[MITgcm-support] is Orlanski radiation condition working in the rotating rank of MITgcm?

[Martin Losch]

Yi-Chih,

I still don’t really know what the problem is. in your png file, which I assume is a vertical section along a boundary, there are some smooth variations of the otherwise homogeneous temperature (scaled density) field. What do you expect to see? Constant temperature?

I would try without the “centrifugal force” in apply_forcing.F, which I assume is your addition (BTW, the masking in the “centrifugal force” is not correct. I should be maskW for gU_arr and maskS vor gV_arr, you have maskW for both), and see if you get what you expect.

More general comments:

The obcs-settings appear to be OK although I still don’t see why you want to use open boundary conditions for your simluation at all.

You seem to use z-coordinates (default). In your data you have very high viscosities (1e6), but very low diffusivities (5e-6, 1e-7). Is that on purpose? I would expect that this would put a strong contraint on your timestep deltaT. Also you use rSphere = 60000.E3, rotationPeriod=38520.0, so a planet rotating about twice as fast as the earth with a radius 10 times larger. Is the larger radius reflected in the grid input fields?

For your experiment, I would just use a cartesian grid centered at the North Pole of the sphere (constant f0), or if the variation of coriolis is important, you can read the (precomputed) coriolis parameter via files fCoriC.bin, fCorCs.bin (for the 2*om*cos(lat)),fCoriG.bin, for that you need to set selectCoriMap = 3 in data. It would make things much easier for you to control.

Martin

> On 18. Dec 2018, at 14:31, Yi-Chih Huang <dscpln at gmail.com> wrote:
> 
> Martin,
> 
>     Thanks much for the reply.  I conduct idealized simulations around the Arctic regions.  Thus, I need to work on curvilinear coordinates to resolve the singularity problem.  I started with the grids on arctic40km and cs_4km.  Generally, I got the numerical disturbances around the lateral boundary as the .png file.  I tried to update thelateral boundary condition with Orlanski b.c. by adding obcs in packages.conf and useOBCS=.TRUE., in data.pkg, along with the data.obcs file.  Hopefully the attached file in code, data.pkg, data.obcs, and data are clear enough.  The input files include rhoRefFile, bathyFile, and hydrogThetaFile.  The hydrogThetaFile is three dimensional so I don't want to attach it.  Probably my update in b.c. was not successful because the temperature patterns are the same as the original one.  Thus, I did not attach another .png file.  I wonder how to update with the Orlanski b.c. in MITgcm?
> 
>     I will study a planet other than the Earth.  Hence, the grids of arctic40km and cs_4km will not be suitable for this work.  I wonder the relations between radius and grids information on the curvilinear coordinates and what to start with?
> 
>     Hopefully, my descriptions are clear enough and thanks much for your help,
>  
>                Yi-Chih
> 
> 
> Date: Mon, 17 Dec 2018 10:49:50 +0100
> From: Martin Losch <Martin.Losch at awi.de>
> To: MITgcm Support <mitgcm-support at mitgcm.org>
> Subject: Re: [MITgcm-support] is Orlanski radiation condition working
>         in the rotating rank of MITgcm?
> Message-ID: <30F990A0-C8E6-45D5-8C24-13EDF0112321 at awi.de>
> Content-Type: text/plain; charset="utf-8"
> 
> Yi-Chih,
> 
> I am sorry. I don?t understand what you are doing (and why, but that?s maybe not so important).
> 
> Does you config have anything to do with verification/rotating_tank?
> This experiment mimics a small tank on a turntable in a lab. It?s not clear to me how to upscale that to the Arctic without fundamentally changing the parameters of the model. 
> Thus, I cannot follow your conclusions that you can fix anything with open boundaries. You need to make sure that your flow parameters are set correctly (eg. horizonal and vertical viscosity, Coriolis parameter, etc ?.)
> 
> Using the grid data from arctic40km or cs_4km confuses me even more in this context. If you do things like this, the coriolis parameter should be automatically set according to the latitudes in the domain. You cannot change the radius of the earth without adjusting the grid information (because grid spacing ~ radius of the earth).
> 
> I don?t think anyone can help you with this unless you are clearer about you configuration. Maybe it would be a good idea to 
> (1) post your configuration somewhere, namelist files, ?code? directory, ?input files" (please no large files on this list)
> (2) post a plot of the ?disturbances? that you observe, with and without orlanski obcs
> 
> Martin
> <apply_forcing.F><DIAGNOSTICS_SIZE.h><packages.conf><OBCS_OPTIONS.h><SIZE.h><CPP_OPTIONS.h><SIZE.h_mpi><data><fig.130x102_bc_T_x65_t7.png><data.obcs><data.pkg>_______________________________________________
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