Comparison of Heat Fluxes from Summertime Observations in the Suburbs of Four North American Cities

Previous measurements of urban energy balances have been restricted to a small number of cities. This paper presents directly measured energy balance fluxes for suburban areas in four cities within the United States: Tucson, Sacramento, Chicago, and Los Angeles. They represent a range of synoptic regimes and surface morphologies (built and vegetative). Ensemble diurnal patterns and ratios of fluxes for clear, cloudy, and all sky conditions are presented. Consideration is given to both the mean and the variability of the fluxes. As expected, the magnitudes of the fluxes vary between cities; however, in general, the diurnal trends of flux partitioning are similar in terms of the timing of the peaks and changes in sign. Chicago is slightly different due to frequent wetting by rain. In the other cities, it seems that daytime Bowen ratios are inversely related to the area irrigated.