The Meridional Structure of Baroclinic Waves

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  • 1 Division of Engineering and Applied Physics, Harvard University, Cambridge, Mass
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Abstract

The two-layer model is used to study how horizontal shear in a baroclinic zonal flow affects the structure of growing baroclinic waves. The solution is simplified by assuming that the radius of deformation is small compared to the planetary scale. The method of solution yields results for waves near neutral stability. For these waves, solutions are found for many different wind profiles. These solutions show: 1) that the waves have a natural meridional scale equal to the radius of deformation, the same as the zonal scale; 2) that the wave perturbation in the lower atmosphere is primarily confined to regions where the vertical shear of the unperturbed zonal flow is greatest; and 3) the horizontal eddy stresses always transport momentum against the horizontal gradient of the zonal flow. Thus, the baroclinic waves tend to increase the intensity of any jets present in the unperturbed zonal flow, no matter what their number or position, and they are accompanied by horizontal shearing and stretching deformation wind fields which are of comparable strength.

Abstract

The two-layer model is used to study how horizontal shear in a baroclinic zonal flow affects the structure of growing baroclinic waves. The solution is simplified by assuming that the radius of deformation is small compared to the planetary scale. The method of solution yields results for waves near neutral stability. For these waves, solutions are found for many different wind profiles. These solutions show: 1) that the waves have a natural meridional scale equal to the radius of deformation, the same as the zonal scale; 2) that the wave perturbation in the lower atmosphere is primarily confined to regions where the vertical shear of the unperturbed zonal flow is greatest; and 3) the horizontal eddy stresses always transport momentum against the horizontal gradient of the zonal flow. Thus, the baroclinic waves tend to increase the intensity of any jets present in the unperturbed zonal flow, no matter what their number or position, and they are accompanied by horizontal shearing and stretching deformation wind fields which are of comparable strength.

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