Aeolian Dust

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Emission and redistribution of dust due to wind erosion in drylands drives major biogeochemical dynamics and provides important aeolian environmental connectivity at scales 11 from individual plants up to the global scale. Yet, perhaps because most relevant research on aeolian processes has been presented in a geosciences rather than ecological context, most ecological studies do not explicitly consider dust-driven processes. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the plant-interspace scale to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. Changes in climate and intensification of land use will both likely lead to increased dust production. To address these challenges, environmental scientists, land managers and policy makers need to more explicitly consider dust in resource management decisions. In a nutshell: • Ecologists and other environmental scientists often overlook the importance of dust and aeolian processes, yet these processes are of fundamental biogeochemical and ecological significance. • The importance of aeolian processes crosses scales from individual plants up to the globe. • Because changes in climate and intensification of land use are expected to result in increased dust production, ecologists, land managers, and policy makers need to more explicitly consider and manage dust.

Measurements used to study wind shear stress and turbulence, surface roughness, sand flux, and dust emissions are typically obtained from stationary instrumentation, and are thus limited spatially. They are also dependent on deployment of instrumentation for specific events and thus the are limited temporally. We have been adapting a rough-terrain legged robot capable of rapidly traversing desert terrain to serve as a semiautonomous, reactive mobile sensory platform (RHex [1]), which would not share these limitations. We report on early trials of the robotic platform at the Jornada LTER and White Sands National Monument to test the feasibility of gathering measurements of airflow and rates of particle transport on a dune, assessing the role of roughness elements such as vegetation in modifying the wind shear stresses incident on the surface, and estimating erosion susceptibility in an arid soil. The robot not only serves as a mobile platform for science instruments; it can also perf...

This study presents the spectral monthly and seasonal variation of aerosol optical depth (τAOD), single scattering albedo (SSA), and aerosol absorption optical depth (AAOD) between 2010 and 2018 obtained from the Aerosol Robotic Network (AERONET) over Pokhara, Nepal. The analysis of these column-integrated aerosol optical data suggests significant monthly and seasonal variability of aerosol physical and optical properties. The pre-monsoon season (March to May) has the highest observed τAOD(0.75 ± 0.15), followed by winter (December to February, 0.47 ± 0.12), post-monsoon (October and November, 0.39 ± 0.08), and monsoon seasons (June to September, 0.27 ± 0.13), indicating seasonal aerosol loading over Pokhara. The variability of Ångström parameters, α, and β, were computed from the linear fit line in the logarithmic scale of spectral τAOD, and used to analyze the aerosol physical characteristics such as particle size and aerosol loading. The curvature of spectral τAOD, α’, computed f...

address the need for a long-term research program to meet critical challenges in wind erosion research 8 and management in the United States. The Network has three aims: (1) provide data to support 9 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.

The present study examines the aerosol characteristics over Patiala in northwestern India from October 2013 to June 2014. The average mass concentration of the total suspended particulates (TSP) varied from 117 to 301 µg m-3 , with PM 10 accounting for ~63-83% from October to February (P1) and decreasing to less than ~40% from March to June (P2). The aerosol optical depth (AOD 500) exhibited its highest values during October (0.818) and its lowest during April (0.332), with the wavelength dependence differing significantly on a temporal scale. The Ångstrom exponent (α 380-870) values indicated a relatively high quantity of fine-mode particles over the study region during P1 as compared to P2, which is consistent with the PM measurements. The average monthly mass concentration of the climate forcing agent black carbon (BC) varied from 2.4 to 12 µg m-3 , with the highest mass concentration in December and the lowest in June. The average monthly single scattering albedo (SSA 500) derived from the OPAC (Optical Properties of Aerosols and Clouds) model varied from 0.890 to 0.947, with lower values during P1 than P2. The average monthly clear-sky direct atmospheric aerosol radiative forcing (ATM ARF) estimated by the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model ranged between +12 and +36 Wm-2 over the study region. Even though the mass fraction of BC averaged over the study period was only 2.4% of the total mass of the composite aerosol, its contribution to net ATM ARF was found to be significant (> 60%), indicating that BC contributes significantly to warming on a regional scale. These results improve our understanding of the impact of BC and composite aerosol on the earth's radiation budget and hence on regional climate.

The present study examines the effect of Diwali festival (17-21 October 2017; 19th October was the Diwali day) on aerosol characteristics over Patiala, northwestern part of India. Diwali being one of the major festivals of India that falls between mid-October and mid-November is celebrated with full enthusiasm by burning crackers, fireworks, etc. During this period, the study site also is engulfed with high aerosol loading because of extensive paddy residue burning emission. During Diwali event, a particulate matter (PM 10) concentration varies from 132 to 155 lg m À3 , while a mass concentration of black carbon aerosols varies from 6 to 9 lg m À3 with the maximum concentration on post-Diwali day. Aerosol optical depth (AOD 500) was maximum (0.852) on post-Diwali day indicating the additional loading of submicron particles due to burning of crackers and fireworks. The magnitude of single scattering albedo (SSA 500) decreases to a minimum value around 0.864 showing abundance of absorbing aerosols on Diwali affected days (19th and 20th October). A sudden jump of +12.9 W m À2 in atmospheric radiative forcing resulting in a heating rate of up to 1.4 K day À1 on next day of Diwali shows the warming state of the lower and middle atmosphere.

