Synergetic Retrieval from GROund based and SATellite measurements for surface characterization and validation (GROSAT)

Reflectance of the Earth surface is one of the natural major components affecting climate. Surface interaction with incoming solar radiation and the atmosphere has a substantial impact on the Earth’s energy budget. Moreover, the accurate description of the surface reflection is crucial for different atmospheric studies including aerosol and trace gases characterization.

One of the grand science challenges in remote sensing and climate studies is the accurate separation of surface and atmosphere contributions to the satellite signal. This separation is a crucial requirement of any algorithm for the accurate retrieval of atmosphere and surface properties from remote sensing measurements (Dubovik et al., 2011, 2021; Hasekamp et al., 2011).

Despite the evident need for the universal and robust reference dataset for surface reflectance, BRDF (Bidirectional Distribution Function) and BPDF (Bidirectional Polarization Distribution Function) retrieval validation, it still does not exist. In this project it is proposed to perform a simultaneous synergistic retrieval of aerosol and surface properties using combined ground-based (for example, AERONET) and satellite measurements for obtaining the surface reflectance product with enhanced accuracy (Figure 1).  In such approach the main information about aerosol comes from AERONET direct sun and diffuse sky-radiance measurements, whereas the information about surface reflection properties originates from satellite observations. The synergetic AERONET + satellite retrieval approach has already been prototyped within GRASP algorithm in the frame of ESA S5P+Innovative AOD/BRDF (Litvinov et al., 2020; https://eo4society.esa.int/projects/sentinel-5pinnovation).

Further adjustment of GRASP algorithm to the synergistic retrieval from the combined ground-based (AERONET) and satellite measurements provides new possibilities for aerosol and surface characterization. This GRASP synergetic approach promises to become a rather robust and universal tool that can be applied to any space-borne instruments independently of spatial resolution or information content: for any spectral bands, radiance only or polarimetric measurements, single or multiple view instruments.