Constraints on 2-Way Transport across the Arctic Tropopause Based on O3, Stratospheric Tracer (SF6) Ages, and Water Vapor Isotope (D, T) Tracers
Constraints on 2-Way Transport across the Arctic Tropopause Based on O3, Stratospheric Tracer (SF6) Ages, and Water Vapor Isotope (D, T) Tracers
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基于 O3、平流层示踪剂 (SF6) 年龄和水蒸气同位素 (D、T) 示踪剂的北极对流层顶双向传输的限制
DOI：
10.1023/a:1010660001775
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发表时间：
2001
影响因子：
2
通讯作者：
A. Zahn
中科院分区：
文献类型：
--
作者：
A. Zahn
根据1991/1992年至1994/1995年冬季大气中痕量气体和同位素的观测资料，研究了中纬度和北极对流层顶大气中痕量气体的输送途径。一个强大的对比传输示踪剂，如氘代水蒸气（HDO），这是显示跟踪水汽从对流层进入最低平流层（LS）的通道，或'SF6年龄'定义为一个空气团在平流层内的存在时间，因为它在对流层顶的入口。在中纬气旋附近（极锋槽斜压侧），存在双向的跨对流层顶输送，其中约80%的平流层-对流层通量沿着300 ± 10 K的位温（θ）面进行。由于这些等熵线在冬季到达南极最低点，在北极对流层顶上方形成了一个至少1.5km厚的混合区。在这里，上升的对流层空气与下降的LS空气混合，LS空气受到来自较高高度、冲浪区和极涡的空气的影响。混合区内水汽D/H同位素比值的显著升高可以用与中纬度气旋有关的暖输送带将副热带水汽输送到对流层顶的注入来解释。向下垂直输送北极LS空气，这可能是由流出的化学扰动极地涡旋空气的影响，到北极对流层被发现是小的。
Based upon airborne trace gas and isotope observations in the winter months 1991/1992 to1994/1995, transport pathways across the mid-latitude and Arctic tropopause areinvestigated. A powerful set of contrasting transport tracers are examined, such asdeuterated water vapor (HDO) which is shown to trace the passage of water vapor from thetroposphere into the lowermost stratosphere (LS), or the `SF6 age' defined as theresidence time of an air parcel within the stratosphere since its entry at thetropopause. Cross-tropopause transport in both directions was found near mid-latitudecyclones (at baroclinic flanks of troughs in the polar front), in which about 80% of thestratosphere-to-troposphere flux proceeded along potential temperature (θ)surfaces of 300 ± 10 K. As these isentropes are the lowest which reach into the LS(in winter), a mixing zone just above the Arctic tropopause (at least 1.5 km thick) isformed. Here, upwelling tropospheric air is mixed with downwelling LS air which isaffected by air from higher altitudes, the surf-zone and the polar vortex. The observedelevated D/H isotope ratio of water vapor within the mixing zone can be explained byinjection of subtropical water vapor that is transported to the tropopause by the warmconveyor belt associated with mid-latitude cyclones. Downward vertical transport ofArctic LS air, which may be influenced by ouflowing chemically disturbed polar vortexair, into the Arctic troposphere was found to be small.