日本地球惑星科学連合2023年大会

講演情報

[J] 口頭発表

セッション記号 A (大気水圏科学) » A-AS 大気科学・気象学・大気環境

[A-AS09] 成層圏・対流圏過程とその気候への影響

2023年5月26日(金) 09:00 〜 10:15 201A (幕張メッセ国際会議場)

コンビーナ:田口 正和(愛知教育大学)、江口 菜穂(九州大学 応用力学研究所)、高麗 正史(東京大学大学院理学系研究科地球惑星科学専攻)、野口 峻佑(九州大学 理学研究院 地球惑星科学部門)、座長:田口 正和(愛知教育大学)


09:30 〜 09:45

[AAS09-03] 北半球冬季成層圏界面付近における極端に強い東風イベントの解析

*原田 やよい1木下 武也2佐藤 薫3廣岡 俊彦4 (1.気象研究所、2.海洋研究開発機構、3.東京大学、4.九州大学)

キーワード:極端に強い東風イベント、成層圏突然昇温、惑星規模波束伝播、3次元波活動度フラックス

We have been investigating the characteristics of atmospheric fields during a major sudden stratospheric warming (MSSW) event occurring in January 2021 (MSSW21) by the use of the Japanese Reanalysis for Three Quarters of a Century (JRA-3Q, Kosaka et al. in preparation). Three-dimensional analysis of planetary-scale wave packets was performed based on 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 this study, we investigate the occurrence frequency of such extremely strong easterly wind (ESEW) events over the past 40+ years and the propagation of planetary scale wave packets during ESEW events. In addition to JRA-3Q, we use the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2, Gelaro et al. 2017). The sampling period for ESEW events is 43 years, from January 1980 to December 2022. The event is defined as a daily zonal-mean zonal wind which is easterly with the magnitude exceeding 70 m/s at either JRA-3Q or MERRA-2 grid points in the Northern Hemisphere north of 60° and in the region from 10 hPa to 0.3 hPa.
As an early result, we found that the ESEW event occurred six other times in addition to MSSW 21: February 1980, January 1985, January 1987, January 2006, January 2012, and January 2013. It is interesting to note that these events are concentrated in the 1980's and after 2000. One of the characteristics of these events is that rapid westerly deceleration (easterly acceleration) occurred within a few days (except for the January 2006 event). The January 1985 event in particular shows a rapid change from 60 m s-1 westerly winds to 90 m s-1 easterly winds at the 0.7-hPa level, which means that a westerly deceleration of 150 m s-1 occurs within a few days.
On the day of the meeting, common features and differences will be presented based on the results of analysis of planetary-scale wave packet propagation observed during each ESEW event.