Temporal versus spatial jet phase LES for near-field contrails: Impacts on ice microphysics

Studying the near-field jet/wake is essential for contrail formation because it sets the ice crystal number and persistence. In contrail simulations, two large eddy simulation (LES) formulations are common: a spatial approach, which explicitly resolves spatial development but is computationally intensive, and a temporal approach, which assumes the frozen turbulence hypothesis and is computationally efficient. Both approaches have been utilized in prior contrail studies; however, comparisons between them are limited. In this paper, temporal and spatial formulations of LES were compared to analyze near-field jet contrails under cruise conditions representative of an Airbus A320neowith a LEAP-1A engine. The wake vortex was then initialized from both spatial and temporals jets at two plume ages (t_j = 0.12 s and t_j = 0.5 s) corresponding to the pre-development and developed microphysical stages, respectively. Microphysics were treated with an online-coupled Lagrangian scheme to evaluate ice activation and growth for (i) soot-only and (ii) soot+ambient nuclei. In the jet phase, the temporal jet produced ice microphysical properties that overall were equivalent to those produced by the spatial jet under soot-rich plume and supersaturated conditions; differences observed were within the same order of magnitude for both the mean ice radius and the ice number-based emission index. In the vortex phase, the ice number concentration was inherited from the jet phase, and differences between the temporal and spatial jet initializations diminished with the plume age. Delaying the vortex onset led to relatively smaller particle radii and a slightly higher ice number concentration. Overall, ambient aerosols increased the ice number but slowed crystal growth via water vapor competition, thereby reducing any sensitivity to vortex initialization.