of modern Saharan dust events, it can be stated that dust deflated from North African source areas is a significant constituent of the atmosphere of the Carpathian Basin and Saharan dust deposition events are identifiable several times in a year. Dust episodes are connected to distinct meteorological situations, which are also the determining factors of the different kinds of depositional mechanisms. By using the adjusted values of dust deposition simulations of numerical models, the annual Saharan dust flux can be set into the range of 3.2-5.4 g/m2/y. Based on the results of past mass accumulation rates calculated from stratigraphic and sedimentary data of loess-paleosol sequences, the relative contribution of Saharan dust to interglacial paleosol material was quantified. According to these calculations, North African exotic dust material can represent 20-30% of clay and fine silt-sized soil components of interglacial paleosols in the Carpathian Basin. The syngenetic contribution of external aeolian dust material is capable to modify physicochemical properties of soils and hereby the paleoclimatic interpretation of these pedogene stratigraphic units.

  8. Dust emission and transport over Iraq associated with the summer Shamal winds

    NASA Astrophysics Data System (ADS)

    Karam Francis, Diana Bou; Flamant, Cyrille; Chaboureau, Jean-Pierre; Banks, Jamie

    2016-04-01

    In this study, we investigate the diurnal evolution of the summer Shamal wind (a quasi-permanent low-level northwesterly wind feature) and its role in dust emission and transport over Iraq, using ground-based and space-borne observations together with a numerical simulation performed with the mesoscale model Meso-NH. A 6-year dataset from the synoptic stations over Iraq allows establishing the prominence of the link between strong near surface winds and reduced visibility in the summer. The detailed processes at play during Shamal events are explored on the basis of a Meso-NH simulation for a given, representative case study (25 June-3 July 2010). The Shamal exhibits an out-of-phase relationship between the surface wind and winds in the lower troposphere (typically 500 m above ground level), the maximum surface wind speeds being observed during the day while in altitude the maximum wind speeds are observed at night. The daytime near surface winds, at the origin of dust emission, are associated with the downward transfer of momentum from the nocturnal low-level jet to the surface due to turbulent mixing after solar heating commences each day. For the first time, an estimate of the dust load associated with summer Shamal events over Iraq has been made using aerosol optical depths derived from the Spinning Enhanced Visible and Infrared Imager, the Moderate Resolution Imaging Spectroradiometer, and the simulation. The dust load exhibits a large diurnal variability, with a daily minimum value of 1 Tg around 0600 UTC and a daily peak of 2.5 Tg or more around 1500 UTC, and is driven by the diurnal cycle of the near surface wind speed. The daily dust load peak associated with the summer Shamal over Iraq is in the same order of magnitude as those derived from simulations downstream of the Bodélé depression in Chad, known to be the world's largest dust source. Keywords: Dust, Low Level Jet, Shamal winds, Middle East, dust sources.

  9. The National Wind Erosion Research Network: Building a standardized long-term data resource for aeolian research, modeling and land management

    USGS Publications Warehouse

    Webb, Nicholas P.; Herrick, Jeffrey E.; Van Zee, Justin W; Courtright, Ericha M; Hugenholtz, Ted M; Zobeck, Ted M; Okin, Gregory S.; Barchyn, Thomas E; Billings, Benjamin J; Boyd, Robert A.; Clingan, Scott D; Cooper, Brad F; Duniway, Michael C.; Derner, Justin D; Fox, Fred A; Havstad, Kris M.; Heilman, Philip; LaPlante, Valerie; Ludwig, Noel A; Metz, Loretta J; Nearing, Mark A; Norfleet, M Lee; Pierson, Frederick B; Sanderson, Matt A; Sharrat, Brenton S; Steiner, Jean L; Tatarko, John; Tedela, Negussie H; Todelo, David; Unnasch, Robert S; Van Pelt, R Scott; Wagner, Larry

    2016-01-01

    The National Wind Erosion Research Network was established in 2014 as a collaborative effort led by the United States Department of Agriculture’s Agricultural Research Service and Natural Resources Conservation Service, and the United States Department of the Interior’s Bureau of Land Management, to address the need for a long-term research program to meet critical challenges in wind erosion research and management in the United States. The Network has three aims: (1) provide data to support understanding of basic aeolian processes across land use types, land cover types, and management practices, (2) support development and application of models to assess wind erosion and dust emission and their impacts on human and environmental systems, and (3) encourage collaboration among the aeolian research community and resource managers for the transfer of wind erosion technologies. The Network currently consists of thirteen intensively instrumented sites providing measurements of aeolian sediment transport rates, meteorological conditions, and soil and vegetation properties that influence wind erosion. Network sites are located across rangelands, croplands, and deserts of the western US. In support of Network activities, http://winderosionnetwork.org was developed as a portal for information about the Network, providing site descriptions, measurement protocols, and data visualization tools to facilitate collaboration with scientists and managers interested in the Network and accessing Network products. The Network provides a mechanism for engaging national and international partners in a wind erosion research program that addresses the need for improved understanding and prediction of aeolian processes across complex and diverse land use types and management practices.

  10. Spatio-Temporal Modelling of Dust Transport over Surface Mining Areas and Neighbouring Residential Zones

    PubMed Central

    Matejicek, Lubos; Janour, Zbynek; Benes, Ludek; Bodnar, Tomas; Gulikova, Eva

    2008-01-01

    Projects focusing on spatio-temporal modelling of the living environment need to manage a wide range of terrain measurements, existing spatial data, time series, results of spatial analysis and inputs/outputs from numerical simulations. Thus, GISs are often used to manage data from remote sensors, to provide advanced spatial analysis and to integrate numerical models. In order to demonstrate the integration of spatial data, time series and methods in the framework of the GIS, we present a case study focused on the modelling of dust transport over a surface coal mining area, exploring spatial data from 3D laser scanners, GPS measurements, aerial images, time series of meteorological observations, inputs/outputs form numerical models and existing geographic resources. To achieve this, digital terrain models, layers including GPS thematic mapping, and scenes with simulation of wind flows are created to visualize and interpret coal dust transport over the mine area and a neighbouring residential zone. A temporary coal storage and sorting site, located near the residential zone, is one of the dominant sources of emissions. Using numerical simulations, the possible effects of wind flows are observed over the surface, modified by natural objects and man-made obstacles. The coal dust drifts with the wind in the direction of the residential zone and is partially deposited in this area. The simultaneous display of the digital map layers together with the location of the dominant emission source, wind flows and protected areas enables a risk assessment of the dust deposition in the area of interest to be performed. In order to obtain a more accurate simulation of wind flows over the temporary storage and sorting site, 3D laser scanning and GPS thematic mapping are used to create a more detailed digital terrain model. Thus, visualization of wind flows over the area of interest combined with 3D map layers enables the exploration of the processes of coal dust deposition at a

  11. Should precipitation influence dust emission in global dust models?

    NASA Astrophysics Data System (ADS)

    Okin, Gregory

    2016-04-01

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

  12. Provenance of Asian Dust Delivered to the Philippine Sea and Its Transport Pathways: Isotopic and Mineralogical Evidences

    NASA Astrophysics Data System (ADS)

    SEO, I.; Lee, Y. I.; Yoo, C. M.; Kim, H. J.; Hyeong, K.

    2014-12-01

    Most dust studies using deep-sea sediment archives from the North Pacific have focused on understanding the mass flux variation of Asian dust in terms of long-term climate variability, but have not considered specific transport pathways or dust source regions (e.g., central/East Asian deserts versus northern Chinese deserts). To characterize the provenance and transport pathways of eolian dust deposited in the western tropical/subtropical Pacific, and to investigate changes over the late Quaternary, we used the clay mineral assemblage, together with the 143Nd/144Nd and 87Sr/86Sr composition of the inorganic silicate fractions of a deep-sea sediment core retrieved from the Palau-Kyushu Ridge in the Philippine Sea. The analyzed attributes of the core resemble those of dust from the central Asian deserts (CADs; e.g., the Taklimakan Desert) as in the North Central Pacific, but published aerosol data collected near the study site during winter/spring has the mineralogical signature of dust originating from the East Asian deserts (EADs; e.g., the Chinese Loess Plateau and nearby deserts). These data indicate that the relative contribution of EAD dust increases with the northeasterly surface winds associated with the East Asian Winter Monsoon (EAWM) during winter/spring, but the Prevailing Westerlies and Trade Winds that carry dust from the CADs have been the dominant transport agent for the last 600 kyr. The results of this study contradict the prevailing view that direct dust transport by the EAWM winds in spring dominates the annual flux of eolian dust in the northwest Pacific.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  14. Geochemical and isotopic characterization of the Bodélé Depression dust source and implications for transatlantic dust transport to the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Abouchami, Wafa; Näthe, Kerstin; Kumar, Ashwini; Galer, Stephen J. G.; Jochum, Klaus Peter; Williams, Earle; Horbe, Adriana M. C.; Rosa, João W. C.; Balsam, William; Adams, David; Mezger, Klaus; Andreae, Meinrat O.

    2013-10-01

    The Bodélé Depression (Chad) in the central Sahara/Sahel region of Northern Africa is the most important source of mineral dust to the atmosphere globally. The Bodélé Depression is purportedly the largest source of Saharan dust reaching the Amazon Basin by transatlantic transport. Here, we have undertaken a comprehensive study of surface sediments from the Bodélé Depression and dust deposits (Chad, Niger) in order to characterize geochemically and isotopically (Sr, Nd and Pb isotopes) this dust source, and evaluate its importance in present and past African dust records. We similarly analyzed sedimentary deposits from the Amazonian lowlands in order to assess postulated accumulation of African mineral dust in the Amazon Basin, as well as its possible impact in fertilizing the Amazon rainforest. Our results identify distinct sources of different ages and provenance in the Bodélé Depression versus the Amazon Basin, effectively ruling out an origin for the Amazonian deposits, such as the Belterra Clay Layer, by long-term deposition of Bodélé Depression material. Similarly, no evidence for contributions from other potential source areas is provided by existing isotope data (Sr, Nd) on Saharan dusts. Instead, the composition of these Amazonian deposits is entirely consistent with derivation from in-situ weathering and erosion of the Precambrian Amazonian craton, with little, if any, Andean contribution. In the Amazon Basin, the mass accumulation rate of eolian dust is only around one-third of the vertical erosion rate in shield areas, suggesting that Saharan dust is "consumed" by tropical weathering, contributing nutrients and stimulating plant growth, but never accumulates as such in the Amazon Basin. The chemical and isotope compositions found in the Bodélé Depression are varied at the local scale, and have contrasting signatures in the "silica-rich" dry lake-bed sediments and in the "calcium-rich" mixed diatomites and surrounding sand material. This

  15. Dust transport and deposition observed from the Terra-Moderate Resolution Imaging Spectroradiometer (MODIS) spacecraft over the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

    Meteorological observations, in situ data, and satellite images of dust episodes were used already in the 1970s to estimate that 100 Tg of dust are transported from Africa over the Atlantic Ocean every year between June and August and are deposited in the Atlantic Ocean and the Americas. Desert dust is a main source of nutrients to oceanic biota and the Amazon forest, but it deteriorates air quality, as shown for Florida. Dust affects the Earth radiation budget, thus participating in climate change and feedback mechanisms. There is an urgent need for new tools for quantitative evaluation of the dust distribution, transport, and deposition. The Terra spacecraft, launched at the dawn of the last millennium, provides the first systematic well-calibrated multispectral measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument for daily global analysis of aerosol. MODIS data are used here to distinguish dust from smoke and maritime aerosols and to evaluate the African dust column concentration, transport, and deposition. We found that 240 ± 80 Tg of dust are transported annually from Africa to the Atlantic Ocean, 140 ± 40 Tg are deposited in the Atlantic Ocean, 50 Tg fertilize the Amazon Basin (four times as previous estimates, thus explaining a paradox regarding the source of nutrition to the Amazon forest), 50 Tg reach the Caribbean, and 20 Tg return to Africa and Europe. The results are compared favorably with dust transport models for maximum particle diameter between 6 and 12 μm. This study is a first example of quantitative use of MODIS aerosol for a geophysical research.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

  18. Bacterial Composition and Survival on Sahara Dust Particles Transported to the European Alps

    PubMed Central

    Meola, Marco; Lazzaro, Anna; Zeyer, Josef

    2015-01-01

    Deposition of Sahara dust (SD) particles is a frequent phenomenon in Europe, but little is known about the viability and composition of the bacterial community transported with SD. The goal of this study was to characterize SD-associated bacteria transported to the European Alps, deposited and entrapped in snow. During two distinct events in February and May 2014, SD particles were deposited and promptly covered by falling snow, thus preserving them in distinct ochre layers within the snowpack. In June 2014, we collected samples at different depths from a snow profile at the Jungfraujoch (Swiss Alps; 3621 m a.s.l.). After filtration, we performed various microbiological and physicochemical analyses of the snow and dust particles therein that originated in Algeria. Our results show that bacteria survive and are metabolically active after the transport to the European Alps. Using high throughput sequencing, we observed distinct differences in bacterial community composition and structure in SD-layers as compared to clean snow layers. Sporulating bacteria were not enriched in the SD-layers; however, phyla with low abundance such as Gemmatimonadetes and Deinococcus-Thermus appeared to be specific bio-indicators for SD. Since many members of these phyla are known to be adapted to arid oligotrophic environments and UV radiation, they are well suited to survive the harsh conditions of long-range airborne transport. PMID:26733988

  19. African dust in the Caribbean: chemical, physical and optical properties of transported African dust across the Atlantic: observations from Atmospheric Observatory in Cabezas de San Juan, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Quiñones Rosado, M.; Vallejo, P. M.; Mayol-Bracero, O. L.; Gutiérrez, I.; Ogren, J. A.; Desboeufs, K.; Formenti, P.

