Provided by: nco_4.7.9-1_amd64 bug

NAME

       ncwa - netCDF Weighted Averager

SYNTAX

       ncwa   [-3]  [-4]  [-5]  [-6]  [-7]  [-A]  [-a  dim[,...]]   [-B  mask_cond]  [-b]  [--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[,...]]   [--glb  att_name=  att_val]]
       [-h]  [--hdf] [--hdr_pad sz_byt][--hpss_try] [-I] [-L dfl_lvl][-l path] [-M val] [-m mask]
       [-N] [--no_cll_msr] [--no_cll_mth] [--no_frm_trm] [--no_tmp_fl] [-O] [-o output-file]  [-p
       path]  [--ppc  var1[, var2[,...]]= prc]] [-R] [-r] [--ram_all] [-T mask_comp] [-t thr_nbr]
       [--unn] [-v var[,...]]  [-w weight] [-x] [-y op_typ] input-file output-file

DESCRIPTION

       ncwa averages variables in a single  file  over  arbitrary  dimensions,  with  options  to
       specify   weights,  masks,  and  normalization.   The  default  behavior  of  ncwa  is  to
       arithmetically average every numerical variable over all dimensions and produce  a  scalar
       result.   To  average  variables  over  only  a  subset of their dimensions, specify these
       dimensions in a comma-separated list following -a, e.g., -a  time,lat,lon.   As  with  all
       arithmetic  operators,  the  operation  may  be  restricted  to an arbitrary hypserslab by
       employing the -d option ncwa  also  handles  values  matching  the  variable's  _FillValue
       attribute correctly.  Moreover, ncwa understands how to manipulate user-specified weights,
       masks, and normalization options.  With these  options,  ncwa  can  compute  sophisticated
       averages (and integrals) from the command line.

       mask  and  weight, if specified, are broadcast to conform to the variables being averaged.
       The rank of variables is reduced by the number of dimensions which they are averaged over.
       Thus arrays which are one dimensional in the input-file and are averaged by ncwa appear in
       the output-file as scalars.  This allows the user to infer which dimensions may have  been
       averaged.   Note that that it is impossible for ncwa to make make a weight or mask of rank
       W conform to a var of rank V if W >  V.   This  situation  often  arises  when  coordinate
       variables  (which,  by  definition,  are one dimensional) are weighted and averaged.  ncwa
       assumes you know this is impossible and so ncwa does not attempt to  broadcast  weight  or
       mask  to  conform  to  var in this case, nor does ncwa print a warning message telling you
       this, because it is so common.  Specifying dbg > 2 does cause ncwa  to  emit  warnings  in
       these situations, however.

       Non-coordinate  variables  are  always  masked  and  weighted  if  specified.   Coordinate
       variables, however,  may  be  treated  specially.   By  default,  an  averaged  coordinate
       variable,  e.g.,  latitude,  appears  in  output-file  averaged  the same way as any other
       variable containing an averaged dimension.  In other words, by default  ncwa  weights  and
       masks coordinate variables like all other variables.  This design decision was intended to
       be helpful but for some applications it may be preferable not to weight or mask coordinate
       variables  just  like  all other variables.  Consider the following arguments to ncwa: “-a
       latitude -w lat_wgt -d  latitude,0.,90.”  where  lat_wgt  is  a  weight  in  the  latitude
       dimension.   Since, by default ncwa weights coordinate variables, the value of latitude in
       the output-file depends on the weights in lat_wgt  and  is  not  likely  to  be  45.---the
       midpoint  latitude of the hyperslab.  Option -I overrides this default behavior and causes
       ncwa not to weight or mask coordinate variables.  In the above case, this causes the value
       of latitude in the output-file to be 45.---which is a somewhat appealing result.  Thus, -I
       specifies simple arithmetic averages  for  the  coordinate  variables.   In  the  case  of
       latitude,  -I  specifies  that you prefer to archive the central latitude of the hyperslab
       over which variables  were  averaged  rather  than  the  area  weighted  centroid  of  the
       hyperslab.   Note  that  the default behavior of ( -I) changed on 1998/12/01---before this
       date the default was not  to  weight  or  mask  coordinate  variables.   The  mathematical
       definition of operations involving rank reduction is given above.

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.

                                                                                          NCWA(1)