不同天气类型下的降雪预报指标分析

Analysis on Indicators of Snow Forecast Under Different Weather Situations

利用常规气象观测资料、NCEP再分析资料和风阔线雷达资料等,分析了2010-2015年湖州降雪过程的天气形势、风阔线雷达产品和气象要素特征。结果表明:湖州降雪天气形势可分为阻高横槽型(Ⅰ型)、南支槽切变型(Ⅱ型)、东阻型(Ⅲ型)三类,Ⅰ型发生频率最高,Ⅱ型次之,Ⅲ型频率最低;综合温度和水汽等因子建立了各种天气型下的降雪预报指标;降雪一般开始于逆温层建立过程中,逆温减弱破坏时降雪减弱停止,降雪量与500 h Pa至700 h Pa水汽通量关系密切;风廓线雷达与温度垂直廓线结合应用效果较好,一般高层西南风加大、低层冷平流向上扩展、上升运动明显加强时预示降雪开始,垂直风的强度能很好地指示降雪量级。

The regular meteorological observation data,the reanalysis data of NCEP and wind profiler radar data are used to study the indicators of snow forecast on 2010-2015 in Huzhou.According to analysis of weather situation and the features of profile data and meteorological elements, the result shows that snow process can be divided into three types of blocking high and horizontal trough(type I), southern sranch srough and shear(type Ⅱ), east blocking high(type Ⅲ).and then the occurrence frequency is type I, type Ⅱ, type Ⅲ. Using the factors of temperature and water vapor, the snowfall forecast indexes of various weather types are established. Generally, snow begins with the inversion layer in the process of the establishment, weakened when the inversion weakened. Snowfall is closely related to moisture flux from 700 hPa to 500 hPa.The combination of wind profile and vertical temperature profile can indicate the beginning of the snowfall,when the southwest wind at high level enhanced,low level cold advection upward extended and ascending movement strengthened significantly.The strength of vertical wind can indicate the magnitude of snowfall.