Satellite Altimetry Data Assimilation In CAS-ESM-C: Benefits For Improving The Simulations

With the motivation to improve the simulation of oceanic interannual variations effectively,the sea surface height(SSH)satellite altimetry data was assimilated into CAS-ESM-C by using Ensemble Optimal Interpolation(En OI).In this study,the best mean dynamic topography(MDT)was selected firstly based on its influences on simulation performance.Using the selected MDT,a SSH assimilation experiment was conducted from 1994 to 2000,comparing with a SST assimilation experiment.The results show:(1)Short-term SSH assimilation based on three MDTs respectively has a correction effect on the upper temperature deviation of the model.However,based on the MDT calculated from the results of the WOA assimilation,has a better effect on model deviation correction.It is mainly reflected in the correction of the SST in the Pacific Ocean and the North Indian Ocean,the improvement of the cold tongue simulation in the eastern equatorial Pacific is better than others.(2)Based on MDT_WOA,the SSH assimilation showed better performance on simulation the subsurface temperature during 0-400 m with the global mean RMSE was lower than 1.0°C,The most improvement region was located at the depth around thermocline.The reason was that SSH showed better correlations with the subsurface temperature than SST.And there is a good correction for the sea surface height deviation in the Pacific warm pool.Although the salinity is better than before in some sea areas,the correlation between SSH and the salinity is weak.Therefore,SSH assimilation cannot directly correct the salinity deviation in theory.(3)Meanwhile,the simulated interannual variations of upper oceanic heat content,Tropical Pacific SST and Tropical Pacific SSH anomalies were largely improved in SSH assimilation,implying that the simulated air-sea coupling and physical process were improved in SSH assimilation.This study showed that the oceanic interannual variability could be largely improved by assimilating SSH rather than SST.This study implied that the SSH assimilation should be considered in short-term climate prediction.