Tag Archives: jet stream

The Jet Stream is Misbehaving

From meteorologist Paul Douglas:

Published on Mar 14, 2014
Weather seems to be staling. Look into how the speed of the jet stream causes this “stuck in a rut” weather pattern. Meteorologist Paul Douglas also takes a look back as to how this winter compares to years past. Checking out extreme drought conditions, snow cover and cooler temperatures overall. This did not only impact the U.S. but other areas of the world. England experienced their wettest winter yet!

More on weather whiplash and the Polar Vortex

Extreme weather events of all kinds seem to be more common now than they were then. By now I mean the last five to ten years, approximately, and by then I mean … well, before that. This is because of global warming.

The current Colding caused by a wandering Polar Vortex (which I’ve heard Rush Limbaugh has declared to be a liberal plot … thanks Obama!) is probably a result of changes in the nature and configuration of the jet streams and related air masses, as discussed here. Warming caused by the release of fossil carbon, mainly as Carbon Dioxide, has affected the Arctic more than most of the rest of the planet, and this has changed the nature of major air mass movement which, in turn, has disrupted the jet streams, which has caused what we call weather whiplash. If you would like to see an example of weather whiplash, you can probably do so by looking outside because it is happening all over the place all the time. Well, it seems that way anyway. Let’s just say that it is happening often enough that the lack of weather whiplash may well be newsworthy.

Peter Sinclair of the Yale Climate Forum has a post and a new video that puts a lot of this together. Here’s the video:

Hey, if you are local to the Twin Cities, come on over to Stillwater on Monday and we’ll talk about it. Unless you are that one guy who wants to put me on trial and execute me because I think global warming is real! You stay home!

A rollicking adventure through the rift valley and rain forests of Central Africa in search of the elusive diminutive ape known locally as Sungudogo.
A rollicking adventure through the rift valley and rain forests of Central Africa in search of the elusive diminutive ape known locally as Sungudogo.
More on climate change HERE.

Also, check out my novella, Sungudogo, HERE. It is an adventure story set in Central Africa which ultimately turns out to be a parody of the skeptics movement. It seems to have struck a nerve with a few of the skeptics, while others seem to have enjoyed it. Who knew?

Linking Weather Extremes to Global Warming

Global Warming is the increase in the Earth’s temperature owing to the greenhouse effects of the release of CO2 and other gasses into the atmosphere, mainly by humans burning fossil fuel, but also by the release of Methane from oil wells and melting of Arctic permafrost, natural gas from leaky pipes, and so on. This increase in temperature occurs in both the atmosphere and the oceans, as well as the land surface itself. During some periods of time most of the increase seems to happen in the atmosphere, while during other times it seems to occur more in the oceans. (As an aside: when you use passive geothermal technology to heat and cool your home, the heat in the ground around your house is actually from the sun warming the Earth’s surface.)

ResearchBlogging.org“Weather” as we generally think of it consists partly of storms, perturbations in the atmosphere, and we would expect more of at least some kinds of storms, or more severe ones, if the atmosphere has more energy, which it does because of global warming. But “weather” is also temperature, and we recognize that severe heat waves and cold waves, long periods of heavy flooding rains, and droughts are very important, and it is hard to miss the fact that these phenomena have been occurring with increasing frequency in recent years.

We know that global warming changes the way air currents in the atmosphere work, and we know that atmospheric air currents can determine both the distribution and severity of storms and the occurrence of long periods of extreme heat or cold and wet or dry. One of the ways this seems to happen is what is known as “high amplitude waves” in the jet stream. One of the Northern Hemisphere Jet Streams, which emerges as the boundary between temperate air masses and polar air masses, is a fast moving high altitude stream of air. There is a large difference in temperature of the Troposphere north and south of any Jet Stream, and it can be thought of as the boundary between cooler and warmer conditions. Often, the northern Jet Stream encircles the planet as a more or less circular stream of fast moving air, moving in a straight line around the globe. However, under certain conditions the Jet Stream can be wavy, curving north then south then north and so on around the planet. These waves can themselves be either stationary (not moving around the planet) or they can move from west to east. A “high amplitude” Jet Stream is a wavy jet stream, and the waves can be very dramatic. When the jet stream is wavy and the waves themselves are relatively stationary, the curves are said to be “blocking” … meaning that they are keeping masses of either cold (to the north) or warm (to the south) air in place. Also, the turning points of the waves set up large rotating systems of circulation that can control the formation of storms.

