- Predictability - a problem partly solved.
Article
Bib No.:
- 429481
Authors:
- Lorenz, E.N.
Publication Date:
- 1996
Physical Description:
- pp.1-18
Citation:
- Predictability, volume I. Proceedings of a seminar held at ECMWF, Reading, 4-8 September 1995.
Holding Location:
- See Parent Record
Link to Parent Record:
Parent Record:
- Predictability, volume I. Proceedings of a seminar held at ECMWF, Reading, 4-8 September 1995.
Media Type:
- Article
Collection:
- Library Collection
Language:
- English
Abstract:
- The difference between the state that a system is assumed or predicted to possess, and the state that it actually possesses or will possess, constitutes the error in specifying or forecasting the state. We identify the rate at which an error will typically grow or decay, as the range of prediction increases, as the key factor in determining the extent to which a system is predictable. The long-term average factor by which an infinitesimal error wil amplify or diminsh, per unit time, is the leading Lyapunov number; its logarithm, denoted by lambda sub 1, is the Leading Lyapunov exponent. Instantaneous growth rates can differ appreciably from the average. With the aid of some simple models, we describe situations where errors behave as would be expected from a knowledge of lambda sub 1, and other situations, particularly in the earliest and latest stages of growth, where their behavior is systematically different. Slow growth in the latest stages may be especially relevant to the long-range predictability of the atmosphere. We identify the predictability of long-term climate variations, other than those that are externally forced, as a problem not yet solved.