Photosynthetically available radiation in the
central and eastern Arabian Sea

T. Suresh, Elgar Desa, R. G. P Desai, A. Jayaraman*and P. Mehra

National Institute of Oceanography, Dona Paula, Goa 403 004, India
*Physical Research Laboratory, Ahmedabad 380 009, India

In this article, we present the analysis of the photosynthetically available radiation (PAR, 400-700 nm) in the eastern and central Arabian Sea ( 21^o 30^o N, 64^oE to 12^oN, 74^oE) during February-March, 1995 using data collected with quantum PAR sensor and maritime solar radiation models for clear sky. The peak values observed were in the range of about 1700 to 1830 umole s^-1m^-2 or equivalent to about 365 to 435 Wm^-2. The radiative transfer models of Gregg and Carder, and Frouin et al were used to investigate the relationship between the quantum and energy of solar radiation available in the PAR region. The average ratio of this quanta per energy was found to be about 4.2 umole W^-1s^-1. Aerosol optical depth obtained using the sunphotometer at 498 nm for the region was found to vary from 0.07 to 0.19.