Cirrus and persistent contrails

[jack.h...@gmail.com]

https://youtu.be/SbQy0v8isdI

Both are KLM Boeing 777s from Amsterdam, the first to Los Angeles, the second to San Francisco.

Trails often persist and spread if there is already a lot of cirrus.

There are suggestions that cruising levels might be adjusted to minimize trailing and hence greenhouse effect.

Both these aircraft were at Flight Level 320 (32,000 feet) - quite low - and maybe that was optimum given the strong winds at altitude.

Jack

Jack

[Len]

Persistence of trails depends on the water vapour content at flight level.

Flight planning atm does not consider this for routeing. As you say, it is all about wind speed.

I think to find some nice dry atmosphere would require considerable re-routeing which would be expensive on fuel

and counter poductive in reducing greenhouse gas emission.

It's a no win situation.

Len

[Freddie]

It also depends on temperature.

[Metman2012]

I remember when at Heathrow in the 70s, plotting tephigrams which had a line called the mintra, which denoted whether contrails could form or not, I assume above it. However I don't remember it ever being used or forecasts of contrails being made on the various sig wx charts.

One bit of useful/less information. The Met Research Flight was formed in 1942 to investigate contrail formation as the Flying Fotresses, on day raids, could be found very quickly when they formed contrails. I was at the 50th anniversary at Farnborough and here's a couple of photos of snoopy and a Spitfire of the type used in the research.

 

[Len]

I'm a bit surprised that the 4 prop flying fortresses left contrails.

Certainly jet engines are more of a problem.

Len

[jack.h...@gmail.com]

On Monday, 2 December 2024 at 15:34:35 UTC Len wrote:

I'm a bit surprised that the 4 prop flying fortresses left contrails.

Take me back to circa 1943/44.  Where I lived, Great Yarmouth, was an assembly point before going to bomb oil installations in Germany.  I can still hear the sound of some 1,500 engines, all leaving contrails.  It was very exciting for a four / five year old but I couldn't at that age appreciate the wanton slaughter of hundreds of German citizens who quite likely in many cases, didn't want Hitler and Co any more than we did.

Jack

[jack.h...@gmail.com]

You cannot see your own contrails.  

However, in some situations, you can watch the shadow (as the contrail forms) moving over the ground, and then you get a real idea how fast you are going.

Jack