摘要:利用机载Ka波段云雷达（Airborne Ka-Band Precipitation Cloud Radar, KPR）和粒子测量系统（Droplet Measurement Technologies, DMT），分析了2018年4月22日黄淮气旋背景系统下积层混合云中对流泡的动力和微物理特征。首先，对Ka波段云雷达观测的山东地区春季36个对流泡样本按照回波强度、水平尺度、回波顶高三个参量进行统计，结果表明平均回波强度为20～30 dBZ的对流泡占69%。对流泡水平尺度为15～30 km，占61%。对流泡最大回波顶高集中在6～8 km，比周边层云高2～4 km。之后，对4月22日积层混合云中的对流泡个例微物理参数进行统计，结果表明对流泡内部以上升气流为主，最大上升气流速度达到1.35 m s?1，平均上升气流速度为0.22 m s?1；对流泡内过冷水含量比较高，最大含水量为0.34 g m?3，平均含水量为0.15 g m?3。对流泡内冰晶数浓度是泡外的5.5倍，平均直径是泡外的1.7倍。结合云粒子图像探头，发现对流泡前沿和尾部冰粒子以柱状和辐枝状为主，而对流泡核心区域冰粒子以聚合体形式存在。冰粒子通过凇附过程和碰并过程增长，过冷水含量不足时冰粒子的凇附增长形成柱状粒子，含量充足时可迅速凇附成霰粒子。对流泡内降水形成的微物理机制不完全相同，主要依赖过冷水含量。当云中有充足的过冷水分布时，高层冰晶通过凇附增长形成霰粒子，通过融化层后形成降水；当云中缺少过冷水时，降水的形成主要通过水汽凝华过程形成冰雪晶，然后雪晶通过聚合过程实现增长。
关键词:对流泡/
Ka波段云雷达（KPR）/
粒子测量系统（DMT）/
降水机制
Abstract:On the basis of airborne Ka-band precipitation cloud radar (KPR) and droplet measurement technologies (DMT), the dynamic and microphysical characteristics of convective generating cells (GCs) embedded in stratiform clouds initiated by the Huanghuai cyclone on April 22, 2018 were analyzed. First, a total of 36 GCs were observed by KPR in spring in Shandong Province. The results based on the echo intensity, horizontal scale, and echo top height of these GCs show that the average echo intensity of GCs is concentrated at 20 to 30 dBZ, accounting for 69%. The horizontal scale of GCs is concentrated at 15 to 30 km, accounting for 61%. The echo top height of GCs is concentrated at 6 to 8 km, which is 2 to 4 km higher than the surrounding stratiform clouds. Afterward, the microphysical parameters of GCs in mixed-phase cumulus clouds on April 22, 2018 were counted. The results showed that the inner part of GCs is dominated by updraft with the maximum wind speed of 1.35 m s?1 and average updraft of 0.22 m s?1. GCs have high supercooled water content with the maximum of 0.34 g m?3 and average of 0.15 g m?3. The ice particle concentration in the inner part of GCs is 5.5 times that of its outer part, and the mean diameter of the inner part of GCs is 1.7 times that of its outer part. The images sampled by the cloud image probe showed that the ice particles on the head and tail of GCs were mainly columnar and radial, respectively, whereas the ice particles in the core of GCs were polymers. The growth of ice crystals depended on the accretion and collision processes. The ice crystals formed columns when the supercooled water was insufficient; otherwise, they rapidly formed graupels. The microphysical formation mechanism of precipitation in GCs is different and strongly depends on the supercooled water content. When the supercooled water content of the cloud was sufficient, graupels were rapidly formed, and surface precipitation was formed after they passed through the melting layer. When the supercooled water content of the cloud was insufficient, the formation of precipitation depended on the water vapor deposition and aggregation processes.
Key words:Convective generating cells (GCs)/
Ka-band precipitation cloud radar (KPR)/
Droplet measurement technologies (DMT)/
Precipitation mechanism
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