Could solar geoengineering cool the planet? U.S. gets serious about finding out

[Hartmann352]

Campaign seeks to understand reflective particles in the stratosphere, which cooling schemes would enhance

14 FEB 2023
BY PAUL VOOSEN


Instruments aboard a modified WB-57F bomber will count and analyze natural particles at altitudes of 20 kilometers, over 12 miles or 63,000 feet. ROBERT MARKOWITZ/NASA-JSC


Any work on solar geoengineering—the notion of artificially making the atmosphere more reflective to cool an overheated planet—is fraught with controversy. Last year, for example, a tech entrepreneur claimed he launched two weather balloons from Baja California into the stratosphere, where they may have released a puff of sulfur dioxide that gave rise to a small patch of reflective sulfate particles. The stunt drew widespread condemnation. But for researchers, it prompted a question: If a rogue actor had conducted a larger release, would they be able to detect it—or know with any certainty what it would do?

The U.S. National Oceanic and Atmospheric Administration (NOAA) is venturing into the fray to answer these questions, with a bid to understand the types, amounts, and behavior of particles naturally present in the stratosphere. Unlike the Mexico caper, the balloons and high-altitude aircraft in the program aren’t releasing any particles or gases. But the large-scale field campaign is the first the U.S. government has ever conducted related to solar geoengineering. It’s very basic research, says Karen Rosenlof, an atmospheric scientist at NOAA’s Chemical Sciences Laboratory. “You have to know what’s there first before you can start messing with that.”

Research on solar geoengineering—also called solar radiation management—has long been anathema to some climate scientists and activists. They fear it could distract from emissions cuts, could have unforeseen risks, and would not address some impacts of rising carbon dioxide, including ocean acidification. Federal agencies have largely steered clear of the work, even after a report from the National Academies of Sciences, Engineering, and Medicine (NASEM) in 2021 recommended a $200 million research program.

Congress directly ordered NOAA to develop a program in a 2020 spending bill. Support for the program, innocuously dubbed Earth’s Radiation Budget, has grown to nearly $10 million annually. SilverLining, an organization supportive of solar geoengineering research, lobbied for it, and gained the support of key legislators, says Kelly Wanser, SilverLining’s executive director, who came to climate advocacy from a career in technology. She says she told the lawmakers that emissions cuts weren’t happening fast enough, and that solar geoengineering might—or might not—be needed to reduce impacts in the next 40 years. “What do we need to know to evaluate those things in a very rigorous and honest-with-ourselves way?” Wanser asks. “I want to know.”

One focus of the NOAA program is sulfates, the reflective particles that would be lofted into the stratosphere in many solar geoengineering proposals. Volcanoes and industrial emissions are the main natural sources of sulfur dioxide, one precursor of sulfates; carbonyl sulfide, a gas emitted by microbes in the oceans, is another. The updrafts in severe storms in the tropics are thought to pump the gases into the stratosphere, but massive forest fires are emerging as another important mechanism for lifting them.

Because of a temperature inversion at the stratosphere's base, sulfate particles linger there for years, which encourages geoengineering advocates. But researchers need a clearer picture of natural stratospheric particles before they can contemplate supplementing them artificially, says Gregory Frost, the NOAA atmospheric chemist who oversees the program.

In 2020, NOAA began regularly launching sensor-equipped weather balloons to gather baseline data on the size and concentration of the particles. The record should allow NOAA to detect shifts in particle distributions, which could indicate a new source, such as an eruption—or a clandestine geoengineering intervention, Frost says.

The measurements could also help climate modelers represent stratospheric particles more realistically. “The only way to know if our models are doing the right thing is to have data to evaluate them,” says Simone Tilmes, a modeler at the National Center for Atmospheric Research (NCAR). At the moment, most models handle particles in a coarse way, categorizing them into a few arbitrary size ranges. With NOAA funding, Tilmes’s team has now upgraded NCAR’s flagship climate model with 40 possible bins for sulfate size, and so far it seems to more reliably capture events like the sulfur-rich eruption of Mount Pinatubo in 1991.

