The model atmosphere is calculated with the skynoise task. The atmosphere is modelled as a Kolmogorov turbulent thin-screen  with a characteristic turnover frequency and scaling law. Different models may be generated for the same parameters using a random number seed (specified or calculated internally using the system clock). The parameters may be modified though the user should be familiar with the details of this model of the atmosphere before exploring the parameter space too widely.
The model atmosphere calculated is generic and may be used for simulations at both 850 m and 450 m. The model is scaled at the time of simulation according to the particular wavelength.
SMURF -- the Sub-Millimetre User Reduction Facility