在利用卫星资料估算地表城市热岛(SUHI)时,选择具有代表性的乡村背景区域对于热岛评估结果的准确性与科学性具有重要意义.通过改进乡村背景选择算法建立一种在区域或全球尺度上相对简单合理的SUHI估算方法,并引入热岛面积、热岛比例指数等指标开展珠三角城市群热岛时空分布特征分析及定量评估.研究结果表明:(1)文章建立的SUHI估算方法能有效监测城市群热岛年/季和昼/夜变化,气候背景可能是城市群季节SUHI变化的一个决定性因子;(2)近5年(2010—2014)珠三角城市群已形成一个广州、佛山、中山、东莞和深圳等城市相连的巨大"区域热岛群",且白天和夜晚存在多个不同的热岛中心,年均SUHI>3.0℃的热岛总面积为700 km2,排名前3的城市分别为佛山(277 km2)、东莞(228 km2)和广州(110 km2),其中心城区SUHI分别为3.1℃、1.9℃和1.5℃;(3)夜晚热岛强于白天,最强热岛出现在秋季夜晚,SUHI>3.0℃的热岛总面积可达6169 km2(占行政区域面积的11%),排名前3的城市分别是东莞(1514 km2)、佛山(1420 km2)和广州(1280 km2),且9个城市有8个中心城区热岛评估等级在4(严重)以上,显示珠三角大部分中心城区热岛都很严重,且经济结构在很大程度上影响着城市热岛强弱;(4)从1994—2014年,城市群SUHI I>3.0℃的热岛总面积从6 km2增加到4812 km2,中心城区平均SUHI从0.1℃增加到1.8℃,热岛评估等级从1级(轻微)上升到4级(严重),这种变化反映了珠三角城市群迅速扩展所导致的热岛强度增加和范围扩大的事实.%When applying the satellite data to estimate the surface urban heat island intensity (SUHI), the selection of a rural background in which the effect of urbanization is minimal poses a great effect on the accuracy and scientificity of SUHI evaluation results. This article proposes a method for estimating the intensity of SUHI which can be computed by improving the selection of rural backgrounds based on topography, land use, vegetation coverage and urban night-light indexes. Based on long time series MODIS and NOAA satellite data, using the SUHI index and urban heat island proportion index (UHPI) , the temporal and spatial variation of urban heat island for the Pearl River Delta urban agglomeration region was quantitatively evaluated . The study revealed that this method is able to objectively monitor regional-scale SUHIs. The climate of the area studied is probably a determining factor in the seasonal variation of SUHIs. Research from the last five years (2010—2014) demonstrates that the Pearl River Delta urban agglomeration has developed a huge cluster of regional heat islands linking Guangzhou, Foshan, Dongguan, Shenzhen and Zhongshan. The annual mean heat island area with SUHI greater than or equal to 3.0 ℃ was 700 km2. The three largest area cities are Foshan at 277 km2, Dongguan at 288 km2, and Guangzhou at 110 km2, The mean SUHI of all central urban areas are 3.1 ℃, 1.9 ℃ and 1.5 ℃, respectively. The heat island intensity for Pearl River Delta urban agglomeration in night is larger than in daytime and is the strongest in autumn nighttime with the heat island area with SUHI greater than or equal to 3.0 ℃ at 6169 km2 (11% of total urban group area). The three largest area cities are Dongguan at 1514 km2, Foshan at 1420 km2, and Guangzhou at 1280 km2, which showed the urban economic structure decided the heat island intensity and scope to a large extent in spite that the area and population of Dongguan and Foshan are smaller than Guangzhou's. There are eight among nine cities with heat island assessment levels more than "severe" grades, which indicates that the phenomenon of heat islands in urban agglomeration is currently severe and a city's economic structure may also have a significant influence on SUHI. During autumn nighttimes in 1994, 2004, and 2014, the areas with SUHI greater than or equal to 3.0 ℃ were 6 km2, 2825 km2 and 4812 km2; the mean SUHI were 0.1 ℃, 1.3 ℃ and 1.8 ℃; and the UHPI were 0.14, 0.42 and 0.68. The heat island assessment levels were slight, relatively severe, and severe, respectively, which reflects the fact that the heat island effect for urban agglomerations has strengthened and expanded in the last 20 years.
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