Phase-dependent perturbation kinetic energy of the Madden-Julian oscillation

We examine the energetics of the 20--90 day Madden-Julian oscillation (MJO) in observational data. The energetics, as expressed by perturbation kinetic energy (PKE), perturbation available potential energy (PAPE), and their associated energy transformation functions, have been used extensively to study transient wave activity in the tropics. Much of the previous work has focused on the spatial distribution of time-mean features of the energetics terms as expressed in the 20--90 day MJO frequency band. In order to further probe the details of energy re-distribution at various stages of the eastward propagation of MJO, here energetics terms are computed for various phases of the MJO's life-cycle. The requisite phase indices have been constructed for both predominantly symmetric and antisymmetric MJO events by extracting spatio-temporal modes of variability from observational infrared brightness temperature data using a recent machine learning technique known as nonlinear Laplacian spectral analysis. Preliminary results with PKE indicate that the methodology could help elucidate the conditions for coherent eastward propagation. There is also indication that symmetric MJO associates with a kinetic energy perturbation off the coast of Central America, which could transport moisture inland, modulating surface hydrology in the region.