Impacts of Changes in Atmospheric Physics Parameterizations in a Coupled Regional Climate Model

The Regional Arctic System Model (RASM) is a coupled atmosphere-land-ocean-sea ice model with a focus on climate simulations of the Arctic. The Weather Research and Forecasting (WRF) model is the atmospheric component of RASM. A series of stand-alone WRF simulations and coupled RASM simulations are completed with changes in the selected physics parameterizations. This study evaluates changes in the climate simulations due to the variations in the WRF physics parameterizations. There is little to no changes in the circulation across the range of simulations. Meanwhile there are significant differences in the surface energy balance and the resultant surface temperature. The changes in surface temperature in the coupled RASM model result in dissimilarities in the corresponding sea ice and SST fields for the RASM climate simulations. A large amount of the differences in the surface temperatures are due to the radiative energy balance, which is impacted by the formation of too much or not enough clouds. The microphysics, cumulus, and planetary boundary layer parameterizations all play a role in the formation of the clouds and in achieving an accurate radiation budget. The conclusions from this presentation will demonstrate the range of results for stand-alone and coupled climate for the Arctic based on changes in the WRF physics parameterizations.