Dynamics of the midlatitude atmosphere

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In direct collaboration with meteorologists, this program of research applies modern mathematical methods of fluid mechanics to improve our knowledge of the basic physical processes that govern atmospheric weather in the midlatitudes (which includes North America).  The proposed work focusses on two features of the atmosphere for which there exist important gaps in our theoretical understanding: the dynamics of tropospheric vortices (high- and low-pressure cells), and the generation and stability of gravity waves. a)  It is well known to meteorologists that the large-scale weather systems we experience in North America have their origins as small-scale vorticity on the tropopause --- a transition zone about 10km high which marks the top of the weather producing layer of the atmosphere.  These small-scale disturbances evolve into large-scale weather structures via a turbulent process of vortex mergers.  This program of research seeks to develop computational models to specifically understand this lifecycle of vortices on the tropopause. b)  Gravity waves are motions of the atmosphere which are faster, and typically of much smaller scale than those governing the continental weather pattern.  As a local phenomenon, the manifestations of gravity waves are directly experienced as "clear air turbulence", or are responsible for vertical motions that trigger precipitation in alpine regions.  As a global phenomenon, these waves can serve as a pathway for energy to cascade to small-scale turbulence, which is the primary mechanism for mixing and dissipation in the atmosphere.  A recent theoretical discovery, by the researchers, of the instability of large-scale mountain waves are further investigated by specialized computer models to ascertain their role in the turbulent dynamics of the atmosphere.