Faquan Li

First report of sporadic K layers and comparison with sporadic Na layers at Beijing, China (40.6°N, 116.2°E)

A double-laser beam lidar was successfully developed to simultaneously measure K and Na layers at Beijing (40.6°N, 116.2°E) in 2010. Statistical analysis of the parameters of sporadic K (Ks) and sporadic Na (Nas) layers was performed over 2 years of lidar data, and different characteristics of them were found. The average Ks occurrence (2.9%) was lower than that of Nas (5.9%); the Nas occurrence had a maximum (19.3%) in May–June months and a minimum (1.6%) in January–February months, while the Ks occurrence had a maximum (4.9%) in January–February months and a minimum (1.0%) in September–October months; most Ks peaks tended to occur around 93 km, which was ~2 km lower than that of Nas (~95 km); the Ks peak density was often at least 1 order of magnitude lower than that of Nas; notably, two Ks with high peak densities (>1000 cm−3) were observed, which were much higher than K density (15–300 cm−3) reported before. The ascending time of Ks was often longer than its descending time, but an opposite trend occurred for Nas. During the 152 cases of joint observation for the K and Na layers, 21% (32/152) were cases in which Ks and Nas events simultaneously occurred, while 79% (120/152) were cases in which only one layer (K or Na) exhibited a strong Ks or Nas.

A Combined Rotational Raman–Rayleigh Lidar for Atmospheric Temperature Measurements Over 5–80 km With Self-Calibration

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.

Development of a solid-state sodium Doppler lidar using an all-fiber-coupled injection seeding unit for simultaneous temperature and wind measurements in the mesopause region

A solid-state sodium (Na) Doppler lidar developed at YanQing Station, Beijing, China (40°N, 116°E) aiming to simultaneous wind and temperature measurement of mesopause region was reported. The 589 nm pulse laser was produced by two injection seeded 1064 nm and 1319 nm Nd:YAG pulse lasers using the sum-frequency generation (SFG) technique. A fiber amplifier is implemented to boost the seed power at 1064 nm, enabling a robust, all-fiber-coupled design for seeding laser unit, absolute laser frequency locking, and cyclic three-frequency switching necessary for simultaneous temperature and wind measurements. The all-fiber-coupled injection seeding configuration together with the solid-state Nd:YAG lasers make the Na Doppler lidar more compact and greatly reduce the system maintenance, which is conducive to transportable and unattended operation. A preliminary observational result obtained with this solid-state sodium Doppler lidar was also reported in this paper.

Joint observation results of Na layer and ionosphere in Wuhan during the Total Solar Eclipse

During the total solar eclipse on July 22, 2009 in Wuhan, the joint observation test of Na layer and ionosphere was conducted by using the daytime observation atmospheric lidar and the GPS ionosphere detector. The results show that the full width at half maximum (FWHM) of Na layer density slightly narrowed during the total solar eclipse and broadened after the eclipse, while the height of Na peak slightly decreased in the eclipse and increased after the eclipse. These implying that Na layer changes reflect the rapid process of sunrise and sunset. The ionosphere total electron content (TEC) and the sky background light noise also presented an obvious fluctuation characteristic with the changes of solar irradiation during the process of total solar eclipse. The difference lies in that the changes of FWHM of Na layer atoms are much slower than that of ionosphere, the reason for this might be that the Na layer, after being disturbed by the total solar eclipse, will generate a series of complicated photochemical reactions and momentum transport processes, and then recombine the Na atoms. The Na atoms to be detected by the lidar need a lag process, which rightly conforms to the theoretical simulated results.

Lidar activity at Wuhan Institute of Physics and Mathematics, China

A multipurpose Lidar was built at Wuhan Institute of Physics & Mathematics, Chinese Academy of Science. The Lidar consists of an YAG laser pumped dye laser system, two receiving telescopes and several detection channels. During the past few years, we conducted some lidar observation in various altitudes of the atmosphere at our location. In this paper, we describe the technical aspects of this multipurpose lidar, and summarize some of the atmosphere observation results obtained by the lidar over Wuhan, China (31 deg N,114 deg E) with the emphasis on the sodium layer detections.

Development of an imaging gas correlation spectrometry based mid-infrared camera for two-dimensional mapping of CO in vehicle exhausts

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.

Demonstration of a mid-infrared NO molecular Faraday optical filter

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-MFOFs 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.

Corrections to “A Combined Rotational Raman-Rayleigh Lidar for Atmospheric Temperature Measurements Over 5–80 km With Self-Calibration”

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: