ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 50 Issue 8 > 2024,50(8):997-1011. DOI:10.7519/j.issn.1000-0526.2024.030501 Prev Next
Comparison of the Train Effect Characteristics of Rainbands After the Landfall of Three Typhoons
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Abstract:
In order to explore the possible formation mechanism and flow pattern of extreme precipitation caused by the train effect of typhoon rainbands, we comparatively analyze the circulation situation and the convection organization of three heavy rainfall processes related to train effect after the landfall of the Typhoon Soudelor (No.1513, process 1)，the Typhoon Fitow (No.1323, process 2) and the Typhoon Matsa (No.0509, process 3) by using multi-source observation data and the ERA5 reanalysis data. The results show that the extreme precipitation of the three processes all occurred on the windward slope of the hills in the eastern part of Zhejiang Province. The directions of the rainbands were consistent with the background air flows, and convergence of water vapor flux was mainly concentrated below 850 hPa. However, the ambient backgrounds of the three processes are different obviously. In process 1, the rainband happend between the low pressure and the subtropical high, the vertical wind shear and the CAPE were large, the water vapor came from tropical ocean surface, and the wet layer was thick. Process 2 took place in a saddle-shaped field between the residual vortex of a typhoon over land and another typhoon over the sea. The vertical wind shear and CAPE were weak, water vapor was from the sea surface at the same latitude, and the wet layer was located in the middle and lower level of the troposphere. Process 3 was caused by the spiral rainband in the core zone of typhoon. The vertical wind shear was strong and the CAPE was the minimum. Moreover, the structure and organization of the rainbands in the three process are obviously different. In process 1, the boundary layer convergence and the convective system highly developed, the baroclinic structure of the mesoscale convergence line promoted the uplift of warm and humid air from the sea surface, and the convergence field strengthenned the degree of organization. In process 2, the wind direction of the weak cold pool was opposited to the easterly airflow, while with similar wind speed and shallow convergence. The warm cloud rain was dominant. The new cells continued to form at the eastern boundary of the rainbands, and dissipated at the western boundary. The stagnation of rainband caused continuous belt-like heavy rainfall area. In process 3, the spiral bands in the inner-core section of typhoon were affected by the typhoon vortex dynamics, the convection developed at lower height, and the structure tilted slightly to the outside. The rainband developed with the wind speed convergence caused by the fluctuating of southeast jet, which resulted in extreme rainfall. The above facts show that the train effect of typhoon rainbands causing extreme precipitation can be formed in various ways, so there are great challenges faced in the short-time forecasting and nowcasting of such extreme precipitation.
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P447,P445
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