Identifying a transport mechanism of dust aerosols over South Asia to the Tibetan Plateau: A case study

Abstract

Dust aerosol, one of the important light-absorbing impurities in snow and ice sheets in the Tibet Plateau (TP), can significantly affect the magnitude and timing of snow melting and glacier recession by altering the surface albedo. It is thus of great importance to understand the potential source and transport mechanism of the dust aerosol over the TP. A typical dust storm case, erupted from the Thar Desert (ThD) in South Asia on 1 to 4 May 2018, was selected to understand synoptic causes and a transport mechanism to the TP using the latest Second Modern-Era Retrospective analysis for Research and Applications (MERRA-2) reanalysis data. Comparing with active/passive satellite-based and AERONET-based observations, the MERRA-2 data provide both the spatio-temporal distribution and evolution process of the dust aerosol more accurately. This study also found that the entire Indian-Gangetic Plain (IGP), Southern India, the Bay of Bengal, and even the TP were influenced by the dust event. The synoptic analysis showed that the dust storm was caused jointly by an upper-level jet stream (ULJS), an upper trough and the subtropical high. A typical south-north secondary circulation adjacent its exit zone, mainly triggered by the ULJS, promoted much stronger and higher vertical uplift of the dust aerosols over the ThD. Consequently, those uplifted dust particles were easily transported to the TP across the majestic Himalayas by the southerly airflows in front of the low-pressure trough over Afghanistan and the southern branch trough over the Bengal Bay. These results indicate that dust aerosol and anthropogenic pollutions constrained and driven by the typical atmospheric circulation condition from South Asia are likely to be transported to the TP. Therefore, it is necessary to further pay attention to the influence of dust aerosols from South Asia on the weather and climate in the TP and its downstream areas.