Inversion of ocean subsurface temperature and salinity struc-ture by multiscale coupled empirical orthogonal decomposition
To address the problem of reconstructing the three-dimensional ocean thermohaline salinity fields based on sea surface information obtained through satellite observation,a three-dimensional thermohaline field-reconstruction method based on multiscale coupled empirical orthogonal decomposition is proposed in this paper.The proposed method involves using a multiscale coupled empirical orthogonal function to iteratively de-compose historical temperature and salinity profiles from a large to a small scale to extract the feature information of three-dimensional thermohaline and salinity fields at different scales in a hierarchical manner.Then,models of the collected satellite information are established and the characteristic information of the involved three-dimensional thermohaline field is obtained at different scales to achieve three-dimensional thermohaline field reconstruction.Herein,multiscale coupled empirical and single-layer orthogonal decompositions are used to recon-struct three-dimensional thermohaline and salinity fields.The results indicate that the former is superior to the latter.Furthermore,with continuous refinement of the decomposition levels,the accuracy of the reconstructed thermoha-line field and its vertical-gradient accuracy are significantly improved,with Scheme 4 resulting in the highest im-provements(25.57%and 27.58%,respectively).Meanwhile,compared with the HYCOM,the proposed method can more effectively capture the spatial characteristics of the involved subsurface ocean.In general,thermohaline-field inversion based on the proposed method deviates less from the Argo thermohaline field;moreover,the accuracy of the inversion is better.Further,the obtained spatial distrtbution tends to be consistent,aiding in effectively analyz-ing the three-dimensional structure and variation characteristics of the ocean thermohaline field.