title: converting an accumulated variable to timestep values in a netcdf file with CDO
body: <p>I have a netcdf-file with about 100 timesteps on a grid with one variable, which is accumulated over the timesteps. I am now interested in calculating the contribution of each timestep to the variable's value (i.e. the difference of consecutive timesteps).</p>
  
  <p>Currently I use the following sequence:</p>
  
  <ol>
  <li>To extract every single timestep into a new file I use <code>cdo seltimestep,$i ...</code>, </li>
  <li>calculate each difference into a new file with <code>cdo sub $i ${i-1} ...</code> </li>
  <li>and merge those new files in the end with <code>cdo mergetime ...</code> into one single result file.</li>
  </ol>
  
  <p>That seems to me to be very cumbersome and not ideal regarding to performance. Because of the amount of timesteps I cannot use a cdo pipeline and need to create many files in the meantime therefore.</p>
  
  <p>Is there one better solution to convert an accumulated variable to timestep values with cdo (or something else like nco/ncl?)</p>