Scientists have observed the formation of extraordinary night-shining clouds in the skies above the Arctic circle for over a week.
NASA’s Aeronomy of Ice in the Mesosphere (AIM) spacecraft initially spotted the small noctilucent clouds on May 17. This is the second earliest start to the northern season of the phenomenon that has been observed yet. You can see how small clouds quickly filled-up the Arctic sky between May 17 – May 25 in the tweet below.
Our AIM satellite has spotted ice-blue clouds drifting high above the Arctic, marking the beginning of the Northern Hemisphere season for these noctilucent clouds. This is the second-earliest start of the nothern season ever observed: https://t.co/MXhYOqOQ3m pic.twitter.com/v0Z8apFNtT
— NASA Sun & Space (@NASASun) May 28, 2020
Noctilucent clouds are a seasonal phenomenon that appears twice a year at latitudes away from the Equator and closer to the North and South Pole. They first appear in the Northern Hemisphere sometime in the month of May and then a second time, in the Southern Hemisphere in the month of November. These clouds are also known as polar mesospheric clouds as they tend to form around the region of Earth’s poles.
The elusive meteorological phenomenon is observed at altitudes of 50 miles (~80 km) up in the mesosphere layer. Noctilucent clouds are so high in the sky that they have the ability to reflect light from the Sun back down to Earth. But most importantly, scientists are able to study the mesosphere in connection to the rest of the atmosphere, weather and climate, all with the help of these clouds.
Noctilucent clouds are thought to consist of tiny crystals of water ice that freeze around meteoric dust as the AIM principal investigator James Russell from Hampton University explains in a NASA article from 2016, “AIM and other research have shown that in order for the clouds to form, three things are needed: very cold temperatures, water vapour and meteoric dust. The meteoric dust provides sites that the water vapour can cling to until the cold temperatures cause the water ice to form.”
So the mesosphere layer is able to slow down incoming meteors and turning them into dust and gases. Water molecules/vapour in the atmosphere can huddle up together around the fine meteoric dust. The water molecules freeze up and turn into ice crystals due to the cold temperatures.
According to the recent NASA article, noctilucent clouds appear when the mesosphere is most humid, meaning all the moisture of the season is high in the atmosphere. These icy clouds then reflect sunlight and appear to shine bright blue and white. But this year, the Arctic season of night-shining clouds had the second earliest start recorded and is expected to run through mid-August.
Scientists have been studying noctilucent clouds with the help of AIM for years. Sometimes they have been observed to stray from their usual region near the poles. But sometimes, the northern night-shining clouds have also been observed at much lower latitudes near southern California and Oklahoma. Scientists hope to understand more about the elusive patterns of this phenomenon with every season.
James Russel, while explaining how the start of each season is a big event, explained his excitement for this year and said, “The reason we’re excited is we’re trying to find out what the causes of the season’s starting are and what does it really mean with regard to the larger picture in the atmosphere.”
Image Credit: NASA/Marek Nikodem
Image Source: NASA AIM