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[IDV #COD-764409]: GrADS ctl with Height (in km) as vertical scale

Hi Stefan-

> Thanks very much! I will upload a small data set in height coordinates 
> tomorrow when I can post process one time step into the dat/ctl pair 
> (otherwise files are way too big).

I put a test ncIdv.jar at:

http://motherlode.ucar.edu/repository/entry/get/ncIdv.jar?entryid=f8d488e4-a3e7-4031-a015-2211f8d1b970

Download that and place it in the IDV installation directory (back up the 
existing one first).  Then add:

@ zdef String units km

to your ctl file.  Make sure there is a space between the "@" and "zdef".

Let me know if you have any problems with this.

Don
> Stefan Cecelski
> Ph.D. Candidate and Graduate Research Assistant
> AOSC Department: University of Maryland College Park
> 2343 Computer and Space Sciences Building(CSS #224)
> 703.801.1370
> address@hidden
> 
> 
> 
> 
> 
> On Feb 22, 2012, at 6:50 PM, Unidata IDV Support wrote:
> 
> > Hi Stefan-
> >
> >> What you suggest is ideal. Another idea I have is similar to how you 
> >> delineate hPa from Pa using an if statement. What if you have another if 
> >> statement that says if values < 30 (or some other #), then the ZDEF has 
> >> units of km and to use height coordinates while opening it up? The only 
> >> issue that will arise with this is if people have grads files for 
> >> stratospheric purposes, with pressures between 50 and 10 hPa. But I am not 
> >> sure how many people you will encounter with this problem! Let me know if 
> >> there is anything I can do on my end.
> >
> > Right now, if the level values are less than 10, it sets the units to be "" 
> > which probably comes out as null, but should come out as unitless.  I don't 
> > have a dataset to test this with but I'm sure I did that because I found 
> > some dataset that just had level numbers.  So, I'm reluctant to change that 
> > to km because I'm sure I did it for a reason and the proposed solution 
> > (which I coded and tested this afternoon) would all the user to specify 
> > whatever units they want for the vertical dimension.
> >
> > I'll work on getting this into the IDV, but it still might take a while 
> > because the netCDF-Java library is in flux.
> >
> > Don
> >
> >> On Feb 22, 2012, at 3:22 PM, Unidata IDV Support wrote:
> >>
> >>> Hi Stefan-
> >>>
> >>>> GrADS is able to open up the ctl/dat pair just fine using height 
> >>>> coordinates. ZDEF can be either in height or pressure for GrADS ctl 
> >>>> files, even though it typically is in pressure. I think the IDV sees the 
> >>>> ctl file having ZDEF as only having pressure as the only possible 
> >>>> vertical coordinate, while it is possible it can contain heights. So, is 
> >>>> there anyway to add this possibility into how the IDV opens up GrADS ctl 
> >>>> files?
> >>>
> >>> As you note there is nothing in the Grads Data Descriptor File (e.g. ctl 
> >>> file) that specifies the unit of the vertical dimension.  When I wrote 
> >>> the GrADS IOSP, I ran into 3 types of vertical level units - hPa, Pa and 
> >>> none (just a level number).  The default is hPa, but if there are values 
> >>> > 1050, I switch to Pa.
> >>>
> >>> Since GrADS is pretty loosey goosey about what can go in a ctl file, one 
> >>> thing we could do is use the attribute metadata 
> >>> (http://www.iges.org/grads/gadoc/descriptorfile.html#ATTR) to specify the 
> >>> units of the vertical dimension like so:
> >>>
> >>> @ zdef String units meter
> >>>
> >>> What do you think about this?
> >>>
> >>> Could you upload you file to the IDV uploads area so I can have something 
> >>> to test with?  It will probably take a while before this can get into the 
> >>> IDV, but I'll try to work on it when I get a chance.
> >>>
> >>> Don Murray
> >>>
> >>>
> >>>> On Feb 22, 2012, at 11:49 AM, Unidata IDV Support wrote:
> >>>>
> >>>>> Hi Stefan.
> >>>>>
> >>>>> First off, sorry for the delayed response. We have been attending 
> >>>>> conferences and giving workshops.
> >>>>>
> >>>>> We believe the GrADS spec is not being adhered to. As far as we can 
> >>>>> tell, GrADS expects levels to be defined as pressure (not KMs). We 
> >>>>> don't think the IDV can help here until the ctl and data file are fixed.
> >>>>>
> >>>>> Best,
> >>>>>
> >>>>> Unidata IDV Support
> >>>>>
> >>>>>
> >>>>>> Full Name: Stefan Cecelski
> >>>>>> Email Address: address@hidden
> >>>>>> Organization: University of Maryland
> >>>>>> Package Version: 3.0u2 build date:2012-02-08 08:06 UTC
> >>>>>> Operating System: Mac OS X
> >>>>>> Hardware: Java: home: 
> >>>>>> /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home 
> >>>>>> version: 1.6.0_29 j3d:1.5.2 fcs (build4)
> >>>>>> Description of problem: Hi all,
> >>>>>>
> >>>>>> I recently converted my wrf output to height levels via ARWpost to 
> >>>>>> create a grads ctl/dat pair. When I open the ctl file (attached) in 
> >>>>>> IDV, the vertical levels are automatically presumed as pressure 
> >>>>>> levels, even though the levels are height above ground in km. Is there 
> >>>>>> anyway to trick the IDV in to seeing the levels as height levels 
> >>>>>> instead of pressure levels?  The advantage of using height levels is 
> >>>>>> evenly spaced vertical cross-sections via a transect view. However, 
> >>>>>> since the IDV sees the levels as pressure levels, all the data is not 
> >>>>>> viewable in the traditional transect view display because the 
> >>>>>> pressures are all between 0 and 20 hPa! Thanks for any advice you 
> >>>>>> might have.
> >>>>>>
> >>>>>> V/R,
> >>>>>>
> >>>>>> Stefan
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>>> Ticket Details
> >>>>> ===================
> >>>>> Ticket ID: COD-764409
> >>>>> Department: Support IDV
> >>>>> Priority: Normal
> >>>>> Status: Closed
> >>>>>
> >>>>
> >>>>
> >>>>
> >>>
> >>>
> >>> Ticket Details
> >>> ===================
> >>> Ticket ID: COD-764409
> >>> Department: Support IDV
> >>> Priority: Normal
> >>> Status: Open
> >>>
> >>
> >>
> >>
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: COD-764409
> > Department: Support IDV
> > Priority: Normal
> > Status: Open
> >
> 
> 
> 


Ticket Details
===================
Ticket ID: COD-764409
Department: Support IDV
Priority: Normal
Status: Open