Recent Variations in MJO-Related Convective Activity overthe Equatorial Indian Ocean and Maritime Continent

The Madden-Julian Oscillation (MJO) is the prominent mode of tropical intraseasonal variability. Because of its profound impact on the weather and climate systems across the globe, it is important to understand the MJO variabilities under the global warming scenario. Most of the studies indicate strengthening of MJO associated precipitation in the warming world. In this study, we examined the variability associated with MJO from 1998 to 2015, when reliable satellite-derived daily precipitation and outgoing longwave radiation (OLR) are available. We observed a weakening in variance of convective activity associated with MJO across the equatorial Indian Ocean (EQIO) and Maritime Continent (MC) in boreal summer as well as winter seasons with a noticeable increase in that over northern Australia during winter months. In the POST (2007-2015) period, MJO displays remarkable reduction in convection for all the wavenumbers compared to that in the PRE (1998-2006) period during northern summer. For the boreal winter, along with similar reduction, MJO related activity preferred to shift from lower to higher wavenumbers in the recent years. Thus, the convection associated with MJO is broken down into smaller scales. Moreover, the multivariate Wheeler-Hendon Index demonstrates a shift from higher probability of stronger events to weaker events over EQIO and MC for both seasons. This variability in the behavior of MJO is accompanied by a southward shift in the location of maximum variance, weakening the northern branch of maximum variance both in summer and winter. As a result, the prevailing asymmetry in MJO variance during boreal summer (winter) is reduced (increased) over the eastern hemisphere. The moderately pronounced asymmetry in the POST period is manifested by a significant increase in MJO variance during boreal winter over northern Australia. We also observed that, the OLR anomalies associated with dry (wet) phase of MJO are higher (lower) in POST as compared to PRE period over western equatorial Indian Ocean possibly due to increased surface temperature during the dry phase and reduced cloud top temperature during wet phase of MJO in recent years. These changes could also indicate that, compared to PRE period, POST period has smaller (in the horizontal) scale convective systems with larger vertical extent embedded in MJO propagation. These variations in MJO strength can have a huge impact on the local and remote climate phenomena and can modulate the extreme events across the globe.