Quality Assurance for Soil Moisture (QA4SM) - A Centralized Soil Moisture Validation and Inter-Comparison Platform

Quality Assurance for Soil Moisture (QA4SM, available at https://qa4sm.eu/) is a centralized, cloud-based online tool for satellite soil moisture data validation that was launched in 2018. Via an easy-to-use web interface, the platform is designed to simplify the systematic intercomparison of satellite measurements, land surface models and reanalysis fields and validate them against globally available fiducial reference measurements (FRMs) from the International Soil Moisture Network (ISMN; https://ismn.earth). The platform delivers reproducible validation results, grounded in consistent methodology and community-agreed best practices, following requirements set forth by the Global Climate Observing System (GCOS) and the Committee on Earth Observation Satellites (CEOS).QA4SM implements an extensive array of regularly-updated satellite products from missions including SMOS, SMAP, ASCAT, and Sentinel-1, along with multi-sensor datasets from the Copernicus Climate Change Services (C3S) and ESA Climate Change Initiative (CCI). It incorporates in situ reference data from the ISMN and reanalysis products such as ERA5(-Land) and GLDAS-Noah. Users can upload their own custom datasets in multiple formats for comparison against state-of-the-art reference products. The platform offers extensive customization options for validation, including dataset filtering, spatial and temporal sub-setting, scaling methods, temporal matching, and anomaly calculation. Results can be archived and published with digital object identifiers (DOIs) for traceability and scientific reproducibility.QA4SM is continuously evolving to keep up with scientific developments and user needs. Several new capabilities are planned for the upcoming Release 4 in March:Automated validation of NRT data streams will enable stable, continuous monitoring of data quality.Spatial validation functionality will complement the existing temporal validation, addressing use cases that involve datasets with limited temporal coverage as well as high-resolution products.A programmatic API will provide command-line access to the platform, enabling seamless integration with automated workflows.A new interactive data viewer will facilitate intuitive exploration of validation results.In this presentation, we demonstrate the functionalities of QA4SM, highlight the features introduced in Release 4, and discuss planned future developments.QA4SM is developed as part of the European Space Agency’s Fiducial Reference Measurement for Soil Moisture (FRM4SM) project.