A new model of the Madden-Julian Oscillation

Abstract

A new model of the Madden-Julian oscillation (MJO) is presented. Cloud-radiation interactions in this model make the tropical atmospheres susceptible to large-scale radiative-convective overturning. The modeled MJO takes the form of such an instability, though its behavior is substantially modified by the effects of surface heat flux variability. The dynamics of the disturbance in the model are quasi-balanced, in the sense that the low-level flow in the disturbance is more associated with the vorticity than with the divergence. The cumulus parameterization used in the model allows a lag of several days to exist between the strongest surface heat flux into a column and the development of heavy precipitation in that column. This lag plays a key role in model dynamics.