ABSTRACT We report on an ensemble predictability study of a barotropic vorticity model that displ... more ABSTRACT We report on an ensemble predictability study of a barotropic vorticity model that displays low-frequency zonal-dipolar regime transitions. Low-frequency regime transitions in the model is reminiscent of regime change phenomena in the weather and climate systems wherein extreme and abrupt qualitative changes occur, seemingly randomly, after long periods of apparent stability. Insofar as the transitions relate to the blocking transition of the extra-tropical winter atmosphere, a novel aspect of the model considered is the lack of any source of background gradient of potential-vorticity and the consequent absence of Rossby waves. Perturbations in our ensemble prediction system are embedded onto the system's chaotic attractor under the full nonlinear dynamics as bred vectors. We find that the evolved perturbations remain globally distinct and align to identify low-dimensional subspaces associated with regions of large forecast error. We further demonstrate that while regime transitions are initiated by higher order non-Gaussian processes, they are predictable.
We describe a propagator renormalized, non-Markovian closure for inhomogeneous turbulent flows wi... more We describe a propagator renormalized, non-Markovian closure for inhomogeneous turbulent flows with particular emphasis on the role of the bare vertex terms. We outline a regularization procedure as an approximation to a formal vertex renormalization and comment on numerical and analytic investigations to higher order corrections.
ABSTRACT We report on an ensemble predictability study of a barotropic vorticity model that displ... more ABSTRACT We report on an ensemble predictability study of a barotropic vorticity model that displays low-frequency zonal-dipolar regime transitions. Low-frequency regime transitions in the model is reminiscent of regime change phenomena in the weather and climate systems wherein extreme and abrupt qualitative changes occur, seemingly randomly, after long periods of apparent stability. Insofar as the transitions relate to the blocking transition of the extra-tropical winter atmosphere, a novel aspect of the model considered is the lack of any source of background gradient of potential-vorticity and the consequent absence of Rossby waves. Perturbations in our ensemble prediction system are embedded onto the system's chaotic attractor under the full nonlinear dynamics as bred vectors. We find that the evolved perturbations remain globally distinct and align to identify low-dimensional subspaces associated with regions of large forecast error. We further demonstrate that while regime transitions are initiated by higher order non-Gaussian processes, they are predictable.
We describe a propagator renormalized, non-Markovian closure for inhomogeneous turbulent flows wi... more We describe a propagator renormalized, non-Markovian closure for inhomogeneous turbulent flows with particular emphasis on the role of the bare vertex terms. We outline a regularization procedure as an approximation to a formal vertex renormalization and comment on numerical and analytic investigations to higher order corrections.
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