Asian Dust

The diurnal temperature range (DTR), representing the difference between daily maximum temperature (Tmax) and minimum temperature (Tmin), is a vital climatic indicator with significant environmental and public health implications. This study examined long-term trends and seasonal patterns of DTR in five cities in Khuzestan Province, Iran (Abadan, Ahvaz, Aghajari, Masjed Soleiman, and Safi Abad) from 1990 to 2022. Materials and Methods: Meteorological data, including Tmax and Tmin, were used to calculate daily DTRs and annual averages. Temporal trends were assessed using linear regression models, while seasonal decomposition analysis identified trend, seasonal, and residual components. Visualization techniques, such as line plots and decomposition graphs, illustrated the findings. Results: The results indicated statistically significant increasing trends in DTR across all cities, with annual increases ranging from 0.0567 to 0.1347 units. Seasonal patterns showed consistent summer peaks and winter troughs, with notable long-term trends and climatic anomalies detected in residual components. These trends mirror global patterns of increasing variability between daytime and nighttime temperatures. Conclusion: The rising DTR, particularly in Abadan and Aghajari, elevates heat stress and public health risks. Ahvaz and Safi Abad also exhibited significant trends, highlighting the need for targeted policy measures. Given the association of high DTR with increased cardiovascular and respiratory diseases, integrating DTR metrics into health action plans is critical, especially for vulnerable populations. In conclusion, DTR serves as a crucial marker of climatic and health risks, reinforcing the urgency of climate adaptation strategies in Khuzestan Province to protect vulnerable groups.

We carried out short-term continuous monitoring of Asian dust every 2 hours in Beijing, China and Nagasaki, Japan and performed chemical analyses during 2 events where there were large differences in the characteristics of the Asian dust blowing into Nagasaki. The first involved typical Asian dust that originated in the Mongolian Gobi Desert on March 30, 2007 (abbreviated to TAD 2007). The second involved a polluted air parcel that arrived in Japan along with Asian dust on May 8, 2007. By comparing temporal changes in PM10 and particulate sulfur (sulfate ions) concentrations with the timing of the Asian dust arrival, we found in the April event (TAD 2007) that the polluted air parcel covering Beijing did not mix with an air parcel containing TAD 2007 coming from the north. In the May event, we inferred that mixing of the polluted air parcel and an air parcel containing Asian dust had occurred. The composition of aerosol particles in the air parcel reaching Nagasaki in the April event reflected the chemical composition of TAD 2007 itself, whereas that of the May event had high concentrations of chemical components originating in anthropogenic pollution, such as sulfate ions, zinc, lead and other heavy metals.

Using an elemental signature for Asian dust derived from events in April 1998, we probed a long-term set of routine aerosol samples to develop the first empirical assessment of the frequency and intensity of dust transport from Asia to midlatitude North America. Our data reveal a pattern of consistent, frequent transport that contradicts the episodic characterization derived from short-term studies and anecdotal reports. We find that fine (<2.5 mm) Asian dust is a regular component of the troposphere over the eastern Pacific and western North America and is common, at least in spring, across North America. Typical Asian fine dust concentrations (24-hour average) are between 0.2 and 1 mg/m 3 and only very rarely exceed 5 mg/m 3 . Our data also indicate that Asian dust is concentrated in an altitude zone ranging from about 500 to 3000 m MSL, consistent with isentropic transport processes previously observed in the western Pacific.

Daily and monthly aerosol optical thickness (AOT) over the ocean, derived from the Geostationary Meteorological Satellite (GMS-5) visible data, were compared with those determined from the sun photometer measurements in March and April 2002. Time variations in the daily AOT derived from the GMS-5 showed good agreements with those from the sun photometer measurements. Correlation coefficient between the GMS-5 and the sun photometer derived daily AOTs was 0.85 for 61 samples taken at three sun photometer observation sites; Ryori, Yonagunijima, and Minamitorishima in Japan. The difference of monthly AOT, the GMS-5 minus the sun photometer, in March and April 2002 were À0.03 and 0.03 at Ryori, À0.01 and 0.18 at Yonagunijima, and 0.01 and 0.07 at Minamitorishima, respectively. Monthly regional AOT, defined as the median of the daily AOTs over 30 latitude  30 longitude region, was calculated in latitude from 60 N to 60 S and in longitude from 80 E to 160 W for March and April

Tajikistan is often affected by atmospheric mineral dust originating from various surrounding deserts. The direct and indirect radiative effects of that dust play a sensitive role in the Central Asian climate system and therefore need to be quantified. The Central Asian Dust Experiment (CADEX) provides for the first time an aerosol climatology for Central Asia based long-term aerosol profiling by ground-based lidar (PollyXT type) in Dushanbe, Tajikistan. For pure dust cases, mean depolarization(lidar) ratios of 0.23±0.03(44±3 sr) at 355 nm and 0.32±0.02(38±3 sr) at 532 nm wavelength have been measured. The mean extinction-related Ångström exponent was 0.18±0.15.

Mineral dust needs to be characterized comprehensively since it contributes to the climate change in Tajikistan / Central Asia. Lidar results from the measurements of mineral dust during CADEX are compared with results of sun photometer measurements, satellite-based measurements, and chemical analysis of ground samples. Although the dust is often advected from far-range sources, it impacts on the local conditions considerably.

Tajikistan is often affected by atmospheric mineral dust. The direct and indirect radiative effects of dust play a sensitive role in the climate system in Central Asia. The Central Asian Dust Experiment (CADEX) provides first lidar measurements in Tajikistan. The autonomous multiwavelength polarization Raman lidar PollyXT was operated for 1.5 years (2015/16) in Dushanbe. In spring, lofted layers of long-range transported dust and in summer/ autumn, lower laying dust from local or regional sources with large optical thicknesses occurred.

