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blogs.scientificamerican.com
Mark Fischetti

[HR][/HR] Editor's note (1/4/18): This week's deep freeze is being caused by the same mechanism that iced the Eastern U.S. three years ago. Our explanation, written at that time, appears below.

As I write these words, temperatures across half the U.S. are plummeting like a rock. Extreme lows are forecast by tonight: -32 degrees Fahrenheit in Fargo, N.D.; -21 degrees F in Madison, Wisc.; -15 degrees F in Chicago and Indianapolis, according to the National Weather Service. Wind chills will reach a bizarre 60 degrees below zero F in some places, freezing exposed skin within one minute. That number is more typical for Mars—at night, according to the Curiosity rover NASA has free-wheeling over there.

As each hour passes, more and more television and radio reporters are attributing the insane cold to a “polar vortex” up in northern Canada. Vortex, yes, but upper Canada? Not exactly. One forecaster called the beast a hurricane in the Arctic, which is dramatic but wrong. So what is this mysterious marvel and why is it invading America?

The polar vortex is a prevailing wind pattern that circles the Arctic, flowing from west to east all the way around the Earth. It normally keeps extremely cold air bottled up toward the North Pole. Occasionally, though, the vortex weakens, allowing the cold air to pour down across Canada into the U.S., or down into other regions such Eastern Europe. In addition to bringing cold, the air mass can push the jet stream—the band of wind that typically flows from the Pacific Ocean across the U.S.—much further south as well. If the jet stream puts up a fight, the moisture it carries can fall out as heavy snow, which atmospheric scientists say is the circumstance that caused the February 2010 “snowmageddon” storm that shut down Washington, D.C.

But why does the vortex weaken? Now it gets interesting. More and more Arctic sea ice is melting during summer months. The more ice that melts, the more the Arctic Ocean warms. The ocean radiates much of that excess heat back to the atmosphere in winter, which disrupts the polar vortex. Data taken over the past decade indicate that when a lot of Arctic sea ice disappears in the summer, the vortex has a tendency to weaken over the subsequent winter, if related atmospheric conditions prevail over the northern Atlantic Ocean. The situation looks something like that shown in the graphic below. (For a full explanation, see the Scientific American article that accompanies the graphic.)

Although the extent of summer sea ice in the Arctic varies year to year, overall it has been disappearing to a notable degree since 2007 and it is forecast to continue to vanish even further. That could mean more trouble for the polar vortex, and more frigid outbreaks—a seeming contradiction to “global warming,” perhaps, but not for “global weirding,” also known as climate change.


Graphic by XNR Productions
Photo courtesy of Wing-Chi Poon on WikimediaCommons


The views expressed are those of the author(s) and are not necessarily those of Scientific American.

Mark Fischetti
Mark Fischetti is a senior editor at Scientific American, overseeing coverage of energy and the environment.
 

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Discussion Starter #2
blogs.discovermagazine.com

One verdict on global warming in 2017 is in: Warmest year with no temperature boost from El Niño, and second warmest overall

This map shows how air temperatures at a height of two meters varied in 2017 from the 1981–2010 average. (Source: Copernicus Climate Change Service, ECMWF)

Today brought another lesson about the difference between weather and climate.

While winds were howling, snow was blowing, and temperatures were plummeting thanks to the bomb cyclone off the U.S. East Coast, a European science agency announced that 2017 was the second warmest year in records dating back to the 1800s. Only 2016 was warmer, according to the Copernicus Climate Change Service.

That year received a very significant temperature boost from a strong El Niño, which is characterized by high surface temperatures in the tropical Pacific Ocean. Among all years without an El Niño, 2017 was the very warmest in the Copernicus analysis.

This finding is particularly noteworthy because 2017 saw cooling in the tropical Pacific from La Niña, the opposite of El Niño, both early and late in the year.

The Copernicus findings are comparable to an independent analysis done by the Japan Meteorological Agency. In coming weeks, we’ll also see analyses by NOAA, NASA, and the U.K.’s Met Office.

