Sunday , June 13 2021

NASA videos show shifting of the polar vortex to spread icy air in the United States.

The purple and blue colors in the animation represent the lowest temperatures that range from minus 40 F to minus 10 F, measured about two to three miles above Earth's surface. The mass of cold air moves like a fluffy finger that repels areas of higher temperature that are represented by green, yellow, and red in the animation.

The polar vortex is a low-pressure mass of cold air that rotates constantly over the polar regions of the Earth. There is one in the Northern Hemisphere – one who is responsible for the recent cold spell in the US – and another in the Southern Hemisphere.

It is normal for the Arctic's Arctic wind to expand in the winter, which leads to colder air to lower latitudes. But sometimes the polar vortex weakens and the fast-moving air stream, known as the jet stream, shifts, allowing the wind to move south to cause unusually low temperatures in those areas.

"This cold air that has gone down over the Arctic has moved south into the real continental states," said David Canter, an Environmental Sciences Assistant at New York University.

It is paradoxical that extreme cold spells can become more common as the Arctic warms up with the rest of the planet.

"Warming in the Arctic leads to a weaker jet stream, leading to more extreme winters," says Canter. So the idea that global warming will save us from the extremes of cold weather – something President Donald Trump mentioned in a recent tweet – is wrong. As Canter said: "We will see more extremes as the climate continues to warm up."

The Aqua satellite has been around the Earth since 2002. Its tools create a global map of atmospheric phenomena, including temperature and humidity, cloud heights, and concentrations of carbon dioxide and other greenhouse gases that contribute to global warming.

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