"However despite the lack of our understanding, lets enjoy them one more time"

2007 December 30

Mammatus Clouds Over Mexico
* Credit & Copyright: Raymundo Aguirre

Explanation:
Normal cloud bottoms are flat because moist warm air that rises and cools will condense into water droplets at a very specific temperature, which usually corresponds to a very specific height. After water droplets form that air becomes an opaque cloud. Under some conditions, however, cloud pockets can develop that contain large droplets of water or ice that fall into clear air as they evaporate. Such pockets may occur in turbulent air near a thunderstorm, being seen near the top of an anvil cloud, for example. Resulting mammatus clouds can appear especially dramatic if sunlit from the side. These mammatus clouds were photographed over Monclova, Mexico.

https://apod.nasa.gov/apod/ap071230.html

The last proposed formation mechanism is that mammatus arise from Rayleigh–Bénard convection, where differential heating (cooling at the top and heating at the bottom) of a layer causes convective overturning. However, in this case of mammatus, the base is cooled by thermodynamical mechanisms mentioned above. As the cloud base descends, it happens on the scale of mammatus lobes, while adjacent to the lobes, there is a compensating ascent. This method has not proven to be observationally sound and is viewed as generally insubstantial.

This plenitude of proposed formation mechanisms shows, if nothing else, that the mammatus cloud is generally poorly understood.

From Wikipedia, the free encyclopedia
CREDITS
Contributors to Wikimedia projects

Video and description:
WikiRigaou

Rayleigh–Taylor instability

is the name given to the instability that exists between two fluids of differing densities, when the denser of the two is atop the less dense fluid. Along a cloud-base/sub-cloud interface, the denser, hydrometeor-laden air could cause mixing with the less-dense sub-cloud air. This mixing would take the form of mammatus clouds. The physical problem with this proposed method is that an instability existing along a static interface cannot necessarily be applied to the interface between two sheared atmospheric flows

From Wikipedia, the free encyclopedia
CREDITS
Contributors to Wikimedia projects

Image:
Shengtai Li, Hui Li - "Parallel AMR Code for Compressible MHD or HD Equations"

"Here is a representative [Representative in both senses of the word (just kidding..)] example of the structural organization of mammatus-cloud-formations by atmospheric gravitational waves:"

2020 December 7

Mammatus Clouds over Mount Rushmore
* Image Credit & Copyright: Laure Mattuzzi

Explanation:
What's that below those strange clouds? Presidents. If you look closely, you may recognize the heads of four former US Presidents carved into famous Mount Rushmore in South Dakota, USA. More obvious in the featured image are the unusual mammatus clouds that passed briefly overhead. Both were captured together by a surprised tourist with a quick camera in early September. Unlike normal flat-bottomed clouds which form when moist and calm air plateaus rise and cool, bumpy mammatus clouds form as icy and turbulent air pockets sink and heat up. Such turbulent air is frequently accompanied by a thunderstorm. Each mammatus lobe spans about one kilometer. The greater mountain is known to native Lakota Sioux as Six Grandfathers, deities responsible for the directions north, south, east, west, up, and down.

https://apod.nasa.gov/apod/ap201207.html

Gravity waves

are proposed to be the formation mechanism of linearly organized mammatus clouds. Indeed, wave patterns have been observed in the mammatus environment, but this is mostly due to gravity wave creation as a response to a convective updraft impinging upon the tropopause and spreading out in wave form over the entirety of the anvil. Therefore, this method does not explain the prevalence of mammatus clouds in one part of the anvil versus another. Furthermore, time and size scales for gravity waves and mammatus do not match up entirely. Gravity wave trains may be responsible for organizing the mammatus rather than forming them.

From Wikipedia, the free encyclopedia
CREDITS
Contributors to Wikimedia projects