Abstract : 2E.8
Experiments on Mesoscale Vortex Activities over the Abrupt Slope of the Plateau

Guangbi He, Yuhua Xiao
Plateau Meteorological Institute of ChengDu, CMA

MM5, mesoscale model, was used to simulate a heavy rain process taking place in northwestern Sichuan Basin over Aug. 8 - 10, 2003 and do some numerical experiments with different kind of changed topographies. The results of experiments show that the mesoscale vortex is advantage to the transportation of positive vorticity and the maintenance of convergent-ascending motion, in addition to arousing and supporting raining; Topography has a great influence on the mesoscale vortex motion, that is, steep and complex topography subserves the generation of mesoscale vortex. In the experiments, when real-like topography is taken, the vortexes are more and active over the Tibet Plateau and the area from eastern Plateau to western Sichuan Basin; when topography is altered in both height and slope, the number of vortexes reduce, the intensity of vortex lessens, and the sources of vortex and their moving paths shift; when the topography is ignored (no topography in model), vortexes are less, moreover, vortexes move faster than usual; if topography is cut down only in height, vortex’s activities change little; when only Tibet Plateau exists, vortexes are still active in the Plateau area, but in no-topography area vortexes deceased apparently. The results also reveal the fact that the activity of vortex has something to do with the distribution of rainfall.