[Support #ZDT-182699]: PV in IDV

Hi Jim-

> I've plotted up the nam211 and the GFS 80 km (I can't recall the
> grid number).  The nam *looks* correct.  The GFS *looks* correct with
> the sign error that you mention below.

Oh, good, it's not just me. ;-)

> I'm at a loss for the cause of the sign error in the GFS.  In the
> southern hemisphere, the PV *would* be negative.  Why it is in the NH I
> don't know.  The absolute vorticity calculated from U_wind and v_wind
> looks correct and this is what determines the sign of the PV normally.
> About all I can think of is that there is some weird convention in the
> NCEP grids (like gravity being negative).

Yeah, I'll try to look more closely at the individual grids.

> Are you doing a conversion to isentropic coordinates for this or
> just using the pressure coordinate absolute vorticity?

No, I'm using the calculated THTA from T and P and the calculated AVOR from U 
and V.  The existing absolute vorticity grid is only 3 levels.

Thanks for checking that at least it looks reasonable (except for the sign).  
I'll dig deeper.  It's probably something simple, but for the life of me I 
can't figure out what.  Maybe it is something to do with the latitude if it 
should be negative in the SH.

Have a great weekend!

Don

 Unidata IDV Support wrote:
> > Hi Jim-
> >
> >
> >> That's interesting.  I haven't had a chance to download the latest
> >> build yet.  Is last nights OK except for the sign error?  Send me the
> >> URL again.
> >>
> >
> > Last night's is okay except for the sign error.  You can grab it at:
> >
> > http://www.unidata.ucar.edu/downloads/idv/nightly/
> >
> > Don
> >
> >
> >
> >> Unidata IDV Support wrote:
> >>
> >>> Hi Jim-
> >>>
> >>> I have a met question for you.  If I negate the grid for the GFS, I get 
> >>> what I would consider as correct results.  However, for the NAM, the 
> >>> values are then wrong.
> >>>
> >>> If you download the nightly build and run the Displays->Favorite 
> >>> Bundles->NAM211->Isentropic Potential Vorticity bundle, you should get a 
> >>> reasonable depiction.  Can you confirm this?
> >>>
> >>> However, if you do a GFS isosurface, the values are negated.  If you set 
> >>> the isosurface value to -2, it should look like the NAM 2 IPVunit 
> >>> surface.   The GEMPAK formula is:
> >>>
> >>> -GRAVTY*AVOR(V)*dTheta/dP
> >>>
> >>> There was a note in the code that using the - gives the wrong values, but 
> >>> I'm stumped as to way it works with one grid and not the other. Both are 
> >>> GRIB1, both have a vertical dimension of P in hectopascals.  Any thoughts 
> >>> on this?
> >>>
> >>> I'll keep looking into it, but thought I'd turn to a professional for 
> >>> some advice.
> >>>
> >>> In the meantime, you can just use the -2 isosurface for the GFS. ;-)
> >>>
> >>> Don
> >>>
> >>>
> >>>
> >>>>> I was trying to plot an isosurface.  That "works", but the result is
> >>>>> best described as "gobbledygook."  The ability to do a 2 PVU isosurface
> >>>>> is really powerful for teaching PV thinking.  That's when I noticed the
> >>>>> error.
> >>>>>
> >>>>>
> >>>> I found one error which was that absolute vorticity was being calculated 
> >>>> incorrectly.  That will be fixed in the nightly build.  However, I'm now 
> >>>> trying to get IPV correct. I compared the results from GEMPAK and they 
> >>>> match.
> >>>>
> >>>> However, IPV is even worse now. :-( I'll have to do some plan view plots 
> >>>> in GEMPAK to compare with since I don't have any other program to show 
> >>>> what the isosurface should look like.
> >>>>
> >>>> Thanks for your patience.
> >>>>
> >>>> Don
> >>>>
> >>>>
> >>>>
> >>>>> Unidata IDV Support wrote:
> >>>>>
> >>>>>
> >>>>>> Hi Jim-
> >>>>>>
> >>>>>> I've moved this to the support system.  Best to send questions to 
> >>>>>> support-idv instead of me directly so we can better track these issues.
> >>>>>>
> >>>>>> Thanks for catching this. Did this ever work?  I've always done this 
> >>>>>> as a volume since IPV needs several levels. If you select 2 (or more) 
> >>>>>> levels in the levels panel, you'll be able to do the slice for a plan 
> >>>>>> view.  However, the list of levels in the control will not reflect the 
> >>>>>> levels you selected, but the entire list of levels.  We're working on 
> >>>>>> a fix to this.
> >>>>>>
> >>>>>> Don
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>> ERROR: Creating display: Contour Plan View
> >>>>>>> org.python.core.PyException
> >>>>>>> Traceback (innermost last):
> >>>>>>> File "<string>", line 1, in ?
> >>>>>>> at visad.FlatField.derivative(FlatField.java:4044)
> >>>>>>> at visad.FlatField.derivative(FlatField.java:4485)
> >>>>>>> at
> >>>>>>> ucar.unidata.data.grid.DerivedGridFactory.partial(DerivedGridFactory.java:2366)
> >>>>>>> at
> >>>>>>> ucar.unidata.data.grid.DerivedGridFactory.createIPV(DerivedGridFactory.java:1954)
> >>>>>>> at
> >>>>>>> ucar.unidata.data.grid.DerivedGridFactory.createIPV(DerivedGridFactory.java:1880)
> >>>>>>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> >>>>>>> at
> >>>>>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> >>>>>>> at
> >>>>>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> >>>>>>> at java.lang.reflect.Method.invoke(Method.java:597)
> >>>>>>>
> >>>>>>> visad.VisADException: visad.VisADException: derivative: d_partial_s 
> >>>>>>> not
> >>>>>>> in domain or reference
> >>>>>>> ERROR: Creating display: Contour Plan View
> >>>>>>> org.python.core.PyException
> >>>>>>> Traceback (innermost last):
> >>>>>>> File "<string>", line 1, in ?
> >>>>>>> at visad.FlatField.derivative(FlatField.java:4044)
> >>>>>>> at visad.FlatField.derivative(FlatField.java:4485)
> >>>>>>> at
> >>>>>>> ucar.unidata.data.grid.DerivedGridFactory.partial(DerivedGridFactory.java:2366)
> >>>>>>> at
> >>>>>>> ucar.unidata.data.grid.DerivedGridFactory.createIPV(DerivedGridFactory.java:1954)
> >>>>>>> at
> >>>>>>> ucar.unidata.data.grid.DerivedGridFactory.createIPV(DerivedGridFactory.java:1880)
> >>>>>>> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> >>>>>>> at
> >>>>>>> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> >>>>>>> at
> >>>>>>> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> >>>>>>> at java.lang.reflect.Method.invoke(Method.java:597)
> >>>>>>>
> >>>>>>> visad.VisADException: visad.VisADException: derivative: d_partial_s 
> >>>>>>> not
> >>>>>>> in domain or reference
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>> Ticket Details
> >>>>>> ===================
> >>>>>> Ticket ID: ZDT-182699
> >>>>>> Department: Support IDV
> >>>>>> Priority: Normal
> >>>>>> Status: Open
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>> Ticket Details
> >>> ===================
> >>> Ticket ID: ZDT-182699
> >>> Department: Support IDV
> >>> Priority: Normal
> >>> Status: Open
> >>>
> >>>
> >>>
> >>
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: ZDT-182699
> > Department: Support IDV
> > Priority: Normal
> > Status: Open
> >
> >
> 
> 


Ticket Details
===================
Ticket ID: ZDT-182699
Department: Support IDV
Priority: Normal
Status: Open