The Impact of the Madden-Julian Oscillation (MJO) upon the Heavy Rainfall Distribution in the East Coast of Peninsular Malaysia during the Northeast Monsoon

Publication Date :
Author : Fatimah Zaharah SallehYip Weng SangFadila Jasmin FakaruddinMat Kamaruzaman Mat AdamNursalleh K ChangFariza YunusMuhammad Helmi Abdullah
Countries : Malaysia
Disaster Management Theme :
Disaster Type : Other
Document Type : Research Paper
Languange : en
Link :

Abstact :

The Madden Julian-Oscillation (MJO) is an atmospheric, large scale eastward propagating circulation anomaly that is confined to the tropics. The MJO is considered a major source of intra-seasonal variability in deep convection in both the tropics and extratropical regions. Outgoing Long Wave Radiation (OLR) composites prove that certain MJO phases enhances deep convection over the Maritime Continent (MC) while other MJO phases suppresses deep convection. The MC is a region of deep cumulus convection and heavy precipitation during the Boreal Winter. Malaysia, located in the middle of the MC, suffers intense rainfall episodes during the Northeast Monsoon that occurs in boreal winter. This work investigates the impact of the MJO upon heavy rainfall episodes in the Peninsular Malaysia East Coast. In mid-November 2009 and 2013, two episodes of heavy rainfall were recorded in the Peninsular Malaysia East Coast. Analysis of the MJO phase diagram constructed using the Real-time Multivariate MJO series 1 and 2 (RMM1 and RMM2) indices together with time-longitude Hovmoller plots of OLR during both heavy rainfall episodes were performed to determine the relationship between the MJO and rainfall amount observed by principal rain-gauge stations in the Peninsular Malaysia East Coast. It was revealed that the heavy rainfall episode in mid-November 2009 was preceded by a significant MJO event and occurred in conjunction with a strong MJO signal signifying enhanced convection over Malaysia, but the heavy rainfall episode in mid-November 2013 happened in the absence of a significant MJO event. Thus, this study concludes that the MJO may not be the only factor in contributing to the initiation of heavy rainfall. Apart from the MJO, other well established heavy rainfall contributors include westward moving equatorial vortices, the synoptic scale Borneo Vortex, anomalous near equatorial disturbances such as Typhoon Vamei and Tropical Storm Greg, and the convergence of northeasterly cold surges with broad Pacific Easterlies.