The present study examines the effect of Diwali festival (17-21 October 2017; 19th October was the Diwali day) on aerosol characteristics over Patiala, northwestern part of India. Diwali being one of the major festivals of India that falls between mid-October and mid-November is celebrated with full enthusiasm by burning crackers, fireworks, etc. During this period, the study site also is engulfed with high aerosol loading because of extensive paddy residue burning emission. During Diwali event, a particulate matter (PM 10) concentration varies from 132 to 155 lg m À3 , while a mass concentration of black carbon aerosols varies from 6 to 9 lg m À3 with the maximum concentration on post-Diwali day. Aerosol optical depth (AOD 500) was maximum (0.852) on post-Diwali day indicating the additional loading of submicron particles due to burning of crackers and fireworks. The magnitude of single scattering albedo (SSA 500) decreases to a minimum value around 0.864 showing abundance of absorbing aerosols on Diwali affected days (19th and 20th October). A sudden jump of +12.9 W m À2 in atmospheric radiative forcing resulting in a heating rate of up to 1.4 K day À1 on next day of Diwali shows the warming state of the lower and middle atmosphere.

In-situ knowledge on characteristics of mineral aerosols is important for weather and climate prediction models, particularly for modeling such processes as the entrainment, transport and deposition of aerosols. However, field measurements of the dust emission flux, dust size distribution and its chemical composition under realistic wind conditions remain rare. In this study, we present experimental data over annual expeditions in the arid and semi-arid zones of the Caspian Lowland Desert (Kalmykia, south of Russia); we evaluate characteristics of mineral aerosol concentration and fluxes, estimate its chemical composition and calculate its long-distance transport characteristics. The mass concentration in different years ranges from several tens to several hundred of μg m−3. The significant influence of wind velocity on the value of mass and counting concentration and on the proposed entrainment mechanisms is confirmed. An increased content of anthropogenic elements (S, Sn, Pb, Bi, ...

Wind erosion is a common cause of land degradation in the arid and semi arid grazing lands of inland Queensland. It is one of the processes leading to desertification. Significant wind erosion occurs when strong winds blow over light-textured soils that have been heavily grazed during periods of drought.

A survey of recent bottom sediments in the Northern Aral Sea was undertaken to elucidate the main direction of the alteration of sedimentation processes as a result of the significant decrease in the level of the sea from the beginning of the 1960s. Investigations were carded out in August-September 1991 from on board helicopter MI-8 MTV-1 which was equipped with the navigation system "LORAN-OMEGA". Sediments were sampled by means of ~gravity coring and grab sampling. The frequency of sampling was about 1 station per 10 km\ At several sites, water samples were collected. Grain-size analysis was undertaken and the mineralogy of the sediments was determined by optical means, using an SEM energy dispersive X-ray microanalysis, and X-ray diffractometry using a DRON-2.0 diffractometer.

The characterisation of mineral dust at emission sources is essential for quantifying the widerscale environmental impacts dust has, as well as improving its incorporation in modelling. Methods of sampling sediments at these source areas for the purposes of dust characterisation are varied and can produce different representations of emitted dust. This study systematically compared dust characterisations from three established approaches for estimating dust emission potential, namely: Big Spring Number Eight (BSNE) traps, a Portable In-situ Wind Erosion Laboratory (PI-SWERL) wind tunnel, and bulk surface sampling, at a known Namib Desert dust source. Individual particle analysis by auto-SEM (QEMSCAN) allowed comparison of size, shape, mineralogy and elemental composition at micrometre-scale for samples from the three approaches. BSNE samples consisted of a lower proportion of fine sediment (<20 µm particle diameter) than PI-SWERL-derived samples, with this performance possibly influenced by atmospheric humidity. In comparison, PI-SWERL characterised the dust with relatively fewer particles between 63-100 µm, a fraction that was more evident in both the BSNE-derived and surface sediments. The reduced representation of this coarser fraction resulted in appreciable differences in particle shape and mineralogic characteristics compared to BSNE and surface-derived samples. The different representations by the three methods return variable dust characteristics at source across fundamental properties of particle size, shape and mineralogy. Awareness of the different representations of dust caused by sampling technique remains essential for the appropriate physical and geochemical characterisation of aeolian dust and highlights how standardised techniques are important for meaningful comparisons, while methods to achieve accurate characterisation remain a priority for the discipline. employed to characterise dust represent a crucial consideration and ideally, varied approaches 52 should yield comparable results. The correct measurement (and subsequent parameterisation) 53 of dust characteristics at source is important for improving our understanding of emissions 54 processes, as well as the modelling of the full dust cycle and assessing the potential downwind 55 impacts of the emitted dust (Kok et al., 2012; Mahowald et al., 2014). 56 Particle size is a primary determinant of the environmental impact of mineral dust due to the 57 fact it has a significant initial control on sediment erodibility and subsequently the duration and distance of transport. However, the representation and measurement of the size distribution of aeolian dust samples remains a challenge (Formenti et al., 2011; Kok et al., 2011a). The particle-size distribution (PSD) in source sediments influences how the suspended dust PSD changes in the atmosphere and consequently how the emission and transport processes are modelled (Mahowald et al., 2014; Shao et al., 2011b; Nousiainen, 2009). The PSD of emitted dust is generally thought to depend on the source soil properties, such as parent soil particle size distribution, and also wind speed (Kok et al., 2011a, 2011b). However, based on empirical observations, Mahowald et al. (2014) contended that this applies only to the >5 µm size fraction and that the size distribution of the emitted dust <5 µm is independent of soil PSD and wind speed. The coarser dust particles (>5 µm) constitute a substantial fraction of the vertical dust flux and despite their size, are recognised as having the potential to travel far from the emission source (Ryder et al., 2013). For example, van der Does et al. (2016) recently found modal grain sizes between 4 and 32 µm along a transect in the Atlantic Ocean up to 4400 km from the north African source region. Their findings provide novel evidence that the transport of coarser dust fractions may be significant over much larger distances than previously considered. Such findings are based on measurement of deposited dust, but field-based methods to sample and measure aeolian dust at emission sources are required to elucidate controls on erodibility and characteristics of dust at uplift. Regional setting The ephemeral river valleys in the Namib Desert are major dust sources in southern Africa (Fig 1a), with large plumes visible on satellite imagery as dust is transported over the ocean during 170 strong autumn and winter easterly winds (Vickery et al., 2013; Dansie et al., 2017b). The Huab river catchment, one such dust bearing system, is located in a basement of the Upper Proterozoic to Cambrian Damara Sequence (Fig 1b), overlain by Carboniferous to Permian Karoo Supergroup sediments of fluvio-lacustrine and fluvio-marine origin (Jerram et al., 2000). An angular unconformity, with a gap of up to 120 Ma, exists between the Karoo Supergroup

