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##

Latitudinal scaling of horizontal diffusion

Scaling of the horizontal diffusion coefficient by
*cos*^{n}(θ)
was introduced, where *θ* is latitude, *n* = 1 for Laplacian mixing
and *n* = 3 for bi-harmonic mixing. This *optional* scaling
prevents horizontal diffusion from limiting the time step severely at
high latitudes, yet keeps diffusion large enough to maintain numerical
stability.

2010-01-14