Parameter sensitivity of primitive equation ocean general circulation models.

Abstract

Experiments with a low resolution, primitive equation ocean general circulation model with idealized basin geometry and surface forcing were carried out in order to identify the processes controlling the climatically important aspects of the circulation. Exphasis 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 Dkman pumping, and there is a multiple gyre circulation in the upper layers. For large vertical diffusivity, diabetic surface forcing dominates the solution. Verical 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 integrated overturning circulations are sensitive to the vertical diffusivity, though not to the same degree. (A)