[ncl-talk] Converting grb to netcdf (jra55 reanalysis): No time dimension created

[Lyndon Mark Olaguera]

Hi Sir Kevin,

Thank you for the help. I got it clearly.


Sincerely,

Lyndz




On Sat, Dec 9, 2017 at 2:14 AM, Kevin Hallock <hallock at ucar.edu> wrote:

> Hi Lyndz,
>
> The command you provided below *will* work to simply convert the file.
> However, in order to assign “forecast time” as a dimension instead of an
> attribute, it is necessary to use ncl_convert2nc’s “-ftime” flag:
> ncl_convert2nc fcst_phy2m125.1979010100.grb -ftime -u -U time
>
> The “-itime” flag also exists for performing the same operation on
> “initial time” attributes, but given that the file in question is a
> forecast (“fcst_*.grb”) that might not be necessary or desired in this case:
> ncl_convert2nc fcst_phy2m125.1979010100.grb -ftime -itime -u -U time
>
> Since you said that you want your forecast time dimension to be unlimited,
> you would also want to include “-u forecast_time0” in the ncl_convert2nc
> command:
> ncl_convert2nc fcst_phy2m125.1979010100.grb -ftime -u forecast_time0 -U
> time
>
> Note: Running “ncl_convert2nc --help” (with both NCL 6.3.0 and 6.4.0)
> indicates that “-u” implicitly makes “initial_time” dimensions unlimited
> for GRIB input files; “forecast time” requires the dimension name to be
> specified. (The web documentation
> <https://www.ncl.ucar.edu/Document/Tools/ncl_convert2nc.shtml> for “-u”
> is not as verbose, but I will make sure that this information is added.)
>
> Also, you could theoretically choose to output the file as a NetCDF 4
> classic format file by adding the “-nc4c” flag:
> ncl_convert2nc fcst_phy2m125.1979010100.grb -ftime -u forecast_time0 -U
> time -nc4c
>
> I hope this helps,
> Kevin
>
> On Dec 8, 2017, at 4:27 AM, Lyndon Mark Olaguera <
> olagueralyndonmark429 at gmail.com> wrote:
>
> Dear NCL experts,
>
> I am trying to convert a grb file to netcdf using ncl_convert2nc.
>
> Attached are the output of ncl_filedump and ncdump -h. The raw file can be
> accessed
> here:
>
> https://www.dropbox.com/s/zcsik2tl8qpgjwi/fcst_phy2m125.1979010100?dl=0
>
>
> I am converting the file using the following command:
>
> *ncl_convert2nc fcst_phy2m125.1979010100.grb -u -U time*
>
> This is weird because the ncl_filedump has the "initial_time" attibute.
> Example:
>
>       float ULWRF_GDS0_SFC_ave3h ( g0_lat_0, g0_lon_1 )
>          sub_center : 241
>          center : Japanese Meteorological Agency - Tokyo (RSMC)
>          long_name : Upward long wave radiation flux
>          units : W/m^2
>          _FillValue : 1e+20
>          level_indicator : 1
>          gds_grid_type : 0
>          parameter_table_version : 200
>          parameter_number : 212
>          forecast_time : 3
>          forecast_time_units : hours
>          initial_time : 01/01/1979 (00:00)
>
> It does not give an error but no "unlimited time" dimension is created:
>
> determining unlimited dimension dynamically
> if   of
> Processing file: fcst_phy2m125.1979010100.grb...
>  Copyright (C) 1995-2017 - All Rights Reserved
>  University Corporation for Atmospheric Research
>  NCAR Command Language Version 6.4.0
>  The use of this software is governed by a License Agreement.
>  See http://www.ncl.ucar.edu/ for more details.
>
> Any suggestion on how to do this correctly?
>
> I'll appreciate any help.
>
> Sincerely,
>
> Lyndz
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