GASEOUS POLLULANT DISPERSION AROUND URBAN-CANOPY ELEMENTS - WIND-TUNNEL CASE-STUDIES

There is an evident lack of reliable and detailed in situ measurement data for verifying numerical predictions of atmospheric dispersion in the urban environment on sub-meso scales. Wind-tunnel studies of dispe rsion around typical elements of the urban canopy (isolated buildings, groups of buildings, street canyons) could provide valuable substitut es for field datasets. They can achieve a high resolution of the measu red concentration fields, and may be used for evaluation of numerical models and for expert estimates of air quality in the urban environmen t. This paper presents results of several case studies of gaseous poll utant dispersion in a neutrally stratified wind-tunnel flow. The follo wing cases have been investigated: (1) Point source: (a) isolated rect angular building, and (b) isolated U-shaped building; (2) Line source in a street canyon: effects of the upwind building configuration and t he roof shape; (3) Line source in a city quarter (four blocks separate d by two perpendicular canyons with rectangular cross-sections). For t he case of a line source in a street canyon, the wind-tunnel results a re compared with numerical model calculations.