利用MODIS卫星资料反演中国地区晴空地表短波反照率及其特征分析

Retrieval of the Surface Albedo under Clear Sky over China and Its Characteristics Analysis by Using MODIS Satellite Date

利用MODIS地表双向反照率产品 (MOD43B1 ) ,结合地表海拔高度和地表覆盖类型资料 ,计算并分析了中国地区晴空反照率的时空分布 ,以及地表反照率与地形和地表覆盖的关系。首先 ,利用改则自动气象站的地基观测对MODIS地表反照率进行了对比验证。验证结果表明卫星观测可以较好地反映反照率随时间的变化 ,MODIS地表反照率与地表实测反照率符合较好。年平均地表反照率与海拔高度有很好的相关 ,反照率的高值出现在高海拔山区。冬春季节 ,我国高海拔山区因积雪覆盖成为反照率的高值区 ;夏秋季节 ,地表反照率主要受地表土壤湿度和植被盖度的影响 ,沙地和沙漠地带反照率最高。最后 ,计算了中国典型地表类型的反照率随时间的变化 ,结果表明大部分地表类型的反照率具有较大的时间变化 ,地表反照率在春秋季节较大 ,夏季反照率较小。

Using MODIS surface albedo product (MOD43B1) of 2002, combining elevation and land cover data, surface albedo under clear sky over China area is computed and its spatial and temporal distribution is analyzed. The ground measurements of albedo at Grz (in the western Tibetan Plateau) are used to validate the satellite data. The result shows that satellite measurement can reflect the trend of surface albedo, and MODIS albedo meets the ground-based measurements well. The year-average albedo is correlative with elevation, and high value center of albedo is corresponding with mountain area. In winter and spring, high value centers of albedo are in mountain area because of the snow cover; and in summer and autumn, deserts become high value centers of albedo because of low soil moisture and low vegetation cover. The temporal variation of albedo of representative land cover types is calculated. The results show that the temporal variation of surface albedo over most land cover is distinct, and the albedo is larger in spring and autumn.