Recalculated Radiating Instabilities Using the Correct Matching and Boundary Conditions

Abstract

Yun et al. (hereafter YPM) have reported results of a study on the radiating instabilities of nonzonal shear flows as a possible source of the energetic internal temperature fluctuations observed in the regions away from the axis of the Kuroshio Extension current. Kamenkovich and Pedlosky, however, pointed out that a matching condition and a boundary condition are incorrect in YPM?s formulation. In this paper, the radiating instabilities of zonal and northeastward flows are recalculated using the correct matching and boundary conditions, and the radiational properties of the solutions are discussed. The solutions of YPM and this study on the northeastward flow are almost the same at short wavelengths up to several 100 km, and their differences become slightly greater as the wavelengths become closer to 2000 km due to a modification by the beta effect. However, the same conclusion made in YPM still holds in this analysis. That is, a strong shear flow with a northward or southward component is more likely than a zonal flow to radiate instability energy toward the far field for a given flow condition representing the midlatitude western North Pacific and it does so with greater realism. This is due to the beta effect and the westward component of the crossflow radiation direction.