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Title assessment of MODIS - aqua chlorophyll-a algorithms in coastal and shelf waters of the eastern Arabian sea
 
Names Gavin, H.
Aneesh A. Lotleker
Peter, I.M.
Ashraf, P.M.
Srinivasa Kumar, T.
Suresh, T.
Raghavan, B.R.
Harilal B. Menon
Date Issued 2013 (iso8601)
Abstract The use of ocean colour remote sensing to facilitate the monitoring of phytoplankton biomass in coastal
waters is hampered by the high variability in absorption and scattering from substances other than
phytoplankton. The eastern Arabian Sea coastal shelf is influenced by river run-off, winter convection
and monsoon upwelling. Bio-optical parameters were measured along this coast from March 2009 to
June 2011, to characterise the optical water type and validate three Chlorophyll-a (Chla) algorithms
applied to Moderate Resolution Imaging Spectroradiometer on Aqua (MODIS-Aqua) data against in situ
measurements. Ocean Colour 3 band ratio(OC3M), Garver–Siegel–Maritorena Model (GSM) and General-
ized Inherent Optical Property (GIOP) Chla algorithms were evaluated. OC3 M performed better than GSM
and GIOP in all regions and overall,was within 11% of in situ Chla. GSMwaswithin24%of in situ Chla and
GIOP on average was 55% lower. OC3M was less affected by errors in remote sensing reflectance Rrs(λ)
and by spectral variations in absorption coefficient (aCDOM(λ)) of coloured dissolved organic material (CDOM) and total suspended matter (TSM) compared to the other algorithms. A nine year Chla time
series from 2002 to 2011 was generated to assess regional differences between OC3M and GSM. This
showed that in the north eastern shelf, maximum Chla occurred during the winter monsoon from
December to February, where GSM consistently gave higher Chla compared to OC3M. In the south eastern shelf, maximum Chla occurred in June to July during the summer monsoon up welling, and OC3M yielded higher Chla compared to GSM. OC3M currently provides the most accurate Chla estimates for the
eastern Arabian Sea coastal waters.
Genre Article
Identifier Continental Shelf Res. 65:14-28