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The REACT4C data comprise simulation data created within the REACT4C project. The REACT4C project is based on current scientific knowledge, that the climate impact of non-CO2 aviation emissions depends on emission location, altitude, prevailing weather situation and local time. The main aim of REACT4C was to investigate the feasibility and the potential of climate-optimised flight routing. The CCFs, which were developed within this project, describe the atmospheric sensitivity to aviation emissions, depending on geographic position, flight altitude and time and constitute the basis for weather dependent climate-optimised trajectories. A modelling chain was established for the optimisation of aircraft trajectories with respect to their weather-dependent climate impact regarding CO2 and non-CO2 aviation emissions. The project showed, that it is possible to significantly reduce the overall climate impact of aviation by means of weather dependent flight trajectory at only moderate cost increases.
Within this study, the ECHAM/MESSy Atmospheric Chemistry Model EMAC was used, the Modular Earth Submodel System (MESSy) couples various submodels to the core atmospheric model ECHAM5. The chemistry is calculated by the submodel MECCA. Non-methane hydrocarbon chemistry is employed. The submodel ATTILA enables Lagrangian transport. Two newly developed submodels (AIRTRAC and CONTRAIL) were employed within the present study. EMAC is used in a T42 spectral resolution with 41 vertical layers from the surface to 5 hPa.
Within this study, EMAC is employed to calculate the atmospheric impact of standardized air traffic emissions of NOx and H2O on chemical composition, formation of contrails and contrail cirrus at predefined longitudes, latitudes, altitudes, and times. The location- and time dependent specific climate impacts per emission are referred to as climate change functions (CCFs). The CCFs are a measure for the sensitivity of a certain emission location to aviation climate impact. To derive the CCFs, a 4-dimensional time-region grid was defined. The time-region grid covers cruise-altitude-relevant pressure levels from 400 to 200 hPa over the North Atlantic area (30-80◦ N, 80-0◦ W), in total yielding 168 grid points. At each of these time-region grid points, a standardized pulse emission of NOx and H2O is released by means of the submodel TREXP within one model time step of 15 min. A Lagrangian approach was chosen as it facilitates the calculation of CCFs for a number of time regions within a single EMAC simulation. The tracer concentration from the pulse emission is equally distributed on 50 air parcel trajectories, which are started from the EMAC grid box in which the time-region grid point lies. The air parcel trajectories are advected and mixed with other air parcel trajectories. The contribution of the pulse emission to the atmospheric composition is calculated proportionally to the background for each air parcel trajectory. Also, the contrail formation is initiated depending on background conditions for each air parcel trajectory. The temporal development according to spreading, sublimation, and sedimentation of ice particles is then parameterized. For the radiative transfer calculations, the properties of air parcel trajectories are transferred to grid point space. The coverage with contrails, their properties, the chemical perturbations and the radiative forcing for each relevant species, each time-region and for 5 winter weather situations and 3 summer weather situations comprise the raw data, which are then further processed to generate the CCFs.