【作者】 敬书珍；

【导师】 倪广恒；

【作者基本信息】 清华大学 ， 水利工程， 2009， 硕士

【摘要】 地表水热通量反映了地气之间水分和能量的交换过程,是目前水资源领域研究的热点。地表的复杂性直接影响着地表水热通量的空间分布,进而影响着区域内及全球的气候环境变化。近年来,随着遥感技术的发展与逐渐成熟,其宏观、实时的特点使得研究大尺度范围的水热通量及地表特性更为便捷。因此,借助遥感手段,研究地表特性对地表水热通量的影响具有重要意义。本文选用北京市为研究区域,以Landsat的TM资料为基本数据源,首先利用监督分类中的最大似然法完成了土地利用/覆盖的遥感分类,并将分类结果与1:1万地形图进行了对比分析,表明其精度较好。同时,采用线性光谱混合分析方法提取了北京市平原区的不透水面信息,通过分析分解结果均方差统计影像,发现其平均误差小于0.02 ,满足精度要求。另外,本文引入DEM数据对原始的SEBAL模型进行了地形(高程、坡度、坡向)校正;部分参数估算时对不同下垫面给出不同的经验公式,从而拓展了SEBAL模型的适用范围,基于改进后的SEBAL模型定量反演了地表水热通量,对模型反演结果进行了初步验证,结果合理可信。在此基础上,本研究定量分析了不同土地利用/覆盖类型对地表水热通量的影响。引入归一化植被指数(NDVI)、不透水率及主要地形参数(高程、坡度、坡向)来表征地表的特性,讨论了这些参数与地表水热通量的相互关系。同时还分析了城市化导致的地表水热通量的城郊差异。研究结果表明,土地利用/覆盖类型的特点影响着各通量及日蒸散发的空间分布。净辐射通量受坡度、坡向的影响较大,其最大值点对应的坡度、坡向与影像获取时刻的太阳高度角及方位角直接相关;除水面以外,土壤热通量和显热通量与不透水率呈正相关,与NDVI呈负相关;潜热通量与不透水率呈负相关,与NDVI呈正相关。各通量的分布呈现明显的城郊差异性,由城市功能核心区到远郊的生态涵养区,净辐射通量及潜热通量呈现增加趋势,而土壤热通量及显热通量呈减小趋势,日蒸散发呈增加趋势。更多还原

【Abstract】 Land surface water/heat fluxes reflect the exchange process of water and energy between land surface and atmosphere, and are the research focus in hydrological field. The complexity of underlying surface, directly determines spatial distribution of land surface water/heat fluxes. Recently, remote sensing technology, due to its macroscopic and real-time properties, is gradually widely used in the study of land surface water/heat fluxes and underlying surface in large-scale region. Therefore, it is essential and feasible to study the impact of land use/cover properties on land surface water/heat fluxes based on remote sensing data.In this study, using Landsat TM remote sensing data in Beijing, land use and land cover classification is conducted by maximum likelihood method and comparison with topographical map with scale 1:10000 proves its accuracy. Then information of impervious surface is extracted by spectral mixture analysis (SMA), and the RMS image indicates the result is reasonable. In addition, the study refines the original algorithms by coupling digital elevation model in the SEBAL model for the topographic correction (elevation, slope and aspect), and formulating different empirical formulas in different land surfaces for estimation of some variables, to expand the application of the regional remote sensing model. Land surface water/heat fluxes were estimated by modified SEBAL mode and the result shows reasonable.Then quantitative analysis of impacts on land surface water/heat fluxes was performed in three aspects, i.e. of typical land use/cover types; NDVI, impervious ratio, and terrain parameters (elevation, slope and aspect); urban and suburb regions.The results indicate that mean values of water/heat fluxes associated with different land use/cover types are significantly different. Net radiation is sensitive to slope and aspect and the maximum value occur at the slope of 25 degree and the aspect of 304 degree. Except water surface, both soil heat flux and sensible heat flux have positive correlation with surface impervious ratio and negative correlation with NDVI, while latent heat flux shows negative correlation with surface impervious ratio and positive correlation with NDVI. Urban and rural regions show obviously different fluxes characteristics, from central urban to suburb, net radiation flux and latent heat flux increase, while soil heat flux and sensible flux decrease, and daily evapotranspiration increase.更多还原