Land and Climate Seminar - Alternative use of GRACE for examining rapid surface mass change including flood and flash drought

Speaker: Shin-Chan Han

The GRACE and GRACE-FO mission data products include monthly mean gravity fields, also known as Level-2 (L2) data, from April 2002 to present. The gravity changes are attributed to surface mass changes and the Level-3 (L3) data products of surface mass block (‘mascon’) were developed with spatial constraints. Both L2 and L3 data products represent monthly mean measurements of full hydrology and cryosphere mass changes as well as residual atmosphere and ocean mass changes (relative to the applied ocean and atmosphere model such as in AOD1B). These L2 and L3 data, however, produce biased estimates when characteristic time scales of mass change processes are shorter than a month. In this presentation, I discuss alternative data processing strategy suitable to address short-term mass changes associated with, for example, onset and demise of atmospheric rivers, flooding, heat waves, rapid glacier melt/outbursts, flash droughts, and tsunamis as well as man-made water spills (for example, the Ukraine dam explosion in 2023). These signals could be large enough to cause detectable orbital perturbations to the GRACE, GRACE-FO and MAGIC satellites, but would not be adequately sampled in the L2 and L3 data products as their lifetime is too short. The technique and data products newly proposed in this presentation will open new science applications of satellite gravity data to rapid mass changes at a time scale as short as hours to days.