Three months of continuous monitoring of atmospheric water vapor with a network of Global Positioning System receivers

Abstract

Abstract. Three months of continuous data from the Global Positioning System (GPS) using 20 sites in Sweden and 5 sites in Finland have been used to estimate the integrated amount of atmospheric water vapor. The quality of the data has been assessed by comparisons with a microwave radiometer (water vapor radiometer (YVVR)) at the Onsala Space Observatory and with data from four different radiosonde stations. We found the agreement in integrated water vapor (IWV) between the GPS estimates and the radiometer data to be 1-2 kg/m 2 in terms of daily root-mean-square (rms) differences. A major part of these rms differences were caused by a bias between the data sets. This bias (WVR-GPS) varied from day to day between -1.0 and +2.5 kg/m 2 with a mean value of +1.3 kg/m 2.Comparisons with radiosonde data showed rms differences around or slightly above 2 kg/m 2 for each station using the entire 3 month data set. Also here the GPS estimates were, on the average, below the radiosonde results. We show that the radomes used to protect the GPS antennas are likely to cause a large part of the observed bias. Spatial structure functions were calculated by using the GPS and the radiosonde data. An overall consistency between the GPS-based and the radiosonde-based structure functions indicates that the spatial correlations between the GPS estimates are not affected by the estimation process used in the GPS data analysis.

Validation of a regional weather forecast model with GPS data

“…Rocken et al, 1993Rocken et al, , 1995Emardson et al, 1998 GPS network. The data were obtained from the Onsala Space Observatory, Onsala, Sweden, and the Finnish Geodetic Institute.…”

“…Details about the measurement procedure were described e.g. by Emardson et al, 1998. The weather forecast model HRM used as boundary conditions 6-hourly analyses (EM3AN) of the EuropaModell of the DWD and was initialized by interpolation of the 0 h analysis.…”

On the relation between the wet delay and the integrated precipitable water vapour in the European atmosphere

“…Emardson et al (1998) derived a relation between the wet delay and the IPWV based on site latitude and the day of the year. In that study almost 30 000 radiosonde profiles from the Scandinavian countries were used.…”

The Sofia University Atmospheric Data Archive (SUADA)

“…3a, is relatively stable on a day timescale. It can be derived by using its dependency on the local atmospheric pressure (Bevis et al, 1992;Emardson et al, 1998):…”