![]() ![]() However, interpretation of apparent scaling results is hindered by large variations in derived scaling rates and divergence from theoretical and modeled projections of systematic increases in extreme precipitation intensities (climate scaling). Observational studies of extreme daily and subdaily precipitation–temperature sensitivities (apparent scaling) aim to provide evidence and improved understanding of how extreme precipitation will respond to a warming climate. Hourly curves at the highest temperatures undergo a less severe reduction in scaling rates, with a more pronounced hook developing for the dry-bulb curve compared to dewpoint temperature. At the highest temperatures (>25☌), associated with predominantly short-duration convective storms, a strong decrease in daily dry-bulb scaling rates produces a hook-shaped curve, with a lessened hook shape for the daily dewpoint curve. This increase in apparent scaling rates also occurs in daily curves, although at a limited and higher temperature range compared to hourly curves. At higher temperatures (20°–25☌), a mixture of convective and stratiform precipitation events results in steeper hourly curves for both temperature variables, close to 2CC (twice the CC rate). At lower temperatures (5°–20☌), predominant stratiform precipitation produces daily and hourly curves close to CC scaling of 7% ☌ −1 for both dry-bulb and dewpoint temperature. Schematic of the influence of precipitation type and duration on apparent scaling of high-percentile extreme precipitation intensities with near surface dry-bulb and dewpoint temperature. The use of daily data in apparent scaling analyses Seasonal characteristics of precipitation–temperature relationships Dewpoint temperature as primary scaling variable Consistent positive apparent scaling across durations and climate zones ![]() Explaining negative apparent scaling at higher temperatures Addressing stronger hook structures in daily apparent scaling ![]() Apparent scaling across event duration and region Pooling of station data across climate zones Scaling of 1-h peak intensities versus average intensities Scaling calculation for individual stations This found a long-term shift to higher daily rainfall totals for this mean with an increase in intensity of the top 10% of events, suggesting that the South Yorkshire region in autumn is more at risk of flooding in the future without effective adaptation measures. A more specific analysis of the November 2019 event looked at the mean of the two highest daily precipitation totals in October–November in the South Yorkshire region. This underlines the importance of high-resolution models for modelling extreme precipitation seen in late autumn and early winter, not just for convective rainfall in the summer. While higher resolution models (12 km spatial resolution) were able to capture the observed changes, lower resolution models were not. R 50mm_OND is projected to increase even further between 20, by 85% (95% CI: 73–97) according to a Representative Concentration Pathway (RCP) 8.5 scenario of anthropogenic emissions. Observations show that the frequency of extreme daily precipitation in the form of R 50mm_OND has already increased by 60% (95% CI: 44–76) in the UK between the beginning of the 20th and 21st centuries. Using high resolution regional model datasets and observations we show that extreme rainfall totals for the UK are increasing exponentially as a result of anthropogenic climate change. Here we investigate the change in risk of such extreme rainfall events in the UK in autumn using a new index R 50mm_OND, representing the mean number of daily precipitation totals in excess of 50 mm in October–December each year. In the light of anthropogenic climate change, it is expected that extreme rainfall events are set to become more intense as a result of increased global mean temperatures and the Clausius-Clapeyron relation. This followed very high 24-h rainfall totals in the region just two weeks earlier of up to just under 50 mm. ![]() The worst of the flooding occurred after very high 24-h rainfall totals of up to 82 mm fell on already saturated ground. The flooding in South Yorkshire in the United Kingdom (UK) in autumn 2019 saw one fatality, at least 500 properties flooded and 1 200 households evacuated. ![]()
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