动力因子对地形影响下的四川暴雨落区的诊断分析

本文分析了2010年7月16～18日地形作用下四川盆地的一次持续性暴雨过程,指出此次暴雨过程是在高低层系统配置较好的情况下发生的。并以NCEP资料为初值场对此次暴雨过程进行了数值模拟,结合实况对模拟结果进行对比分析。分析表明:模式对本次四川暴雨过程的模拟较为成功,能很好地再现此次暴雨的降水落区以及强降水中心。运用广义湿位温、广义对流涡度矢量垂直分量的垂直积分和质量垂直螺旋度对受大巴山脉影响的四川东北部的暴雨落区进行了诊断分析。分析指出,广义湿位温纬向平均的垂直剖面图上,等湿位温线的倒Ω区域与四川东北部的强降水落区吻合较好,等湿位温线的倾斜程度以及湿位温异常的高度可以定性地指示降水的强弱;对广义湿位温从800 hPa到500 hPa垂直积分,用得到的湿位温的水平分布来指示东北部的暴雨落区效果较 好;用改进垂直积分区间后的广义对流涡度矢量垂直分量比用传统的对流涡度矢量垂直分量来示踪四川东北部的暴雨落区效果更好;质量垂直螺旋度能有效刻画出四川东北部地区强降水系统的典型动力场垂直结构,因此与四川东北部的地面强降水具有很好的对应关系。

Diagnostic Analysis of Dynamical Parameters for Sichuan Rainstorm Influenced by Terrain

A continual rainstorm process influenced by the terrain in Sichuan Province that occurred during July 16-18, 2010, is analyzed. Results show that the process took place under a good high-low system configuration. In addition, a numerical simulation performed with National Centers for Environmental Prediction (NCEP) data used for the initial field accurately simulated this rainfall process. The numerical simulation can not only indicate where the rainfall region is but also the center of storm. Generalized moist potential temperature, the vertical integral of the vertical component of generalized convective vorticity vector and quality vertical helicity are chosen to perform diagnostic analysis for the rainfall region, which lies in northeast Sichuan and is influenced by Daba Mountain. The results show that the inverse Ω shape areas of the moist potential temperature isolines in the vertical sections coincide well with the heavy rainfall region, and the steepness of the isolines and the abnormal height of the moist potential temperature can qualitatively indicate the rainfall intensity. The vertical integral of the moist potential temperature from 800 hPa to 500 hPa can more accurately trace the heavy rainfall region in the northeast by using the improved vertical integral rather than the traditional vertical integral. Because the vertical helicity quality can effectively describe the vertical structure of the typical dynamical field of the heavy rainfall system over northeast Sichuan, it strongly correlates with the heavy rainfall region in the same location.