change values of specific levels
Added by Shizhu Wang almost 7 years ago
Hi, I have a nc file temp.nc, with a variable called temp(lon,lat,depth), where the length of depth is 20.
Now I want to replace the values of the last level with the values of the second last level:
temp(:,:,20) = temp(:,:,19)
How can I do this with CDO?
Thanks.
Shizhu
Replies (2)
RE: change values of specific levels - Added by Karin Meier-Fleischer almost 7 years ago
Hi Shizhu,
I think the fastest way you can do this (if you really want it?) is using NCL because in my opinion you can't do it with CDO.
Here is an ksh-shell script creating and running an NCL example script:
#!/bin/ksh
infile=infile.nc #-- name of your input file
outfile=outfile.nc #-- name of the output file
cat << EOF > script.ncl
f = addfile("$infile","r")
temp = f->temp ;-- temp(lon,lat,depth)
ndepth = dimsizes(f->depth) ;-- number of depths
temp_new = temp ;-- copy variable and meta data
temp_new(:,:,ndepth-1) = temp(:,:,ndepth-2) ;-- copy data of next to last plev to last plev
system("rm $outfile") ;-- delete file if it exists
g = addfile("$outfile","c") ;-- create new file
g->temp_new = temp_new ;-- write data to new file
EOF
ncl script.ncl #-- run NCL script
exit
-Karin
RE: change values of specific levels - Added by Shizhu Wang almost 7 years ago
Hi Karin,
Thanks for your suggestion. I know nothing about ncl, but I just made it using nco:
ncap2 -s "temp(19,:,:)=temp(18,:,:)" in.nc out.nc
Two reasons for this:
1. dimensions are reversed: in Matlab or Fortran, it is temp(lon,lat,depth); but in ncdump (i.e., nco), it is temp(depth,lat,lon).
2. every dimension in nco starts from 0. So here temp(19,:,:) in ncap2 is temp(:,:,20) in Matlab or Fortran.
Best,
Shizhu