Coordinated Observations of 8‐ and 6‐hr Tides in the Mesosphere and Lower Thermosphere by Three Meteor Radars Near 60^°S Latitude

Abstract

Atmospheric 8‐ and 6‐hr tides are observed for the first time in the zonal and meridional winds at ~82–97 km altitudes simultaneously at Tierra del Fuego (TDF; 53.7°S, 67.7°W), King Edward Point (KEP; 54.3°S, 36.5°W), and Rothera (ROT; 67.5°S, 68.0°W) at Southern Hemisphere (SH) middle‐to‐high latitudes during long time spans, allowing to reveal climatology and migrating nature. The monthly averaged amplitudes vary between ~1 and 8 m/s for the 8‐hr tides while the amplitudes of 6‐hr tides are smaller ~0.5–4 m/s. Both tides exhibit an annual pattern having the amplitude maxima during SH winter and minima in SH summer. The tidal phases are smaller (earlier) in the zonal wind than in the meridional wind by about 90°. The phase differences observed between TDF and KEP, which are located at similar latitudes but different longitudes suggest the propagation of migrating tides. The study finds that 8‐ and 6‐hr tides are correlated.

Coordinated Observations of Migrating Tides by Multiple Meteor Radars in the Equatorial Mesosphere and Lower Thermosphere

“…As shown in Figure 9, tidal component phases (Universal Time of maxima at the longitude of 0° in hours) are observed earlier in the zonal component than in the meridional component at most altitudes, and these phases are approximately symmetrical around July at all altitudes considered. The phase differences between the zonal and meridional components, shown in Figures 9e and 9f, are mostly equal to −6 and −3 hr (equivalent to −90°) for the diurnal and semidiurnal tides, which are consistent with previous results (Liu et al, 2020;Oberheide et al, 2006). In addition, the vertical phase differences of DW1 migrating tides are approximately 12-15 hr, meaning that the vertical wavelength of DW1 migrating tides is 30-40 km (qualitative estimation) and that in the zonal component are slightly larger than in the meridional component; the vertical phase differences of SW2 tides are approximately 4 hr in the zonal component and 6 hr in the meridional component, meaning that the vertical wavelengths of SW2 tides are ∼60 and ∼40 km, respectively.…”

Occurrence features of intermediate descending layer and Sporadic E observed over the higher mid-latitude ionospheric station of Moscow

“…A 4-h IDL periodicity is apparent, characterized by two descending layers, first appearing at an altitude of 220 km, the first around 8 UT and the second four hours later (~ 12UT). In support to our postulation, gravity waves that may also contribute in the period range between 4 and10 h, should be cancelled out in monthly averaged HTI plots due to their random periodicities (Liu et al 2020).…”

Wind Variations in the Mesosphere and Lower Thermosphere Near 60°S Latitude During the 2019 Antarctic Sudden Stratospheric Warming

“…The MLT winds have been measured near 60°S latitude by three meteor radars at Rio Grande, Tierra del Fuego (TDF; 53.7°S, 67.7°W) in Southern Argentina, King Edward Point station (KEP; 54.3°S, 36.5°W) on South Georgia Island, and King Sejong Station (KSS; 62.2°S, 58.8°W) on King George Island on the Northern tip of the Antarctic Peninsula. These meteor radar winds allow us to identify the wave activities and large‐scale variations in the MLT region in this key dynamic but largely unexplored area (e.g., Eswaraiah et al., 2016; Fritts et al., 2019; Iimura et al., 2015; Lee et al., 2013; G. Liu et al., 2020; de Wit et al., 2017). The radar wind measurements also allow us to assess the impacts of the 2019 Antarctic SSW on the MLT dynamics during the SH winter (e.g., Stober et al., 2020).…”