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Air traffic facilitates our society’s requirements for mobility. However, air traffic also contributes to climate change. Especially in view of the 2°C-climate target, it is important to make aviation eco-efficient. Here, the project Eco2Fly aimed at revising the estimate of the climate impact of aviation, by means of numerical simulations as well as in-situ and remote sensing measurements. Eco2Fly was a DLR funded project, which focuses on the climate impact of aviation, how atmospheric processes can be better understood and how we can reduce the climate impact of aviation. In this poster we focus on the aviation climate impact assessment.Lee et al. (2021) published already a comprehensive climate impact assessment two years ago, which gives an excellent overview of the different climate species and their contribution to nowadays climate impact. Here, we like to add some new methods and processes to a climate impact assessment. One point is the difference between perturbation und tagging approach. While the perturbation approach provides the impact of changed emissions in the chemistry-climate system, the tagging approach gives the contribution of one sector to the total climate impact. Additionally, new insights from numerical simulations for the direct and indirect aerosol impact were obtained.It is important for such a climate impact assessment, to use model results which are based on a realistic spatial distribution of emissions as different emission inventories can cause significantly different climate impact estimates, despite unchanged total emissions. In cooperation with the DLR project TraK (Transport and Climate) emission calculation and climate modelling approaches are applied to assess the climate impacts of the 2019 aviation emissions.

Using climate-optimized flight trajectories is one essential measure to reduce aviation's climate impact. Detailed knowledge of temporal and spatial climate sensitivity for aviation emissions in the atmosphere is required to realize such a climate mitigation measure. The algorithmic Climate Change Functions (aCCFs) represent the basis for such purposes. This paper presents the first version of the Algorithmic Climate Change Function submodel (ACCF 1.0) within the European Centre HAMburg general circulation model (ECHAM) and Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model framework. In the ACCF 1.0, we implement a set of aCCFs (version 1.0) to estimate the average temperature response over 20 years (ATR20) resulting from aviation CO2 emissions and non-CO2 impacts, such as NOx emissions (via ozone production and methane destruction), water vapour emissions, and contrail cirrus. While the aCCF concept has been introduced in previous research, here, we publish a consistent set of aCCF formulas in terms of fuel scenario, metric, and efficacy for the first time. In particular, this paper elaborates on contrail aCCF development, which has not been published before. ACCF 1.0 uses the simulated atmospheric conditions at the emission location as input to calculate the ATR20 per unit of fuel burned, per NOx emitted, or per flown kilometre. In this research, we perform quality checks of the ACCF 1.0 outputs in two aspects. Firstly, we compare climatological values calculated by ACCF 1.0 to previous studies. The comparison confirms that in the Northern Hemisphere between 150–300 hPa altitude (flight corridor), the vertical and latitudinal structure of NOx-induced ozone and H2O effects are well represented by the ACCF model output. The NOx-induced methane effects increase towards lower altitudes and higher latitudes, which behaves differently from the existing literature. For contrail cirrus, the climatological pattern of the ACCF model output corresponds with the literature, except that contrail-cirrus aCCF generates values at low altitudes near polar regions, which is caused by the conditions set up for contrail formation. Secondly, we evaluate the reduction of NOx-induced ozone effects through trajectory optimization, employing the tagging chemistry approach (contribution approach to tag species according to their emission categories and to inherit these tags to other species during the subsequent chemical reactions). The simulation results show that climate-optimized trajectories reduce the radiative forcing contribution from aviation NOx-induced ozone compared to cost-optimized trajectories. Finally, we couple the ACCF 1.0 to the air traffic simulation submodel AirTraf version 2.0 and demonstrate the variability of the flight trajectories when the efficacy of individual effects is considered. Based on the 1 d simulation results of a subset of European flights, the total ATR20 of the climate-optimized flights is significantly lower (roughly 50 % less) than that of the cost-optimized flights, with the most considerable contribution from contrail cirrus. The CO2 contribution observed in this study is low compared with the non-CO2 effects, which requires further diagnosis.

