Relating the developing urban boundary layer to upwind terrain for the Salfex 2002 campaign

Due to the heterogeneous nature of an urban surface, the form of the vertical profile of windspeed and turbulence measured at any point is highly dependent on the extent of the upstream fetch over a consistent type of surface roughness. The roughness sublayer extends to several times the building height, and the inertial sublayer may not be well-developed due to close proximity to a roughness change. Understanding how the wind profile develops with distance over a particular urban surface is important when considering the dispersion of pollutants and its dependence on wind direction.

During the Salfex 2002 urban observation campaign, which took place in Salford, Greater Manchester, UK, in May 2002, a sodar was deployed alongside radiosonde ascents, Doppler lidar, and surface turbulence measurements within a street canyon using sonic anemometers. The aim was to investigate the urban boundary layer at a wide range of scales, and to determine the strength of coupling between flow at street level and the boundary layer above. Profiles of wind and turbulence measured with the sodar up to 200m will be presented and related to upstream surface roughness. The results will be interpreted in the light of results from recent wind tunnel and numerical modelling experiments.