长江三角洲城市群热环境安全格局及土地利用变化影响研究

城市化进程的加快对区域热环境具有重要影响,热环境的改变会引发一系列生态环境问题,科学地评价城市群热环境安全对于城市发展的规划布局和建设舒适的人居环境具有重要意义。本文利用多期MODIS地表温度数据产品,在构建热环境安全等级分级标准的基础上,对长江三角洲城市群热环境安全格局时空变化特征和土地利用变化的影响进行了探讨。结果表明：① 2015年长江三角洲城市群热环境不安全区域多分布于城市建成区及建成区周围,以南京、上海、杭州和宁波等城市形成的“Z”型区域最明显,临界安全区域多分布于郊区,较安全区域集中分布于长江以北平原区域,安全区域则主要分布于杭州及杭州以南山地、丘陵区,太湖大部分区域以及长江三角洲城市群北部区域;② 2005-2015年长江三角洲城市群热环境不安全区域、临界安全区域、较安全区域和安全区域分别呈现扩张、小幅增长、缩减和先缩减后扩张趋势;③ 土地利用结构中建设用地比例过高和林地比例过低是导致热环境安全等级下降的主要原因,其次,建设用地侵占大量耕地也是导致热环境不安全区域扩张的主要原因。

Study on the Security Pattern of the Heat Environment and the Influence of Land Use Change in the Yangtze River Delta Urban Agglomeration

The acceleration of urbanization plays an important role in regional heat environment, whose changes may lead to a series of ecological problems. A scientific evaluation on the heat environment of urban agglomeration is essential to urban planning and construction. Based on the construction of a standard of heat environment security levels, we analyzed the spatio-temporal variation of the heat environment security pattern and its causes from land use changes in the Yangtze River Delta urban agglomeration using the MODIS land surface temperature products. The conclusions are as follows: (1) in 2015, the dangerous zones of the heat environment in the Yangtze River Delta urban agglomeration were mostly located in or closed to the urban built-up regions. For example, the “Z” region of Nanjing, Shanghai, Hangzhou, Ningbo and other cities were most obvious. The critical security zones were mostly located in suburbs while the relative security zones were mainly distributed in the northern plains of the Yangtze River. The security zones were mainly located in Hangzhou and its southern mountain and hilly region, most of the region of Tai Lake and the north of the Yangtze River Delta urban agglomerations; (2) the dangerous zone, the critical security zone, the relative security zone and the security zone showed an upward trend, a slight upward trend, a downward trend and a first downward then upward trend, respectively; (3) the primary reason of the decline in security levels of the heat environment was the high ratio of the build-up areas and the low ratio of woodlands. Additionally, the large quantity of croplands occupied by build-up areas was also the reason of the expansion of dangerous zones.