Our study explores the variation in the occurrence date, peak amplitude and wave period for eastward waves and the role of instability, background wind structure and the critical layer in eastward wave propagation and amplification.

Our results suggest that lightning strokes would probably influence the ionosphere and thus give rise to the occurrence of a sporadic sodium layer (Na_S), with the overturning of the electric field playing an important role. Model simulation results show that the calculated first-order rate coefficient could explain the efficient recombination of Na⁺→Na in this Na_S case study. A conjunction between the lower and upper atmospheres could be established by these inter-connected phenomena.

A long-standing mystery of metal ions within E_s layers in the Earth's upper atmosphere is the marked seasonal dependence, with a summer maximum and a winter minimum. We report a large-scale winter-to-summer transport of metal ions from 6-year multi-satellite observations and worldwide ground-based stations. A global atmospheric circulation is responsible for the phenomenon. Our results emphasise the effect of this atmospheric circulation on the transport of composition in the upper atmosphere.

In this study, we report the climatology of migrating and non-migrating tides in mesopause winds estimated using multiyear observations from three meteor radars in the southern equatorial region. The results reveal that the climatological patterns of tidal amplitudes by meteor radars is similar to the Climatological Tidal Model of the Thermosphere (CTMT) results and the differences are mainly due to the effect of the stratospheric sudden warming (SSW) event.

Gravitational waves (GWs) with periods ranging from 10 to 30 min over 10 h and 20 wave cycles are detected within a 2 km height in the atmospheric boundary layer (ABL) by a coherent Doppler wind lidar. Observations and computational fluid dynamics (CFD) simulations lead to a conclusion that the GWs are excited by the wind shear of a low-level jet under the condition of light horizontal wind. The GWs are trapped in the ABL due to a combination of thermal and Doppler ducts.

To investigate the relationship between BLH and air pollution under different conditions, a compact micro-pulse lidar integrating both direct-detection lidar and coherent Doppler wind lidar is built. Evolution of atmospheric boundary layer height (BLH), aerosol layer and fine structure in cloud base are well retrieved. Negative correlation exists between BLH and PM_2.5. Different trends show that the relationship between PM_2.5 and BLH should be considered in different boundary layer categories.

The seasonal variations in the mesopause densities, especially with regard to its global structure, are still unclear. In this study, we report the climatology of the mesopause density estimated using multiyear observations from nine meteor radars from Arctic to Antarctic latitudes. The results reveal a significant AO and SAO in mesopause density, an asymmetry between the two polar regions and evidence of intraseasonal oscillations (ISOs), perhaps associated with the ISOs of the troposphere.

It reports the long-term climatology of the intensity of E_s layers from COSMIC satellites. The global E_s maps present high-resolution spatial distributions and seasonal dependence. It mainly occurs at mid-latitudes and polar regions. Based on wind shear theory, simulation results indicate the convergence of vertical ion velocity could partially explain the E_s seasonal dependence and some disagreements between observations and simulations suggest other processes play roles in the E_s variations.

This paper explores the relationship between the intensifications of atomic sodium layer and E_s layer in the Mesosphere/Lower Thermosphere (MLT) region (the earth's upper atmosphere at altitudes between 90 and 130 km above ground). The multi-instrument experiment of sodium lidar observations, ionospheric observations and sodium chemical simulations advances our understanding of the dynamical and chemical coupling processes in the mesosphere and ionosphere above thunderstorms.

A total of 154 nights of observations by the USTC Na temperature and wind lidar (32° N, 117° E) suggest significant seasonal variability in the mesopause. Chemistry plays an important role in Na atom formation. More than half of the observed gravity wave (GW) momentum flux (MF), whose divergence determines the GW forcing, is induced by short-period (10 min–2 h) waves. The anticorrelation between MF and zonal wind (U) suggests strong filtering of short-period GWs by semiannual oscillation U.

Thermospheric mass density from the GOCE satellite for Sun-synchronous orbits between 83.5° S and 83.5° N normalized to 270 km during 2009–2013 has been used to develop our GOCE model at dawn/dusk local solar time sectors based on the empirical orthogonal function (EOF) method. We find that both amplitude and phase of the seasonal variations have strong latitudinal and solar activity dependences, and the annual asymmetry and effect of the Sun–Earth distance vary with latitude and solar activity.

We used the NOGAPS-ALPHA reanalysis datasets upto mesopause region to investigate the anomalous Quasi-Two-Day Wave (QTDW) activities during the major Sudden Stratospheric Warming period of January 2006. We found that the SSW in the winter stratosphere could have significant influence on the QTDWs in the summer mesosphere through inter-hemispheric couplings. Our finding sheds new light on the coulings during SSW period.

The influences of sudden stratospheric warming in the Northern Hemisphere on quasi-2-day waves are studied with both observations and simulations. We found the energy of W3 is transferred to W2 through the nonlinear interaction with SPW1 and the instability at winter mesopause could provide additional amplification for W3. The summer easterly is enhanced during SSW, which is more favorable for the propagation of quasi-2-day waves.