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Author: Alexander Dean Naiman
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 201
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Book Description
Aircraft emissions lead to contrails and change cloud coverage in the upper troposphere/lower stratosphere, but their quantitative impact on climate is highly uncertain. As environmental policy turns toward regulating anthropogenic climate change components, it will be necessary to improve quantification of the climate impacts of aviation. Toward this end, we present two models of aircraft emissions. The first model is a large eddy simulation (LES) with three-dimensional, eddy-resolving flow physics and ice deposition/sublimation microphysics. Modeled ice properties, cloud optical depths, and contrail width growth rates are consistent with observational field studies. A series of sensitivity cases shows the effect of various parameters over twenty minutes of simulation time. The analysis focuses on properties such as contrail optical depth and cross-sectional width that are relevant to climate impacts. Vertical wind shear is found to have the strongest effect on these properties through the kinematic spreading of the contrail. In cases with no shear, optical depth is most sensitive to aircraft type and ambient humidity. One model parameter, the effective emission index of ice crystals, is also found to affect optical depth. A subset of the LES cases is run for two hours of simulation time to approach the scale of dynamical time steps modeled by global climate simulations. These cases use more realistic ice microphysics, including sedimentation, and forced ambient turbulence, both of which are processes that control contrail development at late times. The second model is a simple, low cost parameterization of aircraft plume dynamics, intended to be used as a subgrid plume model (SPM) within large scale atmospheric simulations. The SPM provides basic plume cross-section time advancement that has been used as a dilution model within a coupled global atmosphere-ocean climate simulation to study the effects of aviation on air quality and climate. Comparison to the twenty-minute and two-hour LES results demonstrates that the SPM captures important plume development characteristics under the effect of vertical shear and atmospheric turbulence.
Author: Alexander Dean Naiman
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 201
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Book Description
Aircraft emissions lead to contrails and change cloud coverage in the upper troposphere/lower stratosphere, but their quantitative impact on climate is highly uncertain. As environmental policy turns toward regulating anthropogenic climate change components, it will be necessary to improve quantification of the climate impacts of aviation. Toward this end, we present two models of aircraft emissions. The first model is a large eddy simulation (LES) with three-dimensional, eddy-resolving flow physics and ice deposition/sublimation microphysics. Modeled ice properties, cloud optical depths, and contrail width growth rates are consistent with observational field studies. A series of sensitivity cases shows the effect of various parameters over twenty minutes of simulation time. The analysis focuses on properties such as contrail optical depth and cross-sectional width that are relevant to climate impacts. Vertical wind shear is found to have the strongest effect on these properties through the kinematic spreading of the contrail. In cases with no shear, optical depth is most sensitive to aircraft type and ambient humidity. One model parameter, the effective emission index of ice crystals, is also found to affect optical depth. A subset of the LES cases is run for two hours of simulation time to approach the scale of dynamical time steps modeled by global climate simulations. These cases use more realistic ice microphysics, including sedimentation, and forced ambient turbulence, both of which are processes that control contrail development at late times. The second model is a simple, low cost parameterization of aircraft plume dynamics, intended to be used as a subgrid plume model (SPM) within large scale atmospheric simulations. The SPM provides basic plume cross-section time advancement that has been used as a dilution model within a coupled global atmosphere-ocean climate simulation to study the effects of aviation on air quality and climate. Comparison to the twenty-minute and two-hour LES results demonstrates that the SPM captures important plume development characteristics under the effect of vertical shear and atmospheric turbulence.
Author: Alexander Dean Naiman
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Aircraft emissions lead to contrails and change cloud coverage in the upper troposphere/lower stratosphere, but their quantitative impact on climate is highly uncertain. As environmental policy turns toward regulating anthropogenic climate change components, it will be necessary to improve quantification of the climate impacts of aviation. Toward this end, we present two models of aircraft emissions. The first model is a large eddy simulation (LES) with three-dimensional, eddy-resolving flow physics and ice deposition/sublimation microphysics. Modeled ice properties, cloud optical depths, and contrail width growth rates are consistent with observational field studies. A series of sensitivity cases shows the effect of various parameters over twenty minutes of simulation time. The analysis focuses on properties such as contrail optical depth and cross-sectional width that are relevant to climate impacts. Vertical wind shear is found to have the strongest effect on these properties through the kinematic spreading of the contrail. In cases with no shear, optical depth is most sensitive to aircraft type and ambient humidity. One model parameter, the effective emission index of ice crystals, is also found to affect optical depth. A subset of the LES cases is run for two hours of simulation time to approach the scale of dynamical time steps modeled by global climate simulations. These cases use more realistic ice microphysics, including sedimentation, and forced ambient turbulence, both of which are processes that control contrail development at late times. The second model is a simple, low cost parameterization of aircraft plume dynamics, intended to be used as a subgrid plume model (SPM) within large scale atmospheric simulations. The SPM provides basic plume cross-section time advancement that has been used as a dilution model within a coupled global atmosphere-ocean climate simulation to study the effects of aviation on air quality and climate. Comparison to the twenty-minute and two-hour LES results demonstrates that the SPM captures important plume development characteristics under the effect of vertical shear and atmospheric turbulence.
