Russian scientists from MIPT have made an important step towards unraveling the nature of noctilucent clouds — the highest clouds on Earth, which appear at an altitude of about 80–85 km and glow against the background of dawn. Although such clouds have been observed for over a century, their origin has not been fully understood.
Research led by climatologist Olga Zolina has made it possible to put forward and analyze several key hypotheses explaining where the water vapor necessary for their formation comes from at such a height.
One hypothesis suggests that in summer in the mid-latitudes, ascending air currents lift moisture from a height of 25–30 km to the level of the mesopause, where at a temperature of −120 °C, the vapor turns into ice crystals. Another hypothesis — the so-called "solar rain" — suggests that water vapor is formed by the interaction of solar hydrogen atoms with oxygen in the atmosphere. The version about the role of methane is also being considered, which can rise to the upper layers of the atmosphere and, interacting with cosmic dust, form ice particles.
Scientists emphasize the importance of studying noctilucent clouds: they help to better understand the processes in the upper atmosphere of the Earth and the influence of external factors — from climate to space. The discovery of Russian specialists allows us to get closer to answering one of the long-standing mysteries of the science of the Earth's atmosphere.
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