Ireland’s pre-1940 daily precipitation data: data rescue, quality assurance and analysis of extremes

Over much of the globe, the temporal extent of meteorological records is limited, yet a wealth of data remains in paper or image form in numerous archives. This research presents daily rainfall data and metadata for Ireland transcribed from historical manuscripts and printed copies of rainfall registers located in Met Éireann's archives. To facilitate the transcription of rainfall observations from paper records, the historical manuscripts were scanned and integrated into Met Éireann's digital archives. The transcription from digital image to data format was undertaken in collaboration with students at Maynooth University as part of a novel crowdsourcing initiative to integrate data rescue activities into the classroom. In total, 3,616 station years of rainfall data (~1.32 million daily values) and associated metadata for the period 1864-1940 were transcribed and made available. Utilising the rescued data to extend current station records, this research provides the first long‐term assessment of changes in extreme precipitation observed for 30 daily station series across Ireland. Quality control of rescued data was carried out before selected long-term stations were tested for homogeneity using RHtests software. Eleven extreme precipitation indicators were calculated on an annual basis for two fixed periods, 1910-2019 and 1940-2019, and analysed to determine spatial and temporal trends in the frequency, intensity and magnitude of observed precipitation. The persistence of trends for the full record length and different periods of analysis was assessed for all stations and indicators. Results show an overall tendency towards increasing trends, with increases in precipitation extremes and intensity especially notable in the east and southeast of the island. The findings suggest that the contribution of heavy and extreme precipitation events to annual totals are increasing, despite the lack of a robust trend in annual totals. The dataset produced is fully traceable and will have a long legacy of impact for understanding historical extremes, climate variability and change in Ireland, while the procedures for data rescue are already inspiring similar approaches in other University settings. Moreover, the work provides a relatively rare attempt to homogenise daily precipitation data, with a novel study design implemented to ensure the robustness of results. While data rescue activities can be slow and painstaking, the dataset produced resurrects the lifetimes work of many hundreds of weather observers across Ireland and sheds light on the unfolding changes in Irish precipitation.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

National University of Ireland, Maynooth

Year dc:date.issued

2021

Author dc:creator

• Ryan, Ciara

Language dc:language

en