Using Satellite Observation Data To Invert Three Dimensional Temperature And Salt Field Information In Kuroshio Extension

Satellite remote sensing technology,with its ability to rapidly and efficiently provide actual surface observations of the Earth,has become a necessary means for understanding and studying our planet.The ocean temperature and salinity field is one of the core dynamic elements of the ocean,and it is of great significance to infer the subsurface temperature and salinity structure of the ocean based on satellite sea surface observation data.In this study,based on multi-source ocean data,we conducted research on the reconstruction of subsurface temperature and salinity structure in the Kuroshio Extension region using satellite-observed sea surface data.The work carried out is as follows:(1)The empirical residual regression method was primarily used to establish the relationship between sea surface temperature(SST),sea surface height(SSH),their combination(SST&SSH),and the three-dimensional temperature and salinity structure.The subsurface temperature and salinity field in the Kuroshio Extension region were reconstructed.The results show that SST reconstruction mainly captures the characteristics of the shallow region in the mixed layer,while SSH reconstruction mainly captures the characteristics of the deep region in the mixed layer.The combination of both variables allows for obtaining the temperature and salinity features of both shallow and deep layers.The analysis of reconstruction accuracy reveals that the SST&SSH combined reconstruction has the highest accuracy in reconstructing the temperature and salinity field.(2)Using the variational reconstruction method,the impact of SSH,SST,and vertical gradients of temperature and salinity on the reconstruction of the threedimensional temperature and salinity field and its acoustic field was analyzed.The research found that the reconstruction scheme that incorporates all three constraint terms has the highest accuracy and can better capture the spatial characteristics of the temperature and salinity field.SST primarily captures the temperature and salinity characteristics in the shallow region of the mixed layer,which significantly affects the Sound Layer depth(SLD).SSH and the vertical gradients of temperature and salinity enhance the inversion accuracy in the deep region of the mixed layer.According to the acoustic analysis,when SST,SSH,and gradients are simultaneously constrained,the SLD is closest to HYCOM,with a difference of approximately 1 m/s.Without gradient constraints,the SLD differs significantly from HYCOM and fails to reflect the characteristics of the surface sound channel.(3)A three-dimensional temperature and salinity field reconstruction method based on multiscale coupled orthogonal decomposition is proposed.This method utilizes multiscale coupled orthogonal decomposition to iteratively decompose historical temperature and salinity profiles from large scales to small scales,extracting characteristic information of different scales in the three-dimensional temperature and salinity field.Subsequently,reconstruction models are established between satellite observations of the ocean surface and the characteristic information of the threedimensional temperature and salinity field at different scales.In this study,a singlelayer orthogonal decomposition method is also employed for three-dimensional temperature and salinity field reconstruction.The results show that the multiscale coupled orthogonal decomposition method outperforms the single-layer orthogonal decomposition method.With the refinement of the decomposition hierarchy,both the accuracy of the reconstructed temperature and salinity field and the accuracy of vertical gradients exhibit significant improvements,indicating that the multiscale coupled orthogonal decomposition reconstruction method can effectively capture the spatial characteristics of the subsurface ocean.