[netcdfgroup] netCDF Operators NCO version 5.3.4 stick the landing

• To: NCO Announce Mail List <nco-announce@xxxxxxxxxxxxxxxxxxxxx>, netCDF Mail List <netcdfgroup@xxxxxxxxxxxxxxxx>
• Subject: [netcdfgroup] netCDF Operators NCO version 5.3.4 stick the landing
• From: Charlie Zender <zender@xxxxxxx>
• Date: Mon, 16 Jun 2025 12:21:08 -0700

netCDF Operators NCO version 5.3.4 stick the landing

http://nco.sf.net (Homepage, Mailing lists, Help)
http://github.com/nco/nco (Source Code, Issues, Releases)

What's new?
Version 5.3.4 contains of bevy of minor features that improve
NCO in many different areas. These range from reduced monotonicity
WARNINGs from ncrcat, to an easy new method for all operators
to remove global attributes, to bulletproofing ncclimo to work
as intended with instantaneous input, to new urban landunit
diagnostics in ncks.

Skip this release if these changes do not interest you.

Time machine:
The first public release of ncrename was June 14, 1995:
https://www.unidata.ucar.edu/mailing_lists/archives/netcdfgroup/1995/msg00076.html
Happy 30th birthday ncrename!!!

Enjoy,
Charlie

NEW FEATURES (full details always in ChangeLog):

A. All operators can now delete user-specified global attributes.
The option --gad=att1,att2,...,attN (or long-option equivalent
--glb_att_del=att1,att2,...,attN) deletes (rather than adds, like its
sister option --gaa) global attributes in an output file.
Global attribute deletion requires only the name of the global
attribute without any further information, so the argument to the
option is simply a comma-separated list of all attributes to delete.
No information about the attributes' types, sizes, or values need be given.
The option works on attributes of all types, sizes, and values.

ncks --gad=history_of_appended_files,nco_openmp_thread_number,\
           input_file,map_file,remap_version,remap_hostname,\
           remap_command,remap_script,NCO in.nc out.nc

The global attribution deletion feature helps to avoid the performance
penalty incurred by using @command{ncatted} separately to annotate
large files.
http://nco.sf.net/nco.html#gad
http://nco.sf.net/nco.html#gaa

B. ncrcat no longer performs monotonicity checks on CF bounds
variables (which are never monotonic). This eliminates a lot
of noisy monotonicity WARNINGs from many datasets.
http://nco.sf.net/nco.html#ncrcat

C. ncks --is_var var_nm is a new option that checks whether the
single variable var_nm is a ``horizontal variable''.
In this context, horizontal variables means single-level variables
that have horizontal dimensions (e.g., lat and lon) yet no
vertical dimension and no other dimensions except possibly the
temporal dimension (time). ncks prints "Yes" or "No" and then exits.
This capability helps ncclimo determine whether a variable is
suitable for creating a regional average timeseries from.
Due to this context, coordinate variables (including latitude and
longitude) are not identified as horiztonal variables.
Furthermore, variables identified as horizontal may only have two
or three dimensions, and those dimensions must be in this list:
lat, lon, ncol, nCells, time, and Time.

zender@spectral:~$ ncks --is_hrz three_dmn_rec_var ~/nco/data/in.nc
Yes
zender@spectral:~$ ncks --is_hrz one ~/nco/data/in.nc
No
zender@spectral:~$

The E3SM-centric list of allowed dimension names is only a starting point!
Please contact Charlie if you would like this list expanded.
http://nco.sf.net/nco.html#is_hrz

D. ncclimo can now infer the timesteps per day (tpd) to use for
high-frequency instantaneous (in the CF sense) data that lack a
CF temporal bounds variable. ncclimo also uses tpd to help it
discover how many days-per-file there are. Nevertheless, the metadata
in the ncclimo output may be more accurate if the input data contains
a temporal bounds variable.

E. The ncks S1D functionality that "gridifies" ELM/CTSM data has
new features to aggregate and report Urban landunit characteristics.
First, the new S1D option "--rgr lut_out=789" stores the area-weighted
mean of the three Urban landunit types (7, 8, and 9) in the output
for every variable in a restart file that is defined on columns.

ncks --s1d --rgr lut_out=789 --hrz=hst.nc rst.nc s1d.nc # Avg Urban

Second, the frc_column diagnostic variable stores the subtotal of
the three Urban landunits areas in (C-based) index 15 of output files
with MECs, and in index 5 of output files without MECs. Users can now
easily assess the total fraction of a gridcell that is Urban.
http://nco.sf.net/nco.html#s1d
http://nco.sf.net/nco.html#frc_column

F. ncks now inserts line-breaks in NC_STRING-valued text when it
encounters a C-format carriage return "\n". Now printing text
stored as NC_STRING and as NC_CHAR has the same appearance.
This makes it easier to read "history" global attributes that are
stored as NC_STRING:

ncap2 -O -4 -h -s 'global@history="Previous history"s' ~/foo.nc
ncap2 -O -s 'one=1' ~/foo.nc ~/foo.nc
ncks -M ~/foo.nc # NC_STRING history is now more legible

http://nco.sf.net/nco.html#ncks
http://nco.sf.net/nco.html#history

G. ncremap has deprecated the use of the "--alg_typ=tempest"
regridding algorithm value.
This algorithm name simply meantthat NCO invoked the TempestRemap
(TR) regridder with all default choices, i.e., with no options.
However, the default TR algorithm is rarely employed anymore, and many
users misinterpreted the meaning of "tempest".
Instead of supplying ncremap with their own options, they
received the default, which usually was sub-optimal. We encourage
users to migrate to the appropriate and specifically-named TR
algorithms such as "fv2fv_flx", "traave", "trfv2", etc.
http://nco.sf.net/nco.html#alg_typ

BUG FIXES:

A. Fixed recent regression with ncrcat on hieraarchical files.
The symptom is this message: " ERROR: nco_inq_varname() reports
specified dataset ... has no variable ID 2". This problem was
introduced sometime around NCO 5.3.3. There is no workaround.
The solution is to upgrade.

Full release statement at http://nco.sf.net/ANNOUNCE
--
Charlie Zender, Dept. of Earth System Science
University of California, Irvine 949-891-2429