Over the long run, these different independent analyses have produced very similar results, as this graphic shows:

Running 60-month averages of global air temperature at a height of two metres (left-hand axis) and estimated change from the beginning of the industrial era (right-hand axis) according to different datasets: ERA-Interim (Copernicus Climate Change Service, ECMWF); GISTEMP (NASA); HadCRUT4 (Met Office Hadley Centre), NOAAGlobalTemp (NOAA); and JRA-55 (JMA).

The news released by Copernicus today— as a brutal winter storm hammers the Northeast — reminds us that human-caused global warming has not repealed winter.

SEE ALSO: The view from space as the so-called ‘bomb cyclone’ exploded into a dangerous storm

That said, there has been increasing discussion among climate scientists about how long-term warming might influence major winter storms, as well as other forms of extreme weather.



Sea surface temperature anomalies in the Western Hemisphere. Note the orange and red colors.

In a nutshell, the theory goes like this: As temperatures rise more in the Arctic than in the lower latitudes, the jet stream weakens, gets more wavier, and tends to stay in this orientation for longer. This allows cold Arctic air to spill south more readily, and warm, moist air from the south to push north. When a cold, dry airmass runs into a warm, moist one, a cyclonic bomb can go off, just like the one off the East Coast. And when the clash happens over warm ocean waters, like it just did, the storm can get a moisture boost, leading to greater snowfall. In fact, sea surface waters from the Carolinas north into Canada are mostly warmer than average — in some places dramatically so.

A few important caveats are in order here: First, the jet stream theory, advanced by Rutgers climatologist Jennifer Francis and colleagues, is just that — a theory. And while evidence has been accumulating to support it, it is still a contentious area of science with many researchers not yet convinced.

Second, even if this theory offers a reasonably accurate picture of what’s going on, it would be wholly incorrect to say global warming “caused” the East Coast storm. Today, it is going by the term “bomb cyclone.” But this type of storm, known as a Nor’easter in years past, has a long and storied history. Long-term residents of the New England coast are well familiar with these damaging extreme weather events.

Over time, will events like this become stronger as the world warms? Possibly, scientists say. And then there’s the question of how much stronger.
The bottom line is that this is an area of active inquiry. And we just don’t have all the answers.

But this much is clear: The world is warming, humans are primarily to blame, and the trend has reached new heights in the past few years.
 

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So global warming means we'll finally start getting snow in the south? Hell yeah.
 

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Discussion Starter #4
slate.com

Why it’s so hard to accurately predict snowfall.


By Geoff Fox

[HR][/HR] We’ve gotten better, but there are still a lot of calculations at play.

Mackenzie Weber measures 25 inches of snow on furniture on her family's deck on May 18 in Nederland, Colorado. Helen H. Richardson/The Denver Post via Getty Images

How much is it going to snow Thursday? As a meteorologist, the bane of my existence is predicting snow. It is the most difficult forecast I make with dozens of different ways it can go wrong. More troubling, it’s probably the forecast most scrutinized before and after the fact.

But why? What is it about snow that makes it so tough to pin down?

Though temperatures at ground level are important, the critical numbers for assessing snowfall are much higher up in the atmosphere. We’re looking for ice crystal growth, which happens when the air is wet enough and cold enough—sometimes down to -20° Fahrenheit, though the biggest snow growth happens at somewhat warmer temperatures.

The ice crystals start small, but as they collide, they grow, until finally they’re large enough and heavy enough to fall to Earth. Snow is water plus air—air being very important. It’s the fluff factor, the reason an inch of water can be 5 inches of snow or 30 inches or something in between. The snow liquid ratio, or SLR, is different for every storm (high SLRs are good for skiing, bad for snowballs). And that’s what we’re trying to predict—how much liquid is going to produce how much snow.

Most snowstorms are driven by low pressure systems hundreds of miles across. Around the low, warm air rises and cools. That causes water vapor in the air to condense and form clouds. Liquid droplets come next until gravity and temperature begin to dominate. For those who live in snow belts there’s a second method to produce snow, the lake effect. Assessing these two methods of snow production should allow you to get a good idea of how much snow to expect, but often your final estimate is really the combination of two estimates.

