Recent trends in diurnal variation of precipitation at Valentia on the west coast of Ireland

Abstract

An investigation of 54 years of hourly precipitation at Valentia, on the south-west coast of Ireland, shows a change point in the annual amounts in the years around 1975 (identified by the Pettitt—Mann—Whitney statistic). This results in a 10% increase in the mean annual precipitation from a pre-1975 value of 1375 mm to a post-1975 value of 1507 mm. Most of that increase is absorbed in the months of March and October. The frequency of hourly precipitation in March in the post-1975 period is 57% greater than that of March in the pre-1975 period. However, the magnitude of the hourly intensity of precipitation in March for both periods was similar. Significant changes in wet hour frequency also occurred in October with no corresponding change in hourly intensity. These results compliment findings by others, that regions in Northern European latitudes have experienced an increase in precipitation since the mid-1970s.