address the need for a long-term research program to meet critical challenges in wind erosion research 8 and management in the United States. The Network has three aims: (1) provide data to support 9 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.

Records of solar array currents recorded by the InSight lander during its first 200 sols on Mars are presented. In addition to the geometric variation in illumination on seasonal and diurnal timescales, the data are influenced by dust suspended in the atmosphere and deposited on the solar panels. Although no dust devils have been detected by InSight's cameras, brief excursions in solar array currents suggest that at least some of the vortices detected by transient pressure drops are accompanied by dust. A step increase in array output (i.e., a "cleaning event") was observed to be directly associated with the passage of a strong vortex. Some quasiperiodic variations in solar array current are suggestive of dust variations in the planetary boundary layer. Nonzero array outputs before sunrise and after sunset are indicative of scattering in the atmosphere: A notable increase in evening twilight currents is observed associated with noctilucent clouds, likely of water or carbon dioxide ice. Finally, although the observations are intermittent (typically a few hours per sol) and at a modest sample rate (one to two samples per minute), three single-sample light dips are seen associated with Phobos eclipses. These results demonstrate that engineering data from solar arrays provide valuable scientific situational awareness of the Martian environment.

Barren ground and sites with low coverage by vegetation (e.g., dunes, soil surfaces, dry lakes, and riverbeds) are the main source areas of sand and dust storms (SDS). The understanding of causes, processes (abrasion, deflation, transport, deposition), and influencing factors of sandy and dusty particles moving by wind both in the boundary layer and in the atmosphere are basic prerequisites to distinguish between SDS. Dust transport in the atmosphere modulates radiation, ocean surface temperature, climate, as well as snow and ice cover. The effects of airborne particles on land are varied and can cause advantages and disadvantages, both in source areas and in sink or deposition areas, with disturbances of natural environments and anthropogenic infrastructure. Particulate matter in general and SDS specifically can cause severe health problems in human respiratory and other organs, especially in children. Economic impacts can be equally devastating, but the costs related to SDS are no...

Loess accumulated in the Negev desert during the Pleistocene and primary and secondary loess remains cover large parts of the landscape. Holocene loess deposits are however absent. This could be due low accumulation rates, lack of preservation, and higher erosion rates in comparison to the Pleistocene. This study hypothesized that archaeological ruins preserve Holocene dust. We studied soils developed on archaeological hilltop ruins in the Negev and the Petra region and compared them with local soils, paleosols, geological outcrops, and current dust. Seven statistically modeled grain size end-members were identified and demonstrate that the ruin soils in both regions consist of mixtures of local and remote sediment sources that differ from dust compositions deposited during current storms. This discrepancy is attributed to fixation processes connected with sediment-fixing agents such as vegetation, biocrusts, and/or clast pavements associated with vesicular layers. Average dust accretion rates in the ruins are estimated to be~0.14 mm/a, suggesting that 30% of the current dust that can be trapped with dry marble dust collectors has been stored in the ruin soils. Deposition amounts and grain sizes do not significantly correlate with wind intensity. However, precipitation may have contributed to dust accretion. A snowstorm in the Petra region delivered a significantly higher amount of sediment than rain or dry deposition. Snowfall dust had a unique particle size distribution relatively similar to the ruin soils. Wet deposition and snow might catalyze dust deposition and enhance fixation by fostering vegetation and crust formation. More frequent snowfall during the Pleistocene may have been an important mechanism of primary loess deposition in the southern Levant.

