Provided by: nco_4.7.9-1_amd64 bug

NAME

       nces - netCDF Ensemble Statistics

SYNTAX

       nces  [-3]  [-4]  [-5]  [-6]  [-7] [-A] [--bfr sz_byt][-C][-c][--cnk_byt sz_byt][--cnk_csh
       sz_byt][--cnk_dmn nm,sz_lmn] [--cnk_map map] [--cnk_min sz_byt] [--cnk_plc plc] [--cnk_scl
       sz_lmn][-D  dbg_lvl] [-d dim,[ min][,[ max]]] [--dbl|flt] [-F] [--fl_fmt=fmt] [-G gpe_dsc]
       [-g grp[,...]]  [-h] [--hdf] [--hdr_pad sz_byt] [-L dfl_lvl] [-l path]  [--msa]  [-N]  [-n
       loop]  [--no_cll_msr]  [--no_frm_trm]  [--no_tmp_fl]  [--nsm_sfx  grp_sfx]  [-O] [-p path]
       [--ppc var1[, var2[,...]]= prc]] [-R] [-r] [--ram_all] [-t thr_nbr] [--unn] [-v var[,...]]
       [-X box] [-x] [-y op_typ] input-files output-file

DESCRIPTION

       nces  performs gridpoint averages of variables across an arbitrary number (an ensemble) of
       input files, with each file receiving an equal weight in the average.   Each  variable  in
       the output-file will be the same size as the same variable in any one of the in the input-
       files, and all input-files must be the same size.  Whereas  ncra  only  performs  averages
       over  the  record  dimension (e.g., time), and weights each record in the record dimension
       evenly, nces averages entire  files,  and  weights  each  file  evenly.   All  dimensions,
       including the record dimension, are treated identically and preserved in the output-file.

       The  file  is the logical unit of organization for the results of many scientific studies.
       Often one wishes to generate a file which is the gridpoint average of many separate files.
       This  may  be  to  reduce  statistical noise by combining the results of a large number of
       experiments, or it may simply be a step in a procedure whose goal is to compute  anomalies
       from  a mean state.  In any case, when one desires to generate a file whose properties are
       the mean of all the input  files,  then  nces  is  the  operator  to  use.   nces  assumes
       coordinate  variable  are  properties  common  to  all  of the experiments and so does not
       average them across files.  Instead, nces copies the values of  the  coordinate  variables
       from the first input file to the output file.

EXAMPLES

       Consider  a  model  experiment  which generated five realizations of one year of data, say
       1985.  You can imagine that the experimenter slightly perturbs the initial  conditions  of
       the  problem  before  generating  each new solution.  Assume each file contains all twelve
       months (a seasonal cycle) of data and we want to produce  a  single  file  containing  the
       ensemble  average  (mean)  seasonal  cycle.   Here the numeric filename suffix denotes the
       experiment number (not the month):
              nces 85_01.nc 85_02.nc 85_03.nc 85_04.nc 85_05.nc 85.nc
              nces 85_0[1-5].nc 85.nc
              nces -n 5,2,1 85_01.nc 85.nc
       These three commands produce identical answers.  The output file, 85.nc, is the same  size
       as the inputs files.  It contains 12 months of data (which might or might not be stored in
       the record dimension, depending on the input files), but each value in the output file  is
       the average of the five values in the input files.

       In  the  previous  example,  the user could have obtained the ensemble average values in a
       particular spatio-temporal region by adding a hyperslab argument to the command, e.g.,
              nces -d time,0,2 -d lat,-23.5,23.5 85_??.nc 85.nc
       In this case the output file  would  contain  only  three  slices  of  data  in  the  time
       dimension.   These  three  slices are the average of the first three slices from the input
       files.  Additionally, only data inside the tropics is included.

AUTHOR

       NCO manual pages written by Charlie Zender and originally formatted by Brian Mays.

REPORTING BUGS

       Report bugs to <http://sf.net/bugs/?group_id=3331>.

COPYRIGHT

       Copyright © 1995-2018 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 Users
       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  Users  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.

       ncap(1),  ncap2(1),  ncatted(1),  ncbo(1),  ncclimo(1),  nces(1),  ncecat(1),  ncflint(1),
       ncks(1), nco(1), ncpdq(1), ncra(1), ncrcat(1), ncremap(1), ncrename(1), ncwa(1)

HOMEPAGE

       The NCO homepage at <http://nco.sf.net> contains more information.

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