Aviation aims to reduce its climate impact by adopting trajectories, that avoid those regions of the atmosphere where aviation emissions have a large impact. To that end, prototype algorithmic climate change functions can be used, which provide spatially and temporally resolved information on aviation’s climate impact in terms of future near-surface temperature change. These alogorithmic climate change functions can be calculated with meteorological input data obtained from e.g. numerical weather prediction models. We here present an open-source Python Library, an easy to use and flexible tool which efficiently calculates both the individual algorithmic climate change functions of water vapour, nitrogen oxide (NOx) induced ozone and methane, and contrail-cirrus and also the merged non-CO2 algorithmic climate change functions that combine all individual contributions. These merged aCCFs can be only constructed with the technical specification of aircraft/engine parameters, i.e., NOx emission indices and flown distance per kg burnt fuel. These aircraft/engine specific values are provided within CLIMaCCF version V1.0 for a set of aggregated aircraft/engine classes (i.e. regional, single-aisle, wide-body). Moreover, CLIMaCCF allows by a user-friendly configuration setting to choose between a set of different physical climate metrics (i.e. average temperature response for pulse or future scenario emissions over the time horizons of 20, 50 or 100 years). Finally, we demonstrate the abilities of CLIMaCCF by a series of example applications.

Aviation aims to reduce its climate impact, comprising CO2 and non-CO2 effects, by identifying climate-optimized aircraft trajectories. Such climate-optimized routes avoid regions of atmosphere where aviation emissions have a large impact on climate, e.g. by formation of contrails or strong NOx-induced ozone formation. Implementing such climate-optimized routings requires that air traffic management has spatially and temporally resolved information on these non-CO2 climate effects available during the trajectory planning process.An overall modelling chain is required in order to expand the current flight planning procedure by considering climate impact during trajectory optimization in the overall optimization process. We explore a concept how to provide such information as an advanced MET Service: based on numerical weather prediction data and using algorithms climate change functions (aCCFs) such spatially and temporally resolved information can be provided. By integrating an uncertainty and risk analysis, we enable air traffic management (ATM) to identify climate-optimized aircraft trajectories which provide a robust and eco-efficient reduction in aviation’s climate impact. Climate optimization in this feasibility study, which is part of the SESAR ER project FlyATM4E, considers CO2 as well as non-CO2 effects, such as contrails and contrail-cirrus, water vapour, and NOx-induced effects on ozone and methane.We will present the overall modelling concept which has been developed to explore climate-optimized aircraft trajectories considering individual weather situations in a series of one-day case studies. This concept also explores the robustness of estimated benefits in terms of mitigation of climate effects. The approach comprises a comprehensive uncertainty analysis, that provides alternative estimates as upper and lower limit estimates to reflect low level of scientific understanding or unknown efficacy of individual effects, resulting from state-of-the-art understanding from climate science. We also explore how to incorporate different physical climate metrics, as well as the usage of ensemble forecast data. We will present how these individual sources of uncertainty are statistically combined in order to provide a risk analysis together with the performance analysis of the identified alternative trajectory solutions, and hence identify robustness of mitigation gains on alternative trajectories. Finally, we will present an verification concept relying on numerical global chemistry-climate modelling with EMAC in order to explore such alternative routings during a one-year simulation.The current study has been supported by FlyATM4E project, which has received funding from the SESAR Joint Undertaking under grant agreement No 891317 under European Union’s Horizon 2020 research and innovation program. High-performance computing simulations with the chemistry-climate model EMAC were performed at the Deutsches Klima-Rechenzentrum (DKRZ), Hamburg.

Aviation aims to reduce its climate impact by adopting climate-optimized aircraft trajectories, avoiding those regions of the atmosphere where aviation emission have a large climate impact. For this purpose, dedicated MET services have to be made available to the flight planning procedures, which need to be predicted with current numerical weather prediction models.In order to represent spatially and temporally resolved information on the climate impact in terms of future temperature changes due to aviation emissions at a given time and location in such an advanced MET service, we propose to use algorithmic climate change functions (aCCFs) developed in earlier research projects. They include CO2 and non-CO2 effects, comprising nitrogen oxide (NOx), water vapour and contrail-cirrus. These aCCFs allow to derive such climate impact information for flight planning directly from operational meteorological weather forecast data. By combining the individual aCCFs of water vapour, NOx and contrail-cirrus, also merged non-CO2 aCCFs can be generated.With this study we aim to identify specific weather situations which have the potential to provide a robust climate impact reduction despite uncertainties. This work is part of the SESAR project FlyATM4E. For this purpose, a systematic analysis of the meteorological conditions and situations is required. We will present the characteristic water vapour, NOx induced and contrail-cirrus aCCFs for a set of specific weather patterns based on 2018 reanalysis data. A detailed analysis of the variation in aCCFs will be presented, including the dependency of individual and merged aCCFs to seasonal cycle, different synoptical weather situations and cruise altitude. Acknowledgement:The current study has been supported by FlyATM4E project, which has received funding from the SESAR Joint Undertaking under grant agreement No 891317 under European Union’s Horizon 2020 research and innovation program.

