Effects of Localized Grid Refinement on the General Circulation and Climatology in the Community Atmosphere Model

Abstract

Using the spectral element (SE) dynamical core within the National Center for Atmospheric Research-Department of Energy Community Atmosphere Model (CAM), a regionally refined nest at 0.258 (;28 km) horizontal resolution located over the North Atlantic is embedded within a global 18 (;111 km) grid. A 23-yr simulation using Atmospheric Model Intercomparison Project (AMIP) protocols and default CAM, version 5, physics is compared to an identically forced run using the global 18 (;111 km) grid without refinement. 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. 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.

Irrigation impacts on California's climate with the variable‐resolution CESM

“…In particular, simulations at 0.125 ($14 km) conducted in Huang et al [2016] did not show a statistically significant change in temperature statistics over California. In our study, as in Zarzycki et al [2015], general circulation patterns (e.g., wind, pressure and precipitation) do not exhibit apparent artifacts in the variable-resolution transition region. A detailed description of the techniques of VR-CESM employed in this paper can be found in Rhoades et al [2015].…”

Impacts of absorbing aerosol deposition on snowpack and hydrologic cycle in the Rocky Mountain region based on variable-resolution CESM (VR-CESM) simulations

“…With a refined high resolution, VR-CESM has shown significant improvements of the Atlantic tropical storms (Zarzycki and Jablonowski, 2014) and South America orographic precipitation (Zarzycki et al, 2015). The model has also been used in the regional climate simulations over the western US, and the results show that the VR-CESM is capable of reproducing the spatial patterns and the seasonal evolution of temperature, precipitation, and snowpack in the Sierra Nevada Rhoades et al, 2016) and Rocky Mountains (Wu et al, 2017).…”

An evaluation of the variable‐resolution CESM for modeling California's climate

“…Strategies that have been employed for transitioning between coarse and fine‐resolution regions within a VRGCM include grid stretching [ Fox‐Rabinovitz et al ., ; McGregor and Dix , ] and grid refinement [ Ringler et al ., ; Skamarock et al ., ; Zarzycki et al ., ]. VRGCMs have demonstrated utility for regional climate studies and applications at a reduced computational cost compared to uniform‐resolution GCMs [ Fox‐Rabinovitz et al ., ; Rauscher et al ., ; Zarzycki et al ., ].…”

“…Zarzycki et al . [] also compared the large‐scale climatology of VR‐CESM 0.25° and uniform CESM at 1° and found that adding a refined region over the globe did not noticeably affect the global circulation. Rhoades et al .…”