Which process describes the growth of ice crystals in cold clouds?

The growth of ice crystals in cold clouds is best described by the Bergeron process. This process occurs in mixed-phase clouds where both ice crystals and supercooled liquid water droplets exist. In this environment, the vapor pressure over the ice crystals is lower than that over the surrounding liquid water droplets, which causes water vapor to move from the droplets to the ice crystals. As the ice crystals absorb this vapor, they grow larger, while the liquid droplets shrink and may eventually evaporate.

The process involves the transformation of vapor into solid ice rather than liquid water, which distinguishes the Bergeron process from other mechanisms like condensation or freezing. Evaporation refers to the change of liquid water into vapor, which does not apply to the growth of ice crystals. Similarly, condensation is the process of vapor turning into liquid, which does not capture the solid-state growth that occurs in this situation. Freezing, while related to the phase change, does not specifically account for the growth mechanism in cold clouds involving both ice and supercooled water. Thus, the Bergeron process is the most accurate and descriptive term for this phenomenon.