Boreal Summer Intraseasonal Oscillations in the MJO Skeleton Model with Observation-Based Forcing

The Madden-Julian oscillation (MJO) skeleton model is a low-order model for intraseasonal oscillations.  In an extended form, this model includes off-equatorial and antisymmetric components. Using idealized forcing terms, previous studies have shown this extended model produces a wide variety of events, some of which are reminiscent of the observed boreal summer intraseasonal oscillation (BSISO). In the current study, observation-based estimates of these forcing terms are used. Linear solutions to the extended model with this observation-based forcing consist of both equatorially-symmetric convective events and events with a meridional tilt reminiscent of composites of the BSISO in observational studies. Solutions to a nonlinear stochastic form of the model exhibit realistic mean convective activity and intraseasonal variability throughout much of the tropics. These solutions contain several types of events, including meridionally-tilted convective activity that moves both northward and eastward. Solutions to both forms of the model also indicate that this BSISO-like convective activity is coupled to activity over the eastern Pacific. A discussion of these features and their agreement with previous observational studies of the BSISO is given.