The polar dance that caused snow to fall across the South in January has been studied for decades, but scientists still hope to answer many remaining questions.
Miles above the Earth, two bands of fast-moving air – the polar jet stream and the stratospheric polar vortex – sometimes tango together to influence weather in the northern hemisphere.
As the Arctic continues warming up to three times faster than the rest of the planet, some researchers say the two atmospheric patterns are working together to bring about bone-chilling cold air outbreaks more often.
But questions about the interaction aren’t fully settled and remain a subject of scientific debate.
When multiple things are all happening at the same time, “it’s difficult to disentangle the cause,” said Isla Simpson, a scientist with the National Center for Atmospheric Research.
One thing is sure, the phrase “polar vortex” has captured public attention and is now often misused to describe short-term bouts of frigid weather, experts told USA TODAY. Polar vortex is not a synonym for “cold snap,” according to the Polar Vortex Blog at Climate.gov, and it’s not the only weather pattern to blame for blasts of cold air.
What are the polar jet stream and the stratospheric polar vortex?
The high-speed polar jet stream typically spins at a height of 5 to 9 miles above the Earth’s surface, in the lower layer of the atmosphere known as the troposphere.
The jet undulates up and down in ridges and troughs that help steer weather systems around in the northern hemisphere, from cold fronts to hurricanes. When hot, dry conditions occur in one peak or valley of the jet, another may experience colder, wetter conditions.
The polar vortex might be considered the jet stream’s upstairs neighbor in the wintertime. It appears in September, when a seasonal lack of sunlight begins to make it cooler inside the Arctic region than outside, said Laura Ciasto, a meteorologist and co-author of the Polar Vortex Blog. The vortex usually disappears in April.
