The atmospheric correction of MODIS imagery for turbid coastal waters

Abstract

The algorithm for retrieving the normalized water-leaving radiance (reflectance) from MODIS imagery is vital to quantitative determination of oceanic color parameters. The standard MODIS atmospheric correction algorithm, designed for open ocean case 1 waters, has been extended for use over turbid coastal waters. Failure of the standard algorithm over turbid waters can be attributed to invalid assumptions of zero water-leaving radiance at near-infrared wavelengths. In the present paper, these assumptions are replaced by assuming that the 748:869-nm ratios for aerosol reflectance and for water-leaving reflectance are spatial homogenous. The new algorithm separates the water-leaving radiance from the aerosol path radiance at 748 and 869nm for relative clear water pixels by solving a set of simple algebraic equations. The performance of the new algorithm is test for imagery of East China Sea. A comparison with in situ radiance spectra shows this atmospheric correction algorithm can achieve very high accuracy and is more rapid than previous algorithm. This new algorithm can be used to the image where no ideal clear waters pixel existed or clear case 1 waters just been covered by clouds in imagery.