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Dust aerosols persistently affect nearly all landscapes worldwide, and the saltation activity caused by dusty weather (e.g., dust days) releases considerable amounts of aerosol into the atmosphere. Nevertheless, dust-induced saltation activity may also occur on non-dust days. To date, few studies have investigated the saltation activity characteristics on non-dust days. Moreover, the contribution of non-dust days to the total saltation activity remains ambiguous. This study comprehensively investigates the characteristics of saltation activity on non-dust days. Specifically, we analyze the influence of the saltation activity of non-dust days on dust aerosols by utilizing saltation, atmospheric, soil, dust aerosol (i.e., PM10 and aerosol optical depth), and weather record data obtained from the Taklimakan Desert, China, between 2008 and 2010. Our results show that lower temperature, vapor pressure, and soil moisture on non-dust days reduces the saltation threshold velocity (5.9 m/s) more compared to on dust days (6.5 m/s). Furthermore, regarding wind speed, relatively strong monthly saltation activity occurs from March to August, and daily saltation activity occurs from 9:00 to 16:00. Although non-dust days only contribute 18.5% and 7.7% to saltation time and saltation count, respectively, both significantly influence the dust aerosols. Therefore, the effect of saltation activity on non-dust days cannot be undervalued, particularly while performing dust aerosol studies. [ABSTRACT FROM AUTHOR]

Occupying an area of about 1,020,000 km2 with the sparse vegetation and the Taklimakan Desert(TD), The Tarim Basin (TB) is isolated by the surrounding mountains and plateaus, especially to the north of the Tibetan Plateau (TP) with a large drop in elevation. An intense dust storm occurring over TB, Northwest China from April 27 to May 1, 2015 was simulated by using the Weather Research and Forecasting model with chemistry (WRF-Chem v3.8.1). The sources of dust emissions were centered over the northeastern TB with the high dust emission flux reaching 24μgm−2 s−1 injected by strong near-surface northeasterly winds from basin mouth invading the TD. A large amount of dust aerosols accumulated in the windward northern slope of the TP. Dry deposition is the dominant removal process of dust aerosols from the atmosphere over the arid TB. The spatial distribution of dust dry deposition in the TB was similar to the columnar dust loading pattern during this dust storm event. With the impacts of the TB deep terrain structures on atmospheric circulation, the high column loading of dust aerosols was concentrated over the southeastern TB, where dust aerosols mainly accumulated at the lower troposphere below 3000 m. Once dust aerosols were lifted at a high elevation (>3500 m), they were exported from the TB driven by the westerlies in the free troposphere, and the zonal transport flux of dust aerosols (>3000 μgm−2 s−1) peaked at an elevation of approximately 4000 m along 41° N over the TB. The eastern border of TB was found to be the largest contributors to dust export from the TB. It was estimated for this intense dust storm that among the dust aerosols emitted from the dust emission sources over the TD, about 22.28% of dust aerosols were relatively inefficiently exported for the downwind dust regional transport from the TB compared to about 27.17% dust aerosols deposited on the basin surface, and a high fraction of about 50.54% dust aerosols suspending in the atmosphere over the TB, implying a significant implication of dust aerosols from the TD for climate and environment over the central Asian region. The Taklimakan Desert (TD) is located in the Tarim Basin (TB) isolated by the surrounding mountains and plateaus with the only an open in the northeastern TB edge. The effect of topography especially the Tibetan Plateau on dust aerosol distribution over the TB. Once dust aerosols were lifted at a high elevation (>3500 m), they were exported from the TB driven by the westerlies in the free troposphere, and the zonal transport flux of dust aerosols (>3000 μgm−2 s−1) peaked at an elevation of approximately 4000 m along 41° N over the TB. The eastern border of TB was found to be the largest contributor to dust export from the TB. The high fraction of 50.54% dust aerosols suspending in the atmosphere over the TB potentially exerted a large impact on regional changes of climate and environment over the TB for this dust storm event. Unlabelled Image • A strong effect of the Tibetan Plateau on the dust aerosol distribution over the Tarim Basin. • The zonal transport flux of dust aerosols peaked at an elevation of approximately 4000 m over the Tarim Basin. • The eastern border of Tarim Basin was found to be largest contributor to the downwind regional transport of dust aerosols. • A high fraction of about 50.54% dust aerosols suspending in the atmosphere over the Tarim Basin. [ABSTRACT FROM AUTHOR]