The process is very exacting, intricate even. When temperatures are cold enough and the wind properly aligned through the atmosphere, lake effect snow produces narrow bands of intense snow that are extremely hard to predict. For example, I drove from Buffalo, New York, to Erie, Pennsylvania, one winter’s day. Downtown Buffalo had flurries, but as I headed into the “Southtowns,” conditions became dicey. The snow rate was a few inches an hour. And then, a few miles later along Lake Erie’s shore, the snow stopped, clouds parted, and the sun came out. My trip back saw the exact same conditions in the exact same places. Nothing had moved.

Marquette, Michigan, is a good example of how this makes forecasting more difficult. Not only does Marquette get your run-of-the-mill winter storms, it also gets lake effect snow. Lake effect there has an SLR in the 30 to 40:1 range, meaning that one inch of liquid equals 30–40 inches of snow. The larger storms that pass through are 10 to 15:1. Figuring out how this hybrid storm is going to combine includes a lot of room for error. Luckily, Marquette averages around 17 feet of snow per year—lots of time to practice.

So we forecast the amount of water, then how that water will act as it drops. Most of the time the atmosphere warms as the flakes fall … but not always. What starts in the clouds as snow can fall as sleet, rain, freezing rain, or even graupel (snowflakes pocked with rime ice). The form it falls in obviously changes how much snow ends up on the ground.

When and how you measure snow affects the final total, too. Officially it’s measured off the ground on a “snow board,” usually a large piece of plywood. Snowflakes fill gaps in the snow pile as they fall. Measuring every hour, without giving the snow time to settle will give a higher amount than measuring every six.

Over the years forecasts have improved. There are fewer busts. One reason we’ve gotten better is through improved computer modeling: We can now look at the atmosphere a little more finely. The grid points and time steps are closer together. The mathematical integration of physics is better honed.

Your mileage may vary, but accumulation amounts now have real-world usefulness. I couldn’t always say that. I still hate forecasting it, though.

And is it ever going to end?

The forecast map for Friday. NOAA

If you’re east of the Mississippi, you’ve probably noticed it’s been pretty cold outside. Boston hasn’t seen anything above 30 degrees Fahrenheit since Christmas. It isn’t much better in New York City, where temps above 30 degrees have been MIA since Dec. 26.

The cold has penetrated all the way to the Gulf of Mexico. A hard freeze earlier this week blasted across much of south central Texas. Tallahassee, Florida, had itself a winter storm warning and even got a little snow.
 

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The polar vortex can push (through) the jet stream..?

WTF is this utter nonsense.

The waves in the jet stream are called Rossby waves. They're a result of rotational momentum being conserved as circumferential air flows around Earth move from the equator to the poles. The momentum has to go somewhere so the jet stream basically takes a concertina shape.



Note that the red colouring there represents speed, not temperature. It results in this:



North of the jet stream is arctic air, south of the jet stream is mid-tropical air. No air is 'pushed through'.

Global warming means the transfer of energy from the equator to the poles is greater, which means the size of the Rossby waves in the jet stream are greater. It means the phenomena in the above diagram become more common and/or more extreme. This is what causes colder air to make it further south.

I learned all this in advanced geophysical dynamics classes in my final year of university.

The article in the OP reads like the non-physics-non-maths-based opinions of a (scoff scoff fnar fnar) geography student.
 

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scientificamerican.com
Humans Did Not Cause the US Cold Snap

Scott Waldman,ClimateWire

The cold snap that sent temperatures plunging last week and brought the most frigid new year in recorded history, in some places, had nothing to do with climate change, according to a new study.

In recent years, climate scientists have studied the connection between global warming and freezing temperatures. They are examining how shifting air patterns over the Arctic, and their incursion into North America and Europe, are connected to climate change.

But the two-week deep freeze didn't carry the hallmarks of human activity, according to a rapid attribution study from Climate Central, a science communication project based in Princeton, N.J. World Weather Attribution, a group of international researchers, performed the analysis.

Temperatures in some parts of the country, including Buffalo and Detroit, were more than 20 degrees Fahrenheit below normal for this time of year. Such events are increasingly rare, and the group found that wintertime temperatures are actually increasing in the United States. That is to be expected in a warmer world, the authors wrote.

"We conclude that this was an exceptional two-week cold wave in the area in the current climate," the authors wrote. "Cold outbreaks like this are getting warmer (less frequent) due to global warming, but cold waves still occur somewhere in North America almost every winter."

