This study aims to investigate the Stratosphere-Troposphere Exchange (STE) events and ozone changes over Irene (25.5°S, 28.1°E). Twelve years of ozonesondes data (2000–2007, 2012–2015) from Irene station operating in the framework of the Southern Hemisphere Additional Ozonesodes (SHADOZ) was used to study the troposphere (0–16 km) and stratosphere (17–28 km) ozone (O₃) vertical profiles. Ozone profiles were grouped into three categories (2000–2003, 2004–2007 and 2012–2015) and average composites were calculated for each category. Fifteen O₃ enhancement events were identified over the study period. These events were observed in all seasons (one event in summer, four events in autumn, five events in winter and five events in spring); however, they predominantly occur in winter and spring. The STE events presented here are observed to be influenced by the Southern Hemisphere polar vortex. To strengthen the investigation into STE events, advected potential vorticity maps were used, which were assimilated using Modélisation Isentrope du transport Méso–échelle de l’Ozone Stratosphérique par Advection (MIMOSA) model for the 350 K (~12–13 km) isentropic level. These maps indicated transport of high latitude air masses responsible for the reduction of the O₃ mole fractions at the lower stratosphere over Irene which coincides with the enhancement of ozone in the upper troposphere. In general, the stratosphere is dominated by higher Modern Retrospective Analysis for Research Application (MERRA-2) potential vorticity (PV) values compared to the troposphere. However, during the STE events, higher PV values from the stratosphere were observed to intrude the troposphere. Ozone decline was observed from 12 km to 24 km with the highest decline occurring from 14 km to 18 km. An average decrease of 6.0% and 9.1% was calculated from 12 to 24 km in 2004–2007 and 2012–2015 respectively, when compared with 2000–2003 average composite. The observed decline occurred in the upper troposphere and lower stratosphere with winter and spring showing more decline compared with summer and autumn.



中文翻译：

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南非艾琳SHADOZ站点平流层下部和对流层的平流层-对流层交换和O3变异

这项研究旨在调查艾琳（25.5°S，28.1°E）上的平流层-对流层交换（STE）事件和臭氧变化。来自艾琳站的十二年臭氧探测仪数据（2000-2007年，2012-2015年）在南半球其他臭氧层（SHADOZ）的框架内运行，用于研究对流层（0-16公里）和平流层（17-28公里）臭氧（O ₃）垂直剖面。臭氧概况分为三类（2000-2003年，2004-2007年和2012-2015年），并计算了每一类的平均成分。十五O ₃在研究期间确定了增强事件。在所有季节都观察到这些事件（夏季发生一次，秋季发生四次，冬季发生五次，春季发生五次）；但是，它们主要发生在冬季和春季。观察到这里出现的STE事件受南半球极涡的影响。为了加强对STE事件的调查，使用了平移的潜在涡度图，并使用等距线350 K（〜12-13 km）的Méso-échellede l'OzoneStratosphériquepar对流运输（MIMOSA）模型进行了同化。这些图表明高纬度气团的运输导致O ₃的减少在艾琳上空平流层下部的摩尔分数，这与对流层上部臭氧的增加相吻合。通常，与对流层相比，平流层以更高的现代研究回顾性分析（MERRA-2）潜在涡度（PV）值为主。但是，在STE事件中，观察到来自平流层的较高PV值侵入对流层。臭氧从12公里下降到24公里，下降幅度最大，从14公里下降到18公里。与2000-2003年的平均综合水平相比，2004-2007年和2012-2015年的12至24 km分别平均下降了6.0％和9.1％。观测到的下降发生在对流层上部和平流层下部，冬季和春季比夏季和秋季下降更多。