NAME
ncra - netCDF Record Averager
SYNTAX
ncra [-3] [-4] [-6] [-A] [-C] [-c] [-D dbg] [-d dim,[ min][,[ max]][,[
stride]]] [-F] [-h] [-L dfl_lvl] [-l path] [-n loop] [-O] [-p path]
[-R] [-r] [-t thr_nbr] [-v var[,...]] [-X box] [-x] [-y op_typ] input-
files output-file
DESCRIPTION
ncra averages record variables across an arbitrary number of input
files. The record dimension is retained as a degenerate (size 1)
dimension in the output variables.
Input files may vary in size, but each must have a record dimension.
The record coordinate, if any, should be monotonic for (or else non-
fatal warnings may be generated). Hyperslabs of the record dimension
which include more than one file are handled correctly. ncra supports
the stride argument to the -d hyperslab option for the record dimension
only, stride is not supported for non-record dimensions.
ncra weights each record (e.g., time slice) in the input-files equally.
ncra does not attempt to see if, say, the time coordinate is
irregularly spaced and thus would require a weighted average in order
to be a true time average.
EXAMPLES
Average files 85.nc, 86.nc, ... 89.nc along the record dimension, and
store the results in 8589.nc:
ncra 85.nc 86.nc 87.nc 88.nc 89.nc 8589.nc
ncra 8[56789].nc 8589.nc
ncra -n 5,2,1 85.nc 8589.nc
These three methods produce identical answers.
Assume the files 85.nc, 86.nc, ... 89.nc each contain a record
coordinate time of length 12 defined such that the third record in
86.nc contains data from March 1986, etc. NCO knows how to hyperslab
the record dimension across files. Thus, to average data from
December, 1985 through February, 1986:
ncra -d time,11,13 85.nc 86.nc 87.nc 8512_8602.nc
ncra -F -d time,12,14 85.nc 86.nc 87.nc 8512_8602.nc
The file 87.nc is superfluous, but does not cause an error. The -F
turns on the Fortran (1-based) indexing convention. The following uses
the stride option to average all the March temperature data from
multiple input files into a single output file
ncra -F -d time,3,,12 -v temperature 85.nc 86.nc 87.nc
858687_03.nc
Assume the time coordinate is incrementally numbered such that January,
1985 = 1 and December, 1989 = 60. Assuming ?? only expands to the
five desired files, the following averages June, 1985--June, 1989:
ncra -d time,6.,54. ??.nc 8506_8906.nc
AUTHOR
NCO manual pages written by Charlie Zender and Brian Mays.
REPORTING BUGS
Report bugs to <http://sf.net/bugs/?group_id=3331>.
COPYRIGHT
Copyright © 1995-2010 Charlie Zender
This is free software; see the source for copying conditions. There is
NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.
SEE ALSO
The full documentation for NCO is maintained as a Texinfo manual called
the NCO User’s Guide. Because NCO is mathematical in nature, the
documentation includes TeX-intensive portions not viewable on
character-based displays. Hence the only complete and authoritative
versions of the NCO User’s Guide are the PDF (recommended), DVI, and
Postscript versions at <http://nco.sf.net/nco.pdf>,
<http://nco.sf.net/nco.dvi>, and <http://nco.sf.net/nco.ps>,
respectively. HTML and XML versions are available at
<http://nco.sf.net/nco.html> and <http://nco.sf.net/nco.xml>,
respectively.
If the info and NCO programs are properly installed at your site, the
command
info nco
should give you access to the complete manual, except for the TeX-
intensive portions.
HOMEPAGE
The NCO homepage at <http://nco.sf.net> contains more information.