Climate impact mitigation potential of European air traffic in a weather situation with strong contrail formation

Air traffic contributes to anthropogenic global warming by about 5% due to CO2 emissions and non-CO2 effects, which are primarily caused by the emission of NOx and water vapor as well as the formation of contrails. Since-in the long term-the aviation industry is expected to maintain its trend to grow, mitigation measures are required to counteract its negative effects upon the environment. One of the promising operational mitigation measures that has been a subject of the EU project ATM4E is climate-optimized flight planning by considering algorithmic climate change functions that allow for the quantification of aviation-induced climate impact based on the emission’s location and time. Here, we describe the methodology developed for the use of algorithmic climate change functions in trajectory optimization and present the results of its application to the planning of about 13,000 intra-European flights on one specific day with strong contrail formation over Europe. The optimization problem is formulated as bi-objective continuous optimal control problem with climate impact and fuel burn being the two objectives. Results on an individual flight basis indicate that there are three major classes of different routes that are characterized by different shapes of the corresponding Pareto fronts representing the relationship between climate impact reduction and fuel burn increase. On average, for the investigated weather situation and traffic scenario, a climate impact reduction in the order of 50% can be achieved by accepting 0.75% of additional fuel burn. Higher mitigation gains would only be available at much higher fuel penalties, e.g., a climate impact reduction of 76% associated with a fuel penalty of 12.8%. However, these solutions represent much less efficient climate impact mitigation options.Aircraft Noise and Climate Effect

Assessing the climate impact of formation flights

An operational measure to aim for mitigation of aviation climate impact that is inspired by migrant birds is to fly in aerodynamic formation. This operational measure adapted to human aircraft would eventually save fuel and is, therefore, expected to reduce the climate impact of aviation. As this method changes beside the total emission also the location of emission it is necessary to assess its climate impact with a climate response model to assure a benefit for climate. Therefore, the climate response model AirClim was adopted to account for saturation effects occurring for formation flight. The results for case studies comprising typical air traffic scenario show that on average the fuel consumption can be decreased by 5%, the climate impact, however, can be reduced by up to 24%.Aircraft Noise and Climate Effect

Assessing the climate impact of formation flights

An operational measure that is inspired by migrant birds aiming toward the mitigation of aviation climate impact is to fly in aerodynamic formation. When this operational measure is adapted to commercial aircraft it saves fuel and is, therefore, expected to reduce the climate impact of aviation. Besides the total emission amount, this mitigation option also changes the location of emissions, impacting the non-CO2 climate effects arising from NOx and H2O emissions and contrails. Here, we assess these non-CO2 climate impacts with a climate response model to assure a benefit for climate not only due to CO2 emission reductions, but also due to reduced non-CO2 effects. Therefore, the climate response model AirClim is used, which includes CO2 effects and also the impact of water vapor and contrail induced cloudiness as well as the impact of nitrogen dioxide emissions on the ozone and methane concentration. For this purpose, AirClim has been adopted to account for saturation effects occurring for formation flight. The results of the case studies show that the implementation of formation flights in the 50 most popular airports for the year 2017 display an average decrease of fuel consumption by 5%. The climate impact, in terms of average near surface temperature change, is estimated to be reduced in average by 24%, with values of individual formations between 13% and 33%.Aircraft Noise and Climate Effect

Climate impact mitigation potential of european air traffic

Air traffic contributes to anthropogenic global warming by about 5% due to CO2 emissions (about 1/3) and non-CO2 effects (about 2/3) primarily caused by emissions of NOx and water vapour as well as the formation of contrails. Since aviation is expected to maintain its trend to grow over the next decades, mitigation measures are required counteracting its negative effects upon the environment. One of the promising operational mitigation measures which has been subject of the EU project ATM4E, is climate-optimized flight planning using algorithmic climate change functions describing the climate sensitivity as a function of emission location and time. The methodology developed for the use of algorithmic climate change functions in trajectory optimization is described and results of its application to the planning of about 13,000 intra-European flights on one specific day are presented. The optimization problem is formulated as bi-objective continuous optimal control problem with climate impact and fuel burn being the two objectives. Results on individual flight basis indicate that there are three major classes of different routes which are characterized by different shapes of the corresponding Pareto-fronts. For the investigated scenario, results show a climate impact mitigation potential of about 73% which is related with a fuel penalty of 14.5%. However, a climate impact reduction of 50% can already be achieved with 0.75% additional fuel burn.Aircraft Noise and Climate Effect

