Dust Storm Frequency Research Articles

Intensity of dust storms in China from 1980 to 2007: A new definition

In the process of studying dust-storm events, we have to face an important scientific problem: How to define dust-storm intensity (DSI)? This study provides a comprehensive definition of DSI in terms of the frequency, duration, and visibility of dust storms, and uses it to measure the trend of annual changes in dust-storm activities. With dust-storm data from 186 meteorological observation stations in China, the trend in DSI was studied for the period 1980–2007. This trend differs from those based on the frequency of dust storms, which are often used in the literature. In this study, average DSIs after 2000 were underestimated using frequency alone to measure the dust activities, compared with those before 2000. According to the spatiotemporal distribution, there are four modes of change in DSI over the period, namely a significantly decreasing trend, an increasing trend, a mode in which dust storm activity remained constant, and a two-peak mode.

Dust storm frequency and impact over Eastern Australia determined by state of Pacific climate system

Dust storms resulting from synoptic-scale mid-latitude frontal systems affect inland, eastern Australia, predominantly through spring and summer but extend to the east coast only rarely when strong, frontal westerly winds crossing the continent are sustained over the coast. Here it is shown that extreme westerly wind dust events are anomalous to the more pervasive southerly winds that have shaped the sand dunes over inland eastern Australia. It is also shown that while antecedent dry conditions are very important, higher SON and DJF dust storm frequencies from 1957 to the mid-1970s occurred due to both anomalously strong, southerly winds existing on the western side of a cyclonic anomaly adjacent to the east Australian coast, which resulted from the state of the Pacific climate system, and an anticyclonic anomaly at the top of the Great Australian Bight. A change in BoM observing practice, after 1973, is unlikely to be the major cause of changes in total dust frequency from the mid-1970s. Rather, extreme rainfall years are more likely to have been a major contributing factor to the large decreases in dust occurrence from 1973 to 1976, in addition to the other La Niña periods of 2000/01 to 2010/11. Synoptic-scale frontal systems in the westerlies that result in the transport of dust remained low in frequency throughout the whole period from 1957 to 2011. However, those dust storms in the westerlies that do reach the east coast, although infrequent, tend to occur during El Niño-dominated years. On the other hand, they occur during both negative and positive phases of the southern annular mode (SAM). This ambiguity with the SAM phase is consistent with the fact that the mid-latitude westerlies and associated frontal systems are usually at their most equatorward position in Australian longitudes in late winter/spring regardless of the SAM phase. This suggests little change is likely in the frequency of westerly induced dust storms in late winter/spring over central/eastern Australia even though the seasonal westerly winds are expected to contract further poleward under increased global warming. However, a complicating factor is that the increasing likelihood of longer dry spells under climate change would imply reduced vegetation for longer periods over the dust-prone source region of Lake Eyre basin, which could worsen the impact of dust storm events. Furthermore, longer dry spells throughout the year would increase the risk of more frequent westerly dust storm events in other seasons when strong, westerly frontal systems can also occur.

Late Pleistocene variations of the background aeolian dust concentration in the Carpathian Basin: an estimate using decomposition of grain-size distribution curves of loess deposits

AbstractAeolian dust deposits can be considered as one of the most important archives of past climatic changes. Alternating loess and paleosol strata display variations of the dust load in the Pleistocene atmosphere. By using the observations of recent dust storms, we are able to employ Late Pleistocene stratigraphic datasets (with accurate chronological framework) and detailed granulometric data for making conclusions on the atmospheric dust load in the past. Age-depths models, created from the absolute age data and stratigraphic interpretation, allow us to calculate sedimentation rates and dust fluxes, while grain-size specifies the dry-deposition velocity, i.e. the atmospheric residence time of mineral particles. Thus, the dust concentration can be expressed as the quotient of the dust flux and gravitational settling velocity. Recent observations helped to clarify the mechanisms behind aeolian sedimentation and the physical background of this process has nowadays been well established. Based on these two, main contrasting sedimentary modes of dust transport and deposition can be recognised: the short suspension episodes of the coarse (silt and very fine sand) fraction and the long-range transport of a fine (clay and fine silt) component. Using parametric curve fitting the basic statistical properties of these two sediment populations can be revealed for Pleistocene aeolian dust deposits, as it has been done for loess in Hungary. As we do not have adequate information on the magnitude and frequency of the Pleistocene dust storms, conclusions could only be made on the magnitude of continuous background dust load. The dust concentration can be set in the range between 1100 and 2750 μg/m3. These values are mostly higher than modern dust concentrations, even in arid regions. Another interesting proxy of past atmospheric conditions could be the visibility, being proportional to the dust concentration. According to the known empirical dust concentration – visibility equations, its value is around 6.5 to 26 kilometres.

