Chemtrail Thread: How common are contrails?

I have been studying this topic for some time. I feel there are experts on both sides, right here on ATS.

Couple of questions for the skeptics.

1. How common are contrails. For example, if you had 1000 flights, how many would you estimate to form contrails, on average? Is it 10%, 50%. Not holding you to it, just wondering if global warming is causing excessive contrails.

2. I've looked at the Appleman Chart. It suggests when a contrail might form. What are the conditions for a persistant contrail to form, RH%, Temp, etc? There is a big difference between dissapating heat vapor and trails that form into storm systems.

As someone who is VERY concerned about the potential of the implications if the Chemtrail Conspiratists were right, I feel that one who has attempted at debunking the Chemtrailers, should have quick, concise numbers and charts for us to review.

In my time in aviation, I was always under the impression that contrails were a very rare occurence. Have weather conditions changed that much??








[edit on 6-7-2009 by Udontknowme]

While I'm waiting for the skeptics reply, I thought I'd do a little checking.

A probabilistic forecast to accurately predict contrail formation over the contiguous United States (CONUS) is created by using meteorological data based on hourly meteorological analyses from the Advanced Regional Prediction System (ARPS) and from the Rapid Update Cycle (RUC), combined with surface and satellite observations of contrails. Two groups of logistic models were created. The first group of models (SURFACE models) is based on surface-based contrail observations supplemented with satellite observations of contrail occurrence. The most common predictors selected for the SURFACE models tend to be related to temperature, relative humidity and wind direction when the models are generated using RUC or ARPS analyses. The second group of models (OUTBREAK models) is derived from a selected subgroup of satellite-based observations of widespread persistent contrails. The most common predictors for the OUTBREAK models tend to be wind direction, atmospheric lapse rate, temperature, relative humidity, and the product of temperature and humidity.

ams.allenpress.com...

Why do they call it OUTBREAK? Isn't the product of temperature and humidity the dew point? What is an atmospheric lapse rate???

reply to post by Udontknowme

Contrails are common, and uncommon. Where I live (a tropical, marine environment) they are very rare. In other regions they may be more common. Contrails are more prevalent at certain times of year. I don't think you can really call them rare, since they depend on conditions, they form when the conditions are right.

The Appleman chart is a rough but useful guide for determining contrail formation. Generally speaking (very generally) persistent contrails can form when the relative humidity is greater than 60% (assuming that the temperature is low enough).

Contrails, persistent and otherwise have been around for a long time, ever since aircraft started getting to the altitudes required to form them. It is not a change in climate which is causing people to see and/or notice them more.


[edit on 7/6/2009 by Phage]

reply to post by Udontknowme

The dew point is the temperature at which the water vapor in the air condenses and forms clouds. The lapse rate is the rate of change in temperature with altitude.

Originally posted by Phage
reply to post by Udontknowme

 

The dew point is the temperature at which the water vapor in the air condenses and forms clouds. The lapse rate is the rate of change in temperature with altitude.

The dew point has nothing to do with RH (Relative Humidity)? I'm curious, because if clouds are forming from contrails, then the dew point should be the same as if natural clouds are forming, correct?

As for lapse rate, does that mean, as you go higher, it gets colder?

Originally posted by Phage
reply to post by Udontknowme

 

Contrails are common, and uncommon. Where I live (a tropical, marine environment) they are very rare. In other regions they may be more common. Contrails are more prevalent at certain times of year. I don't think you can really call them rare, since they depend on conditions, they form when the conditions are right.

The Appleman chart is a rough but useful guide for determining contrail formation. Generally speaking (very generally) persistent contrails can form when the relative humidity is greater than 60% (assuming that the temperature is low enough).
[edit on 7/6/2009 by Phage]

So, RH needs to be 60%, right?. What does the temp have to be? -75F?

Is the dew factor taken into consideration when calculating the predictability of persistant contrails?




[edit on 6-7-2009 by Udontknowme]

There is a whole forum devoted to Chemtrailes:

www.chemtrailcentral.com...

reply to post by Udontknowme

The dew point is related to relative humidty.

Simply put, the exhaust from the airplane engines contain water vapor. Because the exhaust is hot it can hold more water vapor than the surrounding air, its dew point is higher than that of the surrounding air. As the exhaust cools and if the surrounding temperature and humidty are right the "excess" water vapor condenses and forms a contrail.

Air temperature tends to decreases with altitude. The higher the lapse rate, the lower it gets colder. But it is rarely as simple as that. Temperature inversions can reverse the trend, putting a layer of warm air above a layer of cold air. Lapse rate is never constant. There can be a high lapse rate close to the ground and a very low lapse rate higher.

reply to post by Udontknowme

The temperature at which contrails form also depends on atmospheric pressure (and therefore altitude). Depending on altitude and relative humidity, contrails can form at temperatures as high as -35ºF.

reply to post by TeslaandLyne


There is also a website dedicated to presenting the science of contrails.
contrailscience.com...

