Experiments with a low resolution, primitive equation ocean general circulation model with idealized basin geometry and surface forcing have been carried out in order to identify the processes controlling the climatically important aspects of the circulation. Emphasis was placed on the sensitivity of the model solutions to the magnitude of the vertical diffusivity. Scaling arguments suggest, and the numerical experiments confirm, that the solutions are most sensitive to the magnitudes of the wind stress curl and the vertical diffusivity. For small vertical diffusivity, wind forcing dominates the solution. The vertical scale of the thermocline is set by the strength of the Ekman pumping, and there is a multiple gyre circulation in the upper layers. For large vertical diffusivity, diabatic surface forcing dominates the solution. Vertical diffusion controls the vertical scale of the thermocline, and there is a single large anticyclonic gyre in the upper layers. Both the meridionally and zonally inte... Abstract Experiments with a low resolution, primitive equation ocean general circulation model with idealized basin geometry and surface forcing have been carried out in order to identify the processes controlling the climatically important aspects of the circulation. Emphasis was placed on the sensitivity of the model solutions to the magnitude of the vertical diffusivity. Scaling arguments suggest, and the numerical experiments confirm, that the solutions are most sensitive to the magnitudes of the wind stress curl and the vertical diffusivity. For small vertical diffusivity, wind forcing dominates the solution. The vertical scale of the thermocline is set by the strength of the Ekman pumping, and there is a multiple gyre circulation in the upper layers. For large vertical diffusivity, diabatic surface forcing dominates the solution. Vertical diffusion controls the vertical scale of the thermocline, and there is a single large anticyclonic gyre in the upper layers. Both the meridionally and zonally inte...

High‐resolution global climate modeling holds the promise of capturing planetary‐scale climate modes and small‐scale (regional and sometimes extreme) features simultaneously, including their mutual interaction. This paper discusses a new state‐of‐the‐art high‐resolution Community Earth System Model (CESM) simulation that was performed with these goals in mind. The atmospheric component was at 0.25° grid spacing, and ocean component at 0.1°. One hundred years of “present‐day” simulation were completed. Major results were that annual mean sea surface temperature (SST) in the equatorial Pacific and El‐Niño Southern Oscillation variability were well simulated compared to standard resolution models. Tropical and southern Atlantic SST also had much reduced bias compared to previous versions of the model. In addition, the high resolution of the model enabled small‐scale features of the climate system to be represented, such as air‐sea interaction over ocean frontal zones, mesoscale systems generated by the Rockies, and Tropical Cyclones. Associated single component runs and standard resolution coupled runs are used to help attribute the strengths and weaknesses of the fully coupled run. The high‐resolution run employed 23,404 cores, costing 250 thousand processor‐hours per simulated year and made about two simulated years per day on the NCAR‐Wyoming supercomputer “Yellowstone.”

In this paper an initial analysis of an 0.1° simulation of the North Atlantic Ocean using a level-coordinate ocean general circulation model forced with realistic winds covering the period 1985–96 is presented. Results are compared to the North Atlantic sector of a global 0.28° simulation with similar surface forcing and to a variety of satellite and in situ observations. The simulation shows substantial improvements in both the eddy variability and the time-mean circulation compared to previous eddy-permitting simulations with resolutions in the range of 1/2°–1/6°. The resolution is finer than the zonal-mean first baroclinic mode Rossby radius at all latitudes, and the model appears to be capturing the bulk of the spectrum of mesoscale energy. The eddy kinetic energy constitutes 70% of the total basin-averaged kinetic energy. Model results agree well with observations of the magnitude and geographical distribution of eddy kinetic energy and sea-surface height variability, with the wavenumber–fre... Abstract In this paper an initial analysis of an 0.1° simulation of the North Atlantic Ocean using a level-coordinate ocean general circulation model forced with realistic winds covering the period 1985–96 is presented. Results are compared to the North Atlantic sector of a global 0.28° simulation with similar surface forcing and to a variety of satellite and in situ observations. The simulation shows substantial improvements in both the eddy variability and the time-mean circulation compared to previous eddy-permitting simulations with resolutions in the range of 1/2°–1/6°. The resolution is finer than the zonal-mean first baroclinic mode Rossby radius at all latitudes, and the model appears to be capturing the bulk of the spectrum of mesoscale energy. The eddy kinetic energy constitutes 70% of the total basin-averaged kinetic energy. Model results agree well with observations of the magnitude and geographical distribution of eddy kinetic energy and sea-surface height variability, with the wavenumber–fre...