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》(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)：单向跨对流层顶通量分布和路径密度及其相关的传输速率。这一新方法将通过以前所未有的细节和精确度揭示跨越对流层顶以及通过对流层和平流层的输送的全面图景，扩展关于STE的现有知识。在重新分析的风的驱动下，用Match(大气输送和化学模型)计算的通量分布将允许对现有的STE通量的不同估计进行验证，并作为基本通量分布的不同条件积分来协调。路径密度诊断将量化大气中平流扩散的“传送带”环流，根据不同路径的起点和目的地区域以及起点到目的地的过境时间进行划分。这项研究将首次大量使用理想化的大气环流模式来分析大气示踪和输送。对理想化模型试验的分析将确定不同的气象过程和流态如何控制STE。这些理想化模式的计算效率将允许系统地确定对模式参数的敏感性，从而可以评估结果的稳健性。该项目的结果将对更广泛的大气化学界有价值，因为通量分布和路径密度诊断隔离了输送在确定大气成分中的作用。特别是，将量化边界层和平流层物种进入不同光化学环境的速率和途径。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向平流层移动的速率和路径。将提供详细的STE交通诊断的基线气候学，从中可以评估未来温室气体变暖导致的交通和大气成分的变化。结果将对观测界有价值，因为将量化跨对流层顶通量的地理分布、深层侵入及其寿命的统计数据以及有利于STE的气象过程。这将对规划飞机和其他测量活动很有用。计算的格林函数和理想化的模型配置将向社区提供。这些工具可用于对空气和痕量物种的STE进行广泛的调查。研究活动将纳入教学和教育宣传。一个由来自纽约市地区的一名高中生、一名高中教师和一名本科生组成的团队将通过纽约市研究倡议组织在为期六周的年度暑期推广计划期间参与该项目。

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.