Dryness of ephemeral lakes and consequences for dust activity: The case of the Hamoun drainage basin, southeastern Iran

This study examines the influence of changes in the water coverage in the Hamoun dry-bed lakes on visibility, dust outbreaks, aerosol loading and land–atmospheric fluxes over the region covering the period 1985–2005. The Hamoun basin, located on the southeastern Iran and western Afghanistan borders, has been recognized as one of the major dust source regions in south Asia and is covered by shallow, marshy lakes that are fed by the Helmand and Farahrood rivers. When the water in watersheds that support the lakes is drawn down for natural or human-induced reasons, the end result is a decrease in the water coverage in the basin, or even complete dryness as occurred in 2001. Then, strong seasonal winds, mainly in summer, blow fine sand and silt off the exposed lakebed, enhancing dust activity and aerosol loading over the region. Satellite (Landsat) and meteorological observations reveal that the water levels in the Hamoun lakes exhibit considerable inter-annual variability during the period 1985–2005 strongly related to anomalies in precipitation. This is the trigger for concurrent changes in the frequency of the dusty days, aerosol loading and deterioration of visibility over the region, as satellite (TOMS, MODIS, MISR) observations reveal. On the other hand, soil moisture and latent heat, obtained via model (GLDAS_noah-10) simulations are directly linked with water levels and precipitation over the region. The desiccation of the Hamoun lakes in certain years and the consequent increase in frequency and intensity of dust storms are serious concerns for the regional climate, ecosystems and human health.

Effect of dust accumulation on the power outputs of solar photovoltaic modules

There is a great potential for solar power utilization in the Eastern part of Saudi Arabia by employing solar photovoltaic (PV) modules. Dust accumulation on the surface of solar PV modules, mirrors, reflectors and other solar collectors is of great concern due to occasional to frequent dust storm in the gulf region. The performances of such devices are significantly affected by dust accumulation. This paper presents the result of a study on the effect of dust accumulation on the power output of solar PV modules in the Eastern province of Saudi Arabia. The study indicates that power decrease by as much as 50% can be experienced for solar PV modules that are left unclean for a period of over six months. Solar tracker improves power output and helps reduce dust accumulation effect by 50% at off-peak time.

Characterisation of atmospheric deposited particles during a dust storm in urban areas of Eastern Australia

The characteristics of dust particles deposited during the 2009 dust storm in the Gold Coast and Brisbane regions of Australia are discussed in this paper. The study outcomes provide important knowledge in relation to the potential impacts of dust storm related pollution on ecosystem health in the context that the frequency of dust storms is predicted to increase due to anthropogenic desert surface modifications and climate change impacts. The investigated dust storm contributed a large fraction of fine particles to the environment with an increased amount of total suspended solids, compared to dry deposition under ambient conditions. Although the dust storm passed over forested areas, the organic carbon content in the dust was relatively low. The primary metals present in the dust storm deposition were aluminium, iron and manganese, which are common soil minerals in Australia. The dust storm deposition did not contain significant loads of nickel, cadmium, copper and lead, which are commonly present in the urban environment. Furthermore, the comparison between the ambient and dust storm chromium and zinc loads suggested that these metals were contributed to the dust storm by local anthropogenic sources. The potential ecosystem health impacts of the 2009 dust storm include, increased fine solids deposition on ground surfaces resulting in an enhanced capacity to adsorb toxic pollutants as well as increased aluminium, iron and manganese loads. In contrast, the ecosystem health impacts related to organic carbon and other metals from dust storm atmospheric deposition are not considered to be significant.

