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.

Time Spectral Analysis for the Natural Variability of the Barotropic Model Atmosphere with Annual Cycle Forcing

“…The result of this study is compared with the conclusion derived by Zhao and Takahashi (1996) who have proposed conversely that the intraseasonal and interannual oscillations may be excitation as the result of the superharmonic and subharmonic resonances with the seasonal cycle, respectively. They considered the response of the tropical Kelvin waves to the cumulus heating with a seasonal cycle under a certain form of damping to derive so-called Mathieu equation in a form:…”

“…James and James (1989) reported that the interannual variability with periods of up to 10-40 years was generated internally by the non-linear dynamics of a simple primitive equation model with an imposed annual-cycle forcing. According to the recent study by Zhao and Takahashi (1996) forcing. It is our aim to investigate the parametric instability under a fully non-linear primitive equation model.…”