南京市市域热场变化及其原因分析

Research on the ground-surface thermos changes in Nanjing from 1988 to 2009

为了研究南京市的城市热岛效应空间分布及其变化情况,利用1988年7月5日和2009年6月13日的TM第6波段数据,定量反演了南京市域的热场分布情况,并利用相对亮温从全市与不同区域两个空间尺度对其变化情况进行统计分析。结果表明,南京市的热环境状况总体处于不断下降的过程中,全市平均温度从1988年的28.19℃降到2009年的25.37℃,降幅达2.82℃;但城市核心区外围还处于不断加强的变化趋势中,这种变化主要表现在两个方面:一是热场强度有所增大,最高温2009年比1988年提高了2.77℃;二是亮温极差扩大,2009年温度极差值比1988年提高了2.23℃。全市的高温范围呈现以长江市区段为轴的基本对称格局,并向东、南、北3个方向扩展延伸,但重点集中在以建邺、雨花台、玄武、栖霞4区为主体构成的城区外围热岛区。南京市域热场的变化原因,既有气温升高变化趋势的影响,也有土地利用与城市建设空间变化因素的作用,其中城市建成区面积的急速扩张是市区热岛效应增强的主要原因,而城区绿化与城市外围的绿化和生态建设对于缓解城区热岛效应与市域热场的强度起到了积极作用。

The paper is aimed at investigating the urban thermos is- land（UTI） phenomenon by taking Nanjing as its case-study sample. As is well-known, one of the most important environmental problems in the modern urban development is the greenhouse effect due to the environmental temperature rising, which not only affects the urban environment, but also influences the normal living conditions of their residence. In this paper, we would like first of all to retrieve the statistics of the brightness temperature and the relative brightness tem- perature from Landsat TM thermal-infrared data（July 15, 1988 andJune 13, 2009） to witness the urban heat changes, and then to ana- lyze its spatial and dynamics distribution in all the city sphere, both of its downtown areas and its suburban areas. The results of our in- vestigation indicate that the brightness temperature intensity in Nan- jing has been decreasing from 1988 to 2009, whereas the mean sur- face temperature tends to decrease from 28.19 ℃ in 1988, to 25.37℃ in 2009, though in some special areas, the temperatur keeps in- creasing. From the results mentioned above, two points can be in- ferred： on the one hand, the highest temperature（28.19℃）（2009） exceeded 2.77 ℃ than that（25.37 ℃） in 1988, on the other, the temperature difference between the highest（2009） and lowest showing a gap by 2.23 ℃ than that in 1988. As compared with 1988, in area distribution, the area of hotter surface, including slight, moderate, severe and very severe ranks in 2009, can be thought to spreading from the northern areas to the southern and then to the eastern along the Yangtse River, though it was mainly concentrated in the Jianye, Yuhuatai, Xuanwu and Qixia districts. In 1988, the UTI of the built- up area are mainly concentrated in the Xiaguan, Gulou, Baixia and Qinhuai districts. Moreover, in 2008, the UTI were spreading from this four districts to the Jianye, Yuhuatai, Xuanwu and Qixia dis- tricts. Out of the built-up area, the UTI was spreading to the Liuhe and Pukou districts. Besides, in the county seats of Lishui and Gaochun, the surface brightness temperatures had also been rising from 1988 to 2009. And, finally, we have also discussed the reasons that may account for the surface thermos changes. In our opinion, the changes of climate, land-use manner, and the increasing of urban built-up area are likely to be the main causes that lead to the above mentioned changes.