一次西南涡东北移对川陕大暴雨影响的分析

Analysis on a Heavy Rainstorm from Southwest Vortex Moving Toward Northeast Direction in Sichuan and Shaanxi Provinces

利用常规观测资料、NCEP再分析资料、自动站资料、卫星云图和雷达资料,对2010年7月16—19日西南涡东北移造成川陕大暴雨天气过程的影响系统、高空急流、流场和对流涡度矢量等方面进行了诊断分析,探讨了大暴雨的发生、发展机制及其天气学特征和物理量特征。结果表明,鞍形场的稳定存在为西南低涡的发生、发展及其东北移提供了环流背景,"北槽南涡"形势是西南涡长时间维持的原因。东北—西南急流中心南侧的东北气流和南亚高压东北侧的东南气流构成的分流区对四川东北部和陕南大暴雨的产生提供了有利的上升动力条件。在台风和副热带高压外围之间强气压梯度力产生的偏南暖湿气流为暴雨区带来了丰沛的水汽。西南涡增强阶段的降水强度明显大于减弱阶段,对流涡度矢量(CVV)的垂直分量和气柱云水量中心值的重合区是大暴雨的发生区。

The influential systems, upper jet, stream field and convective vorticity vector for a heavy rainstorm impacted southwest vortex in northeast part of Sichuan and southeast part of Shaanxi on 16--19 July 2010 are diagnostically analyzed based on the conventional observation data, NCEP reanalysis data, automatic station data, satellite cloud image and radar data. The results show that the stable saddle field provides the background for the occurring and developing of the southwest vortex and northeastward mov- ing. A deep trough in north and southwest vortex in south pattern is important reason for the southwest vortex to maintain. The division area, which is formed by between the northeast airflow on south side of the northeast-southwest direction upper jet center and the southeast airflow on northeast side of the South Asia high, offers the dynamic condition for ascending motion. The south warm-wet airflow caused by the strong pressure gradient force between typhoon and Subtropical High supplies the abundant water vapor for the heavy rainstorm area. The precipitation intensity caused by southwest vortex during the developing phase is significantly greater than decaying phase. The heavy rainstorm locates in the coincidence area of the vertical component of convective vorticity vector and atmospheric column cloud water.