Taking in to account the levels in uncertainties present in assessments of the radiative effects of aviation-induced ozone and aerosols (Figure 2.16), along with projected decreases in global sulfate and increases nitrate burdens and the potential for nitrate forcing to become a more dominant forcing component, this thesis aims to help reduce these gaps in knowledge. This thesis aims to help reduce these gaps in knowledge through the use of a size-resolved coupled tropospheric chemistry-aerosol microphysics model (the nitrate-extended version of the TOMCAT-GLOMAP-mode coupled model described and evaluated in Chapter 3) this thesis aims to estimate the impacts of sulfate, nitrates, BC and OC aerosols and their associated climatic effects, while assessing aviation ozone and sulfate formation in tandem with nitrate aerosol formation mechanisms.
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When considering the complex chemical interactions and emission species considered within current aviation emissions inventories, there is a drive to try and represent and replicate aviation emission species as accurately as possible, i.e. through the inclusion of speciated HCs.
Using an expanded aviation emissions inventory created using CMIP5 (5th Coupled Model Intercomparison Project) recommended historical aviation emissions for year 2000 as a base (Chapter 4), this thesis aims to do the same. CMIP5 recommended historical aviation emissions currently only consider aviation-borne NOX and BC emissions (Lamarque et al., 2009). Through using CMIP5 recommended historical emissions as a base for development and comparison, CMIP5-extended allows for atmospheric and climate impacts potentially not evaluated in ACCMIP (Atmospheric Chemistry and Climate Model Intercomparison Project) studies to be evaluated; thus evaluating the need for CMIP5 emissions to consider a wider and more comprehensive range of emissions species. Using the capabilities of the nitrate-extended version of the TOMCAT-GLOMAP-mode coupled model this thesis allows aviation to be represented to the best of the capabilities of the model available, while investigating the atmospheric and climatic impacts of an extended aviation emissions inventory.
Taking aviation’s impact on human health and fuel sulfur content (FSC) reduction strategies in to account this thesis investigates the relationship between variations in FSC, aviation-induced surface-layer aerosols within the PM2.5 size category, aviation-induced mortality from increases in cases of cardiopulmonary disease and lung cancer, resulting impacts on cloud condensation nuclei (CCN), and; climate (Chapter 6).
Finally, as the industry is considering the use of alternative fuels (Section 1.6), in order to reduce emissions from civil aviation, this thesis investigates the use of Fischer-Tropsch (FT) and Fatty Acid Methyl Esters (FAME) in aviation on the atmosphere, climate, air quality and human health impacts (Chapter 7). Here four alternative fuel scenarios are developed in order to investigate the atmospheric, climatic, air quality impacts as well as impacts on human health from the use of the four FT and FAME fuel blends.
The objectives of this thesis are:
Development of a bespoke aviation emissions inventory for year 2000 inclusive of speciated HCs.
o Development of a monthly resolved aviation emissions inventory for year 2000 based on CMIP5 (5th Coupled Model Intercomparison Project) recommended historical aviation emission.
o Emissions inventory developed to include NOX, CO, speciated HCs, SO2, BC and OC.
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Investigate the atmospheric and climatic impact of historical (year 2000) aviation-borne emissions; aiming to reduce uncertainties and expand on estimates obtained using a coupled chemistry-aerosol microphysics model.
o Investigate aviation-induced gas-phase (O3, NOX, OH, HOX and SO2) and aerosol-phase (sulfate, nitrates, BC, OH, ammonium) perturbations.
o Investigate aviation-induced perturbations on cloud condensation nuclei (CCN).
o Assess the radiative effect of aviation; paying attention to the O3 direct radiative (O3DRE), aerosol direct radiative (aDRE), and aerosol cloud albedo effects (aCAE).
o Sensitivity analysis of aviation-borne CO, HCs and SO2 emissions in order to investigate their relative impacts.
Investigate the changes in atmospheric concentrations and air quality, human health impacts, and impacts on climate influenced by variations aviation fuel sulfur content (FSC). In addition to perturbations in ground-level PM2.5 and mortality, perturbations in low-cloud level CCN and radiative effect will be investigated.
o Currently there is little work which considers and assesses premature mortalities due to aviation-induced perturbations in surface layer PM2.5.
Current literature considers aviation-induced PM2.5 from sulfate, nitrate and ammonium aerosols within the size category of <2.5 µm. This thesis will consider the contribution to the PM2.5 size category of a wider range of aerosol species contributing to that size range (sulfates, BC, OC, sodium from sea-salt, dust, nitrates, ammonium and chloride from sea-salt), and their resulting impact on aviation-induced premature mortality.
o This investigation will vary aviation FSC; in relation to the standard FSC of 600 ppm.
Initially FSC will be varied between 0–6000 ppm while, maintaining the distribution of current aviation-borne emissions.
Aviation emissions will be collapsed to ground-level while maintaining relative emitted abundances.
Finally, two scenarios will vary FSC above the cruise phase of flight, while implementing ULSJ fuel below cruise.
Development of alternative fuel scenarios for year 2000.
o Referring to specification for the use of alternative fuels in commercial aviation alternative fuel scenarios will be developed based on the use of:
Fischer-Tropsch fuel blends.
Fatty acid methyl esters (FAMEs) fuel blends.
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o As per the aviation-emissions inventory derived the following species will be included: NOX, CO, speciated HCs, SO2, BC and OC.
Investigate the atmospheric, climatic, air quality, and human health impacts of aviation alternative fuel scenarios.
o Using the alternative fuel scenarios derived above and present day (2000) emissions and meteorology the impact of the use of alternative fuel blends on gas- and aerosol-phase perturbations and resulting climatic impacts will be investigated.
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