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Fig2A.1.4.1-2: An example of the variability of land surface within an approximate grid box illustrating the difficulty in assigning representative HTESSEL "tiles" for the whole grid square area.  The red lines show the extent of a very approximate 9km x 9km schematic Ensemble control forecast grid square.   The flag locates the grid point.  There is a large variation in ground surface type and the proportional contribution to the heat, moisture and momentum fluxes are difficult to assess.   The tile allocation for this grid box is approximately: high vegetation 7%, low vegetation 70%, estuary (lake) 20%, urban 3%.  An ENS meteogram is interpolated from the four grid points surrounding a given station within the box.  See Section on Selection of grid points for Meteograms for details.

Fig2A.1.4.1-3: An example of the variability of land surface within an approximate grid box illustrating the difficulty in assigning a representative HTESSEL "tiles" for the whole grid square area.  The red lines show the extent of a very approximate 9km x 9km schematic Ensemble control forecast grid square.  The flag locates the grid point.  There is some variation in ground surface type but it is predominantly covered by evergreen needle leaf trees.  The proportional contribution to the heat, moisture and momentum fluxes are rather simpler to assess than in Fig2A.1.4.1-2.  In winter snow the tile would be assigned as forest snow.  Runoff would be rapid over Rocky Mountain sides, much slower over low-lying river valleys.   The tile allocation for this grid box is approximately: high vegetation 75%, low vegetation 5%, lake 5%, bare ground 5%, urban 10%.  An  ENS meteogram is interpolated from the four grid points surrounding a given station within the box.  See Section on Selection of grid points for Meteograms for details.

Additional sources of information

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• Read more on HTESSEL in atmospheric physics documentation and scroll down to Soil/Surface. 
• Read more on leaf area index.
• Read more on the ECMWF land surface model developments.
• Read more on a revised hydrology for the ECMWF model.
• Other sources of information on HTESSEL (external to ECMWF) are at:
  • https://www.mdpi.com/2073-4433/12/6/723 (ECLand Land surface Modelling System)

(FUG Associated associated with Cy50r1)