Madden-Julian Oscillation (MJO) Initiation-DYNAMO (DYNAmics of the Madden-julian Oscillation) and Beyond

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The Madden-Julian Oscillation (MJO) is a disturbance of the tropical atmosphere in which clouds and precipitation are enhanced over a broad region near the equator, with an accompanying region of reduced precipitation and cloudiness to the west or east. MJO events typically begin when convective precipitation breaks out over a large portion of the Indian Ocean, and the region of enhanced precipitation gradually propagates eastward, often as far as the central equatorial Pacific before dissipating. MJO events affect weather and climate over much of the globe, with substantial impacts over the US.A field campaign to study the MJO was conducted in the Indian Ocean From October 2011 to February 2012, titled Dynamics of the Madden-julian Oscillation (DYNAMO; see AGS-1022899). This project is a follow-on to DYNAMO in that it seeks to generalize the results from the DYNAMO campaign to a broader region than the area observed in the campaign, and to MJO events occurring outside the deployment period. It also seeks to use results from the campaign to understand why global weather and climate models have difficulty in simulating the initiation of the MJO.A novel approach taken in this research is to consider MJO initiation as a two stage process, in which the outbreak of widespread convective precipitation is the first stage and the onset of eastward propagation is the second. Previous work shows the existence of non-MJO events, in which precipitation occurs over much of the tropical Indian Ocean but eastward propagation fails to develop. Research under this award attempts to understand why eastward propagation occurs in some cases, resulting in a fully developed MJO event and accompanying global impacts, but not in others. One hypothesis is that propagation of the region of precipitation is initiated by propagating precursor disturbances in atmospheric temperature and winds, which occur independently of the MJO but can interact with the precipitation anomalies to form an eastward moving MJO event.Beyond its scientific interest the work has societal relevance due to the widespread impacts of the MJO. For example, the likelihood of hurricane genesis in the Gulf of Mexico and western Caribbean hurricane genesis is much more likely when the MJO propagates into the central equatorial Pacific, and the MJO is also linked to "atmospheric river" events that bring flooding to coastal California. This work has a direct connection to improving MJO predictions through its emphasis on improving the representation of the MJO in global atmospheric models.