Tropical Intraseasonal Variability in Models and Observations

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Work conducted under this project seeks to determine the underlying mechanisms responsible for the development and propagation of the Madden-Julian Oscillation (MJO), a large-scale pattern of precipitation and atmospheric circulation anomalies which forms in the Indian Ocean and propagates slowly eastward. The MJO is associated with droughts, floods, and tropical cyclones (including hurricanes in the Gulf of Mexico). The research is primarily organized around experiments using an atmospheric general circulation model which has been modified to produce credible MJO simulations. The work will be guided by the hypothesis that the MJO is a moisture mode which is destabilized by wind-evaporation feedback (occurring under westerly wind conditions), which propagates eastward through horizontal moisture advection, and in which the essential dynamics are regulated by the processes that control the tropical moisture field. The modeling work is complemented by analysis of wind and precipitation from moored buoys in the Indian Ocean and satellite observations.The work will have broader impacts due to the large societal impacts of the MJO and the practical utility of information which contributes to the development of a predictive understanding of the MJO. The project will also include graduate student training and postdoctoral support, thereby developing the next generation of scientists.