Search

The observations of short-duration meteor showers at different geographic locations are important for well understanding of their outbursts. Using the four all-sky interferometric meteor radars at Mohe (53.49°N, 122.34°E), Beijing (40.3°N, 116.19°E), Wuhan (30.54°N, 114.34°E), and Ledong (18.44°N, 108.97°E) in China, four outbursts (2011, 2012, 2018, and 2019) of the October Draconid meteor shower were observed between 2011 and 2021. The October Draconid meteor velocity was concentrated around 22∼23 km s−1, with an active duration of 6∼9 h and a main peak around the solar longitude 194.73°∼195.63°. When comparing the hourly rates of the October Draconid meteor shower for different years at Mohe, a maximum (minimum) of peak flux was observed in 2012 (2011). The radiants and orbit parameters of the October Draconid meteors derived from the radars at different latitudes are consistent, except that the weighted mean echo height during the peak activity at Mohe was always lower than that at other stations. [ABSTRACT FROM AUTHOR]

The existing distribution of meteor radars located from high- to low-latitude regions provides a favorable temporal and spatial coverage for investigating the climatology of the global mesopause density. In this study, we report the climatology of the mesopause relative density estimated using multiyear observations from nine meteor radars, namely, the Davis Station (68.6 ∘ S, 77.9 ∘ E), Svalbard (78.3 ∘ N, 16 ∘ E) and Tromsø (69.6 ∘ N, 19.2 ∘ E) meteor radars located at high latitudes; the Mohe (53.5 ∘ N, 122.3 ∘ E), Beijing (40.3 ∘ N, 116.2 ∘ E), Mengcheng (33.4 ∘ N, 116.6 ∘ E) and Wuhan (30.5 ∘ N, 114.6 ∘ E) meteor radars located in the midlatitudes; and the Kunming (25.6 ∘ N, 103.8 ∘ E) and Darwin (12.3 ∘ S, 130.8 ∘ E) meteor radars located at low latitudes. The daily mean relative density was estimated using ambipolar diffusion coefficients derived from the meteor radars and temperatures from the Microwave Limb Sounder (MLS) on board the Aura satellite. The seasonal variations in the Davis Station meteor radar relative densities in the southern polar mesopause are mainly dominated by an annual oscillation (AO). The mesopause relative densities observed by the Svalbard and Tromsø meteor radars at high latitudes and the Mohe and Beijing meteor radars at high midlatitudes in the Northern Hemisphere show mainly an AO and a relatively weak semiannual oscillation (SAO). The mesopause relative densities observed by the Mengcheng and Wuhan meteor radars at lower midlatitudes and the Kunming and Darwin meteor radars at low latitudes show mainly an AO. The SAO is evident in the Northern Hemisphere, especially at high latitudes, and its largest amplitude, which is detected at the Tromsø meteor radar, is comparable to the AO amplitudes. These observations indicate that the mesopause relative densities over the southern and northern high latitudes exhibit a clear seasonal asymmetry. The maxima of the yearly variations in the mesopause relative densities display a clear latitudinal variation across the spring equinox as the latitude decreases; these latitudinal variation characteristics may be related to latitudinal changes influenced by gravity wave forcing. In addition to an AO, the mesopause relative densities over low latitudes also clearly show an intraseasonal variation with a periodicity of 30–60 d. [ABSTRACT FROM AUTHOR]

In this work, we used observational data from an all-sky airglow imager at Xinglong (40.2 °N, 117.4 °E), a sodium lidar at Yanqing (40.4 °N, 116.0 °E) and a meteor radar at Shisanling (40.3 °N, 116.2 °E) to study the propagation of a mesoscale gravity wave. During the night of March 1, 2011, the imager identified a mesoscale gravity wave structure in the OH airglow that had a wave period of 2 hours, propagated along an azimuthal direction (clockwise) with an angle of 163°, a phase speed of 73 m/s, and a horizontal wavelength of 566 km. Simultaneous measurements provided by the sodium lidar also showed a perturbation in the sodium layer with a 2-hour period. Based on the SABER/TIMED and radar data, we estimated that the momentum flux and the energy flux of the gravity wave were approximately 0.59 m 2 /s 2 and 0.22 mW/m 2 , respectively. Ray-tracing analysis showed that the gravity wave was likely generated in the center of Lake Baikal owing to the existence of a jet- front system in the upper troposphere at that time. [ABSTRACT FROM AUTHOR]

In this study, we employed the non-uniform rational B-splines surface technique to develop a provisional horizontal wind model of the mesosphere and lower thermosphere at altitudes of 87, 97, and 250 km over Kelan (38.7°N, 111.6°E) in China using Fabry–Perot interferometer (FPI) observations for the period between January 2012 and May 2014. We compared the meridional and zonal winds derived from the Kelan FPI wind model with those based on Meteor Radar wind observations at Beijing (39.92°N, 116.39°E), and those calculated from horizontal wind models, i.e., HWM93 and HWM07, at Kelan. Our analysis showed the following. (1) At 87 and 97 km, the Kelan FPI wind patterns exhibited strong annual variation in the meridional wind and semiannual variation in the zonal wind, as well as diurnal variation, which was dominated by a semidiurnal tidal variation in the meridional and zonal winds during May and September with a diurnal phase difference. The Kelan FPI wind patterns agreed well with the Meteor Radar winds and the HWM07 model results, but less well with the HWM93 model. (2) At 250 km, the FPI wind patterns agreed fairly well with the HWM93 results, where both indicated annual/diurnal variation in the meridional and zonal winds, and weak semidiurnal tidal variation. There were large discrepancies between the Kelan FPI winds and the HWM07 model results, which were mainly due to differences in the annual variation in the nighttime meridional wind. (3) The magnitude of the FPI winds was comparable to the HWM93 results but they were nearly 40–50% lower than the other winds, which is attributable to the inherent limitations of airglow measurement. Thus, this local empirical wind model could be used to investigate the climatological features of local ionospheric spatial–temporal variations. [ABSTRACT FROM AUTHOR]