Changes in UK extreme rainfall projected by the PRUDENCE regional climate models

In the past decade, widespread flooding and landslides in the UK and Europe have
focused attention on perceived increases in rainfall intensities. Climate model
integrations predict increases in both the frequency and intensity of heavy rainfall
in the high latitudes under enhanced greenhouse conditions. These projections are
consistent with recent increases in rainfall intensity seen in the UK and worldwide.
Here we present a regional frequency analysis of changes in UK extreme multi-day annual
rainfall using 6 models from the PRUDENCE set of experiments. The selection of models
encompasses two different driving Global Climate Models and four different Regional
Climate Models, thus maximizing the uncertainty range of response. The representation
of UK extreme rainfall by the regional climate models is explored by comparing them with
observational data for the 1961-2000 period from the UK Meteorological Office gridded 5km
dataset. Further results for a future scenario are then analyzed to provide a comparison
of changes projected by the models and new design estimates of extreme rainfall for different
regions of the UK. This method provides more reliable high return period estimates for design
purposes and a clearer understanding and quantification of uncertainty of changes that may
occur in the future.