Abstract
Abstract. The University of Science and Technology of China narrowband sodium temperature and wind lidar, located in Hefei, China (32∘ N, 117∘ E), has made routine nighttime measurements since January 2012. A total of 154 nights (∼ 1400 h) of vertical profiles of temperature, sodium density, and zonal wind and 83 nights (∼ 800 h) of vertical flux of gravity wave (GW) zonal momentum in the mesopause region (80–105 km) were obtained during the period from 2012 to 2016. For temperature, it is most likely that the diurnal tide dominates below 100 km in spring, while the semidiurnal tide dominates above 100 km throughout the year. A clear semiannual variation in temperature is revealed near 90 km, in phase with the tropical mesospheric semiannual oscillation (MSAO). The variability in sodium density is positively correlated with temperature below 95 km, suggesting that in addition to dynamics, the chemistry also plays an important role in the formation of sodium atoms. The seasonal variability in sodium density observed by both lidar and satellite generally agrees well with a whole atmosphere model simulation using an updated meteoric input function which includes different cosmic dust sources. For zonal wind, the diurnal tide dominates in both spring and fall, while semidiurnal tide dominates in winter. The observed semiannual variation in zonal wind near 90 km is out of phase with that in temperature, consistent with the tropical MSAO. The lidar observations generally agree with satellite and meteor radar observations as well as model simulations at similar latitude. The 50–70 % of zonal momentum flux is induced by short-period (10 min–2 h) GWs. The large zonal momentum flux in summer and winter due to short-period GWs is clearly anticorrelated with eastward zonal wind maxima below 90 km, suggesting the filtering of short-period GWs by the SAO wind.
Highlights
The temperature and wind in the mesopause region (80– 105 km) are key atmospheric parameters for studying the dynamics in this region
We present the seasonal variation in sodium density, temperature, zonal wind and gravity wave (GW) zonal momentum flux observed by the University of Science and Technology of China (USTC) sodium temperature and wind lidar from January 2012 to December 2016 over Hefei, China (32◦ N, 117◦ E)
Another interesting feature in all three figures is that we see a temperature maximum near ∼ 90 km in March and April and a second maximum in September and October, likely related to the mesospheric semiannual oscillation (MSAO), which is dominant in the equatorial middle atmosphere (Dunkerton, 1982; Burrage et al, 1996; Garcia et al, 1997)
Summary
The temperature and wind in the mesopause region (80– 105 km) are key atmospheric parameters for studying the dynamics in this region. Satellite (Russell III et al, 1999), zonal wind observed by a nearby meteor radar (Xiong et al, 2004), and sodium density observed by the Optical Spectrograph and Infrared Imager System (OSIRIS) onboard the Odin satellite (Llewellyn et al, 2004) These measurements are compared with simulations from the Whole Atmosphere Community Climate Model version 5 (WACCM) (Marsh et al, 2013a; Mills et al, 2016; Feng et al, 2017) using an updated meteoric input function (MIF) for Na (Cárrillo-Sanchez et al 2016). Between January 2012 and December 2016, we obtained 154 nights (∼ 1400 h) of valid data, which is sufficient to study the seasonal variations in sodium density, temperature, zonal wind and GW momentum flux (83 nights) in the mesopause region over Hefei. In the case of WACCM, the zonal mean data are first extracted at the coordinates of the lidar site and the monthly mean profiles are generated in the same way as the lidar and radar profiles
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