2013年5月河南一次大暴雨成因分析及数值预报检验

Cause Analysis and Numerical Forecast Verification of a Heavy Rainstorm in Henan in May 2013

利用常规观测资料和NCEP再分析资料,分析了2013年5月25日08时-26日08时河南大暴雨过程的成因,对主要物理量因子的T639预报场进行检验。结果表明:强正涡度平流促使中高空低涡移动、地面低压发展成气旋,最强暴雨区与中高空低涡位置相对应。θse等值面坡度加大使气旋性涡度剧烈增长,产生强烈的上升运动。高空辐散与低空辐合叠加,有利于上升运动加强维持。低空气流带来充沛的水汽,大量水汽辐合有利于产生暴雨。运用正负符号一致率、相关系数和平均距离系数检验T639数值预报产品的结果表明,垂直速度预报最优,其次是涡度、散度、涡度平流预报。水汽通量、假相当位温24-72 h预报产品参考价值较大。

Based on conventional observation data and NCEP reanalysis data,the cause of a heavy rainstorm in Henan from 08：00 May 25 to 08：00 May 26 in 2013 was analyzed, and main physical factors of T639 forecast field were verified. The results showed that strong positive vorticity advection promoted middle and upper low vortex to move, low pressure to develop into cyclone, the strongest rainfall areas correspond with the position of middle and high low vortex. When the θse iso-surface slope increased, cyclonic vorticity increased severely, and formed a strong upward motion. The upper divergence superim- posed the lower convergence was in favor of upward motion strengthened and maintained. The lower flow bring plenty of water vapor,a lot of moisture convergence was conducive to produce heavy rain. By using positive and negative sign concordance rate, correlation coefficient and average distance coefficient, T639 numerical forecast products were tested to be effective. Vertical speed forecasted optimally, the vorticity, divergence and vorticity advection followed. Vapor flux, potential pseudo-equivalent temperature of 24-- 72 hour forecast had large reference value.