Convergence of atmospheric simulations with increasing horizontal resolution and fixed forcing scales
Williamson, David L.
- Publisher: Co-Action Publishing
(issn: 1600-0870, eissn: 0280-6495)
A series of experiments with the NCAR Community Climate Model, Version 2 (CCM2) isexamined in which the grid and scale of the physical parameterizations are held fixed while thehorizontal resolution of the dynamical core is increased. The convergence characteristics ofthese dual-resolution simulations are compared to those of simulations with the standard modelin which the resolutions of both the dynamical core and physical parameterizations are increasedtogether, as traditionally done in atmospheric model convergence studies. With the standardmodel the upward branch of the local Hadley circulation increases in strength with increasinghorizontal resolution and does not converge by T170 truncation. As the dynamical resolutionis increased, but the parameterization resolution held fixed, the dual-resolution model simulationsconverge to a state close to that produced by the standard model at the fixed parameterizationresolution. The mid-latitude transient aspects do not converge with increasing resolutionwhen the scale of the physics is held fixed. The nonlinear interactions in the dynamics createfiner scales, with or without the finer scale forcing. However, the lower resolution T42 scalesappear to converge. These convergence characteristics are shared by both the dual-resolutionmodel and the standard model when horizontal resolution is increased.DOI: 10.1034/j.1600-0870.1999.00009.x