Benefits of future satellite gravimetry missions for characterizing extreme wet events in terrestrial water storage

This is the authors' abstract. We don't add key points for this paper.

50 years-long closed loop simulations of the future satellite gravimetry missions GRACE-C and NGGM/MAGIC are used in this study to rigorously assess the abilities of these upcoming missions to track wet extreme events from space on a global scale. The simulations are based on modeled terrestrial water storage variations from a GFDL-CM4 climate model run that took part in CMIP6. In addition to nominal monthly gravity field solutions, experimental 5-daily solutions were processed for both missions. Besides offering the ability to study return levels of extreme events in a statistical sense, the simulations also offer the opportunity to test the proper identification of various naturally occurring wet extremes with varying magnitude, location, as well as temporal and spatial extent. While the double pair constellation MAGIC always outperforms GRACE-C in any metric tested, we note that the 5-daily MAGIC solution is found to be advantageous over its monthly solution for the estimation of statistical return levels of wet extremes, but not with respect to the identification of individual wet extreme events as measured by recall, precision, and F1-score. Reasons for the inferior performance of the 5-daily solutions are spatial leakage, residual noise, and adverse effects from a sub-optimal combination of data from the polar and inclined pair that manifest as artifacts polewards of 70°. Our results therefore call for further refinements in the MAGIC processing schemes to further optimize in particular the novel 5-daily solutions so that the added-value of those sub-monthly products can be fully exploited.