Interaction between seawater and benthic sediments plays an important role in global biogeochemical cycling. Benthic fluxes of chemical elements (C, N, P, O, Si, Fe, Mn, S) directly affect redox state and acidification (i.e. pH and carbonate saturation), which in turn determine the functioning of the benthic and pelagic ecosystems. The redox state of the near bottom layer can change and oscillate in many regions responding to the supply of organic matter, physical regime and coastal discharge. The goal of this work was to develop a model that captures key biogeochemical processes occurring at the bottom boundary layer and…

This dataset contains supplementary data for the article Khosravichenar et al. (2023): "Assessing a multi-method approach for dryland soil salinization with respect to climate change and global warming – The example of the Bajestan region (NE Iran)" (Ecological Indicators 154, 110639): (1) Figure SF-1: Photos of the six derived soil salinity classes, (2) Table ST-1: The ten soil salinity indices applied during this study, (3) Table ST-2: Annual climatic data from the Tabas synoptic station 1961-2021 (4) Table ST-3: Spatial distribution of the six soil salinity classes, the extension of wet/water-covered areas and the NDVI in the study area 1992 – 2021 (5) Table ST-4: Cross-correlations between soil salinity in the Bajestan region, regional climate parameters, the wet/water-covered area in the playa basin during February/March, and the NDVI.

Dryland soil salinization strongly affects soil properties, with severe consequences for regional ecology, agriculture and the aeolian dust dynamics. Given its climate-sensitivity it forms a serious environmental hazard, and to cope with this challenge during current global warming it needs to be better understood. The Bajestan Playa in the strongly salinization-affected Iranian drylands hosts several protected areas and forms an important regional dust source. Hence, soil salinization in this region affects local and regional ecosystems and societies, but was not systematically studied yet. Using an unprecedented comprehensive approach we systematically monitored regional soil salinity 1992–2021 using remote sensing as well as on-site field and laboratory measurements, and linked these with regional and global climatic data to understand (i) the spatio-temporal soil salinity dynamics, (ii) the impact of regional and global climate changes, and (iii) the potential of our approach for further soil salinity studies.

Our annual time resolution over three decades provided significantly deeper and unprecedented insights into soil salinization: Both regional annual precipitation and temperature control soil salinity, but the latter responds to precipitation with time lags of up to two years and to higher temperatures without any time lag. This probably reflects the transport time of leached soluble salts from their sources following humid years. No systematic soil salinity changes were observed within the playa basin, but outside the basin soil salinity systematically increased. Whereas regional precipitation did not show a systematic trend during the last decades, regional temperature increased and was mostly correlated with the increasing GLOTI, POL and TSA climatic indices. Hence, given ongoing global warming a further increase of regional soil salinization should be expected, with serious consequences for saline dust emissions, the regional protected areas and climate-related migrations. Altogether, our multi-disciplinary pioneer study demonstrates a high future application potential also for other salinity-affected drylands, forming a base to deal with the consequences of ongoing global climate change.

Archaeological structures are often filled with sediments and may serve as effective dust traps. The physical parameters and chemical composition of archaeological soils in hilltop ruins, ancient runoff-collecting terraces, and cleanout spoils of cisterns were determined in the Petra region in southern Jordan and the Northern Negev in Israel. Different types of ruins are characterized by certain soil structures, but could not be distinguished with regard to substrate composition. This reflects a predominance of aeolian processes for primary sedimentation, while fluvial processes seem to only re-distribute aeolian material. In the Petra region, the physical and chemical properties of all archaeological soils show a significant local contribution from associated weathered rocks. Compared to modern settled dust, archaeological soils in Southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This seems connected...

Wind erosion is a global environmental problem. Re-vegetating land is a commonly used method to reduce the negative effects of wind erosion. However, there is limited knowledge on the effect of vegetation pattern on wind-blown mass transport. The objective of this study was to investigate the effect of vegetation pattern on this phenomenon within a land unit and at the border between land units. Wind tunnel experiments were conducted with artificial shrubs representing Atriplex halimus. Wind runs at a speed of 11 m s-1 were conducted and sand translocation was measured after 200-230 s using a graph paper prepared for this purpose. This research showed that: 1) the transport within a land unit is affected by the neighboring land units and by the vegetation pattern within both the unit itself and the neighboring land units; 2) re-vegetation plans for degraded land can take into account the 'streets' effect (zones of erosion areas similar to streets); 3) the effect of neighboring land units includes sheltering effect and the regulation of sediment passing from one land unit to the neighboring land units and 4) in addition to investigation of the general effect of vegetation pattern on erosion and deposition within the region, it is important to investigate the redistribution of sediment at smaller scales depending on the scope of the project.

