ATPL Meteorology Practice Test

Freezing rain (FZRA) and drizzle (DZ) occur under specific atmospheric conditions that involve the presence of supercooled water droplets. Supercooled droplets are liquid water that remains in liquid form even when air temperatures are below freezing.

For freezing rain, while the cloud might be situated in warmer air, the droplets must develop in this warm cloud before descending into a layer of cold air close to the surface. As these supercooled droplets fall through this cold air, they remain liquid until they come in contact with cold surfaces, where they freeze upon impact, creating the characteristic ice coating associated with freezing rain.

This phenomenon is dependent on the presence of warm cloud conditions, which can create droplets that stay in a liquid state despite sub-freezing temperatures encountered closer to the ground. Therefore, for freezing rain or drizzle to occur, the droplets must indeed be supercooled, and the process begins in warm clouds, where conditions are suitable for the formation of these supercooled droplets.