The Long-Term ERA5 Data Series for Trend Analysis of Rainfall in Italy

Francesco Chiaravalloti,Tommaso Caloiero,Roberto Coscarelli

doi:10.3390/hydrology9020018

Abstract

Nowadays, the Mediterranean region is generally recognized as a climate change hot spot given its strong response to global warming, with relevant impacts on rainfall amount and distribution. Within this context, in this work the temporal variability of rainfall at annual, seasonal and monthly scale was analyzed in Italy using rainfall data extracted from the reanalysis dataset ERA5-Land during the period 1950–2020. In particular, rainfall trend magnitude and significance have been estimated by means of non-parametric tests applied to 3215 grid points falling within the Italian territory. The main results of this analysis evidenced only a few relevant trends at the annual scale, mostly involving northern Italy (positive trend) and the Sardinia region (negative trend). At seasonal scale, the results showed a marked negative trend in winter, characterizing almost all the Italian territory, while in the other seasons a positive trend was identified in the majority of grid points, especially in the Alps. Finally, at the monthly scale, September was identified as the month of the year with the highest percentage of grid points with positive trends mainly located in central, southern, and north-eastern Italy.

Highlights

The Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides the most up-to-date physical science understanding of climate change [1]
In this work the temporal variability of rainfall at annual, seasonal and monthly scale was analyzed in Italy using rainfall data extracted from the reanalysis dataset ERA5-Land during the period 1950–2020
The results showed a marked negative trend in winter, characterizing almost all the Italian territory, while in the other seasons a positive trend was identified in the majority of grid points, especially in the Alps

Summary

Introduction

The Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) provides the most up-to-date physical science understanding of climate change [1]. Higher precipitation has been forecast worldwide, with the exception of few specific regions These include the Mediterranean basin, which is considered as a prominent climate change hot spot [2]. Due to the severe impacts of climate change in the Mediterranean basin, several studies on the temporal evolution of the main hydrological variables have been performed in this area, with particular attention been paid to rainfall. The results of these studies performed at different timescales, from monthly to annual, evidenced a general rainfall reduction in the western side of the Mediterranean basin [3,4]. The results of the regional studies performed in Italy mainly evidence a decrease in annual rainfall especially in the southern [6,7,8] and in the central regions of the country [9,10], while in its northern part, the decreasing tendencies in the annual values resulted rarely significant [11]

Objectives

Methods

Results

Discussion

Conclusion