[gradsusr] gradsusr Digest, Vol 75, Issue 29

Sun May 29 12:49:32 EDT 2016

Corey,
I would tend to think the uncommented ZDEF entry should have worked. But
the commented one should have also, unless that line exceeds 255
characters, as specified in the rules for the ZDEF entry of a control file
(see here: http://cola.gmu.edu/grads/gadoc/descriptorfile.html#ZDEF).

Did you mess around with adding "options pascals"? Also, what is your
dtype? It might help if you attached your control file text for
troubleshooting.

Jeff

On Sun, May 29, 2016 at 11:25 AM, Corey Gabriel <cjgabriel7 at gmail.com>
wrote:

> Hi Jeff.
>
> Thanks.  Fortunately I was able to use a couple of other tools to perform
> the calculations
>
> I did try plotting the data with an arbitrary set of vertical levels.
> That leads to an error message stating that ZDEF is now an invalid
> description file record.  Even though I was able to handle this elsewhere,
> I would still like to understand what I am doing wrong with GrADS.  I have
> copied the dimension records from my data descriptor file below.  To the
> ZDEF entries reflect what you mean by plotting the data with an arbitrary
> set of vertical levels?
>
>
> XDEF lon 288 linear 0 1.25
> YDEF lat 192 linear -90 0.94240837
> ZDEF 26 levels 1000 970 930 850 800 700 600 500 420 370 300 270 230 200
> 160 140 120 100 85 70 50 40 25 15 8 4 (arbitrary z axis values)
> *ZDEF 26 levels 992.556 970.554 929.648 867.160 787.702 696.796 600.524
> 510.455 433.895 368.817 313.501 266.481 226.513 192.539 163.662 139.115
> 118.250 100.514 85.439 70.059 53.114 37.230 23.944625 13.967214 7.388 3.544
> (*values matching the sigma-pressure levels)*
> TDEF time 840 linear 01jan2020 1mo
>
> Thanks again!
> Corey
>
>
> On Sun, May 29, 2016 at 12:00 PM, <gradsusr-request at gradsusr.org> wrote:
>
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>> Today's Topics:
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>>    1. Re: Atmosphere_hybrid_sigma_pressure_coordinate (Jeff Duda)
>>
>>
>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Sun, 29 May 2016 00:16:50 -0500
>> From: Jeff Duda <jeffduda319 at gmail.com>
>> Subject: Re: [gradsusr] Atmosphere_hybrid_sigma_pressure_coordinate
>> To: GrADS Users Forum <gradsusr at gradsusr.org>
>> Message-ID:
>>         <
>> CAAig09BEnghZGYfm3kKgX-JWs9xyPSHBoFk+9P+FcsXs92he4A at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Have you actually tried just plotting the data with an arbitrary set of
>> vertical levels? The values you specify for ZDEF in your control file do
>> not have to exactly match the vertical levels of your data. What really
>> matters is how many vertical levels there are.
>>
>> Now, if you want to start performing calculations such as the spatial
>> average of Q at a specific level like 850 mb, that's a bit more tricky,
>> but
>> as long as you know the structure of the vertical levels, you should be
>> able to calculate it.
>>
>> Jeff Duda
>>
>> On Thu, May 26, 2016 at 12:12 PM, Corey Gabriel <cjgabriel7 at gmail.com>
>> wrote:
>>
>> > Dear gradsusr community,
>> >
>> > I am attempting to create a zonal mean plot of a variable (Q), which has
>> > 26 levels.
>> >
>> > The vertical coordinates are "hybrid sigma pressure."  I have created a
>> > data descriptor file and entered the vertical coordinates in the
>> following
>> > manner: ZDEF 26 levels L1 L2 ... L26.
>> >
>> > I have reviewed the GrADS documentation, and it seems that several
>> > examples suggest that the vertical coordinates should be in pure
>> pressure
>> > coordinates and that GrADS may not read these hybrid coordinates.
>> >
>> > The relevant ncdump infomration is provided below.  Just below the
>> > dimensions, you can see that the formula from which the sigma
>> coordinates
>> > are calculated from actual pressure and surface pressure are provided.
>> >
>> > Has anyone attempted to plot hybrid sigma pressure coordinates in GrADS
>> > before?  If so, would someone be able to provide an explanation of how
>> to
>> > convert the vertical coordinate into something GrADS will read?
>> >
>> > Thanks so much!
>> > Corey
>> >
>> > ncdump -c q.corey30.001.cam.2020-01-2089-12.nc
>> >
>> > netcdf q.corey30.001.cam.2020-01-2089-12 {
>> >
>> > dimensions:
>> >
>> > lev = 26 ;
>> >
>> > time = UNLIMITED ; // (840 currently)
>> >
>> > lat = 192 ;
>> >
>> > lon = 288 ;
>> >
>> > nbnd = 2 ;
>> >
>> > variables:
>> >
>> > double lev(lev) ;
>> >
>> > lev:long_name = "hybrid level at midpoints (1000*(A+B))" ;
>> >
>> > lev:units = "level" ;
>> >
>> > lev:positive = "down" ;
>> >
>> > lev:standard_name = "atmosphere_hybrid_sigma_pressure_coordinate" ;
>> >
>> > lev:formula_terms = "a: hyam b: hybm p0: P0 ps: PS" ;
>> >
>> > double time(time) ;
>> >
>> > time:long_name = "time" ;
>> >
>> > time:units = "days since 2004-01-01 00:00:00" ;
>> >
>> > time:calendar = "noleap" ;
>> >
>> > time:bounds = "time_bnds" ;
>> >
>> > double lat(lat) ;
>> >
>> > lat:long_name = "latitude" ;
>> >
>> > lat:units = "degrees_north" ;
>> >
>> > double lon(lon) ;
>> >
>> > lon:long_name = "longitude" ;
>> >
>> > lon:units = "degrees_east" ;
>> >
>> > double time_bnds(time, nbnd) ;
>> >
>> > time_bnds:long_name = "time interval endpoints" ;
>> >
>> > float Q(time, lev, lat, lon) ;
>> >
>> > Q:mdims = 1 ;
>> >
>> > Q:units = "kg/kg" ;
>> >
>> > Q:long_name = "Specific humidity" ;
>> >
>> > Q:cell_methods = "time: mean" ;
>> >
>> >
>> > // global attributes:
>> >
>> > :Conventions = "CF-1.0" ;
>> >
>> > :source = "CAM" ;
>> >
>> > :case = "corey30" ;
>> >
>> > :title = "UNSET" ;
>> >
>> > :logname = "cgabriel" ;
>> >
>> > :host = "ys0861" ;
>> >
>> > :Version = "$Name$" ;
>> >
>> > :revision_Id = "$Id$" ;
>> >
>> > :initial_file =
>> >
>> "/glade/p/acd/tilmes/inputdata/init/ccmi/b.e11.TSREFC2.f19.f19.ccmi23.1deg_26L.001"
>> > ;
>> >
>> > :topography_file = "/glade/p/cesmdata/cseg/inputdata/atm/cam/topo/
>> > USGS-gtopo30_0.9x1.25_remap_c051027.nc"
>> >
>> > _______________________________________________
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>> > gradsusr at gradsusr.org
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>> >
>> >
>>
>>
>> --
>> Jeff Duda
>> Graduate research assistant
>> University of Oklahoma School of Meteorology
>> Center for Analysis and Prediction of Storms
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-- 
Jeff Duda
Graduate research assistant
University of Oklahoma School of Meteorology
Center for Analysis and Prediction of Storms
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