高原山地环境下冻雨微物理特征及成因分析

Microphysics characteristics and causes of freezing precipitation in mountainous area over Yunnan-Guizhou Plateau

本文利用2014年1月贵州西北部威宁观测的激光雨滴谱、探空和常规气象要素等资料,分析了冻雨发生期间的气象条件、雨滴的微物理特征及谱分布特征,并与南方其他地区冻雨进行了对比。结果表明:(1)冻雨发生期间,地面以静止锋系统为主,大气存在逆温,云层薄、云底低,近地面温度低、湿度高、风速小。(2)4次冻雨过程均为冻毛毛雨过程,雨滴平均直径为037 mm,雨量极微弱,平均值为002 mm。数浓度与液水含量高度正相关。平均谱分布拟合结果,Γ分布好于M-P分布。(3)与中国其他南方地区冻雨相比,雨滴直径、雨强均偏小,平均谱分布较窄,小滴多。(4)威宁冻雨的微物理特征符合"过冷暖雨"的形成机制,云贵准静止锋的特性和该地高海拔山地地形可能是导致该地滴谱窄、雨滴直径和雨量小的主要原因。

By using the data from an optical disdrometer, sounding and meteorological elements ob- served by Weining observation site in northwestern Guizhou in January 2014, the meteorological condi- tions, droplets characteristics and raindrop size distribution of the freezing precipitation were analyzed, and compared with the freezing precipitation in other southern cities of China. Results show that： （1） during the freezing precipitation events, the dominate synoptic system was quasi-stationary front, and the inversion existed in troposphere. The cloud thickness was thin and the cloud base was low. The near-surface temperature was below 0℃, relative humidity was above 85%, and the wind speed was low. （2） All freezing precipitation events were freezing drizzle, whose average diameter was 0.37mm and aver- age rain intensity was 0.02mm. The liquid water content was highly correlated with the number concentra- tion. The fitting result of raindrop size distribution shows F distribution was better than the M-P distribu- tion. （3） Compared to other regions of southern China, Weining had smaller raindrops, weaker rain in-tensity and narrower spectra. （4） The freezing precipitation events in Weining took place through ＂super cooled warm rain＂ process, and the Yunnan-Guizhou quasi-stationary front and the high altitude moun- tainous terrain was likely responsible for the droplets characteristics.