APOD: 2021 August 11 - Mammatus Clouds over Saskatchewan

Good morning, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "Mammatus Clouds over Saskatchewan." This image was captured after a thunderstorm in 2012. Thermal differences between cloud temperature, updrafts, and downdrafts are all thought to play a role in the formation of mammatus clouds.

As updrafts carry precipitation enriched air towards a cloud top, upward momentum is lost and the air begins to spread out horizontally. This gives cumulonimbus clouds their characteristic 'anvil' shape. Because of its high concentration of precipitation particles (ice crystals and water droplets), the saturated air is heavier than the surrounding air and sinks back towards the Earth. The subsiding air warms as it descends. However, since heat energy is required to melt and evaporate the ice and water contained within the sinking air, the warming produced by the sinking motion is quickly used as ice melts and water evaporates. If energy is still required for full evaporation, the sinking air will be cooler than its surroundings and will continue to sink downward. The subsiding air eventually appears below the cloud base as mammatus clouds.

Associated convective turbulence is one reason flight rules often warn aviators away from cumulonimbus (anvil-shaped) formations accompanied by mammatus clouds. Like many things, however, they do have their own symmetry and beauty when they can be viewed at a safe distance.