双月刊

ISSN 1006-9895

CN 11-1768/O4

北京“7·20”特大暴雨降水物理过程模拟诊断研究
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中国科学院大气物理研究所

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国家自然科学基金面上项目 42075009,中国气象局沈阳大气环境研究所基本科研业务费重点项目 2020SYIAEZD4


Simulation and diagnosis of physical processes of the heavy rainfall happened on July 20 in Beijing
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IAP

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    摘要:

    利用WRF模式,结合三维降水诊断方程,对北京“7·20”特大暴雨过程主降水时段的强降水物理过程开展了高分辨率模拟诊断分析,结果显示,降水峰值时刻前,强盛水汽辐合支撑强降水,同时加湿大气,后期,水汽辐合显著减弱,降水造成局地大气中水汽含量明显减少;降水峰值时刻前,水汽辐合、凝结和液相水凝物辐合共同助力强降水云系快速发展,后期,动力辐合作用减弱以及水凝物持续消耗和辐散,导致水凝物含量显著减少,降水系统逐步瓦解;主降水时段,垂直上升运动强度和垂直扩展范围逐步增大,并在降水峰值时刻达最大,之后减弱收缩;上升运动峰值高度从初期位于零度层上逐步降到零度层附近,进而回落到零度层之下,伴随“弱-强-弱”的降水强度变化;上升运动控制下,水凝物含量变化明显,但不同水凝物变化幅度不一,霰粒子和雨滴增幅最显著,并于降水峰值时刻含量达最大,随后减小,其他水凝物由于微物理转化和动力辐散等过程,导致其含量的变化幅度弱于上述两者。本文研究同时指出,不同微物理参数化方案对“7·20”特大暴雨强降水物理过程的可能影响以及不同强度降水物理过程的差异,值得深入研究。

    Abstract:

    Using WRF model and three-dimensional precipitation diagnostic equation, the high-resolution simulation and diagnosis analysis of the physical process of heavy precipitation in the main precipitation period of the heavy rain process in Beijing happened on July 20 has been carried out. The results show that before the peak of precipitation, the strong water vapor convergence supports the strong precipitation, while humidifying the atmosphere. In the later stage, the water vapor convergence is significantly weakened, and the precipitation causes the obvious reduction of water vapor content in the local atmosphere. Before the peak time of precipitation, water vapor convergence, condensation and liquid-phase condensate convergence jointly contribute to the rapid development of heavy precipitation cloud system. In the later stage, the weakness of the dynamic convergence effect and the continuous consumption and divergence of water condensate lead to the significant decrease of water condensate content and the gradual disintegration of precipitation system. During the main precipitation period, the intensity and range of vertical upward motion gradually increased, and reached the maximum at the peak of precipitation, and then weakened and contracted. The peak height of the ascending motion is located on the zero level at the initial stage, and then decreases to the lower part of the zero level, accompanied by a "weak-strong-weak" precipitation intensity change. Under the control of ascending motion, the change range of water condensate is obvious, but the change range of different water condensate is different. Graupel particles and raindrops increase most significantly, and the contents reach the maximum at the peak of precipitation, and then decrease. The variation range of other water condensates is weaker than the above two due to the process of microphysical transformation and dynamic divergence. This paper also points out that the possible influence of different microphysical parameterization schemes on the physical process of heavy rain happened on July 20 and the differences of physical processes of precipitation with different intensities are worthy of further study.

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  • 收稿日期:2020-11-25
  • 最后修改日期:2021-04-30
  • 录用日期:2021-08-13
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