WMO Aeronautical Meteorology Scientific Conference 2017

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1 Session 2 Integration, use cases, fitness for purpose and service delivery 2.4 Trajectory-based operations (TBO), flight planning and user-preferred routing Climate optimised aircraft trajectories based on advanced MET service for sustainable aviation Sigrun Matthes, DLR-Institute of Atmospheric Physics Sigrun.matthes@dlr.de co-authors: Volker Grewe, DLR Institute of Atmospheric Physics, also at: TU Delft, ANCE, NL; Benjamin Lührs, Florian Linke, TU Hamburg, D; Emma Irvine, Keith Shine, University Reading, UK, and ATM4E Team Speaker: Sigrun Matthes Abstract Comprehensive assessment of the climate impact of flight movements is of increasing interest to the aviation sector as a requirement for identifying climate-optimal aircraft trajectories when developing strategies for sustainable aviation. Climate impact assessment needs to quantify impacts of CO 2 and non-co 2 emissions, comprising in particular effects of contrailcirrus, and nitrogen oxides on atmospheric ozone and methane. However, such comprehensive environmental impact information is generally not available during flight planning and generation of such data is not yet operational practice. Hence, the purpose of this study is to present a concept how such advanced MET information can be made available as a service via climate and environmental change functions (ECFs), which have the potential to serve as an interface to air traffic management. In that context we present ideas on future implementation of such advanced meteorological services into air traffic management and trajectory planning by relying on ECFs. The work presented here relates to the SESAR2020 Exploratory Research project ATM4E (Air Traffic Management for Environment) which aims to develop MET services required for climate-optimisation, as well as to present a methodology which allows to establish a multi-criteria environmental impact assessment directly in the flight planning process, and to study changing traffic flows due to environmental optimization. Introduction Aviation has the potential to reduce its climate impact by performing a trajectory optimisation under the criteria minimal of climate impact, hence by planning climate-optimized trajectories. Such climate optimized trajectories rely on flying in regions of the atmosphere which are less sensitive to aviation emissions and avoid regions where aviation emissions have a large climate impact. Aviation emissions have an impact on climate change by CO 2 and non-co 2 effects, comprising direct effects, carbon dioxide (CO 2 ) and water vapour, and indirect effects from nitrogen oxide emissions and contrail and contrail cirrus. Nitrogen oxides form ozone (warming) and subsequently influence (reduce) atmospheric lifetime of methane (cooling). It is noted here, that impacts of non-co 2 emission vary strongly with position and time of emission, resulting in a mitigation potential by avoiding regions which are most sensitive. Hence, in order to plan such climate-optimised trajectories, corresponding impact information on climate change needs to be available during the planning process. However, such comprehensive environmental impact information is generally not available during flight planning and generation of such data is not yet operational practice. Overall, air traffic emissions contribute to anthropogenic warming by around 5% through CO 2 and non-co 2 impacts [Sausen und Schumann, 2000; Lee et al., 2010] including contrail cirrus. Aviation stakeholders, European and national authorities implemented a series of initiatives that comprise in their workprogrammes the intention to make future aviation sustainable, e.g., the European

Commission implemented under its Framework Programmes, CleanSky Joint Technology Initiative (JTI), green aeronautical projects and SESAR2020 Joint Undertaking (JU).

2 Commission implemented under its Framework Programmes, CleanSky Joint Technology Initiative (JTI), green aeronautical projects and SESAR2020 Joint Undertaking (JU). Previous research has shown that changing aircraft trajectories to avoid climate sensitive regions has the potential to reduce the climate impact of aviation [Green, 2005]. Studies which focus on individual impact types e.g., [Sridhar et al., 2011; Schumann et al., 2011; Klima, 2005; Frömming et al., 2011; Sovde et al., 2014] presented trade-offs between climate-optimised and cost-optimised trajectories for various regions of the earth (cross-polar, North Atlantic, Pacific traffic). More recent studies similarly exploited benefit and costs of contrails avoidance by analysing an aircraft trajectory [Hartjes et al., 2016] or tested route optimisation for climate optimisation [Matthes et al., 2012; Grewe et al., 2017; Niklaß et al., 2017]. A concept on how perform a multi-criteria environmental assessment of aircraft trajectories was presented recently [Matthes et al., 2017]. This study goes one step beyond and, first, applies algorithmic climate change functions to generate advanced MET data for a specific day in a case study. Second, we present how strategic optimisation targets can be varied in order to perform trajectory optimisation for generating economically-optimal versus climate-optimal solutions. Hence, the purpose of this study is to present algorithmic ECFs which can be made available as designated advanced MET information to Air Traffic Management (ATM) via climate and environmental change functions (ECFs), having the potential to serve as an interface to air traffic management and enabling environmental assessment and optimisation. Climate Impact Assessment via environmental change functions The flight planning tool receives information on climate impact of aviation emissions for the airspace where the aircraft is flying as four dimensional environmental change functions. As interface functions the concept relies on functions which enable a direct link between aviation emissions and environmental impact, so called climate or environmental change functions, CCF and ECF respectively, depending on location, geographic position and altitude, and time of emission. ECFs are provided in climate impact metrics (e.g. change in radiative balance or temperature) per emitted amount, per fuel burnt or per kilometre flown. Figure 1: Algorithmic climate change functions contrails (10-12 K/km), water vapour (10-15 K/kg fuel) and nitrogen oxides (10-12 K/kg NO x ) 18 Dec 2015, 0:00, 18:00, flight level FL390.

