Purpose. The purpose of the study is to parameterize the Langmuir circulation based on experimental data on the main hydrophysical parameters, to determine the relationship between its characteristics and surface waves, and to assess the impact of coherent structures on vertical turbulent exchange in the wave-enhanced surface layer.

Methods and Results. During 2021–2024, hydrophysical fields near the sea surface, including their fluctuation characteristics, were comprehensively measured at the stationary oceanographic platform (Katsiveli) using the acoustic Doppler current profilers (ADCP) DVS-6000 and Workhorse Monitor 1200, as well as a Sigma-1 turbulence meter and a meteorological complex. The vertical velocity component W in the convergence zones was identified at 3–4 m depth based on the ADCP data. The measured values of W allowed the dependences of the Langmuir circulation parameters on wind speed at a height of 10 m (V₁₀) to be determined. To distinguish the modes, the Gaussian mixture model clustering method was applied; it included the selection of the number of clusters based on the Bayesian information criterion. The rate of turbulent kinetic energy dissipation ε was calculated from the velocity fluctuation spectra. Two modes – energy-dependent (La_t > 0.98) and saturated (La_t ≤ 0.98) – were distinguished. The regression relationships W₁ = 0.57V₁₀ + 1.15 (R² = 0.52) and W₂ = −0.29V₁₀ + 7.3 (R² = 0.51) were obtained for these modes. The median values of the Langmuir number La_t were 1.2 (IQR = 0.53) and 0.8 (IQR = 0.34) for the energy-dependent and saturated modes, respectively. It was found that the median values of ε in both modes were close (2.87·10⁻⁶ and 2.62·10⁻⁶ m²/s³), but the IQR of log10(ε) in the energy-dependent mode (0.75) exceeded that in the saturated mode (0.40) by a factor of 1.9. This indicated a significant difference in turbulence variability.

Conclusions. The effect of Langmuir circulation on vertical turbulent exchange lies not so much in altering the mean dissipation rate as in modulating the variability regime, namely, in the transition from a chaotic and inhomogeneous state to an organized and statistically homogeneous one. The proposed parameterizations of W(V₁₀) and quantitative estimates of ε can be used to improve models of turbulence in the wave-enhanced surface layer.