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Abstract

We present an appraisal method for the Gravity Recovery and Climate Experiment (GRACE) gravity field releases based on the Wiener optimal evaluation approach. The Wiener optimal evaluation uses linear convolution filtering and the subsequent addition of multiple inputs to minimize (in a least squares sense) the difference between the combined optimal output and a desired output. Investigating the individual filtered outputs with respect to the desired output provides a measure of the quality of each input. Here, the inputs are linear trends of the gravity field change over Antarctica inferred from the Stokes potential coefficients of the four independent GRACE releases: GFZ RL03, CSR RL01C, JPL RL01C, and CNES RL01C, each with at least 27 months worth of data. The desired output is based on the predicted gravity field change over Antarctica resulting from present-day ice mass changes and ongoing glacial isostatic adjustment. We demonstrate that the combined output of the Wiener optimal evaluator improves the quality of the signal over Antarctica with regards to the desired output. We show that three of the four GRACE releases essentially constitute the desired signal in the optimal combination, while one mainly reduces the contaminating noise over the oceans. The best agreement with the predicted gravity field change over Antarctica is represented by the release CNES RL01C.