That didn't stop politicians from seizing on the cold. President Trump tweeted that the East Coast "could use a little bit of that good old Global Warming," while former Vice President Al Gore tweeted that the bitter cold is "exactly what we should expect from the climate crisis."

Researchers found that such a cold spell was more likely before human-caused global warming. Now, a two-week deep freeze is about 15 times less likely to occur than a century ago, when temperatures in such an event would be 4 degrees lower, according to the international group of researchers. The cold streak was also unique in that it occurred so early in the season.

The group has looked at other extreme weather events. It found that the likelihood of Hurricane Harvey's rainfall was increased by climate change, but a drought in Somalia, in 2016 and 2017, was not connected to global warming.

There is evidence that Arctic blasts of frigid air could become more common as a result of climate change, though scientists say more study is needed to firmly draw any conclusions. That's because the jet stream around the Arctic region seems to be weakening. It typically traps and encircles the coldest air over the Arctic, but as it weakens, colder air can filter down to lower latitudes.

Scientists are looking at the link between the loss of Arctic sea ice and how it affects weather in lower latitudes, but more research is needed.

Gabriel Vecchi, a geosciences professor at the Princeton Environmental Institute and an author of the report, said the climate community is divided on whether or not colder winter temperatures can be traced to global warming. He said most experts in the field likely don't agree with that hypothesis, though he says there is evidence for it.

"The finding that cold spells could become more common due to global warming is an interesting one, but it is also a controversial one in our field," Vecchi said. "There is a lot of discussion about it in the scientific literature, and I think it's a very counterintuitive hypothesis that people have, and I think because of that, it's appealing. But we don't find any support for it in this work."

While the report failed to find human fingerprints on the cold weather, that doesn't raise questions about the broader role that people are having on the globe, he said.

"I think it would be misguided to look at any cold event as evidence for or against global warming," Vecchi said. "There is evidence for global warming on a number of levels, and the planet has been warming, the oceans have been taking up heat, sea levels have been rising, land snow has been melting, glaciers are melting, and all these other things, so the reality of global warming is uncontroversial."

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.
 

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Discussion Starter #7
The polar vortex can push (through) the jet stream..?

WTF is this utter nonsense.

The waves in the jet stream are called Rossby waves. They're a result of rotational momentum being conserved as circumferential air flows around Earth move from the equator to the poles. The momentum has to go somewhere so the jet stream basically takes a concertina shape.


Note that the red colouring there represents speed, not temperature. It results in this:



North of the jet stream is arctic air, south of the jet stream is mid-tropical air. No air is 'pushed through'.
no, not "through"

The polar vortex is a prevailing wind pattern that circles the Arctic, flowing from west to east all the way around the Earth. It normally keeps extremely cold air bottled up toward the North Pole. Occasionally, though, the vortex weakens, allowing the cold air to pour down across Canada into the U.S., or down into other regions such Eastern Europe. In addition to bringing cold, the air mass can push the jet stream—the band of wind that typically flows from the Pacific Ocean across the U.S.—much further south as well.

ie, it diverts the jet stream farther south
 

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When I was a kid (1980's), we just called these "storms". Now they need new scary names.

Back then I was also told the enlarging Ozone hole was going to mean we'd all be wearing sunscreen and special glasses by the year 2020 just to go get the mail. It was believed it would accelerate.

I was also told we were entering the next ice age and to prepare for a global epidemic by 2020. It's apparent on that temperature graph from your linked scale from 1940 to 1980.

I'm no global warming denier, but I don't put a lot of faith into weather-science predictions.
 

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In addition to bringing cold, the air mass can push the jet stream—the band of wind that typically flows from the Pacific Ocean across the U.S.—much further south as well.


ie, it diverts the jet stream farther south
No it does not push, divert or apply any force whatsoever to the jet stream, this is completely wrong.

For a start, cold air regions are at lower pressure and, being further north, they have lower absolute vorticity, meaning they have absolutely no inclination or ability to push southwards.

Rossby waves are the one and only cause. I already explained how. The absolute vorticity link I gave above even mentions Rossby waves and their direct relation to numerical weather forecasting.

