A cold front passing through Chicago last week triggered a roll cloud, shown in the timelapse above. These clouds look like spinning horizontal tubes and form in areas where cool, sinking air displaces warmer, moist air to higher altitudes. The moist air is forced up along the cloud’s leading edge, causing it to cool and condense into cloud. Air on the trailing edge sinks downward again, warming and dissipating the cloud. The clouds are a visible form of soliton, or solitary wave, traveling through the atmosphere. They go by several other names, too, including Morning Glory clouds and arcus clouds. (Image credit: A. King; via Colossal)
Tag: cloud formation
Roll Clouds
The roll cloud, or Morning Glory cloud, is a rare phenomenon that looks rather like a horizontal tornado. In reality, it is part of a soliton wave traveling through the atmosphere. At its leading edge, moist air is forced upward, causing water vapor to condense, and, at the trailing edge, air moves downward, dissipating the cloud. These clouds are most frequently observed in Australia near the Gulf of Carpentaria, where local geography and sea breezes promote their growth during springtime. The clouds do appear elsewhere on occasion; the photos above show rolls clouds in Calgary, Alberta and coastal Uruguay, respectively. (Image credits: G. E. Nyland, D. M. Eberl; see also: Z. Ouazzani)
“Monsoon II”
Every child learns about the water cycle in school, but an academic description of the process often lacks nature’s grandeur. In “Monsoon II” photographer Mike Olbinski captures the majesty of cloud formation and rainfall in a way that rekindles awe for the scale of the process. It begins with bright clouds popping up, the result of warm moist air rising from the ground and cooling at altitude. As more water vapor evaporates, rises, and condenses, water droplets collide in these clouds, coalescing and growing until they grow too large and heavy to stay aloft. These are the droplets that fall in sheets of rain, blurring the air beneath them. There’s an incredible beauty to watching rain fall from a distance; it looks calm and localized in a way that’s utterly at odds with the experience from inside the storm. (Video credit: M. Olbinski; submitted by jshoer)
Cloud Formation
Clouds are so ubiquitous here on Earth that it’s easy to take them for granted. But there’s remarkable complexity in the mechanics of their formation. This great video from Minute Earth steps through the processes of evaporation and condensation that drive basic cloud formation. After evaporation, buoyancy lifts warm, moist air upward. That warm air expands and cools until it reaches an altitude where water droplets can condense onto dust particles in the atmosphere. These droplets form the wispy cloud we see. Turbulence mixes these droplets and helps them collide and grow. Interestingly, although we understand the basic process of cloud formation, relatively little is understood about the details, and the subject is still very much an area of active research. (Video credit: Minute Earth; via io9)
