[Support #ZDT-182699]: PV in IDV

Hi Jim-

> I'm clueless still.  I looked at some of my GFS scripts and didn't
> notice anything weird with the sign, but I wrote them along time ago, so
> it's a bit like reading french.  Perhaps the vertical indicies are
> switched?  I'm grasping at straws.

Me too. ;-)  It looks like dtheta/dp is coming up with inverse signs.  I'm 
trying to track that down now.

> At least now I can do a 3-D demo for the students.  Thanks!

At least that's a positive!  Thanks for your help in tracking this down.

Don
> Unidata IDV Support wrote:
> > 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
> >
> >
> 
> 


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