Transient response to localized episodic heating in the tropics. Part I: excitation and short-time near-field behavior.

The dynamical response to localized, unsteady tropical heating is studied in a stochastic framework. Spectral statistics of the random wave response are derived from those of tropical convection using the primitive equations for a spherical baroclinic atmosphere. For short-term heating fluctuations, typical of tropical convection, the response at tropopause level is in accord with classical observations of the Wallace and Kousky Kelvin wave. The fast and ultra-fast Kelvin waves are secondary ingredients of the initial wave spectrum. In the case of slow transitional heating, eg the seasonal drift in monsoon activity between hemispheres, the Kelvin response assumes the form of a damped transient Walker circulation. This E migrating cell captures the salient characteristics of Madden and Julian's composite of the 40-day wave in the tropical Pacific Ocean. -from Authors