The extensive loess deposits of the Eurasian midlatitudes provide important terrestrial archives of Quaternary climatic change. As yet, however, loess records in Central Asia are poorly understood. Here we investigate the grain size and magnetic characteristics of loess from the Nilka (NLK) section in the Ili Basin of eastern Central Asia. Weak pedogenesis suggested by frequency-dependent magnetic susceptibility (χ fd %) and magnetic susceptibility (MS) peaks in primary loess suggest that MS is more strongly influenced by allogenetic magnetic minerals than pedogenesis, and may therefore be used to indicate wind strength. This is supported by the close correlation between variations in MS and proportions of the sand-sized fraction. To further explore the temporal variability in dust transport patterns, we identified three grain size end-members (EM1, mode size 47.5 µm; EM2, 33.6 µm; EM3, 18.9 µm) which represent distinct aerodynamic environments. EM1 and EM2 are inferred to represent grain size fractions transported from proximal sources in short-term, near-surface suspension during dust outbreaks. EM3 appears to represent a continuous background dust fraction under non-dust storm conditions. Of the three end-members, EM1 is most likely the most sensitive recorder of wind strength. We compare our EM1 proportions with mean grain size from the Jingyuan section in the Chinese loess plateau, and assess these in the context of modern and Holocene climate data. Our research suggests that the Siberian High pressure system is the dominant influence on wind dynamics, resulting in loess deposition in the eastern Ili Basin. Six millennial-scale cooling (Heinrich) events can be identified in the NLK loess records. Our grain size data support the hypothesis that the Siberian High acts as teleconnection between the climatic systems of the North Atlantic and East Asia in the high northern latitudes, but not for the mid-latitude westerlies.

Wind erosion is a global environmental problem. Re-vegetating land is a commonly used method to reduce the negative effects of wind erosion. However, there is limited knowledge on the effect of vegetation pattern on wind-blown mass transport. The objective of this study was to investigate the effect of vegetation pattern on this phenomenon within a land unit and at the border between land units. Wind tunnel experiments were conducted with artificial shrubs representing Atriplex halimus. Wind runs at a speed of 11 m s-1 were conducted and sand translocation was measured after 200-230 s using a graph paper prepared for this purpose. This research showed that: 1) the transport within a land unit is affected by the neighboring land units and by the vegetation pattern within both the unit itself and the neighboring land units; 2) re-vegetation plans for degraded land can take into account the 'streets' effect (zones of erosion areas similar to streets); 3) the effect of neighboring land units includes sheltering effect and the regulation of sediment passing from one land unit to the neighboring land units and 4) in addition to investigation of the general effect of vegetation pattern on erosion and deposition within the region, it is important to investigate the redistribution of sediment at smaller scales depending on the scope of the project.

Human population is interrelated with the demand of fuel, water and food. This is consequently leading to increasing rates of energy use and therefore greenhouse gas (GHG) emissions. Globally, the atmospheric concentrations of GHG have increased by approximately 35% for carbon dioxide, 148% for methane, and 14% for nitrous oxide. Desert ecosystems, in particular, are highly variable and unpredictable, where organisms and humans have utilized arid environments regardless of their naturally uncertain availability of resources. The fast spread of desertification has led to environmental degradation, unstable local political situations and economic losses. The extreme weather events in the past two decades caused many loses in terms of ecosystem alteration, economic impacts as well as social influences. Dryland communities adapt to dynamic climatic and environmental conditions due to rainfall variability. Unfortunately, climate change impact is not fully understood. The effects of clima...

This work presents the analysis of the long-term observations of aerosol optical properties in the central region of Argentina. Monitoring of aerosol parameters was carried out at the Cordoba-CETT AERONET site (311 31′ S, 641 27′ W, 730 m.a.s.l.) from November 1999 until December 2010. Long-term measurements of aerosol optical depth, Ångström exponent, fine mode fraction and single scattering albedo were analyzed and compiled to describe the climatology of the optical properties of the aerosols of the region. The knowledge of the optical properties of aerosols and their spatial distribution is required to evaluate aerosol effects on the climate system. This information provides an opportunity for understanding how aerosols might influence the regional radiation budget. Results show that aerosol optical depth at 340 nm is characterized by low values from February to April (monthly average of 0.15 7 0.05), very low values from May to June (monthly average of 0.08 70.03) and a sustained increase from July to September (monthly average of 0.20 70.09) reaching a value of 0.26. From this dataset, no long-term trends are observable. Results of the inter-annual variations of the Ångström exponent between 440 and 870 nm reflect an important difference in the year 2004 compared to the other 11 years of the study. A possible explanation of this fact is elaborated with the help of back trajectory analysis. Finally, three episodes are described and analyzed, as they produced important increases of the daily aerosol optical depth value. We explained these episodes with a combination of air mass trajectory analysis, meteorology and the MODIS fire counts product.

