Roles of Tibetan Plateau vortices in the heavy rainfall over southwestern China in early July 2018

Abstract

Tibetan Plateau vortices (TPVs), generated over the Tibetan Plateau, are important rainfall triggers in southwestern and eastern China when moving off the plateau. The heavy rainfall event that occurred over southwestern China in early July 2018 caused severe floods and landslides, leading to substantial damage to normal production and life. In this work, the roles of TPVs in the rainfall are investigated based on NCEP FNL (final) operational global analysis and forecast data from the Global Data Assimilation System (GDAS). The results show that TPVs over the eastern Tibetan Plateau favor ascending motion to the east of the plateau, which is conducive to precipitation and therefore the genesis of southwest vortices (SWVs). Generally, the ascending motion in southwestern China is stronger when TPVs exist, compared with the other scenarios in which the TPVs are absent. Ascending motion is always observed on the east side of TPVs, which is greatly attributed to the positive vertical vorticity and warm centers in the TPVs. In this fashion, the influence of TPVs is not merely limited around their centers, but further eastward. Therefore, the effects of TPVs may have been underestimated in previous investigations; the TPVs located over the eastern Tibetan Plateau that do not move off the plateau should also be seriously considered in future precipitation predictions.