Six seconds into this YouTube clip of John Ford’s classic western, “Cheyenne Autumn”, you can hear the narrator identify the date as September 7, 1878. Meanwhile, as the opening scene fades from darkness into view, you can see a vertical contrail hanging in the sky. This creates a slight problem – because contrails are made by airplanes and airplanes didn’t start flying until 1903. Whoops!
The Santa Clarita Valley lies in the flightpath of many local and international airports, so its not surprising to see contrails in the sky above our valley. But what causes contrails? And whey do some quickly disappear, while remain in the sky for a long time.
The term “contrails” is short for “condensation trails”. According to this Smithsonian Air & Space website, “The first recorded sighting of a contrail likely occurred in southern Tirol in the Italian Alps in 1915 when somebody named Ettenreich spotted ‘the condensation of a cumulus stripe from the exhaust gases of an aircraft’”.
According to this NASA website, “Contrails are clouds formed when water vapor condenses and freezes around small particles (aerosols) that exist in aircraft exhaust. Some of that water vapor comes from the air around the plane; and, some is added by the exhaust of the aircraft…Contrails only form at very high altitudes (usually above 8 km) where the air is extremely cold (less than -40 degrees C).” (Click here to see a chart providing greater details.)
Contrails are categorized into three types:
1) Short-lived. The air is relatively dry. “The ice particles that do form quickly return again to a vapor state.” This process is known as sublimation, where ice evaporates directly into a gas without first becoming a liquid. To visualize this, think of how dry-ice “melts”.
2) Persistant (non-spreading). The air is humid, so the ice crystals are slower to evaporate.
3) Persistant (spreading). The air is humid, so the ice crystals are slower to evaporate. AND…there are winds to move it, spread it and fray it’s edges.
NASA has provided a photo gallery of contrails, to help you identify what your are observing. They even have a gallery of “unusual” contrails. I suggest that you be on the look-out just after sunset on Dec. 24. If you see something unusual coming out the north – perhaps 8 tiny contrails merging into one – the reindeer may be huffin’ and puffin’ because the sleigh is extra heavy this year.
Upcoming Outdoor Events:
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at email@example.com for time and place.
Wednesday mornings, December 4, 11, & 18
Saturday mornings, December 7 & 21.
Saturday, December 21, 8-10 AM. TowsleyCanyon. Bird Holiday Habitats. Right in time for many local holiday bird counting festivities, discover the variety of bird families around us, how they interact and their habitats. Beginners are welcome on this easy walk. Binoculars optional. Meet at the Towsley Canyon front parking lot.
2014 PlaceritaCanyon Wild Flower Calendar:
Looking for a unique and local gift? For $10, the Docents and Volunteers at PlaceritaCanyonNatureCenter are offering a calendar filled with original photos of local wild flowers. Best of all, your purchase will help support the fine work of the PlaceritaCanyonNatureCenter. They are available at the Placerita Canyon Nature Center Gift Shop.
New trail maps available. If you’d like to explore a bit on your own, the City of Santa Clarita has a website with trail maps of our local open spaces.
There’s also a new website for bicycle riders.
Ask Dr. Norm: Do you have questions about the flora, fauna, animals, rocks, etc. in our Santa Clarita Valley? Here’s a place for you to ask your questions. Dr. Norman Herr, Ph.D., is a professor of science and computer education at CaliforniaStateUniversity, Northridge.
Tell Us About Your Hike: Here’s a new website where you can post pictures, provide feedback and make suggestions about the City of Santa Clarita’s trails and open spaces.
You can listen to stories like this every Friday morning at 7:10 a.m. on “The SCV Outdoor Report”, brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
Or check out our Facebook page – L.A. Mountains.
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Do you have a news tip? Call us at (661) 298-1220, or drop us a line at firstname.lastname@example.org.
Source: Santa Clarita News