Albedo refers to the percentage of incoming radiation that is reflected. It is specified for a particular wavelength or range of wavelengths. For snow it is generally of interest in the UV through IR part of the spectrum (including visible light).
Snow in general has a very high Albedo, although it can vary widely. For freshly fallen snow it can be up to about .9 (90%), for melting snow about .4 (40%), and as low as 0.2 (20%) for dirty snow.
Wet snow has a lower albedo, so there is a feedback loop involved in the melting process. As the surface snow melts the albedo is lower indicating that less radiation is reflected and more is absorbed. This enhances the melting, which in turn can lower the albedo more.
This glossary is a work in progress and is made possible by AlpenPro.