一次冬季暴雨转雪天气诊断分析

利用NCEP1°×1°资料和常规天气观测资料,对2010年12月15日新余市一次寒潮过程中暴雨转雪天气的环流背景、影响系统及其成因进行了分析。结果表明:1)500 h Pa横槽转竖,低层及地面的冷高压南移,使得冷空气侵入江南地区,是造成此次江南地区降温的主要原因;2)华南准静止锋的长期维持且坡度小、湿层和辐合区较薄且辐合强度较弱,导致本次降水的强度不大,但较长的持续时间使降水达到暴雨量级;3)寒潮带来的降温形成了降雪有利的温度条件,当测站上空整层温度均在0℃以下,925 h Pa温度≤-3℃,地面气温≤1℃时,降水将从雨转变为雪。

A Diagnostic Analysis of a Heavy Rain Turning Snow in Winter

Using the observation data, the NCEP analysis data, diagnostic analyses are made on the causes, circulation background and weather system for a rare cold wave in Xinyu City on December 15,2010. The result show that：The turning of the high-altitude transverse trough （becoming vertical） guided the north cold air to move southwards invade the area south of the Yangtze River, this is the mainly reason of temperature drop;A long-standing Quasi-stationary Front in South China has a small frontal slope ,the thin wet layer and convergence zone and weak convergence intensity leads to the weak precipitation intensity, but a long precipitation time caused heavy rain （ snow ） ; Cold wave brings the cooling forming temperature conditions are favorable snowfall, when the whole temperature over Xinyu Observation station under 0 ℃ ,925 hPa temperature below - 3 ℃, the ground temperatare below1 ℃, precipitation from rain to snow.