Kinematic properties of regions that can involve persistent contrails over the North Atlantic and Europe during April and May 2024

Abstract

Contrails can last for many hours in the sky if they form in ice supersaturated regions (ISSRs). Contrail formation is possible once the ambient air is sufficiently moist and cold (below -40°C). Contrails are persistent when the ambient relative humidity with respect to ice is at least 100%. Cirrus clouds and contrails consist of ice crystals, which move with the wind. Ice supersaturation is an immaterial feature, which does not generally move with the wind. However, the movement of ISSRs relative to the winds is currently unknown. We analyse the movement of ISSRs and the wind using data for aviation weather forecasts, the WAWFOR package, from the German Weather Service (DWD). Our results demonstrate the kinematic differences and similarities of the movement of ISSRs in comparison to the wind. We show that the ISSRs on average move slower than the wind at the same location, the direction of movement is usually quite similar and the distributions of both velocities follow Weibull distributions. The almost identical direction of the movements is beneficial for contrail lifetimes, but the lifetime of contrails is not generally determined by the lifetime of ISSRs. Contrails are blown out of ISSRs with the wind. We assume that our study can be used as a basis for further analyses of the movement of ISSRs. Furthermore, our method of analysis is applicable to other extended features or areas, for instance to areas where aircraft non-CO2 emissions would have a particularly large climate effect.