For the first time, continuous vertically resolved aerosol measurements were performed by lidar in Tajikistan, Central Asia. Observations with the multiwavelength polarization/Raman lidar Polly&lt;sup&gt;&lt;i&gt;XT&lt;/i&gt;&lt;/sup&gt; were conducted during CADEX (Central Asian Dust EXperiment) in Dushanbe, Tajikistan, from March 2015 to August 2016. Co-located with the lidar a sun photometer was operated. The goal of CADEX is to provide an unprecedented data set on vertically resolved aerosol optical properties in Central Asia, an area highly affected by climate change but largely missing vertically resolved aerosol measurements. During the 18-months measurement campaign, mineral dust was detected frequently from ground to cirrus level height. In this study, an overview of the measurement period is given and four typical but different example measurement cases are discussed in detail. Three of them are dust cases and one is a contrasting pollution aerosol case. Vertical profiles ...

In the spring, Asian dust storms that originate in the deserts of Mongolia and China eventually reach the populated areas of East Asia. The dust storm particles usually contain diverse organic matter and nutrients that may have an adverse effect on human health. In winter, northeast monsoon episodes that originate in the mainland China not only bring cold air but also transport dust and air pollutants to Taiwan over long distances. Based on the above, the presence of persistent organic pollutants (POPs), including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), in the suspended particles undergoing long-range transport needs to be investigated. In this study, the atmospheric concentrations of PCDD/Fs were monitored and investigated during an Asian dust storm episode and northeast monsoon episode in northern Taiwan. The sampling results indicate that the atmospheric PCDD/Fs observed at two remote sampling sites ranged from 7.46 ± 0.7 to 37.2 ± 2.0 fg I-TEQ/m 3 during the regular sampling period that covered 2006 and 2007. However, the concentrations of atmospheric PCDD/Fs increase to 61.0 and 69.8 fg I-TEQ/m 3 during the Asian dust storm episode of 3 rd March 2008 and during a northeast monsoon episode on 3 rd December 2008, respectively. Specifically, higher levels of PCDFs (by 70%-76%) were measured in northern Taiwan during these long-range transport periods. As no specific dioxin emission sources exist within 20 km of our sampling sites, the increase in PCDD/F concentrations observed at these two remote sampling sites is likely to be related to the Asian dust storm and northeast monsoon episodes and the pollutants would seem to have come from mainland China.

Bulk aerosol samples were collected from three different coastal rural sites located around the Eastern Mediterranean, (i) Erdemli (ER), Turkey, (ii) Heraklion (HR), Crete, Greece, and (iii) Tel Shikmona (TS), Israel, during two distinct mineral dust periods (October, 2007 and April, 2008) in order to explore the temporal and geographical variability in the aerosol chemical composition. Samples were analyzed for trace elements (Al, Fe, Mn, Ca, Cr, Zn, Cu, V, Ni, Cd, Pb) and water-soluble ions (Cl À , NO 3 and Ca 2þ ). The dust events were categorized on the basis of Al concentrations >1000 ng m À3 , SKIRON dust forecast model and 3-day back trajectories into three groups namely, Middle East, Mixed and Saharan desert. ER and TS were substantially affected by dust events originating from the Middle East, particularly in October, whilst HR was not influenced by dust transport from the Middle East. Higher AOT values were particularly associated with higher Al concentrations. Contrary to the highest Al concentration: 6300 ng m À3 , TS showed relatively lower AI and AOT. Al concentrations at ER were similar for October and April, whilst OMI-AI and AOT values were w2 times higher in April. This might be attributed to the weak sensitivity of the TOMS instrument to absorbing aerosols near the ground and optical difference between Middle East and Saharan desert dusts. The lowest enhancement of anthropogenic aerosol species was observed at HR during dust events (nssSO 4 2À /nssCa 2þ w 0.13). These species were particularly enhanced when mineral dust arrived at sites after passing through populated and industrialized urban areas.

Mineral dust suspended in the atmosphere has significant effects on radiative balance and climate change. The Chinese Loess Plateau (CLP) is generally considered one of the main sources of Asian dust aerosol. After being lifted by wind, dust particles with various size distributions can be transported over different distances. In this study, an original loess sample was collected from Luochuan, which is centrally located on the CLP, and two samples with different size distributions were obtained afterwards. "Pristine loess" was used to represent dust that only affects source regions, part of pristine loess was milled to finer "milled loess" that can be transported over long distances. Light scattering matrices for these two samples were measured at 532 nm wavelength from 5 to 175 • angles. Particle size distribution, refractive index, chemical component, and microscopic appearance were also characterized for auxiliary analyses. Experimental results showed that there are obvious discrepancies in angular behaviors of matrix elements for pristine loess and milled loess, and these discrepancies are different from those for other kinds of dust with distinct size distributions. Given that the effective radii of these two loess samples differ by more than 20 times, it is reasonable to conclude that the difference in size distributions plays a major role in leading to different matrices, while differences in refractive index and microstructure have relatively small contributions. Qualitative analyses of numerical simulation results of irregular particles also validate this conclusion. Gaussian spheres may be promising morphological models for simulating the scattering matrix of loess but need further quantitative verification. Finally, synthetic scattering matrices for both pristine loess and milled loess were constructed over 0-180 • , and the previous average scattering matrix for loess dust was updated. This study presents measurement results of Chinese loess dust and an updated average scattering matrix for loess, which are useful for validating existing models, developing more advanced models for optical simulations of loess dust, and helping to improve retrieval accuracy of dust aerosol properties over both source and downwind areas.

