The impact of aircraft engine emissions and alternative fuels on contrail formation

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Contrails are an important component of the climate impact of aircraft, with long lived contrails contributing 50% or more of the total radiative forcing from aviation. This is particularly true for long lived contrails, which can generate a considerable warming as they spread out over time. Contrails are a key target for reducing the climate impact of aviation. Alternative fuels have been proposed as a potential solution to aviation's climate impact, by reducing lifecycle CO2 emissions and reducing particulate emissions from aircraft engines. Even though alternative fuels currently account for a tiny percentage of overall aviation fuel burn, they are expected to become more prevalent in the coming years and some airlines are already routinely using them on commercial flights. Furthermore, different aircraft engines can have particle emissions which are different by an order of magnitude and the effect that this has on contrail properties has not yet been studied using satellite observations. While different aircraft engine particle emissions have been shown to have an impact on the short-term contrail properties, their impact on the development of contrails is unclear and is currently assessed using models . These models are based on our theoretical understanding of ice crystal behaviour and cloud processes, but are subject to considerable uncertainty, particularly in the behaviour of the contrail over time. To assess the impacts of alternative fuels through improved contrail modelling, new observations linking the contrail lifecycle to the properties of the generating aircraft are required. This will be based around the use and exploitation of satellite data. The overall aim of this project is to improve our simulations of impact of aircraft engine particle emissions and alternative fuels on contrail formation and development. This requires an understanding of which contrails should be visible to satellite (O1), identification and characterisation of contrails in satellite imagery (O2) before the use for constraining model simulations (O3). EPSRC areas: particle technology and biophysics