Temporal analysis of rainfall categories in southern Italy (Calabria region)

A modification in the water cycle is one of the most noticeable consequences of global atmospheric warming. Precipitation is a key point in the process and its temporal distribution is particularly important because it impacts on some extreme phenomena such as drought and flash floods, affecting also water resources management. This study presents an analysis of daily rainfall categories over a region of southern Italy in order to verify earlier report results which indicated a paradoxical increase in extreme rainfall, despite a decrease in the totals, in the Mediterranean basin. A set of daily homogenous precipitation series for the period 1916-2006 has been used in this study. Six daily rainfall categories have been considered: Light, 0-4 mm/day; Light-Moderate, 4-16 mm/day; Moderate-Heavy, 16-32 mm/day; Heavy, 32-64 mm/day; Heavy-Torrential, 64-128 mm/day; Torrential, 128-up mm/day. The analysis was performed considering all the region and separately five Rainfall Zones (RZs) characterized by different climatic conditions. Results showed, with some differences for the various RZs, that Light-Moderate, Moderate-Heavy and Heavy rainfall are the main contributors to the total annual rainfall. Moreover, the trend analysis through the Mann-Kendall test showed a decreasing trend of the higher categories and an increasing trend of the weaker categories. These analyses could be useful because changes in extreme events can impact natural environments and human activities, as well as human health and safety.