风廓线雷达产品在贵州降雪冻雨天气中的特征分析

Characteristics of Various Wind Profile Radar Products in Snowfall and Freezing Rain in Guizhou

利用贵阳机场CFL-03型大气边界层风廓线雷达(Wind Profile Radar,WPR)资料、贵阳机场自观资料等,针对典型降雪和冻雨个例,以及贵阳近三年发生的降雪和冻雨过程的特征进行统计分析,结果表明:①WPR的水平风场反应出降雪期间冷空气厚度及强度都超过冻雨,并且中低层主要为冷平流,而冻雨中低层主要为暖平流;②高层大气折射率结构常数C_(n)^(2)增大/减小在时间上超前于降雪的增强/减弱,可以反应降雪强度变化的趋势;③降雪阶段的回波强度分布在垂直方向上向左倾斜,高层回波强度的变化对降雪强度的变化具有指示性;冻雨的回波在垂直方向呈现“强弱强”的分布,与温度场在垂直方向上的“冷-暖-冷”的层结分布一致;④冻雨天气下粒子的下落速度小于降雪,雨夹雪的下落速度比纯雪更大,小雪下落速度最小。

Based on the data of CFL-03 atmospheric boundary layer wind profiler radar and the automatic weather observation data of Guiyang Airport from January 2019 to June 2022,this paper verifies the availability of WPR data and analyses horizontal wind field,vertical wind speed,echo intensity,atmospheric refractive index structure constant and other physical quantities in detail according to the typical snowfall and freezing rain process;at the same time,the differences of WPR data between different intensity snowfalls and freezing rains are compared.Finally,the WPR data of snowfall and freezing rain in recent three years are statistically analysed.The results show that:(1)The horizontal wind field of WPR reflects that the thickness and intensity of cold air during snowfall exceed that freezing rain,the middle and lower layers are controlled by cold advection during snowfall,while they are warm advection during freezing rain.(2)The greater the central value of C_(n)^(2),the higher the upward development height of the large value area,and the stronger the snowfall intensity;and the increase/decrease of high-level C_(n)^(2)is ahead of the increase/decrease of snowfall,which can reflect the intensity change of snowfall.(3)The radar reflectivity of snowfall leans to the left in the vertical direction,so the change of radar reflectivity in high-level layers is an indicative of the change of snowfall intensity,the radar reflectivity of freezing rain presents a“strong-weak-strong”distribution in the vertical direction,which is consistent with the“cold-warm-cold”stratification distribution of temperature field in the vertical direction.(4)In freezing rain,the falling speed of particles is slower than that of snowfall,and the precipitation particles almost only fall in the cold air area below 1500 m with the speed of 0.2 to 1.0 m/s;while in sleet,the falling speed is faster than that of pure snow,and the falling speed of light snow is the slowest.