Browsing by Author "Sato, Kaoru"

Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Causes of the Abnormally Strong Easterly Phase of the Mesopause Semiannual Oscillation During the March Equinox of 2023 Revealed by a New Reanalysis Data Covering the Entire Middle Atmosphere
    (Wiley, 2025-04-01) Sato, Kaoru; Koshin, Dai; Suclupe, Jose; Chau, Jorge L.; Lima, Lourivaldo M.; Li, Guozhu; Bhaskara Rao, S. Vijaya; Ratnam, M. Venkat; Rodriguez, Rodolfo; Scipión, Danny
    During the March equinox of 2023, a strong easterly wind of ∼80 m s−1 appeared at an altitude of ∼82 km in the equatorial upper mesosphere, which is regarded as an enhancement of the mesopause semi-annual oscillation. In this study, a new reanalysis data available up to 110 km was used to investigate its momentum budget. The strong easterly acceleration was due to a similar contribution from resolved waves and parameterized gravity waves, but largely counteracted by an upward advection of westerly momentum. The significant anomaly in the mean winds was not restricted to the 82 km height, but also included strong westerly winds (∼50 m s−1) at 65 km and easterly winds (∼40 m s−1) at 42 km. The stratospheric quasi-biennial oscillation was westerly. The mean wind intensification at each height is explained by the acceleration due to upward propagating waves, which do not suffer from critical filtering below.
    Palabras clave:Mesopause semiannual oscillationStratopause semiannual oscillationQuasi-biennial oscillation
  • Thumbnail Image
    ItemOpen Access
    On the Abnormally Strong Westward Phase of the Mesospheric Semiannual Oscillation at Low Latitudes During March Equinox 2023
    (American Geophysical Union, 2024-08-13) Suclupe, Jose; Chau, Jorge L.; Conte, J. Federico; Pedatella, Nicholas M.; Garcia, Rolando; Sato, Kaoru; Zülicke, Christoph; Lima, Lourivaldo M.; Li, Guozhu; Bhaskara Rao, S. Vijaya; Ratnam, M. Venkat; Rodriguez, Rodolfo; Scipión, Danny
    Different meteor radars at low latitudes observed abnormally strong westward mesospheric winds around the March Equinox of 2023, that is, during the first phase of the Mesospheric Semiannual Oscillation. This event was the strongest of at least the last decade (2014–2023). The westward winds reached −80 m/s at 82 km of altitude in late March, and decreased with increasing altitude and latitude. A considerable increase in the diurnal tide amplitude was also observed. The Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension constrained to meteorological reanalysis up to ∼50 km does not capture the observed low-latitude behavior. Additionally, these strong mesospheric winds developed during the westerly phase of the Quasi-Biennial Oscillation, in accordance with the filtering mechanism of gravity waves in the stratosphere proposed in previous works. Finally, analysis of SABER temperatures strongly suggests that the breaking of the migrating diurnal tide may be the main driver of these strong winds.
    Palabras clave:Westward windsStrong windsEquinox