Robust 4D climate-optimal aircraft trajectory planning under weather-induced uncertainties: Free-routing airspace

The non-CO2 climate impact of aviation strongly relies on the atmospheric conditions at the time and location of emissions. Therefore, it is possible to mitigate their associated climate impact by planning trajectories to re-route airspace areas with significant climate effects. Identifying such climate-sensitive regions requires specific weather variables. Inevitably uncertain weather forecasts can lead to inefficient aircraft trajectories if not accounted for within flight planning. The current study addresses the problem of generating robust climate-friendly flight plans under meteorological uncertainty characterized using the ensemble prediction system. We introduce a framework based on the concept of robust tracking optimal control theory to formulate and solve the proposed flight planning problem. Meteorological uncertainty effects on aircraft performance variables are captured using the formulated ensemble aircraft dynamical model and controlled by penalizing the performance index variance. Case studies show that the proposed approach can generate climate-optimized trajectories with minimal sensitivity to weather uncertainty.Aircraft Noise and Climate Effect

Robustness of climate-optimized trajectories and mitigation Potential: flying atm4e

Aviation can reduce its climate impact by controlling its CO2-emission and non-CO2 effects, e.g. aviation-induced contrail-cirrus and ozone caused by nitrogen oxide emissions. One option is the implementation of operational measures which aim to avoid those atmospheric regions that are in particular sensitive to non-CO2 aviation effects, e.g. where persistent contrails form. Quantitative estimates of mitigation potentials of such climate-optimized aircraft trajectories are required, when working towards sustainable aviation. Results are presented from a comprehensive modelling approach which is working towards identifying such climate-optimized aircraft trajectories. The overall concept relies on a multi-dimensional environmental change function concept, which is capable of providing environmental impact information to air traffic management (ATM) and which in principal could include the noise and air quality impacts. A one-day case study with a weather situation containing regions with high contrail impacts for European air traffic estimated an overall climate impact reduction of about 30% for an increase of costs of 0.5%, relying on best estimate for climate impact information. The climate impact reduction and mitigation potential varies strongly with individual routes. By using a range of different climate metrics, the robustness of proposed mitigation trajectories is assessed. Sustainable ATM needs to integrate comprehensive environmental impacts and associated forecast uncertainties into route optimisation in order to identify robust eco-efficient trajectories.Aircraft Noise and Climate Effect

Verification of the ozone algorithmic climate change functions for predicting the short-term NOx effects from aviation en-route

For the first time, the algorithmic Climate Change Functions (aCCFs) for ozone, methane, water vapor, and persistent contrails have been developed within the ATM4E project to provide information on the climate sensitive regions, which can be conveniently implemented for the climate based flight routing. These aCCFs need to be verified before they are implemented. In this paper, we focus on the verification of the ozone aCCFs to enable the prediction of the short-term NOx effects from aviation en-route. The verification is conducted from two aspects. Firstly, the climatology of the ozone aCCFs is calculated based on a one-year simulation and verified by the existing literature. Secondly, the effectiveness of the ozone aCCFs for optimizing aircraft trajectories concerning the climate impact is verified by the comprehensive climate-chemistry model calculation.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Flight Performance and PropulsionAircraft Noise and Climate Effect

Case Study for Testing the Validity of NOx-Ozone Algorithmic Climate Change Functions for Optimising Flight Trajectories

