Developing a regionally refined high-resolution and mass-consistent atmosphere-hydrology de‐aliasing data set for GRACE‐FO and Next-Generation Gravity Missions

Abstract

Temporal aliasing of high-frequency mass variations is, next to instrument noise, the biggest obstacle to improving accuracy and resolution of satellite gravimetry products from the GRACE, GRACE Follow-On and next generation gravity missions. In current GRACE/-FO processing, tidal and sub-monthly non-tidal mass variations in ocean and atmosphere are removed from the level-1 data using the Atmospheric Ocean Dealiasing (AOD) data sets. However, these reanalysis- and forecast-based data sets are not perfect and therefore errors are introduced in derived short- and long-term science results. Hence, to a large extent, the quality of the GRACE/-FO level-2 data relies on the consistency of the AOD data. It is therefore an essential task to improve the background models, especially with regard to next generation gravity mission.The research group New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV), funded by the German Research Foundation (DFG), aims at improving GRACE/-FO data products by developing new analysis methods and modeling approaches. This includes a revision of existing geophysical background models as well as their spatial-temporal parameterization. Within this research group we create a consistent global data set of short-term atmospheric and hydrological mass variations with higher temporal and spatial resolution over Europe. For computing the atmospheric dealiasing fields we apply the 3D integration approach developed by Forootan et al. (2013) that also accounts for more realistic approximations of the Earth’s physical and geometrical shape. We compared sub-monthly as well as long-term signals of global atmospheric fields from ERA-Interim and ERA5 to investigate differences arising from different spatial resolution (0.5° & ~0.1°). The regional non-hydrostatic atmospheric reanalysis COSMO-REA6 provides 3D fields on a grid sized even below 0.1° within the EURO-CORDEX domain. We nested COSMO-REA6 into ERA-Interim to obtain a global consistent atmospheric dealiasing data set, but with higher spatial and temporal resolution over Europe. Short-term hydrological signals are not included in the standard dealiasing products, yet, some studies indicate that removing them might further reduce aliasing errors in the monthly GRACE/-FO fields and might be inevitable for next generation gravity missions. Therefore, we developed a hydrological dealiasing product following the same approach as for our refined atmospheric data set by nesting the water storage changes derived by the regional CLM data set (forced by COSMO-REA6) into the global WGHM data set. In this presentation we show the impact of short-term mass changes over Europe on GRACE observations.