Originally posted by Phage
reply to post by Udontknowme

 

The dew point is related to relative humidty.

Simply put, the exhaust from the airplane engines contain water vapor. Because the exhaust is hot it can hold more water vapor than the surrounding air, its dew point is higher than that of the surrounding air. As the exhaust cools and if the surrounding temperature and humidty are right the "excess" water vapor condenses and forms a contrail.

Air temperature tends to decreases with altitude. The higher the lapse rate, the lower it gets colder. But it is rarely as simple as that. Temperature inversions can reverse the trend, putting a layer of warm air above a layer of cold air. Lapse rate is never constant. There can be a high lapse rate close to the ground and a very low lapse rate higher.

This is great.

Let me digest that for a minute...

....

OK. So basically jet exhaust is water vapor?? NOt.

I know you know that it's not just water vapor, but a combination of CO2 and soot (byproduct of co2) and additives and all sorts of things.

We all know this. But my specific question relation to the overall question of this thread, would be, how does water vapor from jet exhaust form into stormy weather??

Thanks for your intelligent responses, by the way.

Originally posted by Phage
reply to post by TeslaandLyne

 

There is also a website dedicated to presenting the science of contrails.
contrailscience.com...

That would be for normal aircraft.
Don't people suspect special aircraft are sending out something
other than water vapor.
That forum most likely suspects chemicals are being sent out for
some reason.

reply to post by Udontknowme

I said the exhaust contains water vapor. Of course there are other components. Your car exhaust contains water vapor along with other components. But you bring up a good point; condensation nucleii.

When the surrounding air is moist enough. The ice crystals which form the contrails can use that moisture to grow in size and number. Particles of soot in the exhaust act as "anchors" for the condensation to begin. It can become sort of a chain reaction. It is exactly the same process which causes natural clouds to grow. Wind and turbulence can move the contrails and spread them, just as it does natural clouds. Through this process, contrails, like naturally formed clouds can spread to cover large areas of the sky.

It is also true that the same conditions which are conducive to producing stormy weather (approaching fronts) are also conducive to the formation of contrails.


[edit on 7/6/2009 by Phage]

I should probably explain my limited understanding of the atmosphere.

Water evaporates off the ocean
As this evaporation travels across land,
it gets warmed up, and condenses, forming clouds, which creates rain.

Oh wait, there need to be dust in there, for rain particles need something to form to.

So..the amount of water in the atmosphere, is very important to the formation of clouds, and consequently, as proposed by the skeptics, contrails.

Another words, a good weather forcaster should be able to predict a day that produces contrails, given altitude, temp, rh%, etc.

Am I correct so far?

[edit on 6-7-2009 by Udontknowme]

reply to post by Udontknowme


Udontknowme,

Perhaps you haven't seen this thread:

www.abovetopsecret.com...

It's more recent than OzWeatherman's other, longer thread on the subject.

Oz may be a young whippersnapper compared to me, but he certainly knows his stuff!!

[edit on 6 July 2009 by weedwhacker]

reply to post by Udontknowme

Yes.
Just as well as they can predict any weather conditions, that is.

Originally posted by Phage
reply to post by Udontknowme

 

I said the exhaust contains water vapor. Of course there are other components. Your car exhaust contains water vapor along with other components. But you bring up a good point; condensation nucleii


[edit on 7/6/2009 by Phage]

Weather Modification and Radar Investigations,
Descriptors : *Weather modification, *Meteorological radar, Convection(Atmospheric) ... Radar equipment, Thunderstorms, Condensation nuclei, Chemicals, Ice, ...
oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix... - Cached - Similar -

www.google.com...

Originally posted by Phage
reply to post by Udontknowme

 

Yes.
Just as well as they can predict any weather conditions, that is.

So, under what conditions would you predict a contrail, And how often do these conditions occur in our common atmosphere?

reply to post by Udontknowme

Give me an altitude and I can give you an estimate of the conditions which would lead to contrail formation at that altitude.

I'm not a climatologist (or a meteorologist for that matter). I can't tell you how "common" those conditions are.

reply to post by Udontknowme

...and consequently, as proposed by the skeptics...

"skeptics"???

Your general, simplified explanation in your latest post is the gist...but of course, weather formation is far more complicated. That's why it's so difficult to forecast with 100% accuracy.

You should learn about terms such as 'isobar', and 'isotherm'. Convection patterns, how winds and terrain interact, 'uplift', really there's a lot to learn. Don't they teach this any more?

Here, this is entertaining (in short doses...Bill Nye!! Love him, or hate him...at least he's enthusiastic!):



Changed vid...visit link to see others.

[edit on 6 July 2009 by weedwhacker]