Assessing Interannual Variability and Trends of Extratropical Stratosphere-Troposphere Exchange: Using a Hierarchy of Atmospheric Global Circulation Models and Measurements

本项目将从对流层化学和大气动力学相结合的角度研究平流层-对流层交换(STE)的变异性。对流层臭氧浓度的年际变化主要受厄尔尼诺/拉尼娜-南方涛动(ENSO)和北大西洋涛动(NAO)的影响。最近的化学-气候模式评估发现，由于气候变化，平流层到对流层的臭氧通量显着增加。这项工作将使用模型模拟和测量的综合。模型模拟将使用大气全球环流模型的层次结构。其中最简单的模型将使用理想化的辐射和海面温度(SST)强迫以及理想的类臭氧示踪剂；最复杂的模型将包括在平流层和对流层都有完整化学成分的气候强迫的现实模拟。研究人员将(I)利用再分析风驱动的化学输送模式，调查和分离近几十年来观测和模式记录中STE的作用；(Ii)调查和分离具有理想化海温和辐射强迫的大气GCM中STE的各种强迫机制；以及(Iii)通过一套自洽的、具有控制的SST和辐射强迫的化学-气候模式模拟，研究STE的观测和模拟变化的原因。该项目将为平流层环流和平流层-对流层耦合的可变性和长期趋势提供进一步的证据。STE对对流层臭氧变化的贡献对区域空气质量和人类健康、对流层辐射强迫和生态系统生产力具有重要影响。这项工作有可能在大气化学和大气动力学领域架起一座桥梁，并培育新的研究方向。它将支持康奈尔大学的研究生和本科生研究经验，并加强几个美国机构之间的合作。

This project will investigate the variability of Stratosphere-Troposphere Exchange (STE) from combined perspectives of tropospheric chemistry and atmospheric dynamics. The interannual variability of tropospheric ozone concentrations are highly impacted by El Niño/La Niña-Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) through changes in STE. Recent chemistry-climate model assessment finds that stratosphere-to-troposphere ozone flux increases significantly as a result of climate change. This work will use a synthesis of model simulations and measurements. The model simulations will use a hierarchy of atmospheric global circulation models. The simplest of these models will use idealized radiative and Sea Surface Temperature (SST) forcing and idealistic ozone-like tracers; the most complex will include realistic simulations of climate forcing with a full chemistry component in both the stratosphere and the troposphere. The investigators will (i) investigate and isolate the role of the STE in the observed and model record during recent decades using a chemistry-transport model driven by reanalysis winds; (ii) investigate and isolate various forcing mechanisms of STE in an atmospheric GCM with idealized SST and radiative forcings; and (iii) investigate the causes of the observed and simulated variability in STE in a set of self-consistent chemistry-climate model simulations with controlled SST and radiative forcings.This project will provide additional evidence for the variability and long-term trend in the stratospheric circulation and stratosphere-troposphere coupling. The STE contributions to tropospheric ozone variability have great implications for regional air quality and human health, tropospheric radiative forcing, and ecosystem productivity. The work has the potential to bridge atmospheric chemistry and atmospheric dynamics communities and foster new research directions. It will support graduate students and undergraduate research experience at Cornell University, and strengthen the collaborations among several US institutions.