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The Five-Year-Old’s Guide to the Polar Vortex

I have never gazed out at a beautiful sunset on the horizon and thought, “what a magnificent high pressure system!” I experience weather, not pressure systems, so I tend to zone out when the meteorologist is all “a high pressure system is stalling cold air over the plains . . . .” But my interest in weather perked up a few weeks ago when the polar vortex came to visit. A catchy name, a whiff of danger, three days off school for the kids—it was hard not to get caught up in the hoopla. And better yet—the polar vortex turned out to be a real thing, not some made-up, sexy headline term, like Snowmaggedon. I needed to learn more about this polar vortex phenomenon, but in terms that a five-year-old could understand. You see, over the holidays, I’d spent way too much time on the subreddit ELI5 (“explain like I’m five”). Kindergarten is now my default.

So here goes. The Earth has two major polar vortices, also known as polar cyclones, one near the North Pole and one near the South Pole. They are a permanent and integral part of the planet’s weather patterns. They get stronger in the winter due to the temperature differential between the poles and the equator and are weaker in the summer. Their average temperature is about -130 degrees F. If you’re a meteorologist, you learned all about them at meteorology school.

Here’s a polar cyclone near Iceland on September 3, 2003. Photo by NASA. We may not be able to land a man on the moon anymore, but we can sure take nice photos of Earth.

Although this photo makes the vortex look like a standalone hurricane, it is actually an elongated system with two separate spiraling centers—one usually hangs around Baffin Island in Canada, the other lives over Siberia. In this image, the Baffin Island cyclone had moved east.

Normally, the polar vortex at the North Pole stays where it belongs. The problems in January began when it decided to take a vacation down south—right on top of millions of unsuspecting Americans and Canadians who were just going about their business. But why did it venture south? ELI5 answer: It was pushed by the jet stream, that undulating halo of westerly winds that encircles the globe at the northern latitudes:

The undulating meanders in the polar jet stream are called Rossby waves. As you can see in image (c), a rogue Rossby wave can push the polar air way down where it doesn’t belong; in this case the polar vortex was jammed right down over the Great Lakes:

To add to the Midwest’s misery, a huge snowstorm just prior to the visitation from the polar vortex exacerbated the cold. The thick layer of snow reflected all heat back up into the atmosphere.

But here’s what’s weird. It’s when the polar vortex is weak that cold air is likely to escape to lower latitudes. That’s right, what we got was a weak vortex that couldn’t defend itself against the jet stream (the explanation involves high pressure and low pressure, so we’ll skip it).

You may not remember, but a similar polar vortex event took place in January, 1985, in that hallowed era before we were tethered to our electronic devices telling us the sky was falling. In Chicago, temperatures with wind chill reached -60 degrees F. Florida’s citrus crop was a total loss and President Reagan’s second inaugural took place in the Capitol Rotunda instead of outside and the inaugural parade was cancelled. In that event, the vortex was centered over Quebec and Maine:

Polar Vortices and Climate Change

The effect of polar vortices on climate change or as the result of climate change are difficult to isolate. Weather systems are just that—systems—and they are the result of many interrelated factors. The polar vortices and the jet stream operate hand-in-hand, and they both operate in the tropopause, which is the transition between the troposphere (the portion of the atmosphere closest to Earth’s surface) and the stratosphere (um, higher up). The tropopause is characterized by a temperature inversion, where the layers of temperature of the troposphere, which go from warm to cool the higher you go, meet the stratosphere, which is characterized by layers of air that go from cooler to warmer the higher you go.

Linking events like the January polar vortex to climate change will take time—like, decades of time. But right now scientists are leaning toward the idea of extreme weather events being part of the feedback loop in which reduced snow and ice near the poles (due to rising global temperatures) results in less sunlight reflecting back up into space. This means more sunlight is absorbed, which further increases evaporation of snow and ice. In turn, the polar vortex weakens, allowing the jet stream to meander further south, bringing with it lower temperatures and blocked weather systems. A Cornell professor presented a convincing case that Hurricane Sandy was the result of one of these blocked weather systems. So in winter time, it seems, some evidence points to on-the-move polar vortices being instrumental in bringing colder weather to a region.

This is just another reason why we all have to get used to saying global climate change instead of global warming. Scientists have been telling us for years that climate change means wild swings in weather patterns and more destructive storms. Anyone forced to spend a couple hours shoveling after one of our recent blizzards is bound to agree, especially if they live in a place where there aren’t supposed to be blizzards.

Kathy Wilson Peacock is a writer, editor, nature lover, and flaneur of the zeitgeist. She favors science over superstition and believes that knowledge is the best super power. Favorite secret weapon: A library card.

 

Posted on: January 22, 2014, 6:00 am Category: Current Issues Tagged with: , , , , , , , , ,

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