Estimation of precipitation and air temperature over western Canada using a regional climate model

Abstract

The Mackenzie River basin (MRB), which covers a geographic region from central Alberta of Canada to the coast of Arctic Ocean, has an area of approximately 1.8 × 106 km2. In this study, the regional climate of MRB, in particular the precipitation and air temperature from the late spring to the fall (May–October), was simulated using a regional climate model Weather Research and Forecasting (WRF). In the open water season of May–October, Mackenzie River provides a critical corridor for Canada's Arctic transportation network. With nine sets of physical parameterizations of WRF selected, we simulated the climate of MRB over representative dry, normal, and wet years to identify the best setting prior to performing the 27‐year simulation for 1979–2005. The major physical parameterizations considered were shortwave (Dudhia, CAM, and RRTMG) and longwave radiation scheme (RRTM, CAM, and RRTMG), microphysics scheme (WRF Double‐Moment 6‐class, WRF Single‐Moment 5‐class, Stony Brook University, and Morrison double‐moment), and cumulus parameterization (Kain–Fritsch, Betts–Miller–Janjic, Tiedtke, and New Simplified Arakawa–Schubert). The simulation for MRB by each set of parameterizations of WRF is assessed using root‐mean‐square error (RMSE), absolute error percentage, and bias maps. After a detailed fine tuning process, and from verifying the 1979–2005 long‐term simulations of WRF, WRF generally simulated realistic air temperature and precipitable water over MRB, but precipitation is over‐simulated, especially at Canadian Rockies.