Weather Phenomena: What Are Asperitas Clouds?

With their Latin route aspero roughly translating to “make rough or uneven”, these distinctive but rare clouds appear to be rippling waves in the skies above. With Asperitas being the first new cloud type in over 50 years, how exactly do these particular clouds form and what exactly are their origins?

Since its cloud classification being accepted in 2015, research has been conducted to pinpoint the exact origin of these clouds, along with trying to understand how these cloud types form. The height of the base of these clouds are anywhere from 4,000 feet to 10,000 feet and they are classified as undulating waves. In fact, these wave-like structures form on the underside of established clouds and make the overall cloud look like a rough sea surface when they are viewed from below. Atmospheric dynamics are definitely in play during the formation and lifespan of these clouds. Like mentioned in a previous article on Kelvin-Helmholtz Instability, atmospheric and fluid dynamics play a role in the origins of these clouds. Shifting wind directions and velocities appear to cause Asperitas’ wave-like structure, much like how velocity and current direction influences a fluid. Winds shifting in the horizontal and vertical direction is thought to help create the structure of these clouds.

How exactly these clouds form is still somewhat of a mystery with much debate on how these wave-like clouds originate. It is hypothesized that they come into existence from the aftermath of convective thunderstorms, although Asperitas clouds have been sighted in calm atmospheric environments. Another theory suggests that these wave-like structures form from descending Mammatus clouds. When wind direction changes with height as Mammatus clouds descend, the clouds seem to present a wave-like structure like ones that can be seen on a sea surface. Regardless of hypotheses of how these clouds form, it is known that atmospheric conditions must be unstable to form a wavy cloud base. This is why convective thunderstorms are favored for the development of these clouds due to the atmospheric instability that is present during thunderstorms.

Like said above, Asperitas clouds are associated with Mammatus clouds and could possibly be associated with rainfall. As also stated, thunderstorms have occurred before and after the formation of Asperitas, but there are cases where an unstable atmosphere has occurred with these formations and no precipitation occurred. Truly, more research needs to be done in order to completely understand this newly classified cloud formation. With their menacing look which mimics rough seas, they are undeniably extravagant in their shape and formation as they traverse across the sky.

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©2019 Weather Forecaster Alec Kownacki