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Hokkaido University Collection of Scholarly and Academic Papers >
Graduate School of Environmental Science / Faculty of Environmental Earth Science >
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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. |
| Rights: | https://creativecommons.org/licenses/by/4.0/ |
| Type: | article |
| URI: | http://hdl.handle.net/2115/76284 |
| 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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Submitter: 藤原 正智
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