Persistent contrails

[Craig]

Hi,
I'm in discussion with someone who discounts the theories of persistant contrails. In fact he says that all the studies have made a major mistake and are "bending the rules of physics". He's convinced that all these studies including Wan's have missed the effects of the sun on these crystals.
I've attached his comments. I'm fairly certain that the sublimation would have negligible effect on the ice crystals.

Ziming Wang's 2023 study (ACP, 23, 1941-1963) looked at contrails-those airplane cloud trails- during a flight on March 26, 2014. His team found these contrails lasted hours, with their plane even measuring ice crystals persisting across a particular 7.5 minute period at low humidity (80%- 90% RHi) between 10:00 and 13:00 UTC.

But here's the catch:

At -50°C, with the morning sun shining (~700 W/m around 11:30 UTC), tiny ice crystals (20 um) should melt away fast-gone in 1-2 seconds at 80% humidity.

Even at normal (100%) or higher humidity (120%- 130%), the sun's heat should zap them in 5-20 seconds. But Wang's data (Figures 2, 5, 6) shows ice sticking around, with contrails visible from 08:30 to 14:45 UTC (Figure 3).

So, why didn't these crystals vanish under sunlight like science expects? The study doesn't explain how they hung on for so long when the rules of heat and humidity say they shouldn't. Something's off, and it's a head-scratcher.

https://acp.copernicus.org/articles/23/1941/2023/

 

[JMartJr]

Perhaps for the same reason that naturally occurring clouds don't just melt away in seconds under the impact of sunlight.

Contrails are clouds. They do what clouds do -- they form on some days but not others, they persist for greater or lesser periods of time, the can spread and cover the sky, they form at some altitudes on a given day but not others....

Clouds do all that all the time, this is not an example of breaking/bending physics, it is BECAUSE of the underlying physics. Contrails are clouds, so they do, too.

Don't know if that argument would be convincing, and it does not address the physics directly as that is beyond my pay grade -- I am sure somebody else will be along shortly who can speak to that!

 

[John J.]

In fact he says that all the studies have made a major mistake and are "bending the rules of physics".

Orange underlining is mine;

At -50 degrees C, with the morning sun shining (~700 W/m squared around 11:30 UTC) tiny ice crystals (20 micrometres) should melt away fast...

Why would we expect the ice crystals to melt? They're not at standard pressure and temperature, they're at low pressure, and much more importantly, they're in an environment which is 50 Celsius below zero!* The surrounding air is cold.
That's largely why the contrails form in the first place (although nucleation around e.g. soot particles also plays an important role).

Edited to add: The quote states 700 Watts per square metre at around 11:30 UTC, but this would vary with longitude and season (the Earth is spherical, angle of incidence changes with location).
Wikipedia says

...averaged over the year and the day, the [hypothetical top of- John J.] Earth's atmosphere receives 340 W/m2​ from the Sun.

https://en.wikipedia.org/wiki/Solar_irradiance
A significant part of the energy that that radiant flux (in W) represents is not absorbed by the atmosphere, it makes it to the surface.
2nd Addition: That 700 (or 340) Watts/ square metre is shared by tens of thousands of cubic metres of atmosphere before it reaches the ground.

*Air at the altitude that e.g. airliners often travel at is often much colder.
It doesn't warm up to 20 Celsius (or indeed above freezing) just because the sun is out.

Link to the paper mentioned by the OP's interlocuter here https://acp.copernicus.org/articles/23/1941/2023/,
"Observations of microphysical properties and radiative effects of a contrail cirrus outbreak over the North Atlantic",
Wang, Z., Bugliaro, L., Jurkat-Witschas, T. et al., 2023, Atmospheric Chemistry and Physics 23 (3)

 

[Mendel]

Why would we expect the ice crystals to melt? They're not at standard pressure and temperature, they're at low pressure, and much more importantly, they're in an environment which is 50 Celsius below zero!* The surrounding air is cold.
That's largely why the contrails form in the first place (although nucleation around e.g. soot particles also plays an important role).

reflectivity takes care of a large part of these 700W/m².
then contact with cold surrounding air dissipates much of the remainder of the energy.
And obviously it's true that contrails don't always persist, so sometimes they do evaporate.

