Two Typical Synoptic-Scale Weather Patterns of Dust Events over the Tibetan Plateau

Abstract

Synoptic-scale weather systems play dominant roles in inducing high tropospheric dust over the Tibetan Plateau (TP). However, few studies have summarized the typical synoptic-scale weather patterns when high tropospheric dust occurs over the TP, as well as the difference between the distribution and transport methods of dust under weather patterns. Based on dust optical depth (DOD) from remote sensing data and reanalysis data during 2000 to 2019, two typical synoptic-scale weather patterns (T1 and T2) in the middle troposphere in association with high DOD in spring over the TP were obtained by using the self-organizing map (SOM) clustering method. The results show that the T1 features a deep trough over the Altai Mountains and the westerly wind increases over the TP. As a result, dust is transported from the Taklimakan Desert and Qaidam Basin to the upper troposphere and extends to the TP and northern China. T2 shows a low-pressure system over the western TP and decreased westerly winds over the TP, resulting in dust from the Taklimakan Desert, Qaidam Basin, and western TP to downstream areas. T1 (T2) contributes more to DOD over the eastern (western) TP. Therefore, we believe that a small increase (decrease) in DOD in the western (eastern) part of the TP from 2000 to 2019 may be related to an increase (decrease) in the occurrence of the T2 (T1). This work may provide a new possibility for projecting dust transport and its influence on tropospheric dust over the TP.