<title>External factors and water Raman scattering in clear ocean waters: skylight, solar angle, and the air-water interface</title>

Abstract

Water Raman scattering is influenced by the optical factors external to the clear marine hydrosol or bounding it (the air/water interface). At shorter wavelengths (< 490 nm) detectable water Raman scattering is confined to the near surface layers, where an increase in solar zenith angle increases the water Raman emission. Among the effects of water Raman scattering is an increase in the irradiance ratio (reflectance) of the surface layers. Skylight tends to lessen the production of water Raman scattering by a few percent at shorter wavelengths. At longer wavelengths (> 500 nm) the surface effects disappear as hydrosol absorption becomes the dominant factor. However, at depth large solar zenith angles cause `shoaling' of Raman production, i.e., water Raman scattering effects occur closer to the surface layers than is the case for smaller zenith angles. The water leaving irradiance, significantly affected by Raman emission in clear ocean waters, changes little or not at all with solar zenith angle.