Jet Trails and weather patterns.

[Buzzsaw]

8:00am: The sky overhead was pristine, no fluffy white in sight. Two commercial airliners held above like toys, miniature models gleaming metal-bright - so tiny they could barely be seen from my ground level spot. What a relief! Finally a day of warming! Tomato plants do not particularly care for the brisk lows offered by my region, and especially living on a creek bed.

Heavy air descends. The evening chill gathers, cool spirits assemble, forming their slow motion ceremonial march - an entranced procession summoned by the marshes and wilderness valleys below. Wispy currents huddle, cradled like a hammock slung between south-ridge copses and tamaracks on the wetland's other side.


Within an hour blemishes were beginning to form. What began as a burning blue morning was now filling with streaky clouds that seemed to be expanding, growing in size. What happened to the cloudless morning? The thermometer reading sat there like a stick-in-mud doing nothing.







This made me curious. Since I could see with my own eyes the phenomenon apparently taking place, the day keeping artificially cool by the travel overhead, it compelled me to investigate. I wanted to find out if any studies had been done, if anyone had researched how jet travel might be affecting weather, and if so, in what way? Are jet planes creating a net cooling effect on our planet? Of course it's widely known that clouds not only block incoming sunlight, but also slow escaping heat.

So what gives? Has anyone read anything about this?

[Jack_Ian]

There was some research into this after 9/11.
The grounding of planes afforded an opportunity to compare weather with/without contrails.

I can remember the findings though.
Probably available online somewhere.

[Courk]

According to cracked (I know, reliable), it got hotter. (Their reference is a downloadable file, which my phone won't let me copy the link to.)

http://www.cracked.com/article_20009_7-bizarre-ways-you-didnt-know-911-changed-world.html

[The Great Crep'er]

I initially thought you would bring up the old theories.
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[Buzzsaw]

I did read a little bit about the data collected when the planes were grounded back in Sept '01. Was thinking though that 3 days is so little time in the realm of measuring weather patterns that it might not be meaningful.

I don't how much potential this has for much discussion but I thought I would not post all the info yet that I have found, thought that would not encourage much discussion to take place.

I would prefer not to talk about the conspiracy theories, the gub'mint spraying the air with chemicals, since there isn't (IMO) really anything to discuss there at all.

But I don't care if this thread devolves into that, would like to let things take their own course. I figure that if the discussion might go the way of conspiracies, then that only means there wasn't much discussion potential for air travel being responsible for cooling (or warming) the planet in any measurable or significant way.

To make it clear though, I don't believe in any conspiracies concerning planes and jet trails. Only wanted to consider the effects cirrus clouds have - specifically the ones created and seeded by the exhaust from high altitude aircraft. :

[Jack_Ian]

Logically I would have expected the contrails to make things hotter.
Energy from the Sun comes as high-energy radiation that can easily penetrate the wispy contrails reaching the ground and heating it up.
The energy from the heated surface gets trapped under the contrails as they provide a small amount of insulation.
This is essentially the premise behind The Greenhouse Effect. Energy checks in but doesn't check out.

[The Potter]

Combustion reactions create a significant amount of water vapor. If I recall correctly, burning a kilogram of fuel should produce about a kilogram of water. Jet trails are created from this water vapor. This water vapor will also from nucleation points for continued cloud growth.


One of the interesting sides of global warming not rising surface temperatures as much as expected is the negative feedback loop of global darkening. Simply put as the world creates more green house gases a larger percentage of solar rays are being trapped but a smaller percentage actually make it to the surface.
The study was spurred from long term data of farmland water evaporation rates. Farmers had noticed an increase in temperatures but not real increase in evaporation rates.

[Buzzsaw]

[Jack_Ian]

[Zag]

Jack_Ian, it is ultraviolet rays that cause sunburn. Their shorter wavelengths are completely unimpressed by clouds and punch right through them. Heat, however, is primarily infrared waves, which have much longer wavelengths and are reflected much more.

[Jack_Ian]

I realise that, but the ultraviolet waves pierce the clouds, heat up the Earth's surface, thereby generating lower wavelength waves that can't escape.

[Buzzsaw]

[The Potter]

So I spent a few days watching the clouds over central Oregon. The jet trails stay and go on different days-- without much rhyme or reason as far as I could see.

One evening they were showing up clearly but also dissipating quickly. It was like a comet with a trail about the size of my fist at arms length.

Another day I am pretty sure I could pinpoint Salt Lake City on the horizon by the converging trails which lasted all afternoon. This only happened one day in the last week. Yet the number of trails didn't increase as the day passed. They just became ribbon like clouds.

Considering the number of commercial flights that fill up the sky in any given day, I am starting to believe visible trails are somewhat uncommon condition.

"I really don't know clouds at all"
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[Buzzsaw]

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The length of time a contrail lasts is directly proportional to the humidity already in the atmosphere. A drier atmosphere leads to a more short-lived contrail, while an atmosphere that has more humidity will lead to longer-lived contrails. However, if the atmosphere is too dry, no contrails will form.

Occasionally a jet plane, especially if ascending or descending, will pass through a much drier or more moist layer of atmosphere which may result in a broken pattern to the contrail, with it appearing in segments rather than in one continuous plume.

Contrails can be found over most of the planet and now that jet plane traffic - both civilian and military - can be at anyplace over the globe at anytime, contrails are becoming more and more common.

Contrails have been recorded throughout the history of jet plane travel.
Many reports exist from World War II of situations where the accumulations of contrails was so extensive that pilots were unable to keep visual contact with neighbor or enemy planes during combat. Contrails have been recorded from the Sahara Desert to the South Pole indicating that contrails are not constrained to only populated regions of the Earth.

If contrails persist for a long enough period of time, say on the order of an hour or more, they can spread out across the sky due to the prevailing winds at the level at which they formed.

Experienced sailors know to look specifically for patterns and persistence of jet contrails for weather forecasting. On days where contrails disappear quickly or don't even form, they can expect continuing good weather. On days where they linger, a change in the weather pattern may be expected.

Cirrus clouds affect Earth's climate by reflecting incoming sunlight during daytime, inhibiting heat loss from the surface of the planet during nighttime, however 70% of commercial jet flights occur during daytime hours.
It has been estimated that in certain heavy air-traffic corridors, cloud cover has increased by as much as 20%. Since contrails can spread out and essentially become cirrus clouds, it is felt that contrails may affect the planetary climate in similar ways. Other studies are underway to better understand the role that jet exhaust itself plays in modifying the chemistry of the upper levels of the atmosphere. So I plan on cking into this later, see if there's any new info available, will report it here for anyone else who's interested.
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[Buzzsaw]

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This was taken by the NOAA-12 satellite as it passed over portions of Europe in 1995.

One can clearly see from this color enhanced satellite image that the atmosphere was very conducive to the development of contrails on this date (April 5, 1995) and that these contrails were long-lived enough to accumulate with many criss-cross patterns over the same heavily traveled portion of air space.



I don't have the stats to back this up but think it safe to say there is greater present-day air traffic than in 1995. In case I did not make it clear from the summary, jet condensation trails are almost certainly changing our weather patterns in the way of creating a net cooling effect - considering the areas of the globe that generally favor the formation of contrails, combined with the sheer number of planes in flight during daytime (over 70% of commercial flights take place during daytime hours.)
(Clouds created during nighttime have potential to create a net-warming effect, as Jack_Ian pointed out earlier.)
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