Extreme precipitation in North Europe region as simulated by high-resolution regional climate models

Friday, 19 December 2014
Tao Feng and Peter D. Ditlevsen, Niels Bohr Institute - University of Copenhagen, Copenhagen, Denmark
The water vapor content in the atmosphere has risen significantly over the past half century and global hydrological cycle has been intensified accordingly. The anthropogenic warming changed not only the mean state of precipitation but also the occurrence of extreme precipitation. The basic science connecting human-induced climate change to more frequent extreme precipitation is relative evident. It is far more challenging to predict how climate change will affect the magnitude and frequency of these events at the relatively fine spatial scales, which is strongly depend on the capability of the regional climate model (RCM).

8-km high-resolution regional climate model simulations from the RiskChange model assessment project were analyzed for changes in extreme precipitation over North Europe. Four regional model simulations were carried out from two RCMs cross-forced by two different GCMs separately. Indices of extreme precipitation included monthly maxima and maximum consecutive 5 days total precipitation. Generalized extreme value (GEV) theory was used to model tail distribution of extreme precipitation. These model results were compared with EOBS observations and intense Denmark station observations of these extremes for the reference period of 1981-2010.

Differences in four cross-forced RCM simulations were analyzed to investigate the capability of high-resolution RCM on simulated extreme precipitation. We are addressing three questions. One, are the GEV parameters of model-simulated heavy rain similar to observed extreme precipitation. Two, how much is model uncertainty came from inter-model variation. Three, can weighted model result perform better skill than individual RCM simulations.