山东北部一次夏末雹暴地面降水粒子谱特征

为了更好地认识雹暴等强对流降水的微物理特征，利用降水现象仪观测资料和CINRAD/SA-D双偏振天气雷达的粒子相态识别和反射率因子等产品，分析2019年8月16日出现在山东北部的一次雹暴降水的雨、冰粒子谱（包括直径2~5 mm的霰粒子和直径大于5 mm的冰雹）的识别以及雨滴谱的演变特征，结果显示:济南双偏振天气雷达0.5°仰角PPI上在德州和陵县观测点附近识别的粒子主要为雨滴，临邑为冰雹加大雨；安装在3个观测点的降水现象仪均识别出少量冰粒子，3个观测点的冰粒子谱数密度低、分布不连续。雹暴降水开始阶段，出现少量大雨滴，这是风的筛选和蒸发作用导致的雨滴谱，具有低的小粒子数密度和较多大雨滴；雹暴强降水增大阶段，雨滴谱特征是小雨滴数密度偏低、大雨滴较多，即总的雨滴浓度低、雷达反射率因子高；雨强减弱阶段，小雨滴数密度显著增大、大雨滴数密度偏少，即总的雨滴浓度显著增大，但雷达反射率因子偏低。

Hydrometeor Particle Characteristics During a Late Summer Hailstorm in Northern Shandong

Based on the data of PARSIVEL disdrometer, particle phase identification and reflectivity factor of CINRAD/SA-D dual polarization weather radar, a hailstorm process occurred in northern Shandong Province on 16 Aug 2019 is analyzed. The rain and hail particles are distinguished, and the evolution of the raindrop size distributions is analyzed. PPI scans at 0.5°elevation of dual polarization weather radar show that there are raindrops at Dezhou and Lingxian observational stations, while it rains heavily and hails at Linyi. As for PARSIVEL disdrometer, a small number of ice particles is identified at all three sites, and the distribution of ice particles varies dramatically. Raindrops are classified into rain or ice particles according to the particle size and falling speed. However, the observational results still need artificial verification. When the hailstorm passes over the three observational stations, ice particles are identified by PARSIVEL disdrometer. At Dezhou station, 5 ice particles are identified, including 2 large hailstones (diameter > 8 mm), 2 small hailstones (diameter between 5-8 mm) and 1 graupel particle (diameter between 2-5 mm). There are 29 ice particles in Lingxian station, including 2 large hailstones, 19 small hailstones and 8 graupel particles. At Linyi station, 17 ice particles are observed, including 10 large hailstones, 3 small hailstones and 4 graupel particles. The Z-R relation retrieved by PARSIVEL disdrometer data is Z=1523R1.21, which has a larger coefficient, but a smaller index compared with the Z-R relation of convective precipitation of the new generation Doppler radar. In the stage of increasing rain intensity in front of hailstorm, the raindrop size distributions feature low number density of small raindrops and more large raindrops, therefore the total raindrop concentration is low, and the radar reflectivity is high. Meanwhile, in the stage of rain intensity weakening, the concentration of small raindrops with a diameter less than 3.0 mm increase significantly, while that of large raindrops is relatively small. Consequently, the total raindrop concentration increases significantly with low radar reflectivity. Furthermore, there are fewer small raindrops and more large raindrops in the vicinity of the main updraft region of hailstorm, the raindrop concentration is low, and the mass weighted diameter D_m and reflectivity factor Z are high. In the downdraft region of the hailstorm, more small raindrops lead to higher total raindrop concentration and small D_m and Z.