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Lulu
Joined: 22 Dec 2000
Posts: 2501
Location: right here |
 Fri Feb 14, 2003 2:46 am
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>>I was hoping you might be able to go into a little more detail on this scale. For example, where on this scale would a contrail that persisted for 5-10 seconds or a contrail that persisted for 2 hours fit?<<
Bumped for canex...
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canex
Joined: 26 Oct 2000
Posts: 164
Location: USA |
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Fri Feb 14, 2003 5:37 am
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Double Lew,
That's a hard one to answer because so many variables are involved. Generally, however, thecloser the dewpoint and air temperatures, the longer a trail will last. If the air is undergoing slow uplift, then the contrail will last longer and conversely, if it is slowly sinking, the trail will persist only a short time.
Contrails typically loft a few hundred meters when they first form because the latent heat release warms the surrounding air. That lifting and subsequent cooling raise the humidity in the air parcel containing the contrail causing the contrail to persist for a while even if the air is slowly sinking. If the layer is very humid, the contrail may disappear within a few hours because the ice crystal sgrow so fast, they fall quickly into lower layers and evaporate, taking the ice crystal nuclei with them.
In short , there are a lot of factors operating at the same time. Rule of thumb, though, is the closer the temps, the longer it persists. |
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