9523479 Mundt and Vallis Numerical and laboratory simulations of baroclinic flows have revealed that moderately supercritical baroclinic systems can exhibit a wide range of behavior (e.g., steady, periodic, chaotic). Moreover, aperiodic, temporally-irregular solutions can exist even when the flow is only marginally unstable, that is, at small values of supercriticality. Most previous dynamics studies have been directed to studying this parameter range which corresponds to lower driving than is geophysically realistic. Studies in more realistic parameter ranges are usually conducted with more complex models and have provided more empirical results, often relying on statistical descriptions, rather than a more thorough understanding of the dynamics. Thus, little is known about the transition from chaos to turbulence in the supercriticality range characteristic of atmospheric flows. The principal investigators will carry out a study focused on the complexity (disorder) of flows with increasing supercriticality, guided by their hypothesis that the level of mean flow supercriticality is directly related to the disorder of the eddy flow. They will explore the extent to which behavior observed at low supercriticality is also observed at more geophysically realistic ranges of supercriticality. Models of varying complexity will be employed, although the initial effort will focus on a two layer, quasi-geostrophic model. A variety of analysis tools, from empirical orthogonal function analysis to wavelet analysis, will be employed. The importance of this study lies in the potential for better understanding of the variability of the atmosphere, and has important implications a wide range of weather and climate issues, including weather regime transitions and parameterization of meridional heat flux in climate models. ***
