Surface chlorophyll a estimation in the Arabian Sea using IRS-P4 Ocean Colour Monitor (OCM) satellite data

The IRS-P4 satellite launched on 26 May 1999 by Indian Space Research Organisation (ISRO) carried an Ocean Colour Monitor (OCM) payload, primarily designed to measure ocean colour, the spectral variations of waterleaving radiance that can be related to the concentration of phytoplankton pigments, coloured dissolved organic matter and suspended particulate matter. Remote sensing data obtained from IRS-P4 OCM sensor is processed for the removal of atmospheric effects of Rayleigh and aerosol scattering to derive normalized water-leaving radiance in visible channels of 412, 443, 490, 512 and 555 nm. Ocean chlorophyll-2 (OC2) global bio-optical algorithm was used to convert normalized water-leaving radiance data to chlorophyll a concentration. For quantitative accuracy assessment, OCM-derived chlorophyll a concentration values were compared to the in situ measurements of chlorophyll a, conducted during ORV Sagar Kanya SK-149c ship cruise during 15-27 November 1999 in Arabian Sea. In general OCM-derived chlorophyll a showed a good correlation (r²=0.90, N= 8, RMS=0.125 mgm^-3) with measured chlorophyll values.