The impact of the winter North Atlantic Oscillation on the frequency of spring dust storms over Tarim Basin in northwest China in the past half-century

The relationship between the frequency of spring dust storms over Tarim Basin in northwest China and the winter North Atlantic Oscillation (NAO) is investigated by using the observed dust storm frequency (DSF) and the 10 m wind velocity at 36 stations in Tarim Basin and the National Centers for Environment Prediction/National Center for Atmospheric Research reanalysis data for the period 1961–2007. The spring DSF (winter NAO) index shows a clear decreasing (increasing) linear trend over 1961–2007. The winter NAO correlates well with the subsequent spring DSF over Tarim Basin on both interannual and interdecadal time scales and its interannual to interdecadal variation plays an important role in the spring DSF. Two possible physical mechanisms are identified. One is related to the large scale anomalous circulations in spring in the middle to high troposphere modulated by the winter NAO, providing the background of dynamical conditions for the dust storm occurrences. The other is related to the shifts in the local horizontal sea level pressure (SLP) gradients and 10 m wind speed, corresponding to changes in the large scale circulations in spring. The decrease in the local 10 m wind speed due to the reduced horizontal SLP gradients over Tarim Basin during the strong winter NAO years contributes to the decline of the DSF in the subsequent spring.

Increasing Ca2+ deposition in the western US: The role of mineral aerosols

Considerable research has focused on the role of industrial emissions in controlling the acidity of precipitation; however, much less research has focused on the role of mineral aerosols emitted from soils. According to data published by the National Atmospheric Deposition Network (NADP), over the past 17 years Ca 2+ deposition has increased over large regions of the US. A trend analysis to determine regions 2+ deposition revealed statistically significant increases in three broad regions within the western half of the country: the inter-mountain west, the midwest, and the northwest. We evaluated potential changes in sources of calcium to the atmosphere including soil erosion, industrial emissions, forest fires, and sea-salt aerosols to determine the cause of rising atmospheric calcium deposition. Based on our evaluation, the most parsimonious explanation for increased Ca 2+ deposition is an increase in mineral aerosol emissions from within the western US. This explanation is corroborated by independent evidence showing increases in the frequency of dust storms and low-visibility days across regions of the western US. Furthermore, our analysis indicates that the increase in mineral aerosol emissions is most likely due to (1) increased aridity and wind transport and (2) increased area and intensity of upwind human activities. Changes in atmospheric dust concentrations can have important ecological implications through the contribution of acid neutralizing capacity to both precipitation and regions of deposition. Thus increased dust emissions have the potential to ameliorate the detrimental effects of acid precipitation on terrestrial ecosystems, though dust may exacerbate the impacts of air quality on human health.

The March 2009 Dust Event in Saudi Arabia: Precursor and Supportive Environment

A case study is presented of the environmental background for a massive Saudi Arabian dust storm event that took place on 10 and 11 March 2009. The dust storm was large enough to be clearly seen from outer space and caused a widespread heavy atmospheric dust load, very low visibility, total airport shutdown, and damage to vehicles and trees across northern and central parts of Saudi Arabia. The precursor and supportive environment for this dust storm outbreak are investigated, drawing upon routine synoptic data and satellite imagery. Analytical evidence is offered to suggest that this dust storm was triggered and sustained by a cold front passage coincident with the propagation of a preexisting intense upperlevel jet streak. The major plume of the 10 March 2009 dust storm originated from several rich dust source areas extending across two regions—the Qasim region and the Adibdibah and As-Summan Plateau region. The intensity and frequency of dust storms triggered from these active areas of dust emissions seem to be dominated by a response to the amount of precipitation during November and December.