Now, the project is launching its next phase, the largest stratospheric aircraft campaign in the past 2 decades, “if not ever,” Frost says. One of NASA’s WB-57 research jets—a heavily modified bomber from the 1960s—has been outfitted with 17 instruments, many of which have never flown to the stratosphere before. One can measure sulfur dioxide levels down to 2 parts per trillion, and another can distinguish different particles by their chemical makeup.

Next week, flights will begin out of Houston, Texas, to altitudes of up to 20 kilometers, and later this month, the team plans to move to Fairbanks, Alaska, where they will fly until late March. At that time of the year, air that entered the stratosphere a half-decade earlier in the tropics descends in the Arctic. “We’re going to get into really old stratospheric air,” says Troy Thornberry, the NOAA atmospheric chemist who leads the flights. By studying aging sulfate particles, the team hopes to witness the chemical reactions that break them apart and release sulfur at the end of their lifetimes. They want to study how such sulfur interacts with organic particles such as soot and the dust of meteorites. Rosenlof says they will also study how soot absorbs the Sun’s heat, causing air parcels to rise and prolonging particle lifetimes in the stratosphere.

Additional flights are planned for Costa Rica in 2024 and the Southern Hemisphere in 2025. But in the meantime, the team is open to missions of opportunity. If a massive volcanic eruption occurs, they’ve assembled the perfect payload to explore its impact, Frost says. “That would be an event we’d want to study if at all possible.” The same goes for any wildfires similar in scale to those in Australia in 2020.

Some researchers want the U.S. government to put together a bigger solar geoengineering research program. Although the NOAA program is well designed, it’s a small piece of the puzzle, says Chris Field, a climate scientist at Stanford University and chair of the NASEM report. “It’s really important to find a way to ask bold questions about where something unexpected could go wrong.” In March 2022, Congress ordered the White House’s Office of Science and Technology Policy to develop such a plan, but it still has not been released. “Federally funded research is a very good idea—and the only way this work ideally should be funded,” says Sikina Jinnah, who studies geoengineering governance at the University of California, Santa Cruz.

Although some climate scientists disagree that such research should go forward or have even called for a ban on it, shutting it down would be a mistake, says James Hurrell, a climate scientist at Colorado State University who previously led NCAR. “If we could help avoid the worst impacts [of climate change] and buy more time for the world to reduce concentrations, don’t we want to know that?” And if it’s a bad idea, he adds, “the best way to prove that is through research.”

Correction, 15 February, 12:45 p.m: A previous version of the story incorrectly stated that the stratosphere has no weather.

See: https://www.science.org/content/art...ontent=alert&et_rid=255259432&et_cid=4598348&

It is interesting when weapons of war, like the WB-57 the former Martin B-57 Canberra, is repurposed for peaceful intentions. Because of the high altitudes plumbed by this aircraft, the two crew members who are positioned at separate tandem stations in the forward section of the fuselage wear full pressure suits like those worn in the U-2 and the SR-71, the latter being the survivors of the experimental fighter aircraft, the YF-12A, designed and constructed by Kelly Johnson at Lockheed's secret Skunk Works. The pilot station contains all the essential equipment for flying the aircraft while the sensor equipment operator (SEO) station contains both navigational equipment and controls for the operation of the payloads that are located throughout the aircraft. The WB-57 can fly for approximately 6.5 hours, has a range of approximately 2500 miles, and can carry up to 8,800 lbs of scientific payload.
Hartmann352


NASA - NOAA


NASA - NOAA

 

[1978robinson]

Those ain't the planes spraying the chemtrails, which are nano particles of aluminum, magnesium and fiberglass. Which don't stay in the atmosphere floating around they fall people breath them in some doctors are smart enough to check those in blood tests depending on what conditions their patients have. And there's been other planes up there flying around behind the planes spraying the chemtrails collecting air samples testing them yep. And for anyone that says there contrails not chemtrails which I heard someone explain that the contrails are water vapor from the engines exhaust. Well how is that run the engine runs of super high octane gasoline called airplane fuel that's made from petroleum? U can't burn oil and get water vapor as the exhaust. Then on top of that there's plenty of videos that show someone taking video from another plane or the ground where the chemtrail plane is spraying and there's more spray lines coming out the planes wings then the amount of engines it has. If it has 2 engines then u would only have 2 trails obviously. But when there's 6 trails and only 2 engines and then all of a sudden the sprayers cut out and then there's no trails being left not even exhaust from the engine then a few seconds later the sprayers start spitting then spraying again they had to switch tanks with sprays coming out the very edge of the wing where theres no engine mounted. Engines are mounted in the middle of each wing. I wonder what else can try to be said that there not chemtrails especially since when trump was president he signed a bill to stop tax payer funding of it. Hmmm

