The influence of bottom morphology on reflectance: Theory and two-dimensional geometry model

Zaneveld, J. Ronald V., Emmanuel Boss

Limnol. Oceanogr., 48(1_part_2), 2003, 374-379 | DOI: 10.4319/lo.2003.48.1_part_2.0374

ABSTRACT: The reflectance of the bottom is of importance when interpreting optical data in shallow water. Closure studies of radiative transfer, interpretation of laser line scanner data, lidar, and remote sensing in shallow waters require understanding of the bottom reflectance. In the Coastal Benthic Optical Properties experiment (CoBOP), extensive measurements of the material reflectance (reflectance very close to the bottom) were made. Far field reflectance will be needed in carrying out closure of the radiative transfer model and observed radiometric and inherent optical properties. The far field reflectance is the bottom reflectance that includes the effect of bottom morphology (such as sand ripples) as well as the material reflectance. We present here a first-order analytical model to derive the relationship between the material and far field reflectances. We show that the effective reflectance of the bottom is proportional to the average cosine of the bottom slope. Using a simple two-dimensional geometry without scattering and absorption, we show that errors in ignoring the bottom morphology can lead to overestimations of the far field reflectance on the order of 30%.

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