Notes on Rayleigh Scattering in Lidar Signals

The correct formulation for Rayleigh scattering using the classical approach [1] is used to analyze the molecular contribution in the lidar signals. Within classical approach, three atmospheric scenarios are considered: 2, 4 and 5-component atmosphere (N2 + O2, N2 + O2 + Ar + CO2 and N2 + O2 + Ar + CO2 +water vapor). Two case studies are performed to see the relative difference between retrievals using these scenarios. First case study considers 23 days measurements of air pressure, temperature and relative humidity at 31.8m. The second case study uses a radiosounding of air pressure, temperature and relative humidity. Retrievals of the aerosol extinction and backscatter coefficient are compared, using lidar signals at 355nm and 387nm. The quantum approach is used to compute the aerosol backscatter coefficient and the correction factors for the temperature-dependence of the molecular cross-sections [2]. The results show that for water vapor between 10 and 20g/kg, the relative difference between 5-component and 2-component atmosphere is between 0.5% and 1% for molecular scattering and between -0.9% and -0.4% for molecular backscattering. For aerosol backscatter (extinction) coefficient, the difference is bellow 1%. Thus a two-component atmosphere is a good approximation. Temperature correction can be ignored for N2.JRC.DDG.H.2-Climate chang