张家界市雨雪相态转换预报着眼点研究

Research on Forecast Focus of Phase Transformation of Rain and Snow in Zhangjiajie City

利用常规天气图、NCEP再分析资料、鄂西站探空资料,对张家界市2014年3次低温雨雪冰冻过程的天气实况、天气背景、环境条件等进行了综合分析。通过分析研究出张家界市出现雨夹雪或纯雪的气温指标值,张家界站、慈利站气温≤2℃,桑植站气温≤1℃。通过分析临近张家界的鄂西T-log P资料得知,降雪前中低层存在逆温层,降雪后在高空冷平流的影响下降温,其逆温减弱直至消失。逆温层的厚度、强度与降雪的强度和维持时间正相关。雨雪的大小,除了考虑水汽条件外,还要综合考虑动力抬升的强弱和降水持续时间的长短。对冬季雨雪相态转换研究可明确雨雪分界线及转换时间,为精细化预报预警提供技术支撑。

Using conventional weather maps, NCEP reanalysis data,Western Hubei Station sounding data,the actual weather,weather background and environmental conditions of low temperature and freezing process for 3 times in Zhangjiajie City in 2014 were analyzed comprehensively in this paper. The results showed that temperature index of sleet or pure snow in Zhangjiajie City was obtained,temperature of Zhangjiajie Station and Cili Station was less than or equal to 2 ℃ ,temperature of Sangzhi Station was less than or equal to 1 ℃.Through the analysis of T-logP data in western Hubei, there was low-level inversion layer before snow, and the inversion weakened until disappear under the influence of high altitude cold advection after snow. Thickness and strength of inversion layer were positively associated with the intensity and duration of snow. The size of the rain and snow was also related to the strength of the dynamic lifting and the rainfall duration, besides water vapor condition. The research on phase transformation of winter snow and rain can provide technical support for fine forecast, because it can confirm the demarcation line and conversion time of rain and snow.