[1] Earlier reports indicated some specific isolated regions exhibiting a paradoxical increase of extreme rainfall in spite of decrease in the totals. Here, we conduct a coherent study of the full-scale of daily rainfall categories over a relatively large subtropical region-the Mediterranean-in order to assess whether this paradoxical behavior is real and its extent. We show that the torrential rainfall in Italy exceeding 128 mm/d has increased percentage-wise by a factor of 4 during 1951 -1995 with strong peaks in El-Nino years. In Spain, extreme categories at both tails of the distribution (light: 0-4 mm/d and heavy/torrential: 64 mm/d and up) increased significantly. No significant trends were found in Israel and Cyprus. The consequent redistribution of the daily rainfall categories -torrential/heavy against the moderate/light intensities -is of utmost interest particularly in the semi-arid sub-tropical regions for purposes of water management, soil erosion and flash floods impacts. INDEX TERMS: 1854

An analysis of 67 sites of daily precipitation records over the 1951-1996 period for Italy is presented. Seasonal and yearly total precipitation (TP), number of wet days (WDs) and precipitation intensity (PI) are investigated, and the trends both for the single station records, and for some different area average series are studied. PI is analysed by attributing precipitation to ten class-intervals, removing the influence of variations in the number of WDs to yield changes in the underlying shape of the WD amount distribution. The results show that the trend for the number of WDs in the year is significantly negative throughout Italy, stronger in the north than in the south: this trend is mainly a result of the winter. Moreover, they show that there is a tendency toward an increase in PI. This increase is globally less strong and significant than the decrease in the number of WDs. It is not concentrated in one specific season, but changes from area to area, and is generally weak in winter, due to a significant decrease of winter TP. In northern Italy, the increase in PI is mainly owing to a strong increase in the heaviest events, while in central-southern Italy, it depends on a larger part of the distribution of WD amounts. The analysis of the evolution of the class-interval contributions shows that the positive trend of the heaviest events starts in the 1970s, as does the negative trend of lightest events. Copyright © 2001 Royal Meteorological Society.KEY WORDS: daily precipitation; heavy precipitation events; Italy; trend analysis; precipitation intensity INTRODUCTIONEver increasing attention is devoted by climatologists to the study of precipitation trends, because, owing to possible variations or changes in the climate, the geographic distribution of rainfall frequency and intensity could be subjected to substantial modifications (IPCC, 1996). This could determine, in some areas, prolonged periods of unusually dry conditions, reducing the availability of water resources, while other areas could be affected by wetter than normal conditions, with an increase in the flood risk. In this respect, we can remember the last two decades, during which, in the winter season, rain scarcity was experienced in many areas of the Mediterranean Basin (Schö nwiese and Rapp, 1997;Piervitali et al., 1998;Buffoni et al., 1999), whereas in central and northern Europe, a tendency towards an increase in precipitation was generally observed (Alexandersson, 1996;Hurrell and Van Loon, 1997;Wibig, 1999).The topic is very complex, and model simulations sometimes give disagreeing forecasts for the future (Henderson-Sellers and Hansen, 1995;IPCC, 1996). On a global scale, an increase in the rainfall should occur at middle and high latitudes, and a reduction at lower ones (Hulme et al., 1998;Trenberth, 1998;Doherty et al., 1999). Moreover, there are some indications of a possible rise in precipitation intensity (PI), pointing to an increase in the number of heavy precipitation events (Fowler and Hennessy, 1995;Gregory and Mitchell,...

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Abstract. In this study we conduct a numerical analysis of an intense and destructive storm that occurred over Calabria, southern Italy, on 10-12 December 2003. More than 250 mm of precipitation was recorded over a large area in southern Calabria and one station reported about 660 mm in two days (more than half of the yearly climatological value). Precipitation fell mainly during 11 and 12 December. The storm was characterized by the entrance of an Atlantic upper-level trough associated with a deep surface low that advected humid marine air toward steep Calabrian orography. The steep mountain ridges favoured landslides, which were reported in several villages. Property damage was extensive.We study the storm at the mesoscale by means of the Regional Atmospheric Modeling System (RAMS). The model was successful at representing the observed accumulated rainfall patterns. This justifies our use of RAMS for further analysis of the physical and dynamic factors involved in the storm event. In particular, we use RAMS to evaluate the roles of Calabrian orography, surface latent heat flux, and upper level forcing.The key role of a potential vorticity (PV) streamer, which forced the entire meteorological system from the upper levels is assessed by the PV inversion technique in a Limited Area Model Ensemble Prediction System (LEPS) framework.Results show that the roles of Calabrian orography and surface latent heat flux are important in our simulations. Indeed, humid marine air masses were advected by the synoptic flow toward Calabrian steep coastal mountain ranges determining intense and abundant rainfall.

Air temperature data of Rome are analysed to point out the variations caused by natural events and human activities. In particular, the influence of the growth of the city on the minimum average temperature is evident. I t is also found that the air temperature seems to be affected by the solar cycle.

SummaryThe analysis of air temperature data covering a period of 12 years in a meteorological station network situated in the low Tiber Valley, shows clearly the effect of the heat urban island due to the city of Rome. This effect occurs with different intensity according to the seasons and to minimum and maximum temperatures. Zusammenfass~angNachweis der st~dtischen W[irmeinsel in Rom durch klimatologische Analysen Die Analyse yon 12j~ihrigen Temperaturbeobachtungen eines meteorologischen Stationsnetzes im unteren Tiber-Tal zeigt deutlich die Auswirkung einer durch die Stadt Rom verursachten W~irmeinsel. Dieser Effekt tritt mit den Jahreszeiten und nach Temperaturminima und Temperatumaaxima unterschiedlicher IntensitSt auf.

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