Zhou Wenqing, Zhang Liping, Wang Gangsheng, Zhang Qin, Cao Hui, Zhang Hairong, Jia Benjun, Tang Zhenyu, Li Xiao, Liu Lina
State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, 430072, China.
State Key Laboratory of Water Resources Engineering and Management, Wuhan University, Wuhan, 430072, China.
Sci Total Environ. 2024 Nov 15;951:175804. doi: 10.1016/j.scitotenv.2024.175804. Epub 2024 Aug 27.
The Yangtze River Delta (YRD) experienced record-breaking heat in the summer of 2022. However, the urban heat pattern and the role of urban expansion over the last two decades in this hot summer have not been explored. Using the advanced mesoscale Weather Research and Forecasting (WRF) model, we reproduced the fine spatial features and investigated the urban heat island (UHI) and dry island (UDI) effects during the two identified heatwaves in 2022. We further replace the current (2020) land use with the historical (2001) land use in WRF to evaluate the impacts of urban expansion from 2001 to 2020 on air temperature and moisture. Our finding revealed that the conversion of land use resulted in near-surface warming and drying, with pronounced diurnal variations, especially during the July heatwave. The analysis of surface energy balance demonstrated that the substantial decrease in evapotranspiration (ET) was the primary driver of daytime warming, elevating temperatures by 7 °C (July heatwave) and 2 °C (August heatwave). This ET reduction also led to the strong daytime coupling of warming and drying effects over new urban areas. At night, the release of stored heat resulted in the temperature increase of 2 °C (1 °C) during July (August) heatwave, highlighting the nighttime as a critical period for heightened thermal risk. Additionally, urban expansion at the periphery contributed modestly to the warming of urban cores, exacerbating conditions in an already hot environment. This study enhances understanding of the impacts of urban expansion on air temperature and humidity during extreme heatwaves, thereby supporting targeted adaptation and mitigation for extreme events within large cities.
2022年夏季，长江三角洲地区经历了破纪录的高温天气。然而，过去二十年中该地区的城市热模式以及城市扩张在这个炎热夏季所起的作用尚未得到研究。利用先进的中尺度天气研究与预报（WRF）模型，我们再现了精细的空间特征，并研究了2022年两次确定的热浪期间的城市热岛（UHI）和干岛（UDI）效应。我们还在WRF模型中用历史（2001年）土地利用数据替换了当前（2020年）的土地利用数据，以评估2001年至2020年城市扩张对气温和湿度的影响。我们的研究结果表明，土地利用变化导致近地表升温及干燥，且昼夜变化明显，尤其是在7月热浪期间。地表能量平衡分析表明，蒸发散（ET）的大幅减少是白天升温的主要驱动因素，使温度分别升高了7°C（7月热浪）和2°C（8月热浪）。ET的减少还导致新城区白天升温与干燥效应的强烈耦合。夜间，储存热量的释放导致7月（8月）热浪期间温度分别升高2°C（1°C），凸显出夜间是热风险加剧的关键时期。此外，周边地区的城市扩张对城市核心区的升温有一定贡献，加剧了本就炎热环境下的状况。这项研究增进了我们对极端热浪期间城市扩张对气温和湿度影响的理解，从而为大城市应对极端事件的针对性适应和缓解措施提供了支持。
