Fundamentals of Middle Atmospheric Dynamics

The middle atmosphere is a highly nonlinear dynamical system whose variability, and forecastability, is very poorly understood. The state of the mesosphere should be highly for sensitive to the propagation of both gravity and Rossby waves from below, and that propagation can be sensitive to various kinds of wave-mean, wave-wave, and wave-turbulence interactions that occur on the way up. On longer timescales, there are trends in, for example, temperatures, chemical composition, and thresholds for aerosol and cloud formation, that may significantly change mean and extreme conditions in the middle atmosphere from year to year. These trends are partly a result of man-made perturbations and involve an intricate interplay of chemical, radiative and dynamical processes over a vast range of space and time scales, depending for example on the statistical properties of the wace-turbulence interactions. The problems thus posed are of formidable technical and conceptual difficulty. Progress is hindered by a lack of knowledge at the most fundamental level, particularly regarding the scale-interactive dynamical processes. The long-term aim of this project is to develop, test and exploit new theoretical concepts and modeling techniques to achieve a radically improved understanding of these processes.