Flux Distributions and Path Densities: A New Look at Stratosphere-Troposphere Exchange (STE)

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目将使用新的传输诊断方法量化平流层-对流层交换（STE）：单向穿越对流层顶通量分布和路径密度及其相关的传输率。这种新方法将以前所未有的细节和精度，揭示出穿越对流层顶、穿越对流层和平流层的运输的全面图景，从而扩展目前对STE的认识。用MATCH（大气输送和化学模型）计算的通量分布，由重新分析的风驱动，将允许现有的STE通量的不同估计得到验证，并作为潜在基本通量分布的不同条件积分进行协调。路径密度诊断将量化大气中的平流扩散“传送带”环流，根据不同路径的起点和终点区域以及起点到终点的传输时间进行划分。这项研究将首次大量使用理想的大气环流模式来分析大气示踪剂和输送。对理想模式实验的分析将确定不同的气象过程和流态如何控制STE。这些理想化模型的计算效率将允许系统地确定对模型参数的敏感性，从而可以评估结果的鲁棒性。这个项目的结果将对更广泛的大气化学社区有价值，因为通量分布和路径密度诊断分离了在确定大气成分中运输的作用。特别是，边界层和平流层物种进入不同光化学环境的速率和途径将被量化。这将对空气质量产生影响，因为它限制了平流层臭氧对边界层空气的贡献，并量化了边界层空气和污染物被移至平流层的速率和路径。将提供详细的STE输运诊断的基线气候学，从中可以评估未来温室气体变暖引起的输运和大气成分的变化。结果将对观测界有价值，因为对流层顶通量的地理分布、深度侵入及其寿命的统计以及有利于STE的气象过程将被量化。这将有助于规划飞机和其他测量活动。计算的格林函数和理想化的模型配置将提供给社区。这些工具可用于对空气和痕量物种的STE进行各种调查。研究活动将纳入教学和教育推广。一个由一名高中生、一名高中教师和一名来自纽约市地区的大学生组成的团队将通过纽约市研究倡议在其为期六周的年度夏季拓展计划中参与该项目。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The project will quantify stratosphere-troposphere exchange (STE) using novel transport diagnostics: one-way cross-tropopause flux distributions and path densities with their associated transport rates. This new approach will extend the current knowledge of STE by revealing, with unprecedented detail and precision, a comprehensive picture of transport across the tropopause and through the troposphere and stratosphere. The flux distributions computed with MATCH (Model of Atmospheric Transport and Chemistry), driven by reanalyzed winds, will allow extant disparate estimates of STE fluxes to be validated and reconciled as differently conditioned integrals of the underlying fundamental flux distributions. The path-density diagnostic will quantify the advective-diffusive "conveyor" circulation in the atmosphere, partitioned according to the origins and destination regions of different paths and the origin-to-destination transit time. This research will make the first substantial use of idealized general circulation models to analyze atmospheric tracers and transport. Analysis of idealized model experiments will determine how different meteorological processes and flow regimes control STE. The computational efficiency of these idealized models will allow the systematic determination of the sensitivities to model parameters so that the robustness of the results can be assessed.The results of this project will be of value to the wider atmospheric-chemistry community, because the flux-distribution and path-density diagnostics isolate the role of transport in determining atmospheric composition. In particular, the rates and pathways with which different photochemical environments are accessed by both boundary-layer and stratospheric species will be quantified. This will have implications for air quality, by constraining the contribution of stratospheric ozone to boundary-layer air and by quantifying the rates and paths with which boundary-layer air and pollutants are removed to the stratosphere. A baseline climatology of detailed STE transport diagnostics will be provided, from which changes in transport and atmospheric composition caused by future green-house-gas warming can be asssessed. Results will be of value to the observational community, because the geographic distribution of cross-tropopause fluxes, the statistics of deep intrusions and their lifetimes, and the meteorological processes that are conducive to STE will be quantified. This will be useful for planning aircraft and other measurement campaigns. The computed Green functions and the idealized model configurations will be made available to the community. These tools can be used for a wide variety of investigations on the STE of air and trace species. Research activities will be integrated into teaching and educational outreach. A team of a high-school student, a high-school teacher, and an undergraduate university student from the New-York-City area will participate in the project through the New York City Research Initiative during its annual six-week summer outreach program.