Diagnostic Analysis of Dynamical Parameters for Sichuan Rainstorm Influenced by Terrain

A continual rainstorm process influenced by the terrain in Sichuan Province that occurred during July 16-18, 2010, is analyzed. Results show that the process took place under a good high-low system configuration. In addition, a numerical simulation performed with National Centers for Environmental Prediction (NCEP) data used for the initial field accurately simulated this rainfall process. The numerical simulation can not only indicate where the rainfall region is but also the center of storm. Generalized moist potential temperature, the vertical integral of the vertical component of generalized convective vorticity vector and quality vertical helicity are chosen to perform diagnostic analysis for the rainfall region, which lies in northeast Sichuan and is influenced by Daba Mountain. The results show that the inverse Ω shape areas of the moist potential temperature isolines in the vertical sections coincide well with the heavy rainfall region, and the steepness of the isolines and the abnormal height of the moist potential temperature can qualitatively indicate the rainfall intensity. The vertical integral of the moist potential temperature from 800 hPa to 500 hPa can more accurately trace the heavy rainfall region in the northeast by using the improved vertical integral rather than the traditional vertical integral. Because the vertical helicity quality can effectively describe the vertical structure of the typical dynamical field of the heavy rainfall system over northeast Sichuan, it strongly correlates with the heavy rainfall region in the same location.