Accurate Boussinesq oceanic modeling with a practical, “Stiffened” Equation of Stateстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 29 сентября 2021 г.
Аннотация:The Equation of State of seawater (EOS) relates in situ density to temperature, salinity and pressure. Most
of the effort in the EOS-related literature is to ensure an accurate fit of density measurements under the
conditions of different temperature, salinity, and pressure. In situ density is not of interest by itself in oceanic
models, but rather plays the role of an intermediate variable linking temperature and salinity fields
with the pressure-gradient force in the momentum equations, as well as providing various stability functions
needed for parameterization of mixing processes. This shifts the role of EOS away from representation
of in situ density toward accurate translation of temperature and salinity gradients into adiabatic
derivatives of density.
In this study we propose and assess the accuracy of a simplified, computationally-efficient algorithm
for EOS suitable for a free-surface, Boussinesq-approximation model. This EOS is optimized to address
all the needs of the model: notably, computation of pressure gradient – it is compatible with the monotonized
interpolation of density needed for the pressure gradient scheme in sigma-coordinates of Shchepetkin
and McWilliams (2003), while more accurately representing the pressure dependency of the
thermal expansion and saline contraction coefficients as well as the stability of stratification; it facilitates
mixing parameterizations for both vertical and lateral (along neutral surfaces) mixing; and it leads to a
simpler, more robust, numerically stable barotropic–baroclinic mode splitting without the need of excessive
temporal filtering of fast mode. In doing so we also explore the implications of EOS compressibility
for mode splitting in non-Boussinesq free-surface models with the intent to design a comparatively accurate
algorithm applicable there.