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Comparison of equatorial wave activity in the tropical tropopause layer and stratosphere represented in reanalyses

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Title: Comparison of equatorial wave activity in the tropical tropopause layer and stratosphere represented in reanalyses
Authors: Kim, Young-Ha Browse this author
Kiladis, George N. Browse this author
Albers, John R. Browse this author
Dias, Juliana Browse this author
Fujiwara, Masatomo Browse this author →KAKEN DB
Anstey, James A. Browse this author
Song, In-Sun Browse this author
Wright, Corwin J. Browse this author
Kawatani, Yoshio Browse this author
Lott, François Browse this author
Yoo, Changhyun Browse this author
Issue Date: 2019
Journal Title: Atmospheric Chemistry and Physics
Volume: 19
Issue: 15
Start Page: 10027
End Page: 10050
Publisher DOI: 10.5194/acp-19-10027-2019
Abstract: Equatorial Kelvin and mixed Rossby–gravity (MRG) waves in the tropical tropopause layer and stratosphere represented in recent reanalyses for the period of 1981–2010 are compared in terms of spectral characteristics, spatial structures, long-term variations, and their forcing of the quasi-biennial oscillation (QBO). For both wave types, the spectral distributions are broadly similar among most of the reanalyses, while the peak amplitudes exhibit considerable spread. The longitudinal distributions and spatial patterns of wave perturbations show reasonable agreement between the reanalyses. A few exceptions to the similarity of the spectral shapes and spatial structures among them are also noted. While the interannual variations of wave activity appear to be coherent for both the Kelvin and MRG waves, there is substantial variability in long-term trends among the reanalyses. Most of the reanalyses which assimilate satellite data exhibit large increasing trends in wave variance (15 %–50% increase in 30 years at 100–10 hPa), whereas one reanalysis (Japanese 55-year Reanalysis assimilating conventional observations only; JRA-55C) produced without satellite data does not. Several discontinuities are found around 1998 in the time series of the Kelvin and MRG wave variances, which manifest in different ways depending on the reanalysis, and are indicative of impacts of the transition of satellite measurements during that year. The equatorial wave forcing of the QBO, estimated by the Eliassen– Palm (EP) flux divergence, occurs in similar phase-speed ranges in the lower stratosphere among the reanalyses. However, the EP flux and its divergence are found to be dependent on the zonal-mean winds represented in reanalyses, exhibiting different magnitudes, altitudes, and phase-speed ranges of the Kelvin wave forcing between the reanalyses, especially at 20–10 hPa. In addition, at around 20 hPa, a wave signal which appears only in easterly mean winds with westward phase speeds is found and discussed.
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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