Spatial filter for log law of the wall

[cbegeman]

Since log law of the wall holds in a spatially-averaged sense, Bou-Zeid et al. (2015) filter the resolved velocity near the wall by 2 times the grid size. The current version of the code has some averaging but perhaps not enough:
https://github.com/xylar/palm_les_lanl/blob/c293074463bb0bda5a6796182b56793a1d163d91/trunk/SOURCE/surface_layer_fluxes_mod.f90#L1054-L1055
(these terms are used to define the surface stress). What do you think about averaging u(i,j,k),u(i+1,j,k),u(i,j+1,k),u(i+1,j+1,k) for the surface stress calculation instead (and likewise for v)? It's probably a minor effect but I don't think it would hurt to implement.

[xylar]

I agree, more spatial averaging would likely make some sense. I think the averaging that you point to is just to move from the respective edges to cell centers, so it's not really intended for smoothing purposes.