The optical turbulence is caused by the fluctuations in the index of refraction of the air. The refractive-index structure constant of the turbulence, Cn2, is a measure of the turbulence strength (units of m-2/3) and depends on the wind and temperature vertical distributions.
The CN2 a key parameter for observing conditions, telescope design and for feasibility studies for adaptive optics.
The technique G-SCIDAR has proved to be the most efficient and reliable to retrieve CN2 profiles. The following figure shows the monthly statistical results of 140 nights of CN2 profiles obtained with this technique at the ORM.