Cao Chang, Li Xu-Hui, Zhang Mi, Liu Shou-Dong, Xu Jia-Ping
Yale-NUIST Center on Atmospheric Environment, Nanjing University of Information Science and Technology, Nanjing 210044, China.
Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology(CICAEET), Nanjing University of Information Science and Technology, Nanjing 210044, China.
Huan Jing Ke Xue. 2017 Oct 8;38(10):3987-3997. doi: 10.13227/j.hjkx.201702127.
Urban heat islands (UHIs), which are urban areas with higher surface or air temperatures than surrounding rural areas, can further enhance the heat stress already exacerbated by global warming. This poses great challenges to human health and sustainable development. China has been burdened with heavy air pollution in recent years, and the effect of haze pollution on UHIs is still far less well understood. This study investigated the spatial variations of daytime, nighttime, and seasonal surface UHI effects in China during 2003-2013, based on MODIS land surface temperature data, and analyzed the correlations between the UHI effect and its impact factors from both biophysical and biochemical perspectives. Our results show that MODIS-derived annual nighttime UHI effect (3.4 K±0.2 K, mean±1 s.e.) is higher than the annual mean daytime UHI effect (2.1 K±0.3 K). The daytime UHI effect is strongest in summer and weakest in winter but contrasts with the seasonal variation characteristics of nighttime UHI effect. During daytime, UHI effects in humid and semi-humid regions are much more obvious than those in semi-arid/arid regions; during nighttime, the UHI effect in semi-humid and semi-arid/arid regions is much stronger than that in humid regions. A Daytime Urban Cool Island effect exists in semi-arid/arid regions during spring, autumn, and winter seasons. Population, vegetation activity, and irrigation are three factors controlling annual mean daytime UHI effect. The nighttime UHI is significantly influenced by latitude, albedo, precipitation, and aerosol concentrations. We provide evidence for a long-held hypothesis that the biogeochemical effect of urban aerosols is an important contributor to the UHI effect. The important role played by rural background environment in calculating the UHI effect is further discussed in terms of surface aerodynamic roughness and the contrast in albedo between urban and rural areas. Mitigation of haze pollution has a co-benefit of reducing the UHI effect and heat stress for urban dwellers. It is also conducive to reducing negative impacts of regional and global climate change.
城市热岛（UHIs）是指地表或气温高于周边农村地区的城市区域，它会进一步加剧全球变暖已经造成的热应激。这对人类健康和可持续发展构成了巨大挑战。近年来，中国一直面临着严重的空气污染问题，而雾霾污染对城市热岛的影响仍远未得到充分了解。本研究基于MODIS陆地表面温度数据，调查了2003 - 2013年期间中国白天、夜间和季节地表城市热岛效应的空间变化，并从生物物理和生化角度分析了城市热岛效应与其影响因素之间的相关性。我们的结果表明，基于MODIS得出的年度夜间城市热岛效应（3.4 K±0.2 K，平均值±1标准误差）高于年度平均白天城市热岛效应（2.1 K±0.3 K）。白天城市热岛效应在夏季最强，冬季最弱，但与夜间城市热岛效应的季节变化特征相反。白天，湿润和半湿润地区的城市热岛效应比半干旱/干旱地区明显得多；夜间，半湿润地区和半干旱/干旱地区的城市热岛效应比湿润地区强得多。在春季、秋季和冬季，半干旱/干旱地区存在白天城市冷岛效应。人口、植被活动和灌溉是控制年度平均白天城市热岛效应的三个因素。夜间城市热岛效应受纬度、反照率、降水量和气溶胶浓度的显著影响。我们为一个长期存在的假设提供了证据，即城市气溶胶的生物地球化学效应是城市热岛效应的重要贡献因素。从地表空气动力学粗糙度以及城乡反照率差异的角度，进一步讨论了农村背景环境在计算城市热岛效应中所起的重要作用。减轻雾霾污染具有降低城市热岛效应和城市居民热应激的协同效益。这也有利于减少区域和全球气候变化的负面影响。