Author: Thibaud M. Fritz
Publisher:
ISBN:
Category :
Languages : en
Pages : 68
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Book Description
The ability to quantitatively assess the environmental impacts of air transport operations is necessary to estimate their current and future impacts on the environment. Emissions from aircraft engines are a significant contributor to atmospheric NOx driving climate change, air quality impacts and other environmental concerns. To quantify these effects, global chemistry-transport models are frequently used. However, such models assume homogeneous and instant dilution into large-scale grid cells and therefore neglect micro-physical processes, such as contrail formation, occurring in aircraft wakes. This assumption leads to inaccurate estimates of NOy partitioning, and thus, an over-prediction of ozone production. To account for non-linear plume processes, a Lagrangian aircraft plume model has been implemented. It includes a unified tropospheric-stratospheric chemical mechanism that incorporates heterogeneous chemistry. Micro-physical processes are considered throughout the entire plume lifetime. The dynamics of the plume are solved simultaneously using an operator splitting method. The plume model is used to quantify how the in-plume chemical composition is affected in response to various environmental conditions and different engine and/or fuel characteristics. Results demonstrate that an instant dilution model overestimates ozone production and accelerates conversion of nitrogen oxides compared to the plume model. Sensitivities to the NOx emission index have been derived and the dependence of the plume treatment on the background atmosphere mixing ratios, pressure and latitude has been investigated for a future regional scale assessment of the aviation sector. The cumulative impact of successive flights has been estimated. Contrail micro-physical and chemical properties have been computed under different scenarios. This aircraft plume model has been extensively validated and enables an in-depth assessment of the impact of one or multiple flights on local atmospheric conditions.
Author: Akshat Agarwal (Scientist in aeronautics and astronautics)
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The number of BC particles emitted by an aircraft engine is required to estimate the number of crystals that form in a contrail. Decreasing the number of crystals that form by 80% could reduce the contrail RF by 50%. The first part of this thesis develops an approach to estimate the number of particles emitted by an engine. Using two complementary datasets, I relate smoke number measurements to the BC mass concentration, quantify losses in the measurement system, and connect mass emissions to particle number emissions. The method is applied to existing BC measurements achieving an R2 of 0.80 and 0.82, respectively. Global BC emissions for all operations in 2015 were estimated to be 2.0 Gg/year (95% CI = 1.7 - 2.3) and 2.42 × 1026 particles/year (95% CI = 1.58 - 3.81 × 1026).
Author: Joyce E. Penner
Publisher: Cambridge University Press
ISBN: 9780521663007
Category : Science
Languages : en
Pages : 392
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Book Description
This Intergovernmental Panel on Climate Change Special Report is the most comprehensive assessment available on the effects of aviation on the global atmosphere. The report considers all the gases and particles emitted by aircraft that modify the chemical properties of the atmosphere, leading to changes in radiative properties and climate change, and modification of the ozone layer, leading to changes in ultraviolet radiation reaching the Earth. This volume provides accurate, unbiased, policy-relevant information and is designed to serve the aviation industry and the expert and policymaking communities.
Author: National Research Council
Publisher: National Academies Press
ISBN: 030917290X
Category : Technology & Engineering
Languages : en
Pages : 60
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Book Description
The NRC Panel on the Atmospheric Effects of Aviation (PAEAN) was established to provide guidance to NASA's Atmospheric Effects of Aviation Program (AEAP) by evaluating the appropriateness of the program's research plan, appraising the project-sponsored results relative to the current state of scientific knowledge, identifying key scientific uncertainties, and suggesting research activities likely to reduce those uncertainties. Over the last few years, the panel has written periodic reviews of both the subsonic aviation (Subsonic Assessment-SASS) and the supersonic aviation (Atmospheric Effects of Stratospheric Aircraft-AESA) components of AEAP, including: An Interim Review of the Subsonic Assessment Project (1997); An Interim Assessment of AEAP's Emissions Characterization and Near-Field Interactions Elements (1997); An Interim Review of the AESA Project: Science and Progress (1998); Atmospheric Effects of Aviation: A Review of NASA's Subsonic Assessment Project (1998). This report constitutes the final review of AESA and will be the last report written by this panel. The primary audience for these reports is the program managers and scientists affiliated with AEAP, although in some cases the topics discussed are of interest to a wider audience.
