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的角度研究平流层-对流层交换（STE）的变率。El Niño/La Niña-Southern涛动（ENSO）和北大西洋涛动（NAO）通过STE的变化影响对流层臭氧浓度的年际变化。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著增加。这项工作将使用模型模拟和测量的综合。模式模拟将使用一系列大气全球环流模式。这些模式中最简单的将使用理想的辐射和海表温度强迫以及理想的臭氧样示踪剂；最复杂的将包括对平流层和对流层中具有完全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运模型，调查并分离STE在近几十年的观测和模式记录中的作用；（ii）在具有理想海温和辐射强迫的大气GCM中，研究和分离海温的各种强迫机制；（iii）在一套具有控制海温和辐射强迫的自洽化学-气候模式模拟中，研究观测到的和模拟的海温变化的原因。该项目将为平流层环流和平流层-对流层耦合的变率和长期趋势提供额外的证据。STE对对流层臭氧变率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大影响。这项工作有可能弥合大气化学和大气动力学的社区和培育新的研究方向。它将支持研究生和本科生在康奈尔大学的研究经历，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.