Climatology of mesopause region nocturnal temperature, zonal wind and sodium density observed by sodium lidar over Hefei, China (32⁰ N, 117⁰ E)
2018
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.
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