Dust events are frequent in the Tarim Basin because of its underlying desert surface; moreover, meteorological conditions under the influence of the surrounding high terrains, especially the Tibetan Plateau, may also trigger dust events. However, the terrain effect of the Tibetan Plateau on the dust aerosol distribution over the Tarim Basin remains unclear. This study aimed to investigate the impact of the Tibetan Plateau terrain on the dust aerosol variations in three dust events over the Tarim Basin using the Weather Research and Forecasting Chemistry model. With decreasing altitude of the Tibetan Plateau, dust concentration (DC) decreased in the upper layers and increased in the low layers. The DC within the entire atmospheric layers increased by 8.52%, 24.03%, and 43.05% on average during three dust events at Tibetan Plateau altitudes of 3000 m, 2000 m, and 1000 m, respectively, thereby indicating that the DC in the lower layers increasingly dominated the entire atmospheric layers as the Tibetan Plateau altitude decreased. Low-elevation terrain enhanced the planetary boundary layer height, near-surface wind speed, and surface air temperature, but weakened atmospheric stratification stability, all of which are beneficial for strengthening dust emissions and vertical mixing in the lower layers of the Tarim Basin. Furthermore, a decrease in the Tibetan Plateau altitude led to forming a vertical circulation, with the south to rise and the north to sink over the Tarim Basin. Meteorological field and vertical circulation could adequately explain the changes in the distribution of dust aerosols over the Tarim Basin. Overall, this study enhances our understanding of the effect of the Tibetan Plateau terrain on changes in the dust aerosol in the Tarim Basin and surrounding central Asian regions. [Display omitted] • Tibetan Plateau altitude decreased leads to less DC of the upper layers and more DC in the low layers over the Tarim Basim; • DC in the lower layers increasingly dominated the entire atmospheric layers with the Tibetan Plateau altitude decreased. • Meteorological field and vertical circulation commonly cause the change of dust aerosols distribution over the Tarim Basim. [ABSTRACT FROM AUTHOR]

The vertical distribution and transport properties of dust aerosols play a key role in regional and even global climate and environmental changes. However, there are still gaps in understanding the optical properties, transport mechanisms, and topographic effects on dust in the dust-prone area-southern margin of the Tarim Basin. In this study, we use the Ground-Based Aerosol Lidar (GBQL-01) installed in Hotan and Minfeng in cooperation with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) to synthesize and analyze the dust formation process at the southern margin of the basin once, and to test the reliability of the ground-based aerosol lidar. The variability characteristics of meteorological elements during this dust process will be discussed. Furthermore, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) was used to reproduce this dust process. The results show that the vertical transport of dust particles reaches about 4 km and 3 km in Hotan and Minfeng, respectively, and the dust aerosol stratification intensity is obvious within 1 km height in both places, and there is a dust aerosol layer at 3 km height in both places. The high winds are blocked by the large topography of the Tianshan Mountains and the northern slopes of the Tibet Plateau, and they change to northeasterly winds, triggering dusty weather outbreaks at the southern margin of the Tarim Basin. When the dusty weather subsided, dust aerosols with concentrations of 300–400 μg m−3 were still present at an altitude of 4 km, and a clear suspended dust phenomenon was formed. Meanwhile, the increase of wind speed and relative humidity, as well as the decrease of temperature, easily contribute to the occurrence of dusty weather and the transport of particulate matter. This work provides a useful reference for the study of regional climate change, topographic effects and "suspended dust". • The evaluation of the ground-based aerosol lidar's performance was conducted in an integrated manner using CALIPSO and particulate matter data. This assessment is essential for future studies. • Data on the height of dust stratification in the southern margin of the Tarim Basin (Hotan and Minfeng) was collected, confirming the presence of a stable aerosol layer at an altitude of 3 km. • The analysis using the WRF-Chem model clearly demonstrates the influence of topographic effects on dust aerosols. Additionally, this study confirms the occurrence of a unique phenomenon known as "suspended dust.". [ABSTRACT FROM AUTHOR]

The vertical distributions of sand-dust aerosols (SDAs) over the Taklimakan Desert (TD; 37°N–41°N, 78°E−88°E) that occurred during the spring are essential for both long-range transport and climate effects, apart from the living environment and health. In this study, we investigated the optical properties of SDAs and evaluated the correlation between optical properties and meteorological factors over the TD area located in the northwest of China. For this, we have utilized the A-train multiple-satellite remote sensing data provided quasi-synchronized observations by the Cloud-aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), CloudSat, and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments for the study period during 2007–2010. Besides, we have verified the meteorological factors observed from the CALIPSO to know the applicability and reliability with the Radiosonde sounding data. We found that the cloud–aerosol discrimination (CAD) algorithm can accurately identify clouds and SDAs over the TD area, especially during blowing dust/floating dust (BD/FD). Overall, it is revealed that the total depolarization ratio of SDAs is below 0.5. Besides, the temperature (T) and pressure (P) of CALIPSO satellite products data are in excellent agreement with the radiosonde sounding measured data over the TD area. Further, most data points during the DS (BD/FD) event spread towards lower (higher) relative humidity (RH) ranged between 0.0386 and 0.6306 (0.1079 and 1.00). Our analysis provides the observational evidence from the CALIOP that the optical properties of vertical dust particles and meteorological elements over the TD have distinct variability below and above 4 km height for DS and BD/FD events. The results obtained will provide not only reliable reference values for the improvement of the CAD algorithm used in the CALIPSO but also provide critical information for model evaluation and enhancement of CALIPSO products. Image 1 • We have investigated the optical properties of sand dust aerosols (SDAs) over the Taklimakan Desert from radiosonde and A-train satellite datasets. • We have evaluated the correlation between SDAs and meteorological factors during spring. • The meteorological factors observed from the CALIPSO are verified using the radiosonde data. [ABSTRACT FROM AUTHOR]