 

[MapperGuy]

Link to the paper mentioned by the OP's interlocuter here https://acp.copernicus.org/articles/23/1941/2023/,
"Observations of microphysical properties and radiative effects of a contrail cirrus outbreak over the North Atlantic",
Wang, Z., Bugliaro, L., Jurkat-Witschas, T. et al., 2023, Atmospheric Chemistry and Physics 23 (3)

The list of citations attached to that article is about one-third of the article.
That is a mighty large group of conspirators (if the error is a conspiracy) or a mighty large group of publications that should have been rejected (if they are all wrong).
Of course large numbers of supporters does not really prove anything, you can find large groups who believe all sorts of silly things.

But OP's interlocuter should be rushing to publication if they have made such a grand discovery. Are they?

 

[Craig]

Thanks for the replies, I've mentioned a lot of those things before. Always get the same reply that all those papers are being produced by people who are being paid by the aviation industry, government .
I've also suggested if he's so convinced of his new discovery to publish his findings. Obviously won't do that either, as he's convinced the paid scientists won't believe him

 

[Mick West]

He's asserting that the crystals should vanish, but his explanation for this is "the sun's heat should zap them in 5-20 seconds"

The obvious answer here, already mentioned, is that cirrus clouds persist in the sun. But beyond that practical example, does he actually give a reason why the sun's heat should zap them? Does he give any math?

For the sun to warm something, it needs a positive "heat budget". Incoming heat has to be higher than outgoing heat. Ice crystals in full sun can be in thermal equilibrium. The interaction of various heat factors with sublimation/deposition is complicated but fairly well understood.

And this isn't new. It's an argument they were making over a decade ago.

 

[Z.W. Wolf]

Seems much like arguing with a Flat Earther...


The Flat Earth Method Of Enquiry And Debate

-Appeal to Common Sense (Argumentum ad Populum or Intuition Fallacy)
Assumes something must be true because it "just makes sense" or "feels right" to a person or a group, without providing evidence or logical reasoning.

-The claim is made without physical calculations (e.g., sublimation rate, solar irradiance, thermal conductivity, ambient temperature, pressure.

-Disregards well-documented scientific observations (e.g., the persistence of cirrus clouds made of ice crystals at high altitudes).

-Disregards well understood science
Assumes that the heat from sunlight is sufficient for sublimation at those altitudes, without taking into account factors like:

The very low ambient temperature (often below -40°C).

The low atmospheric pressure which affects sublimation rates.

The fact that sunlight at high altitudes may not significantly raise the temperature of individual crystals due to low heat capacity and radiative cooling.

-Objections are met with ad hoc excuses
The ad hoc excuses restart the same process with all of the above, plus...

-Objections are met with personal hostility

-Objections are met with alternative facts


And let's add:

Appeal to Emotion - usually negative (e.g. fear, anger, disgust, contempt). Often with paranoid elements.

 

[FatPhil]

He's asserting that the crystals should vanish, but his explanation for this is "the sun's heat should zap them in 5-20 seconds"

The obvious answer here, already mentioned, is that cirrus clouds persist in the sun. But beyond that practical example, does he actually give a reason why the sun's heat should zap them? Does he give any math?

For the sun to warm something, it needs a positive "heat budget". Incoming heat has to be higher than outgoing heat. Ice crystals in full sun can be in thermal equilibrium. The interaction of various heat factors with sublimation/deposition is complicated but fairly well understood.

And this isn't new. It's an argument they were making over a decade ago.

Given the lack of depth of the argument made, why isn't "ice is transparent" an adequate enough rejoinder? If the suns rays are passing straight through, perhaps with a bounce or two, they aren't absorbing energy, and will remain in equilibrium.

img link: https://www.thermopedia.com/content/10179/Fig1b.jpg
via: https://www.thermopedia.com/content/10176/
Emphasis mine:

The extremely low value of κ in the visible and a significant increase of the absorption index in the near-infrared range determine the specific spectral properties of ice grains and snow in these spectral ranges. In particular, the known high value of snow albedo is a result of almost perfect spectral transparency of pure ice (Wiscombe and Warren, 1980; Warren, 1982; Kokhanovsky and Zege, 2004).

 

[deirdre]

Seems much like arguing with a Flat Earther...

is that really necessary?

 

[Ann K]

is that really necessary?

The comparison is apt.

 

[JMartJr]

The obvious answer here, already mentioned, is that cirrus clouds persist in the sun.

Or, sometimes it snows and the snow lasts out in the Sun for days because it's cold and we have to shovel the sidewalk and stuff. Then recall it is even colder "way up yonder."