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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >A barrier to vertical mixing at 14 km in the tropics: Evidence from ozonesondes and aircraft measurements
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A barrier to vertical mixing at 14 km in the tropics: Evidence from ozonesondes and aircraft measurements

机译：热带地区14 km垂直混合的障碍：臭氧探空仪和飞机测量的证据

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We use ozonesondes launched from Samoa (14deg S) during the Pacific Exploratory Mission (PEM) Tropics A to show that O_3 mixing ratios usually start increasing toward stratospheric values near 14 km. This is well below the tropical tropopause (as defined either in terms of lapse rate or cold point), which usually occurs between 16 and 17 km. We argue that the main reason for this discrepancy in height between the chemopause and tropopause is that there is very little convective detrainment of ozone-depleted marine boundary layer air above 14 km. We conjecture that the top of the Hadley circulation occurs at roughly 14 km, that convective penetration above this altitude is rare, and that air that is injected above this height subsequently participates in a slow vertical ascent into the stratosphere. The observed dependence of ozone on potential temperature in the transitional zone between the 14-km chemopause and the tropical tropopause is consistent with what would be expected from this hypothesis given calculated clear-sky heating rates and typical in situ ozone production rates in this region. An observed anticorrelation between ozone and equivalent potential temperature below 14 km is consistent with what would be expected from an overturning Hadley circulation, with some transport of high O_3/low #theta#_e air from midlatitudes. We also argue that the positive correlations between O_3 and N_2O in the transitional zone obtained during the 1994 Airborne Southern hemisphere Ozone Experiment/Measurements for Assessing the Effects of Stratospheric Aircraft) (ASHOE/MAESA) campaign support the notion that air in this region does have trace elements of stratospheric air (as conjectured previously), so that some of the ozone in the transitional zone does originate from the stratosphere rather than being entirely produced in situ.
机译：我们使用太平洋探索团（PEM）热带地区A期间从萨摩亚（14deg S）发射的臭氧探空仪，显示O_3混合比通常开始向接近14 km的平流层值增加。这远远低于热带对流层顶（定义为流失率或冷点），通常在16至17 km之间。我们认为，造成更年期与对流层顶高度差异的主要原因是，在14 km以上，几乎没有对流消耗臭氧层的海洋边界层空气。我们推测，哈德利环流的顶部发生在大约14 km处，在该高度以上的对流穿透极少，并且注入到该高度以上的空气随后会参与到平流层的缓慢的垂直上升过程中。在计算的晴空加热速率和该地区典型的原位臭氧产生速率的情况下，观察到的臭氧对14 km的更年期与热带对流层顶过渡带之间的潜在温度的依赖性与该假设的预期相符。观测到的臭氧与14 km以下的等效潜在温度之间的反相关性与哈德利环流翻转的预期结果是一致的，其中有来自中纬度的高O_3 /低#thee空气输送。我们还认为，在1994年机载南半球臭氧实验/评估平流层飞机效果的措施（ASHOE / MAESA）运动中获得的过渡带中O_3和N_2O之间的正相关性支持了这一地区的空气确实具有微量的平流层空气元素（如先前所推测），因此过渡带中的某些臭氧确实来自平流层，而不是全部原位产生。

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