The surface layer above a landscape with a rectangular windbreak pattern

Observations of the surface layer over a landscape with regularly spaced windbreaks were analyzed to determine the lower boundary conditions for use in larger scale models. Under near neutral conditions, the wind profile was used to estimate the average roughness length of the landscape. The observed roughness length is used to validate several aggregation rules for average exchange between a heterogeneous landscape and the surface layer. It is concluded that drag of the windbreaks must be included to find an acceptable roughness length of the landscape.The zero-plane displacement of the windbreak-dominated landscape is negligible in unstable and neutral conditions, but increases to 8 m in stable conditions. The increase of zero-plane displacement is accompanied by a decrease of roughness length and is explained by a transition from wake interference to skimming flow, The influence of the windbreak system on surface layer turbulence and temperature is discussed for stable and unstable stratification.