Relative to many investigations of inertial gravity waves (IGWs) in the Antarctic, IGW activity in the Arctic region was paid less attention to. We use radiosonde observations at the Ny‐Alesund station (78.9°N, 11.9°E) from April 2012 to June 2016 to study the IGW characteristics in the lower stratosphere over the Arctic. The observation reveals a prevailing eastward zonal background wind below 20 km and an obvious annual cycle of the background temperature from the troposphere to the lower stratosphere, which is different from the results in the middle and low latitudes. By combining Lomb‐Scargle spectrum and hodograph technique, case study demonstrates that the lower stratospheric IGWs exhibit a feature of freely propagating waves. Statistical analysis indicates that the IGWs have dominant horizontal (vertical) wavelength of 50–1,050 km (1–4 km) and ratio (1–2.5) of the intrinsic to inertia frequencies. Wave energy exhibits an annual oscillation with the maximum in winter and the minimum in summer. In winter, the downward propagating waves increase to about 20% due to polar stratospheric vortex. Because of the lower atmospheric filtering, the IGWs display a dominant direction of westward propagation, thus have a mean vertical flux of −0.647 mPa for the zonal momentum, which indicates that the IGWs can put a westward drag on the atmospheric wind field over the Arctic as they break and dissipate. All the vertical wavenumber spectra have spectral slopes from −2.23 to −2.99 close to the universal spectrum index of −3.

By combining observations from three meteor radars and a mesosphere‐stratosphere‐troposphere radar arranged along the 120°E meridian with reanalysis data from 20 February to 20 May 2015, we study the stratospheric final warming (SFW) in 2015 spring and planetary wave activities from the troposphere to the mesosphere and lower thermosphere (MLT) at different latitudes. There are two successive warming events with the polar mean temperature rises of 24 and 9 K at 10‐hPa level. By means of the two warming events separated by only several days, the mean temperature increases by nearly 20 K, and the mean zonal wind decreases from more than 30 m/s to about −10 m/s; thus, seasonal transition of the polar circulation is completed. The investigation shows that the quasi 10‐ (Q10DW) and 16− (Q16DW)day waves occur around the SFW. In the troposphere, their amplitudes are close to 10 m/s in the wind field. At 10‐hPa level of the stratosphere, the strong wave activities arise before the SFW, while in the MLT, the waves are amplified following the SFW with the amplitude peaks about 10 days after the SFW onset. The wave amplitude in the MLT tends to increase in the zonal wind but decrease in the meridional wind with decreasing latitude, which is roughly consistent with the Hough modes. Hence, the Q10DW and Q16DW in the MLT are distinct from those in the stratosphere, and they are likely to be generated and strengthened in situ in the upper stratosphere and MLT.

Based on the temperature and zonal and meridional winds observed with an Na lidar at Andes Lidar Observatory (30.3°S, 70.7°W) on the night of 20–21 July 2015, we report simultaneous upward and downward propagating inertia‐gravity waves (IGWs) in the mesosphere/lower stratosphere (MLT). The ground‐based periods of the upward and downward IGWs are about 5.4 h and 4.8 h, respectively. The horizontal and vertical wavelengths are about 935 km and 10.9 km for the 5.4 h IGW and about 1248 km and 22 km for the 4.8 h IGW, respectively. Hodograph analyses indicate that the 5.4 h IGW propagates in the direction of about 23° west of north, while the 4.8 h IGW travels northward with an azimuth of 20°clockwise from north. These wave parameters are in the typical IGW wavelength and period ranges; nevertheless, the downward propagating IGWs in the MLT are rarely reported in previous observations. The ray‐tracing analysis suggests that the 5.4 h IGW is likely to originate from the stratospheric jet adjustment over the Antarctic, while the 4.8 h IGW source may be above the MLT because it is unlikely to propagate downward through a reflection in the realistic atmospheric wind field. Although both IGWs do not reach their amplitude thresholds of instability, the Richard number reveals that the dynamical and convective instabilities occur intermittently, which indicates that the instability arising from the multiple‐perturbation superposition may have a significant influence on wave saturation and amplitude constraint in the MLT.

A sodium Doppler lidar system with three‐directional measurements of sodium density, atmospheric wind field, and temperature was established at Zhongshan (69.4°S, 76.4°E), Antarctica. On November 14, 2019, a sporadic sodium layer (SSL) was observed at an altitude range of 93–103 km. The temporal/spatial sodium density variations of this SSL are associated with a strong sporadic E (Es) layer at nearly the same height, which is modulated by the convective electric field. By considering the structures and the time lags of the SSL's growth at three positions, the SSL appears to have a horizontal advection in an approximately westward direction with a velocity of the order of 80 m/s. This is consistent with the zonal wind velocity derived from the lidar system itself. The temporal/spatial sodium density variations strongly indicate that the formation and perturbation of SSLs are related to the evolution of ES layers due to varied electric fields and atmospheric gravity waves, while it is advected by the horizontal wind.

Lots of works make contributions to revealing propagation features and excitation mechanisms of intraseasonal oscillations (ISOs) in the tropics; however, there are few reports on ISOs at higher latitudes. By using measurements of mesosphere‐stratosphere‐troposphere radar at Xianghe (39.8°N, 116.5°E) and meteor radar at Beijing (40.3°N, 116.2°E) and reanalysis data for 105 days from 16 November 2013 to 28 February 2014, we study an ISO with about 30‐day period at midlatitude and high latitude. Radar observations indicate that in the troposphere, the oscillation attains an amplitude peak in zonal wind at about 9 km and propagates downward below 9 km. At about 9–16 km, the oscillation gradually decays with height and then strengthens again as it propagates upward in the stratosphere. In the mesosphere, the oscillation obviously appears at 78–86 km with a maximum amplitude at 80 km. Reanalysis data show that in the troposphere, the oscillation propagates southward. At about 100 (~16 km)‐ to 10 (~32 km)‐hPa levels, the oscillation is gradually reflected back to propagate northward, and then propagates poleward at higher altitude. Refractive index can explain its complex propagation characteristics very well. Consistence and coherence of its phase progression indicate that in the lower atmosphere, the oscillation comes from the polar region. Hence, ISOs can not only originate from but also propagate in the atmosphere at mid and high latitudes.