Development Of Middle Atmospheric Temperature And Wind Lidar For Gravity Wave Observation

The middle and upper atmosphere is a very complex and important region. It contains a wealth of important geophysical phenomena, for example, the Earth’s coldest environment; polar mesospheric clouds (PMC) and noctilucent clouds (NLC); the meteoric metal layers of Na, K, Ca, Li and Fe; the airglow layers of OH, O, and O2; and planetary, tidal, and gravity wave activities that play vital roles in overall global atmosphere circulation. Lidar measurements of temperature and density perturbations with high temporal resolutions are frequently used to perform gravity wave studies in the stratosphere and mesosphere in the past few decades. However, wind observations with sufficient resolution enable detailed characterization of inertia gravity waves (IGW). Unfortunately, simultaneous measurements of wind and temperature in the stratosphere and mesosphere are very scarce. Till now, only a few lidar systems are capable to realize longtime and stable wind measurements in the middle atmosphere, such as the Rayleigh-Mie-Raman lidar in ALOMAR, mobile Rayleigh Doppler lidar in USTC, and sodium lidar based on FADOF double edge technique in University of Colorado at Boulder. In this work, discussions start with the existing techniques of wind and temperature measurements. The main work of this dissertation can be summarized as three parts:Firstly, I participated in the development of mobile Rayleigh Doppler wind and temperature lidar at University of Science and Technology of China. In order to improve the frequency locking accuracy and stability of the lidar system, an integrating sphere is incorporated to the front optics of the Fabry-Perot interferometer. While for the system calibration, a non-porlarization dependent cube beamsplitter instead of a fiber optical beam splitter is used, which enables the position of each outing pulse with respect to the double-edge channels of the FPI in frequency domain to be exactly recorded. Verification experiment was performed to check the influence of spectral drift introduced by the seed laser and the FPI. The conclusion is when the temperature fluctuation of the system is controlled within 0.1 K, a systemic wind error of 0.6 m/s can be realized.Secondly, some key technical updates were performed on the STAR lidar system at University of Colorado, Boulder. The procedure how to eliminate aberration for a Newtonian telescope is given. We also made raytracing for the post-fiber optics by ZEMAX software, and as a result, the optical efficiency of lidar receiver is greatly improved.5-10 times as before. Besides, a Faraday anomalous dispersion optical filter (FADOF) is designed and used for daytime observation. Numerical simulation is performed to calculate the equivalent noise bandwidth of the FADOF, which gives the criterion of optimizing the working temperature and magnetic field to get a better performance for the FADOF.Finally, case study of gravity waves are performed by using simultaneous wind and temperature data of these two lidars.2D-FFT algorithm is applied to the power spectrum analysis of wind and temperature perturbations. After filting the power spectrum with a rectangle window, IFFT is used to resolve and reconstruction of wave features. For horizontal wind data of USTC mobile Rayleigh Doppler ldiar, temporal hodograph analysis was performed to the perturbations of meridional and zonal winds to determine its propagation direction.