Minimizing the effects of filtering on catchment scale GRACE solutions

Abstract

AbstractThe Gravity Recovery and Climate Experiment (grace) satellite mission has provided time variable gravity information since its launch in 2002. Due to short‐wavelength noise, the total water storage variations over a catchment observed from grace are usable only after filtering. Filtering smooths both the signal and the noise, inevitably changing the nature of the estimated total water storage change. The filtered estimates suffer from attenuation and leakage, which changes the signal characteristics. Several studies have mainly focused on correcting the changed amplitude with the aid of hydrological models. In this study, it is demonstrated that in addition to the amplitude loss, also significant phase change in the time series of total water storage over a region can occur. The phase change due to leakage from nearby catchments can be around to for catchments with moderate size, which makes it difficult to retrieve signal by only scaling. We propose a strategy to approach the true time series with improved phase and amplitude. The strategy is independent of any hydrological model. It is first demonstrated in a closed‐loop environment over 32 catchments, where we show that the performance of our method is consistent and better than other model‐dependent approaches. Then we also discuss the limitations of our approach. Finally we apply our method to the grace level 2 products for 32 catchments.