Assessment of atmospheric processes driving ozone variations in the subtropical North Atlantic free troposphere
Assessment of atmospheric processes driving ozone variations in the subtropical North Atlantic free troposphere
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DOI：
10.5194/acp-13-1973-2013
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发表时间：
2012-10
影响因子：
6.3
通讯作者：
Emilio Cuevas Agulló;Y. G. Ramos;Sergio Rodríguez González;Juan Carlos Guerra García;Ángel Jesús Gómez Peláez;S. Alonso-Pérez;J. J. Bustos-J.;C. Milford
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文献类型：
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作者：
Emilio Cuevas Agulló;Y. G. Ramos;Sergio Rodríguez González;Juan Carlos Guerra García;Ángel Jesús Gómez Peláez;S. Alonso-Pérez;J. J. Bustos-J.;C. Milford
抽象的。对副热带高山Izana~站（IZO; 2373 m a.s.l.）22年臭氧（O3）系列（1988-2009）的分析，代表的自由对流层（FT）条件。O3的日变化和季节变化以及O3的趋势（0.19 ± 0.05% yr-1或0.09 ppbv yr-1）进行了评估。使用后向轨迹的O3传输路径的气候学表明，较高的O3值与来自北美和北大西洋的4 km以上高度的气团有关，而低O3则来自撒哈拉大陆边界层（CBL）。O3与PM10、210 Pb、7 Be、位涡（PV）和一氧化碳（CO）进行了比较. PM10与地面O3在各季节均呈明显的负对数关系. O3与210 Pb之间也存在类似的关系。最高的每日O3值（第90百分位数）观察到在春季和夏季的前半段时间。全年O3与PV、7 Be均呈正相关，表明IZO较高的O3值来源于对流层中上部。我们发现在冬季的O3和CO之间有很好的相关性，支持长距离运输的光化学产生的O3从北美的假设。在春、夏、秋三季，观测到老化的气团，以及对流层上层的零星输入。在夏季，高的O3值似乎是在邻近加那利群岛的地区平流层到对流层（STT）交换过程的结果。自1995-1996年以来，北大西洋涛动已从一个占主导地位的高正阶段转变为负、中性或正阶段交替出现。这种变化导致中纬度和副热带北大西洋西风气流增加，从而有利于从北美输送O3及其前体，北大西洋风暴频率增加，中纬度STT过程可能发生率较高。这些过程导致1996年后北大西洋副热带地区对流层O3浓度的增加，这在IZO的地面O3记录中得到了反映。
Abstract. An analysis of the 22-yr ozone (O 3 ) series (1988–2009) at the subtropical high mountain Izana~station (IZO; 2373 m a.s.l.), representative of free troposphere (FT) conditions, is presented. Diurnal and seasonal O 3 variations as well as the O 3 trend (0.19 ± 0.05 % yr −1 or 0.09 ppbv yr −1 ), are assessed. A climatology of O 3 transport pathways using backward trajectories shows that higher O 3 values are associated with air masses travelling above 4 km altitude from North America and North Atlantic Ocean, while low O 3 is transported from the Saharan continental boundary layer (CBL). O 3 data have been compared with PM 10 , 210 Pb, 7 Be, potential vorticity (PV) and carbon monoxide (CO). A clear negative logarithmic relationship was observed between PM 10 and surface O 3 for all seasons. A similar relationship was found between O 3 and 210 Pb. The highest daily O 3 values (90th percentile) are observed in spring and in the first half of summer time. A positive correlation between O 3 and PV, and between O 3 and 7 Be is found throughout the year, indicating that relatively high surface O 3 values at IZO originate from the middle and upper troposphere. We find a good correlation between O 3 and CO in winter, supporting the hypothesis of long-range transport of photochemically generated O 3 from North America. Aged air masses, in combination with sporadic inputs from the upper troposphere, are observed in spring, summer and autumn. In summer time high O 3 values seem to be the result of stratosphere-to-troposphere (STT) exchange processes in regions neighbouring the Canary Islands. Since 1995–1996, the North Atlantic Oscillation has changed from a predominantly high positive phase to alternating between negative, neutral or positive phases. This change results in an increased flow of the westerlies in the mid-latitude and subtropical North Atlantic, thus favouring the transport of O 3 and its precursors from North America, and a higher frequency of storms over North Atlantic, with a likely higher incidence of STT processes in mid-latitudes. These processes lead to an increase of tropospheric O 3 in the subtropical North Atlantic region after 1996 that has been reflected in surface O 3 records at IZO.