TITLE:
The Lateral Eddy Viscosity Derived from the Decay of Oceanic Mesoscale Eddies
AUTHORS:
Qiuyang Li, Liang Sun, Chi Xu
KEYWORDS:
Eddy Mixing, Eddy Viscosity, Mesoscale Eddy
JOURNAL NAME:
Open Journal of Marine Science,
Vol.8 No.1,
January
31,
2018
ABSTRACT: The relationship of lateral eddy viscosity depending on length scale is estimated
with the decay rate of mesoscale eddies identified from sea level anomaly
of satellite observations. The eddy viscosity is expressed in terms of the
mesoscale eddy parameters according to vortex dynamics. The census of mesoscale
eddies shows, in general, that the eddy numbers obey the e-folding
decay laws in terms of their amplitude, area and lifetime. The intrinsic values
in the e-folding laws are used to estimate the lateral eddy viscosity. Dislike the
previous theory that diffusivities are proportional to the length square, the
eddy mixing rates (diffusivity and viscosity) from satellite mesoscale eddy datasets
are proportional to rs to power of 1.8 (slightly less than 2), where rs is
the radius of eddy with radius larger than the Batchelor scale. Additionally,
the extrapolation of the eddy mixing to the molecule scale implies that the
above power laws may hold until the value of rs is less than O (1 m). These
mixing rates with the new parameterizations are suggested to use in numerical
schemes. Finally, the climatological distributions of eddy viscosity are calculated.