Boston University, Department of Earth & Environment, 685 Commonwealth Ave., Boston, MA 02215, USA.
Boston University, Department of Environmental Health, 715 Albany St., Boston, MA 02118, USA.
Sci Total Environ. 2023 Jan 20;857(Pt 3):159663. doi: 10.1016/j.scitotenv.2022.159663. Epub 2022 Oct 24.
Extreme heat represents a growing threat to public health, especially across the densely populated, developed landscape of cities. Climate adaptation strategies that aim to manage urban microclimates through purposeful design can reduce the heat exposure of urban populations, however, it is unclear how the temperature impacts of urban green space and albedo vary across cities and background climate. This study quantifies the sensitivity of surface temperature to landcover characteristics tied to two widely used climate adaptation strategies, urban greening and albedo manipulation (e.g. white roofs), by combining long-term remote sensing observations of land surface temperature, albedo, and moisture with high-resolution landcover datasets in a spatial regression analysis at the census block scale across seven United States cities. We find tree cover to have an average cooling impact of -0.089 K per % cover, which is approximately four times stronger than the average grass cover cooling impact of -0.021 K per % cover. Variability in the magnitude of grass cover cooling impacts was primarily a function of vegetation moisture content, with the Land Surface Water Index (LSWI) explaining 89 % of the variability in grass cover cooling impacts across cities. Variability in tree cover cooling impacts was primarily a function of sunlight and vegetation moisture content, with solar irradiance and LSWI explaining 97 % of the cooling variability across cities. Albedo cooling impacts were consistent across cities with an average cooling impact of -0.187 K per increase of 0.01. While these interventions are broadly effective across cities, there are critical regional trade-offs between vegetation cooling efficiency, irrigation requirements, and the temporal duration and evolution of the cooling benefits. In warm, arid cities, high albedo surfaces offer multifaceted benefits such as cooling and water conservation, whereas temperate, mesic cities likely benefit from a combination of strategies, with greening efforts targeting highly paved neighborhoods.
极端高温对公共健康构成了日益严重的威胁，尤其是在人口密集、城市化程度高的地区。旨在通过有针对性的设计来管理城市微气候的气候适应策略可以减少城市人口的热暴露，但目前尚不清楚城市绿地和反照率对温度的影响在不同城市和背景气候下有何差异。本研究通过结合长期遥感观测的地表温度、反照率和湿度数据，以及在七个美国城市的普查区块尺度上的高分辨率土地覆盖数据集，利用空间回归分析，量化了与两种广泛应用的气候适应策略（城市绿化和反照率调整（如白色屋顶））相关的土地覆盖特征对地表温度的敏感性。我们发现，树木覆盖的平均降温影响为每增加 1%覆盖面积降低 0.089 K，大约是草覆盖降温影响（每增加 1%覆盖面积降低 0.021 K）的四倍。草地覆盖降温影响的幅度变化主要是植被湿度含量的函数，陆地表面水分指数（LSWI）解释了城市间草地覆盖降温影响变化的 89%。树木覆盖降温影响的幅度变化主要是阳光和植被湿度含量的函数，太阳辐照度和 LSWI 解释了城市间降温变化的 97%。反照率降温影响在各城市间是一致的，每增加 0.01 反照率平均降低 0.187 K。虽然这些干预措施在各城市普遍有效，但植被降温效率、灌溉需求以及降温效益的时间持续时间和演变之间存在着关键的区域权衡。在温暖、干旱的城市，高反照率表面提供了多方面的效益，如降温和节水，而在温带、湿润的城市，可能需要综合多种策略，绿化工作的重点是高度铺砌的社区。