3 In this study, we present algorithmic climate change functions which allow to calculate the ECFs based on readily available MET info, i.e., temperature, humidity, vorticity, and background concentrations (meteorological key parameters). An overview of how to generate such algorithms, as developed within ATM4E, can be found in Van Manen and Grewe (2017). In Figure 1 we show algorithmic ECFs over Europe for a case study. Separate climate change functions are provided for contrails on a per kilometre flown basis, for water vapour per kilogram fuel burnt and nitrogen oxides per emitted NO x. During the day the ECFs are varying, also related to synoptic weather patterns. In our study, we propose to test the applicability of aecfs derived from meteorological hindcast data which could be substituted by meteorological forecast data in a future implementation. During flight planning in the use case climate-optimised aircraft trajectory, we use a mathematical formulation of objective function which combines economic costs with climate impact using individual ECFs (Equation 1). Such expanded objective functions calculating overall impact I are required for environmental assessment and optimisation of aircraft trajectories, and they use Cash Operating Costs (COC), time of mission t mission, mass fuel burn m fuel, corresponding ECF i and coefficients c i for individual putting weights on individual environmental effects and impacts. (1) Climate Optimisation of aircraft trajectories Using aecfs in an expanded objective function leads to trajectory optimisation which can be performed with different strategic weights for mitigation of climate impact. For a single flight fuel-optimal versus climate-optimized trajectory solutions are evaluated in the flight planning tool TOM (Lührs et al., 2016) using prototypic ECFs and identifying mitigation potential leading to the identification of a Pareto-front relating climate impact mitigation potential with economic costs. Using advanced MET data for an environmental optimisation by adapting corresponding objective functions used in TOM, enables to assess climate impact and to perform a climateoptimisation. For a flight from London Heathrow (LHR) to Istanbul (IST) aircraft trajectory was optimized under a series of objectives functions (Equation (1)), by varying individual weights from fuel optimal case to climate-minimal solution shown in Figure 2. ECFs used in this optimisation are prototypes of ECFs. The resulting Pareto front is shown in Figure 2, together with trajectories from three distinct solutions, the reference case, and solutions for 1% and 5% percent fuel increase, resulting in a climate impact mitigation by reducing ATR by 12% and 25%, respectively.

Figure 2: Pareto-Front for climate optimisation calculated for single aircraft trajectory London to Istanbul, climate metric Average Temperature Response (ATR), from Matthes et al., 2017.

4 Figure 2: Pareto-Front for climate optimisation calculated for single aircraft trajectory London to Istanbul, climate metric Average Temperature Response (ATR), from Matthes et al., Discussion ECFs allow to perform a climate-optimisation by ATM. Beside climate-optimisation shown in this study, aecfs can also be applied to assess overall environmental impact, by calculating during the flight planning process simultaneously associated climate impact. Within the ATM4E project, 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 over Europe. By including additional ECFs representing impact on air quality and noise issues, this MET service concept initially developed for climate optimisation of aircraft trajectories is expanded to a full environmental assessment. In the light of collaborative decision-making such an expanded objective function enables environmental assessment as well as environmental optimisation. This simultaneous provision and integration of environmental change functions via advanced MET services enables to perform a multi-criteria environmental assessment during trajectory planning (Matthes et al., 2017). These ECFs are able to represent environmental impact due to changes in air quality, noise and climate impact. Implementation of advanced MET service for climate-optimisation For future implementation available standard MET information from forecasts will be used in order to calculate individual ECFs, and make them available in the flight planning system. From a conceptual point of view such climate change functions and an expanded objective function can be applied during strategic and tactical phase of flight planning. An algorithm, translated in a mathematical formula, uses standard MET information for the airspace and calculates algorithmic based ECFs to be used for ATM. During trajectory planning either the ATM tool will combine standard MET information with the algorithm or it will rely on an advanced MET service which directly provides algorithm-based ECFs for the airspace or corridor, enabling to identify climate-optimal trajectory solutions. For implementation in the Cockpit, similarly, an architecture can be selected which provides dedicated service only for a limited regions. For this purpose information is extracting from advanced MET data with larger geographic coverage, in order to provide only required data, e.g. in a relevant corridor for an individual flight, in order to have efficient information and limit overall amount of communication.

