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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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Title: Lower-stratospheric aerosol measurements in eastward-shedding vortices over Japan from the Asian summer monsoon anticyclone during the summer of 2018
Authors: Fujiwara, Masatomo Browse this author →KAKEN DB
Sakai, Tetsu Browse this author →KAKEN DB
Nagai, Tomohiro Browse this author →KAKEN DB
Shiraishi, Koichi Browse this author →KAKEN DB
Inai, Yoichi Browse this author →KAKEN DB
Khaykin, Sergey Browse this author
Xi, Haosen Browse this author
Shibata, Takashi Browse this author →KAKEN DB
Shiotani, Masato Browse this author →KAKEN DB
Pan, Laura L. Browse this author
Issue Date: 1-Mar-2021
Publisher: Copernicus Publications
Journal Title: Atmospheric Chemistry and Physics
Volume: 21
Issue: 4
Start Page: 3073
End Page: 3090
Publisher DOI: 10.5194/acp-21-3073-2021
Abstract: Eastward air-mass 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 degrees N, 140.1 degrees E) and Fukuoka (33.55 degrees N, 130.36 degrees E), during the summer of 2018. We observed several events with enhanced particle signals at Tsukuba at 15.5-18 km of altitude (at or above the local tropopause) during August-September 2018, with a backscattering ratio of similar to 1.10 and particle depolarization of similar to 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 air masses 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.
Rights: https://creativecommons.org/licenses/by/4.0/
Type: article
URI: http://hdl.handle.net/2115/81158
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

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