干冷空气侵入在2005年12月山东半岛持续性降雪中的作用

利用常规资料和NCEP再分析资料分析了2005年12月山东半岛持续强降雪事件发生的环流背景及干冷空气活动特征,并运用湿位涡和锋生理论,研究了干冷空气在降雪事件中的作用.分析表明:低层湿度场的演变可以很好地反映山东半岛地区降雪的变化,但降雪事件与高层干冷空气紧密相连.对流层高层高位涡区与相对湿度小值区相对应,干空气主要来源于北侧(高纬度)对流层高层.高位涡区与低湿区都向下向南伸展,与低层MPV1<0的湿对称不稳定区对应.强降雪是低层饱和湿空气受地形强迫、锋生强迫的抬升作用及湿对称不稳定能量释放的共同作用造成的,而干冷空气的侵入是锋生和不稳定能量释放的触发机制.

The Roles of Dry-cold Air Incursion on Persistent Snowfall in Shandong Peninsula During December of 2005

In terms of observed data and NCEP reanalyzed data, circulation background and dry cold activity features of the persistent snowfall in Shandong Peninsula during December of 2005 were analyzed. The roles of dry cold air in this event were researched by using the moist potential vorticity and frontogenesis theories. The results suggested that the change of snowfall in Shandong Peninsula could be well reflected by the low level humidity field, while it was closely associated with upper level dry cold air. The upper troposphere potential vorticity area was corresponded with the low relative humidity area. Dry air came mainly from the northern part (high latitude) of upper troposphere. The down and south stretching of potential vorticity area and low humidity area were corresponded with the low level moist symmetry instability area. The severe snowfall occurred under the common actions of the lifting of topographic and frontogenesis forcing of low level saturation moist air, as well as the releasing of moist symmetry instability energy. The incursion of dry cold air was the trigger mechanism of the releasing of instability energy.