1

I need to get the principal coefficients (daily) of the first EOF of the daily geopotential height field (data = geopot.nc). I use only the cold season (N,D,J,F,M,A). My code is as follows:

cdo selmon,11,12,1,2,3,4 geopot.nc geopotw.nc
cdo --reduce_dim - copy geopotw.nc geopotw3.nc #delete 1 dimension of level=1)
cdo sub geopotw3.nc -ydaymean geopotw3.nc deseason.nc
cdo mulcoslat deseason.nc deseasoncos.nc
cdo eof,3 deseasoncos.nc eval.nc eof.nc

I got a warning message: statistics-module (Warning): Eigenvalue computation with one-sided jacobi scheme did not converge properly. 7017371 of 7244721 pairs of columns did not achieve requested orthogonality of 1e-12.

What I am doing wrong? Maybe I am missing something? Or maybe there are other better ways to achieve the result I am looking for? For example in R. Thank you for the help!

ClimateUnboxed
  • 7,106
  • 3
  • 41
  • 86
Indrute
  • 115
  • 10
  • this is probably not the issue, but did you check the deseason step worked correctly? Your file starts mid-year - just to doublecheck, can you try the more "robust" command cdo ydaysub geopotw3.nc -ydaymean geopotw3.nc deseason.nc and see if it gives the same? – ClimateUnboxed Dec 17 '21 at 12:33
  • ps: helps to check tag met data to target questions ;-) e.g the eof tag="end of file", not the EOF you were looking for ;-) and cdo is for EMF, I've been trying to get that tag renamed to avoid these mis-tag ambiguity issues, but to no avail so far unfortunately... – ClimateUnboxed Dec 17 '21 at 12:38
  • Thank you for the comment. I tried different options and I still have the same warning. I also tried command cdo sub ifile -timmean ifile anom_file and counting eof warning looks like: statistics-module (Warning): Eigenvalue computation with one-sided jacobi scheme did not converge properly. 6116698 of 6239278 pairs of columns did not achieve requested orthogonality of 1e-12 cdo eof: Processed 1 variable [1283.48s 132MB] – Indrute Dec 22 '21 at 11:52
  • hi - did you try the cdo ydaysub though? you opened the deseasonalized file in ncview and checked it looks ok? – ClimateUnboxed Dec 22 '21 at 13:03
  • Did the answer help? – ClimateUnboxed Feb 05 '22 at 13:24

1 Answers1

0

I think this post will help, you can change the max iteration number using an environmental variable in the following way:

export MAX_JACOBI_ITER=100

I'm fairly sure that will help with your convergence issue (see my comment).

ClimateUnboxed
  • 7,106
  • 3
  • 41
  • 86
  • Ok, I just tested this by doing an EOF analysis on SST data from ERA5 from 2015 to 2020, out of the box I get the convergence warning, using this solution, the warning goes away, so this should solve the issue – ClimateUnboxed Mar 16 '23 at 15:49