一次强寒潮引发的浙北不同地区雨雪气象条件差异

Differences of rain and snow meteorological conditions in different areas of northern Zhejiang caused by a strong cold wave

雨雪相态的转化是浙江省冬季降水预报服务的重点和难点。利用NCEP再分析格点资料、浙江省自动气象站和两部风廓线雷达观测资料,对2016年1月一次强寒潮在浙江北部地区导致不同的降水相态进行气象要素的对比分析。结果发现:高空强冷平流、中低层强暖湿气流为雨雪过程提供了良好的动力和水汽条件。对比分析发现:在同等强度的冷空气影响下,浙江北部沿海地区雨夹雪或雪需要大气低层的气温比内陆地区更低。根据不同降水相态下T_(2 m)、Φ_(850-1 000)和Φ_(925-1 000)指标差异对沿海地区和内陆地区分别建立雨雪判别指标。检验表明统计指标对浙北地区雨雪相态预报有较好的指示意义,且风廓线雷达资料500 m以下边界层平均垂直速度变化可以辅助判定地面雨雪的相态变化和地面降雪的强弱。

The transformation of the rain and snow phase is the focus and difficulty of the winter precipitation forecast service in Zhejiang Province.This paper uses the NCEP reanalysis grid data,the data from automatic weather stations in Zhejiang province,and the two wind profile radar observation data to conduct a comparative analysis of meteorological elements for the different precipitation phases of different regions induced by a severe cold wave in Jan.2016.The results showed that:high altitude strong cold advection,middle and low level strong warm and humid air flow provided good dynamic and vapor conditions for the rain and snow process;a comparative analysis found that under the influence of the cold waves of the same intensity,sleet or snow occurred on the coast of North Zhejiang requires a lower temperature of the lower atmosphere than those occurred in the inland of North Zhejiang.According to theФ850-1000,Ф925-1000 and index differences under different precipitation phases,this paper builds the rain and snow evaluation indexes for the coast area and inland area respectively.The test showed that the statistical index is of good reference value for the forecast of rain and snow phases in North Zhejiang.The average changes of vertical velocity of the boundary layer below 500 m from the wind profile radar data can help determine the phase change of ground rain and snow and the strength of ground snowfall.