[MITgcm-support] Need assistance for tuning currents in the physical model

[Matthew Mazloff]

Hi Kunal

Not sure about the plots, but I strongly suspect that you may have OBCS problems. Looks like you may have a waveguide along the boundary…
Try plotting w variance and see if the open boundaries light up. If you have a wave guide and enhanced vertical exchange you will begin to change the stratification in your entire domain 

A few things
1) where did you get this data.obcs?
 set  useOBCSsponge=.TRUE., and uncomment (and likely adjust) 
# Urelaxobcsinner=172800.E0,
# Urelaxobcsbound=172800.E0,
# Vrelaxobcsinner=172800.E0,
# Vrelaxobcsbound=172800.E0,
# spongeThickness=04,
I don’t have experience with orlanski…not sure about it. 

2) You are not prescribing any T, S, U, V on the boundary? That is what your data.obcs shows….if that is true that is why your currents look poor. The open boundaries are vital to get correct for your domain as oscar shows you have a strong through flow

3) you really should make the bathymetry flat in the open boundary restoring region. Otherwise prescribing normal velocity is equivalent to prescribing vertical velocity as well, via divergence, and you don’t want spurious vertical velocity

4) I prefer to set tangential velocity to zero on the boundary, otherwise you do need to prescribe a divergence somewhere….Also setting tangential = 0 damps waves

-Matt


> On Jul 8, 2020, at 9:06 PM, Dimitris Menemenlis <dmenemenlis at gmail.com> wrote:
> 
> Hi Kunal, impressive start!
> 
> It’s best if you keep discussion in MITgcm-support, however,
> that way other MITgcm users might contribute to or benefit from the discussion.
> 
> So you have no river runoff?  Could that explain the lack of low salinity region south of Gulf of Khambhat?
> 
> And you are not specifying currents at the open boundaries?  Could that explain, in part, the differences with OSCAR?
> 
> I have no explanation for the warm SST bias.  Which bulk formulae are you using?
> Or maybe there is a problem in your surface boundary conditions, e.g., wrong time of year?
> Or could you have chosen an anomalously warm year to simulate?
> Remember that WOA is a really weird multi-year space-time average.
> So comparing one month of your model simulation with WOA will not necessarily match.
> 
> D.
> 
> 
>> On Jul 8, 2020, at 8:45 PM, kunal madkaiker <kunal.madkaiker02 at gmail.com <mailto:kunal.madkaiker02 at gmail.com>> wrote:
>> 
>> Hello Matt and Dimitris
>> 
>> Thanks a lot to you both for introducing me to MITgcm_contrib. I am sorry for not knowing it since I have just started my modeling research work with MITgcm.
>> I would like to share with you my model simulation output plot for temperature and salinity. Kindly let me know your thoughts.
>> Simulated current profile isnt coming good, as expected.
>> 
>> Also, attaching my data files and SIZE.h. Thanks once again.
>> 
>> Kunal
> 

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