基于Landsat影像的西宁市主城区热岛效应分析

利用西宁市主城区1987、2001年和2013年3个时期的Landsat遥感影像反演出了不同时期的地表温度，并对地表温度进行归一化处理后得到相应时期的热岛等级分布图。结果表明，西宁市城区的热岛效应呈先减弱后增强的态势，热岛区分布逐渐集中，主要分布在城市边缘未利用地、主城区中商业区、工业区以及城市交通线路周围；热岛效应的范围在扩展，其分布与建成区的扩展范围在空间上基本相吻合，但是强度有小幅减弱；热岛效应与植被覆盖度呈负相关，植被覆盖度每增加10%，地表温度下降约1.23℃；建设用地及未利用地的均温最高，而水体及有植被覆盖区域均温较低；绿色植被和水体有缓解热岛效应的作用，而因建成区的扩大有大规模的不透水面是热岛效应加剧的主要原因；气候和天气因素也对热岛效应有一定的影响。

Analysis of Heat Island Effect Based on Landsat Images in Xining City

To understand the heat island effect and its intensity and scope changes as well as its driving forces in Xining,this paper retrieved the land surface temperature (LST) from Landsat images of Xining in 1987,2001 and 2013.As the Landsat image thermal band data had higher spatial-temporal revolution,it could be usually used to evaluate the heat island effect.To avoid the errors resulting from different seasons,the grade distribution of heat island at different times were derived with the land surface temperature normalization.The analysis results showed that the effect of heat island in Xining was enhancing after weakening firstly.The heat island areas were gradually centralized and mainly were unutilized lands on the edge of city,around the downtown area,industrial areas and urban traffic lines.The area of heat island expanded and the spatial distribution was basically consistent with the layout of construction land,but the intensity of heat island effect weakened slightly.The effect of heat island had negative correlation with vegetation fraction.With every 10% vegetation fraction increased,the land surface temperature drop was about 1.23℃.The mean LST of construction land and unutilized land was the highest while vegetation cover areas and water body had a lower LST.Green vegetation and water body had the role of reducing heat island effect.The masses of impervious surface were the main cause of heat island effect.Climate and weather factors also had a certain influence on heat island effect.