ISSN 1006-9895

CN 11-1768/O4

Feature Analysis of Dynamic Condition and Hydrometeor Transportation among Zhengzhou “7·20” Superheavy Rainfall Event Based on Optical Flow Field of Remote Sensing Data
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1.Institute of Atmospheric Physics, Chinese Academy of Science;2.The Weather Modification Center of Henan Province

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    Abstract:

    In this paper, aiming at the “7·20” superheavy rainfall event in Zhengzhou City, Henan Province on July 20, 2021, the FY-4A stationary satellite imager data and ground-based weather radar data are respectively used to produce optical flow field. Compared with the horizontal wind speed of FNL data and ground observation data, the weather satellite and radar optical flow field can approximately reflect the motion characteristics of the upper-level and lower-level atmosphere and cloud system. On this basis, the feature analysis of dynamic condition and hydrometeor transportation related to the superheavy rainfall event is presented. The results show that, there was a "southwest to northeast" transporting zone of water vapour and cloud on the afternoon of July 20, extending from southern China to northern China through Henan Province. There was actively convective in this transporting zone, extending to the existing cloud system on northern-central parts of Henan, providing favourable transporting condition for superheavy rainfall event. In Zhengzhou region, the anticyclonic vorticity on upper atmosphere increased and the divergence on lower atmosphere converted to strong cyclonic convergent on the afternoon of July 20 and before the severest precipitation, indicating that the updraft in the precipitation system in Zhengzhou region was increasing. The hydrometeor input at south boundary of Zhengzhou region greatly increased ahead of the stage of severest precipitation. These results indicate that there was not only a large amount of water vapour, but also hydrometeors in severe convective cloud transported to the updraft area in large-scale precipitation system. It may greatly accelerate the microphysical process of water vapor transforming into cloud water and finally forming the precipitation, which may be an important cause of the rapid enhancement of the superheavy rainfall. The analysis method based on optical flow field of remote sensing data proposed in this study has significant application potential in short-term and impending rainstorm forecast and early warning.

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History
  • Received:August 17,2021
  • Revised:September 26,2021
  • Adopted:September 27,2021
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