hide
Free keywords:
-
Abstract:
This oral summarizes activities developed under the scope of JWG C.2: Quality control methods for climate applications of geodetic tropospheric parameters. In it, we present results on the effort to assess long-term ground-based GNSS-derived ZTD trends for eventual use in climate models, either for assimilation or validation. We have analyzed the ZTD time series estimated from the six REPRO3 IGS Analysis Centers (ACs) who made them available (COD, ESA, GFZ, GRG, JPL and TUG), comparing their long-term trends, long-term here meaning 20 years or longer. A subset of the IGS global network composed of thirty stations were selected. The estimated ZTD time series goes through a process of homogenization using ERA-5 derived ZTDs as reference, before being averaged to daily values to minimize potential influences coming from different estimation strategies used by individual ACs. Similar averaging is applied to the ERA-5 ZTDs and to the IGS tropo-product if already reprocessed in REPRO3. Two combinations, using weighted mean and (a robust) least median of squares, are generated from the six homogenized ACs. The combinations serve as quality control to each ACs. Analysis of the trends generated from each one of the nine ZTD times series is performed in both time and frequency domains. Results obviously vary depending on the geographical location. For example, for station ALBH, in Canada, inter-AC scatter is 0.47 mm/decade for the trends, 0.11 mm for the annual amplitudes, and 0.29 degrees for the annual phase.