Mass-size distribution of PM10 and its characterization of ionic species in fine (PM2.5) and coarse (PM10−2.5) mode, New Delhi, India

Size distribution of PM10 mass aerosols and its ionic characteristics were studied for 2 years from January 2006 to December 2007 at central Delhi by employing an 8-stage Andersen Cascade Impactor sampler. The mass of fine (PM2.5) and coarse (PM10−2.5) mode particles were integrated from particle mass determined in different stages. Average concentrations of mass PM10 and PM2.5 were observed to be 306 ± 182 and 136 ± 84 μg m−3, respectively, which are far in excess of annual averages stipulated by the Indian National Ambient Air Quality Standards (PM10: 60 μg m−3 and PM2.5: 40 μg m−3). The highest concentrations of PM10−2.5 (coarse) and PM2.5 (fine) were observed 505 ± 44 and 368 ± 61 μg m−3, respectively, during summer (June 2006) period, whereas the lower concentrations of PM10−2.5 (35 ± 9 μg m−3) and PM2.5 (29 ± 13 μg m−3) were observed during monsoon (September 2007). In summer, because of frequent dust storms, coarse particles are more dominant than fine particles during study period. However, during winter, the PM2.5 contribution became more pronounced as compared to summer probably due to enhanced emissions from anthropogenic activities, burning of biofuels/biomass and other human activities. A high ratio (0.58) of PM2.5/PM10 was observed during winter and low (0.24) during monsoon. A strong correlation between PM10 and PM2.5 (r2 = 0.93) was observed, indicating that variation in PM10 mass is governed by the variation in PM2.5. Major cations (NH4+, Na+, K+, Ca2+ and Mg2+) and anions (F−, Cl−, SO42− and NO3−) were analyzed along with pH. Average concentrations of SO42− and NO3− were observed to be 12.93 ± 0.98 and 10.33 ± 1.10 μg m−3, respectively. Significant correlation between SO42− and NO3− in PM1.0 was observed indicating the major sources of secondary aerosol which may be from thermal power plants located in the southeast and incomplete combustion by vehicular exhaust. A good correlation among secondary species (NH+, NO3− and SO42−) suggests that most of NH4+ is in the form of ammonium sulfate and ammonium nitrate in the atmosphere. During winter, the concentration of Ca2+ was also higher; it may be due to entrainment of roadside dust particles, traffic activities and low temperature. The molar ratio (1.39) between Cl− and Na+ was observed to be close to that of seawater (1.16). The presence of higher Cl− during winter is due to western disturbances and probably local emission of Cl− due to fabric bleaching activity in a number of export garment factories in the proximity of the sampling site.

Variability in the Correlation between Asian Dust Storms and Chlorophyll a Concentration from the North to Equatorial Pacific

A long-term record of Asian dust storms showed seven high-occurrence-frequency centers in China. The intrusion of Asian dust into the downwind seas, including the China seas, the Sea of Japan, the subarctic North Pacific, the North Pacific subtropical gyre, and the western and eastern Equatorial Pacific, has been shown to add nutrients to ocean ecosystems and enhance their biological activities. To explore the relationship between the transported dust from various sources to the six seas and oceanic biological activities with different nutrient conditions, the correlation between monthly chlorophyll a concentration in each sea and monthly dust storm occurrence frequencies reaching the sea during 1997–2007 was examined in this study. No correlations were observed between dust and chlorophyll a concentration in the <50 m China seas because atmospheric deposition is commonly believed to exert less impact on coastal seas. Significant correlations existed between dust sources and many sea areas, suggesting a link between dust and chlorophyll a concentration in those seas. However, the correlation coefficients were highly variable. In general, the correlation coefficients (0.54–0.63) for the Sea of Japan were highest, except for that between the subarctic Pacific and the Taklimakan Desert, where it was as high as 0.7. For the >50 m China seas and the North Pacific subtropical gyre, the correlation coefficients were in the range 0.32–0.57. The correlation coefficients for the western and eastern Equatorial Pacific were relatively low (<0.36). These correlation coefficients were further interpreted in terms of the geographical distributions of dust sources, the transport pathways, the dust deposition, the nutrient conditions of oceans, and the probability of dust storms reaching the seas.

