Airborne spectral measurements of surface-atmosphere anisotropy during the SCAR-A, Kuwait oil fire, and TARFOX experiments

During the SCAR-A, Kuwait Oil Fire Smoke Experiment, and TARFOX deployments, angular distributions of spectral reflectance for various surfaces were measured using the CAR mounted on the nose of the University of Washington C-131A research aircraft. Spectral bidirectional reflectances of four surfaces are presented: the Great Dismal Swamp in Virginia with overlying haze layer, the Saudi Arabian Desert and Persian Gulf in the Middle East, and the Atlantic Ocean measured east of Richmond, Virginia. Although the CAR measurements are contaminated by atmospheric effects, results show distinct spectral characteristics for various types of surface-atmosphere systems, including hot spots, limb brightening and darkening, and sunglint. In addition, the hemispherical albedo of each surface-atmosphere system is calculated directly by integrating over all high angular-resolution CAR measurements for each spectral channel. Comparing the nadir reflectance with the overall hemispherical albedo of each surface, we find that using nadir reflectances as a surrogate for hemispherical albedo can cause albedos to be underestimated by as much as 95% and overestimated by up to 160%, depending on the type of surface and solar zenith angle.