Air flow in the urban roughness sublayer is much more complex than its counterpart in the atmospheric surface layer. This is due to the much larger size of the roughness elements and the unevenly distributed heat sources. Thus, the use of surface layer similarity theory (SLST) for the parameterization of the mean flow is limited. Recent evidence from wind tunnel experiments indicates that the basic assumption of SLST, i.e., the constancy of momentum fluxes in the vicinity of the roughness elements, is not fulfilled, Kastner-Klein (2001), Ashie (2000). In both experiments a sharp maximum of the momentum flux was observed above the roughness elements. Kastner-Klein (2001) suggested that in spite of the inconstancy of the momentum flux, a logarithmic velocity law may be reproduced with u obtained from a single reference point. The aim of this paper is to investigate the momentum flux and the wind profile above the roof level in a real urban environment.
展开▼
