An idealized, semi-empirical MJO model

Recent analyses of the Madden-Julian oscillation (MJO) as simulated by general circulation models suggests that surface flux feedbacks are important, that these feedbacks act in an environment of mean westerlies (as in observations), and that horizontal advection of moisture plays an important role in the propagation of the oscillations. We present a highly idealized model which aims to distill to its essence the mechanism of the MJO as found in these GCM simulations, which in turn are hypothesized to capture the essence of the observed MJO. Some key aspects of the model, such as the relationship between moisture and precipitation and the gross moist stability, are directly tuned either to GCM results or to observations. The model is used to understand how these various factors interact to yield intraseasonal disturbances with the desired properties, and what the essential ingredients are.