Monday, 12 January 2009
Development of a Mesoscale Thermal Model for Urban Climate
Hall 5 (Phoenix Convention Center)
A simple energy balance model is created for use in developing mitigation strategies for the Urban Heat Island effect. The model is initially applied to the city of Phoenix, Arizona, USA. There are six primary contributions to the overall energy balance: incident solar radiation, anthropogenic heat input, conduction heat loss, outgoing evapotranspiration, outgoing convection, and outgoing emitted radiation. Meteorological data are input to the model, which then computes an urban characteristic temperature at a calculated time step for a specified time range. The model temperature is shown to have the same periodic behavior as the experimentally measured air temperatures. Predicted temperature changes, caused by increasing the average urban albedo, agree within 0.1 °C with comparable maximum surface temperature predictions from MM5. The present model, while maintaining valid energy-balance physics, allows users to quickly and easily predict the relative effects of urban heat island mitigation measures. Representative mitigation strategies, namely changes in average albedo and long-wavelength emissivity are presented here. Increasing the albedo leads to the greater reduction in daytime maximum temperatures, while increasing the emissivity leads to a greater reduction in nighttime minimum temperatures.