The Cli-DaRe project for the recovery of historical Italian meteorological data and construction of long-term precipitation series

The aim of the Cli-DaRe (Citizen Science for Italian Climate Data Rescue) project is the recovery of historical Italian meteorological data still available only on paper or as scanned documents.

Through the sub-project Cli-DaRe@School, it has been possible, using a citizen-science based approach with the help of high school students and teachers, to digitize the data published in four monographs by the Italian Hydrographic Service: three of them collecting precipitation data for the period prior to 1950 and one with temperature data for the period 1926-1955.

The digitized data are subjected to a quality check to detect transcription errors and inconsistencies in the coordinates. This process is carried out using a hybrid approach, combining automated and manual procedures. This has made it possible to analyze and categorize frequent errors affecting both data and metadata. The methodology has been published in the Bulletin of the American Meteorological Society (https://doi.org/10.1175/BAMS-D-24-0078.1).

For the 1921-1950 precipitation data, the quality check has already been completed, and the records have been compared with those available in existing datasets. Among the 3,614 stations reported in the monograph, 1,907 were already available in digital form in other datasets and were checked for correctness, while the remaining 1,707 stations were digitized within the CliDaRe@School project. The entire dataset is now freely available (https://doi.org/10.5281/zenodo.15084062), and the results of this study have been published in the Bulletin of the Atmospheric Science and Technology (https://doi.org/10.1007/s42865-025-00111-3).

The quality check for the precipitation data for the periods 1916-1920 and pre-1916 is nearly completed, making available respectively 1,526 and 2,193 records. At the same time, two additional processes are ongoing: one aimed at identifying correspondences with existing datasets, and another focused on merging together into single time series records from the three different periods and with the already available more recent data.

These activities will lead to the creation of long-term precipitation series spanning up to 120 years, providing a substantially improved basis for climate analyses over Italy. Such extended and quality-checked time series are expected to support future studies on long-term climate variability and change, as well as the development and validation of high-resolution historical climate reconstructions.