Effect of spatial resolution on cloud area retrievals: a comparison of results derived from the airborne visible/infrared imaging spectrometer (AVIRIS) and the thermal infrared multispectral scanner

摘要

Abstract: Thermal Infrared Multispectral Scanner (TIMS) imagery and Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) imagery are registered to each other for seven scenes. Cloud area, as determined by applying the 3-band ratio method to AVIRIS imagery, is used to determine the optimum temperature threshold in the TIMS imagery. For this set of scenes, a threshold of 2$DGR to 3$DGR below the background temperature provides for the most accurate cloud pixel identification. Five to 8% differences in cloud area are found when comparing cloud pixel identification between AVIRIS and TIMS. Some of the differences are due to misregistration; however, at least half are due to differences in the mensuration process. It is demonstrated that cloud edges have a distribution of temperature thresholds, indicating the difficulty of locating cloud edges with a single temperature threshold. It is found that cloud edges occupy nearly half of the entire range of scene temperatures, significantly overlapping the distribution of background temperatures.!11