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第343回 大気海洋物理学・気候力学セミナー のおしらせ

日　時：12月17日 (木) 9:30 - 12:00
Date ：Thu., 17 Dec. 9:30 - 12:00
ツール：Zoom (Online)
Tool ：Zoom (Online)

注意事項 ：Zoomのミーティング情報が必要な場合は下記のメールアドレスまでお問い合わせください。
Note ：If you need Zoom meeting information, please contact us at the email address below.

発表者：藤原 正智（大気海洋物理学・気候力学コース/教員）
Speaker：Masatomo Fujiwara (Course in Atmosphere-Ocean and Climate Dynamics / Associate Professor)
題目：2018年夏季におけるアジアモンスーン高気圧からの東方流出渦に伴い日本上空下部成層圏に輸送されたエアロゾル粒子の観測
Title：Lower-stratospheric aerosol measurements in eastward shedding vortices over Japan from the Asian summer monsoon anticyclone during the summer of 2018

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2018年夏季におけるアジアモンスーン高気圧からの東方流出渦に伴い日本上空下部成層圏に輸送されたエアロゾル粒子の観測
Lower-stratospheric aerosol measurements in eastward shedding vortices over Japan from the Asian summer monsoon anticyclone during the summer of 2018
藤原 正智 (Masatomo Fujiwara) 発表要旨：

Eastward airmass transport from the Asian summer monsoon (ASM)    
anticyclone in the upper troposphere and lower stratosphere (UTLS) often    
involves eastward shedding vortices, which can cover most of the    
Japanese archipelago. We investigated the aerosol characteristics of    
these vortices by analysing data from two lidar systems in Japan, at    
Tsukuba (36.1°N, 140.1°E) and Fukuoka (33.55°N, 130.36°E), during the    
summer of 2018. We observed several events with enhanced particle    
signals at Tsukuba at 15.5–18 km altitude (at or above the local    
tropopause) during August–September 2018, with a backscattering ratio of    
~1.10 and particle depolarization of ~5% (i.e., not spherical, but more    
spherical than ice crystals). These particle characteristics may be    
consistent with those of solid aerosol particles, such as ammonium    
nitrate. Each event had a timescale of a few days. During the same study    
period, we also observed similar enhanced particle signals in the lower    
stratosphere at Fukuoka. The upper troposphere is often covered by    
cirrus clouds at both lidar sites. Backward trajectory calculations for    
these sites for days with enhanced particle signals in the lower    
stratosphere and days without indicate that the former airmasses    
originated within the ASM anticyclone, and the latter more from edge    
regions. Reanalysis carbon-monoxide and satellite water-vapour data    
indicate that eastward shedding vortices were involved in the observed    
aerosol enhancements. Satellite aerosol data confirm that the period and    
latitudinal region were free from the direct influence of documented    
volcanic eruptions and high latitude forest fires. Our results indicate    
that the Asian Tropopause Aerosol Layer (ATAL) over the ASM region    
extends east towards Japan in association with the eastward shedding    
vortices, and that lidar systems in Japan can detect at least the lower    
stratospheric portion of the ATAL during periods when the lower    
stratosphere is undisturbed by volcanic eruptions and forest fires. The    
upper tropospheric portion of the ATAL is either depleted by    
tropospheric processes (convection and wet scavenging) during eastward    
transport or is obscured by much stronger cirrus cloud signals.
    

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