Objective Climatology of Cyclones in the Mediterranean Region

Trigo IF, Davies TD, Bigg GR
AMS, JCLI June 1999,<1685:OCOCIT>2.0.CO;2

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An objective cyclone detection and tracking analysis is performed over an 18-yr period, for the Mediterranean basin. The high-resolution (1.125 1.125 grid) European Centre for Medium-Range Weather Forecasts data used in this study proved to be particularly suitable for the detection and tracking techniques and to identify subsynoptic-scale Mediterranean lows, which have often been underestimated in previous studies. The major characteristics of Mediterranean cyclones are examined and compared with other Northern Hemisphere depressions. Both cyclogenesis and cyclolysis regions are identified in the domain of study. In addition, characteristics of Mediterranean depressions, such as cyclone duration and intensity, as well as their persistence throughout the year, are shown to be quite variable for different formation areas. Overall, the regions where cyclogenesis is mainly controlled by topography, like the Gulf of Genoa and south of the Atlas Mountains, seem to generally account for the most intense events. Finally, a statistical analysis based on a k-means clustering procedure summarizes trajectory information obtained from the 18-yr climatology. The method proved to be efficient in grouping cyclone paths from similar cyclogenesis regions and with similar characteristics of movement, showing generally more clusters in the western Mediterranean than in the eastern part of the basin.