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Abstract

To determine the terrestrial water change over the Yangtze river basin, an adaptive regularized approach is used to solve the regional mascons constructed with the GRACE level-2 product. By using the adaptive regularized approach the low-frequency terms are not regularized, the mid-frequency terms are regularized by the Tikhonov method and the high-frequency terms are regularized by the TSVD method. The sets of low-, mid-, and high-frequencies are determined with the analytical conditions that are derived based on the criteria that the introduced biases should be smaller than the reduced errors, in other words, the mean squared error (MSE) should be reduced. The observation equation with 3915 mascon parameters at 0.5° resolution is constructed using the Tongji-Grace 2018 monthly gravity field models from April 2002 to December 2016. The results show that the adaptive regularized approach outperforms the ordinary Tikhonov and TSVD regularizations, with mean MSE reductions of mascon parameters of 13.40% and 11.69%, respectively. Furthermore, the spatial resolution of the derived secular trend is significantly improved. The improved singular spectrum analysis and Lomb-Scargle power spectrum analysis are used to investigate the seasonal terrestrial water variation from the derived time series. The results show that the adaptive approach can capture more seasonal signals than ordinary approaches.