Eco-efficient flight trajectories &#8211; Using a Lagrangian approach in EMAC to investigate contrail formation in the mid latitudes&#160;
Authors: Peter Patrick , Matthes Sigrun , Frömming Christine , Grewe Volker 
Published: December 2021

&lt;p&gt;Air transport has for a long time been linked to environmental issues like pollution, noise and climate change. While CO2 emissions are the main focus in public discussions, non-CO2 emissions of aviation may have a similar impact on the climate as aviation's carbon dioxide, e.g. contrail cirrus, nitrogen oxides or aviation induced cloudiness. While the effects of CO2 on climate are independent of location and situation during release, non-CO2 effects such as contrail formation vary depending on meteorological background. Previous studies investigated the influence of different weather situations on aviation&amp;#8217;s climate change contribution, identifying climate sensitive regions and generating data products which enable air traffic management (ATM) to plan for climate optimized trajectories.&lt;/p&gt;
&lt;p&gt;The research presented here focuses on the further development of methods to determine the sensitivity of the atmosphere to aviation emissions with respect to climate effects in order to determine climate optimized aircraft trajectories. While previous studies focused on characterizing the North Atlantic Flight Corridor region, this study aims to extend the geographic scope by performing Lagrangian simulations in a global climate model EMAC for the northern hemispheric extratropical regions and tropical latitudes. This study addresses how realistically the physical conditions and processes for contrail formation and life cycle are represented in the upper troposphere and lower stratosphere by comparing them to airborne observations (HALO measurement campaign, CARIBIC/IAGOS scheduled flight measurements), examining key variables such as temperature or humidity. Direct comparison of model data with observations using clusters of data provides insight into the extent to which systematic biases exist that are relevant to the climate effects of contrails. We perform this comparison for different vertical resolutions to assess which vertical resolution in the EMAC model is well suited for studying contrail formation. Together with this model evaluation using aircraft measurements, the overall concept for studying the life cycle of contrails in the modular global climate model EMAC is introduced. Hereby, the concept for the development of a MET service that can be provided to ATM to evaluate contrail formation and its impact on the climate along planned aircraft trajectories is presented.&lt;/p&gt;
&lt;p&gt;Within the ClimOP collaborative project, we can investigate which physical processes determine the effects of contrails on climate and study their spatial and temporal variation. In addition, these climate change functions enable case studies that assess the impact of contrails on climate along trajectories and use alternative trajectories that avoid these regions of the atmosphere that have the potential to form contrails with a large radiative effect.&lt;/p&gt;
&lt;p&gt;This study is part of the ClimOP project and has received funding from European Union&amp;#8217;s Horizon 2020 Research and Innovation Programme under Grant Agreement N&amp;#176; 875503 (ClimOP) and from the SESAR Joint Undertaking under grant agreements No 699395 (FlyATM4E).&amp;#160;&lt;/p&gt;