Campaign seeks to understand reflective particles in the stratosphere, which cooling schemes would enhance

14 FEB 2023
BY PAUL VOOSEN

View attachment 2611
Instruments aboard a modified WB-57F bomber will count and analyze natural particles at altitudes of 20 kilometers, over 12 miles or 63,000 feet. ROBERT MARKOWITZ/NASA-JSC


Any work on solar geoengineering—the notion of artificially making the atmosphere more reflective to cool an overheated planet—is fraught with controversy. Last year, for example, a tech entrepreneur claimed he launched two weather balloons from Baja California into the stratosphere, where they may have released a puff of sulfur dioxide that gave rise to a small patch of reflective sulfate particles. The stunt drew widespread condemnation. But for researchers, it prompted a question: If a rogue actor had conducted a larger release, would they be able to detect it—or know with any certainty what it would do?

The U.S. National Oceanic and Atmospheric Administration (NOAA) is venturing into the fray to answer these questions, with a bid to understand the types, amounts, and behavior of particles naturally present in the stratosphere. Unlike the Mexico caper, the balloons and high-altitude aircraft in the program aren’t releasing any particles or gases. But the large-scale field campaign is the first the U.S. government has ever conducted related to solar geoengineering. It’s very basic research, says Karen Rosenlof, an atmospheric scientist at NOAA’s Chemical Sciences Laboratory. “You have to know what’s there first before you can start messing with that.”

Research on solar geoengineering—also called solar radiation management—has long been anathema to some climate scientists and activists. They fear it could distract from emissions cuts, could have unforeseen risks, and would not address some impacts of rising carbon dioxide, including ocean acidification. Federal agencies have largely steered clear of the work, even after a report from the National Academies of Sciences, Engineering, and Medicine (NASEM) in 2021 recommended a $200 million research program.

Congress directly ordered NOAA to develop a program in a 2020 spending bill. Support for the program, innocuously dubbed Earth’s Radiation Budget, has grown to nearly $10 million annually. SilverLining, an organization supportive of solar geoengineering research, lobbied for it, and gained the support of key legislators, says Kelly Wanser, SilverLining’s executive director, who came to climate advocacy from a career in technology. She says she told the lawmakers that emissions cuts weren’t happening fast enough, and that solar geoengineering might—or might not—be needed to reduce impacts in the next 40 years. “What do we need to know to evaluate those things in a very rigorous and honest-with-ourselves way?” Wanser asks. “I want to know.”

One focus of the NOAA program is sulfates, the reflective particles that would be lofted into the stratosphere in many solar geoengineering proposals. Volcanoes and industrial emissions are the main natural sources of sulfur dioxide, one precursor of sulfates; carbonyl sulfide, a gas emitted by microbes in the oceans, is another. The updrafts in severe storms in the tropics are thought to pump the gases into the stratosphere, but massive forest fires are emerging as another important mechanism for lifting them.

Because of a temperature inversion at the stratosphere's base, sulfate particles linger there for years, which encourages geoengineering advocates. But researchers need a clearer picture of natural stratospheric particles before they can contemplate supplementing them artificially, says Gregory Frost, the NOAA atmospheric chemist who oversees the program.

In 2020, NOAA began regularly launching sensor-equipped weather balloons to gather baseline data on the size and concentration of the particles. The record should allow NOAA to detect shifts in particle distributions, which could indicate a new source, such as an eruption—or a clandestine geoengineering intervention, Frost says.

The measurements could also help climate modelers represent stratospheric particles more realistically. “The only way to know if our models are doing the right thing is to have data to evaluate them,” says Simone Tilmes, a modeler at the National Center for Atmospheric Research (NCAR). At the moment, most models handle particles in a coarse way, categorizing them into a few arbitrary size ranges. With NOAA funding, Tilmes’s team has now upgraded NCAR’s flagship climate model with 40 possible bins for sulfate size, and so far it seems to more reliably capture events like the sulfur-rich eruption of Mount Pinatubo in 1991.