Mineral dust suspended in the atmosphere has significant effects on radiative balance and climate change. Chinese Loess Plateau (CLP) is generally considered as a main sources of Asian dust aerosol. After being lifted by wind, dust particles with various size distributions can be transported for different distances. In this study, original loess sample was collected from Luochuan, which is centrally located at CLP, and two samples with different size distributions were obtained after then. "Pristine loess" was used to represent dust that only affect source regions, part of "pristine loess" was milled to finer "milled loess" that can be transported for long distance. Light scattering matrices for these two samples were measured at 532 nm wavelength from 5° to 160° angles. Particle size distribution, refractive index, chemical component, and microscopic appearance were also measured for auxiliary analyses. Results showed that discrepancies in angular behaviours of matrix elements for "pristine loess" and "milled loess" cannot be ignored. Given that the effective radii of these two loess samples differ by more than 20 times, it is reasonable to conclude that the difference in size distributions plays a major role in leading to different matrices, while refractive index and micro structure have relatively small impacts. Analyses of numerical simulation results about irregular particles also variety this conclusion. At last, synthetic scattering matrices for both "pristine loess" and "milled loess" were calculated over 0°-180°, and the previous average scattering matrix for loess dust was updated. Mineral dust is a common particulate type in Earth's atmosphere, and accounts for a high fraction of atmospheric aerosol mass loading (Tegen and Fung, 1995). Asian dust contributes a lot to global atmospheric mineral dust load. Dust emitted from East Asia only is about 1.04×10 7 ton/year, 2.76×10 7 ton/year and 5.13×10 7 ton/year for PM10 (particles with aerodynamic equivalent diameter smaller than 10μm), PM30 and PM50 (Xuan et al., 2004). During aerosol characterization experiments (ACE-Asia), mass balance calculations indicated that 45-82 % of the observed total aerosol mass can be attributed to Asian dust . Chinese Loess Plateau (CLP) is usually considered as a main sources or an important supply site of Asian dust aerosol (

Video techniques for monitoring exposure, such as NIOSH's "Helmet-CAM," employ both realtime dust monitors and mobile video cameras to assess workers' respirable dust exposures. Many real-time personally worn dust monitors utilize light scattering sensing elements, which are subject to measurement biases as a function of dust type (size, composition, shape factor) and environmental conditions such as relative humidity. These biased and inaccurate dust measurements impair the monitor's ability to properly represent actual respirable dust concentrations. In the testing described, instrument mass concentration data was collected using three different types of commonly used commercial off-the-shelf personal dust monitors and compared to a reference standard. This testing was performed in a calm air (Marple) dust chamber in which three units of each make and model (for a total of nine monitors) were used for each test. Equivalency factors (EF, a multiplier to match the Thermo TEOM 1400a reference instrument) ranged between 0.746 and 1.879 across all dusts and environmental conditions tested, and between 0.821 and 1.519 on the ISO test dust.

We developed a new methodology for the improved identification of particle microphysical parameters (PMPs) from multiwavelength lidar measurements. The underlying problem is underdetermined and relates to the class of ill-posed problems. In this study, we apply our new methodology to lidar measurements. We investigate how results obtained for typical aerosol mixtures (AMs) in the atmosphere can be improved if information about aerosol types and the number of aerosol types in such an AM is available. We have developed a methodology of Aerosol Typing from Linear estimations for the Analytical Separation (ATLAS) of complex aerosol mixtures in the first part of our study. ATLAS allows us to decompose a complex AM into individual aerosol types in terms of optical data measured by lidar. Optical data derived for individual aerosol types are then separately considered and inverted into PMPs with our automated unsupervised data-inversion methodology TiARA (Tikhonov Advanced Regularization Algorithm). We apply our new two-stage (ATLAS-TiARA) synergetic methodology to three lidar-measurement cases corresponding to two-, three-, and four-component AMs. The measurements we use for this study were carried out in the frameworks of the ORACLES-2016 and SHADOW field campaigns and lidar observations at the University of Lille (France), respectively. Results of the new methodology agree with results obtained with data collected by in situ instruments during the ORACLES-2016 campaign. Deviations of number concentration and single-scattering albedo at 532 nm retrieved with the new methodology from respective in situ measurements do not exceed 25% and 0.05, respectively. We find both fine-and coarse-mode particles from all three measurement cases. Fine-mode particles are represented by urban and smoke (haze), whereas coarse-mode particles can be attributed to dust, marine, and pollen aerosols. In summary, the methodology allows us to obtain a more detailed insight into microphysical particle properties.

The optical properties (extinction-to-backscatter ratio, backscattering, depolarization, and backscatter-related Angstrom exponent) and height distribution of Asian dusts were measured using a two-wavelength Raman/depolarization lidar at Taipei, Taiwan, during the Asian dust seasons in 2004 and 2005. Dust layers were frequently observed in the free atmosphere (1-6 km). Dust optical thickness ranged from 0.01 to 0.55; backscatter-related Angstrom exponents ranged from 0.42 to 1.47; and lidar ratios (extinction-to-backscatter ratio) for 355 nm ranged from 32 to 72 sr (steradian). The mean values of dust particle depolarization and extinction coefficient are 14 AE 6% and 0:16 km À1 , respectively, which are close to the moderate dust depolarizations and extinctions observed in free atmosphere in China and Japan. Backscatterrelated Angstrom exponents were found correlated positively with lidar ratio and negatively with particle depolarization, indicating that the dust optical characteristics are predominated by size distribution. Dusts were found to tend to exhibit unusual low depolarization properties under moist conditions (relative humidity RH470%), and the possible explanations are discussed.

Total suspended particle (TSP) samples were collected at Cape Hedo, Okinawa on a basis of 24, 12 and 3 h intervals in March to April 2007, when the Asian outflow is enhanced. The filter samples were analysed for dicarboxylic acids, oxoacids, benzoic acid and α-dicarbonyls to better understand the sources, chemical composition and photochemical ageing of organic aerosols during long-range transport. Their molecular distributions showed a predominance of oxalic acid (C 2 ) followed by malonic (C 3 ) and succinic (C 4 ) acids. Day/night samples did not show clear diurnal variations, suggesting that local anthropogenic influence is not important. The highest concentrations of C 2 and other diacid species were observed in April 10 when air masses were delivered from north China. Higher concentrations were observed when air masses arrived from East Asia and coastal China. The 3 h samples showed higher concentrations of oxalic acid at 16:30 or at 13:30 during April 14 and 16, whereas higher relative abundance of C 2 in total diacids and higher concentration ratios (C 2 /C 3 , C 2 /C 4 , C 3 /C 4 , C 2 /Gly, and C 2 /ωC 2 ) were observed at 7:30 during April 14-16. These results suggest that aerosols were accumulated in the atmosphere during night and photochemically modified early in the morning. Oxalic acid-C/OC did not show a prominent peak in 3-h samples. Temporal variations in the concentrations of diacids, oxoacids and α-dicarbonyls, relative abundances and diacid-C/OC ratios together with 5 day back trajectory analyses show that the aerosols from Cape Hedo are strongly influenced by long-range atmospheric transport from East Asia, especially in China. Strong correlations of C 2 with nss-SO 4 2-and NO 3 -in night-time suggest a secondary formation of water-soluble diacids via heterogeneous aqueous phase oxidation during long-range transport.