    2012-12-01

    We present results on the assessment of aerosols chemical, physical, and optical properties at the atmospheric observatory of Cabezas de San Juan in Fajardo, PR, during the summer 2011, where periods in the presence and absence of dust were studied as part of the project Dust-ATtACk (Dust- Aging and Transport, from Africa to the Caribbean). Dust events were identified through observation and using air-mass back-trajectories, Saharan Air Layer images, measurements of aerosol optical thickness (AOT), in situ scattering and absorption coefficients, and chemical analyses. We focused on results obtained for intense dust events observed in June 22-24 and July 9, 2011. Those events were characterized by higher concentration of coarse particles, higher concentration of metals associated with mineral dust (e.g., Si 3 μg/m3 compared to background concentrations of 0.15 μg/m3), higher scattering and absorption coefficients (up to 100 Mm-1 and 2.5 Mm-1 at 550 and 530 nm, respectively), and AOT (from 0.4 to 0.8) values. The single scattering albedo (SSA) was calculated for the periods of interest for the PM10 and the PM1 mass fractions and plotted against wavelength. For PM10, SSA values ranged from 0.93 to 0.99 and had the same trend reported for dust, with lower SSA values at shorter wavelengths. For PM1, values ranged from 0.85 to 0.98 and more variability was observed in terms of SSA wavelength dependence, likely as species other than dust contribute. Satellite products (e.g., Calipso, Seviri) are used in the attempt to trace these events back to their source region at North Africa.

  20. Gully annealing by aeolian sediment: field and remote-sensing investigation of aeolian-hillslope-fluvial interactions, Colorado River corridor, Arizona, USA

    USGS Publications Warehouse

    Sankey, Joel B.; Draut, Amy E.

    2014-01-01

    Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This study of gully annealing by aeolian sediment, spanning 95 km along the Colorado River corridor in Glen, Marble, and Grand Canyon, Arizona, USA, employed field and remote sensing observations, including digital topographic modelling. Results indicate that aeolian sediment activity can be locally effective at counteracting gully erosion. Gullies are less prevalent in areas where surficial sediment undergoes active aeolian transport, and have a greater tendency to terminate in active aeolian sand. Although not common, examples exist in the record of historical imagery of gullies that underwent infilling by aeolian sediment in past decades and evidently were effectively annealed. We thus provide new evidence for a potentially important interaction of aeolian–hillslope–fluvial processes, which could affect dryland regions substantially in ways not widely recognized. Moreover, because the biologic soil crust plays an important role in determining aeolian sand activity, and so in turn the extent of gully development, this study highlights a critical role of geomorphic–ecologic interactions in determining arid-landscape evolution.

  1. Meteorological and physical characteristics of dust transport events in the Eastern Great Basin of Utah, U.S.A

    NASA Astrophysics Data System (ADS)

    Hahnenberger, M.; Nicoll, K.; Perry, K. D.

    2011-12-01

    Although the Great Basin physiographic province in North America is a known source area of atmospheric dust, the ascendant controls on its dust events have not been well documented to date. We assess the climatology of these dust events back to the 1930s, and find clear seasonal and diurnal patterns, indicating that dust events are, commonly, an afternoon phenomenon during the spring months. Since 1930, Salt Lake City, UT has had 379 dust event days, or 4.7 per year. Air quality station data from the more populated regions of Utah, available since 1993, indicate that dust events have produced elevated PM10, exceeding NAAQS, on 16 days over the past 18 years, or 0.9 per year. This study identifies deepening cyclonic systems over the northern Great Basin as the primary producer of these dust events affecting the eastern Great Basin; this region is located in the lee of the Sierra Nevada, and is a known region of cyclogenesis. Strengthening synoptic scale weather systems interact at the mesoscale with local topography and dust source regions to cause significant dust storms events that have affected the metropolitan area of Salt Lake City, Utah. Upwind of Salt Lake City, these cyclonic systems produce strong southwesterly winds that exceed threshold friction velocities and entrain sediment at the surface of such dust sources as the Sevier Lake, Tule Lake, and Milford Flat, an area disturbed in 2007 by Utah's largest wildfire in recorded history. Case studies of two significant dust events, occurring on 19 April, 2008 and 4 March, 2009, and producing elevated PM10 levels in this region, highlight the key meteorological features and land surface attributes of "hotspot" source areas, identifiable in satellite imagery, of the dust that affected SLC. BSNE dust samplers at the Sevier Lake source region characterize the source type and magnitude and reveal the composition of dust that is being transported. Understanding the meteorological and physical characteristics of

  2. Publication trends in Aeolian research: An analysis of the biblography of Aeolian research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An analysis of the Bibliography of Aeolian Research has provided information regarding publication trends in aeolian research. Overall, results suggest that there has been a significant increase in the number of publications per year since the first aeolian-research publication appeared in 1646. P...

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

    USGS Publications Warehouse

    Garrison, Virginia; Lamothe, Paul; Morman, Suzette; Plumlee, Geoffrey S.

    2010-01-01

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

  4. The likelihood of observing dust-stimulated phytoplankton growth in waters proximal to the Australian continent

    NASA Astrophysics Data System (ADS)

    Cropp, R. A.; Gabric, A. J.; Levasseur, M.; McTainsh, G. H.; Bowie, A.; Hassler, C. S.; Law, C. S.; McGowan, H.; Tindale, N.; Viscarra Rossel, R.

    2013-05-01

    We develop a tool to assist in identifying a link between naturally occurring aeolian dust deposition and phytoplankton response in the ocean. Rather than examining a single, or small number of dust deposition events, we take a climatological approach to estimate the likelihood of observing a definitive link between dust deposition and a phytoplankton bloom for the oceans proximal to the Australian continent. We use a dust storm index (DSI) to determine dust entrainment in the Lake Eyre Basin (LEB) and an ensemble of modelled atmospheric trajectories of dust transport from the basin, the major dust source in Australia. Deposition into the ocean is computed as a function of distance from the LEB source and the local over-ocean precipitation. The upper ocean's receptivity to nutrients, including dust-borne iron, is defined in terms of time-dependent, monthly climatological fields for light, mixed layer depth and chlorophyll concentration relative to the climatological monthly maximum. The resultant likelihood of a dust-phytoplankton link being observed is then mapped as a function of space and time. Our results suggest that the Southern Ocean (north of 45°S), the North West Shelf, and Great Barrier Reef are ocean regions where a rapid biological response to dust inputs is most likely to be observed. Conversely, due to asynchrony between deposition and ocean receptivity, direct causal links appear unlikely to be observed in the Tasman Sea and Southern Ocean south of 45°S.

  5. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Djuly, Thomas; de Graaf, Stefan; Sakes, Alex; Wijbrans, Jan; Davies, Gareth; Vroon, Pieter

    2015-03-01

    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by continents and receives a large sediment input, part of which is transported down with the subducting slab into the mantle and potentially contributes a major flux to the arc volcanism. An along-arc gradient in the composition of subducting sediment has been evoked to explain the distinct geochemical signature of the easternmost volcanic centre of the Aegean arc, but direct evidence for this proposal is lacking. We present a detailed study of the mineralogical, major-, trace elements and Sr-Nd-Hf-Pb isotope composition of 45 Neogene EMS sediment samples obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites and box cores to characterise their geochemical composition, distinguish provenance components and investigate the temporal and spatial variation in provenance to evaluate the potential changing contribution of subducted EMS sediment to Aegean and Aeolian arc volcanism. Based on trace element characteristics of EMS sediments, we can distinguish four provenance components. Nile sediment and Sahara dust are the main components, but contributions from the Tethyan ophiolite belt and arc volcanic rocks in the north are also recognised. Pliocene and Quaternary EMS sediment records a strong geochemical gradient where Nile River sediment entering the EMS in the east is progressively diluted by Sahara Desert dust towards the west. Pre-Messinian samples, however, have a remarkably homogeneous composition with Nile sediment characteristics. We relate this rapid increase in Sahara dust contribution to a late Miocene climate shift leading to decreased Nile runoff and aridification of the Sahara region. EMS sediment has a restricted range in Pb isotopes

  6. The Rule Of Maximum Gross Bedform-Normal Transport: Constraining Aeolian Bedform Morphology And Formative Wind Regime Using Solely Orbital Imagery

    NASA Astrophysics Data System (ADS)

    Fenton, L. K.

    2012-12-01

    Although the formative wind regime and bedform morphology of several dune fields have been determined through extensive field work, nearly all planetary and many terrestrial dune fields are located in remote regions for which the only existing morphological data are spacecraft images. In the absence of other forms of data (e.g., anemometry, migration patterns), what can be determined about the sand-transporting winds that built these dune fields? We demonstrate that the rule of maximum gross bedform-normal transport (MGBNT) of Rubin and Hunter (1987) and Rubin and Ikeda (1990) can be applied in many remote situations to constrain both the potential wind regime and bedform type. By determining two formative wind directions from nearby unidirectional features (e.g., yardangs, wind streaks), the relative strengths of dune-building winds can be constrained by comparison of MGBNT to bedform orientation. In cases where only one formative wind direction can be identified, a second wind may be partially determined by "inverse-MGBNT" analysis. In these instances, a second wind may be identified from those that combine with a known (or assumed) sand-transporting wind to produce observed dune crestline orientations. We first demonstrate this method in a terrestrial setting where the bedform type and wind regime is well constrained, following with an example in Ganges Chasma on Mars. If the initial assumptions regarding likely sand-transporting wind directions are robust, then this technique proves to be reliable; in many locations on Mars and Titan it can be used as a constraint for atmospheric modeling. a) Linear or oblique dunes in a portion of the largest dune field in Ganges Chasma on Mars. b) Histogram of dune crestline orientations from a). c) Maximum gross bedform-normal transport analysis constraining the transport ratio of two likely sand-transporting winds. A southwesterly wind (black) combines with an east-southeasterly wind (black) with a transport ratio between 1

  7. Polluted dust derived from long-range transport as a major end member of urban aerosols and its implication of non-point pollution in northern China.

    PubMed

    Yan, Y; Sun, Y B; Weiss, D; Liang, L J; Chen, H Y

    2015-02-15

    The contribution of polluted dust transported from local and distal sources remains poorly constrained due to their similar geophysical and geochemical properties. We sampled aerosols in three cities in northern China (Xi'an, Beijing, Xifeng) during the spring of 2009 to determine dust flux, magnetic susceptibility and elemental concentrations. Combining dust fluxes with wind speed and regional visibility records enabled to differentiate between dust transported from long range and derived from local sources, while the combination of magnetic susceptibility and enrichment factors (EF) of heavy metals (Pb, Zn) allowed to distinguish natural aerosols from polluted ones. Our results indicate that polluted dust from long-range transport became a major end member of urban dust aerosols. Human settlements as its potential sources were confirmed by a pollutant enriched regional dust event originating from populated areas to the south as inferred by back trajectory modeling, implying their non-point source nature of dust pollution. PMID:25433377

  8. Transport of mineral dust derived from airborne wind lidar measurements during SALTRACE

    NASA Astrophysics Data System (ADS)

    Chouza, Fernando; Reitebuch, Oliver; Groß, Silke; Rahm, Stephan; Freudenthaler, Volker; Toledano, Carlos; Weinzierl, Bernadett

    2015-04-01

    During the SALTRACE field experiment conducted between the 10 of June and the 15 of July 2013, the transport and properties of Saharan dust were characterized by a 2-µm Doppler wind lidar (DWL) deployed on the DLR Falcon 20 research aircraft. Unlike aerosol lidars, the DLW is able to simultaneously measure wind fields and -by means of an adequate calibration- aerosol optical properties, which is more adequate for aerosol transport studies. The retrieved horizontal and vertical wind speed provide a direct observation of dust long range transport mechanisms across the Atlantic (e.g. by the African easterly jet) from Western Africa to the Caribbean. Vertical wind observations revealed the structure of island induced lee waves in the Cape Verde and Barbados regions. A novel method for the calibration of DWLs based on simultaneous measurements with a ground-based aerosol lidar and sun photometer was developed. After being calibrated, the system is able to retrieve quantitative aerosol backscatter and extinction coefficients, which is usually not obtained from coherent lidars. Results from the validation with a ground-based aerosol lidar in Barbados and the CALIPSO satellite instrument will be discussed.

  9. A new dust transport approach to quantify anthropogenic sources of atmospheric PM10 deposition on lakes

    NASA Astrophysics Data System (ADS)

    Weiss, Lee; Thé, Jesse; Gharabaghi, Bahram; Stainsby, Eleanor A.; Winter, Jennifer G.

    2014-10-01

    Windblown dust simulations are one of the most uncertain types of atmospheric transport models. This study presents an integrated PM10 emission, transport and deposition model which has been validated using monitored data. This model characterizes the atmospheric phosphorus load focusing on the major local sources within the Lake Simcoe airshed including paved and unpaved roads, agricultural sources, construction sites and aggregate mining sources. This new approach substantially reduces uncertainty by providing improved estimates of the friction velocities than those developed previously. Modeling improvements were also made by generating and validating an hourly windfield using detailed meteorology, topography and land use data for the study area. The model was used to estimate dust emissions generated in the airshed and to simulate the long-range transport and deposition of PM10 to Lake Simcoe. The deposition results from the model were verified against observed bulk collector phosphorus concentration data for both wet and dry deposition. Bulk collector data from stations situated outside the airshed in a remote, undeveloped area were also compared to determine the background contribution from distant sources.

  10. Overview of Dust Model Inter-comparison (DMIP) in East Asia

    NASA Astrophysics Data System (ADS)

    Uno, I.

    2004-12-01

    Dust transport modeling plays an important role in understanding the recent increase of Asian Dust episodes and its impact to the regional climate system. Several dust models have been developed in several research institutes and government agencies independently since 1990s. Their numerical results either look very similar or different. Those disagreements are caused by difference in dust modules (concepts and basic mechanisms) and atmospheric models (meteorological and transport models). Therefore common understanding of performance and uncertainty of dust erosion and transport models in the Asian region becomes very important. To have a better understanding of dust model application, we proposed the dust model intercomparison under the international cooperation networks as a part of activity of ADEC (Aeolian Dust Experiment on Climate Impact) project research. Current participants are Kyusyu Univ. (Japan), Meteorological Research Institute (Japan), Hong-Kong City Univ. (China), Korean Meteorological Agency METRI (Korea), US Naval Research Laboratory (USA), Chinese Meteorological Agency (China), Institute of Atmospheric Physics (China), Insular Coastal Dynamics (Malta) and Meteorological Service of Canada (Canada). As a case study episode, we set two huge dust storms occurred in March and April 2002. Results from the dust transport model from all the participants are compiled on the same methods and examined the model characteristics against the ground and airborne measurement data. We will also examine the dust model results from the horizontal distribution at specified levels, vertical profiles, concentration at special check point and emission flux at source region, and show the important parameters for dust modeling. In this paper, we will introduce the general overview of this DMIP activity and several important conclusions from this activity.

