[MITgcm-support] Choosing Leith biharmonic co-efficient?

[Ryan Abernathey]

Jody,

I assume you are talking about the config you got from Dhruv. The values we
use in those runs were taken from Dimitris Menemenlis and Chris Hill's LLC
simulations. The exact same settings are used for 1/12, 1/24, and 1/48
degree global simulations. (Although I do recall that Dhruv had to make
some changes related to boundary conditions.)

-Ryan

On Mon, Apr 16, 2018 at 8:59 AM, Malte Jansen <mfj at uchicago.edu> wrote:

> Just to add on to this: the Leith viscosity is supposed to be "scale
> aware" (at least within a QG turbulence regime), such that the
> non-dimensional coefficient should be independent of the grid-scale.
>
> -Malte
>
>
>
> On 4/16/18 3:16 AM, Martin Losch wrote:
>
>> Hi Jody,
>>
>> my reference is pkg/mom_common/mom_calc_visc.F where you can find this:
>>
>> C     RECOMMENDED VALUES
>> C     viscC2Leith=1-3
>> C     viscC2LeithD=1-3
>> C     viscC4Leith=1-3
>> C     viscC4LeithD=1.5-3
>> C     viscC2smag=2.2-4 (Griffies and Hallberg,2000)
>> C               0.2-0.9 (Smagorinsky,1993)
>> C     viscC4smag=2.2-4 (Griffies and Hallberg,2000)
>>
>> And I think this is where it is described:
>> B. Fox-Kemper and D. Menemenlis. Can large eddy simulation techniques
>> improve mesoscale-rich ocean models? In M. Hecht and H. Hasumi, editors,
>> Ocean Modeling in an Eddying Regime, volume 177, pages 319-338. AGU
>> Geophysical Monograph Series, 2008.
>> http://www.geo.brown.edu/research/Fox-Kemper/pubs/pdfs/FoxKe
>> mperMenemenlis08.pdf
>>
>> Martin
>>
>> On 14. Apr 2018, at 22:42, Jody Klymak <jklymak at uvic.ca> wrote:
>>>
>>>
>>> Hi all,
>>>
>>> Is there a good reference and/or ruls of thumb for choosing the Leith
>>> biharmonic co-efficient? i.e. `viscC4Leith` and `viscC4Leithd`, with
>>> particular interest in how the size of the grid affects the choice?  I’m
>>> using someone else’s setup, using Leith works great for making the flow
>>> look reasonable, but it would be nice if it was turned down as much as
>>> possible, particularly when I downscale to a smaller grid size…
>>>
>>> Thanks a lot,   Jody
>>> _______________________________________________
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>
> --
> Malte F Jansen
> Assistant Professor
> Department of the Geophysical Sciences
> The University of Chicago
> 5734 South Ellis Avenue
> Chicago, IL 60637 USA
>
>
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