Dynamics of Tropical Waves and Instabilities

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9724987 Emanuel The tropical atmosphere exhibits a large variety of wave phenomena, ranging from "synoptic-scale " waves of several thousand kilometers in dimension to the planetary-scale Madden-Julian Oscillation. Complex numerical simulations of the tropical atmosphere also exhibit a spectrum of waves, but their characteristics differ appreciably from one model to another. There is considerable controversy about the dynamics of these waves, particularly concerning their interaction with moist convection. Some argue that such an interaction can be unstable an result in wave amplification while others argue that convection damps the waves. As these waves play a considerable role in tropical weather and climate, including the genesis of tropical cyclones, there is much to be gained by improving general understanding of the basic dynamics of the waves. This project seeks to improve that understanding by carrying out a number of experiments with simplified models under a variety of conditions. By excluding many of the complexities of the real world, such as land-sea contrasts, strongly varying background wind and temperature, and even the Earth's rotation, an appreciation of the most basic underlying dynamics can be attained. Experiments will be performed with a hierarchy of models ranging form sing-column models to fully three-dimensional quasi-geostrophic models. All will share a common design in that the basic state is one of statistical equilibrium in which convection, radiation, and large-scale circulation are in balance and the physical processes of convection and radiation are represented as accurately as possible. This research effort ultimately will contribute to improved models and prediction of the tropical atmosphere.