  11. Direct numerical simulations of aeolian sand ripples

    PubMed Central

    Durán, Orencio; Claudin, Philippe; Andreotti, Bruno

    2014-01-01

    Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873

  12. Direct numerical simulations of aeolian sand ripples.

    PubMed

    Durán, Orencio; Claudin, Philippe; Andreotti, Bruno

    2014-11-01

    Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873

  13. Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core.

    PubMed

    Lambert, F; Delmonte, B; Petit, J R; Bigler, M; Kaufmann, P R; Hutterli, M A; Stocker, T F; Ruth, U; Steffensen, J P; Maggi, V

    2008-04-01

    Dust can affect the radiative balance of the atmosphere by absorbing or reflecting incoming solar radiation; it can also be a source of micronutrients, such as iron, to the ocean. It has been suggested that production, transport and deposition of dust is influenced by climatic changes on glacial-interglacial timescales. Here we present a high-resolution record of aeolian dust from the EPICA Dome C ice core in East Antarctica, which provides an undisturbed climate sequence over the past eight climatic cycles. We find that there is a significant correlation between dust flux and temperature records during glacial periods that is absent during interglacial periods. Our data suggest that dust flux is increasingly correlated with Antarctic temperature as the climate becomes colder. We interpret this as progressive coupling of the climates of Antarctic and lower latitudes. Limited changes in glacial-interglacial atmospheric transport time suggest that the sources and lifetime of dust are the main factors controlling the high glacial dust input. We propose that the observed approximately 25-fold increase in glacial dust flux over all eight glacial periods can be attributed to a strengthening of South American dust sources, together with a longer lifetime for atmospheric dust particles in the upper troposphere resulting from a reduced hydrological cycle during the ice ages. PMID:18385736

  14. Use of MODIS Satellite Images and an Atmospheric Dust Transport Model To Evaluate Juniperus spp. Pollen Phenology and Dispersal

    NASA Technical Reports Server (NTRS)

    Luvall, J. C.; Sprigg, W. A.; Levetin, Estelle; Huete, Alfredo; Nickovic, S.; Pejanovic, G. A.; Vukovic, A.; VandeWater, P. K.; Myers, O. B.; Budge, A. M.; Zelicoff, A. P.; Bunderson, L.; Crimmins, T. M.

    2011-01-01

    Pollen can be transported great distances. Van de Water et. al., 2003 reported Juniperus spp. pollen was transported 200-600 km. Hence local observations of plant phenology may not be consistent with the timing and source of pollen collected by pollen sampling instruments. The DREAM (Dust REgional Atmospheric Model, Nickovic et al. 2001) is a verified model for atmospheric dust transport modeling using MODIS data products to identify source regions and quantities of dust. We are modifying the DREAM model to incorporate pollen transport. Pollen release will be estimated based on MODIS derived phenology of Juniperus spp. communities. Ground based observational records of pollen release timing and quantities will be used as verification. This information will be used to support the Centers for Disease Control and Prevention's National Environmental Public Health Tracking Program and the State of New Mexico environmental public health decision support for asthma and allergies alerts.

  15. Use of MODIS Satellite Images and an Atmospheric Dust Transport Model to Evaluate Juniperus spp. Pollen Phenology and Dispersal

    NASA Technical Reports Server (NTRS)

    Luvall, Jeffrey C.

    2011-01-01

    Pollen can be transported great distances. Van de Water et. al. reported Juniperus spp. pollen was transported 200-600 km. Hence local obse rvations of plant phenology may not be consistent with the timing and source of pollen collected by pollen sampling instruments. The DREAM (Dust REgional Atmospheric Model, Nickovic et al. 2001) is a verified model for atmospheric dust transport modeling using MODIS data produ cts to identify source regions and quantities of dust. We are modifyi ng the DREAM model to incorporate pollen transport. Pollen release wi ll be estimated based on MODIS derived phenology of Juniperus spp. communities. Ground based observations records of pollen release timing and quantities will be used as verification. This information will be used to support the Centers for Disease Control and Prevention?s Nat ional Environmental Public Health Tracking Program and the State of New Mexico environmental public health decision support for asthma and allergies alerts.

  16. Use of MODIS Satellite Images and an Atmospheric Dust Transport Model to Evaluate Juniperus spp. Pollen Phenology and Dispersal

    NASA Technical Reports Server (NTRS)

    Luvall, J. C.; Sprigg, W. A.; Levetin, E.; Huete, A.; Nickovic, S.; Pejanovic, G. A.; Vukovic, A.; VandeWater, P. K.; Myers, O. B.; Budge, A. M.; Zelicoff, A. P.; Bunderson, L.; Crimmins, T. M.

    2011-01-01

    Pollen can be transported great distances. Van de Water et. al. reported Juniperus spp. pollen was transported 200-600 km. Hence local observations of plant phenology may not be consistent with the timing and source of pollen collected by pollen sampling instruments. The DREAM (Dust REgional Atmospheric Model) is a verified model for atmospheric dust transport modeling using MODIS data products to identify source regions and quantities of dust. We are modifying the DREAM model to incorporate pollen transport. Pollen release will be estimated based on MODIS derived phenology of Juniperus spp. communities. Ground based observational records of pollen release timing and quantities will be used as verification. This information will be used to support the Centers for Disease Control and Prevention's National Environmental Public Health Tracking Program and the State of New Mexico environmental public health decision support for asthma and allergies alerts.

  17. Vertical Structure of Aerosols and Mineral Dust Transport Over the Bay of Bengal Using Multi-Satellite Observations.

    NASA Astrophysics Data System (ADS)

    Naduparambil Bharathan, L.

    2015-12-01

    Bay-of-Bengal (BoB), a small oceanic region Eat to Indian land mass, surrounded by heavily inhabited land masses, experiences different types of air-masses in different seasons of contrasting wind patterns, which makes it a region of large heterogeneity in the context of regional climate forcing due to atmospheric aerosols. Heterogeneity of aerosol system over the Bay of Bengal is mainly determined by three distinct source regions, which are east coast of India/central India, China/east Asia and Arabian region. Continental aerosols transported through higher elevations over BoB lead to significant impacts in regional climate by modifying the vertical thermal structure of the atmosphere and associated circulation dynamics. The study aims at a comprehensive understanding on the spatial and temporal heterogeneity of elevated aerosol over the BoB using the observations of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Being capable of short wave scattering and long wave absorption, mineral dust aerosols can affects the energetics of the atmosphere over any region.Owing to its influence on Indian monsoon rainfall and regional climate, the study aims to comprehend on the spatial and seasonal variation of mineral dust transport over the Bay of Bengal. vertical distribution of the dust extinction coefficient over the Bay of Bengal for all seasons, is derived, using a dust separation scheme that uses the depolarization measurements, a priori information on lidar ratio of dust, depolarization ratio of dust and that of non-dust aerosols. Being highly non-spherical, mineral dust significantly depolarize the radiation and possess distinct range of depolarization ratio. This property of dust is made use to identify and quantify dust over the study region. Seasonal variation of dust fraction over the Bay of Bengal is estimated seperately from CALIPSO back scattering coefficients

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

    NASA Astrophysics Data System (ADS)

    Kalenderski, Stoitchko; Stenchikov, Georgiy

    2016-06-01

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

  19. Characterization of the Temporal-Spatial Variability of Trans-Atlantic Dust Transport Based on CALIPSO Lidar Measurements

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin

    2015-01-01

    The trans-Atlantic dust transport has important implications for human and ecosystem health, the terrestrial and oceanic biogeochemical cycle, weather systems, and climate. A reliable assessment of these influences requires the characterization of dust distributions in three dimensions and over long time periods. We provide an observation-based multiyear estimate of trans-Atlantic dust transport by using a 7-year (2007 - 2013) lidar record from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) in both cloud-free and above-cloud conditions. We estimate that on a basis of the 7-year average and integration over 10S - 30N, 182 Tg a-1 dust leaves the coast of North Africa at 15W, of which 132 Tg a-1 and 43 Tg a-1 reaches 35W and 75W, respectively. These flux estimates have an overall known uncertainty of (45 - 70). The 7-year average of dust deposition into the Amazon Basin is estimated to be 28 (8 - 48) Tg a-1 or 29 (8 - 50) kg ha-1 a-1. This imported dust could provide about 0.022 (0.006 - 0.037) Tg P of phosphorus per year, equivalent to 23 (7 - 39) g P ha-1 a-1 to fertilize the Amazon rainforest, which is comparable to the loss of phosphorus to rainfall. Significant seasonal variations are observed in both the magnitude of total dust transport and its meridional and vertical distributions. The observed large interannual variability of annual dust transport is highly anti-correlated with the prior-year Sahel Precipitation Index. Comparisons of CALIPSO measurements with surface-based observations and model simulations will also be discussed.

  20. Transport, vertical structure and radiative properties of dust events in southeast China determined from ground and space sensors

    SciTech Connect

    Liu, Jianjun; Zheng, Y.; Li, Zhanqing; Flynn, Connor J.; Welton, Ellsworth J.; Cribb, Maureen

    2011-11-01

    Two dust events were detected over the Yangtze Delta region of China during March 14-17 and April 25-26 in 2009 where such dust events are uncommon. The transport behavior, spatio-temporal evolution, vertical structure, direct radiative effects, as well as induced heating rates, are investigated using a combination of ground-based and satellite-based measurements, a back-trajectory analysis, an aerosol model and a radiative transfer model.

  1. Evaluation of aeolian desertification from 1975 to 2010 and its causes in northwest Shanxi Province, China

    NASA Astrophysics Data System (ADS)

    Xue, Zhanjin; Qin, Zuodong; Li, Hongjian; Ding, Guangwei; Meng, Xianwen

    2013-08-01

    Efforts to control aeolian desertification in China have focused on the arid and semiarid regions. However, the direct dust emission rates, sediment characteristics and local-scale controls, as well as the measures needed to combat desertification, remain poorly understood in northwest Shanxi Province. Aeolian desertification is regarded as an obstacle to local sustainable socioeconomic development. This paper investigated changes in aeolian desertification between 1975 and 2010 on the northwestern Shanxi Plateau. In this study, remote sensing images were used to classify land suffering from aeolian desertification into four categories: light, moderate, severe, and extremely severe. To evaluate the evolution and status of aeolian desertification as well as its causes, we interpreted and analyzed Landsat multi-spectral scanner (MSS) image (acquired in 1975) and Landsat Thematic Mapper (TM) images (acquired in 1991, 2000, 2006, and 2010) as well as meteorological and socioeconomic data. Results revealed 11,866 km2, 13,362 km2, 14,051 km2, 13,613 km2, and 12,318 km2 of aeolian desertified land (ADL) in the above 5 periods, respectively. The spatial dynamics and patterns showed two stages: expansion during 1975-2000 at a rate of 87.37 km2 a- 1, and spatial transfer of affected areas during 2000-2010 with a net decrease of 173.27 km2 a- 1. During the evolution of aeolian desertification, areas of moderate ADL had the greatest dynamic response (11.45%). The factors controlling ADL dynamics were analyzed from the perspectives of two groups of factors: natural factors and human activities. Our results indicated that the climate-dominated natural factors contribute greatly to the occurrence and development of ADL. However, they are not the fundamental causes of its development. The human factors are the primary and direct driving forces responsible for the increase in ADL area. More thorough quantitative analysis, with more frequent remotely sensed data is needed to assess

  2. Transport of mineral dust to Nepal Climate Observatory - Pyramid (5079 m a.s.l., South Himalayas)

    NASA Astrophysics Data System (ADS)

    Duchi, Rocco; Cristofanelli, Paolo; Marinoni, Angela; Calzolari, Francescopiero; Decesari, Stefano; Laj, Paolo; Vuillermoz, Elisa; Sprenger, Michael; Bonasoni, Paolo

    2010-05-01

    Desert dust is one of the greatest sources of natural aerosol in atmosphere, representing about 37% of the total (natural and anthropogenic) emission of atmospheric primary aerosols. Mineral dust can impact climate through many complex processes, i.e. by scattering and absorbing solar and infrared radiation and by affecting the variability of cloud aerosol optical properties. Moreover, mineral dust can also affect the concentrations of other climate-altering species (e.g. surface ozone) in troposphere. South Asia is a region frequently affected by major dust transport from Africa and Asia. In particular, these "dust clouds" can reach the Himalayas also mixed with the heavy anthropogenic pollution present within the so-called Asian Brown Cloud. With the purpose to define the frequency of long-range mineral dust transport towards the Himalayan range and to evaluate their influence on the atmospheric aerosol background level, in this work we analyse the first 2-year (from March 2006 to February 2008) of coarse (Dp > 1 micron) aerosol number concentration observed at the WMO - GAW station "Nepal Climate Observatory - Pyramid" (NCO-P, 5079 m a.s.l., Nepal). This measurement station, part of UNEP-ABC and EV-K2-CNR SHARE projects, is not far from the Everest Base Camp and the observation here conducted can be considered representative for the South-Eastern slope of the Himalayan range. During the investigated period we detect more than 80 days/year as possibly affected by mineral dust transport. As deduced by the NCO-P measurements, these events significantly influenced the seasonal variation of coarse aerosol number concentration as well as the number and volumetric aerosol size distribution over South Himalayas. Due to the combination of the large-scale westerly circulation and the higher frequency of dust out-breaks, the majority of the identified events occurred during the pre-monsoon season. Although of lesser intensity and frequency, a significant amount of dust

  3. Use Of MODIS Satellite Images And An Atmospheric Dust Transport Model To Evaluate Juniperus Spp. Pollen Phenology And Transport

    NASA Astrophysics Data System (ADS)

    Luvall, J. C.; Sprigg, W. A.; Levetin, E.; Huete, A. R.; Nickovic, S.; Crimmins, T. M.; Van De Water, P. K.; Pejanovic, G.; Vukovic, A. J.; Myers, O.; Budge, A.; Zelicoff, A.; Bunderson, L.; Ponce-Campos, G.

