MODIS数据以及变分订正技术在长沙城市热岛特征分析中的应用

利用EOS/MODIS遥感信息反演地表温度和植被覆盖指数,引进新的变分订正方案,利用常规气象资料,对高分辨率地表温度场实施订正,对长沙市热岛(UHI)空间分布规律及影响因子进行研究.通过分析长沙城市地区的土地覆盖、植被绿地状况与热岛空间分布状况的关系,揭示出研究区域UHI主要特征为:(1)从研究区域地表覆盖图发现,长沙市城区四周均有相对地势较高的山地,但地形梯度不大,接近四面环山的地貌特征,容易造成城区的热量聚集,有利于城市热岛效应的形成,使得长沙城区存在明显的热岛分布;(2)UHI分布与城市结构的轮廓相一致,长沙城区与地势相对平坦的近郊区的地表温度差异为3～5℃,与地势较高的周边远郊区的地表温度差异为6～8℃,长沙城区热岛效应与城市规划呈对应关系,热岛效应最显著的区域为二环线内,并从中心沿三环逐渐向郊区减弱;(3)地表覆盖类型对UHI的效应明显,长沙地区植被绿地状况与UHI呈现明显反相关分布,揭示出植被绿地对降低UHI具有重要的作用,大范围的绿地建设能有效降低UHI.

On urban heat island effect in Changsha based on MODIS data and the new variational processing method

The land surface Temperature(LST) and vegetation index were derived from EOS/MODIS data,and the high resolution LST was Coγrected by AWS(automatic weather station) data acCoγding to a new variational processing method,the character of the urban heat island(UHI) of Changsha and its causes are investigated.By the study of the relationship between vegetation and spatial characteristics of UHI,the mainly spatial characteristics of UHI has been analyzed and it was: (1) The terrain of the suburbs is higher than the urban region,the gradient of the terrain height is small,and this geomorphological featrue is conducive to assemble of the heat,the UHI phenomenon of Changsha is obvious especially in the summer night; (2) The UHI distribution is similar to the outline of the urban construction.The LST of urban is 3-5 ℃ higher than the flat low areas close around the city,and 6-8 ℃ higher than further areas.The region which has the most obvious UHI phenomenon is the region surrounded by the second city ring road,and the UHI phenomenon gradually weakened from the city centre to suburb; (3) The impact of geomorphological character to UHI is notable,the relationship between vegetation index and UHI is Anti-related,it was indicated that the improvement of the vegetational status is very important to the elimination of UHI phenomenon,the implementation of the urban green land planning can reduce UHI effect.