The Analyses of Wave and Eye Region in Tibetan Plateau Vortex

In this study, the process of a Tibet plateau vortex at August 14, 2006 was simulated with triple nested using the new generation of the mesoscale numerical model WRFV3.1.1 which was developed by NCAR/NCEP.The high resolution model output data shows that at the developing and mature stage of the vortex, the distribution of velocity divergence and vorticity both showing a certain degree of fluctuant, which alternating between the distribution of positive and negative values.By analyzing the wave in the Tibet plateau vortex, finding out that there are both generation conditions for Vortex-Rossby (VR) waves and Inertial Gravity (IG) wave.The moving speed of the wave in the vortex is between the theory speed of VR wave and IG wave.In the center region of the vortex, the radial gradient of vorticity and divergence are both high, so the wave shows mixed features of VR and IG wave.At the outer region of the vortex, the radial gradient of vorticity is too weak to support VR wave, so the wave in the vortex shows the feature of IG wave.Further more, Tibetan Plateau Vortex has a very short life cycle compared to Tropical Cyclone, and the wave propagation conditions in the ring are uneven, so the tangential spread of wave can be fracture at somewhere of the circle.This may inferred that it is difficult for the Tibetan Plateau Vortex to form the perfect spiral shape as Tropical Cyclone.In addition, the simulation also found that at the mature stage of Tibet plateau vortex, it has very weak vertical motion in the center compared to the outer area, and there is a warm core in the center like an eye which is calm.