Numerical Simulation and Diagnostic Analysis of a Heavy Rain Occurred in Jiuquan of Gansu Province

Based on the NCEP 1°×1°six hours reanalyzed data and daily observation data,a mesoscale model WRF was used to simulate a heavy rain process occurred on June 15-16,2011 in Jiuquan of Gansu Province.The results show that the model could simulate the location of the rainfall better,it had a good capacity to predict the mesoscale weather systems.During this rainfall process,the rational configuring of cold air and wind-shear line as well as Plateau vortex strengthened the development of vertical circulation in the rainfall region.And the vapour flux from Bay of Bengal provided plenteous mioisture for the rainstorm,and the initial instability energy triggered the rainstorm.The flow field with convergence in the upper level and divergence in the lower level accelerated the rainfall.In addition,the coupling of helicity with a negative(positive) value at upper(lower) levels was the dynamical mechanism of the rain storm,and the vertical helicity had better indication to the rainfall area and intensity.