The Finite Size Lyapunov Exponent (FSLE) is defined as:**

where is the separation in phase space between two trajectories, one perturbed in a finite way from the other, and the denominator represents an ensemble average of doubling times. Here,

(n is an exponent) and r represents an error level proportionality constant.

The predictability time based on the FSLE is:

We expect (and hope) that this T is greater than the T obtained from the (classical) LCE.

It can be shown that the FSLE and the concommitant T reduce to the LCE and its T in the limit as the perturbation becomes infinitesimal.

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**Most of the remaining material is taken from [6].