A comprehensive investigation was performed of how the variable-resolution CESM simulates the Rocky Mountain region when compared with uniform-resolution simulations, observations, and a regional model (CRCM5). This study focused on topographically-sensitive quantities, particularly mountain snowpack, temperatures, and rain-on-snow events.
Variable-resolution global climate modeling systems provide significant value in regions of strong topographic variability, such as the Rocky Mountain region. This paper assesses the performance of a global modeling system as it is pushed down to resolutions typical of regional climate modeling systems.
In this study, the variable-resolution CESM (VR-CESM) is demonstrated to be able to accurately simulate key climatological variables and their associated seasonality in the Rocky Mountains. Using a suite of snow-related metrics related to precipitation, snow cover, snow water equivalent, rain-on-snow events, model performance is observed to be significantly improved over uniform resolution simulations, and comparable to analogous regional climate model simulations. VR-CESM was demonstrated to capture the observed occurrence frequency of heavy precipitation and rain-on-snow (ROS) events. Nonetheless, it was shown that although VR-CESM overestimated winter precipitation, it underestimated snow water equivalent peaks in the Rocky Mountains. Further work is needed to understand the biases related to snow variables in VR-CESM.