From NASA Science News: I’ve always wondered what cumulative effect increased global shipping might have on low level clouds over the ocean. These NASA images suggest ship cloud tracks are much like contrails following jets, though with differing mechanisms.
Clouds form when water vapor condenses or freezes onto tiny solid or liquid particles, such as dust, soot, or crystals of sea salt. Over the remote ocean, the air is usually cleaner than it is over land, so there are fewer particles to act as seeds for cloud droplets. The scarcity of particles means that the droplets that do form grow relatively large.
This pair of images demonstrates how air pollution can change the size of droplets in marine clouds. The top image is a photo-like view of the North Pacific Ocean (south of the Aleutian Islands) on September 29, 2009. A blanket of clouds—a little thin in places—spans the scene. The lower image shows the size of cloud droplets within the area outlined in white in the top image. Bigger droplets are darker colors (blue, purple); smaller droplets are brighter (pink, yellow).
The bright yellow arcs that streak the marine cloud layer are ship tracks—clouds that form when water vapor condenses onto the myriad tiny pollution particles in ship exhaust. There are more seed particles in ship exhaust than are found in clean marine air, and the available water vapor gets spread out more thinly among them. Because the available water is spread among more particles, the cloud droplets that form in the ships’ wakes are smaller than typical marine layer cloud droplets.
By increasing the number and decreasing the size of cloud droplets, pollution often makes clouds brighter (more reflective to incoming sunlight), in the same way that a crushed ice cube is more reflective than a solid one. In this image, however, the ship tracks don’t appear significantly brighter than the surrounding cloud layer, perhaps because the cloud layer was already fairly bright. (A March 2009 image from this area demonstrates the cloud-brightening effect more dramatically).
In marine layer clouds, an abundance of small particles may also delay the onset of precipitation, which depends on cloud droplets colliding and coalescing into larger, heavier drops. Said another way, pollution can increase the lifetime of clouds.
Human pollution has likely been modifying clouds on a global scale throughout the modern (industrial) era. In fact, climate scientists suspect that these modifications—increasing cloud brightness and lifetime—have probably helped offset some of the warming influence of rising greenhouse gas concentrations.
NASA Earth Observatory image created by Jesse Allen, using data obtained from the Goddard Level 1 and Atmospheric Archive and Distribution System (LAADS). Caption by Rebecca Lindsey.
- Instrument:
- Terra – MODIS
Enneagram says:
July 22, 2010 at 8:49 am
“We’ll try to help our Gaia by promoting […] non reproductive sexual behaviors”
Let’s talk.
Well ships and planes aren’t the only culprits.
A few years back; while driving on a freeway; after a recent rain shower; I noticed that the cars whizzing by me were kicking up a lot more water spray off the road than I could explain by how wet the road surface was. Even in places where the road had a decided camber or tilt to one side, so that water drained off it readily, those passing cars were enveloped in a cloud of spray; far more water than the road surface had on it.
I was actually on a higher road (going over the Grapevine) and it was also a bit chilly outside.
So I began studying cars near me; that I could keep up with, and I could clearly see that these ars were moving foraward in clear air (nobody close in front of them) and water spray was streaming off body parts that were forward of any wheels, and coming off places that couldn’t possibly be getting road pick-up spray.
It dawned on me that the low pressure generated by the Bernoulli effect was causing cloud condensation right around the cars; in highly saturated cool air, that just needed a pressure drop to cause condensation.
Since then I have observed the phenomenon many many times; most of the water spray we drive through after rain showers, is not road spray at all; but auto-cloud formation.
TomB says:
July 22, 2010 at 6:50 am
“It’s called “The Great Circle Route”. ”
😉 Fantastic!
There’s a problem with the popular view of the physics. http://www.sciencebits.com/ship_tracks uses the false form publicised by NASA. In reality, the physics is increased optical scattering by clouds with smaller droplets.
The pictures show this apparently greater in the polluted clouds. However, there is no measured albedo difference between unpolluted and polluted thick clouds, probably because of a second optical process at the upper level of clouds. That this exists is proven by the fact that albedo has an angular dependence and regularly reaches 0.7: diffuse scattering can never put back more than half the incoming light [think about it!].
