Detection of marine aerosols using ocean colour sensors

Ocean colour sensors are equipped with atmospheric correction bands operating in the near infrared region of the spectrum. At these wavelengths, the ocean surface, because of high infrared absorption by water, acts as a dark background and the sensor detected radiance is due to solar radiation backscattered by the atmospheric air molecules and aerosols called Rayleigh and aerosol path radiances respectively. From the radiances in the atmospheric correction bands, after accounting for Rayleigh path radiance, it is possible to determine aerosol parameters like aerosol optical depth (AOD) and particle size distribution index. While sensors like IRS P3 MOS-B, IRS P4 OCM, NOAA-AVHRR, etc detect AOD in the total atmospheric column, IRS P3 MOS-A sensor can detect AOD in two atmospheric layers by exploiting the differential absorption property of oxygen at four narrow band channels at the O2 A band around 760nm. The method of determination from ocean colour sensors and the results from IRS P3 MOS-B, IRS P4-OCM and IRS P3 MOS-A radiance data are presented and discussed.