[MITgcm-support] generate a stable current field

guopu at scsio.ac.cn guopu at scsio.ac.cn
Tue Jul 7 18:12:30 EDT 2015


Hi Matt,

Thanks for your reply. I did not enable exf and cal packages, I'll try it now.

By the way, should I ensure the value of "obcsWstartdate1" in data.exf is same as value of "startDate_1" in data.cal ?

Best,

Pu





> 
> Hi Pu
> 
> (1) and (2) seem correct. But you have to define the  obcs time period:
> obcsWperiod         =  86400,
> in data.exf.
> 
> Do you have the cal and exf packages enabled? I am not sure if having a time variable obcs is possible without them?
> 
> Unfortunately there is no verification experiment exactly like what you want, but these may help:
> 
> verification/obcs_ctrl
> verification/seaice_obcs
> 
> Matt
> 
> 
> On Jul 5, 2015, at 2:13 PM, <guopu at scsio.ac.cn> wrote:
> 
> > Hello Sir,
> > 
> > I feel the OBCS package is so complicate, so I start from generating a simple current field to understand this package. Now I have 3 questions:
> > 
> > 1. I build a 2D region with uniform depth 1000m, and set OB_Iwest=1, OB_Ieast=-1. Now I am wondering how to generate a stable barotropic current in this region. The only effective way I found is to use files containing uniform velocity for parameters: "uVelInitFile", "OBWuFile", and "OBEuFile". Is it right? or is there another "standard procedure" ?
> > 
> > 2. I want to generate above current field by only one prescribe file for "OBWuFile", so I make this (1*Nr*50)-dimension file with gradually increased velocity, from 0 (or 0.01) to 0.1m/s in 50 "time levels". However, the model results show that U at west boundary keep to be zero (or 0.01m/s). What could be the reason for this? and what is the meaning of "time levels"?
> > 
> > 3. I add a Gaussian shape obstacle on the bottom and hope to see what will happen in this region. Should I turn on one or some of these flags: useOBCSsponge, useOrlanskiEast/West, useOBCS_balance? I thought the "OB_Iwest=1, OB_Ieast=-1" would be enough to let water/waves flow/propagate out freely.
> > 
> > Studying this package has cost me several weeks, I am hungry for help, thanks!
> > 
> > Pu
> > 
> > 
> > 
> > 
> > 
> > 
> > 
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
> 
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Hi Jody,

Thanks. Keeping cal and exf packages unable, I add:

periodicExternalForcing=.TRUE.,
externForcingPeriod=600.,
externForcingCycle=1800.,

in the "data" file, and expect the velocity at west boundary will increase during 600s from 0 to 0.1m/s, as specified in OBWuFile. However, first: It seems that only the first two values in OBWuFile are valid, west boundary velocity changed linearly between the two values; second: the velocity at starttime (in file U.0000000000.001.001.data) is not equal to the first or second value in OBWuFile, but a value between them, and then this velocity decrease to the first value then increase to the second value with time going. I use many different values of "time levels" and "externForcingCycle", but it always do as above.

I note the case verification/exp4 has the similar set at boundary condition, it works well. I do not know what I do wrong.

In addition, I am not quite understand this sentence "if you want a ramp to a steady forcing in time, you want to make sure this value is quite large, and you will have to set a relatively large number of fields in your external forcing function". Do you mean I need to do much more work to establish the model in your 2010's paper?

Best

Pu





> 
> Hi Pu,
> 
> I set these times in ?data?:
> 
> periodicExternalForcing=.TRUE.,
> externForcingPeriod=1860.,
> externForcingCycle=44640.,
> 
> (this has 24 equally spaced forcings).  So, you need to specify these in your file.  However, note that it is periodic in ?externForcingCylce? so if you want a ramp to a steady forcing in time, you want to make sure this value is quite large, and you will have to set a relatively large number of fields in your external forcing function.  
> 
> I think if you don?t set these, the default is ?0? which means the OBWuFile is read as being a constant boundary condition (i.e. just the first 1*NR values are read).  
> 
> > On 6 Jul 2015, at  11:37 AM, Matthew Mazloff <mmazloff at ucsd.edu> wrote:
> > 
> > Unfortunately there is no verification experiment exactly like what you want, but these may help:
> 
> Hmm, yes, verification/internal_wave could be re-done to force the boundary using obcs or rbcs instead of hardcoding, which is what it does now.  If I have some spare time I?ll submit a modification to the devs.
> 
> Cheers,  Jody
> 
> 
> 
> > verification/obcs_ctrl
> > verification/seaice_obcs
> > 
> > Matt
> > 
> > 
> > On Jul 5, 2015, at 2:13 PM, <guopu at scsio.ac.cn <mailto:guopu at scsio.ac.cn>> wrote:
> > 
> >> Hello Sir,
> >> 
> >> I feel the OBCS package is so complicate, so I start from generating a simple current field to understand this package. Now I have 3 questions:
> >> 
> >> 1. I build a 2D region with uniform depth 1000m, and set OB_Iwest=1, OB_Ieast=-1. Now I am wondering how to generate a stable barotropic current in this region. The only effective way I found is to use files containing uniform velocity for parameters: "uVelInitFile", "OBWuFile", and "OBEuFile". Is it right? or is there another "standard procedure" ?
> >> 
> >> 2. I want to generate above current field by only one prescribe file for "OBWuFile", so I make this (1*Nr*50)-dimension file with gradually increased velocity, from 0 (or 0.01) to 0.1m/s in 50 "time levels". However, the model results show that U at west boundary keep to be zero (or 0.01m/s). What could be the reason for this? and what is the meaning of "time levels"?
> >> 
> >> 3. I add a Gaussian shape obstacle on the bottom and hope to see what will happen in this region. Should I turn on one or some of these flags: useOBCSsponge, useOrlanskiEast/West, useOBCS_balance? I thought the "OB_Iwest=1, OB_Ieast=-1" would be enough to let water/waves flow/propagate out freely.
> >> 
> >> Studying this package has cost me several weeks, I am hungry for help, thanks!
> >> 
> >> Pu
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> 
> >> _______________________________________________
> >> MITgcm-support mailing list
> >> MITgcm-support at mitgcm.org <mailto:MITgcm-support at mitgcm.org>
> >> http://mitgcm.org/mailman/listinfo/mitgcm-support
> > 
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
> 
> --
> Jody Klymak    
> http://web.uvic.ca/~jklymak/
> 
> 
> 
> 
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