The upshot is that if you photograph the scene at different angles, it’ll probably look different, becoming much more uniform when the satellite is in direct line of sight with the sun, but that is very rare. This is I suspect one of the key areas of dubious physics which renders the climate models unsafe. Kiehl wrote about the errors in the aerosol corrections in 2007. The argument is circular: to get high AGW heating, the models have to have a substantial aerosol cooling for which there is little evidence. The alternative explanation is that the assumed feedbacks are too high or the proportion of recent heating attributable to AGW is too high, or a combination!
My initial speculation as the the arc shape of the ship tracks was that it was due to changes in currents. After reading comments and thinking about it further, I’ve convinced myself that most of the curvature is primarily due to changes in cross wind speed carrying the plume away from the ship’s original track. Looking at the scale in the lower left, the large central ship track appears to be about 600 km in length. Assuming a speed of 20 knots (appx 36 km per hour) we’re seeing about 16 hours worth of travel time.
To summarize, the ship itself probably did not travel a straight line course. It may have been powering along at a fixed heading, but variations in currents and wind moving the ship resulted in a non-linear route. Then once the exhaust is aloft, it is carried by the wind. The cloud-inducing exhaust in the lower right of the picture was formed roughly sixteen hours prior to the exhaust being emitted by the ship at the time the image was captured. The amount of time and distance at play here provide plenty of opportunity for changing wind patterns to reshape the exhaust plume.
This is certainly not a great circle route. The scale and curvature are entirely wrong. I do a lot of ocean sailing, so plan great circle routes, and do know. Plus of course, as ArndB observes, there appear to be conflicting tracks in the opposite direction. I confess I have attempted to figure out a cloud movement pattern which would make the combined effect, and have drawn a blank.
One further thing: in my travels I have very often observed clouds forming over islands, which can often identify them long before they appear over the horizon. This is one of the methods of “eyeball navigation”, used in ages past, which is still of use if the instruments go down, etc. This effect takes place even over really extraordinarily low-lying islands, both dry and wet. I suspect it is that the island breaks the continuity of airflow in terms of both drag and (despite the slightness in many cases) height, and causes condensation by increased turbulence. I would consider that a vessel of the likes of a bulk ore or grain carrier, car carrier, or (especially unladen) oil tanker would cause more than enough such turbulence to create clouds, quite apart from any condensation on particulate matter or other exhaust gas effects.
Geroge: I like the “auto cloud” thing. I’ll have to keep an eye out for it.
The curved ship tracks could have to do with navigation by homing on a radio beacon or GPS point. If you home on a point but wind and/or currents push you way from that point, you get to the point but your track is curved.
Small particles in ship exhaust probably do result in more and smaller cloud droplets but there is another fact at work here. Combustion of hydrocarbon fuels results in combining hydrogen from the fuel with oxygen from the air and the result is H2O. Burning natural gas in a gas turbine, for example, can result in an exhaust flow with as much as 8% water vapor, which is about 6% more than normal atmospheric air. So the clouds are at least partly due to the increased water vapor in the exhaust gases.
If you have a gas stove you can see the water vapor in the combustion gases. When you put a pot of water on the burner, you’ll notice that condensation forms on the side of the pot when you first turn the burner on. After a few seconds the pot gets hot enough to evaporate the condensation. You can also wave a spoon or other metal object through the combustion gases above a gas-stove burner and you’ll see the condensation that forms on the surface.
Alexander: Good point about the physics of light scattering by droplets. There is also the point that clouds are good at trapping heat. Farmers know that there is little danger of frost on a cloudy night.
All this raises an interesting point. If burning hydrocarbons results in more or thicker clouds, which cool the planet, then burning carbon should create sellable carbon credits!
Thomas (the doubter)
The Science isn’t settled.
Vapor pressure is a function of temperature but the water cycle over the oceans is difficult to document — especially in terms of salinity changes. As far as I can tell, NASA’s 2011 Aquarius project will be the first attempt to measure global Sea Surface Salinity.
“Sea Surface Salinity Patterns Analysis Tool”
http://aquarius.nasa.gov/education-datatool_jpl.html
Thomas,
“All this raises an interesting point. If burning hydrocarbons results in more or thicker clouds, which cool the planet, then burning carbon should create sellable carbon credits!”
THAT will never make it into the law!
Please note that the radiative properties of ship tracks is quite different from aircraft contrails. The ship tracks don’t change OLR much (the clouds are about the same temperature as the ocean) so they cool the surface (increased albedo, little or no IR warming). Contrails on the other hand increase the albedo (surface cooling) but also decrease OLR (surface warming).