Dieser Buchbeitrag fasst die wesentlichen Ergebnisse der AviClim-Studie zusammen. Es werden die Kosten- und Wettbewerbseffekte einer Limitierung des gesamten Klimabeitrags des Luftverkehrs modellgestutzt abgeschatzt.

Within this study, climate-restricted airspaces are defined in analogy to military exclusion zones. Airspaces are closed if the climate sensitivity of an area exceeds a threshold value, and affecte...

Climate impact of aviation is expected to increase further. Aircraft routings are an important measure for climate impact reductions. To find an effective aircraft routing strategy for reducing the impact, the first version of the submodel AirTraf has been developed; this submodel can simulate global air traffic in the ECHAM/MESSy Atmospheric Chemistry (EMAC) model. This paper describes the updated submodel AirTraf 2.0. Seven new aircraft routing options are introduced, including contrail avoidance, minimum economic costs, and minimum climate impact. Example simulations of the new routing options are presented by using around 100 north-Atlantic flights of an Airbus A330 aircraft for a typical winter day. The results clearly show that the family of optimum flight trajectories (three-dimensional) varies according to the routing options. The comparison of the results for various routing options reveals characteristics of the routing with respect to air traffic performances. The minimum cost option obtains a trade-off solution between the minimum time and the minimum fuel solutions. The aircraft routings for contrail avoidance and minimum climate impact reduce the potential climate impact, which is estimated by using algorithmic Climate Change Functions, whereas these two routings increase flight operating costs. A trade-off between the aircraft operating costs and the climate impact is confirmed. The simulation results are compared with literature data and the consistency of the submodel AirTraf 2.0 is verified.

Air traffic has an increasing influence on climate; therefore identifying mitigation options to reduce the climate impact of aviation becomes more and more important. Aviation influences climate through several climate agents, which show different dependencies on the magnitude and location of emission and the spatial and temporal impacts. Even counteracting effects can occur. Therefore, it is important to analyse all effects with high accuracy to identify mitigation potentials. However, the uncertainties in calculating the climate impact of aviation are partly large (up to a factor of about 2). In this study, we present a methodology, based on a Monte Carlo simulation of an updated non-linear climate-chemistry response model AirClim, to integrate above mentioned uncertainties in the climate assessment of mitigation options. Since mitigation options often represent small changes in emissions, we concentrate on a more generalised approach and use exemplarily different normalised global air traffic inventories to test the methodology. These inventories are identical in total emissions but differ in the spatial emission distribution. We show that using the Monte Carlo simulation and analysing relative differences between scenarios lead to a reliable assessment of mitigation potentials. In a use case we show that the presented methodology can be used to analyse even small differences between scenarios with mean flight altitude variations.

The interdisciplinary research project AviClim (Including Avi ation in International Protocols for Clim ate Protection) has explored the feasibility for including aviation’s full climate impact, i.e., both long-lived CO2 and short-lived non-CO2 effects, in international protocols for climate protection and has investigated the economic impacts. Short-lived non-CO2 effects of aviation are NOx emissions, H2O emissions or contrail cirrus, for instance. Four geopolitical scenarios have been designed which differ concerning the level of international support for climate protecting measures. These scenarios have been combined alternatively with an emissions trading scheme on CO2 and non-CO2 species, a climate tax and a NOx emission charge combined with CO2 trading and operational measures (such as lower flight altitudes). Modelling results indicate that a global emissions trading scheme for both CO2 and non-CO2 emissions would be the best solution from an economic and environmental point of view. Costs and impacts on competition could be kept at a relatively moderate level and effects on employment are moderate, too. At the same time, environmental benefits are noticeable.

Air traffic is important to our society and guarantees mobility especially for long distances. Air traffic is also contributing to climate warming via emissions of CO2 and various non-CO2 effects, such as contrail-cirrus or increase in ozone concentrations. Here we investigate the climate impact of a future aircraft design, a multi fuel blended wing body (MF-BWB), conceptually designed within the EU-project AHEAD. We re-calculate the parameters for the contrail formation criterion, since this aircraft has very different characteristics compared to conventional technologies and show that contrail formation potentially already occurs at lower altitudes than for conventional aircraft. The geometry of the contrails, however, is similar to conventional aircraft, as detailed Large-Eddy-Simulations show. The global contrail-cirrus coverage and related radiative forcing is investigated with a climate model including a contrail-cirrus parameterisation and shows an increase in contrail-cirrus radiative forcing compared to conventional technologies, if the number of emitted particles is equal to conventional technologies. However, there are strong indications that the AHEAD engines would have a substantial reduction in the emission of soot particles and there are strong indications that this leads to a substantial reduction in the contrail-cirrus radiative forcing. An overall climate impact assessment with a climate-chemistry response model shows that the climate impact is likely to be reduced by 20% to 25% compared to a future aircraft with conventional technologies. We further tested the sensitivity of this result with respect to different future scenarios for the use of bio fuels, improvements of the fuel efficiency for conventional aircraft and the impact of the number of emitted soot particles on the radiative forcing. Only the latter has the potential to significantly impact our findings and needs further investigation. Our findings show that the development of new and climate compatible aircraft designs requires the inclusion of climate impact assessments already at an early stage, i.e. pre-design level.

