Abstract : G.2
Analyses of impact of the cold air on moving off the Tibetan plateau of the plateau low vortex

Yu Shuhua, Yuhua Xiao, Wenliang Gao
Institute of Plateau Meteorology,CMA.Chengdu

Cyclonic vortexes often emerge in the Tibetan Plateau in summer, some of which move out of the Plateau and cause heavy rain and even extensive damage in the area to the east of the Plateau.

Investigation on the activities of the Tibetan Plateau Vortexes that last longer time after leaving the Plateau during 1998-2004 and detailed diagnostics of baroclinity and temperature advection as well as numerical experiments are undertaken in this study to elucidate the effect of the cold air. The conclusions are as follows:

1. If a Plateau vortex is affected by the cold air around its leaving the Plateau, its lifespan off the Plateau will be longer than 36 hours;

2. The Tuole Vortex’s moving out of the Plateau is closely related to the strong baroclinity associated with the cold air at 500hPa, especially one extending into the vortex from northeast; temperature position of colder-north and warmer-south is more evident after Tuole Vortex moves out of the Plateau.

3. The cold advection takes an important role in Tuole Vortex movement. When the advection to the west of the Tuole Vortex is stronger than that to the east, Tuole Vortex moves out of the Plateau; when dominated largely by cold advection the vortex moves less.

4. The numerical experiments on the effect of the cold air display that in the absence of the cold air in vortex area or cold temperature trough in the northeastern China, the Plateau vortexes go eastward slowly with weaker intensity and smaller maximum velocity; the cold trough in the northeastern China is more essential to Plateau vortexes’ movement; Without the cold trough, Plateau vortexes even go backward.