Friday, October 23, 2015

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 √Čireann 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 10th EUMETNET Data Management Workshop on 27-30th 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.

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