Ozone‐Forced Southern Annular Mode During Antarctic Stratospheric Warming Events
Ozone‐Forced Southern Annular Mode During Antarctic Stratospheric Warming Events
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DOI：
10.1029/2021gl095270
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发表时间：
2021-07
影响因子：
5.2
通讯作者：
M. Jucker;R. Goyal
中科院分区：
文献类型：
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作者：
M. Jucker;R. Goyal
南半球（SH）平流层变暖事件（SWEs）通常与次年夏季对流层南环模（SAM）的负相有关。相比之下，通过整体气候模式模拟，我们发现，通常在西南风期间发生的异常高臭氧浓度可以通过增加平流层低层静态稳定性和改变对流层到平流层的波传播来强迫南方春季持续的对流层正SAM。最终，对流层SAM信号在春末夏初切换到负相位，但这种平流层信号的“向下传播”在没有季节周期的模拟中不会发生。我们发现，由于季节循环，臭氧对短波的吸收增加，在动态上和辐射上都迫使臭氧向下传播。在模式中捕捉这种臭氧强迫机制需要包括相互作用臭氧，这对当前季节预报系统的预测技能具有重要意义。
Southern Hemisphere (SH) Stratospheric Warming Events (SWEs) are usually associated with a negative phase of the tropospheric Southern Annular Mode (SAM) during the following summer. In contrast, using ensemble climate model simulations we show that the anomalously high ozone concentrations typically occurring during SWEs can force periods of persistent positive tropospheric SAM in austral spring by increasing lower stratospheric static stability and changing troposphere‐to‐stratosphere wave propagation. Eventually, the tropospheric SAM switches sign to its negative phase in late spring/early summer, but this ‘downward propagation’ of the stratospheric signal does not occur in simulations without seasonal cycle. We find that the downward propagation is forced both dynamically by adiabatic heating and radiatively by increased shortwave absorption by ozone due to the seasonal cycle. Capturing this ozone forcing mechanism in models requires the inclusion of interactive ozone, which has important implications for the predictive skill of current seasonal forecasting systems.