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This photo has the largest number of contrails I’ve seen in a single photo:

There seem to be at least 30, possibly more (click the photo for a larger verision).  What is even more remarkable is that it was taken sometime before 1967.  That’s over forty years ago.

The photo is plate 113 of the book Cloud Studies in Colour, by Richard Scorer and Harry Wexler, published in 1967 by Pergamon Press.  The photo was taken by Richard Scorer, probably in England.  The accompanying text reads:

Condensation trails are left by aircraft when the air is sufficiently cold for the mixture of air and exhaust to be saturated.  This does not usually happen except when the temperature is close to or below -40C, in which case the cloud freezes almost instantaneously and does not readily evaporate.  The cloud is then spread out by any wind sheer which may be present.

Another bit of “Chemtrail” mythology was born with this YouTube video:

http://youtube.com/watch?v=MVc9GX5K_As

This video has been seized upon by the Chemtrail community as evidence that “chemtrails” are real, and that the German government has admitted they are spraying “chemtrails”.

Unfortunately the entire video is a very bad translation of a story about one Meterologist, Karsten Brand, who is was concerned that the military was using too much chaff (anti-radar powder). The military admitted that they do use chaff, but not too much, and it’s not harmful. Brandt contend they use so much it can affect the weather, and might be harmful to people. He’s also annoyed because it interferes with his weather radar.

The Meterologist behind all this, Karsen Brandt (show above, supposedly blaming it on “chemtrails”), actually goes out of his way to distinguish these odd cloud images from “chemtrails”, in this article, translated,

http://www.worldweather.net/news/specials.mv?action=show&id=5947

Following the publication of pictures of non-existent clouds on the radar we have many questions. Here are the answers to the most frequently asked questions:

Are they “Chem Trails?
On various Internet sites will be discussed passionately that aircraft chemical balance to either make the ozone hole or act for the United States (who else also ..) changing the weather to world domination. This is - according to the supporters of this conspiracy theory - not just a trial from time to time, but regular, worldwide and especially in Germany. The sprayed chemicals leave greyish-white trails in the sky That is not a normal contrail, “Chem Trails” would quite different and would also behave differently.

The beauty of this conspiracy theory: Everyone can see the trails, everyone may feel threatened, but no (normal) citizens can touch or examine them. On the Web pages are shown photos of various trails, the “strange” pattern in the sky behind.
For the layman, it is at first glance strange that one day contrail stay in the sky for hours, but the next day dissolve within minutes . But this “phenomenon” varies with the humidity and the change is very easy and simple to explain.
Of course, we also can not be excluded with absolute certainty that a plane sprayed chemicals in the atmosphere. But as regularly and to the extent claimed by the conspiracy theorists, you can use common sense to exclude. For such a comprehensive worldwide conspiracy, should not only hundreds, thousands of US pilots be involved, but also scientists, German authorities, etc., etc. . How high is the probability that with such a number of people, there is no leak?

The big problem with the video is the translation. In the shot above, the german word “duppel” is translated as “chemical trails (chemtrails)”, when the actual translation is “chaff”. The German word for “chemtrail” is “chemtrail“.

Another rather obvious distinction is that Brandt is talking about invisible clouds, whereas “chemtrails” are very visible (since they are aircraft contrails).

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Q) How long do contrails last?
A) Anywhere from less than a second, up to several hours.

This is an oft-asked question. The answer is reasonably straightforward, but misunderstanding is common. To understand why a contrail can last as little as a fraction of a second, or as long as several hours, you need to understand what a contrail is, and how it forms.

Here’s another question, which has the same answer:

Q) How long does a snowflake last?

Why is this basically the same question? Because contrails are generally made of ice crystals. Jet exhaust contains a lot of water vapor (the chemical reaction actually produces more water than there was originally jet fuel), and when this gets shot out of the back of the engine at 2000MPH, it hits the frigid air (typically colder than -40 degrees), and the water vapor condenses and freezes, very quickly, into tiny ice crystals, just like snowflakes.

So why do these ice crystals sometimes stay around for a long time, and sometimes vanish in seconds? The temperature is well below freezing, so they can’t melt, can they? This is puzzling, because it involves something that most people know nothing about: “sublimation“.

