Largest Dust Source Research Articles

Wind erosion caused by the change of Chaiwopu lake on the northern foothill of Tianshan Mountain, based on SBAS-InSAR

In arid regions, terminal lakes play a crucial role in maintaining the local ecological environment. However, due to the impact of climate change and human activities, terminal lakes are prone to shrinkage and drying up. The exposed lakebeds became new sources of sand and dust, leading to severe land degradation. This study extracted the water surface area of the Chaiwopu Lake in Urumqi and calculated the fractional vegetation cover (FVC) in the surrounding areas based on Landsat images from 2000 to 2022. The changes in FVC and lake area before and after the implementation of the policies on fallow and groundwater extraction restriction in 2014 were analyzed. Using the SBAS-InSAR method, the surface deformation during the period of minimum lake area from 2014 to 2018 was estimated, and the process of wind erosion and accumulation in the dried lake basin was analyzed. The results showed that from 2011 to 2014, Chaiwopu Lake experienced rapid shrinkage, and the lake almost disappeared. After 2014, the lake rapidly recovered, reaching 70% of its original area by 2021. With the recovery of the lake, the vegetation coverage in the surrounding area has changed from decreasing to increasing. During the period of lake shrinkage, the dried lake basin experienced severe wind erosion, with the maximum erosion rate exceeding 40 mm/year. The sand and dust from the dried lake basin accumulated around the lake under the influence of wind, further accelerating land degradation in the surrounding areas. After 2021, the restored lake and wetland surface covered the once-dry lake basin again, and the largest dust source in the region nearly disappeared. The study results indicated that the restoration of the lake and surrounding vegetation can eliminate the sources of sand and dust and prevent their transportation, effectively preventing land desertification.

Prediction of road dust concentration in open-pit coal mines based on multivariate mixed model.

The problem of dust pollution in the open-pit coal mine significantly impacts the health of staff, the regular operation of mining work, and the surrounding environment. At the same time, the open-pit road is the largest dust source. Therefore, it analyzes the influencing factors of road dust concentration in the open-pit coal mine. It is of practical significance to establish a prediction model for scientific and effective prediction of road dust concentration in the open pit coal mine. The prediction model helps reduce dust hazards. This paper uses the hourly air quality and meteorological data of an open-pit coal mine in Tongliao City, Inner Mongolia Autonomous Region, from January 1, 2020, to December 31, 2021. Create a CNN-BiLSTM-Attention multivariate hybrid model consisting of a Convolutional Neural Network (CNN), a bidirectional long short-term memory neural network (BiLSTM), and an attention mechanism, Prediction of PM2.5 concentration in the next 24h. Establish prediction models of parallel and serial structures, and carry out many experiments according to the change period of the data to determine the optimal configuration and the input and output size. Then, a comparison of the proposed model and Lasso regression, SVR, XGBoost, LSTM, BiLSTM, CNN-LSTM, and CNN-BiLSTM models for short-term prediction (24h) and long-term prediction (48h, 72h, 96h, and 120h). The results show that the CNN-BiLSTM-Attention multivariate mixed model proposed in this paper has the best prediction performance. The mean absolute error (MAE), root mean square error (RMSE), and coefficient of determination (R2) of the short-term forecast (24h) are 6.957, 8.985, and 0.914, respectively. Evaluation indicators of long-term forecasts (48h, 72h, 96h, and 120h) are also superior to contrast models. Finally, we used field-measured data to verify, and the obtained evaluation indexes MAE, RMSE, and R2 are 3.127, 3.989, and 0.951, respectively. The model-fitting effect was good.

Spatial and Temporal Variation of the Near-Surface Wind Environment in the Sahara Desert, North Africa

The Sahara Desert is the largest source of dust on Earth, and has a significant impact on global atmospheric changes. Wind is the main dynamic factor controlling the transport and intensity of dust in the Sahara Desert. This study comprehensively analyzed the spatial and temporal variation in the wind regime of the Sahara Desert from 1980 to 2019 using data from 17 meteorological stations to improve awareness of global atmospheric changes and the intensity of regional aeolian activities. All wind speed parameters decreased from northwest to southeast. While there were significant differences in the trends of temporal variation in wind speed among the different regions, there was an overall decreasing trend across the Sahara Desert, with an average wind speed of 0.09 m s−1 10 a−1. This decrease was closely related to wind frequency. The easterly, westerly, and northerly winds dominated, with more complex wind direction in the northern region. Seasonal differences in wind direction were observed in all regions. The wind direction frequency of wind speeds >6 m s−1 exceeded those with wind speeds <6 m s−1 in the western and northern regions, whereas other regions showed an opposite pattern. The highest drift potential (DP) and resultant drift potential (RDP) were found in the western and northern regions, and during spring and winter. There was a trend of decreasing annual variation in DP and RDP in all regions. The directional variability (RDP/DP) indicated mostly intermediate and high variability in wind direction. Resultant drift direction (RDD) indicated that a mainly southwest wind direction. No apparent trends in temporal variation in RDD and RDP/DP were observed. Total DP was strongly influenced by DP and the magnitude and frequency of strong winds in the prevailing wind direction. No strong correlation between wind regimes and dune types was observed in this desert, indicating the complexity of factors affecting dune morphology.

