The strange glow of the night sky over the European part of Russia on Sunday night a week ago represented noctilucent clouds. These formations, which have long been known to scientists, now appeared unusually early and may indicate climate change.
Unusual glow and flickering of the atmosphere were observed on Sunday night over many cities of the European part of Russia and even beyond the Urals. Observers reported strange undulating structures in the sky from Karelia, Leningrad Oblast, Saratov Oblast, Tatarstan, Perm Krai, Chelyabinsk and Krasnoyarsk.
These structures were visible on the northern side of the sky, and in time, depending on the place of observation, from about one in the morning and almost until sunrise. A rare natural phenomenon - noctilucent clouds - those who did not sleep at night were given the opportunity to observe the night play of the atmosphere for a long time, the residents of Chelyabinsk - to recall the recent meteorite fall, and the television crew - to talk about another anomaly.
“Clear noctilucent clouds detected! Looked closer - they are almost over the entire northern half of the sky. In some places they climb out to the southern half (in the east),”the user lkmnbv was the first to report the observation of the phenomenon on the forum of astronomy lovers.
After that, people began to report the observation of clouds in Kondopoga, in Chelyabinsk (from 2.10 to 2.40 local time), over the Urals and Siberia. "Today in Chelyabinsk I watched gorgeous silvery clouds, and the TV people screwed up again, scaring people with anomalies," wrote a resident of Chelyabinsk.
“In Saratov (51 degrees north latitude), something unreal is happening with the fields of noctilucent clouds! From 2 am to 3 am. City center, brightness 5 points out of 5. The structure - strict stripes parallel to the horizon, - said the astronomer, head of scientific projects of the Ka-Dar observatory Stanislav Korotkiy.
"These atmospheric formations live at an altitude of 80 km - this is already the border with space - and are illuminated by the Sun from under the horizon, when the stars are still visible in the sky!" - he explained.
Noctilucent clouds are usually observed in summer, in areas at latitudes of 50-70 degrees, at a low altitude above the horizon. Previously, people sometimes mistook them for UFOs, someone considered them a sign of an imminent change in the weather. For the first time, these clouds were described in June 1885 by European astronomers who carried out night observations in several European countries, including Russia.
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One of the reasons for the appearance of abundant noctilucent clouds at that time, scientists believe the eruption of the Krakatau volcano in 1883.
Noctilucent clouds were observed in the summer of 1908 - after the fall of the Tunguska meteorite into the taiga. At an altitude of 75–90 kilometers, where clouds form, the temperature is about minus 120 degrees Celsius. Therefore, at first, scientists assumed that the clouds were water ice crystals illuminated by the Sun from under the horizon.
Later, this assumption was confirmed by observations from spacecraft.
Until 2007, when the NASA AIM satellite was sent into space to study noctilucent clouds, much in their nature remained unclear. “It turned out that meteoroids play an important role in the formation of noctilucent clouds. Particles from collapsed meteors serve as nuclei around which water can collect and crystallize,”explains Professor James Russell, AIM Mission Leader.
A hundred years ago, noctilucent clouds were observed only at high latitudes, and only in recent years have scientists observed their gradual "sliding" towards the south. Some researchers believe that this is due to global climate change causing an increase in the concentration of methane, one of the greenhouse gases. “As methane rises higher into the atmosphere, it oxidizes in a complex series of reactions to form water vapor. This vapor is then able to form the crystals that make up the noctilucent clouds,”Russell said.
In 2013, the noctilucent cloud season started earlier than usual: “This season is different in that it began in northern latitudes a week earlier (May 13) than the previous periods observed by the AIM apparatus,” says Cora Randall of the Atmospheric and Space Physics Laboratory at the University Colorado. "They may be the earliest clouds ever observed."
Such an earlier appearance of noctilucent clouds may be associated with the restructuring of the atmospheric layers on a planetary scale.
“Half the globe from northern latitudes, where noctilucent clouds form, powerful winds in the southern stratosphere are changing the global circulation pattern. This year, more water vapor has been lifted high into the atmosphere where noctilucent clouds like to form, and the air has become colder there. All this came as a surprise to us. When we launched AIM, we were interested in the clouds themselves. However, they are now teaching us how different layers of the atmosphere interact with each other over long distances,”says Russell.
Astronomers, however, note that noctilucent clouds are a kind of indicator of cataclysms in surface space, chromospheric flares, and the appearance of bright comets.