Diurnal albedo variation of black spruce and sphagnum–sedge bogs

Diurnal albedo relationships were determined for black spruce (Piceamariana (Mill.) B.S.P.) and sphagnum–sedge bogs in northern Minnesota. Two opposing, cart-mounted, Kipp and Zonen pyranometers traversed a tramway to integrate space and time variations of incoming and reflected solar radiation (waveband 0.3–3.0 microns (μ)).The black spruce stand's diurnal albedo was parabolic. Albedo increased with solar altitude to a maximum at 1200 h (7–8%) and then decreased. Greatest within-season variation occurred during June and September. Canopy roughness was the dominant influence on albedo variation and differences.The sphagnum–sedge type diurnal albedo was M-shaped. A minimum albedo between two maxima occurred at 1200 h. Albedos increased from the 1200-h minimum to each maxima as a result of reported surface 'flattening' effects, increased specular reflection, and changes in solar radiation quality. Albedos before the first and after the second maxima were dominated by the microrelief roughness of the sphagnum–sedge hummocks.