Eolian dust activity during the last ~850 years on the southeastern margin of the arid Central Asia

Eolian dust activity studies on the arid Central Asia (ACA), one of the world's largest dust sources, are of great importance to the global climatic system. Grain size distributions (GSDs) can provide information on sediment sources, transport processes and sedimentary environments. As a result, GSD is the most frequently applied proxy in reconstruction of past eolian dust activities of the ACA using lake sediments. The GSD dataset for a core spanning the last ~850 years from Kuhai Lake on the northeastern Tibetan Plateau was unmixed by end-member analysis (EMA) for reconstruction of past eolian dust activities on the southeastern margin of the ACA. The results suggest that EM 2 and EM 3, which were added together to form an eolian dust activity proxy, represent the proximal eolian suspension and saltation loads, respectively. The fractional abundances of EMs suggest that siliciclastic materials in the studied core were mainly from eolian contributions. The occurrence of enhanced eolian dust activities within the cold Little Ice Age period together with the GSDs of EM 2 and EM 3 indicate that eolian dust activities on the southeastern margin of the ACA were basically governed by the Siberian High-produced Asian Winter Monsoon over the last millennium. At decadal to centennial scales, enhanced eolian dust activities generally correspond to warm periods with high total solar irradiance (TSI). Increased temperatures as the result of high TSI would have caused larger increases in evaporation than in precipitation, and hence deteriorated vegetation cover and increased dust sources availability.

Particulate matter (PM10 and PM2.5) concentrations during a Saharan dust episode in Istanbul

Istanbul, the biggest city of Turkey, is in a common route for air parcels. Air pollutants are carried over the city from Asian, African, and European continents. Sahara Desert, the largest dust source on earth, affects Turkey’s air qualities substantially due to millions of tons of mineral dust being transported from the African continent towards Turkey every year. Although the effect of Saharan dust transportation on PM10 concentrations in Turkey was examined many times, its effect on PM2.5 concentrations has not been studied yet sufficiently. In February 2015, Istanbul experienced a Saharan dust episode and during this event the concentrations of particulate matter rose to very high levels. This study focuses on particulate matter concentrations (PM10 and PM2.5) during this Saharan dust episode to better understand the effect of dust transportation on Istanbul’s air quality. HYSPLIT trajectory model, satellite products, and air quality monitoring data from ground observations were utilized. We show that the PM10 concentrations increased significantly during the dust episode while PM2.5 concentrations didn’t increase considerably. There was only a slight rise in the values of PM2.5. The significant increase for the PM10 values can be explained by the higher gravitational settling velocities of coarse particles in the atmosphere.

African dust deposition in Puerto Rico: Analysis of a 20-year rainfall chemistry record and comparison with models

Dust deposition represents an important flux of rock-derived nutrients such as phosphorus to ecosystems on highly weathered soils. Direct measurements of terrestrial dust deposition and its spatial variability are rare, yet they are essential for testing models of dust deposition processes and understanding the biogeochemical effects of dust. Long-term records of precipitation chemistry are available in the Luquillo Mountains of Puerto Rico, which are downwind of the world's largest dust source in Africa. We analyzed 20-year datasets of openfall, throughfall, and wet-only precipitation chemistry with weekly resolution at two different locations in the Luquillo Mountains to evaluate spatial and temporal variability of dust inputs and compare the observational records with models. Based on rainwater dissolved silica and total suspended solids content, the measured dust flux varied by a factor of 2 over a distance of 10 km despite similarities between sites in elevation and rainfall amount. In comparison with simulated dust deposition from ten models in the Aerosol Comparisons between Observations and Models (AeroCom) project, the empirical rainfall chemistry agrees well with the mean of the models on the seasonal distribution of wet dust distribution. Both the data and the models show a summer maximum in wet dust deposition that is consistent with variation in transport pathways and the dust source area emission strength based on environmental conditions in the Sahel region. The rainfall chemistry record and AeroCom models also agree in terms of attributing ~70% of the total dust deposition overall to dry deposition, although the range of uncertainty in the models is large. The results indicate value in combining long-term analysis of rainfall chemistry with data from satellites and models, and highlight the need for accurate ground-based metrics for dry deposition to improve understanding and modeling of dust deposition processes. The dataset complements earlier studies that characterize the dust plume originating from Northern Africa and its impact on ecosystems in South America and the Caribbean.

