https://researchdata.se/en/catalogue Search results en Accurate long-term GNSS-derived atmospheric water vapour time series are essential when used in climate research. However, these records are frequently affected by interventions, e.g., change of hardware at the station. We investigate the homogenization of integrated water vapour (IWV) time series co-located GNSS stations at 19 sites in Sweden and one site in Denmark. Fri, 04 Sep 2026 15:31:59 GMT https://researchdata.se/en/catalogue/dataset/2026-270 https://researchdata.se/en/catalogue/dataset/2026-270 Chalmers University of Technology Gunnar Elgered Tong Ning We have used eight co-located GNSS stations, with different antenna mounts, to estimate atmospheric signal propagation delays in the zenith direction and linear horizontal gradients. The gradients are compared with the results from a water vapour radiometer (WVR). Water drops in the atmosphere has a negative influence on the retrieval accuracy of the WVR. Hence we see a better agreement using WVR data with a liquid water content (LWC) less than 0.05mm compared to when LWC values of up to 0.7mm are included. We have used two different constraints when estimating the linear gradients from the GNSS data. Using a weak constraint enhances the GNSS estimates to track large gradients of short duration at the cost of increased formal errors. To mitigate random noise in the GNSS data, we adopted a fusion approach averaging estimates from the GNSS stations. This resulted in significant improvements for the agreement with WVR data, a maximum of 17% increase in the correlation and a 14% reduction in the root-mean-square (rms) difference for the east gradients. The corresponding values for the north gradients are both 25%. Overall, no large differences in terms of quality were observed for the eight GNSS stations. However, one station shows slightly poorer agreement for the north gradients compared to the others. This is attributed to the station's proximity to a radio telescope, which causes data loss of observations at low elevation angles in the south-south-west direction. Thu, 16 Jan 2025 09:11:15 GMT https://researchdata.se/en/catalogue/dataset/2024-515 https://researchdata.se/en/catalogue/dataset/2024-515 Chalmers University of Technology Gunnar Elgered Tong Ning Abstract of the published paper using the dataset: We have used one year (2019) of multi-GNSS observations at the Onsala Space Observatory on the Swedish west coast to estimate the linear horizontal gradients in the wet propagation delay. The estimated gradients are compared to the corresponding ones from a microwave radiometer. We have investigated different temporal resolutions from 5 min to one day. Relative to the GPS-only solution and using an elevation cutoff angle of 10° and a temporal resolution of 5 min the improvement obtained for the solution using GPS, Glonass, and Galileo data is an increase in the correlation coefficient of 11 % for the east gradient and 20 % for the north gradient. Out of all the different GNSS solutions, the highest correlation is obtained for the east gradients and a resolution of 2 h, while the best agreement for the north gradients is obtained for 6 h. The choice of temporal resolution is a compromise between getting a high correlation and the possibility to detect rapid changes in the gradient. Due to the differences in geometry of the observations, gradients which happen suddenly, are either not captured at all or captured but with much less amplitude by the GNSS data. When a weak constraint is applied in the estimation of process, the GNSS data have an improved ability to track large gradients, however, at the cost of increased formal errors. Wed, 21 Jul 2021 08:21:52 GMT https://researchdata.se/en/catalogue/dataset/2021-219-1 https://researchdata.se/en/catalogue/dataset/2021-219-1 Chalmers University of Technology Gunnar Elgered Tong Ning