1. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 ESF-MedCLIVAR Workshop Trieste 13-15 October 2008, Influence of Mediterranean cyclones on Alpine precipitation Herbert Formayer Imran Nadeem and Patrick Haas Universität für Bodenkultur, Vienna Institute of Meteorology (BOKU-Met)

2. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 The Mediterranean sea is one of the most important moisture sources for alpine precipitation. Of course it is the main source for the south side of the Alps. But even on the north side of the Alps air masses from the Mediterranean sea are responsible for large scale heavy precipitation events and flooding, as in May 1999, August 2002 and August 2005 Cut-off lows centred near the Alps are mainly responsible for this heavy precipitation events. Introduction

3. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Upper level trough Tear-off Cut-off Final stage Live cycle of cut-off lows

4. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Sub-regions of cut-off lows affecting the alps

5. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Winter (DJF) NW NE SESW Precipitation anomaly associated with cut-off lows close to the alps

6. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Precipitation anomaly associated with cut-off lows close to the alps Summer (JJA) NW NE SW SE

7. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 19.05.199920.05.1999 21.05.199922.05.1999 Case study: May 1999

8. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 20. – 22.05.1999 precipitation sum and track of the cut-off low Case study: May 1999

9. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Observed Precipitation Case study: May 1999

10. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 MM5 Case study: May 1999

11. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 ALADIN Case study: May 1999

12. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Reanalyses Case study: July 1981 19810718 RegCM3 (50 km)

13. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: July 1981 19810719 RegCM3 (50 km) Reanalyses

14. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: July 1981 19810720 Reanalyses RegCM3 (50 km)

15. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: July 1981 19810721 Reanalyses RegCM3 (50 km)

16. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: July 1981 19810718 RegCM3 (50 km) Observations Precipitation sums (daily)

17. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: July 1981 19810719 RegCM3 (50 km) Observations Precipitation sums (daily)

18. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: June 1988 19880605 Reanalyses RegCM3 (50 km)

19. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: June 1988 19880606 Reanalyses RegCM3 (50 km)

20. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: June 1988 19880607 Reanalyses RegCM3 (50 km)

21. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: June 1988 19880605 RegCM3 (50 km) Observations Precipitation sums (daily)

22. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Case study: June 1988 19880606 RegCM3 (50 km) Observations Precipitation sums (daily)

23. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Mediterranean cyclones are important for the Alpine precipitation. Many large scale alpine flooding events even on the north side of the Alps are associated with cut-off lows, transporting Mediterranean air-masses on the north side of the Alps. Cut-off lows are not easy to handle by regional climate models (even so in NWP). Conclusions

24. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Are GCMs able to reproduce Alpine relevant cut-off processes in a proper way concerning frequency, intensity, location and seasonality? Can RCMs improve the behaviour of Alpine relevant cut-off lows? If not, how can the GCMs be improved to do it in a better way and How can hydrological modeller use the information about this important process for the interpretation of their results? Big questions concerning climate change and cut-off lows:

25. BOKU-Met Herbert Formayer ESF-MedCLIVAR Workshop Trieste 13-15 October 2008 Thank you for your attention We try to find some answers in the just started EC- Project: ACQWA http://www.unige.ch/climate/Projects/ACQWA.html