Contrails and their effect on weather?

My name is URL

Does anyone know whether or not the contrails from commercial flights are taken into account when forecasting? Yesterday on RTE Weather they included a mention of 'artificial' clouds caused by aircraft.. I've never seen it included before in a weather report and it made me wonder if it was something which is measured by meteorologists..

I've read some studies which have suggested that these trails do have an affect, particularly on diurnal temperature variations.

So is it something which is measured, and apart from the direct effects on temperatures; is it something which could alter the natural progression of weather patterns?

The RTE forecast is online here, 47 mins in

Su Campu

The contrails issue is bandied about as if they occur everywhere, everyday, when in fact they cover only a small area of the globe at any one time, and most areas are clear of them. They usually only last in areas where there are other natural cirrus anyway, so these would probably overwhelm any contribution from the contrails.

But in theory, any cloud cover can have some effect on nightime temperatures, but I'd say the effect of just a couple of contrails in the sky would be within observational error. You'd need a dense network of long-lasting contrails - the sort we get maybe a couple times a year - to make a big difference.

And before anyone thinks of mentioning the other c-word (chemtrails) - don't! :rolleyes:

BEASTERLY

Su Campu wrote: »

The contrails issue is bandied about as if they occur everywhere, everyday, when in fact they cover only a small area of the globe at any one time, and most areas are clear of them. They usually only last in areas where there are other natural cirrus anyway, so these would probably overwhelm any contribution from the contrails.

But in theory, any cloud cover can have some effect on nightime temperatures, but I'd say the effect of just a couple of contrails in the sky would be within observational error. You'd need a dense network of long-lasting contrails - the sort we get maybe a couple times a year - to make a big difference.

And before anyone thinks of mentioning the other c-word (chemtrails) - don't! :rolleyes:

I wont mention the word but Su, i spotted a military cessena172 over wexford town yesterday and then less than 12 hours later in turned cloudy in the area, thats not a coincidence! LOL:D

My name is URL

Su Campu wrote: »

The contrails issue is bandied about as if they occur everywhere, everyday, when in fact they cover only a small area of the globe at any one time, and most areas are clear of them. They usually only last in areas where there are other natural cirrus anyway, so these would probably overwhelm any contribution from the contrails.

But in theory, any cloud cover can have some effect on nightime temperatures, but I'd say the effect of just a couple of contrails in the sky would be within observational error. You'd need a dense network of long-lasting contrails - the sort we get maybe a couple times a year - to make a big difference.

And before anyone thinks of mentioning the other c-word (chemtrails) - don't! :rolleyes:

I had no intention of mentioning the other c-word anyway =p

Persistent contrail formation can be predicted using the Appleman Chart. So has there been any real attempt to predict them using the meteorological method? Considering they can have an effect on weather variations is it not surprising that very little data is available? I know all about that conspiracy and think it's absolute rubbish, but nor should that crap be used as a means of detracting from more serious questions surrounding the links between contrails and weather conditions.

Su Campu

I'm not aware of any met service that factors in contrails. The systems generating the conditions conducive to contrails are of much more importance, such as warm front shields, etc. We live under one of the busiest airspaces for transatlantic traffic, but how many mornings have you looked up and seen the sky covered in aerocirrus alone? Couple of times a year, at most? Most cirrus we get is either jet fibres or warmfront shields

thetonynator

My name is URL wrote: »

Does anyone know whether or not the contrails from commercial flights are taken into account when forecasting? Yesterday on RTE Weather they included a mention of 'artificial' clouds caused by aircraft.. I've never seen it included before in a weather report and it made me wonder if it was something which is measured by meteorologists..

I've read some studies which have suggested that these trails do have an affect, particularly on diurnal temperature variations.

So is it something which is measured, and apart from the direct effects on temperatures; is it something which could alter the natural progression of weather patterns?

The RTE forecast is online here, 47 mins in

The reason they included it in the forecast i think is because there is so little to talk about that they have been including some educational bits. Yesterday it was about contrails and them being visible as clouds on the satellite, the previous day them mentioned record highs recorded (Mongolia in 2001) and mentioned that this is an unusual high. Didn't see this evenings weather, anyone know if they had anything similar??

Joe Public

Met observations following 9/11 proved there is an effect.

