Strong contributions of local background climate to urban heat islands

Lei Zhao, Xuhui Lee, Ronald B. Smith, Keith Oleson

Research output: Contribution to journalArticlepeer-review

Abstract

The urban heat island(UHI), a commonphenomenon in which surface temperatures are higher in urban areas than in surrounding rural areas, represents one of the most significant human-induced changes to Earth's surface climate1,2. Even though they are localized hotspots in the landscape, UHIs have a profound impact on the lives of urban residents, who comprise more than half of the world's population3. A barrier to UHI mitigation is the lack of quantitative attribution of the various contributions to UHI intensity4 (expressed as the temperature difference between urban and rural areas, DT). A common perception is that reduction in evaporative cooling in urban land is the dominant driver of DT (ref. 5). Here we use a climatemodel to showthat, for cities across North America, geographic variations in daytime DT are largely explained by variations in the efficiency with which urban and rural areas convect heat to the lower atmosphere. If urban areas are aerodynamically smoother than surrounding rural areas, urban heat dissipation is relatively less efficient and urban warming occurs (and vice versa). This convection effect depends on the local background climate, increasing daytimeDT by 3.060.3 kelvin (mean and standard error) in humid climates but decreasingDT by 1.560.2 kelvin in dry climates. In the humid eastern United States, there is evidence of higherDT in drier years.These relationshipsimply that UHIs will exacerbate heatwave stressonhuman health in wet climates where high temperature effects are already compounded by high air humidity6,7 and in drier years when positive temperature anomalies may be reinforced by a precipitation- temperature feedback8. Our results support albedo management as a viable means of reducing DT on large scales9,10.

Original languageEnglish (US)
Pages (from-to)216-219
Number of pages4
JournalNature
Volume511
Issue number7508
DOIs
StatePublished - 2014
Externally publishedYes

ASJC Scopus subject areas

  • General

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