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Title:Study on impacts of aviation emissions and related dynamics and chemistry
Author(s):Lee, Huikyo
Director of Research:Wuebbles, Donald J.
Doctoral Committee Chair(s):Wuebbles, Donald J.
Doctoral Committee Member(s):Jain, Atul K.; Riemer, Nicole; Baidya Roy, Somnath
Department / Program:Atmospheric Sciences
Discipline:Atmospheric Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):air quality
aviation emissions
upper troposphere and lower stratosphere
greenhouse effect
Abstract:The continuing increase in demand for commercial aviation transport raises questions about the effects of resulting emissions on the environment. The upper troposphere and lower stratosphere (UTLS), where most of aviation emissions occur, plays an important role in climate and atmospheric chemistry. The main purpose of this study is to investigate, using chemistry transport models, how the aviation emissions influence radiative forcing in the UTLS and air quality in the boundary layer. Using the MOZART-3.1 chemistry-transport model of the global troposphere and stratosphere, the relative impacts of emissions from the ground and ocean transportation sector to aviation emissions on the atmospheric composition near the tropopause were investigated. The separate contributions of nitrogen oxides (NOx), carbon monoxide (CO) emissions and the combined effects of NOx and hydrocarbons (HC) from surface traffic emissions to UTLS ozone (O3) were considered. The analyses suggest that O3 in the upper troposphere and lower stratosphere is affected more by surface traffic emissions than aviation emissions. The role of peroxyacetylnitrate (PAN) and the quasi-horizontal transport in the UTLS is important for aviation impacts and ground-based HC effect on O3 in the UTLS. Despite its importance, the quasi-horizontal transport process in the UTLS, represented by global chemistry-transport models (CTMs) or chemistry-climate models (CCMs), cannot easily be diagnosed with conventional analyses on isobaric surfaces. So this study suggests some diagnostic tools to better evaluate CTMs and CCMs relative to satellite observations in the region of UTLS. Using the Hellinger distance, vertical profiles of probability density functions (PDFs) of chemical tracers simulated by the MOZART-3.1 are quantitatively compared with satellite data from the Microwave Limb Sounder (MLS) instrument in the tropopause relative altitude to characterize features of tracer distributions near the tropopause. Overall, the comparison of PDFs between MLS and MOZART-3.1 did not satisfy the same population assumption. Conditional PDFs are used to understand the meteorological differences between global climate models and the real atmosphere and the conditional PDFs between MOZART-3.1 and MLS showed better agreement compared to the original PDFs. The low static stability during high tropopause heights at midlatitudes suggests that the variation of tropopause height is related to transport processes from the tropics to midlatitudes. MOZART-3.1 reproduces episodes of tropical air intrusions that are similar to observed. However, some diagnostic analyses show that MOZART-3.1 and CCMs in general need some improvements for better simulating the UTLS especially when the tropopause at midlatitudes is high. We also find that the aviation emissions near cruise altitudes are responsible for most of the small boundary layer perturbations in concentrations of total odd-nitrogen (NOy), O3 and aerosols. Overall the aviation induced perturbations are too small to be important even in areas with heavy air traffic. The small perturbations of NOy, O3 and aerosols show seasonal differences caused by different concentrations of background aerosols and related heterogeneous reactions in the middle troposphere. The effects of aviation emissions on the boundary layer perturbations are stronger in the winter compared to summer for the same amount of emissions. However, the stronger perturbation in winter, especially O3 increase, is not important for air quality. In addition, aircraft emit NOx but aircraft emissions near cruise altitudes actually decrease NOx in urban areas of the Northern Hemisphere in winter. Heterogeneous reactions and nitrate radical (NO3) play an important role to reduce the background NOx so they also limit the O3 increase near the ground in winter. Aviation emissions lead to less than 1% of aerosol enhancement in the boundary layer by slightly increasing ammonium nitrate during cold seasons. However, despite some statistically significant aerosol perturbations at some grid points, the upper tropospheric aviation emissions do not increase the occurrence of extreme aerosol concentrations in the boundary layer, with likely little effect on human health. A sensitivity study with doubled ground ammonia flux shows the high dependence of aviation induced aerosol increase near the ground on background ammonia. This indicates that the aerosol perturbations resulting from aviation emissions are within models’ uncertainty range.
Issue Date:2013-02-03
Rights Information:Copyright 2012 Huikyo Lee
Date Available in IDEALS:2013-02-03
Date Deposited:2012-12

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