Abstract:
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).
Quality
Aerosol backscattering ratio and aerosol volume depolarisation are retrieved from backscattered LIDAR signal by the formulas:
Scattering Ratio Formula: [(Baer+Bmol)/Bmol] Depolarization Ratio Formula : {[Baer+Bmol]s/[Baer+Bmol]p}*Dmol where Baer= backscattering from aerosols ... Bmol= pure molecular atmosphere s = orthogonal polarization p = parallel Dmol = Depolarization ratio for molecules (0.0144)
The aerosol extinction profile (EXT(Z)) [cm-1] is computed from the aerosol back-scattering profile: EXT(Z) = 10^[K0 + K1*X + K2*X^2] where K0 = -5.1973 K1 =-0.3869 K2 = -0.0696 X = Log(BACK(z))
The temperature profile is computed from the air density profile, normalized from 35 to 40 km using an absolute profile (CIRA,1972), by the hydrostatic equilibrium equation
Use Constraints
Research activity supported by the National Program of Antarctic Research
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