Researchers emphasize need for evaluation of tradeoffs in battling urban heat islands

Arizona State University: Urbanization will increase average temperatures in Arizona’s Sun Corridor and white roofs can combat that, but not without consequences for the region’s hydroclimate A team of researchers from Arizona State University has found that warming resulting from megapolitan expansion is seasonally dependent, with greatest warming occurring during summer and least during winter. Among the most practical ways to combat urbanization-induced warming – the painting of buildings' roofs white – was found to disrupt regional hydroclimate, highlighting the need for evaluation of tradeoffs associated with combating urban heat islands (UHI).

“We found that raising the reflectivity of buildings by painting their roofs white is an effective way of reducing higher average temperatures caused by urban expansion,” said Matei Georgescu, an assistant professor in ASU’s School of Geographical Sciences and Urban Planning. “However, increased reflectivity also modifies hydroclimatic processes and, in the case of the ‘Sun Corridor,’ can lead to a significant reduction of rainfall. Our maximum Sun Corridor expansion scenario leads to a 12 percent reduction in rainfall, averaged across the entire state. Painting roofs white leads to an additional 4 percent reduction in rainfall.”

...The paper focuses on Arizona’s Sun Corridor, the most rapidly growing megapolitan area in the United States. Located in a semi-arid environment, the Sun Corridor is composed of four metropolitan areas: Phoenix, Tucson, Prescott and Nogales. With a population projection expected to exceed 9 million people by 2040, the rapidly expanding megapolitan offers the opportunity to identify tradeoffs focused on sustainable expansion of the built environment.

The authors used 2050 projections of Sun Corridor growth developed by the Maricopa Association of Governments (MAG), the regional agency for metropolitan Phoenix that provides long-range and sustainably oriented planning. They conducted continuous multi-year, multi-member, continental scale numerical experiments for several 2050 Sun Corridor growth and adaptation scenarios and compared results with a modern day Sun Corridor representation....

Tucson at dusk, shot by Zereshk, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported license