Publications

Castelli, E; Pettinari, P; Papandrea, E; Premuda, M; Achilli, A; Richter, A; Bösch, T; Hendrick, F; Fayt, C; Beirle, S; Friedrich, MM; Van Roozendael, M; Wagner, T; Valeri, M (2025). Towards a New MAX-DOAS Measurement Site in the Po Valley: Aerosol Optical Depth and NO2 Tropospheric VCDs. REMOTE SENSING, 17(6), 1035.

Abstract
Pollutants information can be retrieved from visible (VIS) and ultraviolet (UV) diffuse solar spectra exploiting Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instruments. In May 2021, the Italian research institute CNR-ISAC acquired and deployed a MAX-DOAS system SkySpec-2D. It is located in the Giorgio Fea observatory in San Pietro Capofiume (SPC), in the middle of the Po Valley, where it has constantly acquired zenith and off-axis diffuse solar spectra since the 1st October 2021. This work presents the retrieved tropospheric NO2 and aerosol extinction profiles (and their columns) derived from the MAX-DOAS measurements using the newly developed DEAP retrieval code. The code has been validated both using synthetic differential Slant Column Densities (dSCDs) from the Fiducial Reference Measurements for Ground-Based DOAS Air-Quality Observations (FRM4DOAS) project and real measured data. For this purpose, DEAP results are compared with the ones obtained with three state-of-the-art retrieval codes. In addition, an inter-comparison with satellite products from Sentinel-5P TROPOMI, for the tropospheric NO2 Vertical Column Densities (VCDs), and MODIS-MAIAC for the tropospheric Aerosol Optical Depth (AOD), is performed. We find a bias of -0.6 x 1015 molec/cm2 with a standard deviation of 1.8 x 1015 molec/cm2 with respect to Sentinel-5P TROPOMI for NO2 tropospheric VCDs and of 0.04 +/- 0.08 for AOD with respect to MODIS-MAIAC data. The retrieved data show that the SPC measurement site is representative of the background pollution conditions of the Po Valley. For this reason, it is a good candidate for satellite validation and scientific studies over the Po Valley.

DOI:
10.3390/rs17061035

ISSN:
2072-4292