地基激光雷达对大气金属层的探测研究

Abstract

Significance The atmospheric detection of the mesosphere (about 80-110 km) is of scientific research and application significance. There are many important spatial features and phenomena in this region, including the coldest altitude of the Earth's atmosphere (~90 km), and special phenomena such as highaltitude noctilucent clouds, temperature inversion layer, and atmospheric metal layers also occur in this region. Gravity wave fragmentation makes the atmospheric disturbances in this region particularly intense, and the wind shear in this region becomes extremely intense. This region is also part of the atmospheric photochemical layer, and the atmospheric compositions have dramatic diurnal variations. With the development of aerospace, the influence of this region needs to be closely focused on. For example, suborbital flights (generally defined as 35 to 300 km to the Earth) involve this region, and these studies will lay a solid foundation for future suborbital commercial flights. This region has long been relatively unknown to humans because of the limitations of traditional detection methods.Fortunately, there are atmospheric metal layers in this region. As the cross section of resonance fluorescence scattering of metal atoms and ions is much larger than those of Rayleigh scattering and Raman scattering, it can be employed to detect lowconcentration atmospheric components. In the past half century, by adopting the transition spectra of atoms and ions at specific wavelengths, the metal layer of the atmosphere has been detected by lasers with specific wavelengths and laser remote sensing technology. These metal atoms and ions are excellent tracers of atmospheric fluctuations, and many parameters such as atomic number density, temperature, and wind have been obtained. In recent years, with the discovery of thermospheric metal layers, the height range of atmospheric metal layers has been expanded, and the study of metal layers has been paid great attention to.Progress Based on the research of our team and collaborators, we introduce the development of atmospheric metal layer lidar and the current situation and trend of atmospheric metal layer detection by lidar. First, the dye laser opens the door to the atmospheric metal layer. Second, the sum frequency of the dye laser and YAG laser increases the laser energy further.Third, with pulsed dye amplifier employing dye as the working substance, directly amplifies the singlemode continuous seed laser into a highpower pulse laser. This meets the dual characteristics of high spectral resolution and sound center frequency stability of wind and temperature detection in metal layers. Fourth, narrowband filtering technology extends lidar detection from night to all time. Fifth, a dye laser needs to change dye frequently with low single pulse energy, and allsolidstate laser solves this problem. Sixth, OPO lasers have many advantages such as high integration degree, good pump light spot, high single pulse energy, and further improved detection ability of atmospheric composition...