Phase transformation of mixed‐phase clouds

• Published in: Quarterly journal of the Royal Meteorological Society Vol. 129; no. 587; pp. 19 - 38
• Main Authors: Korolev, Alexei, Isaac, George
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-01-2003; Wiley
• Subjects: Cloud physics; Earth, ocean, space; Exact sciences and technology; External geophysics; Glaciation time; Meteorology; Vertical speed; Glaciation; Ice; Concentration; Evaporation; Droplet; Mixed layer; Life cycle; Cloud physics; Time average; One dimensional model; Water content; Numerical simulation; Formation mechanism; Glaciation time
• ISSN: 0035-9009; 1477-870X
• DOI: 10.1256/qj.01.203

The glaciation time of a mixed‐phase cloud due to the Wegener–Bergeron–Findeisen mechanism is calculated using an adiabatic one‐dimensional numerical model for the cases of zero, ascending, descending and oscillating vertical velocities. The characteristic values of the glaciation time are obtained for different concentrations of ice particles and liquid‐water content. Steady state is not possible for the ice‐water content/total water content ratio in a uniformly vertically moving mixed‐phase parcel. The vertical oscillation of a cloud parcel may result in a periodic evaporation and activation of liquid droplets in the presence of ice particles during infinite time. After a certain time, the average ice‐water content and liquid‐water content reach a steady state. This phenomenon may explain the existence of long‐lived mixed‐phase stratiform layers. The obtained results are important for understanding the mechanisms of formation and life cycle of mixed‐phase clouds. Copyright © 2003 Royal Meteorological Society