Internal variability and temperature scaling of future sub-daily rainfall return levels over Europe

The range of sub-daily extreme precipitation due to internal variability is quantified within the single model initial-condition large ensemble featuring 50 members of the Canadian regional climate model, version 5 (CRCM5) under the high-emission scenario representative concentration pathway 8.5. Ten-year return levels of sub-daily precipitation are calculated for three future periods (2010-2039, 2040-2069, 2070-2099) and hourly to 24-hourly aggregations over a European domain. The return levels are found to increase by 4%-8% for every future 30 year period averaged for the study area, where short-duration rainfall intensities increase to a greater extent than longer-duration rainfall intensities. The ranges between the median of the 50 members and the 5th and 95th quantile amount to -15.6%-19.3%, -16.0%-20.1%, and -16.5%-20.9% for the near, mid and far future, respectively. It is also shown that the scaling of the precipitation increase with temperature (Clausius-Clapeyron scaling) exhibits substantial variations between the 50 CRCM5 members at regional aggregations. These findings illustrate the large impact of internal variability on the uncertainty of extreme precipitation return level estimates. Here, regions of significant changes are identified, where future median extreme precipitation exceeds the 95th quantile of the reference period (1980-2009). These regions are located in northern Europe, central Europe and the eastern part of the Mediterranean.

Automated summary

This study quantified the range of sub-daily extreme precipitation due to internal variability using the Canadian regional climate model. Results show an increasing trend of extreme precipitation over time, with short-duration rainfall intensities increasing more than longer-duration rainfall. Variations in the scaling of precipitation increase with temperature were significant among the 50 model members.