We studied and reconstructed a severe Central Asian dust storm of November 4, 2021, through high-resolution TROPOMI UVAI spaceborne observations, ground-based aerosol measurements, and Lagrangian particle modeling. The dust storm was caused by the front part of a cold polar anticyclone front from the Ural-Volga regions, which struck the central and eastern parts of Uzbekistan under favorable atmospheric conditions. Two plumes spread out, causing a thick haze to blanket the region. The most severe dust storm effects hit the capital of Uzbekistan (Tashkent) and the Fergana Valley, where the thick atmospheric dust layer dropped the visibility to 200 m. PM 10 concentrations reached 18,000 µg/m 3 (260-fold exceedance of the local long-term average). The PM 2.5 concentrations remained above 300 µg/m 3 for nearly ten days, indicating an extremely long-lasting event. The dust storm was caused by an extremely strong summer heatwave of 2021 in Kazakhstan with unprecedentedly high temperatures reaching 46.5 °C. The long-lasting drought dried up the soil down to 50 cm depth, triggering the soil cover denudation due to drying out vegetation and losing its moisture. This event was the worst since 1871 and considering the increasing aridity of Central Asia, the onset of potentially recurring severe dust storms is alarming. Dust and sandstorms have been traditionally viewed as localized phenomena, occurring mainly in arid and semi-arid regions and exhibiting mostly local-scale effects. However, under global warming, some dust storms (DS) have attained massive scales since the 1990s, thus prompting growing global concerns 1,2 . DSs are officially defined by the World Meteorological Organization (WMO) as the result of surface winds that raise large amounts of dust into the air and reduce visibility to less than 1000 m 3-5 . DS can lift thousands of tons of dust into the atmospheric boundary layer, which not only affects natural ecosystems but also disturbs the daily life of people and inflict economic damage by disrupting logistic/transportation chains, triggering aircraft/motor accidents, and even plaguing crop productivity . Moreover, dust particles can weaken soil fertility, reduce insulation at the surface (which, in turn, reduces the output from solar devices) damage telecommunications, and mechanical systems, and cause or exacerbate respiratory diseases among people 7,9-17 . Despite their global effects, massive DSs occur and develop only in a few regions worldwide with arid or semi-arid climates such as Sahara, Middle East, and Central Asia . These regions experience low precipitation (mean precipitation < 200-300 mm/year), strong winds, scarcity of vegetation cover, long dry summers, and frequent repetition of soil and atmospheric droughts . While severe DSs of the Middle East and Sahara have been thoroughly studied in previous reports, the studies on DSs of Central Asia and, let alone, their drivers, are very scanty. Central Asia is a vast region, primarily composed of arid ecosystems containing abundant mineral and salt aerosols, which, when lifted, can facilitate the development of severe DSs . On top of that, since the 1960s, the region has experienced major land use changes, which exacerbated its aridity. For instance, in Kazakhstan, land degradation was initiated in the 1950-1960s due to the development of so-called "Pristine Lands"-the activities aimed to increase the number of animals and to alter local grazing practices 25 . At the

Simultaneous observations were made in the marine atmospheric boundary layer and surface ocean during spring 2007 to investigate potential impacts of Asian dust on a semi-pelagic region of the northwestern North Pacific. The results suggest that mineral dust aerosols were scavenged by sea fog, and their deposition to the ocean increased the particle concentration in surface seawater. The atmospheric input of mineral dust to the ocean surface from this event was calculated to be 40 to 680 mg m -2 event -1 . A general relationship for the solubility of iron from dust particles led to an estimate of 20 to 330 mg m -2 for the amount of bio-available iron delivered during the dust event. This input of bio-available iron is comparable to total dissolved iron added during an iron fertilization experiment in the northwestern North Pacific in which an enhancement of primary production was observed.

Dust storms that occurred in East Asia during the spring of 2002 and 2003 were simulated by a regional dust deflation and transport model. Particular focus was placed on dust incursion events over Taiwan. Two of the events were analyzed in detail to give a complete picture of the three dimensional transport patterns. The general characteristics of dust incursion events were summarized, including the source locations, transport route and distribution pattern in three dimensions, traveling time, duration of incursion, and the seasonal spatial distribution of dust concentration. Significant differences were also found in these characteristics between the two years, the main cause of which was a change in regional climate patterns. The performance of the model developed for this study was evaluated against other dust forecast models, and found to have superior capability for forecasting in the Taiwan area.

Using 30 years of satellite observations, two sand and dust storms (SDS) source locations (hotspots) were detected on the southern side of the Mesopotamian Flood Plain. Around 40 million people in the region are affected by the two hotspots, including populations in Iraq, Iran, Kuwait, Saudi Arabia, Qatar, Bahrain, and Emirates. Both hotspots encompass roughly 8212 km2 and contribute 11% to 85% in 2005 and 2021, respectively, of the total SDS in the region. Dust physical (particle surface area and size percentages) and chemical (mineralogy, major and trace elements, and radionuclides) properties show close similarities between source and downwind samples during SDS originated solely from the two hotspots. Deposited dust size particles show a finning trend towards the north in the Middle East compared to the south. A comprehensive assessment of the chemical and physical properties of soil and dust samples was conducted as an essential step in developing and implementing a mitigation ...