The WeCare project (Utilizing Weather information for Climate efficient and eco efficient future aviation), an internal project of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR), aimed at finding solutions for reducing the climate impact of aviation based on an improved understanding of the atmospheric impact from aviation by making use of measurements and modeling approaches. WeCare made some important contributions to advance the scientific understanding in the area of atmospheric and air transportation research. We characterize contrail properties, show that the aircraft type significantly influences these properties, and how contrail-cirrus interacts with natural cirrus. Aviation NOx emissions lead to ozone formation and we show that the strength of the ozone enhancement varies, depending on where within a weather pattern NOx is emitted. These results, in combination with results on the effects of aerosol emissions on low cloud properties, give a revised view on the total radiative forcing of aviation. The assessment of a fleet of strut-braced wing aircraft with an open rotor is investigated and reveals the potential to significantly reduce the climate impact. Intermediate stop operations have the potential to significantly reduce fuel consumption. However, we find that, if only optimized for fuel use, they will have an increased climate impact, since non-CO2 effects compensate the reduced warming from CO2 savings. Avoiding climate sensitive regions has a large potential in reducing climate impact at relatively low costs. Taking advantage of a full 3D optimization has a much better eco-efficiency than lateral re-routings, only. The implementation of such operational measures requires many more considerations. Non-CO2 aviation effects are not considered in international agreements. We showed that climate-optimal routing could be achieved, if market-based measures were in place, which include these non-CO2 effects. An alternative measure to foster climate-optimal routing is the closing of air spaces, which are very climate-sensitive. Although less effective than an unconstrained optimization with respect to climate, it still has a significant potential to reduce the climate impact of aviation. By combining atmospheric and air transportation research, we assess climate mitigation measures, aiming at providing information to aviation stakeholders and policy-makers to make aviation more climate compatible.

Impacts of commercial aircraft operation upon the environment, which are caused primarily from emissions of C O 2 , N O x and the formation of contrails, are matter of growing concern, as aviation is one of the fastest developing industrial sectors worldwide and the awareness of its effects is expanding. Recent research has focused on the cost-benefit potential of different mitigation strategies, which optimize flight trajectories with respect to climate and economy, but most of these mitigation strategies cannot be implemented in the near future due to technical challenges. The objective of this paper is to present an interim mitigation strategy, which bridges this time period. In analogy to military exclusion zones, climate restricted airspaces (CRA) are defined based on 3-D climate change functions, characterizing the environmental impact caused by an aircraft emission at a certain location. Regions with climate costs greater than a threshold value are closed in the corresponding month; others are cleared for air traffic. To estimate the cost-benefit potential of this strategy, a preliminary analysis is conducted on the route from Helsinki (EFHK) to Miami (KMIA). Affected flight trajectories are re-routed optimally around resulting CRA with regard to monetary costs for varying threshold values. Therefore, flight simulation algorithms are developed, which solve a non-linear optimal control problem. For each optimized flight trajectory corresponding average temperature response (ATR) and cash operating costs (COC) are expressed relative to a reference great circle trajectory with constant Mach number and compared with the climate mitigation potential of climate optimized trajectories.

Although climate change is a global problem, specific mitigation measures are frequently applied on regional or national scales only. This is the case in particular for measures to reduce the emissions of land-based transport, which is largely characterized by regional or national systems with independent infrastructure, organization, and regulation. The climate perturbations caused by regional transport emissions are small compared to those resulting from global emissions. Consequently, they can be smaller than the detection limits in global three-dimensional chemistry-climate model simulations, hampering the evaluation of the climate benefit of mitigation strategies. Hence, we developed a new approach to solve this problem. The approach is based on a combination of a detailed three-dimensional global chemistry-climate model system, aerosol-climate response functions, and a zero-dimensional climate response model. For demonstration purposes, the approach was applied to results from a transport and emission modeling suite, which was designed to quantify the present-day and possible future transport activities in Germany and the resulting emissions. The results show that, in a baseline scenario, German transport emissions result in an increase in global mean surface temperature of the order of 0.01 K during the 21st century. This effect is dominated by the CO2 emissions, in contrast to the impact of global transport emissions, where non-CO2 species make a larger relative contribution to transport-induced climate change than in the case of German emissions. Our new approach is ready for operational use to evaluate the climate benefit of mitigation strategies to reduce the impact of transport emissions.

