Ongoing Improvements in Atmospheric Physics Parameterizations with the Regional Arctic System Model (RASM)

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 recent upgrade of RASM to WRF v3.7.1 provides a range of new atmospheric physics parameterizations and options within the physics parameterizations. This study evaluates changes in the climate simulations due to the variations in the WRF physics parameterizations in coupled RASM simulations and standalone WRF simulations. An accurate representation of clouds in the atmosphere continues to be a challenging problem. Changes in clouds play a significant role in altering the radiative energy, the resultant surface temperature, and other components of the Arctic climate system such as sea ice and sea-surface temperature (SST). The results of the study highlight the key atmospheric physics parameterizations for a best representation of the Arctic climate. Outstanding issues still lie ahead in providing the most accurate representation of the Arctic climate system. For example, the ability to provide a distinction between selected parameterizations over land or ocean.