城市热岛效应是伴随城市化而产生的生态环境问题,研究城市热力景观格局的演变有助于掌握城市热岛效应变化的机制与规律,为城市产业合理布局、城市生态环境改善提供科学的决策支持.以重庆市主城九区为研究对象,基于2001年Landsat7 ETM+、2007年Landsat5 TM以及2014年Landsat8 OLI_TIRS三期遥感影像数据,利用辐射传输方程法和Jiménez-Mu?oz et al.(2014)的分裂窗算法反演地表温度,并在此基础上,计算热力景观格局指数,研究重庆市热力景观格局的演变过程.结果表明,(1)2001—2014年,重庆市主城九区热岛和强热岛景观类型范围不断扩大,热岛效应明显增强,渝中区热岛和强热岛所占百分比最高,江北区、南岸区、九龙坡区和大渡口区的增长速度较快.(2)热力景观类型中热岛面积的增加主要由正常区斑块转化而来,而强热岛面积的增加主要由正常区和热岛斑块转化而来,跨越正常区的斑块转化较难.(3)在斑块类型水平上,热岛与强热岛斑块优势度增大.2001—2014年热岛斑块密度减小3.33,平均斑块面积增大6倍;强热岛斑块密度减少0.65,平均斑块面积增大5倍.热岛和强热岛斑块变得大而集中,破碎度减小.热岛间的连通性与强热岛斑块间的连通性越来越高,连通性指数分别增大了3.51和8.41,强热岛斑块形状的复杂程度逐期变大.在景观水平上,2001—2014年重庆市的斑块数量和斑块密度减小,平均斑块面积增大,热力景观破碎化程度逐渐降低,斑块连通性指数高,均大于99.5.聚合度和均匀度指数分别增大14.85和0.09,像素间聚合成斑块的程度变大且斑块类型面积越来越均匀.由此可见,随着城市的发展,重庆市的热环境问题越来越严重,利用热力景观格局指数分析城市热环境,可了解城市热力景观格局的演变趋势,为热岛的缓解提供理论依据.%Urban heat island effect is one of the ecological environment issues in the process of urbanization. The study of the dynamic changes of the urban thermal landscape pattern is helpful to find out the mechanisms of urban heat island and provide decision support for urban planning and urban ecological environment improving. In this study, Landsat7 ETM+ (2001), Landsat5 TM (2007) and Landsat8 OLI_TIRS (2014) were used to derive land surface temperature based on radiative transfer equation and Jiménez-Mu?oz's split window algorithm (2014). Then the thermal landscape pattern indices were calculated to analyze the evolution of the thermal landscape pattern in Chongqing City. The results showed that, (1) From 2001 to 2014, heat island and strong heat island expanded, and the heat island effect was significantly enhanced. Heat island and strong heat island in Yuzhong district had the highest percentage, and there was a faster growth rate in Jiangbei, Nanan, Jiulongpo and Dadukou district than which in other areas. (2) The increased heat island area was mainly converted from the normal area, and the increased strong heat island area was mainly converted from the normal area and the heat island. Patch conversion across normal area was generally difficult. (3)At the patch-class level, the preponderance of heat island and strong heat island were increased. From 2001 to 2014, the density of heat island patch decreased by 3.33, while the average patch area increased 6 times. Similarly, the density of strong heat island patch decreased by 0.65, while the average patch area increased 5 times. The heat island and strong heat island patches were larger and more concentrated than before, and the fragmentation was decreased. The connectivity between the heat island and strong heat island increased by 3.51 and 8.41, respectively. The shapes of the strong heat island patches became more complicated. At the landscape level, the patch number and patch density was decreased from 2001 to 2014, while the average patch size was increased, and the thermal landscape fragmentation degree of Chongqing city was gradually reduced in this period. The patch connectivity index was higher than 99.5. The aggregation index and the evenness index had increased by 14.85 and 0.09, respectively. The aggregation of the pixels was enhanced and the area of the patch type became more uniform. We can conclude that the thermal environment of Chongqing became more and more serious with the city's development. Our developed method for analyzing urban thermal environment using thermal landscape pattern index and findings in this study are helpful to understand the evolution trend of urban thermal landscape pattern, and provide a theoretical basis for the mitigation of urban heat island.
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