CDO

Hi everyone,

I have a file cointaining daily snow data for several years. I computed the first day of snow in winter using the muldoy functionality

cdo yearmin -selmonth,7/12 -setctomiss,0 -muldoy -gtc,0.0 daily_snow.nc doy_of_first_snow.nc

What I now need is a mask that sets all days before this day to zero, and all days afterwards to 1. I do have a solution where I split up my files into seperate years, then apply muldoy to a file conatining only ones for each time step to create a day of year time series, and then mask this with the result in doy_of first_snow.nc for that year.

#create file with time steps of daily_snow containing only ones
cdo gec,0.0 daily_snow.nc ones.nc
#create file containing day of year for every time step
cdo muldoy ones.nc doy.nc

#year loop
for iyear in years do
#create file for one year containing day of first snow in every time step
  cdo mul -selyear,$iyear doy_of_first_snow.nc -selyear,${iyear} ones.nc doy_first_snow_fill_${iyear}.nc
#create mask
  cdo gt -selyear,${iyear} doy.nc doy_first_snow_fill_${iyear}.nc mask_doy_first_snow_${iyear}.nc
done

#merge mask files into one file
cdo mergetime mask_doy_first_snow_????.nc mask_doy_first_snow.nc

However, for long time series, this is rather tedious, slow and creates many interim files. I played around with piping commands to reduce the number of intermediate files, but mul is rather picky with what kinds of pipes arguments can have, so I could not make it shorter than what I have above. I wonder if there is a more streamline solution?

Thanks for your help!

Best, Heidrun