气候变化领域集成服务门户(CCPortal): On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016

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DOI	10.5194/acp-20-6541-2020
	On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016
	Li H.; Pilch Kedzierski R.; Matthes K.
发表日期	2020
ISSN	16807316
起始页码	6541
结束页码	6561
卷号	20 期号:11
英文摘要	The westerly phase of the stratospheric Quasi-Biennial Oscillation (QBO) was reversed during Northern Hemisphere winter 2015/2016 for the first time since records began in 1953. Recent studies proposed that Rossby waves propagating from the extratropics played an important role during the reversal event in 2015/2016. Building upon these studies, we separated the extratropical Rossby waves into different wavenumbers and timescales by analyzing the combined ERA-40 and ERA-Interim reanalysis zonal wind, meridional wind, vertical velocity, and potential vorticity daily mean data from 1958 to 2017. We find that both synoptic and quasi-stationary Rossby waves are dominant contributors to the reversal event in 2015/2016 in the tropical lower stratosphere. By comparing the results for 2015/2016 with two additional events (1959/1960 and 2010/2011), we find that the largest differences in Rossby wave momentum fluxes are related to synoptic-scale Rossby waves of periods from 5 to 20d. We demonstrate for the first time, that these enhanced synoptic Rossby waves at 40hPa in the tropics in February 2016 originate from the extratropics as well as from local wave generation. The strong Rossby wave activity in 2016 in the tropics happened at a time with weak westerly zonal winds. This coincidence of anomalous factors did not happen in any of the previous events. In addition to the anomalous behavior in the tropical lower stratosphere in 2015/2016, we explored the forcing of the unusually long-lasting westerly zonal wind phase in the middle stratosphere (at 20hPa). Our results reveal that mainly enhanced Kelvin wave activity contributed to this feature. This was in close relation with the strong El Niño event in 2015/2016, which forced more Kelvin waves in the equatorial troposphere. The easterly or very weak westerly zonal winds present around 30-70hPa allowed these Kelvin waves to propagate vertically and deposit their momentum around 20hPa, maintaining the westerlies there. © 2020 Copernicus GmbH. All rights reserved.
关键词	atmospheric forcing Kelvin wave Northern Hemisphere potential vorticity quasi-biennial oscillation Rossby wave stratosphere wave propagation westerly zonal wind
语种	英语
来源机构	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/131993
推荐引用方式 GB/T 7714	Li H.,Pilch Kedzierski R.,Matthes K.. On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016[J]. Atmospheric Chemistry and Physics,2020,20(11).
APA	Li H.,Pilch Kedzierski R.,&Matthes K..(2020).On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016.,20(11).
MLA	Li H.,et al."On the forcings of the unusual Quasi-Biennial Oscillation structure in February 2016".20.11(2020).