Evaluation of the Lakshadweep Sea as a site for vicarious calibration of the Ocean Colour Monitor

Abstract

The uncertainty in the top-of-the-atmosphere (TOA) radiance is a result of uncertainties in aerosol components, water-leaving radiance (due to seawater constitutions) and whitecap radiance. This paper investigates the variability of these individual terms over the Arabian Sea and particularly in Lakshadweep region, to establish a site for vicarious calibration of the Ocean Colour Monitor (OCM). We found that fractional coverage of whitecap radiance is less than 0.5% for winds lower than 8 m s⁻¹ and its radiance contribution can be assigned to a constant value. For higher winds, the contribution from whitecap radiance to TOA radiance has to be considered along with the atmospheric stability factor. The Lakshadweep Sea, for most of the time, is characterized by a low concentration of chlorophyll-a, an oligotrophic water body and maritime aerosol.

Acknowledgements

We thank the Director of the Space Applications Centre for his constant encouragement during this research. The suggestions received from the Group Director of the Marine and Earth Sciences Group are also gratefully acknowledged and we thank the reviewer for constructive comments.