Using synchrotron radiation to study iron phases in Saharan dust samples from Athens skies

The Sahara desert is the largest source of dust in the world. Saharan dust is characterized by great com- plexity, composed mainly of mixtures of mineral phases (amorphous or crystalline, with particle sizes of the order of μm or even nm). The presence of amorphous components makes it difficult to detect their struc- ture. For this purpose the spectroscopic technique of X–ray absorption fine structure μ–XAFS combined to ultrabright synchrotron SR microbeams is suitable. SR’s main advantage is the recording of spectra in a very short time. In this paper we focus on the study of forms of iron deposited on southeast Mediterranean Sea and mainland of Greece by the waves of Saharan dust. Data collection was carried out at the premises of ANKA (KIT, Germany) on the beamline SUL–X of the environmental research laboratory with advanced X–ray spectroscopic techniques, μ–XRF, μ–XRD and μ–XAFS. Results from the measurements and the simulated spectrum are presented.

Palaeo-dust records: A window to understanding past environments

Dust entrainment, transport over vast distances and subsequent deposition is a fundamental part of the Earth system. Yet the role and importance of dust has been underappreciated, due largely to challenges associated with recognising dust in the landscape and interpreting its depositional history. Despite these challenges, interest in dust is growing. Technical advances in remote sensing and modelling have improved understanding of dust sources and production, while advances in sedimentology, mineralogy and geochemistry (in particular) have allowed dust to be more easily distinguished within sedimentary deposits. This has facilitated the reconstruction of records of dust emissions through time. A key advance in our understanding of dust has occurred following the development of methods to geochemically provenance (fingerprint) dust to its source region. This ability has provided new information on dust transport pathways, as well as the reach and impact of dust. It has also expanded our understanding of the processes driving dust emissions over decadal to millennial timescales through linking dust deposits directly to source area conditions. Dust provenance studies have shown that dust emission, transport and deposition are highly sensitive to variability in climate. They also imply that dust emissions are not simply a function of the degree of aridity in source areas, but respond to a more complex array of conditions, including sediment availability. As well as recording natural variability, dust records are also shown to sensitively track the impact of human activity. This is reflected by both changing dust emission rates and changing dust chemistry. Specific examples of how dust responds to, and records change, are provided with our work on dust emissions from Australia, the most arid inhabited continent and the largest dust source in the Southern Hemisphere. These case studies show that Australian dust emissions reflect hydro-climate variability, with reorganisation of Australian dust source areas occurring during the mid to late Holocene. Dust emissions are shown to sensitively map the structure of the Last Glacial Maximum in Australia, demonstrating that this period was associated with enhanced, but also variable dust emissions, driven by changing sources area conditions. Finally we show how dust emissions have responded to the arrival of Europeans and the associated onset of broad-scale agriculture across the Australian continent.

New Saharan wind observations reveal substantial biases in analysed dust‐generating winds

AbstractFor the remote Sahara, the Earth's largest dust source, there has always been a near‐absence of data for evaluating models. Here, new observations from the Fennec project are used along with Sahelian data from the African Monsoon Multidisciplinary Analysis (AMMA) to give an unprecedented evaluation of dust‐generating winds in the European Centre for Medium‐Range Weather Forecasts ERA‐Interim reanalysis (ERA‐I). Consistent with past studies, near‐surface, high‐speed winds are lacking in ERA‐I and the diurnal variability is under‐represented. During the summer monsoon season, correlations of ERA‐I with observed wind‐speed are low (∼0.35 in Sahel and 0.25–0.4 in the Sahara). Fennec data show for the first time that: (1) correlations are reduced even in the Sahara, not directly influenced by the monsoon, (2) the systematic underestimation of observed winds by ERA‐I in the summertime Sahel extends into the central Sahara: potentially explaining the failure of global models to capture the observed global dust maximum that occurs over the summertime Sahara (such as CMIP5), and demonstrates that modelled winds must be improved if they are to capture this key feature of the climatology.

