Enhancing Climate Studies with High-Quality Reference Observations: Insights from the Copernicus Programme

Accurate and reliable observational data are essential for understanding climate dynamics, assessing climate change impacts, and supporting informed adaptation strategies. This work highlights the pivotal role of reference measurements and climate data records accompanied by robust uncertainty quantification, in ensuring the quality and consistency of observational datasets. These datasets underpin scientific analyses and decision-making processes, particularly in the context of climate studies and applications. Within the framework of the Copernicus program, the European Centre for Medium-Range Weather Forecasts (ECMWF) operates the Copernicus Climate Change Service (C3S) with funding from the European Union. The Institute of Methodologies for Environmental Analysis (IMAA) of the National Research Council (CNR) has been engaged by ECMWF to implement the C3S2 311 Lot2 project, which builds on previous efforts in Copernicus contracts to enhance access to high-quality baseline and reference observations. This project underscores the importance of standardized measurement protocols and rigorous uncertainty assessment methodologies. The study introduces three types of datasets made available on the Copernicus Climate Data Store (CDS), which serves as a key platform for disseminating reference datasets, ensuring accessibility for researchers and stakeholders (1) upper-air reference measurements for GRUAN, (2) near-surface reference measurements from USCRN, and (3) precipitable water vapor derived from reference and reprocessed GNSS time series. The potential applications of these measurements in characterizing atmospheric conditions and investigating climate variability are discussed.