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The sodium atom existed in the metal layer of the earth’s atmosphere has a high atomic number density and a large scattering cross section. Sodium layer can act as a good tracer for atmospheric detection in the middle and lower-thermosphere (MLT) region. The sodium fluorescence lidar uses ultrashort pulsed laser to excite sodium atoms, which enabling simultaneous detection of wind and temperature in the middle and upper atmosphere. This paper reports on the development of sodium fluorescence laser radar in recent years, especially the integration of fiber-coupled optical switches and fiber-coupled acousto-optic frequency modulation technologies, which greatly improved the stability and reliability of lidar system and reduced the maintenance of lidar operation, laying a good foundation for the application of lidar observations under harsh environments. This technology has been applied to the sodium wind/temperature lidar in Yangbajing, Tibet and has been running stably for a long time.

A combined lidar system on the basis of conventional Rayleigh lidar has been extended by two rotational Raman (RR) channels for nocturnal atmospheric temperature measurements from 5 to 80 km over Wuhan, China (30.5°N, 114.5°E). An overlapping altitude range of about 10 km is obtained with the RR-technique temperatures reaching upward to 40 km and the Rayleigh-integration-technique temperatures above 30 km. Temperature values obtained by two different mechanisms match nicely in the overlapping area. By using a data-merge method, complete temperature profiles covering widely from 5 to 80 km are obtained for the observation of the thermal structure and perturbations from the troposphere up to the mesosphere. Based on the overlapping-region (30–40 km) data obtained from this combined RR–Rayleigh lidar system and Rayleigh-integration-technique temperatures initialized with model data at an upper height (90 km), we develop a self-calibration method for the determination of the system-dependent constants for RR temperature retrieval. Compared with the conventional radiosonde calibration method, the self-calibration obtained in the overlap region of both lidar temperature measurement techniques can be extrapolated to the lower temperatures in the tropopause region by using the simpler two-constant calibration function. With this new calibration method, the combined lidar system can perform independent and accurate atmospheric temperature measurements when a coincident (in time and space) radiosonde is not available, as it is often the case. This combined RR–Rayleigh lidar thus has the potential for long-term studies of atmospheric thermal structure and associate perturbations.

Equipped with a 1-meter Cassegrain telescope with 6.2 meter focal length and an electronically gated Intensified Charge-Coupled Device (ICCD), a multilayer Na imager is designed and developed at Wuhan in China. This novel instrument has successfully achieved the first preliminary 3-D image of the mesospheric Sodium (Na) layer when running alongside a Na lidar. The vertical Na layer profile is measured by the lidar, while the horizontal structure of the layer at different altitudes is measured by the ICCD imaging with a horizontal resolution of ~3.7 urad. In this experiment, controlled by the delay and width of the ICCD gating signal, the images of the layer are taken with three-second temporal resolution for every 5 km. The results show highly variable structures in both the vertical and horizontal directions within the Na layer. Horizontal images of the Na layer at different altitudes near both the permanent layer (80–100 km) and a sporadic Na layer at 117.5 km are obtained simultaneously for the first time. The Na number density profiles measured by the lidar and those derived from this imaging technique show excellent agreement, demonstrating the success of this observational technique and the first 3-D imaging of the mesospheric Na layer.

A narrowband sodium lidar for measuring mesospheric temperature and wind has been established at YangBaJing, Tibet (90°E, 30°N, 4300 m a.s.l), China. The system is designed and optimized based on important upgrades using new technology. In the lidar system, single-mode 589 nm seed laser is produced by frequency doubling of 1178 nm diode laser with a periodically poled lithium niobate (PPLN) waveguide. The output power of 589 nm continuous-wave laser is up to 1.5 W with the help of a seed-injected Raman fiber amplifier. Furthermore, fast three-frequency switcher is designed with a couple of fiber magneto optical switches (FMOS) for measuring wind and temperature, simultaneously, which greatly reduces the system maintenance. These improvements greatly simplify the lidar system, thus, achieve robust operation with minimum maintenance requirements.

Real-time imaging of CO in vehicle exhaust was demonstrated using a gas correlation spectrometry based mid-infrared camera for the first time. The novel gas-correlation imaging technique is used to eliminate the spectral interferences from background radiation and other major combustion products, and reduce the influences of the optical jitter and temperature variations, thereby identifying and quantifying the gas. We take several spectral factors into account for the instrument design, concentration calibration and data evaluation, including atmospheric transmission, radiation interference, as well as the spectral response of infrared camera, filter and gas cell. A calibration method based on the molecular spectroscopy and radiative transfer equation is developed to identify the numerical relationship between the CO concentration × length and the measured image intensity. Two-dimensional CO distribution of vehicle exhaust with a time resolution of 50 Hz and detection limit of 20 ppm × meter is achieved when the distance between optical equipment and engine nozzle is 3 m. The gas correlation spectrometry based mid-infrared camera shows a great potential as a future technique to monitor vehicle pollution emissions quantitatively and visually.

In this paper, a lidar system in Wuhan Institute of Physics and Mathematics (WIPM, 30.5 o N,114.5 o E) for atmospheric density, temperature and wind observation was reported. The design and techniques of this lidar were described in detail. The atmospheric temperature of the troposphere, stratosphere and lower mesosphere were measured by the Raman, Rayleigh and sodium channel of this lidar system, respectively.

A molecular Faraday optical filter (MFOF) working in the mid-infrared region is realized for the first time. NO molecule was used as the working material of the MFOF for potential applications in atmospheric remote sensing and combustion diagnosis. We develop a complete theory to describe the performance of MFOF by taking both Zeeman absorption and Faraday rotation into account. We also record the Faraday rotation transmission (FRT) signal using a quantum cascade laser over the range of 1,820 cm-1 to 1,922 cm-1 and calibrate it by using a 101.6 mm long solid germanium etalon with a free spectral range of 0.012 cm-1. Good agreement between the simulation results and experimental data is achieved. The NO-MFOF's transmission characteristics as a function of magnetic field and pressure are studied in detail. Both Comb-like FRT spectrum and single branch transmission spectrum are obtained by changing the magnetic field. The diversity of FRT spectrum expands the range of potential applications in infrared optical remote sensing. This filtering method can also be extended to the lines of other paramagnetic molecules.

In the above paper [1] , there are two errors on page 7058. In addition, the support information has been updated to include an additional funding source. The complete funding statement should be