Assessment of the three-frequency pulse alternation method for simultaneously troposphere wind and aerosol profiling retrieval in a direct detection lidar

The direct detection Doppler wind lidar, which is capable of detecting Rayleigh and Mie scattering signals synchronously and achieving the atmospheric wind field profile detection from the surface to the top of the troposphere, has become an important tool for the meteorology measurements. It is divided into two measurement mechanisms, including the edged technique and the fringe-imaging technique. The single-edge measurement method with use of iodine vapor filter is one of the traditional edge detection methods. The existing iodine molecular filter wind profile retrieval algorithms are based on the precise measurement of aerosol backscatter ratio <i>R_b</i> and sensitivity <i>S</i>, which bring certain wind speed errors. In order to improve the wind retrieval accuracy and measurement sensitivity, this paper proposes a retrieval algorithm based on the three-frequency pulse alternation (TFPA) method by using Rayleigh-Mie scattering, realizing the simultaneous retrieval of wind profile and <i>R_b</i> in the troposphere. Simulation experiments were carried out under different atmospheric conditions to evaluate the effectiveness and applicability of the algorithm and to analyze the main factors that affecting wind speed accuracy. The simulation results show that the TFPA method is mainly suitable for the wind profile retrieval where the aerosol exists in the atmosphere with <i>R_b</i> > 0.1. Compared with the direct measurement sensitivity method, the TFPA method reduced the radial wind speed error by 50%, decreased the standard deviation of the horizontal wind speed from the true value by 71.6%. The radial wind speed error caused by temperature and pressure uncertainties are small, which can to be ignored. Under stable atmospheric conditions, the effect of vertical wind velocity is also slight.