[MITgcm-support] External forcing for deltaT < 1 sec

[linzhenhua]

Hi,

The parameters seem fine to me. I do not know what you plan to model with this two-dimensional configuration, as you use Orlanski in the west boundary, forced flow at the east boundary, perhaps these obc values are altered internally since you have also enabled OBCSbalance.

As a step to validate the model should work with small time step, I advise you first try a forced-inflow and forced-outflow case. If the velocity field in your OBEU_hr.bin file is time dependent, could you first try this file as both easy and west obc condition to check whether you could get the consistent time-dependent velocity field?





--
Zhenhua Lin
Key Laboratory of Ocean Circulation and Waves (KLOCAW)
Institute of Oceanology
Chinese Academy of Sciences
Nanhai Road 7
Qingdao 266071
PR China

At 2014-04-12 09:35:28,"Dustin Carroll" <dcarroll at uoregon.edu> wrote:
Hi,


Thanks for getting back to me, good to know that it should work. I have only used the periodicExternalForcing for wind stress before so perhaps I am setting it up wrong with OBCS. 


Here is how I am setting it up in data for forcing hourly for 30 days.


 periodicExternalForcing=.TRUE.,
 externForcingPeriod=3600.,
 externForcingCycle=2592000.,


Here is my data.obcs file, the bin files contain 720 records (2592000/3600).


# ***************
# Open boundaries
# ***************
 &OBCS_PARM01
 OB_Iwest  =   1*1,
 OB_Ieast  =   1*-1,
 useOBCSprescribe=.TRUE.,
 useOrlanskiWest=.TRUE.,
 useOBCSbalance=.TRUE.,


 OBEtFile='OBET_hr.bin',
 OBEsFile='OBES_hr.bin',
 OBEuFile='OBEU_hr.bin'


 OBWtFile='OBWT_hr.bin',
 OBWsFile='OBWS_hr.bin',


 OBCS_monitorFreq= 3600.,
 OBCS_monSelect = 3,
 &


 &OBCS_PARM02
 &


Just want to check I’m setting this up right — perhaps I am missing a flag somewhere. Everything is running properly with a static BC setup.


Best,
Dustin






On Apr 11, 2014, at 6:20 PM, linzhenhua <linzhenhua at 163.com> wrote:


Hi  Dustin,
I have used this method for high resolution simulation forced with obc, and the results seem reasonable for me. The time step in my configuration is 0.5s.





At 2014-04-12 04:09:57,"Dustin Carroll" <dcarroll at uoregon.edu> wrote:
>Hi All,
>
>I am running some high-resolution experiments where the time step is < 1 second and I need to have time dependent boundary conditions. 
>
>Normally I use EXF for this, but for these experiments I can’t because the cal pkg doesn’t support deltaT < 1. 
>
>I tried using the basic periodicExternalForcing but that didn’t properly loop through my forcing files properly when deltaT < 1. Can anyone confirm that periodicExternalForcing works with deltaT < 1 or recommend a method for time dependent bc's with these small time steps?
>
>Thanks,
>Dustin 
>
>
>
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