So, a major heat wave in a given region can be caused by the northern Jet Stream being both wavy (high amplitude) with a big wave curving north across the region, bringing very warm air with it, at the same time the Jet Stream’s waves are relatively stationary, causing that lobe of southerly warm air to stay in place for many days. Conversely, a lobe of cool air from the north can be spread across a region and kept in place for a while.

Here is a cross section of the Jet Streams in the Norther Hemisphere showing their relationship with major circulating air masses:

Jet Stream Cross Section
Cross section of the atmosphere of the Northern Hemisphere. The Jet Streams form at the highly energetic boundary between major circulating cells, near the top of the Troposphere.

Here is a cartoon of the Earth showing jet streams moving around the planet:

The Jet Streams moving around the planet.  Not indicated is the Intertropical Convergence Zone (ITCA) around the equator which is both not a Jet Stream and the Mother of All Jet Streams.  This post mainly concerns the "Polar Jet."  Note that the wind in the Jet Streams moves from west to east, and the Jet Streams can be either pretty straight or pretty curvy.  Curvy = "high amplitude." This figure and the one above are from NOAA.
The Jet Streams moving around the planet. Not indicated is the Intertropical Convergence Zone (ITCA) around the equator which is both not a Jet Stream and the Mother of All Jet Streams. This post mainly concerns the “Polar Jet.” Note that the wind in the Jet Streams moves from west to east, and the Jet Streams can be either pretty straight or pretty curvy. Curvy = “high amplitude.” This figure and the one above are from NOAA.

Here is a depiction of the Jet Stream being very curvy. The waves in the Jet Stream are called Rossby waves.

The Jet Stream in a particularly wavy state.
The Jet Stream in a particularly wavy state.

(See also this animation on Wikicommons, which will open in a new window.)

Research published in the Proceedings of the National Academies of Science last February, in a paper titled “Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes,” links global warming to the setup of high amplitude waves in the Jet Stream, as well as relatively stationary, blocking, waves that cause extreme warm or cold conditions to persist for weeks rather than just a few days. According to lead author Vladimir Petoukhov, “An important part of the global air motion in the mid-latitudes of the Earth normally takes the form of waves wandering around the planet, oscillating between the tropical and the Arctic regions. So when they swing up, these waves suck warm air from the tropics to Europe, Russia, or the US, and when they swing down, they do the same thing with cold air from the Arctic…What we found is that during several recent extreme weather events these planetary waves almost freeze in their tracks for weeks. So instead of bringing in cool air after having brought warm air in before, the heat just stays.”

So how does global warming cause the northern Jet Stream to become wavy, with those waves being relatively stationary? It’s complicated. One way to think about it is to observe waves elsewhere in day to day life. On the highway, if there is enough traffic, waves of cars form, as clusters of several cars moving together with relatively few cars to be found in the gaps between these clusters. Change the number of cars, or the speed limit, or other factors, and you may see the size and distribution of these clusters (waves) of cars change as well. If you run the water from your sink faucet at just the right rate, you can see waves moving up and down on the stream of water. If you adjust the flow of water the size and behavior of these “standing waves” changes. In a baseball or football field, when people do “the wave” their hand motions collectively form a wave of silliness that moves around the park, and the width and speed of that wave is a function of how quickly individuals react to their fellow sports fan’s waving activity. Waves form in a medium (of cars, water molecules, people, etc.) following a number of physical principles that determine the size, shape, speed, and stability of the waves.

The authors of this paper use math that is far beyond the scope of a mere blog post to link together all the relevant atmospheric factors and the shape of the northern Jet Stream. They found that when the effects of Global Warming are added in, the Jet Stream becomes less linear, and the deep meanders (sometimes called Rossby waves) that are set up tend to occur with a certain frequency (6, 7, or 8 major waves encircling the planet) and that these waves tend to not move for many days once they get going. They tested their mathematical model using actual weather data over a period of 32 years and found a good fit between atmospheric conditions, predicted wave patterns, and actual observed wave patterns.

