Albedo

Albedo

The albedo is taken purely from climatological data.  

The albedo for:

• open snow (includes snow on low vegetation) changes with age but is broadly ~0.85 for fresh snow to ~0.50 for old snow.  
• forest snow (snow beneath high vegetation) depends on vegetation type.  It is broadly ~0.3 just after a heavy snowfall  decreasing to ~0.2 after a few days due to snowmelt (for sufficiently warm temperatures) or wind drift (for cold temperatures).
• ice depends on snow cover but varies between ~0.7 with snow and ~0.4 without snow.
• open water, lakes and sea is <0.1

Considerations

Users need to be aware of the potential effect of any day-to-day anomalies.

• Any likely differences in albedo not captured by the forecast (e.g. in mountainous areas or where observed conditions vary from forecasts).
• Anomalous snowfall is not represented - the albedo chart is purely climatological and anomalous conditions are not taken into account.
• Widespread anomalous snowfall or snowmelt will change the heat energy available to the varying surfaces.
• Transitory local but significant variations in surface characteristics (e.g. extensive burnt vegetation, seasonal variation in lake extent) are not represented.

Additional sources of information

(Note: In older material there may be references to issues that have subsequently been addressed)

Fig2.1.18: Example surface albedo as shown in the surface parameters charts.  The albedo is taken from climatological data on a monthly basis.  Anomalous snowfall has not had an effect.  Higher (whiter) values mean more reflection of incoming radiation and therefore less energy for absorption by the varying surfaces.  See the current albedo chart.