云南东部冻雨的成因分析

Analysis on the reason of ice rain which happened on east of Yunnan province

应用常规气象探测资料,通过天气学及诊断分析研究了2008年2月上中旬云南东部地区出现冻雨天气时的环流形势和物理量场,结果发现:云南冻雨产生的日降水量并不大,但在大气环流背景稳定的条件下可持续较长时间,冻雨发生时天气形势表现为500 hPa上云南大部为西偏北气流控制,有冷平流输送,但无明显南支槽活动;700 hPa上云南西南部有弱的西南气流,具有暖平流输送,但湿度不大;850 hPa上贵州存在152 dagpm以上冷高压,低层冷空气具备较强势力;地面图上云南东部地区处于昆明静止锋后部,且环境温度场低于0℃.进一步分析冻雨地区的探空曲线,发现冻雨形成时大气具有"上下冷中间暖"的层结特征,700 hPa附近有逆温层,且逆温层顶温度在0℃附近或以上,逆温层的存在是形成冻雨的必要条件.形成冻雨的上升运动并不剧烈深厚,但需具备一定的水汽条件,当高层的雪花从静止锋上的雨层云的中上部落入逆温层内0℃以上的暖层时,雪花融化为雨滴,雨滴再落入静止锋内温度低于0℃的冷气层中,雨滴尚未冻结而呈过冷却状态,过冷却水滴降落到地面或其它物体表面形成冻雨,冻雨出现在昆明静止锋后部温度低于0℃的区域.

Conventional observing data and meteorology theories were used to analyze the synoptic background and physical quantity field of ice rain which happened in early February 2008 on east of Yunnan province.Result indicated that,the daily precipitation resulted from the ice was not heavy,but under the consistent atmosphere circulation background it can maintain for a longer time.When ice rain happened,most part of Yunnan province was controlled by north-west air flow on the height of 500 hPa,and there was cold ...