Direct measurement system of water-leaving albedo in the field by the skylight-blocked approach: Monte Carlo simulations

Water-leaving albedo ( α w ( λ )) is an important component of the ocean surface albedo. Direct measurement of α w ( λ ) in the field is not yet available due to difficulties in removing the contribution of surface-reflected solar radiation. Following the concept of the skylight-blocked approach (SBA), a novel system, termed α w SBA, is proposed in this study to directly measure E w ( λ ), where a wide-angle black cone is used to block the surface-reflected radiance. The shading errors associated with the cone and the measuring system are examined via Monte-Carlo (MC) simulations for a wide range of water inherent optical properties (IOPs), solar zenith angle, and different configurations of the α w SBA system ( i.e. , half cone angle, and the length of supporting arm). Based on sensitive analysis using MC simulations, an optimal configuration of α w SBA is recommended. We further propose a mathematical expression to parameterize the shading error ( ɛ ), along with an error correction scheme ( α w OPT). It is found that, with the optimal configuration and α w OPT, the uncertainties of obtained α w ( λ ) by α w SBA are generally less than 7% for a wide range of waters with different IOPs and particulate scattering phase functions.