Dynamics of ENSO-driven stratosphere-to-troposphere transport of ozone over North America
Dynamics of ENSO-driven stratosphere-to-troposphere transport of ozone over North America
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DOI：
10.5194/acp-22-13035-2022
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发表时间：
2022-10
影响因子：
6.3
通讯作者：
J. Albers;A. Butler;A. Langford;D. Elsbury;Melissa Breeden
中科院分区：
文献类型：
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作者：
J. Albers;A. Butler;A. Langford;D. Elsbury;Melissa Breeden
抽象的。众所周知，厄尔尼诺-南方涛动（ENSO）在冬末夏初期间调节太平洋-北美地区平流层至对流层臭氧输送的强度和频率。已提出的解释这种变异性的动力学过程包括平流层最低层中可用于短期气候变化的臭氧量的变化，以及与对流层环流有关的单个短期气候变化事件的频率和地理分布的变化。在这里，我们使用了一个大的合奏全大气社区气候模式（WACCM）模拟（迫使海表温度（SST）的边界条件与ENSO的每个阶段相一致）表明，在较低的平流层臭氧和太平洋对流层急流的变化建设性地有助于在两个ENSO阶段在北美地区的臭氧STT量。就平流层变化而言，厄尔尼诺/南方涛动造成的臭氧异常类似于太平洋-北美遥相关模式，这种模式跨越50百帕以下平流层低层的大部分地区。这些臭氧异常在布鲁尔-多布森环流中占主导地位，超过了其他由厄尔尼诺/南方涛动引起的变化（包括平流层剩余环流和准等熵混合引起的变化），强烈地调节了可用于STT输送的臭氧量。因此，在冬末（2月至3月），平流层臭氧的遥相关反应建设性地加强异常ENSO喷流驱动的臭氧STT。然而，随着春季进入夏季（4 - 6月），ENSO强迫减弱，ENSO急流驱动的STT输送的直接影响减弱。尽管如此，遥相关对平流层下部臭氧量的剩余影响仍然存在，这些异常反过来又继续导致臭氧STT异常。这些结果应有助于解释厄尔尼诺/南方涛动的效用，作为一个亚季节的自由对流层臭氧和平流层臭氧入侵事件的概率，可能会导致地面空气质量标准的偏差预测。
Abstract. The El Niño–Southern Oscillation (ENSO) is known to modulate the strength and frequency of stratosphere-to-troposphere transport (STT) of ozone over the Pacific–North American region during late winter to early summer. Dynamical processes that have been proposed to account for this variability include variations in the amount of ozone in the lowermost stratosphere that is available for STT and tropospheric circulation-related variations in the frequency and geographic distribution of individual STT events. Here we use a large ensemble of Whole Atmosphere Community Climate Model (WACCM) simulations (forced by sea-surface temperature (SST) boundary conditions consistent with each phase of ENSO) to show that variability in lower-stratospheric ozone and shifts in the Pacific tropospheric jet constructively contribute to the amount of STT of ozone in the North American region during both ENSO phases. In terms of stratospheric variability, ENSO drives ozone anomalies resembling the Pacific–North American teleconnection pattern that span much of the lower stratosphere below 50 hPa. These ozone anomalies, which dominate over other ENSO-driven changes in the Brewer–Dobson circulation (including changes due to both the stratospheric residual circulation and quasi-isentropic mixing), strongly modulate the amount of ozone available for STT transport. As a result, during late winter (February–March), the stratospheric ozone response to the teleconnections constructively reinforces anomalous ENSO-jet-driven STT of ozone. However, as ENSO forcing weakens as spring progresses into summer (April–June), the direct effects of the ENSO-jet-driven STT transport weaken. Nevertheless, the residual impacts of the teleconnections on the amount of ozone in the lower stratosphere persist, and these anomalies in turn continue to cause anomalous STT of ozone. These results should prove helpful for interpreting the utility of ENSO as a subseasonal predictor of both free-tropospheric ozone and the probability of stratospheric ozone intrusion events that may cause exceedances in surface air quality standards.