Estimation of Evapotranspiration with Modified SEBAL Model Using Landsat-TM and NOAA-AVHRR Images in Arid Mountains Area

This study examines the method for determining surface energy namely surface energy balance algorithm for land (SEBAL). This particular method utilized the combination of meteorological observations with information extracted from remote sensing data. The modified SEBAL model using data from Landsat TM and NOAA-AVHRR sensors, has been used to estimate net radiation, soil heat flux, sensible heat flux and ETfor Sana´a Basin in Yemen. The area is known for arid and semi-arid weather condition with undulating topographic. Remote sensing data for year 95, 96 and 1998 were used as a primary image for this study. Actual ET was computed during satellite overpass and integrated for 24-h on pixel-by-pixel basis for daily ET distribution. Due to the topographic effects, an attempt has also been made to incorporated DEM information for estimating the net radiation. As a result, a daily ET map generated from metrological observation was compared with estimated ET data simulated from remote sensing data. In conclusion, data from both remote sensing give reasonable values with result from TM are better compare to those of AVHRR due to difference in spatial resolution, which TM data a higher spatial resolution than AVHRR.