Bias-corrected UKCP18 Convection-permitting model projections for England

Abstract

The UKCP18 Convection-permitting model (CPM) provides the latest high-resolution climate projections for the UK. Compared with regional climate model projections, the CPM projections are more capable of simulating small-scale atmospheric convection particularly during extreme weather events such as intense rainfall and localised storms. However, systematic biases still exist in these projections. To improve the reliability of these projections, bias correction is crucial. In this study, we apply and evaluate a quantile mapping (QM) bias correction method for UKCP18-CPM hourly precipitation (with diurnal correction) and daily temperature over England. We quantify how closely the bias corrected simulations align with observations relative to the raw simulations. The raw UKCP18-CPM simulations exhibit wet precipitation biases, particularly in northern England, with annual mean biases ranging from 4.6 % to 18.3 %, and cool temperature biases, with annual mean biases from -0.87 to 0.02 °C. Bias correction substantially improved agreement with observational datasets, increasing R2 values for the 95th percentile of hourly precipitation from 0.80–0.88 to 0.98 and achieving near-perfect alignment (R2 = 1) for temperature extremes. Future projections for the 2070s indicate notable increases in annual maximum precipitation by 25.1 %–39.1 % and mean daily temperature by 3.1 to 4.5 °C, highlighting the potential for more intense climate-related events. Overall, the applied bias-correction method brings UKCP18-CPM simulations into closer agreement with observations for both mean behaviour and extremes, providing a more reliable basis for high-resolution impact modelling and assessments that require hourly precipitation forcing.