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Semidiurnal Tide Modulation by Ozone and Nonlinear Interaction With Planetary Wave During the 2024 Southern Hemisphere Sudden Stratospheric Warmings.

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Title: Semidiurnal Tide Modulation by Ozone and Nonlinear Interaction With Planetary Wave During the 2024 Southern Hemisphere Sudden Stratospheric Warmings.
Authors: Lee, Wonseok1,2 (AUTHOR) andrew.won.lee@nasa.gov, Liu, Guiping1 (AUTHOR), Sassi, Fabrizio1 (AUTHOR), Janches, Diego1 (AUTHOR), Kim, Jeong‐Han3 (AUTHOR), Jee, Geonhwa3 (AUTHOR), Murphy, D. J.4 (AUTHOR), Moffat‐Griffin, Tracy5 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. Apr2026, Vol. 131 Issue 4, p1-20. 20p.
Subject Terms: *Ozone, *Atmospheric tides, *Middle atmosphere, Nonlinear waves, Rossby waves, Stratospheric circulation
Geographic Terms: Antarctica, Southern Hemisphere
Abstract: We investigate the neutral wind and semidiurnal tide (SDT) variations in the mesosphere and lower thermosphere (MLT) during two consecutive minor Southern Hemisphere (SH) sudden stratospheric warmings (SSWs) that occurred unusually early in July–August 2024. Zonal and meridional winds from four meteor radar stations at 50–70°S were analyzed. Zonal winds reversed from eastward to westward between 80 and 100 km altitude during both events, showing a more distinct reversal in the second event. The SDT amplitudes increased and exhibited longitudinal differences around the second event. To elucidate the mechanisms responsible, we analyzed ozone observations from Aura/MLS along with MERRA‐2 shortwave heating. Positive ozone anomalies at 10 hPa (∼32 km) in the SH polar region around each event coincide with enhanced SDT amplitudes from meteor radars. In addition, the shortwave heating rate shows an enhanced 12‐hr component at SH high‐latitudes above 40 km during these events, supporting an ozone‐related radiative contribution to the SDT variability. Using phase‐differences from longitudinally separated meteor radars, we estimated the zonal wavenumber. Based on this analysis, we propose that nonlinear interaction between the quasi‐16‐day zonal wavenumber‐2 planetary wave (Q16DW2) and the migrating semidiurnal tide (SW2) contributed to the observed longitudinal differences in SDT amplitude. Furthermore, nonlinear advection associated with Q16DW2–SDT interactions is examined and shows clear longitudinal differences that lead to longitudinal asymmetry in SDT amplitude. These findings show the strong modulation of the SDT by SH SSWs and underscore the combined roles of ozone variability and nonlinear wave interactions in modulating upper‐atmospheric tidal responses. Plain Language Summary: Sudden Stratospheric Warming (SSW) is a phenomenon in which temperatures in the polar stratosphere rise rapidly due to interactions between planetary waves (PWs) propagating from the troposphere and the background wind flow. While SSWs occur approximately once every 2 years in the Northern Hemisphere, they are extremely rare in the Southern Hemisphere (SH). In July–August 2024, two rare consecutive SH SSWs occurred, making them the earliest events ever recorded during the satellite era. Given the unusual nature of these events, we investigated how winds and atmospheric tides in the mesosphere and lower thermosphere (MLT) responded using four meteor radars located near Antarctica. We found that the semidiurnal tide (SDT) amplitude increased during these events, exhibiting distinct longitudinal asymmetry. To elucidate the mechanisms driving these tidal changes, we examined satellite‐based ozone observations from Aura/MLS and applied a phase‐differencing technique to paired meteor radar sites located at similar latitudes but separated by ∼150° in longitudes. The results indicate that both ozone‐related radiative forcing and nonlinear interactions between PWs and SDT could contribute to the observed enhancement and longitudinal asymmetry in SDT amplitude. These results can improve our understanding of how stratospheric disturbances influence upper atmospheric dynamics on a global scale. Key Points: Meteor radars observe wind and semidiurnal tide (SDT) variations during the 2024 southern hemisphere sudden stratospheric warmingsSDT zonal wavenumber and propagation direction are determined from phase differences between longitudinally separated meteor radarsSDT variability is likely influenced by stratospheric ozone and nonlinear interaction with quasi‐16‐day planetary waves [ABSTRACT FROM AUTHOR]
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Abstract:We investigate the neutral wind and semidiurnal tide (SDT) variations in the mesosphere and lower thermosphere (MLT) during two consecutive minor Southern Hemisphere (SH) sudden stratospheric warmings (SSWs) that occurred unusually early in July–August 2024. Zonal and meridional winds from four meteor radar stations at 50–70°S were analyzed. Zonal winds reversed from eastward to westward between 80 and 100 km altitude during both events, showing a more distinct reversal in the second event. The SDT amplitudes increased and exhibited longitudinal differences around the second event. To elucidate the mechanisms responsible, we analyzed ozone observations from Aura/MLS along with MERRA‐2 shortwave heating. Positive ozone anomalies at 10 hPa (∼32 km) in the SH polar region around each event coincide with enhanced SDT amplitudes from meteor radars. In addition, the shortwave heating rate shows an enhanced 12‐hr component at SH high‐latitudes above 40 km during these events, supporting an ozone‐related radiative contribution to the SDT variability. Using phase‐differences from longitudinally separated meteor radars, we estimated the zonal wavenumber. Based on this analysis, we propose that nonlinear interaction between the quasi‐16‐day zonal wavenumber‐2 planetary wave (Q16DW2) and the migrating semidiurnal tide (SW2) contributed to the observed longitudinal differences in SDT amplitude. Furthermore, nonlinear advection associated with Q16DW2–SDT interactions is examined and shows clear longitudinal differences that lead to longitudinal asymmetry in SDT amplitude. These findings show the strong modulation of the SDT by SH SSWs and underscore the combined roles of ozone variability and nonlinear wave interactions in modulating upper‐atmospheric tidal responses. Plain Language Summary: Sudden Stratospheric Warming (SSW) is a phenomenon in which temperatures in the polar stratosphere rise rapidly due to interactions between planetary waves (PWs) propagating from the troposphere and the background wind flow. While SSWs occur approximately once every 2 years in the Northern Hemisphere, they are extremely rare in the Southern Hemisphere (SH). In July–August 2024, two rare consecutive SH SSWs occurred, making them the earliest events ever recorded during the satellite era. Given the unusual nature of these events, we investigated how winds and atmospheric tides in the mesosphere and lower thermosphere (MLT) responded using four meteor radars located near Antarctica. We found that the semidiurnal tide (SDT) amplitude increased during these events, exhibiting distinct longitudinal asymmetry. To elucidate the mechanisms driving these tidal changes, we examined satellite‐based ozone observations from Aura/MLS and applied a phase‐differencing technique to paired meteor radar sites located at similar latitudes but separated by ∼150° in longitudes. The results indicate that both ozone‐related radiative forcing and nonlinear interactions between PWs and SDT could contribute to the observed enhancement and longitudinal asymmetry in SDT amplitude. These results can improve our understanding of how stratospheric disturbances influence upper atmospheric dynamics on a global scale. Key Points: Meteor radars observe wind and semidiurnal tide (SDT) variations during the 2024 southern hemisphere sudden stratospheric warmingsSDT zonal wavenumber and propagation direction are determined from phase differences between longitudinally separated meteor radarsSDT variability is likely influenced by stratospheric ozone and nonlinear interaction with quasi‐16‐day planetary waves [ABSTRACT FROM AUTHOR]
ISSN:21699380
DOI:10.1029/2025JA034841