Super-and Sub-Harmonic Responses of Tropical Kelvin Waves to the Heating with a Seasonal Modulation

Abstract

By applying a seasonally modulated condensation heating on tropical Kelvin waves with a certain form of damping, the parametric instability and super (sub) harmonic response of the Kelvin waves are investigated. It is suggested that the excitation of intraseasonal oscillation and tropospheric QBO may be related to the superharmonic and subharmonic resonances with the seasonal cycle, respectively. The main features of the spatial structures and propagation of these resonant modes were shown and compared with those of intraseasonal oscillation and tropospheric QBO to examine this point of view.