Transient Suppression in Optimal Sequential Analysis

Daniel P. Petersen National Center for Atmospheric Research, Boulder, Colo. 80302

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Abstract

A problem associated with four-dimensional data assimilation in numerical models of the atmosphere is the excitation of spurious dynamical modes such as gravity-inertial waves. If the desired diagnostic restrictions on the model representation can be expressed in the form of linear constraints such as geostrophic balance or spectral band-limiting, the weighting formulas prescribed by the method of optimal sequential analysis for insertion of successive observational data automatically maintain those restrictions.

For nonlinear constraints such as the full balance condition, quasi-optimal updating formulas which approximately maintain the restrictions can be derived.

Abstract

A problem associated with four-dimensional data assimilation in numerical models of the atmosphere is the excitation of spurious dynamical modes such as gravity-inertial waves. If the desired diagnostic restrictions on the model representation can be expressed in the form of linear constraints such as geostrophic balance or spectral band-limiting, the weighting formulas prescribed by the method of optimal sequential analysis for insertion of successive observational data automatically maintain those restrictions.

For nonlinear constraints such as the full balance condition, quasi-optimal updating formulas which approximately maintain the restrictions can be derived.

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