Central Asian Dust Experiment (CADEX) and Comparison of Lidar Ratios of Asian and Saharan Dust

2016 ◽  
Author(s):  
Dietrich Althausen ◽  
Sabur F. Abdullaev ◽  
Julian Hofer ◽  
Abduvosit Makhmudov ◽  
Konrad Müller ◽  
...  
Keyword(s):  
Asian Dust ◽  
Saharan Dust ◽  
Central Asian

scholarly journals Asian and Saharan dust from a chemical/mineralogical point of view: differences and similarities from bulk and single particle measurements

2019 ◽  
Vol 99 ◽  
pp. 03001 ◽  
Author(s):  
Konrad Kandler ◽  
Dirk Scheuvens
Keyword(s):  
Field Measurements ◽  
Local Variation ◽  
Asian Dust ◽  
Point Of View ◽  
Saharan Dust ◽  
Dust Deposition ◽  
Particle Measurements ◽  
Atmospheric Aging ◽  
Central Asian ◽  
Dust Composition

This paper combines a review on the importance of dust composition with respect to numerous atmospheric impacts with field measurements performed in African and Central Asian dust. In the review part, the most important dust components and their relevance for certain processes are outlined. Typical compositions from bulk measurements for African and Asian dust are presented. Generally the local variation in composition can be higher than the differences between Asian and African dust and their according specific sources. While similar general results are available from individual particle analyses, these investigations add important information on mixing state and homogeneity of composition. Atmospheric aging of mineral dust is observed globally, depending on transport distances from the sources and transport environment. As an illustration, comparative field measurements of African and Asian dust deposition are presented.

scholarly journals Scientists Share Results of Dust Belt Research

Eos ◽  
2019 ◽  
Vol 100 ◽  
Author(s):  
Dietrich Althausen ◽  
Sabur Abdullaev ◽  
Julian Hofer
Keyword(s):  
Asian Dust ◽  
Central Asian

Central Asian Dust Conference; Dushanbe, Tajikistan, 8–12 April 2019

scholarly journals CADEX and beyond: Installation of a new PollyXT site in Dushanbe

2019 ◽  
Vol 99 ◽  
pp. 02010
Author(s):  
Ronny Engelmann ◽  
Julian Hofer ◽  
Abduvosit N. Makhmudov ◽  
Holger Baars ◽  
Karsten Hanbuch ◽  
...  
Keyword(s):  
Asian Dust ◽  
Raman Lidar ◽  
Technical Institute ◽  
Lidar System ◽  
Microphysical Properties ◽  
Source Regions ◽  
Central Asian ◽  
Lidar Measurements ◽  
Academy Of Sciences

During the 18-month Central Asian Dust Experiment we conducted continuous lidar measurements at the Physical Technical Institute of the Academy of Sciences of Tajikistan in Dushanbe between 2015 and 2016. Mineral dust plumes from various source regions have been observed and characterized in terms of their occurrence, and their optical and microphysical properties with the Raman lidar PollyXT. Currently a new container-based lidar system is constructed which will be installed for continuous long-term measurements in Dushanbe.

scholarly journals Long-term profiling of mineral dust and pollution aerosol with multiwavelength polarization/Raman lidar at the Central Asian site of Dushanbe, Tajikistan: Case studies

2017 ◽  
Author(s):  
Julian Hofer ◽  
Dietrich Althausen ◽  
Sabur F. Abdullaev ◽  
Abduvosit N. Makhmudov ◽  
Bakhron I. Nazarov ◽  
...  
Keyword(s):  
Middle Eastern ◽  
Asian Dust ◽  
Raman Lidar ◽  
Dust Event ◽  
Angstrom Exponent ◽  
Central Asian ◽  
Ångström Exponent ◽  
Lidar Ratio ◽  
532 Nm ◽  
Ångstrom Exponent

Abstract. For the first time, continuous vertically resolved aerosol measurements were performed by lidar in Tajikistan, Central Asia. Observations with the multiwavelength polarization/Raman lidar PollyXT 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 of the measured optical properties and the calculated dust and non-dust mass concentrations are presented. Dust source regions were identified by means of backward trajectory analyses. A lofted layer of Middle Eastern dust with an aerosol optical thickness (AOT) of 0.4 and an extinction-related Ångström exponent of 0.41 was measured. In comparison, two near-ground dust cases have Central Asian sources. One is an extreme dust event with an AOT of 1.5 and Ångström exponent of 0.12 and the other one is a most extreme dust event with an AOT of above 4 (measured by sun photometer) and an Ångström exponent of −0.08. The observed lidar ratios (particle linear depolarization ratios) in the presented dust cases range from 40.3 sr to 46.9 sr (0.18–0.29) at 355 nm and from 35.7 sr to 42.9 sr (0.31–0.35) at 532 nm wavelength. The particle linear depolarization ratios indicate almost unpolluted dust in the case of a lofted dust layer and pure dust in the near-ground dust cases. The lidar ratio values are lower than typical lidar ratio values for Saharan dust (50–60 sr) and comparable to Middle Eastern/West-Asian dust lidar ratios (35–45 sr). In contrast, the presented case of pollution aerosol of local origin has an Ångström exponent of 2.07 and a lidar ratio (particle linear depolarization ratio) of 55.8 sr (0.03) at 355 nm and 32.8 sr (0.08) at 532 nm wavelength.