Wait a minute. We know ships travel in virtually a straight line. So, it is understandable that clouds shifting at different rates due to wind gradients would cause arcing of ship tracks. But, how do you explain the ship tracks arcing both upwards and downwards over the same area? Are clouds shifting in opposite directions at the same time? Is there a tear in the space-time continum? Give me a break!
Let me guess: We’re all supposed to believe that line of BS, right?
Ship tracks that move in perfect synchrony to produce IDENTICAL curvatures, even though they all originated from different locations?
Right.
What will we be asked to believe next? That the ships are performing in a gigantic Olympic Synchronized Water Steaming maneuver?
Geez …
I’d mention something about another kind of trail, but that’s a forbidden topic here.
Oh well.
Further to my last: Here, you want to see some really awesome trails in the sky off California? SEE THIS:
http://www.atmos.washington.edu/images/vis_enhanced/201007111900.gif
But DON’T WAIT TOO LONG, because it will disappear in a few days as it rolls off the active archive list.
Then there’s this one:
http://www.atmos.washington.edu/images/vis_enhanced/201007121900.gif
Or this one: TIC TAC TOE in the sky just off LA:
http://www.atmos.washington.edu/images/vis_enhanced/201007211800.gif
The base archive is here:
http://www.atmos.washington.edu/cgi-bin/list.cgi?vis_enhanced
Oh, and hey, this is perfectly –PERFECTLY– ludicrous:
(A March 2009 image from this area demonstrates the cloud-brightening effect more dramatically).
Image here: http://earthobservatory.nasa.gov/IOTD/view.php?id=37455
Okay, now PUH-LEEZE tell me why it is that all those ‘ships’ would be moving in PARALLEL, i.e., next to each other and not following the SAME TRACK as the others?
Savant says:
July 22, 2010 at 2:12 pm
Please note that the radiative properties of ship tracks is quite different from aircraft contrails. The ship tracks don’t change OLR much (the clouds are about the same temperature as the ocean) so they cool the surface (increased albedo, little or no IR warming). Contrails on the other hand increase the albedo (surface cooling) but also decrease OLR (surface warming).
You’re neglecting to consider something QUITE important: WHEN was the last time you saw a jet taking off at an airport which LEFT A VISIBLE CONTRAIL?
I’ve worked in aviation all my life, and NEVER have I ever seen a contrail being left by a jet, even at at a high altitude airspace such as Denver.
NEVER.
Now remember: THOSE SHIPS are on the SURFACE of the ocean, and those photos are VISIBLE photos, i.e., things which are visible to the naked eye.
WHY don’t we see them when they leave port?
WHY don’t we see them when they ENTER port?
WHY is it happening ONLY over open water?
And WHY is it only recently that such visual effects are being seen?
TomB says:
July 22, 2010 at 6:50 am
Tom: “Why do ships move in such daft curves? Or is this a north-westerly wind showing up?”
It’s called “The Great Circle Route”. Going toward the poles decreases the longitudinal distance traveled. It’s actually faster that way. The same reason ballistic missiles are intended to go over the poles.
[reply: Atmospheric effects in this case I think. RT-mod]
So, RT, do tell: How is it that the winds are blowing in entirely contrary directions?
A science free article. And here’s the punchline: “these modifications—increasing cloud brightness and lifetime—have probably helped offset some of the warming influence of rising greenhouse gas concentrations.”
Exec summary: The heat is hidden by the effect of ship’s wakes on the global albedo, and cloud formation.
Speechless.
Ref – Joe Lalonde says:
July 22, 2010 at 6:39 am
“A quote ‘Human pollution has likely been modifying clouds on a global scale throughout the modern (industrial) era.’
Where to start…hmmm…..”
________________________
It’s the Me-thane (I like the way the Brits say it)! That’s what done it! The me-thane, the you-thane, the he-thane, and the she-thane! The impact on climate of this stuff is totally off the chart. We’ll never get things to cool off until we learn to control this constant pollution of the atmosphere and the resulting buildup of heat. As Fat Albert says in moments of utter pleasure at the hands of a masseuse: “For the next 100 years, no one, NO ONE, should have any kids!”
PS: If I recall correctly, Fat Al thinks we also need to go back to wooden sailing ships
I have to assume that a lot of viewers have never looked at clouds moving or aircraft vapor trails either.
