Origins of multi-decadal variability in sudden stratospheric warmings
Origins of multi-decadal variability in sudden stratospheric warmings
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DOI：
10.5194/wcd-2020-56
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发表时间：
2020-11
影响因子：
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通讯作者：
O. Dimdore-Miles;L. Gray;S. Osprey
中科院分区：
文献类型：
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作者：
O. Dimdore-Miles;L. Gray;S. Osprey
抽象。平流层突然变暖是北方平流层极涡的主要扰动，在观测记录中平均每十年发生六次。然而，在这些记录中，观察到明显较高和较低的SSW率的间隔，表明事件发生的低频变化的可能性。更好地了解影响这种年代际变化的因素可能有助于提高北半球中纬度地面气候的可预测性，通过平流层对流层耦合。在这项工作中，SSW事件的多年代际变率在1000年前的工业耦合全球气候模式的模拟研究。使用小波谱分解方法，我们表明，中断事件（间隔十年或更长时间，没有SSW）和连续的SSW事件（延长间隔，至少有一个SSW在每年）变化的多年代际时间尺度的周期在60和90年之间。这些时间尺度上的信号存在于大约450年的模拟中。我们调查了这些长期信号的可能来源，发现热带海面温度变化的直接影响，以及相关的阿留申低压，只能解释SSW变化的一小部分。相反，对长期SSW变化的主要影响与平流层准两年振荡（QBO）振幅的长期变化有关。QBO的影响是一致的著名的霍尔顿-谭的关系，与SSW间断间隔与延长期的特别强，深QBO西风阶段。这些结果支持了最近的研究，即在考虑QBO、极涡和对流层环流之间的耦合时，强调了垂直相干性在QBO中的作用。
Abstract. Sudden stratospheric warmings (SSWs) are major disruptions of the Northern Hemisphere (NH) stratospheric polar vortex and occur on average approximately six times per decade in observation-based records. However, within these records, intervals of significantly higher and lower SSW rates are observed, suggesting the possibility of low-frequency variations in event occurrence. A better understanding of factors that influence this decadal variability may help to improve predictability of NH midlatitude surface climate, through stratosphere–troposphere coupling. In this work, multi-decadal variability of SSW events is examined in a 1000-year pre-industrial simulation of a coupled global climate model. Using a wavelet spectral decomposition method, we show that hiatus events (intervals of a decade or more with no SSWs) and consecutive SSW events (extended intervals with at least one SSW in each year) vary on multi-decadal timescales of periods between 60 and 90 years. Signals on these timescales are present for approximately 450 years of the simulation. We investigate the possible source of these long-term signals and find that the direct impact of variability in tropical sea surface temperatures, as well as the associated Aleutian Low, can account for only a small portion of the SSW variability. Instead, the major influence on long-term SSW variability is associated with long-term variability in amplitude of the stratospheric quasi-biennial oscillation (QBO). The QBO influence is consistent with the well-known Holton–Tan relationship, with SSW hiatus intervals associated with extended periods of particularly strong, deep QBO westerly phases. The results support recent studies that have highlighted the role of vertical coherence in the QBO when considering coupling between the QBO, the polar vortex and tropospheric circulation.