Climatology of mesopause region nocturnal temperature, zonal wind, and sodium density observed by sodium lidar over Hefei, China (32°N, 117°E)

The University of Science and Technology of China narrowband sodium temperature/wind 16 lidar, located in Hefei, China (32°N, 117°E), has made routine nighttime measurements since 17 January 2012. 154 nights (~1400 hours) of vertical profiles of temperature, sodium density, 18 and zonal wind, and 83 nights (~800 hours) of vertical flux of gravity wave (GW) zonal 19 momentum in the mesopause region (80-105 km) have been obtained during the period from 20 2012 to 2016. In temperature, it is most likely that the diurnal tide dominates below 100 km in 21 spring, while the semidiurnal tide dominates above 100 km throughout the year. A clear 22 semiannual variation in temperature is revealed near 90 km, in phase with the tropical 23 mesospheric semiannual oscillation (MSAO). The variability of sodium density is positively 24 correlated with temperature below 95 km, suggesting that in addition to dynamics, the 25 chemistry also plays an important role in the formation of sodium atoms. The seasonal 26 variability of sodium density observed by both lidar and satellite generally agrees well with a 27 whole atmosphere model simulation using an updated meteoric input function which includes 28 different cosmic dust sources. In zonal wind, the diurnal tide dominates in both spring and fall, 29 while semidiurnal tide dominates in winter. The observed semiannual variation in zonal wind 30 near 90 km is out-of-phase with that in temperature, consistent with the tropical MSAO. The 31 GW zonal momentum flux is mostly westward in fall and winter, anti-correlated with eastward zonal wind. The annual mean flux averaged over 87-97 km is ~-0.3 m 2 /s2 32 33 (westward), anti-correlated with eastward zonal wind of ~10 m/s. The lidar observations 34 generally agree with satellite and meteor radar observations as well as model simulations at 35 similar latitudes.