- 1Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, China
- 2Ann \& H. J. Smead Department of Aerospace Engineering Sciences, University of Colorado, Boulder, USA
- 3Institute of Applied Physics \& Oeschger Center for Climate Change Research, Microwave Physics, University of Bern, Bern, Switzerland
- 4Institute for Meteorology, Leipzig University, Leipzig, Germany
- 5Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
This study utilizes meteor radar observations gathered over nine years at two longitudes and 52°N latitude to explore planetary-scale waves in mesospheric winds. By analyzing zonal wavenumbers across various time scales—specifically multi-day, near-24-hour, 12-hour, and 8-hour periods—we were able to distinguish normal modes (NMs) from other planetary waves (PWs), identify migrating and non-migrating tides, and uncover a range of novel nonlinear interactions.
Our statistical analysis revealed that multi-day oscillations were predominantly associated with NMs, which exhibit distinct seasonality in both period and wavenumber, and show a statistical correlation with sudden stratospheric warmings (SSWs). Notably, April featured a prominent 6-day NM (zonal wavenumber 1), followed by a dominance of 4- and 2-day NMs (wavenumbers 2 and 3, respectively) through June. From July to October, we observed peaks in 2-, 4-, and 6-day NMs (zonal wavenumbers 3, 2, and 1, respectively).
Our insights into seasonal variations are based on observational determinations of frequency and zonal wavenumber, in contrast to satellite observations that often use fixed frequencies and wavenumbers to fit individual waves. The statistical link between NMs and SSWs provides significant input to the ongoing debate on this topic. Additionally, for the first time, we identified frequency and zonal wavenumber matching in over ten secondary waves resulting from nonlinear interactions among NMs (16-, 10-, and 6-day), tides (diurnal, semidiurnal, and terdiurnal, both migrating and non-migrating), and stationary planetary waves (SPWs).
Among these interactions, three novel categories were identified: (1) interactions between terdiurnal tides and planetary waves, (2) interactions between stationary and traveling planetary waves, and (3) interactions between non-migrating tides and planetary waves. These interactions with SPWs help explain our finding that the amplitudes of non-migrating tides exceed those of the corresponding migrating tides, particularly evident in the winter diurnal tide and the summer terdiurnal tide. These non-migrating signatures stand out as notable exceptions, as migrating components generally dominate diurnal, semidiurnal, and terdiurnal tides throughout most of the year.
How to cite: He, M., Forbes, J. M., Stober, G., Jacobi, C., Li, G., Liu, L., and Xu, J.: Nonlinear Interactions of Mesospheric Planetary-Scale Waves: Seasonal Variations and Association with Sudden Stratospheric Warmings, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14547, https://doi.org/10.5194/egusphere-egu25-14547, 2025.
