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Abstract:
The global navigation satellite systems (GNSS) signal propagation is affected by the water vapour content in the atmosphere. Thus, a detailed processing of the GNSS observations enables for estimation of integrated moisture content, expressed by the precipitable water vapour (PWV) parameter. Although it is not a direct method of PWV measurement, the reliability of the information obtained in this way enabled the wide application of the GNSS technique in the atmospheric studies, which is generally called GNSS meteorology. Considering the fact that part of the GNSS networks has constantly been operating since 1996, the length of the collected GNSS PWV time series is sufficient for the use in climate studies. In this work, 18-years of GNSS PWV time series have been used to analyse variability of the integrated moisture, with special focus on the global tropics. We show that the interannual changeability may took place due to the occurrence of different climate modes. In the analysed cases, we found strong correlations not only to the El Nino Southern Oscillation (ENSO) but also do the different phenomena. Here we can distinguish Indian Ocean Dipole (IOD) or, even more locally, the Tropical Southern Atlantic (TSA) oscillation. We also found a dependency between PWV variability and extreme ENSO phases on stations that generally does not show clear correlation. Since climate modes influence prevailing weather conditions, we estimated GNSS PWV diurnal cycle and verified its possible changes caused by different climate modes.
