CDO

hi!

I am not completely sure what you want, but pls check this post

the expr has some useful function to create data fields based on coordinates

there is also the built-in docu:

cdo -h expr

best
ralf

Sorry, I wasn't clear. My aim is not to generate the new field but to compute the amplitude and phase of zonal waves of an existing dataset.

Elio Campitelli wrote in RE: Zonal waves:

Sorry, I wasn't clear. My aim is not to generate the new field but to compute the amplitude and phase of zonal waves of an existing dataset.

alright.

I would remap into a regular lon-lat grid an take the dateset along each latitude as a sep. data-series and do some spectral analysis on it.
not sure if climate scientists would do it that way, though. I am just a theoretical physicist.

Yes, that's basically what I would do in R, but in cdo the spectral operators seems to operate exclusively in the time domain.