Pseudo-random Modulation Continuous-Wave Sodium Temperature/Wind Lidar

Utilizing a 589 nm narrowband pulse laser,the sodium fluorescence lidar can measure the sodium number density,atmospheric temperature,and wind field in the mesopause region(80-105km).These observations with high temporal and vertical resolutions make essential contributions to the study of atmospheric dynamics.The sodium lidar with a dye laser pumped by an Nd:YAG laser is usually bulky and high-power-consuming,with complex operation and instability.Therefore,it is only suitable for operation in laboratory conditions.Although the latest all-solid-state ultra-narrowband system has achieved all-solid structure and high stability,it is still challenging to miniaturize its size in a short time due to its complex design.Fortunately,the recent technological development of the all-solid-state fiber continuous-wave(CW)laser with high power and excellent stability is a new opportunity for the light source of the lidar system.This thesis describes the development of a prototype of the world’s first pseudo-random modulation CW(PMCW,Pseudo-random Modulation Continuous-Wave)sodium temperature/wind lidar and its observational results on sodium density,atmospheric temperature,and wind field in the mesopause region.The main results are summarized as follows:(1)We demonstrated the ranging capability of the CW lidar with a pseudorandom M-code.A unique method using residual light in modulation is proposed,which can fully utilize the light source.A computer program was designed to simulate the M-code modulation,transmission,and signal-receiving processes to analyze the signal-to-noise ratio and examine the feasibility of a PMCW sodium lidar system.(2)We developed a prototype of the world’s first PMCW sodium temperature/wind lidar.Several breakthrough technologies are listed here:multiplexing technology of residual light from CW laser during M-code modulation process;near-ground signal suppression and automatic collimation technology based on biaxial structure;high-efficiency optical coupling technology;data acquisition and inversion technology.This prototype has achieved the characteristics of all-solid-state,miniaturization,low power consumption,high energy efficiency,high stability,and automatic operation.(3)Continuous multiple-day observations using the PMCW sodium lidar were carried out.The results of atmospheric temperature and wind field in the mesopause region agree with the simultaneous observations by satellite and nearby meteor radars.Significant atmospheric tidal and gravitational wave perturbations have been found in the temperature and wind fields.These suggest that this system can reliably measure the mesopause region temperature and wind with high temporal and vertical resolutions.