北京城区不透水地表盖度变化及对地表温度的影响

基于QuickBird高分辨率影像、LandsatTM影像及夜间灯光数据,设计了集成CART（Classification and Regression Tree,）算法和多源遥感数据估算亚像元级不透水地表盖度的技术方案,采取适用于典型温带半干旱地区的ISP（Impervious Surface Percentage ）提取方法,提取2001年和2011年北京城区不透水地表盖度,并将不透水地表盖度分为3类,ISP为10%~60%的区域为低密度区,60%~80%的区域为中密度区,大于80%的区域为高密度区。同时采用单窗算法反演2001年和2011年地表温度,对2001-2011年北京六环以内城区不同环路区域ISP发展趋势,以及其与地表温度的相关性进行分析。结果表明：（1）北京城区的不透水地表盖度变化主要集中在低密度区域,与之相比,中密度区域和高密度区域不透水地表盖度变化不大。2001-2011年来北京五环以内区域由于城建区较多,整体不透水地表变化并不明显,主要变化区域集中在五环至六环以内区域,其中低密度区增长明显,中密度区和高密度区主要增长集中在东部,可以看出,近年来五环至六环以内区域发展迅速,城建区范围不断扩大。（2）相较于2001年,2011年北京市中心地表温度明显上升,高温区聚集程度更为明显。其中四环以内地表温度与周边区域地表温度相比,温差明显增大。（3）通过对比2001年和2011年各密度区平均地表温度发现,相较于2001年,2011年北京市六环以内城区各密度区之间的地表温度差异更大,城市热岛效应更为明显。（4）2001年和2011年北京城区各环路区域内不透水地表盖度与地表温度均呈正相关。四环至六环区域,地表温度随不透水地表盖度变化的趋势相近。ISP在10%~20%的区域,地表温度随不透水地表盖度增高而上升的速率明显高于其他区域,ISP大于20%的区域地表温度上升速率下降,且趋于一致。

Influence of Impervious Surface Change on Land Surface Temperature in Beijing

Classification and regression tree (CART) algorithm was used to extract the impervious surface percentage (ISP) of Beijing six ring within the city in 2001 and 2011 based on QuickBird high-resolution images, Landsat TM and night light data. The method is suitable for typical temperate semi-arid climate area. We classified the ISP as three groups. The ISP region for 10%~60% is defined as a low-density region, 60%~80% is defined as a medium-density area and for the rest area which the ISP is more than 80% is high-density area. Meanwhile, based on the Landsat TM, the land surface temperature of 2001 and 2011 were retrieved by using the single window algorithm. The study area has been designated as a region within six rings of Beijing. According to the characteristic of Beijing urban layout, this paper analyzed the development trend of ISP in different ring road and its correlation with land surface temperature from 2001 to 2011. In order to seek an effective way to improve the ecological environment in Beijing and mitigate the urban heat island effect. The results are as follows: (1) The change of ISP in Beijing urban area mainly concentrate in the low-density area. In comparison with the low-density area, the ISP of middle-densitiy area and high-density area does not change so much. Due to the vigorous city construction within the fifth ring road from 2001 to 2011, the whole change of ISP is not obvious. The variation mainly concentrates in the region between the fifth ring road and the sixth ring road, in which the growth of low density area was significant, while the growth in the middle and high density area was mainly in the east part. From the above results, it can be concluded that the development within the fifth ring road and sixth ring road develops rapidly and the range of city construction continued in recent years. (2) Compared with 2001, the land surface temperature of the central areas in Beijing in 2011 increased dramatically, and the aggregation extent of high-temperature region is more evident. The temperature difference increased significantly between the region within the fourth ring road and the surrounding areas. (3) By comparing the average surface temperature of each density area in 2001 and 2011 we find that compared with 2001, the differences in land surface temperature in 2001 also increased between different ISP categories and the urban heat island effect was more and more remarkable. (4) In both 2001 and 2011, there is a positive correlation between the land surface temperature and the ISP in every ring road region of Beijing urban areas. In the regions between the fourth and sixth ring road, the land surface temperature and the ISP shares a similar change trend. In the regions with ISP between 10% and 20%, the rising rate of land surface temperature is obviously higher than other regions. In the regions with ISP higher than 20%, the rising rate of surface temperature decreases, and the change tends is uniform.