OCE-RIG: Role of Air-Sea Coupling on the Madden-Julian Oscillation under Suppressed External Forcing

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Overview: An accurate simulation of the Madden-Julian Oscillation (MJO) using numerical models remains extremely difficult. The problem is further exacerbated by the fact that there is no accepted theory for the initiation mechanism of the MJO. However, several hypotheses have been proposed that broadly include local forcing (i.e., recharge-discharge mechanism) and external influences (i.e., combined influences due to circumnavigating waves and extratropics). Relative influences of these forcings on the MJO and its initiation are being studied using atmosphere only mesoscale models or atmospheric general circulation models (AGCMs), which lack air-sea coupling. However, MJO is greatly modulated by the air-sea interactions in the Indian Ocean where MJO initiation occurs. The primary objective of this study is to explore the extent to which MJO and its initiation are affected by the air-sea coupling in the presence and absence of external influences in different seasons. The key here is to separate the local and external forcing in a model that cannot be achieved using observations. A unique general circulation model (GCM)-based framework is constructed to fulfill the objective. A coupled simulation is compared to an uncoupled simulation of the GCM to explore the role of air-sea coupling in the presence of all forcings. Further simulations are conducted where the influences from extratropics and circumnavigating waves are suppressed in the coupled and uncoupled simulations to explore the roles of air-sea coupling on the MJO in the absence of external influences. Intellectual Merit: In this study, the investigator will attempt to address the role of air-sea interactions in the presence and absence of external influences. Emphasis will also be given to document the structure, organization, and large-scale context of the MJO at its initiation in different seasons. Such an effort has primarily been confined for boreal winter season. This research will improve the understanding of the aspects of physical processes associated with the MJO, especially the role of air-sea interaction and interaction between convection and environmental moisture. This work also targets poorly observed processes relevant to MJO initiation, namely, large-scale moisture advection and convergence. This study would further contribute towards detecting the necessary conditions for MJO initiation and might be greatly useful for operational prediction of the MJO. Broader Impacts: The geographical area (tropical Indian and West Pacific Ocean) that this research is concerned with has a large human population and it is a region of growing strategic interest for the United States. Understanding the MJO initiation and its forecasting is highly important for this part of the world and the MJO's global influence makes it even more relevant. Note that statistically significant connection between the MJO and precipitation along the North American west coast has also been found. Outreach activities for this project will broaden participation of under-represented groups in the ocean sciences. Two established summer programs (field project and summer camp) offered by the Department of Marine and Environmental Systems (DMES) at the Florida Institute of Technology (FIT) will be used as a platform for engaging, motivating, and educating high-school and undergraduate students through intensive training and hands-on field activities related to ocean and atmospheric sciences.