Extraction Method And Optimization Of Tropical Cyclone Strong Wind Radii Based On Microwave Scatterometer Sea Surface Wind Field Data

Typhoon(tropical cyclone)is one of the most frequent and serious disasters in the world.China,located on the northwest Pacific coast and with a long coastline in the southeast,is one of the few countries in the world most affected by typhoons,causing tens of billions yuan losses each year.The strong wind radii is the key parameter to indicate the range of typhoon gale area.It takes the center of the typhoon as the circle,and the average radius corresponding to the average wind speed of different grades is the wind radii of the wind speed of grade,which can directly reflect the influence range of the typhoon.A method for extracting tropical cyclone strong wind radii based on sea surface wind field data of microwave scatterometer is presented in this paper.Based on the wind field products of China marine satellite(HY-2A)microwave scatterometer,the wind field map of sea surface is generated first.Then,based on the wind field map,the main typhoon structure information parameters such as longitude and latitude of typhoon center,maximum wind speed near the center of typhoon,maximum wind speed radius of typhoon and so on are extracted.The above parameters are substituted into the typhoon shape coefficient models of Willoughby and Vickery respectively to obtain the corresponding typhoon shape coefficient,and combined with the Holland wind field model,the typhoon wind speed profile curve is fitted and the typhoon wind radii information is extracted.Finally,the 34 kt and 50 kt annulus radii of typhoons "Sanvu","Fitow" and "Chanhom" are extracted by this method.The results show that the wind radii of 34 kt and 50 kt of typhoons "Sanvu","Fitow" and " Chan-hom " are extracted by this method.The wind radii of Holland model corresponding to the shape coefficient of typhoon is more accurate.The average RMSE of 34 kt wind radii is 25.38 km,average MAE is 19.83 km;The average RMSE of 50 kt wind radii is 20.52 km,average MAE is 18.33 km.Because the Willoughby and Vickery and other major typhoon shape coefficient models are not specially constructed for tropical cyclones in the North-West Pacific,Therefore,there will be some errors in the process of directly fitting the typhoon shape coefficient of tropical cyclones in the Northwest Pacific.In this paper,based on the parameters of the JTWC best tracking dataset,the typhoon shape coefficient fitting experiment is carried out in the Northwest Pacific region,and four optimization models with high degree of fit are proposed and compared with the Willoughby model.A total of 16 typhoons from 2012 to 2017 are selected as examples to verify the inversion accuracy of the optimization model.the results show that the accuracy of the wind radii calculated by the optimization model is higher than that of the Willoughby model,that is,the accuracy of the corresponding typhoon shape coefficient is higher.The total average RMSE of 34 kt wind radii of the optimal model is 29.62 km,the total average MAE is 25.90 km;50 kt wind radii,the total average RMSE is 19.20 km,the total average MAE is 18.29 km.This study provides a new idea for extracting typhoon wind radii in the Northwest Pacific.