RSES Seminar Sept 9, 10am - Khosro Ghobadi-Far, Virginia Tech: New Developments in Earth System Mass Change Observation from Space: Monitoring of Extreme Events

Part 1 of 2 special seminar series

Thu Sep 9, 10:00-11:35 Livestream on Zoom


Earth system mass change offers a unique perspective into Earth dynamics. By measuring temporal variation of the Earth gravity field, GRACE (2002-2017) and GRACE Follow-On (GRACE-FO; 2018- ) satellites have been providing estimates of the mass change caused by various natural (e.g., terrestrial water storage surplus in Australia due to the 2010-2012 La Niña) and anthropogenic (e.g., groundwater depletion in California) processes, as well as climate change (e.g., diminishing ice-sheets/glaciers and rising see level). The standard data products of GRACE/GRACE-FO are the global “monthly-mean snapshots” of surface mass change estimated from one month of inter- satellite tracking data. The monthly sampling limits the GRACE applications to slowly-varying processes with seasonal to interannual variability. However, there is substantial high-frequency (sub-monthly) mass variability in the Earth system caused by extreme, rapidly-changing processes such as tsunamis, floods, and cyclones that cannot be studied using the standard monthly data from the GRACE/GRACE-FO project.

In this seminar, I will present a novel approach based on direct along-orbit analysis of inter- satellite tracking data that pushes the limit of GRACE/GRACE-FO and opens the way for examining mass variability at significantly shorter timescales like hours or days. I will present three examples of such high-frequency, transient processes: (1) GRACE gravitational observations of large tsunamis (e.g., 2004 Sumatra), (2) GRACE-FO monitoring of the Bangladesh flood during 2020 monsoon season, and (3) GRACE-FO observations of high-frequency ocean variability in the Gulf of Carpentaria. The along-orbit gravitational observations in these cases could be used, respectively, for (1) distinguishing among tsunami models with different earthquake sources, (2) providing constraints on runoff routing models as well as tracking the temporal evolution of flood volume during the monsoon season, and (3) validating (high-frequency) ocean models.

I plan to introduce a new along-orbit gravimetric data product for the GRACE and GRACE-FO missions, and release it to the geoscience and hydrology community. This data product will open new opportunities in Earth system mass change monitoring, and also has the potential to become more relevant in the future with climate change likely worsening the frequency and intensity of some extreme events like floods.