A simple method for estimating of evapotranspiration using remotely sensed data in arid regions: a case study in Yemen Mountains

The surface temperature measured by satellite can be the basis of evapotranspiration (ET) computation. The possibility of the daily sum of the regional ET using surface temperature was examined under Yemen mountains weather conditions. A simplified energy balance formula, which relates daily ET to daily net radiation with one measurements of surface and air temperature, was used. A Landsat TM data was used in the study with some field measurements were used to define the initial relationship. Field observations made during the vegetation period of 1995, 1996 and 1998 were used to establish the relationship. The study area measured 90m x 90m located in the Yemen mountains area. In general the study area is an inhomogeneous which consists of cultivated area, urban and metropolitan. For the soil type the area is include of basalt rock, volcanic rock. the inhomogeneous of the study area causes the problems for calibration of hand-held thermometer and the time variation in taking the measurements. Comparison between results produced by the formula and the one measured in the field is very important for evaluating the accuracy of the model and further development