Meris imageries to investigate surface chlorophyll in the upper gulf of Thailand

Abstract

Medium Resolution Imaging Spectrometer Instrument (MERIS) Level 2 data were used to investigate the seasonal patterns of surface chlorophyll-a (chl-a) distribution related to eutrophic conditions in the upper Gulf of Thailand (UGoT). Initial overestimation of chl-a using MERIS Rrs was reduced when Rrs ratios were used. A local in-water algorithm, named Chula algorithm, was embedded into MERIS data due to higher accuracy in chl-a prediction, compared to standard MERIS chl-a products. Subsequent MERIS-derived chl-a maps revealed that during the northeast monsoon, high chl-a water moves westward, while during the southwest monsoon, it accumulates in the northeast corner of UGoT. These seasonal patterns of movement agree well with previous investigations on seasonal circulation and red tides in UGoT. Compared to other satellite data having larger spatial resolutions, MERIS chl-a images provide more details on chl-a distribution which may be useful for oceanographic studies in such a small coastal area as UGoT