Now, the project is launching its next phase, the largest stratospheric aircraft campaign in the past 2 decades, “if not ever,” Frost says. One of NASA’s WB-57 research jets—a heavily modified bomber from the 1960s—has been outfitted with 17 instruments, many of which have never flown to the stratosphere before. One can measure sulfur dioxide levels down to 2 parts per trillion, and another can distinguish different particles by their chemical makeup.

Next week, flights will begin out of Houston, Texas, to altitudes of up to 20 kilometers, and later this month, the team plans to move to Fairbanks, Alaska, where they will fly until late March. At that time of the year, air that entered the stratosphere a half-decade earlier in the tropics descends in the Arctic. “We’re going to get into really old stratospheric air,” says Troy Thornberry, the NOAA atmospheric chemist who leads the flights. By studying aging sulfate particles, the team hopes to witness the chemical reactions that break them apart and release sulfur at the end of their lifetimes. They want to study how such sulfur interacts with organic particles such as soot and the dust of meteorites. Rosenlof says they will also study how soot absorbs the Sun’s heat, causing air parcels to rise and prolonging particle lifetimes in the stratosphere.

Additional flights are planned for Costa Rica in 2024 and the Southern Hemisphere in 2025. But in the meantime, the team is open to missions of opportunity. If a massive volcanic eruption occurs, they’ve assembled the perfect payload to explore its impact, Frost says. “That would be an event we’d want to study if at all possible.” The same goes for any wildfires similar in scale to those in Australia in 2020.

Some researchers want the U.S. government to put together a bigger solar geoengineering research program. Although the NOAA program is well designed, it’s a small piece of the puzzle, says Chris Field, a climate scientist at Stanford University and chair of the NASEM report. “It’s really important to find a way to ask bold questions about where something unexpected could go wrong.” In March 2022, Congress ordered the White House’s Office of Science and Technology Policy to develop such a plan, but it still has not been released. “Federally funded research is a very good idea—and the only way this work ideally should be funded,” says Sikina Jinnah, who studies geoengineering governance at the University of California, Santa Cruz.

Although some climate scientists disagree that such research should go forward or have even called for a ban on it, shutting it down would be a mistake, says James Hurrell, a climate scientist at Colorado State University who previously led NCAR. “If we could help avoid the worst impacts [of climate change] and buy more time for the world to reduce concentrations, don’t we want to know that?” And if it’s a bad idea, he adds, “the best way to prove that is through research.”

Correction, 15 February, 12:45 p.m: A previous version of the story incorrectly stated that the stratosphere has no weather.

See: https://www.science.org/content/art...ontent=alert&et_rid=255259432&et_cid=4598348&

It is interesting when weapons of war, like the WB-57 the former Martin B-57 Canberra, is repurposed for peaceful intentions. Because of the high altitudes plumbed by this aircraft, the two crew members who are positioned at separate tandem stations in the forward section of the fuselage wear full pressure suits like those worn in the U-2 and the SR-71, the latter being the survivors of the experimental fighter aircraft, the YF-12A, designed and constructed by Kelly Johnson at Lockheed's secret Skunk Works. The pilot station contains all the essential equipment for flying the aircraft while the sensor equipment operator (SEO) station contains both navigational equipment and controls for the operation of the payloads that are located throughout the aircraft. The WB-57 can fly for approximately 6.5 hours, has a range of approximately 2500 miles, and can carry up to 8,800 lbs of scientific payload.
Hartmann352

View attachment 2612
NASA - NOAA

View attachment 2613
NASA - NOAA

 

[1978robinson]

