Validation of simulated precipitation patterns over Ireland for the period 1961-2000

The Rotated Empirical Orthogonal Function (REOF) method was used to analyse the annual and interannual variability of the precipitation patterns over Ireland as simulated by the Rossby Centre Regional Climate Model Version 2 (RCA2) for the period 1961-2000. The annual and monthly precipitation results show that the model captures the major spatial pattern of each month, but the simulation shows a larger percentage of the variance explained by the leading spatial pattern and tends to have a less pronounced seasonal cycle compared to the observations. The simulation for the wet winter season is in slightly better agreement with the observations compared with the drier summer season. Spatial analysis of the monthly precipitation over a 40-year period shows two major patterns. The first, showing a precipitation maximum in the southwest, is well simulated; the second, showing a maximum in the west and northwest, shows a strongly increasing trend, which is slightly underestimated in the model simulation. Both patterns show seasonal and interannual variability. The wavelet energy density analysis shows that the interannual variability is more important than the seasonal one. In general, the model captures the major spatial and seasonal patterns observed between 1961 and 2000 but slightly overestimates monthly average precipitation levels. Copyright (C) 2005 Royal Meteorological Society.