2018年安徽东部连续两次回流形势下强降雪成因分析  

Analysis of the causes of strong snowfall after two consecutive reflux situations in eastern Anhui in 2018

作　　者：胡姗姗 熊敏 熊世为 蒋琳 华俊玮 刘倪[2] HU Shan-shan;XIONG Min;XIONG Shi-wei;JIANG Lin;HUA Jun-wei;LIU Ni(Chuzhou Meteorological Bureau,Chuzhou 239000,Anhui,China;Anhui Meteorological Observatory,Hefei 230031,China)

机构地区：[1]滁州市气象局,安徽滁州239000 [2]安徽省气象台,合肥230031

出　　处：《湖北农业科学》2019年第22期87-96,共10页Hubei Agricultural Sciences

基　　金：安徽省气象科技发展基金项目(KM201719)

摘　　要：利用常规气象观测资料、区域自动气象站资料和NCEP 1°×1°逐6 h再分析资料等对2018年1月3-4日和24-28日出现在安徽东部两次极端大暴雪过程的成因及动力、水汽热力、干侵入等结构演变特征进行诊断分析。结果表明,高空冷槽配合中低层低涡切变发展是形成暴雪的重要环流背景,700 hPa西南低空急流带是暴雪区主要水汽输送通道,异常的水汽通量大值中心与水汽通量散度中心相配合是产生极端强降雪的重要原因。从降雪机制看,1月3-4日暴雪过程属暖区冷流降雪,大气处于湿对称不稳定状态,暴雪区位于垂直方向上螺旋度正负值中心相叠置的区域中靠近下沉支的上升支气流中,且高低空急流耦合形成垂直方向上次级环流,高空槽后的强西北气流与高效率的水汽辐合输送相结合,降雪强度大;而1月24-28日属非典型性冷平流降雪,低层先有冷空气南下,干冷空气受底层抬升而直接降雪,过程相对冰面过饱和现象主要在低层,过冷水较弱,持续时间长。且两次强降雪过程中低空急流发生发展与高空急流周围正的涡度平流都有很好的对应关系,辐合强弱与降雪强度相对应。Using conventional meteorological observation data, regional automatic weather station data and NCEP 1°×1° reanalysis data for 6 hours in January 2018, the causes of the two heavy snowstorms in eastern Anhui on January 3 -4 and 24-28 and their structural evolution characteristics, such as power, water vapor thermodynamics and dry intrusion, were diagnosed and analyzed. The results showed that the high-altitude cold trough and the low-altitude vortex shear development were the important circulation background for the formation of snowfall, the southwest low-altitude jet zone of 700 hPa was the main water vapor transportation channel in the snowfall area, and the abnormal water vapor flux center and the water vapor flux divergence center are the important reasons for the extremely strong snowfall. From the snowfall mechanism, January 3-4 big blizzard process belonged to the warm area cold flow snowfall, the atmosphere was in a moist symmetric unstable state, the blizzard region is located in the updraft near the sinking branch in the vertical superposition region with positive and negative spirals. And the high and low space jet coupled to form a vertical secondary circulation. The strong northwest airflow after the high trough was combined with the high efficiency of water vapor convergence transportation, the snowfall intensity was strong;However, January 24-28 was an atypical cold advective snowfall. Cold air moved southward in the lower layer, while dry cold air directly snowed due to the uplift of the bottom layer. The phenomenon of supersaturation is mainly in the lower layer, and the subcooling water is weak and lasts for a long time. Moreover, the occurrence and development of the low level jet stream in the two heavy snowfalls had a good correspondence with the positive vorticity advection around the high level jet stream, and the convergence strength corresponded to the snowfall intensity.

关 键 词：暴雪 低空急流 螺旋度 涡度平流 位涡 

分 类 号：P426.616[天文地球—大气科学及气象学] P458.121.1