We investigated mineral aerosol (dust) deposition in the Aral Sea with intention to understand the variability of dust in central Asia and its implications for atmospheric circulation change in the late Holocene. Using an 11.12-m sediment core of the lake, we calculated bulk sediment fluxes at high time-resolution and analyzed grain-size distributions of detrital sediments. A refined age-depth model was established by combined methods of radiocarbon dating and archeological evidence. Besides, a principal component analysis (PCA) of grain-size fractions and elements (Fe, Ti, K, Ca, Sr) was used to assess the potential processes controlling detrital inputs. The results suggest that two processes are mainly relevant for the clastic input as the medium silt fractions and Ti, Fe and K are positively correlated with Component 1 (C1), and the fine size fractions (<6 µm) are positively correlated with Component 2 (C2). Taking the results of the PCA, geological backgrounds, clastic input processes into account, we propose that the medium silt fractions and, in particular, the grain-size fraction ratio (6-32 µm/2-6 µm), can serve as indicators of the variability of airborne dust in the Aral Sea region. On the contrary, the fine size fractions appear to be contributed mainly by the sheetwash processes. The bulk sediment deposition fluxes were extremely high during the Little Ice Age (LIA; AD 1400-1780), which may be related to the increased dust deposition. As indicated by the variations of grainsize ratio and Ti, the history of dust deposition in central Asia can be divided into five distinct periods, with a remarkably low deposition during AD 1-350, a moderately high value from AD 350-720, a return to relatively low level between AD 720 and AD 1400 (including the Medieval Warm Period (MWP, AD 755-1070)), an exceptionally high deposition from AD 1400 to 1940s and an abnormally low value since 1940s. The temporal variations in the dust deposition are consistent with the changes in the Siberian High (SH) and mean atmospheric temperature of the northern hemisphere during the past 2000 years, with low/high annual temperature anomalies corresponding to high/low dust supplies in the Aral Sea sediments, respectively. The variations in the fine size fraction also show a broadly similarity to a lacustrine δ 18 O record in Turkey (Jones et al., 2006), implying that there was less moisture entering western central Asia from the Mediterranean during the LIA than during the MWP.

Variations in deposition of terrigenous fine sediments and their grain-size distributions from a high-resolution marine sediment record offshore northwest Africa (30°51.0′N; 10°16.1′W) document climate changes on the African continent during the Holocene. End-member grain-size distributions of the terrigenous silt fraction, which are related to fluvial and aeolian dust transport, indicate millennial-scale variability in the dominant transport processes at the investigation site off northwest Africa as well as recurring periods of dry conditions in northwest Africa during the Holocene. The terrigenous record from the subtropical North Atlantic reflects generally humid conditions before the Younger Dryas, during the early to mid-Holocene, as well as after 1.3 kyr BP. By contrast, continental runoff was reduced and arid conditions were prevalent at the beginning of the Younger Dryas and during the mid-and late Holocene. A comparison with high-and low-latitude Holocene climate records reveals a strong link between northwest African climate and Northern Hemisphere atmospheric circulation throughout the Holocene. Due to its proximal position, close to an ephemeral river system draining the Atlas Mountains as well as the adjacent Saharan desert, this detailed marine sediment record, which has a temporal resolution between 15 and 120 years, is ideally suited to enhance our understanding of ocean-continent-atmosphere interactions in African climates and the hydrological cycle of northern Africa after the last deglaciation.

A set of 40 Uranium-series datings obtained on the reef-forming scleractinian cold-water corals Lophelia pertusa and Madrepora oculata revealed that during the past 400 kyr their occurrence in the Gulf of Cádiz (GoC) was almost exclusively restricted to glacial periods. This result strengthens the outcomes of former studies that coral growth in the temperate NE Atlantic encompassing the French, Iberian and Moroccan margins dominated during glacial periods, whereas in the higher latitudes (Irish and Norwegian margins) extended coral growth prevailed during interglacial periods. Thus it appears that the biogeographical limits for sustained cold-water coral growth along the NE Atlantic margin are strongly related to climate change. By focussing on the last glacial-interglacial cycle, this study shows that palaeo-productivity was increased during the last glacial. This was likely driven by the fertilisation effect of an increased input of aeolian dust and locally intensified upwelling. After the Younger Dryas cold event, the input of aeolian dust and productivity significantly decreased concurrent with an increase in water temperatures in the GoC. This primarily resulted in reduced food availability and caused a widespread demise of the formerly thriving coral ecosystems. Moreover, these climate induced changes most likely caused a latitudinal shift of areas with optimum coral growth conditions towards the northern NE Atlantic where more suitable environmental conditions established with the onset of the Holocene.

, a large amount of airborne dust fell with rain over Canberra, located some 200 km from Australia's east coast, and at an average altitude of 650 m. It is estimated that during that night about 6 g m À2 of aeolian dust fell. We have conducted a vast number of analyses to ''fingerprint'' some of the dust and used the following techniques: grain size analysis; scanning electron microscope imagery; major, trace, and rare earth elemental, plus Sr and Nd isotopic analyses; organic compound analyses with respective compound-specific isotope analyses; pollen extraction to identify the vegetation sources; and molecular cloning of 16S rRNA genes in order to identify dust bacterial composition. DNA analyses show that most obtained 16S rRNA sequences belong mainly to three groups: Proteobacteria (25%), Bacteriodetes (23%), and gram-positive bacteria (23%). In addition, we investigated the meteorological conditions that led to the dust mobilization and transport using model and satellite data. Grain sizes of the mineral dust show a bimodal distribution typical of proximal dust, rather than what is found over oceans, and the bimodal aspect of size distribution confirms wet deposition G

Wind erosion is a global environmental problem. Re-vegetating land is a commonly used method to reduce the negative effects of wind erosion. However, there is limited knowledge on the effect of vegetation pattern on wind-blown mass transport. The objective of this study was to investigate the effect of vegetation pattern on this phenomenon within a land unit and at the border between land units. Wind tunnel experiments were conducted with artificial shrubs representing Atriplex halimus. Wind runs at a speed of 11 m s-1 were conducted and sand translocation was measured after 200-230 s using a graph paper prepared for this purpose. This research showed that: 1) the transport within a land unit is affected by the neighboring land units and by the vegetation pattern within both the unit itself and the neighboring land units; 2) re-vegetation plans for degraded land can take into account the 'streets' effect (zones of erosion areas similar to streets); 3) the effect of neighboring land units includes sheltering effect and the regulation of sediment passing from one land unit to the neighboring land units and 4) in addition to investigation of the general effect of vegetation pattern on erosion and deposition within the region, it is important to investigate the redistribution of sediment at smaller scales depending on the scope of the project.

