On the influence of wind and waves on the underwater light field

Abstract

Abstract. We present a detailed study of the influence of various wind and wave conditions on the distribution of downwelling irradiance within the upper ocean mixed layer down to 100 m water depth. The work is based on a two-dimensional Monte Carlo radiative transfer model with high spatial resolution. We treat conditions that are favorable for the development of extreme light fluctuations, e.g. light at 490 nm and very clear oceanic water. Local wind determines the steepness of capillary-gravity waves which in turn dominate the irradiance variability near the surface. Maximum irradiance peaks that exceed the mean irradiance by a factor of more than 10 can be observed at low wind speeds up to 5 m s−1. Sea states influence the light field much deeper; gravity waves can cause considerable irradiance variability even at 100 m depth. The simulation results show that under realistic conditions 50 % radiative enhancements compared to the mean can still occur at 30 m depth.