    2011-12-01

    Pollen can be transported great distances. Van de Water et al., 2003 reported Juniperus spp. pollen, a significant aeroallergen was transported 200-600 km. Hence local observations of plant phenology may not be consistent with the timing and source of pollen collected by pollen sampling instruments. Direct detection of pollen via satellite is not practical. A practical alternative combines modeling and phenological observations using ground based sampling and satellite data. The DREAM (Dust REgional Atmospheric Model) is a verified model for atmospheric dust transport modeling using MODIS data products to identify source regions and quantities of dust (Nickovic et al. 2001). The use of satellite data products for studying phenology is well documented (White and Nemani 2006). In the current project MODIS data will provide critical input to the PREAM model providing pollen source location, timing of pollen release, and vegetation type. We are modifying the DREAM model (PREAM - Pollen REgional Atmospheric Model) to incorporate pollen transport. The linkages already exist with DREAM through PHAiRS (Public Health Applications in Remote Sensing) to the public health community. This linkage has the potential to fill this data gap so that the potential association of health effects of pollen can better be tracked for possible linkage with health outcome data which may be associated with asthma, respiratory effects, myocardial infarction, and lost workdays. Juniperus spp. pollen phenology may respond to a wide range of environmental factors such as day length, growing degree-days, precipitation patterns and soil moisture. Species differences are also important. These environmental factors vary over both time and spatial scales. Ground based networks such as the USA National Phenology Network have been established to provide national wide observations of vegetation phenology. However, the density of observers is not adequate to sufficiently document the phenology variability

  4. Use of MODIS Satellite Images and an Atmospheric Dust Transport Model to Evaluate Juniperus spp. Pollen Phenology and Transport

    NASA Technical Reports Server (NTRS)

    Luvall, J. C.; Sprigg, W. A.; Levetin, E.; Huete, A.; Nickovic, S.; Pejanovic, G. A.; Vukovic, A.; Van de Water, P. K.; Myers, O. B.; Budge, A. M.; Zelicoff, A. P.; Bunderson, L.; Ponce-Campos, G.; Crimmins, T. M.

    2011-01-01

    Pollen can be transported great distances. Van de Water et al., 2003 reported Juniperus spp. pollen, a significant aeroallergen was transported 200-600 km. Hence local observations of plant phenology may not be consistent with the timing and source of pollen collected by pollen sampling instruments. Direct detection of pollen via satellite is not practical. A practical alternative combines modeling and phenological observations using ground based sampling and satellite data. The DREAM (Dust REgional Atmospheric Model) is a verified model for atmospheric dust transport modeling using MODIS data products to identify source regions and quantities of dust (Nickovic et al. 2001). The use of satellite data products for studying phenology is well documented (White and Nemani 2006). In the current project MODIS data will provide critical input to the PREAM model providing pollen source location, timing of pollen release, and vegetation type. We are modifying the DREAM model (PREAM - Pollen REgional Atmospheric Model) to incorporate pollen transport. The linkages already exist with DREAM through PHAiRS (Public Health Applications in Remote Sensing) to the public health community. This linkage has the potential to fill this data gap so that the potential association of health effects of pollen can better be tracked for possible linkage with health outcome data which may be associated with asthma, respiratory effects, myocardial infarction, and lost workdays. Juniperus spp. pollen phenology may respond to a wide range of environmental factors such as day length, growing degree-days, precipitation patterns and soil moisture. Species differences are also important. These environmental factors vary over both time and spatial scales. Ground based networks such as the USA National Phenology Network have been established to provide national wide observations of vegetation phenology. However, the density of observers is not adequate to sufficiently document the phenology variability

  5. Mass Influx of Cosmic Dust Estimated From Vertical Transport of Meteoric Metals

    NASA Astrophysics Data System (ADS)

    Liu, Alan Z.; Guo, Yafang; Gardner, Chester S.

    2016-04-01

    The mesospheric metal layers are formed by the vaporization of high-speed cosmic dust particles in the lower thermosphere and upper mesosphere. The vaporized atoms and ions are transported downward by waves and turbulence to chemical sinks below 85 km, where they form stable compounds. These compounds condense onto meteoric smoke particles and are then transported to the winter pole where they eventually settle onto the surface. The downward fluxes of the metal atoms are directly related to their meteoric influxes and chemical loss rates. In this paper we use Doppler lidar measurements of Na and Fe fluxes made by the University of Illinois and University of Colorado groups, and a chemical ablation model (CABMOD) developed at the University of Leeds, to constrain the velocity/mass distribution of the meteoroids entering the atmosphere and to derive an improved estimate for the global influx of cosmic dust. We find that the particles responsible for injecting a large fraction of the ablated material into the Earth's upper atmosphere, enter at relatively slow speeds and originate primarily from the Jupiter Family of Comets. The global mean Na influx is 21,500±1,100 atoms/cm2/s, which equals 372±18 kg/d for the global input of Na vapor and 186±24 t/d for the global influx of cosmic dust. The global mean Fe influx is 131,000±36,000 atoms/cm2/s, which equals 5.5±1.5 t/d for the global input of Na vapor.

  6. Video monitoring of meso-scale aeolian activity on a narrow beach

    NASA Astrophysics Data System (ADS)

    Hage, Pam; Ruessink, Gerben

    2014-05-01

    The morphologic evolution of coastal dunes is inextricably linked to the neighbouring beach through the incessant exchange of sand. Intense storm-wave processes erode the foredune within a few hours and transport its sand sand seaward, while aeolian processes return the eroded sand from the beach into the dune system, although at a much lower pace (months to years, or meso scale). Here we use an 8-year long data set of half-hourly snapshot video images, collected from an ≡ 50 m high tower on Egmond Beach (The Netherlands), and a concurrent meteorological and water level data set, to examine which factors affect aeolian sand delivery into the dunes. Egmond is a north-south oriented, micro- to meso-tidal, wave-dominated site that faces the North Sea. Its beach is relatively narrow ( ~ 100 m at spring low tide) and mildly sloping (~ 1 : 30), and consists of quartz sand with a median diameter of about 300 μm. Aeolian activity is clearly visible on the images as sand streamers and, in particular, sand strips, defined as low-amplitude, large-wavelength and slipfaceless deposits that migrate slowly in the wind direction and, depending on wind direction, can have orientations from almost shore-parallel to shore-normal. Beach width in combination with wind direction appeared to be the dominant factors in controlling aeolian activity. Many high wind (>≡ 13 m/s) events, especially from the west and northwest, were associated with a storm surge that inundated almost the entire beach with, accordingly, no possibility for aeolian transport. In contrast, sand-strip fields covered the entire beach during medium wind (≡ 12 - 13 m/s) events, especially when the wind was nearly shore-parallel. Many sand-strip events were observed to be regulated by the tide. Prominent sand-strip fields on the intertidal and upper beach were largely limited to low-tide situations with a wide beach, with a rising tide obviously destroying the intertidal sand strips and sometimes also negatively

  7. Aeolian process-induced hyper-concentrated flow in a desert watershed

    NASA Astrophysics Data System (ADS)

    Ta, Wanquan; Wang, Haibin; Jia, Xiaopeng

    2014-04-01

    Ephemeral desert channels are characterized by very high rates of sediment transport during infrequent flood events. Here we show that aeolian process-induced hyper-concentrated (AHC) flows occur in the Sudalaer desert watershed in the Ordos Plateau of China, which primarily transport 0.08-0.25 mm non-cohesive aeolian sand and have a peak suspended sediment concentration of 1.1-1.4 × 106 mg l-3. Aeolian sand supply and storage in the channel play a crucial role in causing hyper-concentrated flow. Our results indicate that non-cohesive aeolian sand can be entrained from the bed and suspended in the turbulent flow when the channel bed slope exceeds a critical threshold (0.0003). We also show that if the frequency ratio of wind-blown sandstorms to rainstorms Tw/Tp exceeds β(γ - γ0)/α (P/V3) (A/L) (where α is the wind-blown sand transport coefficient, β is the runoff coefficient, γ - γ0 is the increase in suspension concentration caused by addition of aeolian sands, P is the density of rainstorms, V is the wind speed of sandstorms, A is the runoff-generating area, L is the aeolian sand-filled channel length), an AHC flow occurs during the passage of a flood in a desert channel. Since high-frequency aeolian processes provide an adequate quantity of transportable sediment and promote AHC flow, most of the infrequent rainfall-induced floods occurring in arid zones can develop as AHC flows.

  8. Quantifying the provenance of aeolian sediments using multiple composite fingerprints

    NASA Astrophysics Data System (ADS)

    Liu, Benli; Niu, Qinghe; Qu, Jianjun; Zu, Ruiping

    2016-09-01

    We introduce a new fingerprinting method that uses multiple composite fingerprints for studies of aeolian sediment provenance. We used this method to quantify the provenance of sediments on both sides of the Qinghai-Tibetan Railway (QTR) in the Cuona Lake section of the Tibetan Plateau (TP), in an environment characterized by aeolian and fluvial interactions. The method involves repeatedly solving a linear mixing model based on mass conservation; the model is not limited to spatial scale or transport types and uses all the tracer groups that passed the range check, Kruskal-Wallis H-test, and a strict analytical solution screening. The proportional estimates that result from using different composite fingerprints are highly variable; however, the average of these fingerprints has a greater accuracy and certainty than any single fingerprint. The results show that sand from the lake beach, hilly surface, and gullies contribute, respectively, 48%, 31% and 21% to the western railway sediments and 43%, 33% and 24% to the eastern railway sediments. The difference between contributions from various sources on either side of the railway, which may increase in the future, was clearly related to variations in local transport characteristics, a conclusion that is supported by grain size analysis. The construction of the QTR changed the local cycling of materials, and the difference in provenance between the sediments that are separated by the railway reflects the changed sedimentary conditions on either side of the railway. The effectiveness of this method suggests that it will be useful in other studies of aeolian sediments.

  9. The birth and death of transverse aeolian ridges on Mars

    USGS Publications Warehouse

    Geissler, Paul E.

    2014-01-01

    Transverse aeolian ridges (TARs) are small bright windblown deposits found throughout the Martian tropics that stand a few meters tall and are spaced a few tens of meters apart. The origin of these features remains mysterious more than 20 years after their discovery on Mars. This paper presents a new hypothesis, that some of the TARs could be indurated dust deposits emplaced millions of years ago during periods of higher axial obliquity. It suggests that these TARs are primary depositional bed forms that accumulated in place from dust carried by the winds in suspension, perhaps in a manner comparable to antidunes on Earth, and were subsequently indurated and eroded to their current states by eons of sandblasting. It points out examples of modern dust drifts and dune-like features that appear to have been recently formed by dust accumulating directly onto the surface from atmospheric suspension. It shows how these pristine dust deposits could evolve to explain the range of morphologies of the TARs. Finally, it explains how the known properties of many TARs are consistent with this hypothesis, including their composition, thermal behavior, and distribution.

  10. Remote monitoring of aerosol layers over Sofia during Sahara dust transport episode (April, 2012)

    NASA Astrophysics Data System (ADS)

    Stoyanov, Dimitar; Grigorov, Ivan; Deleva, Atanaska; Kolev, Nikolay; Peshev, Zahari; Kolarov, Georgi; Donev, Evgeni; Ivanov, Danko

    2013-03-01

    In this work we present results of lidar remote sensing of aerosol layers in the atmosphere above Sofia during an episode of Sahara dust transport, 02-07 April, 2012. The investigations were made using two lidar systems, one equipped with a CuBr-vapor laser, emitting at wavelength 510.6 nm, and a second one - with Nd:YAG laser, at wavelengths 1064 nm and 532 nm. The results of lidar measurements are presented in terms of vertical atmospheric backscatter coefficient profiles and color maps of the aerosol stratification evolution. The involved into discussions ceilometer data (CHM 15k ceilometer) and satellite data from CALIPSO lidar, enhance the synergy of observations. Conclusion about atmospheric aerosol's origin was made upon analyses of the information of weather-forecast maps provided by the Forecast system of Barcelona Supercomputing Centre, which are accessible via Internet. Additional information was provided by calculations of the backward air mass trajectories, using online software of NOAA about HYSPLIT model. The comparison between the data from the two lidars and the ceilometer showed similar behavior of aerosol layers development in the atmosphere above Sofia. All information about aerosol layers origin, their altitude above ground, persistence during lidar observations, confirmed the conclusion of observation of a long-distance Sahara dust transport beyond Balkans and Sofia. An interesting completion of CALIPSO lidar and ground based lidars results of measurement is presented in case of thick opaque cloud layer in the atmosphere, which slices the path of lidar sensing in both directions.

  11. Mineralogical controls on dust emissions in the Bodele Depression, Chad

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface mineralogy is critical in the understanding of aeolian processes, however its role in dust production is currently underestimated. Recent research indicates that discrepancies between predicted and observed dust loads by dust models may be attributed to inadequacies within their associated d...

  12. Satellite Monitoring of Long-Range Transport of Asian Dust Storms from Sources to Sinks

    NASA Astrophysics Data System (ADS)

    Hsu, N.; Tsay, S.; Jeong, M.; King, M.; Holben, B.

    2007-05-01

    Among the many components that contribute to air pollution, airborne mineral dust plays an important role due to its biogeochemical impact on the ecosystem and its radiative-forcing effect on the climate system. In East Asia, dust storms frequently accompany the cold and dry air masses that occur as part of spring-time cold front systems. China's capital, Beijing, and other large cities are on the primary pathway of these dust storm plumes, and their passage over such popu-lation centers causes flight delays, pushes grit through windows and doors, and forces people indoors. Furthermore, during the spring these anthropogenic and natural air pollutants, once generated over the source regions, can be transported out of the boundary layer into the free troposphere and can travel thousands of kilometers across the Pacific into the United States and beyond. In this paper, we will demonstrate the capability of a new satellite algorithm to retrieve aerosol optical thickness and single scattering albedo over bright-reflecting surfaces such as urban areas and deserts. Such retrievals have been dif-ficult to perform using previously available algorithms that use wavelengths from the mid-visible to the near IR because they have trouble separating the aerosol signal from the contribution due to the bright surface reflectance. The new algorithm, called Deep Blue, utilizes blue-wavelength measurements from instruments such as SeaWiFS and MODIS to infer the properties of aerosols, since the surface reflectance over land in the blue part of the spectrum is much lower than for longer wavelength channels. Deep Blue algorithm has recently been integrated into the MODIS processing stream and began to provide aerosol products over land as part of the opera-tional MYD04 products. In this talk, we will show the comparisons of the MODIS Deep Blue products with data from AERONET sunphotometers on a global ba-sis. The results indicate reasonable agreements between these two. These new

  13. Evidence for dust-driven, radial plasma transport in Saturn's inner radiation belts

    NASA Astrophysics Data System (ADS)

    Roussos, E.; Krupp, N.; Kollmann, P.; Paranicas, C.; Mitchell, D. G.; Krimigis, S. M.; Andriopoulou, M.

