Atmospheric horizontal gradients measured with eight co-located GNSS stations and a microwave radiometer

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.