Descrizione 1
Piero Fraschetti, Francesca Lena, Walter Perconti, Emanuela Piervitali, Giulio Settanta
The indicator describes the amount and distribution of total precipitation in Italy. In 2023, the annual cumulative precipitation in Italy was approximately 4% lower than the average value calculated over the 1991–2020 reference period.
Precipitation is one of the key variables characterising the climate of a specific geographical area. Cumulative precipitation over a given time period represents the total amount of rainfall that occurred during that period.
The variation of precipitation compared to long-term normal values is assessed through the calculation of anomalies, defined as the percentage differences between the values recorded in a given year and the long-term average over the 1991–2020 reference period.
The annual time series of cumulative precipitation anomalies, expressed as deviations from a climatological baseline, enables the estimation of long-term precipitation trends.
Understanding the temporal evolution of precipitation is crucial for assessing ongoing climate change trends and serves as a fundamental basis for developing appropriate climate change adaptation strategies and actions.
The indicator has no direct links to regulatory or legislative frameworks.
Descrizione 2
https://scia.isprambiente.it;
SNPA, 2024, Il clima in Italia nel 2023;
ISPRA, 2022, I normali climatici 1991-2020 di temperatura e precipitazione in Italia;
ISPRA, 2016, Controlli di qualità delle serie di temperatura e precipitazione;
ISPRA, 2015, Valori climatici normali di temperatura e precipitazione in Italia;
ISPRA, 2016, Analisi statistica degli estremi di precipitazione in Italia;
ISPRA, 2014, Focus on "Le città e la sfida ai cambiamenti climatici";
ISPRA, 2013, Variazioni e tendenze degli estremi di temperatura e precipitazione in Italia;
ISPRA, 2012, Elaborazione delle serie temporali per la stima delle tendenze climatiche ;
Jones P.D. e Hulme M., 1996, Calculating regional climatic series for temperature and precipitation: methods and illustrations, Int. J. of Climatol., 16, 361-377;
Toreti A., Fioravanti G., Perconti W., Desiato F., 2009, Annual and seasonal precipitation over Italy from 1961 to 2006, International Journal of Climatology, DO I: 10.1002/joc.1840
Precipitation is a variable characterized by significant spatial variability. For this reason, the availability of a large number of monitoring stations meeting the requirements of time series duration, completeness, and continuity is essential to ensure the full reliability of precipitation estimates.
Improvements in the estimation of cumulative precipitation in Italy could result from the extension of the indicator calculation system to include additional data sources. This would enhance the availability of historical precipitation series that meet the requirements of duration, continuity, and completeness of time series.
Qualificazione dati
SCIA – Sistema nazionale per l’elaborazione e diffusione di dati climatici (https://scia.isprambiente.it)
Italy
1961-2023
Qualificazione indicatore
The programme used by the SCIA system (National System for the Collection, Processing and Dissemination of Climate Data) processes raw data and returns a value of daily cumulative precipitation, which is only accepted as valid if it has passed specific quality control checks. Subsequently, the programme calculates 10-day, monthly, and annual values of the indicator by aggregating daily values over respective time intervals of ten days, one month, and one year. These aggregated values are considered valid only if at least 90% of daily data within each time interval are valid.
The climatological baseline used for calculating anomalies has been updated to the most recent 30-year period, 1991–2020, in line with the latest recommendations from the World Meteorological Organization (WMO), which call for a decadal update of climatological reference periods for operational climate monitoring purposes.
By analysing long-term time series using appropriate statistical models and methods, it is possible to detect the presence or absence of precipitation trends across the Italian territory, estimate their magnitude, and compare them with results from global or regional studies.
In 2023, the annual cumulative precipitation in Italy was approximately 4% below the 1991-2020 climatological average (close to the climatological average in the North and Centre, and about -8% in the South and Islands) (Figure 2).
The time series of cumulative precipitation, both on an annual and seasonal basis, calculated using a linear regression model, for Italy (Figure 1) and the macro-regions (North, Centre, South, and Islands), do not show any significant trend (at the 5% significance level) for the period examined (1961-2023).
Dati
Figure 1: Time series of the average anomalies, expressed as percentage values, of annual cumulative precipitation in Italy compared to the normal value 1991-2020.
ISPRA
Figure 2: Average monthly and annual anomaly for 2023, expressed as percentage values, of cumulative precipitation in the North, Centre, South, and Islands, compared to the normal value 1991-2020
ISPRA
The series from 1961 to 2023 of the average anomalies (expressed as percentage values) of annual cumulative precipitation compared to the mean value calculated for the reference period 1991-2020 shows that 2023 is nearly in line with the climatological mean (Figure 1). In 2023, as shown in Figure 2, precipitation was below the normal across all regions in February, March, September, and December, while it was above the normal in January and May. The most pronounced anomalies occurred in the South and Islands: positive anomalies in May (+222%) and June (+154%), and a negative anomaly in July (-84%). In this macro-region, precipitation was below average for the entire second half of the year. In the North, anomalies ranged from -81% (February) to +92% (May), while in the Centre they ranged from -61% (September) to +111% (May).