Noctilucent Clouds: Meaning, Formation, Facts

How often do we admire clouds? Almost every time we see them! Their shades, shapes and location in the sky have always fascinated us. Whether we watch them near a sunrise or sunset, or beneath us from the height of a high-flying aeroplane. But do you know clouds also exist much above the layer of the atmosphere where the aeroplanes fly? Such clouds are called noctilucent clouds. 

What are Noctilucent Clouds?

Noctilucent Clouds look as astonishing as they sound. Only some people have seen them on summer evenings after sunset. These clouds are only visible from 45 degrees to 80 degrees latitude. Also, these are clouds that are formed at very high altitudes and are not very commonly visible. When they are, they appear like streaks of blue or silver far up in the sky. 

The word ‘Noctilucent’ is also derived from the Latin words nocto and lucent translating to night and shining respectively. Another interesting name for these clouds is Polar Mesospheric Clouds. Let’s explore the origins of this name while discussing the formation of these clouds. 

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How are Noctilucent Cloud Formed? 

Noctilucent clouds are located nearly 76 to 85 km above the Earth’s surface, which is too far from the normal clouds. They are formed with scarce water vapour and dust that escapes the lower layers of the atmosphere to reach the third layer, which is the Mesosphere. 

When viewed from space, these clouds are detectable as a layer of icy crystals that diffuse the light across the polar mesopause. Mesopause is the lowest layer of the Mesosphere. Hence they are called the Polar Mesopheric Clouds. 

The dust particles present in this layer of the atmosphere are either the remains of meteor dust or the remains of volcanic eruptions and pollutants released from the Earth. 

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Fun Facts About the Night Clouds

These clouds have fascinated skywatchers for years due to their appearance and some interesting facts like the following; 

• These clouds are mostly spotted in the months of May and June.
• The frequency of these clouds changes each year due to changes in the atmosphere and solar cycle. 
• Night clouds appear as electric blue clouds after the sunset.  
• These clouds need extremely low temperatures to form and are still seen in summer. (This is because the Mesospheric layer near the poles experiences the lowest temperatures during that time.)
• You can join Facebook groups to watch live telecasts of these clouds online. 

For more such informative blogs on Science and Technology stay tuned to our General Knowledge section.