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Abstract

Understanding how the statistical properties of daily rainfall will respond to a warming climate requires ensembles of climate model data which are much larger than those typically available from existing model experiment frameworks (like the SSP-RCP simulations from CMIP6). These ensemble size constraints often result in regional climate change assessments restricting their focus to annual- or season-mean rainfall projections. Here, we make use of multi-thousand member ensembles of regional climate model output from the Weather@Home project to explicitly resolve how the wettest and driest days of the year over New Zealand will respond to simulations of a 3°C world, relative to the climate of today. Using a novel framework to disentangle changes during the wettest and driest days of the year, we show that many regions which show no change in annual mean rainfall are in fact experiencing significant changes in the amount of rain falling during both the wettest and driest spells. Exploring these changes through the lens of drought risk, we find many agricultural regions in New Zealand will face significant changes in the frequency of low-rainfall extremes in a warmer world.