“7.27”陕北暴雨数值模拟与诊断分析

Numerical simulation and diagnostic analysis of heavy rainstorm on 27 July 2012 in north Shaanxi

利用NCEP/NCAR1°×1°再分析资料、地面观测降水资料、FY-2E卫星相当黑体温度资料,采用WRF(Weather Research Forecasting)中尺度数值模式对2012年7月27日陕西省北部一次暴雨过程进行了数值模拟与诊断分析。结果表明:此次暴雨处于西太平洋副热带高压西北边缘带与贝加尔湖低压之间,中低层水汽由孟加拉湾经青藏高原东部输送到陕北;无规则小云团的自组织过程,促使中尺度对流系统得以发展。200hPa急流出口区的右侧由于地转调整作用,在槽线上激发了中尺度重力波。高空重力波能量下传并被近地面中性层结大气吸收,引起低层大气对流发展,对暴雨的发生发展过程有很好的促进作用。

A rainstorm process in north Shaanxi on 27 July 2012 is studied by using the 1°×1° NCEP/NCAR reanalysis data, observed surface precipitation data and black-body temperature （ TBB ） data from FY-2E satellite. The rainstorm process is simulated by WRF（ Weather Research Forecasting） mesoscale numerical model and diagnostic analysis is made by using WRF model outputs. Results show that the rainstorm took place in regions between the northwest marginal zone of the western Pacific sub- tropical high and the Baikal cyclone. In the middle and low layers ,the water vapor originated from the Bay of Bengal,passed the eastern Tibetan Plateau and arrived in north Shaanxi. The process from the small non-organized cloud clusters to self-organized cloud clusters stimulated the development of me- soscale convection system. Near the trough line, the mesoscale gravity wave could be caused by geo- strophic adjustment in the right of jet stream exit region at 200 hPa. The energy of downward propaga- tion of mesoscale gravity wave was absorbed by the atmospheric neutral layer near surface, which lea- ded to the convection development in lower atmosphere layer, and promoted the genesis and develop- ment of rainstorm.