High Supersaturation in the Wake of Falling Hydrometeors: Implications for Cloud Invigoration and Ice Nucleation

Abstract:

Aerosol particles, cloud droplets, and ice crystals, coupled through the supersaturation field, play an important role in the life cycle of convective clouds. We report laboratory observations of copious cloud droplets and ice crystals formed in the warm wake of a falling water drop, which is a laboratory analog for a relatively warm hydrometeor in atmospheric clouds, such as a graupel/hail particle in the wet growth regime. Aerosols were activated in the regions of very high supersaturation due to mixing in the wake. A mechanism is explored for attaining very high supersaturations capable of activating significant fractions of the interstitial aerosols within the lifetime of a convective cloud. The latent heat released from the activation of interstitial aerosols and subsequent growth may provide an additional source of buoyancy for cloud invigoration and may lead to larger concentrations of ice crystals. We explore the potential implications of this mechanism based on a 2D squall line simulation with the Lagrangian particle model McSnow.