A tale of two cities: different urban heat mitigation efficacy with the same strategies
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ORIGINAL PAPER
A tale of two cities: different urban heat mitigation efficacy with the same strategies Meiling Gao 1 & Fei Chen 2 & Huanfeng Shen 3 & Huifang Li 3 Received: 9 June 2020 / Accepted: 15 September 2020 / Published online: 30 September 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Recent intensification of urban heat islands (UHIs) poses a great threat to public health, promoting studies on UHI mitigation strategies. However, the question about the transferability of a mitigation method from a specific city to another remains largely unanswered. This study compares common UHI mitigation strategies (including green roofs, cool roofs, and changing urban building structure) for two Chinese megacities suffered from summer heat stress: Xi’an with a semi-humid climate and Wuhan with a humid climate, through the use of the urbanized-high-resolution land data assimilation system (u-HRLDAS) modeling tool and remote-sensing data. The results reveal that (1) all UHI mitigation strategies work more efficiently for Xi’an than that for Wuhan, particularly for the strategy of modifying urban fraction and associated green roof fraction; (2) the difference in cooling efficacy between the two cities is insignificant during relatively cool periods. Under hot weather conditions, the best choice of UHI mitigation strategy depends on urban land use categories in Xi’an; and (3) the differences in UHI mitigation efficacy are likely caused by the differing regional climate. This study highlights the need to better understand the transferability of UHI mitigation strategies in different climate zones.
1 Introduction This study is a follow-up to Gao et al. (2019) study on urban heat island (UHI) mitigation strategies for the Wuhan megacity and aims to explore the transferability of these strategies to other cities. UHI is a phenomenon that the temperature of urban regions is higher than its surrounding rural regions (Oke 1982, 1995). Urbanization increases impervious surfaces, reduces vegetation evaporation, and releases more anthropologic heat (Doan et al. 2019; Grimmond 2007; Huang et al. 2009; Oleson et al. 2015), which significantly affect city air quality, thermal stress, and public health (Jiang et al. 2008; Zhang et al. 2011; Bakhsh et al. 2018; Cao et al. 2016). It is imperative, especially under future warming * Huanfeng Shen [email protected] 1
School of Geology Engineering and Geomatics, Chang’an University, Xi’an 710054, China
2
National Center for Atmospheric Research, Boulder, CO 80301, USA
3
School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China
climate, to take actions to mitigate the UHI. Recently, an increasing number of studies explore UHI mitigation strategies to help policymakers estimate its influence on people’s life. Those common summer-UHI-mitigation strategies include the implementation of green roofs (GR, Sharma et al. 2016; Li et al. 2014) and the expansion of urban green space (Chatterjee et al. 2019; Oliveira et al. 2011); using higher
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