    2016-08-01

    between the magnetosphere and Saturn's faint rings that may drive such radial transport processes may also exist in previously reported measurements of plasma density by Cassini. Alternative explanations that do not involve enhanced plasma transport near the rings require the presence of a transient absorbing medium, such as E-ring clumps. Such clumps may form at the L-shell range where microsignatures have been observed due to resonances between charged dust and corotating magnetospheric structures, but remote imaging observations of the E-ring are not consistent with such a scenario.

  14. Transport, vertical structure and radiative properties of dust events in southeast China determined from ground and space sensors

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Zheng, Youfei; Li, Zhanqing; Flynn, Connor; Welton, E. J.; Cribb, Mareen

    2011-11-01

    Two dust events were detected over the Yangtze Delta region of China during March 14-17 and April 25-26 in 2009 where such dust events are uncommon. The transport behavior, spatio-temporal evolution, vertical structure, direct radiative effects, as well as induced heating rates, are investigated using a combination of ground-based and satellite-based measurements, a back-trajectory analysis, an aerosol model and a radiative transfer model. Back-trajectories, wind fields and aerosol model analyses show that the first dust originated in northern/northwestern China and the second generated in the Taklimakan desert in northwest China, and traveled across the Hexi corridor and Loess Plateau to the Yangtze Delta region (the so-called "dust corridor"). The mean lidar extinction-to-backscatter ratio (LR) during the two dust events was 38.7 ± 10.4 sr and 42.7 ± 15.2 sr, respectively. The mean aerosol depolarization ratio ( δa) for the first dust event was 0.16 ± 0.07, with a maximum value of 0.32. For the second, the mean δa was around 0.19 ± 0.06, with a maximum value of 0.29. Aerosol extinction coefficient and δa profiles for the two events were similar: two aerosol layers consisting of dust aerosols and a mixture of dust and anthropogenic pollution aerosols. The topmost aerosol layer is above 3.5 km. The maximum mean aerosol extinction coefficients were 0.5 km -1 and 0.54 km -1 at about 0.7 km and 1.1 km, respectively. Significant effects of cooling at the surface and heating in the atmosphere were found during these dust events. Diurnal mean shortwave radiative forcings (efficiencies) at the surface, the top-of-the-atmosphere and within the atmosphere were -36.8 (-80.0), -13.6 (-29.6) and 23.2 (50.4) W m -2, respectively, during the first dust event, and -48.2 (-70.9), -21.4 (-31.5) and 26.8 (39.4) W m -2, respectively, during the second dust event. Maximum heating rates occurred at 0.7 km during the first dust event and at 1.1 km during the second dust event

  15. Aeolian Coastal Landscapes in changes (a study from Tahkuna, Estonia)

    NASA Astrophysics Data System (ADS)

    Anderson, A.

    2012-04-01

    berms. Erosion can cause lost of some habitats. Changes of landfroms can also be due to human activities (construction of roads, buildings, harbours), which affect sediment transportation along the coast. Changes in habitats are caused by their own development and also invasion of non-indigenous species. Aeolian coastal landscapes are unique, but easily altered ecosystems in Estonia. Therefore it is essential to improve the strategies for preserving these valuable areas. Aeolian coastal landscapes require greater attention and more complex scientific studies that contribute to the maintaining of natural values.

  16. Holocene aeolian sediments on the NE Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Stauch, G.; Lehmkuhl, F.; Hilgers, A.; Zhao, H.

    2012-04-01

    The semiarid climate of the northeastern Tibetan Plateau supports the formation of different types of aeolian sediments and landforms during the Holocene. Aeolians silts and sands in the catchment of the Donggi Cona in an elevation above 4000m to 4800 m asl reflect variable climate conditions during that time as well as different sediment sources. Based on 51 OSL datings and catchment wide geomorphological mapping a complex pattern of long and short distance sediment transport has been reconstructed. Only few aeolian archives are preserved from the late Pleistocene in this mountain environment indicating cold and dry climate conditions which prevented a continuous accumulation. During the early Holocene a phase of increased aeolian sedimentation of sand at the slopes of the mountains has been reconstructed. The sand originated from a large alluvial fan which was highly active during the Pleistocene. In addition, a thin loess cover is preserved at a few sites in the neighboring mountains ranges. The sedimentation of the loess started around 2000 years later than the sedimentation of the sand at the foot slope. Both archives are related to an increase in precipitation at the northern margin of the Tibetan Plateau which was related to a strengthening of the Asian Monsoon during that time. The wetter climate conditions favored the development of a vegetation cover which leads to the trapping and fixation of the aeolian sediments. However, with a further strengthening of the Monsoon systems these archives subsequently eroded due to higher run off and accumulated as colluvial and fluvial deposits in the basins. These phase lasted until 6 ka. A second aeolian period started at around 3 ka with the formation new dunes in the basins. This period can be associated with dry and cold climate of the late Holocene supporting the reactivation of the sand in the area. This might be further enhanced by an increased human impact by grazing during the late Holocene and resulting

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

    NASA Astrophysics Data System (ADS)

    Chouza, Fernando; Reitebuch, Oliver; Rahm, Stephan; Weinzierl, Bernadett

    2016-06-01

    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.

  18. Case study of the Asian dust and pollutant event in spring 2006: source, transport, and contribution to Taiwan.

    PubMed

    Tsai, Fujung; Tu, Jien-Yi; Hsu, Shih-Chieh; Chen, Wei-Nai

    2014-04-15

    Surface measurements and a regional dust model were used to analyze the source, transport, and contribution of a dust event transporting with aerosol pollutant over Taiwan from 16 to 19 March, 2006. During the event, the hourly aerosol concentrations reached close to 400 μg m(-3) in northern Taiwan, and approximately 300 μg m(-3) in other areas of the island. Trajectory and regional dust models show that the dust event originated in eastern Mongolia and northern China, and the dust layer can descend from 2 to 3 km in the source area to below 1.5 km over Taiwan. On the other hand, model results show that pollution was transported near the surface from coastal China to Taiwan. During this dust event, polluted aerosol was first observed over northern Taiwan right after a frontal passage, and the concentration was strongly enhanced following the passage of the light rainfall 12h later. The descent of dusty air from the free troposphere lagged the arrival of polluted air by 7h, and was partially mixed with polluted aerosol when the transport decelerated over Taiwan. During the event, dust particles accounted for up to 60% of observed particulate matter less than 10 μm (PM10) over Taiwan, but decreased to less than 35% for particulate matter less than 2.5 μm (PM2.5) over most areas of the island. On the other hand, the long-range transport of non-dust aerosols, mainly anthropogenic pollutants, accounted for close to 30% of observed PM10 concentration in northern and western Taiwan prior to dust arrival, and the contribution of PM2.5 increased to close to 40% over the same areas. Local emission of aerosols accounted for less than 25% of PM10 concentrations in northern Taiwan, but was about 60% for PM2.5 in central and southern Taiwan because these areas are less influenced by long-range transport. PMID:24530595

  19. Aeolian processes over gravel beds: Field wind tunnel simulation and its application atop the Mogao Grottoes, China

    NASA Astrophysics Data System (ADS)

    Zhang, Weimin; Tan, Lihai; Zhang, Guobin; Qiu, Fei; Zhan, Hongtao

    2014-12-01

    The aeolian processes of erosion, transport and deposition are threatening the Mogao Grottoes, a world culture heritage site. A field wind tunnel experiment was conducted atop the Mogao Grottoes using weighing sensors to quantify aeolian processes over protective gravel beds. Results reveal that aeolian erosion and deposition over gravel beds are basically influenced by gravel coverage and wind speed. Erosion is a main aeolian process over gravel beds and its strength level is mainly determined by gravel coverage: strong (<30%), medium (30-50%) and slight (>50%). Aeolian deposition only occurs when gravel coverage is equal to or greater than 30% and wind speeds are between 8 and 12 m s-1, and this process continues until the occurrence of the equilibrium coverage. In addition, the change in conditions of external sand supply affects the transition between aeolian deposition and erosion over gravel beds, and the quantity of sand transport at the height of 0-24 mm is an important indicator of aeolian deposition and erosion over gravel beds. Our results also demonstrate that making the best use of wind regime atop the Mogao Grottoes and constructing an artificial gobi surface in staggered arrays, with 30% coverage and 30-mm-high gravels and in 40 mm spacing can trap westerly invading sand flow and enable the stronger easterly wind to return the deposited sand on the gravel surface back to the Mingsha Mountain so as to minimize the damage of the blown sand flux to the Mogao Grottoes.

  20. Selective deposition response to aeolian-fluvial sediment supply in the desert braided channel of the upper Yellow River, China

    NASA Astrophysics Data System (ADS)

    Wang, H.; Jia, X.; Li, Y.; Peng, W.

    2015-09-01

    Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such cross-dune braided rivers. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. The Ulan Buh desert is the main coarse sediment source for this desert braided channel, and the mean percentage of the coarser (> 0.08 mm) grains on the aeolian dunes surface is 95.34 %. The lateral selective deposition process is developed by the interaction between the flows and the aeolian-fluvial sediment supplies, causing the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel centre and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces, forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of an "above-ground" river in the braided reach of the upper Yellow River in response to aeolian and fluvial sediment supplies.

  1. Lunar Surface Charging and Dust Transport during the Passage of a Coronal Mass Ejection

    NASA Astrophysics Data System (ADS)

    Stubbs, T. J.; Farrell, W. M.; Zimmerman, M. I.; Collier, M. R.; Glenar, D. A.; Halekas, J. S.

    2012-12-01

    The surface of the Moon is directly exposed to the surrounding space plasma and energetic particle (> 10 keV) populations, as well as solar ultraviolet and soft X-ray radiation on the dayside, which result in it becoming electrically charged. Under certain conditions it is possible that the resulting near-surface electric fields could have a significant influence on the transport of charged lunar dust (< ~10 microns in radius). These processes are anticipated to be most extreme at various periods during the passage of a coronal mass ejection (CME). Such an event is studied here using solar wind observations from April/May 1998 as part of the Solar Storm-Lunar Atmosphere Modeling (SSLAM) Lunar Extreme Workshop (LEW) to investigate the entire lunar surface-exosphere-space plasma system during a space weather event at the Moon. This workshop was organized by the NASA Lunar Science Institute (NLSI) Dynamic Response of the Environment At the Moon (DREAM) team. In this study, surface charging models are used to predict surface potentials and electric fields during the April/May 1998 CME event, as well as assess the importance of the different current sources and the implications for electrostatic dust transport. As expected, at the subsolar point it is found that surface charging is dominated by photoemission currents, although secondary electron emission due to plasma electrons can often have a noticeable influence. Meanwhile at the terminator, surface charging is dominated by plasma electrons and the associated secondary electron emission. At certain times the secondary electron emission is predicted to be sufficiently intense to be able to charge the shadowed surface positive. In addition, it is found that intervals with high fluxes of particles with energies > 10 keV could be very important when their current contribution exceeds that of the plasma ions. The location of the transition from positive to negative surface charging on the lunar dayside, also referred to

  2. Transport of North African dust from the Bodélé depression to the Amazon Basin: a case study

    NASA Astrophysics Data System (ADS)

    Ben-Ami, Y.; Koren, I.; Rudich, Y.; Artaxo, P.; Martin, S. T.; Andreae, M. O.

    2010-08-01

    Through long-range transport of dust, the North-African desert supplies essential minerals to the Amazon rain forest. Since North African dust reaches South America mostly during the Northern Hemisphere winter, the dust sources active during winter are the main contributors to the forest. Given that the Bodélé depression area in southwestern Chad is the main winter dust source, a close link is expected between the Bodélé emission patterns and volumes and the mineral supply flux to the Amazon. Until now, the particular link between the Bodélé and the Amazon forest was based on sparse satellite measurements and modeling studies. In this study, we combine a detailed analysis of space-borne and ground data with reanalysis model data and surface measurements taken in the central Amazon during the Amazonian Aerosol Characterization Experiment (AMAZE-08) in order to explore the validity and the nature of the proposed link between the Bodélé depression and the Amazon forest. This case study follows the dust events of 11-16 and 18-27 February 2008, from the emission in the Bodélé over West Africa (most likely with contribution from other dust sources in the region) the crossing of the Atlantic Ocean, to the observed effects above the Amazon canopy about 10 days after the emission. The dust was lifted by surface winds stronger than 14 m s-1, usually starting early in the morning. The lofted dust, mixed with biomass burning aerosols over Nigeria, was transported over the Atlantic Ocean, and arrived over the South American continent. The top of the aerosol layer reached above 3 km, and the bottom merged with the boundary layer. The arrival of the dusty air parcel over the Amazon forest increased the average concentration of aerosol crustal elements by an order of magnitude.

  3. Source-to-sink cycling of aeolian sediment in the north polar region of Mars

    NASA Astrophysics Data System (ADS)

    Ewing, R. C.; Kocurek, G.

