The lifetime of ozone in the troposphere is approximately 3 weeks. Prevailing westerly winds at northern midlatitudes can transport air around the globe in that time. Hence, within these latitudes zonal similarity is expected in long‐term changes and seasonal cycles of concentrations of baseline ozone. We quantify the degree of zonal similarity by examining eight in situ baseline ozone data sets near the west coasts of North America and Europe, that is, upwind of those continents and downwind of the Pacific and Atlantic Oceans, where the impacts of local and regional ozone sources have been largely mixed into the troposphere, giving the best‐defined baseline ozone signature. Zonal similarity is found in both long‐term changes and seasonal cycles. The decades‐long increase in Northern Hemisphere, midlatitude baseline mixing ratios (average ~0.60 ppb year⁻¹ from 1980–2000), has ended, with a maximum reached in the mid‐2000s, followed by slow decrease (average = −0.09 ± 0.08 ppb year⁻¹ from 2000 to the present). The year of the ozone maximum exhibits little if any statistically significant difference with location, altitude, or season. The ozone seasonal cycle differs markedly between sea‐level coastal stations representative of the marine boundary layer and the free troposphere sampled at elevated sites and by sondes and aircraft. However, within each of these broad tropospheric layers, the seasonal cycles are similar at all locations. Vertical profiles of the parameters that define the long‐term trends and the seasonal cycle are also similar between North America and Europe.

中文翻译：

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北中纬度基线臭氧长期变化和季节性周期的区域相似性

对流层中臭氧的寿命约为3周。那时，北半球盛行的西风可以在全球范围内输送空气。因此，在这些纬度内，预期基线臭氧浓度的长期变化和季节性周期的区域相似性。我们通过检查北美和欧洲西海岸附近的八个原位基准臭氧数据集（即这些大陆的上风以及太平洋和大西洋的下风）对区域相似度的程度进行量化，在那里当地和区域臭氧的影响对流层中的碳氢化合物主要是混合的，从而提供了最佳的基线臭氧特征。在长期变化和季节性周期中都发现了区域相似性。北半球，中纬度基线混合比（平均〜0。^-1从1980年至2000年），已结束，在2000年代中期达到最大，随后缓慢降低（平均= -0.09±0.08 ppb的年^-1从2000年到现在）。臭氧最大值年份与位置，高度或季节相比，几乎没有统计学上的显着差异。代表海洋边界层的海平面沿海站点与在高空站点以及由探空仪和飞机采样的自由对流层之间，臭氧季节周期明显不同。但是，在这些对流层的每一层中，所有位置的季节周期都相似。北美和欧洲之间定义长期趋势和季节周期的参数的垂直剖面也相似。