Computational modeling of the effect of wind-driven ocean waves on the underwater light field distributions

We have developed a numerical model, which is a combination of ray-tracing and optical propagation, to study underwater downwelling irradiance fluctuations, which occur due to the focusing of light by wind-driven surface waves, at different depths and under various conditions. In particular, to have more realistic results, we utilized the Gerstner model to simulate sea surface waves and to take account of water effects such as scattering and absorption, the point spread function (PSF) of water is used. The effects of physical factors such as wind speed, water depth, and light wavelength on the underwater irradiance spatial distribution, probability density function (PDF) and coefficient of variation (CV) of the irradiance are investigated. Irradiance fluctuations occur at high frequencies immediately below the surface, which means they are related to surface waves with short wavelengths. As we look deeper, the effect of surface waves with longer wavelengths becomes apparent. The simulation also shows the dependence of the average of the downwelling irradiance on the surface profile, depth and incident wavelength. The variance of the irradiance reaches a maximum at a certain depth and then rapidly decreases.