Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 9 3 2009 10.5194/nhess-9-957-2009 http://www.nat-hazards-earth-syst-sci.net/9/957/2009/ http://www.nat-hazards-earth-syst-sci.net/9/957/2009/nhess-9-957-2009.html http://www.nat-hazards-earth-syst-sci.net/9/957/2009/nhess-9-957-2009.pdf 957 965 2009-06-25 Cyclogenesis in the Mediterranean basin: a diagnosis using synoptic-dynamic anomalies M. Kaspar kaspar@ufa.cas.cz M. Müller Institute of Atmospheric Physics AS CR, Prague, Czech Republic Charles University, Faculty of Science, Prague, Czech Republic This work deals with the hypothesis that synoptically-driven heavy rains in the Mediterranean region are connected with the occurrence of synoptic-dynamic anomalies. We investigate this hypothesis by conducting a diagnostic study of a cyclogenesis event from 18–21 July 2001. Cyclogenesis started over the western Mediterranean Sea and was triggered by the approach of a pre-existing upper trough over a lower frontal zone. The event was first accompanied by heavy convective rains in northern Italy and later by heavy, widespread and steady rains of non-convective character in Central Europe. <br><br> Using re-analyses from the database ERA-40, we evaluate the synoptic-dynamic anomalies by the cumulative distribution function relatively to July–August area-related climatology over the reference period from 1958 to 2002. For the duration of cyclogenesis, we detect significant anomalies associated with the processes that support the completion of vertical coupling between the lower frontal zone and the upper vorticity maximum. The periods of heavy rains in both the Mediterranean region and Central Europe were characterised by the occurrence of anomalies that created synoptic-scale conditions favourable for triggering and sustaining heavy rains. Although these anomalies were somewhat weaker in the period of heavy rains in Central Europe than in the Mediterranean region, the analysis of their spatio-temporal correspondence over the reference rainfall events in the Czech Republic shows that they are typical of heavy rains there. Due to the relatively high variability of the causal synoptic-scale conditions, this study would benefit post-processing procedures aimed at improving warning about this hazardous weather phenomenon to further investigate which anomalies generally occur during synoptically-driven heavy rains in the Mediterranean region and the strengths of these anomalies. % vor jede Referenz Bocheva, L., Christo, G. G., and Simeonov, P.: A climatic study of severe storms over Bulgaria produced by Mediterranean cyclones in 1990-2001 period, Atmos. Res., 83, 284–293, 2007. Campins, J., Genovesa, A., Jansa, A., Guijarro, J. A., and Ramis, C.: A catalogue and a classification of surface cyclones for the Western Mediterranean, Int. J. Climatol., 20, 969–984, 2000. Doswell III, C. A., Ramis, C., Romero, R., and Alonso, S.: A diagnostic study of three heavy precipitation episodes in the Western Mediterranean region, Weather Forecast., 13, 102–124, 1998. Fernandez, C., Gaertner, M. A., Gallardo, C., and Castro, M.: Simulation of a long-lived meso- bscale convective system over the Mediterranean coast of Spain. Part I: Numerical predictability, Meteorol. Atmos. Phys., 56, 157–179, 1995. Homar, V., Jansá, A., Campins, J., Genovés, A., and Ramis, C.: Towards a systematic climatology of sensitivities of Mediterranean high impact weather: a contribution based on intense cyclones, Nat. Hazards Earth Syst. Sci., 7, 445–454, 2007. Jansá, A., Genoves, A., Picornell, M. A., Campins, J., Riosalido, R., and Carretero, O.: Western Mediterranean cyclones and heavy rain.Part 2: Statistical approach, Meteorol. Appl., 8, 43–56, 2001. Kaspar, M. and Müller, M.: Selection of historic heavy large-scale rainfall events in the Czech Republic, Nat. Hazards Earth Syst. Sci., 8, 1359–1367, 2008a. Kaspar, M., Müller, M., Kakos, V., Rezacova, D, and Sokol, Z.: Severe Storm in Bavaria, the Czech Republic and Poland on 12–13 July 1984: a statistic- and model-based analysis, Atmos. Res., 93, 99–110, 2009. Kurz, M. and Fontana, A. D.: A case of cyclogenesis over the western Mediterranean Sea with extraordinary convective activity, Meteorol. Appl., 11, 97–113, 2004. Kysely, J. and Picek, J.: Probability estimates of heavy precipitation events in a flood-prone central-European region with enhanced influence of Mediterranean cyclones, Adv. Geosci., 12, 43–50, 2007. Martín, M. L., Santos-Munoz, D., Morata, A., Luna, M. Y., and Valero, F.: An objectively selected case study of a heavy rain event in the Mediterranean Basin: A diagnosis using numerical simulation, Atmos. Res., 81, 187–205, 2006. Mudelsee, M., Börngen, M., Tetzlaff G., and Grünewald, U.: Extreme floods in central Europe over the past 500 years: Role of cyclone pathway "Zugstrasse Vb", J. Geophys. Res., 109, D23101, doi:10.1029/2004JD005034, 2004. Müller, M., Kaspar, M., and Matschullat, J.: Heavy rains and extreme rainfall-runoff events in Central Europe from 1951 to 2002, Nat. Hazards Earth Syst. Sci., 9, 441–450, 2009a. Müller, M., Kaspar, M., Rezacova, D., and Sokol, Z.: Extremeness of meteorological variables as an indicator of extreme precipitation events, Atmos. Res., 92, 308–317, 2009b. Petterssen, S. and Smebye, S. J.: On the development of extratropical cyclones, Q. J. Roy. Meteorol. Soc., 97, 457–482, 1971. Ramis, C., Llasat, M. C., Genovrs, A., and Janszi, A.: The October-1987 floods in Catalonia: Synoptic and Mesoscale Mechanisms, Meteorol. Appl., 1, 337–350, 1994. Romero, R., Sumner, G., Ramis, C., and Genovés, A.: A classification of the atmospheric circulation patterns producing significant daily rainfall in the Spanish Mediterranean area, Int. J. Climatol., 19, 765–785, 1999. Uppala, S. M., K&aring;llberg, P. W., Simmons, A. J., Andrae, U., Da Costa Bechtold, V., Fiorino, M., Gibson, J. K., Haseler, J., Hernandez, A., Kelly, G. A., Li, X., Onogi, K., Saarinen, S., Sokka, N., Allan, R. P., Andersson, E., Arpe, K., Balmaseda, M. A., Beljaars, A. C. M., Van De Berg, L., Bidlot, J., Bormann, N., Caires, S., Chevallier, F., Dethof, A., Dragosavac, M., Fisher, M., Fuentes, M., Hagemann, S., Hólm, E, Hoskins, B. J., Isaksen, L., Janssen, P. A. E. M., Jenne, R., McNally, A. P., Mahfouf, J. F., Morcrette, J. J., Rayner, N. A., Saunders, R. W., Simon, P., Sterl, A., Trenberth, K. E., Untch, A., Vasiljevic, D., Viterbo, P., and Woollen, J.: The ERA-40 re-analysis, Q. J. Roy. Meteorol. Soc., 131, 2961–3012, 2005. Ustrnul, Z. and Czekierda, D.: Circulation background of the atmospheric precipitation in Central Europe (based on the Polish example), Meteorol. Z., 10, 103–111, 2001.