台风“鮎鱼”极端降水分析

1617号台风"鮎鱼"的降水异常强大,温州、丽水部分县市的过程雨量和日雨量超过历史极值,灾害严重。利用NCEP 0.5°×0.5°再分析资料、FY-2G卫星资料、多普勒雷达探测资料和自动站加密观测等资料,对其成因展开分析。结果表明:"鮎鱼"东面与强大稳定的副高之间构成东南急流;北面与缓慢东移的华北高压之间构成偏东风急流;南面是与西南季风相连接的西南急流;3支低空急流构建的切变辐合区是水汽辐合和不稳定能量的集合区,也是中尺度对流的强烈发展区,温州、丽水部分县市的极端降水由中尺度对流的持续发生发展引发。低空急流的长时间持续,特别充沛的水汽输送和冷空气的影响是"鮎鱼"极端降水的主要影响机制。冷空气影响期间,降雨回波发展旺盛,结构紧密,回波强度和降水效率等明显强于无冷空气影响时台风本体环流降雨回波。云顶相当黑体亮度温度(TBB)与台风降水有较好的对应关系,有一定预报参考价值。

Extreme Precipitation Analysis of Typhoon Megi

The precipitation caused by Typhoon Megi is abnormally enormous with the rainfall in part counties in Wenzhou and Lishui breaking the historical records, which caused a severe disaster. Its causes are analyzed by the use of NCEP 0.5°×0.5° reanalysis data, FY 2G satellite data, Doppler radar data, the intensive observation data, and so on. The results show that there were three low jet streams: the south east jet stream between Megi and subtropical high, the eastward jet stream between Megi and Huabei high, and the south west jet stream connected with south west monsoon. The shear and convergence zone consisted of three low jet streams was the area of vapor and instability energy convergence and also the trigger zone of mesoscale convection. The extreme precipitation in Wenzhou and Lishui was triggered by the strong development of continual mesoscale convection. Long time low level jet streams, particularly abundant vapor transportation and cold air are the main influencing mechanism of Megi extreme precipitation. During the cold air influencing, the precipitation echo with tight structure developed strongly. The echo intensity and precipitation efficiency were obviously stronger than those of the typhoon circulation echo with no cold air influence. The cloud top black body brightness temperature (TBB) has good relationship with typhoon precipitation, which has reference value for operational forecasting.