Long-term regional changes in inter-annual precipitation variability in the Campania Region, Southern Italy

Abstract

Precipitation variability in space and time has been a focus of research over the past decades. The largest body of literature was essentially focused on long-term changes in average climates and in climate extremes. Analyses of the changes in the inter-annual climate variability (the year-to-year variability), which represent an index of climatic risk, received instead very less attention, but it represents an important issue in order to quantitatively measure the socioeconomic impact of climate change impact over water resources. In order to depict a general characterization of the long-term climate variability for the Campania region, located in Southern Italy within the Mediterranean basin, an analysis of the precipitation coefficient of variation, assumed as an index of inter-annual climate variability, was performed over the period 1918–2015 and compared with the annual precipitation regime and the intra-annual precipitation variability of the same region. The Mann–Kendall and the modified Mann–Kendall tests were applied to detect the sign and significance of the temporal changes and Sen’s test was applied to quantify the temporal changes in inter-annual variability. The results illustrated a generalized condition (73% of total stations) of statistically significant increase of inter-annual variability distributed almost over the whole analyzed area, even though the detected change appeared rather moderate in magnitude. The relationship between annual precipitation, intra-annual precipitation variability, and inter-annual precipitation variability was not clearly identified for the studied region, likely because of the characteristics of climatic homogeneity for the area under investigation. However, the comparative analyzes clearly showed how, if the variations in the annual precipitation regime and in the intra-annual precipitation variability are poorly significant (respectively for 9% and 11% of total station), changes in inter-annual precipitation variability are strongly marked over the studied region.

Signals of change in the Campania region rainfall regime: An analysis of extreme precipitation indices (2002–2021)

“…According to the results of those works, in the period from 1918 to 2015, the annual precipitation in Campania region shows a general negative trend, although statistically relevant only for a very limited number of stations. From the work of Longobardi and Boulariah (2022), a change in intra‐annual variability of precipitation events also emerged, but the statistical significance is restricted to a small number of stations also in this case. Avino et al (2021) have investigated the maximum annual rainfall amounts for the period 1970–2018.…”

“…Few previous studies have been dedicated to the characterization and to the analysis of the precipitation regime of this area (Avino et al, 2021; Califano et al, 2015; Longobardi & Boulariah, 2022; Longobardi & Villani, 2010). According to the results of those works, in the period from 1918 to 2015, the annual precipitation in Campania region shows a general negative trend, although statistically relevant only for a very limited number of stations.…”

“…However, it is necessary bearing in mind that trends direction and significance are strongly dependent on the considered time period, so it is clearly challenging to obtain coherent and robust results regarding changes in precipitation pattern in Italy over the last several decades. The precipitation amounts, on annual basis, exhibited a negative trend in southern regions (Caloiero et al, 2020), in central regions (Gentilucci et al, 2019; Pavan et al, 2019; Scorzini & Leopardi, 2018) and in the inner parts of northern plans (Pavan et al, 2019), whereas on seasonal basis different tendencies have been found: a negative trend for winter and autumn and a positive trend for summer (Caloiero et al, 2020; Longobardi & Boulariah, 2022). Regarding the wet days, in northern Italy there is a clear negative trend on the annual basis and for summer and winter seasons (e.g.…”

“…The main novelties of this work can be synthesized in the two following key‐points: For the first time, the complete set of ETCCDI indices and the SPI have been applied to a dataset of daily rainfall measurers collected in the Campania region. Although several previous studies have been devoted to this area (Avino et al, 2021; Califano et al, 2015; Longobardi & Boulariah, 2022; Longobardi & Villani, 2010), none of them has employed a wide and complete spectrum of precipitation indices to fully characterize the complex variability of extreme rainfall events in terms of frequency, intensity and duration. The reference period of our work includes the last two decades (2002–2021), which were the hottest on the global scale in the instrumental period (Skea et al, 2022). According to a very recent study (Rodell & Li, 2023), an increase of global total intensity of extreme events (including both floods and droughts), mirroring the Earth's rising temperature, occurred between 2002 and 2021.…”

Detectable Increase in Global Land Areas Susceptible to Precipitation Reversals Under the RCP8.5 Scenario

“…Quantifying changes of wet/dry events at the inter‐annual scale is a non‐trivial task. If the inter‐annual volatility of the hydroclimate within water‐sensitive regions is changing, it could present new challenges for water management and require adaptation through shorter‐term operational decision‐making or through longer‐term changes in management or infrastructural planning (Longobardi & Boulariah, 2022; Marston & Ellis, 2018).…”