Analysis on the Process of Extreme Precipitation in Shandong Province Caused by Typhoon Lekima
Using NCEP-GFS reanalysis data,this article analyzes the process of how 1909 Typhoon Lekima produced extremely severe precipitation in Shandong Province in August 10-11,2019,and com-pares it to Typhoon Ampil which had in a similar track with Lekima.The results show that the long-time maintenance of the strong convergence and jet stream were the direct cause for the extreme precipitation.Wind and temperature field were asymmetry,leading to the long-time maintenance of warm and humid airflow in the central part of Shandong.The cold and warm advections converged in the inverted trough of the Typhoon Lekima in central Shandong,resulting in the long-time maintenance of the large value area of the frontogenesis function in the inverted trough of the typhoon.The cold air invaded from the west and south sides of the typhoon,without quickly destroying the warm and humid characteristics of the airflow on the northeast side of the typhoon.The water vapor image can intuitively reflect the continuous process of the cold air's intruding eastward.The strong convergence area of water vapor flux at 850 hPa was con-centrated in the central part of Shandong,providing water vapor conditions for the emergence of extreme precipitation.In contrast,the intensities of wind convergence center,frontogenesis,and convergence center of water vapor flux of the similar-path Typhoon Ampil were greatly weaker than those of Lekima.Therefore,the precipitation intensity caused by Typhoon Ampil and other similar typhoon processes was much weaker than that of Lekima in Shandong.
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