基于TM影像的城市地表湿度对城市热岛效应的调控机理研究

论文以探究城市热岛效应调控机理为研究目的,以徐州地区1985-2010 年夏季四期Landsat TM影像为研究数据,应用单窗算法、K-T变换、空间叠加分析以及缓冲区分析等研究方法,对徐州市城市热岛时空变化特征进行了反演,重点对徐州市城市热岛强度的调控机理进行了分析并提出了通过K-T变换提取表示城市建成区内部植被与水体覆盖程度的城市地表湿度(ULSW)这一新指标.研究结果显示:城市地表湿度显著区对城市热岛效应起到了有效的调控作用,并且随着城市地表湿度值的提高,区域内部以及周围环境的温度都会随之下降.城市地表湿度指标对于城市热岛效应的调控水平具有一定的代表意义.

Mechanism Research of Urban Land SurfaceWetness Regulating Urban Heat Island Effect Based on TM Images

In recent years, the study of urban heat island effect regulation mechanism mainly focused on the influence of urban green space, urban landscape park and urban water on urban land surface temperature, few studies have considered the impact of land surface humidity on environment temperature. The purpose of this paper is exploring the regulation mechanism of urban land surface humidity on urban heat island effect. Xuzhou city was chosen to be the study case. The administrative boundary vector data of Xuzhou and four summer TM images of Xuzhou area from 1985 to 2010 were used. Research methods are as follows: First, Monowindow Algorithm was used to calculate the land surface temperatures of four periods. From 1985 to 2010, the acreage proportion of urban heat island area obviously increased from 31.87% to 38.57%, but from 1991 to 2010, the acreage proportion of high intensity urban heat island decreased from 23.32% to 20.52%. Second, a new index—Urban Land Surface Wetness (ULSW) which is on behalf of the vegetation and water coverage inside the city built-up area was extracted by using K-T transformation. The mean values of ULSW index of the four TM images from 1985 to 2010 are 5.91, 5.89, 6.33 and 6.94 respectively, which showed a trend of growth. Then, using spatial overlay analysis to calculate the correlation between the land surface temperature and the ULSW, the result showed that the slope of the four linear fitting equations are all negative which means the correlation of these two indicators are negative. At last, buffer analysis was used to compute the influence of ULSW index on the surrounding environment temperature. Four typical areas were chosen in each of the four TM images, and five buffers at the interval of 60 m were set up for each selected area. The result showed that the surrounding environment temperature of the center area of higher ULSW is cooler. The cooling effect of the first buffer layer is most obvious, the average temperature drop being 1.47 ℃. The cooling effect of the outermost buffer layer is minimum, the average temperature drop being 0.12 ℃ . The further the buffer is from the center area, the less the average surrounding environment temperature drops. The final research conclusions are: 1) ULSW index simplifies the extraction process of the vegetation and water in the construction land. 2) The area where the ULSW index value is high can effectively reduce the effect of urban heat island. 3) The inside and outside temperature of the area will decrease with the increase of ULSW. 4) ULSW index can be used to indicate the urban heat island regulation ability of an area. ULSW index can be also applied to other researches such as urban cooling channel planning, urban landscape and ecology planning, urban ecology and environment evaluation.