Gratton, Serge

Rincon-Camacho, Monserrat

Simon, Ehouarn

Toint, Ph

English

We propose to use a decomposition of large-scale incremental fourdimensional (4D-Var) data assimilation problems in order to make theirnumerical solution more efficient. This decomposition is based on exploiting an adaptive hierarchy of the observations. Starting with a low-cardinality set and the solution of its corresponding optimization problem, observations are adaptively added based on a posteriori error estimates. The particular structure of the sequence of associated linear systems allows the use of a variant of the conjugate gradient algorithm which effectively exploits the fact that the number of observations is smaller than the size of the vector state in the 4D-Var model. The method proposed is justified by deriving the relevant error estimates at different levels of the hierarchy and a practical computational technique is then derived. The new algorithm is tested on a 1D-wave equation and on the Lorenz-96 system, the latter one being of special interest because of its similarity with Numerical Weather Prediction (NWP) systems

Repository of the University of Namur

Observations Thinning In Data Assimilation Computations

https://pure.unamur.be/ws/files/10881647/grst_ES.pdf

Observations Thinning In Data Assimilation Computations

Abstract

Similar works

Full text

Available Versions

Repository of the University of Namur