Surface and Aerosol Retrieval from S5P and S4: Baseline Requirements and Expected Performance

Sentinel-4 and Sentinel-5p instruments provide hyperspectral measurements in UV, VIS and infrared spectral range. Though the main purpose of the satellites is trace gas characterization, both instruments are capable of aerosol and surface characterization. In particular, S4 and S5p measurements in UV have unique information about absorption and elevation properties of aerosol. Moreover, measurements in wide spectral range are very sensitive to aerosol size and surface type. On one hand, aerosol and surface characteristics are important input parameters for different trace gases such as ozone, NO2, BrO, CH2O, H2O, CO2, CO, and CH4. On another hand, aerosol and surface characteristics are very important on their own for climate studies, air pollution and surface monitoring.The quantitative characterization of aerosol (AOD (Aerosol Optical Depth), aerosol type) and surface properties (BRDF (Bidirectional Reflectance Distribution Function)) from Sentinel-4 and Sentinel-5p instruments is a topic for several ESA/EUMETSAT projects. In particular, in the framework of S5P+I AOD/BRDF project an innovative algorithm will be developed which integrates the advanced GRASP algorithm (Dubovik et al. 2011, 2014) with the heritage AOD and DLER algorithm previously applied to TOMS, GOME(-2), SCIAMACHY and OMI sensors (Tilstra et al., 2017). Innovative GRASP algorithm is expected to provide surface BRDF and AOD with the accuracy required by most trace gas retrieval algorithms.Here the requirements on aerosol and surface characterization from S4 and S5p instruments will be analyzed. On the basis of inversion results from the synthetic (S4) and real (S5p) measurements we discuss how expected AOD and BRDF accuracy from the innovative and GRASP/S4 algorithms meet these requirements. New advanced possibility of aerosol and surface characterization with GRASP from S5p instrument will be discussed.ReferencesDubovik, O., et al., “Statistically optimized inversion algorithm for enhanced retrieval of aerosol properties from spectral multi-angle polarimetric satellite observations”, Atmos. Meas. Tech., 4, 975-1018, 2011. Dubovik, O., et al. “GRASP: a versatile algorithm for characterizing the atmosphere”, SPIE: Newsroom, doi:10.1117/2.1201408.005558, Published Online: http://spie.org/x109993.xml, September 19, 2014. Tilstra, L. G., et al., “Surface reflectivity climatologies from UV to NIR determined from Earth observations by GOME-2 and SCIAMACHY”, J. Geophys. Res. Atmos., 122, 4084–4111.