High-resolution modelling of early contrail evolution from hydrogen-powered aircraft

Abstract. In this study, we investigate the properties of young contrails formed behind hydrogen-powered aircraft, particularly compared to contrails from conventional kerosene combustion. High-resolution simulations of individual contrails are performed using the EULAG-LCM model, a large-eddy simulation model with fully coupled particle-based ice microphysics.

Previous studies on early contrail evolution during the vortex phase explored a range of meteorological and aircraft-related parameters but focused on contrails with ice crystal numbers and water vapor emissions typical of kerosene combustion.

This study examines the early H₂-contrail evolution, starting tenths of a second after exhaust emission when ice crystal formation is complete. Two key parameters are adjusted: the amount of emitted water vapor and the number of ice crystals formed during the initial stage. The emitted water vapor varies between 3.7 and 38.6 g per flight meter, depending on the fuel and aircraft type. The initial ice crystal number spans four orders of magnitude, from approximately 10¹⁰ to 10¹⁴ ice crystals per flight meter. Additionally, we extend our atmospheric scenarios to ambient temperatures up to 235 K as H₂ contrails can form in warmer conditions where kerosene plumes typically cannot.

Our results show that vortex phase processes reduce the four-order magnitude difference in ice crystal number to two orders of magnitude. Moreover, relative ice crystal loss increases with increasing ambient temperatures and decreasing relative humidity levels.

Finally, we extend the parametrization of ice crystal loss from a previous study to include scenarios of contrails from hydrogen propulsion systems.