BBC: Biofuels 'could limit jet contrails'

[MikeC]

Looks like the chemtrail activism is working, because why else would TPTB be doing stuff like this??

http://www.bbc.com/news/science-environment-39286079

US space agency-led scientists flew small, instrumented, chase planes directly in the exhaust plume of a big jet to measure the sorts of gases and particles being thrown out.

The data suggests aircraft burning a mix of aviation kerosene and biofuel could reduce their climate impact.

This would come from a substantial reduction in the production of the sooty particles that make contrails.

"Those soot particles serve as nuclei for water vapour in the very cold atmosphere to condense on and for the artificial-looking linear contrails that we see when we look out the window," explained Richard Moore from Nasa's Langley Research Center.

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[NoParty]

Because why else would TPTB be doing stuff like this??

http://www.bbc.com/news/science-environment-39286079

US space agency-led scientists flew small, instrumented, chase planes directly in the exhaust plume of a big jet to measure the sorts of gases and particles being thrown out.

The data suggests aircraft burning a mix of aviation kerosene and biofuel could reduce their climate impact.

This would come from a substantial reduction in the production of the sooty particles that make contrails.

"Those soot particles serve as nuclei for water vapour in the very cold atmosphere to condense on and for the artificial-looking linear contrails that we see when we look out the window," explained Richard Moore from Nasa's Langley Research Center.

Content from External Source

Hmmm...I can't say that "activism is working" was my first impression:

They have this Moore fellow saying:
"We know these contrails and cirrus clouds have a warming effect on the Earth's climate..."
but isn't that the opposite of what most chemtrailers believe? Don't they think that nefarious
sources are spraying these plumes in order to reduce sunlight, and to lower the temperature?

 

[MikeC]

Sorry - I should probably have put a smilie or 12 on the post - but i'll give you dollars to knobs of goat dung that such a claim will be made by believers when they find this and justify it against their mantra.

 

[Ross Marsden]

Even if there is no soot, sulfur, or other introduced ice nuclei, some of the condensation droplets will spontaneously freeze, and there will still be visible contrails and aviation induced cirrus.

Ice crystal formation by Homogeneous Freezing
(bullet points and a diagram)

Ice and Mixed Phase Clouds

Homogeneous freezing is the process by which a supercooled liquid drop freezes without the assistance of an ice nuclei. Homogeneous freezing becomes statistically more likely as temperature decreases such that below -39C all drops will freeze.

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[Clouds Givemethewillies]

Even if there is no soot, sulfur, or other introduced ice nuclei, some of the condensation droplets will spontaneously freeze, and there will still be visible contrails and aviation induced cirrus.

Ice crystal formation by Homogeneous Freezing
(bullet points and a diagram)

Ice and Mixed Phase Clouds

Homogeneous freezing is the process by which a supercooled liquid drop freezes without the assistance of an ice nuclei. Homogeneous freezing becomes statistically more likely as temperature decreases such that below -39C all drops will freeze.

Content from External Source

I imagine that the plan is to make the ice crystals bigger, and the clouds optically thinner.

 

[Hama Neggs]

Even if there is no soot, sulfur, or other introduced ice nuclei, some of the condensation droplets will spontaneously freeze, and there will still be visible contrails and aviation induced cirrus.

This seems related to the question which was raised some months ago as to whether contrails would be formed by introducing ONLY nuclei particles but no added. Apparently you are saying that at some temperature no nuclei at all are needed?

 

[Spectrar Ghost]

This seems related to the question which was raised some months ago as to whether contrails would be formed by introducing ONLY nuclei particles but no added. Apparently you are saying that at some temperature no nuclei at all are needed?

Precisely. It's called homogenous nucleation.

• Nucleation without preferential nucleation sites is homogeneous nucleation (Lecture 10-11).
  
  Homogeneous nucleation occurs spontaneously and randomly, but it requires superheating or supercooling of the medium.
  
  
• Compared to the heterogeneous nucleation (which starts at nucleation sites on surfaces),
  Homogeneous nucleation occurs with much more difficulty in the interior of a uniform substance. The creation of a nucleus implies the formation of an interface at the boundaries of a new phase.
  
  
• Liquids cooled below the maximum heterogeneous nucleation temperature (melting temperature), but which are above the homogeneous nucleation temperature (pure substance freezing temperature) are called supercooled.
  
  
• An example of supercooling: Pure water freezes at −42°C rather than at its freezing temperature of 0°C. So, if cooled slowly below the freezing point, pure water may remain liquid (supercooled).

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• 
  http://www.eng.utah.edu/~lzang/images/lecture-10.pdf

 

[Hama Neggs]

Maybe it's not that relevant to contrail formation since nuclei are always present, yes?

 

[Ross Marsden]

Maybe it's not that relevant to contrail formation since nuclei are always present, yes?

Well, no. There are two kinds of nuclei.
There are Cloud Condensation Nuclei. There are plenty of them and they are everywhere. You cannot get water supersaturated air (in the free atmosphere), that is RHw above 100% because the CCN are always there to initiate condensation.
There are Ice Nuclei. There are very few in the free atmosphere. Aircraft exhaust provide them in the exhaust plume, and they are in the condensed water droplets, and the droplets readily freeze on them.

Ice will not nucleate on a condensation nucleus; it needs an ice nucleus.

That there are none (or very few) naturally occurring in the atmosphere is why you can have vast regions of ice-supersaturated air where the RHi is above 100%, and up to like 140% at the point where RHw is just reaching 100%.
And this is why large parts of the sky can be filled with persistent contails that cannot dissipate in these ice-supersaturated regions.

If there were Ice Nuclei, then these ice-saturated regions would be full of ice cloud, just as water-saturated regions are full of water droplet cloud.

 

[Trailblazer]

If there were Ice Nuclei, then these ice-saturated regions would be full of ice cloud, just as water-saturated regions are full of water droplet cloud.

Do you think it is the case that with more and more flights, the increasing "background amount" of ice nuclei could mean that ISSRs (ice-supersaturated regions) will tend to simply spontaneously fill with cloud in the future? I don't know what the typical residence time of these particles is, but if it is relatively long then you would expect the increasing number of flights to keep increasing the levels of ice nuclei in this part of the atmosphere.

If the nuclei linger after the aircraft have passed, then they could drift into ISSRs and initiate "contrail" formation even when the plane is not near. Or do the particles have to be relatively freshly produced in order to function as ice nuclei?

 

[Ross Marsden]

Yes, I do think that logically follows. Maybe the trails of sparse soot and SO2 are too diffuse/dilute, or few relative to the volume available, for trails of ice cloud to be visible.