A turbulent microstructure experiment was undertaken at a low latitude of 10°N in the South China Sea in late August 2012. The characteristics of the eddy diffusivity above 650 m were analyzed, which is one order...A turbulent microstructure experiment was undertaken at a low latitude of 10°N in the South China Sea in late August 2012. The characteristics of the eddy diffusivity above 650 m were analyzed, which is one order of magnitude larger than that in the open ocean at that low latitude. Enhanced eddy diffusivities by strong shears and sharp changes in topography were observed. The strongest eddy diffusivity occurred in the mixed layer, and it reached O（10^-2 m^2/s）. Strong stratification in the thermocline inhibited the penetration of surface eddy diffusivities through the thermocline, where the mixing was weakest. Below the thermocline, where the background eddy diffusivity was approximately O（10^-6 m^2/s）, the eddy diffusivity increased with depth, and its largest value was O（10^-3 m^2/s）.展开更多
The turbulent mixing in the upwelling region east of Hainan Island in the South China Sea is analyzed based on in situ microstructure observations made in July 2012. During the observation, strong upwelling appears in...The turbulent mixing in the upwelling region east of Hainan Island in the South China Sea is analyzed based on in situ microstructure observations made in July 2012. During the observation, strong upwelling appears in the coastal waters, which are 3℃ cooler than the offshore waters and have a salinity 1.0 greater than that of the offshore waters. The magnitude of the dissipation rate of turbulent kinetic energy ε in the upwelling region is O（10–9 W/kg）, which is comparable to the general oceanic dissipation. The inferred eddy diffusivity Kρ is O（10–6 m2/s）, which is one order of magnitude lower than that in the open ocean. The values are elevated to Kρ≈O（10–4 m2/s） near the boundaries. Weak mixing in the upwelling region is consistent with weak instability as a result of moderate shears versus strong stratifications by the joint influence of surface heating and upwelling of cold water.The validity of two fine-scale structure mixing parameterization models are tested by comparison with the observed dissipation rates. The results indicate that the model developed by Mac Kinnon and Gregg in 2003 provides relatively better estimates with magnitudes close to the observations. Mixing parameterization models need to be further improved in the coastal upwelling region.展开更多
基金The "CAS/SAFEA International Partnership Program for Creative Research Teams" of Chinese Academy of Seiences under contract Nos XDA11010202,2013CB430303 and 41376022,41276021 and 41276023
文摘A turbulent microstructure experiment was undertaken at a low latitude of 10°N in the South China Sea in late August 2012. The characteristics of the eddy diffusivity above 650 m were analyzed, which is one order of magnitude larger than that in the open ocean at that low latitude. Enhanced eddy diffusivities by strong shears and sharp changes in topography were observed. The strongest eddy diffusivity occurred in the mixed layer, and it reached O（10^-2 m^2/s）. Strong stratification in the thermocline inhibited the penetration of surface eddy diffusivities through the thermocline, where the mixing was weakest. Below the thermocline, where the background eddy diffusivity was approximately O（10^-6 m^2/s）, the eddy diffusivity increased with depth, and its largest value was O（10^-3 m^2/s）.
基金The National Natural Science Foundation of China under contract Nos 41476009,41776034 and 41476010the Natural Science Foundation of Guangdong Province of China under contract No.2016A030312004+1 种基金the Global Air-Sea Interaction Project of State Oceanic Administration under contract No.GASI-IPOVAI-01-02the Laboratory of Tropical Ocean Open Foundation under contract No.LT1404
文摘The turbulent mixing in the upwelling region east of Hainan Island in the South China Sea is analyzed based on in situ microstructure observations made in July 2012. During the observation, strong upwelling appears in the coastal waters, which are 3℃ cooler than the offshore waters and have a salinity 1.0 greater than that of the offshore waters. The magnitude of the dissipation rate of turbulent kinetic energy ε in the upwelling region is O（10–9 W/kg）, which is comparable to the general oceanic dissipation. The inferred eddy diffusivity Kρ is O（10–6 m2/s）, which is one order of magnitude lower than that in the open ocean. The values are elevated to Kρ≈O（10–4 m2/s） near the boundaries. Weak mixing in the upwelling region is consistent with weak instability as a result of moderate shears versus strong stratifications by the joint influence of surface heating and upwelling of cold water.The validity of two fine-scale structure mixing parameterization models are tested by comparison with the observed dissipation rates. The results indicate that the model developed by Mac Kinnon and Gregg in 2003 provides relatively better estimates with magnitudes close to the observations. Mixing parameterization models need to be further improved in the coastal upwelling region.
