The netCDF Operators NCO version 4.6.1 are ready.
http://nco.sf.net (Homepage, Mailing lists)
http://github.com/nco (Source Code, Releases, Developers)
What's new?
4.6.1 is mainly a stability release to polish existing features and to
add minor new ones. The main new feature is that ncclimo supports
incremental climatologies. ncatted works much better with special
characters in attribute names, while preserving its ability to handle
regular expressions. ncflint gains a weight-normalization option.
Work on NCO 4.6.2 has commenced and will better support regridding
variables whose horizontal dimensions are not most-rapidly-varying.
Enjoy,
Charlie
NEW FEATURES (full details always in ChangeLog):
A. ncks supports new provenance features released in netCDF-4.4.1.
These provenance (and other) metadata are revealed by the --hdn (or
--hidden) switch when dumping global metadata from a netCDF4 file:
ncks --cdl --hdn -M ~/nco/data/in_grp.nc
http://nco.sf.net/nco.html#ncflint
B. Wenshan Wang of UCI contributed a Quick Reference Card suitable
for printing. Thanks, Wenshan!
http://nco.sf.net/nco_rfr_crd.pdf
C. Add ncflint -N, --nrm, --normalize option so w1:=w1/(w1+w2),
w2:=w2/(w1+w2)
http://nco.sf.net/nco.html#ncflint
D. ncap2's array() function can now take a dimension list as the
third argument, e.g., n2=array(1.0,2.0,/$time,$lat,$lon/)
http://nco.sf.net/nco.html#ncap2
E. ncclimo will now generate incremental climatologies, e.g., it will
extend an existing climatology with the new files from a simulation
to create an extended climatology. Only the new monthly files and
the existing climatolgoy need be accessible---the old monthly files
are not used. Invoke ncclimo incremental mode with, e.g.,
ncclimo -c caseid -s 1982 -e 1983 -i raw -o clm -r map.nc -S 1980
http://nco.sf.net/nco.html#ncclimo
BUG FIXES:
A. ncatted now allows special characters in attribute and variable
names. Previously, ncatted interpreted most special characters
as indicating a regular expression. Now ncatted first tries to
interpret most special characters as literals, and if that does
not work, then it interprets them as a regular expression.
Thanks to emontgomery for reporting the problem.
B. ncap2 fixed handling of implicit array bounds for slabs of form
var(3:). Previously ncap2 would exit with an error.
http://nco.sf.net/nco.html#ncap2
C. When inferring grid coordinates from 2D files, ncremap in 4.6.0
sometimes would confuse dimension names with coordinate names.
This has been fixed. The workaround is to downgrade to 4.5.6 or
upgrade to 4.6.1.
D. ncremap now automatically chooses distinct output spatial and
temporal bounds names when for non-rectangular output datasets.
Previously ncremap might use, e.g., "nbnd" for both. This could
fail for curvilinear datasets.
E. Resolve an issue that caused spurious warnings from nco_fl_mv().
KNOWN PROBLEMS DUE TO NCO:
This section of ANNOUNCE reports and reminds users of the
existence and severity of known, not yet fixed, problems.
These problems occur with NCO 4.6.1 built/tested under
MacOS with netCDF 4.3.3.1 on HDF5 1.8.16 and with
Linux with netCDF 4.4.1-development (20160212) on HDF5 1.8.13.
A. NOT YET FIXED (NCO problem)
Correctly read arrays of NC_STRING with embedded delimiters in
ncatted arguments
Demonstration:
ncatted -D 5 -O -a
new_string_att,att_var,c,sng,"list","of","str,ings" ~/nco/data/in_4.nc
~/foo.nc
ncks -m -C -v att_var ~/foo.nc
20130724: Verified problem still exists
TODO nco1102
Cause: NCO parsing of ncatted arguments is not sophisticated
enough to handle arrays of NC_STRINGS with embedded delimiters.
B. NOT YET FIXED (NCO problem?)
ncra/ncrcat (not ncks) hyperslabbing can fail on variables with
multiple record dimensions
Demonstration:
ncrcat -O -d time,0 ~/nco/data/mrd.nc ~/foo.nc
20140826: Verified problem still exists
20140619: Problem reported by rmla
Cause: Unsure. Maybe ncra.c loop structure not amenable to MRD?
Workaround: Convert to fixed dimensions then hyperslab
KNOWN PROBLEMS DUE TO BASE LIBRARIES/PROTOCOLS:
A. NOT YET FIXED (netCDF4 or HDF5 problem?)
Specifying strided hyperslab on large netCDF4 datasets leads
to slowdown or failure with recent netCDF versions.
Demonstration with NCO <= 4.4.5:
time ncks -O -d time,0,,12 ~/ET_2000-01_2001-12.nc ~/foo.nc
Demonstration with NCL:
time ncl < ~/nco/data/ncl.ncl
20140718: Problem reported by Parker Norton
20140826: Verified problem still exists
20140930: Finish NCO workaround for problem
Cause: Slow algorithm in nc_var_gets()?
Workaround #1: Use NCO 4.4.6 or later (avoids nc_var_gets())
Workaround #2: Convert file to netCDF3 first, then use stride
B. NOT YET FIXED (netCDF4 library bug)
Simultaneously renaming multiple dimensions in netCDF4 file can
corrupt output
Demonstration:
ncrename -O -d lev,z -d lat,y -d lon,x ~/nco/data/in_grp.nc ~/foo.nc
# Completes but file is unreadable
ncks -v one ~/foo.nc
20150922: Confirmed problem reported by Isabelle Dast, reported to
Unidata
20150924: Unidata confirmed problem
20160212: Verified problem still exists in netCDF library
20160512: Ditto
Bug tracking: https://www.unidata.ucar.edu/jira/browse/fxm
More details: http://nco.sf.net/nco.html#ncrename_crd
C. NOT YET FIXED (would require DAP protocol change?)
Unable to retrieve contents of variables including period '.' in name
Periods are legal characters in netCDF variable names.
Metadata are returned successfully, data are not.
DAP non-transparency: Works locally, fails through DAP server.
Demonstration:
ncks -O -C -D 3 -v var_nm.dot -p
http://thredds-test.ucar.edu/thredds/dodsC/testdods in.nc # Fails to
find variable
20130724: Verified problem still exists.
Stopped testing because inclusion of var_nm.dot broke all test scripts.
NB: Hard to fix since DAP interprets '.' as structure delimiter in
HTTP query string.
Bug tracking: https://www.unidata.ucar.edu/jira/browse/NCF-47
D. NOT YET FIXED (would require DAP protocol change)
Correctly read scalar characters over DAP.
DAP non-transparency: Works locally, fails through DAP server.
Problem, IMHO, is with DAP definition/protocol
Demonstration:
ncks -O -D 1 -H -C -m --md5_dgs -v md5_a -p
http://thredds-test.ucar.edu/thredds/dodsC/testdods in.nc
20120801: Verified problem still exists
Bug report not filed
Cause: DAP translates scalar characters into 64-element (this
dimension is user-configurable, but still...), NUL-terminated
strings so MD5 agreement fails
"Sticky" reminders:
A. Reminder that NCO works on most HDF4 and HDF5 datasets, e.g.,
HDF4: AMSR MERRA MODIS ...
HDF5: GLAS ICESat Mabel SBUV ...
HDF-EOS5: AURA HIRDLS OMI ...
B. Pre-built executables for many OS's at:
http://nco.sf.net#bnr
--
Charlie Zender, Earth System Sci. & Computer Sci.
University of California, Irvine 949-891-2429 )'(
