摘要
城市热岛的定量化分析对于客观刻画热岛的物理特征、了解其对城市人居环境质量的影响等具有重要意义。针对区域尺度上城市热岛遥感研究缺乏定量、有效衡量指标的状况,为充分反映热岛信号的空间变化特征,按照热岛检测-热岛信号函数模拟-热岛容量建模的思路,建立了城市热岛容量模型。以北京城市热岛为对象的应用实例证明该模型能够综合热岛强度和热岛面积等多方面信息,满足城市热岛定量化分析的需求。研究结果表明,由于不同主导因子的影响,北京城市热岛存在显著的昼夜和季节差异。
Along with rapid urbanization,urban heat island(UHI) has become one of the most serious urban problems,because of its impacts on the urban microclimate,air quality,energy consuming,public health and so on.With the advent of thermal remote sensing technology,remote observations of UHIs become the focus of urban remote sensing.While some progresses have been made,remote sensing study of UHI has been slow to improve qualitative description of thermal patterns and simple correlations.As a common indicator of UHI,magnitude is often used to reflect the degree of UHI occurrence,and it can be computed as the different indicator between the temperatures of urban surfaces and rural surfaces.However,the extent of UHI is often neglected when measuring an UHI as a whole.In order to explore a quantitative and more effective indicator for UHI dynamic monitoring at regional scale,aiming at deriving its spatial feature and facilitating the comparisons between different UHIs occur at different time or different areas based on remote sensing imageries such as NOAA AVHRR and Terra/Aqua MODIS data,this paper proposes a new parameter-UHI volume to integrate UHI magnitude with extent effectively.After the subtraction of the rural contribution in the land surface temperature(LST) image,the isolated UHI signature is suitable to use a least-squares Gaussian surface and then the UHI volume is calculated as a double integral of the UHI signature function over its footprint,to which the extent UHI happens.This study investigates the applicability of this volume model based on examination of thirty EOS-Terra MODIS level 1B imageries of Beijing city and its surrounding suburban areas,and the imageries were acquired between 2004—2006.These imageries include fifteen nighttime scenes,with their corresponding daytime scenes.Firstly,the resampled digital elevation model(DEM) data of the study area,the normalized difference vegetation index(NDVI) and the modified normalized difference water index(MNDWI) are used to extract the urban areas.Secondly,a simplified method is applied to retrieve the land surface temperature from MODIS channel 31 and channel 32,accounting for the land surface emissivity.Thirdly,four transects across the center of Beijing city at different directions including N-S,W-E,NW-SE and NE-SW are selected to detect the UHIs to ensure the application of the volume model is valid.The detections reveal that each of the UHI in Beijing City at different time has a single core and its spatial distribution is symmetrical as a whole,despite there are some small UHIs in the outskirts,so the volume model presented is appropriate for the UHI simulations.Results of the UHI simulations demonstrate that:(1)The correlation between the modeled UHI signatures and the corresponding true values is close,especially for the nocturnal UHIs.This fact indicates that the Gaussian is suitable and the volume model is valid for UHI simulation at regional scale in Beijing.(2)There is obvious UHI effect in both daytime and nighttime in the summer.In the spring,autumn and winter,there is UHI effect in the nighttime,while no UHI in the daytime;the UHI magnitude and volume shows that the diurnal UHI is intenser than the nocturnal UHI,and the difference of the volume between the diurnal and nocturnal UHIs seems to be stable.(3)Because of different dominant factors including natural and anthropogenic factors and their different influences,the changes of the nocturnal UHIs are complicated,especially the extents of UHIs.The UHI magnitude and volume shows that the nocturnal UHI effect is intensest in the winter,while weakest in the summer.The application in Beijing suggests that the volume model may be a promising routine to measure UHIs quantitatively based on remote sensing imageries.However,the precondition of this model urges that its applicability in other cities should be varified further.
出处
《遥感学报》
EI
CSCD
北大核心
2008年第5期734-742,共9页
NATIONAL REMOTE SENSING BULLETIN
基金
国家自然科学基金项目(编号:40671130,40771136)
遥感科学国家重点实验室开放基金项目
国家重点基础研究发展计划项目(编号:2007CB714403)
关键词
城市热岛容量
地表温度
MODIS
遥感
urban heat island volume
land surface temperature
MODIS
remote sensing
