par J. LACAZE* et AL. GRIGORIU**
* Faculté des Sciences de Pau, Laboratoire Hydrodynamique de la Pollution
Atmosphé des Sciences de Pau, Laboratoire Hydrodynamique de la Pollution
Atmosphérique, Pau France
** Faculté de Physique, Bucarest, Roumanie
If an acoustical-optical signal is produced (airplane, captive-baloon, etc.)
in P0, at a height comparable with that of the ground
inversion layer, then the optical signal arrival may be considered instantaneous,
but the acoustical
one is received in O, A, A', B, B', after the corresponding intervals 
.
By Vm is denoted the sound propagation speed in the subjacent air layer
with mean temperature T, and by the mean wind velocity. The successive centers
of
the sound propagation spheres developed in the air are denoted by 
.
The authors obtained the equations for the wind direction and velocity at the
Observatory in O, and for the sound speed V, which gives the mean temperature
of the layer under experiment.
For air pollution studies the relation giving the wind direction is exceedingly
easy to obtain.