Hi Peter
Several NCO functions can do the classic
float->short (packing) and short->float (unpacking) conversions,
with the scale_factor and add_offset calculated from the
min and max data values (or the expected data range):
http://nco.sourceforge.net/nco.html#Packed-data
Specifically, ncap2 has pack() and unpack() functions:
http://nco.sourceforge.net/nco.html#Methods-and-functions
In my experience packing/unpacking is fine in many cases,
but can be problematic with variables that
have a wide dynamic range, covering several orders of magnitude,
such as specific humidity,
tracer and chemical species concentration, etc,
as the important/relevant detail may be squeezed into a few or a single
compressed value.
In these cases, a possible workaround would be to apply
a logarithm function beforehand (for positive variables),
and store the short_variable=packed(ln(float_variable)),
but also remember to apply an exponential when unpacking
float_variable=exp(unpack(short_variable)).
NcView (with --minmax all) shows the minimum and maximum
values of each variable, but other tools such as NCL can
be used for that as well.
I hope this helps,
Gus Correa
On 01/18/2018 12:23 PM, Pete Pokrandt wrote:
NetCDFers,
Got the following question from one of our scientists (Mike Notaro,
mnotaro@xxxxxxxx, cc'd). Any ideas?
Does anyone know of an efficient (hopefully command line) method to
convert an entire netcdf file (and all of its float variables) to
short integers?
Thanks,
Pete
<http://www.weather.com/tv/shows/wx-geeks/video/the-incredible-shrinking-cold-pool>--
Pete Pokrandt - Systems Programmer
UW-Madison Dept of Atmospheric and Oceanic Sciences
608-262-3086 - poker@xxxxxxxxxxxx
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