1NCWA(1)                     General Commands Manual                    NCWA(1)
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NAME

6       ncwa - netCDF Weighted Averager
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SYNTAX

9       ncwa  [-3] [-4] [-5] [-6] [-7] [-A] [-a dim[,...]]  [-B mask_cond] [-b]
10       [--bfr  sz_byt][-C][-c][--cnk_byt  sz_byt][--cnk_csh  sz_byt][--cnk_dmn
11       nm,sz_lmn]   [--cnk_map   map]   [--cnk_min   sz_byt]  [--cnk_plc  plc]
12       [--cnk_scl sz_lmn][-D dbg_lvl] [-d  dim,[  min][,[  max]]]  [--dbl|flt]
13       [-F]  [--fl_fmt=fmt]  [-G  gpe_dsc]  [-g  grp[,...]]   [--glb att_name=
14       att_val]]  [-h]  [--hdf]  [--hdr_pad   sz_byt][--hpss_try]   [-I]   [-L
15       dfl_lvl][-l path] [-M val] [-m mask] [-N] [--no_cll_msr] [--no_cll_mth]
16       [--no_frm_trm] [--no_tmp_fl] [-O] [-o  output-file]  [-p  path]  [--ppc
17       var1[,  var2[,...]]=  prc]]  [-R]  [-r]  [--ram_all] [-T mask_comp] [-t
18       thr_nbr] [--unn] [-v var[,...]]  [-w weight] [-x]  [-y  op_typ]  input-
19       file output-file
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DESCRIPTION

22       ncwa  averages  variables  in  a single file over arbitrary dimensions,
23       with options to specify weights, masks, and normalization.  The default
24       behavior  of ncwa is to arithmetically average every numerical variable
25       over all dimensions and produce a scalar result.  To average  variables
26       over  only  a subset of their dimensions, specify these dimensions in a
27       comma-separated list following -a, e.g., -a time,lat,lon.  As with  all
28       arithmetic  operators,  the operation may be restricted to an arbitrary
29       hypserslab by employing the -d option ncwa also handles values matching
30       the  variable's  _FillValue attribute correctly.  Moreover, ncwa under‐
31       stands how to manipulate user-specified weights, masks, and  normaliza‐
32       tion options.  With these options, ncwa can compute sophisticated aver‐
33       ages (and integrals) from the command line.
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35       mask and weight, if specified, are broadcast to conform  to  the  vari‐
36       ables  being  averaged.  The rank of variables is reduced by the number
37       of dimensions which they are averaged over.  Thus arrays which are  one
38       dimensional  in  the  input-file and are averaged by ncwa appear in the
39       output-file as scalars.  This allows the user to infer which dimensions
40       may  have  been  averaged.  Note that that it is impossible for ncwa to
41       make make a weight or mask of rank W conform to a var of rank V if W  >
42       V.   This  situation  often arises when coordinate variables (which, by
43       definition, are one  dimensional)  are  weighted  and  averaged.   ncwa
44       assumes  you  know  this  is impossible and so ncwa does not attempt to
45       broadcast weight or mask to conform to var in this case, nor does  ncwa
46       print  a  warning  message  telling  you this, because it is so common.
47       Specifying dbg > 2 does cause ncwa to emit  warnings  in  these  situa‐
48       tions, however.
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50       Non-coordinate  variables  are always masked and weighted if specified.
51       Coordinate variables, however, may be treated specially.   By  default,
52       an averaged coordinate variable, e.g., latitude, appears in output-file
53       averaged the same way as any  other  variable  containing  an  averaged
54       dimension.   In  other words, by default ncwa weights and masks coordi‐
55       nate variables like all other  variables.   This  design  decision  was
56       intended  to  be helpful but for some applications it may be preferable
57       not to weight or mask coordinate variables just like  all  other  vari‐
58       ables.   Consider  the  following  arguments  to  ncwa: “-a latitude -w
59       lat_wgt -d latitude,0.,90.” where lat_wgt is a weight in  the  latitude
60       dimension.   Since,  by  default ncwa weights coordinate variables, the
61       value of latitude in the output-file depends on the weights in  lat_wgt
62       and  is  not likely to be 45.---the midpoint latitude of the hyperslab.
63       Option -I overrides this default behavior and causes ncwa not to weight
64       or mask coordinate variables.  In the above case, this causes the value
65       of latitude in the output-file to be 45.---which is a somewhat  appeal‐
66       ing  result.   Thus,  -I  specifies  simple arithmetic averages for the
67       coordinate variables.  In the case of latitude, -I specifies  that  you
68       prefer  to  archive  the  central  latitude of the hyperslab over which
69       variables were averaged rather than the area weighted centroid  of  the
70       hyperslab.   Note  that  the  default  behavior  of  (  -I)  changed on
71       1998/12/01---before this date the default was not  to  weight  or  mask
72       coordinate   variables.   The  mathematical  definition  of  operations
73       involving rank reduction is given above.
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AUTHOR

77       NCO manual pages written by Charlie Zender and originally formatted  by
78       Brian Mays.
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REPORTING BUGS

82       Report bugs to <http://sf.net/bugs/?group_id=3331>.
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86       Copyright © 1995-2018 Charlie Zender
87       This is free software; see the source for copying conditions.  There is
88       NO warranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR
89       PURPOSE.
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SEE ALSO

93       The full documentation for NCO is maintained as a Texinfo manual called
94       the NCO Users Guide.  Because NCO is mathematical in nature, the  docu‐
95       mentation  includes  TeX-intensive  portions not viewable on character-
96       based displays.  Hence the only complete and authoritative versions  of
97       the NCO Users Guide are the PDF (recommended), DVI, and Postscript ver‐
98       sions at <http://nco.sf.net/nco.pdf>, <http://nco.sf.net/nco.dvi>,  and
99       <http://nco.sf.net/nco.ps>,  respectively.   HTML  and XML versions are
100       available         at          <http://nco.sf.net/nco.html>          and
101       <http://nco.sf.net/nco.xml>, respectively.
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103       If  the  info and NCO programs are properly installed at your site, the
104       command
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106              info nco
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108       should give you access to the complete  manual,  except  for  the  TeX-
109       intensive portions.
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111       ncap(1), ncap2(1), ncatted(1), ncbo(1), ncclimo(1), nces(1), ncecat(1),
112       ncflint(1), ncks(1), nco(1), ncpdq(1), ncra(1), ncrcat(1),  ncremap(1),
113       ncrename(1), ncwa(1)
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HOMEPAGE

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