Sublimation is when a substance (in this case, water), goes directly from being solid to being vapor (a gas), without actually melting into a liquid. It’s like evaporation, except instead of a liquid evaporating, it’s a solid (ice). If the air is dry (i.e. there is little water vapor in it), then the ice crystals will quickly sublimate into vapor, and the trail will vanish quickly.

However, if the air already has a lot of water vapor in it, then the ice will sublimate slower, and the trail will last longer.

If the air has so much water vapor in it already that it can’t hold any more (i.e. it’s “supersaturated”), then the ice crystals can’t sublimate, and so the contrail will stay around for a long time. The ice crystals might even attract water from the air, if there is enough, and the contrail will get thicker. Winds might make the contrail spread out to even cover the whole sky.

The above is a simplification, as other factors like temperature, pressure, and sunlight have an effect. But it explains the basic reasons why some trails last only a few seconds, and some can last for hours, and spread out to cover the sky.

Finally, there is one more way of asking the question:

Q) How long do clouds last?

This is the same question because contrails are clouds. Contrails are physically very similar to cirrus clouds (except they are long and thin), and so they act almost exactly the same. You see cirrus clouds that last for hours, so why not contrails?

I took this photo on December 16, 2007, at around noon. It’s facing south from Los Angeles, California.

It was a particularly good day for contrails. You can see about seven in this photo. There’s also a nice contrail shadow, and a halo around the sun.

I was looking at the MODIS archive of satellite photos, and realized they had one for that date, and rather luckily it seems to have been taken within an hour of the photo I took, so it shows the exact same contrails from space. LA is just a bit to the right of the center of this photo.

As the photos are about an hour apart, the trails have shifted and distorted a little. But you can still match them up. Here I’ve color coded them.

It’s interesting also to look at the full size satellite photo of the area, so you can see where trails form, and where they do not form.

Los Angeles is in the middle of the photo. You can see the trails forming over Los Angeles, and it’s quite clear from looking the the cloud bands that they are forming in an area of high humidity.

Lookin up the coast, there is a gap in the clouds, and a corresponding lack of contrails. Then in the top left corner the clouds resume, and so do the contrails. In fact you can see several much thinner trails there. Here’s a close up:

These are probably the same planes that created the trails over Los Angles, just about an hour later, as they continue to fly north. The abrupt start of the trail as it enters the moist air is very obvious here.

This is all interesting in the context of the “chemtrail” theory. You often hear the chemtrailers posting things like “heavy spraying over Los Angeles today!!!” Then there are days with “no spraying”. MODIS is a wonderful resource for explaining why this perception happens. Sometimes there is a moist region of air at the right level over a particular place, and that place gets a lot of persistent contrails.

Looking at contrails from the ground only gives you a little bit of the picture. The satellite photos tell the whole story.

For example, here’s a “Massive Chemtrail Assault” Youtube video, from Austin, TX, 11/15/07

http://www.youtube.com/watch?v=GXJRNnmx0h8

And here is the satellite image of the greater area from that day. Austin is on the right, towards the end of the huge sweep of clouds. It’s clear that the contrails are just forming around the edges of a region of high humidity.

http://rapidfire.sci.gsfc.nasa.gov/subsets/?USA6/2007319/USA6.2007319.aqua.1km.jpg

Full Size original images here, about 1MB each:
My Photo: img_3175a.jpg
MODIS photo: aeronet_la_jolla2007350terra250m.jpg

Here’s a newly discovered photo of contrail in WWII, this was taken by William Anderson, and uploaded by a grandchild of his, here. ( Creative Commons, Some rights reserved)

You can see it’s taken from a photo album. I cropped, sharpened, and contrasted it a bit to bring out the details of the contrails. The text “Note Little Friends” probably refers to the fighter escorts making curved contrail in the background.

It looks similar to this more famous photo:

That’s know as “Top Cover for the J Group”, and is detailed here. This photo was also taken over Emden, on September 27th, 1943, by Stanley M. Smith. Given the weather, and the planes involved, it might well have been taken on the same mission, within a few minutes of the first photo.

