Unified Satellite Observation of Thermal Infrared-Absorbing Aerosol Composition

Aerosol composition plays a key role in quantifying its impacts on climate and human health, as well as in understanding aerosol sources, transport, and evolution. Using the high spectral resolution of thermal infrared radiances measured by the spaceborne IASI sensor, the AEROIASI approach has been developed to quantify aerosol species that significantly absorb in the thermal infrared spectral domain (Cuesta et al., 2015; Guermazi et al., 2021; Kutzner et al., 2021). To date, this approach has been applied using dedicated configurations that allow the retrieval of only one aerosol species at a time. These species include desert dust, sulfuric acid, and ammonium sulfate.

In this work, we present a new unified retrieval framework capable of simultaneously quantifying these three aerosol species and their respective fractions when they coexist in the atmosphere. This is achieved by exploiting the Generalized Retrieval of Atmosphere and Surface Properties (GRASP) methodology (Dubovik et al., 2021), newly adapted to thermal infrared observations in the framework of the PANORAMA European Horizon 2020 project. The initial results establish a premise of the ability of the proposed approach to analyze mixed aerosol events over Europe using IASI measurements.

This GRASP-based method represents a first step toward a multispectral synergistic retrieval exploiting IASI-like thermal infrared measurements from IASI-NG together with observations from the multi-angular polarimeter 3MI, both onboard the MetOp-SG satellite since 2025. Such synergism is expected to significantly enhance aerosol speciation capabilities, including the characterization of fine-mode aerosol species primarily constrained by polarimetric measurements.