Vol. 563 No. 4
585 Mr. Cuffe asked the Minister for the Environment and Local Government his views on whether there may be a discrepancy between the table of predicted extreme rainfalls supplied by Met Éireann and the extreme rainfall predictions that can be derived from analysing the stock of hourly recorded rainfall parameters obtained from synoptic weather stations on a multi-annual basis. [7641/03]
Met Éireann provides tables of extreme rainfalls of durations from one minute to 96 hours with return periods from half year to 100 years for any location in Ireland. This statistical information is based on the methods as outlined in the British and Irish Flood Studies Report – Natural Environment Research Council 1975 – and employs long time series of rainfall data from hundreds of stations around the country, including some which reported at hourly or higher temporal resolution. Due to the high spatial variability of rainfall, this comprehensive countrywide service cannot be based on data from synoptic stations only, of which, at any one time, there are at most 16.
All estimates of extreme rainfall are statistically based and, as such, have an associated uncertainty. In particular, they depend on the period covered by the observational data and will thus produce somewhat different results depending on the basic data used. Work is under way within Met Éireann to produce quality assured data up to the end of 2002 from several hundred stations, and to develop some refinements of the methods that were used in the above mentioned publication. This work will update extreme rainfall tables and allow them to be used with increased confidence. No generally accepted method exists at this stage to take into account future climate change in the area of extreme rainfall return periods.