We present a dust plume source inventory for southern Africa. In order to locate and track the local, short-lived plume events, source and frequency data have been derived from Meteosat Second Generation (MSG) thermal infrared composite data (4 km data using 8.7, 10.8, and 12.0 μm) and Moderate Resolution Imaging Spectroradiometer (MODIS) visible composite data (0.25 km data utilizing 0.620-0.670 μm, 0.545-0.565 μm, and 0.459-0.479 μm). Between January 2005 and December 2008, a total of 328 distinct daytime dust plumes more than 10 km in length were detected. These plumes were attributed to 101 distinct point sources, consisting largely of ephemeral inland lakes, coastal pans as well as dry river valleys in Namibia, Botswana, and South Africa. These data also provided sub-basin scale source observations for large basins such as Etosha and Makgadikgadi Pans.

A decline in water quality attributed to excessive inputs of phosphorus has been observed in Lake Simcoe over the past few decades. Various studies have estimated that 25-50% of the total phosphorus entering the lake is from atmospheric deposition. Bare soil exposure in the spring due to lack of vegetative cover, along with soil disturbance related to agricultural activities, results in higher susceptibility to wind erosion and dust emission. This study introduces the new concept of Dust Response Units (DRUs), which combine soil type and land use to determine the dust emission susceptibility based on the hourly variation of wind speed and monthly changes in soil cover due to crop growth. The Wind Erosion Prediction System (WEPS) was used to determine dust emission suppression factors for a combination of 11 different soils and 6 dominant agricultural land uses, totaling 66 different DRUs in the Lake Simcoe airshed. Employing a widely used dust emission model and applying these dust emission suppression factors resulted in the identification of high risk DRUs. Twelve of the potential 66 DRUs were determined to contribute 85% of the total crop dust emissions within the Lake Simcoe airshed, including sand, loam, sandy loam, and loamy sand soils combined with row crop, mixed, and hay and pasture land management operations. This study demonstrates a new method to map high priority areas for targeted implementation of dust control best management practices that could be useful in agricultural areas both within and beyond the Lake Simcoe airshed.

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.

The direct aerosol radiative effects of biomass-burning (BB) aerosols over northern Indochina were estimated by using aerosol properties (physical, chemical, and optical) along with the vertical profile measurements from ground-based measurements with integration of an optical and a radiative transfer model during the Seven South East Asian Studies/ Biomass-Burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment (7-SEAS/BASELInE) conducted in spring 2013. Cluster analysis of backward trajectories showed the air masses arriving at mountainous background site (Doi Ang Khang; 19.93°N, 99.05°E, 1536 m above mean sea level) in northern Indochina, mainly from near-source inland BB activities and being confined in the planetary boundary layer. The PM 10 and black carbon (BC) mass were 87 ± 28 and 7 ± 2 µg m-3 , respectively. The aerosol optical depth (AOD 500) was found to be 0.26-1.13 (0.71 ± 0.24). Finer (fine mode fraction ≈0.95, angstrom-exponent at 440-870 nm ≈1.77) and significantly absorbing aerosols (singlescattering albedo ≈0.89, asymmetry-parameter ≈0.67, and absorption AOD ≈0.1 at 440 nm) dominated over this region. BB aerosols (water soluble and BC) were the main contributor to the aerosol radiative forcing (ARF), while others (water insoluble, sea salt and mineral dust) were negligible mainly due to their low extinction efficiency. BC contributed only 6% to the surface aerosol mass but its contribution to AOD was 12% (2 times higher). The overall mean ARF was-8.0 and-31.4 W m-2 at top-of-atmosphere (TOA) and at the surface (SFC), respectively. Likely, ARF due to BC was +10.7 and-18.1 W m-2 at TOA and SFC, respectively. BC imposed the heating rate of +1.4 K d-1 within the atmosphere and highlighting its pivotal role in modifying the radiation budget. We propose that to upgrade our knowledge on BB aerosol radiative effects in BB source region, the long-term and extensive field measurements are needed.

The most important properties affecting the soil loss and runoff were investigated, and the effects of land use on the soil properties, together with the erodibility indices in a semiarid zone, central Iran, were evaluated. The locations of 100 positions were acquired by cLHS and 0-5-cm surface soil layer samples were used for laboratory analyses from the Borujen Region, Chaharmahal-Va-Bakhtiari Province, central Iran. To measure in situ runoff and soil erodibility of three different land uses comprising dryland, irrigated farming, and rangeland, a portable rainfall simulator was used. The results showed that the high variations (coefficient of variation, CV) were obtained for electrical conductivity (EC), mean weight diameter (MWD), soil organic carbon (SOC), and soil erodibility indices including runoff volume, soil loss, and sediment concentration (CV ~ 43.6-77.4%). Soil erodibility indices showed positive and significant correlations with bulk density and negative correlations w...

