Khosro Ghobadi-Far, Shin-Chan Han, Nico Sneeuw

The conventional approach of processing GRACE and GRACE-FO data for monitoring mass redistribution in the Earth system relies on monthly mean L2, L3, or mascon solutions. The monthly sampling confines the application of GRACE and GRACE-FO to geophysical processes that are mainly characterized by seasonal and inter-annual changes. To open the way for a new family of geophysical processes at time-scales of significantly less than one month, we present an alternative approach which is based on direct analysis of inter-satellite tracking measurements of GRACE and GRACE-FO missions. We use residual inter-satellite ranging data that represents the gravitational change (with respect to a certain set of background models such as static gravity field and tide models) due to instantaneous mass change happening at the Earth’s surface. We present two new geophysical applications to examine high-frequency, transient gravitational changes at hourly and daily time-scales; Gravitational observation of tsunamis triggered by the great earthquakes during the GRACE era (2002-2017), and transient gravitational changes due to Earth’s free oscillation excited by the 2004 Sumatra earthquake. In addition, we discuss other possible examples of extreme events that could be detected by GRACE and GRACE-FO, and examine the potential of high-precision GRACE-FO LRI data in this context. Such new developments could eventually lead to low-latency science applications of the GRACE-FO mission for studying transient geophysical mass changes.