Group seminar on 5. July, 14:15 CET

The Kelvin wave and the Madden-Julian Oscillation

Katharina Holube

The atmospheric Kelvin waves (KWs) are equatorially trapped solutions of the rotating shallow-water equations. The properties of KWs filtered with the MODES software for the eight phases of the Madden-Julian Oscillation (MJO) are studied. During a MJO event, an anomaly in deep convection appears over the Indian Ocean and slowly moves towards the western Pacific Ocean. The divergent flow in the upper troposphere associated with deep convection is shown to project onto the KWs with different zonal wavenumbers and vertical structures. Kelvin wave energetics is compared among the MJO phases. The eight phases of the MJO appear as differences in the strength of the KW in low zonal wavenumbers and vertical structure functions with maxima in the upper troposphere. The KW energy is greater during the MJO phases with enhanced convection over the Maritime Continent. The results corroborate the relation between the MJO and KW, although their cause-effect relationship remains unclear. Some hypotheses will be discussed in the seminar.