[gradsusr] Problem Displaying Templated Multiple File Data

Tue Aug 30 17:52:42 EDT 2011

Hi Jennifer,

I did a "q attr" check on the 1948 file and found this:
air Float32 add_offset 512.81
air Float32 scale_factor 0.01

Trying to follow example in the GrADS documentation and a few
trial-and-error runs, here's my revised descriptor:

DSET h:\cdf\dailymeans\air.sig995.%y4.nc
TITLE Daily Air Temperature Sig995 01Jan1948-current
DTYPE netcdf
OPTIONS template yrev
UNDEF -9.99e+33
UNPACK scale_factor add_offset 512.81
XDEF 144 linear 0 2.5
YDEF 73 linear -90 2.5
ZDEF 1 linear 0 1
TDEF 3653 linear 01jan1948 1dy
VARS 1
air=>tmp 0 t,y,x  Mean Daily Air Temperature at sigma level 995 (degK)
ENDVARS

Initially, after re-running, the numbers looked "okay" (a reasonable range)
but I noticed they were upside-down mirror images of what I got using yearly
files separately.  So I added the "yrev" OPTIONS keyword and that appears to
have fixed it.

I believe everything works correctly now, so thanks for pointing me in the
right direction!

Stephen McMillan

On Tue, Aug 30, 2011 at 4:40 PM, Jennifer Adams <jma at cola.iges.org> wrote:

> Looks like you need the UNPACK entry in your descriptor file. Check your
> netcdf files for scale_factor and add_offset attributes.
> --Jennifer
>
> On Aug 30, 2011, at 4:31 PM, Stephen McMillan wrote:
>
> I am having a problem correctly displaying multiple file data using a
> template control file.  My objective is to open, for example, the set of
> daily air temperature data files (in yearly files) from 1948 to current as a
> single file, then display/analyze the data as needed without having to open
> each file separately.  Contents of control file
> (air.sig995.daily.1948-.ctl):
>
> DSET h:\cdf\dailymeans\air.sig995.%y4.nc
> TITLE Daily Air Temperature Sig995 01Jan1948-current
> DTYPE netcdf
> OPTIONS template
> UNDEF -9.99e+33
> XDEF 144 linear 0 2.5
> YDEF 73 linear -90 2.5
> ZDEF 1 linear 0 1
> TDEF 3653 linear 01jan1948 1dy
> VARS 1
> air=>tmp 0 t,y,x  Mean Daily Air Temperature at sigma level 995 (degK)
> ENDVARS
>
> For test purposes, I set TDEF to cover only the first 10 years.  When I
> launch it in GrADS, it opens "normally" but the data displays with values
> much lower than expected.  Following is the GrADS session transcript:
>
> Grid Analysis and Display System (GrADS) Version 2.0.a7.oga.3
> Copyright (c) 1988-2008 by Brian Doty and the
> Institute for Global Environment and Society (IGES)
> GrADS comes with ABSOLUTELY NO WARRANTY
> See file COPYRIGHT for more information
>
> Config: v2.0.a7.oga.3 little-endian readline printim grib2 netcdf hdf4-sds
> hdf5
> opendap-grids,stn athena geotiff
> Issue 'q config' command for more information.
> Loading User Defined Extensions table </bin/gex/udxt> ... ok.
> GX Package Initialization: Size = 11 8.5
> ga-> open c:\cdf\dailymeans\air.sig995.daily.1948-.ctl
> Scanning description file:  c:\cdf\dailymeans\air.sig995.daily.1948-.ctl
> Data file h:\cdf\dailymeans\air.sig995.%y4.nc is open as file 1
> LON set to 0 360
> LAT set to -90 90
> LEV set to 0 0
> Time values set: 1948:1:1:0 1948:1:1:0
> E set to 1 1
> ga-> q ctlinfo
> dset h:\cdf\dailymeans\air.sig995.%y4.nc
> title Daily Air Temperature Sig995 01Jan1948-current
> undef -9.99e+33
> dtype netcdf
> xdef 144 linear 0 2.5
> ydef 73 linear -90 2.5
> zdef 1 linear 0 1
> tdef 3653 linear 00Z01JAN1948 1440mn
> vars 1
> air=>tmp  0  t,y,x  Mean Daily Air Temperature at sigma level 995 (degK)
> endvars
> ga-> set time 25dec1953 5jan1954
> Time values set: 1953:12:25:0 1954:1:5:0
> ga-> d tmp-273.15
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> Contouring: -29000 to -21000 interval 1000
> ga->
> ______________________________________
>
> I was expecting data to display in deg C, i.e., in the range of roughly -50
> to 30, which is what I would get if I open a yearly file separately.  I also
> noticed that the display pattern itself is not consistent with the original
> files' data.  The data folder contains valid yearly files from 1948 through
> 2011.
>
> I did search the gradsusr.org archives for help, but could not find a
> solution.  I would appreciate someone suggesting a fix.  I am using
> Opengrads Version 2.0.a7.oga.3 on a Windows XP.
>
> Stephen McMillan
>
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>
> --
> Jennifer M. Adams
> IGES/COLA
> 4041 Powder Mill Road, Suite 302
> Calverton, MD 20705
> jma at cola.iges.org
>
>
>
>
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>

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