Now showing 1 - 7 of 7
- ItemVariations of the aerosol chemical composition during Asian dust storm at Dushanbe, Tajikistan(Les Ulis : EDP Sciences, 2019) Fomba, Khanneh Wadinga; Müller, Konrad; Hofer, Julian; Makhmudov, Abduvosit N.; Althausen, Dietrich; Nazarov, Bahron I.; Abdullaev, Sabur F.; Herrmann, HartmutAerosol 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. © 2019 The Authors, published by EDP Sciences.
- ItemVertical profiles of dust and other aerosol types above a coastal site(Les Ulis : EDP Sciences, 2019) Althausen, Dietrich; Mewes, Silke; Heese, Birgit; Hofer, Julian; Schechner, Yoav; Aides, Amit; Holodovsky, VadimMonthly mean vertical profiles of aerosol type occurrences are determined from multiwavelength Raman and polarization lidar measurements above Haifa, Israel, in 2017. This contribution presents the applied methods and threshold values. The results are discussed for one example, May 2017. This month shows more often large, non-spherical particles in lofted layers than within the planetary boundary layer. Small particles are observed at higher altitudes only when they are observed in lower altitudes, too. © 2019 The Authors, published by EDP Sciences.
- ItemThe regime of Aerosol Optical Depth and Ångström exponent over Central and South Asia(Les Ulis : EDP Sciences, 2019) Floutsi, Athina Avgousta; Korras Carraca, Marios Bruno; Matsoukas, Christos; Hatzianastassiou, Nikos; Biskos, GeorgeCentral and South Asia are regions of particular interest for studying atmospheric aerosols, being among the largest sources of desert dust aerosols globally. In this study we use the newest collection (C061) of MODIS-Aqua aerosol optical depth (AOD) at 550 nm and Ångström exponent (a) at 412/470 nm over the 15-year period between 2002 and 2017, providing the longest analyzed dataset for this region. According to our results, during spring and summer, high aerosol load (AOD up to 1.2) consisting of coarse desert dust particles, as indicated by a values as low as 0.15, is observed over the Taklamakan, Thar and Registan deserts and the region between the Aral and Caspian seas. The dust load is much lower during winter and autumn (lower AOD and higher a values compared to the other seasons). The interannual variation of AOD and a suggests that the dust load exhibits large decreasing trends (AOD slopes down to-0.22, a slopes up to 0.47 decade-1) over the Thar desert and large increasing trends between the Aral and Caspian seas (AOD and a slopes up to 0.23 decade-1 and down to-0.61 decade-1, respectively.) The AOD data are evaluated against AERONET surface-based measurements. Generally, MODIS and AERONET data are in good agreement with a correlation coefficient (R) equal to 0.835. © 2019 The Authors, published by EDP Sciences.
- ItemModelling mineral dust in the Central Asian region(Les Ulis : EDP Sciences, 2019) Heinold, Bernd; Tegen, InaIn Central Asia, climate and air quality are largely affected by local and long-travelled mineral dust. For the last century, the area has experienced severe land-use changes and water exploitation producing new dust sources. Today global warming causes rapid shrinking of mountain glaciers with yet unknow consequences for dust and its climate effects. Despite the importance for a growing population, only little is known about sources, transport pathways and properties of Central Asian dust. A transport study with a global aerosol-climate model is undertaken to investigate the life cycle of mineral dust in Central Asia for the period of a remote-sensing campaign in Tajikistan in 2015-2016. An initial evaluation with sun photometer measurements shows reasonable agreement for the average amount of dust, but a significant weakness of the model in reproducing the seasonality of local dust with maximum activity in summer. Source apportionment reveals a major contribution from Arabia throughout the year in accordance with observations. In the model, local sources mainly contribute in spring and autumn while summer-time dust production is underestimated. The results underline the importance of considering long-range transport and, locally, a detailed representation of atmospheric dynamics and surface characteristics for modelling dust in Central Asia. © 2019 The Authors, published by EDP Sciences.
- ItemLidar/radar approach to quantify the dust impact on ice nucleation in mid and high level clouds(Les Ulis : EDP Sciences, 2019) Ansmann, Albert; Mamouri, Rodanthi-Elisavet; Bühl, Johannes; Seifert, Patric; Engelmann, Ronny; Nisantzi, Agyro; Hofer, Julian; Baars, HolgerWe present the first attempt of a closure experiment regarding the relationship between ice nucleating particle concentration (INPC) and ice crystal number concentration (ICNC), solely based on active remote sensing. The approach combines aerosol and cloud observations with polarization lidar, Doppler lidar, and cloud radar. Several field campaigns were conducted on the island of Cyprus in the Eastern Mediterranean from 2015-2018 to study heterogeneous ice formation in altocumulus and cirrus layers embedded in Saharan dust. A case study observed on 10 April 2017 is discussed in this contribution. © 2019 The Authors, published by EDP Sciences.
- ItemEstimation of dust related ice nucleating particles in the atmosphere: Comparison of profiling and in-situ measurements(Les Ulis : EDP Sciences, 2019) Haarig, Moritz; Ansmann, Albert; Walser, Adrian; Baars, Holger; Urbanneck, Claudia; Weinzierl, Bernadett; Schöberl, Manuel; Dollner, Maximilian; Mamouri, Rodanthi; Althausen, DietrichVertical profiles of number concentrations of dust particles relevant for ice nucleation in clouds are derived from lidar measurements. The results are compared to coincidental airborne in-situ measurements of particle number and surface area concentrations in the dust layer. The observations were performed in long-range transported Saharan dust at Barbados and Asian dust at Cyprus. The Asian dust data analysis is ongoing. A comparison of Asian and Saharan dust will be given at the conference. Concentrations of ice nucleating particles in the order of 10 to 1000 per cm-3 in the dust layer are derived for a temperature of-25°C at Barbados. The method can be used to continuously monitor the concentration of ice nucleating dust particles vertically resolved from lidar measurements. © 2019 The Authors, published by EDP Sciences.
- ItemCADEX and beyond: Installation of a new PollyXT site in Dushanbe(Les Ulis : EDP Sciences, 2019) Engelmann, Ronny; Hofer, Julian; Makhmudov, Abduvosit N.; Baars, Holger; Hanbuch, Karsten; Ansmann, Albert; Abdullaev, Sabur F.; Macke, Andreas; Althausen, DietrichDuring 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. © 2019 The Authors, published by EDP Sciences.