The Largest Wet and Dry Events in the GRACE and GRACE-FO Data Record

Abstract:

Since 2002, the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow On (GRACE-FO) missions have used satellite gravimetry to provide a nearly continuous record of terrestrial water storage (TWS) anomalies (departures from the long-term mean). Satellite gravimetry is unique in that it detects changes in the total mass of all water at all depths, from the base of the deepest aquifer up to the top of the soil column, surface water, vegetation, and/or snowpack. Previous studies have applied GRACE data to identify and quantify droughts and to assess flood potential. In this study we used GRACE and GRACE-FO data assimilation within a land surface model to fill the 1-year gap between the two missions and to replace other missing data. We then applied a novel approach to delineate regional- to continental-scale wet and dry events, without the need to pre-define study regions or basins, and to rank their severity based on total gain or loss of TWS. Here we present a ranking of the most severe droughts and pluvials in each continent and discuss how the frequency, intensity, and extent of extreme events have changed during the 18-year period.