Comparison of CERES and MODIS surface albedo products over cryosphere

Surface albedo is an important input parameter in climate research and weather forecasting. Charlock et al recently showed that surface albedo forcing (the difference of computed fluxes for the natural target and fluxes re-computed assuming zero surface albedo) is comparable with cloud forcing over cryosphere. This work addresses the differences in some existing surface albedo products in the areas covered with snow or ice.

In this work we analyzed existing surface albedo products such CERES SARB surface albedo, MODIS albedo derived from MODIS BRDF product ground measurements from 2000 to 2009. We also analyzed CERES and MODIS products over permanently ice/snow covered areas such as Greenland.

It was shown that MODIS TERRA is ~3% brighter than CERES TERRA under clear sky conditions and ~1% while under overcast conditions. Comparison of CERES and MODIS products with the ground measurements in Fort Peck, Montana shows that these satellite retrievals are 9% and 8% darker, respectively.

The difference between MODIS and CERES albedo is explained with calibration problem with CERES. The problem is already addressed in forthcoming new edition of CERES product. It is also important to mention that MODIS product is 16-day average product thus it is not sensitive to fast surface changes while CERES product is instantaneous.

We will also discuss the reasons for discrepancy between satellite and ground measurements of albedo.