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F. L. MARTIN and J. B. TUPAZ

Abstract

A numerical procedure for the computation of emergent terrestrial flux has been developed after the model described by Elsasser and Culbertson. By application of this procedure, a set of emergent fluxes has been computed for each of 63 soundings drawn from the model atmospheres developed by Wark et al. The latter authors have also made available for this study the results of their radiative model for outgoing intensities. Both radiative models included contributions from atmospheric water vapor, carbon dioxide, and ozone, as well as transmitted interface (cloud or ground) effects. Both sets of fluxes computed for the 63 model atmospheres were subjected to a stepwise-screening multiple linear regression analysis, using empirically tested parameters grossly representative of the radiosondes. In terms of these parameters as independent variables, the fluxes computed by the radiative model of Wark et al. were specified in accordance with a multiple correlation coefficient of 0.98, while the fluxes computed here gave rise to a multiple correlation of 0.625. The chief reason advanced for the smaller statistical specification by the present model, as contrasted with that of Wark et al. is considered to be due to the differing number of sounding levels used in carrying out the two sets of computation.

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J. B. Tupaz, R. T. Williams, and C-P. Chang

Abstract

The structure and behavior of barotropically unstable and stable waves in the vicinity of a zonally varying easterly jet are studied numerically with a linearized barotropic vorticity equation on a β plane. The easterly jet is approximated by a Bickley jet with a slow zonal variation. The numerical results are also compared with a simple mechanistic analytical model using the local phase speed and growth rate concepts. In several aspects the results are grossly similar to that expected from the parallel flow theory of barotropic instability. However, in the unstable region the resultant structure of the waves causes a spatial growth rate greater than predicted by the local growth rates computed with a parallel flow model. In the stable region, the structure leads to a strong dynamic damping. When a uniform advective velocity is added to a variable mean flow, the difference between the magnitude of the growth rate of the computed waves and that implied by the parallel flow theory is somewhat reduced. However, in this case a stronger zonal asymmetry in the spatial growth rate curve with respect to the jet maximum occurs as a result of slower adjustment of the wave structure to the local stability conditions.

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