贵阳机场冻雨统计特征及一次典型案例分析

Statistical Characteristics of Freezing Rain and a Typical Case Analysis at Guiyang Airport

摘要: 利用2008~2021年地面逐时观测数据和再分析资料等，对贵阳龙洞堡机场冬季冻雨进行统计分析，并针对发生在2018年12月底的冰冻雨雪过程，分析对比冻雨和降雪时段的环流形势、微物理特征及云内垂直热动力结构的差异，结果表明：1) 贵阳机场年冻雨日数多在5日以下，1月份最多，且多发于凌晨，午间最少；2) 所选冻雨过程是典型的“二层模式”，具有较浅的冷垫和较厚的暖层，冷空气由偏北路径入侵贵州，孟加拉湾和南海的水汽沿西南气流输送，过程中700 hPa西南气流的加强与减弱所造成逆温层温度是否大于0℃是降水相态转变的关键；3) 相比降雪，冻雨时段的动力强迫主要位于中低层，强度偏弱，云中以液相粒子为主；4) 此次冻雨主要由高空槽前暖湿气团沿锋面爬升所引起，水汽和风场辐合中心从850 hPa逐渐抬升至700 hPa，且较为浅薄，冻雨落区位于冷锋后部一定距离处。

Abstract: Using ground hourly observation data and reanalysis data from 2008 to 2021, the winter freezing rain at Longdongbao Airport in Guiyang was statistically analyzed. In view of the freezing rain and snow process at the end of December 2018, the differences in circulation situation, microphysical characteristics and cloud vertical thermodynamic structure between freezing rain and snowfall periods were analyzed and compared. The results show that: 1) The number of annual freezing rain days in Guiyang Airport is mostly below 5 days, and the maximum is in January, and it occurs in the morning and the minimum is at noon; 2) The selected freezing rain process is a typical “two-layer model” with shallow cold cushion and thick warm layer. The cold air invades Guizhou from the northerly path, and the water vapor in the Bay of Bengal and the South China Sea is transported along the southwesterly. During the process, whether the temperature of the inversion layer caused by the strengthening and weakening of the southwest airflow at 700 hPa is greater than 0˚C is the key to the transformation of precipitation phase. 3) Compared with snowfall, the dynamic forcing during the freezing rain period is mainly located in the middle and lower layers, and the intensity is weak, and the cloud is dominated by liquid particles; 4) The freezing rain was mainly caused by the warm and humid air mass climbing along the front of the upper trough. The convergence center of water vapor and wind field gradually increased from 850 hPa to 700 hPa, and it was relatively shallow and thin. The freezing rain falling area was located at a certain distance behind the cold front.