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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. [ABSTRACT FROM AUTHOR]

Based on observations from daytime lidars in eastern China, diurnal cycles of the sodium layer over Wuhan (30.5°N, 114.6°E) and Beijing (40.5°N, 116°E) are investigated. Diurnal variations of Na density, root mean square (RMS) layer width, and centroid height of the sodium layer are analyzed. Results reveal that the large diurnal cycles of the sodium layer are controlled mainly by 24-hr oscillations at the two observation sites. The diurnal variation of the sodium layer over Wuhan was modulated mainly by tidal perturbations during the lidar observation campaign. Conversely, the diurnal variation over Beijing was controlled principally by photoionization and photochemistry effects during another campaign, and there was little evidence of direct tidal perturbations. These comparisons suggest that the diurnal variation of the sodium layer perhaps has obvious regional characteristics across China. The variation can be either controlled mainly by tidal perturbations or by photoionization and photochemistry effects in different seasons. [ABSTRACT FROM AUTHOR]

Mid-infrared quantum-cascade laser (QCL) absorption spectroscopy of CO near 4.2 μm has been developed for measurement of temperature and concentration in hot gases. With stronger absorption line-strengths than transitions near 1.5, 2.0, and 2.7 μm used previously, the fundamental band (001-000) of CO near 4.2 μm provides greatly enhanced sensitivity and accuracy to sense CO in high-temperature gases. Line R(74) and line R(96) are chosen as optimum pair for sensitive temperature measurements due to their high-temperature sensitivity, equal signal-to-noise ratio (SNR), weak interference of HO transitions, as well as relatively strong line-strengths in high temperature and weak absorption in room temperature. The high-resolution absorption spectrum of the far wings of the R-branch (R56-R100) in the fundamental vibrational band of CO is measured in a heated cell over the range 2,384-2,396 cm at different temperatures from 700 to 1,200 K. Taking three factors into consideration, including SNR, concentration detectability, and uncertainty sensitivity, the absorption line R(74) is selected to calculate CO concentration. The tunable QCL absorption sensor is validated in mixtures of CO and N in a static cell for temperature range of 700-1,200 K, achieving an accuracy of ±6 K for temperature and ±5 % for concentration measurements. [ABSTRACT FROM AUTHOR]

Sporadic sodium layers (SSLs) were studied with sodium (Na) lidar at Beijing (40.5°N, 116.0°E) and Haikou (19.5°N, 109.1°E) in China. The altitude distribution, strength factors, and occurrence time of SSL and sporadic E (E) layer events were statistically analyzed at both observing sites. SSL occurrence had a maximum near 22:00 local time, and E layer occurrence had a maximum before midnight. The altitude distributions of SSL and E layer events were better correlated at Haikou than at Beijing. All the average values of height and strength factor for SSL and E layer events, as well as the average of the maximum frequency that can be reflected by the E layer (fE), at Beijing were higher than those at Haikou. A better correlation between SSL and E layer events was also found at Haikou, and the formation of SSLs was considered to likely depend on the seasonal variability of chemical and dynamical processes. [ABSTRACT FROM AUTHOR]