Two-Dimensional Turbulence Generated by Energy Sources at Two Scales

Observational results and theories suggest that the atmospheric energy spectrum is at least partly produced by quasi-two-dimensional turbulence generated by energy sources at both large and small scales. This hypothesis is investigated further with the aid of turbulence closure models. Inertial range solutions are found for which the energy spectrum function exhibits an approximately −3 slope at low wavenumbers and a −5/3 slope at high wavenumbers. The spectral energy transport is constant and upscale (toward lower wavenumbers) and the spectral enstrophy transport constant and downscale throughout this range. The results indicate that there is no need for a special dissipation mechanism in the transition region between the two spectral slopes.