Figure 3: Flowchart of Environmental Assessment of aircraft trajectory management using ATM4E algorithmic environmental change functions (aecf) concept, elements newly introduced by ATM4E highlighted

5 Figure 3: Flowchart of Environmental Assessment of aircraft trajectory management using ATM4E algorithmic environmental change functions (aecf) concept, elements newly introduced by ATM4E highlighted in green, from [Matthes et al., 2017] For a use case on climate optimisation, such advanced MET service would allow planning of climate-optimised trajectories by ATM, as well as studying and characterising changes in traffic flows due to environmental optimisation and associated trade-offs between distinct strategic measures. The ultimate goal of such a concept is also to make available a comprehensive assessment framework for environmental performance of aircraft operations, by providing key performance indicators (KPIs) on climate impact, air quality and noise, as well as a tool for environmental optimisation of aircraft trajectories. When developing future sustainable aviation, a quantitative validation of environmental performance requires an expansion of currently defined environmental KPIs. Acknowledgement The project ATM4E has received funding from the SESAR Joint Undertaking under grant agreement No under European Union s Horizon 2020 research and innovation programme.

6 References Frömming, C.; Ponater, M.; Dahlmann, K.; Grewe, V.; Lee, D.S.; Sausen, R. Aviation-induced radiative forcing and surface temperature change in dependency of the emission altitude. J. Geophys. Res. Atmos. 2012, 117, D Grewe, V.; Frömming, C.; Matthes, S.; Brinkop, S.; Ponater, M.; Dietmüller, S.; Jöckel, P.; Garny, H.; Tsati, E.; Dahlmann, K.; et al. Aircraft routing with minimal climate impact: The REACT4C climate cost function modelling approach (V1.0). Geosci. Model Dev. 2014, 7, Grewe, V.; Matthes, S., Frömming, C., Brinkop, S., Jöckel, P., Gierens, K., Champougny, T., Fuglestvedt, J., Haslerud, A., Irvine, E., and Shine, K. Feasibility of climate-optimized air traffic routing for trans-atlantic flights, Environ. Res. Lett. 2017, Hartjes, S.; Hendriks, J.; Visser, H. Contrail Mitigation through 3D Aircraft Trajectory Optimization. In Proceedings of the 16th AIAA Aviation Technology, Integration, and Operations Conference, Washington, DC, USA, June Irvine, E.A.; Hoskins, B.J.; Shine, K.P.; Lunnon, R.W.; Frömming, C. Characterizing North Atlantic weather patterns for climate-optimal aircraft routing. Meteorol. Appl. 2013, 20, Klima, K. Assessment of a Global Contrail Modeling Method and Operational Strategies for Contrail Mitigation. Ph.D. Thesis, Massachusetts Institute of Technology, Cambridge, MA, USA, 23 June Lee, D.; Pitari, G.; Grewe, V.; Gierens, K.; Penner, J.; Petzold, A.; Prather, M.; Schumann, U.; Bais, A.; Berntsen, T.; et al. Transport impacts on atmosphere and climate: Aviation. Atmos. Environ. 2010, 44, Lührs, B.; Niklass, M.; Froemming, C.; Grewe, V.; Gollnick, V. Cost-Benefit Assessment of 2D and 3D Climate And Weather Optimized Trajectories. In Proceedings of the 16th AIAA Aviation Technology, Integration, and Operations Conference,Washington, DC, USA, June 2016; American Institute of Aeronautics and Astronautics: Reston, VA, USA, Matthes, S.; Grewe, V.; Dahlmann, K.; Frömming, C.; Irvine, E.; Lim, L.; Linke, F.; Lührs, B.; Owen, B.; Shine, K.; Stromatas, S.; Yamashita, H.; Yin, F. A Concept for Multi-Criteria Environmental Assessment of Aircraft Trajectories. Aerospace 2017, 4, 42. Matthes, S.; Schumann, U.; Grewe, V.; Frömming, C.; Dahlmann, K.; Koch, A.; Mannstein, H. Climate optimized air transport. In Atmospheric Physics: Background-Methods Trends; Schumann, U., Ed.; Springer: Berlin/Heidelberg, Germany, 2012; pp Niklaß, M.; Lührs, B.; Grewe, V.; Dahlmann, K.; Luchkova, T.; Linke, F.; Gollnick, V. Potential to reduce the climate impact of aviation by climate restricted airspaces. Trans. Policy 2017, DOI: /1.D0045. Sausen, R.; Schumann, U. Estimates of the climate response to aircraft CO2 and NOx emissions scenarios. Clim. Chang. 2000, 44, Søvde, O.; Matthes, S.; Skowron, A.; Iachetti, D.; Lim, L.; Owen, B.; Hodnebrog, T.; Di Genova, G.; Pitari, G.; Lee, D.; et al. Aircraft emission mitigation by changing route altitude: A multi-model estimate of aircraft NO x emission impact on O 3 photochemistry. Atmos. Environ. 2014, 95, Van Manen, J. und Grewe, V., Algorithmic climate change functions for the use in eco-efficient flight planning, submitted to Transp. Res. Part B, 2017.

Climate optimised aircraft trajectories based on advanced MET service for sustainable aviation

Climate optimised aircraft trajectories based on advanced MET service for sustainable aviation Sigrun Matthes DLR, Institute of Atmospheric Physics Volker Grewe, Benjamin Lührs, Florian Linke, Emma Irvine,