Raman lidar for profiling atmospheric CO 2

Based on laser atmosphere backscattering spectrum, the design and experiment of a Raman lidar system for measurement of atmospheric CO 2 are presented. 354.7nm third harmonic of Nd∶YAG laser is transmitted with 350mJ pulse energy and repetition rate of 20Hz. The receiver employs a photomultiplier tube with quantum efficiency of 25% and 200MHz photon counter, and it detects Raman backscattering 371.66nm(shift 1285cm -1 ) signal. At 1h integration, the signal to noise ratio below 2.5km is greater than 8. Combinatorial filter is used to reject interference presented by 354.7nm intense Mie-Rayleigh backscattering and 375.4nm Raman backscattering from O 2 . We compare the Raman return signal at 371.66nm from atmospheric CO 2 with the reference Raman return signal at 386.7nm from atmospheric N 2 to retrieve the atmospheric CO 2 concentration.