江西持续性冻雨的行星尺度特征分析

Planetary-scale characteristics of the persistent freezing rain events over Jiangxi province

应用常规气象地面观测资料和NECP 2.5°×2.5°的再分析资料,对1959—2008年期间发生在江西的持续5 d及以上的冻雨天气过程进行行星尺度的特征分析,结果表明：江西持续性冻雨天气期间,500 hPa高纬度地区的阻塞高压、中纬度的低槽以及低纬度的分裂小槽和地面沿中国中东部侵入的强冷空气有利于江西持续性冻雨天气的维持;同时,700 hPa有来自低纬地区的稳定的＂湿舌＂和西南急流存在,不仅有利于中层逆温结构的形成,也是水汽输送的主要机制。距平相关分析得到,持续性强冻雨天气发生期间,海平面气压、1 000~500 hPa和1 000~925 hPa厚度场的距平相关系数基本都在0.7以上,多数情况下达到0.8以上,表明江西持续性强冻雨天气期间高层和底层的天气系统是稳定少变的。

Based on the conventional surface observation data and NECP 2.5°×2.5° reanalysis dataset,the planetary-scale characteristics of the persistent freezing events over Jiangxi province for the period of 1959—2008 have been investigated.The results show that the 500 hPa pattern with the blocking high in high-latitude,the trough in middle latitude and the splintering trough in lower latitude is favorable to freezing rain event occurrences in Jiangxi.The surface strong cold air invading along middle and east China,offers a favorable thermal condition for freezing rain.At 700 hPa,there are stable ＂moist tongue＂ and southwesterly jet stream from lower latitude,which are propitious to the formation and maintenance of temperature inversion structure at middle level,and also are the major mechanisms of vapor transportation.The results of anomaly correlation（AC） analysis reveal that during the persistent freezing rains,the ACs of sea level pressure,1 000—925 hPa thickness and 1 000—500 hPa thickness are larger than 0.7,most of which are larger than 0.8,which indicates that during the persistent freezing rains,the influencing systems at upper and lower levels are stable and unchangeable.