Gravity Waves and Trace Gas Mixing in the Arctic Winter Tropopause Region

在这个项目中，我们将在对流层顶进行传输和交换过程的空中观测，对流层顶构成了通常良好混合的对流层和稳定分层的平流层之间的边界。这个小区域对大气的辐射收支起着重要的作用，因此，由于混合而引起的化学成分的微小变化可能直接影响辐射活性物质，从而影响表面温度。在北极冬季三角顶地区的航空测量将特别关注地形诱导重力波对痕量气体输送和混合的作用，并确定相关条件和潜在过程。因此，我们将使用高精度测量CO和N2 O作为示踪剂的运输。特别是N2 O是大气动力学的有价值的示踪剂，因为它在对流层中几乎是惰性的，并且几乎均匀地分布在对流层中。由于它的惰性和平流层垂直梯度，它允许测量整个平流层中波浪引起的示踪剂扰动。对流层顶的垂直梯度很弱，对其定量要求很高。自2013年8月以来，美因茨大学大气物理研究所拥有一台仪器，其仪器精度为N2 O，这是解决这一梯度所必需的。利用该仪器，我们将在位于基律纳（瑞典北方）的DLR研究飞机Falcon上进行测量，这是一个有利于产生重力波的区域，目的是：1）确定这种波对示踪气体分布的影响，并探测波致湍流的局部发生; 2）确定和量化对流层间示踪气体交换的相关波长和时间尺度; 3）确定对流层间波致示踪剂通量; 4）确定导致波致湍流和混合的相关过程。由于N2 O测量的精度有限，根据机载现场数据和N2 O与CO的相关性对混合和湍流进行这种量化迄今为止是不可能的。与风和湍流测量的ELACON飞机相结合，可以量化波浪诱导示踪剂通量，并确定这些通量的相关波长，与EULAG模式的比较，可以确定相关的小尺度大气过程，导致波浪诱导湍流和示踪气体混合。

Within this project we will perform airborne observations of transport and exchange processes at the tropopause, which constitutes the boundary between the generally well-mixed troposphere and the stable stratified stratosphere. This perticular region plays an important role for the radiation budget of the atmosphere, such that small changes of the chemical composition due to mixing may directly affect radiatively active species, which in turn influence the surface temperatures. The airborne measurements in the arctic winter triopopause region will focus especially on the role of orographically ijndiuced gravity waves for trace gas transport and mixing and to identify the relevant conditions and underlying processes. Therefore we will use high precision measurements of CO and N2O as tracers of transport. Particularly N2O is a valuable tracer for atmospheric dynamics, since it is virtually inert in the troposphere and almost homogenously distributed in the troposphere. Due to its inertness and its stratospheric vertical gradient it allows to measure wave induced tracer perturbations throughout the stratosphere. The vertical gradient at the tropopause is only weak, which requires a very high precision for its quantification. Since August 2013 the institute for atmospheric physics of the university Mainz owns an instrument, with the instrumental precision for N2O, which is required to resolve this gradient. With this instrument we will perform measurements onboard the DLR research aircraft Falcon in Kiruna (Northern Sweden), which is a reguion favourable for the generation of gravity waves to:1) identify the effect of such waves on the trace gas distribution and to probe local occurrence of wave induced turbulence2) identify and quantify the relevant wavelengths and time scales for trace gas exchange across the tropopause3) determine wave induced tracer fluxes across the tropopause4) identify the relevant processes which lead to wave induced turbulence and mxing. Such a quantification of mixing and turbulence on the basis of airborne in-situ data and correlations of N2O and CO was so far not possible due to the limited precision of the N2O measurements. The combination with the wind and turbulence measurements of the FALCON aircraft allows quantifying wave induced tracer fluxes and to identify the relevant wave lengths for these fluxes.The comparison with the EULAG model allows to identify the relevant atmospheric processes on the small scale which lead to wave induced turbulence and trace gas mixing.