Articles | Volume 19, issue 19
https://doi.org/10.5194/amt-19-6209-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/amt-19-6209-2026
© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
02 Oct 2026
Research article |
| 02 Oct 2026
| 02 Oct 2026
Long-term climatology of vertical profiles of polarimetric variables and ice-microphysical retrievals at X-band – Part 1: Radar calibration
Section Meteorology, Institute of Geosciences, University of Bonn, Bonn, Germany
Velibor Pejcic
Section Meteorology, Institute of Geosciences, University of Bonn, Bonn, Germany
Silke Trömel
Section Meteorology, Institute of Geosciences, University of Bonn, Bonn, Germany
Laboratory for Clouds and Precipitation Exploration, Geoverbund ABC/J, Bonn, Germany
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With more than 1000 hours of weather radar observations from the X-band radar in Bonn, Germany, collected over ten years, we examined how stratiform clouds change through the seasons and how particle properties change from ice to the liquid phase. We found that summer conditions favor larger particle concentrations, stronger snow aggregation accompanied by riming, and thicker melting layers. These results provide an important reference for e.g. improving weather prediction models.
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With more than 1000 hours of weather radar observations from the X-band radar in Bonn, Germany, collected over ten years, we examined how stratiform clouds change through the seasons and how particle properties change from ice to the liquid phase. We found that summer conditions favor larger particle concentrations, stronger snow aggregation accompanied by riming, and thicker melting layers. These results provide an important reference for e.g. improving weather prediction models.
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Lucas Reimann, Clemens Simmer, and Silke Trömel
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Polarimetric radar observations were assimilated for the first time in a convective-scale numerical weather prediction system in Germany and their impact on short-term precipitation forecasts was evaluated. The assimilation was performed using microphysical retrievals of liquid and ice water content and yielded slightly improved deterministic 9 h precipitation forecasts for three intense summer precipitation cases with respect to the assimilation of radar reflectivity alone.
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On 14 July 2021, heavy rainfall fell over central Europe, causing considerable damage and human fatalities. We analyzed how accurate our estimates of rainfall and peak flow were for these flooding events in western Germany. We found that the rainfall estimates from radar measurements were improved by including polarimetric variables and their vertical gradients. Peak flow estimates were highly uncertain due to uncertainties in hydrological model parameters and rainfall measurements.
Prabhakar Shrestha, Silke Trömel, Raquel Evaristo, and Clemens Simmer
Atmos. Chem. Phys., 22, 7593–7618, https://doi.org/10.5194/acp-22-7593-2022, https://doi.org/10.5194/acp-22-7593-2022, 2022
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The study makes use of ensemble numerical simulations with forward operator to evaluate the simulated cloud and precipitation processes with radar observations. While comparing model data with radar has its own challenges due to errors in the forward operator and processed radar measurements, the model was generally found to underestimate the high reflectivity, width/magnitude (value) of ZDR columns and high precipitation.
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Geosci. Model Dev., 15, 291–313, https://doi.org/10.5194/gmd-15-291-2022, https://doi.org/10.5194/gmd-15-291-2022, 2022
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The article focuses on the exploitation of radar polarimetry for model evaluation of stratiform precipitation. The model exhibited a low bias in simulated polarimetric moments at lower levels above the melting layer where snow was found to dominate. This necessitates further research into the missing microphysical processes in these lower levels (e.g. fragmentation due to ice–ice collisions) and use of more reliable snow-scattering models in the forward operator to draw valid conclusions.
Silke Trömel, Clemens Simmer, Ulrich Blahak, Armin Blanke, Sabine Doktorowski, Florian Ewald, Michael Frech, Mathias Gergely, Martin Hagen, Tijana Janjic, Heike Kalesse-Los, Stefan Kneifel, Christoph Knote, Jana Mendrok, Manuel Moser, Gregor Köcher, Kai Mühlbauer, Alexander Myagkov, Velibor Pejcic, Patric Seifert, Prabhakar Shrestha, Audrey Teisseire, Leonie von Terzi, Eleni Tetoni, Teresa Vogl, Christiane Voigt, Yuefei Zeng, Tobias Zinner, and Johannes Quaas
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The article introduces the ACP readership to ongoing research in Germany on cloud- and precipitation-related process information inherent in polarimetric radar measurements, outlines pathways to inform atmospheric models with radar-based information, and points to remaining challenges towards an improved fusion of radar polarimetry and atmospheric modelling.
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Short summary
For the X-band radar in Bonn, the birdbath method has proven to be insufficient for calibrating differential reflectivity. This study raises awareness of the need for critically applying the birdbath method. A novel technique for calibrating the reflectivity factor is presented and compared with satellite measurements, serving as ground truth, and a known standard calibration method. The offset values agree well with the satellite and even exceed the accuracy of the standard calibration method.
For the X-band radar in Bonn, the birdbath method has proven to be insufficient for calibrating...
