2nd Symposium of IAG Commission 4 “Positioning and Applications”
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Multi-GNSS tomography: Case study of the flood in Europe in July 2021

Karina Wilgan1,2, Hugues Brenot3, Michael Bender4, Ricardo Biondi5, Galina Dick2, Florian Zus2, and Jens Wickert1,2
Karina Wilgan et al.
  • 1Technische Universität Berlin, Germany (wilgan@gfz-potsdam.de)
  • 2German Research Centre for Geosciences (GFZ), Potsdam, Germany
  • 3Royal Belgium Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium
  • 4Deutscher Wetterdienst (DWD), Offenbach, Germany
  • 5University of Padova, Italy

Due to climate change, intensive storms and severe precipitation will continue to happen, causing destructive flooding. These natural hazards have dramatic impact on humanity. In July 2021, a series of storms with prolonged rain episodes took place over Europe. Several countries were affected by severe floods that followed that rainfall, causing many deaths and material damage. A good understanding and forecasting of severe weather events is thus of uttermost importance.

This study is a combined effort of two research projects: Advanced MUlti-GNSS Array for Monitoring Severe Weather Events (AMUSE) funded by the German Research Foundation DFG and the ALARM äH2020 SESAR project from EU (https://alarm-project.eu). We highlight the interest of multi-GNSS tomography for the 3D-modelling of the neutral atmosphere refractivity and the water vapour density. We obtain these tropospheric parameters for the July 2021 flood in Germany and four tomographic solutions with different constraining options and time resolutions using either GPS only or multi-GNSS estimates. In the constrained solution, we take hourly a priori information from the numerical weather model ICON-D2 (provided by the German Weather Service, DWD), while in the stand-alone solution, the a priori is used only to initiate the tomography. Our investigations show that the stand-alone solution is producing more patterns of refractivity, especially for the multi-GNSS solution, while is it also temporally more stable. We compare the tomographic results with external observations such as radiosondes and GNSS radio occultations from Metop-A and Metop-B satellites. The results show that tomography is producing wetter conditions than the reference data sources. However, we can see the precursor information of the initiation of deep convection in the ground-based GNSS technique.

How to cite: Wilgan, K., Brenot, H., Bender, M., Biondi, R., Dick, G., Zus, F., and Wickert, J.: Multi-GNSS tomography: Case study of the flood in Europe in July 2021, 2nd Symposium of IAG Commission 4 “Positioning and Applications”, Potsdam, Germany, 5–8 Sep 2022, iag-comm4-2022-30, https://doi.org/10.5194/iag-comm4-2022-30, 2022.