Page History

...

Forecast air temperature at 2m is derived by interpolation between: 

• the model forecast temperature at the lowest model level (L137 at 10m) and 
• the model forecast temperature of the underlying surface (the skin temperature). 

The skin temperature is itself derived using HTESSEL which employs one or more “tiles” to describe the characteristics of the land.  These “tiles” evaluate heat fluxes into and from the underlying surfaces.

...

• exposed snow - for areas without vegetation above the snowpack, and therefore without interference to the weak incoming and outgoing heat and momentum fluxes.
• forest snow - for areas where there is tree cover sufficient to interfere with incoming and outgoing heat and momentum fluxes.   The heat flux at the snow/atmosphere interface is rather larger than over exposed snow. 

Widespread benefits are seen in the northern hemisphere winter troposphere, particularly the Rocky Mountains and Tibetan Plateau areas.  Results show in improvements in geopotential height, vector wind and humidity forecasts.

...

Fig2.1.4.4-3: Schematic representation of the multi-layer snow scheme for permanent snow (e.g. Greenland, Antarctica) and for glaciers.  Snow depth is defined as ≥10m.   Any additional snow accumulation is added into the fifth snow layer.  This is ito to preserve the characteristics and thermal flux qualities of thinner layers at the top of the snowpack.

...