LIDAR measurements for PSC studies at middle and high latitudes in southern hemisphere

Ozone depletion is one of the key issues on which the investigation of the
international community is directed. Its great importance is due to the fact
that ozone depletion results in an alteration of the chemical physical
equilibrium of the atmosphere. Such alteration can induce variation in the
climatology and then potential and real influences on the planetary ecosystem.
The phenomenon of ozone depletion is much more evident in the polar
stratospheres because of the very low temperatures existing there during the
winter (particularly in Antarctica). The observations have established that the
phenomenon is directly related to the presence of polar stratospheric clouds
(PSCs). The PSCs, which can only form in the low polar temperatures, also
produce the dehydration and the denitrification of the stratosphere by the
sedimentation of their particles. The removal of water and nitrates increase
the lifetime of the active chlorine improving the catalytic ozone depletion.

Recently, observations of clouds at high tropospheric and low stratospheric
altitudes have established the importance of cirrus clouds for their
contribution to the ozone destruction at lower stratospheric levels. Our group
possesses two LIDAR stations in Antarctica, one at the American base of McMurdo
(MCM), and the second at the French base of Dumont d'Urville (DDU). Both the
stations are LIDAR primary stations for the NDSC (Network for Detection of
Stratospheric Change). The MCM and the DDU base are favorably placed for the
study of the stratospheric phenomena connected to the polar vortex activity,
the American base being well inside the polar vortex area and the French base
in position such as to make possible measurements at the vortex edge. LIDAR
systems operates with a Nd:YAG laser, the transmitter being equipped with a 532
nm channel, pulsed at 10 Hz repetition rate with pulse energy of 200 mJ about.
By LIDAR observation retrievals we measure PSC microphysics characteristics,
aerosol extinction in the 8-35 km range and the temperature profile in the
30-60 km range, in absence of PSC and aerosol. The LIDAR stations operate
continuously since 1993 (MCM) and 1989 (DDU).