MONITORING LONG TERM VARIABILITY IN THE ATMOSPHERICWATER VAPOUR CONTENT USING GROUND-BASED GPS RECEIVER NETWORKS

Other conference contribution, 2011

We have processed 14 years of observations acquired from 33 GPS sites in Sweden and Finland. Estimated linear trends in the atmospheric Integrated Water Vapour (IWV), using a 10 degree elevation cutoff angle, are in a range from -0.4 to +0.6 kg/m^2/decade with a typical uncertainty of 0.3–0.4 kg/m^2/decade. The data from 13 GPS sites were processed for 8 different elevation cutoff angles from 5 degree to 40 degree. The resulting IWV trends were compared to the trends obtained from the data acquired at seven nearby radiosonde sites. The results show a clear variation in the trend correlation between the two techniques when different elevation cutoff angles are applied to the GPS data analysis. The best agreement is seen for the 25 degree solution resulting in a correlation coefficient of 0.79.