The Designing Technology Of Dual-wavelength Lidar And The Preliminary Research Results Of Gravity Waves In The Middle And Upper Atmosphere Over Wuhan

In the early of 1996, lidar systems, respectively used for detecting Rayleigh scattering and Na resonance fluorescence, were successfully designed in Wuhan Institute of Physics and Mathematics. But the lidar system can operate only at one kind of wavelength every time due to lack of laser equipment, so it can detect either the mesosphere of 30～80km or the sodium layer of 80～110km at a time and can't detect both simultaneously. This leads to the discontinuity of collected data in the space and time field. To simultaneously detect the wide altitude ranging from 30km to 110km, the original lidar systems have been improved and upgraded to be a multi-function one named dual-wavelength high-altitude detecting lidar.Two parts are concerned in this paper: the designing of dual-wavelength lidar, and the preliminary research results of gravity wave activities over Wuhan by analysis of newly collected data.In the first part, several aspects about dual-wavelength lidar are described, such as its aim of designation, detecting mechanism, designing scheme, basic structure, working principle and data-processing methods as well as the source of the inversion error. Also, several performance-testing experiments are given. The experimental results indicate that, due to adopting the following key technologies:(1) the twice-frequency-doubling residual-light-reusing technology(2) the dual-fiber focal-plane light-separating technology(3) more collimated transmitting beam and smaller field of view The dual-wavelength lidar can not only successfully detect the mesosphere and sodium layer simultaneously, but also can achieve the good performance comparable to that of the original two lidar systems operated separately.In the second part, by analyzing the data collected by the dual-wavelength lidar, the preliminary research results of the gravity wave activities in the mesosphere and the sodium layer over Wuhan are given. To be specific, it contains the following:(1) searching gravity wave activities phenomenon in the mesosphere and sodium layer over Wuhan through the relative density perturbation contours.(2) introducing the method of extracting parameters of the chromatic gravity waves and the observed results over Wuhan.(3) a wave breaking phenomenon observed in the sodium layer over Wuhan (4) preliminarily attempting to research the atmosphere dynamical characteristics through connecting the mesosphere to sodium layer by dual-wavelength lidarThe preliminary results indicate that the dual-wavelength lidar is a useful tool forresearching the atmosphere dynamical characteristics over Wuhan.