Japan Geoscience Union Meeting 2021

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS06] Stratosphere-troposphere Processes And their Role in Climate

Thu. Jun 3, 2021 1:45 PM - 3:15 PM Ch.06 (Zoom Room 06)

convener:Takenari Kinoshita(Japan Agency for Marine-Earth Science and Technology), Takatoshi Sakazaki(Graduate School of Science, Kyoto University), Masashi Kohma(Department of Earth and Planet Science, Graduate School of Science, The University of Tokyo), Nawo Eguchi(Kyushu University), Chairperson:Masashi Kohma(Department of Earth and Planet Science, Graduate School of Science, The University of Tokyo)

2:35 PM - 2:55 PM

[AAS06-16] Characteristics of planetary-wave packet propagation during a major sudden stratospheric warming event in January 2021

★Invited Papers

*Yayoi Harada1, Takenari Kinoshita2, Kaoru Sato3, Toshihiko Hirooka4 (1.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 that occurred in January 2021 (MSSW21) are analyzed using the Japanese 55-year Reanalysis, and a 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 observed in early January 2021 and a mixed signature of wavenumber 1 (WN1), WN2 and WN3 planetary waves, although WN1 has been predominant during MSSW21 except its early stage (from late December 2020 to early January 2021). In the early stage, the polar vortex was displaced from the North Pole and simultaneously broken up into two centers. After a couple of days, they were merged into one but again broken around mid-January. After that the two centers were again merged and the polar vortex begun to travel eastward around the North Pole. Thus, the synoptic feature of the polar vortex was very variable. Resultantly, MSSW21 lasted until mid-February and several warming peaks were observed during the course of its time evolution.

Further analyses revealed that wave packets repeatedly propagated upward in the Eastern Hemisphere during MSSW21. During the early stage, localized wave packets propagated upward into the upper stratosphere over western Siberia. During the mature stage (mid-January 2021), upward wave-packet propagation was observed over eastern Siberia and even in the easterly region of the upper stratosphere.