We present a 3-D climatology of the desert dust distribution over South-East Asia derived using CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) data. To distinguish desert dust from total aerosol load we apply a methodology developed in the framework of EARLINET (European Aerosol Research Lidar Network), the particle linear depolarization ratio and updated lidar ratio values suitable for Asian dust, on multiyear CALIPSO observations (01/2007&ndash;12/2015). The resulting dust product provides information on the horizontal and vertical distribution of dust aerosols over SE (South-East) Asia along with the seasonal transition of dust transport pathways. Persistent high D_AOD (Dust Aerosol Optical Depth) values, of the order of 0.6, are present over the arid and semi-arid desert regions. Dust aerosol transport (range, height and intensity) is subject to high seasonality, with highest values observed during spring for northern China (Taklimakan/Gobi deserts) ...

The mass concentration of Asian dust in the atmosphere is an essential parameter of the atmospheric environment in East Asia. In April 2016, we conducted simultaneous observations using an optical particle counter (OPC) installed on a tethered balloon and a ceilometer in the Gobi Desert. We estimated the mass-extinction conversion factor MECF (gm -2 ) from the relationship between the dust extinction coefficient and dust mass concentration obtained by simultaneous observations. The MECF at Dalanzadgad in the Gobi Desert is 2.16 gm -2 at 910 nm and 1.91 gm -2 at 532 nm. A previous study on Asian dust showed that the values of the MECF were 1.78 gm -2 in Beijing, 1.40 gm -2 in Seoul, 1.18 gm -2 in Tsukuba (Japan), and 1.04 gm -2 at averaged AD-Net lidar stations in Japan. The MECF values decreased from the Asian dust source to the lee-side areas. This result suggests that the MECF depends on the size distribution of the dust.

A large-scale dust event occurred in East Asia during early May 2017, and transported dust was measured all over Japan. We performed an analysis of the entire dust event using multiple sources: a local ceilometer measurement, measurements from an optical particle counter in the Gobi Desert (Dalanzadgad, Mongolia), a study of Dust RGB imagery obtained from Himawari-8, lidar measurements from Japan, and meteorological data. Our results show that three extratropical low pressure systems occurred consecutively in Mongolia and generated dust storms in the Gobi Desert. Remarkably, the Dust RGB imagery shows both the occurrence and the transportation of the dust, and was able to detect two dust outbreaks in the Horqin Sandy Land of Northern China and their transportation to eastern Japan; this shows that the Horqin Sandy Land was one of the source regions of this dust event.

A large-scale dust event occurred in East Asia during early May 2017, and transported dust was measured all over Japan. We performed an analysis of the entire dust event using multiple sources: a local ceilometer measurement, measurements from an optical particle counter in the Gobi Desert (Dalanzadgad, Mongolia), a study of Dust RGB imagery obtained from Himawari-8, lidar measurements from Japan, and meteorological data. Our results show that three extratropical low pressure systems occurred consecutively in Mongolia and generated dust storms in the Gobi Desert. The dust generated by the third low pressure system was transported to Japan by a cold front and two pressure troughs, which were associated with the low pressure system. Remarkably, the Dust RGB imagery shows both the occurrence and the transportation of the dust, and was able to detect two dust outbreaks in the Horqin Sandy Land of Northern China and their transportation to eastern Japan; this shows that the Horqin Sandy Land was one of the source regions of this dust event.

Asian dust is transported over a long range via the mid-latitude westerlies when dust is lifted to the free troposphere over the source regions, whereas dust remaining in the atmospheric boundary layer is not transported far. In the Gobi Desert, a major source region of Asian dust, a ceilometer (compact lidar) monitors the vertical distribution of dust at Dalanzadgad, Mongolia. On 29-30 April 2015, the ceilometer observed a developed dust storm over the ground, followed by a dust layer within a height of 1.2-1.8 km. The dust storm had already developed in the upwind region before reaching Dalanzadgad. This feature was also shown in the ceilometer observation data. The dust layer remained at almost the same height for 12 h, because the dust became trapped within an inversion layer at a height of 1.2-1.5 km over cold air. This result suggests that the inversion layer prevented the dust from reaching the free troposphere, thereby restraining the long-range transport of the dust via the westerlies. This is the first paper that reports this type of vertical distribution of dust in the source region based on observation data.

Recent climate change, especially during the 2000s, may be the primary reason for the expansion of the Asian dust source region. The change in the dust source region was investigated by examining anthropogenic radionuclides contained in surface soil samples from Mongolia. Surface soil was globally labeled by radioactive fallout from nuclear testing during the late 1950s and early 1960s, but there are no current direct sources for anthropogenic radionuclides in the air (before the Fukushima nuclear power plant accident in 2011). Radionuclides in the atmosphere are therefore carried mainly by wind-blown dust from surface soil, that is, aeolian dust. Asian dust carries traces of 90 Sr, 137 Cs, and other anthropogenic radionuclides; the heaviest deposition occurs in spring and has been recorded in Japan since the early 1990s. The composition of anthropogenic radionuclides in atmospheric depositions would be affected by a change in the dust source. Previous studies of atmospheric deposition at long-term monitoring sites (e.g. in Tsukuba, Japan) have detected changes in the 137 Cs/ 90 Sr ratio and in the specific activity of the radionuclides. These changes in the composition of observed atmospheric depositions are supposed to reflect changes in the climatic conditions of the dust source region. To investigate this dust source change, we conducted a field survey of radionuclides ( 90 Sr and 137 Cs) in surface soil samples in September 2007 in the eastern and southern regions of Mongolia, where dust storms have occurred more frequently since 2000. The specific activities of both radionuclides as well as the 137 Cs/ 90 Sr ratio in the surface soil were well cor-

The distribution and transport of windblown dust that occurred in Northeast Asia from 28 March to 2 April 2012 was investigated. Data of particulate matter less than 10 micrometers (PM10) near the surface and light detection and ranging (LiDAR) measurements from the ground up to 18 km were used in the study. A severe dust event originated over southern Mongolia and northern China on 28 March 2012, and the widespread dust moved from the source area southeastward toward Japan over several days. Windblown dust reached Japan after two days from the originating area. LiDAR measurements of the vertical distribution of the dust were one to two km thick in the lower layer of the atmosphere, and increased with the increasing distance from the source area.

