The Impact of Split and Displacement Sudden Stratospheric Warmings on the Troposphere
The Impact of Split and Displacement Sudden Stratospheric Warmings on the Troposphere
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DOI：
10.1029/2020jd033989
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发表时间：
2021-04
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影响因子：
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通讯作者：
Ian P. White;C. Garfinkel;J. Cohen;M. Jucker;Jian Rao
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作者：
Ian P. White;C. Garfinkel;J. Cohen;M. Jucker;Jian Rao
虽然平流层突然变暖（SSW）可以改善次季节到季节的预测，但目前还不清楚这两种类型的SSW-位移和分裂-是否具有不同的近地面效应。为了更长期地研究（即，多周领先）对流层对位移和分裂的响应，我们利用一个中等复杂度的模型，并施加从控制运行中分离出来的波1和波2平流层加热扰动。在较长的滞后，对流层的响应被发现是不敏感的波数和位置的施加加热，在协议中确定的控制运行中的自由发展的位移和分裂。然而，在较短的滞后，在控制运行和不同的波数强迫事件的位移和分裂之间发现了很大的差异。特别是，在控制运行中，自由运行的分裂在整个平流层和对流层中具有立即的正压响应，而位移在近地面响应变得明显之前需要1-2周。有趣的是，在CTRL分裂期间发现的正压响应并没有被正压强迫的波2事件捕获，这表明纬向平均对流层环流在某种程度上与波2分裂的产生相耦合。还发现，在控制运行中，位移产生更强的极帽温度异常比分裂，但两者仍然产生类似的量级对流层响应。因此，平流层变暖的强度并不是地面响应的唯一决定因素。总体而言，SSW分类的基础上涡形态可能是有用的亚季节，但不是季节对流层预测。
Although sudden stratospheric warmings (SSWs) can improve subseasonal‐to‐seasonal forecasts, it is unclear whether the two types of SSW ‐ displacements and splits ‐ have different near‐surface effects. To examine the longer‐term (i.e., multi‐week lead) tropospheric response to displacements and splits, we utilize an intermediate‐complexity model and impose wave‐1 and wave‐2 stratospheric heating perturbations spun‐off from a control run. At longer lags, the tropospheric response is found to be insensitive to both the wavenumber and location of the imposed heating, in agreement with freely evolving displacements and splits identified in the control run. At shorter lags, however, large differences are found between displacements and splits in both the control run and the different wavenumber‐forced events. In particular, in the control run, the free‐running splits have an immediate barotropic response throughout the stratosphere and troposphere whereas displacements take 1–2 weeks before a near‐surface response becomes evident. Interestingly, this barotropic response found during CTRL splits is not captured by the barotropically forced wave‐2 events, indicating that the zonal‐mean tropospheric circulation is somehow coupled with the generation of the wave‐2 splits. It is also found that in the control run, displacements yield stronger Polar‐Cap temperature anomalies than splits, yet both still yield similar magnitude tropospheric responses. Hence, the strength of the stratospheric warming is not the only governing factor in the surface response. Overall, SSW classification based on vortex morphology may be useful for subseasonal but not seasonal tropospheric prediction.