    2012-12-01

    Aeolian sand dunes are prominent features on the landscapes of Earth, Mars, Venus and Titan and sedimentary deposits interpreted as aeolian in origin are found in the rock records of Earth and Mars. The widespread occurrence of aeolian dunes on the surface of these worlds and within their deep-time depositional records suggests that aeolian systems are and likely have been a default depositional environment for the Solar System. Within an aeolian source-to-sink context, we hypothesize that planet-specific boundary conditions strongly impact production, transport, accumulation and preservation of aeolian sediment, whereas dunes and dune-field patterns remain largely similar. This hypothesis is explored within the north polar region of Mars, which hosts the most extensive aeolian dune fields and aeolian sedimentary deposits yet recognized on Mars and appears to be a region of dynamic source-to-sink cycling of aeolian sediments. The Planum Boreum Cavi Unit rests beneath north polar ice cap of Mars and is composed of several hundred meters of niveo-aeolian dune cross-stratification. The overall architecture of the unit consists of sets of preserved dune topography with an upward increase in the abundance of ice. Dune sets are defined by stabilized, polygonally fractured bounding surfaces, erosional bounding surfaces and typical internal lee foresets made of sediment and ice. The accumulation of the Cavi Unit is interpreted as occurring through freezing and serves as an example of a cold temperature boundary condition on aeolian sediment accumulation. Preservation of the Cavi Unit arises because of deposition of the overlying ice cap and contrasts with preservation of aeolian sediment on Earth, which is largely driven by eustasy and tectonics. The Cavi Unit is thought to be one source of sediment for the north polar Olympia Undae Dune Field. The region of Olympia Undae near the Cavi Unit shows a reticulate dune field pattern composed of two sets of nearly orthogonal

  4. Semiarid landscapes response to Aeolian processes during Holocene in Baikal Region

    NASA Astrophysics Data System (ADS)

    Dan'ko, Lidia; Opekunova, Marina

    2010-05-01

    Arid and semiarid landscapes play a significant role in global climate, biogeochemical, and hydrological processes. Regional analysis of the past aeolian processes is essential for improve our understanding of how various landscape and ecosystems responded to climate change in the past. Our investigation presents details on sand dunes and on loess-like sediments. The study areas are situated in the northern part of Baikal Region (Eastern Siberia). In its depressions, the so-called Barguzinskaya and Tunkinskaya Valley surrounded mountain ranges local dunefieds and loess-like sediments have developed. Present climate in the study areas is continental, characterized by low precipitation(mean annual 250-450 mm) and wide annual range of temperature. Field investigations indicate that the Holocene deposits of the Barguzinskaya and Tunkinskaya Valley are sealed the pedo-sedimentary interface. The analytical results suggest that one's represents a changeover from intensified soil formation to accelerated aeolian dust accumulation. The original content of calcium carbonate and gypsum at the base of some sections of loess-like sediments indicates the aeolian origin of these sediments. In whole, the soil horizons are a proof for humid phases. The change was forced by climatic aridity. Absolute dating of the organogenic components of soils (14C) indicate the age positions of the arid and humid climate phases. Our results indicate not only 1-4 long-time episodes of aeolian dust accumulation during the Holocene, but shot-time aeolian accumulation episodes, that were specific for Late Holocene. For example, in the Tunkinskaya Valley the Late Holocene soil formation replaced by aeolian deposit at 1700 - 1900, 800 and 200-250 years ago, in the Barguzinskaya Valley - about 3100 - 2900, 2300 and 600 years ago. It can be concluded that a periodical formation of the aeolian deposits in the semiarid landscapes during Holocene can be postulated. Aeolian and loess-like sediments of the

  5. Implications of high altitude desert dust transport from Western Sahara to Nile Delta during biomass burning season.

    PubMed

    Prasad, Anup K; El-Askary, Hesham; Kafatos, Menas

    2010-11-01

    The air over major cities and rural regions of the Nile Delta is highly polluted during autumn which is the biomass burning season, locally known as black cloud. Previous studies have attributed the increased pollution levels during the black cloud season to the biomass or open burning of agricultural waste, vehicular, industrial emissions, and secondary aerosols. However, new multi-sensor observations (column and vertical profiles) from satellites, dust transport models and associated meteorology present a different picture of the autumn pollution. Here we show, for the first time, the evidence of long range transport of dust at high altitude (2.5-6 km) from Western Sahara and its deposition over the Nile Delta region unlike current Models. The desert dust is found to be a major contributor to the local air quality which was previously considered to be due to pollution from biomass burning enhanced by the dominant northerly winds coming from Europe. PMID:20797813

  6. A 1400-year terrigenous dust record on a coral island in South China Sea

    PubMed Central

    Liu, Yi; Sun, Liguang; Zhou, Xin; Luo, Yuhan; Huang, Wen; Yang, Chengyun; Wang, Yuhong; Huang, Tao

    2014-01-01

    We present analyses of a lacustrine sediment core (DY6) on Dongdao Island, which provides high-resolution paleoclimate records for the South China Sea (SCS). Results of element analyses indicate that the concentrations of Ti and Al in DY6 are much higher than the background on the island. Morphological characteristics of acidic insoluble particles are similar to aeolian in East China. Sr and Nd isotope compositions in these particles are consistent with those in Asian aeolian dust. We inferred that dust in DY6 may have been transported by East Asian Winter Monsoon (EAWM) from inland Asia. The continuous dust records for the past 1400 years in North SCS were presented based on the measured Ti flux, which revealed an opposite trend to the variations in the EAWM for the past 50 years. A comparison of wind fields between cold and warm years shows that north surface wind in southeast China was stronger in cold years. However, 850 hPa wind vector along the east coast of China, the key level of wind for long-distance dust transmission, weakened in cold years. We conclude that differences in the EAWM records can be attributed to the 850 hPa wind pattern in different areas. PMID:24845372

  7. Observational evidence for the convective transport of dust over the Central United States

    NASA Astrophysics Data System (ADS)

    Corr, C. A.; Ziemba, L. D.; Scheuer, E.; Anderson, B. E.; Beyersdorf, A. J.; Chen, G.; Crosbie, E.; Moore, R. H.; Shook, M.; Thornhill, K. L.; Winstead, E.; Lawson, R. P.; Barth, M. C.; Schroeder, J. R.; Blake, D. R.; Dibb, J. E.

    2016-02-01

    Bulk aerosol composition and aerosol size distributions measured aboard the DC-8 aircraft during the Deep Convective Clouds and Chemistry Experiment mission in May/June 2012 were used to investigate the transport of mineral dust through nine storms encountered over Colorado and Oklahoma. Measurements made at low altitudes (<5 km mean sea level (MSL)) in the storm inflow region were compared to those made in cirrus anvils (altitude > 9 km MSL). Storm mean outflow Ca2+ mass concentrations and total coarse (1 µm < diameter < 5 µm) aerosol volume (Vc) were comparable to mean inflow values as demonstrated by average outflow/inflow ratios greater than 0.5. A positive relationship between Ca2+, Vc, ice water content, and large (diameter > 50 µm) ice particle number concentrations was not evident; thus, the influence of ice shatter on these measurements was assumed small. Mean inflow aerosol number concentrations calculated over a diameter range (0.5 µm < diameter < 5.0 µm) relevant for proxy ice nuclei (NPIN) were ~15-300 times higher than ice particle concentrations for all storms. Ratios of predicted interstitial NPIN (calculated as the difference between inflow NPIN and ice particle concentrations) and inflow NPIN were consistent with those calculated for Ca2+ and Vc and indicated that on average less than 10% of the ingested NPIN were activated as ice nuclei during anvil formation. Deep convection may therefore represent an efficient transport mechanism for dust to the upper troposphere where these particles can function as ice nuclei cirrus forming in situ.

  8. Transverse Aeolian Ridges on Mars: Sediment sources, volumes, and ages.

    NASA Astrophysics Data System (ADS)

    Berman, D. C.; Balme, M. R.

    2014-12-01

    Transverse Aeolian Ridges (TARs) are aeolian bedforms that are morphologically and dimensionally distinct from Large Dark Dune (LDD) fields, being generally brighter than, or of similar albedo to, the surrounding terrain. These features are significantly smaller than the LDDs, appear to form normal to local winds, and tend to have simple, transverse, ripple-like morphologies. Whether these small martian bedforms represent large granule ripples, small transverse dunes, or something else entirely is currently under debate. The spatial distribution of TARs provides important information about where on Mars aeolian sediments are concentrated, and determining their volume can help us constrain the sediment transport regime on Mars. Also, if we can determine if TARs were active only in the past, or whether TARs are mobile under today's wind conditions, then we can begin to assess when and where TARs are/were active over Mars' recent geological history. Thus TARs have the potential for being indicators/records of climate change on Mars. In this work we build on previous work [1,2] and focus on the local/regional scale. We have identified six regional study areas, each 5° by 5°, to investigate the behavior of TARs in detail; one in the northern hemisphere, three in the equatorial band, and two in the southern hemisphere. We have systematically mapped TAR and LDD deposits in each study area to constrain sediment transport pathways and identify sediment sources. In general, TAR sediments appear to be tied to local sources such as LDDs or layered terrains. HiRISE DTMs were utilized to measure TAR heights, widths, wavelengths, and lengths to calculate sediment volumes and estimate volumes over entire study areas based on mapping. Crater count analyses on contiguous TAR fields in the equatorial regions, where the bedforms appear more lithified, reveal ages of several million years. Mid-latitude TAR fields do not show any superposed craters, suggesting much younger deposits

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  10. Aeolian and fluvial processes in dryland regions: the need for integrated studies

    USGS Publications Warehouse

    Belnap, Jayne; Munson, Seth M.; Field, Jason P.

    2011-01-01

    Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it difficult to assess their relative importance in drylands, as well as their potential for synergistic interaction. Land degradation by accelerated wind and water erosion is a major problem throughout the world's drylands, and although recent studies suggest that these processes likely interact across broad spatial and temporal scales to amplify the transport of soil resources from and within drylands, many researchers and land managers continue to view them as separate and unrelated processes. Here, we illustrate how aeolian and fluvial sediment transport is coupled at multiple spatial and temporal scales and highlight the need for these interrelated processes to be studied from a more integrated perspective that crosses traditional disciplinary boundaries. Special attention is given to how the growing threat of climate change and land-use disturbance will influence linkages between aeolian and fluvial processes in the future. We also present emerging directions for interdisciplinary needs within the aeolian and fluvial research communities that call for better integration across a broad range of traditional disciplines such as ecology, biogeochemistry, agronomy, and soil conservation.

  11. Lunar dust simulant charging and transport under UV irradiation in vacuum: Experiments and numerical modeling

    NASA Astrophysics Data System (ADS)

    Champlain, A.; Matéo-Vélez, J.-C.; Roussel, J.-F.; Hess, S.; Sarrailh, P.; Murat, G.; Chardon, J.-P.; Gajan, A.

    2016-01-01

    Recent high-altitude observations, made by the Lunar Dust Experiment (LDEX) experiment on board LADEE orbiting the Moon, indicate that high-altitude (>10 km) dust particle densities are well correlated with interplanetary dust impacts. They show no evidence of high dust density suggested by Apollo 15 and 17 observations and possibly explained by electrostatic forces imposed by the plasma environment and photon irradiation. This paper deals with near-surface conditions below the domain of observation of LDEX where electrostatic forces could clearly be at play. The upper and lower limits of the cohesive force between dusts are obtained by comparing experiments and numerical simulations of dust charging under ultraviolet irradiation in the presence of an electric field and mechanical vibrations. It is suggested that dust ejection by electrostatic forces is made possible by microscopic-scale amplifications due to soil irregularities. At low altitude, this process may be complementary to interplanetary dust impacts.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  13. The effects of combined application of inorganic Martian dust simulant and carbon dots on glutamate transport rat brain nerve terminals

    NASA Astrophysics Data System (ADS)

    Borisova, Tatiana; Krisanova, Natalia; Nazarova, Anastasiya; Borysov, Arseniy; Pastukhov, Artem; Pozdnyakova, Natalia; Dudarenko, Marina

    2016-07-01

    During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the central nervous system (Oberdorster et al., 2004). Recently, the research team of this study found the minor fractions of nanoparticles with the size ~ 50 -60 nm in Lunar and Martian dust stimulants (JSC-1a and JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin), whereas the average size of the simulants was 1 mm and 4mm, respectively (Krisanova et al., 2013). Also, the research team of this study discovered new phenomenon - the neuromodulating and neurotoxic effect of carbon nano-sized particles - Carbon dots (C-dots), originated from ash of burned carbon-containing product (Borisova et al, 2015). The aims of this study was to analyse acute effects of upgraded stimulant of inorganic Martian dust derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, carbon dots, on the key characteristic of synaptic neurotransmission. Acute administration of carbon-containing Martian dust analogue resulted in a significant decrease in transporter-mediated uptake of L-[14C]glutamate (the major excitatory neurotransmitter) by isolated rat brain nerve terminals. The ambient level of the neurotransmitter in the preparation of nerve terminals increased in the presence of carbon dot-contained Martian dust analogue. These effects were associated with action of carbon component of the upgraded Martian dust stimulant but not with its inorganic constituent.

  14. Long-range Transport of Asian Dust Storms: A Satellite/Surface Perspective on Societal and Scientific Influence

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Among the many components contributing to air pollution, airborne mineral dust plays an important role due to its biogeochemical impact on the ecosystem and its radiative forcing effect on the weather/climate system. As much as one-third to half of the global dust emissions, estimated about 800 Tg, are introduced annually into Earth's atmosphere from various deserts in China. Asian dust storm outbreaks are believed to have persisted for hundreds and thousands years over the vast territory of north and northwest China, but not until recent decades that many studies reveal the compelling evidence in recognizing the importance of these eolian dust particles for forming Chinese Loess Plateau and for biogeochemical cycling in the North Pacific Ocean to as far as in the Greenland ice-sheets through long-range transport. The Asian dust and air pollution aerosols can be detected by its colored appearance on current Earth observing satellites and its evolution monitored by satellite and surface network. In this paper, we will demonstrate the capability of a new satellite algorithm, called Deep Blue, to retrieve aerosol properties, particularly but not limited to, over bright-reflecting surfaces such as urban areas and deserts. Recently, many field campaigns were designed and executed to study the compelling variability in spatial and temporal scale of both pollution-derived and naturally occurring aerosols, which often exist in high concentrations over eastern Asia and along the rim of the western Pacific. We will provide an overview of the outbreak of Asian dust storms, near source/sink and their evolution along transport pathway, from space and surface observations. The climatic effects and societal impacts of the Asian dusts will be addressed in depth. (to be presented in the International Workshop on Semi-Arid Land Surface-

  15. Transport of Saharan dust from the Bodélé Depression to the Amazon Basin: a case study

    NASA Astrophysics Data System (ADS)

    Ben-Ami, Y.; Koren, I.; Rudich, Y.; Artaxo, P.; Martin, S. T.; Andreae, M. O.

