Aerosol retrieval from space – how does geometry of acquisition impact our ability to characterize aerosol properties. (November 2020)

• Record Type: Journal Article
• Authors: Fougnie, Bertrand; Chimot, Julien; Vázquez-Navarro, Margarita; Marbach, Thierry; Bojkov, Bojan
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 256(2020)
• Publication Date: 2020-11
• Subjects: AATSR Advanced Along-Track Scanning Radiometer -- ACT Across-track -- AEF Aerosol Error Factor -- ALT Along-track -- AOD Aerosol Optical Depth -- APS Aerosol Polarimetry Sensor -- BRDF Bidirectional Reflectance Distribution Function -- DPC Directional Polarimetric Camera -- ECT Equatorial Crossing Time -- EPS-SG EUMETSAT Polar System – Second Generation -- GRASP Generalized Retrieval of Aerosol and Surface Properties -- HARP Hyper-Angular Rainbow Polarimeter -- MAP/CO2M Multi-Angle Polarimeter/CO2 Monitoring mission -- PACE Pre-Aerosol, Clouds, and ocean Ecosystem mission -- MISR Multiangle Imaging SpectroRadiometer -- MODIS Moderate-Resolution Imaging Spectroradiometer -- MSIP MultiSpectral Imaging Polarimeter -- OLCI Ocean and Land Colour Instrument -- PARASOL Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar -- POLDER Polarization and Directionality of the Earth's Reflectance instrument -- RSP Research Scanning Polarimeter -- ScanPol Scanning along track Polarimeter -- ScARD Scattering Angle Range Distribution, -- SGLI Second Generation Global Imager -- SLSTR Sea and Land Surface Temperature Radiometer -- SPEX Spectro-Polarimetric Experiment -- TOA Top-of-Atmosphere -- 3MI Multi-View Multi-Channel Multi-Polarization Imaging mission; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2020.107304
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: How aerosol retrieval is influenced by the geometry. Definition of the scattering angle range distribution. Typical information content for some earth observing sensors. Recommendation for the development of aerosol retrieval and products. Abstract: For decades now, the retrieval of aerosol property has been successfully achieved from space-borne sensors from which measurements it is possible to derive specific parameters such as optical thickness, absorption, type, refractive index, or size distribution. In the reflective spectral domain, remote sensing of aerosol properties relies on the top-of-atmosphere measurement of the sun irradiance scattered by aerosols in different directions. This measure is intrinsically linked to the aerosol phase function. Ground-based measurements are made for many viewing directions providing a good description of this phase function. For satellite remote sensing, the phase function cannot be measured in so much detail. Only a single scattering angle for mono-viewing sensors, or a limited range for multi-view sensors, is accessible. The associated geometry varies very significantly along the swath, from East to West, and along the orbit, from North, to Tropics, and South. Whatever the considered aerosol retrieval approach, the performance cannot be the same from these very different geometrical configurations, and may significantly differ. This aspect is in general not well documented. In this paper, the scattering angle range distribution (ScARD) is described in the case of the EPS-SG/3MI multi-view polarimeter. Based on reference aerosol phase functions, it is anticipated how the retrieval performance could be impacted. Other cases are simulated trying to extrapolate the conclusion to other types of sensors having more limited swath or number of views. The ScARD is described for these different situations, including the variation along the orbit and along the swath. Important recommendations are drawn including the need to document the geometrical part of the information content provided by the sensor (not only spectral), to better consider the associated classes of viewing geometry for the development of retrieval algorithms (which could limit the ability to retrieve some parameters), but also for the validation of products.