Left: ratio between the two physical contributions to either mode damping or the surface effect (turbulent pressure vs. turbulent dissipation and redistribution of kinetic energy), as a function of the drift tensor anisotropy factor, Φ_G, for a mode of frequency ν = ν_max = 3 mHz. The turbulent velocity anisotropy is set to Φ_u = 0.5 and the turbulent frequency to ω_t = 0.03 rad.s⁻¹. The vertical dashed line marks the limit Φ_G = 1: to the left, the dissipation of the vertical turbulent motions prevails over the redistribution of turbulent kinetic energy between horizontal and vertical motions, and vice versa to the right. The horizontal dashed line is the same as in Fig. 1. Right: same ratio, as a function of the turbulent frequency, ω_t, for a mode of frequency ν = ν_max = 3 mHz. The two anisotropy factors are set to Φ_u = 0.5 and Φ_G = 1.0. The horizontal dashed line is the same as in Fig. 1. (a) R as a function of Φ_G (b) R as a function of ω_t