[ncl-talk] Convert unpacked netCDF file to packed one

[Dave Allured - NOAA Affiliate]

I see.  I suggest the best solution would be a simple upgrade to the model
code, so that it could read both packed and unpacked air temp files.  This
will enable the model to use future data updates without extra processing.

In fortran, this would be an if statement to check whether there is a
scale_factor attribute.  If not, then skip reading scale_factor and
add_offset, also skip the unpacking statement or loop that converts packed
data values to unpacked.  Just read in the unpacked values directly.  You
would need two read statements, the original one for the packed data type,
and a new one for the unpacked data type (fortran real).

If something prevents you from changing the model code, then just convert
the air temp file to packed using the NCL *pack_values* function.  See the
general documentation for how to read and write a netcdf file.


On Mon, Jan 11, 2021 at 12:00 PM Setareh Rahimi <setareh.rahimi at gmail.com>
wrote:

> Dear Dave,
> Thank you for your reply. Yes I am sure, because the model I am running
> only accept packed nc file with scale factor.
> Please have a look at attached file showing the error I face while running
> the model with mentioned nc file.
> Best regard
>
> On Mon, Jan 11, 2021 at 22:20 Dave Allured - NOAA Affiliate <
> dave.allured at noaa.gov> wrote:
>
>> That file is already compressed to 31% of its natural array size, using
>> netcdf-4 internal compression.  Are you sure you want to do that?  If yes,
>> then use the NCL function *pack_values*.
>>
>>
>> On Mon, Jan 11, 2021 at 11:07 AM Setareh Rahimi via ncl-talk <
>> ncl-talk at mailman.ucar.edu> wrote:
>>
>>> Dear all,
>>> I need to convert an unpacked netCDF file to a packed one (
>>> ftp://ftp2.psl.noaa.gov/Datasets/ncep.reanalysis2/pressure/air.2019.nc),
>>> I wonder if this possible using NCL?
>>> Many thanks in advance,
>>> Best wishes,
>>> --
>>> S.Rahimi
>>>
>>
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