Interactions between urban heat islands and heat waves

Lei Zhao, Michael Oppenheimer, Qing Zhu, Jane W. Baldwin, Kristie L. Ebi, Elie Bou-Zeid, Kaiyu Guan, Xu Liu

Research output: Contribution to journalArticle

Abstract

Heat waves (HWs) are among the most damaging climate extremes to human society. Climate models consistently project that HW frequency, severity, and duration will increase markedly over this century. For urban residents, the urban heat island (UHI) effect further exacerbates the heat stress resulting from HWs. Here we use a climate model to investigate the interactions between the UHI and HWs in 50 cities in the United States under current climate and future warming scenarios. We examine UHI2m (defined as urban-rural difference in 2m-height air temperature) and UHIs (defined as urban-rural difference in radiative surface temperature). Our results show significant sensitivity of the interaction between UHI and HWs to local background climate and warming scenarios. Sensitivity also differs between daytime and nighttime. During daytime, cities in the temperate climate region show significant synergistic effects between UHI and HWs in current climate, with an average of 0.4 K higher UHI2m or 2.8 K higher UHIs during HWs than during normal days. These synergistic effects, however, diminish in future warmer climates. In contrast, the daytime synergistic effects for cities in dry regions are insignificant in the current climate, but emerge in future climates. At night, the synergistic effects are similar across climate regions in the current climate, and are stronger in future climate scenarios. We use a biophysical factorization method to disentangle the mechanisms behind the interactions between UHI and HWs that explain the spatial-temporal patterns of the interactions. Results show that the difference in the increase of urban versus rural evaporation and enhanced anthropogenic heat emissions (air conditioning energy use) during HWs are key contributors to the synergistic effects during daytime. The contrast in water availability between urban and rural land plays an important role in determining the contribution of evaporation. At night, the enhanced release of stored and anthropogenic heat during HWs are the primary contributors to the synergistic effects.

Original languageEnglish (US)
Article number034003
JournalEnvironmental Research Letters
Volume13
Issue number3
DOIs
StatePublished - Mar 1 2018

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Infrared Rays
heat island
Climate
Hot Temperature
climate
climate modeling
warming
evaporation
Climate models
heat wave
wave climate
air conditioning
Air Conditioning
effect
energy use
arid region
water availability
Evaporation
Temperature
surface temperature

Keywords

  • climate change
  • heat wave
  • surface biophysical processes
  • surface evaporation
  • urban heat island

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Environmental Science(all)
  • Public Health, Environmental and Occupational Health

Cite this

Zhao, L., Oppenheimer, M., Zhu, Q., Baldwin, J. W., Ebi, K. L., Bou-Zeid, E., ... Liu, X. (2018). Interactions between urban heat islands and heat waves. Environmental Research Letters, 13(3), [034003]. https://doi.org/10.1088/1748-9326/aa9f73

Interactions between urban heat islands and heat waves. / Zhao, Lei; Oppenheimer, Michael; Zhu, Qing; Baldwin, Jane W.; Ebi, Kristie L.; Bou-Zeid, Elie; Guan, Kaiyu; Liu, Xu.

In: Environmental Research Letters, Vol. 13, No. 3, 034003, 01.03.2018.

Research output: Contribution to journalArticle

Zhao, L, Oppenheimer, M, Zhu, Q, Baldwin, JW, Ebi, KL, Bou-Zeid, E, Guan, K & Liu, X 2018, 'Interactions between urban heat islands and heat waves', Environmental Research Letters, vol. 13, no. 3, 034003. https://doi.org/10.1088/1748-9326/aa9f73
Zhao L, Oppenheimer M, Zhu Q, Baldwin JW, Ebi KL, Bou-Zeid E et al. Interactions between urban heat islands and heat waves. Environmental Research Letters. 2018 Mar 1;13(3). 034003. https://doi.org/10.1088/1748-9326/aa9f73
Zhao, Lei ; Oppenheimer, Michael ; Zhu, Qing ; Baldwin, Jane W. ; Ebi, Kristie L. ; Bou-Zeid, Elie ; Guan, Kaiyu ; Liu, Xu. / Interactions between urban heat islands and heat waves. In: Environmental Research Letters. 2018 ; Vol. 13, No. 3.
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AB - Heat waves (HWs) are among the most damaging climate extremes to human society. Climate models consistently project that HW frequency, severity, and duration will increase markedly over this century. For urban residents, the urban heat island (UHI) effect further exacerbates the heat stress resulting from HWs. Here we use a climate model to investigate the interactions between the UHI and HWs in 50 cities in the United States under current climate and future warming scenarios. We examine UHI2m (defined as urban-rural difference in 2m-height air temperature) and UHIs (defined as urban-rural difference in radiative surface temperature). Our results show significant sensitivity of the interaction between UHI and HWs to local background climate and warming scenarios. Sensitivity also differs between daytime and nighttime. During daytime, cities in the temperate climate region show significant synergistic effects between UHI and HWs in current climate, with an average of 0.4 K higher UHI2m or 2.8 K higher UHIs during HWs than during normal days. These synergistic effects, however, diminish in future warmer climates. In contrast, the daytime synergistic effects for cities in dry regions are insignificant in the current climate, but emerge in future climates. At night, the synergistic effects are similar across climate regions in the current climate, and are stronger in future climate scenarios. We use a biophysical factorization method to disentangle the mechanisms behind the interactions between UHI and HWs that explain the spatial-temporal patterns of the interactions. Results show that the difference in the increase of urban versus rural evaporation and enhanced anthropogenic heat emissions (air conditioning energy use) during HWs are key contributors to the synergistic effects during daytime. The contrast in water availability between urban and rural land plays an important role in determining the contribution of evaporation. At night, the enhanced release of stored and anthropogenic heat during HWs are the primary contributors to the synergistic effects.

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