The equatorial wave skeleton of the Madden-Julian Oscillation

An analysis of the energy equation of the three-dimensional normal modes of the atmospheric circulation provides evidence on the behaviour of the most important equatorial waves which compose the Madden-Julian Oscillation. They are the equatorial Rossby waves of zonal wavenumber 1 and 3 and the Kelvin waves of zonal wavenumber 1. In the mean, the equatorial Rossby waves gain energy by convective heating and atmospheric column stretching and transfer it to the circulation field, whereas the Kelvin waves draw energy from the circulation field and dissipate it by surface friction. The convergence associated with the Kelvin waves contributes to the moisture fuelling of the convection centre. Therefore, the coupling between equatorial Rossby and Kelvin waves is mediated by convective heating/column stretching excitation of Rossby waves and moisture convergence by Kelvin waves.