Geo engineering is a stupid idea. Got all these wanna be smart people that think they know everything until like always something happens that they said shouldn't of. According to their to their what? Science? Lol. Test? U can run a fake test that's not to size and call it good when it's not involving the extent of everything involved especially when the so called smart people run a controlled test with simulated conditions. Which doesn't mean jack crap except for ur an idiot. Scientist what certification does one get to become a scientist? What scientist courses are required to get that scientist degree? Where the specialty science university at? Like it's that hard to manipulate a test scientist do to show the outcome that they need the test to show? Get real. Made me think of the old TV show get smart lol. Any moron can claim their a scientist and can be one they only need to know the one thing that their trying to prove. And hey if the test fails 1000 times then on a fluke or manipulation all of sudden the test passed 1 time well guess what it's now valid cuz it passed but don't figure in or tell anyone that it failed 1000 times before that. Now they get their scam of tax payers money in the form of a grant for 1 out of a 1000 times which probably couldn't be repeated unless manipulated again. Jokes, scammers, self righteous narcissist that think their better n smarter then everyone else cuz they have this idea and wanna play inspector gadget crossed with Macgyver. Like there isn't better things for tax payers money to be spent on. Then hog wash trial and error ideas that how many even pan out for each scientist getting grants in the first place? I doubt that every scientist even has 1 patent. Some might have more I bet a lot have less. Good job inventing just cuz ur God complex won't let u work a regular job that is until ur grant money runs out which will be here pretty soon in less then 7 years....

Those ain't the planes spraying the chemtrails, which are nano particles of aluminum, magnesium and fiberglass. Which don't stay in the atmosphere floating around they fall people breath them in some doctors are smart enough to check those in blood tests depending on what conditions their patients have. And there's been other planes up there flying around behind the planes spraying the chemtrails collecting air samples testing them yep. And for anyone that says there contrails not chemtrails which I heard someone explain that the contrails are water vapor from the engines exhaust. Well how is that run the engine runs of super high octane gasoline called airplane fuel that's made from petroleum? U can't burn oil and get water vapor as the exhaust. Then on top of that there's plenty of videos that show someone taking video from another plane or the ground where the chemtrail plane is spraying and there's more spray lines coming out the planes wings then the amount of engines it has. If it has 2 engines then u would only have 2 trails obviously. But when there's 6 trails and only 2 engines and then all of a sudden the sprayers cut out and then there's no trails being left not even exhaust from the engine then a few seconds later the sprayers start spitting then spraying again they had to switch tanks with sprays coming out the very edge of the wing where theres no engine mounted. Engines are mounted in the middle of each wing. I wonder what else can try to be said that there not chemtrails especially since when trump was president he signed a bill to stop tax payer funding of it. Hmmm

 

[Hartmann352]

There seems to be some confusion about the nature and chemistry of contrails.


Contrails over Lucerne, Switzerland; photo from our 10/2022 vacation.

Jets leave white trails, or contrails, in their wakes for the same reason you can sometimes see your breath. The hot, humid exhaust from jet engines mixes with the atmosphere, which at high altitude is of much lower vapor pressure and temperature than the exhaust gas. The water vapor contained in the jet exhaust condenses and may freeze, and this mixing process forms a cloud very similar to the one your hot breath makes on a cold day.

A contrail will form behind a jet if, as exhaust gases cool and mix with surrounding air, the humidity is high enough and the temperature low enough for liquid water to condense and freeze.


The sheer number of contrails generated on a typical day in busy air corridors can come as a shock. A NASA satellite took this enhanced infrared image of the southeastern U.S. on January 29, 2004. Image credit: NASA Langley Research Center

Jet engine exhaust contains carbon dioxide, oxides of sulfur and nitrogen, unburned fuel, soot and metal particles, as well as water vapor. The soot provides condensation sites for the water vapor. Any particles present in the air provide additional sites.

Depending on a plane's altitude, and the temperature and humidity of the atmosphere, contrails may vary in their thickness, extent and duration. The nature and persistence of jet contrails can be used to predict the weather. A thin, short-lived contrail indicates low-humidity air at high altitude, a sign of fair weather, whereas a thick, long-lasting contrail reflects humid air at high altitudes and can be an early indicator of a storm.

The mixing gases contained in the contrail rotate with respect to the ambient air. These regions of rotating flow are called vortices. (Any sharp surface, such as the tip of a wing, can cause vortical flow in its wake if it is sufficiently large or the flow is sufficiently fast.) On occasion, these trailing vortices may interact with one another.

