Amazing Noctilucent Clouds

One of the most extraordinary and beautiful sights this time of year are the delicate noctilucent clouds that can appear after sunset and before sunrise.

Take a look at a video made by Greg Johnson of Skunk Bay weather showing the celestial show yesterday morning:



Noctilucent clouds are the highest visible clouds, located around 50 miles above the earth surface. Such clouds form when moisture is deposited on dust in the upper atmosphere, generally from meteoritic dust.  Major volcanic ejections can also supply the small particles.

These cloud form in the layer of the atmosphere called the mesophere, where the temperatures are the coldest in the atmosphere.  Specifically, we are talking about temperatures below approximately -185F.   Midsummer is favored because paradoxically that is when the mesosphere is coldest.

NASA even has a satellite (AIM) dedicated to seeing these clouds, as illustrated by an example from June 13th below:

The first report of noctilucent clouds was in 1885 and a number of studies suggest that such clouds are getting more frequent.  

Human's may well have contributed to this increase.  But how?  

It appears that increasing human emission of methane (CH4) into the atmosphere (see below) may be the major cause, with methane breaking down in the upper atmosphere into several components, including water vapor.  More water vapor leads to enhanced ice cloud formation in upper atmosphere.

Another example of the profound effects of human activities on the environment.