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WIND FIELD

Posted: Tue Sep 15, 2020 6:09 pm
by T.P.A
Hi Tim,
I've been working with ENVI-met for months, and now I've a new question.
I want to see the performance of wind within and surrounding a depression on the ground.

I've established Simple Forcing, with the following Initial meteorological conditions:
-Wind speed measured in 10m height (m/s): 4
-Wind direction (deg): 270
-Roughness length at measurement site: 0.001

I've read that “the wind speed is always assumed to be 0m/s at ground level (0m). For the top of the model it is extrapolated logarithmically to 2500m from the next lower height level for which a value is given”
I’ve forced the wind speed at 10m, so I expected the wind field has been, 4m/s at 10m, less in the lower levels to 0m/s at ground level, and 4m/s constant to the higher levels.
However, when I simulate with Z=40m, the wind speed never reaches 4m/s.
So… I do not understand the specific behaviour of wind speed.
The wind velocity of 4m/s is forced at 10m or at the top of the model, at 2500m?
I attach the vector layer of my model to facilitate the understood of my question.

Best regards.
Teresa

Re: WIND FIELD

Posted: Wed Sep 16, 2020 12:22 pm
by Tim
Hi,

I think your quote is about FullForcing. However, you are right that the 4 m/s in 10 m cannot be found in the simulation results. It is not like the temperature or humidity values which are attached at the inflow border in the specified height. The geostrophic wind in 2500 m is calculated logarithmically by the wind speed, height of 10 m and z0. A new wind profile is then calculated together with basic exchange and mixing coefficients for each height.

Best regards,
Tim

Re: WIND FIELD

Posted: Mon Sep 21, 2020 7:15 am
by T.P.A
Okay... However is a little bit difficult to understand the method...
I'll remember that.

So grateful for you response.
Best regards