Performance Simulation and Preliminary Measurements of a Raman Lidar for the Retrieval of CO2 Atmospheric Profiles

Within the frame of the project CONCERNING (COmpact RamaN lidar for Atmospheric CO₂ and ThERmodyNamic ProfilING), we investigated the feasibility and the limits of a ground-based Raman lidar system dedicated to the measurement of CO₂ profiles. The performance of the lidar system was evaluated through a set of numerical simulations. The possibility of exploiting both CO₂ Raman lines of the ν1:2ν2 resonance was explored. An accurate quantification of the contribution of the Raman O₂ lines on the signal and other (e.g., aerosol, absorbing gases) disturbance sources was carried out. The signal integration over the vertical and over time required to reach a useful signal to noise ratio both in day-time and night-time needed for a quantitative analysis of carbon dioxide sources and sinks was evaluated. The above objectives were obtained developing an instrument simulator software consisting of a radiative transfer model able to simulate, in a spectrally resolved manner, all laser light interaction mechanisms with atmospheric constituents, a consistent background signal, and all the devices present in the considered Raman lidar experimental setup. The results indicate that the simulated lidar system, provided to have a low overlap height, could perform measurements on the low troposphere (<1 km) gradients (1-5 ppm) with sufficient precision both in day-time and night-time with an integration time of 1-3 h and a vertical resolution of 75 m. The selected Raman lidar setup is currently being tested and we aim to present preliminary results during the conference.