EGU2020-8593
https://doi.org/10.5194/egusphere-egu2020-8593
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Extreme precipitation events in the Mediterranean region: their characteristics and connection to large-scale atmospheric patterns

Nikolaos Mastrantonas1,2, Linus Magnusson1, Florian Pappenberger1, and Jörg Matschullat2
Nikolaos Mastrantonas et al.
  • 1European Centre for Medium-Range Weather Forecasts (ECMWF), Forecast, United Kingdom of Great Britain and Northern Ireland (nikolaos.mastrantonas@ecmwf.int)
  • 2Technische Universität Bergakademie Freiberg (TUBAF), Germany

The Mediterranean region is an area with half a billion population, about 10 percent contribution to the world’s GDP, and locations of global natural, historical and cultural significance. In this context, natural hazards in the area have the potential for severe negative impacts on society, economy, and environment. 

Some of the most frequent and devastating natural hazards that affect the Mediterranean relate to extreme precipitation events causing flash floods and landslides. Thus, given their adverse consequences, it is of immense importance to better understand their statistical characteristics and connection to large-scale atmospheric patterns. Such advances can substantially support the accurate and early identification of these extreme events, improve early warning systems, and contribute to mitigating related risks. 

This work focuses on the characteristics and spatiotemporal variability of extreme precipitation events of large spatial coverage across the Mediterranean region. The study uses the ERA5 dataset, the latest, state of the art, reanalysis dataset from Copernicus/ECMWF. Initially, exploratory analysis is performed to assess the different characteristics at various subdomains within the study area. Furthermore, composite analysis is used to understand the connection of extreme events with large-scale atmospheric patterns. Finally, the Empirical Orthogonal Function (EOF) analysis is implemented to quantify the importance of weather regimes with respect to the frequency of extreme precipitation events. 

Preliminary results indicate that there is a spatial division in the occurrence of identified events. Winter and autumn are the seasons of the highest frequency of extreme precipitation for the east and west Mediterranean respectively. Troughs and cut-off lows in the lower and middle-level troposphere have a strong association with such extreme events, and the effect is modulated by other parameters, such as local orography. Results of this work are in accordance with previous studies in the region and provide information that can be utilized by future research for improving the predictability of such events in the medium- and extended-range forecasts. 

This work is part of the Climate Advanced Forecasting of sub-seasonal Extremes (CAFE) project. The project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813844.

How to cite: Mastrantonas, N., Magnusson, L., Pappenberger, F., and Matschullat, J.: Extreme precipitation events in the Mediterranean region: their characteristics and connection to large-scale atmospheric patterns, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8593, https://doi.org/10.5194/egusphere-egu2020-8593, 2020

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Presentation version 1 – uploaded on 22 Apr 2020
  • CC1: Comment on EGU2020-8593, Cristina Deidda, 07 May 2020

    Good morning,

    Very interesting work! I would like to know how do you exploit the information of Sea Level Pressure and mean temperature in your research. Do you in some way associate or found correlation between these variables and the occurence of extreme events? Or in some way understand which atmospheric conditions can lead to extreme event occurence?

    Thank you very much,

    Cristina Deidda- Polimi

    • AC1: Reply to CC1, Nikolaos Mastrantonas, 07 May 2020

      Dear Cristina,

      Thank you for your interest in our work.

      It is established that strong precipitation events are associated with unstable atmospheric conditions over the focus area. Cyclonic patterns in the various levels of the atmosphere lead to such instabilities and convergence/divergence of air masses around extended areas, which can consecutively lead to extreme precipitation events.

      One way to identify such patterns is to use the anomalies of various atmospheric variables and at various vertical levels (altitudes). In this work, we checked the anomalies at lower (SLP) and middle (Z500) troposphere and confirmed once more that extreme precipitation events are significantly connected to negative anomalies over the focus area. Negative anomalies of SLP and Z500 can also be understood as cyclonic patterns and more unstable conditions compared to the climatology.

      For the temperature at 850 hpa (T850), the results can be understood as the outcome of the SLP and Z500 anomalies. More specifically, the cyclonic (anticlockwise circulation in the North hemisphere) conditions over the area of extreme precipitation, lead to northerly airflow on the west part of the anomaly, and southerly to the east. As the temperature (and the air) gets colder at higher latitudes, there is this intrusion of cold (warm) air west (east) of the SLP and Z500 anomalies.

      As a next step, we would like to investigate 'False Alarms' of such patters and be able to quantify the conditional probability of extreme precipitation events, given that such a negative anomaly pattern is observed over the region.

      Hope this reply can answer your question. Feel free to contact me at nikolaos.mastrantonas@ecmwf.int for more information.

      Thanks,

      Nikos