ET from snow

The ET module will remove water from snow storage before any other ET is removed.

1.       ET is removed first from wet snow as evaporation because the energy requirements for evaporation are lower than sublimation. The ET is removed from wet snow at the full rate, assuming that wet snow can be treated the same as ponded water.

2.       If there is no wet snow (either because it is too cold or all the wet snow has been evaporated) then ET will be removed from dry snow as subli­mation.

However, sublimation has a higher energy requirement than evaporation, so MIKE SHE includes a user defined factor for controlling sublimation. This is found on the Snow Melt (V1 p. 239) dialog. The sublimation factor is a multi­plier that reduces the actual ET rate from the snow. If the sublimation factor = 0, then the ET rate is 0. If the sublimation factor = 1.0, then the ET rate is the specified Reference ET rate. Thus,

Maximum ET = (Reference ET) * (Crop Coefficient) * (Sublimation Factor)

See, Reference Evapotranspiration (V1 p. 234) and the Crop Coefficient specified in the Vegetation Properties Editor (V1 p. 403).