Feasibility of Raman lidar for profiling CO2 mixing ratio in the lower troposphere

This study explores the potential of Raman lidar technology for vertical profiling CO2 mixing ratios in the atmosphere. Measurements taken in 2023 at the ATOLL observatory, Laboratoire d’Optique Atmosphérique, University of Lille, France, demonstrate the promising capabilities of a Raman lidar system. This system is equipped with a 355 nm laser emitting 90 mJ pulses and a receiving telescope with a 400 mm aperture. It effectively derives vertical CO2 distributions with a vertical resolution of 200 meters up to heights of 4 kilometers, given several hours of signal accumulation. Notably, the lidar operates without calibrating CO2 concentrations, allowing only for the assessment of relative changes in CO2 mixing ratios with height. However, aerosol fluorescence introduces uncertainties in the CO2 measurements. To address this issue, a correction approach using single-channel fluorescence measurements is proposed, which could potentially enhance the measurement precision.