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CN 11-1768/O4

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基于机载Ka雷达和DMT云粒子测量系统同步观测的积层混合云对流泡特征
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作者单位:

1.山东省人民政府人工影响天气办公室;2.中国科学院大气物理研究所

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山东省气象局面上项目2016sdqxm09


The properties of convections embedded in the stratiform cloud on basis of airborne Ka radar and DMT system
Author:
Affiliation:

1.Shandong Weather Modification Office,Jinan,Shandong Province;2.Institute of Atmospheric Physics,Chinese Academy of Sciences

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    摘要:

    利用机载Ka波段云雷达(A Compact Airborne Ka-Band Precipitation PMS Probe Radar,KPR)和云粒子测量系统(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1.35m/s,平均上升气流速度为0.22m/s;对流泡内过冷水含量比较高,最大含水量为0.34g/m3,平均含水量为0.15g/m3。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。冰粒子通过淞附过程和碰并过程增长,过冷水含量不足时冰粒子的淞附增长形成柱状粒子,含量充足时可迅速淞附成霰粒子。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,高层冰晶通过淞附增长形成霰粒子,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。

    Abstract:

    Based on a compact airborne Ka-band Precipitation PMS probe Radar (KPR) and the Droplet Measurement Technologies(DMT), the dynamic and microphysical characteristics of convective bubbles embedded in stratiform clouds initiated by the huanghuai cyclone on April 22, 2018 were analyzed. At first,a total of 36 convective bubbles were observed by KPR in spring in Shandong province. The results based on the echo intensity, horizontal scale and echo-top height of these bubbles show that the average echo intensity of convective bubbles is concentrated at 20 to 30 dBz, accounting for 69%. The horizontal scale of convective bubbles is concentrated at 15 to 30 km, accounting for 61%. The echo-top height of convective bubbles is at 6 to 8 km, which is 2 to 4 km higher than the surrounding stratiform cloud. Afterwards, the microphysical parameters of convective bubbles in the cumulus mixed cloud on April 22 were counted.The results show the inside of convective bubbles is dominated by updraft with maximum wind speed of 1.35m/s, the average updraft is 0.22m/s. There is high supercooled water content in the bubbles with maximum water content of 0.34g/m3, and the average is 0.15g/m3. The ice particle concentration in the convection bubbles is 5.5 times of that outside of bubbles, and their mean diameter is 1.7 times of that outside. The images sampled by cloud image probe show that the ice particles in the front and tail of convective bubbles were mainly columnar and radial, while the ice particles in the core of convective bubbles were polymers. The growth of ice crystals depended on the accretion and collision processes, they showed columnar form when the supercooled water was insufficient, otherwise, they could quickly form graupels. The microphysical formation mechanism of precipitation in the convective bubble is different, and strongly depends on the supercooled water content. When supercooled water content was sufficient in the cloud, graupels were quickly formed, and the surface precipitation was formed after they passed through the melting layer. When less supercooled water existed in the cloud, the formation of precipitation depended on water vapor deposition and aggregation processes.

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  • 收稿日期:2019-07-08
  • 最后修改日期:2019-11-21
  • 录用日期:2020-04-23
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