Numerical Tests on Impact of Southwest Airflow upon Tibetan Vortex Migration

Tibetan Plateau Vortices(TPV),when moving eastward out of the plateau,usually cause catastrophic weather in East China.This study analyzes the effect of southwesterly wind along the south periphery of Tibetan Plateau(often called the south branch of the subtropical westerly jet) on five such vortices moving eastward out of the plateau(with their lifespan 48 hrs downstream) by numerical simulations of one case with a mesoscale model.Evidence suggests that i) weak Southwesterlies or lack of Southerly pulse in certain area would slow down eastward migration of a plateau vortex,weaken its intensity and make it disappear within 12 hours;ii) The Southwesterlies plays a role in transportation of both vapor and positive vorticity advection,which are favorable for a vortex to sustain a longer time.These numerical tests not only enrich our knowledge of plateau vortices' eastward movement but also provide us guidance to the prediction of heavy rain and flood in the southwestern China.