Comparing MODIS daily snow albedo to spectral albedo field measurements in Central Greenland

- Daily spectral snow albedo measurements at Summit Station, Greenland, summer 2011.
- Results are compared to the MODIS v005 and new v006 daily snow albedo products.
- RMSE with MODIS is 0.033 (shortwave), and narrow bandwidths range 0.022-0.077.
- Field measurements show much higher temporal variability than MODIS.
- Temporal variability is controlled by changes in snow grain size.

The albedo of the Greenland ice sheet plays a key role in the energy balance and climate of the arctic. Change in snow albedo values associated with changing climate conditions can be monitored remotely from satellite platforms viewing the entire Greenland ice sheet, yet comparisons to high quality surface measurements are necessary to assess the accuracy of satellite measurements as new snow albedo algorithms are developed with higher spatial and temporal resolution.During May, June, and July 2011, we obtained daily measurements of spectral albedo at Summit, Greenland with an Analytical Spectral Devices (ASD) spectroradiometer, scanning at 350-2200 nm. We compare our spectral albedo field measurements to the Moderate Resolution Imaging Spectrometer (MODIS), using both the Version 005 Direct Broadcast daily albedo product and the recently developed Version 006 MCD43A daily albedo product. The spectral field measurements allow calculation of weighted integrals to compare to seven MODIS narrow bandwidths ranging the UV through Infrared, as well as a broadband integration to compare to the MODIS shortwave albedo. We additionally compare our field measurements to albedo measured at the Baseline Surface Radiation Network (BSRN) station at Summit.Using the MODIS Version 005 Direct Broadcast product, high-quality retrievals only, comparison to field measurements results in root mean square error (RMSE) of 0.033 for the MODIS shortwave product, and RMSE for the MODIS narrow bandwidths ranging 0.022-0.077. The new MODIS Version 006 product shows considerable improvement, with shortwave RMSE of 0.026, and narrow bandwidths ranging 0.020-0.048. These error values for the Version 006 albedo product show an improvement in reported error values from previous MODIS field validations in Greenland, which have been limited to broadband data from the Greenland Climate Network Automatic Weather Stations.