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roughness lenght at the lowest cells

Posted: Tue Mar 10, 2020 8:41 pm
by kac116
Hi all,
I read a previous post about the roughness length (z0) at the lowest cells. I know that a high value of z0 is not recommendable, because z0 is automatically reduced to half the size of the lowest grid cell.
So, if my model has 50 × 50 × 30, the grid resolution is 1, 1, 2, and my roughness length is 0.1 I want to know how to calculate the roughness length at the lowest cells. Is roughness length the same for the 5 lowest cells?
Thank you!

Best regards,

Re: roughness lenght at the lowest cells

Posted: Wed Mar 11, 2020 2:12 pm
by Tim
Hi,

z0 is a parameter of the surface and thus connected to the size of the lowest grid cell. If your resolution is 2 m and you use splitting, the five lowest cells are 0.4 m high each. Max value for z0 would thus be 0.2. Your option of 0.1 would work then.

Best regards,
Tim