Geophysical wave-vortex interactions and turbulence

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This fluid dynamics study is aimed at improving the theoretical understanding of turbulent atmosphere ocean processes at small scales, which are unresolvable in today's global-scale computer models. The key components of the project are the improved understanding of turbulent energy transfers between large and small scales in the fluid. This involves vigorous interactions between current systems like the Gulf Stream and fast wave motions that cannot be seen by current global ocean computer models. Overall, the proposed work has broad impacts within fluid mechanics, physical oceanography, and its training aspects include both graduate and undergraduate students.The fluid dynamics of these complex systems is characterized by a nonlinear jigsaw puzzle of intermingling turbulent waves and vortices, especially at small scales, such as those relevant to submesoscale oceanography, for instance. Here classical wave-mean interaction theory fails, direct numerical simulation of the fluid motion with global computational models is not possible, and theoretical innovations for diagnostic and predictive models are needed. In this connection the present proposal seeks to break new ground with a multi-pronged approach that combines theory and numerical modelling. First, the long term evolution of turbulent internal wave spectra under refraction by the balanced mean flow is studied using a novel wave action advection-diffusion theory. Second, vigorous two-way interactions between internal waves and the balanced mean flow are studied using new wave-mean interaction equations derived from generalized Lagrangian-mean theory. These equations allow for strong interactions that cut both ways: the waves feel the mean flow and vice versa. This is an important but understudied regime for submesoscale oceanography.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.