A mixing layer height profile input file must consist of two lines:

the first line must begin with time and should be followed by space-separated real scalars, giving the times (in s after the start of the simulation) of the height set points — the times must be in increasing order
the second line must begin with height and should be followed by space-separated real scalars, giving the mixing layer heights (in m) at the corresponding times

The mixing layer height profile is linearly interpolated between the specified times, while before the first time it takes the first height value and after the last time it takes the last height value.

Example:

 time    0    600   1800  # time (in s) after simulation start
 height  500  1000  800   # mixing layer height (in m)

Here the mixing layer height starts at 500 m at the start of the simulation, rises to 1000 m after 10 min, and then falls again to 800 m at 30 min. Between these times the mixing layer height is linearly interpolated, while after 30 min it is held constant at 800 m.