xenial (1) ncwa.1.gz

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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_min sz] [--cnk_plc plc] [--cnk_scl sz][-D dbg_lvl] [-d  dim,[
       min][,[  max]]]  [--dbl|flt]  [-F]  [-G  gpe_dsc] [-g grp[,...]]  [--glb att_name= att_val]] [-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] [--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 © 1995-2016 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),  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)