典型地表对长沙主城区地表温度的影响分析

Typical Land Cover Impacts on Land Surface Temperature of Changsha Metropolitan Area

城市热岛是一种城市地区温度比郊区温度高的现象,它可改变城市的自然和社会过程,引发一系列环境问题。利用Landsat 8 TIRS10波段的单通道算法(TIRS10_SC算法)反演了长沙主城区2013年7月、2016年3月、7月和11月4景Landsat 8影像的地表温度,并进一步分析了地表温度的时空分布特征,建设用地、绿地、河流以及不同材质的屋顶等典型地表对主城区地表温度的影响。结果表明:①长沙火车站沿线、高桥大市场和部分工厂在各个时期均为高温区。2016年7月浏阳河周边区域热岛效应相对于2013年7月有所缓解,主要由天气情况的不同以及拆迁改变地表覆盖性质等造成。3月建设用地中比率最大的为中温,7月建设用地中比率最大的为次高温。3月和7月,绿地中比率最大的为次低温,水体中比率最大的为低温。而11月,建设用地和绿地中比率最大的为中温,水体中比率最大的次高温。②河流周边120 m范围内,由陆地向河流每减少30 m,7月建设用地平均温度减少0.93~1.26℃,绿地平均温度减少0.57~0.99℃;3月建设用地平均温度减少0.51~0.78℃,绿地平均温度减少0.3~0.57℃。河流的降温强度与河水温度和距离河流120 m以上的地表温度的差值大小有关。③负的MNDWI(非水体)与地表温度呈正相关关系,正的MNDWI(水体区域)与地表温度3月和7月呈负相关关系,11月呈正相关关系。④地表比辐射率对地表温度反演的结果影响显著,利用NDVI估算地表比辐射率难以区分高反射率的屋顶与其他类型的建设用地。因此,针对高反射率屋顶对地表比辐射率的影响有待进一步研究,以提高城区地表温度的反演精度,为减缓城市热岛效应提供参考依据。

Urban heat island is a phenomenon that the temperature of urban area is higher than suburb,which can change the natural and social process of city and causes a series of environmental problems.In this paper,Single-channel algorithm for Landsat 8 TIRS10 band(TIRS10_SC algorithm)is used to retrieval the land sur⁃face temperature of four landscape Landsat 8 images in Changsha metropolitan area in July 2013,March 2016,July 2016 and November 2016.This paper further analyzes the influence of typical land surfaces such as con⁃struction land,green land,rivers and roofs of different materials on the land surface temperature,the results in⁃dicate that:(1)The areas with high LST were located in Changsha Railway Station,the Gaoqiao Market and some factories at all times.Compared with July 2013,the heat island effect in the surrounding area of Liuyang River was alleviated in July 2016,which was mainly caused by the different weather conditions and the change of land cover nature by demolition.The largest ratio of construction land in March was moderate LST zone.The highest ratio of construction land in July was sub-high LST zone.In March and July,the highest ratio among green areas is sub-low LST zone,the largest ratio in water is low LST zone.In November,the highest ratio of construction land and green space was medium LST zone,and the sub-highest LST zone in water was the highest;(2)Within 120 m around the river,for every 30 m decrease from land to river,the average temper⁃ature of construction land decreased by 0.93~1.26℃and the average temperature of green land decreased by 0.57~0.99℃in July.The average temperature of construction land decreased by 0.51~0.78℃and the average temperature of green land decreased by 0.3~0.57℃in March.The cooling intensity of the river is related to the difference between the river temperature and LST more than 120 m away from the river;(3)Negative MND⁃WI is positively correlated with land surface temperature and positive MNDWI is negatively correlated with land surface temperature in March and July.However,MNDWI is positively correlated with land surface tempera⁃ture in November;(4)Emissivity has a significant effect on the results of land surface temperature inversion.It is difficult to distinguish the high reflectivity roofs and other types of construction land by using NDVI to esti⁃mate emissivity.Therefore,the influence of high-reflectivity roofs on emissivity needs to be further studied to improve the inversion accuracy of land surface temperature and provide a reference for mitigating the urban heat island effect.