城市热岛的生态环境效应

A review of the eco-environmental consequences of urban heat islands

城市热岛效应(Urbanheatislandeffect,简称UHI)是一种由于城市建筑及人类活动导致热量在城区空间范围内聚集的现象,是城市气候最显著的特征之一。热岛引起地表温度的提高,必将强烈地影响着城市生态系统的物流、能流,改变城市生态系统结构和功能,产生一系列生态环境效应,影响着城市气候、城市水文、城市土壤理化性质、城市大气环境、城市生物习性、城市物质循环、城市能量代谢以及城市居民健康等。提高能量利用效率、优化城市格局、建设绿色屋顶、采用高反射率地表材料以及增加城市绿地均可有效地控制城市热岛效应。利用遥感手段和数值模型技术,开展多尺度的城市热岛生态环境效应研究,为改善城市生态环境、实现城市可持续发展提供理论依据。

One of the most well known forms of anthropogenic climate modification is the phenomenon of urban heating. Throughout various studies, the ambient temperatures of numerous urban centers have been determined to be several degrees higher than the ambient air temperatures of surrounding rural areas. This phenomenon, first documented in London by Lake Howard in1833, is referred to as the Urban Heat Island Effect （UHI）, and is still studied in many of the largest cities around the world. Based on the 34 English and 12 Chinese publications, we summarize the effects of urban heat islands on urban ecoenvironment. This review finds the urban heat islands have a number of meteorological and eco-environmental consequences. Long-term research is being conducted in urban areas to determine if UHIs plays a role in altering macro-scale meteorological patterns, such as snow frequency, snow cover, average dates of last freeze in spring and the first freeze in autumn. The thermal signature of UHIs has been found to increase the incidence of downwind precipitation, and catalyzes complicated interactions in urban photochemistry reactions. The effect of the urban heat island on urban soil＇s physical and chemical characters is also very pronounced. UHIs not only increases urban soil temperature, but also affects soil metabolism. The high levels of emissions of heat and pollutants in urban areas have significant impacts on the local environmental qualities of air temperature and air chemistry. This phenomenon does exert an influence on the behaviors of urban biology, urban biogeochemical cycle, urban energy utilization, resident bioclimatological conditions and health, etc. While, in many places, the heat island effect contributes to fuel saving in the colder seasons, this is often outweighed by the additional energy needs for airconditioning in summer. The intensity of UHIs can be mitigated by reducing artificial heat and greenhouse gas emissions, planning cities rationally, constructing rooftop gardens, preserving more water, planting more street trees, and using high-albedo building materials. Furthermore, used strategically, plants can absorb large quantities of solar radiation and modify air temperatures through transpiration. Referencing trends in related scientific fields, it can be gathered that further research on the ecological effects of urban heat islands should be encouraged. Finally, this review ends with a summary of future development trends of urban heat island assessment and abatement.