Mysterious, mystical and eerie, multi-coloured glowing clouds have been seen in the skies over America and Europe over the past few days.
These clouds may have an almost supernatural ambience but there is in fact a scientific explanation. These Noctilucent clouds are made of crystals of water ice and are the highest clouds in the Earth’s atmosphere, normally too faint to be seen. They are usually observed in the summer months at latitudes between 50 and 70 degrees north and south of the equator, illuminated by sunlight from below the horizon.
These clouds hover high above the ground but the Sun, in certain places, can still reach them and make them glow when the earth below is in darkness.
Once a rare phenomenon it seems like now these high altitude clouds are showing at lower levels. Noctilucent clouds have been observed since the 1800s but more recently they’ve brightened and have been observed more regularly. Even so very little is known about them; they are mysterious and photographs are sought after by researchers making this field of astronomy and meteorology one of the few areas where amateur observers can contribute to science.
Some scientists suggest this increase in these clouds appearance could be related to increasing greenhouse gases which cause the upper reaches of the atmosphere to cool.
If the noctilucent cloud height were to change, it would indicate a change in the temperature structure of the atmosphere. Thus, the more frequent appearance of these clouds could be a possible sign of global warming and other effects.
It has also been suggested that water vapour in the upper atmosphere has increased in the past fifty years, perhaps due to increased methane in the atmosphere. Methane is released from landfills, coal mines, the burning of biomass and from a variety of other human activities. This gas can carry more water vapour into the upper atmosphere where it condenses at much high altitudes to form more clouds that the sun’s rays can strike long after sunset.
These ghostly, shimmering images in the night skies could therefore be a signal of the loss of ecological balance now in progress.
According to the Noctilucent Cloud Observer’s Homepage, this is an unusual phenomenon of the Earth’s upper atmosphere. These clouds are often seen at times close to the summer solstice when they appear against the backdrop of deep evening twilights.
Although these clouds usually appear at arctic latitudes they have been sighted in recent years in Colorado, Utah and Virginia. They are seasonal, appearing most often in late spring and summer. The period when Nocticulent clouds appear in the northern hemisphere usually ends towards the close of the eighth month of the year. The best times to see these clouds in the northern hemisphere is therefore between mid-May and August. About thirty to sixty minutes after sunset when the Sun has dipped 6 to 16 degrees below the horizon, look west. If you see luminous blue-white tendrils spreading across the sky you are likely to have spotted a noctilucent cloud.
Example of these clouds can be seen here: mysterious clouds