A multivariate balance operator for variational ocean data assimilation.

A multivariate balance operator for variational ocean data assimilation.
Technical memorandum
Date Published
Secondary Title
ECMWF Technical Memoranda
A.T. Weaver
C. Deltel
E. Machu
S. Ricci
N. Daget
Abstract It is common in meteorological applications of variational assimilation to specify the error covariances of the model background state implicitly via a transformation from model space where variables are highly correlated to a control space where variables can be considered to be approximately uncorrelated. An important part of this transformation is a balance operator which effectively establishes the multivariate component of the error covariances. The use of this technique in ocean data assimilation is less common. This paper describes a balance operator that can be used in a variable transformation for oceanographic applications of three-and four-dimensional variational assimilation. The proposed balance operator has been implemented in an incremental variational data assimilation system for a global ocean general circulation model. Evidence that the balance operator can explain a significant percentage of background-error variance is presented. The multivariate analysis structures implied by the balance operator are illustrated using single observation experiments.
URL https://www.ecmwf.int/en/elibrary/76869-multivariate-balance-operator-variational-ocean-data-assimilation
DOI 10.21957/a1q77nvm8