2011年“7·3”暴雨过程的卫星云图特征和湿位涡分析

Analysis of the Satellite Nephogram Characteristic and Moist Potential Vorticity of Rainstorm on July 3,2011

2011年7月2-3日豫西北出现局地暴雨天气,降雨强度大、时段集中,具有明显的强对流暴雨持征,其中有2站达大暴雨。采用1°×1°NCEP再分析资料进行环流背景分析和物理量诊断,结果表明:这次暴雨是由高空低槽和中低空切变线直接影响所致,高湿不稳定区的稳定持续为雨区积累了大量不稳定能量,在冷空气入侵的激发下,不稳定能量释放产生强对流降水;低层气旋性环流的形成和气旋性弯曲的存在利于上升运动加强,水汽的输送和辐合作用配合强烈的上升运动使得强降水持续;高层干位涡向对流层低层扰动下传具有促使低层气旋性涡旋生成和加强的作用,位涡的传播特征与未来4-6 h的雨势强弱对应较好。利用FY-2E卫星资料结合自动站逐小时降水量对暴雨中尺度特征进行分析,结果显示,这次暴雨过程中存在明显的中尺度云团自组织现象,强降水是组织、合并后的一个中α尺度对流云团内部两个中β尺度的强雨团直接造成的;Tbb<221 K的冷云覆盖区与暴雨落区相对应。

A heavy rain process occurred in northwest Henan on July 2-3, 2011. There was two stations＇ 24 h rainfall achieved heavy rain, and the rainfall intensity was large and period was concentrat-ed, which presented obviously severe convection rainstorm characters. The circulation background analy-sis and physical diagnosis were studied to adopt NCEP 1°×1° reanalysis data. The result shows that ： the middle and low-altitude low trough and shear line directly bring on the storm. Humidity unstable region continuously stabled has accumulated a large amount of unstable energy for the rain ; excited by the inva-sion of cold air, unstable energy release generates strong convective precipitation. The formation of cy-clonic circulation and the existence of cyclonic curvature in low-level are conducive to strengthen the up-ward motion; the water vapor transport and convergence as well as the strong upward motion cause the heavy precipitation continued. Dry potential vorticity in high-level propagating downstream perturbation to the lower troposphere prompts to cyclonic vortex formation and intensification. The propagation character-istics of potential vorticity match corresponding rain intensity in 4-6 h. Combined with the automatic sta-tion hourly precipitation, local heavy rain was analyzed by using FY-2E satellite data. The result shows： The rainstorm exists obviously cloud self-organization phenomena. The heavy precipitation is di-rectly occurred by two β-seale strong rain cloud, which is internal in one α-scale convective cloud after organization and combination. Cold cloud covered region （Tbb 〈 221 K） is corresponding to the heavy rainfall area.