一次大范围暴雪天气的大气环境形成机理研究

The formation mechanism of atmospheric environment for a heavy snowstorm event

通过分析2009年11月9—12日的一次大范围暴雪天气事件,探讨其发生前期和过程中的大气环境条件及形成机理。通过研究分析环流特征、星载雷达有关能数、物理量场诊断等表明:此次天气过程中暴雪区域上空对流层中低层一直存在着一层具有增温增湿特征的层状云,暴雪前大气低层高温高湿的环境为暴雪的发生提供了一个有利的温湿能量蓄积场;东北回流冷空气的入侵是层状云开始形成的触发机制;大气低层因水汽凝结产生的大量凝结潜热促进了垂直上升运动,大气中低层在水汽条件具备时,通过垂直上升运动的作用使水汽大量凝结增长,形成层状云。

A heavy snowfall took place in large region of China during Nov. 9 to 12, 2009 which caused serious disasters and losses. In this paper, the formation mechanism of the atmospheric environ- ment was explored by analyzing the atmospheric environment conditions before and during this severe weather process. The results show that ： （ 1 ） During this weather process there had been an increasing tem- perature and wet characteristics layer of stratus over the heavy snowfall region in mid-low troposphere, which favored the occurrence of the heavy snowfall. （2）The high temperature and humidity environmen- tal conditions provided a field of energy accumulation for the heavy snowfall. （ 3 ） The incursion of the northeast backflow cool air was the trigger mechanism of stratus. （4）The large amount of latent heat of condensation generated in the lower atmosphere promoted the vertical motion. When the water vapor con- dition was satisfied in mid-low atmosphere, the condensed water vapor was increased due to the vertical motion and then stratus was formed.