Latent heat feedbacks and the self-lofting of seeded ice plumes: Insights from bin microphysics simulations

Abstract. The interaction between environmental dynamics and microphysical processes governs the efficacy of glaciogenic cloud seeding, yet the extent to which initial vertical wind conditions dictate the evolution of seeded ice plumes remains poorly constrained. We investigate the dynamical and microphysical life cycle of ice plumes in supercooled stratiform clouds using idealized Large-Eddy Simulations (LES) coupled with the bin microphysics scheme SCALE-AMPS. Simulations of a targeted CLOUDLAB seeding experiment are constrained and validated by in situ observations. An ensemble of 20 simulations initialized with varying vertical wind velocities reveals a fundamental transition: while the initial trajectory is kinematically governed by the environmental vertical wind at cloud seeding, the long-term evolution is dominated by internal thermodynamic feedbacks. We identify a "self-lofting" mechanism wherein buoyancy generated by latent heat release from rapid ice growth overcomes initial subsidence, causing even downdraft-seeded plumes to eventually ascend. This thermodynamic response creates a structural trade-off: plumes initiated in updrafts are terminated by the cloud-top inversion, whereas those in downdrafts experience delayed ascent, resulting in a lager vertical dispersion. This expanded vertical extent compensates for the lower mean altitude of downdraft plumes, ensuring their geometrical detectability by downstream sampling in in observations. Microphysically, downdraft plumes undergo transient sublimation near cloud base but recover following buoyancy-driven re-ascent. These findings demonstrate that glaciogenic seeding is dynamically robust in low stratus clouds, as the seeded ice plume acts as an active thermodynamic agent capable of sustaining its residence time in the mixed-phase layer independent of the initial vertical wind state.