Diurnal vertical distribution and transport of dust aerosol over and around Tibetan Plateau from lidar on International Space Station

Abstract

Tibetan Plateau (TP) and its surroundings play a vital role in the emission and transport of dust in Eastern Asia. Using the CATS (Cloud-Aerosol Transport System) retrievals during 2015–2017, the spatiotemporal distributions and diurnal variations of dust over the study region were presented. The results showed that the dust could exceed 6 km aloft Taklimakan Desert (TD) in spring and summer, and could easily be transported to TP. The dust of Thar Desert and Indo Gangetic Plains (TDIP) reached the maximum of intensity and uplift height in summer, and was transported to TP mostly through the Yarlung Zangbo Grand Canyon aera in the longitudes of 90°−100°E. A long-standing dust layer with thickness of 1–2 km appeared over the whole region, and it was thicker over TD and TDIP. The thickest dust layer over TD appeared in the southeast part. The dense dust top showed a consistency with boundary layer height (BLH), both of which started to increase after sunrise and reached the maximum after the noon. The dust of TD appeared easier to break through the boundary layer top during daytime mainly due to stronger updraft, while it was confined below the BLH over TDIP. High wind speed and CAPE benefitted the emission and vertical transport of dust. The mountain-valley circulation also played an important role in the diurnal variation of dust. The valley wind facilitated to form a thicker dust layer during daytime, while the mountain wind helped to accumulate dust in lower level during nighttime. It showed a similar diurnal change of dust aerosol optical depth (DAOD) for CATS and MERRA-2, especially in the regions with high dust loading.