A Kinetic Energetic Diagnosis Of The Seasonal Asymmetry Of The MJO Using The Localized Multiscale Energy And Vorticity Analysis (MS-EVA)

Using the newly developed localized multiscale energy and vorticity analysis (MS-EVA) and the MS-EVA-based theory of canonical transfer and hydrodynamic instability, this study conducts a kinetic energetic(KE) diagnosis for the variability of the boreal summer and winter Madden-Julian oscillation(MJO). It is found that the MJO KE shows a seasonal asymmetric character which is mainly due to the interscale energy transfers and pressure work. Buoyancy conversion, pressure work, and the transfer between the mean flow and the MJO scale window are the major MJO KE sources. In contrast, the transfer between the MJO and the synoptic scale windows directs toward the latter, making a sink of the MJO.A deeper study reveals the relationship between the MJO KE and the convection over Pacific Ocean in winter and summer. In this particular region the MJO KE is also governed by buoyancy conversion and pressure work. Buoyancy conversion takes positive value in the north of the convection center; pressure work then transports the energy through the region, with negative value near the convection center and positive value on the southern and northern flanks. The transfer to the MJO from the mean flow is mainly influenced by the MJO circulation. What’s more, the MJO KE in summer has its own special energetic structure:in the middle-lower troposphere, it comes mainly from the canonical transfer across the scales.