Research On Optimization Method Of Storm Surge Wind Field Based On Satellite Cloud Motion Wind Extraction Technology

China is one of the countries severely influenced by typhoon disaster.The wind and waves in typhoon disaster seriously ruin the coastal areas.The numerical simulation of storm surge model is the most direct method to study storm surge,which has a wide applied range.Through the simulation of typhoon storm surge,the tide level and inundated area can be predicted,which is of great significance for the warning and the management of disasters.However,the result of typhoon storm surge model is greatly affected by the driving typhoon wind field,so the optimization of driving typhoon wind field is the key to improve the accuracy of storm surge simulation.At present,the semi empirical and semi theoretical wind field model is widely used,but it can only simulate the structure of typhoon wind field approximately,while the actual wind field distribution is more complicated,and the simulation precision remains to be increased.As an important source of meteorological data,satellite remote sensing data supply the relevant meteorological observation information,which can also make up for the shortcomings of conventional meteorological observation.In the existing methods,the ensemble Kalman filter assimilation method avoids the complicated mode adjoint operation,achieves the optimization of data,and has been widely used.Therefore,the research extracts the typhoon wind field?including cloud motion wind and cloud height?by satellite cloud image,optimizes the semi empirical and semi theoretical wind field model parameters,then selects the suitable method to combine the cloud motion wind retrieved from satellite cloud map with the semi empirical and semi theoretical wind field,so as to realize the optimization of typhoon wind field and improve the accuracy of storm surge model simulation.In conclusion,the research combines the observed wind field retrieved by meteorological satellite with the improved theoretical wind field model to realize the optimization of typhoon wind field.At the same time,it analyzes and compares three Ensemble Kalman filter assimilation methods,selects the best one,and applies the optimized wind field to storm surge model for realizing the numerical simulation of storm surge.The main research contents and achievements of this paper are as follows:?1?Obtain the observed typhoon wind fieldThis study aims at the problem that the ocean observation network is obviously insufficient and the large-scale synchronous observation wind field information is hard to obtain.Based on the Himawari-8 weather satellite with the spatial resolution of 4 km,it realizes the extraction of wind field of observation typhoon based on cloud motion wind technology,the correction of wind field of cloud height,the automatic extraction of typhoon center and the estimation of maximum wind speed radius,and tests the observed typhoon wind field by typhoon data.?2?Inversion of the semi empirical and semi theoretical typhoon wind fieldIn this study,Holland theoretical wind field model is selected to simulate the wind field.Compared the influence of different maximum wind speed radius R₀ and parameter value B formula on the maximum wind speed simulation results,then improved the calculation method of the model parameters,and verified by the measured wind speed,obtained the improved theoretical typhoon wind field at last.?3?Optimization of the observed wind field and theoretical wind fieldIn this study,the sequence assimilation method is used for reference to design the wind field optimization scheme,the optimization methods of EnKF,DEnKF and ETKF are selected to combine the observation wind field and the theoretical wind field.Design experiments to perform sensitivity analysis on the influence factors of optimization methods to determine the optimal combination of influence factors for each method.According to the optimal combination of influencing factors,the simulation case of wind speed optimization based on the above optimization method is designed,and the influence of different optimization methods on the results of optimization simulation is analyzed.The results show DEnKF has the best optimization effect.?4?Application of optimization wind field to numerical simulation of storm surge in the Pearl River EstuaryBased on the FVCOM ocean numerical model,the Pearl River Estuary Storm Surge Pattern is constructed.The observed wind field,theoretical wind field and optimization wind field are used as the driving wind field to input the storm surge model to simulate sea level.The results show that the simulation of storm surge based on the optimization wind field improves the simulation effect and accuracy.