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Table 2.1.4.1-1: Assignment of height characteristic and vegetation coverage for each type of vegetation or surface.  In cases of snow, vegetation assigned as high (H) can have snow cover beneath; vegetation assigned as low (L) are considered as snow covered.  See "Modelling snow" section.  The assigned vegetation coverage gives information to the soil model regarding transpiration and root depth.  See "Modelling soil" section.   Albedo values are associated with the Leaf Area Index.

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Fig2.1.4.1-2: 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 (ex-HRES) 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.

Fig2.1.4.1-3: 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 (ex-HRES) 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.  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.

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