Development and comparison of documentary-instrumental and circulation-based multi-centennial precipitation reconstructions for Dublin, Ireland

Abstract. This study develops a multi-centennial reconstruction of precipitation for the Greater Dublin Area, Ireland, using documentary, instrumental, circulation-based, and proxy evidence. Three independent reconstructions are produced for two contrasting water-resource domains, including: a monthly scaled version of the Jenkinson documentary-instrumental rainfall dataset for 1711–1977 produced by an earlier analysis for the island of Ireland; a circulation-informed monthly statistical ensemble based on Lasso and Random Forest models for 1748–1994; and an annual oak cellulose δ¹⁸O reconstruction of May–August precipitation extending to 1200 CE. Reconstructions were assessed against 1 km gridded rainfall observations for the common overlap period 1865–1977 using correlation, bias, error metrics, SPI-based event detection, and agreement in ranked wet and dry extremes. Long-term UK rainfall series and an extended Dublin snow and sleet series were used as independent comparators. Both the Jenkinson and statistical ensemble reconstructions reproduce observed monthly, seasonal, and annual rainfall variability, but the Jenkinson reconstruction shows the strongest agreement across most metrics and better captures wet and dry extremes. The statistical ensemble provides an independent, physically interpretable reconstruction, although it tends to smooth variability and under-represent event magnitude. The δ¹⁸O reconstruction shows weaker interannual agreement with observed May–August rainfall but provides a valuable longer-term perspective on summer hydroclimatic variability. Divergence between the Jenkinson and ensemble reconstructions before the mid-nineteenth century, particularly in winter and spring, is consistent with possible snow- and sleet-related undercatch in early precipitation sources which affects the Jenkinson reconstruction. Summer rainfall during the eighteenth century remains uncertain, with evidence for increased regional hydroclimatic heterogeneity. Together, these reconstructions provide a stronger basis for contextualising historical droughts and pluvials affecting Dublin and for stress-testing water-resource systems beyond the instrumental period.