Characteristics of Rainstorm in Southeast Coastal Area Caused by Typhoon Passing Through Taiwan Island
Based on the typhoon data of Shanghai Typhoon Institute and the daily typhoon precipitation data of national stations of China during 1961-2020, the climatic characteristics of different levels of typhoon precipitation caused by typhoon passing though Taiwan Island in southeast coastal of China including Zhejiang, Fujian and Guangdong provinces are statistically analyzed, and the causes for the differences in extreme precipitation are discussed.The study results show that 90% of the typhoons passing though Taiwan Island can bring rainstorms to the southeast coastal area of China. There are 1.6 typhoon rainstrom events every year. The interannual variation of the daily maximum precipitation amount of shows an obvious increasing trend. Especially, the rainstrom extreme events have increased significantly since 2003.The variation of monthly frequency of daily precipitation at different levels shows a single peak pattern, and the peak months are from July to September.The occurrence frequency of the daily maximum precipitation at different levels shows that the frequency of extreme precipitation over 100 mm decreases with the increase of precipitation intensity, and the frequency of extreme precipitation over 300 mm decreases obviously. In terms of spatial distribution, the daily rainstorm frequency shows an uneven and rapid decrease from the coastal areas to the inland areas.The rainstorms from the typhoon through Taiwan Island have most prominent impact on the northern coast of Fujian Province, and Zherong Station in Fujian is the extreme rainstorm center. Based on NCEP reanalysis data, the largescale environmental comparison of the difference between the two similar typhoon groups shows that to the heavy precipitation typhoon group, strong wind speed area on the north side of the typhoon center leads to strong onshore winds. With the effect of mountain terrain, there is stronger convergence and very strong deep vertical upward movement, in front of mountains. With better moisture conditions, theupward motion can take the lowlevel highenergy water vapor to the middlehigh levels. The precipitation dynamics and water vapor conditions are significantly stronger than those of the weak precipitation typhoon group, thus resulting in more typhoon rainstorms.