Regional and Seasonal Dependence of the Potential Contrail Cover and the Potential Contrail Cirrus Cover over Europe

Ambient weather conditions strongly impact contrail formation and persistence. The implementation of contrail avoidance and mitigation strategies, therefore, requires regional and altitude-dependent information on the frequency of contrail occurrence. To this end, we have developed a method to quantify the potential contrail cover based on 10 years of high-resolution reanalysis of climatology and weather data from the European Center for Medium-Range Weather Forecast (ECMWF). We use the Schmidt-Appleman threshold temperature for contrail formation and additionally select thresholds for the relative humidity to evaluate the occurrence of persistent contrails and assess their regional and seasonal variation. We find a potential contrail cirrus cover of 10% to 20% above Europe at higher altitudes of 200 and 250 hPa in the 10-year climatology and a weak seasonal variation. At lower altitudes, near 300 hPa, a steep onset and a high potential contrail cirrus cover of 20% is found in late fall and in winter, decreasing to 2% potential contrail cirrus cover in summer. In comparison to ECMWF data, evaluations using data from the National Centers for Environmental Prediction (NCEP) show a significantly lower potential contrail cirrus cover. Our results help to investigate the seasonal and altitude dependence of contrail mitigation strategies, in particular for warming nighttime contrails that contribute strongly to the total climate impact from aviation

The sketch map tool facilitates the assessment of OpenStreetMap data for participatory mapping

A worldwide increase in the number of people and areas affected by disasters has led to more and more approaches that focus on the integration of local knowledge into disaster risk reduction processes. The research at hand shows a method for formalizing this local knowledge via sketch maps in the context of flooding. The Sketch Map Tool enables not only the visualization of this local knowledge and analyses of OpenStreetMap data quality but also the communication of the results of these analyses in an understandable way. Since the tool will be open-source and several analyses are made automatically, the tool also offers a method for local governments in areas where historic data or financial means for flood mitigation are limited. Example analyses for two cities in Brazil show the functionalities of the tool and allow the evaluation of its applicability. Results depict that the fitness-for-purpose analysis of the OpenStreetMap data reveals promising results to identify whether the sketch map approach can be used in a certain area or if citizens might have problems with marking their flood experiences. In this way, an intrinsic quality analysis is incorporated into a participatory mapping approach. Additionally, different paper formats offered for printing enable not only individual mapping but also group mapping. Future work will focus on advancing the automation of all steps of the tool to allow members of local governments without specific technical knowledge to apply the Sketch Map Tool for their own study areas

Measurements of particle emissions and contrail ice particle properties behind a large passenger aircraft burning 100% sustainable aviation fuel in cruise

The use of sustainable aviation fuels (SAF) derived from biomass and waste materials can provide one approach to partially decarbonize air traffic relatively quickly and offers a pathway to mitigate the non-CO2 climate impacts from long-lived contrails on short time scales. Many SAFs naturally contain no or only low amounts of aromatic compounds which act as soot precursors during combustion. As soot particles serve as primary nucleus for contrail ice, lower soot emissions should result in lower contrail ice particle numbers. In the joint project ECLIF3 (Emissions and Climate Impact of alternative Fuels), DLR, Airbus, Rolls-Royce, Neste and other participants aimed to characterize emissions and contrail properties behind a modern passenger aircraft burning both conventional Jet A-1 fuel and HEFA-SPK (Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene) and a blend of HEFA-SPK and Jet A-1 on both engines on the ground and in flight. For the first time, flight tests in cruise using 100% HEFA-SPK on all engines were feasible in this framework. In two field campaigns in 2021 an Airbus A350-900 equipped with Rolls Royce Trent XWB-84 engines served as source aircraft. With the DLR Falcon 20E5 research aircraft we probed trace gases, volatile and non-volatile particles, and ice particle properties. The independent fuel tanks of the A350 permitted us to sample emissions from reference Jet A-1 and HEFA-SPK in similar meteorological conditions. Measurements of the exhaust closely behind the engine exit and up to several minutes behind the lead aircraft allowed us to characterize both, direct engine emissions depending on engine thrust conditions and the effects on contrail formation and properties. With respect to the Jet A-1 used here, we find a significant reduction in non-volatile particle emissions when burning HEFA-SPK; similar trends are seen in the ice particle numbers in the contrails. The results outline the importance of fuel composition (e.g. sulfur and aromatics content) on particle emissions and contrail formation. The analysis also shows the complexity of the contrail formation process and its dependence on fuel composition, engine thrust and meteorological conditions in the ambient atmosphere

