Precipitation over Ireland - Observed change since 1940

Using a low pass-filter (10 year moving average), the non-parametric Pettitt-Mann-Whitney-Statistic and the Mann-Whiteny-Wilcoxon-Test, time series of hourly precipitation records for 8 meteorological stations in Ireland were investigated for the period since the 1940's to determine trends in the precipitation. Three of the stations are located on the West-cost, one on the North, one on the South coast, two on the East-coast and one inland. We analysed the time series of the annual, half-yearly, quarterly and monthly precipitation for each site and applied the statistical tests to these time series. Change points in these time series were identified at all sites and most of the change points occur in the mid seventies. For the annual series two sites on the West-cost and the one site on the North-cost show an increase in precipitation after the change point year. For the monthly time series we found change points at six of the eight stations for the month of March. The change in the precipitation is concentrated in the months February to April and October. A decrease in the time series was determined for three of the time series of monthly precipitation in the summer-months and statistically not as significant as the increase between autumn and spring. The increased trend is clearly identified at the stations on the West-coast. The stations on the east coast show insignificant change. (C) 1998 Elsevier Science Ltd. All rights reserved.