Large-scale atmospheric and sea surface processes leading to excessive rainfall in Tuscany, Italy

Monthly extreme rainfalls at several gauges and several durations (1, 3 and 5 days) in Tuscany, Italy, are compared with simultaneous and previous patterns of large scale circulation, synthetized by the North Atlantic Oscillation (NAO) index, and patterns of sea surface temperature (SST) in central-western Mediterranean. Several statistical methods are employed, from simple contingency tables to frequency histogram. Scenarios of global change considering Mediterranean SST anomalies changes are considered and the quantitative consequences in terms of extreme rainfalls are derived. The relevant hydrological consequences of such regional interpretation of global change scenarios are inferred in terms of flood risk and hydraulic works in small-medium size basins in Tuscany.