Major activities in Work Package 1 - Management were the scientific steering of the consortium, the reporting and the organization of meetings, especially of the General Assemblies (GA). Due to Covid-19 the latter were mainly held as online meetings. Further activities included composing the Consortium’s management guidelines, the Data Management Plan (DMP), setting up of a process to establish a quality assessment system for G3P product development using the CORE-CLIMAX System Maturity Matrix (SMM, EUMETSAT (2014)), and managing the efficient preparation of any deliverable.
In Work Package 2 – satellite gravity data processing the handling of low-level (L1A) data of the GRACE-FO mission was successfully implemented. With the main focus on retrieving GRACE-D accelerometer data, we present a novel approach to recover the GRACE-D ACT1B data by incorporating non-gravitational force models and analyze its impact on monthly gravity field solutions. Level-1B to Level-2 Processing has been successfully performed for GRACE-FO at all G3P analysis centers (ACs) and are operationally computed at all ACs. The combination of the Level-2 products of the G3P ACs in the frame of the Combination Service of Time-variable Gravity Fields (COST-G) is on an operational level. Internal validation procedures have been established. User-friendly grids of the combined solutions have been produced and are available from GFZ's GravIS. The mass anomaly products are generated for a) terrestrial water storage over non-glaciated regions, b) ocean bottom pressure variations in the oceans and c) ice-mass changes in Antarctica and Greenland.
Work carried out in Work Package 3 – Quantification of storage compartments focused on adapting existing and developing additional operational Copernicus service products quantifying water storage variations in individual terrestrial water cycle compartments. All water storage compartments (WSCs) (glaciers, snow, soil moisture, surface water) were successfully brought to a status to be implemented in the G3P subtraction approach.
Work Package 4 – Groundwater product development, evaluation and service preparation (WP4) included (1) the scientific development of the subtraction process that is necessary to calculate groundwater from terrestrial water storage, (2) the evaluation and validation of the resulting data set of groundwater storage variations with in-situ data, and (3) creating the technical framework for the prototype G3P service. Activities in (1) included the test of different filters to make WP3 data compatible with GRACE observations, the evaluation of spatial correlation lengths of the different water storage data sets to find a best fitting filter width, and designing and coding the subtraction procedure for the groundwater product. For (2), a set of suitable aquifers for the evaluation of the groundwater product was selected and characterized, in-situ data was retrieved, and an extensive assessment of the groundwater product was carried out. In (3), the G3P processing chain has been set up as a basis for future operational implementation of G3P in the Copernicus Climate Change Service (C3S). The maturity of the components has been assessed and next steps towards an operational service have been defined.
Activities within Work Package 5 included G3P dissemination via publications and various other channels, exploitation and provision of a demonstrator use case by integrating G3P into a drought early warning system, the development and operation of the G3P website, and providing open access and visualizazion of G3P data via the online platforms GGMN and GravIS.
