Microscale evaluation of the urban heat island in Phoenix, Arizona.

摘要

This dissertation analyzed the urban heat island (U11l) in Phoenix, Arizona at a fine scale using both field-based measurements and numerical modeling. A 24 hr field {CAB campaign was conducted within central Phoenix 4-5 April 2008 and included mobile, ground-based, and helicopter-based measurements of temperatures along an 18 kin route and at three specific locations within the city. Model simulations were then run with the numerical microclimate model, environmental meteorology (ENVI-met), to compare with field observations. Research questions focused on (I) testing, refining, and validating EN V1-met for the hot arid city of Phoenix, 2) evaluating thermal comfort outputs from ENVI-met for various seasons within central Phoenix, and 3) evaluating the effect of downtown Phoenix building facade and street canyon temperatures on flow with computational fluid dynamics (CFD) modeling and analysis of thermal infrared imagery from the 24 hr April 2008 field experiment.;ENVI-met simulation results over the 24 hr experimental period generally predicted afternoon maximum temperatures well, but over predicted minimum temperatures, with a smaller than observed diurnal temperature range. Surface temperature predictions closely matched observations at night, with a slight over-prediction of temperature during the daytime hours. Seasonal comfort maps indicated that the higher density downtown has more comfortable afternoon temperatures during most seasons, with lower density areas with higher vegetation being more comfortable in the early evening. CFD simulations found a distinct temperature change at 30 m along certain building facades measured by hand-held IR thermography during the 24 hr field day. This distinct vertical temperature gradient found along building facades in downtown correlates with similar findings in physical models investigating buoyancy and thermal stratification within street canyons. This dissertation aids planners and civic leaders in gaining a better understanding of the fine scale effects of the built environment on the UHI within different landscapes in the city and devising heat mitigation strategies to increase the quality of life in Phoenix and other cities in hot and arid climates.