George B
Extinct but not forgotten Staff Member
You are correct about it being drier than the troposphere, but about the rest you are apparently misinformed.
For "on occasion" read "continually, with few exceptions".
Stratospheric clouds called CIRRUS CLOUDS are observed. They are made of ice: there is no presumption to it. They have always lived at their stated address*. Their exact composition is known, and has been known ever since lasers were first used from ground and space to assay their contents and composition.
The link given is for noctilucent clouds, which are clouds up in the high stratosphere of elemental particles in association with ice. These are much less substantial or understood.
I live on Tenerife at Latitude 27 degrees. It is VERY sunny here, but there is never a day that passes without some cirrus visible somewhere, even on the clearest, bluest day.
The vertical upward transfer of water vapor** through the apparently impermeable tropopause has TWO mechanisms:
- The quasi-biennial oscillation, where Hadleigh Cell boundaries mix twice a year, and
- Aircraft.
The proportion of the latter is beneath the resolution of monitoring. If aviation expands at its current rate for a further forty years then this proportion will achieve significance. That isn't very likely.
* If 17% of the lower stratosphere is known to be fully saturated with water vapor, then any reduction in temperature anywhere (possibly caused by falling over a tropospheric "bulge", or by vertical standing waves) will cause ice crystals to nucleate out, and cirrus cloud appear. As this occurs in sheets and layers all over the Earth, then cirrus clouds will be everywhere, over 17% of the earth's surface. The ice crystals composing cirrus clouds are often very temporary indeed... ... a lenticular cloud is a form of cirrus. It appears stationary while its component ice crystals are forever coming into and winking out of existence, much as a rainbow appears stationary when it is being continually remade with falling drops of water - although one is real, the other virtual, of course.
Also jet streams are visible - though more easily visible from space. they can travel much faster than laminar flow will allow, and become turbulent at their edges. This turbulence produces ice clouds by stirring with colder material, which is normally beneath it.
There is enough water in a jet stream to wash out anything which has an affinity with water. The energy of such streams derives itself from the heat stored in the ice crystals and water vapor, and hardly at all from atmospheric air molecules. If water were not to be there, such flows would STOP. Or at least slow right down to a crawl...
** The downward is of course gravity, upon ice crystals, and the QBO.
Thanks for your details but just what part do you think I am misinformed about???
1) The fact that scientific proposals were published to inject Sulfur Compounds into the stratosphere in the 1990s and until at least the mid 2000s with existing aircraft as well as proposed aircraft designed for higher altitudes?
2) The projected tons of Sulfur Compounds proposed?
3) The location of injection and number of aircraft proposed?
4) I never said it would work, or that the science was on point . . . I just said it was discussed, cost analysis accomplished, and the pros and cons discussed . . .