The northern Jet Stream originates as a function of the gradient of heat from the Equatorial regions to the Polar regions. If air temperature was very high at the equator and very low at the poles, the Jet Stream would look one way. If air temperatures were (and this is impossible) the same at the Equator and the poles, there would probably be no Jet Stream at all. At various different plausible gradients of temperature from Equator to the poles, various different possible configurations of Jet Streams emerge.

One of the major effects of global warming has been the warming of the Arctic. This happens for at least two reasons. First, the atmosphere and oceans are simply warmer, so everything gets warmer. In addition, these warmer conditions cause the melting of Arctic ice to be much more extreme each summer, so that there is more exposed water in the Arctic Ocean, for a longer period of time. This means that less sunlight is reflected directly back into space (because there is less shiny ice) and the surface of the ice-free northern sea absorbs sunlight and converts it into heat. For these reasons, the Arctic region is warming at a higher rate than other regions farther to the south in the Northern Hemisphere. This, in turn, makes for a reduced gradient in the atmospheric temperature from tropical to temperate to polar regions.

Changing the gradient of the atmospheric temperature in a north-south axis is like adjusting the rate of water flowing from your faucet, or changing the number of cars on the highway, or replacing all the usual sports fans at the stadium with stoned people with arthritis. The nature of the waves changes.

This video shows how Donald Trump and Bill O’Reilly are like global warming.

In the case of the atmosphere of Earth’s Northern Hemisphere, global warming has changed the dynamic of the northern Jet Stream, and this has resulted in changes in weather extremes. This would apply to heat waves, cold snaps, and the distribution of precipitation. The phenomenon that is increasingly being called “Weather Whiplash” … more extremes in all directions, heat vs cold and wet vs. dry, is largely caused by this effect, it would seem.

This study is somewhat limited because it covers only a 32 year period, but the findings of the study are in accord with expectations based on what we know about how the Earth’s climate system works, and the modeling matches empirical reality quite well.

See also: Killer Heat Waves and Floods Linked to Climate Change by Stephen Leahy and Slowing Rossby Waves Leading to Extreme Weather? by Stuart Staniford.

More about Climate Change HERE

Petoukhov, V., Rahmstorf, S., Petri, S., & Schellnhuber, H. (2013). Quasiresonant amplification of planetary waves and recent Northern Hemisphere weather extremes Proceedings of the National Academy of Sciences, 110 (14), 5336-5341 DOI: 10.1073/pnas.1222000110

Why are we having such bad weather?

I think most people will agree that in North America (and other places) we’ve been having some bad weather. Some of the weather is not necessarily intrinsically bad … so what if it is a little cooler or a little warmer than you expect. Aridity? Deserts are nice! Extra rainfall? Great for the plants. But actually that sort of thing has its down side since important systems like agriculture, the water supply, and Spring Break work reasonably well because of expectations that might not be met if the weather is different.

Other weather is intrinsically bad. I’d mention tornadoes but at the moment climate and weather experts are not at all agreed on whether or not we are having more, worse, bigger, or otherwise badder tornadoes and if there are differences in tornadoes this decade compared to earlier decades, why that is the case. But other things can be pointed to. Superstorm Hurricane Sandy was the hurricane that should not have gone where it went, should not have been so strong, perhaps should not have been at all. Droughts. Widespread wildfires caused by droughts. Lots and lots and lots of rain causing widespread flooding. Heat waves and cold waves. As a category of things that can happen, these things are in the “bad weather” category, and it is reasonable to ask why they are happening so much “these days.”

It is possible that these changes in weather, or more exactly, these examples of rapidly changing weather that have come to be known as “Weather Whiplash,” are caused by global warming which in turn is caused by the unchecked release of large amounts of fossilized carbon into the atmosphere with the burning, by humans, of fossil fuels. But before I get to that argument (short answer: Weather Whiplash is caused by global warming, but hold on just a sec..) I want to point something else out that is very important.

I want to point out the problem of understanding shifting conditions. Let’s say you are a storekeeper and every day you make a certain amount of profit. How much you make each day varies a great deal owing to a large number of factors. I knew a guy who worked in a camera shop just off Wall Street. He would sell no cameras for days on end and then suddenly sell a gazillion cameras. That would be on a day that the stock market went way up and traders felt flush, and went and bought the expensive cameras and lenses they had been coveting for weeks. I know people who had businesses on Cape Cod and how much money they made on a given weekend depended on the weather forecast for “The Cape” shown to Boston area audiences on Friday (regardless of the actual weather itself, generally). But underlying all this is another set of factors that do not vary day to day or hour to hour (or week to week or even seasonally). One is the overall long term state of the economy (how much stuff do people buy, based on how free they feel with their cash). Another is the overall demand for your particular goods, which may vary little if you sell food but a lot if you sell some trendy widget.