Mass concentration of PM10 and PM2.5 fine-dispersed aerosol fractions in the Eastern Gobi Desert

Results are presented of monitoring measurements of the mass concentration of PM10 (particles with the size of less than 10 μm) and PM2.5 (less than 2.5 μm) fine-dispersed aerosol fractions at the Sainshand and Zamyn-Uud stations located in the Gobi Desert of Mongolia. Revealed are the annual variations of the mass concentration of PM10 and PM2.5 fine-dispersed aerosol fractions at these stations in 2008. The maximum values of monthly mean concentration during the year were observed in May in the period of dust storms. On the days with the steady calm weather, the mass concentrations of PM10 and PM2.5 varied within 5–8 μg/m3 (PM10) and 3–5 μg/m3 (PM2.5) at the Sainshand station. During the dust storms, the maximum values of concentration exceeded 1400 μg/m3 (PM10) and 380 μg/m3 (PM2.5) that is by 28 (PM10) and 15 (PM2.5) times higher than the maximum permissible concentration for the European Union. Results are given of studying the frequency and duration of dust storms in recent 20 years (1991–2010) in the Eastern Gobi Desert.

The temporal and spatial distribution of dust storms on the North China Plain, ad 1464–1913

Using 1844 different chorographies (regional descriptions) from the Ming Dynasty to the Republic Period and other related historical documents, 1180 records of dust storms on the North China Plain from 1464 to 1913 have been identified. These data are used to describe and analyse the temporal and spatial distribution of dust storms on the North China Plain during these years. Dust storms on the North China Plain occurred mainly in spring. Of all the identified dust storms, 72.85% occurred in the spring, 16.39% in winter, 8.71% in summer, and 2.05% in the fall. These storms occurred in cycles of 16–36 years. There was a negative correlation between the frequency of dust storms and the level of precipitation, and also a negative correlation between the frequency of dust storms and the frequency of spring or winter temperature departures. Spatially dust storms clustered in three fairly discrete northern, central, and southern districts. This spatial pattern was closely related to the movement of cold air systems in North China in winter or spring.

The influence of vegetation variation on Northeast Asian dust activity

In this study, we investigate the influence of vegetation variations on dust activity (dust load, dust transport in the troposphere, and dust weather frequency) over Northeast Asia during springtime. By using the Integrated Wind Erosion Modeling System, two model experiments are run over four-month periods, from February 1 to May 31, for each year from 1982 to 2006; one experiment uses the observed atmospheric conditions and vegetation (OBS), and the other uses the specified atmospheric conditions in 2006 and the observed vegetation (CTRL). Comparison of the two model experiments reveals that there are sensitive regions in southeastern Mongolia and central northern China, in which vegetation has a large potential to influence dust activity due to both the high dust emission rate and large variations in vegetation coverage. Over these sensitive regions, vegetation effectively lessens dust loads on interannual and interdecadal timescales; dust load is decreased by 2864 μg m−2 for an increment of 0.1 in the normalized difference vegetation index (NDVI). Vegetation increase in the sensitive areas also reduces two major branches of dust transports in the low troposphere; one stretches from eastern Mongolia to regions northeastward, and the other flows across the south of northeastern China to Korea. In addition to dust loads and transports, vegetation increase in the sensitive areas evidently decreases dust storm frequency and blowing dust frequency, but it exerts a weak influence on the floating dust frequency. In the sensitive regions, as NDVI increases by 0.1, dust storms, blowing dust, and floating dust decrease by 4.0 days/spring, 1.5 days/spring, and 0.2 days/spring, respectively. In summary, vegetation variations in southeastern Mongolia and central northern China have considerable impact on northeast Asian dust during springtime.

