Measurement of methane content in the atmosphere by OPO lidar system

A series of laboratory experiments was carried out to measure the absorption of the IR OPO laser radiation by methane within a calibrated CH4:N2 molecular mixture in a gas cell. The results of measurements of the laser radiation absorption at sounding wavelengths selected are presented and compared with the calculation results. Backscattered signals in the 3.30–3.43 μm spectral range are detected and processed with the use of the IR OPO lidar system designed along a horizontal sounding path in the atmosphere. Based on the experimental results, the absorption coefficients are estimated and the CH4 concentrations along a 800 m surface path are retrieved in the spectral range under study with a spatial resolution of 100 m.