POLAR MESOSPHERIC CLOUDS Meaning and
Definition
-
Polar Mesospheric Clouds (PMC), also known as noctilucent clouds or "night shining clouds," are thin and wispy cloud formations that appear in the upper mesosphere, typically found at altitudes of 76-85 kilometers (47-53 miles) above the Earth's surface. These clouds are usually observed in polar regions during the summer months when the mesosphere becomes extremely cold, allowing for the formation of ice crystals.
PMC are characterized by their unique appearance, displaying a glowing or luminous quality during the twilight hours after sunset or before sunrise. These clouds have a distinctive bluish or silvery color that can be easily distinguished from lower-level cloud formations. Despite being located at high altitudes, polar mesospheric clouds can be observed from the ground due to their high reflectivity of sunlight.
The formation of PMC is believed to be closely associated with the presence of water vapor and extremely low temperatures in the upper atmosphere. It is thought that these clouds form from the condensation of water vapor onto tiny particles, such as dust or meteoric smoke, that act as nucleation sites for ice crystal growth.
Polar mesospheric clouds provide valuable insights into atmospheric dynamics and climate change. They are indicators of atmospheric conditions at high altitudes and serve as visual markers for studying processes related to global warming. Understanding the formation and behavior of PMC contributes to the comprehension of complex interactions between the Earth's atmosphere and space, making them a subject of interest for atmospheric scientists and researchers.
