Analysis of the chemical kinetic mechanisms of ozone depletion and halogen release in the polar troposphere based on numerical modeling and field observation

活性卤素（RHS，如Br， Br2, BrO, Cl, Cl2, ClO， OClO等）在极地对流层中的作用自从发现它们对极地春季边界层臭氧破坏的重要性以来，人们一直在研究它们在极地对流层中的作用。RHS参与自催化化学反应循环，从海盐气溶胶、新鲜海冰或积雪中释放Br2和BrCl，导致臭氧消耗。在第一个项目期间，在零维模型中研究了三种化学反应方案，并与现场观察结果进行了比较：(1)纯溴反应方案；(2)包含含氮化合物的扩展Br方案；(3)额外包含氯种和相应化学反应的进一步扩展方案。我们还通过敏感性分析研究了特定反应及其速率常数的重要性，从而建立了用于一维和三维构型的骨架反应机制，以澄清臭氧消耗事件。尽管取得了良好的进展，使人们对极地对流层卤素化学的机制有了更深入的了解，但仍有许多悬而未决的问题。因此，我们申请项目的延续，解决以下问题：气象条件在局地尺度（如风速、边界层高度、垂直温度剖面）和天气尺度上的影响，特别是气象锋面对卤素活化的作用。大气成分，即气溶胶（在模型中明确包括气溶胶相，以便可以研究可能影响物种浓度和温度的微物理），特别是氮氧化物（N2O5化学）在卤素活化中的作用是什么？br活化和O3损失的季节变化是怎样的？北极和南极（以及极地外）的卤素激活事件在持续时间、卤素成分等方面有区别吗？如果有，造成这些差异的原因是什么？触发卤素释放的先决条件和因素是什么？表面类型（如新鲜的海冰，积雪覆盖的表面，开放的铅，霜花等）起什么作用？它如何与气相相互作用？IO的存在可以大大提高卤素破坏臭氧的效率，其机制是什么？此外，还将对模型进行一系列的技术改进：在3D模型中，由于模拟时间相对较长，不可能在靠近地面的地方使用非常精细的网格。然而，通过将盒子模型扩展为具有规定湍流扩散率的一维模型，可以在表面附近使用非常精细的网格。我们还将研究不同的子网格模型是否会影响大涡模拟（LES）的计算结果。

The role of reactive halogen species (RHS, e.g., Br, Br2, BrO, Cl, Cl2, ClO, OClO, etc.) in the polar troposphere has been investigated since the discovery of their importance for boundary layer ozone destruction in the polar spring. RHS take part in an auto-catalytic chemical reaction cycle, which releases Br2 and BrCl from sea salt aerosol, fresh sea ice or snowpack, leading to ozone depletion. In the first project period, three chemical reaction schemes were investigated in a zero dimensional model and compared to field observations: (1) a bromine-only reaction scheme (2) an extended Br scheme including nitrogen-containing compounds and (3) a further extended scheme additionally including chlorine species and corresponding chemical reactions. We also studied the importance of particular reactions and their rate constants by a sensitivity analysis, leading to a skeletal reaction mechanism for use in one-dimensional and three-dimensional configurations, which were set up to clarify the ozone depletion event.Despite good progress leading to considerably better insight into the mechanism of polar tropospheric halogen chemistry, many open questions remain. Therefore, we apply for the continuation of the project, which addresses the following questions: What is the influence of meteorological conditions on a local scale (e.g. wind speed, boundary layer height, vertical temperature profile) and on synoptic scales, in particular, the role of meteorological fronts on halogen activation. What is the role of atmospheric composition, i.e. aerosol (explicitly include the aerosol phase in the model so that the microphysics, which may affect the species concentration and temperature, can be investigated.) and in particular, NOX (N2O5 chemistry) in halogen activation? How is the seasonal evolution of Br-activation and O3 loss? Are there differences between Arctic and Antarctic (and extra-polar) halogen activation events with respect to their duration, halogen composition, etc.? If so, what are the reasons for these differences? What are the prerequisites and factors actually triggering the halogen release? Which role does the surface type (e.g. fresh sea ice, snow covering surface, open leads, frost flowers, etc.) play and how does it interact with the gas phase? The presence of IO can largely enhance the efficiency of ozone destruction by halogens, what is the mechanism? Moreover, a series of technical improvements to the model will be made: In the 3D model, due to the relative long simulation time, it is impossible to use a very fine grid close to the ground surface. However, by extending the box model to a 1D model with a prescribed turbulent diffusivity, it is feasible to use a very fine mesh near the surface. We will also investigate whether different sub-grid models affect the computational results in the large eddy simulation (LES).