The Effect of Large-Scale Eddies on Climatic Change

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  • 1 Goddard Space Flight Center, NASA, New York, N. Y., and Dept. of Meteorology, M. I. T., Cambridge, Mass.
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Abstract

A parameterization for the fluxes of sensible heat by large-scale eddies developed in an earlier paper is incorporated into a model for the mean temperature structure of an atmosphere including only these fluxes and the radiative fluxes. The climatic changes in this simple model are then studied in order to assess the strength of the dynamical feedback and to gain insight into how dynamical parameters may change in more sophisticated climatic models. The model shows the following qualitative changes: 1) an increase in the solar constant leads to increased static stability, decreased dynamic stability, and stronger horizontal and vertical winds; 2) an increase in the amount of atmospheric absorption leads to decreased static and dynamic stability, and stronger horizontal and vertical winds; and 3) an increase in rotation rate leads to greater static and dynamic stability, weaker horizontal winds, and stronger vertical winds. The quantitative results provide support for the common assumption that the static stability remains constant during climatic changes. Twenty-five percent changes in the external parameters cause changes in the static stability of the order of only a few tenths of a degree per kilometer. The results also show that the assumption that the horizontal eddy flux can be represented by a diffusion law with a constant eddy coefficient is a bad one, because of the strong negative feedback in the eddy fluxes.

Abstract

A parameterization for the fluxes of sensible heat by large-scale eddies developed in an earlier paper is incorporated into a model for the mean temperature structure of an atmosphere including only these fluxes and the radiative fluxes. The climatic changes in this simple model are then studied in order to assess the strength of the dynamical feedback and to gain insight into how dynamical parameters may change in more sophisticated climatic models. The model shows the following qualitative changes: 1) an increase in the solar constant leads to increased static stability, decreased dynamic stability, and stronger horizontal and vertical winds; 2) an increase in the amount of atmospheric absorption leads to decreased static and dynamic stability, and stronger horizontal and vertical winds; and 3) an increase in rotation rate leads to greater static and dynamic stability, weaker horizontal winds, and stronger vertical winds. The quantitative results provide support for the common assumption that the static stability remains constant during climatic changes. Twenty-five percent changes in the external parameters cause changes in the static stability of the order of only a few tenths of a degree per kilometer. The results also show that the assumption that the horizontal eddy flux can be represented by a diffusion law with a constant eddy coefficient is a bad one, because of the strong negative feedback in the eddy fluxes.

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