[ecco-support] Access to ECCOV4

[Fenty, Ian G (329C)]

Guancheng,

Salinity transport by resolved eddies occurs through advection terms and by unresolved eddies through diffusion terms.   The specific parameterizations used in ECCO version 4 are described in Forget et al., (2015) and references therein.  Pay close attention to Appendix B.

Forget et al.,  (2015) ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation Doi: 10.5194/gmd-8-3071-2015

Tracer advection and diffusion in the MITgcm are described here:
http://mitgcm.org/public/r2_manual/latest/online_documents/node71.html

> Finally, i tried to compare with the location of different variables like SALT, MXLD, ADVx_SLT, and found that there is no regularity to establish their distance like a half grid and make sure they are in the same grid cell.

The geometry of the MITgcm is described here:
http://mitgcm.org/public/r2_manual/latest/online_documents/node43.html

It may be also helpful for you to consult with the documentation describing the ECCO version 4 grid, geometry, and routines written by G. Forget to process the output on the native grid:
ftp://mit.ecco-group.org/ecco_for_las/version_4/release2/doc/ECCOV4R2_gcmfaces.pdf

The ECCO v4 state estimate provides all geometric terms required to calculate budgets  (length, area, volume).

Salt and MXLD are located in the same location (located at the “tracer” or center of the model grid cell) while advective and diffusive fluxes are located on the grid cell faces.

Each face of a grid cell has advective and diffusive terms.  Side faces have one advection and one diffusion terms.  The diffusion term of side faces is the sum of parameterized eddy transport by the Gent-Mcwilliams and Redi schemes.  The top and bottom faces have each have one advection and two diffusive terms (implicit and explicit components that parameterize to background mixing and convection.)

Doing budgets on the model grid used in ECCO is not simple because the grid is unusual.  One day we will perhaps have a tutorial.  If you are still having trouble after reading through the documentation then let us know.

-Ian



From: ecco-support-bounces at mit.edu [mailto:ecco-support-bounces at mit.edu] On Behalf Of Ligc
Sent: Monday, April 10, 2017 1:02 AM
To: ecco-support at mit.edu
Subject: [ecco-support] Access to ECCOV4

Dear Mr Ian，
            Recently, i tried to analyze the natural model grid data below the surface and met some trouble. Because it's a brand new area to me, i hope that you could give me some suggestion if you are convenient.
            Firstly, i want to ask you whether Advection or Diffusion terms has included the Eddy Effects, which may be play an important role in closing its budget. Then, thanks again for your introduction of different terms which can close the budget for grid cells, but i think it will be more helpful if you can tell me some more details of every flux term and whose formula will account for these works. Finally, i tried to compare with the location of different variables like SALT, MXLD, ADVx_SLT, and found that there is no regularity to establish their distance like a half grid and make sure they are in the same grid cell.
            Please forgive my poor work and my unprofessional questions.
            Thank you for your patient reading! I really appreciate your help!



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