Comparison of measured and modelled wind and turbulence over London during the 2004 DAPPLE field campaign

Dispersion in urban areas is determined by the complex transport and mixing processes within the street network and ventilation into the boundary layer above. Monin Obukhov similarity theory is often assumed to hold in the urban surface layer above the buildings, assuming a logarithmic wind profile in full adjustment to the urban surface. However, the heterogeneity of the urban surface can lead to growth of internal boundary layers, and hence the assumption of an equilibrium boundary layer should be tested by observations. Simulations of wind profiles in the boundary layer above the urban canopy are hard to verify given the difficulty of measuring wind profiles to sufficient height above the buildings. This talk will present comparisons of measured and simulated wind profiles for the 2004 DAPPLE field campaign. The DAPPLE project (Dispersion of Air Pollution and its Penetration into the Local Environment) had a general aim of characterising street level pollutant dispersion around an intersection in central London, UK. Full-scale measurements included use of ultrasonic anemometers, and a scanning Doppler lidar. Measured data will be compared with output from the UK Met Office Unified Model, used as input to the NAME dispersion model.