The terrorist attacks of September 11, 2001 was the aforementioned event, and it was likely to have excited meteorological researchers involved in contrail impact studies. The national airspace was shut down for three days, something that had not yet occurred since the jet age began in the 1960s and is not likely to occur ever again. Scientists took advantage of this unique three day period in history that lacked contrails. What they learned was shocking and is enough evidence to effectively silence any counterargument to their case. One measure of climate is the average daily temperature range (DTR). For thirty years this had been recorded and extra cirrus clouds in the atmosphere would reduce this range by trapping heat. “September 11 – 14, 2001 had the biggest diurnal temperature range of any three-day period in the past 30 years,” said Andrew M. Carleton1. Not in three decades had there been such a large temperature spread between the daytime highs and the nighttime lows. Furthermore, the increase in DTR during those three days was more than double the national average for regions of the United States where contrail coverage was previously known to be most abundant, such as the Midwest, northeast, and northwest regions. The specific increase in the range was 2°F, which in three days was twice the amount the average temperature had increased by over thirty years time1. This is evidence that contrails do alter the climate of the land they drift above.


Full article here:-
http://www.airliners.net/aviation-articles/read.main?id=85

peasant

This is just from observation, totally non-scientific.

From my old place of work you could see a fair bit of sky and on a clear day you could clearly see the planes going over as well.
This was on the transatlantic routes and you'd get planes coming in very early in the morning and a fair lot of them going back between 9 and 12-ish ...so many that there almost always was one to be seen somewhere.

Now, depending on weather conditions, their contrails would be non-visible, visible, lingering or lingering and building.

Most of the time, contrails would hang around for 15 minutes / half an hour and then they'd be gone again ...but sometimes they would linger all day and get bigger and bigger and "seed" other clouds.

There were days when at 9 in the morning you could still see the traces of the contrails of the first batch of early morning incoming planes. These would hang about until the outgoing planes added their contrails and by the afternoon all those contrails would have seeded further cirrus clouds so that the sky would almost be totally overcast with thin, whispy cloud ..but with the streaky pattern of the original contrails still visible.

This really came to my notice when during the days of the ash cloud there were no flights over Ireland. The sky was visibly and very noticeably clearer and bluer than it usually was ...especially around noon and early afternoon.

As soon as flights picked up again, the mid-day streaky cirrus clouds were back.

You'd still have a beautiful, sunny day ...but without plane traffic you would have had absolutely clear blue sky.

My personal conclusion is that all this plane traffic must have an influence on air temperatures and sunshine intensity on the ground.

Su Campu

peasant wrote: »

This is just from observation, totally non-scientific.

From my old place of work you could see a fair bit of sky and on a clear day you could clearly see the planes going over as well.
This was on the transatlantic routes and you'd get planes coming in very early in the morning and a fair lot of them going back between 9 and 12-ish ...so many that there almost always was one to be seen somewhere.

Now, depending on weather conditions, their contrails would be non-visible, visible, lingering or lingering and building.

Most of the time, contrails would hang around for 15 minutes / half an hour and then they'd be gone again ...but sometimes they would linger all day and get bigger and bigger and "seed" other clouds.

There were days when at 9 in the morning you could still see the traces of the contrails of the first batch of early morning incoming planes. These would hang about until the outgoing planes added their contrails and by the afternoon all those contrails would have seeded further cirrus clouds so that the sky would almost be totally overcast with thin, whispy cloud ..but with the streaky pattern of the original contrails still visible.

This really came to my notice when during the days of the ash cloud there were no flights over Ireland. The sky was visibly and very noticeably clearer and bluer than it usually was ...especially around noon and early afternoon.

As soon as flights picked up again, the mid-day streaky cirrus clouds were back.

You'd still have a beautiful, sunny day ...but without plane traffic you would have had absolutely clear blue sky.

My personal conclusion is that all this plane traffic must have an influence on air temperatures and sunshine intensity on the ground.

The fact that you saw no contrails when flights were grounded means nothing. There are many days where no contrails are visible, even for just a few seconds behind a plane. A whole morning's batch of incoming traffic can pass over unnoticed, so to say that the clear blue days you mention were due to grounded flights is wrong - it may have been, but it equally may not.

