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• downwards from the atmosphere (e.g. by advection of warmer air,  by insolation, or by underlying an area of warm based cloud). 
• upwards from lower in the snowpack, though this could be offset by latent heat extraction where melting of snow occurs.

Over flat terrains:

• for snow depth <12.5cm only only one snow layer is modelled (Fig1A).  Note: Partial cover of the 'tile' is assumed if snow depth is less than 10cm. 
• for snow depth >12.5cm the number of snow layers varies up to a maximum of 5 layers according to the total snow depth (Fig1B).

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• permanent snow is defined as snow depth ≥1000cm with 5 snow layers (Fig1C).

Fig1A: Schematic representation of the multi-layer snow scheme. Shallow snow layer.  Snow depth <12.5cm.  (Note: Snow depth < 10cm implies only a partial cover of snow) 

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