Urban heat island phenomenon explained

The urban heat island effect is a real phenomenon, documented by observations and substantiated by mathematical models.

Matei Georgescu, assistant professor of geography at ASU, explained the science behind the phenomenon to viewers of China Central TV - America, a Washington D.C.-based arm of China’s primary state television station, in a broadcast that aired at 9 a.m., July 17, in Beijing (9:30 p.m., July 16, EDT).

“In essence, urban areas are heat sinks – they absorb incoming solar radiation differently than the natural landscape would,” explained Georgescu. "In cities, incoming solar radiation is trapped in the built environment during the day, and is not released as efficiently in the evening as it would be, had the megapolitan environment not been present.”

The greater the extent and height of the built environment, the larger the heat island effect, Georgescu pointed out. Higher night-time temperatures, like those seen in Phoenix and other large cities, create problems for humans and animals, and lead to greater energy use.

Can urban planners or governments reduce the urban heat island effect? There are no silver bullets, Georgescu said, but strategies proven to be effective include use of “cool,” light-colored roofs, increasing vegetation cover (especially in arid and semi-arid cities), and permeable surfaces that allow rain to evapotranspire back into the atmosphere.

CCTV-America broadcast Georgescu’s interview as part of its prime news broadcast. The interview built on issues presented in a prior feature on urban heat problems in Bangkok, Thailand and that city’s efforts to address the situation.

Matei Georgescu is an Assistant Professor in ASU’s School of Geographical Sciences and Urban Planning, an academic unit in the College of Liberal Arts and Sciences, and a Senior Sustainability Scientist with ASU’s Global Institute of Sustainability.