Intercomparison between in situ and AVHRR polar pathfinder-derived surfaceAlbedo over Greenland

The Advanced Very High Resolution (AVHRR) Polar Pathfinder (APP) data provi des the first long-time series of consistent, calibrated surface albedo and surface temperature data for the polar regions. Validations of these produ cts have consisted of individual studies that analyzed algorithm performanc e for limited regions and or time periods. This article reports on comparis ons made between the APP-derived surface albedo and that measured at 14 aut omatic weather stations (AWS) around the Greenland ice sheet from January 1 997 to August 1998. Results show that satellite-derived surface albedo valu es are on average 10% less than those measured by the AWS stations. However , the station measurements tend to be biased high by about 4% and thus the differences in absolute albedo may be less (e.g., 6%). In regions of the ic e sheet where the albedo variability is small, such as the dry snow facies, the APP albedo uncertainty exceeds the natural variability. Further work i s needed to improve the absolute accuracy of the APP-derived surface albedo . Even so, the data provide temporally and spatially consistent estimates o f the Greenland ice sheet albedo. (C) 2001 Elsevier Science Inc. All rights reserved.