In one well-known example of this fact, the Crow Instability* causes the vortices to develop symmetric sinusoidal oscillations and eventually to merge and form vortex rings behind the jet. This instability can be triggered by turbulence in the surrounding air or by local variation in air temperature or density, which may itself be the result of the stratification of the atmosphere. When the contrails are visible and strong, it is possible to see the white streaks become wavy and then leave rings floating high in the sky, like smoke rings from a giant cigar.

Recent research has suggested that the ice clouds contained in contrails cause greenhouse effects and contribute to global warming as part of the insulating blanket of moisture and gases in the atmosphere. Researchers in this area seized on the opportunity presented on September 11 and 12 over the U.S. The complete cessation of commercial air traffic offered a control sky without contrails for use in quantifying the environmental effects of contrails.

Other research indicates that contrails serve to reflect sunlight and therefore lower the solar flux reaching the Earth's surface.


This photo was taken over Emden, Germany, on September 27th, 1943, by General Stanley M. Smith.

Contrails can be left by any hydrocarbon fueled engine. If you could take your car up to 30,000 or 40,000 feet it, too, would make contrails. (Actually, in Alaska, cars make a kind of contrail on the ground when it gets to -40F).

You see a lot more from jets as prop planes usually don’t have a reason to go that high. Many images from WWII show contrails be left by propeller driven bombers and fighter aircraft. The wartime contrails are generally from planes that are flying very high to avoid anti-aircraft fire and to give their escorting fighter aircraft better visibility against their adversaries.

Burning hydrocarbons (Gasoline, AvGas, Kerosene, diesel, Jet fuel, etc) makes mostly water and carbon dioxide. The water is what creates the contrail.

Contrails ARE artificial clouds – they form with basically the same mechanism as cirrus clouds. They “create” cirrus clouds simply by spreading out, being blown by the wind, and sometimes by growing larger (as clouds sometimes do, quite normally).

When water vapor condenses into the tiny drops and ice crystals that form clouds, the process is called nucleation. For liquid clouds to form there needs to be the small particles you mention, these are called Cloud condensation nuclei. They are found everywhere in the atmosphere, but if there are more of them, then clouds can form quicker and easier.

Contrails are ice clouds (like cirrus clouds are), and form via an Ice nucleus this can be the same kind of thing as the cloud condensation nucleus, but if the air is cold and humid enough, then the water can directly sublimate into an ice crystal without a nucleus (homogeneous nucleation). But that’s not generally a large part of the ice in a contrail.

Aircraft exhaust does contain a lot of particles that can act as nuclei, most in the form of soot, and that, together with the particles already in the atmosphere, is what the contrail cloud forms upon.

See: https://www.scientificamerican.com/article/why-do-jets-leave-a-white/

See: https://contrailscience.com/some-more-wwii-contrails/

See: https://contrailscience.com/some-more-wwii-contrails/

* Crow instability: The antisymmetric mode was neglected in the original Crow instability. In this study, a general-instability-analysis method was used to obtain the upper bounds of the instability growth rates, which are independent of the cutoff parameter in the self-induction integral. This result suggests that, not only do the antisymmetric modes exist, but also they are most amplified. These antisymmetric modes can occur in both the long- and short-wave modes. An example of the growth histories of the symmetric and antisymmetric modes for an aircraft wake is given. It is shown that the presence of the antisymmetric modes can cause the time of linking of the wake vortices to be shortened, which could lead to the reduction of the wake-vortex hazard to following aircraft.

Vortices are basic ingredients of transitional and turbulent flows, and studying their fundamental dynamics and interactions helps us understand the behavior of the often-complicated flows encountered in nature or industry. A pair of straight parallel vortices is one of the elementary vortex configurations considered in the literature, motivated to a large extent by its relevance to the problem of aircraft trailing wakes. Any horizontally flying vehicle generates a counter-rotating vortex pair in its far wake, which can represent a potential hazard for following vehicles, and corotating configurations are present in the near wake of aircraft wings with lowered flaps.

