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Multi-wavelength lidar measurements of the particle linear depolarization ratio of mineral dust layers at various locations around the Earth are presented from a comprehensive literature review. The values at a wavelength of 532 nm as well as the spectral slope of the depolarization ratio exhibits no significant difference between the Sahara, Arabia and Central Asia. The main difference was observed between freshly emitted and transported dust. Fresh dust has a higher depolarization ratio probably due to a higher amount of large dust particles. The depolarization ratio tends to decrease during transport time. This effect is strongest at 1064 nm and almost not present at 355 nm.

A mineralogical database is included in the simulation of mineral dust atmospheric life cycle for the chemistry and transport model COSMO5.05-MUSCAT. Evaluation of the ability of the model to reproduce the atmospheric drivers and the spatial-temporal resolution of mineral dust in the atmosphere is done through comparisons with remote sensing measurements in the Sahara Desert region for January-February 2022. Results show simultaneously good agreements and suggest that discrepancies could be explained due to the methods used for calculating mineral dust in the atmosphere not considering compositional differences.

First ever lidar observation in Tajikistan were conducted during the Central Asian Dust Experiment 2015–2016 (CADEX) in Dushanbe. Analysis of layer-mean optical properties revealed frequently low lidar ratios at enhanced depolarization ratios. These cases were categorized as background aerosol since they occurred at low extinction conditions. Such optical properties are similar to dried and therefore cubic-like shaped sea salt particles. This led to the hypothesis that Central Asian background aerosol and its optical properties are influenced by dry lakes and saline playas which are frequent in Central Asia. The goal of this study is to extend the existing data analysis with a backward trajectory-based time– height resolved air mass source attribution tool which was not yet available at the time of the CADEX campaign and its data analysis. Despite on average similar air mass origins for all cases irrespective of their optical properties, results suggest slightly more southern and south-western influenced air masses for cases with larger lidar ratios than for cases with lower lidar ratios.

In the Central Asian region, susceptibility to dust storms and escalating anthropogenic emissions poses challenges for air quality as well as environmental health. This study explores the temporal and seasonal dynamics of oxygenated polycyclic aromatic hydrocarbons (OPAHs) and aliphatic ketones in particulate matter during the Central Asian Dust Experiment (CADEX) in Dushanbe, both determined by Curie-Point Pyrolysis / Gas Chromatography Mass Spectrometry (CPP-GC/MS). The results revealed pronounced variations in the concentrations of OPAHs, particularly 9,10-anthracendione, as the most dominant compound, with a marked dominance in winter. The aliphatic ketones also displayed robust temporal variations, closely associated with combustion sources with 2-nonadecanone and 2-heptadecanone emerging as the dominant compounds. Both compound groups showed higher concentrations in winter. The impact of dust events on OPAHs was more noticeable during summer, with limited influence observed in winter. Combustion sources, particularly wood and coal burning, played a predominant role in shaping the observed concentrations, explaining most of the winter dominance. The elevated levels of OPAHs and ketones in Dushanbe underscore the need for implementing local mitigation strategies to curb exposure and potential health risks. This comprehensive analysis enhances our understanding of the intricate interplay between mineral dust, combustion sources, and atmospheric chemical composition, contributing to the development of air quality management strategies, in regions prone to dust events.

Focusing on Tajikistan, a region facing critical environmental challenges, this extended abstract provides insights into the relationship between aerosols and clouds in Central Asia by means of lidar observations. Since 2019, a novel Dual-Field-of-View (DFOV) Raman polarization lidar system in Dushanbe has provided highly-resolved data on aerosol and cloud microphysical properties. Given the limited observational experiments in Central Asia, these measurements might play a crucial role in addressing climaterelated concerns. In fact, this technological deployment might not only provide a better picture regarding the spatio-temporal distribution of mineral dust and urban emissions, but also improve our understanding regarding the complex interactions between aerosol and clouds. One of the most uncertain aspects when predicting future temperature and precipitation patterns. Furthermore, an extended trajectory-based source attribution tool has been implemented to track air masses in Tajikistan, providing enhanced support for this and future studies. This research focuses on data evaluation and analysis, building upon established lidar methodologies. The resulting insights can potentially contribute to a better understanding of the relationship between aerosols and clouds in the dry continental conditions that persists in this region.

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.

Monthly 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.