If the “curvature” of these “ship tracks” were due to cloud motion as a result of winds; just what do you think is the likelihood that the wind blows an a nice almost Gaussian profile beam so it displaces the center of the beam more than both ends; and in a nice smoothly graded fashion.
Baloney ! the air currents (winds) aren’t that consistent or unchaotic as to allow for those nice parabolic looking arcs. They would have bumps all over them with a quite eratic end to end profile.
I would vote for the tracks being closer to actual ship movement than anything else.
Would you like to try and convince me, that those much lower curvature tracks going from upper left towards lower left, and the far more curved tracks that are like upside down parabolas (Y = – x^2) are all being driven by the same winds.
How can you possibly explain a wind cause or any sort of cloud motion cause for these overlapping tracks of totally differnt curvature in the same place ?
Some remedial problem solving course would probably be a good seller if someone put some on line.
George E. Smith says:
July 23, 2010 at 11:50 am
I have to assume that a lot of viewers have never looked at clouds moving or aircraft vapor trails either.[–snip rest–]
I’m calling you out, George:
[1] IF the wind were blowing constantly in one direction, from the point of first emission by the ship, then the emission trail would NOT be curved. Rather, it would be ragged by dint of the fact that the emission trail would be constantly broken up and dispersed by that wind.
[2] To presume as you do that the emission trail will remain a cohesive mass from the time of emission to the time it reaches altitude extremely begs, and I DO mean ‘BEGS.’
But since you seem to think such, then PUH-LEEZE: SHOW ME THE SCIENCE!
Additionally, when I was in the USN, I served on 4 aircraft carriers, 3 of which were bunker-fired. At NO TIME did ANY of those oil-fired ships create long-standing clouds which trailed them.
Oh, and there’s this: If steamships were to produce such LONG-STANDING TRAILS, then WHY weren’t those used to track enemy ships in the various modern wars? I can’t wait to read of THAT!!!
I mean, after all, if modern ships are burning the very same distillates as the older ships did, why merely tracking the trails would have made matters waaaaaay easier!
Now, let’s get down to the science here, shall we?
Tell me: How is it that a ‘condensation trail’ is able to expand AND remain entirely opaque, such that it ALSO is able to generate an albedo far in excess of the moisture which it initially contained?
NOTE: A CONVENTIONAL contrail is nought but the condensed water vapor which had originally been ingested by an internal combustion engine. Ergo, you CANNOT get MORE vapor than from what had been ingested to begin with.
Therefore, with a conventional contrail, it expands and dissipates, become translucent and then finally transparent. IT DOES NOT HANG AROUND DAYS.
The ‘trails’ in the sky expand to cover whole cities and then some. Hell, sometimes a few hundred miles in width, all the while maintaining an albedo HIGHER than the surrounding moisture in the atmosphere.
Further, those ‘trails’ DO NOT DISSIPATE when the background clouds do. What’s up with that?
Pascvaks says:
July 23, 2010 at 5:52 am
[–snip–] “For the next 100 years, no one, NO ONE, should have any kids!”
Geez man, if you hate yourself that much, why not just commit seppuku and be done with it?
George E. Smith says:
July 23, 2010 at 11:50 am
*
*
Now, George, let us tackle THIS problem: Here are three weather sat photos. The first is visible, the second a moisture map, and the third is an Infrared map of the same place, time, and date: 1800 hours GMT, 23, July, 2010.
[1] Visible:
http://www.atmos.washington.edu/images/vis_enhanced/201007231800.gif
[2] Water vapor:
http://www.atmos.washington.edu/images/wv_enhanced/201007231800.gif
[3] Infrared:
http://www.atmos.washington.edu/images/ir_enhanced/201007231800.gif
QUESTION: Why is it that the trails —all having an apparent HIGH albedo, at least as high as the surrounding clouds— DO NOT show up in either the water vapor or infrared maps?
Their all supposed to be ‘moisture,’ right?
Further to my last: Now, if ships are ~supposedly~ producing such ‘vapor trails’ in the sky, then DO TELL: What are not the major urban areas with HIGH surface traffic producing FAR MORE of the ‘vapor trails’ inasmuch as all those engines are producing far more effluent emissions?
