Estimating uncertainties from high resolution simulations of extreme wind storms and consequences for impacts

A simple method is presented designed to assess uncertainties from dynamical downscaling of regional high
impact weather. The approach makes use of the fact that the choice of the simulation domain for the regional
model is to a certain degree arbitrary. Thus, a small ensemble of equally valid simulations can be produced
from the same driving model output by shifting the domain by a few of grid cells. Applying the approach to
extra-tropical storm systems the regional simulations differ with respect to the exact location and severity of
extreme wind speeds. Based on an integrated storm severity measure, the individual ensemble members are
found to vary by more than 25% from the ensemble mean in the majority of episodes considered. Estimates
of insured losses based on individual regional simulations and integrated over Germany even differ by more
than 50% from the ensemble mean in most cases. Based on a set of intense storm episodes, a quantification
of winter storm losses under recent and future climate is made. Using this domain shift ensemble approach,
uncertainty ranges are derived representing the uncertainty inherent to the used downscaling method.