The article is wrong. You don't need to get defensive, you didn't write it.


When I was a kid (1980's), we just called these "storms". Now they need new scary names.

Back then I was also told the enlarging Ozone hole was going to mean we'd all be wearing sunscreen and special glasses by the year 2020 just to go get the mail. It was believed it would accelerate.

I was also told we were entering the next ice age and to prepare for a global epidemic by 2020. It's apparent on that temperature graph from your linked scale from 1940 to 1980.

I'm no global warming denier, but I don't put a lot of faith into weather-science predictions.
Well you should.

Do you know why the ozone hole problem went away? Because national leaders listened to weather-science predictions all over the world and agreed to put a ban on CFCs, the chemicals which cause ozone depletion. This year it was finally reported that the ban was having a positive effect - the ozone hole is shrinking. That's why you haven't seen any hint of the doomsday scenario that was predicted.
 

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Discussion Starter #10 (Edited)
No it does not push, divert or apply any force whatsoever to the jet stream, this is completely wrong.

For a start, cold air regions are at lower pressure and, being further north, they have lower absolute vorticity, meaning they have absolutely no inclination or ability to push southwards.

Rossby waves are the one and only cause. I already explained how. The absolute vorticity link I gave above even mentions Rossby waves and their direct relation to numerical weather forecasting.

The article is wrong. You don't need to get defensive, you didn't write it.

I wasn't being "defensive"

I simply pointed out your error; the article didn't claim the cold polar air pushed "through" the jet stream, as you asserted:


The polar vortex can push (through) the jet stream..?

WTF is this utter nonsense.

and your article didn't mention the polar vortex

what it showed is that the vortex remains intact even as the jet stream meanders south, viz


note the streamlines of the vortex that don't divert down into the trough of the jet stream
 

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Discussion Starter #11 (Edited)
For a start, cold air regions are at lower pressure and, being further north, they have lower absolute vorticity, meaning they have absolutely no inclination or ability to push southwards.

Rossby waves are the one and only cause. I already explained how.

the polar vortex lies in the upper atmosphere above the cold polar air which lies along the earth's surface...it creates a low pressure zone that acts to contain the frigid air in the poles...when the vortex weakens, the pressure increases allowing the cold air to escape south...where it moves is probably influenced by the low pressure troughs of the rossby waves, but the waves themselves don't cause the cold snaps
 

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Discussion Starter #12
The polar vortex can push (through) the jet stream..?

WTF is this utter nonsense....

...I learned all this in advanced geophysical dynamics classes in my final year of university.

The article in the OP reads like the non-physics-non-maths-based opinions of a (scoff scoff fnar fnar) geography student.

the op is based on recent research findings:

http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-16-0259.1


More-Persistent Weak Stratospheric Polar Vortex States Linked to Cold Extremes


Marlene Kretschmer*[SUP],1,[/SUP][SUP]2[/SUP], Dim Coumou[SUP]1,[/SUP][SUP]3[/SUP], Laurie Agel[SUP]4,[/SUP][SUP]5[/SUP], Mathew Barlow[SUP]4[/SUP], Eli Tziperman[SUP]6[/SUP], and Judah Cohen*[SUP],7[/SUP][SUP]1[/SUP] Potsdam Institute for Climate Impact Research, Earth System Analysis, Potsdam, Germany
[SUP]2[/SUP] Department of Physics, University of Potsdam, Germany
[SUP]3[/SUP] Institute for Environmental Studies (IVM), VU University Amsterdam
[SUP]4[/SUP] Department of Environmental, Earth, and Atmospheric Sciences, University of Massachusetts Lowell, Lowell, MA, USA
[SUP]5[/SUP] Intercampus Marine Science Graduate Program, University of Massachusetts, MA, USA
[SUP]6[/SUP] Department of Earth and Planetary Sciences and School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
[SUP]7[/SUP] Atmospheric and Environmental Research, Lexington, MA, USA

https://doi.org/10.1175/BAMS-D-16-0259.1
Published Online: 22 September 2017


Abstract

Over the last decades, the stratospheric polar vortex has shifted towards more frequent weak states which can explain Eurasian cooling trends in boreal winter in the era of Arctic amplification.

