High-Resolution Atmospheric-hydrological Background Modelling for GRACE/GRACE-FO – regional refinement and validation

Abstract

<p>We will give an insight into the atmospheric physics contribution to the New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV) research group, which is funded by the German Research Foundation (DFG). Since May 2019, NEROGRAV develops new analysis methods and modeling approaches to improve data analysis of the GRACE and GRACE-FO mission. Our contribution to this research unit is the High-Resolution Atmospheric-hydrological Background Modelling for GRACE/GRACE-FO – regional refinement and validation (HIRABAM). One of our goals in this individual project (IP) is the development of improved Atmospheric Ocean Dealiasing (AOD) products by integrating high-resolution regional atmospheric modeling. Furthermore, we are interested in whether and how extreme hydrometeorological events map into GRACE L1/2 data.</p> <p>The 1995-2019 COSMO-REA6 regional reanalysis and the July 2021 ICON-EU/D2 analysis are non-hydrostatic regional atmospheric models with 3D fields on grid sizes below 10 km, with mass densities of dry air and all water phases (gaseous, liquid clouds and rain, icy snow, sleet, and hail) available in each of their 40-50 vertical layers. By integrating over all layers, the total local and column-by-column atmospheric mass density can be calculated without using the hydrostatic assumption. Unfortunately, such high-resolution atmospheric model data is currently only available within the EURO-CORDEX domain, which covers the European continent. Nevertheless, to compute global spherical coefficients for our AOD products that benefit from the high resolution of the regional models, we nested COSMO-REA6 in a lower-resolution but global model. Here we want to answer the question: does high-resolution mass variability leaves a significant fingerprint in the global loading coefficients? The heavy rainfall observed in the Ruhr/Ahr/Erft/Maas basin in July 2021 are clearly visible in ICON-EU/D2 atmospheric data. The question to be answered here is: are mass variations of such extreme weather events visible in GRACE/GRACE-FO data and do they exceed typical uncertainties?</p>