Sun/sky photometry and polarimetry of atmospheric light have been undertaken by multispectral photometers (CE-318-1 and -2, Cimel Electronique, France) and a polarimeter (PSR-1000, Opto Research, Japan) over Amami, Noto, and Shirahama, Japan, during APEX-E1, -E2, and ACE-Asia field campaigns. Radiometers provide us with the optical thickness of aerosols and A ˚ngstro ¨m exponent. Other aerosol characteristics, e.g., size distribution, refractive index, etc., are retrieved based on each inversion method corresponding each equipment. The former takes a standard AERONET processing, and the latter is according to our own procedure to analyze the polarimetry with PSR-1000. After several aerosol parameters are derived, the HYSPLIT4 backward trajectory analysis is adopted to search the origin of aerosols. It is shown from these ground measurements that aerosol optical thickness, A ˚ngstro ¨m exponent, and refractive index are classified into two typical categories as a background type detected in winter, and a soil dust type appeared in Asian dust events in spring. Further, it is found that the obtained size distribution of Asian dust indicates the dominance of large particles.

Production, transport and deposition of mineral dust have significant impacts on different components of the Earth systems through time and space. In modern times, dust plumes are associated with their source region(s) using satellite and land-based measurements and trajectory analysis of air masses through time. Reconstruction of past changes in the sources of mineral dust as related to changes in climate, however, must rely on the knowledge of the geochemical and mineralogical composition of modern and paleodust, and that of their potential source origins. In this contribution, we present a 13,000-yr record of variations in radiogenic Sr-Nd-Hf isotopes and Rare Earth Element (REE) anomalies as well as dust grain size from an ombrotrophic (rain fed) peat core in NW Iran as proxies of past changes in the sources of dust over the interior of West Asia. Our data shows that although the grain size of dust varies in a narrow range through the entire record, the geochemical fingerprint of dust particles deposited during the lowflux, early Holocene period (11,700-6,000 yr BP) is distinctly different from aerosols deposited during high dust flux periods of the Younger Dryas and the mid-late Holocene (6,000-present). Our findings indicate that the composition of mineral dust deposited at the study site changed as a function of prevailing atmospheric circulation regimes and land exposure throughout the last deglacial period and the Holocene. Simulations of atmospheric circulation over the region show the Northern Hemisphere Summer Westerly Jet was displaced poleward across the study area during the early Holocene when Northern Hemisphere insolation was higher due to the Earth's orbital configuration. This shift, coupled with lower dust emissions simulated based on greening of the Afro-Asian Dust Belt during the early Holocene likely led to potential sources in Central Asia dominating dust export to West Asia during this period. In contrast, the dominant western and southwest Asian and Eastern African sources have prevailed during the mid-Holocene to modern times.

A long- and large-range heavy dust episode occurred from 3 to 8 May 2017 in China. To explore the impacts of this long-range dust transport episode on the chemical compositions and size distributions of urban aerosols, such instruments as an online analyzer for monitoring aerosols and gases (MARGA) and a wide-range particle spectrometer (WPS) were mainly used to monitor chemical components, such as PM2.5 and aerosol size distributions in the range of 10 nm to 10 μm, in Nanjing in this study. During the dust episode, the average concentrations of PM2.5 and PM10 and ions of Ca2+, Mg2+, Cl-, SO42−, NO3−, and NH4+ were 66.2, 233.9, and 1.1, 1.5, 1.1, 11.4, 7.8 and 4.4 μg·m−3, which were 4.4, 5.8, 3.7, 15, 1.38, 1.84, 1.66 and 1.83 times higher than the values observed before the episode and 2.2, 3.3, 5.5, 5.0, 1.57, 1.97, 1.39 and 1.69 times the levels after the episode. The dusts were demonstrated to have differential impacts on the water-soluble gases in the air. During the dust episo...

over the Iberian Peninsula (IP). We report on aerosol optical properties observed under this extreme dust intrusion through passive and active remote sensing techniques. For that, AERONET (AErosol RObotic NETwork) and EARLINET (European Aerosol Research LIdar NETwork) databases are used. The sites considered are: Barcelona (41.38°N, 2.17°E), Burjassot (39.51°N, 0.42°W), Cabo da Roca (38.78°N, 9.50°W), Évora (38.57°N, 7.91°W), Granada (37.16°N, 3.61°W) and Madrid (40.45°N, 3.72°W). Large aerosol optical depths (AOD) and low Ångström exponents (AE) are observed. An AOD of 2.0 at 675 nm is reached in several stations. A maximum peak of 2.5 is registered in Évora. During and around the peak of AOD, AEs close to 0 and even slightly negative are measured. With regard to vertically-resolved aerosol optical properties, particle backscatter coefficients as high as 15 Mm −1 sr −1 at 355 nm are recorded at the lidar stations. Layer-mean lidar ratios are found in the range 40-55 sr at 355 nm and 34-61 sr at 532 nm during the event. The particle depolarization ratios are found to be constant inside the dust layer, and consistent from one site to another. Layer-mean values vary in the range 0.19-0.31. Another remarkable aspect of the event is the limited vertical distribution of the dust plume which never exceeds 5 km. The extreme aspect of the event also presented a nice case for testing the ability of two dust forecast models, BSC-DREAM8b and NMMB/BSC-Dust, to reproduce the arrival, the vertical distribution and the intensity of the dust plume over a long-range transport region. In the particular case of the February 2017 dust event, we found a large underestimation in the forecast of the extinction coefficient provided by BSC-DREAM8b at all heights independently of the site. In contrast NMMB/BSC-Dust forecasts presented a better agreement with the observations, especially in southwestern part of the IP. With regard to the forecast skill as a function of lead time, no clear degradation of the prognostic is appreciated at 24, 48 and 72 h for Évora and Granada stations (South). However the prognostic does degrade (bias increases and/or correlation decreases) for Barcelona

