The roles of deep convection and extratropical mixing in the tropical tropopause layer: An in situ measurement perspective
The roles of deep convection and extratropical mixing in the tropical tropopause layer: An in situ measurement perspective
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热带对流层顶层深对流和温带混合的作用：现场测量视角
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
James G. Anderson
中科院分区：
文献类型：
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作者：
M. Sargent;Jessica B. Smith;D. Sayres;James G. Anderson
进入平流层的大部分空气通过热带对流层顶（TTL），在那里的温度分布和深层对流的数量决定了平流层水汽的进入水平。我们使用同时在现场测量的臭氧，一氧化碳，二氧化碳，水蒸气，和重水蒸气（HDO）从2006年哥斯达黎加Aura验证实验和2007年热带成分，云，气候耦合运动在一维混合模式，以研究如何在TTL的不同传输路径的影响进入平流层的水蒸气的量。我们重点研究了四种主要路径：（1）缓慢上升，（2）来自中纬度平流层最低层的等熵输送，（3）对流注入，（4）TTL内与对流耦合的下降。每一条通道都将带有特定化学特征的空气带入TTL，这样，同时测量的示踪剂浓度的异常就可以用来识别空气质量的来源。我们发现，来自中纬度最低平流层的等熵输送占TTL低层空气的20-60%和对流层顶上方空气的20-40%，使臭氧浓度升高，辐射加热TTL，影响发生的脱水量。在夏季和冬季，对流输入平均占370 K以下测得的空气的30%，对流层顶以上的空气的10%，对流层顶以上的水汽浓度平均增加0.3 ppmv，在一些气团中增加1.6 ppmv。
The majority of air which enters the stratosphere passes through the tropical tropopause layer (TTL), where the temperature profile and amount of deep convection set the entry level for stratospheric water vapor. We use simultaneous in situ measurements of ozone, carbon monoxide, carbon dioxide, water vapor, and heavy water vapor (HDO) from the 2006 Costa Rica Aura Validation Experiment and 2007 Tropical Composition, Cloud, and Climate Coupling campaigns in a one‐dimensional mixing model to investigate how different transport pathways in the TTL impact the amount of water vapor which enters the stratosphere. We focused on four main pathways: (1) slow upward ascent, (2) isentropic transport from the midlatitude lowermost stratosphere, (3) convective injection, and (4) descent within the TTL coupled to convection. Each pathway brings air into the TTL with a specific chemical signature, such that anomalies in simultaneously measured tracer concentrations can be used to identify the source of the air mass. We found that isentropic transport from the midlatitude lowermost stratosphere accounted for 20–60% of the air in the lower TTL and 20–40% of air above the tropopause, bringing elevated ozone concentrations which radiatively warm the TTL, impacting the amount of dehydration which takes place. Convective input accounted for on average ~30% of the air measured below 370 K potential temperature, and ~10% of air above the tropopause in both summer and winter, increasing water vapor concentrations above the tropopause by 0.3 ppmv on average and by up to 1.6 ppmv in some air masses.