Simulating the interannual variability of major dust storms on Mars using variable lifting thresholds

The redistribution of a finite amount of martian surface dust during global dust storms and in the intervening periods has been modelled in a dust lifting version of the UK Mars General Circulation Model. When using a constant, uniform threshold in the model’s wind stress lifting parameterisation and assuming an unlimited supply of surface dust, multiannual simulations displayed some variability in dust lifting activity from year to year, arising from internal variability manifested in surface wind stress, but dust storms were limited in size and formed within a relatively short seasonal window. Lifting thresholds were then allowed to vary at each model gridpoint, dependent on the rates of emission or deposition of dust. This enhanced interannual variability in dust storm magnitude and timing, such that model storms covered most of the observed ranges in size and initiation date within a single multiannual simulation. Peak storm magnitude in a given year was primarily determined by the availability of surface dust at a number of key sites in the southern hemisphere. The observed global dust storm (GDS) frequency of roughly one in every 3years was approximately reproduced, but the model failed to generate these GDSs spontaneously in the southern hemisphere, where they have typically been observed to initiate. After several years of simulation, the surface threshold field—a proxy for net change in surface dust density—showed good qualitative agreement with the observed pattern of martian surface dust cover. The model produced a net northward cross-equatorial dust mass flux, which necessitated the addition of an artificial threshold decrease rate in order to allow the continued generation of dust storms over the course of a multiannual simulation. At standard model resolution, for the southward mass flux due to cross-equatorial flushing storms to offset the northward flux due to GDSs on a timescale of ∼3years would require an increase in the former by a factor of 3–4. Results at higher model resolution and uncertainties in dust vertical profiles mean that quasi-periodic redistribution of dust on such a timescale nevertheless appears to be a plausible explanation for the observed GDS frequency.

Relationship between thermal anomalies in Tibetan Plateau and summer dust storm frequency over Tarim Basin, China

The dust storm is the most important and frequent meteorological disaster over Tarim Basin, which causes huge damages on local social economics. How to predict the springtime and summertime dust storm occurrence has become a hot issue for meteorologists. This paper employed the data of dust storm frequency and 10-m wind velocity at 35 stations over Tarim Basin and the reanalysis data from the National Center for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) during 1961–2007 to study the relationship between dust storm frequency (DSF) in summer over Tarim Basin and the thermal anomalies in Tibetan Plateau in May by using the statistical methods, such as Empirical Orthogonal Function (EOF), correlation and binomial moving average. The results show when negative anomalies in Tibetan Plateau and positive anomalies in its southern region are present along 30°N (the second mode of surface temperature anomalies by EOF decomposition) in May, the time coefficient (PC2) plays an important role in summer DSF variation and has a close relation with the summer DSF at both inter-annual and decadal time scales. When negative anomalies in Tibetan Plateau and positive anomalies are present in its southern region (PC2 in positive phase), there is an anomalous anticyclone in North China, which weakens the northwest wind and is not beneficial for cold air moving from high latitude to the Tarim Basin, and the circulation pattern is hard to result in dust storm weather. Furthermore, the sea level pressure (SLP) increased over Tarim Basin and the direction of SLP gradient reversed, which resulted in the 10-m wind velocity slowing down, so the DSF decreased. From above all, it can be conclude that the thermal anomalies in Tibetan Plateau in May has important effects on the summertime dust storm frequency over Tarim Basin and the PC2 can be used as a prediction factor for the summertime dust storm occurrence.

Observation of saltation activity at Tazhong area in Taklimakan Desert, China

A two-year field observation of saltation activity was carried out at Tazhong area, the hinterland area of the Taklimakan Desert with highly frequent dust storms. From 1 September 2008 to 31 August 2010, a piezoelectric saltation sensor (Sensit) was used to continuously collect the data on saltation activity at a level sand surface. Analysis on the data suggests that saltation activity can occur at any time of the year when conditions are favorable; however, the necessary conditions are rarely satisfied in most time. In the daytime of spring or summer, saltation activity can persist even over a continuous one-hour-or-so period. It is found that, from 1 September 2008 to 31 August 2010, saltation activity accounts for more than 3% of the total yearly time, and it tends to peak in spring and summer months with strong winds. During winter months when winds are weak, however, it is often at a minimum. It seems that precipitation does not appear to be significant in reducing saltation activity in arid regions like Tazhong.

