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Journal of Tropical Oceanography

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Reflections on the causes of under reporting a warm area rainstorm process in Shandong Peninsula under the background of cold vortex

CHU Zihe1，MEI Chanjuan2*，ZHANG Can3，WAN Fujing4，XIN Wenpeng3   

  1. 1. Guangdong Ocean University, Zhanjiang 524003;

    2. Key Laboratory for Meteorological Disaster Prevention and Mitigation of Shandong, Jinan 250031, China; Weihai Meteorological Bureau of Shandong Province, Weihai 264200;

    3. Weihai Meteorological Bureau of Shandong Province, Weihai 264200;

    4. Qingdao Meteorological Bureau of Shandong Province,Qingdao 266000

  • Received:2024-01-18 Revised:2024-04-10 Accepted:2024-04-22
  • Supported by:

    Natural Science Foundation of Shandong Province (ZR2021MD010), the Innovation Fund Project of the Public Service Center of China Meteorological Administration (M2021019), the Innovative Team of Typhoon and Marine Meteorology of Shandong Province (SDCXTD2021-2), the Key Scientific Research Project of Shandong Provincial Meteorological Bureau (2022sdqxz11), and the Scientific and Technological Research Project of Shandong Provincial Meteorological Bureau (2022sdqxm12)

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Abstract: Using conventional observations and ERA5 reanalysis data, a diagnostic analysis of the thermal and dynamical characteristics of a heavy rainfall process in the eastern coastal area of Shandong on June 14, 2022, was conducted, and the results show that the heavy rainfall process occurred in the context of the cold trough at the bottom of the cold vortex in North China moving eastward to the coast of the Peninsula to induce a cold low vortex. Southeasterly cold and humid advective transport in the boundary layer from the Yellow Sea provides abundant water vapour for the heavy precipitation on the peninsula. The precipitation process was stage-specific. In the first stage of precipitation, the low level was continuously influenced by the western warm advection, and the atmosphere had convective instability, while in the second stage of precipitation, the atmosphere was gradually transformed from neutral laminar junctions to convective instability by the combined influence of the cold and warm advection, and was accompanied by obvious energy fronts. The early stage of both stages of precipitation is caused by the convergence of onshore wind speeds as well as topographic uplift. The cold pool caused by convection in the first stage has an important effect on the maintenance of precipitation in front of the Kunshan Mountains, while the maintenance of the strong precipitation in the second stage is closely related to the generation and maintenance of the mesoscale low eddy in the low altitude, and the obliquely pressurized frontal generation plays an important role in the generation of the mesoscale low eddy. The vorticity analysis shows that the boundary layer low-level convergence and absolute positive vorticity advection are the main vortex sources for the positive vorticity growth of the mesoscale low vortex, and with the emergence of the 500 hPa cutoff cold vortex, the negative effect of the vertical transport of vorticity is obviously strengthened, and the horizontal vorticity tilting effect above the boundary layer, which is related to the mesoscale convective activity, is weaker.

Key words: coastal rainstorm, low vortex, topographic uplift, frontogenesis