PRECISION OF PRECIPITABLE WATER VAPOR FROM RADIOSONDE DATA FOR GPS SOLUTIONS

Abstract

The determination of Precipitable Water Vapor, PWV, is one of the basic objectives of GPS meteorology. PWV calculated from radiosonde data is used as a reference to assess GPS-derived PWV. The radiosonde-based PWV is derived by integrating the water vapor density along a balloon's rising path, which is a function of the observed temperature and relative humidity at different heights. Hence, the meteorological observation errors are propagated to the calculated PWV. Moreover, these meteorological observations are discrete, and a numerical integration scheme is employed to calculate the PWV. Therefore, the density of observations also influences the precision of the PWV (approximation errors). In this study, we analyze these two error sources in the determination of PWV using 50 days of Hong Kong radiosonde data. We estimate an approximation error of ± 0.5 mm and an observation error of ± 1.2 mm in calculating PWV. The total error is about ± 1.3 mm.