When we couple

• Every hour
  • Snr has 3/4 similar sized timesteps
  • Jnr's timesteps are quick until the last timestep which is very slow because the full chemistry is run
• This means that we can only couple between Snr and Jnr every hour to avoid Snr and Jnr waiting a lot for one another.
• We couple on the hour, just after full chemistry is finished in Jnr