Overland supersonic flight bans due to the sonic boom are often said to be the reason for civil high-speed aircraft not being able to make a breakthrough. However, there is an apparent lack of studies actually quantifying the disadvantage of law-compliant supersonic flight paths versus optimum overland tracks. This paper presents a framework of city pair-specific flight routes and mission-performance simulation for accurate operational assessment of supersonic airplane designs. By application to a supposedly realistic representation of a future civil supersonic air transportation system as a use case, the impact of rerouting on flight distance, block times, and block fuels is quantified locally as well as globally. It was found that, for most of the city pairs relevant for high-value airline service, supersonic rerouting requires only small tradeoffs manifesting in detours and subsonic overland segments. Accordingly, on many itineraries, flight durations in scenarios of overland restriction were calculate...

In addition to CO2, the climate impact of aviation is strongly influenced by non-CO2 emissions, such as nitrogen oxides, influencing ozone and methane, and water vapour, which can lead to the formation of persistent contrails in ice-supersaturated regions. Because these non-CO2 emission effects are characterised by a short lifetime, their climate impact largely depends on emission location and time; that is to say, emissions in certain locations (or times) can lead to a greater climate impact (even on the global average) than the same emission in other locations (or times). Avoiding these climate-sensitive regions might thus be beneficial to climate. Here, we describe a modelling chain for investigating this climate impact mitigation option. This modelling chain forms a multi-step modelling approach, starting with the simulation of the fate of emissions released at a certain location and time (time-region grid points). This is performed with the chemistry–climate model EMAC, extended via the two submodels AIRTRAC (V1.0) and CONTRAIL (V1.0), which describe the contribution of emissions to the composition of the atmosphere and to contrail formation, respectively. The impact of emissions from the large number of time-region grid points is efficiently calculated by applying a Lagrangian scheme. EMAC also includes the calculation of radiative impacts, which are, in a second step, the input to climate metric formulas describing the global climate impact of the emission at each time-region grid point. The result of the modelling chain comprises a four-dimensional data set in space and time, which we call climate cost functions and which describes the global climate impact of an emission at each grid point and each point in time. In a third step, these climate cost functions are used in an air traffic simulator (SAAM) coupled to an emission tool (AEM) to optimise aircraft trajectories for the North Atlantic region. Here, we describe the details of this new modelling approach and show some example results. A number of sensitivity analyses are performed to motivate the settings of individual parameters. A stepwise sanity check of the results of the modelling chain is undertaken to demonstrate the plausibility of the climate cost functions.

Aviation guarantees mobility, but its emissions also contribute considerably to climate change. Therefore, climate impact mitigation strategies have to be developed based on comprehensive assessments of the different impacting factors. We quantify the climate impact mitigation potential and related costs resulting from changes in aircraft operations and design using a multi-disciplinary model workflow. We first analyze the climate impact mitigation potential and cash operating cost changes of altered cruise altitudes and speeds for all flights globally operated by the Airbus A330-200 fleet in the year 2006. We find that this globally can lead to a 42% reduction in temperature response at a 10% cash operating cost increase. Based on this analysis, new design criteria are derived for future aircraft that are optimized for cruise conditions with reduced climate impact. The newly-optimized aircraft is re-assessed with the developed model workflow. We obtain additional climate mitigation potential with small to moderate cash operating cost changes due to the aircraft design changes of, e.g., a 32% and 54% temperature response reduction for a 0% and 10% cash operating cost increase. Hence, replacing the entire A330-200 fleet by this redesigned aircraft ( M a c r = 0.72 and initial cruise altitude (ICA) = 8000 m) could reduce the climate impact by 32% without an increase of cash operating cost.