scholarly journals Mineral dust in Central Asia: Combining lidar and other measurements during the Central Asian dust experiment (CADEX)

2018 ◽  
Vol 176 ◽  
pp. 04009 ◽  
Author(s):  
Dietrich Althausen ◽  
Julian Hofer ◽  
Sabur Abdullaev ◽  
Abduvosit Makhmudov ◽  
Holger Baars ◽  
...  
Keyword(s):  
Climate Change ◽  
Chemical Analysis ◽  
Central Asia ◽  
Mineral Dust ◽  
Asian Dust ◽  
Local Conditions ◽  
It Impacts ◽  
Central Asian ◽  
Sun Photometer

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.

scholarly journals Comparison of key absorption and optical properties between pure and transported anthropogenic dust over East and Central Asia

2016 ◽  
Vol 16 (24) ◽  
pp. 15501-15516 ◽  
Author(s):  
Jianrong Bi ◽  
Jianping Huang ◽  
Brent Holben ◽  
Guolong Zhang
Keyword(s):  
Optical Properties ◽  
Climate Models ◽  
Complex Refractive Index ◽  
Asian Dust ◽  
Global Climate Models ◽  
Dust Aerosol ◽  
Asymmetry Factor ◽  
Anthropogenic Aerosol ◽  
Sensing Applications ◽  
Central Asian

Abstract. Asian dust particulate is one of the primary aerosol constituents in the Earth–atmosphere system that exerts profound influences on environmental quality, human health, the marine biogeochemical cycle, and Earth's climate. To date, the absorptive capacity of dust aerosol generated from the Asian desert region is still an open question. In this article, we compile columnar key absorption and optical properties of mineral dust over East and Central Asian areas by utilizing the multiyear quality-assured datasets observed at 13 sites of the Aerosol Robotic Network (AERONET). We identify two types of Asian dust according to threshold criteria from previously published literature. (1) The particles with high aerosol optical depth at 440 nm (AOD440 ≥  0.4) and a low Ångström wavelength exponent at 440–870 nm (α < 0.2) are defined as Pure Dust (PDU), which decreases disturbance of other non-dust aerosols and keeps high accuracy of pure Asian dust. (2) The particles with AOD440 ≥  0.4 and 0.2 < α < 0.6 are designated as Transported Anthropogenic Dust (TDU), which is mainly dominated by dust aerosol and might mix with other anthropogenic aerosol types. Our results reveal that the primary components of high AOD days are predominantly dust over East and Central Asian regions, even if their variations rely on different sources, distance from the source, emission mechanisms, and meteorological characteristics. The overall mean and standard deviation of single-scattering albedo, asymmetry factor, real part and imaginary part of complex refractive index at 550 nm for Asian PDU are 0.935 ± 0.014, 0.742 ± 0.008, 1.526 ± 0.029, and 0.00226 ± 0.00056, respectively, while corresponding values are 0.921 ± 0.021, 0.723 ± 0.009, 1.521 ± 0.025, and 0.00364 ± 0.0014 for Asian TDU. Aerosol shortwave direct radiative effects at the top of the atmosphere (TOA), at the surface (SFC), and in the atmospheric layer (ATM) for Asian PDU (α < 0.2) and TDU (0.2 < α < 0.6) computed in this study, are a factor of 2 smaller than the results of Optical Properties of Aerosols and Clouds (OPAC) mineral-accumulated (mineral-acc.) and mineral-transported (mineral-tran.) modes. Therefore, we are convinced that our results hold promise for updating and improving accuracies of Asian dust characteristics in present-day remote sensing applications and regional or global climate models.

scholarly journals Central Asian Dust Experiment (CADEX): Multiwavelength Polarization Raman Lidar Observations in Tajikistan

