Abstract The summertime Eastern Mediterranean experiences among the highest worldwide near-surface ozone values often exceeding the EU air-quality standard for human health protection. Downward transport of stratospheric ozone-rich air masses through tropopause folds has been shown to significantly contribute to these high tropospheric ozone levels. The summer circulation over the Eastern Mediterranean is dominated by large-scale subsidence and persistent northerly winds, the Etesians, as well as tropopause fold activity affecting tropospheric ozone levels and variability. This is the first study that directly investigates the connections of the Etesians with tropopause folds and tropospheric ozone over the Eastern Mediterranean region using the state-of-the-art ECHAM5/MESSy Atmospheric Chemistry (EMAC) climate model and a tropopause fold identification algorithm for the period June‐August 1979 to 2013. Model validation against reanalysis and observational measurements indicates that EMAC simulates well the sea level pressure gradient over the Aegean Sea reproducing the occurrence frequency of the Etesians. The shared variance between the simulated and the observed year-to-year frequency of the Etesian winds is higher than 80%. The year-to-year variability of summertime tropopause folds frequency is significantly correlated with the Etesian winds with a correlation coefficient close to 0.7. In addition, a significant increase of the fold activity and the ozone concentrations are observed during intense Etesians. Our findings may have implications for air quality studies and could support human health policy, as the Etesians coincide with favorable conditions for the formation of tropopause folds and stratosphere-to-troposphere transport and therefore, with enhanced ozone levels over the Eastern Mediterranean.

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关于夏季东地中海埃特西亚风、对流层顶褶皱和对流层臭氧之间的联系

摘要 夏季东地中海经历了世界上最高的近地表臭氧值，通常超过了欧盟保护人类健康的空气质量标准。平流层富含臭氧的气团通过对流层顶褶皱向下传输已被证明对这些高对流层臭氧水平有显着影响。东地中海夏季环流主要受大规模沉降和持续偏北风、埃特西亚风以及影响对流层臭氧水平和变率的对流层顶褶皱活动的支配。这是第一项使用最先进的 ECHAM5/MESSy 大气化学 (EMAC) 气候模型和对流层顶褶皱识别算法直接调查东地中海地区埃特西亚人与对流层顶褶皱和对流层臭氧之间的联系的研究。 1979 年 6 月至 8 月至 2013 年期间。根据再分析和观测测量的模型验证表明，EMAC 很好地模拟了爱琴海上空的海平面压力梯度，再现了埃特西亚人的出现频率。埃特西亚风的模拟和观察到的逐年频率之间的共享方差高于 80%。夏季对流层顶褶皱频率的逐年变化与埃特西亚风显着相关，相关系数接近 0.7。此外，在强烈的埃特西亚人期间观察到倍数活动和臭氧浓度的显着增加。我们的研究结果可能对空气质量研究产生影响，并可能支持人类健康政策，因为埃特西亚人恰逢对流层顶褶皱形成和平流层到对流层传输的有利条件，因此，东地中海上空的臭氧水平增强。