SeaWiFS atmospheric correction by an approximate model and vicarious calibration

An approximate atmospheric model accounting for Rayleigh-and aerosol multiple scattering, and Rayleigh-aerosol coupling, is proposed for the atmospheric correction of SeaWiFS data. The accuracy of predicting water-leaving radiance is shown to improve by the use of vicarious calibration factors trimming the absolute radiometric calibration inaccuracy of the space-borne sensor and the model inaccuracy. Making use of data from three field campaigns carried out in 1998 at a calibration/validation site in the North Adriatic Sea, adjustment factors in the range of +/-3% for the SeaWiFS channels between 412 and 765 nm have been computed for the pre-launch sensor calibration constants. The utilization of these adjustment factors in the atmospheric correction process is discussed making use of 12 match-ups exhibiting almost coincident in situ and remote sensing data of the study area. Results show differences generally smaller than 10% in the 490 over 555 nm ratio of satellite-derived and in situ normalized water-leaving radiances.