Interpretation of hydrosol reflectance

Sensitivity of volume bidirectional reflectance of a deep, homogeneous body of water to measurement conditions (solar zenith angle, ratio of sunlight irradiance to skylight irradiance) and medium optical parameters (single scatter albedo, scattering phase function) is analyzed by singular eigenfunction solution of the radiative transport equation. Volume reflectance is shown to be non-Lambertian, and dependent on sunlight/ skylight irradiance ratio. Deviation of volume reflectance from Lambertian behavior is shown to be strongly dependent on phase function peaking, with deviation increasing with peaking. For forward/backward phase function peaking of 180, fractional deviation from Lambertian behavior at from the normal direction is approximately 0.15, at approximately 0.30. Fractional change in reflectance magnitude as sunlight/ skylight irradiance ratio changes from 3.00 (hazy sky) to 1.00 (lightly cloudy) is shown to be approximately 0.10.