黄河中下游地区持续性低温天气成因分析

利用常规观测资料和我国气象台站温度资料,采用天气学原理、天气动力学和热力学诊断分析方法,对2010年1月上、中旬黄河中下游地区强降温和持续性低温天气过程进行了环流形势、影响天气系统及成因分析。结果表明,500hPa槽后偏北气流引导极地冷空气不断向南输送,东北亚稳定的冷涡中心起到了阻挡冷空气东移、促使冷空气堆积和加强的作用,西伯利亚深厚低槽压迫高压脊崩溃,强冷空气爆发南下。850hPa强盛的温度冷平流是造成气温骤降和持续性低温天气的主要原因,冷平流中心的演变与强冷空气移动路径相一致。黄河中下游地区从高空到低层均有负涡度平流,深厚的负涡度平流输送有利于高压系统的移动,其值越小冷空气越强,负涡度平流中心与强降温中心相对应。冷平流中心比强降温中心提前12～24h出现,＂负涡度平流核＂先于强降温天气出现,这些特征为预报强降温天气提供了有利的参考依据。

Causes of Continuous Cold Temperature Weather in Middle and Lower Reaches of Yellow River

Based on conventional observation data and temperature data of meteorological stations in China,the circulation and weather systems and causes were analyzed by principles of weather and weather dynamics and thermodynamic diagnosis for the strong cooling and the continuous low temperature weather process on 1-20 January 2010 in middle and lower reaches of the Yellow River. The results showed that cold air from polar region was transported to south by northerly airflow behind trough at 500 hPa; stable cold vortex center in Northeast Asia blocked the cold air to move east,made cold air accumulate and strengthen. Deep trough in Siberia oppressed pressure ridge to collapse,the strong cold air broke out and moved southward. The main reason for the rapid air temperature decrease and continuous cold temperature weather was the intense cold advection of temperature at 850 hPa,the evolution of the cold advection center of temperature was consistent with the strong cold air moving path. There were negative vorticity advection from the upper to the lower in Middle and Lower Reaches of Yellow River,strong negative vorticity advection was conducive to movement of the high-pressure system,the smaller the value of negative vorticity advection,the stronger cold air. The negative vorticity advection center corresponded with strong cooling center. The cold advection center appeared 12-24 h in advance than strong cooling center,and the negative vorticity advection core appeared early than strong cooling weather,these features will provide a favorable reference for weather forecast of strong cooling.