Here’s a contrail you don’t see every day: the racetrack contrail (or, as I like to call this one, the paperclip contrail)

This photo was taken near Portland, Oregon on December 11th, 2005, at around 11AM.

So why would a plane be flying in this unusual pattern? Well, it turns out it’s not really very unusual. It’s called a “holding pattern“, and it’s a very specific pattern that planes fly in when they need to hold their position. Holding patterns have this very distinctive shape because the aircraft have to fly them in a very particular way that takes exactly four minutes to complete, so the ATC can know where they are, and when they will be facing in a particular direction. They fly straight for a minute, then turn 180 degrees over a minute, and then fly straight again. It looks like this:

For passenger jets, holding patterns are most common on the approach to busy airports (the one above is for Martha’s Vineyard), and it’s not too uncommon to make a few turns in a holding pattern shortly before landing. The contrails in the above photo is probably not this, as it’s at too high an altitude. Passenger jets do sometimes enter high altitude holdings (I’ve been in one once as a passenger), which could account for this.

High altitude holds are also used by refueling tankers, as they wait for the planes they are going to refuel. Pilots obviously also have to train to fly in high altitude holds, and given the number of turns above, that’s the most likely explanation for this particular photo.

Remember the winds at altitude are typical around 50-100mph, so after the four minutes loop, the previous contrail could be blown around five miles away, giving the illusion that the plane is now holding over a different area. It’s not. The plane is playing over the same area, but the contrails have moved.

Of course, if you don’t know this, it might look a bit odd to you. Some people work these racetrack contrails into the “chemtrails” conspiracy theory. Look at this poster on the right. There’s a photo of a racetrack contrail with five turns, separated and distorted by the wind. Overlaid is the text “Look up, Phone Radio DJs”.

These racetrack contrails are pretty rare (unless you live near a training area), but hopefully now if you see one, you’ll be able to tell what is going on, and not feel the urge to call a DJ.

[BTW, the plane in the upper right of the poster is a Boeing E-6 Tacamo, dumping fuel]

In a fascinating article: Wakes of war: contrails and the rise of air power, 1918-1945 Part I–early sightings and preliminary explanations, 1918-1938, (Air Power History. 54.2 (Summer 2007): 16(16).), Donald R. Baucom give an account of the rise of high altitude flight, and the inevitable accounts of contrails, both persistent and otherwise, that occurred during that time. The first powered plane had only flown in 1903, and the very earliest report of a contrail is just 15 years later, in the autumn of 1918, in an account of Captain Ward S. Wells, Army Medical Corps, who was serving with the 60th Infantry, 5th Division, American Expeditionary Force, during the Meuse-Argonne campaign.

Our attention was first drawn to the sky by the sudden appearance of several strange and startling clouds–long, graceful, looping ribbons of white. These were tapering to a point at one end and at the other where they dissolved into nothingness 60 degrees across the sky, were about as broad as the width of a finger held arm’s distance from the eye. On close observation we noticed some distance ahead of each cloud point the tiny speck of a chasse [sic] plane…. [N]ever before had I seen a plane writing in white upon the blue slate of sky.

This is very interesting, as it’s the earliest known account of contrails (note that these are non-persistent). It was also very novel and interesting at the time, and was reported in a letter to Scientific American, (”Clouds formed by Airplanes“, Jun 7, 1919, p 60) by Wells’ brother, Everett Wells, and provoked some discussion of what might be forming these clouds.

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I snapped this a few minutes ago, looking west from Santa Monica:

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It’s been interesting weather here in Los Angeles, as a couple of storm systems have rolled through we’ve had some days of nice looking clouds, and some days with lots of contrails. I snapped this one this morning:

It shows a contrail from the lower left that then turns into a distrail on the upper right, cutting through a layer of clouds.

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Either by day or a little after sunset, in fine weather, a little, light, long-drawn cloud is seen, like a long very straight line.
- Aristotle, Meteorologica, 340BC

Not every long straight line in the sky is a contrail. Here Aristotle suggests it’s “a sort of wave-mark in the air”. Basically an isolated row cloud, low on the horizon.

Aristotle’s take on the weather is very interesting. He has quite an extensive section on atmospheric optics - halos, sundogs, etc. Pretty advanced for 2347 years ago.

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