ISSN 1006-9895

CN 11-1768/O4

The properties of convections embedded in the stratiform cloud on basis of airborne Ka radar and DMT system
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1.Shandong Weather Modification Office,Jinan,Shandong Province;2.Institute of Atmospheric Physics,Chinese Academy of Sciences

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    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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History
  • Received:July 08,2019
  • Revised:November 21,2019
  • Adopted:April 23,2020
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