Turbulent transfer relationships over an urban surface. I. Spectral characteristics

A comprehensive study of atmospheric turbulence over an urban surface has been carried out. In this Part I of the study the spectral characteristics are analysed. Results involving all the important atmospheric variables, Measured at two heights (z'/z0=21 and 37) under unstable conditions, are presented, normalized by the respective variances/covariances, and within the Monin‐Obukhov similarity framework. Although the shapes and location of the peaks of the urban spectra/cospectra are in good agreement with homogeneous surface layer data, the analysis of the normalized dissipation rates and spectral correlation coefficients reveals differences which can be attributed to the rough surface. For example, the dissipation of turbulent kinetic energy is relatively small, perhaps owing to an increase in the transport and export of locally produced turbulent energy; there is a very efficient transfer of Momentum which it is suggested may be a result of wake production associated with bluff bodies, and it is found that the transfer of heat and moisture are dissimilar.