Spatial and temporal variability of anthropogenic heating in US cities

To address the growing need for detailed anthropogenic heating data in support of mesoscale meteorological modeling of the urban climate we have developed and applied an approach for estimating hourly profiles for anthropogenic heating in cities at high spatial resolutions. These profiles combine weather-adjusted aggregate per capita energy consumption and traffic pattern data with estimates of the diurnal variation of population density at the census-tract scale. Anthropogenic heating profiles have been developed for both weekdays and weekends for each month of the year for several sample cities. Diurnal variability in population density is shown to be a key driver of the spatial variability in the magnitude of anthropogenic heating. At the city scale, the daytime population is nominally double that of the nighttime population. At finer scales corresponding to census tracts within the central business district this ratio can increase by an order of magnitude or more. The anthropogenic heating magnitude scales with population density, and is found to locally exceed 500 W/m² in the urban core of many US cities. Hence, the spatial and temporal variability in anthropogenic heating may play a crucial role in the formation of the urban heat island and mixing processes of importance to air pollution studies.