Adjustment of color indices for the Far East region using MUMM atmospheric correction
A.I. Aleksanin1,2, M.A. Lebedev2
1Institute of Automation and Control Prosesses Far Easten Branch of the Russian Academy of Science, Vladivostok, Russia
2Far Eastern Federal University, Vladivostok, Russia
Keywords: ocean color indices, atmospheric correction, MUMM algorithm, MODIS/AQUA, AERONET-OC, chlorophyll a concentration
Abstract
Bio-optical parameters of seas of the Far East region obtained from the MODIS/AQUA radiometer data are analyzed. The results of two main atmospheric correction algorithms based on the following assumptions are compared: the absence of water-leaving radiance in the near-infrared spectral bands and the stability of the sea water spectral shape in this range (MUMM). Verification was carried out using data of Japanese and Korean AERONET-OC stations. An approach to improving the results of MUMM atmospheric correction by using a regional adjustment of the color indices is considered. The MUMM correction after adjustment is not inferior to NIR correction in terms of the calculation accuracy of chlorophyll- a concentration. It was found that the recommended NIR correction leads to negative reflectivity coefficients Rrs at a wavelength of 412 nm in 10% of cases. These cases correspond to highly trophic waters and are accompanied by an overestimation of the chlorophyll-a concentration by an average of 1.8 times. The proposed correction of the color indices does not lead to negative values of Rrs; the color indices in the blue spectral range have significantly lower errors than those of the NIR algorithm. The proposed approach ensures more reliable estimates of bio-optical parameters of the sea based on satellite data.
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