Our previous studies showed that the Fluorescence Line Height (FLH) product, which uses 3 NIR bands at 667, 678, and
746 nm on the MODerate-resolution Imaging Spectroradiometer (MODIS) sensor, and similar bands on MERIS sensor,
is not reliable in coastal waters because of a peak in the elastic reflectance spectra which occurs due to the confluence of
chlorophyll and water absorption spectra and which overlaps spectrally the chlorophyll fluorescence. This combination
of two overlapping peaks makes fluorescence signal retrieval inaccurate. As a consequence, the present FLH algorithm
significantly underestimates fluorescence magnitudes in coastal waters. To overcome this problem, we introduce a new
and more accurate approach for the retrieval of FLH in turbid waters by the MODIS sensor, which exploits the
correlation between the blue-green and red bands reflectance ratios. We show that by making use of the combined
remote sensing reflectance's (Rrs) at 488nm, 547nm, 667nm and 678nm we can retrieve fluorescence accurately in case
2 waters even for low fluorescence quantum yield when fluorescence magnitudes are low. The derivation and validation
of our algorithm was performed using extensive synthetic datasets which cover a large variability of parameters typical
of coastal waters: with CDOM absorption at 400nm 0-2 m-1, mineral concentration 0-5g/m3 and chlorophyll
concentration of 0.5-100 mg/m3. In addition, we applied this proposed algorithm to MODIS satellite data and compared
it with the traditional FLH algorithm.
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