AN ANALYSIS OF THE CIRCULATION CHARACTERISTICS AND ENERGY BUDGET OF ADRY, ASYMMETRIC, EAST-WEST URBAN CANYON .1. CIRCULATION CHARACTERISTICS

Wind characteristics within urban canyons are of considerable signific ance for pollution diffusion, for assessing the nature of the atmosphe ric environment at street level, and in determining the energy budget of the canyon. This study presents an analysis of the circulation char acteristics for a deep, east-west, asymmetric urban canyon (located in Columbus, Ohio, USA), based on measurements of ambient wind at roof l evel, vertical velocities at the canyon-top, and within-canyon horizon tal winds. Canyon-top vertical velocity was normally directed upward, even with cross-canyon winds, indicating along-canyon horizontal conve rgence. Its speed was approximately related to the magnitude of the so utherly, easterly, and westerly components of the roof-level wind. Thr ee-fifths of the data sets showed evidence of a vortex circulation sup erimposed upon the mean vertical motion, although its speed and direct ion were not clearly related to the direction of the cross-canyon wind . Some of the perplexing aspects of the results may be attributable to the asymmetric structure of the canyon. Overall, these results sugges t that wind fields within and above urban canyons may not be as simply as empirical studies hitherto have suggested and that attempts at mod elling these characteristics of the urban climate must recognize this.