Definition
The amount of liquid water present in a cloud or air mass at temperatures below 0°C (32°F), expressed as grams of water per cubic meter of air. Supercooled water remains in liquid form despite being below freezing, and it freezes on contact with an aircraft surface, producing structural icing.
Plain English
How much liquid water is floating in the air at below-freezing temperatures. The water has not frozen yet, but it will the moment it touches the aircraft.
Context Anchor
Seen in icing forecasts, cloud physics discussions, and aircraft icing certification or performance information.
Derivation
Supercooled' comes from Latin super- ('above, beyond') and 'cooled' -- meaning cooled beyond the normal freezing point without actually freezing. The term highlights that the water has gone past the temperature where it should have turned to ice but hasn't yet.
Why Pilots Care
High values signal rapid ice buildup on aircraft surfaces, directly affecting lift, drag, and engine performance.
Grounding Statement
Picture flying through a cloud at -10°C. The cloud is full of tiny liquid droplets that haven't frozen because they have nothing to freeze onto -- until your wing arrives and they freeze on it instantly.
Intuition Check
Do not assume water below freezing is already ice. In this term, the water is still liquid until it hits a surface or otherwise freezes.
Example Sentence 1
The pilot reviewed the icing forecast and saw a band of high supercooled liquid water content along the route.
Example Sentence 2
Forecasters use supercooled liquid water content values to predict how quickly ice will accumulate on the wings during flight through the cloud.