Effects of Localized Grid Refinement on General Circulation and Climatology in the Community Atmosphere Model
A team of scientists from the University of Michigan and Sandia National Laboratories investigated the impact of a regionally refined nested area in the Community Atmosphere Model (CAM version 5) with its Spectral Element (CAM-SE) from the Department of Energy/National Center for Atmospheric Research.. They found that the addition of a refined patch over the Atlantic basin does not noticeably affect the global circulation. In the area where the refinement is located, large-scale precipitation increases with the higher resolution. This increase is partly offset by a decrease in precipitation resulting from convective parameterizations, although total precipitation is also slightly higher at finer resolutions. Large-scale equatorial waves are not significantly impacted when traversing multiple grid spacings. Despite the grid transition region bisecting northern Africa, local zonal jets and African easterly wave activity are highly similar in both simulations. The frequency of extreme precipitation events increases with resolution, although this increase is restricted to the refined patch. Topography is better resolved in the nest as a result of finer grid spacing. The spatial patterns of variables with strong orographic forcing (such as precipitation, cloud, and precipitable water) are improved with local refinement. Additionally, dynamical features, such as wind patterns, associated with steep terrain are improved in the variable-resolution simulation when compared to the uniform coarser run. This study indicates that the variable-resolution modeling with CAM-SE is free of numerical artifacts and has become a mature technique for regional climate studies.
Zarzycki, C. M., C. Jablonowski, D. R. Thatcher, and M. A. Taylor. 2015. “Effects of Localized Grid Refinement on the General Circulation and Climatology in the Community Atmosphere Model,” Journal of Climate 28, 2777–803. DOI: 10.1175/JCLI-D-14-00599.1.