Despite their conceptual simplicity, vortex pairs exhibit a variety of complex behaviors, ranging from two-dimensional dynamics (rotation, merging) to three-dimensional instabilities. Figure 1 shows an example in which the simultaneous growth of two distinct instabilities of a counter-rotating vortex pair is observed in a laboratory experiment, a numerical simulation, and a full-scale aircraft wake.

Figure 1  Visualizations of long-wave and shortwave instabilities developing in counter-rotating pairs of equal-strength vortices. (a) Dye visualization in a water tank at Re = 2,750. The field of view is approximately 14 cm×42 cm. Panel a taken with permission from Leweke & Williamson (1998). (b) Numerical simulation with Re = 2,400. Panel b taken with permission from Laporte & Corjon (2000), copyright AIP Publishing LLC. (c) Photograph of the jet condensation trails from a Boeing 747 at Re≈6×107. The field of view is approximately 150 m×520 m. Panel ccopyright 2011, Herbert Raab, reproduced with permission. Download Full-ResolutionDownload PPT

In the following, we review the dynamics and instabilities of vortex pairs in a homogeneous incompressible fluid. After recalling the properties of the two-dimensional base flows, which depend primarily on the circulation ratio of the two vortices, we focus on three major evolution mechanisms characterizing these flows: two-dimensional merging of corotating vortices, the three-dimensional Crow instability of counter-rotating vortices**, and shortwave elliptic instability. The results concerning the structure and growth rate of these instabilities are then used to analyze the configuration of a vortex pair approaching a solid wall. We also address the interactions between the various phenomena.

See: https://www.annualreviews.org/doi/10.1146/annurev-fluid-122414-034558

** The long-wavelength instability involves sinusoidally radial displacement of vortices without influence on their core structure. It can be observed behind aircraft where the wake vortices are visualised by condensation (Jacob 1995), resulting in long axially sinusoidal wavelengths relative to the initial vortex separation distance. Crow (1970), who undertook the first theoretical study of this instability, showed that counter-rotating vortex pairs mutually interact, leading to the amplification of low wavenumber perturbations and resulting in the deformation of the vortex pair into axially periodic long-wavelength structures. By using a vortex filament model, Crow found that the instability mode is symmetric and sinusoidal, and initially confined to planes inclined at close to 45◦ to the plane on which both vortices initially lie.

The dynamics of this eponymous ‘Crow’ instability arises from a balancing of three plane rotation mechanisms resulting in radial stretching of the perturbation. Kelvin (1880) illustrated the self-induced rotation of the instability plane of a single sinusoidally perturbed vortex. The introduction of the second vortex mutually induces counter-rotation and radial stretching on the plane where the perturbation grows. When the plane rotation effects cancel, the wave is held at a constant angle with a positive component of radial strain, leading to exponential growth in amplitude. To tackle the issue of the singularity of the vortex filament model, Crow introduced a ‘cutoff’ technique, which involves integrating the Biot–Savart law for the self-induced motion of the vortex filament up to a finite region near the vortex core.

The choice of the cutoff distance was based on solutions by Thompson (1910) for both a vortex ring and rotating sinusoid with constant vorticity in the core. Bliss (1970) and Widnall, Bliss & Zalay (1971) extended the stability analysis by asymptotic matching of the inner (close to the vortex core) solution of the vorticity conservation equation and the outer filament based Biot–Savart law. This allowed for general vortex velocity profiles with axial flow to be considered, and an analytical expression for the appropriate cutoff.

Downloaded from https://www.cambridge.org/core. Monash University, on 07 Jan 2020 at 03:36:50, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/jfm.2019.816

Vortex pair wall interaction distance to be used in Crow’s approach was derived. This expression was based on a Batchelor vortex of radius a and axial flow parameter W. The effects of vorticity distributions on the stability of vortex pairs was further studied by Moore & Saffman (1973) and Klein, Majda & Damodaran (1995).

