Atmospheric Science Letters (Sep 2021)
Vorticity and moisture budget analyses on a plateau vortex that cause an intense rainfall event within the Qaidam Basin
Abstract
Abstract As one of the most seriously arid areas in China, the Qaidam Basin (QB) features a notable growing probability of intense rainfall under global warming. Compared to a normal/humid region, intense rainfall usually results in more severe disasters in an arid area. Considering that few studies focused on intense rainfall within the QB, there is an urgent need to understand the mechanisms governing intense rainfall in this region. A type of Tibetan Plateau vortex (TPV) associated intense rainfall within the QB was investigated in this study, which partly fills the existing research gaps in the field. The main findings are as follows: (a) the intense‐rainfall‐producing TPV formed and maintained in a favorable background environment which was characterized by a notable upper‐level divergence north of a strong upper‐level jet and a strong middle‐level warm advection ahead of a shortwave trough over the Tibetan Plateau. (b) Vorticity budget indicates that two factors affected the vortex's formation notably, one was the convergence‐related vertical stretching, which dominated the vortex's formation and the other was the import of the horizontal transport of anticyclonic vorticity which was the most detrimental factor for the formation of the TPV. Tilting and vertical transport only exerted weak effects on the TPV's formation, since convective activities were relatively weak in this event. (c) Moisture budget shows that the southwestern and southern moisture transport channels, which were mainly driven by the wind field associated with the shortwave trough over the Tibetan Plateau, contributed ~70% to the total moisture income of the intense rainfall within the QB. The transport was accomplished primarily through the southern boundary of the QB, with the moisture mainly coming from the Indian Peninsula and Indochina Peninsula.
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