[MITgcm-support] [SPAM] Re: [SPAM] Re: [SPAM] Re: FW: Diagnose momentum equation

Sun Oct 4 03:03:12 EDT 2015

Hi Jean-Michel：

Thank you so much for your help, your comments are really helpful.
One more thing, does "U/Vm_Advec" also include "U/Vm_Cori" in flux-form momentum equation ?
Cheers
Lianzhan

From: Jean-Michel Campin
Date: 2015-10-01 05:57
To: mitgcm-support
Subject: [SPAM] Re: [MITgcm-support] [SPAM] Re: [SPAM] Re: FW: Diagnose momentum equation
Hi Lianzhan,

Few comments here:
1) One thing that I woud suggest to try is to also output the statistics of
the same diagnostics you already output in 3-D.
It's easy to do from the 2nd namelist "DIAG_STATIS_PARMS" in file "data.diagnostics",
e.g.:
&DIAG_STATIS_PARMS
diagSt_mnc = .FALSE.,
#--
stat_fields(1:13,1) = 'ETAN    ','THETA   ','SALT    ',
                       'UVEL    ','VVEL    ','WVEL    ',
                       'Um_Advec','Um_Cori ','Um_dPHdx',
                       'Vm_Advec','Vm_Cori ','Vm_dPHdy',
                       'Um_AdvRe',
  stat_fName(1) = 'dynStDiag',
   stat_freq(1) = -86400.,
  stat_phase(1) = 0.,
&
and this will produce an ASCII file with the per level statistics 
and global staticstics (min,max,mean and standard-deviation) for 
each of the stat_fields in the list.

Since these stats are computed from the same place as the 3-D diagnostics
are filled up, it's a simple & quick way to check:
1) if a diagnostics is really filled up ; if not, a warning message
  is printed and the "Volume" column indicates "0."
  For instance here this will happen with diagnostics "Um_AdvRe"
  which is specific to pkg/mom_vecinv, not used in your case (the
  default is to use pkg/mom_fluxform) 
2) which levels are filled up (by checking the "Volume" column)
3) the precise min/max for each level.

2) I noticed in your "data" file:
tRef=20.,
but since Nr > 1, it would be safer to specify something like:
tRef=31*20.,
(assuming Nr=31)

3) regarding some momentum diagnostics:
a) there is no specific diagnostics for "-gravity * Grad( SSH )" term
   since it's a linear term (time-mean of gradient = gradient of mean SSH)
   which can easily be computed from SSH output (Eta).
b) "U/Vm_Advec" does include the Coriolis acceleration (U/Vm_Cori)
   (except if using the CD-scheme): the reason is that in vector-invariant,
   advection and coriolis can be (partly) combined.
c) some momentum diagnostics are specific to one momumtum formulation, e.g.:
  only in vector-invariant: Um_AdvRe, Um_AdvZ3 
  only in flux-form: ADVx_Um, ADVy_Um, ADVrE_Um

Cheers,
Jean-Michel

On Tue, Sep 29, 2015 at 08:28:49AM +0800, lianzhan at fio.org.cn wrote:
> Hi Jean-Michel
> 
> I am sorry, maybe you can find the attachments this time. 
> 
> In this set-up, the barotropic model is driving by wind stress on sea surface.
> 
> Thanks again.
> 
> Cheers
> 
> Lianzhan
>  
> From: Jean-Michel Campin
> Date: 2015-09-29 01:57
> To: mitgcm-support
> Subject: [SPAM] Re: [MITgcm-support] [SPAM] Re: FW: Diagnose momentum equation
> Hi Lianzhan,
>  
> Two quick things:
> 1)
> > The attachements are "data" and "dada.pkg" files of my exp. 
> I did not find these attached files. Are you sure you really included them ?
>  
> 2)
> > What type of forcing do you have in this set-up ?
> An answer to this question would be useful.
>  
> Cheers,
> Jean-Michel
>  
> On Mon, Sep 28, 2015 at 05:44:07PM +0800, lianzhan at fio.org.cn wrote:
> > Hi Jean-Michel:
> > 
> > Thank you so much for your help!
> > 
> > The attachements are "data" and "dada.pkg" files of my exp. 
> > 
> > About U/Vm_dPHdx, I think you are right. But in this exp, I have used Non-linear free-surface and apply free surface effect to column total thickness (implicSurfPress = 0.5 & nonlinFreeSurf=4 ...). So how could I output the pressure anomaly horizontal gradient caused by the fluctuation on sea surface?
> > 
> > I am still trying to figure out what happen with U/Vm_Cor and U/Vm_Advec. Does "U/Vm_Advec" respresent the "UdU/dx+VdU/dy+WdU/dz" term in momentum equation? What is the different between "U/Vm_Advec" and "U/Vm_AdvZ3"?
> > 
> > Thanks again!
> > 
> > Cheers
> > 
> > Lianzhan
> > 
> >  
> > From: Jean-Michel Campin
> > Date: 2015-09-26 23:19
> > To: mitgcm-support
> > Subject: [SPAM] Re: [MITgcm-support] FW: Diagnose momentum equation
> > Hi Lianzhan,
> >  
> > It's likely that if Temp & Salt remains uniform, U/Vm_dPHdx will be zero
> > (no hydrostatic pressure anomaly horizontal gradient).
> > Not very clear why U/Vm_Cori would be zero everywhere except for surface level,
> > unless the velocity (uVel,vVel) is also zero everywhere below k=1.
> >  
> > What type of forcing do you have in this set-up ?
> >  
> > If you could send (in attachement) the 2 parameter files "data" and
> > "data.pkg", this would help to figure out what is happening.
> >  
> > Cheers,
> > Jean-Michel
> >  
> > On Sat, Sep 26, 2015 at 01:27:27PM +0000, lianzhan wrote:
> > > Hello everyone
> > > 
> > > I want to diagnose the effect of all items in momentum equation (as below for zonal).
> > > dU/dt+UdU/dx+VdU/dy+WdU/dz=fv-1/rho*dP/dx+Fx+taux/rho
> > > Fx is dissipative stress, taux is wind stress. Is there any corresponding variable in pkg/diagnostics ? I have tried "U/Vm_Advec" for nonlinear term, but this variable is zero expect for the surface layer. Its value is as same as "U/Vm_Cori", the value of "U/Vm_Cori" is also zero below surface. And "U/Vm_dPHdx"(pressure gradient force ? ) is all zero.
> > > The settings of my exp is that there is an island located in an ideal rectangular bay,  near which there is a sill. The model has 32 vertical layers and with free surface. The Temp/Salt is uniform. 
> > > Do you have any recommendations or suggestions?
> > > Thanks in advance for your helpCheers,Lianzhan
> > > 
> > > 
> > > xiaober at outlook.com
> > > 
> > >             
> >  
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