STUDY ON THE VORTEX OF THE QINGHAI-XIZANG (TIBET) PLATEAU IN SUMMER

In this paper an ideal model for the formation and development of the Qinghai-Xizang Plateau vortex is presented by a large number of statistical data and typical case studies. It points out that the Plateau vortex is shallow and thermal originated from a strong heat source near the surface of the west of the Plateau. Then moving eastward, it develops and becomes stronger and thicker with larger upward vertical velocity, and causes great precipitation in the middle Plateau. But at this time the heat source in the vortex becomes weaker, and even the heat sink occurs near the surface. Consequently, it disappears in a cold trough with a strong heat sink in the east of the Plateau. The heat source (sink) is mainly determined by the vertical eddy flux convergence (divergence) of the sensible heat caused by the cumulus convection and turbulance. Both the nonuniform heating (cooling) at the surface and the convergence (divergence) of the eddy kinetic energy coact and play an important role in the genesis (disappearance) of the Plateau vortex in the west (east) Plateau. The transformation value from the mean kinetic energy to the eddy kinetic energy increases when the Plateau vortex moves eastward, helping the formation of the cold trough and the increase in + zeta and large-scale precipitation in the east Plateau.