Abstract: Based on the turbulence data overall 4000 m directly observed at station of （17°N，116°E） in the South China Sea in 2022, this paper studies the spatial distribution and correlation of turbulent mixing parameters ( including dissipation rate, mixing rate, Thorpe scale, etc. ), and verifies the applicability of the MG (MacKinnon-Gregg) model in this station. The real turbulent kinetic energy dissipation rate is around O(10^-9)Wkg^-1, while the dissipation rate estimated with the MG method is around O(10^-9~10^-10)Wkg^-1 ,whose average mixing rates were O(10^-4)m²s^-1 and O(10^-5)m²s^-1respectively, with a similar magnitude order, indicating that MG model at this station has a high estimation accuracy. The two methods show that in the range of 1300~4000m in the deep sea, mixing rate is highly consistent with the average fluctuation of Thorpe scale, showing the overall large-small-large-small distribution ("inverse-z shape"), and the correlation coefficient is as high as 0.7, especially results of which in the depth of [1300~3000m] are relatively consistent, both reaching 0.8. Applying wavelet to analyze the multiscale he two methods show that in the range of 1300~4000m in the deep sea, the mixing rate is highly consistent with the average fluctuation of Thorpe scale, showing the overall large-small-large-small distribution ("inverse-z shape"), and the correlation coefficient is as high as 0.7, especially results of which are relatively consistent in the depth of 1300~3000m, both reaching 0.8. Applying wavelet to analyze the multiscale series of the energy, the positional energy changes more significantly at high correlation, which demonstrate the importance of introducing the correlation coefficient of mixing rate and Thorpe scale to analyze the turbulent mixing intensity. This research combines direct observation with parameterization estimation, which can provide useful reference for microstructure observation, spatial distribution of mixing parameters and theoretical study of turbulent mixing in the intermediate and deep layers of the South China Sea.

Key words: Turbulence mixing in the South China sea, Thorpe scale, turbulent dissipation rate, mixing rate, MG model