“2010.12.11”云南冬季暴雨成因分析

An Analysis on a heavy rain weather process on December 11th,2010 in Yunnan Province

应用常规观测资料、FY-2C卫星云图和NCEP再分析资料,通过诊断分析研究了2010年12月11日发生在滇中及以南地区的云南暴雨天气过程.结果发现,这次冬季暴雨天气过程发生在有利的环流背景下,ITCZ位置偏北较活跃,孟湾存在大片对流云系,中印度洋10°N附近存在一支异常的大尺度西南气流,孟加拉湾低层有一个热带气旋生成,在卫星云图上表现出明显的气旋式云系,孟湾热带气旋和90°E附近的南支槽及槽前西南低空急流东移造成了这次暴雨天气过程;引发暴雨的水汽和能量由低空急流从孟加拉湾输送而来,充沛的水汽在云南上空强烈辐合,暴雨区θse呈陡立状,暴雨发生在低层辐合高层辐散的上升运动区,水汽通量散度辐合区和湿Q矢量辐合区与暴雨区对应较好.

Based on the daily observation data,satellite images of FY-2C and NCEP 1×1°6 h interval reanalysis data,a heavy rain event on December 11th,2010 which occurred at middle and south of Yunnan Province has been nalyzed.Results show that the heavy rain weather process in winter occurred at a favorable circulation background,ITCZ whose position was northward was comparatively active;a cluster of convective cloud existed at Bay of Bengal,a branch of abnormal southwest flow existed in Indian Ocean around 10°N;a tropical cyclone generated on low-layer at Bay of Bengal which presented cyclone-type on satellite images;the tropical cyclone at Bay of Bengal,southern trough around 90°E and southwest jet at low-level in the front of southern trough moved eastward causing the heavy rain weather process;the water vapor and energy which caused heavy rain transporting from Bay of Bengal by low-level jet,plentiful vapor was strongly converged at Yunnan province,θse shows vertical shape along heavy rain area,heavy rain occurred at the regions of upward motion which lower layer convergence and higher layer divergence,the convergence region of moisture flux divergence and wet Q vector was well coincident with the heavy rain region.