Trace Gas Budgets and Interhemispheric Differences of Composition and Transport in the UTLS

UTLS区域（对流层上部/平流层下部，即8-20公里之间的区域）的组成对气候和地表温度起着重要作用。该区域的微量气体收支是由动力过程决定的，这些动力过程包括小尺度湍流、超破碎斜压波和行星波以及平流层环流。由此产生的成分变化导致气候模拟和未来地表气候估计的重大不确定性。因此，基于测量的气团来源、输送过程和时间尺度的量化对于定量了解该区域至关重要。最近的测量主要集中在北方半球，并显示出北方UTLS组成的明显季节性周期。在夏季短的运输时间尺度的周运输，特别是从热带和季风地区占主导地位的北方UTLS，而在冬季长的时间尺度和非绝热下降的老年平流层空气质量占上风。对流层的贡献在20-60%之间，取决于季节。与输送相关的主要大气结构（例如极地涡旋和亚洲夏季风）引入了强烈的半球不对称性，因此季节不对称的组成，年龄和输送结构。基于测量的空气质量预算和南半球UTLS的量化仍然缺失。在本项目内，将根据示踪剂测量结果并与北方半球包括空气质量分数和传输时间尺度进行比较，对这一预算进行量化。这将包括研究有助于南半球内部以及两个半球之间的输送和混合的有关过程。

The composition of the UTLS region (upper troposphere / lower stratosphere, i.e. the region between 8-20 km) plays a fundamental role for climate and surface temperatures. The trace gas budget of this region is determined by dynamical processes, which range from small scale turbulence, over breaking baroclinic and planetary waves to the stratospheric circulation. The resulting variability of the composition leads to significant uncertainties of climate simulations and estimates of future surface climate. A measurement based quantification of air mass origin, transport processes and time scales is therefore essential for a quantitative understanding of this region.Recent measurements mainly focused on the northern hemisphere and showed a clear seasonal cycle of the composition of the northern UTLS. During summer short transport time scales of weeks for transport particularly from the tropics and the monsoon region dominate the northern UTLS, whereas in winter long time scales and diabatic descent of aged stratospheric air masses prevail. The tropospheric contribution varies between 20-60% depending on season.The dominating atmospheric structures relevant for transport (e.g. the polar vortex and the Asian summer monsoon) introduce a strong hemispheric asymmetry and therefore seasonal asymmetric composition, age and transport structures. A measurement based air mass budget and quantification of the southern hemisphere UTLS is still missing. Within this project, this budget will be quantified on the basis of tracer measurements and the compared with the northern hemisphere including air mass fractions as well as transport time scales. This will include a study of the relevant processes which contribute to transport and mixing within the southern hemisphere, but also between both hemispheres.