The role of meridional momentum flux in the IPEDS multiscale models of the Madden-Julian oscillation

The multiscale IPESD models provide a framework in which to study the effect of synoptic and planetary scale heating on planetary scale flows. In the IPESD theory, synoptic scale flows respond to synoptic scale heating fluctuations through weak temperature gradient linear balanced dynamics. The planetary scale flows are driven directly through a planetary scale mean heating envelope plus the upscale fluxes from the synoptic scale fluctuations. The simplicity and multi-linearity of the theory allows to separately understand each of the effects of meridional and vertical momentum and temperature flux convergences and planetary scale mean heating on the planetary scale flow. This talk elaborates on the models of the Madden-Julian oscillation of Majda and Biello by considering synoptic scale heating fluctuations which drive meridional momentum flux convergences. It will be shown that meridionally tilted synoptic scale heating fluctuations alone drive upscale momentum fluxes which can produce some of the observed organization of the Madden-Julian oscillation, but also miss key features which arise from vertical tilted heating. A more plausible model contains both meridionally and vertically tilted synoptic scale fluctuations.