Preprints
https://doi.org/10.5194/amt-2021-197
https://doi.org/10.5194/amt-2021-197

  31 Aug 2021

31 Aug 2021

Review status: this preprint is currently under review for the journal AMT.

Towards operational multi-GNSS tropospheric products at GFZ Potsdam

Karina Wilgan1,2,3, Galina Dick2, Florian Zus2, and Jens Wickert2,1 Karina Wilgan et al.
  • 1Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany
  • 2GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany
  • 3Wroclaw University of Environmental and Life Sciences, C.K. Norwida 25, 50-375 Wroclaw, Poland

Abstract. The assimilation of Global Navigation Satellite Systems (GNSS) data has been proven to have a positive impact on the weather forecasts. However, the impact is limited due to the fact that solely the Zenith Total Delays (ZTD) or Integrated Water Vapor (IWV) derived from the GPS satellite constellation are utilized. Assimilation of more advanced products, such as Slant Total Delays (STDs) from more satellite systems may lead to improved forecasts. This study shows a preparation step for the assimilation, i.e. the analysis of the multi-GNSS tropospheric advanced parameters: ZTDs, tropospheric gradients and STDs. Three solutions are taken into consideration: GPS-only, GPS/GLONASS (GR) and GPS/GLONASS/Galileo (GRE). The parameters are compared with two global Numerical Weather Models (NWM): European Centre for Medium Weather Forecast (ECMWF) ERA5 reanalysis and a forecast model ICON run by the German Weather Service. The results show that for ZTDs and horizontal gradients, all three GNSS solutions show similar level of agreement with the NWM data. For ZTDs, the agreement is better for the ERA5 model with biases of approx. 1.5 mm and standard deviations (SDs) of 7.7 mm than for ICON with biases of 3.2 mm and SDs of 10 mm. For tropospheric gradients, the agreement with both NWMs is very similar: the biases are negligible and SDs equal to approx. 0.4 mm. For the STDs, the GPS-only solution has an average bias w.r.t. ERA5 of 4.2 mm with SDs of 25.2 mm. The statistics are very slightly reduced for the GRE solution and further reduced to a bias of 3.5 mm with SDs of 24.5 mm for the Galileo-only observations. This study shows that all systems are of comparable quality. However, the advantage of combining more GNSS systems in the operational data assimilation is the geometry improvement by adding more observations, especially for low elevation angles.

Karina Wilgan et al.

Status: open (until 05 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Karina Wilgan et al.

Karina Wilgan et al.

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Short summary
The assimilation of the GNSS data in weather models have a positive impact on the forecasts. The impact is still limited due to using only the GPS zenith-direction parameters. We calculate and validate more advanced tropospheric products from three satellite systems: the US American GPS, Russian GLONASS and European Galileo. The quality of all the solutions is comparable, however combining more GNSS systems enhances the observations geometry and improves of the quality of the weather forecasts.