Question

Define polar stratospheric cloud

Answer 1

Polar stratospheric clouds or PSCs, also known as nacreous clouds (/ˈneɪkriəs/, from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 meters (49,000–82,000 ft). They are best observed during civil twilight when the sun is between 1 and 6 degrees below the horizon as well as in winter and in more northerly latitudes.[1] They are implicated in the formation of ozone holes.[2] The effects on ozone depletion arise because they support chemical reactions that produce 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 destruction.[

Answer 2

Polar stratospheric clouds are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m. They are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes.