Retrieval of atmospheric water vapor and land surface temperature from AVHRR thermal imagery

AVHRR thermal imagery is sensitive to both water vapor and surface temperature. A new algorithm for simultaneously estimating the water vapor content and land surface temperature from the two thermal channels on AVHRR is developed. Simple functional profiles of atmospheric temperature and pressure are derived from LOWTRAN-7 standard atmospheres. A simplified radiative transfer model is specified from this information which permits, using an optimum procedure based on the Powell algorithm inversion to derive vertically-integrated atmospheric water vapor content and land surface temperature simultaneously from two AVHRR thermal channels. This algorithm has been tested using measurements from a few FIFE field observation stations, and results indicate that its accuracy is much better than the split-window approach for the land surface temperature and channel 5 and channel 4 difference for the water vapor content