What attaches itself to the jet stream and tells you where the stratosphere begins
At the start of February 2021, a major snowstorm hit the northeast Usa, with some areas receiving well over two anxiety of snow. Just a few weeks earlier, Espana experienced a celebrated and deadly snowstorm and dangerously low temperatures. Northern Siberia is no stranger to common cold, but in mid-January 2021, some Siberian cities reported temperatures beneath minus 70 F (minus 56 C). Media headlines hint that the polar vortex has arrived, as if it were some sort of ice tornado that wreaks wintry havoc wherever it strikes.
As atmospheric scientists, we blench when the term polar vortex is used to loosely refer to blasts of cold weather condition. The actual polar vortex can't put snowfall in your backyard, but changes in the polar vortex can load the dice for wintry weather – and this year, the die rolled Yahtzee.
The Winds of Winter
The polar vortex is an enormous, three-dimensional ring of winds that surrounds the North and Southward poles during each hemisphere'southward winter. These winds are located about x to 30 miles (16 to 50 kilometers) above Earth'due south surface, in the layer of the atmosphere known as the stratosphere. They blow from w to east with sustained speeds easily exceeding 100 mph (160 kph). In the darkness of the winter polar night, temperatures inside the polar vortex can hands get lower than minus 110 F (minus 79 C).
Fortunately for everyone, the stratospheric polar vortex itself won't appear outside your front door. The polar vortex does influence winter weather, but it is more like a domino – when it is knocked over, it tin can start a chain of events that afterwards result in wild weather.
The strength of the polar vortex tin can vary widely during winter, and these variations can pb to shifts in the strength and position of the jet stream, the fast-flowing river of air in the troposphere beneath the polar vortex. When the jet stream changes, information technology affects the motion of weather systems, causing different parts of the earth to see much warmer or colder, or much wetter or drier weather.
The Domino Effect
Since the Earth's atmosphere is one behemothic shell of air that moves like a fluid, the polar vortex is interconnected with the weather that moves around the World at lower altitudes. Normal variations in the jet stream and weather tin can disturb the structure of the vortex in the stratosphere. Like an rubberband band, the vortex ordinarily rebounds dorsum to its normal shape and size, maintaining its strong winds and low temperatures.
Merely sometimes, these weather and jet stream variations tin can knock the polar vortex off residue, causing meaning wobbles in its shape, location, temperatures and winds. When this happens, the structural integrity of the polar vortex begins to break down. If this happens often enough over a period of time, everything can go haywire with the polar vortex equally the winds interruption down and the vortex warms upwardly.
This is precisely what has unfolded this year: On January. v, the polar vortex was completely thrown out of whack by an event called a sudden stratospheric warming. Sudden stratospheric warming is the technical name for these violent disturbances that severely distort and weaken the vortex, knocking it off of the pole or even ripping it apart. When this happens, temperatures in the normally cold polar stratosphere explosively rise by as much as 90 F (50 C) over the span of a few days – hence the name of these events.
Here is my "official" 3D animation of this year's stratospheric #PolarVortex separate. Another beautiful event! pic.twitter.com/ml59N1cDoh
— Zac Lawrence (@zd1awrence) January xiv, 2019
At this bespeak, the domino has tipped over: Eventually the jet stream feels the effects of the weakened polar vortex above, and it can begin to undulate. When the jet stream gets wavy, it tin can dip farther southward, bringing cold air and winter storms with it.
The Jan 2021 effect pushed the polar vortex from its normal position over the North Pole all the way over to Europe and Siberia, nearly pulling it apart multiple times in the procedure. It can accept weeks or months for the polar vortex to recover from something like this. While the vortex pieces itself back together, the undulating, curvy jet stream can bring frigid Arctic air and wintertime storms to the U.S. and Europe while assuasive unusually warm atmospheric condition to go into the far north.
A Potent Polar Vortex Means Warmer, Not Colder, Weather
In some winters, weather systems barely bear upon the polar vortex at all, allowing the vortex to grow colder with faster winds. This can have the reverse effect on the jet stream, causing it to keep cold Arctic air from the polar regions locked up northward. This is what happened during the Northern Hemisphere winter of 2020, when the polar vortex was extraordinarily strong and many regions experienced an exceptionally warm and balmy winter.
Calling whatever blast of cold air a polar vortex is wrong. The beliefs of the polar vortex doesn't merely portend colder weather – it can also foreshadow much warmer weather condition. About of the time the polar vortex has little influence on winter atmospheric condition equally information technology flows like normal, miles above the surface. Only forecasting and monitoring huge disturbances to the polar vortex allows united states to conceptualize the concatenation of events that may leave feet of snow and frigid weather at your doorstep.
This is an accented *must read* for people confidently linking polar air outbreaks to climate modify.
Please be careful. The science on this is not conclusive at all, and calculation more years of data has weakened the instance according to this report. https://t.co/Fag4QAGR7R
— Dr. Jonathan Foley (@GlobalEcoGuy) February 16, 2021
By Zachary Lawrence, enquiry scientist at the University of Colorado Boulder, and Amy Butler, Chemistry & Climate Processes enquiry scientist at the National Oceanic and Atmospheric Assistants.
Source: https://www.theepochtimes.com/what-exactly-is-the-polar-vortex_3703138.html
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