The extra-tropical stratosphere in boreal winter is characterized by a strong circumpolar westerly jet, confining the coldest temperatures at high latitudes. The jet, referred to as the stratospheric polar vortex, is predominantly zonal and centered around the pole; however, it does exhibit large variability in wind speed and location. Previous studies showed that a weak stratospheric polar vortex can lead to cold-air outbreaks in the mid-latitudes but the exact relationships and mechanisms are unclear. Particularly, it is unclear whether stratospheric variability has contributed to the observed anomalous cooling trends in mid-latitude Eurasia. Using hierarchical clustering, we show that over the last 37 years, the frequency of weak vortex states in mid to late winter (January and February) has increased which were accompanied by subsequent cold extremes in mid-latitude Eurasia. For this region 60% of the observed cooling in the era of Arctic amplification, i.e. since 1990, can be explained by the increased frequency of weak stratospheric polar vortex states, a number which increases to almost 80% when El Niño/Southern Oscillation (ENSO) variability is included as well.

* Corresponding authors: [email protected] (M.K.), [email protected] (J.C.)
 

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the polar vortex lies in the upper atmosphere above the cold polar air which lies along the earth's surface...it creates a low pressure zone that acts to contain the frigid air in the poles...when the vortex weakens, the pressure increases allowing the cold air to escape south...where it moves is probably influenced by the low pressure troughs of the rossby waves, but the waves themselves don't cause the cold snaps
Why are you pretending to know everything about a topic from a random article you posted on a web forum. I'm telling you right now with absolute certainty, Rossby waves are the one and only thing that allow cold air to head further south. Without that phenomenon, North America and Europe would have steady weather all year round.

the op is based on recent research findings:
And? The research abstract looks fine. But your article said this:

In addition to bringing cold, the air mass can push the jet stream—the band of wind that typically flows from the Pacific Ocean across the U.S.—much further south as well.
which is wrong.

Rossby wave amplitude will surely change because the energy gradient changes between the hot air and cold air which is released from a weak polar vortex. But nothing is being pushed anywhere. It doesn't work like that.

I wasn't being "defensive"
You are definitely being defensive of a questionably worded pop science article you that you didn't write.
 

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Discussion Starter #14 (Edited)
Why are you pretending to know everything about a topic from a random article you posted on a web forum.
I'm not pretending to know everything about a topic I post...I'm simply pointing out the error of your claim


I'm telling you right now with absolute certainty, Rossby waves are the one and only thing that allow cold air to head further south. Without that phenomenon, North America and Europe would have steady weather all year round.
if rossby waves were the "only mechanism"--as you wrongly claim--outbreaks of polar air would happen routinely, since these waves are always present

the point of the op is that it is the variability of the polar vortex--caused, it is believed, by the melting of the ice cap--that produces cold snaps, not rossby waves


And? The research abstract looks fine. But your article said this:

which is wrong.

first, the abstract said this:

The extra-tropical stratosphere in boreal winter is characterized by a strong circumpolar westerly jet, confining the coldest temperatures at high latitudes. The jet, referred to as the stratospheric polar vortex, is predominantly zonal and centered around the pole; however, it does exhibit large variability in wind speed and location. Previous studies showed that a weak stratospheric polar vortex can lead to cold-air outbreaks in the mid-latitudes but the exact relationships and mechanisms are unclear.

there is no mention of rossby waves, only the polar vortex


second, winds are large air masses that move from high pressure to low pressure zones...air in low pressure zones are literally pushed out by incoming air from high pressure zones

F=ma

newton's law works in the atmosphere, too


(and, yes, I understand that winds are also infuenced by the coriolis force)



Rossby wave amplitude will surely change because the energy gradient changes between the hot air and cold air which is released from a weak polar vortex. But nothing is being pushed anywhere. It doesn't work like that.

yeah, it does....cold polar air pushes south, displacing warmer air...this colder air sitting farther sourth in turn changes where convection cells lie...since the jet stream arises from the circulation of these cells, the stream is literally pushed south by the incoming polar air


You are definitely being defensive of a questionably worded pop science article you that you didn't write.
the op is based on the scientific research I linked above

what I question is your understanding of undergraduate physics
 

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what I question is your understanding of undergraduate physics

Ha, politely fuck off.