In the absence of good information, how do you know if your business is about to either tank, because people stopped buying your goods, or take off, because people can’t get enough of your goods? If your sales shift a great deal in one day, is that enough information? No. If your sales shift for an entire week, does that tell you something? Maybe, probably not. Most likely, you can identify normal pseudo-cycles, ups and downs, that occur in your business and estimate their length. Some factors cause your business to go up and down over scales of weeks, some over scales of days. Perhaps you can estimate that if you get an average amount of business over six months, and that is higher or lower than the previous six months, then you can say that a basic shift has happened.

Weather has cycles and pseudo-cycles just like businesses do, and they run over the course of days, seasons, years, and somewhat longer cycles that have to do with the position and relationships of major high pressure systems that shift around over cycles of five to fifteen years, and a few other thigns.

Now think about what we expect from global warming.

A simple yet usable model is this: More CO2 in the atmosphere = more heat (energy) in the atmosphere = climate change. But the expected climate change is not linear. Models that seem to work together with direct observation show us that more CO2 has resulted in aridity and wildfires in certain areas. But if we go back in time to when there was even more CO2 in the atmosphere, it seems like everything was wetter, so the whole drought and wildfire thing may be something that gets worse and worse through the 21st century, but at some point is replaced by a whole different set of problems. With respect to sea level rise, which I think is one of the biggest problems we face, it is not likely that the continental glaciers will melt steadily. Most likely they will melt, once their melting really gets going, both steadily and in fits and starts, causing the occasional large rise in sea level.

In other ways, the climate system is likely to change rapidly from one state to another. We are seeing the melting of Arctic Sea Ice each year doing this now, going from one system where there was melting and re-freezing at a certain rate, and changing to a completely different system. Along with this we may be seeing a fundamental long term shift in the nature of Arctic air masses from one way of being to another.

It is like making ice cream, or butter, shaking catchup out of a bottle, or going steady. You work on it and work on it and work on it and all you have is cream and ice, or cream in the churn, or catchup stuck in the bottle, or a friend. Then, suddenly, you have ice cream, or butter, catchup spewing out all over the place, and a significant other. There are many things in life that work this way, where there is not a steady change over long periods of time, but rather, a lot of one thing followed by a sudden shift to a whole different kind of other thing.

So, here’s the problem. If cycles of normal climate change are in the order of a dozen years, but a particular true shift in the basic pattern of climate takes, say, five years and thereafter everything is different, how do you know it happened? How do you know that the “new normal” is a long term change rather than a temporary shift?

There are two ways to know this. One is to wait and see, but if you were thinking of doing something about it but only taking action after you are sure, this is foolish. The other is to use reason and science and stuff to figure out what is going on and then make your best estimate of the situation.

And this brings us back to Weather Whiplash, the New Normal, and the nature of the climate change we may very well be experiencing now. There is an explanation for Superstorm Hurricane Sandy, for Nemo and some of the other storms we’ve had over the last year or so, and for the strange spring and early summer we are experiencing now, and please don’t forget, the strange winters and summers we’ve been having for the last few years. This explanation applies mainly to the Northern Hemisphere and has to do with the Arctic and the Polar Jet Stream.

The Earth’s climate operates as a mechanism for moving excess heat form equatorial regions towards the poles in air and oceanic currents. In the atmosphere, part of this happens when warm tropical air rises and moves away from the equator, drops, and then flows back towards the equator. Farther from the equator, a separate cycling of air currents is thus set up, where air moves up then south at altitude, then drops along side that first cycle of air. Then, there is a third similar giant rotating donut of air closer to the poles. At those positions where the air is moving up, there tend to form high pressure systems, and where the air flows away from these high pressure ridges or mounds, low pressure systems develop. If you stand back and look at the Earth from a distance you can see bands of wet and bands of dry, and regions where certain kinds of storms (like hurricanes, for example) tend to be confined.

