Abstract
Diapycnal diffusivity is an important parameter to characterize oceanic turbulent mixing and vertical transport. However, due to the challenging accessibility of field observations, the observation of diapycnal diffusivity in the South China Sea (SCS) is rare. In this study, a three-dimensional field of diapycnal diffusivity in the SCS with high spatial resolution is performed by interpolating the rare field observations, which aims to provide a reference for the value of diapycnal diffusivity in ocean models. Given the anisotropy of diapycnal diffusivity and its rapid change in the magnitude in the vertical direction, several typical interpolation methods are compared in this study. Results of two cross-validation methods demonstrate that the three-dimensional (3D) thin-plate spline interpolation method yields the most reasonable and accurate results among a total of five typical methods used in this study.
Highlights
Turbulent mixing is a microscale process that makes the properties of water bodies more uniform, which is extremely important for regulating climate and marine productivity [1,2]
Oceanic turbulent mixing is commonly characterized by turbulent kinetic energy dissipation rate and diapycnal diffusivity, and there is a strong correlation between these two indicators [5]
Tian et al [3] found that the diapycnal diffusivity in the deep ocean basin of the South China Sea (SCS) was two orders larger than that in the western Pacific, based on a fine scale parameterization and hydrographic observations obtained from the northern SCS and the western Pacific
Summary
Turbulent mixing is a microscale process that makes the properties of water bodies more uniform, which is extremely important for regulating climate and marine productivity [1,2]. Due to the limitations of field observations, diapycnal diffusivity in the SCS calculated by the GHP parameterization method has only patchy spatial distribution. The advantage of the spatial interpolation method is that the 3D field of diapycnal diffusivity can be obtained with low computational cost and high spatial resolution. The horizontal distribution of diapycnal diffusivity ranges from 110◦ E to 121◦ E and 11◦ N to 21◦ N with a resolution of 0.5◦ × 0.5◦, and the vertical distribution ranges from 200 m to 5000 m with a resolution of 200 m Based on these data (a total of 2353 data), a 3D spatial interpolation analysis is performed in this paper to reconstruct the 3D spatial distribution of diapycnal diffusivity in the SCS. In the subsequent 3D interpolation methods used in this study, the weight in the vertical direction is always set to 1/100 of that in the horizontal direction
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