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

Abstract

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.

Synoptic climatology of winter intense precipitation events along the Mediterranean coasts

“…In both EM and WM, results show that intensity of the circulation (depth of the cyclone, Laplacian, gradient and extension) and in some cases moisture content of the middle atmosphere play an important role in the characterization of C 90+98 (cyclones producing severe precipitation events) with respect to C 25 (cyclones producing mild precipitation events). Also, the speed of a cyclone center is an important characteristic explaining the severity of the precipitation event, though significant statistical evidence is not always present, as already shown by previous studies for Italy (Tartaglione et al, 2006) and the Alps (Frei and Shär, 2001). These links between synoptic patterns and precipitation represent a tool that can be applied to GCM results to associate changes of precipitation rainfall patterns to synoptic dynamics (Lionello and Giorgi, 2007) and to help diagnosing increases in hazardous intense precipitation events and drier conditions for the Mediterranean region.…”

Extreme Value Statistics of the Total Energy in an Intermediate-Complexity Model of the Midlatitude Atmospheric Jet. Part II: Trend Detection and Assessment

“…[See, e.g., Brunetti et al (2002, Lucarini et al (2004Lucarini et al ( , 2006, Speranza et al (2006), Speranza and Tartaglione (2006), Tartaglione et al (2006), and the Mediterranean Experiment (MEDEX) phase 1 report (available at http://medex.inm.uib.es/) for related results and activities.] The study reported in Part I revealed, among other things, that diagnostics of extreme statistics can highlight interesting dynamical properties of the analyzed system.…”

“…Part I was originally motivated by the interest in weather having "major impact" (on human life and property) in the Mediterranean area, in particular intense precipitation and heat waves over Italy. See, for example, Brunetti et al (2002Brunetti et al ( , 2004; Lucarini et al (2004Lucarini et al ( , 2006b; ; Speranza and Tartaglione (2006); Tartaglione et al (2006) and the MEDEX Phase 1 report (available at http://medex.inm.uib.es/) for related results and activities. The study reported in Part I has revealed, among other things, that diagnostics of extreme statistics can highlight interesting dynamical properties of the analyzed system.…”

Extreme Value Statistics of the Total Energy in an Intermediate-Complexity Model of the Midlatitude Atmospheric Jet. Part I: Stationary Case

“…See, for example, Brunetti et al (2002Brunetti et al ( , 2004; Lucarini et al (2004Lucarini et al ( , 2006b); ; Speranza and Tartaglione (2006); Tartaglione et al (2006) and the MEDEX Phase 1 report (available at http://medex.inm.uib.es/) for related results and activities. The study reported in Part I has revealed, among other things, that diagnostics of extreme statistics can highlight interesting dynamical properties of the analyzed system.…”