State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China.
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China; School of Government, Beijing Normal University, Beijing 100875, China.
Sci Total Environ. 2018 Jan 1;610-611:1092-1102. doi: 10.1016/j.scitotenv.2017.08.082. Epub 2017 Aug 30.
Western China has experienced rapid urbanization since the Chinese reform process began in the late 1970s. It is essential to study the spatiotemporal patterns of warming induced by historical and future urban expansion and to evaluate adaptation strategies for the Chengdu-Chongqing metropolitan region (CCMR) in western China. The observed urban heat island intensity was ~1.5K in July 2009-2011. We employed the weather research and forecasting (WRF) model using real and projected urban land-use data to simulate near-surface air temperatures for a crop, urban in 2010 and urban in 2030 scenarios in summer over the CCMR. The difference between urban 2010 and cropland scenarios is 0.93K. Warming induced by urban development in 2010-2030 is in the range of 1-1.5K, but warming induced by future urban development will be less intense than historical warming over eastern China. We increased roof albedo to 0.8 to assess the difference in near-surface air temperature between cool roofs (CR) and urban 2030 scenarios, which represents the maximum potential impact of CR; we also assessed the cooling caused by green roofs (GR) (i.e., the difference between the GR and urban 2030 scenarios). Greater cooling occurs during the day due to reflection of solar radiation by CR and additional water evaporation by GR. We provided an evaluation criterion, cooling efficiency (CE), to measure the local performances of CR and GR. CE represents the local cooling capability based on urban warming rather than absolute cooling over a larger spatial scale. CE reveals a lower nocturnal cooling capability, which poses a significant challenge to the applications of CR and GR at night. CR has a better cooling capability across CCMR than GR, only when roof albedo of CR exceeds 0.68. Measures enacted should be appropriately adjusted to optimize for cost, technology and energy savings.
中国西部自 20 世纪 70 年代末改革开放以来经历了快速的城市化进程。研究历史和未来城市扩张引起的变暖的时空格局，并评估中国西部成渝都市区（CCMR）的适应策略至关重要。观测到的城市热岛强度在 2009-2011 年 7 月约为 1.5K。我们使用天气研究和预报（WRF）模型，使用真实和预测的城市土地利用数据，模拟了 CCMR 夏季作物、2010 年城市和 2030 年城市情景下的近地表气温。2010 年城市与耕地情景之间的差值为 0.93K。2010-2030 年城市发展引起的变暖在 1-1.5K 范围内，但未来城市发展引起的变暖将弱于中国东部的历史变暖。我们将屋顶反照率增加到 0.8，以评估冷屋顶（CR）与 2030 年城市情景之间的近地表气温差异，这代表了 CR 的最大潜在影响；我们还评估了绿色屋顶（GR）引起的冷却（即 GR 与 2030 年城市情景之间的差异）。由于 CR 反射太阳辐射和 GR 增加额外的水蒸发，白天会发生更大的冷却。我们提供了一个评估标准，即冷却效率（CE），以衡量 CR 和 GR 的局部性能。CE 基于城市变暖而不是较大空间尺度上的绝对冷却来表示本地冷却能力。CE 揭示了夜间冷却能力较低，这对 CR 和 GR 在夜间的应用构成了重大挑战。只有当 CR 的屋顶反照率超过 0.68 时，CR 在整个 CCMR 上的冷却能力才优于 GR。所采取的措施应适当调整，以优化成本、技术和节能。
