Abstract
In this paper non-neutral approaching flows were employed in a meteorological wind tunnel on a regular urban-like array of rectangular buildings. As far as stable stratication is concerned, results on the flow above and inside the canopy show a clear reduction of the Reynolds stresses and an increment of the Monin-Obukhov length up to 80%. The roughness length and displacement height were also affected, with a reduction up to 27% for the former and an increment up to 5% for the latter. A clear reduction of the turbulence within the canopy was observed. In the convective stratication cases, the friction velocity appears increased by both the effect of roughness and unstable stratication. The increased roughness causes a reduction in the surface stratication, reflected in an increase of the Monin-Obukhov length, which is double over the array compared to the approaching ow. The effect on the aerodynamic roughness length and displacement height are specular to the SBL case, an increase up to 55% of the former and a reduction of the same amount for the latter.