Notes on the appropriateness of ‘‘bred modes’’ for generating initial perturbations used in ensemble prediction
Errico, Ronald M.
- Publisher: Co-Action Publishing
Papers by Szunyogh and co-workers and Iyengar and co-workers, among others, claim that‘‘bred growing vectors’’ (BGVs) are appropriate for generating initial perturbations for applicationto ensemble weather prediction. The theoretical bases for this claim are purported relationshipsbetween the bred vectors and what are called local Lyapunov vectors (LLVs). Severalstatements in these papers are inaccurate, however, regarding: the properties of LLVs in contrastto those of singular vectors; the relationship between LLVs and BGVs; the relationship betweenBGVs and analysis errors; the relationship between singular vectors and dynamic imbalances;and the adequacy of very low-resolution models to characterize singular vectors of models usedfor numerical weather prediction. These inaccuracies and their implications for the use of BGVsin ensemble weather prediction are discussed here.DOI: 10.1034/j.1600-0870.1999.t01-3-00007.x