Pair dispersion and doubling time statistics in two-dimensional turbulence

Experimental measurements of pair separation statistics in two-dimensional turbulence are reported for an electromagnetically forced stratified-layer system with simultaneous ranges of direct-enstrophy and inverse-energy transfer separated by a well-defined spatial injection scale. Data for pair separation as a function of time are analyzed to determine the dependence of separation statistics in both regimes. Using doubling-time statistics, we show how the measured scalings of the mean quantities are consistent with exponential behavior in the enstrophy range and power-law behavior in the inverse-energy range. Exponential scaling of the doubling-time probability distribution function agrees well with theoretical predictions. Finite size effects are shown to play an important role in the interpretation of the data.