A study examines the effects of canopy and impervious surface cover on air temperatures in urban environments. The urban heat island effect causes increased temperatures in urban environments compared with surrounding areas, with potential human health consequences. As the climate warms, cities explore strategies to mitigate heat. Carly D. Ziter and colleagues examined the relationship between canopy cover, which reduces heat, and impervious surface cover, which increases heat, on urban air temperature in Madison, Wisconsin. In the summer of 2016, the authors used a bicycle-mounted sensor to repeatedly sample the air temperature approximately every 5 meters along 10 urban transects during the day, as well as four transects at night, spanning gradients of both impervious and canopy cover. Daytime temperature decreased nonlinearly with increasing canopy cover, with the greatest cooling occurring when canopy cover was more than 40% and at the scale of a typical city block (60-90 m). However, canopy cover exhibited limited cooling at night, whereas air temperatures increased with the amount of impervious surfaces both during the day and at night. The results suggest that effective urban heat mitigation requires efforts to both increase urban canopy cover and decrease impervious surface cover, according to the authors.
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Article #18-17561: "Scale-dependent interactions between tree canopy cover and impervious surfaces reduce daytime urban heat during summer," by Carly D. Ziter, Eric J. Pedersen, Christopher J. Kucharik, and Monica G. Turner.
MEDIA CONTACT: Carly D. Ziter, Concordia University, Montreal, CANADA; tel: 514-848-2424 ext. 3267, 709-763-8792; e-mail: < carly.ziter@concordia.ca >; Monica G. Turner, University of Wisconsin-Madison, WI; e-mail: < turnermg@wisc.edu >
Proceedings of the National Academy of Sciences