摘要：Relations between hourly precipitation extremes and atmospheric temperature and
moisture derived for the present-day climate are studied with the aim of understanding the
behavior (and the uncertainty in predictions) of hourly precipitation extremes in a
changing climate. A dependency of hourly precipitation extremes on the daily mean 2 m temperature of
approximately two times the Clausius–Clapeyron (CC) relation is found for temperatures above
10 °C. This is a robust relation obtained in four observational records across western Europe. A
dependency following the CC relation can be explained by the observed increase in
atmospheric (absolute) humidity with temperature, whereas the enhanced dependency
(compared to the CC relation) appears to be caused by dynamical feedbacks owing to
excess latent heat release in extreme showers. Integrations with the KNMI regional climate model RACMO2 at 25 km grid spacing
show that changes in hourly precipitation extremes may indeed considerably
exceed the prediction from the CC relation. The results suggests that increases of + 70% or even more are possible by the end of this century. However, a different regional
model (CLM operated at ETHZ) predicts much smaller increases; this is probably
caused by a too strong sensitivity of this model to a decrease in relative humidity.