Hell, virtually EVERY city in the U.S. would have a ‘permanent’ cloud over it!!
re 899’s comments:
Ship trails form in certain conditions. When an air mass is saturated with water vapour and the air lacks nuclei on which the droplets can form, a cloud will form only when more nuclei are added. You wouldn’t expect e.g. an aircraft to always create a contrail and in just the same way you wouldn’t always expect a ship to leave a trail. It does seem surprising to see such a big effect from a small cause, but if you watch a contrail you will see the same thing happening, a clear space behind the aircraft and then a trail which at times becomes very large. And, of course, many aircraft leave no trail at all because the water vapour is insufficient to form one. They are, after all, just clouds and you wouldn’t expect clouds to form all the time everywhere, only when the temperature and humidity are right and the aerosols are there to form the droplets. When a smoke-emitting ship is ploughing through fog it will almost always leave a trail of whiter cloud behind it, but the effect is small and not noticeable to the naked eye. Professor Salter in his cloud ship proposal even allowed for this effect and plans to use more salt particles than really required, so that politicians, who don’t trust scientific measurement, can see the trails for themselves.
Towns may push up a lot of dust as nuclei, but only rarely will there be enough water vapour at the right temperature to make a cloud. It will happen sometimes over power stations and in the right conditions you can see a cumulus cloud towering up into a still sky.
Why is it white? For the same reason that snow is white or crushed glass, the little particles bounce the incoming light round and round instead of just letting it through. Those with an experimental bent and ample protective clothing and masks might try crushing a pane of glass into smaller and smaller pieces, recording the results to show how the tinier fragments make the pile of fragments whiter. In just the same way, smaller droplets in a cloud make the cloud whiter (when viewed from above as it bounces the sun’s radiation back into space). Safety of the experiment will be enhanced if you use ice instead of glass, so that’s what I’d advise: those in warmer climes should do this in an ice house or wait until winter.
I’m pleased to that aerosols are becoming more involved in the AGW explanations — I see them used in a recent Real Climate post to paper over the cracks in one explanation. Once they take over from the simple CO2 theory as the dominant explanation then someone will wonder if the A in AGW might involve unintended manipulation of the aerosol population. Dr Curry will be on solid ground as this is her area of expertise and the world will assess the Kriegesmarine Hypothesis with renewed interest.
We need a new set of words to refer to them, though. Aerosols can be all sorts of things and the different types really need different designations. For the ones which cause droplet formation I usually use ‘CCN’.
JF
Re.: Julian Flood says:
July 24, 2010 at 1:32 pm
*
*
Your reply is rather specious given that the mentioned ‘clouds’ DON’T dissipate even when the surrounding natural clouds DO dissipate as the day wears on.
Pretending as you do to declare that emissions of the vessels are white is as about as asinine a remark as any I’ve read lately. Show me a ship emitting white smoke and I’ll show you a ship that about to catch fire, because the flame in the boiler is running far too hot for the internals to sustain that condition for more than a few minutes as a time.
I should know: My first four years in the USN were as a boiler tender on an aircraft carrier. Burning white is to be avoided in the same way a burning black, only black smoke tends to load up the piping with carbon and thence reduces the efficiency by dint of the fact that the carbon acts as an insulator on the pipes, which then requires more fuel to generate the same amount of steam.
And you’ve not explained how it is that a SMOKE trail causes water vapor to both collect as well expands into a opaque mass which covers literally HUNDREDS of miles in width. There isn’t that much smoke coming out of the stack!!
So, your explanation is so full of holes that it sinks into the waters of the ludicrous!
And once again you sidestepped the obvious question: How is it that said ‘ship trails’ shown in the pictures have coequal curvatures which bend in one direction, whilst an adjacent other set of trails are bending in opposition?
Additionally, those trails appear BOTH adjacent to land as well as in the wide-open expanses of the ocean. Some appear right adjacent to large cities. So your hypothesis fails on that aspect alone: WHY are not the cities producing that same amount of clouding from their surface traffic?
Go ahead, render up yet another Twilight Zone explanation!
Bonus question: I’ve been watching the Pacific basin sat pictures for several years now and have saved copies of those. Many of those trails are in the deep water areas where no fishing takes place. Yet those trails snake back and forth in loops, and others criss-cross each other.
THAT is one heck of a lot of fuel being expended for to do nothing.
Who has the time and wherewithal for such meandering travel?
AND, why didn’t those trails appear until a certain date?
In all the years that I travelled at sea, NOT ONCE, NOT A SINGLE TIME in the span of 18 years in whatever ocean I happened to find myself, did I witness any such cloud formations being produced by sea surface traffic.