Turbulence Measurements in the Urban Boundary Layer and Comparison of Roughness Length with Land Use

Results will be presented of measurements made during experimental campaigns in the urban environment of Birmingham UK, a city of approximately 1 million inhabitants. The campaigns took place within a factory complex, in a mixed industrial and residential area in the northeastern quarter of the city. Turbulence data were collected in 1998 using sonic anemometers mounted at heights of 30m and 15m, and in 1999 at heights of 45m and 15m. Various other met instruments were also deployed during these campaigns. Initial results will also be presented from a study scheduled for summer 2000, in which sonic anemometers will be deployed at 75m, 45m, 30m and 15m.

The results from 1998/99 show that calculated displacement heights and roughness lengths are comparable to those of other urban studies. Mean wind shear, potential temperature gradient and vertical-velocity variance also compare well with local Monin-Obukhov scaling. Finally it will be shown that the mean roughness lengths calculated at the highest measuring position increase in a quantitatively plausible manner with the fraction of upwind urban and suburban cover in the source area, calculated using a source-area model.