Ice storms are weather phenomena caused by freezing rain. The falling rain comes into contact with surfaces and turns into a thin sheet of ice. Ice storms cause accidents, take power lines down and cause serious damage.
It starts with a layer of warmer (not freezing) air above a layer of huge-freezing temperatures lower down. Frozen precipitation melts to rain while falling into the warm air layer, and then begins to refreeze in the cold layer below.
- If the precipitate refreezes while still in the air, it will land on the ground as sleet.
- Or, the liquid droplets continue to fall without freezing. They pass through the cold air just above the surface. This thin layer of air cools the rain to a temperature below freezing (0 °C or 32 °F), but the drops themselves do not freeze. This is a phenomenon called supercooling.
When the supercooled drops strike ground or anything else below 0 °C (32 °F) (e.g. power lines, tree branches, aircraft), a layer of ice builds up, hence "freezing rain".
- Gay, David A.; Robert E. Davis (December 30, 1993). "Freezing rain and sleet climatology of the southeastern USA" (PDF). Climate Research. 3 (1): 209–220. doi:10.3354/cr003209.
- "Ice Storms". City of Savannah, Georgia. Archived from the original on July 28, 2007. Retrieved January 8, 2009.
- University of Illinois. "Cyclones and Fronts: the definition of freezing rain". Retrieved January 9, 2009.