Author: Inés Sanz-Morère
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Environmental impacts from the aviation sector are in continuous growth. The total sector contribution to anthropogenic climate forcing is approximately 3.5%, representing up to 9% of US greenhouse gas emissions from transportation in 2018. Despite the COVID-19 crisis, it is also expected to grow at a global rate of approximately 4% per year in the next 20 years, and a full sector recovery is expected by 2024. The total impacts of aviation emissions on the climate, however, are still uncertain. This is due to factors including (i) the uncertainty regarding the radiative effects of short- and long-term climate forcers; (ii) the difficulty of validating modeling tools e.g. contrail formation and persistence or stratospheric chemical response to emissions; and (iii) the growing interest in new air transportation technologies such as unmanned aerial vehicles, supersonic aviation, or hydrogen and alternative fuels. These factors together require a persistent effort to improve the available tools assessing aviation environmental footprint. The objective of this thesis is to provide additional insights into aviation climate impacts, by improving current modeling capabilities. Specially, I aim to resolve elements that will be of increasing interest as the sector evolves. The work is divided into two parts. The first part focuses on improving climate impact estimates from contrails, ice clouds which form behind aircraft. Those are estimated to cause approximately half of the total climate forcing from aviation. The second part focuses on developing modeling tools for assessing climate impacts from future commercially viable supersonic fleets, as multiple companies are currently designing projects of that type (Aerion, Boom, Spike Aerospace, NASA, Lockheed Martin, etc.). In the first part, I develop a new contrail radiative forcing model with a new parameterization to model exchanges of radiation when multiple cloud layers overlap occur. My parameterization also reduces current uncertainties related to uncertainties in contrail microphysical structure. I find that, assuming maximum possible overlap, cloud-contrail overlap in 2015 increased the net radiative forcing from contrails. This effect was greatest in the North-Atlantic corridor. For 2015, contrail-contrail overlap results in a 3% net reduction in the estimated radiative forcing. Finally, using "in situ" measurements to constrain contrail microphysical evolution pathways, I find that the global net radiative forcing due to contrails in 2015 is between 8.6 and 10.7 mW/m2. Relative to the mid-point, this uncertainty range is less than one quarter of that previously reported in the literature. In the second part, I estimate the sensitivity of the global supersonic market and its climate impacts to factors such as design choice, regulations and economic assumptions. For this, I develop a detailed supersonic aircraft design model providing robust information on cruise altitude, fuel burn and emissions variation with aircraft design choice. I also, in order to address overland restrictions, develop a high-resolution routing algorithm, capable of assessing optimal routing for multiple regulatory options. I obtain that, in the absence of flight path restrictions, a fleet of 130-870 supersonic aircraft can be feasible, operating up to 2.5% of the seat-kilometers in the global aviation market. This will result in a net increase of fuel burn from commercial passenger aviation of up to 7%. However, between 78% and 100% of the global unrestricted market potentials cannot be addressed when supersonic flight is restricted over land or over areas with a population density of more than 50 inhabitants per square kilometer. When evaluating environmental impacts, aircraft design choice can change the sign of supersonic aviation impact on non-CO2 aviation climate forcing. In general, implementing supersonic aviation results in a global warming effect. However, if reducing fleet average NOx emission index by 58%, through an increase in fuel burn of 7%, climate forcing can change from positive (increase) to negative (reduction). Designs aiming to address high-value demand, at the upper bound of supersonic speeds (cruise Mach number = 2.2), are the most environmentally harmful because of their higher cruise altitude and fuel burn. While based on my results, we shouldn't expect any significant viable market from them, a 10% fleet substitution would be responsible of a doubling in global non-CO2 radiative forcing impact.
Author: Stefan Gössling
Publisher: Earthscan
ISBN: 1844076199
Category : Aeronautics
Languages : en
Pages : 409
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Book Description
First Published in 2009. Routledge is an imprint of Taylor & Francis, an informa company.
Author:
Publisher:
ISBN:
Category : Aircraft exhaust emissions
Languages : en
Pages : 24
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Book Description
"Based essentially on the Special Report on Aviation and Global Atmosphere, this booklet summarises the authoritative assessments of the effects of aviation emissions on the environment."--Forward.
Author: Fujung Tsai
Publisher:
ISBN:
Category : Aircraft exhaust emissions
Languages : en
Pages : 191
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Book Description