    2010-02-01

    Through long-range transport of dust, the Sahara desert supplies essential minerals to the Amazon rain forest. Since Saharan dust reaches South America mostly during the Northern Hemisphere winter, the dust sources active during winter are the main contributors to the forest. Given that the Bodélé depression area in Southwestern Chad is the main winter dust source, a close link is expected between the Bodélé emission patterns and volumes and the mineral supply flux to the Amazon. Until now, the particular link between the Bodélé and the Amazon forest was based on sparse satellite measurements and modeling studies. In this study, we combine a detailed analysis of space-borne and ground data with reanalysis model data and surface measurements taken in the Central Amazon during the Amazonian Aerosol Characterization Experiment (AMAZE-08) in order to explore the validity and the nature of the proposed link between the Bodélé depression and the Amazon forest. This case study follows the dust events of 11-16 and 18-27 February 2008, from the emission in the Bodélé over West Africa, the crossing of the Atlantic Ocean, to the observed effects above the Amazon canopy about 10 days after the emission. The dust was lifted by surface winds stronger than 14 m s-1, usually starting early in the morning. The lofted dust mixed with biomass burning aerosols over Nigeria, was transported over the Atlantic Ocean, and arrived over the South American continent. The top of the aerosol layer reached above 3 km, and the bottom merged with the marine boundary layer. The arrival of the dusty air parcel over the Amazon forest increased the average concentration of aerosol crustal elements by an order of magnitude.

  16. Evidence for dust transport in Viking IR thermal mapper opacity data

    NASA Technical Reports Server (NTRS)

    Martin, Terry Z.

    1993-01-01

    Global maps of 9-micron dust opacity derived from radiometric observations made by the Viking Orbiter IR Thermal Mapper instruments have revealed a wealth of new information about the distribution of airborne dust over 1.36 Mars years from 1976-1979. In particular, the changing dust distribution during major dust storms is of interest since the data provide a point of contact with both Earth-based observations of storm growth and with global circulation models.

  17. Reduction in soil aggregation in response to dust emission processes

    NASA Astrophysics Data System (ADS)

    Swet, Nitzan; Katra, Itzhak

    2016-09-01

    Dust emission by aeolian (wind) soil erosion depends on the topsoil properties of the source area, especially on the nature of the aggregates where most dust particles are held. Although the key role of soil aggregates in dust emission, the response of soil aggregation to aeolian processes and its implications for dust emission remain unknown. This study focuses on aggregate size distribution (ASD) analyses before and after in-situ aeolian experiments in semiarid loess soils that are associated with dust emission. Wind tunnel simulations show that particulate matter (PM) emission and saltation rates depend on the initial ASD and shear velocity. Under all initial ASD conditions, the content of saltator-sized aggregates (63-250 μm) increased by 10-34% due to erosion of macro-aggregates (> 500 μm), resulting in a higher size ratio (SR) between the saltators and macro-aggregates following the aeolian erosion. The results revealed that the saltator production increases significantly for soils that are subjected to short-term (anthropogenic) disturbance of the topsoil. The findings highlight a decrease in soil aggregation for all initial ASD's in response to aeolian erosion, and consequently its influence on the dust emission potential. Changes in ASD should be considered as a key parameter in dust emission models of complex surfaces.

  18. What is driving changes in long-range transport of dust from Africa to the Americas? A 30 year synthesis of the GEOS-Chem model and observations

    NASA Astrophysics Data System (ADS)

    Ridley, D. A.; Heald, C. L.

    2012-12-01

    The Sahara and Sahelian regions produce approximately half of the world's dust emissions, resulting in significant radiative effects, air quality issues and mineral deposition, not only in Africa, but across the Atlantic and in the Americas. Determining how these impacts may change in the future requires a thorough understanding of the processes controlling emission, transport and deposition of dust. Long-term records of dust concentration measured in the Caribbean have, until the nineties, correlated with Sahelian precipitation and climatic indicators, potentially providing ways to predict changes in dust. However, this relationship is no longer clear and there are significant changes in the seasonality of dust transported to the Americas currently with no obvious explanation. We use the GEOS-Chem global chemical transport model with NASA GMAO meteorological re-analyses (MERRA) to simulate the 30 year period 1979 - 2008. A synthesis of observations from multiple satellite and surface-based platforms is used to evaluate the model, primarily in terms of its ability to simulate the long-range transport of mineral dust from Africa. We then investigate what drives the changes in long-range transport of African dust to the Americas over diurnal to decadal timescales. This enables understanding of the relative importance of the individual processes controlling these changes, and the sensitivity of air quality and dust deposition downwind. This work aims to determine 1) how sensitive air quality and dust deposition in the Americas is to changes in African dust emissions, 2) the role of meteorological variables affecting the inter-annual variability of dust emission and deposition, and 3) the impact that land use changes and desertification in the Sahel may have in terms of the influence on dust transported to the Americas.

  19. Avalanche grainflow on a simulated aeolian dune

    NASA Astrophysics Data System (ADS)

    Sutton, S. L. F.; McKenna Neuman, C.; Nickling, W.

    2013-09-01

    Avalanches maintain the slipface of aeolian dunes, which alters their airflow characteristics and sediment dynamics, and results in the development of grainflow cross-bedding. We report on a series of experiments in which avalanches were observed on a 1:1 replica of a small (1.2 m brink height) transverse dune in the Dune Simulation Wind Tunnel under wind velocities of 8-11 m s-1. Changes in slipface topography were observed photographically and measured utilizing a 3-D laser scanner with 1 mm2 spatial resolution. Avalanches in noncohesive sands were observed to progress through scarp recession from the point of initiation and continue until the slope angle is reduced. Changes in local slope confirm that the steep, pre-avalanche mean slope relaxes to a uniform value equal to the angle of repose of the test sand (32°) over all involved portions of the slipface. Avalanche volumes are measured, and demonstrate that avalanche magnitude is independent of wind speed over the range of velocities observed. This independence provides the potential to significantly simplify the modeling of grainflow as a function of only the total cross brink sediment transport.

  20. Effects of River Regulation on Aeolian Landscapes, Grand Canyon National Park, USA

    NASA Astrophysics Data System (ADS)

    Draut, A. E.

    2010-12-01

    Sediment deposits in the Colorado River corridor include fluvial sandbars and aeolian dune fields, and the fluvial deposits are the primary sediment source for sand in the aeolian dunes. This 7-year study examined the effects of river regulation at Glen Canyon Dam (alteration of flow regime, sediment-supply reduction, and consequent loss of fluvial sandbars) on aeolian landscapes downstream in Grand Canyon National Park. A comparative study was developed between aeolian landscapes in Grand Canyon, Arizona, and Cataract Canyon, Utah, upstream of Glen Canyon Dam and its reservoir (Lake Powell), where hydrology and sediment supply of the Colorado River are affected substantially less by artificial river regulation than occurs in Grand Canyon. Before closure of Glen Canyon Dam in 1963, sediment-rich floods (mean annual peak 2400 m3/s) formed sandbars from which wind moved sand inland to form aeolian dunes. After dam operations reduced the amplitude and frequency of high flows, and eliminated the mainstream fluvial sediment supply, Grand Canyon’s fluvial sandbars lost open sand area owing to erosion by river flows and the spread of riparian vegetation. Two types of aeolian landscapes now occur in Grand Canyon: (1) modern fluvial sourced, those downwind of post-dam sandbars; and (2) relict fluvial sourced, whose primary sediment source was deposits from pre-dam floods that were larger than any post-dam flows have been. Sediment supply has been reduced to type (1) dune fields because post-dam sandbars are smaller than in the pre-dam era; new sediment supply to type (2) dune fields essentially has been eliminated. Type 1 aeolian landscapes can receive new windblown sand from sandbars formed by controlled floods (1160 m3/s), which occurred in 1996, 2004, and 2008. Type 1 dune fields, being downwind and within 100 m of controlled-flood sandbars, have significantly higher aeolian sand-transport rates, more open sand, and less biologic soil crust than relict type 2 dune

  1. Facies architecture and stratigraphic evolution of aeolian dune and interdune deposits, Permian Caldeirão Member (Santa Brígida Formation), Brazil

    NASA Astrophysics Data System (ADS)

    Jones, Fábio Herbert; Scherer, Claiton Marlon dos Santos; Kuchle, Juliano

    2016-05-01

    The Permian Caldeirão Member (Santa Brígida Formation), located in the Tucano Central Basin, northeast region of Brazil, is characterized by a sandstone succession of aeolian origin that comprises the preserved deposits of dunes and interdunes. Grainflow and translatent wind-ripple strata, and frequent presence of reactivation surface, compose the cross-bedding of crescent aeolian dune deposits. The aeolian cross-strata show a mean dip toward the ENE. In places, interlayered with dune cross-beds, occur interdune units composed of facies indicative of dry, damp and wet condition of the substrate, suggesting spatial and/or temporal variations in the moisture content of the interdune accumulation surface. The presence of NNW current ripple cross-lamination in wet interdune areas indicates streamflows confined to interdune corridors and oriented perpendicular to aeolian transport direction. Lenses of damp and wet interdune strata exhibit mainly interdigitated and transitional relationships with the toe-sets of overlying aeolian dune units in sections parallel to aeolian transport, indicating that dune migration was contemporaneous with accumulation in adjacent interdunes. Lateral variations in the preserved thickness of the interdune units and the associated rare occurrence of abrupt and erosive contacts between interdune and overlying dune sets, suggest temporal variations in the angle of dune and interdune climb that may be related to high-frequency changes in water table position. Four stratigraphic intervals in the Caldeirão Member can be identified, two intervals showing cross-bedding of aeolian dunes without wet interdune areas and two intervals exhibiting aeolian dunes separated by wet interdune areas, marking the transition between dry aeolian systems (Intervals I and III) and wet aeolian systems (Intervals II and IV). The temporal alternations between dry and wet aeolian systems reflect changes in the availability of dry sand and/or the rate in the water

  2. Aeolian Sediments on the northeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Stauch, G.; Lehmkuhl, F.

    2013-12-01

    The timing and spatial distribution of aeolian sediments on the northeastern Tibetan Plateau have gained increasing interest during the last decades. The formation of the aeolian deposits is often related to cold and dry climate conditions. However, further important parameters are the local geomorphological setting and sediment availability in the source areas of the sediments. Aeolian sediments including loess, sandy loess and sands are widespread in the catchment of the Donggi Cona on the northeastern Tibetan Plateau at around 4000 m asl. Detailed geomorphological mapping of the deposits and geochemical analyses of the sediments revealed varying sources throughout the Holocene. The timing of the sediment deposition is based on 43 OSL (optical stimulated luminescence) ages. Several phases of enhanced aeolian deposition took place during the Holocene. The accumulation of aeolian sands lasted from 10.5 until 7 ka. The main source area of these sands was a large alluvial fan. Parallel to the formation of the dunes loess was deposited on the adjacent slopes from 10.5 until 7.5 ka. These sediments most probably originate in the nearby Qaidam Basin. In contrast to the general linkage of aeolian sediments to dryer climate conditions formation of these aeolian deposits is related to wetter conditions due to a strengthening of the Asian Summer Monsoons. The wetter climate enhanced the trapping and continuous fixation of the aeolian sediments by vegetation. With the further strengthening of the Monsoon fluvial processes eroded the aeolian deposits at least until 6 ka. From about 3 ka to the present a reactivation of aeolian sands and the formation of new dunes took place. This reactivation is related to drier conditions on the north-eastern Tibetan Plateau. Additionally, an increased human influence might have enhanced the aeolian activity. Similar phases of enhanced aeolian activity have been documented in more than 170 available OSL ages from loess and aeolian sands in

  3. Transport of carbon-bearing dusts from Iraq to Japan during Iraq's War

    NASA Astrophysics Data System (ADS)

    Tazaki, Kazue; Wakimoto, Rie; Minami, Yukiya; Yamamoto, Masayoshi; Miyata, Koshirou; Sato, Kazuhiro; Saji, Ichiro; Chaerun, S. Khodijah; Zhou, Guoping; Morishita, Tomoaki; Asada, Ryuji; Segawa, Hiromi; Imanishi, Hiroki; Kato, Rie; Otani, Yusuke; Watanabe, Tomoko

    Rainwater collected during the period of February-April, 2003 in Kanazawa University and Hakui, Ishikawa Prefecture, Japan, was investigated by ion chromatography of the dissolved ions, and Scanning electron microscopy equipped with energy dispersive analyzer (SEM-EDX), electron microprobe analyzer (EPMA), transmission electron microscopy, and X-ray powder diffraction (XRD) analyses of the filtered samples. The pH, Eh, EC, dissolved oxygen (DO) and depleted U (DU) of the rainwater were also measured. The results show a rare case with low pH value of rain and high value of electrical conductivity (EC) in the rainwater during certain period. The NO 3-, SO 42- and NH 4+ concentrations on 26th March, show quite high values after oil field fires on 21st March 2003. The powdery dust and carbon-bearing nm sized particles contained in the rainwater have characteristics different from that of the Asian dust (Kosa). Since 21 March, 2003 the Iraq plunged into the war, the 9 oil field fires were reported on 25 March, 2003 in Rumaylah oil field near the borderline of Kuwait. The first precipitation was caught in Kanazawa on 24 March, 2003. The pH value of the rainwater indicated a strong acid rain (pH 3.6) with black powdery dusts. The acid rain on 27th March to 2nd April (pH 3.4-4.3; 5-17 mm) associated with WNW wind (2.7-4.1 m/s) has continued to the first 10 days of April in Kanazawa, during the 9 oil fields were burning in Iraq. The EC in rainwater collected from 24 March to 15 April, 2003, shows high concentrations of ions, suggesting high contents of water soluble-carbon particles and soot. In the meantime, it was the highest season of sandstorms at bare dried land in Iraq from the end of March to the beginning of April. Westerly wind blew around 5500 m high, and the sandstorm with 2000 m wide was transported by strong wind to Zagros 3000 m high mountains. The hot wind hit the Zagros Mountains and easily to join and rise to Westerly wind high by a rising air current. The

  4. Laboratory study of PCB transport from primary sources to settled dust.

    PubMed

    Liu, Xiaoyu; Guo, Zhishi; Krebs, Kenneth A; Greenwell, Dale J; Roache, Nancy F; Stinson, Rayford A; Nardin, Joshua A; Pope, Robert H

    2016-04-01

    Dust is an important sink for indoor air pollutants, such as polychlorinated biphenyls (PCBs) that were used in building materials and products. In this study, two types of dust, house dust and Arizona Test Dust, were tested in a 30-m(3) stainless steel chamber with two types of panels. The PCB-containing panels were aluminum sheets coated with a PCB-spiked primer or caulk. The PCB-free panels were coated with the same materials but without PCBs. The dust evenly spread on each panel was collected at different times to determine its PCB content. The data from the PCB panels were used to evaluate the PCB migration from the source to the dust through direct contact, and the data from the PCB-free panels were used to evaluate the sorption of PCBs through the dust/air partition. Settled dust can adsorb PCBs from air. The sorption concentration was dependent on the congener concentration in the air and favored less volatile congeners. When the house dust was in direct contact with the PCB-containing panel, PCBs migrated into the dust at a much faster rate than the PCB transfer rate due to the dust/air partition. The dust/source partition was not significantly affected by the congener's volatility. For a given congener, the ratio between its concentration in the dust and in the source was used to estimate the dust/source partition coefficient. The estimated values ranged from 0.04 to 0.16. These values are indicative of the sink strength of the tested house dust being in the middle or lower-middle range. PMID:26849196

  5. Aerosol Transport Over Equatorial Africa

    NASA Technical Reports Server (NTRS)

    Gatebe, C. K.; Tyson, P. D.; Annegarn, H. J.; Kinyua, A. M.; Piketh, S.; King, M.; Helas, G.

