一次基于风廓线雷达观测的北京夏季降水的垂直观测研究

本文利用风廓线雷达数据反演了降水云体的大气垂直速度、雨滴下落末速度等云动力特征和云水混合比、雨水混合比等云微物理参数，并结合天气雷达、探空、自动站、雨滴谱仪和微波辐射计等数据对2020年5月7～8日发生在北京市海淀区的一次夏季降水过程进行垂直综合观测。结果表明:垂直探测仪器观测及其反演的数据可以获得降水云体的详细动力参数和微物理特征。站点位于主体降水回波边缘，降水为层状云类型，整体回波较弱（主要在0～20 dBZ），4 km高度的水平风垂直切变贯穿整个降水过程，降水分为两个阶段:前期7日20时（北京时，下同）至8日02时低层存在浅对流结构，云顶较高（平均高度8207 m），低层水平风切变促进了对流发展，10～20 dBZ的回波比重较大，粒子谱较窄，直径＜1 mm，雨强较弱，但粒子数浓度值大，最大值26305 m?3，2～3 km处存在暖平流，水汽和液水值大，雨水混合比0.02～0.15 g/kg，云水混合比0.5～2 g/kg，且强值区域大，雨滴下落末速度3.2～4.2 m/s，大气垂直速度在±0.6 m/s之间，上升气流和下沉气流变换明显；后期8日02～10时转为典型层状云降水，云顶较低（平均高度7831 m），＜10 dBZ的回波比重较大，3100 m处形成亮带的强值中心，粒子谱展宽，最大直径接近1.5 mm，粒子数浓度值减小，最大值＜3000 m?3，雨水和云水值比对流期小了一个量级，且强值范围变窄，雨滴下落末速度减小为2.8～3.6 m/s，大气垂直速度也比对流时期小了一个量级，并且在亮带高度以下（2.5～2.8 km）范围内出现明显横向带状的上升和下沉气流区。

Vertical Observation Study of Summer Rainfall in Beijing Based on Wind Profiler Radar

Wind profiler radar data was used to retrieve cloud dynamic characteristics, including vertical velocity, droplet terminal velocity, and microphysical parameters such as cloud and rain water mixing ratios. Summer precipitation in Haidian District of Beijing on 7–8 May 2020, was observed and analyzed by retrieval results using weather radar, sounding, automated meteorological readings, disdrometer, and microwave radiometer. Results indicated that the vertically scanning instruments and retrieval results obtained precipitation dynamic and microphysical information that can be used for further studies. The station was near the edge of the main precipitation reflectivity factor and had stratiform cloud precipitation. The overall precipitation reflectivity factor was weak (mainly at 0–20 dBZ), with the vertical shear of horizontal wind at 4 km running through total precipitation. The precipitation was divided into two stages. The earlier stage 2000 BJT (Beijing time) 7 to 0200 BJT 8 May 2020] had shallow convective structures at a lower height, and the convective precipitation cloud top was relatively high (average height 8207 m). Horizontal wind shear at low-level aided the development of convection, and the proportion of 10–20 dBZ was large. The particle spectrum was narrow, with a diameter ＜1 mm, and the rain rate was weak. However, the number concentration was large, reaching a maximum of 26305 m?3. Warm advection was present at 2–3 km, water vapor and liquid water values were high, and the rain water mixing ratio range was 0.02–0.15 g/kg. The cloud water mixing ratio range was 0.5–2 g/kg, with a large value and wide distribution. Droplet terminal velocity was 3.2–4.2 m/s, with vertical velocity in the range of ±0.6 m/s, and updraft and downdraft alternated. The later stage (0200–1000 BJT 8 May 2020) became typical stratiform cloud precipitation, with a relatively low cloud top (average height 7831 m). The proportion of ＜10 dBZ was large, the strong value center of the bright band was formed at 3100 m, the particle spectrum broadened, and the maximum diameter was close to 1.5 mm. However, the number concentration decreased, with a maximum value ＜3000 m?3. The rain and cloud water values were one order of magnitude lower than that of the convective stage. The intensity range was narrow, the droplet terminal velocity was reduced to 2.8–3.6 m/s, and the vertical velocity was reduced by an order of magnitude compared to the convective stage. There was obvious horizontal orientation upward and downward areas below the height of the bright band (2.5–2.8 km).