[ncl-talk] reading GRIB2 files

[Adam Phillips]

Hi Matt,
Thanks for sending your complete code along with a pointer to the file. I
was able to read your file into NCL v6.2.1 and v6.3.0 here, so I would
suggest making sure you downloaded the entire file and/or redownload the
file. Here's what I did:

a = addfile("Downloads/rap_130_20150706_0000_000.grb2","r")
varnames = getfilevarnames(a)
print(varnames)

Variable: varnames
Type: string
Total Size: 816 bytes
            102 values
Number of Dimensions: 1
Dimensions and sizes: [102]
Coordinates:
(0) TMP_P0_L1_GLC0
(1) TMP_P0_L7_GLC0
(2) TMP_P0_L100_GLC0
(3) TMP_P0_L103_GLC0
(4) TMP_P0_2L108_GLC0
(5) POT_P0_L7_GLC0
(6) POT_P0_L103_GLC0
(7) EPOT_P0_L1_GLC0
(8) DPT_P0_L103_GLC0
(9) DEPR_P0_L103_GLC0
(10) SPFH_P0_L103_GLC0
(11) RH_P0_L4_GLC0
.....


I searched the NCL website for "RUC" and got pointed to skewt example #6
here:
http://www.ncl.ucar.edu/Applications/skewt.shtml#ex6

Looking at that code, they add a setfileoption:

setfileoption("grb","SingleElementDimensions","Initial_time")


As you can see I did not need that setfileoption to open the file
correctly, but perhaps for some reason your set up does?

Hope that helps, if you continue to have trouble with the file let the
ncl-talk email list know.

Adam






On Fri, Sep 4, 2015 at 8:56 AM, Matt Flournoy <mflournoy37 at gmail.com> wrote:

> Hi all,
>
> Does anyone have experience reading RUC GRIB2 files? I'm trying to read
> GRIB2 output from 13km RUC model data, which is available on the NOMADS
> site (http://nomads.ncdc.noaa.gov/data.php#hires_weather_datasets).
> Specifically, I am trying to read files from 06 July 2015, but I suspect
> this problem is universal among at least all of the 13km RUC GRIB2 output
> files.
>
> I've tried a couple ways to read the GRIB2 data, including reading the
> GRIB2 file and also trying to convert the GRIB2 file to netcdf. When I try
> to read the GRIB2 data directly (specifically
> "rap_130_20150706_0000_000.grb2"), I get the following warning message:
>
> warning:getfilevarnames: rap_130_20150706_0000_000 contains no variables
> readable by NCL
>
> I've pasted my NCL script that yields this warning at the bottom of my
> message.
>
> Second, when I try to convert the GRIB2 file to netcdf using
> "ncl_convert2nc" in the command line, I get this similar warning:
>
> warning:getfilevarnames: rap_130_20150706_0000_000 contains no variables
> readable by NCL
> ./rap_130_20150706_0000_000.grb2 contains no variables readable by NCL:
> converting global attributes only
>
> Then, when I "ncl_filedump" the created netcdf file, I get this:
>
> Variable: f
> Type: file
> filename: rap_130_20150706_0000_000
> path: rap_130_20150706_0000_000.nc
>    file global attributes:
>       creation_date : Fri Sep  4 09:52:47 CDT 2015
>       NCL_Version : 6.2.1
>       system : Linux bigbang.protect.nssl 2.6.32-504.12.2.el6.x86_64 #1
> SMP Sun Feb 1 12:14:02 EST 2015 x86_64 x86_64 x86_64 GNU/Linux
>       Conventions : None
>       grib_source : rap_130_20150706_0000_000.grb2
>       title : NCL: convert-GRIB-to-netCDF
>    dimensions:
>    variables:
>
> Do you know how to address this issue? I am currently using NCL version
> 6.2.1 on bigbang, and this problem also appears in other NCL versions.
>
> Thank you,
> Matt
>
>
>
> ------------ begin NCL script ---------------
>
>
> ;******************************************************************************;
> ; Load libraries.
>
> ;******************************************************************************;
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
>
>
> ;-----------------------------------------------------------------------------;
> ; Synoptic overview plots of the July 06 2015 case from the RUC.
>
> ;-----------------------------------------------------------------------------;
>
> begin
>
>   ruc_filepath =
> ("/home/matt.flournoy/PECAN/overview/data/RUC_data/rap_130_20150706_0000_000.grb2")
>   ruc_file     = addfile(ruc_filepath,"r")
>
>   varnames = getfilevarnames(ruc_file)
>
>   if(.not.any(ismissing(varnames))) then
>
>     do i=0,dimsizes(varnames)-1
>
>       printFileVarSummary(ruc_file,varnames(i))
>
>     end do
>
>   end if
>
> end
>
> --------------- end NCL script ----------------
>
> --
> Matthew Flournoy
> M.S. Meteorology Candidate, University of Oklahoma
> B.S. Meteorology, Penn State University
>
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>


-- 
Adam Phillips
Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
www.cgd.ucar.edu/staff/asphilli/   303-497-1726

<http://www.cgd.ucar.edu/staff/asphilli>
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