滨州市两次春季雨转雪天气过程对比分析

The Analysis of Binzhou City Twice in the Spring Rain Turning Snow Weather Process Comparison

利用常规观测资料,对2011年2月26日和2013年4月19日两次雨转雪过程进行对比诊断分析.结果表明:两次过程均是产生在中高纬两槽一脊的大环流形势背景下,低层回流的冷空气与中高层槽前的西南暖湿气流形成的典型回流降水,低空急流的建立为降水提供了充足的水汽和能量,切变线的位置决定了降水的范围和强度.高层辐散形成的抽吸效应加强低层辐合和上升运动,利于强降水的产生.降水相态的转变时间表明除了850 h Pa温度小于-4℃作为雨转雪指标外,近地面温度可作为雨转雪的补充预报指标.

Using conventional observation data,two rain turning snow processes on February 26,2011 and April 19,2013 were analyzed. The results show that two processes was produced under the background of the large circulation of middle-high latitudes two troughs and one ridge,the typical reflux precipitation was formed by cold air of low-level reflux and southwest warm air in front of high level trough,and the establishment of low level jet stream provided sufficient water vapor and energy for rainfall and the location of the shear line determined the range and intensity of precipitation. The suction effect of upper level divergence strengthened the low- level convergence and upward motion,accelerated the causing of the strong precipitation. The transit time of the precipitation phase state indicated that the near surface temperature could be used as a supplementary forecast index of the rain turn snow,beside the 850 h Pa temperature was less than- 4℃ as rain turn to snow indicators.