Abstract
In this paper the observation of sodium (Na) layer in mesosphere and lower thermosphere (MLT) region over complete diurnal cycles based on broadband Na lidar at Yanqing Station, Beijing, China (40.5°N,116°E ) was reported. Faraday filters with dual-channel design were used in the lidar receiving unit to suppress the strong background light in the daytime, which allow observation of Na layer with an acceptable signal-to-noise ratio (SNR) under sunlit condition. Several special structures of Na layer observed in the daytime was discussed. The simultaneous continuous observation of zonal wind by meteor radar was presented for comparison. These observation results can provide direct and reliable supports for the study of mesopause dynamics and solar effect on Na layer.
Highlights
Metallic Na layer in the mesopause region is a good tracer for studying atmospheric dynamics and photochemistry
The observation of Na layer over complete diurnal cycles based on the lidar of Chinese Meridian Project in Beijing was reported
Narrowband Faraday anomalous dispersion optical filters (FADOF) were used for Na lidar receiving to suppress sky background light [Chen et al, 1996], so that reliable Na echo signal can be obtained under sunlit condition, allowing diurnal continuous observation of Na layer
Summary
Metallic Na layer in the mesopause region is a good tracer for studying atmospheric dynamics and photochemistry. Based on resonance fluorescence scattering of Na atoms, Na lidar can achieve the measurement of Na layer parameters with high temporal and vertical resolution, which effectively promotes the development of the scientific research of the middle and upper atmosphere [Krueger et al, 2015]. Due to the severe interference of the strong solar background light on the received signal in the daytime, there are far fewer lidar observations of the Na layer in daytime than at night, which limit our understanding of the diurnal variations of Na layer, especially on its underside where neutral chemistry plays a major role [Clemesha et al, 2002; States and Gardner, 1999]. The observation of Na layer over complete diurnal cycles based on the lidar of Chinese Meridian Project in Beijing was reported. The special structures of Na layer observed in the daytime, including sporadic Na layer (Nas) and the downward extension of the layer bottom side, were discussed
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