Airborne spectral measurements of surface reflectivity at ultraviolet and visible wavelengths

Spectral reflectivities at ultraviolet and visible wavelengths (290-500 nm) have been measured from an airborne platform (Cessna light aircraft) at several heights in the boundary layer, and at ground level, using an Optronic Laboratories 742 spectroradiometer with specially adapted input optics. Ground level measurements of vegetation and man-made surfaces show a general increase in reflectivity with wavelength. Airborne measurements over vegetation and ocean (from heights of 700-5500 ft) show an increase in effective reflectivity with the height at which measurements were made and also a reversal in spectral character, so reflectivity decreases with increasing wavelength at height. This suggests significant backscattering from the boundary layer air which rapidly dominates the surface influence for low-albedo surfaces.