Poster Session 4, Thursday, October 6, 11:00–12:40
Radiative transfer code OSOAA – Ocean Successive Orders with Atmosphere – Advanced
In this work, a radiative transfer model, so-called OSOAA, acronym for “Ocean Successive Orders with Atmosphere – Advanced”, which has been developed for the purpose of ocean color remote sensing studies, is presented. OSOAA is a radiative transfer code, based on the successive orders of scattering method [Deuzé et al, 1989] [Lenoble et al., 2007], which simulates the propagation of the polarized solar light in the coupled system « ocean / atmosphere » from 400 nm to 900 nm [Chami et al., 2015]. The radiance and degree of polarization are provided at various viewing angles and at any level from the top of atmosphere to the ocean seabed. The scattering of light in the water column accounts for interactions of photons with molecules and hydrosols, namely phytoplankton and mineral-like particles, thus providing a complete description of the directional effects of hydrosols on the water leaving radiances. The absorption by colored dissolved organic matter (CDOM) and detritus is taken into account as well. In addition, OSOAA simulates a realistic air / sea interface by considering the roughness of the sea surface based on the wind speed and wave statistics as modelled by Cox & Munk  . This latter point is a major improvement of OSOAA model relatively to its previous version, so-called OSOA model, which was developed considering a flat sea surface [Chami et al., 2001]. Another main improvement brought by OSOAA is to offer a user friendly interface (GUI) and a user manual that describes all the physical models that are implemented in the code as well as how to run the OSOAA model for simulations. Another originality of the OSOAA model relies on its ability to simulate various realistic atmospheric conditions such as pressure, aerosol optical thickness and, more importantly, aerosol models taken either from the literature (e.g., WMO or Shettle & Fenn  models), or from user-defined conditions using mono-modal or bi-modal size distributions. Note, however, that the current version of OSOAA (v1.5) does not take into account the atmospheric gaseous transmittance. The validation of OSOAA model has been carried out through comparisons with another operational radiative transfer model [Chowdhary et al., 2006]. Satisfactory agreements for the intensity within 0.5% at sea surface and 0.2% at top of the atmosphere in the blue spectral domain, and within 0.8% for the polarization Stokes parameters, were found. The scientific community working on coastal waters remote sensing or open ocean applications can take benefit of the exact modeling proposed by the OSOAA model, for example to better understand marine ecosystems, or to develop and improve inverse ocean color algorithms. Note that OSOAA model is publicly available for the scientific or industrial community with a distribution ensured by CNES (https://github.com/CNES/RadiativeTransferCode-OSOAA).
Malik Chami, Laboratoire Atmosphères Milieux Observations Spatiales (LATMOS), Sorbonne Université, CNRS-INSU, [email protected]
Bertrand Fougnie, CNES (when the poster was made, currently EUMETSAT), [email protected]
Aimé Meygret, CNES, [email protected]