COMPARISON OF SIMPLIFIED ALGORITHMS FOR ATMOSPHERIC CORRECTIONS OF MERIS DATA OVER LAND

摘要

This paper describes two approaches to derive ground reflectances from satellite images without the need for any atmospheric observations. The first method makes use of the known reflectance of water, while the second method assumes zero ground reflectance for the darkest pixel in the scene. Both algorithms are very fast since they employ simplified equations for the radiation transport instead of using detailed radiation transport simulations. Additionally a method based on the assumption of a very clear atmosphere has been developed. The algorithms are applied to the different spectral channels of MERIS and to MERIS data of different geographic regions. To estimate the accuracy of the different algorithms when applied to various conditions, the results of the different methods are verified with measured aerosol optical depth retrieved by ground stations. The different methods are furthermore analyzed to determine the effect of modeling errors and uncertainties, i.e. knowledge of the ground reflectance for the first two methods. The results show the strengths and weaknesses of the different methods when applied to MERIS data. Based on these results some guidelines are derived to decide which algorithm should be selected for which conditions, i.e. wave length and geographic region.