Passive scalars in stratified turbulence

Abstract

The statistics of a passive scalar in randomly forced and strongly stratified turbulence is investigated by numerical simulations including a horizontal passive scalar mean gradient. We observe that horizontal isotropy of the passive scalar spectrum is satisfied in the inertial range. The spectrum has the form E_theta(k_h) = C_theta*epsilon_theta*epsilon_K^{-1/3}* k_h^{-5/3}, where epsilon_theta, epsilon_K are the dissipation of scalar variance and kinetic energy respectively, and C_theta about 0.5 is a constant. This spectrum is consistent with atmospheric measurements in the mesoscale range. The calculated passive scalar structure functions show that intermittency effects are significant.