Can hail and rain nucleate cloud droplets?

Abstract

We present results from moist convection in a mixture of pressurized sulfur hexa-flouride (liquid and vapor) and helium (gas) to model the wet and dry components of the earth's atmosphere. To allow for homogeneous nucleation, we operate the experiment close to critical conditions. We report on the nucleation of microdroplets in the wake of large cold liquid drops falling through the supersaturated atmosphere and show that the homogeneous nucleation is caused by isobaric cooling of the saturated sulfur hexaflouride vapor. Our results carry over to atmospheric clouds: falling hail and cold rain drops may enhance the heterogeneous nucleation of microdroplets in their wake under supersaturated atmospheric conditions. We also observed that under appropriate conditions settling microdroplets form a rather stable horizontal cloud layer, which separates regions of super and sub critical saturation.

6 pages, 3 figures

References in corpus (2)

• Collisional Aggregation due to Turbulence
• Dynamics and Selection of Giant Spirals in Rayleigh-Benard Convection

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• Droplets in isotropic turbulence: deformation and breakup statistics
• Supersaturation in the Wake of a Precipitating Hydrometeor and its Impact on Aerosol Activation
• On the ice-nucleating potential of warm hydrometeors in mixed-phase clouds