Emissions of nitrogen oxides (NOx) lead to formation of ozone, which is an important greenhouse gas. Despite its relevance, little emphasis was previously given on verifying approaches to calculate contributions of individual emissions to ozone and hence to climate change. Basically two methods (perturbation method and tagging method) were used in the past. We demonstrate that both methods are valid and have their area of application, but only tagging calculates contributions of emissions to concentrations, whereas the perturbation method identifies changes in the ozone concentrations due to emission changes. Our results show that the contribution of road traffic emissions to climate change is underestimated by a factor of 5 in the perturbation method. This is caused by non-linear compensating effects from other emission sectors, which are concealed in the perturbation method but disclosed with tagging. Consequently, the effectiveness of mitigation measures for individual sectors (i.e. concentrating on road traffic induced ozone) is only correctly expressed by the tagging method. The perturbation method provides accurately the total impact (i.e. total ozone) of a mitigation measure. However, current approaches, which evaluate the effectiveness of a mitigation measure based on the perturbation approach, do not reflect changes in the chemical state of the atmosphere (i.e. ozone production rates). These largely affect the effectiveness of subsequent measures and hence make the evaluation of the effectiveness of two measures dependent on their chronology of application. We show that also in this regard, the tagging method is better suited to evaluate the effectiveness of a mitigation measure than the perturbation method.

Source attribution of ozone radiative forcing (RF) is a prerequisite for developing adequate emission mitigation strategies with regards to climate impact. Decadal means of ozone fields from transient climate-chemistry simulations (1960–2019) are analysed and the temporal development of ozone RF resulting from individual NOx sources, e.g. road traffic, industry and air traffic, is investigated. We calculated an ozone production efficiency which is mainly dependent on the altitude of NOx emission and on the amount of background NOx with values varying over one order of magnitude. Air traffic and lightning are identified as NOx sources with a two and five times higher ozone production efficiency, respectively, than ground based sources. Second, radiative efficiency of source attributed ozone (i.e. total induced radiative flux change per column ozone) shows clear dependence on latitudinal structure of the ozone anomaly and, to a lesser extent, to its altitude. Lightning induced ozone shows the highest radiative efficiency because lightning primarily enhances ozone in low latitudes in the mid-troposphere (higher altitudes). Superimposed on these effects, a saturation effect causes a decreasing radiative efficiency with increasing background ozone concentrations. Changes in RF attributed to NOx induced ozone from 1960 to 2019 are controlled by three factors: changes in emissions, changes in ozone production efficiency and changes in the radiative efficiency. Leading effect is emission increase, but changes in ozone production efficiency increase ozone RF by a factor of three for air traffic, or reduce ozone RF by around 30% for ships. Additionally, changes in the radiative efficiency due to saturation effects change ozone RF by 2–5%.

Im Rahmen der Veroffentlichung werden die wesentlichen Ergebnisse des BMBF-geforderten Projekts "AviClim" vorgestellt.

• Posing the adequate climate question reduces a large amount of a perceived ambiguity of climate metrics.

Overland supersonic flight bans due to the sonic boom are often said to be the reason for civil high-speed aircraft not being able to make a breakthrough. However, there is an apparent lack of studies actually quantifying the disadvantage of law-compliant supersonic flight paths versus optimum overland tracks. This paper presents a framework of city pair-specific flight routes and mission performance simulation for accurate operational assessment of supersonic airplane designs. By application to a supposedly realistic representation of a future civil supersonic air transportation system as a use-case, the impact of rerouting on flight distance, block times, and block fuels is quantified locally as well as globally.

[1] The present study provides a detailed assessment of the net impact of global flight altitude changes on radiative forcing and temperature response. Changes in contrail coverage, chemical perturbations (H2O, O3 ,C H4) and associated radiative forcings were determined from simulations with a quasi CTM. Future development of global mean radiative forcing and temperature response was calculated by means of a linear response model. The range of possible effects arising from various future scenarios is analyzed, and tradeoffs between partially counteracting short- and long term effects are studied. Present-day global mean radiative forcing of short-lived species and CH4 is reduced when flying lower, whereas that of CO2 increases. The opposite effect is found for higher flight altitudes. For increasing and sustained emissions, the climate impact changes are dominated by the effect of short-lived species, yielding a reduction for lower flight altitudes and an increase for higher flight altitudes. For future scenarios involving a reduction or termination of emissions, radiative forcing of short-lived species decreases immediately, that of longer lived species decreases gradually, and respective temperature responses start to decay slowly. After disappearance of the shorter lived effects, only the counteracting CO2 effect remains, resulting in an increased climate effect for lower flight altitudes and a decrease for higher flight altitudes. Incorporating knowledge about the altitude sensitivity of aviation climate impact in the route planning process offers substantial mitigation potential. Scenarios and time horizons for the evaluation of future effects of mitigation instruments must be chosen carefully depending on the mitigation aim.

