Version 4.3.5 of the netCDF Operators (NCO) has been released. NCO is an Open Source package that consists of a dozen standalone, command-line programs that take netCDF files as input, then operate (e.g., derive new data, average, print, hyperslab, manipulate metadata) and output the results to screen or files in text, binary, or netCDF formats.
The NCO project is coordinated by Professor Charlie Zender of the Department of Earth System Science, University of California, Irvine. More information about the project, along with binary and source downloads, are available on the SourceForge project page.
From the release message:
The current release brings group support to
ncra, ncea, and ncrcat.
Now ten operators fully support group hierarchies: ncbo,
ncea, ncecat, ncflint, ncks,
ncpdq, ncra, ncrcat, ncrename,
and ncwa. The operators that do not yet fully
support group hierarchies are ncatted and ncap2.
Rounding errors can accumulate to worrisome levels during arithmetic
performed on large (>~10,000) arrays of single precision floats.
Now NCO has the --dbl switch that forces operators to coerce
single-precision numbers to double-precision for arithemetic.
It is expensive in terms of time and RAM, and often not warranted.
Use this switch to guarantee preserving maximum precision.
Or if you want your NCO answers on single-precision fields to always
agree exactly with tools that always promote (NCL, Matlab, IDL).
The manual now contains a detailed discussion of the issues.
Unfortunately progress sometimes comes at a price in bugs.
4.3.5 fixes a nasty ncwa bug present in 4.3.3 and 4.3.4.
Nasty means that it could produce wrong answers that look right.
Fortunately, it could only occur when simultaneously averaging and
hyperslabbing, e.g.,
ncwa -a lat,lon -d lat,0.,90. in.nc out.nc
Such users should immediately upgrade to 4.3.5 and re-check results.
For more information see the Known Problems list.
Additional details are available in the ChangeLog.
