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Rare clouds that glow in the dark are the most vibrant in 15 years for sky watchers in the upper US, Canada and Europe
Some of the rarest clouds on Earth that haven’t been seen this bright in around 15 years were spotted by sky watchers in parts of western US, Europe and Canada over the weekend. Known as noctilucent, these clouds were glowing a stunning blue in the sky just after the sun moved below the horizon. Pictured is Alberta, Canada.
Reports of the eerie-looking clouds came from Oregon, Washington, Alberta, the UK and Denmark. Noctilucent clouds (NLCs) form in the mesosphere, which is at altitudes of around 50 miles – making them the highest in Earth’s atmosphere. The clouds consist of ice crystals that become visible during twilight when the sun is shining from blow the horizon. Pictured: Seattle, Washington.
‘There’s really nothing else quite like them,’ the National Weather Service office in Seattle wrote on social media, noting that these are the ‘most vivid displays of noctilucent clouds’ that have been seen in decades in the area. The clouds typically form in late spring and early summer when the lower atmosphere becomes warmer. Atmospheric circulation pushes air upwards, which then expands and cools. Water vapor becomes trapped in the clouds, freezes into ice crystals and forms meteoric dust. Pictured: The clouds over London.
The clouds appear with electric blue and silver streaks and are typically spotted at latitudes of 45 and 80 degrees in the northern and southern hemispheres. Some scientists believe climate change is impacting the clouds development – causing them to be seen at latitudes never seen before. For example, in 2019, they were seen as far south as Joshua Tree, California, which suggests that with more greenhouse gases in the atmosphere, there is more water vapor available for the glowing clouds to form. Pictured in Denmark.
Cora Randall, a professor at the University of Colorado Boulder, told The Washington Post that the increase in clouds could be due to excessive water vapor in the atmosphere from rocket launches. Another study suggests that the appearance of NLCs does fluctuate from year to year and even from decade to decade, but that overall, they have become ‘significantly’ more visible. In 2020, a photographer shared a stunning image of the phenomenon in the early morning hours that gave a 12th century church a ghostly glow (pictured).
Noctilucent clouds were first described in the mid-19th century after the eruption of Krakatau. Volcanic ash spread through the atmosphere, making for vivid sunsets around the world and provoking the first known observations of NLCs. At first, people thought they were a side effect of the volcano, but long after Krakatau’s ash settled, the wispy, glowing clouds remained.