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Mixing processes and exchanges in the tropical and the subtropical UT/LS

机译：热带和亚热带UT / LS的混合过程和交换

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Both in situ measurements and satellite observationsindicate evidence of mixing in the upper troposphere (UT) and thelower-stratosphere (LS). In this study, the measurements performedduring the Pre-AVE and Costa-Rica AVE campaigns are analysed withdiffusive back-trajectories to assess mixing properties in thetropical and the subtropical UT/LS. A description ofcross-tropopause pathways and mixing time scales is provided.In the subtropics, Troposphere-Stratosphere mixing processes arefound to differ in the vicinity of the tropopause and at higheraltitudes. Below 350 K, a mixing line observed during Pre-AVE isshown to result from fast and local cross-tropopause irreversibleexchange, involving two initially distant air masses with distinctchemical compositions. For measurements located above 350 K, mixingof the tropospheric air in the subtropical stratosphere occurs overa period of a month, the origins of the tropospheric source beinglocalised in the tropical UT and the tropical boundary layer.In the tropics, quantitative reconstructions of CO andO3 profiles above 360 K are obtained for one monthback-trajectories calculations, pointing out that long term mixingis essential to determine the chemical composition in the tropicalascent. In particular, the existence of two-way meridionalirreversible exchanges between 360 and 450 K is found to exporttropical air in the subtropical stratosphere and to entrain oldstratospheric air in the tropical ascent. Mean age of aircalculated with a Lagrangian model is shown to be in agreement withthe CO2 observations.
机译：实地测量和卫星观测都表明在对流层上层（UT）和平流层下层（LS）混合的证据。在这项研究中，在Pre-AVE和哥斯达黎加AVE运动期间进行的测量具有扩散的后向轨迹，以评估热带和亚热带UT / LS的混合特性。提供了对流层顶径流途径和混合时间尺度的描述。 在亚热带地区，对流层-平流层的混合过程在对流层顶附近和更高的海拔高度存在差异。低于350 K，显示在Pre-AVE期间观察到的混合线是由于快速和局部的对流层顶不可逆交换引起的，涉及两个初始遥远的空气团，具有不同的化学成分。对于位于350 K以上的测量，对流层空气在一个月内会发生副热带平流层的混合，对流层源的起源位于热带UT和热带边界层。 在热带，定量的进行了一个月后的轨迹计算，获得了360 K以上的CO和O 3 剖面的重建结果，指出长期混合对于确定热带上升的化学组成至关重要。特别是，发现360和450 K之间存在双向子午不可逆交换，从而在亚热带平流层中输出热带空气，并在热带上升中夹带旧的平流层空气。拉格朗日模型计算出的平均空气年龄与CO 2 观测值一致。

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