Transient Response to Localized Episodic Heating in the Tropics. Part II: Far-Field Behavior.

TLDR: In this paper, the authors examined how these disturbances are modified as they propagate through the far field in the presence of spatially-varying background states, which can still be understood in terms of projection and barotropic components of the response.

Abstract: In Part I of this investigation, we described the stochastic, near-field behavior of disturbances excited by randomly evolving tropical heating. In the present paper, we examine how these disturbances are modified as they propagate through the far field in the presence of spatially-varying background states. Although the behavior can no longer be broken down into individual Hough modes, it can still be understood in terms of projection and barotropic components of the response. Responses to fast heating, as may be produced by daily fluctuations in convection, and to slow heating, evolving over seasonal time scales, are studied separately. For fast heating the projection response consists mainly of a spectrum of Kelvin waves which, in the lower stratosphere, is centered at frequencies corresponding to twice the effective depth of the heating. The spectrum shifts to higher frequency with increasing altitude due to differential damping. As a result, the slow, fast and ultrafast Kelvin waves identifi...