
In
applied mathematics, bred vectors are
perturbations
Perturbation or perturb may refer to:
* Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly
* Perturbation (geology), changes in the nature of alluvial deposits over time
* Perturbatio ...
related to
Lyapunov vector
In applied mathematics and dynamical system theory, Lyapunov vectors, named after Aleksandr Lyapunov, describe characteristic expanding and contracting directions of a dynamical system. They have been used in predictability analysis and as initial ...
s, that capture fast-growing dynamical
instabilities of the solution of a
numerical model. They are used, for example, as initial perturbations for
ensemble forecasting in
numerical weather prediction. They were introduced by Zoltan Toth and
Eugenia Kalnay.
Method
Bred vectors are created by adding initially random perturbations to a
nonlinear model. The control (unperturbed) and the perturbed models are
integrated in time, and periodically the control solution is subtracted from the perturbed solution. This difference is the bred vector. The vector is scaled to be the same size as the initial perturbation and is then added back to the control to create the new perturbed initial condition. After a short transient period, this "breeding" process creates bred vectors dominated by the naturally fastest-growing instabilities of the evolving control solution.
References
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Functional analysis
Mathematical physics
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