Symmetric and antisymmetric Madden - Julian oscillation signals 1 in tropical deep convective systems

5 This work studies the significance of asymmetry in systems of organized convection asso6 ciated with the Madden-Julian oscillation (MJO). Satellite infrared brightness temperature 7 data for the period 1983–2006 were decomposed into subsets symmetric and antisymmetric 8 about the equator. Using a recent nonlinear objective method called nonlinear Laplacian 9 spectral analysis, modes of variability were extracted representing symmetric and antisym10 metric features of MJO convective systems, along with a plethora of other modes of tropical 11 convective variability. It was found that the boreal winter MJO emerges as a single pair 12 of modes in both symmetric and antisymmetric convection signals. Phase composites of 13 the corresponding kinematic and thermodynamic anomalous fields were constructed using 14 reanalysis data. It was found that the predominantly symmetric convective systems are 15 potentially short-lived due to equatorial dry air intrusion eradicating equatorial convection 16 when the MJO crosses the Maritime Continent. The predominantly antisymmetric convec17 tive systems, however, are less affected by dry intrusion; the strength of the MJO convective 18 systems as well as anomalous circulations can be maintained and enhanced in the West Pa19 cific. It was also found that the off-equatorial convective systems enhanced during the MJO 20 are mostly deep convection and stratiform anvils, unlike the typical complex of shallow21 congestus-deep convection to stratiform anvils on the equator. The multiscale interactions 22 between the diurnal, MJO, and ENSO modes of convection were studied. It was found that 23 the symmetric component of MJO convection is out of phase with the symmetric component 24 of the diurnal cycle, while the antisymmetric component of MJO convection is in phase with 25 the antisymmetric diurnal cycle. The former relationship breaks down during strong El Niño 26 events, and both relationships break down during prolonged La Niñas. 27