Mesoscale thermal model for urban heat island mitigation.

摘要

A simple energy balance model is created for use in developing mitigation strategies for the Urban Heat Island (UHI) effect. The model is 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. The model temperature is shown to have the same periodic behavior as the experimentally measured air temperatures. 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. Accordingly, this model is applied here to show the relative effects of four common mitigation strategies: increasing the overall (1) emissivity, (2) percentage of vegetated area, (3) thermal conductivity, and (4) albedo of the urban environment in a series of percentage increases by 5, 10, 15, and 20 percent from baseline values. In addition to modeling mitigation strategies, the model is utilized to evaluate human health vulnerability from excessive heat-related events, based on heat-related emergency service data from 2002 to 2006. The four modeled UHI mitigation strategies, taken in combination, would lead to a 48 percent reduction in annual heat-related emergency service calls, where increasing the albedo is the single most effective UHI mitigation strategy.;Finally, a spatial superposition design is presented that couples this model with the more robust fifth-generation Pennsylvania State University - National Center for Atmospheric Research Mesoscale Model (MM5). As a result, a new hypothesis is conceived which states that perturbation values from the norm temperature do not change when certain mitigation strategies are imposed. It is shown from demonstrative spatial mitigation schemes that having a fewer number of mitigated points (by almost half) on a square urban grid in Phoenix with the same average albedo leads to a greater reduction in average hourly temperature when these mitigated points are distributed appropriately. All model developments and analysis are validated against MM5 with high confidence.