The Effect of Building Shadows on the Vertical Temperature Structure of the Lower Atmosphere in Downtown Denver

Abstract

Denver's Continuous Air Monitoring Program (CAMP) site, typically recording the highest carbon monoxide levels in the metropolitan area; lies within a large region of downtown Denver shadowed by tall buildings. Two studies conducted during the winters of 1987/88 and 1988/89 indicated several possible scenarios leading to the high-pollution episodes often reported at CAMP. Sodar records and stability calculations at CAMP indicate that building shadows may be a contributing factor. The building shadowing was simulated by a computer model and its effects were examined from 2 days of detailed vertical temperature profiles taken in the vicinity of CAMP. The vertical temperature structure was mapped both spatially and temporally as it pertains to the shadowed and unshadowed regions. Results show that shadowing at CAMP is quickly followed by the formation of a shadow surface-based inversion and a local rise in carbon monoxide concentrations. Strength of the inversion depends on the meteorology and surface albedo and relates to a difference in solar radiation intensity of >100 W m?2 between shadowed and unshadowed regions.