Physical variables.
ref_physics
Name of the physical variable: "salt", "NO3", "NH3", "Temp", "Chl_a" and "Denitrifiction".
Boxid starting from 0 to numboxes - 1.
Layerid starting from 0 to numlayers - 1.
Simulation time in years. Modeltimestep was converted to actual time based on the settings in the 'run.prm' file.
Obseravtion column storing the actual output value. units are salt = PSU; NO3, NH3 = mg N m-3; Temp = degrees Celcius; Chl_a, Denitrifiction = ?