Homogenization and analysis of an expanded long‐term monthly rainfall network for the Island of Ireland (1850–2010)

Abstract

Long-term precipitation series are critical for understanding emerging changes to the hydrological cycle. To this end we construct a homogenized Island of Ireland Precipitation (IIP) network comprising 25 stations and a composite series covering the period 1850-2010, providing the second-longest regional precipitation archive in the British-Irish Isles. We expand the existing catalogue of long-term precipitation records for the island by recovering archived data for an additional eight stations. Following bridging and updating of stations HOMogenisation softwarE in R (HOMER) homogenization software is used to detect breaks using pairwise and joint detection. A total of 25 breakpoints are detected across 14 stations, and the majority (20) are corroborated by metadata. Assessment of variability and change in homogenized and extended precipitation records reveal positive (winter) and negative (summer) trends. Trends in records covering the typical period of digitization (1941 onwards) are not always representative of longer records. Furthermore, trends in post-homogenization series change magnitude and even direction at some stations. While cautionary flags are raised for some series, confidence in the derived network is high given attention paid to metadata, coherence of behaviour across the network and consistency of findings with other long-term climatic series such as England and Wales precipitation. As far as we are aware, this work represents the first application of HOMER to a long-term precipitation network and bodes well for use in other regions. It is expected that the homogenized IIP network will find wider utility in benchmarking and supporting climate services across the Island of Ireland, a sentinel location in the North Atlantic.

A 305-year continuous monthly rainfall series for the Island of Ireland (1711–2016)

“…Neither step change is identified by Noone et al (2016) for the IoI_1850 series given they occur so close to the start of that record. Levene's test reveals no significant differences in variance between each of the three 100-year sections analysed for all four seasons.…”

“…First, is the Noone et al (2016) IoI composite series (1850-2010) (henceforth IoI_1850 series). This dataset consists of monthly rainfall data for 25 stations across the island, each 20 homogenised using the HOMogenisation softwarE in R (HOME, 2013) software package and making recourse to available metadata.…”

“…Each AAR estimate was used to reconstruct annual totals and subsequently monthly rainfall totals for the years 1711-1849. Post-1850 data remain the homogenised IoI_1850 series of Noone et al (2016). Resampling the missing 20 AAR from IoI_1850 has two advantages.…”

“…Emphasis is placed on the pre-1850 series as post-1850 has already been interrogated by Noone et al (2016). Datasets used are listed in Table 2.…”

“…Given the painstaking work of the original authors in constructing the series, together with the possibility of extending IoI rainfall records to the early 18 th Century, revisiting the work of Jenkinson et al (1979) holds considerable 5 potential for better understanding long-term Irish precipitation climatology. Therefore, this paper (i) presents the previously unpublished Jenkinson et al (1979) data and its constituent sources; (ii) merges the Jenkinson data with the homogenised Noone et al (2016) series to produce a continuous monthly rainfall series for Ireland from 1711 to present (henceforth IoI_1711); (iii) assesses confidence in the early record through comparison with other long records of relevant meteorological parameters from the BI region, as well as available proxy and documentary sources; and, (iv) investigates the 10 nature of variability and change in the reconstructed record.…”