对甘肃酒泉一次暴雨的数值模拟和诊断分析

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

利用NCEP 1°×1°的6 h再分析资料和常规观测资料,使用WRF模式模拟了2011年6月15～16日出现在甘肃酒泉的一次暴雨天气过程。结果表明:WRF模式能较好地模拟出这次降水的区域,对这种中尺度天气系统具有良好的预报能力。在这次降水过程中,切变线和冷空气以及与高原低涡的合理配置加强了强降水区垂直环流的发展;同时来自孟加拉湾的水汽是暴雨产生的重要原因;初始不稳定能量是触发暴雨发生的条件之一;而高空辐散、低空辐合的流场特征也促进了强降水的产生5,00 hPa辐散和600 hPa正涡度和强降水区域有较好的对应关系;螺旋度的高低层耦合是触发并维持低压暴雨的动力机制,垂直螺旋度对暴雨的落区和强度有较好的指示性。

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.