A visible mass of condensed water vapor floating in the atmosphere, typically high above the ground. Cloud Reporter reports on clouds from all over the world.
These are called PSCs (polar stratospheric clouds). They are also known as nacreous or mother of pearl, due to its iridescence.
PSCs form at very low temperatures, below −78 °C (−108 °F). These temperatures can occur in the lower stratosphere in polar winter.
PSCs are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m (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.