The Study Of The Sensitivity Measurement And Calibration For Doppler Wind Lidar Using Raman Scattering

Wind field is one of the necessary parameters for meteorology research. Doppler lidar is able to detect wind field in high spatial and temporal resolution.By detecting the Doppler frequency shift caused by atmosphere movement, Doppler lidar can retrieve the wind velocity. The technologies of Doppler wind lidar include coherent method and incoherent method (also called direct detection technique). Coherent method is only applied to aerosol scattering but not molecular scattering due to the broadened scattering spectrum. On the other hand, incoherent method can detect both of aerosol and molecular scattering by measuring the energy of returning signal and is one of the most effective way of wind measuring in clear air. In direct detection method, aerosol backscattering ratio is essential to define the measuring sensitivity of the wind speed. However, the measurements of aerosol backscattering ratio and wind are asynchronous among the state of the art Doppler lidars so that the uncertain error could be brought by the temporal and spatial variation of aerosol particles.The article analyses the problem of Doppler lidar sensitivity measurement and proposes the solution. Basing on the backscattering spectrum, a new receive channel of inelastic scattering is added to acquire Raman scattering with beam splitters and interference filters. With the pure molecular scattering, Raman scattering, the novel system probes aerosol backscattering ratio in real time with wind measurement. Meanwhile, it is capable of retrieving the extra parameters of aerosol backscattering coefficient, extinction coefficient and atmosphere temperature profile to develop a multi-function meteorology lidar.The article designs tow blue prints of vibrational Raman method and pure-rotational Raman method for calibration research, respectively. The vibrational Raman method is testified with experiment. The results show that this method is capable of measuring aerosol backscatter ratio profile of low-altitude troposphere (below 7km) at the same time as wind measurement, which can define the wind measurement sensitivity. Aerosol extinction coefficient and lidar ratio are additional parameters acquired in measurement. A new arithmetic of aerosol backscatter ratio is proposed and proved to be more effective. The pure rotational Raman method is assessed by simulation. The results of calculation testify the feasibility of system and establish the theory foundation of developing the multi-function meteorology lidar.