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Open AccessArticle

Impacts of Urban Expansion on Relatively Smaller Surrounding Cities during Heat Waves

1
Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China
2
Department of Meteorology, University of Reading, Reading RG6 6BB, UK
*
Author to whom correspondence should be addressed.
Atmosphere 2019, 10(7), 364; https://doi.org/10.3390/atmos10070364
Received: 28 May 2019 / Revised: 21 June 2019 / Accepted: 24 June 2019 / Published: 1 July 2019
(This article belongs to the Section Biometeorology)
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Abstract

Urban-induced thermal stress can threaten human health, especially during heat waves (HWs). The growth of cities further exacerbates this effect. Here, weather research and forecasting (WRF) with an urban canopy model (UCM) is used to assess the effects of megacities and their growth on the thermal regime of proximal cities during heat waves. Analysis of the heat fluxes shows that advection impacts cities downwind. Results indicate that as urban areas change size (50%–100% and 100–150% of their current size), the local 2 m temperature increases by 2.7 and 1.7 °C, and the 2 m specific humidity decreases by 2.1 and 1.4 g kg−1, respectively. A small city downwind is impacted with a 0.3–0.4 °C increase in 2 m temperature. Green roof is a potential mitigation strategy for these regions (i.e., beyond the megacity). With 50% green roofs in an urban area, a 0.5 °C decrease in 2 m temperature and 0.6 g kg−1 increase in specific humidity is simulated. Urbanization upwind of a megacity will contribute to regional climate change. View Full-Text
Keywords: heatwave; urban expansion; city position; city size; green roofs heatwave; urban expansion; city position; city size; green roofs
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Huang, B.; Ni, G.-H.; Grimmond, C.S.B. Impacts of Urban Expansion on Relatively Smaller Surrounding Cities during Heat Waves. Atmosphere 2019, 10, 364.

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