Climate-optimal flight planning developed within REACT4C taking into account specific weather conditions

Aviation contributes to climate change by CO2 and non-CO2 effects. Mitigation of aviation climate impact is one strategic goal spelled out for a durable development of air traffic. One mitigation strategy are operational measures for route optimisation by air traffic management (ATM) to identify climate-optimal flight trajectories. We present a comprehensive approach developed within the collaborative project REACT4C (Reducing Emissions from Aviation by Changing Trajectories for the benefit of Climate, 2010-2013) funded under the European FP7 programme in order to identify such environmental or climate-optimized trajectories. Main objective in this transdisciplinary research project, coordinated by DLR, is to explore the feasibility of and to establish a modelling chain for adopting flight altitudes and flight routes that lessen the climate impact. Second objective is to estimate the overall global effect of such ATM measures in terms of climate change. Flying on a fuel and hence CO2 optimal trajectory requires flight planning based on detailed airspace structure and meteorological conditions. Climate impact of non-CO2 emissions depends on time and position of aircraft, as they are related to atmospheric processes, which vary with background conditions and transport pathways within the atmosphere. Hence, flying climate-optimal requires detailed knowledge on spatial dependence of climate impact. However, such information is in general not available during flight optimisation. Here, REACT4C has expanded an air traffic planning tool in order to be able to identify climate-optimized flight trajectories. We present the overall modelling chain for climate-optimized flight planning, stretching from aviation meteorology over climate impact and leading to climate-optimized flight trajectories. First step is a characterisation of meteorological situations for daily weather conditions with respect to spatial and temporal dependence of atmospheric response and climate impact of aviation emissions. Interface between climate impact and flight planning is established via climate cost functions, which quantify atmospheric climate response (sensitivity) on aviation emissions depending on latitude and time of emission. Our modelling chain development for climate-optimal flight planning was complemented by scientific studies which explore the uncertainty of our procedure and related atmospheric processes. Among aviation climate impact we consider in detail CO2, NOx (via formation ozone and influence on methane), soot, contrail and contrail-cirrus.