Trans-Atlantic Connections between North African Dust Flux and Tree Growth in the Florida Keys, United States

Abstract Atmospheric mineral aerosols include multiple, interrelated processes and feedbacks within the context of land–atmosphere interactions and thus are poorly understood. As the largest dust source in the world, North Africa supplies mineral dust aerosols each year to the Caribbean region and southeastern United States that alter cloud processes, ocean productivity, soil development, and the radiation budget. This study uses a suite of Earth Observation and ground-based analyses to reveal a potential novel effect of atmospheric aerosols on Pinus elliottii var. densa cambial growth during the 2010 CE growing season from the Florida Keys. Over the Florida Keys region, the Earth Observation products captured increased aerosol optical thickness with a clear geographical connection to mineral dust aerosols transported from northern Africa. The MODIS Terra and Aqua products corroborated increased Ozone Monitoring Instrument (OMI) aerosol optical thickness values. Anomalously high Aerosol Robotic Network aerosol optical depth data corresponding with low Ångstrom coefficients confirm the presence of transported mineral dust aerosols during the period circa 4–20 July 2010. The fraction of photosynthetically absorbed radiation over the region during July 2010 experienced an anomalous decrease, concurrent with reduced incoming total and direct solar radiation resulting in a reduced growth response in P. elliottii. The authors pose one of the primary mechanisms responsible for triggering growth anomalies in P. elliottii is the reduction of total photosynthetically active radiation due to a dust-derived increase in aerosol optical depth. As a rare long-lived conifer (300+ years) in a subtropical location, P. elliottii could represent a novel proxy with which to reconstruct annual or seasonal mineral dust aerosol fluxes over the Caribbean region.

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

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

The Saharan Aerosol Long-Range Transport and Aerosol–Cloud-Interaction Experiment: Overview and Selected Highlights

Abstract North Africa is the world’s largest source of dust, a large part of which is transported across the Atlantic to the Caribbean and beyond where it can impact radiation and clouds. Many aspects of this transport and its climate effects remain speculative. The Saharan Aerosol Long-Range Transport and Aerosol–Cloud-Interaction Experiment (SALTRACE; www.pa.op.dlr.de/saltrace) linked ground-based and airborne measurements with remote sensing and modeling techniques to address these issues in a program that took place in 2013/14. Specific objectives were to 1) characterize the chemical, microphysical, and optical properties of dust in the Caribbean, 2) quantify the impact of physical and chemical changes (“aging”) on the radiation budget and cloud microphysical processes, 3) investigate the meteorological context of transatlantic dust transport, and 4) assess the roles of removal processes during transport. SALTRACE was a German-led initiative involving scientists from Europe, Cabo Verde, the Caribbean, and the United States. The Falcon research aircraft of the Deutsches Zentrum für Luft- und Raumfahrt (DLR), equipped with a comprehensive aerosol and wind lidar payload, played a central role. Several major dust outbreaks were studied with 86 h of flight time under different conditions, making it by far the most extensive investigation on long-range transported dust ever made. This article presents an overview of SALTRACE and highlights selected results including data from transatlantic flights in coherent air masses separated by more than 4,000-km distance that enabled measurements of transport effects on dust properties. SALTRACE will improve our knowledge on the role of mineral dust in the climate system and provide data for studies on dust interactions with clouds, radiation, and health.

Influence of dry‐season vegetation variability on Sahelian dust during 2002–2015

AbstractThe drivers of dust emission interannual variability in North Africa, the largest dust source on Earth, are still debated. Early studies outlined the role of previous‐season rainfall and vegetation growth, while some recent studies emphasize the role of wind variability. Here we use a newly developed estimation of dry‐season nonphotosynthetic vegetation cover in the Sahel based on Moderate Resolution Imaging Spectroradiometer (MODIS) short‐wave infrared bands over the 2002–2015 period. The vegetation growth anomalies caused by variability of rainfall in June–September translate to anomalies of dry vegetation cover that persist throughout the dry season until May. These vegetation anomalies explain 43% (50%) of the year‐to‐year variance in Sahelian‐mean dry‐season aerosol optical depth (AOD) as derived from MODIS Deep Blue (Sun photometers). Similar explained variance is found with 10 m wind speed and dust uplift potential. The central Sahel proves more important than the western Sahel for dry‐season AOD variability.

Dust emission and transport over Iraq associated with the summer Shamal winds

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.