You are completely wrong. How do I know?

Because you said this:

I'm not pretending to know everything
and then you said this:

second, winds are large air masses that move from high pressure to low pressure zones...air in low pressure zones are literally pushed out by incoming air from high pressure zones

F=ma

newton's law works in the atmosphere, too
You are wrong and don't be so condescending you cunt. F=ma? What you need is this one and don't pretend you know what you're looking at because I know you don't.


Pressure variation is the primary cause of air flow but only on a very very largescale, i.e. global air convection from equator to the poles. Once the coriolis force kicks in, winds in fact go around areas of pressure. It's a phenomenon called geostrophic balance. Don't pretend you knew that. You didn't.



undergraduate physics
Not all physics courses are the same. I sat through advanced fluid mechanics and geophysical fluid mechanics courses that the vast majority of institutions do not offer. Stop pretending to know about these subjects and don't ever try to say my understanding is wrong. I may well be incorrect about some things, for sure, but you would never even know. You don't know enough about the subject.

the point of the op is that it is the variability of the polar vortex--caused, it is believed, by the melting of the ice cap--that produces cold snaps, not rossby waves
No, the point is that a weaker polar vortex lets some cold air further south than normal, which is then further released by large rossby waves. But this is already common knowledge. The article simply made comments on what causes the polar vortex to weaken in the first place - melting ice caps - and then the author claimed the air pushes the jet stream further south which is wrong.

Many people even with full physics degrees are of the same opinion as you, believing pressure is the main driver of wind direction. It isn't. Geostrophic balance sees to that. Most physics students don't learn about the principles of fluid dynamics on rotating reference frames. Hell, a large amount of students don't learn any fluid dynamics at all. In fact a lot of physics student don't even learn about the basic mechanics of rotating frames.

All of this is advanced stuff that the disinterested student can avoid if they prefer other areas of physics. For example, I have no idea about astrophysics, I have no idea beyond the basics of condensed matter physics, and I can barely tell you anything other than the basics of special relativity. These aren't my areas. Physics is a huge discipline. I chose advanced mechanics and fluid dynamics as my more specialist areas of study. I can safely say I know more than most physics graduates on these topics.

I wrote my final project on a very similar topic and got a top grade for it. It may even be published in a journal soon. Stop trying to outsmart me on this stuff.
 

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Discussion Starter #16 (Edited)
Ha, politely fuck off.

You are completely wrong. How do I know?

Because you said this:


and then you said this:

knowing a few things =/= "knowing everything"


guess they didn't teach you basic logic in that fluid dynamics course


pity


Don't be so condescending you cunt. F=ma? What you need is this one and don't pretend you know what you're looking at because I know you don't.

navier-stokes IS F=ma!

LOLOLOLOLOLOLOLOLOL



Pressure variation is the primary cause of air flow but only on a very very largescale, i.e. global air convection from equator to the poles. Once the coriolis force kicks in, winds in fact go around areas of pressure. It's a phenomenon called geostrophic balance. Don't pretend you knew that. You didn't.
actually, I did know that...I've seen weather maps showing high and low pressure zones

and winds do flow from high to low pressure zones...a pressure zone is not a single point on a map....it's a region of high or low pressure...air masses move between these regions


Not all physics courses are the same. I sat through advanced fluid mechanics and geophysical fluid mechanics courses that the vast majority of institutions do not offer. Stop pretending to know about these subjects and don't ever try to say my understanding is wrong. You have no idea about this.

you are wrong

rossby waves don't cause cold snaps


just admit your understanding is flawed, intp


No, the point is that a weaker polar vortex lets some cold air further south than normal, which is then further released by large rossby waves. But this is already common knowledge. The article simply made comments on what causes the polar vortex to weaken in the first place - melting ice caps.

no

the cold air mass pushes the mid-latitude convection cell farther south, thereby pushing the jet stream farther south

you can see the effect of cold weather on the jet stream in this figure:




this is common knowledge


so it is common knowledge that you are wrong
 

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Discussion Starter #17
Many people even with full physics degrees are of the same opinion as you, believing pressure is the main driver of wind direction. It isn't. Geostrophic balance sees to that. Most physics students don't learn about the principles of fluid dynamics on rotating reference frames. Hell, a large amount of students don't learn any fluid dynamics at all.

