Model spread in multidecadal North Atlantic Oscillation variability connected to stratosphere–troposphere coupling

Rémy Bonnet, C. McKenna, A. Maycock
{"title":"Model spread in multidecadal North Atlantic Oscillation variability connected to stratosphere–troposphere coupling","authors":"Rémy Bonnet, C. McKenna, A. Maycock","doi":"10.5194/wcd-5-913-2024","DOIUrl":null,"url":null,"abstract":"Abstract. The underestimation in multidecadal variability in the wintertime North Atlantic Oscillation (NAO) by global climate models remains poorly understood. Understanding the origins of this weak NAO variability is important for making model projections more reliable. Past studies have linked the weak multidecadal NAO variability in models to an underestimated atmospheric response to the Atlantic Multidecadal Variability (AMV). We investigate historical simulations from Coupled Model Intercomparison Project Phase 6 (CMIP6) large-ensemble models and find that most of the models do not reproduce observed multidecadal NAO variability, as found in previous generations of climate models. We explore statistical relationships with physical drivers that may contribute to inter-model spread in NAO variability. There is a significant anticorrelation across models between the AMV–NAO coupling parameter and multidecadal NAO variability over the full historical period (r=-0.55, p<0.05). However, this relationship is relatively weak and becomes obscured when using a common period (1900–2010) and de-trending the data in a consistent way, with observations to enable a model–data comparison. This suggests that the representation of NAO–AMV coupling contributes to a modest proportion of inter-model spread in multidecadal NAO variability, although the importance of this process for model spread could be underestimated, given evidence of a systematically poor representation of the coupling in the models. We find a significant inter-model correlation between multidecadal NAO variability and multidecadal stratospheric polar vortex variability and a stratosphere–troposphere coupling parameter, which quantifies the relationship between stratospheric winds and the NAO. The models with the lowest NAO variance are associated with weaker polar vortex variability and a weaker stratosphere–troposphere coupling parameter. The two stratospheric indices are uncorrelated across models and together give a pooled R2 with an NAO variability of 0.7, which is larger than the fraction of inter-model spread related to the AMV (R2=0.3). The identification of this relationship suggests that modelled spread in multidecadal NAO variability has the potential to be reduced by improved knowledge of observed multidecadal stratospheric variability; however, observational records are currently too short to provide a robust constraint on these indices.\n","PeriodicalId":383272,"journal":{"name":"Weather and Climate Dynamics","volume":" 661","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Weather and Climate Dynamics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.5194/wcd-5-913-2024","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0

Abstract

Abstract. The underestimation in multidecadal variability in the wintertime North Atlantic Oscillation (NAO) by global climate models remains poorly understood. Understanding the origins of this weak NAO variability is important for making model projections more reliable. Past studies have linked the weak multidecadal NAO variability in models to an underestimated atmospheric response to the Atlantic Multidecadal Variability (AMV). We investigate historical simulations from Coupled Model Intercomparison Project Phase 6 (CMIP6) large-ensemble models and find that most of the models do not reproduce observed multidecadal NAO variability, as found in previous generations of climate models. We explore statistical relationships with physical drivers that may contribute to inter-model spread in NAO variability. There is a significant anticorrelation across models between the AMV–NAO coupling parameter and multidecadal NAO variability over the full historical period (r=-0.55, p<0.05). However, this relationship is relatively weak and becomes obscured when using a common period (1900–2010) and de-trending the data in a consistent way, with observations to enable a model–data comparison. This suggests that the representation of NAO–AMV coupling contributes to a modest proportion of inter-model spread in multidecadal NAO variability, although the importance of this process for model spread could be underestimated, given evidence of a systematically poor representation of the coupling in the models. We find a significant inter-model correlation between multidecadal NAO variability and multidecadal stratospheric polar vortex variability and a stratosphere–troposphere coupling parameter, which quantifies the relationship between stratospheric winds and the NAO. The models with the lowest NAO variance are associated with weaker polar vortex variability and a weaker stratosphere–troposphere coupling parameter. The two stratospheric indices are uncorrelated across models and together give a pooled R2 with an NAO variability of 0.7, which is larger than the fraction of inter-model spread related to the AMV (R2=0.3). The identification of this relationship suggests that modelled spread in multidecadal NAO variability has the potential to be reduced by improved knowledge of observed multidecadal stratospheric variability; however, observational records are currently too short to provide a robust constraint on these indices.
与平流层-对流层耦合有关的多年代北大西洋涛动变率的模型传播
摘要全球气候模式对冬季北大西洋涛动(NAO)多年变率的低估仍然鲜为人知。了解这种微弱的北大西洋涛动变率的起源对于提高模式预测的可靠性非常重要。过去的研究认为,模式中的多年期北大西洋涛动(NAO)微弱变率与低估了大气对大西洋多年变率(AMV)的响应有关。我们对耦合模式相互比较项目第 6 阶段(CMIP6)大集合模式的历史模拟进行了调查,发现大多数模式都没有再现观测到的十年多期北大西洋环流变率,前几代气候模式也是如此。我们探讨了可能导致模型间北大西洋环流变率差异的物理驱动因素的统计关系。在整个历史时期,AMV-NAO 耦合参数与多年期 NAO 变率之间存在明显的反相关关系(r=-0.55,p<0.05)。然而,这种关系相对较弱,当使用一个共同的时期(1900-2010 年)并以一致的方式对数据进行去趋势化处理时,这种关系就会变得模糊不清,同时还要进行观测,以便对模型和数据进行比较。这表明,NAO-AMV 耦合的表示方法在多年代 NAO 变率的模式间差异中占了一定比例,尽管这一过程对模型差异的重要性可能被低估,因为有证据表明模式对耦合的表示方法系统性较差。我们发现,在多年代NAO变率和多年代平流层极地涡旋变率以及平流层-对流层耦合参数之间存在着明显的模式间相关性,该耦合参数可量化平流层风与NAO之间的关系。NAO 方差最小的模式与较弱的极地涡旋变率和较弱的平流层-对流层耦合参数有关。这两个平流层指数在各模式间不相关,它们与 NAO 变率的总 R2 为 0.7,大于与 AMV 有关的模式间差分(R2=0.3)。这种关系的确定表明,通过改进对观测到的十年多平流层变率的了解,有可能减小模拟的十年多NAO变率的差异;然而,观测记录目前太短,无法对这些指数提供有力的约束。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
CiteScore
6.40
自引率
0.00%
发文量
0
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信