posted on May, 1 2013 @ 05:31 PM
Originally posted by tsurfer2000h
reply to post by smarterthanyou
Now when you say "isn't fully saturated" are you talking about at ground level, or are you saying that about the height contrails will form?
Because there is a difference...
And jsut to explain that to those who might not understand "fully saturated" at ground level means rain or other precipitation, because there is
plenty of nucleation material around - so much so that the atmosphere cannot actualy be "supersaturated" - ie it cannto hold more than 100% relative
Fully saturated with respect to ice at 30,000+ feet does not mean you see anything at all - because without ice nucelation material such as dust teh
moisture does nto actually precipitate out of the air!! As a result you CAN have an atmosphere wher there is more than 100% humidity!
then as soon as you intriduce nucleation material such as the soot and other particles in the exhaust of a jet aircraft the moisture DOES get somewher
to nucleate, and precipitate outs "en mass" to the extent that it has been estimated that the moisture from the engine is only a small % of the
total in a contrail.
And of course the ice crystals int ht contrail are also nucleation sites - so they can cause even more precipitation!
So if you have a wide swathe of the atmosphere that is super saturated then you MUST get a could sheet from a contrail as it causes all that excess
moisture to condense out - it is not possible for anything else to happen in those circumstances!