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

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

Role of surface wind and vegetation cover in multi-decadal variations of dust emission in the Sahara and Sahel

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

Correction of dust event frequency from MODIS Quick-Look imagery using in-situ aerosol measurements over the Lake Eyre Basin, Australia

Abstract Subjective visual interpretation of MODIS Quick-Look imagery has proven useful in characterising dust source geomorphology and dust event frequency over diverse areas, but is limited by the small temporal sampling window of polar orbiting platforms, and obscuration by cloud. In this paper we seek to quantify the inevitable under-reporting of dust events in Quick-Look imagery, via a three-year case study over the Lake Eyre Basin (LEB), the largest dust source in Australia and the southern hemisphere. Dust event identification from MODIS imagery is compared with the level of dust mobilization inferred from measurements of near-surface aerosol made by a continuously-operating integrating nephelometer, located at the AeroSpan/AERONET station at Tinga Tingana in the Strzelecki Desert, adjacent to major dust sources in the LEB. The analysis indicates a major upward revision in the overall dust event frequency by ~ 72%, including a doubling of the incidence of major dust outbreaks. The intensity of missed events increases toward late afternoon and evening, although without a net day-night bias. These factors suggest the potential of new geostationary sensors and the analysis of night-time polar orbiting imagery in improving the reporting of dust mobilization over active dust-source regions. For the LEB, the corrections are crucial in understanding not only the seasonal distribution of dust mobilization, but its interannual variability and climatology.

Saharan dust transport by Mediterranean cyclones causing mud rain in Istanbul

North Africa is the largest dust source on Earth. Mediterranean cyclones occasionally transport Saharan dust to Turkey in late winter and early spring, leading to mud rain events in some regions. Two mud rain events which occurred in Istanbul on 11 February 2010 and 8 March 2010 were simulated using the WRF‐ARW mesoscale model. Met Office analysis charts, backward trajectories, ground based observations, and satellite images from EUMETSAT Meteosat Second Generation were examined to explain the underlying mechanisms.

Can land use intensification in the Mallee, Australia increase the supply of soluble iron to the Southern Ocean?

The supply of soluble iron through atmospheric dust deposition limits the productivity of the Southern Ocean. In comparison to the Northern Hemisphere, the Southern Hemisphere exhibits low levels of dust activity. However, given their proximity to the Southern Ocean, dust emissions from continental sources in the Southern Hemisphere could have disproportionate impact on ocean productivity. Australia is the largest source of dust in the Southern Hemisphere and aeolian transport of dust has major ecological, economic and health implications. In the Mallee, agriculture is a major driver of dust emissions and dust storms that affect Southeastern Australia. In this study, we assess the dust generating potential of the sediment from the Mallee, analyze the sediment for soluble iron content and determine the likely depositional region of the emitted dust. Our results suggest that the Mallee sediments have comparable dust generating potential to other currently active dust sources in the Southern Hemisphere and the dust-sized fraction is rich in soluble iron. Forward trajectory analyses show that this dust will impact the Tasman Sea and the Australian section of the Southern Ocean. This iron-rich dust could stimulate ocean productivity in future as more areas are reactivated as a result of land-use and droughts.

The role of deep convection and nocturnal low-level jets for dust emission in summertime West Africa: Estimates from convection-permitting simulations.

[1] Convective cold pools and the breakdown of nocturnal low-level jets (NLLJs) are key meteorological drivers of dust emission over summertime West Africa, the world’s largest dust source. This study is the first to quantify their relative contributions and physical interrelations using objective detection algorithms and an off-line dust emission model applied to convection-permitting simulations from the Met Office Unified Model. The study period covers 25 July to 02 September 2006. All estimates may therefore vary on an interannual basis. The main conclusions are as follows: (a) approximately 40% of the dust emissions are from NLLJs, 40% from cold pools, and 20% from unidentified processes (dry convection, land-sea and mountain circulations); (b) more than half of the cold-pool emissions are linked to a newly identified mechanism where aged cold pools form a jet above the nocturnal stable layer; (c) 50% of the dust emissions occur from 1500 to 0200 LT with a minimum around sunrise and after midday, and 60% of the morning-to-noon emissions occur under clear skies, but only 10% of the afternoon-to-nighttime emissions, suggesting large biases in satellite retrievals; (d) considering precipitation and soil moisture effects, cold-pool emissions are reduced by 15%; and (e) models with parameterized convection show substantially less cold-pool emissions but have larger NLLJ contributions. The results are much more sensitive to whether convection is parameterized or explicit than to the choice of the land-surface characterization, which generally is a large source of uncertainty. This study demonstrates the need of realistically representing moist convection and stable nighttime conditions for dust modeling.Citation: Heinold, B., P. Knippertz, J. H. Marsham, S. Fiedler, N. S. Dixon, K. Schepanski, B. Laurent, and I. Tegen (2013), The role of deep convection and nocturnal low-level jets for dust emission in summertime West Africa: Estimates from convection-permitting simulations, J. Geophys. Res. Atmos., 118, 4385–4400, doi:10.1002/jgrd.50402.