鲁南初冬一次罕见特大暴雪的成因分析

利用常规气象观测资料和NCEP/NCAR逐6 h再分析资料，对2015年11月23—24日山东南部出现的一次罕见特大暴雪天气过程进行诊断分析。结果表明：1）这是一次典型的回流形势降雪，850 hPa东南风急流影响的鲁南地区降雪强度较大，而东北风急流影响的区域降雪强度较弱。2）700 hPa强西南低空急流、850 hPa东南低空急流为鲁南地区降雪提供了充沛的水汽，水汽通量的强辐合区域即为大暴雪的发生区域。3）暴雪区上空散度呈现出弱辐散—强辐合—强辐散的垂直结构；暴雪落区与高空的强辐合中心以及强上升运动中心吻合度较高。4）暴雪期间，850～925 hPa之间维持一个逆温层；强冷空气使得925 hPa以下边界层温度锐降导致降雨迅速转雪，降雪持续时间长是鲁南地区产生异常强降雪的重要原因。

Case study on the historic blizzard in the southern region of Shandong in early winter

Using the conventional meteorological observation data and NCEP/NCAR data, a severe blizzard weather event which occured in the southern part of Shandong on 23-24 November 2015 is analyzed. The results show that this is a typical backflow situation snowfall. The snowfall which is impacted by the northeast wind jet is weaker than the areas by southeast wind jet at 850 hPa. The strong southwest low-level jet at 700 hPa and the southeast low-level jet at 850 hPa provided enough water vapor. The strong convergence area of water vapor flux is the area with the heaviest blizzard.The divergence area over the blizzard area shows a vertical structure with weak divergence-strong convergence-strong divergence. Blizzard area, the high-altitude convergence center and strong ascend movement center coincidence are consistent. During the Blizzard, an inversion layer was maintained between 850 hPa and 925 hPa. The long duration of snowfall is an important reason for the heavy snowfall in the southern part of Shandong.