Two-dimensional distributions for long-lived species, N20, CFCl3,and CF2Cl2 , have been calculated by using a 2-D model extending from the ground to 70 km. The model utilizes a residual mean meridional circulation and a set of eddy diffusion coefficients.Both these fields have been obtained from the output of the MIT-GIT three-dimensional general circulation model of the stratosphere.The calculation of the residual mean circulation takes into account consistent fields of temperature and diabatic heating, meridional temperature advection, and vertical eddy fluxes. The diffusion tensor is obtained following Holton (1981) and utilizes the eddy field that is an output of the 3-D model. The chemical source term is treated by introducing an additional tensor,f ollowing the suggestion by Tung (1982). This approach has the advantage of using the same matrix for all the chemical compounds. Values obtained for the residual mean meridional mass flux are in good agreement with similar results. The trace gas distributions obtained show a fairly good agreement in the equatorial regions but overpredict the concentrationin the mid-latitude stratosphere. This is a common modeling problem, especially with fluorocarbons, and is attributed,in our case,to values of the Kyy and Kzz components that are too large in the lower stratosphere.This particular result is probably due to the heating parameterization adopted in the original general circulation model.

TWO-DIMENSIONAL TRACER TRANSPORT - DERIVATION OF RESIDUAL MEAN CIRCULATION AND EDDY TRANSPORT TENSOR FROM A 3-D MODEL DATA SET

PITARI, Giovanni;
1985

Abstract

Two-dimensional distributions for long-lived species, N20, CFCl3,and CF2Cl2 , have been calculated by using a 2-D model extending from the ground to 70 km. The model utilizes a residual mean meridional circulation and a set of eddy diffusion coefficients.Both these fields have been obtained from the output of the MIT-GIT three-dimensional general circulation model of the stratosphere.The calculation of the residual mean circulation takes into account consistent fields of temperature and diabatic heating, meridional temperature advection, and vertical eddy fluxes. The diffusion tensor is obtained following Holton (1981) and utilizes the eddy field that is an output of the 3-D model. The chemical source term is treated by introducing an additional tensor,f ollowing the suggestion by Tung (1982). This approach has the advantage of using the same matrix for all the chemical compounds. Values obtained for the residual mean meridional mass flux are in good agreement with similar results. The trace gas distributions obtained show a fairly good agreement in the equatorial regions but overpredict the concentrationin the mid-latitude stratosphere. This is a common modeling problem, especially with fluorocarbons, and is attributed,in our case,to values of the Kyy and Kzz components that are too large in the lower stratosphere.This particular result is probably due to the heating parameterization adopted in the original general circulation model.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11697/12883
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