Lyapunov Vectors and Error Growth Patterns in a T21L3 Quasigeostrophic Model

The authors report a systematic study on the short and intermediate time predictability properties of a quasigeostrophic T21L3 model in which emphasis is placed on the role of the Lyapunov vectors in the growth patterns of generic initial error fields. It is found that under scale-independent small-amplitude initial perturbations the evolution of the mean error is intimately related to the spectral distribution of the Lyapunov vectors. In the case of perturbations at a particular scale of motion the picture turns out to be more involved, particularly as far as mean error growth over all wavenumbers is concerned, and must appeal to coupling mechanisms between different scales. The role of the norm used for the measure of the mean error growth and the specific predictability properties at different vertical levels of the model are also analyzed.