  The characterization of the wind speed vertical distribution V(h) is
fundamental for an astronomical site for many different reasons: (1) the wind
speed shear contributes to trigger optical turbulence in the whole troposphere,
(2) a few of the astroclimatic parameters such as the wavefront coherence time
(tau_0) depends directly on V(h), (3) the equivalent velocity V_0, controlling
the frequency at which the adaptive optics systems have to run to work
properly, depends on the vertical distribution of the wind speed and optical
turbulence. Also, a too strong wind speed near the ground can introduce
vibrations in the telescope structures. The wind speed at a precise pressure
(200 hPa) has frequently been used to retrieve indications concerning the tau_0
and the frequency limits imposed to all instrumentation based on adaptive
optics systems, but more recently it has been proved that V_200 (wind speed at
200 hPa) alone is not sufficient to provide exhaustive elements concerning this
topic and that the vertical distribution of the wind speed is necessary. In
this paper a complete characterization of the vertical distribution of wind
speed strength is done above Mt.Graham (Arizona, US), site of the Large
Binocular Telescope. We provide a climatological study extended over 10 years
using the operational analyses from the European Centre for Medium-Range
Weather Forecasts (ECMWF), we prove that this is representative of the wind
speed vertical distribution at Mt. Graham with exception of the boundary layer
and we prove that a mesoscale model can provide reliable nightly estimates of
V(h) above this astronomical site from the ground up to the top of the
atmosphere (~ 20 km).

Instrumentation and Methods for Astrophysics;Atmospheric and Oceanic Physics