The evaluation of climate change mitigation options addresses the whole air traffic system. Any optimization with respect to climate change requires a representation of this system and hence a simplification of the individual components and models. AirClim is such a model for simplified evaluation of the approximate chemistry-climate impact of air traffic emissions. The model represents the major responses of the atmosphere to emissions in terms of composition and climate change. The model is used to evaluate both the mean response and the uncertainty range of the climate impact of any change in the air traffic system. The uncertainty range is derived by a Monte-Carlo simulation using random variations of uncertain model input parameters. This uncertainty range is found to be much smaller than the uncertainties in knowledge of the air traffic climate impact in general.

Aviation climate impact is caused by CO2 and non-CO2 emissions where the climate effect of non-CO2 emissions depends on weather and aircraft route. An aviation system with minimum climate impact differs from a system with minimum emissions. Considerable potential exists to reduce the climate impact of aviation by weather- and cost-dependent climate-optimized air traffic management (“smart routing”) and aircraft design (“green aircraft”). Current research provides a unique opportunity to systematically investigate the trade-offs between various mitigation concepts and cost functions. Here various approaches are presented to minimize the climate impact on a climatological and weather basis, some being applicable to aircraft designs for reduced climate impact and others offering alternative operational concepts.

Decadal means of ozone fields from transient E39/C climate-chemistry simulations (1960–2019) are analysed and temporally developing ozone radiative forcings (RF) are investigated which result from individual ozone precursor sources like road traffic, industry, air traffic, etc. We study how effective NOx emissions from different sources produce ozone. This ozone production efficiency is mainly dependent on the altitude of NOx emission and on the amount of background NOx. For example, our study shows that the ozone production efficiency of lightning and air traffic have a five and two time higher ozone production efficiency than ground based sources. The radiative efficiency of ozone (i.e. the radiative forcing per molecule) is mainly dependent on the surface temperature, but also, to a lesser degree, on the altitude of added ozone. Lightning, for example, causes the highest specific RF due to the fact that lightning primarily enhances ozone in low latitudes in the mid-troposphere. Superimposed on these effects, is a saturation effect which causes a decreasing RF efficiency with increasing background ozone. A consequence of this saturation effect is an underestimation of total RF by about 10% if the component RFs of individual ozone sources are calculated separately and added up afterwards. The results show that the time development of emissions (1960–2019) control the RF changes for most sources. RF changes are slightly reduced due to a changing atmospheric composition (10–25%) for all but the aircraft sources, and due to RF saturation (2–5%).

Here we present a methodology, which allows for an optimization of aircraft design aspects with regard to climate change. During the optimization, each iteration requires an estimate of a 3d emission distribution and from that an estimate of the climate impact. Hence it is necessary to distinguish the climate impact of two emission sets. This is difficult because considerable uncertainties of the overall climate impact from air traffic still exist. These uncertainties arise to a large extend from uncertainties in atmospheric processes. We address this problem by determining the difference in climate impact of two aircraft configurations for a large subset of parameter settings representing those atmospheric processes. Therefore a Monte-Carlo-Simulation for uncertainties of climate impacts is performed with AirClim, an efficient tool for climate evaluation of aircrafttechnology. The methodology is introduced and the principle mechanism is presented exemplarily with an application to aircraft emission inventories. The results show that although large uncertainties exist in the overall climate impact estimate of current air traffic, small differences in the emission pattern lead to stochastic significant changes in the climate impact. In the future this approach can be applied to evaluate and possibly minimize the climate impact of new aircraft technology.

Aviation affects the Earth’s atmosphere and radiative balance through the emission of greenhouse gases, greenhouse gas precursors, aerosols, contrails and induced cirrus cloudiness. The resulting climate impact is a response of the complex interactions between the amount and type of emitted constituents, their geographical position, altitude and time of emission as well as the actual weather and climate situation. In 2005 aviation accounted for 3.5 % of the global anthropogenic radiative forcing (excluding the impact of contrail cirrus clouds). As the global air traffic is predicted to grow approx. 5% per year, the development of a climate compatible air transport system is of increasing importance for society and science. To achieve this goal, different technological and operational options can be applied to reduce the climate impact by air travel. The range of possibilities is wide, including new propulsion concepts such as open rotors or intercooler recuperative engine cycles, improved combustion chambers for low NOX and soot, novel aircraft configurations such as Blended Wing Bodies, innovative subsystem architectures for minimal engine cycle disturbance through secondary power off take and operational procedures such as multi-step operations and changed cruise altitudes for contrail avoidance. In order to provide a solid basis for decision and policy makers, the remaining uncertainties in climate modeling have to be reduced and the different options and their interrelations have to be assessed in a reliable way. To catch all relevant effects of the coupled disciplines, sophisticated numerical models for climate response, mission calculation, propulsion, aircraft subsystems and overall aircraft design are combined to an integrated simulation and assessment chain. In addition, further efforts are made to reduce remaining uncertainties in modeling emissions and their corresponding climate impact. This complex and multidisciplinary task further requires the contribution of experts from the included areas to ensure a secure evaluation of the obtained results. Here we present such an integrated approach as it is applied within the DLR project Climate compatible Air Transport System (CATS).

