Spatio-temporal precipitation downscaling at hourly resolution based on km-scale regional simulations

Effectively preparing for changes in extreme flooding requires understanding present and future rainfall extremes with return periods up to (\sim)100-1000 years, including changes in intensity, spatial structure at km-scale and sub-daily temporal variability. Conventional km-scale climate models give greatly increased realism compared to typical global climate models (GCMs) but are too computationally costly to allow enough simulations for robustly quantifying changes in extremes. This work presents an approach based on video diffusion to generate realistic precipitation at 8.8km-hourly resolution by spatially and temporally downscaling daily, GCM-scale atmospheric variables. The emulator is trained to produce similar output to the Met Office’s 2.2km-resolution UK convection-permitting model. An application for such an emulator is to downscale large-ensemble GCM simulations to allow quantification of (\sim)100–1000-year return level rainfall, which in turn can be used to drive hydrological and flood models for improved projections of future changes in flood risk.