5.5 WRF as the atmospheric model in the Regional Arctic System Model (RASM)

Seefeldt, Mark W., and John J. Cassano, University of Colorado - Boulder, Cooperative Institute for Research in Environmental Sciences

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 presentation will provide an overview of WRF in a couple model framework and evaluates changes in the climate simulations due to the variations in the WRF physics parameterizations. An accurate representation of clouds in the atmosphere continues to be a challenging problem for RASM simulations in the sub-polar and Arctic regions. 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, sea-surface temperature (SST) and snow cover. The results of the study highlight the key atmospheric physics parameterizations for a best representation of the Arctic climate and the potential benefits of using different parameterizations over land and ocean portions of the model domain. Outstanding issues still lie ahead in providing the most accurate representation of the Arctic climate system.