Regular papers

Monte Carlo code for the study of the dynamic light field at the wavy atmosphere-ocean interface

Institute of Coastal Research, Helmholtz-Zentrum Geesthacht (HZG), Max-Planck-Str. 1, 21502 Geesthacht, Germany

^* martin.hieronymi@hzg.de

Received: 3 May 2013
Revised: 7 June 2013

Abstract

A radiative transfer model has been developed to study the solar radiation budget at the wave-deflected air-sea interface. The model is used to characterize fluctuations of the underwater light field, i.e. down- and upwelling irradiance, irradiance reflectance, and upwelling radiance just below the surface, subject to changing sun zenith angles and percentages of diffuse sky radiation to the total insolation. The focusing of sunlight is most effective under clear skies; the variability of downwelling irradiance is significantly smaller under overcast conditions. In general, maximum and deep-reaching fluctuations arise at high sun positions, but the behaviour is much more differentiated and exceptions are discussed. Furthermore, wave shadowing effects have been studied; these become increasingly important for low sun elevations. There are indications that the light transmission into water up to now is overestimated for solar zenith angles near the horizon.