广东近60年一次最大范围的降雪过程分析

Analysis of a Snowing Process Covering Most Extensively For the Past 60 Years in Guangdong

利用地面、探空实时业务观测以及NCEP 1°×1°分析数据等资料,对2016年1月下旬寒潮过程地面气压场、过程最低气温、广东降雪空间分布、大气温湿结构以及天气系统等方面进行了分析,结果发现:该次寒潮过程广东地面气压突破了有气象记录(1951年)以来的历史极值,但大部分市县最低气温未破历史记录;降雪南界较历史南界(1951—2015年)明显南压,即西部压到信宜、阳春一带,中东部则南压到了沿海;t850<0℃或t925<0℃的单层温度指标难以判断广东雨雪相态;当高空整层温度都在0℃以下,且近地面0℃层高度低时降水相态多为雪,0℃层高度过高时则降水相态为雨,其余为雨夹雪(霰);当高空有暖层存在时,出现纯雪的可能性较小,若地面0℃层高度低,且高空暖层厚度<位于其下方的冷冻层,则有雨夹雪(霰)的可能;降雪时大气湿度呈下干上湿状态,90%以上的高湿度区主要在800~500 h Pa之间;降雪时的辐合抬升主要发生在700~500 h Pa,中层的槽和西到西南急流是重要的动力因子。

Using real-time operational surface and sounding observations as well as NCEP 1°×1° reanalysis, we analyzed the surface pressure field, minimum temperature for the whole process, the spatial distribution of snow in the province and the structure of atmospheric temperature and humidity as well as weather processes concerning a cold wave during the last ten days of January, 2016. The result is shown as follows. While the surface pressure of the province reached the historical extreme since 1951 （the year in which meteorological observation began in Guangdong） , the minimum temperature did not break the historical record in most of other cities and counties. The southern boundary of snow is much more southward than the historical line （1951 -2015）, advancing to Xinyi and Yangehun in the western section and the coast in the middle and eastern sections. To determine whether it is snow or rain, it is difficult to use a single-layer temperature index of ts50 〈 0℃ or t925 〈 0℃; when the whole upper level of below 0℃ is accompanied with a low surface 0℃ layer, the precipitation phase is mostly snow, and when the former goes with a high surface 0 ℃ layer, it is rain. It is snow pellet when the layer is neither high nor low. If a warm layer exists in the upper level, it is unlikely for pure snow to occur. It the surface 0℃ layer is low and an upper warm layer is less thick than the freezing layer underneath, it is likely to have snow pellet. During the snow, the atmosphere is drier in the low level than in the upper level and more than 90% of the high humidity area is between 800 hPa and 500 hPa. Convergence and uplifting mainly occur at 700 - 500 hPa in the snow. A mid-layer trough and a west-to-southwesterly jet stream are important dynamic factors.