Analysis of Coupling between Oceanic Kelvin Waves and Atmospheric Convection, and Its Impacts on Weather over the Tropical Pacific

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The westerly wind phase of the Madden-Julian Oscillation (MJO) often triggers oceanic Kelvin waves in the equatorial West Pacific Ocean. Occasionally these waves are associated with eastward moving warm sea surface temperature (SST) anomalies. The anomalously warm ocean destabilizes the atmosphere to convectively coupled waves, and the associated enhanced deep convection accelerates westerly winds to the west of the Kelvin wave crests; this, in turn, amplifies the Kelvin waves. This pattern suggests that oceanic Kelvin waves and atmospheric convection are coupled. Preliminary results indicate that this coupling organizes high impact weather events across the tropical Pacific, including westerly wind bursts and tropical cyclones. While such weather events can occur within the MJO prior to the development of oceanic Kelvin waves, the waves influence the further development of weather. Such coupling to the ocean is not included in traditional views of the MJO. In this project the evolutions of atmospheric structures associated with these convectively coupled oceanic waves will be investigated, as well as their associations with high-impact weather.Observations of such coupled events will be analyzed to diagnose the details of their three dimensional spatial structures in the atmosphere and their evolution over time. Particular attention will be paid to the evolution of weather events in the vicinity of the Kelvin waves, in order to determine how these events participate in the coupling process. The approach is to prepare and analyze composites of many events, to analyze individual cases, and to make a census of the population of all events. Results will contribute to a synoptic-dynamic model for the coupled events and their links with the associated weather.This study will enhance our understanding of the interactions of oceanic Kelvin waves with the MJO, some westerly wind bursts, and tropical cyclones. Broader impacts of this project include the potential to predict the development of coupled events along with their associated extreme weather. This work should lead to further analyses of the potential connections between the intraseasonal coupling and the evolution of El Nino. The project will support the work of a beginning investigator and the training of a graduate student.