[A-AS10] Stratosphere-troposphere Processes And their Role in Climate

[AAS10-08] Characteristics of planetary-wave packet propagation during a major sudden stratospheric warming event in January 2021 (second report)

*Yayoi Harada¹, Takenari Kinoshita², Kaoru Sato³, Toshihiko Hirooka⁴ (1.Meteorological Research Institute, 2.Meteorological Research Institute, Japan Meteorological Agency, 2. The Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3.Department of Earth and Planetary Sciences, University of Tokyo, 4.Department of Earth and Planetary Sciences, Kyushu University)

Keywords:Sudden stratospheric warming, Planetary-wave packet propagation, Three-dimensional wave activity flux

Observational features of atmospheric fields during a major sudden stratospheric warming (MSSW) event occurring in January 2021 (MSSW21) are investigated by the use of the Japanese 55-year Reanalysis (JRA-55) on the basis of the three-dimensional wave activity flux (3D-flux-W, Kinoshita and Sato 2013; Sato et al. 2013; Harada et al. 2019). MSSW21 is characterized by strong easterlies over 70 m s^-1 around the stratopause in early January 2021, a mixed signature of wavenumber 1 (WN1), WN2 and WN3 planetary waves, and repetition of polar vortex splitting. In relation to that, wave packets repeatedly propagated upward in the Eastern Hemisphere during MSSW21: In the early stage, localized wave packets propagated upward into the upper stratosphere over western Siberia. On the other hand, in the mature stage (mid-January 2021), upward wave-packet propagation was observed over eastern Siberia even in the easterly region of the upper stratosphere.
In this report, we add Japanese Reanalysis for Three Quarters of a Century (JRA-3Q) as a dataset for analysis, which is being conducted by the Japan Meteorological Agency (JMA). In JRA-3Q data assimilation system, vertical levels are increased up to 100 layers (the top level of is 0.01 hPa) which covers the whole stratosphere and the lower mesosphere, and includes non-orographic gravity wave drag based on Scinocca (2003). As an early result, we found that the consistency of momentum budget in JRA-3Q is improved compared with that of JRA-55 not only in the upper stratosphere but also in the lower mesosphere. We are going to show further results on MSSW21 using 3D-flux-W.