CDO

My problem: I want to filter data that exceed a threshold like +/- 1 standard deviation.

I've created a binary time series mask consisting of 1 and 0.

cdo ge -timstd ifile.nc ifile.nc mask.ge.nc

How can I now
a) separate this time series in two (unevenly) spaced ones
b) or at least, output those timesteps that belong to value 1 in the mask
to apply this mask on my data?

An alternative solution would be applying the mask on other datasets.
The problem is that I can apply the mask on another time series with same dimensions

  cdo ifthen mask.nc ts.ns ts.masked.nc

but not on field data:

  cdo ifthen mask.nc field.ns field.masked.nc

breaks with a dimension mismatch.

Thanks in advance,
Stephan