A new process-oriented gross moist stability (GMS) plane is proposed for characterizing the energetics (energy and moisture cycles) of Madden–Julian Oscillation (MJO). From a pair of column-integrated dry static energy and moisture equations subject to convective quasi-equilibrium constraints, we adopt two physical quantities, i.e., “gross dry stability” and “gross moisture stratification” (both in energy unit of \(\text{J }{\text{kg}}^{-1}\) ), which respectively represent the efficiency of energy release and moisture removal by convection, to construct the GMS plane. Based on the relative position of the daily GMS points to the critical GMS line, one can predict whether the MJO is in an amplifying or a decaying phase. This process-oriented GMS plane provides a simple way to visualize the energy recharge-discharge and water vapor moistening-drying processes associated with the evolution of MJO. The marked contrast in critical GMS over the Indo-Pacific warm pool also highlights the potential (optimal) path of MJO, which is to detour southward around the Maritime Continent along a region with smaller critical GMS values, in particular, during the boreal winter.
