High-frequency terrestrial water storage signal capture via a regularized sliding window mascon product from GRACE

Abstract

The Gravity Recovery and Climate Experiment (GRACE) mission has provided an unprecedented global, homogeneous observational data set of time variation in terrestrial water storage since 2002. The typical GRACE product uses approximately 30 equally weighted days of data to estimate a monthly mean gravity field with 300+ km resolution. The coarse spatial and temporal resolution of the typical GRACE solution, however, limits scientific analysis to primarily seasonal and long-term hydrological processes. In this study, we enhance the temporal and spatial resolution of the GRACE data product through the use of sliding windows, regularization, and mascon basis functions in the estimation process. Each regularized sliding window mascon (RSWM) gravity field is composed of 21 days of observational data differentially weighted to optimize the frequency retention while ensuring sufficient observability for a global solution. Tikhonov regularization informed by RL05 error is applied in the estimation process, and the product is derived in mascon basis functions to increase the amplitude and localization of signal retention. The final RSWM data product is the first daily time-variable gravity data set created solely from GRACE information. The improved filter design reduces aliasing, increases the signal bandwidth, and better captures the amplitude and power of geophysical signals. Comparison with land surface model and in situ data sets shows a similar spatial and temporal signal content at all frequencies within the filter bandwidth and highlights the overall accuracy of the product. The new data set expands opportunities for scientific analysis of subseasonal terrestrial water storage variability.