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These processes are mostly not well resolved because of their small scales compared to model resolution.  To deal with this, they are handled by physical parameterisation in a statistical way that describes the mean effect of sub-grid processes.

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Other models running at the same time describe energy, moisture and momentum fluxes from the underlying land or sea water surfaces.  These are:

• the land-surface model (HTESSEL).  
• the lakes and coastal waters model (FLake).  This also provides information on water temperature changes and the development , and decay and movement of areas of ice.  The forecasts of ice cover impact upon heat flux and albedo.
• the Wave Model (ECWAM).
• the Dynamic Ocean Model (NEMO).  This includes a program (LIM2) which provides information on the development, decay and movement of areas of sea ice.  The forecasts of ice cover impact upon heat flux and albedo.
  
  

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Fig2.1.2: A schematic pie-chart showing approximate proportions of computer processing time during execution of an atmospheric model forecast based on T799 (regular 25km resolution on regular grid) and 91 levels (.  The current resolution for ENS is T_co1279 (9km resolution) and 137 levels).   Parameterised physical processes consume about 30% of computer processing time.  Computations in grid point space and spectral space together take about 20% of computer processing time while rather more time (~27%) is taken in transposing data from one space to the other.

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