Simulation study of the aerosol information content in OMI spectral reflectance measurements
Résumé
The Ozone Monitoring Instrument (OMI) is designed and used primarily to retrieve trace gases like O3 and NO2 from the measured Earth reflectance spectrum in the UV-visible (270?500 nm). However, also aerosols are an important science target of OMI. Therefore, a Principal Component Analysis (PCA) is performed to quantify the information content of OMI reflectance measurements on aerosols. This analysis is applied to synthetic reflectance measurements for desert dust, biomass burning aerosols, and weakly absorbing anthropogenic aerosol with a variety of aerosol optical thicknesses, aerosol layer altitudes, refractive indices and size distributions. The range of aerosol parameters considered covers the natural variability of tropospheric aerosols. This theoretical analysis is performed for a large number of scenarios with various geometries and surface albedo spectra for ocean, soil and vegetation. When the surface albedo spectrum is accurately known and clouds are absent, OMI reflectance measurements have 2 to 4 degrees of freedom that can be attributed to aerosol parameters. This information content depends on the observation geometry, the surface albedo spectrum, and on the aerosol parameters themselves. An additional wavelength band is evaluated, that comprises the O2-O2 absorption band at a wavelength of 477 nm. It is found that this wavelength band adds significantly more information than any other individual band. The PCA is applied to assess the capability of the aerosol retrieval to discern various aerosol types as well as clouds.
Domaines
Océan, Atmosphère
Origine : Accord explicite pour ce dépôt
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