城市生态气象监测评估初步研究与实践——以北京为例

气象条件作为影响生态系统最活跃、最直接的驱动因子,影响着生态系统的质量和人类生存的环境,关系着生态保护和建设的成果,而城市生态系统具有与其他系统不一样的气候特征,目前还未形成一套有关城市的生态气象监测评估方法。基于生态气象学理论,分别从城市气候环境、与气候相关的陆表环境、大气环境、人居环境以及城市高影响天气气候事件等5个方面选择不同的要素和指标开展了城市生态气象监测评估初步研究,并以北京为例,利用2018年国家和区域自动气象站资料、大气成分观测资料、2002—2018年MODIS卫星资料、Landsat及环境一号卫星资料,开展了2018年北京城市生态气象监测评估。监测评估显示,(1)2018年北京城市“热岛”和“干岛”气候特征明显,并在北京二环与五环之间存在一个“冂”形风速低值区。(2)2018年北京陆表生态环境、大气环境、人居环境进一步好转:其中植被覆盖度达61.6%,创2002年以来新高,气象条件贡献率达50%,生态涵养区植被生态质量处于正常偏好的面积比例达93.2%;中心城区陆表温度为2011年以来最低值;重要水源地密云水库、官厅水库水体面积均为2000年以来最大值;气溶胶光学厚度、霾日数、大气静稳指数分别较过去4年平均值下降14%、31%和8%,大气扩散条件偏好,对霾日减少贡献率达21%,外地污染传输对PM2.5贡献达到53%;城市生态冷源较2013年明显增加,城市“热岛”得到缓解。(3)历史罕见的夏季高温闷热、冬季阶段低温、极端强降水以及持续无降水等高影响天气气候事件给城市安全运行和生态环境带来不利影响。综合评估表明2018年北京气象条件总体利于陆表生态环境改善,有利的气候条件提高了生态环境的质量,但城市生态质量仍面临着极端天气气候事件、城市热岛、低风速以及外来大气污染输送等风险。

Preliminary Study and Practice of Urban Ecological Meteorological Monitoring and Evaluation:A Study in Beijing

Meteorological conditions,as the most active and direct driving factors affecting the ecosystem,affect the quality of the ecosystem and the humans live environment,and are related to the results of ecological protection and construction.Urban ecosystems have different climatic characteristics from other systems.A set of methods for monitoring and evaluating urban eco-meteorology has not yet been developed.Based on the theory of ecometeorology,this paper selects different elements and indicators for urban eco-meteorological preliminary study from five aspects:urban climate environment,climate-related land surface environment,atmospheric environment,living environment and high-impact weather and climate events.Taking Beijing as an example,this paper used 2018 national and regional automatic weather station data,atmospheric composition observation data,2002?2018 MODIS satellite data,Landsat,and environmental satellite data to monitor and evaluate 2018 Beijing urban ecological environment.The result shows that the climatic characteristics of the“hot island”and“dry island”of Beijing in 2018 are obvious,and there is a“冂”-shaped low wind speed zone between the second and fifth rings of Beijing.In 2018,Beijing’s terrestrial ecological environment,atmospheric environment,and living environment improved further.Among them,the vegetation coverage reached 61.6%,the highest since 2002,and the contribution rate of meteorological conditions reached 50%.The proportion of the area of vegetation ecological quality in the ecological conservation area at the normal preference level reached 93.2%.The land surface temperature in the central city is the lowest since 2011 and the water area of Miyun Reservoir and Guanting Reservoir,which are important water sources,are the largest since 2000.Aerosol optical thickness,number of haze days,and atmospheric stability index decreased by 14%,31%,and 8%,respectively,compared with the average of the past four years.Atmospheric diffusion conditions are preferred,contributing 21%to the reduction of haze days.Contribution of foreign pollution transmission to PM2.5 reaches 53%.Urban ecological cold sources have increased significantly compared to 2013,helping to alleviate the urban heat island.The high-impact weather and climate events such as historically rare hot and sultry weather in summer,low-temperature in winter,extreme heavy precipitation,and continuous precipitation-free weather have adversely affected the city’s safe operation and ecological environment.Comprehensive assessment shows that Beijing’s meteorological conditions are generally conducive to the improvement of the terrestrial ecological environment in 2018.Favorable climatic conditions have improved the quality of the ecological environment,but urban ecological quality is still facing extreme weather and climate events,urban heat islands,low wind speeds,and transportation of external air pollution risk.