Quasi-two-dimensional turbulence

We review the results of numerical and experimental studies in quasi-two-dimensional (Q2D) turbulence. We demonstrate that theoretical energy spectra with slopes –5/3 and –3 (Kraichnan – Batchelor – Leith) can be observed only for a special set of external parameters. The bottom drag, beta effect, finite Rossby – Obukhov radius or vertical stratification, which distinguish geophysical Q2D turbulence from its purely 2D counterpart, determine the organization of a Q2D flow on a large scale. Since the spectral energy flux in 2D turbulence is directed upscale, the bottom friction takes on a special role. In the absence of bottom drag the energy condenses on the largest resolvable scale and flow equilibration is not attained.