MM5模式对2008年1月25—30日我国南方强冰雪过程的数值模拟

Numerical Simulation by Mesoscale Model MM5 on the Severe Snow and Freezing-Rain During 25—30 January of 2008 Over the Southern China

利用NECP1°×1°6h再分析资料,分析2008年1月25—30日我国南方一次强降雪天气的大尺度环流形势。结果表明,高空环流波动为此次强降雪提供了有利的高空环流形势,中低层阻塞高压及其南部低涡的长期维持是导致低层锋区形成和强降雪发生的关键;由于部分地区大气垂直结构呈上下冷、中间暖的状态,致使冻雨形成。同时,利用中尺度模式MM5对此次过程进行72h数值模拟,并以模拟结果对湖南湘潭的冰冻成因进行再分析,进一步证实了低层低温、逆温层的存在及充足的水汽是冰冻形成的主要原因。

Using NECP 1°×1° 6 h data, it can be seen from the analyses of large-scale circulation of a heavy ice-damage in January 2008 that the disturbance in upper air offers the advantage circulation pattern for heavy snow, and the longtime keeping of the blocking high in the lower level and ist southern eddy is the key of frontogenesis and heavy snowfall. Meantime, the vertical state which is cold in upper and lower layer and warm in middle layer caused the freezing rain. The numerical simulation results making use of MM5 show that prognosis in 72 hour was perfect. And reanalysis made by using the simulative result to the ice forming in Changsha Xiangtan reconfirm that the exist of cold in lower layer, inversion layer and enough water vapor were the main reasons for forming ice.