| As an active optical remote sensing instrument, Rayleigh lidar has been widely used for measuring atmospheric density and temperature with reasonably high accuracy for the range of ~30-80 km since decades ago. Rayleigh lidar can provide continuous observational data with high spatial and temporal resolution, which is very essential for understanding the middle atmospheric structure, variations, and characteristics of thermodynamics and kinetics. The dual-wavelength Rayleigh lidar located in Yanqing, Beijing(40.3°N, 116.2°E) was enrolled in the Meridian Space weather Monitoring Project of China in November 2009 to measure the density and temperature variations of middle atmosphere. To overcome the non-linear effects of photomultiplier tubes(PMT), we improve the method of data retrieval process with dual-receiving channels to obtain the atmospheric density profile for the range of ~35-90 km and the atmospheric temperature profile for the range of ~35-85 km. The precision analysis indicates that the error of atmospheric density was 1%~5% and the error of atmospheric temperature was 2~10K for the whole range. Lidar observation results show good agreements with SABER temperature data sets, which justify that the lidar system and the data retrieval algorithm are both reliable.According to the observational data of the Rayleigh lidar from May 2012 to April 2013, the middle atmospheric thermal structure(35-85 km) over Beijing was obtained. Lidar observation results showed a characteristic warm summer and cool winter structure in the stratosphere and a characteristic warm winter and cool summer structure in the mesosphere. To characterize the seasonal variations of the atmospheric temperature structure over Beijing, the amplitude and phase profiles of the annual, semi-annual and 3-month sinusoidal oscillations were extracted by multi-parameter sinusoidal regression. In the mesopause region above 70 km altitude, the temperature is dominated by an annual oscillation. In the lower mesosphere between 55 and 70 km altitude, the temperature is dominated by annual and semi-annual oscillations. In the upper stratosphere below 55 km altitude, annual, semiannual and 3-month oscillations work together to determine the temperature structure. We also study the stratopause variations over Beijing using lidar measurements. The stratopause height showed significant semiannual oscillation(SAO) characteristics and the stratopause temperature showed significant annual oscillation(AO) characteristics. Long-term comparative study between lidar results and the NRLMSISE-00 empirical model shows that lidar temperatures are usually colder than the model data during the observational time, which may be due to the associations of high level of solar activity, greenhouse gases and the frequent “haze” weather in North China.In the early winter of 2012/2013, middle atmospheric temperature anomalies involving a stratospheric temperature enhancement(STE) event and a long-term mesospheric temperature inversion layer(MIL) are observed by both the lidar and the SABER. By analyzing the lidar data and the SABER data, we proposed that the long-term MIL could be due to gravity wave-background field-planetary wave interactions in the masopause region. The satellite data indicated that the observed STE event over North China could be correlated to the enhancement of planetary wave(k=1) activity and it might be the premonition of the major sudden stratospheric warming(SSW) in January 2013.A Rayleigh-Mie Doppler lidar utilized for atmospheric wind observations has been installed at Yanqing station. Based on the observational data in January 2015, the vertical wind profiles in the range of 15~35km were calculated with 384 m spatial resolution and 1 hour temporal resolution. The error of horizontal wind velocity was less than 5m/s. Preliminary results indicate that the Rayleigh-Mie Doppler lidar system already has the capacity for continuous wind observations in the nighttime, which paves the way for routine operation in the future. |
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