A Spontaneous Rayleigh-Brillouin Scatteing Study For The Characterization Of Atmospheric

As the main human survival environment, the atmosphere is of great significanceto our daily life and production. For Doppler wind lidar (DWL) based on Rayleighscattering and using direct detection techniques, a systematic wind speed dependenterror in the retrieved wind speed occurs if the scattered frequency spectrum is assumedto be Gaussian and Brillouin scattering is neglected. The wind speed is overestimatedby10%at sea level and still by3%for10km altitude. For this reason, we develop thespontaneous Rayleigh-Brillouin scattering study for the characterization of atmosphere,which can get the more accurate atmosphere parameters. At the same time, the methodis also can be used to measure three-dimensional temperature field with the moreconvenience and the higher accuracy. In addition, with the Brillouin scattering spectrumand laser scanning technology, we can get the pressure, molecular density, velocity andbulk viscosity from different altitude. Therefore, the method has get the more and moreattention in aerodynamics, atmospheric laser radar and military detection.In the paper, analysis the Rayleigh–Brillouin scattering spectral characteristics ofatmosphere in the theory, derive the theoretical equation of Rayleigh–Brillouinscattering, discuss the method of detecting Rayleigh–Brillouin scattering spectrum andthe factors on the influence of atmospheric spontaneous Rayleigh-Brillouin scatteringcombined with Rayleigh–Brillouin scattering feature, simulate the scattering spectrumon the different conditions; in the experiment, we design the experiment system tomeasure the Rayleigh–Brillouin line shape, give the introduction of detailed parametersand the influence factors about laser source、scattering cell、Fabry-Perot spectrometer、data acquisition device, then perform the relative experiment about spontaneousRayleigh-Brillouin scattering at the90degrees direction study for the characterizationof atmosphere at the same temperature(at300k), different pressure(at1atm、2atm、3atm),and acquire the Rayleigh-Brillouin scattering spectrum in the experiment, then comparethe experiment results with simulation, and find that the experiment spectrum withoutBrillouin is different from simulation at2atm, the frequency range of experimentspectrum with Brillouin is different from simulation at3atm; At the end of the paper,analysis the possible reason for the difference between experiment and simulation,discuss the problem met in experiment and the factors on the influence of experiment SNR, and then we put forward the suggestion to the better experiment SNR and solutionto the experiment problems, which is the practical experience for the future experimentswith the different conditions(different pressure, different temperature and differenthumidity).