Résumé
The future Cherenkov Gamma Ray experiment CTAO will reach a sensitivity and energy resolution never obtained until now by any other high energy gamma–ray experiment. Raman lidars can help reduce the systematic uncertainties of the molecular and aerosol components of the atmosphere so these performances can be reached. The motivation for Raman lidars and the design and development of the Montpellier Raman lidar system, to be installed at the CTA south site, is described. It provides both multiple elastic and Raman readout channels and custom-made optics design. Preliminary lidar tests and signals acquired at the OHP observatory confirms the actual performance of the lidar been consistent with the desired CTAO goals.