The microphysics of ice and precipitation development in tropical cumulus clouds

The process was analyzed from data collected using state-of-the-art cloud particle probes during 54 Learjet penetrations of strong cumulus updraft cores over open ocean in a temperature range from 5° to -20°C. Repeated Learjet penetrations of an updraft core containing 3-5 g m⁻³ supercooled liquid showed an order-of-magnitude decrease in liquid mass concentration 3 min later at an elevation 1-1.5 km higher in the cloud.

The aircraft observations were simulated using a one-dimensional cloud model with explicit bin microphysics. The model was initialized with drop and ice particle size distributions observed prior to rapid glaciation. Simulations show that the model can explain the observed rapid glaciation by the drop-freezing secondary ice production process and subsequent riming, which results when large supercooled drops collide with ice particles.