基于多源观测资料的雄安一次雾转暴雪的过程分析

Process Analysis of a Fog to Blizzard in Xiong’an New Area Based onMulti-source Observation Data

利用多源高时空分辨率观测资料对2021年11月6—7日河北雄安新区一次雾转暴雪天气过程进行深入分析.结果表明:(1)微波辐射计观测特征:整个过程大气层湿度深厚,雨转雨夹雪再转雪阶段,3~6 km大气层相对湿度逐渐增大至80%以上;雾转雪过程中大气层温度明显下降,雾转雨100 m以下大气层温度下降4~5℃;雨转雨夹雪1~6 km大气层温度明显降低2~3℃;100 m以下大气层温度低于0℃时,预示着雨夹雪转雪.(2)毫米波云雷达观测特征:大雾阶段反射率因子强度较弱为-16.0~0.3 dBz,雾滴下降速度基本为0 m/s;雨转雨夹雪2 km以下大气层反射率因子强度增强至33~45 d Bz,径向速度明显增大至-6.9~-4.2 m/s;雨夹雪转雪云顶升高1~2 km,3 km以下大气层最强反射率因子减弱6~12 dBz,径向速度减弱约3 m/s.(3)雨滴谱观测特征:雨转雨夹雪时降水粒子直径增大,最大为4.5 mm,下降速度1~7 m/s;雨夹雪转雪时直径1.5~5.0 mm的降水粒子数量增多,但下降速度明显减小至0.5~3.0 m/s.(4)此次雾转暴雪过程,3种产品对雾、雨,雪相态转换和持续过程均有较好反映,其中毫米波云雷达产品的宏观、微观及云物理特征对临近预报预警有明显参考价值.

Based on multi-source observation data with high spatial and temporal resolution,an in-depth analysis is made for a fog to blizzard weather process in Xiong’an New Area of Hebei Province on November 6-7,2021.The results show that:①Observation characteristics of microwave radiometer:the atmospheric humidity is deep in the whole process.In the stage of rain to sleet and then to snow,the relative humidity of 3-6 km atmosphere gradually increases to more than 80%.In the process of fog to snow,the atmosphere temperature drops obviously.When fog turns to rain,the temperature of the atmosphere below 100 m drops by 4-5℃.When rain turns to sleet,the temperature of the 1-6 km atmosphere decreases by 2-3℃.When the atmospheric temperature below 100 m is below 0℃,it indicates that the sleet turns to snow.②Observation characteristics of millimeter wave cloud radar:the reflectance factor intensity is weak in the fog stage,ranging from-16.0 to 0.3 dBz,and the falling speed of fogdrop is basically 0 m/s.When rain turns to sleet,the reflectivity factor intensity of the atmosphere below 2 km increases to 33-45 dBz,and the radial velocity obviously increases to-6.9--4.2 m/s.When sleet turns to snow,the cloud top increases by 1-2 km,the maximum reflectance factor of the atmosphere below 3 km decreases by 6~12 dBz,and the radial velocity decreases by about 3 m/s.③Observation characteristics of raindrop spectrum:when rain turns to sleet,the diameter of precipitation particles increases to 4.5 mm at most,and the falling rate is 1-7 m/s.When sleet turns to snow,the number of precipitation particles with diameter of 1.5-5.0 mm increases,but the falling velocity decreases significantly to 0.5-3.0 m/s.④In this fog to blizzard process,the three products have a good reflection on the phase transition and continuous process of fog,rain and snow.Among them,the macro,micro and cloud physical characteristics of millimeter wave cloud radar products have obvious reference value for nowcasting and early warning.