ATMOSPHERIC CORRECTION OVER COASTAL AND INLAND WATERS: DOING BETTER WITH MERIS?

摘要

This work first illustrates the potential use of the oxygen absorption in improving the atmospheric correction over water. First, this oxygen absorption can be used to better flag cloud contamination, mainly with cirrus clouds. It can be used as well to better flag the sunglint complementary to the current radiometric classification. After flagging these anomalous circumstances, we propose simple methods to remove both the contribution of the cirrus clouds and of the sunglint. It appears more to be new developments rather than new operational methods. But the recommendations to conducts such studies are straightforward. First of all the simplified "6S" like formulation of the signal should be validated by reference to "exact" computation. Then, this formulation has to be applied on an operational basis at least to remove the Rayleigh contribution. The remaining will inform on the effective altitude of the scatters. Regular values will inform on the vertical distribution of the aerosols, higher values will flag cirrus clouds and lower values will reflect the sunglint contribution. Then a correct identification will offer possibilities to correct for cirrus clouds as well as for sunglint. MERIS full resolution imagery offers the possibility to do water quality monitoring near to the coast line and or in inland waters. This opportunity raises first the problem of the adjacency effects. We simply illustrate this effect knowing than a theoretical formulation of the problem exits. For inland waters, both land and water algorithms exist to remote sense the aerosols. We propose simple comparison between the two as indicators of the quality of the atmospheric correction.