I wrote my final project on a very similar topic and got a top grade for it. It may even be published in a journal soon. Don't tell me I don't know about this stuff.

I said that wind is the motion of air masses caused by pressure gradients AND the coriolis force
 

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rossby waves don't cause cold snaps
No they do not 'cause' them, but they absolutely bring them down to the population areas of North America and Europe. Without rossby waves you would never have any cold air making its way further south than the average circumferential route that the jet stream takes. Waves in the jet stream are caused by energy variation. This is probably linked to the cold air, but not by a basic 'pushing' mechanism that you are attempting to describe. The cold air cannot merrily push something as leviathan as the jet stream.

I said that wind is the motion of air masses caused by pressure gradients AND the coriolis force
Yes, everyone knows the fun little coriolis fact that winds are driven in a latitudinal direction due to coriolis forces. But no you absolutely did not know that geostrophic balance causes wind to go around high and low pressure zones.

You make this claim:

and winds do flow from high to low pressure zones...a pressure zone is not a single point on a map....it's a region of high or low pressure...air masses move between these regions
but just look at any weather map and you'll see how absolutely wrong you are. Here are some examples:




Look at all those pressure isobars, and look at how the wind goes along the isobars. That means the wind is going around pressure regions. There is no movement into or out of higher or lower pressure. This is geostrophic balance and it's what dictates wind direction. It has nothing to do with pressure at this scale. You can see clear as day where the wind is going, and it is most certainly not doing what you described.

this is common knowledge


so it is common knowledge that you are wrong
I give up.

This is the third time you and I have ended up in a discussion where you desperately attempt to show working knowledge in an area you know no more than the amateur enthusiast.
 

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Discussion Starter #19 (Edited)
No they do not 'cause' them, but they absolutely bring them down to the population areas of North America and Europe. Without rossby waves you would never have any cold air making its way further south than the average circumferential route that the jet stream takes.

no, you're wrong (as usual)

rossby waves wouldn't exist if the earth didn't rotate...however, atmospheric circulation of air induced by differential solar heating would still happen and would carry cold air from the poles towards the equator--ie, there would be one large convection cell in each hemisphere


Waves in the jet stream are caused by energy variation. This is probably linked to the cold air, but not by a basic 'pushing' mechanism that you are attempting to describe.

this is a red herring...the op didn't claim the cold air "creates" rossby waves


The cold air cannot merrily push something as leviathan as the jet stream.

yeah, it can...and it does

the jet stream follows the boundary between the polar and mid-latitude convection cells...cold polar air pushes this boundary farther south, carrying the jet stream with it

put in your terms, colder air is the "energy variation" that causes the jet stream to move farther south in the same way the colder winter north american landmass causes the jet stream to divert farther south



Yes, everyone knows the fun little coriolis fact that winds are driven in a latitudinal direction due to coriolis forces. But no you absolutely did not know that geostrophic balance causes wind to go around high and low pressure zones.

yeah, I did

fluid streamlines can't terminate at a point unless it is a source or sink

you don't need a degree in physics to know that


You make this claim:

but just look at any weather map and you'll see how absolutely wrong you are. Here are some examples:




Look at all those pressure isobars, and look at how the wind goes along the isobars. That means the wind is going around pressure regions. There is no movement into or out of higher or lower pressure. This is geostrophic balance and it's what dictates wind direction. It has nothing to do with pressure at this scale. You can see clear as day where the wind is going, and it is most certainly not doing what you described.

in the first figure, the streamlines flow towards the low pressure zone from a high pressure zone which is not shown...some of this air is entrained in the vortex of the low pressure zone where it spirals inwards towards the center (where it is pushed up into the atmosphere above)

so some of the air from high pressure zones does, in fact, get sucked into the center of the low pressure zone


I give up.

This is the third time you and I have ended up in a discussion where you desperately attempt to show working knowledge in an area you know no more than the amateur enthusiast.

yes, and I schooled you every other time I interacted with you just as I schooled you here
 
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