[MITgcm-support] from C- to A-grid (particle tracking)
Andrea Cimatoribus
andrea.cimatoribus at epfl.ch
Mon Mar 6 04:36:02 EST 2017
Dear all,
many shared some interest on lagrangian tools for MITgcm, so it's
probably a good idea to share the repository where I am adapting
tracmass to my MITgcm output:
https://github.com/sambarluc/tracmass
Tracmass nicely deals natively with C-grids, and only has some indexing
differences with respect to MITgcm. For now I have a working example,
but have done only a few tests and no documentation. Depending on how
much time I will devote to this project, I may try to wrap things up in
a nicer package in the future.
Thanks again to those who provided very valuable feedback.
Andrea
Andrea Cimatoribus
postdoctoral researcher
EPFL ENAC IIE ECOL
https://people.epfl.ch/andrea.cimatoribus
On 22/02/17 17:02, Andrea Cimatoribus wrote:
> Thanks for all the feedback, I have to study the material and may get
> back to (some of) you later.
> Cheers,
>
> Andrea Cimatoribus
> postdoctoral researcher
> EPFL ENAC IIE ECOL
> https://people.epfl.ch/andrea.cimatoribus
>
> On 22/02/17 15:34, Ryan Abernathey wrote:
>> Andrea,
>>
>> Moving from an A grid to a C grid does require interpolation. If you are
>> doing Lagrangian particles, the induced divergence might not be a
>> problem, since a slightly non-divergent velocity field won't cause any
>> serious problems. So a naive multilinear interpolation may be fine.
>>
>> If you need to advect tracers offline, you need a velocity field that is
>> exactly non divergent and satisfies the boundary condition at the side
>> walls. This can be obtained by decomposing the velocity into
>> streamfunction and velocity potential components, which requires solving
>> an elliptic Poisson PDE. The MITgcm can be hacked to solve this for you.
>>
>> We have done exactly what you describe in the following papers, where we
>> use AVISO geostrophic velocities (on an A-grid) to advect tracers and
>> particles within MITgcm.
>> http://doi.org/10.1002/jgrc.20066
>> http://doi.org/10.1175/JPO-D-13-0159.1
>> http://doi.org/10.1175/JPO-D-16-0215.1
>>
>> If you like, I can provide you more details.
>>
>> Cheers,
>> Ryan
>>
>>
>> On Wed, Feb 22, 2017 at 9:20 AM, Blundell J.R. <jeff at noc.soton.ac.uk
>> <mailto:jeff at noc.soton.ac.uk>> wrote:
>>
>> Hi Andrea,
>> This isn't a simple answer to your question, but you might
>> like to have a look at ARIANE:
>> http://stockage.univ-brest.fr/~grima/Ariane/
>> <http://stockage.univ-brest.fr/~grima/Ariane/>
>> (original webpage)
>> which is heavily used here at NOC, Southampton. It has native support
>> for some curvilinear C-grid models, such as OPA-NEMO and ROMS,
>> though not (as far as I can see) MITgcm. Given that it has support
>> for
>> several models, I would imagine that the logic of adding another
>> might
>> not be too bad, perhaps easier that interpolating onto a regular
>> A-grid.
>> We use v2.2.8_05 .
>> See also
>> http://salishsea-meopar-docs.readthedocs.org/en/latest/particles/
>> <http://salishsea-meopar-docs.readthedocs.org/en/latest/particles/>
>> which seems to have some of the most up-to-date documentation.
>> I should explain that I build the software (that part works quite
>> well)
>> for others to use; I'm not a user myself.
>> http://earthscience.stackexchange.com/questions/761/what-are-some-
>> options-for-online-and-offline-particle-tracking-in-ocean-models
>> <http://earthscience.stackexchange.com/questions/761/what-are-some-
>> options-for-online-and-offline-particle-tracking-in-ocean-models>
>> seems to suggest that CMS can handle "various Arakawa-staggered
>> grids",
>> as presumably it must if it handles HYCOM and ROMS output.
>>
>> Jeff Blundell
>>
>> ======================================================================
>> | Research Fellow in Physical
>> Oceanography |
>> | e-mail: jeff at noc.soton.ac.uk
>> <mailto:jeff at noc.soton.ac.uk> |
>> | Jeff Blundell, Room 256/09 | OES Physical Oceanography
>> Group, |
>> | phone: +44 [0]23 8059 6201
>> <tel:%2B44%20%5B0%5D23%208059%206201> | National Oceanography
>> Centre, |
>> | fax : +44 [0]23 8059 6204
>> <tel:%2B44%20%5B0%5D23%208059%206204> | Southampton, European
>> Way, |
>> | | SOUTHAMPTON SO14 3ZH,
>> UK. |
>> | WWW: http://www.southampton.ac.uk/oes/about/index.page
>> <http://www.southampton.ac.uk/oes/about/index.page>? |
>>
>> ======================================================================
>>
>> ________________________________________
>> From: Andrea Cimatoribus [andrea.cimatoribus at epfl.ch
>> <mailto:andrea.cimatoribus at epfl.ch>]
>> Sent: 22 February 2017 13:49
>> To: mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org>
>> Subject: [MITgcm-support] from C- to A-grid (particle tracking)
>>
>> Dear all,
>> I am in the process of setting up some particle tracking experiments.
>> After some research and some thinking about my needs, I am
>> inclined to
>> use an offline tool rather than the MITgcm flt package, most
>> likely CMS
>> (https://www.rsmas.miami.edu/users/cparis/oss.html
>> <https://www.rsmas.miami.edu/users/cparis/oss.html>).
>>
>> In order to use CMS, I need to interpolate the MITgcm results from my
>> native curvilinear C-grid to the non curvilinear, non rotated A-grid
>> which CMS requires. My questions then are:
>> - is there a way to do this interpolation maintaining the flow (at
>> least
>> approximately) non divergent? (with complex boundaries)
>> - does anyone have any suggestion on working with MITgcm+CMS, or
>> more in
>> general with MITgcm+particle tracking?
>>
>> The alternative is to implement C-grids in CMS, which would be
>> interesting but I'm not yet sure it's realistic.
>>
>> Thanks, Andrea
>>
>>
>> --
>> Andrea Cimatoribus
>> postdoctoral researcher
>> EPFL ENAC IIE ECOL
>> https://people.epfl.ch/andrea.cimatoribus
>> <https://people.epfl.ch/andrea.cimatoribus>
>>
>>
>>
>> PS: To answer the obvious question one may have: I think that the flt
>> package is not the right tool for me, since I would like to have
>> several
>> particles (>>1000), doing repeated experiments over the same
>> period of
>> time, in a rather small domain. I think that an offline tool is in
>> this
>> case not only much faster, but also much more flexible.
>>
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