Mineral dust influences climate and weather by direct and indirect effects. Surrounded by dust sources, Central Asian countries are affected by atmospheric mineral dust on a regular basis. Climate change effects like glacier retreat and desertification are prevalent in Central Asia as well. Therefore, the role of dust in the climate system in Central Asia needs to be clarified and quantified. During the Central Asian Dust EXperiment (CADEX) first lidar observations in Tajikistan were conducted. Long-term vertically resolved aerosol measurements were performed with the multiwavelength polarization Raman lidar PollyXT from March 2015 to August 2016 in Dushanbe, Tajikistan. In this contribution, a climatology of the aerosol layer heights is presented, which was retrieved from the 18-month lidar measurements. Automatic detection based on backscatter coefficient thresholds were used to retrieve the aerosol layer heights and yield similar layer heights as manual layer height determination. The significant aerosol layer height has a maximum in summer and a minimum in winter. The highest layers occurred in spring, but in summer uppermost layer heights above 6 km AGL are frequent, too.

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.

We 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.

The presented study investigates the efficiency of heterogeneous ice formation in natural clouds over Lauder, New Zealand / Aotearoa. Aerosol conditions in the middle troposphere above Lauder are subject to huge contrasts. Clean, pristine air masses from Antarctica and the Southern Ocean arrive under southerly flow conditions, while high aerosol loads can occur when air masses are advected from nearby Australia. This study assesses how these contrasts in aerosol load affect the ice formation efficiency in stratiform midlevel clouds in the heterogeneous freezing range (- 40 to 0 ∘C). For this purpose, an 11-year dataset was analyzed from a dual-wavelength polarization lidar system operated by National Institute of Water and Atmospheric Research (NIWA), Taihoro Nukurangi, at Lauder in collaboration with the National Institute for Environmental Studies in Japan and the Meteorological Research Institute of the Japan Meteorological Agency. These data were used to investigate the efficiency of heterogeneous ice formation in clouds over the site as a function of cloud-top temperature as in previous studies at other locations. The Lauder cloud dataset was put into context with lidar studies from contrasting regions such as Germany and southern Chile. The ice formation efficiency found at Lauder is lower than in polluted midlatitudes (i.e., Germany) but higher than, for example, in southern Chile. Both Lauder and southern Chile are subject to generally low free-tropospheric aerosol loads, which suggests that the low ice formation efficiency at these two sites is related to low ice-nucleating-particle (INP) concentrations. However, Lauder sees episodes of continental aerosol, more than southern Chile does, which seems to lead to the moderately increased ice formation efficiency. Trajectory-based tools and aerosol model reanalyses are used to relate this cloud dataset to the aerosol load and the air mass sources. Both analyses point clearly to higher ice formation efficiency for clouds which are more strongly influenced by continental aerosol and to lower ice formation efficiency for clouds which are more influenced by Antarctic/marine aerosol and air masses. [ABSTRACT FROM AUTHOR]

The presented study investigates the efficiency of heterogeneous ice formation in natural clouds over Lauder, New Zealand/Aotearoa. Aerosol conditions in the middle troposphere above Lauder are subject to huge contrasts. Clean, pristine airmasses from Antarctica and the Southern Ocean arrive under southerly flow conditions while high aerosol loads can occur when air masses are advected from nearby Australia. This study assesses how these contrasts in aerosol load affect the ice formation efficiency in stratiform midlevel clouds in the heterogeneous freezing range (−40 °C to 0 °C). For this purpose, an 11-year dataset was analyzed from a dual-wavelength polarization lidar system operated by National Institute of Water & Atmospheric Research (NIWA) at Lauder in collaboration with the National Institute for Environmental Studies in Japan and the Meteorological Research Institute of the Japan Meteorological Agency. These data were used to investigate the efficiency of heterogeneous ice formation in clouds over the site as a function of cloud-top temperature as in previous studies at other locations. The Lauder cloud dataset was put into context with lidar studies from contrasting regions such as Germany and southern Chile. The ice formation efficiency found at Lauder is lower than in polluted mid-latitudes (i.e., Germany) but higher than for example in southern Chile. Both, Lauder and southern Chile are subject to generally low free-tropospheric aerosol loads, which suggests that the low ice formation efficiency at these two sites is related to low ice-nucleating particle (INP) concentrations. However, Lauder sees episodes of continental aerosol, more than does southern Chile, which seems to lead to the moderately increased ice formation efficiency. Trajectory-based tools and aerosol model re-analyses are used to relate this cloud dataset to the aerosol load and the air mass sources. Both analyses point clearly to higher ice formation efficiency for clouds which are more strongly influenced by continental aerosol, and to lower ice formation efficiency for clouds which are more influenced by Antarctic/marine aerosol and air masses. [ABSTRACT FROM AUTHOR]