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A prediction system was developed to determine the maximum Rayleigh altitude (MRA) by improving the automated detection of LIDAR power-on conditions and adapting to advancements in middle- and upper-atmosphere LIDAR technology. The proposed system was developed using observational data and nighttime sky imagery collected from multiple LIDAR stations. To assess the accuracy of predictions, three key parameters were employed: mean square error, root mean square error, and mean absolute error. Among the three prediction models created through multivariate regression and autoregressive integrated moving average (ARIMA) analyses, the most suitable model was selected for predicting the MRA. One-month predictions demonstrated the accuracy of the MRA with a maximum error of no more than 5 km and an average error of less than 2 km. This technology has been successfully implemented in numerous LIDAR stations, enhancing their automation capabilities and providing key technical support for large-scale, unmanned, and operational deployments in the middle- and upper-atmosphere LIDAR systems. [ABSTRACT FROM AUTHOR]

Temperature profiles at altitudes of 5–80 km are obtained with a self-calibrated Rayleigh–rotational Raman lidar over Wuhan, China (30.5°N, 114.5°E). By using the synchronous Rayleigh lidar temperature, rotational Raman temperature in the lower atmosphere could be calibrated and retrieved, which is free of other instruments (like local radiosondes). The results are comparable to the radiosonde calibration method. Based on the self-calibration approach, one-night (August 4–5, 2014) lidar temperature profiles are presented with radiosondes, NRLMSISE-00 model and TIMED/SABER data. Some interesting temperature characteristics have been present for studies of waves propagating from near ground level into the mesosphere. Temperature perturbations are found to increase exponentially with a scale height of ~10 km. The wavy structure shows minimal perturbations (‘nodes’) at some altitudes of 39, 52, 64 and 73 km. Dominant wavelengths and temperature variations are also analyzed at different time and altitudes. By comparison of the temperature and associate perturbations from the tropopause up to the stratopause, different amplitudes, phase fronts and vertical wavelengths are discovered as well. These discoveries indicate that some waves may originate in the lower atmosphere and propagate upward with decreasing static stability. [ABSTRACT FROM AUTHOR]

Sporadic sodium layers (SSLs) have been observed all over the globe and always has been of great concern. However, most researches on SSLs are based on only nocturnal observations due to strong daytime solar background noise, thus there is still insufficient understanding of the diurnal variation of SSLs. In this paper, a statistical analysis of SSLs observed by a diurnal sodium (Na) lidar at Beijing (40.5 ° N, 116 ° E) from April 2014 to December 2016 has been reported. A total of 54 and 87 events that peaked during daytime and nighttime, respectively, are identified. The average occurrence interval for daytime observations is ~36 h per SSL, which is slightly longer than the value of ~29 h per SSL for nighttime observations. Both daytime and nighttime SSLs show evident seasonal variations with summer SSLs occurring much more frequently and tending to appear at higher altitude with lower peak density while larger strength factor. The seasonal dependence of SSL occurrence is consistent with that of sporadic E (Es) occurrence, however, their diurnal variations are found to be totally different. The SSLs are observed more frequently around 03–04 LT during nighttime and 16–17 LT during daytime when Es layers appear at lower altitudes (below 110 km), while have a lowest occurrence rate around midday when Es layers occurrence rate peak. The average peak altitude of SSLs during the second half of the night is lower compared to that during the first half of the night. Around midday, the average peak width of SSLs is narrower and peak density tends to be smaller when compared to those at other times. The possible explanations for the diurnal and seasonal variations of SSLs characteristics are discussed, and the key role of the evolution of Es layer height modulated by semidiurnal tide in the local time variation of SSL is highlighted. • The occurrence rate of daytime SSLs has a similar seasonal dependence to those of nighttime SSLs as well as Es. • SSLs occurred more frequently around 03–04 LT during nighttime and 16–17 LT during daytime, while rarely around midday. • Both daytime and nighttime observations SSLs tend to have higher peak altitude, larger strength factor, lower peak density in summer. • Diurnal variation of SSL occurrence is related to tidal-modulated Es height and photochemistry and ionization reactions. [ABSTRACT FROM AUTHOR]