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• high (high albedo) less radiation is absorbed at the earth's surface.  In particular albedo is high where sea-ice is present or there is snow cover.
• low reflectivity (low albedo) more radiation is absorbed at the earth's surface.  The albedo depends upon the characteristics of the underlying surface.

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• for snow-covered areas:
  • at analysis time by a combination of the background climate (climatological 10-day average), satellite measurements, and observed surface fields (notably snow depth and extent).
  • throughout the forecast by snow cover or ice sheets that are produceddeveloped, maintained or reduced by the model.  The albedo varies throughout the forecast period.  
• for snow-free land areas:
  • by a climatology from the MODIS satellite.  This is slow to change through the forecast period.

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It is important to consider the effects of any day-to-day differences from model in albedo values between those deriving from actual conditions and those used in model forecasts.  

Important points are:

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