Projected Changes in Precipitation Extremes over Western Canada

Abstract:

The projection of future hydro-climatic extremes due to anthropogenic climate change is a major research focus, as well as a major challenge for regional climate modeling. An analysis of hydro-climatic extremes is presented based upon a small ensemble of dynamically downscaled climate projections. The ensemble is comprised of four independent, identically configured CESM integrations (RCP 8.5), which were downscaled over Western Canada using WRF in two different configurations at 10 km resolution. In the climate projections presented here, changes in precipitation extremes generally follow changes in the (seasonal) mean, even though precipitation changes in general are found to differ strongly between seasons and regions. At the end of the 21st century the highest projected increase in precipitation (extremes) is approximately 30% in fall at the coast and in winter away from the coast. In summer only a small increase in precipitation (extremes) is projected, and the statistical significance of the signal is weak. Nevertheless, cumulus precipitation consistently increases by 20-30%. Furthermore, the total summer precipitation change appears to be sensitive to the choice of the cumulus scheme. In order to detect a robust climate change signal in the Extreme Value Analysis that has been performed, a novel method of aggregating data from climatologically similar stations is introduced and discussed.