#tropopause

Thousands of private fireworks shows carry on unseen beneath a veil of clouds while another show unfolds above in the tropopause…more private, more serene, unconcerned with patriotic causes, the light flares from deep within a distant storm, illuminating the deep blue recesses of twilight passing over a storm tossed sea of clouds.

Nacreous (‘mother of pearl’) cloud Nacreous clouds, also known as polar stratospheric clouds (PSCs), appear high in the atmosphere, some 15 to 30km (10 to 20 miles) above the Earth, generally in latitudes higher than 50°, particularly in the northern hemisphere. They form in the freezing temperatures of the lower stratosphere, often below -80°C (-112°F), and are usually a mixture of nitric acid and ice crystals, sourced from parcels of moist air that are forced up through the tropopause by the same orographic oscillations that are responsible for producing high lenticular wave clouds.

Cumulonimbus Incus

A cumulonimbus incus is a subspecies of a cumulonimbus cloud, a vertical cloud formed when water vapor is carried by powerful upward air currents and associated with atmospheric instability and thunderstorms. In Latin the word literally means 'heaps of rain'. Cumulonimbus clouds can evolve into a variety of other (often spectacular-looking) clouds such as mammatus, pannus, pileus, venum or tuba clouds.

A mature Cumulonimbus incus (heaps of rain with an anvil shaped top) has reached the boundary between the troposphere and the stratosphere (at approximately 9km height), the tropopause. Here air ceases to cool with height and becomes utterly dry. Because of this abrupt change the cloud flattens and takes on an anvil shape. Remarkably, in equatorial regions the tropopause lies at a much higher altitude of 18km, so these clouds must similarly go higher in tropical areas.

It should not be surprising that the Cumulonimbus incus can produce dangerous atmospheric disturbances such as hail, heavy rain, strong winds, lightning and in some cases tornadoes.

If the correct atmospheric conditions are met these giants can eventually turn into supercells.

See here for a timelapse video of how these clouds are formed (and disappear):https://www.youtube.com/watch?v=C3Ny9lddzUk%2F

-OW-

Image: Copyright Fir0002/Flagstaffotos. A Cumulonimbus incus over Swifts Creek, Victoria, Australia.

Original caption: