The MERIS TOA infra red similarity spectrum
Gerald Moore(1), Susanne Kratzer(2) and Jean-Paul Huot(3)
(1) Plymouth Marine Laboratory, Prospect Place, Plymouth PL1 3DH, United Kingdom
(2) Stockholm University, Marine Ecology Group, S-106-91 Stockholm, Sweden
(3) ESA / ESTEC, Postbus 299 2200 AG, Noordwijk, Netherlands
The MERIS bright pixel (BP) atmospheric correction depends on the parameterization of the pure water absorption in the near infra-red (NIR). Literature values, from laboratory measurements, show differences in absorption varying by up to 20%, additionally there is a potential variation in the pure water absorption due to changes in temperature and salinity.
Observations of the ‘similarity’ spectrum between the NIR bands from above water surface hyperspectral observations (Ruddick, De Cauwer et al. 2006) have show that at least in certain regions the pure water absorption properties can be constrained. This similarity spectrum approach can be extended to top of atmosphere MERIS observations, since the scale length of aerosol variability (~100km) is far greater than that of mesoscale oceanic features (~10km). The NIR ‘similarity’ spectrum at top of atmosphere is determined by the by the pure water optical properties, the diffuse and gaseous transmission, and the variation of f/Q, path radiance (including adjacency effects) and glint are only apparent from systematic offsets. Variations in f/Q are modeled using Hydrolight where inherent optical properties are available. Selections of oceanic and coastal regions are used to validate the procedure and explore the effects of temperature and salinity. There are: the Baltic; the Amazon plume; a coccolitophore bloom; and the mesotrophic Atlantic (Atlantic Meriodional Transect). Results from these regions are used to determine the most appropriate Most appropriate selection of BP bands, and to determine the reliability of the atmospheric transmission terms,
Ruddick, K. G., V. De Cauwer, et al. (2006). "Seaborne measurements of near infrared water-leaving reflectance: The similarity spectrum for turbid waters." Limnology and Oceanography 51(2): 1167-1179.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,