The Dynamics of Error Growth and Predictability in a Model of the Gulf Stream. Part I: Singular Vector Analysis

Abstract

The recently developed ideas of generalized linear stability theory for dynamical systems are applied to time evolving flows of the Gulf Stream using a quasigeostrophic numerical model. The potential for the growth of perturbations arising from errors and uncertainties in forecasts of the Gulf Stream is investigated by computing the singular vectors, or so-called optimal perturbations, of time evolving flows using a linearized model and its adjoint. The authors? calculations reveal that the potential for rapid perturbation growth is greatest in regions of developing straining and shearing flows. Such regions include developing meanders and regions where eddies form and where existing eddies interact with the main Gulf Stream. It is found that the optimal perturbations of the Gulf Stream share many features in common with those of the jet streams in the atmosphere. The ideas and techniques developed in this paper have been applied to the problem of ensemble prediction of the Gulf Stream in Part II.