The Essential Dynamics of Tropical Rain Belts: Monsoons and Inter-Tropical Convergence Zone (ITCZ) in a Multi-model Ensemble of Idealized Simulations

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Knowing where, when, and how much rainfall falls over oceans and continents across the tropics matters directly to the people who live there and is also a key piece of information to understand the atmospheric circulation over the entire globe. This is because -as moisture is evaporated from the ocean, transported by winds, and finally rained out - energy is moved with it across a planetary heat engine that affects climate everywhere. This project aims at elucidating how tropical rainfall changes in response to changes in the way energy enters the tropical atmosphere, be they the results of the alternating of seasons, the wobble of the earth's orbit, or the man-made changes in atmospheric composition. The goal of this research is to address the essential similarities and differences in their dynamics between the oceanic rain belt and the regional monsoons; its approach is to analyze a hierarchy of simulations performed with an ensemble of computer models of the global atmosphere, to compare the climates produced in idealized model setups, and to identify those mechanisms that are robust across a range of simplifications. This research effort will have major impacts in two realms: our understanding of tropical dynamics and our design of model hierarchies. Progress on both fronts is necessary if we want to better our models and improve our prediction of future climate change in the tropics and globally. The effort will support continuous and focused leadership of a community effort to spur innovative research on the dynamics of monsoons and oceanic rain belts. The design and coordination of the ensemble simulations at the base of this project will continue through the organization of sessions and informal meetings at international conferences in which participants to this Grand Challenge can exchange results and plan additional research activities. One post-doctoral scientist, one graduate student and three undergraduates will be trained by this project and benefit from the interactions with the larger community that has gathered around these themes. Knowledge gained from this project will be incorporated in lectures and outreach activities, including the Lamont Open House and adult education at the American Natural History Museum. Results will also be reported via the State of the Planet Blog of the Earth Institute of Columbia University.