Monitoring Droughts and Floods through the Assimilation of GRACE and GRACE Follow-On Data

The GRACE and GRACE Follow On satellite missions have the amazing ability to quantify changes in total terrestrial water storage (TWS), including deep soil moisture and groundwater. Thus they can be used to help quantify both hydrological droughts, when TWS is low, and floods, when TWS is high. However, the observations have coarse spatial (~100,000 km²) and temporal (monthly) resolutions and a latency of a couple of weeks or longer, which greatly limits their value for operational applications. To overcome those issues we synthesize GRACE and GRACE Follow On data with other ground and space based meteorological observations within a land surface model, using the Land Information System software. We then use the resulting high resolution, near real-time fields of soil moisture and shallow groundwater storage variations to generate weekly drought/wetness indicator maps for the conterminous U.S. Since 2011 those maps have been distributed through the University of Nebraska’s National Drought Mitigation Center website and incorporated into the U.S. and North American Drought Monitors. Recently we expanded this capability to the global scale in order to address the scarcity of operational drought/wetness monitoring products outside of the U.S., and the results are under evaluation. We are also working to develop 30-90 day drought/wetness forecasts for the U.S. Progress to date on both of these efforts will be presented.