Trends in the atmospheric water vapour estimated from two decades of ground-based GPS data: sensitivity to the elevation cutoff angle
Konferensbidrag (offentliggjort, men ej förlagsutgivet), 2017
We have analysed 20 years of data from 13 GPS sites in Sweden and Finland, using two different elevation cut-off angles, 10° and 25°, to estimate the atmospheric integrated water vapour (IWV). Then we estimated the linear long-term trends of IWV which were compared to the corresponding trends from the radiosonde data at 7 nearby (< 120 km) sites and the trends given by the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis data (ERA-Interim). The IWV trends given by the GPS elevation 10° and 25° solutions show similar results when compared to the trends from the radiosonde data, with correlation coefficients of 0.71 and 0.74, respectively. When compared to the IWV trends obtained from ERA-Interim, the GPS solution for the 25° elevation cutoff angle gives a significantly higher correlation (0.90) than the one obtained for the 10° solution (0.53). The results indicate that a higher elevation cutoff angle is meaningful when estimating long term trends, and that the use of different elevation cutoff angles in the GPS data processing is a valuable diagnostic tool for detection of any time varying multipath impacts.