Recently published work by researchers at ICARUS

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

S. Noone, C. Murphy, J. Coll, T. Matthews, D. Mullan, R. L. Wilby and S. Walsh

INTERNATIONAL JOURNAL OF CLIMATOLOGY

Int. J. Climatol. (2015)

Published online in Wiley Online Library

(wileyonlinelibrary.com) DOI: 10.1002/joc.4522     (http://onlinelibrary.wiley.com/doi/10.1002/joc.4522/epdf)

In Ireland there is a lack of suitable quality controlled homogenised long term data sets. Long-term precipitation series are critical for understanding emerging changes to the hydrological cycle. In addressing this issue researchers at Irish Climate Analysis and Research UnitS (ICARUS), have been involved in a collaborative study with Met Éireann and various researchers based in Universities across the UK and Northern Ireland. This study constructs a homogenised 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.

A homogeneous climate time series is defined as one where variability is only caused by changes in weather or climate. Unfortunately most atmospheric data have been impacted adversely by non-climatic influences, such as changes in instrumentation or observer practices, station moves, or changes in the local environment. Following data bridging and updating of stations HOMER homogenisation software is employed to detect breaks/ potential issues. Detected issues are meticulously checked with available station metadata and any identified issues are corrected by HOMER.

Some of the key findings of this study reveal increasing (winter) and decreasing (summer) trends in precipitation over the period 1850-2010 (Figure 1). Table 1 presents the top 10 ranked wettest and driest season and years from the IIP series 1850-2010.

This work will be presenting by Simon Noone at the 10^th EUMETNET Data Management Workshop on 27-30^th October 2015 in St Gallen, Switzerland. (http://www.meteoswiss.admin.ch/home/research-and-cooperation/international-cooperation/eumetnet/10th-eumetnet-data-management-workshop.html )

The IIP series data is freely available for use and download at www.met.ie/downloads/Long-Term-IIP-network.zip.

Figure 1 IIP series moving windows trends calculated using the Mann–Kendall test with MK Z statistic plotted for all combinations of start and end years (minimum of 10 years).Significant (0.05 level) trends have a MK Zs >|1.96|. The y-axis denotes start year and x-axis the end year of analysis. Blue indicates positive trends; red indicates negative trends.

	Winter		Spring		Summer		Autumn		Annual
Rank	Wettest	Driest	Wettest	Driest	Wettest	Driest	Wettest	Driest	Wettest	Driest
1st	1994	1891	1947	1893	1861	1995	2000	1933	1872	1887
2nd	1995	1964	1981	1990	2008	1913	2006	1922	2002	1933
3rd	1883	1855	1913	1929	1879	1869	1954	2007	2009	1855
4th	1915	1934	1986	1944	2009	1870	1875	1919	1852	1971
5th	1877	1953	1920	1887	1912	1976	1982	1912	1928	1893
6th	1966	2006	1897	1915	1958	1975	1944	1879	1903	1975
7th	1990	1858	1993	1975	1860	1983	1960	1854	1877	1953
8th	1869	1874	2002	1984	2007	1940	2002	1855	1960	1921
9th	1937	1963	1862	1875	1985	2006	1916	1893	1924	1854
10th	1974	1888	2006	1938	1852	1959	2009	1942	1958	1919

Table 1 Top 10 ranked wettest and driest seasons and years from the homogenised and extended Island of Ireland precipitation (IIP) series 1850-2010.