2016 ◽  
Vol 119 ◽  
pp. 18006 ◽  
Author(s):  
Julian Hofer ◽  
Dietrich Althausen ◽  
Sabur F. Abdullaev ◽  
Ronny Engelmann ◽  
Holger Baars
Keyword(s):  
Asian Dust ◽  
Raman Lidar ◽  
Central Asian ◽  
Lidar Observations

scholarly journals Variations of the aerosol chemical composition during Asian dust storm at Dushanbe, Tajikistan

2019 ◽  
Vol 99 ◽  
pp. 03007
Author(s):  
Khanneh Wadinga Fomba ◽  
Konrad Müller ◽  
Julian Hofer ◽  
Abduvosit N. Makhmudov ◽  
Dietrich Althausen ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Trace Metal ◽  
Mineral Dust ◽  
Anthropogenic Activities ◽  
Inorganic Ions ◽  
Asian Dust ◽  
Saharan Dust ◽  
Industrial Emissions ◽  
Aerosol Mass ◽  
Aerosol Chemical Composition

Aerosol chemical composition was characterized during the Central Asian Dust Experiment (CADEX) at Dushanbe (Tajikistan). Aerosol samples were collected during a period of 2 months from March to May 2015 using a high volume DIGITEL DHA-80 sampler on quartz fiber filters. The filters were analyzed for their ionic, trace metals as well as organic and elemental carbon (OC/EC) content. The aerosol mass showed strong variation with mass concentration ranging from 18 μg/m3 to 110 μg/m3. The mineral dust concentrations varied between 0.9 μg/m3 and 88 μg/m3. Days of high aerosol mass loadings were dominated by mineral dust, which made up to about 80% of the aerosol mass while organic matter and inorganic ions made up about 70% of the aerosol mass during days of low aerosol mass loadings. The mineral dust composition showed different trace metal signatures in comparison to Saharan dust with higher Ca content and Ca/Fe ratios twice as high as that observed in Saharan dust. Strong influence of anthropogenic activities was observed in the trace metal concentrations with Zn and Pb concentrations ranging from 7 to 197 ng/m3 and 2 to 20 ng/m3, respectively. Mineral dust and anthropogenic activities relating to traffic, combustion as well as metallurgical industrial emissions are identified as the sources of the aerosol during this period.

scholarly journals Saharan and Asian dust: similarities and differences determined by CALIPSO, AERONET, and a coupled climate-aerosol microphysical model

2011 ◽  
Vol 11 (7) ◽  
pp. 3263-3280 ◽  
Author(s):  
L. Su ◽  
O. B. Toon
Keyword(s):  
Lower Layer ◽  
Single Scattering ◽  
Asian Dust ◽  
Dust Removal ◽  
Saharan Dust ◽  
Dust Source ◽  
African Dust ◽  
Dust Flux ◽  
Dust Lifting ◽  
Local Dust

Abstract. This study compares the properties of atmospheric dust from the Saharan deserts and the Asian deserts using data from CALIPSO and AERONET during 2006 and 2007 along with simulations using a coupled climate-microphysical sectional model. Saharan deserts are largely south of 30° N, while Asian ones are primarily north of 30° N, hence they experience different meteorological regimes. Saharan dust lifting occurs all year long, primarily due to subtropical weather systems. However, Asian dust is lifted mostly in spring when mid-latitude frontal systems lead to high winds. Rainfall is more abundant over Asia during the dust lifting events, leading to greater local dust removal than over the Sahara. However, most dust removal is due to sedimentation. Despite the different meteorological regimes, the same dust lifting schemes work in models for Asian and Saharan dust. The magnitudes of dust lifted in Africa and Asia differ significantly over the year. In our model the yearly horizontal dust flux just downwind of the African dust source is about 1088 Tg (10° S–40° N, 10° W) and from the Asian dust source it is about 355 Tg (25° N–55° N, 105° E) in 2007, which is comparable to previous studies. We find the difference in dust flux is mainly due to the larger area over which dust is lifted in Africa than Asia. However, Africa also has stronger winds in some seasons. Once lifted, the Saharan dust layers generally move toward the west and descend in altitude from about 7 km to the surface over several days in the cases studied. Asian dust often has multiple layers (two layers in the cases studied) during transport largely to the east. One layer stays well above boundary layer during transport and shows little descent, while the other, lower, layer descends with time. This observation contrasts with studies suggesting the descent of Saharan dust is due to sedimentation of the particles, and suggests instead it is dominated by meteorology. We find the size distributions of Asian and African dust are similar when the dust is lifted, but the mode size can differ and secondary size modes can develop probably due to differences in vertical wind velocities during transport. The single scattering albedo of African and Asian dust does differ, due primarily to the imaginary parts of the refractive indexes being different, which in turn is likely due to different dust composition. This study is a step towards a global understanding of dust and its properties.

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