  Knowledge of the optical refractive index structure parameter $C_n^2$ is of
interest for Free Space Optics (FSO) and ground-based optical astronomy, as it
depicts the strength of the expected scintillation on the received optical
waves. Focus is given here to models using meteorological quantities coming
from radiosonde measurements as inputs to estimate the $C_n^2$ profile in the
atmosphere. A model relying on the $C_n^2$ statistical definition is presented
and applied to recent high-density radiosonde profiles at Trappes (France) and
Hilo, HI (USA). It is also compared to thermosonde measurements coming from the
T-REX campaign. This model enables to obtain site-specific average profiles and
to identify isolated turbulent layers using only pressure and temperature
measurements, paving the way for optical site selection. It offers similar
performance when compared to a Tatarskii-based model inspired by the
literature.
