Water Cycle Extremes in the GRACE and GRACE-FO Data Record

A unique aspect of satellite gravimetry is its ability to quantify changes in all water stored at all depths on and beneath the land surface.  Hence, GRACE and GRACE-FO are well suited for quantifying both hydrological droughts, when terrestrial water storage (TWS) is low, and pluvial events, when TWS is high.  In this study we use 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 apply a cluster analysis approach to identify the locations and extents of TWS extreme events in resulting data record.  We then rank these events based on their intensity, i.e., the integral of the non-seasonal water mass anomaly over the period of the event.  In this presentation we report on the largest wet and dry events over each continent.  During the period of study, Africa, North America, and Australia each had a wet event with an intensity that exceeded 10,000 km³ * month, although the 2010-2012 event in Australia can largely be attributed to a depressed baseline TWS during the period caused by the millennial drought.  With 30 more years of data it is probable that the intensity of that drought would have been greater than the recovery and wet event during 2010-2012.  As it stands, the biggest drought event was determined to be one occurred in South America during 2015-2016, with an intensity of over 10,000 km³ * month.