[gradsusr] Problem Displaying Templated Multiple File Data

Tue Aug 30 17:59:22 EDT 2011

d (air+-512.81)*0.01
d air*0.01+-512.81

???
Sender: Stephen McMillan
Date: 2011年8月31日(星期三) 上午5:52
To: GrADS Users Forum
Subject: Re: [gradsusr] Problem Displaying Templated Multiple File Data
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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The information contained in this e-mail message 
is intended only for the use of the recipient(s) 
named above and may contain information that is 
privileged, confidential, and/or proprietary. 
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review, copy or distribute this message. If you have
received this communication in error, please notify 
the sender immediately by e-mail, and delete the original message.
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