Caption title. At head of title: Project summary. Distributed to depository libraries in microfiche. "August 1982." "EPA/600-S3-82-062."

The structure of turbulence in the urban surface boundary layer is discussed. Wind and temperature fluctuations were measured with fast-response sensors at a height of 31 m in four land-use areas in the St. Louis environs (a rural and three urban sites). The second moments of the fluctuations were computed for one-hour time series and analyzed within the framework of the Monin-Obukhov similarity theory (i.e., normalized by appropriate velocity and temperature scales). The results are discussed relative to observed land-use features and calculated surface roughness lengths for each of the sites. Average surface roughness lengths ranged from 0.7 to 1.7 m for the urban sites, varying by several meters as a function of wind direction at individual sites. The normalized velocity and temperature variances for the rural site were consistent with the Monin-Obukhov similarity theory. For the urban sites, plots of the normalized velocity variances showed an orderly departure from similarity theory for both neutral and unstable stratifications; they were smaller than the corresponding normalized variance for the rural site. The urban anomalies to similarity theory are discussed relative to the terms in the turbulent kinetic energy budget equation. For neutral stratification, the anomaly is suggested to be due to the wake region of the roughness elements extending to near the height of the measurements. For unstable stratification, it is suggested to be due to increased importance of vertical transport processes within the urban area. Ancillary analyses suggest that the spectral peak wavelength may be a more appropriate scaling length for free convection similarity than the height of the mixed layer, z,. During the afternoon transition period the two scales may differ significantly.