Comparison of GRACE-FO Fields and In Situ Ocean Bottom Pressure Observations

The Gravity Recovery and Climate Experiment (GRACE) mission provided the first global-scale observation of ocean bottom pressure (OBP) variability, and this time series continues with new solutions from the GRACE Follow-On (GRACE-FO) mission. In order to assess the quality of these new solutions, we look to compare these observations to those recorded by the Deep-ocean Assessment and Reporting of Tsunamis (DART) network. We collect and process the data provided by the DART network data daily to generate daily-averaged values for comparison to different ocean models used in de-aliasing (e.g. the AOD1B RL06 product; Dobslaw et al., 2017) and to estimates derived from the GRACE-FO solutions.

By comparing historic DART data to estimates from the GRACE mission, we have identified a number of stations where GRACE consistently improved both the correlation and relative variance change above the background ocean model on each deployment. To better illustrate the improvement, we also compare the change introduced by GRACE to the background ocean model estimate (i.e. the GSM-type solution) to the residual of the in situ OBP observation after the removal of the AOD1B model prediction. Our primary comparison is with the CSR RL06 mascons, but we also compare the Level-2 spherical harmonic releases and other mascon solutions with sub-monthly variability (e.g. Sakumura et al, 2016). This presentation will demonstrate the in situ OBP observation's ability to assess the GRACE-FO fields and will provide the current state of the comparison.