Of course, if conditions were right for contrails on those days of no flights then yes, it made a difference, but even then, in most cases contrails don't grow and cover the sky like you described. It happens only a couple of times a year I reckon.

peasant

A pretty poor picture for illustration purposes, taken just minutes ago:



The contrail in the middle is just being drawn, it seems to be disappearing fairly quickly as well.

The contrail at the top is about 20 mins old ...but the (in this picture hardly visible) whispy cloud at the bottom is an ex contrail, left over from a plane that passed over hours ago.

At the moment from my place I can see 7 distinctive, long and thin whispy clouds that can't be anything else but ex contails.
Today is not too bad, in that they really are very thin and fairly dispersed. On other days, by early afternoon, there is enough of them around to form almost complete (albeit very, very thin) cloud cover

Su Campu wrote: »

Of course, if conditions were right for contrails on those days of no flights then yes, it made a difference, but even then, in most cases contrails don't grow and cover the sky like you described. It happens only a couple of times a year I reckon.

The difference between day one (no flights) and day two (flights resumed) in identical weather was so remarkable that several people noticed and mentioned it. Both days were so clear that you could actually see the planes going over even when they didn't have contrails. (on the same day not all planes have contrails ...it seems to depend on their height and the conditions up there). Day one offered clear blue skies in the afternoon ...day two had large areas of sky covered in thin whisps.

peasant

A somewhat larger shot of the same area, taken just now, 30 odd minutes later:


The thin, whispy ex contrail is still lingering in the bottom right and the ca. one hour old contrail at the top is starting to "go to seed" in the top left.


Today is not the best example, contrails are still dispersing pretty well, but in slightly different conditions almost every single contrail would end up as a lingering whispy cloud. And with the amount of planes going over here, by late afternoon that amounts to almost complete cover.


EDIT:
Just to clarify ...I do in no way buy into the tinfoil-hat contrail conspiracy (in that contrails are some sort of chemical spray to poison us) but from my own observation I am convinced that they do influence cloud cover in certain conditions. To what degree that extra cloud cover influences the weather in general is for others to measure.

thetonynator

Did anyone measure the DTR in ireland as being different to normal when there were no planes flying with the volcanic ash?

My name is URL

Here's some pics I took a while back. Apart from the contrails the sky was completely devoid of cloud. I've seen trails which spread like this quite a bit in the last year or so, but not many to the extent of the ones below.

http://i50.tinypic.com/2iasgua.jpg
http://i45.tinypic.com/2r2ve68.jpg
http://i47.tinypic.com/28md63a.jpg

Su Campu

Yes, today is a day where they last a bit longer, but in my opinion it's the exception rather than the rule.

Take last Thursday. This MODIS satellite image was taken at 1235UTC. Around 95% of the sky is clear of contrails. Now compare it with the screenshot of the actual traffic in the sky at that same time. Most of those planes are invisible on the satellite image. Maybe just the couple off the Wexford coast show up briefly, but the cluster over north leinster don't show up at all.




Friday was a day with more long-lasting contrails, but there was a warm front shield along the north and Scotland anyway, so there was already cirrus there to begin with. But yes, the contrails did enhance it on that occasion.

http://rapidfire.sci.gsfc.nasa.gov/subsets/index.php?subset=Europe_2_01.2011021.aqua.500m


On days such as Friday, where contrail coverage is at a maximum, I'm sure there is a small effect when it comes to radiative cooling, but I'd say it's not too discernable. The fact that we need to go examining a high-res image to see these contrails, and that they don't appear on the regular visible or IR imagery (see the ones below for the same time Friday (~13:20UTC)) means the other natural clouds, that do appear, are of much more importance when you look at the big picture.

peasant

Su Campu wrote: »

Yes, today is a day where they last a bit longer, but in my opinion it's the exception rather than the rule.

Speaking simply as someone who enjoys sitting in the sun as much as possible, there have been plenty of times (on the few nice days that we get here in the whest) where sun&fun activities had been planned in the morning, (after looking out of the window and seeing clear blue sky) only to carry them out in the afternoon/evening under a milky sky, wearing a sweater instead of a t-shirt.

So ..from my very egotistical standpoint it seems to be the rule rather than the exception

Su Campu

This is a Dust Microphysics image of half of the globe at 1700UTC today, which will pick up high thin ice clouds (including contrails) as a dark greenish/black colour. It makes them much more visible than basic IR or visible imagery, so is the best way to see the coverage at any one time.

