Storminess Forecast Skills in Naples, Southern Italy

Abstract

The objective of this study is to investigate the simulation skill of extreme rainfalls in Naples (Italy). The coasts of Italian peninsula have been affected by frequent damaging hydrological events in the last decade, driven by intense rainfall and deluges. The internal mechanisms for rainfall variability that generate these hydrological events in the Mediterranean are still unknown. In the present study, an annual series of daily maximum rainfall spanning the period 1866–2010 was used to skill projection at intradecadal scale. A procedure was developed where a predictable structure was first provided by reducing noise via low-pass band Gaussian filter, and successively elaborated by an exponential smoothing approach for the purposes of simulation – in testing period – and forecast – in projection time. The analysis was based on a set of online tools that are suitable to discover the manifestation of a possible trajectory of projected extreme rainfall changes. Hindcast experiments by model runs were tested, and pattern simulated with horizon placed in the year 2050. Projections discover a clear rising of extreme rainfall with cyclical pattern similar to the past. The oscillation of simulated extreme rainfalls was coupled with variations attributed to internal climate variability, such as the Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation. This suggests that a correlation exists between the occurrence of extreme rainfalls at Naples and large-scale climatic phenomena.