On the link between the Etesian winds, tropopause folds and tropospheric ozone over the Eastern Mediterranean during summer
On the link between the Etesian winds, tropopause folds and tropospheric ozone over the Eastern Mediterranean during summer
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DOI：
10.1016/j.atmosres.2020.105161
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发表时间：
2021-01
影响因子：
5.5
通讯作者：
Stella Dafka;D. Akritidis;P. Zanis;A. Pozzer;E. Xoplaki;J. Luterbacher;C. Zerefos
中科院分区：
文献类型：
--
作者：
Stella Dafka;D. Akritidis;P. Zanis;A. Pozzer;E. Xoplaki;J. Luterbacher;C. Zerefos
夏季东地中海地区是世界上近地表臭氧层数值最高的地区之一，常常超过欧盟保护人类健康的空气质量标准。通过对流层顶褶皱向下输送平流层富含臭氧的气团，已被证明是造成这些高对流层臭氧水平的重要原因。东地中海夏季环流主要受大范围下沉和持续的北风以及对流层顶褶皱活动影响对流层臭氧水平和变异性的影响。这是首次使用最先进的ECHAM5/混乱大气化学(EMAC)气候模式和对流层顶折叠识别算法直接研究东地中海地区对流层顶折叠和对流层臭氧之间的联系。模式与再分析和观测测量的对比验证表明，EMAC很好地模拟了爱琴海的海平面气压梯度，再现了东太平洋的出现频率。东太平洋风的模拟频率与观测频率之间的共同方差大于80%。夏季对流层顶折叠频率的年际变化与东亚风有显著的相关关系，相关系数接近0.7。此外，在强烈的东太平洋期间，观测到折叠活动和臭氧浓度显著增加。我们的发现可能会对空气质量研究产生影响，并可能支持人类健康政策，因为埃特斯半岛恰好符合形成对流层顶褶皱和平流层到对流层输送的有利条件，因此东地中海上空的臭氧水平增加。
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.