Extreme dust storm disaster in northern China in AD 1523

The dust storm disaster in northern China in AD 1523 was extremely severe. In the present study, the history of the disaster was reconstructed by using historical Chinese documents. Our results show that during the dust storms, the horizontal visibility dropped below 0.05 km, while the wind speed surpassed Scale 10 of the Beaufort Wind Force Scale (i.e., 88–103 km/h). The dust storms severely affected agriculture, resulting in crop failures and famines. The blowing sand of the dust storms buried and killed about 100 people. Such damage and fatalities has never happened in northern China in modern times. Furthermore, the dust storm disaster happened against a background of normal climate and therefore might have been caused by factors other than temperature and precipitation. It implies that global warming may not result in more frequent extreme dust storm events because their occurrence can be unrelated to climatic factors.

Spatial and temporal distribution of the dust deposition in Central Asia – results from a long term monitoring program

Abstract The aeolian transport of dust is an important process in Central Asia. Anthropogenic desertification and the desiccation of the Aral Sea have increased the overall dust emission and transport from this region and the local dust storm frequency during the last decades. Reliable ground data, however, are collected only sporadically, so the knowledge about the spatial and temporal distribution and dynamics of the dust deposition in the Aral Sea basin is fragmented and inconsistent at best. A long-term monitoring program was installed and sustained by three research projects. The results included in this article cover the dust deposition between 2003 and 2010 from 21 stations in Uzbekistan, Kazakhstan, and Turkmenistan. They confirm that the aeolian dust transport occurs mainly in the Southern direction. The highest average monthly deposition rate was registered in Uzbekistan (56.2 g m−2), while the percentage of months with a very intense (and potentially harmful) dust deposition flux was highest in Turkmenistan (36.4%). A majority of samples were collected during months with a dust deposition of less than 10.0 g m−2, while only 6% of all samples showed high monthly deposition intensities of more than 100 g m−2. The Kyzyl Kum, Kara Kum, and Aral Kum were identified as the main sources for aeolian dust in the Aral Sea basin. The impact of the Aral Kum as the dominant source of aeolian dust is limited to a region of approximately 500,000 km2 surrounding the former Aral Sea. The Kara Kum is characterized by a very high frequency of dust storms of a local and regional magnitude, and close to the Kyzyl Kum, monthly dust deposition rates of up to 9,600 g m−2 were registered. An analysis of the temporal distribution of the dust deposition showed a slight increase in the dust deposition activity and intensity between 2003 and 2010, with a strong inter-annual and seasonal dynamic. The highest average dust deposition was registered in June, and a second phase of intense dust deposition was identified in February. As this research covers less than a decade, a continuous monitoring program is strongly advised for a better understanding of the processes of aeolian dust transport and the impact of aeolian dust on arable land and human health.

Potential impacts of northeastern Eurasian snow cover on generation of dust storms in northwestern China during spring

The effects of the northeastern Eurasian snow cover on the frequency of spring dust storms in northwestern China have been examined for the period 1979–2007. Averaged over all 43 stations in northwestern China, a statistically significant relationship has been found between dust-storm frequency (DSF) and Eurasian snow-water equivalent (SWE) during spring: mean DSF of 7.4 and 3.3 days for years of high- and low SWE, respectively. Further analyses reveal that positive SWE anomalies enhance the meridional gradients of the lower tropospheric temperatures and geopotential heights, thereby strengthening westerly jets and zonal wind shear over northwestern China and western Inner Mongolia of China, the regions of major dust sources. The anomalous atmospheric circulation corresponding to the Eurasian SWE anomalies either reinforces or weakens atmospheric baroclinicity and cyclogenesis, according to the sign of the anomaly, to affect the spring DSF. This study suggests that Eurasian SWE anomalies can be an influential factor of spring DSF in northwestern China and western Inner Mongolia of China.