One possibility to reduce the climate impact of aviation is the avoidance of climate-sensitive regions, which is synonymous with climate-optimised flight planning. Those regions can be identified by algorithmic Climate Change Functions (aCCFs) for nitrogen oxides (NOx), water vapour (H2O) as well as contrail cirrus, which provide a measure of climate effects associated with corresponding emissions. In this study, we evaluate the effectiveness of reducing the aviation-induced climate impact via ozone (O3) formation (resulting from NOx emissions), when solely using O3 aCCFs for the aircraft trajectory optimisation strategy. The effectiveness of such a strategy and the associated potential mitigation of climate effects is explored by using the chemistry–climate model EMAC (ECHAM5/MESSy) with various submodels. A summer and winter day, characterised by a large spatial variability of the O3 aCCFs, are selected. A one-day air traffic simulation is performed in the European airspace on those selected days to obtain both cost-optimised and climate-optimised aircraft trajectories, which more specifically minimised a NOx-induced climate effect of O3 (O3 aCCFs). The air traffic is laterally and vertically re-routed separately to enable an evaluation of the influences of the horizontal and vertical pattern of O3 aCCFs. The resulting aviation NOx emissions are then released in an atmospheric chemistry–climate simulation to simulate the contribution of these NOx emissions to atmospheric O3 and the resulting O3 change. Within this study, we use O3-RF as a proxy for climate impact. The results confirm that the climate-optimised flights lead to lower O3-RF compared to the cost-optimised flights, although the aCCFs cannot reproduce all aspects of the significant impact of the synoptic situation on the transport of emitted NOx. Overall, the climate impact is higher for the selected summer day than for the selected winter day. Lateral re-routing shows a greater potential to reduce climate impact compared to vertical re-routing for the chosen flight altitude. We find that while applying the O3 aCCFs in trajectory optimisation can reduce the climate impact, there are certain discrepancies in the prediction of O3 impact from aviation NOx emissions, as seen for the summer day. Although the O3 aCCFs concept is a rough simplification in estimating the climate impact of a local NOx emission, it enables a reasonable first estimate. Further research is required to better describe the O3 aCCFs allowing an improved estimate in the Average Temperature Response (ATR) of O3 from aviation NOx emissions. A general improvement in the scientific understanding of non-CO2 aviation effects could make climate-optimised flight planning practically feasibleAircraft Noise and Climate Effect

Analysis of aircraft routing strategies for north atlantic flights by using airtraf 2.0

Climate-optimized routing is an operational measure to effectively reduce the climate impact of aviation with a slight increase in aircraft operating costs. This study examined variations in the flight characteristics among five aircraft routing strategies and discusses several characteristics of those routing strategies concerning typical weather conditions over the North Atlantic. The daily variability in the North Atlantic weather patterns was analyzed by using the European Center Hamburg general circulation model (ECHAM) and the Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model in the specified dynamics mode from December 2008 to August 2018. All days of the ten complete winters and summers in the simulations were classified into five weather types for winter and into three types for summer. The obtained frequency for each of the weather types was in good agreement with the literature data; and then representative days for each weather type were selected. Moreover, a total of 103 North Atlantic flights of an Airbus A330 aircraft were simulated with five aircraft routing strategies for each representative day by using the EMAC model with the air traffic simulation submodel AirTraf. For every weather type, climate-optimized routing shows the lowest climate impact, at which a trade-off exists between the operating costs and the climate impact. Cost-optimized routing lies between the time-and fuel-optimized routings and achieves the lowest operating costs by taking the best compromise between flight time and fuel use. The aircraft routing for contrail avoidance shows the second lowest climate impact; however, this routing causes extra operating costs. Our methodology could be extended to statistical analysis based on long-term simulations to clarify the relationship between the aircraft routing characteristics and weather conditions.Aircraft Noise and Climate Effect

Comparison of various aircraft routing strategies using the air traffic simulation model airtraf 2.0

A climate-optimized routing is expected as an operational measure to reduce the climate impact of aviation, whereas this routing causes extra aircraft operating costs. This study performs some air traffic simulations of nine aircraft routing strategies which include the climate-optimized routing, and examines characteristics of those routings. A total of 103 trans-Atlantic flights of an Airbus A330 is simulated for five weather types in winter and for three types in summer over the North Atlantic by using the chemistry-climate model EMAC with the air traffic simulation submodel AirTraf. For every weather type, the climate-optimized routing shows the minimum climate impact, whereas a trade-off exists between the costs and the climate impact. The cost-optimized routing lies between time- and fuel-optimized routings, and minimizes the costs. The aircraft routing for minimum contrail formation shows the second-lowest climate impact, whereas this routing also causes extra costs.Aircraft Noise and Climate Effect