Very low persistent contrail over UK (<12,000ft)

[Trailblazer]

This morning there was quite a dramatic sunrise with some interesting clouds and contrails, and I was taking some photos. I live fairly close to Heathrow and planes often pass over fairly low on approach to the airport.

I saw a plane passing over and thought it might add some interest to a photo silhouetted against the clouds so I got the camera ready – and was then surprised to see it starting to leave a contrail even though, visually, it was clearly at quite low altitude...

This is the first picture, timed at 7:53:18 this morning.

I took a couple earlier through the window and the camera didn't focus properly, but it's possible to see that the trail started between 7:53:06 and 7:53:16. This is the last one in the sequence, at 7:53:38:

Flightradar24 identified it as BAW22E, and there wasn't any other possible traffic nearby that it could have been confused with.

Putting the track into Google Earth at my location also confirms it was the right aircraft.

At the time I took those photos, the plane was at less than 12,000 feet, which seems much too low for a persistent contrail to form.

And yet the trail hung around for at least 15 minutes. Any ideas why this would be?

Weather conditions were frosty after rain yesterday, about 2ºC at ground level. Model sounding shows high humidity most of the way up...

 

[Mick West]

Possibly it triggered something like a fallstreak (virga)?

What was the actual RHi and Temperature at that altitude?

 

[Trailblazer]

Possibly it triggered something like a fallstreak (virga)?

What was the actual RHi and Temperature at that altitude?

The pressure at that height would have been about 640mb so from the sounding chart temperature would have been about -10C and dewpoint -13C. So RH about 79% and RHi 87% if my sums are right.

But there was clearly higher humidity than that nearby as you can see from this photo that a subsequent flight on the same path and similar altitude cut a distrail into the cloud layer, aligned with the previous trail.

 

[Mick West]

The pressure at that height would have been about 640mb so from the sounding chart temperature would have been about -10C and dewpoint -13C. So RH about 79% and RHi 87% if my sums are right.

Yeah, I think that is correct. 87% RHi isn't a million miles from 100%, so it could simply be variations in local conditions. As you note, there are clouds nearby, so that would be 100% RHw (110% Rhi).

And it would have to be an aerodynamic contrail (which is what it looks like). Similar to other low altitude trails

https://www.metabunk.org/threads/an-unusual-persistent-aerodynamic-contrail.6681/

 

[Trailblazer]

Yeah, I think that is correct. 87% RHi isn't a million miles from 100%, so it could simply be variations in local conditions. As you note, there are clouds nearby, so that would be 100% RHw (110% Rhi).

And it would have to be an aerodynamic contrail (which is what it looks like). Similar to other low altitude trails

https://www.metabunk.org/threads/an-unusual-persistent-aerodynamic-contrail.6681/

Interesting though that it's about 25°C warmer than the Appleman max temperature for persistence. Clearly aerodynamic trails have different requirements.

The lowest I've seen persistent trails in this part of the world previously has been about 23,000ft.

 

[Mrs.A]

If people realized the number of variables that affect contrails, it would be so much easier to dismiss the nefarious accusations about them.

I am a science teacher and I spend time on contrail science because students believe so much pseudoscience about contrails.

https://www.nasa.gov/wp-content/uploads/2023/06/contrails-k-12.pdf

 

[Ann K]

If people realized the number of variables that affect contrails, it would be so much easier to dismiss the nefarious accusations about them.

I am a science teacher and I spend time on contrail science because students believe so much pseudoscience about contrails.

https://www.nasa.gov/wp-content/uploads/2023/06/contrails-k-12.pdf

I get "the url can't be shown" error message.

 

[Smythe Bacchus]

I get "the url can't be shown" error message.

Attached here for posterity

NASA Contrails K-12
Lesson Overview
Through demonstration, students will learn about properties and changes of properties of matter, as they witness firsthand how contrails are formed. This is shown by combining water vapor and the soot
from an extinguished match within a glass flask, then adjusting the internal air pressure to form a cloud.

 

[Mauro]

Attached here for posterity

NASA Contrails K-12

Nice !

Ps: towards the end of page 3 I think there is a 'vapor' which would be better if deleted:

 

[FatPhil]

Nice !

Ps: towards the end of page 3 I think there is a 'vapor' which would be better if deleted:
View attachment 87040

Typographers have their "gothic", botanists have thier "berry" and "nut", and physicists have their "weight" and "vapour". Traditionally, "vapour" was the visible suspension of fine particles of a liquid (or even a solid), lifted straight from the French who lifted it straight from Latin. It's only centuries later that scientists barged into the language and tried to tell people they were using words incorrectly, and that a vapour is actually a gas.

 

[Mauro]

Typographers have their "gothic", botanists have thier "berry" and "nut", and physicists have their "weight" and "vapour". Traditionally, "vapour" was the visible suspension of fine particles of a liquid (or even a solid), lifted straight from the French who lifted it straight from Latin. It's only centuries later that scientists barged into the language and tried to tell people they were using words incorrectly, and that a vapour is actually a gas.

Thanks for the explanation! I stand corrected.