[MITgcm-support] [EXTERNAL] Issue with surface ocean currents

[kunal madkaiker]

Hello Dimitris,

I tried adding sponge parameters in my data.obcs. But It seems that the
turbulence has amplified, rather than getting damped.
Attaching my data.obcs and surface currents comparison plot. My model
resolution is ~5km and I have considered a thickness
of 25 grid points (~125km).

# Open-boundaries
 &OBCS_PARM01
# This flag turns off checking and fixing problematic topography across
# open boundaries. We set it here to override the default because
# we want to reproduce old results (including their bugs).

 OBCSfixTopo=.TRUE.,
 useOBCSprescribe=.TRUE.,
 useOBCSsponge=.TRUE.,
#OBCS_monitorFreq= 1200.,

 OB_Jsouth=660*1,
 OB_Iwest=480*1,
 OB_Ieast=480*-1,

 OBSsFile='OBSs_J2D_obcs',
 OBStFile='OBSt_J2D_obcs',
 OBSuFile='OBSu_J2D_obcs',
 OBSvFile='OBSv_J2D_obcs',
 OBWsFile='OBWs_J2D_obcs',
 OBWtFile='OBWt_J2D_obcs',
 OBWuFile='OBWu_J2D_obcs',
 OBWvFile='OBWv_J2D_obcs',
 OBEsFile='OBEs_J2D_obcs',
 OBEtFile='OBEt_J2D_obcs',
 OBEuFile='OBEu_J2D_obcs',
 OBEvFile='OBEv_J2D_obcs',

 useOBCSbalance=.TRUE.,
 OBCS_balanceFacW= 0.,
 OBCS_balanceFacS= 1.,
 OBCS_balanceFacE= 0.,
 &

 &OBCS_PARM03
 Urelaxobcsinner=432000.E0,
 Urelaxobcsbound=43200.E0,
 Vrelaxobcsinner=432000.E0,
 Vrelaxobcsbound=43200.E0,
 spongeThickness=25,
 &
Kindly suggest if I am doing something wrong.

Thanks,
Kunal

On Mon, Mar 21, 2022 at 10:12 AM kunal madkaiker <
kunal.madkaiker02 at gmail.com> wrote:

> Thank you Dimitris,
>
> I would be adding relaxation for U,V at the lateral boundary.
> I'll certainly update once I get the results.
>
> Thanks
> Kunal
>
> On Thu, Mar 17, 2022 at 11:17 PM Menemenlis, Dimitris (US 329B) <
> dimitris.menemenlis at jpl.nasa.gov> wrote:
>
>> Hi Kunal, I will be interested to know what you find, that is, whether it
>> is indeed reflections at the lateral boundaries that cause trouble.
>> With prescribed boundary conditions, everything that does not match
>> exactly the specified boundary conditions will be reflected.
>> You can sometimes get away with prescribed boundary conditions when you
>> are downscaling from a simulation with the same forcing.
>> But this is not your case where the lateral boundary conditions and the
>> atmospheric forcing are not directly related.
>> Some relaxation at the boundaries might be able to damp these reflections.
>>
>> Dimitris
>>
>>
>> On Mar 17, 2022, at 8:07 AM, kunal madkaiker <kunal.madkaiker02 at gmail.com>
>> wrote:
>>
>> Thank you Dimitris for your reply.
>>
>> Yes, I am prescribing the BCs on 3 sides, and not using a sponge yet.
>> I'll take a look at your suggestion.
>>
>> Thanks,
>> Kunal
>>
>> On Wed, Mar 16, 2022 at 6:27 AM Menemenlis, Dimitris (US 329B) <
>> dimitris.menemenlis at jpl.nasa.gov> wrote:
>>
>>> Hi Kunal, are you “prescribing” the boundary conditions or do you use a
>>> sponge?
>>> If the former, I wonder whether the accumulation of turbulence inside
>>> the domain could be caused
>>> the reflection of circulation features generated or evolved inside the
>>> domain that then
>>> reach the lateral boundaries and are inconsistent with the prescribed
>>> obcs?
>>>
>>> Dimitris
>>>
>>
>>
>> _______________________________________________
>> MITgcm-support mailing list
>> MITgcm-support at mitgcm.org
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>>
>
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