Global Terrestrial Water Storage Anomaly Dataset Now Operationally Available via Copernicus
As of April 2026, a global Terrestrial Water Storage Anomaly (TWSA) dataset is operationally available through the Climate Data Store of the Copernicus Climate Change Service (C3S). This marks the culmination of a decade of coordinated efforts by the European GRACE/GRACE-FO community to bring mass redistribution products into operational climate services.
A Decade of Groundwork
The journey began in 2015 with the H2020 project EGSIEM (European Gravity Service for Improved Emergency Management, egsiem.eu), coordinated by the Astronomical Institute at the University of Bern (AIUB). EGSIEM initiated activities to integrate observations of environmental mass redistribution into Copernicus services an
d envisaged their future embedding within IAG service structures.
Building on this momentum, the IAG Combination Service for Time-Variable Gravity Fields (COST-G, cost-g.org) was established at AIUB as a product center of the International Gravity Field Service (IGFS). Since 2019, COST-G has combined monthly global gravity field models — expressed as spherical harmonic coefficients (Level-2 products) — from multiple analysis centers into consolidated products. Derived grids are provided by GFZ Helmholtz Centre for Geosciences via the Gravity Information Service (GravIS, gravis.gfz.de).
From 2020 to 2022, the H2020 project G3P (Global Gravity-based Groundwater Product, g3p.eu), coordinated by GFZ, further advanced both GRACE data processing and its application in a global remote-sensing-based groundwater product.
ECV Recognition and C3S Integration
In 2022, the Global Climate Observing System (GCOS) defined Terrestrial Water Storage as a new Essential Climate Variable (ECV), explicitly recognizing its observability with satellite gravimetry. Simultaneously, GCOS added Groundwater Storage Change (GWSC) to the climate-relevant variables of the ECV Groundwater. Following these designations, C3S decided to include both TWSA and GWSC in its portfolio of Climate Data Records.
Based on a successful response by GFZ to an ECMWF invitation to tender, C3S began operational provision of the TWSA dataset on 7 April 2026. The dataset is based on the COST-G RL02 GRACE/GRACE-FO Level-2 products (Meyer et al., 2025, doi: 10.5880/COST-G.ICGEM_02_L2) and represents deviations from the long-term average of water stored on or below Earth’s surface, encompassing soil moisture, groundwater, surface water, snow, and ice.
The dataset is freely accessible via the Copernicus Climate Data Store:
https://cds.climate.copernicus.eu/datasets/satellite-terrestrial-water-storage
The companion GWSC product is expected to follow in the coming months.
Author: Adrian Jäggi