The jet streams form at the boundaries between these large scale systems, at altitude, near the top of the troposphere. The jet streams don’t really shape the larger scale systems; rather, they exist because the larger scale systems exist. But once they are in place, the jet streams can determine what happens in those systems.

One of the major jet streams is the Polar Jet Stream that separates temperate regions form more arctic regions. This boundary between two major air masses, defined by that jet stream, can be thought of as analogous to the partition that separates the freezer compartment in the top of a typical refrigerator from the fridge part down below. With this partition in place, the stuff in the freezer stays very cold, and the stuff in the refrigerator stays less cold. If you kept all the cooling coils in place but removed that partition, the difference between the freezer and refrigerator compartments of your Frigidair would be reduced significantly.

Another thing the Polar Jet Stream does is to generate the overall shape of the boundary between temperate and more northerly air masses. The jet stream can be straight, like a big ring around the earth, or it can be all wavy, with major undulations north and south. In the latter case, these undulations can move around the planet or they can sit in place. When they sit in place, they may cause an entire region to be habitually wet, or dry, or more importantly cool or warm, for a long period of time. (This is called “blocking.”) The shape and movement pattern of the Polar Jet Stream ultimately determines the overall pattern of weather everywhere in temperate and subarctic regions.

Now, remember that the position and shape, and movement pattern, of the Polar Jet Stream is determined by high pressure ridges and the low pressure systems they set up (more accurately, these things interact). High pressure systems are relative; A warmish region of the earth, warm relative to nearby cooler regions, will set up a high pressure system. So, during the summer, land masses tend to create high pressure relative to nearby oceans, but during the winter, the oceans may create stronger high pressure relative to land.

And at this point we can see how climate change caused by CO2 increases create Weather Whiplash and other effects.

Warming conditions have caused the Arctic sea to have much less sea ice on it for much longer periods of the summer. This, in turn, allows more sunlight to heat the arctic, because less sunlight is reflected away by shiny ice, and more sunlight provides heat to the sunlight absorbing open water. This changes the relationship between high and low pressure areas in the Northern Hemisphere. This, in turn, has caused the Polar Jet Stream to freak out. Sometimes it is very wavy, often it is blocked, and sometimes it is simply weakened to the point that it almost goes away and allows the freezer and refrigerator compartments to meld.

Cool weather in the United States is not really cool wether. It is the more even, less compartmentalized, distribution of heat across the region north to south. Everything is on average warmer (because of warming) but there is not a very stark boundary between the northern colder regions and the more southerly warmer regions. Last April when we were busy getting snowed on every few days in Minnesota, the Arctic was warmer (but still cold) than it normally would be. Last fall, the shape of these weather systems caused Superstorm Hurricane Sandy to be stronger, and to fail to do what these storms normally do: head north by northeast and dissipate. Instead, the storm turned left and blotto’ed New York, Connecticut and New Jersey.

Peter Sinclair of Climate Denial Crock of the Week, famous for his videos, in a post on Weather Whiplash, has produced a video that covers some of this very nicely:

So, lets get back to the original question. Why are we having such bad weather? Because the system that is usually in place, with a strong Polar Jet Stream that tends to be linear during the summer, has changed to a different system where the Arctic Oscillation … a high-low pressure system pattern … has shifted to a “negative” configuration because of warming of the Arctic sea. This different system has a number of effects that combine with other effects of global warming to produce strange weather. Those other effects include there being more energy in the atmosphere, and more moisture concentrated in more discrete dense patches, which therefore also means some very dry conditions. Blocking may have caused dry conditions to persist longer over selected areas than otherwise, and at the moment, blocking and added moisture seems to be causing the midsection of the United States to become the world’s largest water park. And, between storm fronts, the overall weather of the region is cool, yet the storm systems are very energetic.

Weather Whiplash. It makes sense because everything that is happening conforms to expectations based on what we know about climate and weather. Will this really be the “new normal?” Is a few years in a row of a strange acting Polar Jet Stream and that other stuff the result of a fundamental change in the way our climate system works, or is it just a typical variation that we can expect to happen now and then. Well, if this was a typical variation of the type we normally see on occasion, there would be less incredulity among climatologists, meteorologists, and forecasters. It makes more sense to explain Weather Whiplash as a new state that the climate has shifted to (mostly, expect some more back and forth, I assume) because of the unchecked release of fossil Carbon into the atmosphere by the burning of fossil fuels by humans.