In this study, the accuracy of the MODerate resolution Imaging Spectroradiometer (MODIS) combined Terra (MOD) and Aqua (MYD) 16-day albedo product (MCD43) is evaluated through comparisons with eleven years of in situ measurements at 17 automatic weather stations on the Greenland Ice Sheet. Taking into consideration accuracy issues with in situ observations, results show that utilizing all high-quality, cloud-free MODIS retrievals gives physically realistic ice sheet albedo values for solar zenith angles less than 75°, with a root-mean-square error of 0.067 (RMSE) and an overall mean bias of +. 0.022 (with the MODIS data biased slightly high relative to the in situ data). Using this data set, changes in ice sheet albedo from 2000 to 2012 are documented. Analysis reveals negative trends in ice sheet albedo during summer over the 13-year data record, with persistent negative albedo anomalies in recent years over western Greenland. During summer 2012, extensive surface melt resulted in a Greenland area-averaged albedo anomaly for June, July August relative to 2000-2009 of -. 0.044 that significantly increased the amount of total absorbed solar radiation and surface melt.
- Programområde 5: Natur og klima