a Comparison of Baroclinic Eddy Heat Transport Parameterizations to a Simplified General Circulation Model.
Abstract
A numerical model of the atmospheric general circulation is developed and its results are compared to the predictions of several theories of meridional heat transport by transient baroclinic eddies. The model is based on the primitive equations and resolves the variable fields by zonal harmonics in longitude and by a discrete grid in latitude. In the standard configuration the model employs zonal wave-numbers 3 and 6 with vertical resolutions of 2, 6 or 10 layers. The model's physical processes are highly simplified compared to those incorporated in comprehensive general circulation models. The atmosphere is assumed to be dry and the surface flat and featureless. The model circulation is driven by diabatic heating determined from parameterizations of the net radiation at the top of the atmosphere. Simulations in which the meridional distribution of absorbed insolation is perturbed produce variations in eddy sensible heat transport roughly proportional to the changes in the meridional gradient of net radiation. However, these heat transport changes are not accompanied by large changes in the meridional temperature gradient, especially in 6 and 10-layer model versions. As a result, the predictions of the diffusive eddy heat transport parameterizations of Green (1970), Stone (1972) and Held (1978a) do not agree with model results. Nor does the model consistently maintain a meridional temperature gradient near the critical gradient for baroclinic instability in a linear 2-level model as suggested by Stone (1978a). The difference between the radiative equilibrium and time averaged meridional temperature gradients increases with increasing static stability when the mid-latitude lapse rates are not arbitrarily constrained. This behavior is in disagreement with the baroclinic adjustment theories of both Stone (1978a) and Lindzen and Farrell (1980).
- Publication:
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Ph.D. Thesis
- Pub Date:
- 1983
- Bibcode:
- 1983PhDT........30T
- Keywords:
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- Physics: Atmospheric Science