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Long Term Data Sets

Rainfall time series from 1850-2010 for Ireland.

Homogenisation and analysis of an expanded long-term monthly rainfall network for the Island of Ireland (1850-2010)

An Island of Ireland Precipitation (IIP) series covering the period 1850-2010 for 25 locations has been constructed by researchers at Maynooth University and Met Éireann. Such long-term series are critical for understanding past and emerging changes to the precipitation regime and the hydrological cycle. The resulting dataset provides the second-longest regional precipitation archive in the British-Irish Isles.

In developing the dataset researchers rescued data from the archives in Met Éireann’s library and combined them with previously available long-term records for stations on the Island. Attention was also given to compiling metadata for all stations. Following bridging and updating of stations, HOMER homogenisation software was used to detect breaks in individual series and to extend all series to a common period of record. Only breaks confirmed by metadata were subject to adjustment.

Assessment of variability and change in homogenised and extended precipitation records reveal positive (winter) and negative (summer) trends over the period 1850-2010. Trends in records covering the typical period of digitisation (1941 onwards) are not always representative of longer records, indicating the importance of long term records. Furthermore, trends in post-homogenisation series change magnitude and even direction at some stations. While cautionary flags are raised for some series, confidence in the derived network is increased given attention paid to metadata, coherence of behaviour across the network and consistency of findings with other long-term climatic series such as the England and Wales precipitation series.

This research was recently published in the International Journal of Climatology:

The homogenised and extended data for all 25 stations in the network, the Island of Ireland composite series and supporting metadata are available here

Please cite the original paper if using this dataset.

Composite Rainfall Time Series from 1711-2016 for Ireland.

A continuous 305-year (1711-2016) monthly rainfall series has been created for the Island of Ireland using two key data sources, i) a previously unpublished UK Meteorological Office Note which contains annual rainfall anomalies and corresponding proportional monthly totals based on weather diaries and early observational records for the period 1711-1977 and, ii) a long-term, homogenised monthly rainfall series for the island for the period 1850-2016.

Using estimates of long-term average precipitation sampled from the homogenised series, the new 305-year record is reconstituted and insights drawn about notable extremes, climate variability and change. The consistency of the series was evaluated using long-term observations and reconstructions of precipitation, temperature, circulation indices and the North Atlantic Oscillation. All sources were compiled from across the British-Irish Isles and screened for circularity.

Strong decadal consistency is evident throughout the record amongst all series in spring, summer and autumn. Strong consistency with other records strengthens confidence from 1790 onwards while the winter series is probably too dry during the 1740s to the 1780s. The new series reveals statistically significant trends in winter (increasing) and summer (decreasing). However, given uncertainties in the early winter record, the former should be treated as tentative. In particular we show that the years 1940 to present the period typical of available digitised records, is unrepresentative of long-term changes in all seasons. Although there are recognized uncertainties in the early record, it is concluded that the derived series offers valuable insights for understanding multi-decadal rainfall variability in Ireland, a sentinel location in northwest Europe and provides a firm basis for benchmarking other long-term records and future reconstructions.

A paper on this work has been submitted to Climate of the Past, data set available here.

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