2012年8月中旬四川大暴雨的数值模拟及地形影响试验

Numerical Simulation and Topography Effects Analysis on 17th～18th August,2012 Heavy Rainstorm in Sichuan Province

利用WRF模式对2012年8月17~18日四川出现的一次大暴雨过程进行模式模拟和诊断分析,并通过对地形敏感性试验讨论川西高原至川东过渡带陡峭地形对此次暴雨的影响。结果表明,WRF基本成功模拟出2012年8月中旬四川中部大暴雨过程,对环流形式预报与实况较为一致。此次过程水汽来源台风低压及副高外围携带的水汽。川中云团发展阶段对应四川中部多个站出现强降水,该对流云团发展是引发本次降水的重要因素,而对流层中低层高温高湿环境对对流云团发展提供有力的环境。地形敏感性试验表明,陡峭地形高度与降水强度呈正比,通过影响陡峭地形周边物理量特征场分布从而影响暴雨区降水强度;相对湿度的影响小于温度对降水强度的影响作用。

A heavy rainstorm during 17th - 18th August, 2012 in Sichuan Province was simulated by WRF model. Diagnoses were made bases on the output data to get the influence of complex topography. Results show that, the WRF model successfully revealed the circulation and the rainfall. The water vapor comes from typhoon - low itself carrying moisture and the outside of subtropical high. The development stage of cloud in central Sichuan corresponds more than one stations appear strong precipitation, the convective cloud cluster development is an important factor in triggering the precipitation. The environmental conditions of high temperature and humidity in the lower troposphere provided a favorable thermodynamic condition for the forming and developing of convective cloud cluster. The topography sensitivity experiment shows, cliffy topography height is proportional to rainfall intensity, by influencing the cliffy topography surrounding the physical quantity field distribution and influence of rainstorm precipitation intensity ; the effect on the intensity of precipitation of relative humidity is less than the temperature.