Process-oriented Diagnosis of Four types of MJO

Abstract:

We present a process-oriented diagnosis of four types of MJO with different propagating features, including standing, jumping, fast and slow events. The moisture budget, dry static energy budget, cloud-radiation feedback, and boundary layer moisture convergence in the subseasonal time scale are diagnosed. The pre-moistening process and high-level radiation heating are found essential to MJO propagation. For slow and fast MJO events, the pre-moistening over the Maritime Continent (MC) is mainly controlled by the meridional moisture advection, which is vital to their penetration through the MC. The leading high-level radiation heating is also strong in slow and fast MJO events, destabilizing the air column and creating a favorable environment for the development of shallow convection leading the main convection. Standing MJO events show strong high-level radiation heating ahead of the main convection, but the leading shallow convection is missing. For jumping MJO events, the leading shallow convection is evident, but the high-level radiation heating is weak. Also, the moisture tendency indicates a slowly westward-propagating wave structure over the central-east Pacific during the standing and jumping MJO life spans, mainly related to the zonal moisture advection. Therefore, MJO propagation characteristics are also likely affected by interaction between other convectively coupled equatorial waves.