Estimation and Analysis of Precipitable Water Vapor Using GPS Data and Satellite Altimeter

Determination of water vapor in the atmosphere plays an important role in forecasting weather conditions and precipitation studies. For this reason, it is very important to study the tropospheric delay, especially the wet component, which is due to the presence of water vapor in the atmosphere. In this paper, the amount of water vapor was estimated by altimeter satellite radiometer and GPS data, which were based on GPS results and compared with satellite altimeter results. For this purpose, observations of 16 and 133 transmissions of Jason-3 satellites with a period of 10 days in 2018 were used. After processing the altimeter satellite observations using BRAT 3.3 software, the average amount of precipitation water vapor in this method for Tonekabon, Urmia and Bandar Abbas cities was 45, 44 and 30 mm, respectively. In the GPS method, using the Precise point positioning algorithm (PPP), the total tropospheric delay in the vertical direction was obtained (ZTD) and then the hydrostatic delay (ZHD) was subtracted from the total delay and finally by applying the relevant conversion factor to Non-hydrostatic delay (ZWD), the amount of precipitating water vapor was estimated.With processing GPS observations of three permanent stations of Tonekabon, Urmia and Bandar Abbas in 2018 corresponding to the observations of 16 and 133 transmissions of Jason-3 satellite with a time interval of 10 days and using From Bernese 5.2 software, the average amount of precipitable water vapor was estimated to be 47, 45 and 31 mm, respectively. Finally, the amount of RMS and standard deviation from the two methods were estimated to be 1 to 1.5 mm and 5 to 5.5 mm, respectively. The closeness of the results obtained from the two methods shows a very high agreement and compatibility between these two methods with a correlation coefficient of about 0.98 and the ability to combine them for climate and weather studies.