Radiative control of surface temperature is a key characteristic of the martian environment and its lowdensity atmosphere. Here we show through meteorological modeling that surface temperature can be far from radiative equilibrium over numerous sloping terrains on Mars, where nighttime mesoscale katabatic winds impact the surface energy budget. Katabatic circulations induce both adiabatic atmospheric heating and enhancement of downward sensible heat flux, which then becomes comparable to radiative flux and acts to warm the ground. Through this mechanism, surface temperature can increase up to 20 K. One consequence is that warm signatures of surface temperature over slopes, observed through infrared spectrometry, cannot be systematically associated with contrasts of intrinsic soil thermal inertia. Apparent thermal inertia maps retrieved thus far possibly contain wind-induced structures. Another consequence is that surface temperature observations close to sloping terrains could allow the validation of model predictions for martian katabatic winds, provided contrasts in intrinsic thermal inertia can be ruled out. The thermal impact of winds is mostly discussed in this paper in the particular cases of Olympus Mons/Lycus Sulci and Terra Meridiani but is generally significant over any sloped terrains in low thermal inertia areas. It is even general enough to apply under daytime conditions, thereby providing a possible explanation for observed afternoon surface cooling, and to ice-covered terrains, thereby providing new insights on how winds could have shaped the present surface of Mars.

In this study, the summer total cloud cover (TCC) weekly cycle over Europe is investigated using MODIS and ISCCP satellite data in conjunction with aerosol optical depth (AOD) MODIS data. Spatial weekly patterns are examined at a 1°× 1°(MODIS) and 250 × 250 km 2 (ISCCP) resolution. Despite the noise in the TCC weekly cycle patterns, their large-scale features show similarities with the AOD 550 patterns. Regions with a positive (higher values during midweek) weekly cycle appear over Central Europe, while a strong negative (higher values during weekend) weekly plume appears over the Iberian Peninsula and the NorthEastern Europe. The TCC weekly variability exhibits a very good agreement with the AOD 550 weekly variability over Central, SouthWestern Europe and NorthEastern Europe and a moderate agreement for Central Mediterranean. The MODIS derived TCC weekly variability shows reasonable agreement with the independent ISCCP observations, thus supporting the credibility of the results. TCC and AOD 550 correlations exhibit a strong slope for the total of the 6 regions investigated in this work with the slopes being higher for regions with common TCC-AOD 550 weekly variabilities. The slope is much stronger for AOD 550 values less than 0.2 for Central and SouthWestern Europe, in line with previous studies around the world. Possible scenarios that could explain the common weekly variability of aerosols and cloud cover through the aerosol indirect effects are discussed here also taking into account the weekly variability appearing in ECA&D E-OBS rainfall data.

Surface-based measurements of terrestrial and martian dust devils/convective vortices provided from mobile and stationary platforms are discussed. Imaging of terrestrial dust devils has quantified their rotational and vertical wind speeds, translation speeds, dimensions, dust load, and frequency of occurrence. Imaging of martian dust devils has provided translation speeds and constraints on dimension, but only limited vertical constraints on vertical motion within a vortex. The longer mission durations on Mars afforded by long operating robotic landers and rovers have provided statistical quantification of vortex occurrence (time-of-sol, and recently seasonal) that has until recently not been a primary outcome of more temporally limited terrestrial dust devil measurement campaigns. Terrestrial measurement campaigns have included a more extensive range of measured vortex parameters (pressure, wind, morphology, etc.) than have martian opportunities, with electric field and direct measure of abundance not yet obtained on Mars. No martian robotic mission has yet provided contemporaneous high frequency wind and pressure measurements. Comparison of measured terrestrial and martian dust devil characteristics suggests that martian dust devils are larger and possess faster maximum rotational wind speeds, that the absolute magnitude of the pressure deficit within a terrestrial dust devil is an order of magnitude greater than a martian dust devil, and that the time-of-day variation in vortex frequency is similar. Recent terrestrial investigations have demonstrated the presence of

Introduction. The predominance of aeolian (wind-driven) activity as a surface modifying agent on Mars has been recognized throughout the history of telescopic, satellite, and robotic investigation of the planet. The most obvious expressions of aeolian processes are manifested in dunes, yardangs (aerodynamic ridges in bedrock) [1,2], sand ripples [3,4], and Transverse Aeolian Ridges (TARs) [5]. TAR is a nongenetic general term proposed for linear to curvilinear aeolian features. Since their first recognition, the origin of TARs remains an area of healthy debate, are TARs small dunes or are they large ripples? The answer to this question is critical to understanding the way the wind works on the martian surface and this has implications for NASA strategic interests in area of sustained human and robotic exploration of Mars. The challenge is that to answer the questions of origin, we need to understand the details of shape, size, and spatiotemporal development of the bedforms, and the size and density of the grains that form them. Although the resolution of remotely sensed data improves rapidly, down to 25cm/pixel with HiRiSE, we are still not capable of resolving sediment-size distributions [6]. Until we can do this, our understanding of aeolian processes on Mars will remain limited to the few lander and rover sites. Thus, we still rely heavily on our understanding of similar features on Earth as analogs both in terms of form and process. Recent rover investigations of Martian TARs provide perhaps the most definitive data [7].