Dynamically constrained ensemble perturbations – application to tides on the West Florida Shelf

[摘要] A method is presented to create an ensemble of perturbations that satisfieslinear dynamical constraints. A cost function is formulated defining theprobability of each perturbation. It is shown that the perturbations createdwith this approach take the land-sea mask into account in a similar way asvariational analysis techniques. The impact of the land-sea mask isillustrated with an idealized configuration of a barrier island.Perturbations with a spatially variable correlation length can be alsocreated by this approach. The method is applied to a realistic configurationof the West Florida Shelf to create perturbations of the M2 tidal parametersfor elevation and depth-averaged currents. The perturbations are weaklyconstrained to satisfy the linear shallow-water equations. Despite that theconstraint is derived from an idealized assumption, it is shown that thisapproach is applicable to a non-linear and baroclinic model. The amplitude ofspurious transient motions created by constrained perturbations of initialand boundary conditions is significantly lower compared to perturbing thevariables independently or to using only the momentum equation to compute thevelocity perturbations from the elevation.

[学科分类] 海洋学与技术