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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. [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]