Evaluation and Projection of Population Exposure to Temperature Extremes over the Beijing–Tianjin–Hebei Region Using a High-Resolution Regional Climate Model RegCM4 Ensemble

Abstract

Temperature extremes over rapidly urbanizing regions with high population densities have been scrutinized due to their severe impacts on human safety and economics. First of all, the performance of the regional climate model RegCM4 with a hydrostatic or non-hydrostatic dynamic core in simulating seasonal temperature and temperature extremes was evaluated over the historical period of 1991–99 at a 12-km spatial resolution over China and a 3-km resolution over the Beijing–Tianjin–Hebei (JJJ) region, a typical urban agglomeration of China. Simulations of spatial distributions of temperature extremes over the JJJ region using RegCM4 with hydrostatic and non-hydrostatic cores showed high spatial correlations of more than 0.8 with the observations. Under a warming climate, temperature extremes of annual maximum daily temperature (TXx) and summer days (SU) in China and the JJJ region showed obvious increases by the end of the 21st century while there was a general reduction in frost days (FD). The ensemble of RegCM4 with different land surface components was used to examine population exposure to temperature extremes over the JJJ region. Population exposure to temperature extremes was found to decrease in 2091–99 relative to 1991–99 over the majority of the JJJ region due to the joint impacts of increases in temperature extremes over the JJJ and population decreases over the JJJ region, except for downtown areas. Furthermore, changes in population exposure to temperature extremes were mainly dominated by future population changes. Finally, we quantified changes in exposure to temperature extremes with temperature increase over the JJJ region. This study helps to provide relevant policies to respond future climate risks over the JJJ region.

摘要

由于较高的人口密度, 发生在快速城市化等地区的极端气温事件对人类安全和社会经济影响更剧烈, 已引起广泛关注. 本文首先评估了采用静力及非静力动力核的区域气候模式RegCM4对中国(空间分辨率12公里)及京津冀城市群(空间分辨率3公里)1991–99历史时期季节气温和极端气温的模拟性能. 通过采用静力及非静力动力核RegCM4模拟的京津冀城市群极端气温事件与观测结果的空间相关性较高, 相关系数超过0.8. 全球变暖背景下, 21世纪末中国及京津冀地区的年最大日最高气温和夏日日数明显增加, 而霜冻日数则普遍减少. 利用包含不同陆面模块的区域气候模式RegCM4集合对京津冀地区极端气温人口暴露度作了进一步研究. 与1991–99年相比, 除京津冀核心城区外, 预计在2091到2100年期间, 京津冀大部分地区极端气温人口暴露度将有所下降. 这主要是由于未来极端气温事件增加及人口减少共同影响引起的. 进一步分析发现, 未来人口变化对极端气温人口暴露度变化起主导作用. 最后, 我们量化了京津冀地区极端气温人口暴露度随气温的变化. 本研究为京津冀地区应对未来气候风险制定相关政策提供了参考依据.