School of Architecture and Urban Planning, Chongqing University, Chongqing, 400045, China; Key Laboratory of New Technology for Construction of Cities in Mountain Area, Ministry of Education, Chongqing University, Chongqing, 400045, China.
State Key Laboratory of Subtropical Building Science, South China University of Technology, Guangzhou, 510641, China.
Environ Res. 2021 Feb;193:110584. doi: 10.1016/j.envres.2020.110584. Epub 2020 Dec 4.
Heat waves (HWs) and urban heat islands (UHIs) can potentially interact. The mechanisms behind their synergy are not fully disclosed. Starting from the localized UHI phenomenon, this study aims i) to reveal their associated impacts on human thermal comfort through three different definitions of HW events, based on air temperature (airT), wet-bulb globe temperature (WBGT) and human-perceived temperature (AppT) respectively, and ii) to understand the role of air moisture and wind. The analysis was conducted in four districts (NH, JD, MH and XJH) with different urban development patterns and geographic conditions, in the megacity of Shanghai with a subtropical humid climate. Results evidenced the localized interplay between HWs and UHIs. The results indicate that less urbanized districts were generally more sensitive to the synergies. JD district recorded the highest urban heat island intensity (UHII) amplification, regardless of the specific HW definition. Notably, during AppT-HWs, the increment was observed in terms of maximum (1.3 °C), daily average (0.8 °C), diurnal (0.4 °C) and nocturnal UHII (1.0 °C). Nevertheless, localized synergies between HWs and UHIs at different stations also exhibited some commonalities. Under airT-HW, the UHII was amplified throughout the day at all stations. Under WBGT-HW, diurnal UHII (especially at 11:00-17:00 LST) was consistently amplified at all stations. Under AppT-HW conditions, the nocturnal UHII was slightly amplified at all stations. Air moisture and wind alleviated the synergistic heat exacerbation to the benefit of thermal comfort. The extent depended on geographic condition, diurnal and nocturnal scenarios, temperature type and HW/normal conditions. Stronger HW-UHI synergies indicate the necessity to develop specific urban heat emergency response plans, able to capture and intervene on the underlying mechanisms. This study paves to way to their identification.
热浪（HWs）和城市热岛（UHIs）可能会相互作用。它们协同作用的机制尚未完全揭示。本研究从局部的城市热岛现象出发，旨在通过三种不同的热浪事件定义（基于空气温度（airT）、湿球 globe 温度（WBGT）和人体感知温度（AppT）），揭示其对人体热舒适度的相关影响，i）并理解空气湿度和风速的作用。该分析在上海这个具有亚热带湿润气候的特大城市的四个具有不同城市发展模式和地理条件的区（NH、JD、MH 和 XJH）进行。结果表明了热浪和城市热岛之间的局部相互作用。结果表明，城市化程度较低的地区通常对协同作用更为敏感。无论特定的热浪定义如何，JD 区记录的城市热岛强度（UHII）放大幅度最高。值得注意的是，在 AppT-HWs 期间，最大（1.3°C）、日平均（0.8°C）、昼夜（0.4°C）和夜间 UHII（1.0°C）都观察到了增量。然而，不同站点之间的热浪和城市热岛的局部协同作用也表现出一些共同性。在 airT-HW 下，所有站点的 UHII 在白天都得到放大。在 WBGT-HW 下，所有站点的昼夜 UHII（特别是在 11:00-17:00 LST）都持续放大。在 AppT-HW 条件下，所有站点的夜间 UHII 略有放大。空气湿度和风速缓解了协同热加剧对热舒适度的不利影响。这种缓解程度取决于地理条件、昼夜场景、温度类型和热浪/正常条件。更强的 HW-UHI 协同作用表明需要制定特定的城市热应急响应计划，以便能够捕捉和干预潜在机制。本研究为其识别铺平了道路。
