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Note: HRES and Ensemble Control Forecast (ex-HRES) are scientifically, structurally and computationally identical.  With effect from Cy49r1, Ensemble Control Forecast (ex-HRES) output is equivalent to HRES output where shown in the diagrams.   At the time of the diagrams, HRES had resolution of 9km and ensemble members had a resolution of 18km.

Derivation of 2m Temperatures

Model output of 2m temperature is a diagnostic.  It is not a direct output from the atmospheric model.  Forecast screen level variables are not directly evaluated but are determined via knowledge of the the lowest model level temperature (at 10m) and the "skin" temperature of the underlying surface.  In turn the skin temperature is determined via the land surface scheme HTESSEL, or the lake surface scheme FLake, or the sea-surface temperature (through NEMO). 

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Fig9.2-1:  Values at the 2m level (e.g. temperature) are not taken from a model level as such but are computed via interpolation between skin temperature and the level of the lowest atmospheric model level (level 137). 2m dew point is derived from the humidity interpolated in a similar way.  The nature of the interpolation profile used depends on other factors, such as wind speed.

Additional Sources of Information

(Note: In older material there may be references to issues that have subsequently been addressed)

• Read more on "Reducing surface temperature errors at coastlines".
• Read more on Bias in IFS.

(FUG Associated with Cy49r1)