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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]

A special topography and ultra-high atmospheric boundary layer conditions in the Tarim Basin (TB) lead to the unique spatial–temporal distribution characteristics of dust aerosols. A typical dust storm with persistent floating dust over the TB from 27 April to 1 May 2015 was used to investigate the characteristics of the dust radiative effect using the Weather Research and Forecasting Model with Chemistry (WRF-Chem). Based on reasonable evaluations involving in situ sounding observations, as well as remotely sensed MODIS observations of meteorology, dust aerosols, and the ultra-high atmospheric boundary layer, the simulation characterized the complete characteristics of the dust direct radiative effect (DDRE) during the dust storm outbreak stage and persistent floating dust stage over the TB. During the daytime, the shortwave (SW) radiative effect heated the atmosphere and cooled the land surface (SUR), whereas the longwave (LW) radiative effect had the opposite effect on the TB. Regarding low-level dust, the LW radiative effect was greater than the SW DDRE in the atmosphere, while for high-level dust the situation was reversed. During the nighttime, the LW DDRE at the top of the atmosphere (TOA), at the SUR, and in the atmosphere was less than that during the daytime, when the DDRE at the SUR was the most significant. In contrast to the daytime, the near-surface dust aerosols exerted an LW warming effect in the atmosphere during the nighttime; however, the dust LW radiative effect had a cooling effect from above a 100 m altitude until the top of the dust layer. In contrast, the DDRE heating rate peaked at the top of the dust layer within the TB. The event-averaged net DDRE was 0.53, −5.90, and 6.43 W m−2 at the TOA, at the SUR, and in the atmosphere over the TB, respectively. The dust SW radiative effect was stronger than the dust L4W radiative effect over the TB at the SUR and in the atmosphere. Moreover, the DDRE at the TOA was weaker than that at the SUR. Overall, the study revealed noteworthy radiative effect features of dust aerosols during typical dust storms with persistent floating dust over the TB. [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]