[netcdfgroup] netCDF Operators NCO version 5.0.0 are unshackled

• To: netcdfgroup@xxxxxxxxxxxxxxxx, NCO Announce Mail List <nco-announce@xxxxxxxxxxxxxxxxxxxxx>
• Subject: [netcdfgroup] netCDF Operators NCO version 5.0.0 are unshackled
• From: Charlie Zender <zender@xxxxxxx>
• Date: Fri, 18 Jun 2021 10:56:46 -0700

The netCDF Operators NCO version 5.0.0 have arrived.

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

What's new?
Version 5.0.0 contains mostly ncremap features and fixes.
You can probably skip this release unless you use ncremap.
ncremap has crucial fixes for applying and exporting the mask field,
if any. It also provides new flags to control the application of
_FillValue attributes in empty destination cells, and to accomodate
map-files that ignore or violate proper treatment of masked grids.
ncks auxiliary coordinates (-X) support wrapped longitude regions.

Work on NCO 5.0.1 has commenced and and it targeted to offer ncremap
support for the MOAB offline regridding package mbtempest.

A slightly "meta" question on version numbering: NCO 4.0.0 was
released Jan 5, 2010, and subsequent versions were bumped by ~0.0.1
increments for about eleven years. We might change to YY.MM-numbering,
e.g., 21.6, or something similar, in subsequent releases. What do you
think would be a better version system for NCO?

Enjoy,
Charlie

NEW FEATURES (full details always in ChangeLog):

A. The ncremap regridder now creates a "title" global attribute in the
   the output file if the input file did not already have a title.
   This title attribute is described and supported by the NUG and CF.
   Moreover, the Panoply file catalog uses it to describe open files.
   http://nco.sf.net/nco.html#ncremap

B. ncremap now accepts a --no_prm (--no_permute) flag that causes
   the regridder to skip the default permutation of dimensions
   before regridding (notably MPAS) datasets known to store data
   with most-rapidly varying dimensions that are not horizontal.
   ncremap normally ensures that input fields are stored in the
   shape expected by regridder weights (horizontal dimensions last)
   by permuting the dimensions with ncpdq. However, permutation
   consumes time and generates an extra intermediate file.
   Avoid this time penalty by using the --no_prm flag if the input
   fields are known to have trailing horizontal dimensions.
   ncremap --no_prm -P mpas -v sic -m map.nc in.nc out.nc
   http://nco.sf.net/nco.html#no_prm
   http://nco.sf.net/nco.html#ncremap

C. ncremap now accepts a --add_fll (--add_fill_value) flag that causes
   the regridder to add a _FillValue attribute to fields with empty
   destination cells. Empty destination cells are those that have no
   non-zero weights from the source grids. Should a field (e.g.,
   air temperature) without a _FillValue be mapped to such a grid,
   the empty destination values are normally set to 0.0, since no
   source grid cells contribute. However, 0.0 is a valid value for
   many geophysical fields. Use this switch to ensure that empty
   destination gridcells are always set to _FillValue. The default
   _FillValue will be used in the output file for input fields that
   lack a _FillValue. This flag has no effect on input fields that
   already have a _FillValue.
   ncremap --add_fll -v FLNS -m map.nc in.nc out.nc
   http://nco.sf.net/nco.html#add_fll
   http://nco.sf.net/nco.html#ncremap

D. ncremap now accepts a --msk_apl (--mask_apply) flag that causes
   the regridder to apply msk_out (i.e., mask_b) to variables after
   regridding. Some weight generators (e.g., Tempest) ignore masks
   and thus produce non-zero weights for masked destination cells,
   and/or from masked source cells. This flag causes regridded files
   produced with such map-files to adhere to the destination mask
   rules (though source mask rules may still be violated). This
   feature is especially useful in placing missing values (aka,
   _FillValue) in destination cells that should be empty, so that
   regridded files have distributions of _FillValues identical
   with output from other weight-generators such as ESMF and NCO.
   ncremap --msk_apl -v FLNS -m map.nc in.nc out.nc
   http://nco.sf.net/nco.html#msk_apl
   http://nco.sf.net/nco.html#ncremap

E. ncremap now includes the coordinates xgrid, ygrid in its internal
   database so that it can automatically recognize and infer grids
   from NOAA SSM/I, AMSR-E, and SMMR Climate Data Record (CDR)
   datasets. Thanks to Mat Maltrud of LANL for prompting this.
   ncremap -d ~/ssmi_cdr_raw.nc -g ${DATA}/grids/ssmi_304x448.nc
   http://nco.sf.net/nco.html#ncremap

BUG FIXES:

A. MacOS Conda builds now behave correctly with OpenMP, which was
   buggy with 4.9.9 on MacOS with Conda.
   This will make map-file generation with the NCO algorithms much
   faster for high-resolution maps.
   Thanks to Xylar Asay-Davis of LANL for helping to test this.

B. ncremap fixes a recently introduced problem with node-indexing
   in MPI mode. The workaround is to use background mode, and the
   solution is to upgrade.
   http://nco.sf.net/nco.html#par_typ_ncremap

C. ncremap now skips the stdin check when -i in_fl is used.
   The previous behavior led to hangs with some queuing systems
   (Slurm) on some machines (Chrysalis) that reserve stdin for
   the batch queue commands (srun). The workaround is to use the
   --no_stdin flag, and the solution is to upgrade. Thanks to Xylar
   Asay-Davis of LANL for reporting this issue.

D. ncks -X now handles branch cut rules correctly when WESN bounding
   box of auxiliary (e.g., unstructured) coordinate grids wrap in
   longitude. This permits ncremap RRG to work correctly in those same
   situations. Thanks to Po-Lun Ma of PNNL for prompting this fix.

E. ncremap corrects a few issues that prevented --msk_out from
   working correctly. In particular, msk_out will be correctly
   stored as an integer field, with name specified by msk_nm,
   if provided. Otherwise it will be named mask_b. There is no
   workaround, the solution is to upgrade.

Full release statement at http://nco.sf.net/ANNOUNCE

--
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(