[MITgcm-support] phiHydLow

Mon Aug 16 08:55:34 EDT 2004

Benny, Ichiro, are you on the MITgcm support mailing list.  Did you receive
following discussion?  As far as I can gather, computation of phiHydLow is OK.
Also I plotted some diagnostics: http://ecco.jpl.nasa.gov/cube_sphere/PHL/
and they look reasonable.

Dimitris

On Monday 16 August 2004 12:18 am, Martin Losch wrote:
> Hi,
> 
> I extensively used the diagnostic of phyHydLow and there were never any 
> problems with it in the MITgcm-code, the masking of the (non-zero) 
> density values below the ocean floor is correct, no reasons to worry. 
> We looked at this closely, because we wanted to compare to the pressure 
> coordinate model, and found everything consistent.
> 
> But here is a small caveat, which does not really affect your 
> discussion:
> unless Jean-Michel has found a miraculous way to do it, I remember that 
> there is no way to consistently diagnose the pressure or phiHyd 
> (perturbation) at the bottom unless you use the (non-conservative) form 
> of the discretization of the phiHyd computations (integr_GeoPot.EQ.1). 
> If you don't use this discretization, phyHydLow will not be 100% 
> consistent, but since this variable is not used for any dynamic 
> computations it shouldn't matter.
> 
> Martin
> 
> On Aug 14, 2004, at 9:40 PM, Chris Hill wrote:
> 
> > In general you need to repect the masks and hfac values appropriately 
> > for
> > any vertical integral. For example depth averaged salinity or vertical 
> > heat
> > content or vertical average temperature etc.... would all come out 
> > awry if
> > you account for land incorrectly. This sounds like the same thing so I 
> > think
> > its not an issue in the prognostic model so much as in making sure 
> > correct
> > formula are implemented for analysis.
> >
> > Chris
> >
> >> -----Original Message-----
> >> From: mitgcm-support-bounces at mitgcm.org
> >> [mailto:mitgcm-support-bounces at mitgcm.org] On Behalf Of
> >> Dimitris Menemenlis
> >> Sent: Saturday, August 14, 2004 8:25 AM
> >> To: mitgcm-support at mitgcm.org
> >> Subject: [MITgcm-support] phiHydLow
> >>
> >> Does anyone have experience in using phiHydLow ?
> >>
> >> Dimitris
> >>
> >> ----------  Forwarded Message  ----------
> >>
> >> Subject: Re: [Fwd: Re: bottom pressure]
> >> Date: Friday 13 August 2004 06:11 pm
> >> From: Ichiro Fukumori <fukumori at jpl.nasa.gov>
> >> To: Dimitris Menemenlis <menemenlis at jpl.nasa.gov>
> >> Cc: Benny Cheng <bcheng at jpl.nasa.gov>, christopher Hill <cnh at mit.edu>
> >>
> >> Dimitris,
> >>
> >> phiHydLow seems to have a bug for it to be ocean bottom pressure.
> >> Benny was able to reproduce phiHydLow offline from TS and ETA
> >> but we found that that calculation had a bug; density is
> >> non-zero below ocean bottom and pressure calculation sums up
> >> the contribution from these non-zero densities below
> >> topography.  The problem is in how values below ocean bottom
> >> are masked.  A similar bug may be present in MITGCM itself.
> >>
> >> -- Ichiro
> >>
> >>> From: Dimitris Menemenlis <menemenlis at jpl.nasa.gov>
> >>> Organization: JPL
> >>> To: Benny Cheng <bcheng at jpl.nasa.gov>
> >>> Subject: Re: bottom pressure
> >>> Date: Fri, 6 Aug 2004 13:39:47 -0700
> >>> User-Agent: KMail/1.6.2
> >>> Cc: Ichiro Fukumori <fukumori at jpl.nasa.gov>,
> >>> dimitri at pacific.jpl.nasa.gov
> >>> References: <5.1.0.14.2.20040806101117.02854ec0 at pacific.jpl.nasa.gov>
> >>>         <1091823500.12635.81.camel at lochness.jpl.nasa.gov>
> >>> In-Reply-To: <1091823500.12635.81.camel at lochness.jpl.nasa.gov>
> >>> MIME-Version: 1.0
> >>> Content-Disposition: inline
> >>> Content-Type: text/plain; charset="utf-8"
> >>> Message-Id: <200408061339.47797.menemenlis at jpl.nasa.gov>
> >>> X-UIDL: 1950fbdc7128ef9d4dfd71bc77ad4489
> >>> Content-Transfer-Encoding: 7bit
> >>>
> >>> On Friday 06 August 2004 01:18 pm, Benny Cheng wrote:
> >>>> how do you enable bottom pressure output on the MITgcm ?
> >>>
> >>> Benny, you need to save the variable
> >>>
> >>> C     phiHydLow  :: Phi-Hydrostatic at r-lower boundary
> >>> C                  (bottom in z-coordinates, top in p-coordinates)
> >>>
> >>> or
> >>>
> >>> C     phiHydLowtave:: Hydrostatic (ocean) pressure / (atmos)
> >> geo- Potential
> >>> C                     at the fixed boundary: (ocean) bottom pressure
> >>> C                     (atmos) geo- Potential
> >>>
> >>> I had disabled the dump of phiHydLowtave in pkg/timeave
> >> using CPP flag
> >>> HRCUBE.  So you can either reenable it there for
> >> time-averaged values,
> >>> or you can dump instantaneous values of phiHydLow directly.
> >>>
> >>> D.
> >>>
> >>> --
> >>> Dimitris Menemenlis <menemenlis at jpl.nasa.gov> Jet Propulsion Lab,
> >>> California Institute of Technology MS 300-323, 4800 Oak Grove Dr,
> >>> Pasadena CA 91109-8099
> >>> tel: 818-354-1656;  fax: 818-393-6720
> >>
> >> ===============================================================
> >> Ichiro Fukumori               | Jet Propulsion Laboratory
> >> e-mail: fukumori at jpl.nasa.gov | Mail Stop 300-323
> >> phone: +1 (818) 354-6965      | 4800 Oak Grove Drive
> >> fax: +1 (818) 393-6720        | Pasadena, California 91109, U.S.A.
> >> ===============================================================
> >>
> >>
> >>
> >> -------------------------------------------------------
> >>
> >> --
> >> Dimitris Menemenlis <menemenlis at jpl.nasa.gov> Jet Propulsion
> >> Lab, California Institute of Technology MS 300-323, 4800 Oak
> >> Grove Dr, Pasadena CA 91109-8099
> >> tel: 818-354-1656;  fax: 818-393-6720
> >> _______________________________________________
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> >> MITgcm-support at mitgcm.org
> >> http://dev.mitgcm.org/mailman/listinfo/mitgcm-support
> >>
> >
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> 
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-- 
Dimitris Menemenlis <menemenlis at jpl.nasa.gov>
Jet Propulsion Lab, California Institute of Technology
MS 300-323, 4800 Oak Grove Dr, Pasadena CA 91109-8099
tel: 818-354-1656;  fax: 818-393-6720