The Influence of Climate Change on Heavy Rainfalls in Central Italy

In recent years there is a growing concern by the community, scientific and not, about global warming and climate changes. The fact that the global temperature is growing up after the increase of the greenhouse gases emissions is already known, but there is still wondering about its effect on the hydrological cycle and most of all, on rainfalls. Many studies supported by the Intergovernmental Panel on Climate Change (IPCC) showed that there is a general increase of heavy rainfalls also in areas where total annual precipitation is not prominently changed. Changings about frequency, intensity, duration in rainfalls and in weather events in general are still objects of uncertainty and past studies referred to different regions do not give an unanimous answer about their trends. The Mediterranean area, which includes Italy, is supposed to be one of the most reactive to climate change and deep effects are expected. This paper deals with rainfall tendencies in the Umbria Region, Central Italy, since almost all the regional territory is included in the Upper Tiber River Basin and many areas are prone to risk of flooding. The climate in the Umbria region is different from zone to zone, in fact the weather is cold and wet in the East areas, near the Apennine Mountains and hotter and drier in the West, close to Tuscany region. Because of this variability a lot of rain gauges were placed in the last 10-15 years. Nowadays a very dense rain gauge network is present (more than 90 rain gauges for a regional area of 8464.33 km2, about one station each 90 km2). The aim of this paper is to analyze if climate change affects rainfall intensity in Umbria. Three meteorological stations have been selected: Città di Castello, Todi and Orvieto. They provide the longest series of data and the best quality in rainfall measurements. Rainfall measurements began in the thirties and have gone on until nowadays even if there are some interruptions (most of all during the years of the Second World War). The analyses of heavy rainfalls of the three stations, and most of all the data referred to Todi, whose geographical position is barycentric in the regional territory; show that there are not considerable changes in rainfall maxima and intensities in the last seventy years.