利用TM影像分析天山北坡三工河流域地表反照率的时空变化

下垫面状况是影响地表反照率分布的主要因素之一。利用遥感方法获取地表反照率时空特征是研究地表下垫面状况的有效手段。天山北坡具有典型的山地－绿洲－荒漠景观和山盆地貌格局,这一独特且复杂多样的地表下垫面特征形成了特有的垂直分布的地表反照率。通过对三工河流域TM影像进行地形校正,基于6S(Second Simulation of Satellite Signal in the Solar Spectrum)模型分析地表反照率的时空分布。结果表明:基于中空间分辨率遥感数据的地表反照率反演适合于地表起伏明显的天山北坡地表反照率的分析。由于受到地表覆被类型及地表干湿程度的影响,三工河流域地表反照率呈明显的垂直地带性分布。中山森林带和低山干草原带受地形起伏和阴阳坡作用,其地表反照率表现出有规律的上下波动。绿洲区随着地表覆被类型、作物结构和作物物候的变化,地表反照率波动较大。

Analysis of the spatio-temporal distribution of the surface albedo in Sangong River Basin on the northern slope of Tianshan Mountains using TM image

The difference in land surface features and land cover conditions have a great impact on anisotropy surface albedo distribution. Remote sensing is an effective means to study the land surface features by obtaining spatial and temporal characteristics of surface albedo. The northern slope of the Tianshan Mountains is well-known with its typical mountain-basin geomorphology pattern system and mountains-oasis-desert landscape. The unique and complicated background forms the special vertical distribution of the surface albedo. This paper examines the spatial distribution of surface albedo on the northern slope of the Tianshan Mountains using Landsat TM images. Topographic correction was implemented on the images using topographic normalization model based on DEM and atmospheric correction was completed using 6S (Second Simulation of Satellite Signal in the Solar Spectrum) model. The results indicate: (1) The methodology for surface albedo inversed from the moderate spatial resolution remotely sensed data is reliable to be used for estimation of the surface albedo over the northern slope of the Tianshan Mountains with significant heterogeneity in elevation. (2) The distribution of the surface albedo on the northern slope of the Tianshan Mountains is affected by the land surface features, land cover conditions and surface soil moisture. Therefore, the spatial distribution of the surface albedo on the northern slope of the Tianshan Mountains presents a distinctly vertical zonal feature. As to the mountainous forest and the dry grassland in low mountain area, the surface albedo presents regular fluctuation under the effects of the undulating terrain and elevation changes. (3) Influenced by the cover types, the crop structure and the crop phenology of the cropland, the variation of the surface albedo of the oasis in the Sangong River Basin shows instability. In the oasis area, the surface albedo varies obviously with growth seasons of the crops as well.