A pilot receives a PIREP reporting freezing drizzle at 4,000 feet with tops at 4,500 feet, while another PIREP from a different aircraft at 3,000 feet reports freezing rain. Which explanation best accounts for the difference between these two icing reports?
- AFreezing drizzle indicates a temperature inversion aloft, while freezing rain indicates that no inversion is present
- BFreezing drizzle only occurs in cumuliform clouds, while freezing rain only occurs in stratiform clouds
- CThere is no meteorological difference between freezing rain and freezing drizzle other than droplet size
- DFreezing rain forms when rain falls from a warmer layer aloft into a subfreezing layer near the surface, while freezing drizzle forms from small droplets within a shallow, stratiform supercooled cloud
Show answer & explanationAnswer & explanation
Correct answer: D. Freezing rain forms when rain falls from a warmer layer aloft into a subfreezing layer near the surface, while freezing drizzle forms from small droplets within a shallow, stratiform supercooled cloud
Freezing rain typically results from rain falling from a warm layer above the freezing level (associated with a temperature inversion) into a subfreezing layer near the surface, refreezing on contact with cold surfaces. Freezing drizzle instead forms from small supercooled droplets within a shallow stratiform cloud without necessarily passing through a warm layer aloft, and both can produce hazardous clear icing.
Why the other options are wrong
- A. Freezing rain, not freezing drizzle, is the one associated with a temperature inversion aloft.
- B. Both freezing rain and freezing drizzle are typically associated with stratiform, not cumuliform, cloud types.
- C. There is a meteorological difference beyond droplet size, involving the vertical temperature profile through which the precipitation falls.
Freezing Rain vs. Freezing Drizzle
Freezing rain forms when precipitation falls from an above-freezing layer aloft into a subfreezing surface layer (inversion), while freezing drizzle forms from small droplets within a shallow supercooled stratiform cloud without a warm layer aloft.
- Freezing rain = warm layer aloft + subfreezing surface layer
- Freezing drizzle = shallow stratiform supercooled cloud
- Both indicate hazardous clear icing risk (SLD)
Memory trick: Rain falls through warmth then freezes below; drizzle stays cold throughout.