2009年河北省初冬暴雪天气过程的诊断分析

Diagnostic Analysis of a Snowstorm Occurred in Early Winter of 2009 in Hebei Province

2009年11月10～12日河北省出现了近50 a来最强的一次持续暴雪天气过程,给该地人民生活、生产造成一些不利影响。通过分析暴雪发生时的大尺度天气环流,探讨形成这次极端天气物理机制。结果表明,这次暴雪天气是在高空纬向环流形势稳定,700 hPa切变线长时间维持,低空西南气流源源不断地从海上输送暖湿空气使得该地的水汽含量不断升高,850 hPa到地面的东北风回流的冷空气等共同影响造成。诊断分析结果进一步表明,降雪期间高空辐散低层辐合、中低层存在较强的垂直上升运动、暖空气被冷空气抬升是暴雪发生的动力机制。

A continuous snowstorm occurred on November 10 to 12,2009 in Hebei Province,which was the most serious in recent 50 years.The objective of this study is to explore the possible mechanism responsible for this extreme weather event by analysis the large scale atmospheric circulation.The results show that the snowstorm occurred under weather conditions of the stable zonal circulation at high level,700 hPa shear line maintaining a long time,the abandant vapour coming from the southwest warm and humid airstream at the lower layer,the northeasterly cold air return from 850 hPa to the ground.The divergence at high level and convergence at low level,the strong ascending motion and the warm air forced to lift by cold air were the important dynamic mechanism of this weather event.