Predictability of the inverse energy cascade in 2D turbulence

The predictability problem in the inverse energy cascade of two-dimensional turbulence is addressed by means of high resolution direct numerical simul ations. The growth rate as a function of the error level is determined by m eans of a finite size extension of the Lyapunov exponent. For errors within the inertial range, the linear growth of the error energy, predicted by di mensional argument, is verified with great accuracy. Our numerical findings quantitatively confirm the results of the classical TFM closure approximat ion. (C) 2001 American Institute of Physics.