Phoenix Regional Heat and Air Quality Knowledge Repository

This study examines the impact of spatial landscape configuration (e.g., clustered, dispersed) on land-surface temperatures (LST) over Phoenix, Arizona, and Las Vegas, Nevada, USA. We classified detailed land-cover types via object-based image analysis (OBIA) using Geoeye-1 at 3-m resolution (Las Vegas) and QuickBird at 2.4-m resolution (Phoenix). Spatial autocorrelation (local Moran’s I ) was then used to test for spatial dependence and to determine how clustered or dispersed points were arranged. Next, we used Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data acquired over Phoenix (daytime on 10 June and nighttime on 17 October 2011) and Las Vegas (daytime on 6 July and nighttime on 27 August 2005) to examine day- and nighttime LST with regard to the spatial arrangement of anthropogenic and vegetation features. Local Moran’s I values of each land-cover type were spatially correlated to surface temperature. The spatial configuration of grass and trees shows strong negative correlations with LST, implying that clustered vegetation lowers surface temperatures more effectively. In contrast, clustered spatial arrangements of anthropogenic land-cover types, especially impervious surfaces and open soil, elevate LST. These findings suggest that city planners and managers should, where possible, incorporate clustered grass and trees to disperse unmanaged soil and paved surfaces, and fill open unmanaged soil with vegetation. Our findings are in line with national efforts to augment and strengthen green infrastructure, complete streets, parking management, and transit-oriented development practices, and reduce sprawling, unwalkable housing development.

Public transit systems have been identified as a critical component to reducing energy use and greenhouse gas emissions associated with the transportation sector to mitigate future climate change impacts. A unique aspect of public transit is its use almost always necessitates environmental exposure and the design of these systems directly influences rider exposure via rider ingress, egress, and waiting. There is a tension between policies and programs which promote transit use to combat climate change and the potential impact an uncertain climate future may have on transit riders.

In the American Southwest, extreme heat events, a known public health threat, are projected to increase between 150 and 840% over the next decade, and may be a health hazard for transit riders. There are opportunities to incorporate rider health risks in the overall planning process and develop alternative transit schedules during extreme heat events to minimize these risks. Using Los Angeles Metro as a case studies, we show that existing transit vehicles can be reallocated across the system to significantly reduce exposure for riders who are more vulnerable to heat while maintaining a minimum level of service across the system. As cities continue to invest in public transit it is critical for them to understand transit use as an exposure pathway for riders and to develop strategies to mitigate potential health risks.