低涡东北部一次暴雨的成因分析  

Cause Analysis of a Torrential Rain Process in the Northeast Low Vortex

作　　者：张雪慧[1] 谢大勇[1] 何斌[1] 潘士雄 

机构地区：[1]嘉兴市气象局,浙江嘉兴314050

出　　处：《气象与环境科学》2015年第3期107-113,共7页Meteorological and Environmental Sciences

基　　金：嘉兴市科技局项目"多模式集成预报技术研究及‘两区’农业气象服务应用"(2012BZ6007)资助

摘　　要：2013年5月15-17日长江下游地区多地出现连续暴雨,数值模式检验显示雨量预报值误差较大。利用常规天气资料、NCEP 0.5°×0.5°格点资料和多普勒雷达资料,对这次暴雨过程进行了成因分析,结果表明：槽前西南气流、低涡切变和深厚湿层提供了有利的大尺度形势背景;低涡东北部产生的暴雨与低层东风急流的扰动和曲率增大密切相关,地面辐合抬升触发了上升运动;700 h Pa切变线和地面中小尺度辐合线的叠加处、925 h Pa水汽通量散度负值中心区都与暴雨区有较好的对应关系;多普勒雷达平均径向速度图像上显示强烈的辐合区,正、负速度区面积比达到1∶3,回波不断在辐合线处生成,下游地区出现＂列车效应＂,强降水时段雷达回波强度为30~40d Bz,小时雨量达到16~20 mm。对比模式预报场,中低层偏东急流量级和气旋性弯曲偏小导致了暴雨区漏报,地面辐合线位置和强度的偏差造成了雨量中心位置的偏差,可通过与实况对比、雷达分析等手段对预报进行订正。A continuous torrential rain occurred during 15 -17 May 2013 in the lower reaches of the Yangtze River, and the error of predicted precipitation numerical model was significant. By using the conventional meteorological data, NCEP 0.5° ×0. 5°grid data and Doppler radar images to analyze this process, it is indicated that the synoptic scale background was southwest airflow, low-vortex shear and thick wet layers. The torrential rain in the northeast of low vortex was related closely to disturbance and curvature of lower easterly jet. Convergence line on the ground layer triggered the upward movement. The torrential rain areas had good relationship with the superposition of wind shear line at level 700 hPa and surface mesoscale convergence line, and also related closely to negative divergence center of moisture flux at level 925 hPa. The velocity product of Doppler radar indicated obviously convergence, velocity area ratio of positive to negative reached to 1 ： 3. The radar echoes continuously generated, the ＂train effect＂ emerged at the downstream area. During the heavy rain period, echoes intensity was between 30 to 40 dBz, and precipitation per hour was between 16 to 20 mm. Numerical model tests showed that the easterly jet intensity and cyclonic curvature were underestimated at mid and low-atmospheric layer, which resulted in the heavy rain. The position and intensity deviation of ground convergence line resulted in deviation of rainfall center position. Predicted results could be corrected by analyzing real observation and radar data.

关 键 词：暴雨 东风急流 水汽通量散度 雷达回波特征 模式检验 

分 类 号：P458.3[天文地球—大气科学及气象学]