Polar Stratospheric Clouds

Polar Stratospheric Clouds are clouds in the winter polar stratosphere at latitudes of 15,000-25,000 m. The stratosphere is very dry, it rarely allows to form clouds. These high altitude clouds form only at very low temperatures helps destroy ozone in two ways : By providing surface to reactive chlorine, and removing nitrogen that moderates chlorine reaction. These clouds are of mainly two types as follows –

Type 1 PSC –

They are generally stratiform appearance resembling cirrostratus or haze. They contain water, nitric acid and/or sulfuric acid and are a source of ozone depletion. They depletes ozone by producing active chlorine which catalyzes ozone destruction, and also because they remove gaseous nitric acid, perturbing nitrogen and chlorine cycles in a way which increases ozone depletion.

• Type 1a :- Contains large aspherical particles, consisting of nitric acid trihydrate.
• Type 1b :- Consists of small, aspherical particles of a liquid supercooled ternary solution of sulfuric acid, nitric acid and water.
• Type 1c :- They consists of metastable water rich nitric acid in a solid phase.

Type 2 PSC –

References :

• www.nasa.gov
• https://www.antarctica.gov.au/about-antarctica/ice-and-atmosphere/atmosphere/clouds-and-radiation/polar-stratospheric-clouds/
• https://en.wikipedia.org/wiki/Polar_stratospheric_cloud