In order to achieve global environmental goals like the 2-degree-target, as well as to reduce longer-term emission levels, mitigation measures have to be introduced, preferably as early as possible. In aviation, the implementation of the most promising mitigation strategies, e.g. climate optimized routing, is linked with several technical challenges. An early introduction of interim mitigation strategies, which bridges the time period until most auspicious approaches reach market maturity, may pave the way for a prompt reduction of aviation's induced global warming. Within this study, climate restricted airspaces (CRA) are de�ned in analogy to military exclusion zones. Climate cost functions (CCF) characterize the environmental impact caused by an aircraft emission at a certain location and time. To estimate the monthly climate sensitivity of an area, CCFs are derived with the climate-response model AirClim. Within this study, we close regions with climate sensitivities greater than a threshold value for a period of time (e.g. a month) and a�ected ight trajectories are re-routed cost optimally around them. The evaluation of the climate impact mitigation potential of climate restricted areas is performed based on optimal control techniques. Monetary costs are integrated into the cost functional of the Trajectory Optimization Module (TOM). Further, high penalties are introduced within restricted airspaces in order to ensure the avoidance of CRA. The cost-bene�t potential (climate impact mitigation vs. rise in operating costs) for this interim mitigation concept is investigated for varying threshold values for the closure of airspace and compared with climate optimized trajectories (COT) for di�erent routes and seasons of the year.

Comprehensive assessment of the environmental aspects of flight movements is of increasing interest to the aviation sector as a potential input for developing sustainable aviation strategies that consider climate impact, air quality and noise issues simultaneously. However, comprehensive assessments of all three environmental aspects do not yet exist and are in particular not yet operational practice in flight planning. The purpose of this study is to present a methodology which allows to establish a multi-criteria environmental impact assessment directly in the flight planning process. The method expands a concept developed for climate optimisation of aircraft trajectories, by representing additionally air quality and noise impacts as additional criteria or dimensions, together with climate impact of aircraft trajectory. We present the mathematical framework for environmental assessment and optimisation of aircraft trajectories. In that context we present ideas on future implementation of such advanced meteorological services into air traffic management and trajectory planning by relying on environmental change functions (ECFs). These ECFs represent environmental impact due to changes in air quality, noise and climate impact. In a case study for Europe prototype ECFs are implemented and a performance assessment of aircraft trajectories is performed for a one-day traffic sample. For a single flight fuel-optimal versus climate-optimized trajectory solution is evaluated using prototypic ECFs and identifying mitigation potential. The ultimate goal of such a concept is to make available a comprehensive assessment framework for environmental performance of aircraft operations, by providing key performance indicators on climate impact, air quality and noise, as well as a tool for environmental optimisation of aircraft trajectories. This framework would allow studying and characterising changes in traffic flows due to environmental optimisation, as well as studying trade-offs between distinct strategic measures. Comprehensive assessment of the environmental aspects of flight movements is of increasing interest to the aviation sector as a potential input for developing sustainable aviation strategies that consider climate impact, air quality and noise issues simultaneously. However, comprehensive assessments of all three environmental aspects do not yet exist and are in particular not yet operational practice in flight planning. The purpose of this study is to present a methodology which allows to establish a multi-criteria environmental impact assessment directly in the flight planning process. The method expands a concept developed for climate optimisation of aircraft trajectories, by representing additionally air quality and noise impacts as additional criteria or dimensions, together with climate impact of aircraft trajectory. We present the mathematical framework for environmental assessment and optimisation of aircraft trajectories. In that context we present ideas on future implementation of such advanced meteorological services into air traffic management and trajectory planning by relying on environmental change functions (ECFs). These ECFs represent environmental impact due to changes in air quality, noise and climate impact. In a case study for Europe prototype ECFs are implemented and a performance assessment of aircraft trajectories is performed for a one-day traffic sample. For a single flight fuel-optimal versus climate-optimized trajectory solution is evaluated using prototypic ECFs and identifying mitigation potential. The ultimate goal of such a concept is to make available a comprehensive assessment framework for environmental performance of aircraft operations, by providing key performance indicators on climate impact, air quality and noise, as well as a tool for environmental optimisation of aircraft trajectories. This framework would allow studying and characterising changes in traffic flows due to environmental optimisation, as well as studying trade-offs between distinct strategic measures.