    1999-01-01

    Long-range and inter-hemispheric transport of atmospheric aerosols over equatorial Africa has received little attention so far. Most aerosol studies in the region have focussed on emissions from rain forest and savanna (both natural and biomass burning) and were carried out in the framework of programs such as DECAFE (Dynamique et Chimie Atmospherique en Foret Equatoriale) and FOS (Fires of Savanna). Considering the importance of this topic, aerosols samples were measured in different seasons at 4420 meters on Mt Kenya and on the equator. The study is based on continuous aerosol sampling on a two stage (fine and coarse) streaker sampler and elemental analysis by Particle Induced X-ray Emission. Continuous samples were collected for two seasons coinciding with late austral winter and early austral spring of 1997 and austral summer of 1998. Source area identification is by trajectory analysis and sources types by statistical techniques. Major meridional transports of material are observed with fine-fraction silicon (31 to 68 %) in aeolian dust and anthropogenic sulfur (9 to 18 %) being the major constituents of the total aerosol loading for the two seasons. Marine aerosol chlorine (4 to 6 %), potassium (3 to 5 %) and iron (1 to 2 %) make up the important components of the total material transport over Kenya. Minimum sulfur fluxes are associated with recirculation of sulfur-free air over equatorial Africa, while maximum sulfur concentrations are observed following passage over the industrial heartland of South Africa or transport over the Zambian/Congo Copperbelt. Chlorine is advected from the ocean and is accompanied by aeolian dust recirculating back to land from mid-oceanic regions. Biomass burning products are transported from the horn of Africa. Mineral dust from the Sahara is transported towards the Far East and then transported back within equatorial easterlies to Mt Kenya. This was observed during austral summer and coincided with the dying phase of 1997/98 El

  6. Dust transport over the eastern Mediterranean derived from Total Ozone Mapping Spectrometer, Aerosol Robotic Network, and surface measurements

    NASA Astrophysics Data System (ADS)

    Kalivitis, N.; Gerasopoulos, E.; Vrekoussis, M.; Kouvarakis, G.; Kubilay, N.; Hatzianastassiou, N.; Vardavas, I.; Mihalopoulos, N.

    2007-02-01

    Multiyear surface PM10 measurements performed on Crete Island, Greece, have been used in conjunction with satellite (Total Ozone Mapping Spectrometer (TOMS)) and ground-based remote sensing measurements (Aerosol Robotic Network (AERONET)) to enhance our understanding of the evolution of mineral dust events over the eastern Mediterranean. An analysis of southerly air masses at altitudes of 1000 and 3000 m over a 5 year period (2000-2005), showed that dust can potentially arrive over Crete, either simultaneously in the lower free troposphere and inside the boundary layer (vertical extended transport (VET)) or initially into the free troposphere with the heavier particles gradually being scavenged inside the boundary layer (free troposphere transport (FTT)). Both pathways present significant seasonal variations but on an annual basis contribute almost equally to the dust transport in the area. During VET the aerosol index (AI) derived from TOMS was significantly correlated with surface PM10, and in general AI was found to be adequate for the characterization of dust loadings over the eastern Mediterranean on a climatological basis. A significant covariance between PM10 and AOT was observed during VET as well, indicating that AOT levels from AERONET may be estimated by PM10 levels at the surface. Surface measurements are thus crucial for the validation of remote sensing measurements and hence are a powerful tool for the investigation of the impact of aerosols on climate.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  8. Dust storms on Mars: Considerations and simulations

    NASA Technical Reports Server (NTRS)

    Greeley, R.; White, B. R.; Pollack, J. B.; Iverson, J. D.; Leach, R. N.

    1977-01-01

    Aeolian processes are important in modifying the surface of Mars at present, and appear to have been significant in the geological past. Aeolian activity includes local and global dust storms, the formation of erosional features such as yardangs and depositional features such as sand dunes, and the erosion of rock and soil. As a means of understanding aeolian processes on Mars, an investigation is in progress that includes laboratory simulations, field studies of earth analogs, and interpretation of spacecraft data. This report describes the Martian Surface Wind Tunnel, an experimental facility established at NASA-Ames Research Center, and presents some results of the general investigation. Experiments dealing with wind speeds and other conditions required for the initiation of particle movement on Mars are described and considerations are given to the resulting effectiveness of aeolian erosion.

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

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  10. Nearly a Decade of CALIPSO Observations of Asian and Saharan Dust Properties near Source and Transport Regions

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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 and 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 small-scale phenomena such as 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.

  11. Transpacific transport of mineral dust: Its impact in the United States and on sulfate, nitrate, and ozone in Asian pollution plumes

    NASA Astrophysics Data System (ADS)

    Fairlie, Thomas Duncan

    This thesis examines the transpacific transport of mineral dust from Asia, its impact on aerosol concentrations in the United States, and on nitrate, sulfate, and ozone in Asian pollution plumes. We use observations from ground stations, aircraft, and satellite platforms, interpreted using a global three-dimensional chemical transport model (GEOS-Chem) in which we have represented dust mobilization, transport, and deposition. We find that the best simulation of North American surface observations is achieved when we restrict dust sources to year-round arid areas, but include a significant wind threshold for mobilization. The model captures the seasonal cycle in surface dust concentrations over the northern Pacific, the outflow of dust from Asia in the free troposphere, and the timing and distribution of Asian dust outbreaks in the United States in spring 2001. We find that Asian dust persists in surface air in western states beyond these sudden spring outbreaks, and accounts for 40% of the worst visibility days due to dust in the West in 2001. Thus, state governments need to account for transpacific dust in setting attainable visibility goals. We have also represented the uptake of acid gases SO2, H 2SO4, and HNO3 on dust in the model, and used it to interpret aircraft observations of nitrate and sulfate partitioning in transpacific dust plumes during April-May 2006. The observations show that particulate nitrate was primarily associated with the dust, sulfate was primarily associated with ammonium, and that Asian dust remained alkaline across the Pacific. To reproduce this in the model requires that uptake of HNO3 and SO2 on dust is much weaker than assumed in previous model studies. The model overestimates gas-phase HNO3 by a factor of 2-3, typical of other models; we demonstrate that this cannot be corrected by uptake on dust. Dust remains alkaline in the model because the uptake of acid gases is slow relative to the lifetime of dust against deposition. This

  12. Persistent aeolian activity at Endeavour crater, Meridiani Planum, Mars; new observations from orbit and the surface

    NASA Astrophysics Data System (ADS)

    Chojnacki, Matthew; Johnson, Jeffrey R.; Moersch, Jeffrey E.; Fenton, Lori K.; Michaels, Timothy I.; Bell, James F., III

    2015-05-01

    Aeolian-driven bedform activity is now known to occur in many regions of Mars, based on surface and orbital observation of contemporary martian ripple and dune mobility events. Many of these sites have only been monitored with sufficient resolution data for the last few Mars years, when the High Resolution Imaging Science Experiment (HiRISE) began acquiring images of Mars. One exception is the well-monitored Endeavour crater in Meridiani Planum, which was one of the first known sites of unambiguous dune activity (migration and deflation). However, those early detections used lower resolution images over longer temporal baselines (versus the HIRISE data now available), leaving some measurements poorly constrained. New orbital and surface observations of Endeavour show multiple spatial (cm, m, km) and temporal (seasons, Mars year) scales of aeolian-driven surface change, which confirms earlier reports. Dome dunes in the eastern portion of the crater persistently deflate, disseminating dark sand across lighter-toned regolith and/or eroded bright dust, and likely contribute to the crater interior's episodic decreases in orbital albedo measurements. Other dome dunes are detected with the highest migration rates (4-12 m per Mars year) and volumetric sand fluxes reported yet for Mars. Estimated dune construction times or "turnover times" here and elsewhere on Mars are significantly shorter than martian obliquity cycles, implying that it is not necessary to invoke paleoclimate wind regimes to explain current dune morphologies. Located on the crater rim, the Opportunity rover detected evidence for near- and far-field aeolian-driven activity, with observations of spherules/sand movement in the rover workspace, bedform albedo alteration, and dust-lifting events. Observations of intracrater dunes show periodic shifting dark streaks that significantly constrain local wind regimes (directionality and seasonality). Constraints on wind directions from surface and orbital images

  13. Triton's streaks as windblown dust

    NASA Technical Reports Server (NTRS)

    Sagan, Carl; Chyba, Christopher

    1990-01-01

    Explanations for the surface streaks observed by Voyager 2 on Triton's southern hemisphere are discussed. It is shown that, despite Triton's tenuous atmosphere, low-cohesion dust trains with diameters of about 5 micron or less may be carried into suspension by aeolian surface shear stress, given expected geostrophic wind speeds of about 10 m/s. For geyser-like erupting dust plumes, it is shown that dust-settling time scales and expected wind velocities can produce streaks with length scales in good agreement with those of the streaks. Thus, both geyserlike eruptions or direct lifting by surface winds appear to be viable mechanisms for the origin of the streaks.

  14. A theoretical note on aerodynamic lifting in dust devils

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Ting

    2016-02-01

    The stress distribution of a known rotating flow near the ground in fluid mechanics indicates that the horizontal aerodynamic entrainment of particles within dust devils is attributed to friction force rather than pressure force. The expression of dust emission rate on Earth was theoretically discussed based on simulated flow field and our current understanding of the physics of aeolian dust. It seems that transition flow is vital to dust devils on Mars.

  15. Atmospheric stability and diurnal patterns of aeolian saltation on the Llano Estacado

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aeolian transport is driven by aerodynamic surface stress imposed by turbulent winds in the Earth’s atmospheric boundary layer (ABL). ABL regime is influenced by stratification, which can either enhance or suppress production of turbulence by shear associated with the vertical gradient of streamwise...

  16. Aeolian nutrient fluxes following wildfire in sagebrush steppe: Implications for soil carbon storage

    USGS Publications Warehouse

    Hasselquist, N.J.; Germino, M.J.; Sankey, J.B.; Ingram, L.J.; Glenn, N.F.

    2011-01-01

    Pulses of aeolian transport following fire can profoundly affect the biogeochemical cycling of nutrients in semi-arid and arid ecosystems. Our objective was to determine horizontal nutrient fluxes during an episodic pulse of aeolian transport that occurred following a wildfire in a semi-arid sagebrush steppe ecosystem in southern Idaho, USA. We also examined how temporal trends in nutrient fluxes were affected by changes in particle sizes of eroded mass as well as nutrient concentrations associated with different particle size classes. In the burned area, total carbon (C) and nitrogen (N) fluxes were as high as 235 g C m????'1 d????'1 and 19 g N m????'1 d????'1 during the first few months following fire, whereas C and N fluxes were negligible in an adjacent unburned area throughout the study. Temporal variation in C and N fluxes following fire was largely attributable to the redistribution of saltation-sized particles. Total N and organic C concentrations in the soil surface were significantly lower in the burned relative to the unburned area one year after fire. Our results show how an episodic pulse of aeolian transport following fire can affect the spatial distribution of soil C and N, which, in turn, can have important implications for soil C storage. These findings demonstrate how an ecological disturbance can exacerbate a geomorphic process and highlight the need for further research to better understand the role aeolian transport plays in the biogeochemical cycling of C and N in recently burned landscapes. ?? 2011 Author(s).

  17. Aeolian sand preserved in Silver Lake: a new signal of Holocene high stands of Lake Michigan

    USGS Publications Warehouse

    Fisher, Timothy G.; Loope, Walter L.

    2005-01-01

    Aeolian sand within lake sediment from Silver Lake, Michigan can be used as a proxy for the timing of high lake levels of Lake Michigan.We demonstrate that the sand record from Silver Lake plotted as percent weight is in-phase with the elevation curve of Lake Michigan since the mid-Holocene Nipissing Phase. Because fluctuations in Lake Michigan's lake level are recorded in beach ridges, and are a response to climate change, the aeolian sand record within Silver Lake is also a proxy for climate change. It appears that increases in dune activity and lake sand are controlled by similar climatic shifts that drive fluctuations in lake level of Lake Michigan. High lake levels destabilize coastal bluffs that drive dune sand instability, and along with greater wintertime storminess, increase niveo-aeolian transport of sand across lake ice. The sand is introduced into the lake each spring as the ice cover melts.

  18. 10 years of aeolian geomorphology at the EGU: past achievements and future challenges

    NASA Astrophysics Data System (ADS)

    Baas, Andreas C. W.; Wiggs, Giles F. S.; Claudin, Philippe

    2016-04-01

    On this tenth anniversary of the Aeolian Processes & Landforms session at the EGU the original conveners review and reflect on the recent achievements and expansion in aeolian geomorphological research, focussing on advances in ou