Characteristics Of Sea Surface Height Response On Both Sides Of Tropical Cyclones And Its Applicatio

The response and feedback mechanism of the upper ocean to moving Tropical Cyclones(TCs)is the key to accurately predict their intensity and track.The sea surface height is an important parameter to characterize the vertical thermal structure of the upper ocean.Combined with reanalysis data of field observation,multi-source satellite remote sensing data and numerical model calculation,this study focused on exploring the response characteristics of Sea Surface Height(SSH)to mobile TC,and verified and applied the semi-empirical model to calculate SSH anomalies.The relationship between TC intensity and TC structure based on high resolution microwave remote sensing observation is revealed.The research contents and main conclusions are as follows:Above all,the case analysis of super typhoons Mangkhut and Yutu in 2018 shows that SSH anomalies are generated in their wake after transit,which appeared as sea surface grooves according to satellite altimeter observation.Then,we present the characteristics of the SSH response to TCs,based on a statistical analysis of long time series of satellite altimeter observations.SSH anomalies are found to be dependent on TC intensity and translation speed.Larger sea surface troughs correspond to the stronger and slower moving TCs.The most striking trough features are located in the vicinity of the TC center.The amplitudes of wedge-shaped troughs decay in the direction normal to the storm track.In extreme weather conditions,these troughs are primarily caused by the vertical displacement of isopycnals in the thermocline.For very strong and slow-moving TCs,the magnitude of the sea surface depressions can reach-21 cm.For fast-moving TC,the radial distribution of SSH anomalies is asymmetrical,which is because sea level rise caused by baroclinic effect is skewed to the right by geostrophic deflection force.Additionally,regional differences in TC occurrence frequency and coastal upwelling also affect the spatial distribution characteristics of SSH anomalies.Given that there is a gap between the observation tracks of traditional satellite altimeters,the monitoring accuracy of SSH is limited,we also apply a semi-empirical model to estimate SSH anomalies induced by fast-moving storms,using TC and ocean stratification parameters.When applying the maximum wind speed and radius of the maximum wind derived from high-resolution synthetic aperture radar(SAR)data,the semi-empirical model estimates are in good overall agreement with collocated along-track altimeter observations.These results suggest that indirect calculations of SSH anomalies may serve as an important complement for TC inner-core areas,when altimeter observations are not available.In addition,based on the effective application of TC wind field information of microwave observation,this study collects wind field data of C-band SAR and Soil Moisture Active Passive(SMAP)satellite L-band passive microwave radiometer from 2012 to 2022.The intensity(10-minute maximum sustained wind speed)and structure(34-knot wind circle radius)parameters are extracted,and the nonlinear relationship between them is found by the least square fitting method.Compared with the optimal path data parameters,the determination coefficients(R~2)are 0.8 and 0.5,respectively.This result again shows that accurate strength and structure parameters are crucial to the fitting of the relationship and the numerical calculation of SSH anomalies.