A multi-method and multi-scale approach for estimating city-wide anthropogenic heat fluxes

A multi-method approach estimating summer waste heat emissions from anthropogenic activities (Q(F)) was applied for a major subtropical city (Phoenix, AZ). These included detailed, quality-controlled inventories of city-wide population density and traffic counts to estimate waste heat emissions from population and vehicular sources respectively, and also included waste heat simulations derived from urban electrical consumption generated by a coupled building energy regional climate model (WRF-BEM + BEP). These component Q(F) data were subsequently summed and mapped through Geographic Information Systems techniques to enable analysis over local (i.e. census-tract) and regional (i.e. metropolitan area) scales. Through this approach, local mean daily Q(F) estimates compared reasonably versus (1.) observed daily surface energy balance residuals from an eddy covariance tower sited within a residential area and (2.) estimates from inventory methods employed in a prior study, with improved sensitivity to temperature and precipitation variations. Regional analysis indicates substantial variations in both mean and maximum daily Q(F) which varied with urban land use type. Average regional daily Q(F) was similar to 13 W m(-2) for the summer period. Temporal analyses also indicated notable differences using this approach with previous estimates of Q(F) in Phoenix over different land uses, with much larger peak fluxes averaging similar to 50 W m(-2) occurring in commercial or industrial areas during late summer afternoons. The spatio-temporal analysis of Q(F) also suggests that it may influence the form and intensity of the Phoenix urban heat island, specifically through additional early evening heat input, and by modifying the urban boundary layer structure through increased turbulence. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license.