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

Conor Murphy,Mary Curley,Timothy J Osborn,Gerard Mccarthy,Peter W Thorne,Timothy P Burt,Julia Hall,John Sweeney,Ciara Ryan,Mark P Mccarthy,Robert L Wilby,Shaun Harrigan,Seamus Walsh,Tom K R Matthews,Catriona Duffy,Ciaran Broderick,Simon Noone,Neil Macdonald,Donal Mullan

doi:10.5194/cp-14-413-2018

Abstract

Abstract. A continuous 305-year (1711–2016) monthly rainfall series (IoI_1711) is created for the Island of Ireland. The post 1850 series draws on an existing quality assured rainfall network for Ireland, while pre-1850 values come from instrumental and documentary series compiled, but not published by the UK Met Office. The series is evaluated by comparison with independent long-term observations and reconstructions of precipitation, temperature and circulation indices from across the British–Irish Isles. Strong decadal consistency of IoI_1711 with other long-term observations is evident throughout the annual, boreal spring and autumn series. Annually, the most recent decade (2006–2015) is found to be the wettest in over 300 years. The winter series is probably too dry between the 1740s and 1780s, but strong consistency with other long-term observations strengthens confidence from 1790 onwards. The IoI_1711 series has remarkably wet winters during the 1730s, concurrent with a period of strong westerly airflow, glacial advance throughout Scandinavia and near unprecedented warmth in the Central England Temperature record – all consistent with a strongly positive phase of the North Atlantic Oscillation. Unusually wet summers occurred in the 1750s, consistent with proxy (tree-ring) reconstructions of summer precipitation in the region. Our analysis shows that inter-decadal variability of precipitation is much larger than previously thought, while relationships with key modes of climate variability are time-variant. The IoI_1711 series reveals statistically significant multi-centennial trends in winter (increasing) and summer (decreasing) seasonal precipitation. However, given uncertainties in the early winter record, the former finding should be regarded as tentative. The derived record, one of the longest continuous series in Europe, offers valuable insights for understanding multi-decadal and centennial rainfall variability in Ireland, and provides a firm basis for benchmarking other long-term records and reconstructions of past climate. Correlation of Irish rainfall with other parts of Europe increases the utility of the series for understanding historical climate in further regions.

Highlights

Long historical weather records are essential for understanding climate variability and change, as well as contextualising extreme events, identifying emerging trends, evaluating climate models and supporting vulnerability and risk assessments (e.g. Matthews et al, 2016)
Consistency in the timing of these breaks across stations, along with an absence of evidence from metadata describing widespread measurement changes across the island, suggests that this break is due to natural climate variability
The timing of breaks is consistent with an increase in annual totals associated with a shift to a positive phase of the North Atlantic Oscillation around this time (Harrigan et al, 2014)

Summary

Introduction

Long historical weather records are essential for understanding climate variability and change, as well as contextualising extreme events, identifying emerging trends, evaluating climate models and supporting vulnerability and risk assessments (e.g. Matthews et al, 2016). The earliest meteorological observations in Ireland began at the end of the 17th Century. These early instrumental records, taken in Dublin by William and Samuel Molyneux, have been lost (Shields, 1983). Systematic weather observing did not begin in Ireland until 1789 when Richard Kirwan set up a series of instruments in Dublin (Shields, 1983). With the exception of Butler et al (1998) who analysed the record for Armagh Observatory (commencing in 1838), there has been little work on Irish precipitation measurements prior to 1850, due primarily to the lack of suitable digitised data. Irish rainfall climatology over the last 300 years remains poorly understood

Results

Discussion

Conclusion