乐清四中型水库库区的大暴雨成因分析

THE TORRENTIAL RAIN ANALYSES OF YUEQING RESERVOIRS

大暴雨是浙江省乐清水库致洪的直接原因。利用NCEP1°×1°全球再分析资料、常规资料、雷达资料和地面中尺度自动站资料,详细分析了2004—2008年乐清四中型水库大暴雨过程的发生、发展机制。水库大暴雨是在有利的大尺度环流背景下,不断有中小尺度系统的发生发展而产生。主要影响系统为登陆台风、西风低槽和低空急流。物理量诊断分析表明,低层强辐合,高层辐散、旺盛的上升运动以及强大的低空急流和充沛的水汽供给,为水库大暴雨的发生发展提供了极为有利的动力条件。台风强降水出现在台风螺旋雨带或者台风眼周围的密闭云团中的强降雨中心内。业务预报中可利用新一代天气雷达的基本反射率叠加风暴跟踪信息和冰雹指数,结合基本速度和垂直积分液态含水量等指标来跟踪台风强降雨中心,对水库大暴雨的监测和预警有重要意义。

Torrential Rain can directly lead to flooding of Yueqing reservoirs. NCEP global re-analysis data, routine data, Radar data and ground medium-scale automatic observation data are used to analyze the occurring and developing mechanism of Yueqing reservoirs＇ torrential rains from 2004 to 2008. The torrential rains over the reservoirs occur in the favorable large scale circumlation background with the development of meso- and micro- scale weather systems. The main affecting systems include landfall typhoon, low-level jet stream and west trough. Physical quantity diagnoses show that low-level convergence and high-level divergence, strong rising , low-level jet stream and abundant water vapor supplies offer favorable dynamical condition for the torrential rain occurring and developing. The severe precipitation occurs in strong rain centers within typhoon spiral rain belts or thick clouds near typhoon eye. Typhoon＇s strong rain centers are tracked by following basic reflectivity, storm tracking information and hailstorm index, combined with basic velocity and vertical integrate liquid water, which has significance to the supervising and forecasting of reservoirs heavy precipitation.