气候变化领域集成服务门户(CCPortal): Does the coupling of the semiannual oscillation with the quasi-biennial oscillation provide predictability of Antarctic sudden stratospheric warmings?

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DOI	10.5194/acp-21-12835-2021
	Does the coupling of the semiannual oscillation with the quasi-biennial oscillation provide predictability of Antarctic sudden stratospheric warmings?
	Nordström V.J.; Seppälä A.
发表日期	2021
ISSN	1680-7316
起始页码	12835
结束页码	12853
卷号	21 期号:17
英文摘要	During September 2019 a minor sudden stratospheric warming took place over the Southern Hemisphere (SH), bringing disruption to the usually stable winter vortex. The mesospheric winds reversed and temperatures in the stratosphere rose by over 50gK. Whilst sudden stratospheric warmings (SSWs) in the SH are rare, with the only major SSW having occurred in 2002, the Northern Hemisphere experiences about six per decade. Amplification of atmospheric waves during winter is thought to be one of the possible triggers for SSWs, although other mechanisms are also possible. Our understanding, however, remains incomplete, especially with regards to SSW occurrence in the SH. Here, we investigate the effect of two equatorial atmospheric modes, the quasi-biennial oscillation (QBO) at 10ghPa and the semiannual oscillation (SAO) at 1ghPa during the SH winters of 2019 and 2002. Using MERRA-2 reanalysis data we find that the easterly wind patterns resembling the two modes merge at low latitudes in the early winter, forming a zero-wind line that stretches from the lower stratosphere into the mesosphere. This influences the meridional wave guide, resulting in easterly momentum being deposited in the polar atmosphere throughout the polar winter, decelerating the westerly winds in the equatorward side of the polar vortex. As the winter progresses, the momentum deposition and wind anomalies descend further down into the stratosphere. We find similar behaviour in other years with early onset SH vortex weakening events. The magnitude of the SAO and the timing of the upper stratospheric (10ghPa) easterly QBO signal was found to be unique in these years when compared to the years with a similar QBO phase. We were able to identify the SSW and weak vortex years from the early winter location of the zero-wind line at 1ghPa together with Eliassen-Palm flux divergence in the upper stratosphere at 40-50ĝ gS. We propose that this early winter behaviour resulting in deceleration of the polar winds may precondition the southern atmosphere for a later enhanced wave forcing from the troposphere, resulting in an SSW or vortex weakening event. Thus, the early winter equatorial upper stratosphere-mesosphere, together with the polar upper atmosphere, may provide early clues to an imminent SH SSW. © Authors 2021.
语种	英语
scopus关键词	climate prediction; mesoscale meteorology; numerical model; quasi-biennial oscillation; stratosphere; vortex; winter; Southern Ocean
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/246623
作者单位	Department of Physics, University of Otago, Dunedin, New Zealand
推荐引用方式 GB/T 7714	Nordström V.J.,Seppälä A.. Does the coupling of the semiannual oscillation with the quasi-biennial oscillation provide predictability of Antarctic sudden stratospheric warmings?[J],2021,21(17).
APA	Nordström V.J.,&Seppälä A..(2021).Does the coupling of the semiannual oscillation with the quasi-biennial oscillation provide predictability of Antarctic sudden stratospheric warmings?.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(17).
MLA	Nordström V.J.,et al."Does the coupling of the semiannual oscillation with the quasi-biennial oscillation provide predictability of Antarctic sudden stratospheric warmings?".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.17(2021).