Case study of thermographic observations of surface materials' cooling rates and neighborhood design in suburban Phoenix, Arizona

Phoenix, Arizona, USA, has a well defined and documented UHI. With explosive population growth in the metropolitan area in the last half century, nighttime minimum temperatures have risen 6oC. Expectations are that the population growth will continue and the UHI will expand. The way neighborhoods are designed can impact UHI expansion. This study used thermography to examine the cooling rates of surfaces in three adjacent, suburban neighborhoods in Scottsdale, Arizona, a suburb of Phoenix. The neighborhoods incorporate different designs in regard to layout and open space. One neighborhood reflects the typical design of new communities being built in the metropolitan area – single family homes with small yards surrounded by high block walls. The other two are less densely built. One is custom homes on one acre lots resulting in approximately 62 percent open space. The third neighborhood incorporates open space between most backyards which are surrounded only partially by block fences, with substantial amounts of iron “view fencing” allowing for advection. Ambient temperatures across and within the neighborhoods often varied considerably. Thermography was used during a typical summer evening to observe surface temperatures and determine cooling rates for similar materials (ie: turf, bare ground, roofs, building exteriors, etc) within these neighborhoods, producing cooling rates that varied considerably. These cooling rates correlate with ambient temperatures, in that surfaces in warmer neighborhoods and areas within the neighborhoods experienced slower cooling rates than the cooler neighborhoods and locations. Of particular interest were cooling rates of “open spaces” in the neighborhoods, which could potentially provide a means for cooling a neighborhood – yet were not necessarily cooler than the surrounding environs.