Internal variability of a dynamically downscaled future climate over North America

Abstract:

This study investigates the internal variability (IV) of a regional climate model, considering the impacts of horizontal resolution as well as spectral nudging. Ten one-year WRF simulations driven by the CCSM4 are conducted for three sets of simulations respectively. They are ten 50 km simulations without nudging, ten 12 km simulations without nudging, and ten 12 km simulation with nudging. All simulations are generated over North America and cover a completed annual cycle. The ten members for each set of simulations differ only by the starting time — a standard procedure used to trigger internal variability in RCMs. The IV of the 12 km simulation with spectral nudging is also compare with the future climate projections done previously using the same model setup. We will answer three questions: 1) What is the impact of high resolution on IV? 2) What is the impact of spectral nudging in comparison with that of spatial resolution on IV? 3) How important of IV for the future climate projections?