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 simulations. The growth rate as a function of the error level is determined by means of a finite size extension of the Lyapunov exponent. For errors within the inertial range, the linear growth of the error energy, predicted by dimensional argument, is verified with great accuracy. Our numerical findings quantitatively confirm the results of the classical TFM closure approximation. (C) 2001 American Institute of Physics.