一次春季强降雪过程相态变化的成因分析

Cause Analysis on the Phase Transformation of a Heavy Snowfall Process in Spring

利用常规气象观测资料、区域自动站加密观测资料和NCEP1°×1°再分析资料,对2013年4月19日山东一次强降雪过程的相态变化进行诊断分析。结果表明:1前期冷空气入侵形成冷垫,西南暖湿气流沿冷垫爬升,是一次典型的回流形势下的强降雪过程;雨雪分界线随时间自西北向东南方向推进,地面2℃线可以作为这次过程雨转雪预报的一个参考点;20℃层下降到925h Pa以下可以做为降水相态转为雪的识别判据;3降雪时刻H700-850从148~155dagpm,H850-1000≤129dagpm;44月份出现如此低的温度除了有利的大尺度环流背景外,地形也发挥了重要作用。

Based on conventional observational data,automatic meteorological observing station data and the NCEP1° × 1° reanalyzed data,the phase transformation of the heavy snowfall process in spring on 19 April,2013 was analyzed. The results showed that: The early stage of the cold air invasion formed cold pad,cold pad warm moist air flows southwest along the climb,and this is a typical flow situation of heavy snowfall process. Rain and snow line advanced from northwest to southeast with time. The 2 ℃ line on ground could be a reference point for the snow forecast in the process of rain. when 0℃ layer was down to below 925 h Pa,it could be used as the precipitation phase to the recognition criteria of snow. Snow moment H700- 850 was from 148- 155 dagpm,H850- 1000 was ≤129 dagpm. Topography played an important role in the formation of the low temperature besides the favorable large scale circulation background in April.