干旱区生态环境知识资源中心

The spatial and temporal variability of surface reflectance has been recognized as a good indicator of the condition of arid and semi-arid landscapes. However, radiometric, attmospheric, and topographic factors all affect the measurement of surface reflectance from satellites such as Landsat Thematic Mapper (TM) and NOAA Advanced Very High Resolution Radiometer (AVHRR). The effect of deriving surface reflectance from satellites with different spectral wavebands is an important issue if regional or global scale monitoring of arid landscapes is to be successful with satellite observations. Radiometric, atmospheric, and topographic influences on surface reflectance were examined in this study of surficial geologic units in Death Valley National Monument with coincident TM, AVHRR, and in situ measurements of surface reflectance. The results of this study indicated that spectral wavelength affected the estimate of surface reflectance more than any other factor. The short-wave surface reflectance waveband covering red through near-infrared provided both the closest agreement between satellites, and between satellites and in situ measurements. Topographic effects on surface reflectance were apparent in the mountains surrounding Death Valley National Monument, but for the relatively gentle slopes along the alluvial fans adjacent to the valley floor, significant topographic effects were not observed.