The ReData project: engaging citizen scientists in the recovery and digitization of historical daily weather bulletins

In recent decades, many countries around the world have initiated climate data digitization projects. The aim of these projects is to preserve data recorded in paper documents, which are prone to deterioration, and to make them available to the scientific community. These new dataset will improve the accuracy of the description of the spatial distribution of particular events and will allow a reconstruction with a lower error of the evolution of the climate of the past. In this context, global reanalysis datasets play a crucial role, as their accuracy depends directly on the homogeneity and spatial distribution of the underlying historical observations. This study aims to design a new framework for the ReData (Recovery of Data) project, launched by the Meteonetwork Association in 2017. The aim of the project is to digitize the meteorological data collected by the Italian Royal Central Meteorological Office (RCMO) from 1879 to 1940 for the publication of its daily meteorological bulletins. The network used for this bulletin started with 11 meteorological stations and rapidly expanded to about 70 within a few decades. The use of telegraph technology to transmit observations in real time to the Central Office in Rome enabled the publication of the Daily Meteorological Bulletin, which also included observations from foreign stations and was one of the first steps towards international atmospheric monitoring. Currently, the RCMO daily bulletins available in digital form, as first result of the project, cover the period from December 1879 to December 1934, with the remaining years still to be scanned. In total, 55 years of data are accessible, encompassing 20,120 daily bulletins. Since the bulletins have been scanned page by page, over 84,000 scans have been performed. Given the number of meteorological variables recorded in the bulletins, which has increased over time, it is possible to estimate the amount of data that could potentially be digitized using ReData: more than 20 million data points. The project aims to digitize this huge amount of data through Citizen Science activities. Specifically, as a second outcome of the project, since the end of 2024 a website of the project is available on the online platform Zooniverse (https://www.zooniverse.org/projects/meteonetwork/redata). Here, volunteers from all over the world can contribute to the digitization of a station with data for 12 variables in only about 1 minute per day. Today, almost three years (1882-1884) have been completed for 37 stations, considering that each data is digitized three times.