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空气团从地面输送到对流层上部和平流层下部，对平流层化学和地球辐射收支有着至关重要的影响。这些气团从季风区输送到北方半球平流层最低层（LMS）的特征是从季风反气旋中脱落出较小尺度的涡旋，并分离出细丝（流光），这通常与罗斯贝波破碎有关。这是一个悬而未决的问题，哪些途径主导这种涡旋输送，它们在最低平流层的寿命以及它们对平流层成分的影响。在这个项目中，我们将研究从亚洲季风到LMS的污染的涡脱落传输路径，基于前所未有的高分辨率现场测量的组合从PHILEAS HALO飞机运动和一种新的模型诊断方法来识别和表征这种传输路径。我们将进行测量C2H6，CO，CH4和N2O具有不同的化学寿命和互补的源和汇特性。化学惰性的N2O允许精确测定化学对流层顶，以推断LMS中污染物示踪剂的最小特征。互补的，新的1Hz C2H6测量将用于明确诊断对流层传输到LMS，因为C2H6没有化学平流层源。这将被用来推断一个定量的空气质量预算的季风贡献的LMS。LMS中污染物示踪剂的不同增强比将与将在本项目中进行的新模型诊断相关联。开发的新诊断将允许识别和跟踪全球PV场中的低PV异常的脱落涡流，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）的最新一代高分辨率ERA5再分析驱动。这一项目的成果将大大提高对污染物从季风输送到全球平流层以及对化学成分影响的认识。特别是，我们将采用一种新的组合运输诊断和原位示踪剂，重点放在 - 通过结合N2O、CH4、CO和C2H6的测量和新的拉格朗日方法通过涡动脱落从亚洲季风输出空气质量。- 涡脱落路径和时间尺度的调查，以及混合和侵蚀过程的纤维相结合的PV演变和对流层顶参考污染物增强率。- 用示踪剂预算和模式诊断来量化这种涡旋脱落输送对全球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