Eddy shedding transport from the Asian monsoon as a source of pollution for the lowermost stratosphere

亚洲季风环流将污染气团从地表输送到对流层上层和平流层下层，对平流层化学和地球辐射收支有重要影响。这些气团从季风区输送到北半球最下层平流层（LMS）的特点是，从季风反气旋中脱落较小规模的涡流和细丝（飘带）的分离，通常与罗斯比波破裂有关。哪些途径主导了这种涡旋输送，它们在平流层最底层的寿命，以及它们对平流层组成的影响，都是一个悬而未决的问题。在这个项目中，我们将研究从亚洲季风到LMS的污染的涡流脱落输送途径，基于PHILEAS HALO-aircraft campaign的前所未有的高分辨率原位测量和一种新的模型诊断方法来识别和表征这种输送途径。我们将测量具有不同化学寿命和互补源汇特性的C2H6、CO、CH4和N2O。化学惰性的N2O可以精确测定化学对流层顶，从而推断出LMS中污染物示踪剂的最小特征。补充的，新颖的1Hz C2H6测量将用于明确诊断对流层输送到LMS，因为C2H6没有化学平流层源。这将用于推断季风对LMS贡献的定量气团预算。LMS中污染物示踪剂的不同增强比率将与将在本项目中进行的新模型诊断相关联。即将开发的新诊断将允许识别和跟踪全球PV领域的低PV异常的棚状涡流，并将与平流层化学拉格朗日模型（CLaMS）的3D化学模拟相结合，由欧洲中期天气预报中心（ECMWF）最新一代高分辨率ERA5再分析驱动。该项目的结果将大大提高对从季风到全球平流层的污染输送及其对化学成分的影响的认识。特别是，我们将应用一种新的运输诊断和原位示踪剂的组合，通过结合N2O、CH4、CO和C2H6的测量与新颖的拉格朗日方法，将重点放在通过涡流脱落从亚洲季风输出的气团上。-结合v - v演化和对流层顶参考污染物增强比研究涡旋脱落途径和时间尺度，以及细丝的混合和侵蚀过程。-使用示踪剂预算和模式诊断量化这种涡流脱落输送对全球LMS化学成分的影响

Transport of polluted air masses from the surface into the upper troposphere and lower stratosphere by the Asian monsoon circulation has crucial effects on stratospheric chemistry and the Earth's radiation budget. The transport of these air masses from the monsoon region into the Northern hemisphere lowermost stratosphere (LMS) is characterised by shedding of smaller scale eddies from the monsoon anticyclone and the separation of filaments (streamers), frequently related to Rossby wave breaking. It is an open question which pathways dominate this eddy transport, their lifetime in the lowermost stratosphere as well as their impact on stratospheric composition. In this project we will study the eddy shedding transport pathway of pollution from the Asian monsoon into the LMS, based on a combination of unprecedented high-resolution in-situ measurements from the PHILEAS HALO-aircraft campaign and a novel model diagnostic approach to identify and characterize this transport pathway. We will perform measurements of C2H6, CO, CH4 and N2O with different chemical life times and complementary source and sink characteristics. The chemically inert N2O allows a precise determination of the chemical tropopause to infer smallest signatures of pollutant tracers in the LMS. Complementary, novel 1Hz C2H6 measurements will be used to diagnose unambiguously tropospheric transport into the LMS, since C2H6 has no chemical stratospheric sources. This will be used to infer a quantitative air mass budget for the monsoon contribution to the LMS. Varying enhancement ratios of pollutant tracers in the LMS will be linked to the new model diagnostics which will be carried out in this project. The novel diagnostic to be developed will allow identification and tracking of shed eddies as low-PV anomalies in the global PV field and will be coupled to 3D chemistry simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS), driven with the newest generation high-resolution ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). The outcome of this project will significantly enhance understanding of pollution transport from the monsoon into the global stratosphere and impacts on chemical composition. In particular we will apply a novel combination of transport diagnostics and in-situ tracers to focus on - Export of air masses from the Asian monsoon via eddy shedding by combining measurements of N2O, CH4, CO, and C2H6 with novel Lagrangian methods. - Investigation of the eddy shedding pathways and time scales, and the mixing and erosion process of the filaments combining PV-evolution and tropopause referenced pollutant enhancement ratios. - Quantification of the impact of this eddy shedding transport on the chemical composition of the global LMS using tracer budgets and model diagnostics