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Representation of the equatorial stratopause semiannual oscillation in global atmospheric reanalyses

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Title: Representation of the equatorial stratopause semiannual oscillation in global atmospheric reanalyses
Authors: Kawatani, Yoshio Browse this author →KAKEN DB
Hirooka, Toshihiko Browse this author →KAKEN DB
Hamilton, Kevin Browse this author
Smith, Anne K. Browse this author
Fujiwara, Masatomo Browse this author →KAKEN DB
Issue Date: 31-Jul-2020
Publisher: Copernicus Publications
Journal Title: Atmospheric Chemistry and Physics
Volume: 20
Issue: 14
Start Page: 9115
End Page: 9133
Publisher DOI: 10.5194/acp-20-9115-2020
Abstract: This paper reports on a project to compare the representation of the semiannual oscillation (SAO) in the equatorial stratosphere and lower mesosphere within six major global atmospheric reanalysis datasets and with recent satellite Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) and Microwave Limb Sounder (MLS) observations. All reanalyses have a good representation of the quasi-biennial oscillation (QBO) in the equatorial lower and middle stratosphere and each displays a clear SAO centered near the stratopause. However, the differences among reanalyses are much more substantial in the SAO region than in the QBO-dominated region. The degree of disagreement among the reanalyses is characterized by the standard deviation (SD) of the monthly mean zonal wind and temperature; this depends on latitude, longitude, height, and time. The zonal wind SD displays a prominent equatorial maximum that increases with height, while the temperature SD reaches a minimum near the Equator and is largest in the polar regions. Along the Equator, the zonal wind SD is smallest around the longitude of Singapore, where consistently high-quality near-equatorial radiosonde observations are available. Interestingly, the near-Singapore minimum in SD is evident to at least similar to 3 hPa, i.e., considerably higher than the usual similar to 10 hPa ceiling for in situ radiosonde observations. Our measurement of the agreement among the reanalyses shows systematic improvement over the period considered (1980-2016), up to near the stratopause. Characteristics of the SAO at 1 hPa, such as its detailed time varia- tion and the displacement off the Equator of the zonal wind SAO amplitude maximum, differ significantly among the reanalyses. Disagreement among the reanalyses becomes still greater above 1 hPa. One of the reanalyses in our study also has a version produced without assimilating satellite observations, and a comparison of the SAO in these two versions demonstrates the very great importance of satellite-derived temperatures in the realistic analysis of the tropical upper stratospheric circulation.
Type: article
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)

Submitter: 藤原 正智

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