Behaviors of variational and nudging assimilation techniques with a chaotic low-order model

Variational and nudging data-assimilation schemes are examined within the framework of a model initialization problem using the Lorenz three-component model of Rayleigh-Benard convection. Since the intent of this study is to explore what factors influence the abilities of the two assimilation techniques to produce accurate initial conditions, identical twin experiments are conducted for various lengths of the data-assimilation window when the flow is both steady state and chaotic. These experiments illustrate that the location of the model solution in phase space is an important consideration when applying either data-assimilation scheme. Decision points, were the model "chooses' which stationary point to orbit, are found to affect the ability of the assimilation techniques to find an accurate initial condition. -from Authors