Contribution of permanent stations GPS data to estimate the water vapor content over Algeria

Abstract

In the last decade, important studies have demonstrated that GPS can be also used as an efficient tool for measuring the integrated water vapor (IWV) in the atmosphere which is a useful quantity for climatological and weather forecasting applications. This study presents the first results obtained by using the time series GPS stations of six local stations belonging to the continuously operating Algerian network, and 13 stations of the IGS (International GNSS Service) for the estimation of the value of the IWV locally. In this paper, tropospheric parameters are obtained from double difference processing of GPS observations, collected from 2008 to 2015, using the Bernese 5.2 software. For the validation of GPS IWV values, three approaches are used. In the first, the GPS IWV are compared with the corresponding ERA-Interim values derived from interpolations in time and space. The results show a good agreement with correlation coefficients exceeding 85% and an RMS (root mean square) between 2.22 and 5.53 kg m⁻². In the second approach, we compare GPS IWV and radiosondes over two stations, where the results showed an acceptable concordance and equivalent to those of the first approach. In the third approach, the GPS ZWD (zenith wet delay), roughly IWV, values are compared with the daily rainfall data provided by the Algerian Meteorological Office. The results show that the temporal variation of ZWD and the high rainfall collected by rain gauges (not far from those of GPS) present a perfect coincidence over the surrounding observed peaks. Finally, the analysis of the annual time cycle of ZWD and precipitation carried out on the data of geographically and climatically different GPS stations shows that these two parameters depend on the latitude of the site. The first experimental results of this study further strengthen the strong potential of GPS in meteorological applications.