Provided by: nco_4.4.2-1_amd64 bug

NAME

       ncwa - netCDF Weighted Averager

SYNTAX

       ncwa   [-3]   [-4]   [-6]   [-7]   [-A]   [-a   dim[,...]]   [-B  mask_cond]  [-b]  [--bfr
       sz][-C][-c][--cnk_byt sz][--cnk_dmn nm,sz]  [--cnk_map  map]  [--cnk_plc  plc]  [--cnk_scl
       sz][-D  dbg_lvl]  [-d  dim,[  min][,[  max]]] [--dbl|flt] [-F] [-G gpe_dsc] [-g grp[,...]]
       [-h]  [--hdf]  [--hdr_pad  sz]  [-I]  [-L  dfl_lvl][-l  path]  [-M  val]  [-m  mask]  [-N]
       [--no_cll_mth]  [--no_tmp_fl]  [-O]  [-o  output-file] [-p path] [-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 © 1995-2010 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.

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

HOMEPAGE

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

                                                                                          NCWA(1)