Water vapor and relative humidity in contrail regions

Kondensstreifen liefern den größten individuellen Beitrag zur Klimawirkung des Luftverkehrs, mehr noch als dessen CO2 Emissionen. Die Vorhersage von Kondensstreifen basierend auf Wettervorhersagemodellen, die Charakterisierung ihrer Eigenschaften und ihre Vermeidung erfordern genaue Messungen der Wasserdampfverteilungen in den sich schnell verändernden Kondensstreifen-Regionen. Diese Arbeit entwickelt (1) eine neue Darstellung von Regionen, in denen sich Kondensstreifen bilden können. (2) Es wurden flugzeuggetragene Wasserdampfmessungen durchgeführt und im Hinblick auf Kondensstreifenprozesse ausgewertet. (1) Die Wahrscheinlichkeit der Kondensstreifenbildung über Europa wurde anhand von ECMWF ERA5-Daten in verschieden Höhen saisonal für die Kampagnenplanung analysiert und dargestellt. Die besten Bedingungen für die Bildung von Kondensstreifen wurden Ende Herbst und im Winter in Höhen zwischen 250 hPa und 300 hPa gefunden. (2) Während der Flugmesskampagne Emission and Climate Impact of Alternative Fuels 3 (ECLIF 3) im April 2021 wurden mittels Massenspektrometer auf dem Forschungsflugzeug Falcon Wasserdampfmessungen in und außerhalb von Kondensstreifen durchgeführt. In jungen Kondensstreifen wurde aufgrund der hohen Eisanzahlkonzentrationen eine Verschiebung der relativen Feuchte in Richtung EisSättigung beobachtet. Außerdem führen die Wasserdampfemissionen des Triebwerks zu einer Erhöhung der Wasserdampfkonzentration in jungen Kondensstreifen von bis zu 10%. Neben den Prozessstudien sollen die Messungen zur Evaluation von Modellen genutzt werden, um zukünftig die Reduzierung von Kondensstreifen zu ermöglichen. Contrails provide the largest individual contribution to the climate impact of aviation, even more than its CO2 emissions. Predicting contrails based on weather prediction models, characterizing their properties, and avoiding them require accurate measurements of water vapor distributions in rapidly changing contrail regions. This work develops (1) a new visualization of regions where contrails may form. (2) Airborne water vapor measurements were performed and evaluated regarding contrail processes. (1) The probability of contrail formation over Europe was analyzed seasonally for campaign planning using ECMWF ERA5 data at different altitudes. The best conditions for contrail formation were found during late autumn and in winter at altitudes between 250 hPa and 300 hPa. (2) During the flight measurement campaign Emission and Climate Impact of Alternative Fuels 3 (ECLIF 3) in April 2021, water vapor measurements were performed in and outside contrails using a mass spectrometer on the research aircraft Falcon. In young contrails, a shift in relative humidity toward ice saturation was observed due to high ice number concentrations. In addition, water vapor emissions from the engine lead to an increase in water vapor concentration in young contrails of up to 10%. In addition to the process studies, the measurements will be used to evaluate models to enable contrail reduction in the future

The sketch map tool facilitates the assessment of OpenStreetMap data for participatory mapping

A worldwide increase in the number of people and areas affected by disasters has led to more and more approaches that focus on the integration of local knowledge into disaster risk reduction processes. The research at hand shows a method for formalizing this local knowledge via sketch maps in the context of flooding. The Sketch Map Tool enables not only the visualization of this local knowledge and analyses of OpenStreetMap data quality but also the communication of the results of these analyses in an understandable way. Since the tool will be open-source and several analyses are made automatically, the tool also offers a method for local governments in areas where historic data or financial means for flood mitigation are limited. Example analyses for two cities in Brazil show the functionalities of the tool and allow the evaluation of its applicability. Results depict that the fitness-for-purpose analysis of the OpenStreetMap data reveals promising results to identify whether the sketch map approach can be used in a certain area or if citizens might have problems with marking their flood experiences. In this way, an intrinsic quality analysis is incorporated into a participatory mapping approach. Additionally, different paper formats offered for printing enable not only individual mapping but also group mapping. Future work will focus on advancing the automation of all steps of the tool to allow members of local governments without specific technical knowledge to apply the Sketch Map Tool for their own study areas