Projected increases in summer and winter UK sub-daily precipitation extremes from high-resolution regional climate models

Summer (June-July-August; JJA) UK precipitation extremes projections from two UK Met Office high-resolution (12 km and 1.5 km) regional climate models (RCMs) are shown to be resolution dependent. The 1.5 km RCM projects a uniform (approximate to 10%) increase in 1 h JJA precipitation intensities across a range of return periods. The 12 km RCM, in contrast, projects decreases in short return period (<= 5 years) events but strong increases in long return period (>= 20 years) events. We have low physical and statistical confidence in the 12 km RCM projections for longer return periods. Both models show evidence for longer dry periods between events. In winter (December-January-February; DJF), the models show larger return level increases (>= 40%). Both DJF projections are consistent with results from previous work based on coarser resolution models.