Aerosol particles represent fine particulate matter suspended in the air. These particles interact with the climate conditions (indirectly) and the radiation balance (directly) of the Earth. Iraq represents one of the aerosol hot spots in southwest Asia because of repeated dust storms that need further in-depth studies to describe and understand the dust activity. This research assesses the spatiotemporal pattern variability of the aerosol index values obtained from TOMS-OMI satellite platforms and compares it with selected surface weather factors to describe the dust phenomena over Iraq during 1980-2015. The results show a significant monthly and seasonal variability of aerosol index AI distributions between the northern and southern regions of Iraq. The monthly average AI data display maximum values during the hot summer months and minimum values in the cold winter months over the study regions. Maximum AI values occur above the southern area during March-October, reducing gradually towards the north, whereas the minimum values are recorded between December and February. The highest values of AI distribution from the TOMS satellite were 2.06, 1.93, and 1.87 and for the OMI sensor were 2.32, 2.27 and 2.24 in June above the northern, central and south regions, respectively, with lower values in December. The correlation between aerosol index and relative humidity, air temperatures, wind velocity and rainfall can be employed effectively to estimate and predict dust activity. This study can enhance awareness and understanding of atmospheric dust activity over Iraq and the Middle East region.

Aerosols in Southeast Asia (SEA) are entangled with complex land–sea–atmosphere–human interactions, and it is difficult for scientists to understand their dynamic behaviors. This study aims to provide an insightful understanding of aerosols across SEA with respect to their radiative properties using several lines of evidence obtained from remote sensing instruments, including those from onboard Earth observation satellites (MODIS/Terra and MODIS/Aqua, CALIOP/CALIPSO) and from ground-based observation (AERONET). The findings, obtained from cluster analysis of aerosol optical properties, showed seven aerosol types which were dominant across the country, exhibiting diverse radiative forcing potentials. The light-absorbing (prone to warm the atmosphere) aerosols were likely found in mainland SEA, both for background and high-aerosol events. The light-scattering aerosols were associated with aging processes and hygroscopic growth. The neutral potential, which comprised a mixture of ocean...

Comprehensive modelling of dust events requires a full physical representation of small-scale emission mechanisms and description of long-range transport dynamic. In this paper we propose a simulation system that integrates three different models in order to represent the whole dust cycle. The RAMS atmospheric model configuration has two nested grids, at 50 km and 10 km horizontal resolution, and is used to force both the dust emission model DUSTEM, and the transport model CAMx. The performance of the three-model simulation system was evaluated using a major dust storm that occurred in March 2002 in the desert of the Alashan Prefecture (Inner Mongolia, China) and which had a significant impact over a large area in northern China. In order to identify potential active dust sources, a specific remote sensed analysis, calibrated through a field campaign in the Alashan Prefecture region, has been assimilated in the modelling system. Simulated dust storm features, from the higher resolution grid, are in good agreement with observed data: surface wind values discrepancies are less than 2 m/s in the Alashan area and less than 5 m/s along the dust storm track. In comparison to ground observations, the modelled dust surface concentration peaks in Beijing differ by only 2 mg/m 3 although the timing of dust peaks is delayed in the model. As a consequence this integrated numerical model, along with the remote sensed land surface characterization, is suggested to be a practical and flexible tool for simulating and analysing the whole dust storm dynamics.

Central Asia is a relatively understudied region of the world in terms of characterizing ambient particulate matter (PM) and quantifying source impacts of PM at receptor locations, although it is speculated to have an important role as a source region for long-range transport of PM to Eastern Asia, the Pacific Ocean, and the Western United States. PM is of significant interest not only because of its adverse effect on public health but also due to its more recently realized role in climate change. To investigate the sources and characteristics of PM in the region, a series of PM 2.5 and PM 10 samples were collected on an every-other-day basis at two sites (termed "Bishkek" and "LIDAR") in the Central Asian nation of the Kyrgyz Republic (also known as Kyrgyzstan) for a full year from July 2008 to July 2009. These samples were analyzed using standard methods for mass, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-insoluble organic carbon by difference (OC minus WSOC) and a variety of molecular marker chemical species to be used in a chemical mass balance (CMB) model to apportion the sources of OC. These analyses indicate that approximately 19 ± 6.4 % of the PM 2.5 mass at both sites throughout the year consists of OC. The carbonaceous component of PM 2.5 is dominated by OC, with OC/Total Carbon (TC) ratios being around 0.8 in the winter to almost 0.95 in the summer months. The CMB analysis indicated that mobile sources, i.e., gasoline and diesel engine exhaust, biomass combustion, and biogenic secondary organic aerosol (SOA) formation from isoprene and α-pinene precursors in the summer months were the dominant sources of OC. A strong positive correlation was observed between non-biomass burning WSOC and the un-apportioned OC from the CMB analysis, indicating that some of this un-apportioned OC is WSOC and likely the result of SOAforming atmospheric processes that were not estimated by the CMB analysis performed. In addition, a comparison of the predominant contributors to OC between the two sites indicates that biomass combustion is a stronger relative source of OC at the LIDAR site, particularly in the winter, while contributions of isoprene-and α-pinene-derived SOA to the measured OC was relatively similar between the sites. * "N.D." indicates that the molecular marker critical to this source profile was not present above the detection limit. Table 4 Click here to download Table: Table 4.doc

A Mie lidar was used to make observations of Asian dust over Hefei (31.90°N, 117.16°E) in spring 2000. This paper presents main features of vertical distribution and temporal variation of Asian dust extinction coefficient at 532-nm wavelength. It was found that the Asian dust events contributed significantly to very large aerosol extinction coefficients in the boundary layer or middle troposphere. Extinction coefficient value as large as 0.7 km À1 at 3 km above ground level (AGL) has been observed. The Asian dust extinction coefficient profiles showed very big changes from early morning to evening and also appeared substantial amount of temporal variation during the nighttime. For the severe Asian dust days the depth of boundary layer rose up to around 4 km AGL, but only 1$2 km AGL for normal days. The seasonal average aerosol extinction coefficient profiles also showed that larger aerosol extinction coefficients from 1-to 10-km altitude range were observed in the springtime rather than in any other season. Meanwhile, solar extinction and radiation measurements indicated that the Asian dust particles were composed of larger size particles and they produced significantly perturbation in solar radiation on the Earth surface.

