Validation of L2 EarthCARE Aerosol Products with co-located SKYNET and AERONET photometers observation complemented by lidar profilers at the Rome Tor Vergata atmospheric observatory (Italy)

This work presents preliminary results of the validation of ESA EarthCARE (EC) Level-2 aerosol products using ground-based observations in Rome–Tor Vergata (Italy), where a suite of instruments continuously measures aerosols, clouds, gases, and precipitation. The study is carried out within the EC-VALMED.it project funded by the Italian Space Agency (ASI), aiming to assess the accuracy of EC aerosol, cloud, and precipitation products over the Mediterranean. Here, we focus on aerosol columnar properties  comparing EC satellite products with observations from ground-based photometers (AERONET and SKYNET) complemented by vertical profiles from high- and low-power lidar measurements operating within ACTRIS and ALICENET/E-PROFILE.  

Satellite validation is challenging due to differences in observation geometry, mismatches in spatial and temporal resolution, and high spatiotemporal variability of aerosol optical properties. To address these issues, we defined specific match-up criteria between satellite and ground-based measurements. For EC MSI (Multi Spectral Imager) Aerosol Optical Thickness (AOT), spatial averages over 3×3, 9×9, 25×25, and 51×51 pixel areas around the Rome-Tor Vergata observatory were computed. For EC ATLID (Atmospheric Lidar), both AOT and vertical profiles were averaged over different temporal windows (i.e., along-track path-length), centered at the time of minimum distance between the satellite ground track and the Rome-Tor Vergata observatory. Only ATLID overpasses within 100 km and MSI-AOT overpasses within 150 km of the station were considered. Ground-based photometer data were also temporally averaged over different intervals, and only high-quality satellite retrievals (status 0/1) were retained. 

First results indicate a good agreement between EC-ATLID AOT at 355 nm and 15-min averaged AERONET/SKYNET data at 340 nm (R = 0.86), with the best match obtained using ATLID 20-s averages. MSI-AOT shows a  lower correlation at 670 nm (R = 0.65), though improvements were observed moving from EC product baseline BA to BB. In specific cases, reasons for satellite-photometers disagreements are disclosed based on vertical profiles. 

This work is supported by the Italian Space Agency (ASI, ECVALMED project, agreement n. 2024-1-HB.0).