Spatial and temporal variations in surface albedo of a subarctic landscape using surface-based measurements and remote sensing

Spatial and temporal variation in summertime albedo of a subarctic landscape near the Hudson Bay coast is examined using ground-based measurements and Landsat Thematic Mapper (TM) imagery. Temporal variation in surface albedo was determined using an extensive data set from six tower sites with multiple years of data. Four distinct patterns in evolution of the seasonal trend in daily albedo were discovered for the six sites and appeared to be related to vegetation and surface moisture characteristics. All sites showed an albedo response to solar zenith angles greater than 60 degrees, at smaller zenith angles hourly albedo was a good representation of daily values. TM imagery from a dry year (1984) and a wet year (1991) were used to derive maps of albedo for the study area. Spatial variation of albedo was examined within representative training areas centered on the six tower sites. The magnitude of spatial variation in albedo was typically less than 0.04 for all sites. Spatial variability was slightly greater in the wet year. A one pixel transect of albedo across the study area showed the largest difference between lakes and terrestrial surfaces. However, within the terrestrial zones, alternating patches of open forest and tundra and differences in wetness create a coherent pattern in albedo across the landscape.