Shape Factors, Two-Flow Models, and the Problem of Irradiance Inversion in Estimating Optical Parameters

• Published in: Limnology and oceanography Vol. 34; no. 8; pp. 1426 - 1441
• Main Authors: Stavn, Robert H., Weidemann, Alan D.
• Format: Journal Article
• Language: English
• Published: Waco, TX American Society of Limnology and Oceanography 01-12-1989
• Subjects: Absorptivity; Animal, plant and microbial ecology; Biological and medical sciences; Coefficients; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Irradiance; Marine; Oceans; Optical properties; Radiance; Scattering coefficients; Scattering functions; Sea water; Theoretical Aspects of Hydrologic Optics; Upwelling water; World Oceans; Irradiation; Environmental factor; Inversion; Upwelling; Hydrosol; Optical properties
• ISSN: 0024-3590; 1939-5590
• DOI: 10.4319/lo.1989.34.8.1426

The problem of the inversion of irradiance measurements for the inherent optical properties of a hydrosol such as the world ocean has been examined with the NOARL optical model. This model is a Monte Carlo simulatin of the radiative trasfer equation that, given the optical properties of a hydrosol, generates the zonal radiances and the commonly measured irradiances of that hydrosol. This information allows us to test the optical inversion capability of any irradiance model. We have demostrated that the two-flow model, used often in atmospheric optics, cannot be inverted to yield the inherent backscatter coefficient of natural hydrosols due to the extreme asymmetry of the hydrosol volume scattering function. The asymmetry of the volume scattering function interacting with the radiance distribution introduces parameters called shape factors into the models for irradiance inversion. The presence of shape factors in an irradiance model renders it unsolvable; thus, somplifying assumptions are required for an inverse solution. We inquire into the possibilities for irradiance inversion given the existence of shape factors.