Research PaperModeling investigation of wet tropospheric delay error and precipitable water vapor content in Egypt

A set of 1092 radio soundings was performed at the Egyptian stations in the south of Egypt, near the Mediterranean Sea, and near the Red Sea in 2005. These measurements are mean monthly data that were used to determine the mean vertical profiles of water vapor pressure and its effect on GPS signal propagation (wet tropospheric delay) in the troposphere and lower stratosphere. Temperature data were corrected for errors due to radiation, heat exchange processes, and for the lag errors of the sensor. Due to temperature dependence and other dry bias effects, the humidity errors were also taken into account. The results showed that partial water vapor pressure in Egypt varies from 6.43 to 23.19 mb and decreases significantly with height. In addition, the quantity of water vapor pressure above 8 km is negligible. Results showed that, in Egypt zenith wet delay varies from 66.84 mm to 239.34 mm. It can be concluded that, the best model to predict zenith wet tropospheric delay for the atmospheric conditions of Egypt is the Saastamoinen model with a mean error of 11 mm and rms of 3.12 mm.