Abstract: Based on the NCEP 1°×1° data with 6 h interval and the meso-scale WRF (V3.2) model, the physical mechanism of severe rainstorm caused by debris flow disaster on August 8, 2010 was diagnosed. The results indicated that the severe rainstorm happened under the common action of short-wave trough at high altitudes, low vortex with shear line, the subtropical high and so on. The triple nested WRF model has simulated this rainstorm event quite well. The prime dynamic conditions of this process include strong convergence in the lower level, non-divergence in the middle level and strong divergence in the upper level as well as strong ascending motion. A lot of instability energy that rainstorm needs is transported by vertical wind shear and high energy tongue of pseudo equivalent potential temperature (θse)isoline which extends upward from the lower level. Convergence of water vapor in the middle and lower levels is favorable to rainstorm occurrence.

Key words: Severe rainstorm in Zhouqu, WRF model, Numeric simulation, Diagnostic analysis