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Assessment of the upper‐ocean mixed layer parameterizations using a large eddy simulation model
Author(s) -
Furuichi Naoki,
Hibiya Toshiyuki
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2014jc010665
Subject(s) - turbulence , turbulence kinetic energy , mixed layer , buoyancy , dissipation , large eddy simulation , stratification (seeds) , entrainment (biomusicology) , meteorology , forcing (mathematics) , mechanics , environmental science , atmospheric sciences , geology , physics , thermodynamics , seed dormancy , germination , botany , dormancy , biology , rhythm , acoustics
Abstract A large eddy simulation (LES) of the upper ocean mixed layer processes in the winter northwestern Pacific is carried out and compared with concurrent microstructure measurements. We find that dissipation rates of turbulent kinetic energy ( ε ) and temperature variance from LES agree well with field observations in the areas where the Ozmidov length scale, calculated from the modeled ε and buoyancy frequency, exceeds the grid size of LES. It is also found that, even though the Ozmidov length scale is less than the grid size of LES, model estimates of the vertical turbulent heat flux near the base of the mixed layer are very similar to observed values, suggesting that this LES model reproduces the intensity of entrainment well. This enables us to use the results from LES to assess the turbulence closure models of Mellor and Yamada [1982, MY] and Nakanishi and Niino [2009, NN] for several forcing scenarios consisting of strong winds, surface heating, and surface cooling. It is found that NN performs better than MY in reproducing the results from LES for each forcing scenario, particularly when the turbulent length scale is adjusted to be more restricted by density stratification.