Roughness parameters over regular rough surfaces: Experimental requirements and model validation

This paper discusses the possibilities to evaluate the aerodynamic roughness of a homogeneous building group by experiments or by analytical models. It is shown that experimental errors - and as a consequence model uncertainties - in z(o) can be larger than a factor 2. The various error sources are discussed, and suggestions are given for improved experiments. Finally, the effects of the propagation of z(o) errors are discussed, as well as wind engineering and environmental applications of roughness modelling.