Abstract This work focuses on the near-surface O3 variability over the eastern Antarctic Plateau. In particular, eight years (2006–2013) of continuous observations at the WMO/GAW contributing station “Concordia” (Dome C–DMC: 75°06′S, 123°20′E, 3280 m) are presented, in the framework of the Italian Antarctic Research Programme (PNRA). First, the characterization of seasonal and diurnal O3 variability at DMC is provided. Then, for the period of highest data coverage (2008–2013), we investigated the role of specific atmospheric processes in affecting near-surface summer O3 variability, when O3 enhancement events (OEEs) are systematically observed at DMC (average monthly frequency peaking up to 60% in December). As deduced by a statistical selection methodology, these OEEs are affected by a significant interannual variability, both in their average O3 values and in their frequency. To explain part of this variability, we analyzed OEEs as a function of specific atmospheric variables and processes: (i) total column of O3 (TCO) and UV-A irradiance, (ii) long-range transport of air masses over the Antarctic Plateau (by Lagrangian back-trajectory analysis – LAGRANTO), (iii) occurrence of “deep” stratospheric intrusion events (by using the Lagrangian tool STLEFLUX). The overall near-surface O3 variability at DMC is controlled by a day-to-day pattern, which strongly points towards a dominating influence of processes occurring at “synoptic” scales rather than “local” processes. Even if previous studies suggested an inverse relationship between OEEs and TCO, we found a slight tendency for the annual frequency of OEEs to be higher when TCO values are higher over DMC. The annual occurrence of OEEs at DMC seems related to the total time spent by air masses over the Antarctic plateau before their arrival to DMC, suggesting the accumulation of photochemically-produced O3 during the transport, rather than a more efficient local production. Moreover, the identification of recent (i.e., 4-day old) stratospheric intrusion events by STEFLUX suggested only a minor influence (up to 3% of the period, in November) of “deep” events on the variability of near-surface summer O3 at DMC.

中文翻译：

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WMO/GAW“Concordia”站（75°06′S，123°20′E，3280 m asl – 南极洲）的多年近地表臭氧观测分析

摘要 这项工作的重点是南极高原东部近地表 O3 的变化。特别是，在框架中介绍了 WMO/GAW 贡献站“Concordia”（Dome C-DMC：75°06'S, 123°20'E, 3280 m）的八年（2006-2013）连续观测意大利南极研究计划 (PNRA)。首先，提供了 DMC 季节性和昼夜 O3 变化的特征。然后，在数据覆盖率最高的时期（2008-2013 年），我们研究了特定大气过程在影响近地表夏季 O3 变率中的作用，当时 DMC 系统地观察到 O3 增强事件（OEE）（平均每月频率达到峰值） 12 月达到 60%）。根据统计选择方法推断，这些 OEE 受到显着的年际变化的影响，包括平均 O3 值和频率。为了解释这种可变性的部分原因，我们将 OEE 作为特定大气变量和过程的函数进行了分析：(i) O3 (TCO) 和 UV-A 辐照度的总列数，(ii) 南极高原上空气团的远程传输（通过拉格朗日反向轨迹分析 – LAGRANTO），（iii）“深层”平流层入侵事件的发生（通过使用拉格朗日工具 STLEFLUX）。DMC 的整体近地表 O3 变化受日常模式控制，这强烈表明发生在“天气”尺度而不是“局部”过程的过程的主要影响。即使之前的研究表明 OEE 和 TCO 之间存在反比关系，我们发现当 TCO 值高于 DMC 时，OEE 的年频率略有升高的趋势。DMC 每年发生的 OEE 似乎与气团在到达 DMC 之前在南极高原上空花费的总时间有关，这表明在运输过程中光化学产生的 O3 的积累，而不是更有效的本地生产。此外，STEFLUX 对最近（即 4 天前）平流层入侵事件的识别表明，“深部”事件对近地表夏季 O3 的变异性只有很小的影响（高达 11 月期间的 3%）在 DMC。