EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Climate Change’s Influence on June 2009 Extreme Precipitation Event Over Southeast Austria

Aditya N. Mishra1,2, Douglas Maraun1,2, Heimo Truhetz1, Emanuele Bevacqua3, Raphael Knevels4, Herwig Proske5, Helene Petschko4, Alexander Brenning4, and Leopold Philip6
Aditya N. Mishra et al.
  • 1Wegener Centre for Climate and Global Change, University of Graz, Graz, Austria
  • 2FWF-DK Climate Change, University of Graz, Graz, Austria
  • 3Department of Meteorology, University of Reading, Reading, UK
  • 4Friedrich Schiller University of Jena, Jena, Germany
  • 5FH JOANNEUM, Graz, Austria
  • 6Austrian Institute of Technology, Seibersdorf, Austria

During 22-24 June 2009, Austria witnessed a rampant rainfall spell that spread across populated areas of the country. High-intensity rainfall caused 3000+ landslides in Feldbach, and property damages worth €10,000,000 in Styria itself. Numerous synoptic-scale studies indicated the presence of a cut-off low over the Adriatic and excessive moisture convergence behind the extreme event. In a warmer climate change scenario, such an extreme precipitation event may become more intense due to higher water holding capacity of air with increased temperatures, but this reasoning may not be so straightforward considering the complex physics of precipitation.

Precipitation, as a natural atmospheric phenomenon, is dependent upon the dynamic and thermodynamic characteristics of the atmosphere. While it is safe to say that the thermodynamic characteristics of the atmosphere are relatively easier to simulate with confidence using available global models, the same cannot be said about the dynamics. This can be blamed on the chaotic non-linear behaviour of the atmosphere and problem in resolving sub-grid scale processes that reduce the model accuracy for longer spatial scales.

CCLM regional model is used to study this extreme precipitation event. Our setup uses IFS data to calculate initial and boundary conditions for the simulations of the ‘present’ case where our attempt is to recreate the event over the same location as the original event. Further we use CMIP5 global climate models (at the RCP8.5) scenario. In particular, these will be applied in the ‘surrogate climate change’ method. Here, the climate change signals are calculated by computing the difference between the thermodynamic fields of the CMIP5 simulations for the future and the past. These climate change signals are applied to the original fields to obtain the ‘changed’ fields which are used to calculate new initial and boundary conditions resembling a climate-change future. A similar approach is to be applied for the ‘past’ case simulations.

The idea behind this experimental setup is to establish a ‘storyline’ for the event as it would have occurred in the past, present and the future. The storyline approach provides an alternative to the traditional probabilistic approach for assessing risk enhancement and can serve to study responses of different mechanisms to climate change. The storyline approach also helps in decision-making as event-oriented risk management is easy for people to perceive and respond to. An associated landslide modelling study, which uses the precipitation output of our simulations as input, looks into the probable increased risks of landslides in the region and will directly aid the lives of those living in Southeast Austria.

How to cite: Mishra, A. N., Maraun, D., Truhetz, H., Bevacqua, E., Knevels, R., Proske, H., Petschko, H., Brenning, A., and Philip, L.: Climate Change’s Influence on June 2009 Extreme Precipitation Event Over Southeast Austria, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14631,, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 03 May 2020
  • CC1: Comment on EGU2020-14631, Linda van Garderen, 04 May 2020

    Dear Aditya,

    Thank you for your presentation and work. It is very interesting.

    I was wondering if you have any idea if the difference between the models and there output in precipitation could be depending or influenced by how orography is managed in the model. There might be large differences between the regional and global models in this case and for the chose region the effect of that management may be large.


    Thank you.

    Linda van Garderen

    • AC1: Reply to CC1, Aditya N. Mishra, 04 May 2020

      Dear Linda,

      Valid point.
      As you understand already, the simulating model is the CCLM, while the driving data in all cases is from the IFS (modified IFS in some cases). The idea behind choosing the selected 4 GCMs is based on the amount of precipitation they simulate over the concerned region. Obviously the representation of orography in each of them is different and in no way compared to CCLM's detailed topography, the GCMs are used only to calculate the so-called climate change signals, which are indicative of how much more warm and humid the atmosphere may become with rcp8.5 driving that particular model. Aforementioned, 'modified IFS' is thus calculated using this 'climate change' signal driving the CCLM run.

      Let me know if there's still lack of clarity,