VARIABILITY OF AT-SATELLITE SURFACE REFLECTANCE FROM LANDSAT TM AND NOAA AVHRR IN DEATH-VALLEY-NATIONAL-MONUMENT

The spatial and temporal variability of surface reflectance has been r ecognized as a good indicator of the condition of arid and semi-arid l andscapes. However, radiometric, attmospheric, and topographic factors all affect the measurement of surface reflectance from satellites suc h as Landsat Thematic Mapper (TM) and NOAA Advanced Very High Resoluti on 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 succe ssful with satellite observations. Radiometric, atmospheric, and topog raphic influences on surface reflectance were examined in this study o f surficial geologic units in Death Valley National Monument with coin cident 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 sa tellites and in situ measurements. Topographic effects on surface refl ectance were apparent in the mountains surrounding Death Valley Nation al Monument, but for the relatively gentle slopes along the alluvial f ans adjacent to the valley floor, significant topographic effects were not observed.