Luminous Night Clouds: The Relationship Between Meteors and Climate Change | Jeddah Astronomy Society
A mesmerizing celestial phenomenon on the edge of space
The head of the Jeddah Astronomical Society, Engineer Majid Abu Zahra, explained that the skies of the polar regions witness annually, as summer approaches in the Northern Hemisphere, a remarkable astronomical and atmospheric phenomenon known scientifically as "noctilucent clouds." This phenomenon is characterized by the appearance of glowing, undulating, silvery-blue clouds after sunset. It is considered one of the most beautiful and mysterious atmospheric phenomena in Earth's atmosphere, forming at very high altitudes, reaching approximately 85 kilometers, making them the highest clouds observable from our planet.
General context: How are luminous night clouds formed?
Unlike typical clouds that form in the lower troposphere, these clouds form in the mesosphere, one of the highest layers of the atmosphere. For a long time, scientists were unable to fully explain their formation mechanism. However, recent studies have revealed that these clouds form when temperatures in this layer drop to extremely low levels, as low as -125 degrees Celsius, allowing rare water vapor to freeze. This freezing process requires a nucleus around which the water molecules can condense, and this is where outer space comes in. The microscopic particles of "meteoroid smoke," produced when meteors burn up upon entering the atmosphere, act as ideal nuclei for the accumulation of tiny ice crystals, which in turn form these glowing clouds.
The importance of the phenomenon: a sensitive indicator of climate change
These clouds were first widely observed in 1885, two years after the massive eruption of Krakatoa, initially leading scientists to believe there was a connection between the two. But as their appearances continued, research turned to other causes. In recent decades, scientists have noticed that these noctilucent clouds have become brighter and more frequent, and have begun appearing at lower latitudes than usual. This change has attracted international attention, as it is considered a sensitive indicator of global climate change. One leading theory links this spread to an increase in atmospheric methane concentration. When methane reaches the mesosphere, it oxidizes through a series of chemical reactions, producing water vapor. This increase in water vapor provides additional "fuel" for the formation of ice crystals, making the clouds denser and more widespread. Thus, studying them is not only about their beauty but also about their potential as a scientific tool for understanding the impact of human activity on the upper atmosphere.
Why does it look blue?
The distinctive electric blue color of these clouds is due to the size of their constituent ice crystals, which are only about 100 nanometers in diameter. This minute size makes them very efficient at scattering short-wavelength sunlight (blue and violet) and transmitting long-wavelengths (red and yellow). When the sun is below the horizon after sunset, its rays illuminate these high clouds, making them appear to us in a captivating silvery-blue hue against the dark sky.
Monitoring opportunities in the Arab region
Abu Zahra confirmed that this phenomenon is generally limited to areas located at high latitudes between 50 and 65 degrees north and south, making its observation in the skies of Saudi Arabia and most of the Arab world extremely rare and almost impossible. He pointed out that any luminous clouds that might appear at night in the region are mostly ordinary high-altitude clouds illuminated by city lights or the moon, and not the true noctilucent clouds that remain a celestial mystery connecting our planet to the vastness of space.
