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1. Equipment

The backscatter lidar used at Palaiseau includes a Nd/Yag pulsed laser Quantel 481 (wavelengths :1064 and 532 nm, energy per pulse : 250 mJ at 532 nm, pulse duration : 12ns, frequency: 10Hz, beam divergence : 0.7 mrd). Telescope field of view is 3mrd. Its vertical axis is tilted 5 degrees of the zenith in order to avoid specular reflexion by oriented ice plates. Parallel and cross polarized signals are detected at 532 nm. Lidar signal inversion is made using usual methods described in Elouragini (1995) or Young (1995).

Thermodynamical parameters (temperature, wind speed and direction, relative humidity) are collected from local radiosondes launched at 0000 and 12000 UT every day from the METEOFRANCE station of Trappes nearby Palaiseau.
We also use AVHRR data for radiance measurements in IR channels. Hence, ECMWF data are used to draw divergence field maps and to calculate ageostrophic velocities and potential vorticity.