By Wendy Langhans
Tucked away in on a shelf in my office is a can of compressed gas, which I use occassionally use to clean the dust off my computer keyboard.
The first time I used it, I noticed that the can became really cold, almost too cold to hold. Physicists refer to this cooling as adiabatic expansion: “As the gas expands and does work, its internal energy drops, resulting in cooling.” We see this process at work whenever air flows up and over our surrounding mountain ranges, especially when there’s a bit of humidity in the air: “When the cooled gas makes contact with water vapor in the air, it condenses and forms a mist.”
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Sometimes adiabatic expansion results in a special kind of cloud formation – Lenticular Clouds. They look a bit like flying saucers and seem to hover in place.
Lenticular clouds form when cool, moist air rises up over a mountain, and like a wave of wind, it crests, drops down and rises up again. Each time the air rises in altitude, adiabatic expansion causes causes the temperature to drop; water vapor condenses and forms a cloud at the crest of the wind wave. The cloud seems to hover in place, perpendicular to the air flow, because new air is constantly moving into and out of the cloud. Check out this video on YouTube, which was filmed earlier this year in Santa Clarita, to get a better view of how it works.
One last tidbit about lenticular clouds: they have a double convex lens shape. So where do you think the word “lenticular” comes from? The lens of a telescope? The lens of a pair of glasses? Or from a legume known as a lentil? (Hint – lentils have been grown since Neolithic times, while the first wearable eyeglass were developed in the 13th century and telescopes were developed in the 17th century.)
On taking a closer look, lenticular clouds do look a bit like lentils. But I wonder, does their name have to do with their similar shape or with their composition? After all, lenticular clouds are formed by gasses, while lentils have been know to produce gas. Ah well, some questions are better left unanswered.
Upcoming Outdoor Events:
Saturday, September 18, 8:00-10:00 AM. Morning Bird Hike at Towsley Canyon. Bring water and your binoculars and wear closed-toed shoes. Meet at the park entrance. 2 hours. For a map, click here.
Tuesday, September 21, 7:00–9:00 PM. Public Comment for the National Park Service’s “Rim of the Valley Corridor Study”. “The purpose of this special resource study is to determine whether any portion of the Rim of the Valley Corridor study area (the mountains encircling the San Fernando, La Crescenta, Santa Clarita, Simi and Conejo Valleys of Los Angeles and Ventura Counties) is eligible to be designated as a unit of the national park system or added to an existing national park unit.” For more information, go here. Meeting to be held at the George A. Caravalho Sports Complex Activities Center Building, 20880 Centre Point Parkway, Santa Clarita.
Thursday, September 23, 7:00-9:00 PM. Full Moon Adventure in Towsley Canyon. The canyon is a whole ‘nother world at night. Bring water and wear closed-toed shoes. Meet at the park entrance. 2 hours. For a map, click here.
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, September 1, 8, 15, 22, & 29.
Saturday mornings, September 11 & 25.
You can listen to stories like this every Friday morning at 7:10 a.m. on “The Hike Report”, brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.