黑河流域地表反照率估算及其时空特征分析

基于不同空间尺度、长时间序列的地表反照率产品探究黑河流域2000—2012年的反照率时空变化特征。首先基于角度格网化(AB)算法对黑河流域30 m环境卫星一号HJ-1/CCD大气层顶方向反射率进行了地表反照率估算,作为高空间分辨率的地表反照率产品;选择同种算法计算的1 km空间分辨率的Global LAnd Surface Satellite(GLASS)反照率产品作为低空间分辨率反照率产品。结果表明:1利用AB算法反演的HJ卫星反照率具有较高精度,满足流域尺度反照率时空特征分析的精度要求;2黑河流域地表反照率空间分布差异显著,流域上游植被覆盖区域反照率较低,中下游荒漠地表反照率较高;3流域地表反照率的年内变化与季节性降雪和作物物候周期性变化一致。从季节变化角度,黑河流域反照率月平均值的年变化呈"U"字型,其中,冬季反照率最高,春季和秋季次之,夏季最低。从年际变化角度,黑河下游反照率呈上升趋势,上游和整个流域呈下降趋势。

Estimation of Land Surface Albedo and Spatio-Temporal Variability over Heihe River Basin

We used both high resolution with short-term albedo and moderate resolution with long-term albedo products to analyze the spatial-temporal characteristis of the Heihe River Basin during the years of 2000-2012. The 30 m land surface albedo product derived from HJ-1/CCD image by Angular Bin(AB) algorithm was evaluated through ground Automatic Weather Stations (AWS) measurements and compared with Global LAnd Surface Satellite (GLASS) albedo product.The spatial and temporal heterogeneity of land surface albedo over the Heihe River Basin were investigated by using both the HJ albedo product and GLASS albedo product. Preliminary validation results show that the HJ albedo product is well consistent with field measurements. The spatial patterns of annual average albedo during 2000-2012 are heterogeneous across the Heihe River Basin,lower in the upstream covered with vegetation and higher in the middle and down reaches of the desert. The heterogeneity of land surface albedo is consistent with the seasonal snowfall and the phenological cycles of crop. The albedo of upstream decreases year by year,while the downstream and the total basin increased. The annual cycles of albedo present an U-shape. The albedo has an obvious seasonal difference,which is highest in winter,followed by spring and autumn,lowest in summer.