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

Cornell University, Ithaca NY

Investigators

Abstract

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.