Improved Understanding of Moist Atmospheric Circulations Through an Effective Static Stability Framework

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This project explores the validity and implications of an effective stability parameter that takes into account the effect of latent heat release on large-scale eddy circulations in the atmosphere. The static stability of the atmosphere is a key factor which influences many aspects of atmospheric circulation, including the size and propagation speed of various kinds of atmospheric wave motions including the baroclinic waves associated with frontal systems, the horizontal size required for atmospheric circulation patterns to be strongly influenced by the Coriolis force, and the strength of the atmospheric greenhouse effect. Furthermore, much of our understanding of the dynamics of the atmosphere is built on dry theories that do not take water vapor and latent heat release into account. Thus the effective stability parameter, developed by the PI in previous research, could potentially allow the dynamical theories developed for dry atmospheres to be applied to the real-world moist atmosphere. The research will examine the application of the effective stability parameter to a variety of topics, including the response of atmospheric circulation to global warming (for example, the expansion of the dry subtropical belts), and the transition of extratropical thermal stratification from control by eddies to control by moist convection alone.In addition to its intellectual merit, the work has broader impacts through the development of a better understanding of the atmospheric response to climate change. Model simulations and recent observations show circulation changes associated with a warming climate which could have an impact on regional climate and water balance, and the work performed here could improve our ability to understand and anticipate these impacts. In addition, the project will support and train a graduate student, thereby developing the scientific workforce in this area. Undergraduate students will also be involved in the research through the MIT Undergraduate Research Opportunities Program.