Revealing the three-dimensional structure and composition of atmospheric aerosols from space

Air pollution is a major global challenge, responsible for more than 4 million premature deaths worldwide each year. Because aerosols are transported over long distances, often far beyond national borders, effective air quality and climate mitigation strategies critically rely on our ability to identify source regions and characterize atmospheric transport pathways. Satellite observations are indispensable for this purpose, providing global and continuous monitoring capabilities. However, until recently, spaceborne observations of aerosols were largely limited to horizontal distributions, typically expressed as aerosol optical depth, or to sparse vertical information restricted to narrow orbital tracks from active lidar instruments.

In this presentation, we will demonstrate how recent advances in multi-hyperspectral satellite remote sensing have led to a major observational breakthrough: the first-ever observation of the three-dimensional (3D) distribution of aerosols from space using passive satellite measurements. By exploiting the complementary information content of hyperspectral observations across different spectral domains, two innovative approaches have been developed. The AEROIASI method uses hyperspectral thermal infrared measurements from the IASI instrument to retrieve vertical profiles of aerosol species that significantly absorb in the thermal infrared, including coarse desert dust (Cuesta et al., 2015; 2020) as well as finer particles such as sulfuric acid (Guermazi et al., 2021) and ammonium sulfate (Kutzner et al., 2021). Complementarily, the AEROS5P approach employs hyperspectral visible and near-infrared measurements from TROPOMI to provide, for the first time, vertically resolved observations of fine aerosols emitted by wildfires and anthropogenic sources (Lemmouchi et al., 2022; Maheshwarkar et al., 2024). Together, these methods show that passive satellite sensors can now resolve not only the horizontal extent of aerosol plumes, but also their vertical structure, composition, and transport pathways throughout the troposphere.

Looking ahead, this innovative methodology will be unified into a joint approach based on the new MeOp-SG mission. Within the framework of the European PANORAMA project, a synergetic approach combining these two methods with polarimetric satellite measurements will aim to achieve an extended aerosol speciation in 3D, with far-reaching implications for air quality and climate assessment.