We can see that the only occurence of contrails is the over the mid Atlantic, west of Ireland, as a series of these dark lines converging at various waypoints. They are only developing along the warm front shield, where conditions are starting to become favourable for cirrus.
There are other dark clouds but these are all naturally occuring (especially over Scandinavia, which is lee cloud produced by the strong westerly flow over the Norwegian highlands).

It's pretty clear from this that a very small percentage of the sky is affected by contrails.

All images are from http://oiswww.eumetsat.org

Dust Microphysics of Globe
http://oiswww.eumetsat.org/IPPS/html/MSG/RGB/DUST/FULLRESOLUTION/

Zoomed in to Western Europe

Joe Public

How do you explain the findings of the post 911 tests?

Su Campu

Joe Public wrote: »

How do you explain the findings of the post 911 tests?

Coincidence?

From the same article:

“At flight altitudes, conditions that support contrail-generated cirrus exist 10% – 20% of the time in clear air and within standing cirrus”. Although this is a small percentage, the diverse weather of North America coupled with the staggering number of commercial flights in the air results in at least some part of the United States being good contrail weather on any given day. Worldwide, contrails are estimated to cover 0.1% of the Earth’s surface area and that number is forecast to rise to 0.5% by 2050".

The US isn't covered in contrails every day, so only a small percentage of it would have been covered had there been flights (and there's no guarantee that those areas most prone would have been covered these days either). It is therefore highly unlikely that this small area would contribute in such a huge way to temperature anomalies.

In fact, the morning of September 11th, the vast majority of the continental US was cloud free anyway, as is visible from these charts West / East. And this was before any planes hit any towers. So with such a clear landmass from coast to coast, it's little wonder that there was a big diurnal variation.

With only 0.1% of global coverage, and only predicted to rise to 0.5% by 2050, I really don't think there's much to worry about.

Sponge Bob

Joe Public wrote: »

How do you explain the findings of the post 911 tests?

Horizon did a really interesting program on it called Global Dimming (transcript) Another PBS program is referenced here ( the full Horizon Documentary in 5 parts is available here in a collection of conspiracy stuff as it happens )

isle of man

This really came to my notice when during the days of the ash cloud there were no flights over Ireland. The sky was visibly and very noticeably clearer and bluer than it usually was ...especially around noon and early afternoon

have to say,
them days all the flights were stopped we had 3 days of perfect blue skys,
the day before it was hazy, then as soon as they started flying again, it became hazy again.

And i can remember the day they started flying again, we watched 10 planes mid moring making there way across the sky,

Had the site dumppy lvl and what not out, and you could see the tail markings on the planes!!!!!!!
now thats some site to see for something so far up,
But you want to try tracking one across the sky with just 15-20mm of view, fook they move fast.:D.

come the afternoon we were back to haze again:mad:

im in no dowt in my mind that they effected it a lot,

thetonynator

Airspace is closed on christmas day, could data from christmas day every year be compared against similar days around then to compare DTR?

Su Campu

thetonynator wrote: »

Airspace is closed on christmas day, could data from christmas day every year be compared against similar days around then to compare DTR?

Airspace isn't closed on Christmas Day, only the Irish airports. Flights transit overhead as normal.

There have also been many brilliant blue skies on days where planes have been flying but of course people don't seem/want to notice these. There was nothing unusual about the days during the volcanic grounding last year, plus cruising jets don't cause haze.

stevenmu

On at least one occasion I've watched contrails on a perfectly clear day expand and expand to fill the sky with cloud. Without knowing much about this kind of thing, I assumed that the conditions were just about right for cloud formation and that the contrails just triggered the process acting as a kind of seed. I expected this to be well understood phenomenon so I didn't pay much attention to the details, but I believe it stayed cloudy and wet for a day or two after. Again just an assumption, but I assumed that it would have been cloudy and wet anyway, but that the contrails triggered the cloud formation slightly earlier. It may just have been by minutes, or it may have been by a number of hours (I've no way of even guessing at this). If the latter, then I'd consider that a noticeable and significant effect on the weather.

For reference this was on the west side of Lough Mask in Mayo (west coast). It's fairly common to be able to watch either clouds blowing in over the mountains to the west, or to watch clouds forming over them, but this was different in that the clouds were forming directly over head expanding from the contrails.