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Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 6, issue 3
Nat. Hazards Earth Syst. Sci., 6, 451–458, 2006
https://doi.org/10.5194/nhess-6-451-2006
© Author(s) 2006. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
Nat. Hazards Earth Syst. Sci., 6, 451–458, 2006
https://doi.org/10.5194/nhess-6-451-2006
© Author(s) 2006. This work is licensed under
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.

  06 Jun 2006

06 Jun 2006

The mobility of Atlantic baric depressions leading to intense precipitation over Italy: a preliminary statistical analysis

N. Tartaglione1, A. Speranza2, F. Dalan3, T. Nanni3, M. Brunetti3, and M. Maugeri4 N. Tartaglione et al.
  • 1Dipartimento di Fisica, Università di Camerino, Italy
  • 2Dipartimento di Matematica e Informatica, Università di Camerino, Italy
  • 3Istituto per lo Studio dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche Sezione di Bologna, Italy
  • 4Istituto di Fisica Generale Applicata, Università di Milano, Italy

Abstract. The speed of Atlantic surface depressions, occurred during the autumn and winter seasons and that lead to intense precipitation over Italy from 1951 to 2000, was investigated. Italy was divided into 5 regions as documented in previous climatological studies (based on Principal Component Analysis). Intense precipitation events were selected on the basis of in situ rain gauge data and clustered according to the region that they hit. For each intense precipitation event we tried to identify an associated surface depression and we tracked it, within a large domain covering the Mediterranean and Atlantic regions, from its formation to cyclolysis in order to estimate its speed. "Depression speeds" were estimated with 6-h resolution and clustered into slow and non-slow classes by means of a threshold, coinciding with the first quartile of speed distribution and depression centre speeds were associated with their positions. Slow speeds occurring over an area including Italy and the western Mediterranean basin showed frequencies higher than 25%, for all the Italian regions but one. The probability of obtaining by chance the observed more than 25% success rate was estimated by means of a binomial distribution. The statistical reliability of the result is confirmed for only one region. For Italy as a whole, results were confirmed at 95% confidence level. Stability of the statistical inference, with respect to errors in estimating depression speed and changes in the threshold of slow depressions, was analysed and essentially confirmed the previous results.

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