Large-eddy simulation of contrail evolution in the vortex phase and its interaction with atmospheric turbulence
Abstract. In this work, the evolution of contrails in the vortex and dissipation regimes is studied by means of fully three-dimensional large-eddy simulation (LES) coupled to a Lagrangian particle tracking method to treat the ice phase. In this paper, fine-scale atmospheric turbulence is generated and sustained by means of a stochastic forcing that mimics the properties of stably stratified turbulent flows as those occurring in the upper troposphere and lower stratosphere. The initial flow field is composed of the turbulent background flow and a wake flow obtained from separate LES of the jet regime. Atmospheric turbulence is the main driver of the wake instability and the structure of the resulting wake is sensitive to the intensity of the perturbations, primarily in the vertical direction. A stronger turbulence accelerates the onset of the instability, which results in shorter contrail descent and more effective mixing in the interior of the plume. However, the self-induced turbulence that is produced in the wake after the vortex breakup dominates over background turbulence until the end of the vortex regime and controls the mixing with ambient air. This results in mean microphysical characteristics such as ice mass and optical depth that are slightly affected by the intensity of atmospheric turbulence. However, the background humidity and temperature have a first-order effect on the survival of ice crystals and particle size distribution, which is in line with recent studies.