Airplanes Unexpectedly Modify Weather

reillymj writes "Commercial airliners have a strange ability to create rain and snow when they fly through certain clouds. Scientists have known for some time that planes can make outlandish 'hole-punch' and 'canal' features in clouds. A new study has found that these odd formations are in fact evidence that planes are seeding clouds and changing local weather patterns as they fly through. In one case, researchers noted that a plane triggered several inches of snowfall directly beneath its flight path."

Cloud Seeding

[illumastorm]

Interesting. So the effect of cloud seeding is just as likely to be caused by the planes flying through the clouds rather than the silver iodide alone?

Not surprising

[JWSmythe]

    This isn't terribly surprising. Clouds are a delicate formation of moisture that hasn't collected into dense enough masses to fall. Aircraft disturb the air, blowing that moisture around. We've known about contrails for an awful long time. I wouldn't be terribly surprised to find that particles in the exhaust give the moisture something to cling to (i.e., cloud seeding).

    Those are some nice pictures though.

Re:Cloud Seeding

[Kral_Blbec]

Its a matter of distribution and degree. Just a plane might be enough to start off what was almost rain in a area near its flight path, but theoreticly silver seeding would generate rain where it was unlikely and over a wider area that just directly below.

I thought this was well established?

[Deagol]

The data from the near-universal grounding of US airspace the days following the 9/11/01 attacks shows pretty conclusively that air traffic has a non-trivial affect on weather patterns. Or at least that's what's I recall from the time.

Tenerife

[bigtomrodney]

It is well known locally on the Canary Islands that this happens. Almost all flights come in on Tuesdays and Saturdays if I remember correctly - they're almost all package deals and charters. By the afternoon on those two days the temperature drops several degrees celsius and you'll see clouds. I even saw a dribble of rain once.

I was a complete skeptic when I was told this as I arrived, but like clockwork on those days I always saw the same thing. The crazy thing is that any other day of the week around the summer you can expect mid-to-high thirties and rarely a cloud in the sky. So maybe not scientific, but anecdotal evidence anyway.

Re:Cloud Seeding

[bunratty]

I would think anyone who understands how to design experiments would see the need for a proper control group. If you fly a plane through some clouds and dump iodide crystals, and don't fly any plane though other clouds, what caused the difference in precipitation? Was it the plane or the iodide crystals? Didn't they carry out such a proper experiment?

Potential AGW support?

[OzPeter]

I'm not deep into the AGW/anti-AGW arguments (and not trying to start a flame war), but I thought that one of the anti-AGW arguments was that in general humans can't affect climate. This sort of research would seem to suggest that humans can affect climate and hence nullify some of the anti-AGW stance - or are these effects so localized that you can only state that the humans are affecting weather and not climate?

Re:Chemtrails?

[PhreakOfTime]

I got sucked into a similar discussion once. I will never make that mistake again.

After doing some back of the envelope calculations, using the average size of cloud droplets, the velocity those droplets fall, and the average height those clouds are... I pointed out that the clouds seen over your head would take up to 10 hours(or substantially longer) to fall to ground, and even with a small breeze, would end up hundreds of miles away from the location seen by the time they would reach the ground.

Even faced with that simple math, they would STILL insist that they could see the 'residue' falling into their yard from the airplanes above....

Forcing

[ShakaUVM]

>>The contrail cover from planes reflect more light from the sun.

Also, it's important to state that up until this point, climatologists thought that contrails had a forcing effect helping to cause global warming. And still show it that way, for example: http://en.wikipedia.org/wiki/Radiative_forcing [wikipedia.org]

However, papers like this: http://www.nature.com/nature/journal/v418/n6898/full/418601a.html [nature.com] rather convincingly argued that they have a rather strong forcing in the opposite direction (i.e. that they help to dim sunlight more than they trap heat).

While honest climatologists will admit that some areas in AGW are very well understood, and others are much less understood, dishonest climatologists will pretend that they know everything and how dare you for questioning the global warming groupthink. In fact, how they respond to reasoned criticism is often a clear giveaway as to which camp they fall into.

Opposite effect

[GaryOlson]

Anyone who has watched weather fronts as they approach DFW airport can provide anecdotal data showing the reverse effect -- aircraft disperse clouds. Huge storm fronts slam into Fort Worth, the middle dissipates as it approaches and passes over DFW airport, then storm fronts reconnect east to reform a single storm front. How far east depends on the strength of the storm. Or the splitting of the front at DFW airport will cause the storm front to degrade to localized cells. Very few storm fronts survive the impact of DFW airport as a continuous front. YMMV....

Re:Cloud Seeding

[sexconker]

I would think anyone who understands how to design experiments would see the need for a proper control group.

We've already seen that no one who understands how to design experiments has anything to do with the study of weather or climate.

Re:Chemtrails?

[JWSmythe]

    I don't know about the 10 hours or 100 miles, but I didn't do the math. :) I live in Florida, so frequently watch the weather formations on TV (and now the Internet), so I'm very aware of cloud movements. We get some pretty nasty storms here in the summer (think instant hurricane type weather), so it's advantageous for us to know what's happening around us. Usually we can see bands of rain forming miles off the coast, and time our activities accordingly. If I have to go for a long drive, sometimes it's a race against the weather. More than a few times, I've been caught in it, and had to stop because I couldn't see more than a few feet in front of my car. When that breaks, you see the line of cars that pulled over because they couldn't see either.

    The only "residue" falling from an aircraft that I could imagine that they could see falling into their yards immediately under the flight path would be if a part fell off the plane. That should be pretty obvious. "Look honey, there's a jet engine in the front yard." :)