See: https://www.flair.monash.edu/public...ating_vortex_pair_interacting_with_a_wall.pdf

A contrail is an aircraft condensation trail that appears as line-shaped or intertwined clouds, due to the Crow instabilities, in the sky. They are composed of ice particles that form in the exhaust of an aircraft when flying in a narrow range of altitudes in the upper atmosphere, several miles or more above the ground. Contrails are easily identifiable in the sky behind a jet-engine aircraft at the head of the trail or from propeller driven aircraft at sufficient altitude for them to form. Contrails can form within a few wingspans of the aircraft behind the exhaust and can dissipate within a few aircraft lengths from the engine exhaust because of the lack of available water vapor in the atmosphere.
Hartmann352

The contrarian view of chem trails:

Surveyed scientists debunk chemtrails conspiracy theory

UCI, Carnegie paper explains persistent aircraft trails, substances in soil and water
August 12, 2016

The world’s leading atmospheric scientists overwhelmingly deny the existence of a secret, elite-driven plot to release harmful chemicals into the air from high-flying aircraft, according to the first peer-reviewed journal paper to address the “chemtrails” conspiracy theory.

Researchers from the University of California, Irvine, the Carnegie Institution for Science and the nonprofit Near Zero organization asked 77 atmospheric chemists and geochemists if they had come across evidence of such a large-scale spraying program, and 76 responded that they had not. The survey results were published Wednesday in Environmental Research Letters.

Heat from aircraft engines produces condensation trails that can be clearly seen from the ground. A small but vocal segment of the population firmly believes that these are composed not merely of condensed water vapor but of chemicals and elements such as strontium, barium and aluminum that powerful, high-level entities have been intentionally and covertly releasing into the atmosphere for decades.

They find the increased number and lingering presence of these aerial streaks suspicious and claim to have identified toxic substances in soil and water samples.

“The chemtrails conspiracy theory maps pretty closely to the origin and growth of the internet, where you can still find a number of websites that promote this particular brand of pseudoscience,” said study co-author Steven Davis, UCI associate professor of Earth system science. “Our survey found little agreement in the scientific community with claims that the government, the military, airlines and others are colluding in a widespread, nefarious program to poison the planet from the skies.”
The belief in chemtrails parallels increasing public distrust of elites and social institutions, according to earlier social science research. To those convinced, the chemicals are sprayed to regulate the food supply, control human population and/or manipulate weather patterns. In recent years, the theory has expanded to include government-sponsored geoengineering to mitigate climate change.
Some of the surveyed specialists suggested that global warming may in itself be a cause of longer-lasting condensation trails from aircraft engines. Another contributor, outlined in the study, is the steady growth of air travel in recent decades, which leads airplanes to fly higher, where contrails are more likely to form and remain in the sky.

“Despite the persistence of erroneous theories about atmospheric chemical spraying programs, until now there were no peer-reviewed academic studies showing that what some people think are chemtrails are just ordinary contrails,” said Carnegie investigator and co-author Ken Caldeira. “Contrails are becoming more abundant as air travel expands. Also, it is possible that climate change is causing contrails to persist for longer than they used to.”

The survey’s respondents – many of them currently active in research on atmospheric dust and pollution – stressed that methods of collecting samples of water, snow and soil recommended by chemtrails-focused groups may be to blame for faulty results. Obtaining and transporting samples via Mason jars with metal lids, for example, was cited as a poor practice that could lead to erroneous outcomes.

One of the experts questioned wrote: “The jar will contaminate the sample, as will the metal lid, particularly if you shake it. I cannot imagine a worse protocol for collecting a sample; the data would be totally worthless.” Another said, “To analyze metals in environmental samples, glass needs to go through an acid wash to remove any residual metals. Otherwise, plastic should be used.”

UCI’s Davis said: “We don’t imagine that we’re going to sway the beliefs of hardcore adherents to the chemtrails conspiracy theory with this study. But we thought it was important to go on the record with fundamental scientific facts to refute claims that the government is deliberately spreading harmful chemicals from jet aircraft.”

Founded in 1965, UCI is the youngest member of the prestigious Association of American Universities. The campus has produced three Nobel laureates and is known for its academic achievement, premier research, innovation and anteater mascot. Led by Chancellor Howard Gillman, UCI has more than 30,000 students and offers 192 degree programs. It’s located in one of the world’s safest and most economically vibrant communities and is Orange County’s second-largest employer, contributing $5 billion annually to the local economy. For more on UCI, visit www.uci.edu.

See: https://news.uci.edu/2016/08/12/surveyed-scientists-debunk-chemtrails-conspiracy-theory/