Asian dusts exert significant influences on regional air quality, weather, and climate. Detection of these highly variable aerosol events is challenging due to several factors, such as short lifetime, multiple scales, and strong interactions with local and regional surface and meteorological conditions. Since dust particles can directly alter solar and earth radiation in both visible (VS) and infrared (IR) spectral regions through scattering and absorption processes, both VS and IR remote sensing techniques can be used to detect dust plumes in the atmosphere. A dust detection system for multi-channel satellite imagers was applied in this study. The detection is based on the analysis of reflectance (or radiance) in VS channels or brightness temperature (BT) in IR channels. The magnitude of the difference in reflectance and/or BTs in selected channels due to dust is used to infer the signature of the dust particles. Descriptions of the detection system and its application for Asian dust using the Moderate-resolution Imaging Spectroradiometer (MODIS) satellite measurements are provided. The performance of the algorithm for Asian dust detection and its usefulness for monitoring the outbreaks and dispersion of Asian dust events were emphasized in the current study.

The concept of RGB (red-green-blue) composites is to combine the information of three different satellite channels or channel combinations, marking each part in one of the three colors: red, green and blue. The Dust RGB enables the discrimination between clouds and dust particles. Dust RGB implements the information provided by three different infra-red channels (12.0, 10.8 and 8.7 µm). Dust is seen as pink colour in the RGB composite.

Transboundary transport of air pollution in the South Asian region has been an issue of increasing importance over the past several decades. Long-range transport of anthropogenic pollution is contrasted with that of pollution produced by natural processes such as dust storms or natural forest fires. Airborne particulate matter datasets covering the period from 2002 to 2007 from the neighboring countries like Bangladesh, India, Pakistan and Sri Lanka were used to find the source areas that are primarily responsible for long range transported pollutants. All four countries collected samples with the same type of sampler and follow the same technique for mass and BC measurements. It was found that high fine soil contributions were from dust storms. On the other hand, smoke in this region mainly comes from northern India where agricultural waste is often burned.

Environmental context. Dust particles produced from wind blown soils are of global significance as these dust particles not only impact visibility, as evident in the recent 2009 Australian dust storm, but also atmospheric chemistry, climate and biogeochemical cycles. The amount of water vapour in the atmosphere (relative humidity) can play a role in these global processes yet there are few studies and little quantitative data on water-dust particle interactions. The focus of this research is on quantifying water-dust particle interactions for several dust sources including Asia and Africa where dust storms are most prevalent.

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

Through atmospheric transport, coming from the mainland, an important amount of dust arrives to surface waters of open-ocean regions and many coastal zones. Semi-arid and desert areas tend to act as important sources of dust. The Gulf of California (GC) is one of the most productive marginal seas of the world, and it is surrounded by the semi-arid deserts located in Baja California Peninsula, United States, and Sonora (Mex). Dust uxes coming from the BCP during the summer are relevant due biological impact on the California Gulf. In the northern region of the BCP, meteorological events have not been well studied. These events are known in popular slang as "El Torito". The characterization of a dust event that originated in the Baja California Peninsula (BCP) on June 14, 2016, is presented. Meteorological variables (from North American Regional Reanalysis-NARR), daily sea surface temperature, and aerosol optical thickness (from MODIS) to explain the dust event genesis, are used. Results suggest that sea surface temperature uctuations in the Paci c Ocean off the coast of the BCP generate changes in hydrometeorological variables (wind, relative humidity, and atmospheric pressure) that can give rise to dust events. These atmospheric dust intrusions in the foothills of the San Felipe desert are originated. They are distributed from the source areas to the northern Gulf of California, as shown by aerosol optical thickness images and HYSPLIT trajectory simulations, which establish vertical distributions with predominant heights between 0 and 500 m during June 14.

Atmospheric dust has wide‐reaching effects, not only influencing climate conditions, but also ecosystems. The eastern region of the Asian continent is one of the largest emitters of dust in the world, and recent economic growth in the region has been accompanied by an increase in anthropogenic emissions. However, the effects of increased Asian dusts on aquatic ecosystems are not well understood. We examined fossil pigments and zooplankton remains from 210Pb‐dated sediments taken from high mountain lakes of Hourai‐Numa and Hachiman‐Numa, located in the Towada‐Hachimantai National Park of Japan Islands, to uncover historical changes in the phyto‐ and zooplankton community over the past 100 years. Simultaneously, we measured the geochemical variables of TOC, TN, TP, δ13C, δ15N, and lead isotopes (207Pb/206Pb, 208Pb/206Pb) in the sediments to identify environmental factors causing such changes. As a result, despite few anthropogenic activities in the watersheds, alpine lakes in Japan ha...

The Chinese loess/palaeosol succession is one of the most comprehensive and intensively studied archives of Neogene and Quaternary global palaeoclimate events. Its stratigraphic details are widely recognised to indicate close links to the history and function of the East Asian Winter Monsoon (EAWM)-one of the most active components of the Earth's climate system. But the formal meteorological links between the EAWM and dust emission, both in the present day and in the past, have not been established and with it, the veracity of the loess record as an indicator of the EAWM questioned. Here we show that present day major dust events over northern China, while largely occurring during spring, are nevertheless 'conditioned' by the strength of the preceding EAWM. We also demonstrate, for the first time, a close link between the occurrence of dust events and the strength of the EAWM. From these findings, linked to global-scale climate model simulations, we conclude that the Chinese loess succession provides a convincing proxy record of the strength of the East Asian Winter Monsoon.