乌鲁木齐地区春季第一场暴雪型寒潮天气过程分析

根据常规天气资料、NCEP1°×1°的6h分析资料和数值预报产品，对2008年4月18日～2008年4月20日强寒潮天气发生前后环流及物理因子分析认为，强寒潮天气暴发前期，里黑海脊发展东移与东欧脊同位相叠加后顺转，脊前东北风带加强，使泰米尔半岛冷空气沿脊前偏北气流在横槽中堆积。高压脊部分东南垮，导致强冷空气大举东南下，强寒潮天气暴发；里海到巴尔喀什湖的水汽在北疆上空聚积，为这次寒潮天气提供了水汽条件；ECMWF数值预报产品在这次强寒潮天气过程中准确的预报了高度场的环流场演变趋势，地面冷高压的位置、强度、路径和移速；850hPa格点温度预报值与最低温度实况值具有很好的对应关系。

Analysis on Cold Wave Process of the First Snowstorm at Urumchi Region in Spring

According to normal weather recourse,6 h analysis data of NCEP1°×1°and numerical forecast product,the circulation and physical factors at pre and post of the strong cold wave in 2008-4-18～2008-4-20 were analyzed.The results showed that at early stage of the cold wave,the caspian-black sea ridge moved eastward and combined with the eastern Europe ridge at the same position and then veered,the northeast wind zone in front of ridge strengthened,it made the cold air in Taymyr peninsula stacked in transversal trough along with north air stream in front of the ridge.The pressure ridge partly moved to southeast,it led to the cold air stream more moved to southeast,and the strong cold wave broke out.The water vapor from Caspian sea to Bslkhash lake accumulated at the upper of north Xinjiang,and it provided the water vapor condition for the cold wave.The ECMWF numerical forecast product accurately predicted the evolution trend of circulation(the position,intensity,path and speed of ground surface cold high pressure) of height field in this cold wave process.The predicted temperature at 850 hPa had good corresponding relation with the actual lowest temperature.