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

In recent decades, numerous climate data digitization projects have been initiated in many countries worldwide. These projects aim to preserve data recorded in paper documents, which are vulnerable to deterioration, and to make them accessible to the scientific community to improve the accuracy of climatological studies and historical reconstructions for specific events. In this context, global reanalysis data sets play a crucial role, as their accuracy directly depends on the homogeneity and spatial distribution of the historical observational data on which they are based.

This study aims to design a new framework for the ReData (Recovery of Data) project, launched by the Meteonetwork Association in 2017. The project leverages the potential of Citizen Science, and it was upgraded in 2024 on the online platform Zooniverse, which engages volunteers in scientific research activities.

The project’s objective is to digitize the meteorological data collected by the Italian Royal Central Meteorological Office (RCMO) from 1879 to 1940 for issuing its daily meteorological bulletin. The network used for this bulletin started with 11 meteorological stations and rapidly expanded to approximately 70 within a few decades. By utilizing telegraph technology, real-time observations were transmitted to the Central Office in Rome, enabling the publication of the Daily Meteorological Bulletin, which also included observations from foreign stations, representing one of the earliest steps toward international atmospheric monitoring.

Currently, the daily RCMO bulletins available to the project cover the period from December 1879 to December 1934, while the remaining years still require scanning. In total, 55 years of data are accessible, encompassing 20,120 daily bulletins. Since the bulletins were scanned page by page, over 84,000 scans have been performed. Considering the number of meteorological variables recorded in the bulletins—which increased over time—it is possible to estimate the amount of data that could potentially be digitized through ReData. The result is impressive: over 20 million data points.

Following an in-depth analysis of the evolution of these bulletins, both in terms of the monitoring stations considered and the meteorological variables observed, this study presents the design of the project’s website, structured to facilitate the digitization process for users. In addition, the potential applications of the digitized data are explored, presenting a case study for the year 1882 that has already been entirely digitized: a synoptic reconstruction of the flood event that affected the Polesine area in northeastern Italy in September 1882. This disaster, caused by persistent heavy rainfall, led to severe flooding in the Veneto region, particularly along the Po and Adige rivers. This latter overflowed in Verona, causing extensive damage, including the collapse of the Ponte Nuovo bridge. The bulletins provide valuable information about the event, revealing particularly rainy conditions that worsened mid-month.

Such reconstruction demonstrates how the project has significant cultural and scientific value, offering benefits to students, researchers, institutions, and weather services. It addresses the lack of a comprehensive historical observational network of synoptic stations in Italy, adding critical data to reanalysis models and advancing studies of past and present climate trends.