The Hub Talks: Advancing atmospheric composition monitoring for Sentinel-5

Title: Advanced combined retrieval of aerosol, green-house gases and surface properties with GRASP algorithm. Application to Multiangular polarimeters and SWIR spectrometers. 

Abstract:
One of the primary challenges in achieving the necessary precision in satellite retrievals of XCO2 and XCH4 is accurately characterizing atmospheric aerosols. Multiangular-Polarimetric measurements (MAP) represent the most advanced approach for understanding aerosol properties from space-borne platforms. Conversely, the optimal sensitivity to CO2 and CH4 concentrations, while minimizing scattering effects, is typically found within the SWIR-1 and SWIR-2 spectral bands. As a result, upcoming Copernicus missions such as Sentinel-7 CO2M or MetOp-SG Sentinel-5 with 3MI onboard are equipped with both MAP and SWIR spectrometric measurements. The Generalized Retrieval of Atmosphere and Surface Properties (GRASP) is a recently developed versatile algorithm designed for various remote sensing observations (Dubovik et al., 2021). GRASP relies on comprehensive and rigorous modeling of atmospheric radiation, applicable to simulating a wide range of observations. Its numerical inversion is executed through highly statistically optimized fitting, following the Multi-Term Least Square minimization concept. Originally applied to MAP-like measurements in various applications (POLDER, 3MI, CO2M/MAP), the GRASP approach has now been extended to combine MAP and SWIR spectrometric measurements, offering a synergistic combined product of aerosol properties alongside additional information on columnar XCO2 and XCH4 (Li et al., 2019; Chen et al., 2020).  The GRASP algorithm is set to be employed with two different combinations of MAP and SWIR spectrometer instruments: CO2M/MAP+CO2M/CO2I (Lu et al., 2022) and 3MI+S5/UVNS. Theinherent generality and high flexibility of the GRASP code will demonstrate the advantages of incorporating MAP measurements for improved XCO2 and XCH4 accuracy compared to standalone spectrometers. Additionally, it will highlight the benefits of combining additional spectrometric bands around the O2 A-Band to enhance aerosol layer height characterization (Herreras-Giralda et al., 2022).  

Speaker: Dr. Marcos Herreras Giralda is a scientific officer at GRASP SAS, he has participated in several projects focused on the remote characterization of all the elements of the climate system: aerosols, gases and surface. Furthermore, some of them, such as DIVA III (ESA), involve the connection of different satellite products, models and ground based reference for its validation and the creation of joint products. Dr. Herreras works in thedevelopment of different new applications of GRASP from different sensors (from UV to thermal infrared) and platforms (ground-based and space-borne) to retrieve optical and microphysical properties of aerosol, gases and surface. One of main tasks is the coordination of all the parallel developments in the code and the organization of therealisations of the new versions of GRASP.