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Global LAnd Surface Satellite Products System(GLASS)反照率产品基于Angular Bin(AB)算法,仅使用单一观测角度的地表或大气层顶反射率数据就能较为准确地反演地表宽波段反照率,具有较高的时间分辨率,可以反映降雪、融雪、收割等状况下地表反照率的快速变化。遵循“一检两恰”的验证流程对这一反照率产品进行验证,首先使用FLUXNET站点验证数据对AB算法反演的Landsat Thematic Mapper (TM)高分辨地表反照率数据进行验证,再将TM高分辨反照率聚合到GLASS像元尺度对GLASS反照率产品进行验证。挑选FLUXNET的5个站点,筛选无云条件下的TM高分辨率影像,共获得103组有效验证数据。验证结果表明,GLASS反照率产品具有较高的精度,总体误差约为 0.0163,可以满足大多数应用的精度需求。
The Global LAnd Surface Satellite Products System (GLASS) albedo product provides a gap-filled shortwave albedo map with high temporal resolution through which the occurrence of snow and rain and the variation of vegetation status can be detected. The GLASS albedo is retrieved with the Angular Bin (AB) algorithm, which can estimate the shortwave albedo from a single observation of reflectance. To assess the accuracy of this albedo product, FLUXNET observations were used to calculate the actual surface albedo as the true value to validate the high-spatial resolution albedo derived from Landsat Thematic Mapper (TM) imagery at 30 m by the AB algorithm. The Landsat TM albedo was then aggregated to 1 km resolution and was compared with the GLASS albedo at 1 km. The absolute error of the GLASS albedo is less than 0.0163, which demonstrates itsreliabilityfor most application requirements.