Differences in the values produced by " cdo infon " and " cdo fldmean "

Dear Support,

The command cdo infon dt_blacksea_twosat_phy_l4_19930101_20170110.nc produces:

    -1 :       Date     Time   Level Gridsize    Miss :     Minimum        Mean       Maximum : Parameter name
     1 : 1993-01-01 00:00:00       0     6720    3471 :    -0.11470    *0.051625*     0.20910 : sla           
     2 : 1993-01-01 00:00:00       0     6720    3471 :    0.020400    *0.046611*    0.089000 : err           
     3 : 1993-01-01 00:00:00       0     6720    3800 :    -0.45600  *0.00050024*     0.48360 : ugosa         
     4 : 1993-01-01 00:00:00       0     6720    3800 :    -0.45330  *-0.0058005*     0.31460 : vgosa

The commands cdo fldmean dt_blacksea_twosat_phy_l4_19930101_20170110.nc out.nc; cdo infon out.nc produce:

    -1 :       Date     Time   Level Gridsize    Miss :     Minimum        Mean       Maximum : Parameter name
     1 : 1993-01-01 00:00:00       0        1       0 :                *0.051200*             : sla           
     2 : 1993-01-01 00:00:00       0        1       0 :                *0.046500*             : err           
     3 : 1993-01-01 00:00:00       0        1       0 :               *0.0014000*             : ugosa         
     4 : 1993-01-01 00:00:00       0        1       0 :              *-0.0057000*             : vgosa

As you can see, the averages are different. Variable ugosa is the most striking case.

Which one of the commands give the right results, or are both wrong ?

Kind regards,
Eduardo

cdo -V
Climate Data Operators version 1.7.2 (http://mpimet.mpg.de/cdo)
Compiled: by usxa on capgros (x86_64-unknown-linux-gnu) Aug 10 2016 09:22:44
Compiler: gcc -O3 -fopenmp 
 version: gcc (build by usxa) 5.3.0
Features: DATA PTHREADS OpenMP4 HDF5 NC4/HDF5 SZ UDUNITS2 PROJ.4 XML2  SSE2
Libraries: HDF5/1.8.17 proj/4.92 xml2/2.9.3
Filetypes: srv ext ieg grb grb2 nc nc2 nc4 nc4c 
     CDI library version : 1.7.2 of Aug 10 2016 09:22:26
 CGRIBEX library version : 1.7.5 of Jun  3 2016 14:44:00
GRIB_API library version : 1.15.0
  NetCDF library version : 4.4.1 of Aug  3 2016 11:10:49 $
    HDF5 library version : 1.8.17
 SERVICE library version : 1.4.0 of Aug 10 2016 09:22:21
   EXTRA library version : 1.4.0 of Aug 10 2016 09:22:19
     IEG library version : 1.4.0 of Aug 10 2016 09:22:20
    FILE library version : 1.8.2 of Aug 10 2016 09:22:19

dt_blacksea_twosat_phy_l4_19930101_20170110.nc (113 KB) dt_blacksea_twosat_phy_l4_19930101_20170110.nc

Replies (2)

RE: Differences in the values produced by " cdo infon " and " cdo fldmean " - Added by Uwe Schulzweida over 6 years ago

Both results are correct!
The CDO operator info shows the arithmetic mean and fldmean computes the area weighted mean.

RE: Differences in the values produced by " cdo infon " and " cdo fldmean " - Added by e ddc over 6 years ago

Thanks Uwe, I missed that important detail!
Cheers,
Eduardo

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