A 17 year time series of ground-based GNSS for sensing of atmospheric water vapour

Other conference contribution, 2015

We have analysed 17 years of GPS data from 123 sites in Europe and obtained time series of the amount of Integrated Water Vapour (IWV) in the atmosphere. In total 69 sites have data from a period longer than 10 years and 35 sites have data from more than 15 years. Two different data analyses have been carried out to study the impact of the use of different models. We find that the impact is small, but the IWV results from different data analyses shall not be mixed when studying the long term stability of the IWV, e.g. when estimating trends. Using the IWV results from the analysis using the more recent models we estimate linear trends as well as the amplitude and the phase of the diurnal signal in the IWV at the different sites. The estimated trends are sensitive to different periods analysed and are comparable to the corresponding uncertainties. The estimated amplitude of the diur- nal cycle during the summer varies from 0.16 kg/m^2 to 1.46 kg/m^2 while the peak time of the hourly IWV mean is around 18 local solar time for the most of sites.