鲁南初冬一次罕见特大暴雪的成因分析

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

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 h Pa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 h Pa强西南低空急流、850 h Pa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 h Pa之间维持一个逆温层;强冷空气使得925 h Pa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。

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 h Pa. The strong southwest low-level jet at 700 h Pa and the southeast low-level jet at 850 h Pa 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 h Pa and 925 h Pa. The long duration of snowfall is an important reason for the heavy snowfall in the southern part of Shandong.