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In addition to the “normal” model area as defined in the Area Input File, ENVI-met creates an area of nesting grids around the core model in order to move the model boundary away from the area of interest and to minimise undesired boundary effects.
Different to ENVI-met version 2.x, the number of nesting grids as well as the soil profiles used for the nesting grids are now stored in the Area Input File, not longer in the configuration file.
Therefore, the purpose of the [NESTINGAREA] section is different to its meaning in the versions before.
From ENVI-met 3.1 on, the model has improved the handling of the nesting grids in terms of shortwave radiation fluxes. As no objects can be placed inside the nesting area, the solar radiation can reach the surface undisturbed which often results in an unrealistic high temperature of the ground surface in the nesting area, especially when non-evaporating surface materials have been used.
The new model version allows to use an averaged solar radiation on the ground surface inside the nesting grid area instead of the original one. Using this option, the solar input at the ground surface is averaged over all free grid points inside the core model and is used as solar input for the nesting grids. If, for example, 50% of the ground in the main model is shaded by buildings or trees, the solar input used in the nesting grids will also be only 50% of the actual possible solar input. This procedure ensures, that the average radiative conditions found in the core model area are also used in the nesting area. Without this modification, the model behaves as if your core area is surrounded by flat terrain without any shading (which might be true in some cases).
You can turn this modification on or off by setting “1” or “0” in the first option line:
00: [NESTINGAREA]__________Settings for Nesting area 01: Use aver. solar input in nesting area (0:n,1:y) = 1 02: Include nesting grids in output (0:n, 1:y) = 0
What do the lines mean?
01: Use aver. solar input in nesting area (Default 1, yes)
Turns the solar input averaging as described above on or off.
02: Include nesting grids in output (Default: 0, no)
Defines if the nesting area should be included in the output files or not.