A revised 4D-Var algorithm
Outline
Used Data
ECMWF forecast model
geometry
The current operational
4D-Var system
A few 4D-Var Characteristics
The incremental formulation
of 4D-Var
Approximations at inner
iterations
The outer iterations
Slide 10
Slide 11
Test of incremental
approximation
Evolution of TL model error
Impact of TL model
resolution
Small scales
Impact of TL model
resolution (adiab.)
Hessian eigenvector
preconditioning
Trajectory (in)consistency
The revised 4D-Var
algorithm: Motivation
The revised 4D-Var
algorithm: Specification
Conjugate Gradients and
Lanczos Algorithms
Conjugate Gradients and
Lanczos Algorithms
Preconditioning
Preconditioning
Preconditioning
Preconditioning
Preconditioning: Spectrum of
Hessian
Multi-incremental: RMS of T
analysis increments
Conjugate-gradient:
Reduction of Norm of gradient
C.G. and Lanczos Summary
Slide 31
Interpolated trajectory
Performance: Jo cost
function
Scores
Performance: CPU cost
Conclusions