Response of atmospheric quasi-stationary waves to La Niña conditions in Northern Hemisphere winter
Response of atmospheric quasi-stationary waves to La Niña conditions in Northern Hemisphere winter
复制标题
北半球冬季大气准定常波对拉尼娜现象的响应
DOI：
10.1002/qj.4261
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发表时间：
2022
影响因子：
8.9
通讯作者：
Wolf G
中科院分区：
文献类型：
--
作者：
Wolf G
大规模大气准稳态波（QSW）与天气变化和极端事件（例如阻塞和热浪）密切相关。因此，有必要更深入地了解 QSW 变异的驱动因素。先前的研究强调，厄尔尼诺南方涛动是全球 QSW 变异的主要驱动因素之一，拉尼娜现象尤其令人感兴趣，因为它们与异常的强 QSW 振幅有关。本研究使用一组板状海洋的水生行星实验来分析北半球拉尼娜现象与 QSW 活动之间的联系，模拟不同强度的拉尼娜现象条件。实验表明，拉尼娜现象与较弱的纬向平均哈德来环流以及与绝对涡度强经向梯度相关的中纬度波导相应的北移一致。 QSW 区域通常遵循波导中的这种转变，QSW 幅度沿着稍弱的平均涡度梯度整体增加。对于海洋热通量收敛的弱到中度修改，与相关的 QSW 响应存在近似线性关系，但对于较强的板片热通量，整体响应变得高度非线性。因此得出结论，ENSO 状态可能对整个北半球的 QSW 活动产生重大影响。
Large‐scale atmospheric quasi‐stationary waves (QSWs) are strongly linked to synoptic variability and extreme events such as blocking and heatwaves. It is therefore essential to gain a deeper insight into the drivers of QSW variability. Previous research highlighted the El Niño Southern Oscillation as one of the main drivers for global QSW variability with La Niña conditions of particular interest because of their link to anomalous strong QSW amplitudes. This connection between La Niña and QSW activity in the Northern Hemisphere is analysed in this study using a set of aquaplanet experiments with a slab ocean, mimicking La Niña conditions of varying strengths. The experiments demonstrate La Niña conditions are consistent with a weaker zonal mean Hadley cell and a corresponding northward shift in the midlatitude wave guide associated with strong meridional gradients in absolute vorticity. The QSW region generally follows this shift in the wave guide with an overall increase in QSW amplitudes along a slightly weaker mean vorticity gradient. For weak to moderate modifications of the ocean heat flux convergence, there is an approximately linear relationship with the associated QSW response, though for stronger slab heat fluxes the overall response becomes highly nonlinear. It is therefore concluded that the ENSO state may have significant consequences for QSW activity across the Northern Hemisphere.